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Lane definition in grillage model

Question:

How to assign traffic lanes in grillage models?

Example:

I am currently carrying out a assessment of a bridge using HA, HB and SV loads.

I am getting very high load effects, both bending and shear under live loads only i.e. HA,HB and SV.

For self weight and other static loads the load effects are ok.

I have looked in to various things and I am unable to find the cause.

I have attached the Midas model for you to investigate.

see example of very high bending load effect under HA.

Answer:

Step 1: Create a structure group containing transverse cross-beam members, as shown below. The bridge is a grillage model, so the transverse cross-beams group should be used for live load lane definition.

Step 2: Activate the crossbeam group in each live load lane definition as shown below.

Note: High loads will be experienced if the vehicular distribution of lane elements is selected in grillage bridges.

Referring to the example: After changing the vehicular distribution in traffic lanes to crossbeams from lane element, live load result for MVall: HA for bending moment values reduces drastically.

cross beam group grillage moving load

Creation date: 6/4/2021 3:57 PM Updated: 5/21/2023 2:06 PM

FA8 Group [bents 58-14 58-15 58-16] - full slab width model one span.mcb

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