| Recycled aggregate concrete is a kind of green concrete that prepared by partially or completely replacing natural aggregates with recycled aggregates obtained from the crushed construction and demolition waste concrete,the mechanical properties of which are inferior to those of normal aggregate concrete(NAC).The steel-concrete composite slab is a kind of structural member with higher construction efficiency,higher bearing capacity,the advantages of which can compensate the weakened mechanical properties of RAC and help promote the application of RAC in structures.Up to date,the research in terms of this new green composite structural member has focused primarily on those made with coarse recycled aggregate(CRA),while no studies have been conducted on those with fine recycled aggregate(FRA).Therefore,this study aims at,through experiment and finite element analysis,investigating the influence of CRA and FRA on the longitudinal shear behaviour of simply-supported and continuous closed formed profiled steel sheeting-recycled aggregate concrete composite slabs.In this context,the following investigations are conducted in the present work:(1)Fourth-point concentrate loading tests were carried out on three steel-RAC simply supported composite slab with a span of 3m to study the influences of CRA and FRA and the magnitude of the sustained load on the longitudinal shear behaviour of the composite slabs.The failure mode,deflections at midspan and loading points,relative slip between steel deck and concrete,and strain distribution through the slab depth were monitored.The test results show that ductility failure occurred in all the three composite slabs,and the maximum relative slip at the end of the composite slab is up to 11.3mm.Within the range of test parameters in this study,the influence of CRA and FRA on the longitudinal shear capacity of simply supported composite slabs is less significant with the maximum influence of 2%.The sustained load applied prior to the test help increase the longitudinal shear capacity of the simply supported composite slabs.(2)The fourth-point loading test of three 6m long two-span continuous steel-RAC composite slabs was carried out to study the influence of the replacement ratios of CRA and FRA and the sustained load on longitudinal shear behaviour of continuous composite slabs.The failure mode,mid-span deflection and loading point deflection of continuous composite slab,relative slip of steel plate-concrete interface,and strain distribution of key sections were investigated.The test results show that the longitudinal shear failures of all three continuous composite slabs were ductile,and the maximum relative slip of the end of the composite plate can reach 23 mm.100% incorporation of CRA and FRA decreased the longitudinal shear bearing capacity of continuous composite slabs by 8%.The sustained load prior to the test decreased the longitudinal shear bearing capacity of the continuous composite slabs,but with a maximum percentage of 5% that can be ignored in the design.(3)The 3D solid finite element models(FEM)for simply-supported and continuous composite slabs were established using the ABAQUS/Explicit analysis method.The shear-slip behaviour between steel decking and concrete was modelled by combining the Radial-Thrust constraint based on the available shear-slip constitutive relationship.The key parameters used in the FEM,such as mesh size,parameters for the constitutive relationships of concrete,and loading rate,were determined through analysis.The FEM was validated using available test data.Based on the validated model,a parametric study was conducted to analyse the longitudinal shear behaviour of simply-supported and continuous composite slabs made with RAC.The considered parameters include the thickness of slabs,the replacement ratios of CRA and FRA,and the thickness of steel decking.The results show that,for simply supported slabs,the influence of CRA and FRA on the longitudinal shear bearing capacity is limited,which can be ignored in the design;while for the continuous slabs,the influence of CRA and FRA is larger,and a 10% reduction in the bearing capacity is recommended in the design for the conservative purpose. |
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