Stud shear connectors for composite beams

The published results of push tests were analysed statistically in order to determine the main parameters that affect the strength of stud shear connectors. The results of the statistical analysis were used to design a series of seventy-nine push tests. A finite element analysis program was developed which allowed for the interaction between the tensile and compressive failure of concrete and hence predicted the variation in the bearing strength of concrete prisms of varying size and with varying amounts of lateral restraint, when subjected to concentrated loads. A combination of-theoretical and empirical analyses was used to determine the load at which the stud broke, the strength of concrete prisms which were subjected to patch loads of varying size and eccentricity and hence the strength of concrete slabs, the effect of lateral forces and transverse reinforcement on the strength of the stud and the slab, the-strength of shear connections in which the reinforcement is looped around the stud and the load-slip curve for a stud shear connection

Composite Steel and Concrete Structural Members Fundamentals Behaviour

xxxvii, 549hlm ; 25c

The FRP reinforced shear-friction mechanism

The ability of reinforced concrete to resist shear forces across possible sliding planes is a well established area of research and is also recognised as an important aspect of the ability of reinforced concrete members to both resist loads and deformation. This characteristic of reinforced concrete is often referred to as the shear-friction or aggregate interlock mechanism and much of the previous research in this area has dealt with ductile steel reinforcement, which is assumed to yield prior to the shear-friction capacity being attained. In this paper, it is shown that, as FRP is an elastic material, the shear friction behaviour of FRP reinforced concrete is different to that with ductile steel reinforcement. However, and perhaps surprisingly, the shear-friction capacity of FRP reinforced concrete can be just as ductile and strong as steel reinforced concrete

Concrete component of the rotational ductility of reinforced concrete flexural members

Reinforced concrete flexural members inherently rely on member ductility to ensure a safe design by allowing for: redistribution of applied stress resultants; quantification of drift for determining magnified moments; and for the absorption of seismic, blast and impact energy. Structural engineers have recognised that much of the member rotation is concentrated in a small region referred to as the plastic hinge and because of the complexity of the problem this has been quantified mainly through testing. In this paper, a new plastic hinge approach that is based on well established shear-friction theory is postulated. The generic behaviour of this novel shear-friction hinge is shown to agree with that exhibited in tests. Furthermore, the shear-friction hinge explains the mechanics of the benefits of confinement, such as that due to FRP encasement or steel stirrups, on the rotational capacity of RC members

The FRP reinforced shear-friction mechanism

The ability of reinforced concrete to resist shear forces across possible sliding planes is a well established area of research and is also recognised as an important aspect of the ability of reinforced concrete members to both resist loads and deformation. This characteristic of reinforced concrete is often referred to as the shear-friction or aggregate interlock mechanism and much of the previous research in this area has dealt with ductile steel reinforcement, which is assumed to yield prior to the shear-friction capacity being attained. In this paper, it is shown that, as FRP is an elastic material, the shear friction behaviour of FRP reinforced concrete is different to that with ductile steel reinforcement. However, and perhaps surprisingly, the shear-friction capacity of FRP reinforced concrete can be just as ductile and strong as steel reinforced concrete.Wade Lucas, Deric J. Oehlers, M.S. Mohamed Ali and Michael C. Griffit

A generic unified reinforced concrete model

The behaviour of reinforced concrete members with ductile steel reinforcing bars at the ultimate limit state is extremely complex. Consequently, there has been a tendency for the seemingly disparate research areas of flexure, shear and confinement to follow separate paths in order to develop safe approaches to design. In this paper, it is shown how the already much researched and established, but somewhat peripheral, areas of reinforced concrete research of shear friction, partial interaction and rigid body displacements can be combined to produce a single unified reinforced concrete model that simulates the moment-rotation of hinges and their capacities, the shear deformation across critical diagonal cracks leading to failure and the effect of confinement on these behaviours. It is shown that this unified reinforced concrete model is completely generic, as it can be used to simulate reinforced concrete members with any type of reinforcement material (including brittle steel or fibre-reinforced polymer), various cross-sectional shapes of reinforcement (not only round bars but also flat externally bonded or rectangular near surface mounted adhesively bonded plates) and any type of concrete (e.g. high-strength or fibre-reinforced concrete). This new model, therefore, should allow the development of more accurate and safe design procedures as well as enabling more rapid development of new technologies

Bond strength of near-surface mounted FRP strip-to-concrete joints

The retrofitting technique of near-surface mounting (NSM) fiber-reinforced polymer (FRP) bars/strips is receiving more attention recently due to a number of advantages over the externally bonded technique. However, there is insufficient data available in the existing literature to quantify the intermediate crack (IC) debonding mechanism of reinforced concrete members retrofitted with longitudinal NSM strips. As it is recognized that simple push-pull specimens simulate the IC debonding mechanism observed in retrofitted flexural members, this paper presents the results of a series of 36 push-pull tests using NSM strips to quantify the bond strength of such FRP-to-concrete joints. It is proposed that the confinement effect of the concrete surrounding the interface debonding crack improves the shear stress transfer mechanism resulting in higher debonding plate strains compared with externally bonded plates. A nonlinear statistical analysis of the experimental data was undertaken to develop a model to predict the maximum axial plate force for IC debonding, taken at a critical bonded length of 200 mm. © 2007 ASCE