دانلود رایگان مقاله انگلیسی روش طراحی پلاستیک بر اساس عملکرد برای قاب هایی با مهاربندی کمانش تاب به همراه ترجمه فارسی
| عنوان فارسی مقاله: | روش طراحی پلاستیک بر اساس عملکرد برای قاب هایی با مهاربندی کمانش تاب |
| عنوان انگلیسی مقاله: | Performance-based plastic design method for buckling-restrained braced frames |
| رشته های مرتبط: | مهندسی عمران، مدیریت ساخت، زلرله و سازه |
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| توضیحات | ترجمه این مقاله به صورت خلاصه انجام شده است. |
| نشریه | الزویر – Elsevier |
| کد محصول | F487 |
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بخشی از مقاله انگلیسی: 1. Introduction Buckling-restrained braced frames (BRBFs) are emerging systems used as primary lateral load resisting systems for buildings in high seismic areas. The main characteristics of buckling-restrained braces (BRBs) are enhanced energy dissipation potential, excellent ductility, and nearly symmetrical hysteretic response in tension and compression. Different types of BRBs have been developed and tested in United States and elsewhere in recent years [1]. A typical BRB consists of a yielding steel core encased in a mortarfilled steel hollow section to restrain buckling, non-yielding and buckling-restrained transition segments, and non-yielding and unrestrained end zones (Fig. 1). The length of the buckling-restrained (core) segment of BRB is about 60%–70% of the total length between work points (e.g [2,3]). Axial forces in BRBs are primarily resisted by steel cores which are laterally braced continuously by the surrounding mortar and steel encasement to avoid their buckling under compressive loads. This allows the steel core to yield in tension and compression, thereby significantly increasing the energy dissipation capacities of BRBs as compared to conventional steel braces. A more comprehensive background on BRBs can be found elsewhere [4]. Recent analytical and experimental studies [5,6] have shown that BRBFs can be used to overcome several potential problems associated with the conventional steel concentrically braced frames (CBFs), such as, sudden degradation in strength and stiffness, reduced energy dissipation capacity, and limited ductility. Because of the nearly symmetrical behavior of BRBs in tension and compression resulting in much smaller unbalanced vertical brace forces, BRBFs also require smaller beam sections as compared to conventional CBFs with chevron bracing configurations [7]. It is expected that BRBFs will experience large inelastic deformation when subjected to major earthquake ground motions. However, most current seismic design methods are still based on the elastic analysis approach and use indirect ways to account for inelastic behavior. As such, the current performance-based design methodology relies heavily on an iterative ‘‘Assess Performance’’, ‘‘Revision Design, and ‘‘Assess Performance’’ process to reach a design capable of achieving the intended performance [8]. On the other hand, the proposed design methodology addresses the need for developing a systematic design approach that results in predictable and targeted seismic performance of structures under stated levels of seismic hazards. This in turn minimizes, if not totally eliminates, the assessment and redesign tasks as required by current code provisions. 6. Summary and conclusions A direct design methodology, called performance-based plastic design (PBPD), based on energy–work balance, pre-selected target drift and yield mechanism was developed in this study to achieve predictable behavior of BRBFs by incorporating the inelastic characteristics of components in the design. The PBPD design procedure is not too different from what is done in current practice, yet it can be readily incorporated within the context of broader Performance-Based Earthquake Engineering (PBEE) framework. It does differ from the way PBEE is practiced currently, which usually starts with an initial design according to conventional elastic design procedures using applicable design codes, followed by cumbersome and time-consuming iterative assessment process by using inelastic static or dynamic analyses till the desired performance objectives are achieved. The iterations are carried out in a purely trial-and-error manner. No guidance is provided to the designer as to how to achieve the desired goals such as, controlling drifts, distribution and extent of inelastic deformation, etc. In contrast, the PBPD method is a direct design method, which generally requires no evaluation after the initial design because the nonlinear behavior and key performance criteria are built into the design process from the beginning. In this study, this design methodology is applied to three low-to-medium rise BRBFs and the robustness and versatility of this method was evaluated by the seismic performance of these BRBFs under forty recorded ground motions representing the DBE and the MCE hazard levels. Following conclusions are drawn from the present study: 1. BRBFs designed as per PBPD methodology can successfully limit the maximum drifts within the pre-selected target drift level (1.75%), as well as achieve the intended yield mechanism under the DBE hazard level. The maximum drifts are generally uniformly distributed along the building height. 2. Mean values of maximum story drift ratios of the study BRBFs under the MCE hazard level are approximately 4%. However, previous experimental studies have shown that a well-detailed BRBF will experience minor damage at this drift level. 3. No iteration is required to achieve the desired performance objectives of all BRBFs since the inelastic characteristics of structural components and target drift ratio are directly considered in the design. Further, due to well-controlled drift, it is possible to achieve the desired seismic performance by neglecting additional force due to P-Delta effect in the design for simplicity. 4. The PBPD design base shears for the 3-, 6-, and 9-story BRBFs are 91%, 57%, and 64% of that calculated based on the modern codes. This indicates that a more economical design can be realized by the PBPD method, while maintaining the desirable seismic performance. |