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The following example, which demonstrates the implementation of [influence-based moving-load|kb:Influence-based moving-load analysis] analysis, considers a bridge system which will be subjected to a [moving load|kb:Moving-load analysis] such that a maximum response quantity may be resolved. Influence-based analysis proceeds as follows:


h1. Step 1: Obtain deflected shape

{new-tab-link:http://www.csiberkeley.com/}CSI{new-tab-link} Software first generates [lane-load points|kb:Lane-load point] along and across each [lane|kb:Lane] according to [lane discretization|kb:Lane discretization]. Deflected shapes are then obtained by placing a unit load at each lane-load point along the gravity direction. These unit loads are then transferred from the lane surface to [joints|kb:Joint] within the structural system according to their tributary distribution. The [lane-to-object connections|kb:Lane-to-object connection] which govern this transfer of load path may be reviewed through Display > Show Lanes > Show Structural Connection For Selected Point. If, for example, the model contains 1000 lane-load points, 1000 deflected shapes will be calculated, from which response quantities are determined.


h1. Step 2: Obtain influence surfaces for response quantities of interest

For each response quantity (reaction, member axial force, etc.), the [influence surface|kb:Influence surface] is then derived from the deflected shapes previously calculated. Values are exact at lane-load point locations, and linearly interpolated between points.


h1. Step 3: Find minimum and maximum response quantities

Once the influence surface is generated, a software algorithm locates vehicular loading such that minimum and maximum effect is induced. Response is enveloped to obtain the maximum absolute value.


h1. Summary

In summary, deflected shapes are first resolved for each unit influence load, then the influence surface is calculated for each response quantity as vehicle loads move along the structure. Since the first step provides for analysis, it must be done in its entirety, then the second and third steps may be done selectively for the response quantities desired.

Computational time for each phase of analysis may vary depending on model parameters, including the number of degrees of freedom, lane-load points, vehicles and axles, response measures, etc. Additional information is available in the {new-tab-link:http://www.csiberkeley.com/}CSI{new-tab-link} [_Analysis Reference Manual_|doc:CSI Analysis Reference Manual] (Computation Considerations, page 467).


h1. See Also

* [Reducing computational time for influence-based moving-load analysis|kb:Reducing computational time for influence-based moving-load analysis]

* [Parallel processing|kb:Parallel processing]