Fatih Mehmet Özkal

A FULLY STRESSED DESIGN METHOD TO DETERMINE THE OPTIMUM STRUT-AND-TIE MODEL FOR BEAM–COLUMN CONNECTIONS

Topology optimization and strut-and-tie model methods have a remarkable success in the detailing of reinforced concrete structures, especially for discontinuity regions of the beam–column connections. However, it has always been complicated to determine an optimum design throughout all the offers of an optimization process, since it is not obvious which of the decision variables should be considered in order to select the optimum design. This paper presents the application of a new selection method on topology optimization and strut-and-tie modeling of the beam–column connections. A performance index formulation assists the selection of the optimum design from the process by considering the fully stressed design concept unlikely other performance indices. Former indices take just one of the structural criterions into consideration such as stress, strain energy, displacement, etc. The efficiency and capability of the approach have been demonstrated by the comparison of element removal criterions and different parameter values on several bidimensional design examples.

A computational and experimental study for the optimum reinforcement layout design of an RC frame

Purpose – Compared with conventional design methods, strut-and-tie modeling is a more suitable and even a superior method for the reinforcement layout design of structural members with uncommon geometrical shapes and/or regions essentially subject to shear effects. Because determination of the optimum strut-and-tie model for each of the members is an important task, implementation of a topology optimization method could be useful before the detailing stage. The paper aims to discuss these issues. Design/methodology/approach – Optimum reinforcement layout of a concrete frame was designed by an integrated approach, which consists of topology optimization and strut-and-tie modeling methods. Subsequently, an experimental comparison of the new model with the conventional model was performed based on their structural behaviors. Findings – Depending on the experimental results, it was concluded that the new integrated design method presents more successful results than does the conventional method for the design...

Finite element analysis of the impact of screw insertion distal to the trochanter minor on the risk of iatrogenic subtrochanteric fracture

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.

Experimental investigation on the applicability of geogrid: A comparison between conventional and hybrid-reinforced irregular reinforced concrete members

Since geogrid is a new and under-researched material in terms of reinforced concrete members, this study focuses on the experimental validation of the feasibility of this material to be used instea...