Key Engineering Materials Vols. 348-349

Abstract: In this study, an anti-plane crack in a functionally graded magnetoelectroelastic materials is investigated. It is assumed that the material properties such as elastic stiffness c44(y), piezoelectric coefficient e15(y), dielectric constant ε11(y), piezomagnetic coefficient α15(y), magnetoelectric coupling coefficient μ11(y) and magnetic permeability υ11(y) vary one-dimensionally on the ycoordinate with a series of functions f(y).An asymptotic analysis is done and the problem is solved by means of singular integral equation technique. The influence of the material inhomogeneity on crack tip stress, electric displacement and magnetic induction intensity factors are studied. The results are considered to reveal the effect of material inhomogeneity and geometry of the crack on the field intensity factors.

Abstract: Reduced Beam Section (RBS) moment connections are developed for Special Moment Resisting Frames (SMRF). According to the beam web attachment the column flange RBS connections are classified into Reduced Beam Section with Bolted web connections (RBS-B), and the Reduced Beam Section with Welded web connections (RBS-W). Beam flanges are welded to the column. Regardless of different web attachment details in RBS-B and RBS-W connections current design procedures (FEMA 350) assumes that they could develop plastic moment of the beam gross section. In current design procedures, RBS-B connections should provide the sufficient strength that can reach the plastic moment capacity of the connected beam. However, some experimental researches reported that the beams in RBS-B connections fractured before the connection reached its plastic moment capacity. Such undesirable fracture shows that RBS-B connections have less strength than RBS-W connections. And if RBS-B connections designed in current design procedures, it might fail in a brittle manner and not satisfy SMRF due to undesirable fracture. Thus, this study develops a new set of equations for accurately computing the moment strength of RBS-B connections. The proposed strength equation accurately predicts connection moment capacity for RBS-B connections.

Abstract: System identification(SI) techniques using dynamic responses and behaviors of structural systems become an outstanding issue of researchers. However the conventional SI techniques are identified to be non-practical to the complex and tall buildings, due to limitation of the availability of an accurate data that is magnitude or location of external loads. Thus a technique to estimate structural properties of building without input measurement data and using limited response is essential in structural health monitoring. In this study, the improved least square method for damage detection is proposed and verified by shaking table tests on three-story plane frame steel structures. In results damage detection was performed in each member level.

Abstract: In this study, the structural optimization of laminated composite plates for maximum buckling load capacity is performed by using genetic algorithm. The composite plate under consideration is a 64-ply laminate made of graphite/epoxy, is simply supported on four sides, and subject to in-plane compressive static loads. The critical buckling loads are determined for several load cases and different plate aspect ratios using 2-ply stacks of 02, ±45, 902. The problem has multiple global solutions, the results of which are compared with previously published results.

Abstract: In most studies, deterioration of concrete due to carbonation or chloride penetration is investigated separately. However, the deterioration of concrete is normally caused by the combination. The purpose of this study is to investigate the interaction between carbonation and chloride penetration and their effects on concrete. This was examined experimentally under various boundary conditions. For concrete under the double condition, the risk of deterioration due to carbonation was not severe. However, it was found that the carbonation of concrete could significantly accelerate chloride penetration. As a result, chloride penetration in combination with carbonation can cause harmful deterioration of concrete.

Abstract: The aim of this paper is to present the failure process of cement paste at different ages subjected to tensile loading. The input structure (cement paste) is generated by means of the cement hydration model HYMOSTRUC3D. A 2D-slice of this generated microstructure is subsequently transferred to the Delft Lattice Model, in which the failure process is analysed. Failure of cement paste microstructures at different degree of hydration, various water-cement ratios and different particle size distributions are analysed and discussed in the paper.

Abstract: The purpose of this study is to compare the seismic behaviors of interior post-tensioned (PT) and reinforced concrete (RC) flat plate slab-column connections designed to resist only gravity loads. In general, flat plate systems have been used to support gravity loads, which should be constructed with lateral system such as shear walls or moment frames. Flat plate systems should retain the ability to undergo the lateral drift associated with the lateral system without loss of gravity load carrying capacity. Although these systems are common, relatively little experimental study has been conducted to assess actual behavior under lateral loads. Therefore, this study was undertaken to assess the seismic performance of two PT and one RC slab-column interior connection under high gravity loads. This study observed that PT connections had a better seismic performance than corresponding RC connections in terms strength, deformability, energy absorption.

Abstract: A 2D rectangular plate model has been established to study the residual stress fields of cold expansion hole. Experiments were carried out to measure the residual stress of cold expansion hole and verify simulation results. The FEM results show, with interference values developing, the maximum values of circumferential residual compressive/tensile stress increase and higher positive stress values are obtained at the boundary of the rectangular plate. However, higher positive stresses at the boundary of plate are harmful to the capacity of fatigue resistance, the determinations of best interference value to a certain wide plate were proposed. Finally, the effect of the plate width on the residual stress distribution was analyzed.

Abstract: Economic losses due to the corrosion of steel structures in concrete is almost about 4% of GNP. It is almost 70 billion dollars in America. Also, The Korean economy is expected to experience a 4～5% loss in GNP in the near future in by considering the industrial background that has been formed by heavy industries. Although deteriorations in concrete structures demonstrate a high diversity of factors, it finally comes down to the lowering of water resistance performance in structures based on the crack generation due to the corrosive expansion of steel bars. Thus, it is very important to investigate the lowering of water resistance performance in structures according to the level of the corrosion in steel bars.