Asian journal of civil engineering
Volume:16 Issue: 4, Aug 2015

The response of a steel moment resisting frame (MRF) depends on the specifications of its main components, namely the columns, beams and connections. One important connection element which can significantly affect frame behavior is the panel zone (PZ). The PZ is described to be an element mainly subjected to shear stresses and its failure mode is often governed by shear yielding. Several analytical models for PZ behavior exist, in terms of shear force-shear distortion relationships. Among these models, the Krawinkler PZ model is the most popular one which is used in codes. Some studies have pointed out that Krawinkler’s model gives good results for the range of thin to medium column flanges thickness. The model presented here is applicable to both thin and thick column flange. More than four-hundred beam-column connections are included in the parametric study, with varied parameters being: beam depth, column flange thickness, column web thickness, and beam flange thickness. The elastic stiffness, shear yield strength and ultimate shear strength of the PZ obtained from FE analysis, are compared with those obtained from available mathematical models to show differences, especially in the case of thick column flanges. In the paper a simple mathematical model for estimating the stiffness and shear strength in the PZ is introduced. In this model both shear and bending deformations are considered. A comparison between the results of proposed method herein with FE analyses shows the average error is significantly reduced which demonstrates the accuracy, efficiency, and simplicity of the proposed model.

Traditional limit-equilibrium techniques are the most commonly-used analysis methods for slope stability problems. Recently, finite element method has emerged as an efficient and viable tool for analyzing various geotechnical problems. The Strength Reduction Technique (SRT) technique enables the FEM to calculate factors of safety for slopes. Despite the SRT‟s many obvious benefits, it has not yet received widespread acceptability among geotechnical engineers for routine slope stability analysis. To help change this situation this paper will compare the method‟s performance to those of the most widely used limit-equilibrium methods on a broad range of slope stability problems. Keywords: Slope stability; limit equilibrium methods; finite element method; strength

Different methods are used for the formation of the null basis matrix of a structure followed by calculating the element forces when the force method of structural analysis is utilized. Singular value decomposition (SVD) method is one of the algebraic methods in force method that uses equilibrium matrix in its computation of finding element forces. By increasing the dimensions of the equilibrium matrix in large scale structures, the time needed for making orthogonal matrices grows. In recent decades many researchers have worked on block-diagonalization of structural matrices such as stiffness matrix in symmetric structures to reduce the computational time and simplify the equations. Block-diagonalization of equilibrium matrix can also reduce the computational time in algebraic force methods. In this paper block-diagonalization of equilibrium matrices of circulant structure is performed using Kronocker product and SVD method is utilized to calculate the block-diagonalization null basis matrix. Finally the results are compared to those of the method without block-diagonalization and other algebraic methods.

Alkali Activated Slag (AAS) concrete is a combination of blast furnace slag and alkaline solution that is used as a binder. In this paper, Taguchi method was used to design of AAS mixtures. By considering four affecting factors including concentration of sodium hydroxide (NaOH) solution, sodium hydroxide to sodium silicate ratio, alkaline solution to slag ratio, and aggregate content, the optimal mixture design that provides the maximum compressive strength and flexural strength was identified. To verify the results, the optimal mixture was produced and tested. The mixture resulted in more compressive strength and flexural strength than other mixes.

The barrel vaults are composed of member elements arranged on a cylindrical surface. This kind of structure is utilized to cover the long spans. In this paper, the hybrid charge system search and particle swarm optimization algorithm is improved and utilized to optimal design of single-layer barrel vault frames. Some modifications on parameter values are performed to enhance the performance of the hybrid algorithm. Comparison of the results with other meta-heuristic algorithms illustrates the efficiency of the hybrid CSS and PSO algorithm. Also some discussion on the loading conditions and group selecting are presented.

In this paper two recently developed meta-heuristic optimization methods, known as Colliding Bodies Optimization (CBO) and Enhanced Colliding Bodies Optimization (ECBO), are used for optimum nodal ordering to minimize bandwidth of sparse matrices. The CBO is a simple optimization algorithm which is inspired by a collision between two objects in one-dimension. Each agent is modeled as a body with a specified velocity and mass. A collision happens between pairs of bodies and the new positions of the colliding bodies are updated based on the collision laws. The enhanced colliding bodies optimization (ECBO) utilizes memory to save some best so-far-solution to improve the performance of the CBO without increasing the computational cost. This algorithm utilizes a mechanism to escape from local optima. The bandwidth of some graph matrices, which have equivalent pattern to structural matrices, is minimized using these approaches. Comparison of the obtained results with those of some existing methods shows the robustness of these two new meta-heuristic algorithms for bandwidth optimization.

This paper aims to develop an innovative statistical model for building vulnerability of 2004 Tsunami facts provided the factors affecting it. This vulnerability is based on parameters that may cause major damages to a building after the Tsunami. In this formulation, the influencing factors are taken into account through a specifically defined combination of six parameters. In this paper, an approach called discriminant analysis is applied for assessing the vulnerability of buildings based on a combination of different factors that affect the building resistance. From the results, building vulnerability index (B.V.I) model is estimated in accordance with structures which can be a key element to preparedness. The present data is applied on the suggested model and as an output the building vulnerability is obtained.

Pre-stressing is becoming a most common and indispensable technique in the recent past for beams and girders in buildings and bridges. This paper presents the application of Finite Difference Method (FDM) for finding deflections in Pre-Stressed Concrete (PSC) beams with non-prismatic sections. Equations are derived for dead and live load bending moment, eccentricity, and depth at any required section. Based on these equations, it is initially established that conventional techniques cannot be adopted for finding deflections in pre-stressed concrete beams with non-prismatic cross-sections and hence FDM was adopted as an alternative. The calculated deflections using FDM are compared with those obtained from equivalent STAAD.Pro. Model and they found to be in close agreement.