Shahrizan Baharom

Self-adaptive conjugate method for a robust and efficient performance measure approach for reliability-based design optimization

The advanced mean value and hybrid mean value methods are commonly used to evaluate the probabilistic constraint of reliability-based design optimization (RBDO) problems. These iterative methods can yield unstable solutions to highly nonlinear performance functions. The conjugate gradient analysis (CGA) and modified chaos control (MCC) algorithms have recently been employed to achieve the stabilization of reliability analysis in RBDO problems. However, the CGA and the MCC methods can be inefficient for convex performance functions. In this paper, a self-adaptive conjugate gradient (SCG) method is proposed to improve the efficiency of the minimum performance target point (MPTP) search based on an adaptive conjugate scalar factor for highly nonlinear concave and convex problems. With this aim, the conjugate search direction is adaptively computed using the mean value of the previous performance function with a limited conjugate scalar factor. The efficiency and robustness of the proposed SCG algorithm are compared with those of different reliability methods using five nonlinear concave/convex reliability problems and two mathematical/structural RBDO examples. The results indicate that the SCG method accurately converges after less iterations compared to other existing reliability methods. The SCG method is a robust iterative formula for inverse reliability analysis and RBDO.

Evaluation of steel shear walls behavior with sinusoidal and trapezoidal corrugated plates

Reinforcement of structures aims to control the input energy of unnatural and natural forces. In the past four decades, steel shear walls are utilized in huge constructions in some seismic countries such as Japan, United States, and Canada to lessen the risk of destructive forces. The steel shear walls are divided into two types: unstiffened and stiffened. In the former, a series of plates (sinusoidal and trapezoidal corrugated) with light thickness are used that have the postbuckling field property under overall buckling. In the latter, steel profile belt series are employed as stiffeners with different arrangement: horizontal, vertical, or diagonal in one side or both sides of wall. In the unstiffened walls, increasing the thickness causes an increase in the wall capacity under large forces in tall structures. In the stiffened walls, joining the stiffeners to the wall is costly and time consuming. The ANSYS software was used to analyze the different models of unstiffened one-story steel walls with sinusoidal and trapezoidal corrugated plates under lateral load. The obtained results demonstrated that, in the walls with the same dimensions, the trapezoidal corrugated plates showed higher ductility and ultimate bearing compared to the sinusoidal corrugated plates.

Predicted behaviour of partially restrained connection with cold formed high strength steel by 3D finite element modelling

Thispaper investigates the behavior prediction of partially restrained (PR) connection with high strength steel bythree-dimensional nonlinear finite-element (FE) analyses. The connectionmodel is such that angle cleats are represented by radiuses corner section shell elements. The full interaction between angle and beam and/or column is simulated by contact element. The analysis results of the moment- rotation relationship and behaviour characteristic of the connection with high strength steel are compared and discussed. It is found that contact element and strength enhancement of the corner regions employed to the model are very important parameters for accurate prediction of PR connection behaviour with cold-formed high strength steel. The moment capacity prediction of top and seat angle connections based on EC3 has been shown to be reasonable compared with FE modeling. Theproposed connection FE model is capable of predicting the ultimate load capacity and the plastic strain pattern with good accuracy. The model presented gives excellent results for increasing the connection capacity significantly due to employed higher strength steel section.

Quantification of delamination in a composite floor using a novel damage index

ABSTRACT The delamination of concrete from steel decking will reduce the strength and decrease the stiffness of the composite slab. Visual monitoring of delamination is typically not possible in many cases. A possible alternative is ultrasonic-based health monitoring. In this study, a novel damage index (DI) based on the absolute energy change (AEC) of the ultrasonic waves is adopted to quantify delamination damage in the composite floor. AEC-DI was constructed based on the decomposed signals provided by the wavelet transform. The monitoring process of the composite floor was conducted ultrasonically under flexural loading. An ultrasonic surface (Rayleigh) wave is employed for damage detection using gel-coupled piezoceramic sensors. The results revealed that the reliability and accuracy of AEC-DI in detecting composite floor separation is better than that of RMSD-DI.