循环载荷下箱型梁极限强度性能实验研究

通过系列箱型梁模型实验,研究了箱型梁在极值循环弯曲载荷下的极限承载性能。分别对四个加筋箱型梁模型进行了循环载荷下的四点纯弯实验,实验分别采取单向及双向循环载荷两种施加方式。在单向循环弯曲实验中,模型的后续循环的极限强度与前一循环的后极限强度阶段的卸载点接近,但塑性变形有明显增加,极限承载能力下降显著;双向循环弯曲中,反向弯矩虽然抵消了部分塑性变形,但箱型梁的极限承载能力仍有明显下降。实验表明,实验加载过程中,箱型梁在承受极值循环载荷初期,其构件崩溃速率较缓,而一旦进入后极限阶段,崩溃速率显著加快;箱型梁在极值循环弯曲载荷下的极限承载性能,即后极限强度性能,相比一次性极限强度值逐步下降。

Experimental research on the ultimate strength behavior of box-girders under cyclic bending

The load carrying capacity of box-girders under cyclic bending is studied by a series of tests on box-girders.The specimens are tested under four-point load bending to have a uniform moment occur in the central part of the girder. During the tests, two cyclic loading patterns, namely one-side cyclic loading and two-side cyclic loading, are employed to examine their effect on the load carrying capacity of box-girders. In the one-side cyclic bending test, the ultimate bending strength point of the specimen is nearly approach-ing to the unloading point in previous cyclic process, but plastic deformation increases significantly, ulti-mate capacity of specimen decreases with an increasing number of cycles.In the two-side cyclic bending test, ultimate capacity of specimen decreases obviously even though reversed bending moment offset some plas-tic deformation. The experiment shows that the collapse rate of the structure members is relatively slow in the initial loading stage,while become fast in the post-ultimate stage.Besides,the ultimate bending moment of box-girders under cyclic bending is decreased gradually.