Challenges in Modeling Live Loads for Seismically Isolated and Cable-Stayed Bridges

[reixdark127]

I am designing a seismically isolated urban bridge, and one of my concerns is how to account for live vehicle loads during the design earthquake. The bridge spans half a kilometer and has multiple supports. If I were to model the live load as a static load, I would need to consider numerous load variations, making the analysis impractical. My main challenge is determining how to incorporate these loads into a time-history analysis effectively.

Similarly, I have another project currently under evaluation in terms of quantities and budget, where a cable-stayed bridge has been proposed. This raises another concern since, due to the flexibility of such structures, geometric nonlinear analysis is required. Given the complex configuration and the many possible live load scenarios on both the deck and the cables, I am unsure how to model and analyze live loads in these types of bridges.

 

[bugbus]

It is not common to consider vehicle loading in combination with the design earthquake (at least based on the codes I'm familiar with). Which code is this designed to?

 

[BridgeSmith]

It is not common to consider vehicle loading in combination with the design earthquake (at least based on the codes I'm familiar with). Which code is this designed to?

In lieu of location-specific information, AASHTO recommends half of the design live load in combination with seismic or other extreme event load combinations.

 

[reixdark127]

It is not common to consider vehicle loading in combination with the design earthquake (at least based on the codes I'm familiar with). Which code is this designed to?

I am specifically using the AASHTO LRFD as the baseline code. The traffic study indicated that a significant portion of vehicles is expected to be on the bridge during the design earthquake. This is because the structure will be located in an urban center, specifically on one of the city's main arterial roads.

 

[bugbus]

Interesting, I wasn't aware about that part of AASHTO, thanks