Extended end-plate connections, which act as joints providing resistance against moments between beams and columns, are commonly categorized as semi-rigid or partial-strength connections. The reason for their extensive application in steel frame constructions lies in their straightforward design, their ability to be reproduced easily, and the convenience they offer in the fabrication process. This research used the ABAQUS FE software to construct a three-dimensional finite element model (FEM) with the main objective of exploring how different geometric parameters impact the behavior of the extended end-plate bolted connection, which functions as a semi-rigid, partial-strength beam-to-column connection. Accurately determining the moment-rotation relationship and connection stiffness is of utmost importance for semi-rigid connections. The developed FEM models incorporate various factors such as geometric and material non-linearities, bolt pretension force, as well as contact and sliding between the connection elements. To establish the credibility of the numerical outcomes, the developed FEM model was meticulously calibrated and verified against experimental data obtained from previous studies available in the literature. Subsequently, using the validated finite element model, a parametric investigation was undertaken to evaluate the influence of distinct geometric parameters, namely the thickness of the end plate and column web stiffeners. This numerical model facilitates a comprehensive analysis of the extended end-plate bolted connection, encompassing critical aspects such as the moment-rotation curve and failure mode. The results demonstrated that the analyzed finite element model aligns well with experimental findings and that the use of column stiffeners is inevitable in the joint, as well as a moderated thickness of the end plate. Doi: 10.28991/HIJ-2023-04-02-04 Full Text: PDF

This study presents an experimental and numerical investigation of reinforced concrete beams incorporating micro polypropylene, macro polypropylene, and steel fibers. Three concrete series of equal strength classes were prepared and tested to evaluate compressive strength, splitting tensile strength, flexural performance, and deformation behavior under short-term loading. Strain development in both concrete and reinforcement was measured using strain gauges and mechanical deformometers. In parallel with the experimental program, a nonlinear finite element model was developed using the DIANA FEAsoftware 10.5 to simulate the deformation behavior and strain development of the tested beams. The concrete material was represented using a total strain-based smeared crack model with rotating crack orientation, while the contribution of fiber reinforcement was incorporated through a CMOD-based post-cracking tensile constitutive law. The numerical results showed good agreement with the experimental load–deflection and strain measurements, confirming the suitability of the adopted modeling approach. These findings demonstrate that the combined experimental–numerical framework provides a reliable tool for assessing the deformation and cracking behavior of fiber-reinforced concrete beams. The experimental results indicate that fiber type and combination strongly influence the deformation behavior and mechanical performance of reinforced concrete beams, with hybrid systems incorporating steel fibers exhibiting enhanced flexural response, improved strain compatibility, and more ductile behavior compared to polypropylene-only reinforcement. The inclusion of steel fibers led to distributed cracking, delayed stiffness degradation, increases of up to approximately 6.3% in concrete strains and 10.3% in reinforcement strains, and a substantial improvement in compressive strength (up to approximately 28.8%), confirming the synergistic effect of hybrid fiber reinforcement.