No abstract

Structural deterioration during fire leads to significant economic losses, severe injuries, and deaths. Research to accurately estimate the impact of fire on structural security and performance, and to identify ways to reduce it, has been increasing recently with capital investments in the building and infrastructure sectors. This research aims to establish a reliable algorithm for simulating the behavior of reinforced concrete (RC) beams under thermal and structural loads. The proposed algorithm is based on the combination of thermal and structural analyses using the sequential link technique. These analyses use material characteristics such as conductivity, specific heat, stress–strain relationship, and thermal expansion to capture thermal and structural responses during the heating phases according to Eurocode 1 and Eurocode 2 using the finite element method. Beam models in the study, which have been exposed to the ISO-834 fire curve, were designed to exhibit flexural failure. Nonlinear numerical analysis results have mostly coincided with the previous studies regarding the residual load-bearing capacity. Depending on the outcomes of the previous experimental studies, an RC member’s structural strength increases when the internal temperature is between 150 and 250 °C and degradation starts after 300 °C. This outcome has been supported by the previous numerical and experimental studies, propounding the accuracy of preferred modeling and analysis approaches. As the essential distinctness of the research, the effects of elevated temperatures on the bonding behavior between concrete and rebar were considered for numerical analyses.

Iatrogenic subtrochanteric fractures are rarely encountered after cannulated screw fixation of femoral neck fractures; however, when they do occur, there can be several complications. Many orthopedic surgeons have concerns about the potential for iatrogenic subtrochanteric fractures after screw fixation distal to the trochanter minor; therefore, some surgeons are typically reluctant to perform this procedure. This study focused on the risk of an iatrogenic subtrochanteric fracture after treating femoral neck fractures with cannulated screws. The main purpose of the study was to understand iatrogenic subtrochanteric fractures and evaluate the effects on these fractures of an inverted triangular-shaped configuration for placement of the cannulated screws. A femur bone with an femoral neck fracture at a 40° incline to the horizontal plane was generated along with a representation of a three-dimensional finite element model, and three inverted triangular-shaped configurations for placement of the cannulated screws were investigated using finite element analyses. Statistical results indicated that the occurrence risk of ISF increases when the screw is located distal to the trochanter minor. Moreover, the risk of occurrence of intertrochanteric fracture increases when the screw is located medial to the trochanter minor because of local concentrated stress on the surface of the screw canals. To avoid the vulnerability of the subtrochanteric region, it was found that proximal placement of the screws using the inverted triangular-shaped configuration could yield better results. In addition, the results of this study provide suggestions on improved screw configurations.

Using a finite element strategy, this study investigates the behavior of beam-to-column connections in storage rack systems exposed to high temperatures. The purpose of this research was to develop moment−rotation (M−θ) curves after painting various structural members with varied configurations in order to evaluate the performance of intumescentcoated beams, uprights, and connectors, which are components of storage rack systems. Within the scope of this work, finite element analyses were carried out in two stages. First, thermal analyses were performed using the transient thermal analysis system of ANSYS Workbench software to estimate the ultimate temperatures of the beam, upright, and connector, which were painted with 1 mm thick paint and exposed to standard (ISO-834) fire. The results were then compared to the Eurocode 3 Part 1.2 with a satisfactory agreement. In the second stage of the analysis, a total of 9 possible alternative models were investigated in the static structural analysis system, reflecting the effect of applying fire protection to the different portions of the rack system. Since the most critical stress level is achieved around the connector tabs, it has been observed that protection of the connector in individual or binary conditions provides higher performance while protection of the beam causes divergent joint behavior. Additionally, comparison of fully protected and unprotected conditions presents an increment of more than 7% on the joint's ultimate moment capacity and initial stiffness, which is an explicit contribution of the intumescent coating to fire resistance.

No abstract