A comparative analysis of resistance models for austenitic stainless steel girders subjected to concentrated loads

The increasing use of stainless steel in construction has led to the need of developing resistance models for structural elements made of this material. Unlike carbon steels, stainless steel alloys exhibit stress-strain curves with a pronounced strain hardening capacity and reasonable ductility that should be considered in the design. This difference in behavior makes the formulations used for carbon steel conservative when designing with stainless steel. Therefore, this paper presents a comparative analysis of resistance models for slender austenitic stainless-steel beams subject to concentrated loads. First, the failure mechanisms of stainless-steel beams are presented using a nonlinear finite element model. From this validated numerical model, a database obtained from a parametric analysis that covers a wide range of geometries is presented. Subsequently, this database is used to perform a comparison between various resistance models available in the literature. These models correspond to both international design codes and models obtained through machine learning. Finally, the numerical results show considerable improvement in the predicted ultimate resistances for slender stainless steel plate girders subjected to patch loading.

Urethral Tissue Reconstruction Using the Acellular Dermal Matrix Patch Modified with Collagen-Binding VEGF in Beagle Urethral Injury Models

Objectives. Urethral tissue reconstruction for hypospadias is challenging for urologists. In this study, bovine acellular dermal matrix (ADM) patch loading with collagen-binding vascular endothelial growth factor (CBD-VEGF) was used to repair the urethral injury in beagles. Methods. The safety and effectiveness of the scaffold implantation were carefully evaluated by comparing among the urethral injury control group, ADM implantation group, and ADM modified with CBD-VEGF implantation group during 6 months. Urodynamic examination, urethral angiography, and pathological examination were performed to evaluate the recovery of urethral tissue. Results. Stricture, urethral diverticulum, and increased urethral closure pressure were observed in the control group. Fistula was observed in one animal in the ADM group. By contrast, no related complications or other adverse situations were observed in animals treated with ADM patch modified with CBD-VEGF. The average urethra diameter was significantly smaller in the control animals than in scaffold implantation groups. Pathological examination revealed more distribution of proliferative blood vessels in the animals treated with ADM modified with CBD-VEGF. Conclusions. Overall, ADM patches modified with CBD-VEGF demonstrated an optimized tissue repair performance in a way to increase tissue angiogenesis and maintain urethral function without inducing severe inflammation and scar formation.

Influence of geometrical and structural imperfections on the behavior of steel plate girders

The girders or parts of the girders are not ideally flat in terms of their geometry. The deviations that occur are defined as geometric imperfections. Also, in the material from which the girder is made, a certain deviation may occur during factory production or for some other reason, which is known as structural imperfection. This paper presents the analysis of the behavior of plate girders (welded steel I girders), with and without material stiffening and loaded with patch loading. The results were obtained by numerical simulation in the ANSYS for models with included geometric imperfections. The model was performed in accordance with the recommendations for different behavior curves of materials from Eurocode 3. The limit load obtained by numerical simulation corresponded to the experimental results from the literature. Stress values for girders with and without geometric imperfections for the same load value were compared.