高轴压比钢纤维超高强混凝土短柱延性的试验研究

Experimental study on ductility of steel fiber super-high-strength concrete short columns under high axial load ratio

试验旨在研究在较高轴压比条件下,钢纤维对超高强混凝土短柱抗震延性的改善作用。短柱试件的剪跨比均为2.0,强度为103.6~114.8MPa,钢纤维的体积含纤率分别为0.5%、1.0%、1.5%。采用简支梁加载图式进行了低周反复荷载试验。观测了试件在荷载作用下的开裂和破坏的发展过程,分析了不同钢纤维含量对短柱的破坏形态、滞回特性的影响。试验结果表明:未掺钢纤维的试件,在高轴压作用下,发生了脆性特征明显的剪切破坏,延性很差;随着钢纤维含量的增加,试件的破坏形态向具有一定延性特征的弯剪破坏转变;同时延性得到大大改善,位移延性和极限弹塑性位移角分别可最大增加50.2%、96.1%,最后给出了抗震设计条件下的最小钢纤维体积含纤率的建议值。

The main objective was to study steel fiber's effect to improve the seismic performance of super-high-strength concrete short columns,which subjected to high axial load ratio.The shear span ratio of all short columns was 2.0,and their concrete strength ranged from 103.6MPa to114.8MPa.The steel fibers were added at the volume fractions of 0.5%,1.0%,1.5%.Specimens under low cyclic reversed lateral load were designed to simulate the simply supported beam condition.The cracking and damage process of the specimens were studied.The failure patterns and hysteretic behavior of short column specimens with different steel fiber volume fractions were analyzed.The test results indicated: under high axial load,the specimen without steel fiber occurred brittle shear failure,and its ductility was poor.However,with increasing the fiber volume fractions,the failure patterns transferred into flexure-shear failures with certain ductile character.At the same time,the ductility also improved greatly,displacement ductility and drift ratio of specimens being 50.2%,96.1% improvements at most,respectively.Finally,the minimum steel fiber volume fraction under seismic design condition was suggested.