Research On The Shear Behaviors Of New-Beam And Old-Slab Composite Component

Reinforced concrete frame structure system composed of wide column and double beams is especially suitable for the transforming the small space into large space in the hybrid structure. At the supporting stage, the mechanical properties of the original structure are not changed. At the same time, the stress characteristics of the non replacement parts are also not changed after the replacement in the new structure system. Structural system transformation during the transformation process is natural and the stress is reasonable. In the process of underpinning and transforming, the underpinning beams should be added to the both sides of the original wall, the concrete of the underpinning beam is placed through some open-holes of the floor slab and the open-holes should be tightly filled with the concrete, then the new-beam and old-slab composite structure is cast and composited. It is very important for the new underpinning beam to coordinate with the old floor slab. Placing the reinforced connection in the concrete open-holes and using the open-holes and the reinforced connection properly can design a shear connector whose structure is simple and construction is convenient, which can guarantee that the new-beam and old-slab can work together.Although many scholars at home and abroad have conducted lots of experimental studies and theoretical analyses and put forward relevant design proposals, the stress characteristics of the new-beam and old-slab composite structure based on the practical engineering have not been studied. This paper has studied on the shear behaviors of reinforced concrete beam and slab composite component. Therefore, it is necessary to do some experimental research and finite element analysis on the shear behaviors of new-beam and old-slab composite component, study the influence of the shear connector on the overall mechanical behaviors, analyse the influences of the shear span ratio and the stirrup spacing on the shear behaviors, perfect its design theory and have an important significance for reinforcement and reconstruction of old buildings.Based on the national natural science fund project Research on Flame Structure System of Double Reinforced Concrete Beam and Wide Column in the Old Masonry Underpinning Reconstruction, static shear experiment and theoretical analysis of 9 RC Beam-Slab Composite Components and 3 Beam-Slab casting components were made to observe the experiment process and the destructive pattern and study on the cracking load, distribution of the crack, the ultimate load of the specimens, and so on. Based on finite element software ABAQUS, simulation of nonlinear finite element was done and the finite element analysis results were compared with the experimental results. The research results show that:(1) the main stress stirrup on the middle of the loading point-support line yielded and at last, the concrete of the two sides of the web shearing diagonal crack produced obvious dislocation, the composite component failed and presented the form of shear compression failure; (2) the diagonal crack developing from the end of the shear connector to the support was produced in all of the composite components and horizontal crack was produced in the combined interface from the end of the component to the point of loading point; (3) the failure patterns, ultimate load and load displacement curve gained based on finite element analysis method fitted relatively well with the test results, which showed that enough accuracy simulation on the shear behaviors of Beam-Slab Composite Component was conducted based on ABAQUS and the accuracy of the test was also verified at the same time; (4) the shear bearing capacity formula derived from the Truss-arch Model can be applied to the Beam-Slab Composite Component and by referencing the standard, simplified calculation method of formula for shear was proposed and the results showed that the established calculation formula of ultimate bearing capacity was applicable.