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LARSA Section Composer Manual

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2. The section can be rendered in LARSA 4D 21 LARSA Section Composer Manual 22 LARSA Section Composer Manual Computations The Section Composer is able to compute many properties of section definitions in real time for arbitrarily shaped cross sections Section Properties The following computations are made for the sections Details on some of these computations are listed below The units of the computations are all in the length unit chosen in Section Units The member local axis refered to below is at the section centroid with axes parallel to the member reference axes The principle axes are also located at the centroid but may have a different orientation Area The cross sectional area of the section ze ye The coordinates of the centroid of the section which determines the location of the member local axes with respect to the position of the member reference line The reference line is the imaginary joint to joint line plus any specified member end offsets in LARSA 4D Izz Moment of inertia about the member local z axis at the centroid Iyy Moment of inertia about the member local y axis at the centroid Izy Product of inertia for the member local y and z axes at the centroid It is zero if the principle axes correspond to the local axes Ipzz Moment of inertia about the principal z axis The principle axes are not used in the LARSA 4D analysis only Iyy and Izz about the loc
3. LARSA Section Composer Manual in several cases In the case of a cross section representing a bridge deck the alignment of the cross section with the structure geometry is made at a special centerline reference point on the surface of the deck In that case the cross section would be positioned so that the top surface of the section aligns with the reference z axis putting the centroid not on the reference line but below This is depicted in the figure below Recall that the joints are positioned on the reference x axis reference axes Member Reference and Local Axes With A Centroid Offset If the section has nonprismatic variation it is especially helpful to align the cross section at the point on the section that is not varying If the section varies in depth the it is useful to align the section with the model at the section s top which has constant elevation local axes z comes out ofthe screen Member Reference and Local Axes Nonprismatic Variation In the figure above the joints are located on the member reference x axis reference line The I shape is created in Section Composer such that its top surface is flush with the member reference z axis The centroid is below the reference line When this section is applied to the LARSA 4D model the centroid of the member will be automatically offset from the joint to joint line In fact the centroid will automatically follow the haunch of the section with the top face of
4. LARSA Section Composer Manual A manual for LARSA 4D Finite Element Analysis and Design Software Last Revised July 2009 Copyright C 2001 2012 LARSA Inc All rights reserved Information in this document is subject to change without notice and does not represent a commitment on the part of LARSA Inc The software described in this document is furnished under a license or nondisclosure agreement No part of the documentation may be reproduced or transmitted in any form or by any means electronic or mechanical including photocopying recording or information storage or retrieval systems for any purpose without the express written permission of LARSA Inc LARSA Section Composer Manual Table of Contents Introduction About LARSA Section Composer Overview Sections Shapes and Parameters Composite Sections Screen Overview Section Axes Creating a Section Starting Up Adding Shapes Editing Shape Size and Position Align and Snap Other Shape Tools Stress Recovery Points Torsion Constant J Computation Other Section Tools Using the Section in LARSA 4D Computations Section Properties Torsion Constant J Shear Area Factors Free Shapes Cutouts and Composite Shapes Drawing the Outer Rectangle Drawing the Cutout Starting a Section Section Composite Shapes Parameterizing the Section Parameters and Formulas Parameterizing the Tube Section Parameter Scope Formula Language Shape Templates Reinforcement Bars
5. 28 6 ir 24 in 76 lb ft fhe r Z ile 4375 in b amp 33 jl Cancel angles V Show dimension lines HAEE ajal kau Adding a Standard Shape For this tutorial we will use the Insert Custom Shape tool in the Shape menu which is used to create shapes based on standard forms but with user supplied dimensions Thirteen basic shape types I rectangle Angle etc and many complex shape types are included with Section Composer The complex types include code based box girders and AASHTO type I and T beams The dimensions of custom shapes can be edited later on 14 LARSA Section Composer Manual Standard Custom Sections Standard Custom in Box Bridge Beam Manbar Y Section Name Hollow Rectangle 2 I Shape Rectangle Solid Circle T Shape Trapezoid Triangle Z Shape Columns Box Beams Box Bridge Beam Box Girders Box Bridge Beam _ Box Bridge Beam d 10 00 1 000 1 000 1 000 1 000 Bl Add Cancel i v Show dimension lines 2 x ajal Adding a Custom Shape When a section requires a shape that doesn t fit any of the provided templates the Draw Free Shape tool can create a shape with arbitrary point coordinates This will be demonstrated later on 3 Use the Insert Custom Shape tool to add an I shape to the section It will be found in the Basic Shapes category Enter arbitrary dimensions for the parameters
6. The horizontal distance from the extreme left edge z of the section to the centroid e Cty The vertical distance from the extreme top edge ty of the section to the centroid When Principal Axes are turned on in the View menu the direction of the principal axes of the section are drawn at the section s centroid Torsion Constant J The torsion constant J can also be computed by the Section Composer Because it may take several seconds to compute J it is only computed on request At other times the value of J may be listed as N C for not computed To compute the torsion constant use the menu command Section Compute Torsional Constant A torsion constant J can only be sensibly computed in certain circumstances Sections should be entirely connected meaning there should not be two pieces of the section which are not connected by some material When a section is composed with two disconnected parts the torsion constant calculated will be the sum of the torsion constants calculated for the two parts as a rough approximation of the true value Rebars page 35 do not affect the computation of the torsion constant Shear Area Factors Shear Area Factor Y and Z can be entered by the user These parameters faciliate the computation of shear areas Shear area is computed as the cross sectional area multiplied by the shear area factor in the y and z directions 24 LARSA Section Composer Manual Free Shapes Cutouts and Com
7. which is different from the member reference coordinate system Member loads and results are about the local coordinate system In the Properties Explorer the values for lyy and Izz are the moments of inertia about these axes The principle axes of the section are also shown however these are informational and diagnostic only Principle axes are not used in the LARSA 4D analysis The principle axes are drawn with a red dashed line and are distinguished by the Ipyy and Ipzz labels The principle axes are located at the section centroid but may be rotated from the member reference local axes if the section s strong axis does not coincide with the member reference z axis Editing Shape Size and Position Shapes are positioned and modified by selecting them To select a shape click on it To select multiple shapes at once drag a window with the mouse enclosing the shapes or hold the and click on multiple shapes The dimensions of shapes are set through parameters which are listed in the Shape Explorer on the right side of the screen when shapes are selected The parameters for I shapes are d b tf and tw for instance To change the dimensions of a shape click the shape to select it Make sure the Parameters tab is active in the Shape Explorer and then click the parameter to change in the parameters spreadsheet Try changing some of the parameters of the shapes to resize them A description of the parameter will appear below the paramet
8. 3D graphics window there is a 2D canvas to define a cross section There is also the header bar where we can see the active section name and the mouse coordinates as we move our mouse on the graphics window Instead of a window bar a section list allows the toggling between sections defined in the same database file An additional explorer called calculations can be found at the top right side of the screen and displays the properties of the current section in real time Section Axes Section Composer shows a two dimensional cross sectional picture of the section The y axis of the member is the vertical axis and the z axis of the member is the horizontal axis We will always be dealing with the y and z coordinates in the Section Composer The 0 0 coordinate at the intersection of the y and z axes on the canvas is at the member reference line This is like an x axis that goes into the screen The member reference line lines up with the line between the start and end joints of the member in the LARSA 4D model assuming the member does not have member end offsets We call these axes the member reference axes The centroid of the section will not necessarily fall on the member reference line If shapes are placed off center LARSA 4D will assume the user wants the physical member offset from the member reference line which can be convenient for aligning the section with a bridge centerline or modeling nonprismatic variation In most cases t
9. But for pedagogical purposes we will assume the model is more complicated Unselect everything in the project Use Selection Unselect Objects Unselect All or any of the alternatives Using the Pointer mouse tool right click any of the members Choose Select Chain This tool selects all of the members running up and down the model from the one that was clicked e Goto Draw From Selected Members Span The nonprismatic variation is revised to go smoothly across the span After creating a span the nonprismatic variation is applied as intended Spans are visible in the graphics window if the option is turned on in Graphics Show There is also a spreadsheet for spans in the geometry group in the members tab Turn off complete rendering In the figure the span is depicted as the thick green line The members are depicted as the yellow line at the member centroid S When complete rendering is off members are shown at their centroids Analys s of nonprismatic sections The beam column element used in the LARSA 4D analysis has constant section properties throughout When a member has nonprismatic variation the nonprismatic variation must be approximated member properties are taken at the mid point of the member and are assumed to apply throughout As a result members with nonprismatic variation should be sufficiently broken down into smaller pieces so that the variation within each member
10. a material see Materials in LARSA 4D Reference Manual is assigned to the member see Members in LARSA 4D Reference Manual in LARSA 4D as is usually done to make a composite section use Section Composite Materials to choose a material for each shape A reference material must be chosen at the top of the Properties Explorer so that the section properties page 23 can be computed Parametric Section Composite Section Example p Section Diagram Properties Composite Parts External Databases If this section is a composite section select a material for each shape below If this section is made of only one material leave each shape s material as unassigned Shape Material Outer Concrete Fc_ Inner Steel A36 v Choosing materials for a composite material section If a material is chosen for any component shape or if any shape has rebars then a material must be chosen for all component shapes and a reference material must be chosen In LARSA 4D version 7 and earlier the material assigned to members of a composite section must be the same as the Reference Material set in the section definition In LARSA 4D version 8 and later a material must not be set on members who have been assigned a composite material section This change is intended to guarantee the consistency of model input While the Reference Material is necessary to compute section properties such as Iyy and Izz the choice
11. and linearly increasing at a slope of 1 12 The formula FREVA EA creates parabolic variation To save time when devising formulas Section Composer has a formula helper On the Parameters spreadsheet there is a small f button to the right of each value or equation Clicking this button opens the formula helper which can be used to create formulas for several common situation linear variation parabolic variation and sinusoidal curves The formula helper is shown in the figure Parametric Equation Editor es Custom Equation Linear Growth Parabolic Curve Sinusoidal 10 Growth Slope Value at End in 25 Start Yalue in Growth slope is only available when x is set in length units Formula helper Click the f button beside the d parameter The formula helper opens to the linear variation tab filling in the fields as determined by the equation we had previously entered by hand This tool allows the user to enter the start and end values of depth rather than creating a formula by hand If we had not entered a formula you could enter the values here and it would create the formula e Revise the formula and then click OK Notice how the parameters spreadsheet updates with a new formula 43 LARSA Section Composer Manual Positioning the Centroid We have the non prismatic variation defined however there is one issue to be noted before we move on Normally members in LARSA 4D are positioned
12. each parameter using a special 4 variable Parameter A parameter is a named value that can be referenced in equations for the locations of points The coordinate of a point might be for instance b 2 d 2 for the lower left coordinate of a rectangle shape where b and d are parameters Cutout Shape Shapes are generally solid In order to create a shape with a hole such as for a tube or box girder a second shape called a cutout must be placed inside the outer shape The cutout defines the inside perimeter of the shape Multiple cutouts can be placed in the same shape such as for multiple cell box girders Composite Shape Shapes are generally made of the same material throughout Composite shapes are placed within other shapes to indicate a change of material within the shape If a section has two independent parts of different material composite shapes are not necessary A composite shape is necessary only when one material completely encloses another Member Reference Line The member reference line is the joint to joint line of a member plus any member end offsets set in LARSA 4D This is a reference point that determines how shapes placed on the Section Composer canvas line up with the member element in LARSA 4D Normally shapes are positioned by the user so that the computed section centroid lines up with the member reference line Member Reference Axes The member reference axes are the x y z axes that determine how a S
13. figure below The start I and end J joints of a member are depicted as blue spheres If there are no member end offsets left the reference x axis also called the reference line runs from the start to the end joint If there are member end offsets right the reference line is shifted accordingly AZ Z no member z ffsets X Az _ reference axes _ y N at y y Irene A x ER A d offset Joint cd J Joint pr gt ee emoe y poa i reference axes Bi ots l 7 I Joint l Joint gt global axes x global axes x Member Reference Axes Alignment With Joints The y and z axes of the reference coordinate system are perpendicular to the reference line and are oriented in the LARSA 4D model according to the orientation angle of the member The convention for orienting these axes is described in detail in Members in LARSA 4D Reference Manual For horizontal members generally a 90 degree orientation angle is used so that the member reference z axis points horizontally In that case the member reference z axis should be parallel to the section s flanges if applicable Positioning the Section When creating a section the user has the freedom to place the shapes anywhere relative to the reference axes As a result the section centroid may not coincide with the member reference line While in most cases the section centroid does line up with the reference line offsetting the centroid can be useful 38
14. spreadsheet in the Shapes Explorer shows all of the parameters available to the selected shape If no shape is selected only the parameters with global scope are shown If an outer shape is selected global parameters as well as parameters whose scope is that shape are shown If a cutout or composite shape is selected global parameters the outer shape s parameters and any parameters scoped to the cutout or composite shape are shown When editing formulas in the Points spreadsheet the list of available parameters is shown below the spreadsheet Formula Language Formulas follow a simple and intuitive format The following describes the formulas recognized by Section Composer Numbers Numbers must be entered with a period for a decimal point Commas separating thousands cannot be used Engineering notation with an e followed by an exponent at the end of the number may be used Examples 10 25 5280 3 2e 1 The standard arithmetic operators exponent can be used and are interpreted with the standard order of operations Parentheses can be used to group expressions Example 10 20 5 2 Special constants Use pi as a stand in for the value 3 14159 Example 30 pi 180 Calling functions The following functions are available sqr square root deg convert radians to degrees rad convert degrees to radians sin cos tan atn arc tangent arcsin arccos and abs absolute value The trigonometric function
15. stayed bridges and guyed towers The engine became popular for analyses of these types of structures because of its unprecedented accuracy at a reasonable price The engine has been powerful since day one using both tangent stiffness and the full Newton Raphson method with iterations in nonlinear analysis LARSA software has come a long way since it was first available on the VAX super mini computers decades ago LARSA Inc has always been an industry leader LARSA was the first to offer an individual PC based DOS structural analysis package with geometric nonlinear analysis capabilities in 1986 In 1994 LARSA took the early next step to Microsoft Windows with a point and click graphical user interface and two years later was the first to offer elastic perfectly plastic pushover analysis Today LARSA s flagship product is LARSA 4D released in 2006 and featuring new seismic and inelastic elements major improvements to influence and staged construction analysis and many new features for bridge design and analysis About LARSA Section Composer LARSA Section Composer is powerful and easy to use software that is an essential graphical tool in the analysis and design of any bridge or building structure with nonstandard or nonprismatic sections It supports nonprismatic and composite sections based on standard parametric and custom shapes and it is able to compute section properties for standard as well as user drawn shapes The program also calc
16. template it is important to define the shape s dimensions parametrically as we have here In addition the parameters must have shape scope rather than global scope Parameters with global scope will not be included in the template To create a template select the shape Then in the Shape menu choose Export As Shape Template You will be prompted for a file name Save the file in the directory where you are prompted This is where Section Composer will look for user created shape templates You may need administrative privileges to save a shape template 34 LARSA Section Composer Manual Reinforcement Bars Reinforcement bars rebars provide tensile strength to concrete sections The types and locations of rebars within sections can be entered in Section Composer and will be used in moment curvature and capacity analyis Rebars are entered in the Shapes Explorer in the Rebars tab Start a new section and add a 20 by 10 inch horizontal rectangular custom shape Then click the shape to make sure it is selected Open the Rebars tab in the Shapes Explorer The left button in the rebars panel adds a new rebar into the selected shape The rebar s shape from a standard database its material and its coordinates must be entered The coordinates are given in the shape local axes Shape local axes differ from the member reference and local coordinate systems Each shape has an arbitrary origin for its local axes This is useful becaus
17. the section held at constant elevation LARSA 4D displays members as their centroid lines rather than at the member reference line The figure below shows how LARSA 4D displays a member nonprismatic cross section variation in depth The members are strung across the joints however the centroid falls below the joints and this is where the members are drawn In LARSA 4D members are displayed as their centroid lines indicating centroid offsets from joints When LARSA 4D s complete rendering is turned on it is easy to verify that the section is positioned correctly relative to the joints 39 LARSA Section Composer Manual Local Coordinate System The member local coordinate system is always placed at the member centroid This is the system in which the section lyy and Izz properties page 23 are given and the system in which member loads see Member Loads in LARSA 4D Reference Manual and results such as end forces see Member End Forces in LARSA 4D Reference Manual sectional forces see Member Sectional Forces in LARSA 4D Reference Manual end stresses see Member Stresses in LARSA 4D Reference Manual span deflections see Member Displacements in LARSA 4D Reference Manual and analyzed loads see Analyzed Member Loads in LARSA 4D Reference Manual are specified If the section centroid is at the member reference line which is always the case for sections from a standard database then the member refe
18. time at which shapes in a section are constructed is not set in the Section Composer Rather than setting the times of construction of component shapes instead various construction sequence states are set Each state is a configuration of component shapes that are either active or inactive at any given time Casting a shape corresponds to changing a member from one construction sequence state omitting the shape to one including the shape For example consider a section consisting of two shapes a web shape and a flange shape The web is steel and the flange is concrete In the Staged Construction Analysis model the model will be constructed in four steps constructing piers and other structural elements unrelated to this section placing the steel web into the model pouring the concrete flange so that it contributes weight but no stiffness and then considering the concrete flange set and load bearing Note that because the casting day and weight only characteristics of this section apply to a single shape only and not the whole section the casting day option on members see Members in LARSA 4D Reference Manual and the weight only option for constructing structure groups see Setting Up the Model in LARSA 4D Reference Manual are not used for this purpose Instead three construction sequence states will be created for this section in the Section Composer The first state includes the steel web only The second state includes the steel
19. web and the concrete flange but with the flange set to weight only The third state includes both shapes with both weight and stiffness Note here that there is no need for a construction sequence state that does not include the steel web When no shape is active the member element should not be included in the model at all Construction Sequence If the section will be used in Staged Construction Analysis and if it will be assembled in parts the sequence of assembly of the parts of the section must be set Use the Construction Sequence Explorer to created construction states A construction state represents one possible state that the section may be in during its construction ol LARSA Section Composer Manual Activate the Construction Sequence Explorer by clicking the Const Seq tab of the section explorer Shapes Parameters Paints Rebars Const Seq Construction Sequence I Add State gt Add Shape 3 State Ag P Type J State B P Type Symmetrical Beams Add Two Construction Sequence States In this example the section has two states In the first state only the Type V shape the shape on top is present In the second state the symmetric I shape has been poured so both shapes are present Click the Add State button twice to add the two states The first state is always considered the initial state of the section When a state is clicked the shapes that are not activated in that state are shown unshaded t
20. will have their edges aligned A concrete plate sitting atop a beam will for instance have its bottom edge aligned with the beam s top edge The six alignment tools on the toolbar are used to quickly put shapes side by side align left align horizontal center align right align top align vertical center align bottom Each command aligns the indicate edge of the selected shape s To align a shape first make the shape selected by clicking it Then click the align tool for the side of the shape to align A menu will appear with a list of what the shape can be aligned to another shape s corresponding side or the member axes Snap Align Tools Rotate Shift B83 E mE 0 0 i a aa de Member Reference Y Axis Align and Snap Tools 17 LARSA Section Composer Manual Click on the rectangle shape so that it is selected Then click the Align Left the leftmost alignment tool in the toolbar The two choices are Member Reference Y Axis and I Shape Left The first choice will align the left edge of the rectangle with the member s vertical reference axis The second option aligns the left edge of the rectangle with the left edge of the I shape Choose that The snap tool works like the align tool but instead of choosing a common side of a shape to align two shape edges are chosen and they are brought together The two edges must be parallel Click the snap tool in the toolbar to begin a snap operation Then click the edge of th
21. As you click a parameter a description of its meaning is provided below the parameters table Click Add once the dimensions are set After adding a shape you may want to give the shape a name Shape names are used to idenfity shapes and to group parameters To change a shape s name right click the shape and choose Rename or use the Rename tool in the Shape menu Use the Insert Custom Shape tool a second time to insert a rectangular shape it is the Rectangle shape type in Basic Shapes whose depth is on par with the I shape s flange thickness and whose width is the width of that of the I shape e Move the shapes around by dragging them with the mouse to position the rectangle above the I shape You may need to click the Zoom Out tool in the toolbar Rectangle z Jens I Shape an out as al u 7 ee Adding Two Shapes 15 LARSA Section Composer Manual We do not set the material of shapes in the Section Composer when the material is uniform throughout Rather the material is specified in LARSA 4D The display canvas as in the figure above shows the centroid and principle axes of the combined cross section The centroid is indicated by the small blue Iyy Izz axes near the center Note how it is offset from the Member Reference Line We will correct this later on If the centroid is left where it is it would define the member local coordinate system in LARSA 4D
22. Member Reference Line and Local Coordinate System Reference Coordinate Systems Positioning the Section Local Coordinate System co N 10 10 13 13 14 16 17 18 19 20 20 20 23 23 24 24 25 25 27 27 28 29 l 31 32 33 34 30 37 38 38 40 LARSA Section Composer Manual Nonprismatic Variation Starting an Example The x Variable Formula Helper Positioning the Centroid Multi Member Spans Analysis of nonprismatic sections Composite Material Sections Composite Construction Sections Construction Sequence Composite Assembly Section Analysis Ultimate Strength Check Moment Curvature Analysis Moment Curvature and Yield Surface Glossary 41 41 41 43 44 45 46 49 ol 51 52 53 53 53 53 55 LARSA Section Composer Manual Introduction About LARSA 4D LARSA 4D is an advanced multipurpose 3D structural analysis package featuring a powerful graphical user interface and an analysis engine with unmatched analytical features including influence line and surface based live load analysis staged construction analysis time dependent material properties and segmental construction analysis hysteretic and seismic elements and seismic analysis and progressive collapse The LARSA structural analysis engine has been in commercial use for over 25 years It was originally developed to perform nonlinear static analysis of structures that have large displacements such as suspension and cable
23. SA 4D Although members have Section At Start and Section At End fields only Section At Start is used for sections defined with nonprismatic varition using Section Composer Section At End is an alternative method to create nonprismatic variation from two separate sections of similar shape but different dimensions Multi Member Spans When a section with nonprismatic variation is initially assigned to a member the variation runs from the start of the member to the end of the member only Each member will be treated separately and the x variable resets at the end of each member This is usually not what is desired as often many so called analytical members are used to model a single physical member se Use Break Members in the Modify menu to break the member into six pieces The result clearly needs some work After breaking the member a span needs to be defined When multiple analytical members make up a single physical member LARSA 4D calls it a span see Spans in LARSA 4D Reference Manual Spans have several uses in LARSA 4D One is to indicate that nonprismatic variation is to continue smoothly from the start of the span to the end The x variable does not reset at the ends of members within spans When using relative units 1 0 corresponds to the end of the last member in the span 45 LARSA Section Composer Manual To create the span we will want to have only the members on the span selected This is already the case
24. al axes Ipyy Moment of inertia about the principal y axis The principle axes are not used in the LARSA 4D analysis only Iyy and Izz about the local axes Ipa The angle between the member local z axis and the principle z axis giving the orientation of the principle axes J Torsion constant described below Perimeter The perimeter of the cross section including the perimeter of any holes in shapes e Sz Elastic section modulus about the member z axis Izz divided by the distance from the centroid to the furthest edge in the y direction e Sy Elastic section modulus about the member y axis lyy divided by the distance from the centroid to the extreme edge in the z direction Rz Radius of gyration about the member z axis Sqrt Izz Area Ry Radius of gyration about the member y axis Sqrt lyy Area Qz Moment of area about the member z axis Qy Moment of area about the member y axis e WeightArea Adjusted cross sectional area factored by material density When shapes are set to have different materials creating a composite section the weight area reports the sum of the shape areas factored by the ratio of the shape density to the density of the chosen base material WeightArea is used for the computation of self weight in LARSA 4D version 7 In 293 LARSA Section Composer Manual version 8 this field is not used in the analysis as the self weight of each shape is applied independently e Clz
25. be edited Local indicates that the coordinates are relative to the shape s local coordinate system origin point Replace the z coordinate of point 1 which reads 10 with b 2 Recall that b is 20 so the value should be unchanged when the formula is entered If the shape s dimensions change in the graphical view something is wrong Replace the y coordinate of point 1 with d 2 Replace the coordinates of the remaining points b 2 d 2 b 2 d 2 and b 2 d 2 Shapes Oe Parameters Points Rebars Edit Local v A Point z y Origin 0 0000 0 0000 1 b 2 d 2 b 2 d 2 b 2 d 2 b 2 m w N Currently available parameters are d b t Parameterized coordinates for the Outer shape e Click the empty space within the cutout to select the Inner shape Then replace the numeric coordinates with b 2 t d 2 t b 2 t d 2 t b 2 t d 2 t and b 2 t d 2 t The shape is now completely parameterized Return to the Parameters tab and trying changing the parameters to see the dimensions of the shape change Parameter Scope Each parameter has what is called its scope Parameter scope determines which shapes the parameter can be used in and is chosen in the Shape field when creating a parameter which was mentioned above There are two types of parameter scope Global scope Parameters with global scope are applicable to all shapes meaning they can be used in the formulas for any poi
26. cludes a diagram of each section cross sectional properties and parameter settings Using the Section in LARSA 4D The section is saved in an LPSX database file that needs to be linked into LARSA 4D projects that will use the section se Open LARSA 4D It is not necessary to close LARSA Section Composer A section database is first connected to a LARSA 4D project Once the database is connected the sections defined in the database become available to assign to members Use the Connect Databases command from the Input Data menu Choose Connect User Database Select the section database file in this example Test Section lpsx The section s in the database are then added to the list of sections in the project You can view the section from Input Data Properties Sections or in the Model Data Explorer The section is applied to members just as with standard sections using the Model Data Explorer or the geometry spreadsheet 20 LARSA Section Composer Manual Because of LARSA 4D s conventions for member local axes an orientation angle of 90 degrees must be set on horizontal members to have the section oriented with its y side up A nice feature of using Section Composer sections is that they render their true shapes when Complete Rendering is turned on Add a member to the project and assign it the section from the section database Set its orientation angle to 90 degrees Click Graphics Complete Rendering
27. cond section in the same database for a composite section ee Rename the section to Tube using Section Rename 27 LARSA Section Composer Manual Start a new section by clicking Section Add New Give it the name Composite Section Example Notice how the two sections are listed in the section list at the bottom of the Section Composer screen You can switch between editing the two sections by clicking their names When the database file is saved t will contain both sections Composite Shapes As before create a 20 in x 20 in solid rectangle shape You can use either the free draw or the custom shape tool A composite shape is placed inside a shape to indicate that part of its volume is made up of a different material from the outer shape The composite shape gives the perimeter of this material As with cutout shapes the outer shape can contain any number of composite parts This example will model a steel rectangular core surrounded by a rectangular concrete form The outer shape is the concrete part The cutout to be drawn will be specified to have a steel material Right click the rectangle shape and choose Insert Composite Subshape Draw Free Composite Subshape Click four points and then the first again to create a shape within the rectangle that will have a different material Shape 1 The composite material section with an outer shape and an inner composite part The composite shape part is repr
28. d shape s outline It is generally used when creating a custom or free shape from scratch Reverse Point Order When creating a new custom or free shape from scratch this reverses the order of the points on the polygon of the selected shape There is no rule about whether the points should be ordered clockwise or counter clockwise It is a matter of user preference Shift Points Forward Backward Again as a matter of user preference this changes the numbering of the points on the polygon outline of the selected shape so that the first point becomes point number 2 and so on for the other points or the points are shifted so that the first point becomes the point numbered last and so on Duplicate This command duplicates the selected shape It creates a new shape with the same parameters points and formulas but with a new name Merge This command merges several adjoining shapes into a single shape Select the shapes to merge before activating this command Stress Recovery Points Before moving on to the next section we need to define the stress recovery points When the section is analyzed in LARSA 4D the stresses will be reported at these points only Typically a section should have four stress recovery points one in each quadrant at the most extreme fibers of the cross section Stress recovery points can be placed at any vertex on the perimeter of a shape a Inthe View menu make sure Show Stress Points is turned on to display stres
29. databases or created as user drawn arbitrary shapes The parametric shape library contains over fifty predefined parametric shapes including simple predefined shapes such as I C T L and Box as well as complicated shapes like box girders You can also draw any arbitrary shapes by using free draw tool Shapes are generally given names such as Rectangle Cutout Flange or Web The dimensions of shapes are set either through coordinates or parameters such as Bl Fy and for I shapes depth width flange thickness and web thickness The values of parameters can be numbers or equations such as RABJA Equations are used especially for defining nonprismatic variation changes in the shape of a section along the length of a span but also can be used to create a parametric shape definition When a section requires shapes not found in the standard tables or in the parametric shape library they may be modeled as user drawn arbitrary shapes The Section Composer is able to automatically compute the properties of arbitrary shapes no matter what the shape Section A section is a collection of one or more shapes Sections are given names and are stored in section databases All of the shapes in a section must be touching see the torsion constant computation later in this manual All of the properties of a section needed for an analysis are computed by the Section Composer Section Database lpsx file A section database is a file wit
30. e shape to be moved In this example choose the bottom edge of the rectangle Last click another edge where the first shape should be moved to Here click the top edge of the I shape Rectangle Using the Snap Tool The two shapes are now connected appropriately We must now put the combined section centroid on the member reference line The sections are currently positioned with the I shapes center on the member reference line But with the addition of the rectangle the centroid moved up The two shapes must be shifted down Section Composer has a command to do this automatically In the Section menu choose Move Section Centroid to Member Center The shapes will be shifted into position Other Shape Tools There are a number of other shape tools available that we will not need for this example They can be found on the Shape menu or toolbar Shift This command performs a translation on the selected shape The user is asked for a distance along the z and y axes to shift the shape Rotate This command roatates the selected shape by a specified angle in degrees Rotate 90 CW CCW This command rotates the selected shape 90 degrees either clockwise or counter clockwise Flip Horizontal Vertical This command mirrors the selected shape either horizontally or vertically about its local axis 18 LARSA Section Composer Manual Add Remove Points s This command adds or removes a point on the polygon that defines the selecte
31. e the rebars will stay in the same location even if the shape is repositioned on the Section Composer canvas The shape local axes is indicated by dashed lines if Shape Local Axes are turned on in the View menu Click the left button in the rebars panel to add a new rebar 3 Choose a standard rebar type in the first column and a standard steel material in the last column Enter the coordinates for the rebar relative to the shape s local origin Put the rebar at the lower left of the shape at z 8 and y 4 Repeat the process to put two more rebars at the bottom of the shape at z 0 and z 8 Shapes Parameters Points Rebars Reinforcement Bars 8 00 0 00 4 00 A36 8 00 4 00 436 Rebar type material and locations are entered in the Rebars tab of the Shapes Explorer The rebars are shown as grey circles on the drawing canvas 30 LARSA Section Composer Manual Rectangle The rebars are shown in the drawing canvas Because the rebar is of a different material than the rest of the section it is necessary to tell Section Composer the material of the rectangle shape so that the cross section properties can be computed This is a similar process as to creating a composite shape page 25 Use Section Composite Materials to choose the concrete material for the rectangle shape This becomes the reference material for the purposes of the computations You must choose the same reference material as the ma
32. ection Composer section lines up with the member element in LARSA 4D The member reference x axis is the same as the member reference line The member reference y and z axes are perpendicular to the reference x axis Their orientation in LARSA 4D is determined by the member orientation angle By convention the web of a section is parallel to the member reference y axis which corresponds to an orientation angle of 90 degrees in LARSA 4D Note that the reference axes do not necessarily correspond to the section s principle axes but often do Member Local Coordinate System If the section s centroid is placed at the member reference line then the member reference axes also correspond to the member local coordinate system The member reference axes are used for the placement of lanes and tendons in the model while the local coordinate system is 56 LARSA Section Composer Manual used for forces but loads and results If the section centroid does not line up with the member reference line the membeer local coordinate system s origin is at the centroid with y and z axes parallel to the reference axes Note that the local coordinate system does not necessarily correspond to the section s principle axes if the section is asymmetric Nonprismatic Section Normally a member has the same dimensions along its entire length it 1s a prism Members may vary in depth width or in any other dimension along their length Such members are said to have no
33. ection is created Section Composer continuously updates the computations displayed in the Properties Explorer The definitions of these properties are included later on But because the torsion constant J can take several seconds to compute it 1s not updated automatically When it has not been calculated N C standing for not computed is shown in the explorer To have Section Composer compute J go to the Section and choose Calculate Torsional Constant The value is then displayed in the explorer This is the last step in creating a basic section The section database can be saved and then later attached to a LARSA 4D project 3 Save the section database as Test Section lpsx Other Section Tools Several other section tools are available that we will not need in this example The Duplicate toolin the Section menu as opposed to the duplicate tool in the shape menu duplicates the entire cross section definition including all shapes in it as a new section in the same database Duplicating a section is a good way to start a new similar section with different dimensions File Import can be used to add a shape to the section from either an AutoDesk DXF file or another Section Composer LPSX database file File Export can be used to export the section either as an AutoDesk DXF file or as an image file BMP format File Report creates a printable report for all sections in the open section database file The report in
34. eference coordinate system Glossary 55 Member Reference Line and Local Coordinate System 37 member reference line 55 merge shapes 13 mirror shape 13 moment capacity 53 moment curvature 53 moment of area 23 moment of inertia 23 moment yield surface 53 move shape 13 multi member spans 41 nonprismatic section 55 nonprismatic variation 41 overview 7 parameter Glossary 55 Overview 7 parameter scope 31 parameters 31 parametric sections 31 parametric shape Creating a Section 13 Glossary 55 Overview 7 perimeter 23 physical members 41 principle axes 23 Qz Qy 23 radius of gyration 23 reference coordinate system 55 reference line Glossary 55 Member Reference Line and Local Coordinate System 37 reference material 49 reinforcement bars 35 remove points from shape 13 reverse shape point order 13 rotate shape 13 Rz Ry 23 section Glossary 55 Overview 7 section database 55 section database lpsx file 25 section modulus 23 section properties 23 shape Glossary 55 Overview 7 shape local axes 13 60 LARSA Section Composer Manual shape templates 31 shapes 13 shift point order in shape 13 shift shape 13 snap 13 spans 41 standard shape Creating a Section 13 Glossary 55 Overview 7 stress recovery points 13 Sz Sy 23 torsion constant Computations 23 Creating a Section 13 ultimate strength 53 units 13 weight area 23 x varlable 41 ZC yc 23 61
35. ers spreadsheet and the corresponding dimension line for the parameter will appear in red in the drawing area Shapes Parameters Points Rebars Parameters in Flange Thickness tf gt Parameters for an I Shape Shapes are positioned either by dragging them with the mouse or by setting their origin coordinates The origin is a reference point for each shape and often but not necessarily the shape s center of gravity It is indicated by dashed lines and y z labeled axes when the Local Axes display option is on To turn on local axes click Shape Local Axes in the View menu 16 LARSA Section Composer Manual Member Y Shape Origin Rectangle Shape Local Axes gt Member Reference Axes Member Member Z Reference Line Shape Local Axes The origin coordinates can be set by going to the Shapes Explorer changing to the Points tab and making sure the View Edit option reads Edit Local The origin coordinates are the position of the shape y z origin relative to the Member Reference Line Shapes Parameters Paints Rebars Edit Local Y Currently available parameters are d b Editing the Origin of the Rectangle It is up to the user to position shapes by dragging or setting origin coordinates so that the combined section centroid lines up with the Member Reference Line which is almost always desired Align and Snap Often two shapes in a section
36. esented on the canvas as a different color although we have not specified that the shapes have different materials yet As it is now the two shapes have the same material Click the outer shape and rename it to Outer Then click the composite shape and rename it to Inner 3 Goto Section Composite Materials For the Outer shape choose a concrete material For the Inner shape choose a steel material Then click Close 28 LARSA Section Composer Manual Parametric Section Composite Section Example po p Section Diagram Properties Composite Parts External Databases If this section is a composite section select a material for each shape below If this section is made of only one material leave each shape s material as unassigned Shape Material Concrete Fc_ Steel A36 Selecting materials for the composite parts The Properties Explorer has a new option reference material You must now choose a reference material for the section The cross sectional properties are computed as if the section had this material uniformly throughout by factoring the cross sectional properties of the parts with other materials according to their modulus of elasticity In LARSA 4D version 7 this base material must also be set as the material of the members which will be assigned this section property In version 8 the material field on members with composite shapes must be left as none as LARSA will choose a
37. eters and the point coordinates of standard shapes cannot be modified Their analytic properties are read from the database as well Shapes where the z y coordinates of the corners of the polygon are entered directly are called free shapes They are simply polygons with point coordinates You can later on define parameters for a free shape and change the point coordinates to use these parameters Parametric shapes are sized according to length width and other easy to understand dimensions rather than through coordinate points A parameter is a placeholder for a dimension Formulas can then be used based on this parameter to define the coordinates of a point There are number of predefined parametric shapes available in Section Composer but you can create your own by starting with free shapes and adding parameters and formulas after An example of the parameters and formulas to define the 12 points around the perimeter of an I shape is given in the figure below Shapes EE F SSeS Shapes iste eee Parameters Points Rebars Parameters Points Rebars Parameters in Points in Edit Local Dt p Symmetrical I Beam 8 00000 1 2 3 4 5 6 7 8 Currently available parameters are d b tf tw Parameters and point formulas for an I shape We could define an I shape by setting the z y coordinates of the points clockwise around the perimeter Each point could be entered as a coordinate Starting at the top oute
38. h the extension which contains section definitions These files are edited using the Section Composer and can be linked to a LARSA 4D project in LARSA 4D using the Connecting Databases in LARSA 4D User s Manual command A section database may contain more than one section as a convenience so that all of the sections relevant for a project can be saved within a single file However updating a section in a section database will affect all LARSA 4D projects that make use of the database Standard Shape Standard shapes are those which come from a standard table such as AISC or EURO Many section tables are available in Section Composer The properties of standard shapes cannot be modified in Section Composer their d mensions and properties are guaranteed to be exactly what is found in the original section table Because these shapes are fixed they cannot be used for creating nonprismatic sections 55 LARSA Section Composer Manual Parametric Shape Section Composer derives most of its power from parametric shapes These shapes which come in a variety of flavors are dimensioned using parameters not points Whereas an I shape has 12 vertices it only has 4 parameters d b t and w Only those parameters need to be set in Section Composer for it to be able to calculate all of the shape s properties and to display it graphically In addition parametric shapes may be given nonprismatic variation by assigning equations of variation to
39. he user must take care to place shapes so that the section centroid falls on the 0 0 coordinate in the Section Composer window When the section reference line and centroid do not coincide the reference axes serves as the origin for geometry including the alignment of the section and the placement of lanes and tendons while the centroid serves as the origin of the member local coordinate system which is used for loads and results This is discussed in more detail in the section on nonprismatic variation later in this manual 10 LARSA Section Composer Manual yoser n Databas File Edit View Section Shape Analysis Hep Menubar amp Toolbar oZBuseiklagaagagaus zz DFKL EE ee EEEE New Parametric Section 2 5837 in 4 7509 in Opens an existing parametric section database 5 7 6 5 4 3 2 1 b E 3 4 5 6 ite A 1 00000 Member Reference Y yo 0 00000 Computations ns Section Canvas 11 1667 0 00000 116 667 11 1667 0 00000 Area The total cross sectional area of the section Shapes Enere Parameters Paints Rebars Parameters in Member Reference Z FRE Symmetrical I Beam Symmetrical I Beam Sectjon List New Parametric Section Unit in Symmetrical I Beam Screen overview and section axes 11 LARSA Section Composer Manual 12 LARSA Section Composer Manual Creating a Section Sections can be prepared in several ways The tutorial below introduces Sec
40. implicity of a model with a single line of member elements representing what is conceptually a single girder However in this model parts cannot be constructed at different times and neither time dependent material changes such as creep and shrinkage nor thermal gradient loads can be used Composite sections are a best of both worlds approach By allowing a single cross section to be defined with different parts i e shapes only a single line of member elements need be created in the LARSA 4D model to represent the whole girder Because the parts are a part of a single cross section they will necessarily deform together During an analysis the cross sectional properties and the location of the centroid of each individual member element for the purposes of the assembly of the global stiffness matrix are computed as the equivalent properties as if the member had a uniform cross section Additionally construction activities in Staged Construction Analysis allow the user to change the cross sectional properties of the members over time by constructing parts of the section individually Self weight time dependent material effects and thermal gradient loads are computed for the parts of the section separately allowing the parts to have different responses and are them lumped onto the centroid of the combined whole section LARSA Section Composer Manual Screen Overview Section Composer s screen has menus toolbars and explorers Instead of a
41. inate in the Section Composer window When the section reference line and centroid do not coincide the reference axes serves as the origin for geometry including the alignment of the section while the centroid serves as the origin of the member local coordinate system which is used for loads and results The two systems are the reference coordinate system and the local coordinate system In most cases the two systems are the same They differ only when a member has been assigned a section created in Section Composer with a centroid that is offset from the reference coordinate system Reference Coordinate Systems The member reference coordinate system is used for the alignment of structure geometry It determines how the cross section is placed relative to the member element and it is also used for the placement of tendons see Tendons in LARSA 4D Reference Manual within members and lanes see Lanes in LARSA 4D Reference Manual when they have offsets The x axis of this coordinate system runs from the start of the member meaning the start joint plus any member end offsets applied to the start of the member to the end joint plus any end offsets at the end of the member The member reference line point on the Section Composer canvas represents this x axis and so the locations of shapes relative to this point determine how the section lines up in the LARSA 4D model The location of the reference coordinate system is depicted in the
42. indicating that from this step forward both shapes in the section are active Also see Composite Section Construction Activities in 52 LARSA Section Composer Manual Section Analysis Several section analysis tools are provided in Section Composer and LARSA 4D Moment Curvature and Yield Surface computation Ultimate Strength Check and Moment Curvature Analysis Ultimate Strength Check The Ultimate Strength Check tool allows users to compute flexural strength also known as moment capacity on prestressed and or reinforced concrete or steel structures Currently the tool has support for the following codes AASHTO LRFD 2006 BS5400 and EN 1992 1 1 2004 The utlimate strength check computes the flexural strength for the section taking into account the placement of reinforcement bars within the section and if run from LARSA 4D post tensioning tendons running through the section and either their short term or long term forces The tool is described in Ultimate Strength Check in LARSA 4D User s Manual Moment Curvature Analysis The Moment Curvature Analysis tool allows users to perform moment curvature analysis on cross sections capable of taking prestressing post tensioning and reinforcements into account Currently the tool has support for the following codes AASHTO LRFD 2006 BS5400 and EN 1992 1 1 2004 The moment curvature analysis takes into account the placement of reinforcement bars within the section and if ru
43. ing drag and drop Copy Paste Align Transform Shift Rotate Flip and Snap tools Point and click to assign the stress calculation points Export to DXF Yi LARSA Section Composer project_sections psx os amp je File Edit View Section Shape Analysis Help Da gt QQQQQH RIK B efo t Pelt er sein ss California State Box Type 1 2 331 3960 in 1 223 8210 in 536 4032 3528 3024 2520 2016 1512 1008 504 D 504 1008 1512 2016 2520 3024 3528 4032 4636 a 3042 l 0 00000 2704 Member Y 0 00000 7 6750e12 5 8387e13 2366 2028 i 0 06085 7 6750e12 5 8387e13 0 00000 2 0165e13 33 707 7 4 7310e9 v 1690 1352 tb 8 700 1014 E 676 Area The total cross sectional area of the a 338 section D m es Member Z a Parameters Points Rebars 676 s Parameters in 1014 E Btt 1352 1690 2028 DRABO 2366 2704 3042 Ion i nd a 4 Ul p California State Box Type 1 Unit in California State Box Type 1 F LARSA Section Composer LARSA Section Composer Manual Overview This section provides an overview of the terminology used in LARSA Section Composer Sections Shapes and Parameters Sections are assembled by combining shapes which may be taken from standard databases including AISC ARBED CAND EURO and UK created from parametric shape templates I T
44. ion Close the nonprismatic variation window Al LARSA Section Composer Manual Section Diagram Properties Composite Parts External Databases Member Y s Variable 5 14 Relative Span Position 0 to 1 recomended Absolute Length from Span Start in Parameters v pzz Member a 0 0 Side 4 Setting the x Variable Type For both settings the 0 0 value for x always corresponds to the location of the start joint of the first member in a span We will make this I shape vary in depth First notice how the I shape has been designed when the depth parameter varies Change the value of the depth parameter d a few times Notice how the top edge of the section remains in place while the bottom edge changes It has been set up this way rather than keeping the shape centered for the benefit of nonprismatic variation In actual models it is more likely that the top surface of the member will lie flat while the lower surface moves rather than the member growing taller or shorter in both directions simultaneously To make this section nonprismatic we will replace the value for the d parameter currently 10 with a formula in terms of the x variable To apply formulas to parameters make sure the Parameters tab is active in the Shapes Explorer at the lower right corner of the Section Composer screen Click the shape to activate it and then find the appropriate pa
45. is negligible for the purpose of analysis While member force results reflect this simplification member stresses are computed at stree recovery point locations that follow the nonprismatic variation defined in Section Composer That is the locations of stress recovery points are taken according to the parameter formulas applied at the start or end of the member not at the midpoint 46 LARSA Section Composer Manual For More Information please refer to the following documentation Members in LARSA 4D Reference Manual Spans in LARSA 4D Reference Manual 47 LARSA Section Composer Manual 48 LARSA Section Composer Manual Composite Material Sections Sections composed of parts of different material properties can be created in Section Composer Starting with LARSA 4D version 8 0 these sections account for the differential effects of self weight thermal loads and time dependent material effects and stresses can be reported in each material part A composite material section 1s a section composed of shapes that have different material properties see Free Shapes Cutouts and Composite Shapes page 25 or a Shape plus rebars page 35 In composite sections the overall section properties depend on the materials of the parts and the forces and stresses in each shape may be different from that in other shapes While in non composite sections the material of the section is not specified in the Section Composer instead
46. n from LARSA 4D post tensioning tendons running through the section and either their short term or long term forces The tool is described in Moment Curvature Analysis in LARSA 4D User s Manual Moment Curvature and Yield Surtace To view the moment curvature diagram or yield surfaces for a section based on a simple computation procedure use Moment Curvature and Yield Surface from the Section menu The moment curvature tool described above is a more advanced analysis option Choose either Y or Z axis moment Enter the appropriate maximum curvature and extreme fiber strain values If the section 1s not composite choose the section s material Finally to evaluate moment curvature at multiple values of axial force enter the axial force increment to use and the number of axial force steps to take Switch between the Moment Curvature and Yield Surface tabs to see the two diagrams 53 LARSA Section Composer Manual Yield Suet Computation bment Curvature amp lace Canaput ation fionei tos ri EI an CC IE Moment Curvature computation This tool does not take into account the presence of rebars in the section 54 LARSA Section Composer Manual Glossary Shape The shape is the basic component that can be used to create sections The properties of individual shapes are determined automatically based on its dimensions and material properties Shapes can be inserted from the parametric shape library from standard
47. nd not each coordinate in order to change the dimensions of the section Parameters are also important in defining nonprismatic variation We will revise the tube section so that its points use parameters and formulas Three parameters will be used depth d width b and thickness t From the parameters the coordinates of each of the points can be computed automatically Click the solid area of the section to select the outer shape To create a parameter go to the Parameters tab in the Shapes Explorer Click the plus sign button The first parameter to create will be depth For the name enter d For value enter 20 for the current value of 20 inches In the description field enter depth Leave two other parameter fields as they are The shape field will be discussed below The unit type field is only used for saved shape templates Edit Parameter 3 Shape Name d Value Unit Type Length Description depth ce Creating a parameter for depth Click Add and then create two more parameters b for width with value 20 and t for thickness with value 2 Although this creates parameters the eight points that make up the section still use numeric coordinates The next step is to replace the numeric coordinates with formulas l LARSA Section Composer Manual Open the Points tab of the Shapes Explorer Make sure Edit Local is chosen In this mode the coordinates can
48. nprismatic sections The analytic properties of nonprismatic sections also vary along the length of the member Varying dimensions and properties are taken into account in LARSA 4D when modeled in the Section Composer Composite Material Sections Sections may be made of a composition of multiple shapes each having a different material Such sections are called composite material sections Section Composer will take the composite nature of a section into account when calculating section properties The differential effects of self weight thermal loads and time dependent material effects on the shapes making up composite material sections are accounted for in the LARSA 4D analysis starting with version 8 0 Composite Construction Section Sections may assembled during the construction of a structure For instance a steel web may be placed first into a structure with a concrete slab on top for the deck poured and placed at a different time While such structures can be modeled with the web and slab as independent elements in the LARSA 4D model this approach fails to account for the continuity of displacement along the length of the web and slab Instead a single section definition containing both the web and slab can be created in the Section Composer They will however be set up so as to be added to the model at separate times The differential effects of self weight thermal loads and time dependent material effects on the shapes making
49. nted around the member in the LARSA 4D model The axes are highlighted in the figure below Fi LARSA Section Composer New Section Database baba File Edit View Section Shape Analysis Help Menubar amp Toolbar a 9 QQA AHLI AE O agak ap Be Less VOD a G New Parametric Section 2 5837 in 4 7509 in Properties C 0 G in Opens an existing parametric section database 5 7 6 5 4 3 2 1 D Us Ah 3 4 5 6 He a 14 0000 zc 0 00000 ye 0 00000 Computations 116667 lyy 11 1667 lzy 0 00000 Ipzz 116 667 Ipyy 11 1667 D 0 00000 Area The total cross sectional area of the section Shapes eee eae Parameters Paints Rebars _ F Parameters in Bt Symmetrical I Beam Member Reference Y Section Canvas m 8 00000 f a Symmetrical I Beam 4 4 Section List A 4 m j New Parametric Section Unit in Symmetrical Beam THe member reference axes on the Section Composer canvas 37 LARSA Section Composer Manual The centroid of the section will not necessarily fall on the member reference line If shapes are placed off center LARSA 4D will assume the user wants the physical member offset from the member reference line which can be convenient for aligning the section with a bridge centerline or modeling nonprismatic variation In most cases the user must take care to place shapes so that the section centroid falls on the 0 0 coord
50. nts in the section To use global scope select Global in the Shape field when creating the parameter Global scope should be used when two separate shapes in the section must have the same dimensions However because there can only be one parameter with a given name in any scope it cannot be used when two shapes have separate parameters with the same name For instance if there are two I shapes then a depth parameter in global scope would enture that the two I shapes have the same depth If they can have different depths global scope should not be used Shape scope Parameters with shape scope are applicable only within formulas for the points in that shape or any of its cutouts or composite parts To use shape scope select the shape name in 32 LARSA Section Composer Manual the Shape field when creating the parameter Shape scope should be used when a parameter is meant to determine the dimensions of one shape in the section but not other shapes Each shape can have its own set of parameters and will not conflict with parameters of the same name whose scope is another shape When parameterizing the tube section above the scope of the three parameters was set to the Outer shape This allowed the parameters to be used in the Outer shape as well as within its cutout Ifa new separate shape were added to the cross section such as a plate adjoined to the tube the parameters would not be available to define the plate s points The Parameters
51. o indicate they are not active Add the Type V shape into the first state by first clicking State A Then select the Type V shape by clicking it in the main drawing area Last click the Add Shape button to activate that shape in State A Repeat the process for State B to indicate the shape is still active in that state Then repeat the process to add the symmetric I shape into State B The times at which these states are used are set later as construction activities in LARSA 4D See the next section Composite Assembly For sections assembled part by part during Staged Construction Analysis the construction states defined earlier are applied as construction activities A composite construction activity 1s used each time the section changes These activities are assigned within construction steps to structure groups containing members with the same section The members whose sections will change during the Staged Construction Analysis are put into a structure group here named Group 1 A composite construction activity is created by right clicking the step in the Construction Stages Explorer at the point where the activity is to occur Choose Activities gt Composites The composite activity spreadsheet for that step will be shown Add a row for the structure group containing the members whose sections are changing and choose the new construction state for the section that takes effect beginning with this step Here State B is chosen
52. of Reference Material is irrelevant for the final analysis because only combined material section values such as E Iyy are needed which come out the same for any choice of Reference Material 49 LARSA Section Composer Manual 50 LARSA Section Composer Manual Composite Construction Sections In LARSA 4D version 8 s Staged Construction Analysis it is possible to construct individual component shapes of sections such as in casting additional concrete sections onto what is treated as a single cross section A composite construction section is a section composed of multiple shapes that are assembled e g cast at different points in time during a Staged Construction Analysis in LARSA 4D Reference Manual In composite sections the overall section properties depend on the materials of the parts and set of shapes that are active at each point in time Additionally the forces or stresses in each shape may be different from that in other shapes In Staged Construction Analysis in LARSA 4D Reference Manual different component shapes of a composite section can be constructed 1 e cast at different times The Section Composer and LARSA 4D have been designed so that different members in a model can use the same section definition but cast component parts at different times That is a single section created in the Section Composer can have different construction sequences depending on the member it is assigned to As a result the precise
53. on Rename and name this section I Shape With Plate Next we set up the units of this section 13 LARSA Section Composer Manual Goto Section Units and if itis not already selected select inch as the section unit Then click OK to close the window Next make sure that the grid is properly set up Goto View Grid Setup and set the grid width to 1 inch Click OK to close the dialog 3 Also in the View menu turn on all the options except the stress recovery points and the point numbers Grid Lines Dimension Lines Shape Local Axes Centroid Position and Principal Axes We can now start adding some shapes into this section Adding Shapes The Shape menu has several tools to add shapes to the section being edited Any number of shapes can be added into a section The Insert Standard Shape tool inthe Shape menu is used to add a predefined shape from a standard database such as the AISC and Indian databases Sectional properties and a preview of the shape are shown as the database shapes are browsed The dimensions of standard shapes cannot be modified by the user once they are inserted into the section Standard Custom Sections Standard Custom Member Y American v W 8 99 in 0 68 in All W242104 W242103 W24n94 W24x84 W 24x68 W 24x62 W24x55 W21x201 Cwatt 2 W21 182 v 0 44 in 22 4 ir 2 68 in 4 2100 in 4 82 5 in 4 200 ir
54. pipe several types of box girders and more or free drawn Section Composer automatically computes cross section properties A parametric section database contains one or more sections and is saved n a file with a lpsx extension Section databaes can be connected to LARSA 4D projects where the section properties become available LARSA 4D can also create rendered images of sections defined in Section Composer A shape is a polygon The polygon determines the outline of the cross section Each point on the polygon has a z y coordinate on the section canvas Points can be positioned by entering coordinates dragging them with the mouse or using parameters and formulas The cross section is solid unless a cutout shape is placed inside of it the cutout shape defines the outline of the hole like the hole in a box girder Circle Shape Plus a Circle Cutout A cutout shape creates a hole within a solid shape Shapes can also be embedded within other shapes to model composite action A composite shape not to be confused with composite sections is used if a shape has an internal part with different material properties LARSA Section Composer Manual Rectangle merican Outer Shape Composite Shape A composite shape is a shape embedded within another shape of a different material There are three ways the geometry of a shape can be set Standard shapes are ones that come from a standard section database e g AISC The param
55. posite Shapes In a previous section standard and custom shapes were used to build up a section In this section three more shape types free shapes cutouts and composite shapes will be used This section will build a tube section with dimensions 20 in x 20 in and a thickness of 2 in This shape can be found in the custom section command see Creating a Section page 13 Instead we will create all the shapes of this section using only the free draw method The outer perimeter of the section will be set by first drawing a free shape The perimeter of the hole will be set using a cutout shape Cutouts are shapes that create holes within other shapes Without a cutout all shapes would be solid Drawing the Outer Rectangle When a section requires a shape that doesn t fit any of the provided templates use the free shape tool to create a shape with arbitrary point coordinates First we will start with the outer shape of the tube Analysis Help 24Q QW DIK Free Draw Tool s From the toolbar click the free draw tool It is shown in the figure above e Click in the drawing canvas where the corners of the shape should be one by one Use the guidance of gridlines and make sure to verify the coordinate under your mouse in the header bar before clicking Click in the canvas at 10 10 then at 10 10 10 10 and 10 10 25 LARSA Section Composer Manual 4 LARSA Section Composer New Section Database Eile Edi
56. r vertex of the lower left flange and working clockwise the points might be 2 7 0 5 7 0 5 1 etc the top of the shape is at y 0 But if the dimensions of the box change later you ll need to fix each of the twelve coordinates Rather than explicitly inputting the coordinates we use dimensions parameters and formulas That LARSA Section Composer Manual means we need to define the coordinates of the points not with actual numbers but with placeholders for the dimensions For a symmetric I shape we four parameters d for the depth of the shape and b for the width tf for flange thickness and tw for web thickness Using simple equations for each coordinate the coordinates of the points can be set to b 2 d tf tw 2 d tf tw 2 tf etc We will return to how to enter this information into Section Composer later in this manual Keep in mind that although the formulas used in this example are quite simple the Section Composer uses an advaned formula language which is powerful enough to handle very complicated equations It is described later in this manual Composite Sections LARSA 4D and Section Composer starting with version 8 0 support two new types of composite sections A composite construction section 1s one in which parts of the section are cast at different times For instance a web may be placed before a deck is poured above it A composite material section is one in which parts of the section are made
57. rameter back in the Shapes Explorer that will have variation The simplest formula will be to give it linear variation between 10 and 25 This formula is EEE When x 0 at the span start the formula has the value of 10 so the depth will be 10 At the span end where x 1 the formula has the value 25 The depth will vary linearly in between Replace the numeric value with the formula Nothing changes on the Section Composer canvas Because it is a 2D representation of the section the variation is into the screen and cannot be seen The Section Composer canvas always shows the cross section properties at the start of the span Return to the Nonprismatic Variation window in the Section menu to preview the variation A preview of the variation from a side view is displayed at the bottom of the window The cross section image at the top left can show the section shape at any point along the span Drag the slider below the image to move to a different point on the span 42 LARSA Section Composer Manual Parametric Section Nonprismatic I p s k a u Section Diagram Properties Composite Parts External Databases s Variable Relative Span Position 0 to 1 recomended Absolute Length from Span Start in Previewing nonprismatic variation Formula Helper When the x variable is in absolute length units another useful formula might be which would vary depth starting at 5 units
58. reference material automatically Properties C 0 G_ in Reference Material Fc_8 7 a Area 475 016 zc 0 00000 ye 0 00000 lzz 13 433 4 Iyy 13 433 4 lzy 0 00000 Ipzz 13 433 4 Ipyy 13 433 4 Ipa 0 00000 J 22 637 7 Perimeter 80 0000 Sz 1 343 34 Area The total cross sectional area of the section The Properties Explorer has an option to choose a reference material when shape materials are set More details on the use of composite shapes is given in Composite Material Sections page 49 Parameterizing the Section The next section will discuss how to parameterize the tube section 29 LARSA Section Composer Manual 30 LARSA Section Composer Manual Parameters and Formulas Parametric sections are created through the use of parameters and formulas which allows section dimensions to be altered parametrically without the need to alter point coordinates This section explains more about the use of parameters and describes the formula language Parameterizing the Tube Section In the last section a hollow tube section was created using the free draw tool This tool creates a shape in which the points are located with numerical coordinates If the dimensions of a shape need to be revised the coordinates of each of the point defining the perimeter of the shape will need to be updated with new values By making the coordinates determined in terms of a formula only a few section parameters need to be revised a
59. rence and local coordinate systems are identical Otherwise the member local coordinate system will be different The member local coordinate system x axis corresponds to the line of the member centroid from the start of the member to the end If the section does not have nonprismatic variation then the local axes are merely a translation of the reference axes from the reference line to the centroid The local y and z axes are thus oriented at the centroid so that they are parallel to the y and z reference axes respectively This can be seen in the figure above without nonprismatic variation Note that the local member axes are then not necessarily principal axes since the section could have been placed arbitrarily on the drawing canvas Only if the product of inertia Iyz is zero will the local axes coincide with the principal axes The user is responsible for orienting the section so that the principle axes line up with the reference local axes if that is desired If the section has nonprismatic variation the local coordinate system y and z axes are positioned slightly differently so that they are perpendicular to the local coordinate system x axis The local axes are positioned by first translating the reference axes to the centroid at start and then rotating them so that the x axis passes through the location of the centroid at the end of the member This can be seen in the figure above with nonprismatic variation If the centroid of the sec
60. rigin coorindates without affecting its own geometry The location of the origin is editable in the first row of the points tab It is relative to the member reference line Keep in mind that on this explorer you can modify the coordinates add remove points and copy paste data perhaps from another program like Excel Also notice that the coordinates of the points can be viewed and edited in the shape s local axes or viewed relative to the member reference axes global After adding a shape you may want to give the shape a name Shape names are used to identify shapes and to group parameters Change the name of the shape we just created using either of these methods Right click the shape and choose Rename and then enter Outer or use the Rename tool in the Shape menu and enter Outer 26 LARSA Section Composer Manual Drawing the Cutout Although cutouts are part of the section with no actual material their dimensions are given as shapes This allows their dimensions to be controlled parametrically if desired in addition to the geometry of the outer perimeter of the shape An outer shape can contain any number of cutouts ee Create a cutout in the rectangle by right clicking it and choosing Insert Cutout Draw Free Cutout This will allow you to click on points within the rectangle that define the interior perimeter It is also possible to insert cutouts based on standard shapes Given the thickness of the
61. s recovery point icons When we added the first shape Section Composer chose stress recovery points automatically as the four outermost points of the I shape They are shown in blue filled ovals S 2 and S 3 meaning the second and third stress recovery points can remain as they are S 1 and S 4 must be moved to the top right and left corners of the rectangle To set the location of the first stress point first click the rectangle shape to select it and then put your mouse on the top right point of the rectangle shape the new location for the stress recovery point Notice that if the mouse is on the shape the cursor is a four headed arrow If the mouse is on a point the cursor becomes a two headed arrow The mouse should be two headed Right click and choose Set as Stress Point 1 Top Right The S 1 indicator moves to the new location Stress points are generally set in counter clockwise order on the screen starting at the top right The first point is positioned in the y z quadrant The second point is positioned in the top left the y z quadrant The third in y z And the fourth in y z The stress recovery points need not be positioned this way but this convention is assumed when stress recovery points are used as references for the placement of lanes and tendons in LARSA 4D Do the same to move S 2 to the top left corner of the rectangle 19 LARSA Section Composer Manual Torsion Constant J Computation As the s
62. s require their arguments to be given in radians rather than degrees Example sin rad 30 Parameters Parameters used in formulas can have names only consisting of the letters a z upper or lower case Parameter names are not case sensitive meaning d is the same as D Examples b thickness Logical operators and the if function The if function is used to evaluate one expression if something is true or another expression if something is false This is best demonstrated by example f a lt 0 0 a is a conditional expression that evaluates to the value of the parameter a if a is positive otherwise it is zero Conditional expressions can make use of the logical operators lt gt lt gt lt gt not equal AND and OR Example a lt 10 OR a b In nonprismatic sections x has a special meaning It represents the position along the span either in absolute length units or as a fraction from 0 to 1 depending on the section settings See Nonprismatic Variation page 41 33 LARSA Section Composer Manual Shape Templates If you will be frequently reusing the same shape in many sections it is possible to save a shape as a template so that it can be called up again in the Insert Custom Shape tool along with the pre defined shapes that come with Section Composer A shape template can be made out of a single shape the selected shape in the section When creating a shape
63. t View Section Shape Analysis Help B u DEU 9 8 QQQQqgag Ru Bz tm ac PEPP 3 ei 2s S 90 40 sola alo New Parametric Section 20 18 16 14 12 10 0 00000 0 00000 0 00000 0 00000 0 00000 0 00000 0 00000 0 00000 Area The total cross sectional area of the section 2 Shapes No shapes defined 0 Parameters Points Rebars Member 20 88in 106 7deg Member Z 2 Reference Line Parameters in 54 No active shape Please select a shape to view the parameters New Parametric Section f Unit in Using the Free Draw Tool After clicking all of the corners click the first corner again to indicate that the shape is complete Now we have our outer rectangle Take a quick look at the properties explorer on the right hand side at the top You will see that as soon as we create a shape the values in the properties explorer have changed to reflect the changes made to the section What we have at th s point is a solid rectangle and that is what the properties explorer is showing Also look at the parameters explorer notice that we have no parameters defined for this section Switch to the points tab You will see that all the points are defined using numeric values Shape point coordinates are relative to the shape s own local coordinate system rather than the member reference line This allows the shape to be repositioned by editing the shape s o
64. terial of the members that this section is assigned to in LARSA 4D 36 LARSA Section Composer Manual Member Reference Line and Local Coordinate System Each member element in a LARSA 4D model has its own local coordinate syetem Having a local coordinate system simplifies the description of forces and moments on the member because they are more often parallel or perpendicular to the member than to the global axes LARSA 4D and the Section Composer make use of a second member coordinate system the reference coordinate system also to simplify modeling Section Composer shows a two dimensional cross sectional picture of the section The y axis of the member is the vertical axis and the z axis of the member is the horizontal axis The 0 0 coordinate at the intersection of the y and z axes on the canvas is at the member reference line This is an x axis that goes into the screen The member reference line lines up with the line between the start and end joints of the member in the LARSA 4D model assuming the member does not have member end offsets We call these axes the member reference axes The reference y axis is displayed vertically by default matching the convention most often used for horizontal members and the z axis is displayed horizontally If a different orientation angle is used or if the member is not horizontal care must be taken to understand how the reference axes displayed on the Section Composer canvas will be orie
65. th the member reference z axis Y LARSA Section Composer Test Section Database 2 lpsx Sa K oj File Edit View Section Shape Analysis Help Dad QQQQ AHAT B Bl o felt ar SSS 000 gace Nonprismatic 11 1684 in 1 5146 in AS ES OS BS ES RS ee ee SA Se Be l 0 00000 Member Y 5 00000 i 590 375 251 969 I Shape 0 00000 590 375 251 969 0 00000 NAC 57 0000 118 075 Area The total cross sectional area of the section Shapes share Parameters Points Rebars Parameters in Ate p 1 5 m oe Ne m gt I 1h IP IP IP ol 13 14 m j i Tube Composite Section Example Parameterized Tube Nonprismatic Unit in Shape The I shape s top edge is aligned with the member reference z axis When modeling this girder in LARSA 4D the members should be positioned at the top of the section me Save the database Then open LARSA 4D and attach the database to the project 44 LARSA Section Composer Manual Create a member 10 feet long Assign the section to the member and give it an orientation angle of 90 degrees a Use Graphics Complete Rendering to view the physical section Notice how the section is aligned as intended with the top face of the section on the member reference line 1 e the joint to joint line with the depth varying below The nonprismatic section applied to a member in LAR
66. tion Composer s basic functionality including setting database options adding standard and custom shapes editing shape dimensions with parameters align and snap tools setting stress recovery points and using the section in LARSA 4D Starting Up Let s go into the details of the program with a basic example The first section we will create will be a steel I girder with a steel plate deck on top The final section is shown below 2 Wy LARSA Section Composer Test Section lpsx lo amp File Edit View Section Shape Analysis Help D alll 9 e QAQA AHLT r eZ o t xe ot oP sa 553 0 A ak a de l Shape With Plate 55 5000 0 00000 0 00000 955 088 0 00000 955 088 376 969 0 00000 97 0199 60 0000 145 725 75 3938 lyy The moment of inertia about the y axis at m II LIT LLL BAER MR z 3 Parameters Points Rebars 5 Ee 9 k No active shape Please select a shape to 2 F view the parameters Shape With Plate Unit in No active shape An example section If you do not have Section Composer open from the start menu of Windows go to Start All Programs Larsa 4D and select Section Composer Otherwise start a new database in Section Composer using File New Notice that when a new database is opened it automatically comes up with a new section called New Parametric Section in it From the menu go to Secti
67. tion does not meet the member reference line as we have been discussing LARSA 4D will apply the necessary rigid offsets from the joint to the centroid similar to member end offsets see Members in LARSA 4D Reference Manual to the members in order to ensure that the model is analyzed properly Because member end offsets are specified in global coordinate system directions they are not convenient for specifying a centroid offset from the reference axes For More Information please refer to the following documentation Members in LARSA 4D Reference Manual 40 LARSA Section Composer Manual Nonprismatic Variation Nonprismatic variation is the variation of section dimensions along the length of a member It 1s created in Section Composer by applying formulas to shape parameters Recall that shapes can be defined through parameters such as d b tf and tw for the I shape Normally the parameters are given numeric values 1 e 25 inches To set up nonprismatic variation the parameters are given as formulas in terms of the special x variable This variable represents the position along the length of a span If an I shape varies in depth the d parameter might be set to DEE This might represent a depth of 10 inches at member start x 0 and 25 inches at member end x 1 which a linear slope in between Any formula supported by the formula language page 31 can be used Because the physical dimensions of nonprismatic sections var
68. tube as 2 inch we need a 16x16 cutout inside the outer shape ee Again using the help of the grid lines click points at 8 8 8 8 8 8 and 8 8 Do not forget to click to the first point to finalize the drawing If by any chance you clicked an incorrect coordinate press on the keyboard to cancel the drawing or if you have already finalized the drawing but the shape has invalid points right click on the cutout and choose Delete to remove it Then start the cutout again Outer z z Member Ipzz an Reference Line y The tube section after creating the cutout shape You will see the tube on the canvas You can also see that the properties of the section have changed in the Properties Explorer at the upper right of the Section Composer screen The only property that is not shown is the torsion constant J as discussed in Creating a Section page 13 Notice how the points spreadsheet in the shapes explorer now shows the points of just the cutout shape The explorer shows the points of the selected shape Click the solid portion of the tube to select the outer shape Then click in the empty space to select the cutout again Try editing the coordinates of these points to change the interior perimeter of the tube Reset the values as above when you are done Starting a Section Section A single Section Composer database file may contain more than one section definition We will put the tube shape on hold and create a se
69. ulates the section properties of shapes that are needed in structural analysis and it performs moment curvature analysis and ultimate strength check Sections made in Section Composer are modeled in an intuitive user interface which provides a variety of editing tools A user friendly and completely integrated format based on the same powerful LARSA 4D technology makes it an absolute must for LARSA 4D users Features Adding custom sections to LARSA model e Built up sections using any shape from AISC steel tables standard AASHTO bridge girders and LARSA s modifiable parametric shape tables e Build plate girders including box girders and hybrid girders Graphically create and edit any arbitrary shape by drawing with the mouse or specifying coordinates LARSA Section Composer Manual Parametrically define shapes with dimensions and formulas Create a customized library of sections 3D visualization with rendering via LARSA 4D Section properties calculation even for custom shapes Area Moment of Inertia Torsion Constant Section modulus Center of Gravity Shear Center Shear Area Plastic Module and Warping Constants plastic resisting moments Section Analysis of Moment Capacity and Moment Curvature Composite sections with multiple materials and rebars Nonprismatic sections applied to a span of multiple members Linear parabolic or user defined variation for nonprismatic sections Easily move and rotate shapes us
70. up composite construction sections are accounted for in the LARSA 4D analysis starting with version 8 0 ov LARSA Section Composer Manual 58 LARSA Section Composer Manual Index add points to shape 13 adding shapes 13 align 13 area 23 centroid Computations 23 Creating a Section 13 Overview 7 centroid offset 37 clearance 23 Clz Cly 23 composite activity 51 composite construction section 55 composite construction sections 51 composite material section 55 composite material sections 49 composite section 7 composite shape Free Shapes Cutouts and Composite Shapes 25 Glossary 55 Overview 7 construction sequence section state 51 cross section properties 23 custom shape 13 cutout shape Free Shapes Cutouts and Composite Shapes 25 Glossary 55 Overview 7 database 7 duplicate section 13 duplicate shape 13 editing parameters 13 export DXF 13 export image 13 flexural strength 53 flip shape 13 formula 7 formula helper 41 formula language 31 free draw tool 25 free shape 7 erid 13 import DXF 13 import LPSX 18 inserting shapes 13 integration of Section Composer with LARSA 4D 13 introduction 5 Ipzz Ipyy Ipa 23 Izz Iyy 23 J Computations 23 Creating a Section 13 59 LARSA Section Composer Manual local coordinate system 55 lpsx 7 member local coordinate system Glossary 55 Member Reference Line and Local Coordinate System 37 member reference axes 7 member r
71. up of different materials such as a steel web with a concrete plate on top which can respond differently to time dependent material effects Versions prior to 8 0 also support a type of composite material section without material time effects and other effects that affect the parts of a section differently A section can also be both composite construction and composite material These sections require special attention both for the user as well as for the program because their gross properties change over time and their parts respond to effects such as time dependent material changes and thermal gradients differentially The use of composite sections serves as an alternative to two other possible modeling techniques The first modeling technique is to model each composite part as a separate member element in LARSA 4D i e making parallel girders for each composite part Each part or member can be assigned a different material in LARSA 4D and can be constructed at different times using Staged Construction Analysis In this way the member elements each have constant properties throughout the cross section however they will need to be tied at regular intervals to ensure they deform together either using rigid elements constraints such as slave masters or member end offsets Ties add additional modeling complexity The second modeling technique is to average the properties of the parts into an equivalent non composite section The advantage is the s
72. where their centroids are In other words the centroid of the member is what is modeled in LARSA 4D as the joint to joint line Or member end offsets are used to specify that the member centroid is at a different location from the joint to joint line Since this section has nonprismatic variation its centroid is moving as you go down the span That would mean that in LARSA 4D we would need to adjust either the joint locations or the member end offsets at the start and end of each member in order to locate the centroid in the LARSA 4D model at each of these positions This would be a tedious task Thankfully this is not necessary because we can align any part of the section with the joint to joint line not just the centroid by positioning the section properly relative to the member reference line page 37 In this case we want the top edge of the section to align with the member reference line This way if the members in LARSA 4D are creating with joints on a straight line the top of the girder will stay flat while the centroid and bottom edges move according to the nonprismatic variation If the centroid of the section does not meet the section reference line LARSA 4D will apply the necessary rigid offsets from the joints to the centroid in order to ensure that the model is analyzed properly If itis not already selected select the I shape by clicking on it e Use the Align Top tool in the toolbar to align the top edge of the shape wi
73. y along the length of the span so do the sectional properties of the span The LARSA 4D analysis engine and the stress reports will take into account nonprismatic variation when a nonprismatic section 1s assigned to members see Members in LARSA 4D Reference Manual or spans see Spans in LARSA 4D Reference Manual in a project It may be necessary to create spans depending on the setup of the variation Starting an Example To begin the example in this section start a new Section Composer section Add an I shape using the Insert Custom Shape tool It must be a custom I shape and not a standard I shape so that the dimensions can be modified by applying a formula The x Variable The special x variable gives the position along the length of the span in one of two ways The variable may be in absolute linear dimensions e g feet or meters from the start of the span The unit of length depends on the unit chosen for the section in the Units window in the Section menu Alternatively the x variable may be a value from 0 0 to 1 0 where 0 0 is the start of the span and 1 0 is the end of the span This is called relative position because it is relative to span length which might not be known ahead of time or might vary from span to span 3 To choose the type of x variable to use open the Nonprismatic Variation window from the Section menu The choice is at the top right In this case we will leave the choice as Relative Span Posit

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