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## Key

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{info}ThisWhile this tutorial was initially developed for the Bridge Modeler in SAP2000, but [SAP2000|sap2000:home] bridge modeler, the concept also applies also to [CSiBridge|csibridge:Home].{info}.

As
of SAP2000 V14.1.0, it is possible to assign parametric variation to girder spacing and to offsets from reference point to the insertion points.

{toc}

h1. Key modeling steps

The* keyCreate modelinga stepsparametric involve:variation through * Creating parametric variations via "the Bridge > Parametric Variations" option.

* AssigningAssign the parametric variation viathrough "the Bridge > Bridge Objects > Modify/Show Bridge Object > Spans > Modify/Show > Modify/Show Section Variation Along Selected Span" option.

h1. ExamplesExample

Consider a 2two-span bridge with two 15m long spans. The deck superstructure consists of 4four steel girders supporting a cast -in -place slab. TheTotal total superstructure width is 12m, thegirder spacing of the girders is 3m, and the overhangsoverhang on each side areis 1.5m long.

These specifications may be defined as shown in Figure 1:

\\

!Variable_girder_spacing_-_bridge_deck_section_definition.png|align=center,border=1!

The width of {center-text}Figure 1 - Bridge deck section definition{center-text}

\\

For the second span, the width linearly increases from 12m to 15m. Let's consider the following two cases: uniform Uniform flare and "one-sided" flare will be considered.

h2. Uniform Flareflare

TheGirder girder spacing increases from 3m to 4m,. whileThe the structure is symmetric about the [layout line|tutorials:Layout-line geometry]. This canmay be modeled as follows:

* Assign For all girders in the second span, assign linear parametric variation (from 0m to 1m) to girder spacing.
for
all* girdersFor in the second span., *assign Assign linear parametric variation (from 0m to 3m) to the total deck width.
for
second\\
span.

!Variable_girder_spacing_-_uniform_flare_screenshot.png|align=center,border=1!

{center-text}Figure 2 - Variable girder spacing for uniform flare{center-text}

h2. "One-Sided"sided Flareflare

TheGirder girder spacing increases from 3m to 4m, but while for both spans, the right edge of the bridge for both spans is a straight line. This canmay be modeled by assigning the following parametric variation , in addition to the parametric variations assigned for uniform flare, the following:

* AssignLinear linear parametric variation (from 0m to 1.5m) to X offset from the reference point to the insertion point.

\\

!Variable_girder_spacing_-_one_way_flare.png|align=center,border=1!

{center-text}Figure 3 - Variable girder spacing for one-sided flare{center-text}

h1. Attachments

* [Relevant SAP2000 models |Variable girder spacing^SAP2000 models.zip]```