为探究钢-薄层超高性能混凝土(ultra-high performance concrete,UHPC)轻型组合桥面体系在局部轮载下的抗弯性能,设计并开展了 4块基于高强螺栓连接的可拆卸式钢-UHPC组合板的四点弯曲试验,研究了钢板类型、抗剪连接件间距对可拆卸式钢-UHPC组合板的破坏模式、荷载-挠度曲线、界面相对滑移、裂缝宽度、截面应变分布等影响规律,研究结果表明:在正弯矩荷载作用下,采用Q355钢板的组合板的破坏模式为高强螺栓被剪断,而采用负泊松比(negative Poisson's ratio,NPR)钢板的组合板的破坏模式为部分高强螺栓被剪断、部分预埋带垫加长螺母被拔出、UHPC板由于失稳大面积压溃等;在相同的高强螺栓间距下,采用NPR钢板的组合板的板端相对滑移较小,说明NPR钢板有效延缓并限制了钢板与UHPC板的相对滑移,从而提升两者的协同变形能力,继而提高组合板的抗弯刚度及承载力等;由截面应变分析可知,由于NPR钢板的负泊松比效应、高刚度、高屈服强度,整个加载过程NPR钢板与底部UHPC层的拉应变保持着应变协调性,随着荷载的增大截面塑性中和轴的上移幅度可忽略不计.因此,在采用NPR钢板提升钢-UHPC组合板抗弯性能的前提下,应使UHPC厚度与NPR钢板的性能进行匹配,充分发挥两者的材料性能,避免失稳破坏先于UHPC材料强度破坏.
In order to investigate the flexural behavior of ultra-high performance concrete(UHPC)lightweight composite decks under local wheel load,four demountable steel-UHPC composite slabs connected by high-strength bolts were designed and four-point bending test was conducted.The influence of steel plate type and spacing of shear connector on the flexural characteristics of demountable steel-UHPC composite slabs was analyzed,including failure mode,load-deflection curve,interface relative slip,crack width,and sectional strain distribution.Results showed that under positive bending moment,the failure mode of composite slabs adopting Q355 steel plate was that the high-strength bolt was cut off.While the failure mode of composite slabs using steel plate with negative Poisson's ratio(NPR)was as follows:part of high-strength bolts was cut off,part of pre-embedded elongated nuts with cushion was pulled out,and UHPC collapsed due to instantaneous instability.Besides,under the same spacing of high-strength bolts,the relative slip of plate end of composite slabs employing NPR steel plate was relatively small,indicating that NPR steel plate can effectively delay and restrain the relative slip between steel plate and UHPC plate,thus improving the synergistic deformation capacity,flexural stiffness,and flexural bearing capacity for composite slabs.According to the sectional strain distribution analysis,due to the negative Poisson's ratio effect,high stiffness,and high yield strength of NPR steel plate,the tensile strain between NPR steel plate and the bottom UHPC layer maintained strain compatibility during the whole loading process,and the upward displacement for sectional plastic neutral axis could be ignored with increasing load.Therefore,under the premise that NPR steel plate is employed to improve the flexural performance of steel-UHPC composite slab system,the thickness of UHPC should be reasonably matched with the performance of NPR steel plate,so as to give full play to their material properties,and avoid the buckling failure prior to the material strength failure of UHPC.