چكيده فارسي :
يكي از مناسب ترين روش هاي ارزيابي عملكرد لرزه اي، بررسي خسارت هاي ايجاد شده در اجزاي سازه است. شاخص هاي خسارت معيارهايي هستند كه سعي مي كنند با رصد چند متغير خسارت، آسيب هاي ايجاد شده در اعضا و كل سازه را كمي كنند. يكي از مهمترين شاخص هاي خسارت موجود شاخص خسارت پارك- انگ است كه خسارت اعضا را به صورت تركيب خطي خسارت هاي ناشي از بيشينه تغييرشكل ها و رفتار چرخه اي بيان مي كند. در اين مقاله شاخص خسارت پارك-انگ در سطوح عملكرد لرزه اي سازه هاي بتن مسلح مورد بررسي قرار گرفته است. براي اين منظور سه قاب خمشي بتن مسلح با تعداد طبقات مختلف در نظر گرفته شده و بر اساس آيين نامه هاي عملكردي و با تحليل ديناميكي غيرخطي تاريخچه زماني در سطوح عملكرد طراحي شده اند. قابها تحت هفت شتاب نگاشت، تحليل ديناميكي غيرخطي شده و در نهايت بر اساس نتايج حاصل، تحليل خسارت روي آنها صورت گرفته است. بر اساس نتايج حاصل نحوه ارتباط ميان شاخص خسارت پارك- انگ و معيار طراحي در آيين نامه هاي عملكردي و همچنين ارتباط ميان شاخص خسارت ها مورد ارزيابي قرار گرفته است. در اين مطالعه حدود شاخص خسارت پارك- انگ در سطوح عملكرد تعيين شده و مشاهده شد كه اين شاخص هاي خسارت در سطح عملكرد آستانه فروريزش نياز به بررسي بيشتر دارد. اين شاخص خسارت حساسيت كمي نسبت به خسارت هاي ستون داشته و نمي تواند خسارت هاي ناشي تمركز خسارت در يك طبقه را به طور مناسب تبيين كند.
چكيده لاتين :
The main goal of seismic design is to provide required safety level during earthquake, and to make a structure remain repairable. According to the available reports of recent earthquakes, structures designed using force based design procedures are not precise enough in eliminating the damage of structures. Therefore, a new generation of design codes based on the performance level design procedure is introduced. In order to estimate the amount of damage in structural elements, related criteria are defined as damage indices. Damage indices are functions of damage variables and indicate the effect of the variables on the element’s damage. Park-Ang damage index is among the most important damage indices, which shows the damage of reinforced concrete elements as a linear combination of maximum deformations and absorbed cyclic energy. The analytical value for this damage index is set to be zero if there is no damage, and 1.0 for the collapse of the element. The Park-Ang damage index in non-negative and shows the reduction of element’s resistance in cyclic loading. It also specifies energy dissipation and the strength damage of the elements. This factor has been used for calibrating damage index. It has been found that the damage index is merged with one in the failure point. Applying this model in structural systems requires determination of an overall member’s deformation. Since inelastic behavior is limited to plastic zones adjacent to the ends of a member, it is difficult to define the relationship between overall member deformation, local plastic rotations and the damage index. Therefore, a modified version of this model has been developed by Kunnath et al.
The most important difference between Kunnath model and Park-Ang model is representing the equation based on the moment-curvature diagram and replacing the non-dimensional factor with the strength deterioration factor in a hysteretic model. Supposing this factor as a constant will increase the diversion of the damage index in collapse prevention performance level. In this paper, the Park-Ang damage index and its improved relations has been evaluated for the various performance levels, including immediate occupancy, life safety and the collapse prevention levels. For this purpose, three reinforced concrete frames with different numbers of stories, was each designed for three performanc levels. Nonlinear dynamic analysis has been carried out with seven earthquake acceleration records. Finally, the damage analysis has been performed. The damage index has been derived for all of the nine frames and the values of damage indices have been evaluated. The beam damage indices are related directly to the rotation which happens in the plastic hinges. In components with immediate occupancy level, this linear characteistic is more clear; however, by increase in the rotation of the componenets or in the collapse prevention level, damage indices will diverge more. It has been shown that this damage index needs to be investigated at the collapse prevention level and the second part of the damage index (strength damage) shall be determined by the element’s type and level of performance. The sensitivity of damage index to the column damages is little and the damage caused by the weak story is low and needs to be evaluated.
