Papers by Keyword: Finite Element Analysis (FEA)

Abstract: Extended stiffened end-plate connections are widely used in seismic area due to their good performance in terms of both resistance and ductility. The most of existing studies focused on the all-steel behavior of these joints, disregarding the composite action of the concrete slab that is generally disconnected. However, the presence of the concrete slab can have beneficial effects on the structural stiffness for both gravity and lateral loads. Hence, most of the building frames are usually designed considering steel-concrete composite solution. However, the slab can strongly influence the hierarchy between beam and column and the ductility of the joint. In this paper the influence of composite deck on the response of extended stiffened end-plate joins has been investigated by means of finite element analyses (FEAs). In particular, the following details have been investigated: (i) all steel joints without slab; (ii) steel joint with disconnected slab; (iii) composite joint.

Abstract: Recently, several lives were lost because of the collapse of structures under fire. Steel members are mainly used in the columns and beams of buildings for improving construction efficiency. The fire resistance of steel structure is very important because when it don’t have fire resistive covering, it rapidly changes with high temperature. In fire resistance design of steel, steel structure must have fire resistive covering. But many facilities as temporary facilities, parking lot don’t have it. The buckling behavior of steel structures under fire is also significant because it can cause local buckling failure through the reduction in structural material properties by temperature. In this study, the elastic buckling behavior of a circular steel tube under fire was investigated using finite element analysis. The parameters for this analysis used were, diameter–thickness ratio, fire exposure area, and fire scenarios. The elastic buckling strength of circular steel tube rapidly decreased when subjected to the fire curve. Local buckling occurred and this can lead to global failure. When fire resistance design of circular steel tube was performed, buckling behavior must be considered.

Abstract: Eccentrically braced frames (EBF) with detachable short links are an efficient solution for buildings in seismic areas owing to their high energy dissipation capacity and ductility and ease of repair in the earthquake aftermath. Past studies revealed that short links can develop shear overstrength (i.e. V_u/V_p, where V_u is the ultimate shear strength and V_p the corresponding plastic resistance) larger than the value recommended in EC8 [1] (i.e. V_u/V_p =1.5). One of the factors causing the higher shear overstrength is the presence of axial restraints that leads to the development of tensile forces in the link at large levels of rotation. Another reason for higher shear overstrength is the composite slab that can resist the shear distortion together with the short link. Within the DUAREM project [2], full scale pseudo-dynamic experimental tests were carried out on 3D EBF allowing thus the investigation of replaceable links considering two arrangements: (i) steel solution – the link was uncoupled from the slab (ii) composite solution – the slab and link are connected. The aim of this paper is to present the results of finite element analyses (FEAs), based on calibrated models and the comparison between the obtained results and the experimental tests performed by [2]. The numerical investigation carried out aims to evaluate the shear overstrength and the level of axial force in the link for both tested configurations.

Abstract: Steel eccentrically braced frames (EBFs) are expected to sustain damage during an ultimate limit state design level earthquake through repeated cyclic plastic deformation of the active link. Traditionally the active link has been integral with the collector beam, but following the 2010/2011 Canterbury earthquakes, the benefit of having a readily replaceable active link became apparent. The development of this was undertaken by New Zealand Heavy Engineer Research Association (HERA) and Steel Construction New Zealand (SCNZ), with input from the University of Auckland. This paper describes the finite element analyses performed to determine the behaviour of the system including the bolted endplate connections through the range of inelastic cyclic loading expected. The numerical simulations answer a number of questions, like at which loading cycle the von Mises stress is above 300MPa in collector beam adjacent to the removable link; history of all bolt forces; component forces (shear) in slab and removable link; rotation of the link versus cycles; equivalent plastic strain contour for the last cycle and others. This paper also describes how the interaction with the concrete slab was modelled in the elastic and inelastic range.

Abstract: In concentrically braced frames (CBF), gusset plates as the connected members are subjected to forces not only from brace but also from frame action. When the braced frame is deformed, the beam-column connection will deform, and the deformation of beam-column connection either “open” or “close” as the brace under “compression” or “tension”. Therefore, the design of gusset plate should consider the effect of such frame action, in addition of the brace axial load. Six finite element models were developed using ABAQUS to investigate the force distribution of gusset plate under the two actions. It is noted that force in gusset plate can be divided into two parts and frame action is so small that can be neglected during brace buckling.

Abstract: This paper aims to examine the cyclic behavior of panels in steel moment frame subjected to bidirectional and unidirectional loading and to demonstrate the differences of panel behavior under two loading modes. The specimens were composed of wide-flange beams and square tube columns, and the panel zones were designed to yield before columns and beams. Experimental results showed that specimens subjected to bidirectional loading suffered severe damage, caused by the weld fracture at the corner of panel-to-diaphragm weld, and failed at 0.06 rad and 0.04 rad story drift for specimens with panel aspect ratio of 1.4 and 2.0, respectively. Specimens subjected to unidirectional loading developed a story drift of 0.06 rad without strength reduction. The panels contributed about 60%-80% story drift and dissipated approximately 80% of total input energy. Panels with higher aspect ratio showed smaller plastic shear strength because of the effect of flexural yielding in panels. Moreover, the beams were found to present plastic moments 20%-50% lower than theoretical values, which was attributed to the small panel-to-beam strength ratio.

Abstract: The concept of moment resisting frames with K-type external braces is proposed to increase the lateral stiffness, which has short external span and large lateral stiffness. In order to investigate the lateral stiffness, overstrength coefficient and the reduction factor of K-type external brace under horizontal load, ABAQUS was applied to study the different slenderness ratios (from50 to 150) of K-type external steel braced frames. The results showed that the lateral load and displacement curve can be divided into elastic stage, the buckling of the compressive brace-yield of the tensile brace stage and plastic stage. The overstrength of K-bracing is related to the potential bearing capacity of the frame when the compressive brace buckled, and the potential growth of the tensile brace. The overstrength coefficient increases with increasing of the brace slenderness ratio. The range of recommended values of slenderness ratios of K-type external steel braces and design values of unbalanced force of column sections are proposed.

Abstract: A fully coupled thermo-electro-mechanical models of cylindrical and truncated conical GaN/AlN Functionally Graded Quantum Dot (FGQD) systems with and without WL are analyzed in this study to determine the effect of lattice mismatch strain grading on the electromechanical behavior of the FGQD system. This has a technological and fundamental importance because the production methodology adopted for manufacturing QDs enables the composition of the QD material to be graded in the growth direction, so the material properties as well as the induced mismatch strain between the QD and the carrier matrix are accordingly graded. The power law is used to describe the grading function. Based on the obtained results, grading of material properties and lattice mismatch strain have significant effect on the distribution of the electromechanical quantities inside the QD and can be used as another tuning parameter in the design of QD systems.

Abstract: High rotational motion from the welding tool generates a significant amount of the heat during friction stir welding (FSW). Basically, during FSW the heat is mostly coming from the frictional force between the tool shoulder and the plates. Therefore, a precise calculation of the friction coefficient can increase the accuracy of the finite element analysis (FEA) of the process. However, researchers have applied constant values, and that causes a gap between the reality and the simulated model especially after the welding plunging step. In this study, a mathematical formulation is proposed in order to calculate the temperature dependent values of the friction coefficient and also to explore the influence of the temperature in the friction coefficient. To solve the governing equations of the process, the MATLAB^® software is used. The results indicate that, from 25°C to the AA 6061-T6 melting point (580°C), the values of the friction coefficient fall steadily in a range of 0.207089 to 0.000582. Furthermore, the material shear stress and the material yield stress decrease consistently as the temperature rises. Consequently, the influence of the temperature in the contact input parameters and the material properties are discussed in detail and a good correlation with the published results is achieved.

Abstract: The effect of the elastic modulus of the adhesive for primer on the impact response of the steel butt joint bonded by multi-layer under the Izod impact test is investigated using the elasto-plastic finite element method (FEM). The results obtained from numerical simulation show that both the elastic strain and plastic strain occurred at the point 0.5 mm away from the upper or lower surface after a certain time is increased significantly when the elastic modulus of the primer is decreased from 2.875 GPa to 0.825 GPa. The absolute value of the stress Sx response at these to nodes is decreased when the elastic modulus of the primer is decreased. The value of the stress Seqv is the highest one after 0.1 ms at the points 0.5 mm away from the upper or lower surface when the butt joint is bonded by the multi layer consisted of Epoxy-Phenolic-Epoxy adhesives.