螺旋箍筋约束叠合剪力墙14 mm竖向钢筋搭接性能试验研究

Experimental study on performance of 14 mm reinforcement splices confined by spiral stirrups in the composite concrete shear wall

针对螺旋箍筋约束叠合剪力墙14 mm竖向钢筋搭接试件进行了拉拔试验,共设计了7个试件.为避免加载偏心,试件采用2对2搭接方式,试验参变量为搭接长度(0.25l_(a),0.45l_(a),l_(a)为钢筋基本锚固长度),配箍率(0,0.8%,2.8%,3.1%)和混凝土强度(C45,C55).其中,4个试件的搭接钢筋预先开槽,重点研究不同参变量对粘结应力分布规律的影响.搭接长度为0.45l_(a)试件组的试验结果表明:当配箍率为0.8%时,搭接试件叠合界面不发生劈裂破坏,钢筋屈服后拔出,峰值强度和对应滑移值较无箍筋约束试件的特征值分别提升了27.1%、158.4%;当配箍率从0.8%增加到2.8%时,峰值强度和对应滑移值分别提升了2.1%、38.1%,钢筋被拔出并拉断.开槽钢筋的搭接性能试验结果表明:搭接长度为0.45l_(a)时,试件的应力分布均呈多峰型分布,无箍筋试件的最大应力峰靠近自由端,2.8%配箍率试件的最大应力峰靠近加载端,两试件最大应力峰峰值分别为20.9 MPa,20.2 MPa,相差3%;搭接长度为0.25l_(a),配箍率为3.1%时,两种不同混凝土强度试件的粘结应力分布均呈双峰型分布,两试件最大应力峰峰值分别为17.37 MPa,17.5 MPa,相差1%.

The pull-out test was carried out on 14 mm reinforcement splice specimens confined by spiral stirrups in the composite concrete shear wall,and seven specimens were designed with the test variables of splice length(0.25l_(a),0.45l_(a),l_(a) is the basic anchorage length),spiral ratio(0,0.8%,2.8%,3.1%),and concrete strength(C45,C55).To avoid the eccentric loading,the specimens were designed as a double lapping configuration.Among them,four specimens had the slotted reinforcement to investigate the bond stress distribution.The test results of specimens with 0.45l_(a) splice length showed that no splitting failure along the concrete interface was observed in the specimens with spiral ratio of 0.8%.The reinforcement was pulled out after yielding,and the peak load and the corresponding slip increased by 27.1%and 158.4%respectively compared with those of specimen without spiral stirrups.When the spiral ratio increased from 0.8%to 2.8%,the peak load and the corresponding slip value of specimen increased by 2.1%and 38.1%,and the reinforcement ruptured after it was pulled out.The test with slotted reinforcement demonstrated that when the splice length was 0.45l_(a),the bond stress distribution was a multi-peak type.The maximum stress peak of the specimen without stirrups was close to the free end,and the location of maximum stress peak of the specimen with 2.8%stirrup ratio was close to the loaded end.The maximum stress peak values of the two specimens were 20.9 MPa and 20.2 MPa respectively,with a difference of 3%.When the splice length was 0.25 and the spiral ratio was 3.1%,the bond stress distributions of two specimens with different concrete strength were double-peak distribution,and the maximum stress peaks of two specimens were 17.37 MPa and 17.5 MPa,respectively,with a difference of 1%.