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Hybrid application of conventional concrete and Strain Hardening Cementitious Composite (SHCC) is recently shown to be promising for crack width control. In this paper, a combined experimental and numerical study is performed to validate the concept and to study the effect of interface treatment on crack width control. The interface is varied between smooth, profiled, partially debonded and completely debonded surfaces. The beams are tested under a four-point bending configuration. The crack development is monitored using digital image correlation throughout the loading, and maximum crack width of 0.3 mm at the surface is taken as the limiting criterion for analyses. The hybrid and control beams are simulated using the lattice model. Both experimentally and numerically, it is observed that stronger interfaces enable the composite action in the hybrid beams and provide better crack width control compared to the artificially weakened interfaces.

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The bond between concrete and reinforcement is one of the critical parameters influencing the structural behavior of reinforced concrete (RC). This research proposes a mathematical methodology to scale the reinforcement-concrete bondslip relationship in a beam lattice modeling framework. A simplified, generalized approach based on stochastic analysis is proposed to model the interaction between the reinforcing bar and surrounding concrete at the macroscale. The approach considers the randomness of the lattice mesh and the mesh size and adopts an analytical model for the interface assuming the pull-out failure of reinforcement as input, thereby including also the mesoscale geometric effect of ribs. By using the geometric configuration of Delaunay triangulation in the random lattice mesh, the interface elements can reproduce the basic conical stress transfer mechanism in concrete. Consequently, depending on boundary conditions, and without changing the interface properties, a splitting failure and bond-slip relation for splitting failure can be predicted. The model is systematically validated in different types of pull-out tests, through flexural and finally shear tests. With limited input (properties of the concrete and analytical equation for pullout failure), having a (strong) physical background, the model was shown to capture the fundamental fracture mechanisms in RC under different loading and confinement conditions.

The safety of existing slab-between-girder bridges is subject to discussion in the Netherlands. Current design codes are conservative for shear-critical girders, and nonlinear finite element analysis is considered a more accurate assessment method. This paper investigates if the Dutch guidelines for nonlinear finite element analysis, which were largely based on laboratory experiments, can safely predict the behavior of large-scale shear-critical post-tensioned girders. The simulation results are compared with experimental observations on girders taken from a demolished bridge (the Helperzoom bridge) after serving for more than 50 years. Predicted and experimentally observed material properties are used as inputs for numerical models. For both, safe predictions of inclined cracking and ultimate capacities are obtained. Parameter studies for load positions and prestress levels are also performed to get a deeper insight into the structural behavior of such girders. This work shows that the guidelines can be used for assessment.