不同配箍率和钢纤维掺量UHPC柱抗震性能试验

Experimental Study on Seismic Behavior of UHPC Columns with Different Stirrup Ratios and Steel Fiber Contents

为明确超高性能混凝土(Ultra-high Performance Concrete,UHPC)柱中配箍率和钢纤维掺量对抗震性能的影响,对不同配箍率(0%、0.25%和0.5%)与钢纤维体积掺量(0%、1%和2%)的5根超高性能混凝土足尺柱试件进行了抗震性能试验研究,分析了配箍率和钢纤维掺量对超高性能混凝土柱耗能能力、自复位能力、强度退化性能、刚度退化性能以及弯矩曲率关系的影响规律。基于对超高性能混凝土柱构件性能、箍筋应变以及等效侧向约束力的分析,提出钢纤维体积掺量与配箍率的等效计算公式。研究结果表明:①配箍率对正截面破坏超高性能混凝土柱的延性、耗能能力以及自复位能力均有影响,当配箍率从0%提高到0.5%时,柱试件的延性系数提高15%,耗能能力提高55%,自复位能力提高32%;②钢纤维体积掺量对超高性能混凝土柱破坏形态的影响显著,随着钢纤维体积掺量的增加,混凝土的压碎剥落现象得到明显改善,延缓了受压钢筋屈曲现象的发生,从而提高了柱的延性,当钢纤维体积掺量从0%提高到2%时,柱试件的延性系数提高45%,耗能能力提高142%,自复位能力提高42%;③对于正截面破坏的受压构件而言,采用钢纤维代替箍筋具有一定的可行性。对于所研究的超高性能混凝土柱而言,2%的钢纤维体积掺量可等效于0.51%的配箍率。

To elucidate the influence of the stirrup ratio and steel fiber content on the seismic behavior of ultra-high-performance concrete(UHPC)columns,five full-scale UHPC columns with different stirrup ratios(0%,0.25%,and 0.5%),and steel fiber volume ratios(0%,1%,and 2%)were tested,and the effects of the stirrup and steel fiber volume ratios on the energy dissipation capacity,self-centering capacity,strength degradation capacity,stiffness degradation capacity,and moment-curvature relationship of the UHPC columns were analyzed.Based on the analysis of structural performance,stirrup strain,and equivalent lateral binding force,a formula for the equivalence between the steel fiber volume ratio and stirrup ratio was proposed.The results indicate that:(1)The influences of the stirrup ratios on the failure mode of the UHPC columns were limited;however,they have certain effects on the ductility,energy dissipation,and self-centering capacity of the UHPC columns.When the stirrup ratio increased from 0%to 2%,the ductility factor,energy dissipation capacity,and self-centering capacity of the UHPC column increased by 15%,55%,and 32%,respectively.(2)The influence of the steel fiber volume ratio on the failure mode of the UHPC columns was significant.With an increase in the steel fiber volume ratio,the crushing and spalling of the concrete was mitigated,thereby delaying the buckling of the compressive bars,and improving the ductility of the columns.When the steel fiber volume ratio increased from 0%to 2%,the ductility factor,energy dissipation,and selfcentering capacity of the UHPC columns increased by 45%,142%,and 42%,respectively.(3)In the case of compressive members with normal section failure,using steel fibers to replace certain stirrups is feasible.For the tested UHPC columns,steel fibers with a volume ratio of 2%can be equivalent to a stirrup ratio of 0.51%.