A Nonlinear Model For Analyzing Combined Bending And Compression Beam-columns Of Bamboo/wood-based Composites

The great challenge arises ever before in the analysis and design of bamboo/wood structures as the development of high-rise bamboo/wood buildings,the nonlinear analysis of bamboo/wood members under ultimate state and the ductile and energy dispassion design of structures,for instance.The present study aims at the nonlinear analyses of intermediate slender bamboo/mood beam-columns.Considering the similar microscopic structure and macro mechanical properties of solid wood,bamboo-and wood-based composites,the thesis categories these materials as one type of material,i.e.bamboo/wood-based composite based the fact that they have similar constitutive law.On the basis of theoretical and experimental investigation,an empirical stress-strain relationship in parallel-to-grain direction is proposed;analytical models for nonlinear analyses of in-plane and out-of-plane bending of intermediate slender beam-column loaded with eccentric compression are developed,and the associated formulas for ultimate load-carrying capacity and deformation calculation are derived.The major innovative achievements are summarized as follows.(1)Based of the conclusions of literatures about wood stress-strain relationships and the achievements of constitutive law of bamboo-based composite made by our team,an empirical formula of stress-strain relationship of bamboo/wood-based is proposed.For the sake of simplified nonlinear analysis,the formula ignores the stress soft brunch and models the stress hardening brunch is by parabolic equation.(2)By taking the differences of parallel-to-grain stress-strain relationship between tension and compression into account and on the basis of Euler elementary beam theory,an analytical model for nonlinear analysis of in-plane bending and compression of eccentrically loaded beam-column is developed.A formula based on this model for ultimate load-carrying capacity calculation is derived.(3)An analytical model for nonlinear analysis of beam-column loaded with combined biaxial-bending and compression is developed.A step by step method for computing the ultimate load-carrying capacity of bi-axial eccentrically compressive beam-column is proposed.(4)An inelastic incremental calibration method for estimate nonlinear lateral deformation of beam-column is proposed.The formula on the basis of this method for lateral deformation calculation is derived.All the models and formulas provided in this thesis are verified through experiments of parallel strand bamboo beam-columns.The consistence of analysis method of beam-columns and pure bending members is discussed through comparing the analytical model for in-plane compression and bending analysis and for in-plane bending analysis.Thus the reasonable of treating beam and column as one category is discussed.