LARSA Section Composer

Overview

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 calculates 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. Section Composer is fully integrated with LARSA 4D and can also be used on its own. Sections created in the Section Composer are used directly in LARSA 4D like any other section. When graphical rendering is turned on, the true shape of member sections are shown in the LARSA 4D graphics window.

LARSA Section Composer

Parametric Sections

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, pipe, several types of box girders, and more), or free-drawn. Section Composer automatically computes cross-section properties. Sections can contain holes (e.g. for box sections) and composite material parts.

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. 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.

Section formulas are very flexible and can include any operations like the standard arithmetic operations, trigonometric functions, and special functions for haunches.

I-Shape Parametric Definition

If the dimensions of the section change later, rather than recomputing twelve coordinates one needs only to update the four dimensions, d, b, tw, and tf.

Shape Tools

Shape tools include align, snap, shift, rotate, flip, add/remove points, reverse or shift point order, duplicate, and merge, import and export DXF, and reports.

Calculations

Section Composer is able to compute many properties of section definitions in real-time, for arbitrarily-shaped cross-sections. Computations include area, centroid, moment of inertia, torsion constant (J), perimeter, elastic section modulus, radius of gyration, and moment of area.

Properties and principle axis updates in real time

Reinforcement bars can be placed within sections.

Nonprismatic Variation

Nonprismatic variation is the variation of section dimensions along the length of a member. It is created in Section Composer by applying formulas to shape parameters. 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 10 + x*15. 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 can be used.

LARSA 4D member elements make use of separate reference and local coordinate systems to simplify the modeling of sections with nonprismatic variation.

Section Analysis

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 ultimate strength check computes the flexural strength for the section taking into account the placement of reinforcement bars within the section and post-tensioning tendons running through the section and either their short-term or long-term forces.

Ultimate Strength Check

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 post-tensioning tendons running through the section and either their short-term or long-term forces.