Experimental Study And Analysis On Free Demoulding Concrete Beams

The free demoulding concrete component is a component that concrete and permanently template into a whole together to bear the load,This kind of component is not like the traditional components of the mold and demolition mode in the production process.The concrete beams without demoulding proposed by our research group are essentially concrete composite beams,the prefabricated part of the composite beam(U-shaped concrete formwork)is standardized in the factory,then transported to the construction site for assembly,being hoisted,and finally being banded steel cage and being poured into laminated concrete.After the completion of the construction of the concrete beams,it has the advantages overall,saving manpower and material resources,the construction speed and so on.As a new type of composite beams,it is necessary to study the mechanical properties and failure characteristics of free demoulding concrete beams by experimental method.In this thesis,the two full-scale specimens(a free demoulding concrete beams,a cast-in-place contrast beam)were tested by one-way static loading.The failure patterns,load characteristic value,rebar and concrete strain,deflection,stiffness and ductility were obtained,and the experimental data of the two components were compared and analyzed.The test results show that:the development of cracks in the free demoulding concrete beams and the cast-in-place concrete beam has great difference at the beginning of testing,but the overall failure characteristics of the two members are similar at the end.U-shaped concrete formwork of the free demoulding concrete beam works well with internal post pouring concrete,and through the entire loading process,U-shaped concrete formwork did not fall off from internal post pouring concrete.The cracking load of the free demoulding concrete beam is about 8%lower than that of the cast-in-place beam,but the ultimate load of the two specimens are roughly the same.In practical engineering project,the current code for design of concrete structures can be used to calculate the cracking load and the ultimate load of free demoulding concrete beam,and the result is safe.When the ultimate bearing capacity is reached,the ultimate deflection of the cast-in-place beam is slightly larger than that of the free demoulding concrete beam,but the load-deflection curves at mid-span of the two specimens are basically the same.The damage of without demoulding concrete beam in the whole test process is obvious,steel bars aren't pull off,displacement ductility is better,and the feature is close with cast-in-place beam.Finally,based on the engineering practice,this thesis summarizes the composition,production process,construction sequence and advantages of the free demoulding structure system,and introduces its economic and social benefits in the application.