كليدواژه :
زوال سختي و مقاومت , اتصالات فولادي , رفتار غيرخطي , ورق‌هاي فوقاني وتحتاني , بار چرخه‌اي
چكيده فارسي :
جهت بررسي جامع عملكرد اجزاي سازه بايد بتوان رفتار آن‌ها را در محدوده‌ي وسيعي از رفتار غيرخطي ارزيابي و پيش‌بيني كرد و براي اين منظور نياز به مدل‌هاي هيسترزيس تحليلي است كه قابليت در نظر گرفتن همه‌ي مدهاي زوال سختي و مقاومت را داشته باشند. به منظور استفاده از اين مدل‌ها نياز به مجموعه‌اي از داده‌ها است كه بر اساس آن بتوان مدل‌ها را صحت سنجي كرد. در اين مقاله روابطي براي تعيين پارامترهاي مدل زوال اصلاح شده‌ي ايبارا-كراوينكلر در قابهاي خمشي فولادي در نواحي مفاصل پلاستيك تشكيل شده در تيرهاي I متصل شده به ستون‌هاي قوطي توسط ورق‌هاي فوقاني و تحتاني ارايه مي‌شود. به اين منظور ابتدا تعدادي اتصال مطابق ضوابط مبحث دهم طراحي مي‌شوند. در ادامه اتصالات طراحي شده به صورت عددي مدل‌سازي و تحليل مي‌گردند. با استفاده از نتايج تحليل عددي اتصالات، پارامترهاي مدل زوال واسنجي شده و روابط مورد نظر با استفاده از وايازش غيرخطي ارايه مي‌گردند.
چكيده لاتين :
Seismic design in current codes is elastic and the nonlinear behavior is only incorporated indirectly. Structures which are designed by these codes are subjected to large excessive inelastic deformations under heavy earthquakes, which could lead to undesirable response or even collapse of the structure. Although elastic methods have been satisfactory in the past, public demands are leading design procedures to higher levels of performance, safety and economy. So due to the above mandate, performance based design is suggested for the seismic design. Performance based design is defined as a design procedure in which the structure performs in a predefined manner under different levels of loading. Therefore, in order to determine structure behavior under different loading, analytical models are needed to predict structural components behavior. In many buildings, steel moment frames are used as lateral loading system. In the steel moment frames buildings, connections play an important part in seismic performance and ductility of the structure. On the other hand, I-beam sections with box columns sections are widely used in steel moment frames. As a result, it is of great importance to predict these type of connections’ behavior for the deformations in the nonlinear range. For feasibility of modeling of structural components considering stiffness and strength deterioration, relations are needed to correlate hysteresis model parameters to physical and geometrical factors, which practically determine deterioration. To obtain these relations, sufficient experimental results are required to calibrate deteriorating hysteresis model parameters. However due to the lack of enough experimental results for each particular connection, numerical models with acceptable accuracy could be used instead, and the obtained results can be used to calibrate the parameters. Considering the importance of I-beam to box column connections utilizing top and bottom plates and introducing these connections in the tenth code of Iranian national building regulations, and the WFP connections in FEMA-350 and AISC as one of the accepted connections, specifying the relations that determine the deterioration behavior of this type of connection is of particular importance. Thus the aim of this research is to propose relations in order to predict the behavior of the I-beam to box column moment connection . For this reason, WFP connections that were previously designed and tested by few researchers are used as the benchmark and verification samples. Essentially, the purpose is to propose relations to predict the behavior of these connections under cyclic loading considering all modes of stiffness and strength deterioration. The proposed relations made be simple and practical so that can be used in the design of structures. Hence, the simplified model of the concentrated plastic hinge can be used for both beam ends. To determine the behavior of these hinges under uniform cyclic loading, the Ibarra-Krawinkler hysteretic model is used. Deterioration model parameters are calibrated by using the results from numerical analysis and the intended relationships are represented by nonlinear regression. In conclusion, the detoriation model developed for WFP connections of I-beam to box column can provide efficiently for acceptance criteria of moment frames and can be used in special moment frames.
