塑性铰区采用高延性混凝土梁变形性能研究

AN INVESTIGATION OF DEFORMATION BEHAVIOR OF BEAMS WITH HIGH DUCTILE CONCRETE IN POTENTIAL PLASTIC REGION

为提高钢筋混凝土(RC)梁的变形能力,考虑在其塑性铰区采用高延性混凝土(HDC)代替普通混凝土。共设计6个剪跨比为3.6的RC梁试件,包含5个塑性铰区采用HDC的试件和1个RC对比试件。考虑HDC区长度、纵筋配筋率以及配筋方式和梁端配箍率的影响,研究试件在低周反复荷载下的滞回特性、变形能力及耗能能力。结果表明:与RC梁相比,塑性铰区采用HDC后,试件的破坏形态由弯剪破坏向弯曲破坏转变,延性和耗能能力均得到显著提高;纵筋配筋率、配筋方式相同时,在梁端塑性铰区采用HDC,试件的位移延性系数和极限位移角分别提高30%和53%,而同时采用HDC和箍筋时分别相应提高33%和76%;梁端局部采用HDC替换混凝土可减少箍筋用量;梁端塑性铰区的HDC长度对试件延性的影响较小。分别计算塑性铰区采用HDC梁在开裂荷载、屈服荷载、峰值荷载、极限荷载时的顶点位移,其计算值与试验值吻合较好。

In order to improve the deformability of RC beams,high ductile concrete(HDC)was locally applied in the potential plastic hinge region of RC beams.Six RC beam specimens with a shear span ratio of 3.6 were designed,including five specimens with HDC in the plastic hinge region,and one RC beam designed for comparison.The hysteretic behavior,deformability and energy dissipation capacity were analyzed by using low cyclic loading tests,considering the effect of HDC region length,the reinforcement ratio of the longitudinal reinforcement and the stirrup ratio in the beam ends.The experimental results show that,the failure mode of the beams with HDC in the potential plastic region is changed from bending-shear failure to bending failure with better ductile characteristics and better energy dissipation capacity compared with the RC beams.With identical longitudinally reinforcement arrangement,the displacement ductility factor and ultimate drift ratio in RC beam with HDC in its plastic hinge are increased by 30%and 53%,respectively,while both HDC and stirrup are applied in the plastic hinge region,the displacement ductility factor and ultimate drift ratio are increased by 33%and 76%,respectively.The locally used HDC in the beam end can reduce the amount of stirrups,and the HDC length of the plastic hinge area at the beam end has little effect on the ductility of the specimen.The lateral displacements of the beams at cracking load,yield load,peak load and ultimate load are calculated,respectively,and the calculated values are in good agreement with the experimental values.