This paper develops a new type of shear connection for steel-concrete composite bridges using Ultra-High Performance Concrete (UHPC) as the connection grout. The UHPC-grout strip shear connection is fabricated by preforming a roughened slot in the concrete deck slab, welding an embossed steel rib longitudinally to the upper flange of the steel girder, and casting the strip void between the slot and the steel rib with UHPC grout. The structural performance of the new connection was validated by two sets of experimental tests, including push-out testing of shear connectors and static and fatigue testing of composite beams. The results of push-out testing indicate that the UHPC-grout strip shear connection exhibits a significant improvement of ductility, ultimate capacity, and fatigue performance. The interface shear strength of the UHPC-grout strip connection is beyond 15 MPa, which is about three times that of the strip connection using traditional cementitious grouts. The ultimate capacity of the connection is dominated by the interface failure between the embossed steel and the UHPC grout. The results of composite-beam testing indicate that full composite action is developed between the precast decks and the steel beams, and the composite action remained intact after testing for two million load cycles. Finally, the trail design of a prototype bridge shows that this new connection has the potential to meet the requirements for horizontal shear.

For simplified shear design of slender reinforced concrete (RC) beams with stirrups, a modified variable-angle truss model is developed in this paper. In this model, an analytical solution of the inclination of struts (θ) is derived by combining the theory of plasticity and the concrete softening of the modified compression field theory (MCFT). It is found that there is a decreasing linear relationship between cotθ and lnω, where lnω is the natural logarithm of the mechanical shear-reinforcement ratio. On this basis, a new shear design equation is proposed for slender RC beams with stirrups, which is shown to be not only simpler, but to also provide improved prediction compared with the shear design provisions of some of the existing codes.

Shear deformations of reinforced concrete (RC) beams are not negligible after shear cracking. However, unlike the well-established procedure for calculating bending deformations of cracked beams, the calculation of shear deformations is still ignored in codes of practice due to a lack of practical models. This study aims to develop a practical approach for estimating instantaneous shear deformations of RC beams under service loads. Based on the truss analogy, an explicit equation for evaluating the yield shear stiffness of fully diagonally cracked beams is derived. It is discovered that the shear retention factor (ratio of the yield shear stiffness to the initial elastic shear stiffness) is approximately the cubic root of the shear-reinforcement ratio. An analytical approach for evaluating the degradation of effective shear stiffness and the development of shear deformation is proposed. Two restrained I-beams with thin webs are tested. This test and shear-deformation tests available in the literature are used to validate the analytical approach.

The steel–concrete hybrid girder bridge structure is a combination of steel and concrete members in the direction of the bridge length. In long-span segmental concrete box girder bridges, the utilization of lightweight steel girders in the middle portion of the main span would greatly reduce the bridge self-weight while decreasing concrete creep and shrinkage effects. A critical parameter in the design of hybrid girder bridges is the rational length of the steel portion as a part of the main span (in other words, the rational location of the steel–concrete connection). Based on the concept of system equivalence, the steel–concrete hybrid system is equivalent to a full-concrete system with a reasonable span arrangement. The governing condition of the equivalence is that both systems have the same magnitude of self-weight hogging bending moments over the piers. Applying the system equivalence method, the rational length ratio of the steel portion to the main span (ξ) is explicitly solved, and its relationship with the length ratio of side span to main span (λ) is established. Finally, the proposed analytical approach is validated by five case studies, indicating that it is an effective and efficient method for the preliminary design of hybrid girder bridges.

The balanced cantilever method is the most widely used technique for the construction of large-span segmental prestressed concrete box-girder bridges. In order to control shear cracks at the service limit state, the principal tensile stresses in the webs are analyzed for all segmental bridges. Web shear cracking may occur for a number of reasons, one of them is the ignoring of shear stresses induced by the anchorage of cantilever tendons during the cantilevering process. This study aims to provide a clear understanding of anchorage-induced shear stresses in the webs of segmental box-girder bridges, including the underlying mechanisms, mechanical models, adverse effects, and design considerations. Case studies show that the peak shear stresses in the webs might have a significant increase due to this localized effect, while it cannot be captured by the beam-element analysis and is usually not considered in the routine design. To solve this problem, a practical approach is developed for evaluating the anchorage-induced shear stresses in the webs of segmental concrete box-girder bridges.