Study on the Shear Behaviors of RC New-Beam and Old-Slab Composite Component

Abstract

In order to study the influences of shear span ratio and stirrup spacing on the shear behaviors of RC beam-slab composite component, static shear experiment of 9 RC beam-slab composite component and 3 beam-slab casting component were made. The results show that the development trend of flexural-shear crack of composite component is associated with both the shear span ratio and the stirrup spacing. The outer shear connector of the composite component produces the diagonal crack which develops and extends to the support and a horizontal crack to the load point is accompanied on the bond face oblique crack. The lower end of the oblique crack extends to the support and the upper end extends to the load point or the off second shear connector. The diagonal crack of beam-slab casting component extends to the load point and the interface of the beam and slab has no horizontal crack. Introduction The composite beam has been used in engineering practice for many years. ACI-ASCE Committee 333 proposed “suggestion on composite beam for building design” in the 1960s. By the contrast test between the composite beam and the cast-in-place beam, Guo pointed out that the stress of the composite beam under the secondary load exceeded and must be limited. Based on the I-shape test beam, Kang proposed the computational schema and calculation formula of the failure shear strength of the diagonal compression on the reinforced concrete I-shape beam (including T-shape beam) under concentrated load and the results of calculation were in good agreement with the results of tests. The shear performance, seismic measures and shear connector design in the combined interface of composite beam are the key to ensure the two part of the concrete before and after casting to work together and have also been concerned about by many scholars so far. A lot of theoretical analyses and experimental studies show that taking appropriate seismic measures in the combined interface can guarantee the composite beams to 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. Experiment situation Considering the influences of the different shear span ratio and the stirrup spacing on the shear behaviors of the composite beam, 9 reinforced concrete beam-slab composite components were made and 3 beam-slab casting components were also made to contrast with the beam-slab composite components. The length of the composite beam was 2000mm, the width was 100mm and the height was 250mm. To ensure that shear failure occurs to the components, 2 grade III steel of diameter 16mm and 3 grade III steel of diameter 18mm were at the bottom part of beam-end. 2 2nd International Conference on Machinery, Materials Engineering, Chemical Engineering and Biotechnology (MMECEB 2015) © 2016. The authors Published by Atlantis Press 888 grade III steel of diameter 10mm was used as the handling reinforcement. Grade III steel of diameter 6mm was used as stirrup reinforcement and the spacing was 100mm, 125mm and 150mm. The length of the composite slab was 2000mm, the width was 600mm and the thickness was 60mm. Two-layer two-way reinforcement of grade III steel of diameter 6mm and spacing 100 was reinforced into the slab to simulate the actual reinforcement situation of the original slab. The thickness of the cover to reinforcement was 10mm. The design intensity level of concrete was c30 and the concrete was fine aggregate and commercial. Cross-sectional reinforcements of the composite components and the casting components are shown in figure 1. In order to ensure the integrity of the composite beam and slab was fine, the number of shear connector was designed 6. the collocation of the shear connectors took equidistance. The diameter of the concrete open-holes was 90mm. 1grade III steel of diameter 10mm was used as the reinforced connection. Schematic view of shear connector collocations of beam-slab composite component is shown in figure 2. the parameters of specimens are shown in table1. the test set-up is shown in figure 3.