碳纤维增强重组竹受弯构件的极限承载力试验

重组竹是一种竹基高强复合材料,适用于装配式梁柱结构,但还难以满足现代大跨建筑结构的需求。在重组竹梁受拉区粘贴轻质高强的CFRP(carbon fiber reinforced polymer),可充分发挥重组竹的受压性能,提高重组竹受弯构件的极限承载力。虽然重组竹的顺纹受拉应力-应变关系呈完全线性,但由于重组竹的顺纹受压应力-应变关系具有明显的非线性,故CFRP增强重组竹梁的极限承载力分析需要采用非线性模型。笔者通过CFRP增强重组竹梁采用简支梁4点弯曲试验,在研究其受弯破坏模式与破坏机理的基础上,导出了CFRP增强重组竹梁的极限承载力计算公式,并通过试验结果验证了公式的正确性。试验与计算结果表明,CFRP增强重组竹梁的破坏显示了明显的非线性特征,梁底分别粘贴一层、二层CFRP时,其极限承载力可分别提高14%和27%。
Parallel strand bamboo(PSB)is a bamboo-based and fiber reinforced anisotropic composite which is increasingly used to fabricate beams and columns in building constructions. It is difficult for PSB to meet the needs of modern building structures with a large span. On the other hand, carbon fiber reinforced polymer(CFRP)is often used for enhancing and strengthening bamboo and wood structural member because of its lightweight. The CFRP pasted in convex side of PSB beams may fully utilize the compressive performances of this material and increase the load-carrying capacity of the member. The results of previous studies showed that the tensile constitutive law had linearity in parallel-to-grain direction, and the failure mode was brittle failure. However, its compressive constitutive law of PSB has obvious nonlinearity, and the failure mode is ductile failure. Therefore, the analysis on ultimate load-bearing capacity of CFRP reinforced PSB beams need to adopt the nonlinear model. The flexural performance of PSB beams reinforced with CFRP sheets was investigated in this study. Mechanical performances and failure mode of PSB bending members with and without CFRP reinforcement were studied by using 4-point bending experiments. Test results indicated that the damage of PSB beams presented pronounced nonlinear progressive process, and the load-carrying capacities of CFRP reinforced PSB beams could be obviously improved. However, the effect of enhancement on its stiffness was not obvious on account of not making the best of the strength of CFRP. An analytical model, taking into consideration the nonlinear constitutive relation of PSB composite, was developed to estimate the flexural performances of CFRP reinforced PSB beams. It was found that the load-bearing capacities of two-layer CFRP reinforced PSB beams averagely increased by about 27% when compared with the unreinforced members, and experimental results verified the validity of developed model