No abstract

In this paper, the steel plate-concrete composite (SPCC) beam is developed, in which traditional steel beam in the steel-concrete composite beam is replaced by a steel plate. The aim to develop this type of composite beam is to provide a theoretical basis for design of SPCC structures and SPCC-strengthened structures. In order to investigate the flexural behavior of SPCC beams, tests were conducted on five specimens with loading cases of four-point or three-point bending. All the beams were identical in geometry, longitudinal reinforcement, stirrup, and concrete strength but various in steel plate thickness, shear connection degree, shear span length and cut-off position of steel plate. The structural behavior of the tested SPCC beams, including strain, deflection, crack width, load carrying capacity and deformability, etc., were measured and analyzed. Based on test results, it can be concluded that by means of appropriate shear connection degree and anchorage length, steel plate and concrete can work together very well and the SPCC beams have a very good ductility. The ultimate strength of the SPCC beams can be calculated by means of the same plastic method as reinforced concrete beams.

Concrete slab in the negative moment area of continuous steel-concrete composite beams is prone to crack due to the low tension strength of common concrete, which could result in the decreasing of the strength and durability. To solve this problem, a method of replacing the concrete slab with reactive powder concrete (RPC) slab which is of super high strength, durability, toughness and volume stabilization is presented. According to the constitutive relation and the high tension strength of RPC, the normal section failure mode is defined as the critical crack state, and the calculation formula of ultimate bearing capacity is deduced. Finally, some parameters that influence the ultimate bearing capacity are analyzed, such as the height ratio of RPC slab to whole beam, width ratio of RPC slab to steel beam, and the ratio of reinforcement of RPC slab. Compared with the steel-concrete composite beams, it is indicated that in the precondition of RPC slab unallowable crack in negative moment area, the ultimate bearing capacity of steel-RPC composite beams can still be increased, and the crack resistance, stiffness and durability can all be enhanced greatly.

Nonlinear finite element (FE) analysis models of CFT composite frames with floor slab were established by Msc.Marc to investigate the seismic behavior of composite frames. A number of material nonlinearities and contact nonlinearities, as well as geometry nonlinearities, were taken into account, including elastoplastic properties of steel and concrete, concrete cracking and tension stiffening, steel fracture, interface slip between concrete slabs and steel beams, P-D effects etc. The elasto-plastic behavior, as well as fracture and post-fracture behavior, of the FE analysis models agreed well with those of the test specimens. The beam and panel zone deformation of the analysis models is also in good agreement with that of the test specimen. It is concluded that FE analysis is useful not only for monotonic load analysis but also for cyclic load analysis. It is a helpful tool to expand the information on seismic behavior of composite frame.