عنوان مقاله
واکنش سیسمیک غیرخطی چهارچوبهای مستحکم با یک مرکز با استفاده از مدلهای المان محدود
فهرست مطالب
مقدمه
اجرای آزمون آزمایشی و نتایج
مدل عددی
مطالعه پارامتری
نتیجه گیری
بخشی از مقاله
شبیه سازی های سیکلی
باریکی قابل قبول سازه بست نشان داده شده است تا نه تنها به ظرفیت کمانشی خودش ، بلکه همچنین به شکل پذیری و قابلیتهای اتلاف انرژی خودش نیز تاثیر بگذارد. Eurocode 8 محدودیتهای مربوط به نابسندگی طبیعی سازه های بست در CBFها را مشخص می سازد. در رابطه با سیستمهای بست ایکس، نابسندگی طبیعی می بایست محدود به 1.3 ≤ λ ≤ 2.0 و کمتر و یا برابر با 2.0 برای CBFها بجای چهارچوبهای بست ایکس باشد. آنچه که مربوط به منفعت قابل توجه می باشد این می باشد که نابسندگی طبیعی بست معمولا بدون در نظر گرفتن تاثیر صفحه اتصال مورد برآورد قرار می گیرد.
کلمات کلیدی:
Nonlinear Seismic Response of Concentrically Braced Frames using Frames using Finite Element Models Blank line 11 pt Blank line 11 pt J.P. English & J. Goggins College of Engineering and Informatics, National University of Ireland, Galway, Ireland SUMMARY This paper investigates the accuracy of three dimensional finite element models (FEMs) in predicting the response of dissipating members in a concentrically braced frame (CBF) under cyclic actions. The brace together with its connecting gusset plate are the main focus of this study. While it is acknowledged that the brace is the primary dissipating member of a CBF, the inelastic behaviour of the gusset plate as a second source of energy dissipation is of particular significance. A number of gusset-brace configurations were modelled with varying geometries and slenderness and verified against physical pseudo-static component and member tests. Recommendations are then made for modelling and designing end connections of brace members containing beam-column connections. Blank line 10 pt Keywords: Finite element modelling, gusset plates, concentrically braced frames, cyclic loading. Blank line 11 pt Blank line 11 pt 1. INTRODUCTION Blank line 11 pt Concentrically braced frames (CBFs) are an economic means of resisting lateral demands induced from earthquakes. This lateral resistance is predominately associated with the brace member, although a certain amount will inevitably come from the beam-column connection and the gusset plate. For simple CBFs, it is standard practice to ignore any lateral resistance from the connection of the brace member to the beam and column. In other words, the beam-column connections, as shown for example in Figure 1.1, are assumed to be pinned, when in fact the presence of the gusset plate can add significant lateral stiffness to the joint. The actual stiffness of the frame is complex in nature due to the behaviour of the gusset-brace system. When the brace member is subject to tension demands, the gusset plate will experience an added compressive stress in conjunction with the tensile stresses induced by the brace. This compressive stress is associated with the rotation of the beam-column joint as the CBF drifts laterally. The extent of this rotation is dependent on the amount of lateral drift and also the dimensions of the frame. The overall stiffness of the CBF is thus a combination of that provided by the brace member and gusset plate connection to both brace and beam-column. This total stiffness will vary significantly depending on the relevant level of frame drift. At low cyclic demands the stiffness of the CBF will have similar contributions from both the tension and compressive gusset-brace system. As these cyclic demands increase and the brace and/or gusset plate experience buckling from compression loading, the lateral stiffness of the frame will become predominantly dependent on the tension resistance of the gusset-brace system only. These observations were also made by Goggins et al. (2005) for cyclic tests on brace members only. Currently, standard practice in Europe (CEN 2004) is that CBFs are designed so that yielding of the diagonals in tension will take place before failure of the connections and before yielding or buckling of the beams or columns. In the analysis of the structure, in frames with diagonal bracings only the tension diagonals are taken into account, while in frames with V bracings, both the tension and compression diagonals are taken into account for the seismic action. If a non-linear static (pushover) global analysis or non-linear time history analysis is used and certain criteria are met, both
