# Midas Transverse Moving Load Analysis

**Question:**

Midas Support -

I am looking for some clarification on how moving load analyses are being performed by Midas Civil. The bridge width that I am considering has up to 10 design lanes. I am performing a transverse moving load on the abutment using the "Transverse Moving Load Code". The vehicle being analyzed is "HL-93 Tandem+Lane: User Defined". Analysis run times become exponentially slow as I increase the max. number of lanes. Run times for various max. numbers of lanes are shown below (reported from "Tandem + Lane" LL case). This is a simple model with comparatively few degrees of freedom, I am concerned with the run times and I am looking for ways to improve performance and/ or workarounds. Computer specifications are also shown below. Are there ways to limit which results are saved? Is multi-core processing an option? Is the unit load used for influence line analysis being moved at too small a distance? I appreciate your time and consideration with this matter.

Regards,

Run times:

1-4 lanes < 1 min.

5 lanes = 1 min.

6 lanes = 4 min.

7 lanes = 10 min.

8 lanes = 19 min.

10 lanes = 33 min.

The computer specs that this model was run on are as follows:

Windows: Windows 7 Enterprise

Processor: IntelÂ® XeonÂ® CPU E5-1620 0 @ 3.60GHz 3.60 GHz

RAM: 32.0 GB

System: 64-bit OS

Model: Dell Precision T3600

**Answer:**

Hi,

The number of combinations to be considered is exponentially increased with the maximum number of lanes. The moving load analysis in midas Civil is performed based on the influence line analysis. You can save some run time as follows:

1. The 'Calculation Filter' option. For example, you can check off 'Displacements', which will reduce a lot of run time.

2. The 'Influence Generation Method' option. You can reduce the number of positions to which wheel loads are applied. It can reduce run time but the accuracy of results can be decreased as well.

3. The 'Analysis Results' option. The 'Normal+Concurrent Force/Stress' option calculates concurrent forces, i.e. moment and corresponding shear, shear and corresponding moment. However, the 'Normal' option only calculates maximum/minimum forces without considering simultaneity of forces, which leads to reduced run time.

4. You can control the number of processing cores a shown below.

Regards,

DK Lee

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