Dear all,
I am working on "Integral Bridge Abutment" (Geotechnical aspect). I am a beginner in this area of study. I have some following doubts.
Why their is limited amount of research/literature on seismic performance of integral bridge abutment are available. Most of the studies are related to Thermal loading. Does performance of integral bridge abutment is resistant to earthquakes?? Damages of integral abutment bridge due earthquake is reported ??
Thank you in advance
Hi Mr Sakhare,
It could be that they are found to withstand the dynamical loads from traffic and wind, very well, and by that they are maybe too stiff, such that thermal expansion is the crucial load case.
Smaller Earthquakes could be embraced in the other dynamics, if a bit scaled, but since rare, that will not cause failure.
We do not have significant records on the behavior of contemporary integral bridges under earthquake. We do have very bad records of fixed bearings on abutment collapsing under earthquake excitation though.
Integral bridges should behave very decently under small to medium seismic input. When your expected seismic input is very strong and you need to isolate your bridge you obviously cannot have integral abutments.
The above reasoning is because we have sort of record for integral abutments under earthquake and those are all the masonry arches still standing around Europe. These arches did behave satisfactorily under earthquake, less so under differential foundation settlements, soil instabilities and riverbed scouring which are the main causes for their ageing and collapse.
Integral bridges tend to perform quite well under earthquake loads. You can see an example in Rodríguez, J., Martínez, F., and Martí, J. (2011) “Integral Bridge for High-Speed Railway”, Structural Engineering International, Vol. 21, No. 3, pp. 297-303, ISSN 1016-8664.
If I put on my professional engineering practice hat from US west coast, I will say that use of integral abutments in highly seismic zones is NOT worth investigating. Many governing agencies located in highly active seismic zones (e,g.: state departments of transportation in Washington State, Oregon, and California, etc.) will outright prohibit any use of conventional integral abutments. My understanding is that this practice was adopted to help mitigate the excessive amount of passive earth pressure which is generated during a seismic event. Numerous post-earthquake assessments of failed bridges also support that conclusion. Since integral abutments are rigidly connected to the superstructure, any damage to abutments can be easily transferred to the entire bridge often requiring earthquake-damaged bridges to be fully replaced (instead of replacing its broken back walls or resetting its bearings which are less expensive and quick fix). Integral abutment also makes the post-earthquake damage assessment difficult (below ground) which is typically not acceptable from a risk management point of view. Having said all that, perhaps an integral abutment can still be designed that it can overcome above drawbacks and provides s value-based performance. I hope this helps to shed light on why there is not much research out there for integral bridges in seismic zones.
Bridge with integral abutment will attract more seismic force due to high stiffness resulting more pressure on surrounding earth. The research will be in soil structure interaction area, Due to less case studies, much research is not available..
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