往复水平荷载作用下不同桩型单桩水平承载性能足尺对比试验研究
Experimental study on horizontal bearing behaviors of different types of full-scale piles under reciprocating horizontal loads
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摘要: 选取天津市汉沽区典型软土场地,针对预应力管桩、预应力空心方桩、钻孔灌注桩共38根足尺桩,展开现场原位土体条件下的单桩拟静力试验;探究各桩型足尺桩在考虑桩-土相互作用条件下受到桩顶低周往复水平荷载作用时的承载性状及抗震性能,并基于不同桩型做出对比。通过对预应力桩、增配不同数量非预应力筋形成的复合配筋桩及灌注桩的破坏形态、荷载-位移关系、位移延性的对比分析,结果表明:常规预应力桩延性较差,呈脆性破坏;增配非预应力筋是提高预应力桩抗震性能的有效措施;复合配筋桩的位移延性及耗能能力得到显著改善,呈延性破坏;不同配筋率的灌注桩的位移延性系数均在4.5以上,具有较好的延性及耗能性能;复合配筋桩及灌注桩的位移延性系数均随非预应力筋配筋率的增加呈先增大后减小的趋势,存在一个最优的非预应力筋配筋率,使得其位移延性最好。Abstract: The field pseudo-static tests on 38 prototype piles in in-situ soil conditions, which contain prestressed pipe piles, prestressed squared piles and bored cast-in-situ piles, are made in a typical soft soil site of Hangu, Tianjin. The bearing and seismic behaviors of all kinds of full-scale piles under the pile-soil interaction subjected to low-cycle reciprocating horizontal loads at the pile top are studied. The failure modes, load-displacement relationships and displacement ductility among the prestressed pipe piles, composite-reinforced piles with distributed non-prestressed reinforcements and bored cast-in-situ piles are compared. The results indicate that the regular prestressed pipe pile has poor ductility and is brittle during failure. The displacement ductility and energy dissipation capacity of the composite-reinforced piles are obviously improved by adding non-prestressed reinforcements in addition to prestressed steel bars. This consequently leads to the ductile failure mode. Therefore, adding conventional steel without prestress is an effective measure to improve the seismic performance of prestressed piles. The displacement ductility factor of all the bored cast-in-situ piles with different reinforcement ratios exceeds 4.5, which means that their ductility and energy dissipation capacity are good. The displacement ductility factors of both the composite-reinforced piles and bored cast-in-situ piles increase at first then decrease with the reinforcement ratio of the increasing non-prestressed reinforcements while there is an optimal reinforcement ratio of the displacement ductility.