张弦式钢-竹组合工字形梁的短期受弯性能

Short-term bending performance of prestressed steel-bamboo composite I-shaped beams

为研究张弦式钢-竹组合工字形梁的受弯性能,以预应力水平、张弦及加载方式为基本参数,设计制作了12根张弦式钢-竹组合工字形梁进行受弯试验,观察分析了加载过程中组合梁的试验现象、破坏特征,探究了各参数对组合梁承载能力、应变分布、变形性能等的影响规律,并推导得出了张弦式组合梁承载力的近似计算公式。结果表明:张弦式组合梁的整体性能优良、组合效应突出,具有良好的变形性能及承载能力;张弦试件的破坏形态主要为翼缘竹材撕裂、局部钢材屈曲等破坏;施加预应力及提高预应力水平能有效增加组合梁的变形性能,以及在相同挠度控制条件下的承载能力,且采用二点张弦布置预应力筋时可获得更好的效果;张弦式组合梁跨中截面应变分布符合平截面假定,且随着预应力水平提高而中性轴下移;最后,基于理论计算得出的承载力与试验值较为接近且相对保守,近似计算公式具有较好的适用性。

To study the bending performance of prestressed steel-bamboo composite I-shaped beams,12 prestressed composite I-shaped beams were designed and manufactured for bending tests,considering prestress loads,prestressing schemes,and loading schemes as basic parameters.The experimental phenomenon was observed,and failure characteristics were analyzed during the test.The influences of different parameters on the load-bearing capacity,strain distribution,and deformation performance were explored,and an approximate formula for the bearing capacity of the prestress composite beam was proposed.The results indicated that the prestressed composite beams have relatively good performances from the perspectives of combination effect,deformation characteristic,and bearing capacity.Failure modes of tested specimens were mainly owing to the bamboo flanges damage and the local buckling of steel plates.With the technique of prestress and the increase of prestress level,the deformation performances can be improved effectively,as well as the load-bearing capacity considering the same deflection situation.Moreover,the improvements can be more significant with the two-point prestressing scheme.The mid-span strain distribution of prestressed composite beams conforms to the plane section assumption,and the neutral axis moves down with the increase of the prestressing level.Finally,the bearing capacities based on the theoretical calculation matched well with the experimental results,which showed the applicability of the proposed methods.