Investigation On Mechanical Properties Of T-shaped Reinforced Concrete Laminated Beams With Defects

Assembly structural system is widely implemented in the process of the building industrialization for its great deal advantages.However,due to the complex material characteristics of concrete,there is going to be inevitable bonding defects on the contact surface between precast concrete and secondary poured concrete.In the current academic research,it is mostly assumed that the bonding of the laminated surface is complete,and less attention is paid to the harm caused by the bonding defects.Therefore,it is essential to investigate the influence of the bonding defects on the mechanical performance of the laminated structure.In this paper,the static loading tests of T-shaped reinforced concrete laminated beams with defects under monotonic load were firstly carried out on the basis of simulation.For verifying the consequences of tests,the numerical models of corresponding T-shaped laminated beam were established through the finite element software ABAQUS.Then a large number of numerical models were established to carry out parametric analysis on the bearing performance of bending T-shaped laminated beams with defects and shearing T-shaped laminated beams with defects.The main conclusions are as follows:1.The static loading tests results showed that the defects had little effect on the failure mode of T-shaped laminated beams.There was no obvious slip in the laminated surface when the failure occurred,but the concrete around the defects was damaged partly.The results of numerical models corresponding to the test components verified the accuracy of the test consequences.2.In view of the influence of defecs’ length and defects’ position on the bearing performance,taking the peak load and the peak deflection as the indexes for the analysis of mechanical parameters.The laws of the influence of the change of defects’ length at different positions on the bearing performance of the laminated beam were summarized.There is a characteristic length for the loading section defects which is about 0.15 times of calculating span.When the length is lower than that,the effect of the defects on the flexural bearing performance is relatively small,and the structural safety can be guaranteed.However,when the length exceeds that value,the weakening effect will increase significantly.The change of mid-span section defects’ length has little effect on the bending performance of laminated beam,and the curve of peak eigenvalues is relatively flat.In the shear laminated beam models with defects in bend-shear section,the peak eigenvalue and defects’ length basically obey linear distribution.The larger the defects’ length is,the more obvious the weakening effect is.3.In view of the influence of defects on the bearing performance under different cast-in-place thicknesses,a method of accumulating the deviation percentage of the peak eigenvalue was proposed.The relationship between the cumulative deviation percentage and the cast-in-place thickness was compared under different defect locations.The analysis results showed that there is an optimal cast-in-place thickness.At that value,the bearing capacity and ductility of the laminated beam are the best,and the influence of defects is at a low level.In the data background of this paper,the optimal cast-in-place thickness is about 0.43 times of the section height.4.By comparing the load-deflection curves and their peak eigenvalues,it was considered that the defects mainly affected the failure stage of the laminated beam,and had little effect on the bearing capacity,but more effect on the ductility.The above research contents expounded the influence of the laminated surface defects on the mechanical properties of T-shaped reinforced concrete laminated beams,and provided certain reference for the structural design,engineering application and academic research of laminated beams.