Performance of a novel bent-up bars system not interacting with concrete

Increasing the bending and shear capacities of reinforced concrete members is an interesting issue in structural engineering.In recent years,many studies have been carried out to improve capacities of reinforced concrete members such as using post and pre-tensioning,Fiber Reinforced Polymer and other techniques.This paper proposes a novel and significant technique to increase the flexural capacity of simply supported reinforced concrete beams.The proposed method uses a new reinforcement bar system having bent-up bars,covered with rubber tubes.This technique will avoid interaction of bent-up bars with concrete.They are located in the zone where compressive and tensile forces act against one anothe匚The compressive force in the upper point of the bent-up bars is exerted to the end point of these bars located under neutral axis.Moreover,the tensile stress is decreased in reinforcements located under the neutral axis.This will cause the Reinforced Concrete(RC)beam to endure extra loading before reaching yield stress.These factors may well be considered as reasons to increase bending capacity in the new system.The laboratory work together with finite element method analysis were carried out in this investigation.Furthermore,bending capacity,ductility,strength,and cracking zone were assessed for the new proposed system and compared with the conventional model.Both the FEM simulation and the experimental test results revealed that the proposed system has significant impact in increasing the load bearing capacity and the stiffness of the RC beams.In the present study,an equation is formulated to calculate bending capacity of a new reinforcement bar system beam.

Novel decoupled framework for reliability-based design optimization of structures using a robust shifting technique

In a reliability-based design optimization (RBDO), computation of the failure probability (Pf) at all design points through the process may suitably be avoided at the early stages. Thus, to reduce extensive computations of RBDO, one could decouple the optimization and reliability analysis. The present work proposes a new methodology for such a decoupled approach that separates optimization and reliability analysis into two procedures which significantly improve the computational efficiency of the RBDO. This technique is based on the probabilistic sensitivity approach (PSA) on the shifted probability density function. Stochastic variables are separated into two groups of desired and non-desired variables. The three-phase procedure may be summarized as: Phase 1, apply deterministic design optimization based on mean values of random variables;Phase 2, move designs toward a reliable space using PSA and finding a primary reliable optimum point;Phase 3, applying an intelligent self-adaptive procedure based on cubic B-spline interpolation functions until the targeted failure probability is reached. An improved response surface method is used for computation of failure probability. The proposed RBDO approach could significantly reduce the number of analyses required to less than 10% of conventional methods. The computational efficacy of this approach is demonstrated by solving four benchmark truss design problems published in the structural optimization literature.

Border-search and jump reduction method for size optimization of spatial truss structures

This paper proposes a sensitivity-based border-search and jump reduction method for optimum design of spatial trusses.It is considered as a two-phase optimization approach,where at the first phase,the first local optimum is found by few analyses,after the whole searching space is limited employing an efficient random strategy,and the second phase involves finding a sequence of local optimum points using the variables sensitivity with respect to corresponding values of constraints violation.To reach the global solution at phase two,a sequence of two sensitivity-based operators of border-search operator and jump operator are introduced until convergence is occurred.Sensitivity analysis is performed using numerical finite difference method.To do structural analysis,a link between open source software of OpenSees and MATLAB was developed.Spatial truss problems were attempted for optimization in order to show the fastness and efficiency of proposed technique.Results were compared with those reported in the literature.It shows that the proposed method is competitive with the other optimization methods with a significant reduction in number of analyses carried.