In the paper, the method of a numerical simulation concerning diagonal crack propagation in con-crete beams was presented. Two beams reinforced longitudinally but without shear reinforcement were considered during the Finite Element Method analysis. In particular, a nonlinear method was used to simulate the crack evaluation in the beams. The analysis was performed using the commercial program ANSYS. In the numerical simulation, the limit surface for concrete described by Willam and Warnke was applied to model the failure of concrete. To solve the FEM-system of equations, the Newton-Raphson method was used. As the results of FEM calculations, the trajectories of total stains and numerical images of smeared cracks were obtained for two analyzed beams: the slender beam S5 of leff = 1.8 m and the short beam S3k of leff = 1.1 m. The applied method allowed to generate both flexural vertical cracks and diagonal cracks in the shear regions. Some differences in the evaluation of crack patterns in the beams were observed. The greater number of flexural vertical cracks which penetrated deeper in the beam S5 caused the lower stiffness and the greater deformation in the beam S5 compared to the short beam S3k. Numerical results were compared with the experimental data from the early tests performed by Słowik [3]. The numerical simulation yielded very similar results as the experiments and it confirmed that the character of failure process altered according to the effective length of the member. The proposed numerical procedure was successfully verified and it can be suitable for numerical analyses of diagonal crack propagation in concrete beams.
The scope of the paper is to investigate analytically and determine experimentally the shear resistance of low height reinforced precast concrete lintels. The chosen procedures included in national and international standards applied for the design of structural concrete elements to an estimation of shear behaviour of reinforced concrete elements are described. The characteristic and designed shear strength of precast concrete lintels are determined and compared with experimentally obtained results. The shear resistance for precast concrete lintels was determined by laboratory tests according to a European standard. The assessment of the in-situ compressive strength of concrete in precast concrete lintel is specified. The designed compressive strength class is confirmed. The real reinforcement distribution is verified to assess the wide scatter of experimentally obtained failure forces. A short literature outlook of the papers concerning investigations on lintels and shear resistance of concrete is given also. The paper can provide scientists, engineers, and designers a theoretical and experimental basis in the field of precast concrete lintels shear resistance.
The aim of this paper is a comparative analysis of the experimental test results of twenty T-section beams reinforced with glass fiber reinforced polymer (GFRP) bars without stirrups with predicted values of the shear capacity according to the following design guidelines: draft Eurocode 2, Japanese JSCE, American ACI 440, Italian CNR- DT-203/2006, British BS according to fib Bulletin 40, Canadian CSA-S806-12 and ISIS-M03-07. Standard procedures for FRP reinforced beams based on traditional steel reinforced concrete guidelines. The longitudinal FRP reinforcement has been taken into account by its stiffness reduction related to the steel reinforcement. A basis of this modification is the assumption that the FRP-to-concrete bond behaviour is the same as it is for steel reinforcement. To assess the compatibility of predicted values (Vcal) with the experimental shear forces (Vtest) the safety coefficient η = Vtest / Vcal was used. The results corresponding to values η < 1 indicates overestimation of the shear capacity, but η > 1 means that shear load capacity is underestimated. The most conservative results of the calculated shear capacity are obtained from the ACI 440 standard. In contrast to them the best compatibility of the calculated shear values to the experimental ones indicated British BS standard, fib Bulletin 40 and Canadian CSA-S806-12 standard.
This paper presents probabilistic assessment of load-bearing capacity and reliability for different STM of beams loaded with a torsional and bending moment. Three beams having different reinforcement arrangement obtained on the basis of STM but the same overall geometry and loading pattern were analysed. Stochastic modelling of this beams were performed in order to assess probabilistic load-bearing capacity. In the analysis, the random character of input data - concrete and steel was assumed. During the randomization of variables the Monte Carlo simulation with the reduce the number of simulations the Latin Hypercube Sampling (LHS) method was applied. The use of simulation methods allows for approximation of implicit response functions for complex in description and non-linear reinforced concrete structures. On the basis of the analyses and examples presented in the paper, it has been shown that the adoption of different ST models determines the different reliability of the analysed systems and elements.
The paper presents the method of simplified parametric analysis of the sensitivity of a pre-tensioned concrete beam. The presented approach is based on the DOE (design of experiments) data collection which is simulation technique allowing for identification of variables deciding about the effectiveness and costs of designed structures. Additionally, application of the hyper-surface of the construction response allows designers to the development of multi-dimensional trade-off graphs to facilitate, the assessment of the scope of changes in random state variables permitted due to the adequate criteria and selection of their values close to optimum. Design basics, procedures and results of the presented considerations of sensitivity assessment and reliability of the structure has been shown on the example of a pre-stressed concrete beam designed in accordance with the requirements and procedures of Eurocode 2.