Izian Abd. Karim

A two-step Taylor-Galerkin formulation for fast dynamics

Purpose – The purpose of this paper is to present a new stabilised low-order finite element methodology for large strain fast dynamics. Design/methodology/approach – The numerical technique describing the motion is formulated upon the mixed set of first-order hyperbolic conservation laws already presented by Lee et al. (2013) where the main variables are the linear momentum, the deformation gradient tensor and the total energy. The mixed formulation is discretised using the standard explicit two-step Taylor-Galerkin (2TG) approach, which has been successfully employed in computational fluid dynamics (CFD). Unfortunately, the results display non-physical spurious (or hourglassing) modes, leading to the breakdown of the numerical scheme. For this reason, the 2TG methodology is further improved by means of two ingredients, namely a curl-free projection of the deformation gradient tensor and the inclusion of an additional stiffness stabilisation term. Findings – A series of numerical examples are carried out ...

Evaluation of response modification factor for steel structures with soft story retrofitted by viscous damper device

The soft story located in the basement of tall buildings for parking or shopping lot. Considering the limitation in architecture, these structures may be retrofitted by implementing earthquake energy dissipation such as viscous damper devices in soft story level. Nevertheless, an extensive review of related literature indicates that the effect of viscous damper on response modification factor is not considered. Therefore, this study proposed the response modification factors for steel structures furnished with viscous damper devices in soft story level and investigated the effect of implementing such devices on the response modification factor. In this research, steel structures with numerous stories were considered to evaluate the response modification factor, which was formulated based on three aspects, namely, strength, ductility, and redundancy factors. Quasi-static nonlinear analysis was performed using finite element software based on structural models equipped with damper devices installed in different locations of the parking level. No open bay is available in other floors to install the damper devices. Meanwhile, the overstrength, ductility, and response modification factors were established by conducting pushover analysis. Results of the study revealed that the response modification factors for structures equipped with damper devices are higher than those of structures without damper devices. Moreover, the value of response modification factor was affected by the number of stories and number of dampers. Considering the analytical results for different cases, the equation for determining the response modification factor for steel structures furnished by viscous damper devices in soft story level was proposed.

Dynamic Analysis of Variable Stiffness Bracing System in Structure

In this paper, the application of a variable stiffness bracing (VSB) system in structures subjected to earthquake excitation is presented. The considered variable stiffness system is includes of four curve leaf springs. The nonlinear geometry of leaf springs which are acting as bending component lead to nonlinear stiffness performance. The variable stiffness bracing system does not act much for small to intermediate vibration amplitudes but it’s operated to control unpredictably large story displacement. It means this retrofit’s technique avoid an increase force in structural component due to ordinary brace action. The single degree of freedom system (SDOF) is considered and dynamic analysis of aforementioned system, with Bare and normal braced frames are conducted and the results are compared. The efficiency of the proposed system is discussed and proved in light of numerical analysis.

Composite Slab Numerical Strength Test Method Under Partial Connection Approach

The present uneconomic strength determination approach for profiled composite slab (PCS) constitutes a serious challenge that contributed significantly to design conservatism. This study seeks to address this challenge by developing and a subsequent experimental validation of a numerical strength determination function for PCS through implementing a rational-based approach. Hence, a procedural algorithm lead to the development of PCS determination function using longitudinal shear estimation method by considering section slenderness and deck characteristics. The strength test performance between the developed scheme and the experiment-based test results indicates high similarity, demonstrating the viability of the proposed strength determination methodology developed.