| With the development of building industrialization,prefabricated concrete structures are beginning to emerge.Using RPC as the precast beam shell,the RPC-NSC composite beam formed by post-casting NSC can play the advantages of both RPC and prefabricated structure.However,existing research results show that the bonding interface is the weakest position of the composite structure.Therefore,it is necessary to study the bonding properties of precast RPC and post-cast NSC.This subject takes precast RPC slotting density and post-cast NSC strength as the main influencing factors.The mechanical properties of the bonding interface of RPC-NSC composite specimens were tested,and the bending test and finite element simulation of bonding performance of U-shaped RPC-NSC composite beams were tested.The results of this topic are as follows:The bonding stress generated by the precast RPC slotting treatment was much greater than the shear strength of the post-cast NSC;The shear strength of the bonding interface increased with the increase of the precast RPC slotting density and the post-cast NSC strength;The precast RPC slotting density 1.33,2.67,4 corresponding to the single slotting shear strength were 1.398MPa,1.226MPa,1.044MPa;The precast RPC slotting density and post-cast NSC strength had a significant effect on the shear strength of the bonding interface,and the effect of precast RPC slotting density was much greater than that of post-cast NSC strength;Based on the Eurocode 2 and the conversion relationship between NSC compressive strength and NSC tensile strength,the shear strength calculation formula of RPC-NSC bonding interface was established;Through precast RPC slotting treatment,bonding failure was not occurred under bending load,and it had better overall working performance;In the linear elastic stage,the stiffness of the combination of the two materials at the bonding layer was slightly weaker,but the full cross-section also approximately conformed to the assumption of a flat cross-section;Through range analysis,the degree of influence of each factor from large to small was as follows:RPC-NSC thickness ratio,precast RPC slotting density and post-cast NSC strength;The best level combination was precast RPC slotting density 2.5,post-cast NSC strength C40 and RPC-NSC thickness ratio 45/55;The crack control ability of RPC was better than that of old C40;The mechanical engagement force provided by the roughness was the main source of the shear bearing capacity of the bonding interface;For the RPC-NSC bending specimens damaged by shearing,the calculation formula of the shear capacity of diagonal section was established;For the RPC-NSC bending specimens damaged by bending,the calculation method of the bending strength of the normal section was proposed;The interfacial slotting treatment can meet the bonding performance of the composite beam,so that it can not occur the phenomenon of bonding failure;When the precast RPC slotting density was between 1.2-3.6,the greater the slotting density,the greater the load of the RPC-NSC composite beam,and the smaller the deflection under the same load,but the impact of the slotting density on the overall working performance of the composite beam was not significant;It was recommended that in the design of the RPC-NSC composite beam,the slotting density in the tensile zone should not be less than 3.6,the slotting density of the pressure zone should not be less than 2.4,to ensure that RPC and NSC can have a strong cooperative deformation ability;Combined with the test and ABAQUS finite element analysis,when the precast RPC slotting density was not less than 3.6,RPC-NSC composite beam had good overall working performance.The finite element simulation can use the "TIE" contact to define the contact between the two materials.Not only was the modeling simple and convenient,the calculation efficiency was high,but also the data results and damage morphology were relatively close to the test. |
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