Shear Model Analysis Of High-strength Lightweight Aggregate Concrete Deep Beams Considering Crack Softening Effect

The mechanism of shear failure of high-strength lightweight aggregate concrete deep beams is complicated,and the failure mechanism of high-strength lightweight aggregate concrete is different from that of ordinary concrete.Cracks in high-strength lightweight aggregate concrete pass through the middle of aggregate,while ordinary concrete cracks pass through the aggregate surface,resulting in differences in the softening and softening effects of the two.Therefore,in the analysis of the shear behavior of high-strength lightweight aggregates deep beams,the cracking softening effect of the concrete members is insufficient,and the calculation method of the softening coefficient of the struts needs to be further clarified.So this thesis takes the high-strength lightweight aggregate concrete deep beam as the object,and selects the strut isolation test piece to carry out the compression performance test research.Based on the strut-and-tie model and the modified compression field theory,considering the cracking softening effect,the shear model analysis of high-strength lightweight aggregate concrete deep beams was carried out.The paper completed the compression performance test of the specimens of the 12high-strength lightweight aggregate concrete struts with different size parameters and reinforcement parameters,and analyzed its compression performance.The main contents are as follows:(1)The compression performance test of 12 high-strength lightweight aggregate concrete inclined struts is carried out.The research shows that the smaller the height-thickness ratio of the strut test piece,the higher the effective coefficient of the strut,and the size effect is significant.The larger the cross-sectional area of the strut test piece,the higher the effective coefficient of the strut;the higher the concrete strength grade of the strut test piece,the higher the effective coefficient of the strut.(2)Collecting and arranging four kinds of normative design methods and eight classical calculation models,calculating and analyzing the specimens of the strut test piece: The calculation results of national norms are lower than the test results.,and the calculation results of CSA A23.3-04 agree well with the test results;The results of the classical calculationmodel are conservative,and the Mikame model has the best results.(3)Analysis of the correlation between the test piece of struts and the deep beams: When the shear span ratio is less than 1,the force behavior of the strut test piece is in good agreement with the performance of the strut in the deep beam member.As the shear span ratio increases,due to the influence of the bending action,the correlation between the strut test piece and the strut in the deep beam member.(4)Based on the modified compression field theory,considering the stress distribution in the deep beams and the failure characteristics of high-strength lightweight aggregate concrete,the particle size parameters of the lightweight aggregate are corrected to zero.based on the characteristics of lightweight aggregate concrete established and the modified compression field theory,The calculation model of the compressive bearing capacity of the strut in the deep beam member is established.The paper studies on the compression performance and modeling of the strut in high-strength lightweight aggregate concrete deep beams,which has important theoretical significance for analyzing the shear performance and calculation model of deep-bending members.At the same time,it has important practical value for high-strength lightweight aggregate concrete in engineering applications.