基于STM理论钢纤维混凝土深受弯构件裂缝宽度试验研究

通过7根钢纤维混凝土深受弯构件的弯曲性能试验,分析了钢纤维掺量及配筋率对深受弯构件跨中截面混凝土应变、纵筋应变、破坏形态及裂缝宽度的影响。基于STM理论量化钢纤维、钢筋以及混凝土三者在受力过程中的组合作用,提出了适用于钢纤维混凝土深梁最大裂缝宽度的理论计算式,并与实测结果进行比对分析。研究结果表明:较普通深受弯构件而言,钢纤维混凝土深受弯梁的开裂荷载增幅11%~20%,极限荷载提高10%~16%,提高配筋率,开裂荷载提高约22%,极限荷载提高20%~31%;提高配筋率或钢纤维掺量,均可使试件破坏模式由正截面破坏向斜截面破坏转变;钢纤维掺加50、78 kg/m^3后,裂缝宽度可减少13%~29%;试件配筋率提高0.142%,裂缝宽度减少33%;推导出的理论计算式计算得到的最大裂缝宽度与实测值吻合。

Experimental and calculation of crack width of SF reinforced deep flexural members based on the STM theory

In order to study the effects of volume fraction and reinforcement ratio of steel fibers on the strain,longitudinal reinforcement strain,failure mode and crack width of steel fiber reinforced concrete(SFRC)deep flexural members are analyzed through bending tests of 7 deep flexural members.Based on the strut and tie model(STM)theory to quantify the combined effect of steel fiber,steel bar and concrete in the process of stress,the theoretical calculation formula for the maximum crack width of steel fiber concrete deep beam is proposed and compared with the measured results.Results show that compared with ordinary deep flexural members,the cracking load of steel fiber reinforced concrete deep flexural beams increases by 11%~20%,the ultimate load increases by 10%~16%,the reinforcement ratio increases by 22%,and the ultimate load increases by 20%~31%.The failure mode of test specimens is changed from the normal section to the oblique section by increasing the reinforcement ratio or the amount of steel fiber.The crack width can be reduced by 13%~29%,by the steel fiber is added with 50 kg/m^3 and 78 kg/m^3.The component reinforcement ratio is increased by 0.142%,the crack width is reduced by 33%.The maximum crack width calculated by the derived theoretical formula is in agreement with the measured value.