Study on Combined Effects of Bridge Temperature and Seismic Actions Based on F-J-M Method
Currently,the design of railway bridges is gradually transitioning from the allowable stress method to the limit state method.However,the Code for Design on Railway Bridge and Culvert(Limit State Method)(Q/CR 9300-2018)does not account for the combined effects of seismic actions and variable factors such as temperature,posing significant challenges for seismic design for bridges in areas of extreme cold and high seismic intensity.In order to promote bridge resistance to external loads in a more cost-effective way,the partial coefficient of the optimal seismic design condition load combination was determined by target reliability indices,thereby optimizing the seismic design stan-dards in current bridge design codes.A probability model for temperature effects on a bridge in cold re-gions was established.The distribution characteristics of the effects of earthquake and ambient temper-ature were explored using the Ferry Borges load combination theory.Expressions of the load factor of earthquake and temperature effects were established using JC method and multi-hazard load factor de-sign method(MH-LRFD).Taking a practical bridge engineering project as an example,the failure probabilities of a bridge under earthquake,temperature,and their combined actions were explored re-spectively.The results showed that both the temperature internal force response caused by ambient temperature and the variation in properties of the bridge's main components significantly affected its failure probability.For extreme cold regions with significant temperature variations,ignoring ambient temperature in the current codes would significantly underestimate the failure probability under seismic actions.The proposed F-J-M(Ferry Borges-JC-MH-LRFD)method can be used to calculate the com-bined coefficients for earthquake and temperature actions,providing a necessary theoretical basis for the seismic design of bridges in extreme cold regions.
probability model of temperature effectsfailure probabilityFerry Borges methodMH-LRFDload factor
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