预应力钢-竹组合梁受弯挠度计算方法与试验研究

CALCULATION METHOD AND EXPERIMENTAL STUDY ON BENDING DEFLECTION OF PRESTRESSED STEEL-BAMBOO COMPOSITE BEAMS

为分析预应力钢-竹组合梁的受弯挠度,以加载方式、张弦位置、预应力度为变量,对12根组合梁试件进行了设计与试验研究。在此基础上,假定梁变形分布符合正弦半波曲线,并考虑梁加载过程中几何关系变化与预应力反拱的影响,采用弹性理论建立了组合梁中预应力筋应力增量的计算方法,推导得出一点或两点加载、一点或两点张弦时,组合梁受弯挠度计算的统一公式。试验与理论计算结果的对比表明:该文提出的挠度计算方法可较好的预测组合梁在正常使用阶段的挠度;随着预应力度的增加,组合梁的等效抗弯刚度不断提高,且两点张弦时可获得更高的等效抗弯刚度。此外,对于初始预应力为零的试件,需采用可靠预紧措施,以保证体外预应力筋能够有效发挥作用。

To investigate the bending deflection of prestressed steel-bamboo composite beams,twelve composite beams were designed and tested with loading mode,prestressing position and prestressing level as variables.Based on the assumed half-wave sine curve for the deformation distribution and taking the consideration of the influence of geometric change and prestressing camber of the beam in the loading process,a method for calculating the stress increment of prestressed strands in composite beams is established using the elastic theory.A unified formula for calculating the bending deflection of composite beams under one-point or two-point loading(prestressing)schemes is also developed.The comparison between the experimental and theoretical results indicates that:the proposed method can provide suitable estimations for the deflection of composite beams in the serviceability limit state.With the increase of the prestressing level,the equivalent bending stiffness of composite beams increases continuously,and higher equivalent bending stiffness can be obtained when two-point prestressing scheme is applied.Moreover,For the specimens with zero initial prestress,reliable pre-tightening measures should be adopted to ensure that the external prestressing strands can play an effective role.