Generalised fracture mechanics approach to the interfacial failure analysis of a bonded steel-concrete joint

Steel-concrete joints are often made by welded shear studs. However, this connection reduces the fatigue strength, especially in situations where locally concentrated loads occur with a large number of load cycles e.g. in bridge decks. In this paper the shear bond strength between steel and ultra-high performance concrete (UHPC) without welded mechanical shear connectors is evaluated through push-out tests and a generalized fracture mechanics approach based on analytical and finite element analyses. The connection is achieved by an epoxy adhesive layer gritted with granules. In the tests, specimens made with various manners of preparation of the epoxy interlayer are tested experimentally. Numerical-analytical 2D and 3D modelling of a steel-concrete connection is performed without and with the epoxy interlayer. The model of a bi-material notch with various geometrical and material properties is used to simulate various singular stress concentrators that can be responsible for failure initiation. Thus conditions of crack initiation can be predicted from knowledge of the standard mechanical and fracture-mechanics properties of particular materials. Results of the fracture-mechanics studies are compared with each other and with experimental results. On the basis of the comparison, the 2D simulation of the steel-concrete connection without the epoxy interlayer is shown to be suitable for the estimation of failure conditions

Generalised fracture mechanics approach to the interfacial failure analysis of a bonded steel-concrete joint

Steel-concrete joints are often made by welded shear studs. However, this connection reduces the fatigue strength, especially in situations where locally concentrated loads occur with a large number of load cycles e.g. in bridge decks. In this paper the shear bond strength between steel and ultrahigh performance concrete (UHPC) without welded mechanical shear connectors is evaluated through push-out tests and a generalized fracture mechanics approach based on analytical and finite element analyses. The connection is achieved by an epoxy adhesive layer gritted with granules. In the tests, specimens made with various manners of preparation of the epoxy interlayer are tested experimentally. Numerical-analytical 2D and 3D modelling of a steel-concrete connection is performed without and with the epoxy interlayer. The model of a bi-material notch with various geometrical and material properties is used to simulate various singular stress concentrators that can be responsible for failure initiation. Thus conditions of crack initiation can be predicted from knowledge of the standard mechanical and fracture-mechanics properties of particular materials. Results of the fracture-mechanics studies are compared with each other and with experimental results. On the basis of the comparison, the 2D simulation of the steel-concrete connection without the epoxy interlayer is shown to be suitable for the estimation of failure conditions

Experimental investigation of shear bond strength between steel and self-compacting concrete

In this article the shear bond strength between steel and self-compacting concrete (SCC) without mechanical shear connectors is evaluated by means of push-out tests. The test members differ by steel surface texture, adhesive properties, and SCC mixture. Both smooth and sandblasted steel plates are used and test members are cast with fresh epoxy or hardened epoxy, gritted with granulates. The influence of steel fibre reinforcement on the bond strength is also examined. The ultimate shear bond stresses are recorded as well as the slip between steel and concrete. Also the theoretical distribution of the shear bond stress between steel and concrete is examined by means of a finite element analysis (FEA). Test members fail either by steel plate - adhesive failure, by concrete - adhesive failure, or by shear failure of the concrete sample. Test results point out nominal shear bond stresses between 0.37 and 2.25 N/mm2. However, the values are widely scattered and therefore it's difficult to make definite conclusions about the influence of the studied parameters. According to the FEA of the specimens used in this test program, a non-uniform stress distribution between steel and concrete is found and the maximum shear bond stress is 2.98 times higher tan the nominal shear stress

Fatigue assessment of a lightweight steel-concrete bridge deck concept

This paper presents results of a constant amplitude fatigue test on a lightweight steel-concrete deck concept, in which a network of longitudinal and transverse concrete ribs transmit shear forces between thin top and bottom steel plates. In order to achieve a lightweight composite structure, the concrete volume is only 32% of the volume between the plates. In previous research the deck was tested statically, indicating that the lightweight steel-concrete sandwich bridge deck concept possesses the necessary static resistance to bridge loads. This paper describes a constant amplitude fatigue test on a full-scale bridge deck test panel (3.60 m×1.50 m) up to 6 million cycles. During this dynamic test, the deflection of the bridge deck, and steel and concrete strains are recorded on predetermined intervals in order to evaluate the fatigue behavior of the sandwich deck as a function of the number of cycles. The results indicate that the lightweight steel-concrete sandwich bridge deck concept possesses the necessary fatigue resistance to traffic loads

Influence of steel fibre reinforcement on the shear resistance and crack pattern formation of self-compacting concrete beams

This paper presents the results of experimental tests carried out on steel fibre reinforced self-compacting concrete (SFR-SCC) beams without stirrups. Sixteen beams are cast using four mixtures of SCC with different steel fibre content, while the longitudinal reinforcement is kept constant in all test members. The beams are subjected to four point bending tests at a shear span-to-depth ratio of 2. The ultimate shear stress is recorded, as well as the crack pattern and the mid-span beam deflection. Test results show that as fibre content increases, higher ultimate shear stresses are achieved. When fibres are included, test members exhibit an increase in ductility and a more extensive crack pattern is observed. The experimental values of the ultimate shear stresses are also compared with theoretical values as given by empirical expressions in literature