The loads that are used for the assessment of existing reinforced concrete slab bridges are the self-weight, superimposed loads, and distributed and concentrated live loads. As such, the shear capacity of reinforced concrete slabs under a combination of distributed and concentrated live loads is a topic of practical relevance. For slabs subjected to a single concentrated load, a plastic model for assessment exists: the Extended Strip Model, developed based on the Strip Model for concentric punching shear. A further adaptation of the model to assess slabs subjected to distributed and concentrated loads is presented in this paper. The proposed model is compared to experiments on slabs subjected to a single concentrated load and a line load. The conclusion of this comparison is that the Extended Strip Model results in a safe estimate of the maximum concentrated load on the slab, and that the method can be used for the assessment of existing bridges subjected to heavy truck loads.

Full probabilistic assessment of the structural reliability of reinforced concrete structures holds the key to proper calibration of the existing safety formats. The scope of the present work is to compare different level II reliability methods that take into account variability and perform accurately in the left side tail of the probability density function of the resistance, in the framework of nonlinear finite element analysis. Alongside, the effectiveness and accuracy of these probabilistic methods are investigated and, through a comparative study, the most reliable method is determined. As a numerical example, structural reliability of a reinforced concrete beam is assessed through Probabilistic Nonlinear Finite Element Analysis (PNLFEA). The methods investigated in the paper are: Directional Adaptive Response Surface, Directional Simulation, Response Surface combined with Crude Monte Carlo Simulation and First Order Reliability Method. The software facilitated for the implementation of the aforementioned methods is the probabilistic module of DIANA finite element software and Matlab.