ارايه‌ي روشي براي تعيين نيروي وارده بر ساختمان هاي با سيستم جداسازي لرزه ‌يي در ايران بر مبناي آيين نامه هاي ژاپن

Development of a Procedure for Evaluation of Seismic Forces on Buildings with Isolation System in Iran; Based on Japanese Codes

هدف از اين پژوهش، ارايه‌ي يك پروسه‌ي پيشنهادي براي تعيين نيروي وارده بر ساختمان هاي با سيستم جداسازي لرزه‌يي و طراحي آن‌ها در ايران است. بدين منظور آيين نامه‌ي طراحي ساختمان هاي با جداسازي لرزه‌يي ژاپن به عنوان مبناي پروسه‌ي پيشنهادي در نظر گرفته شده است. براي درنظرگرفتن شرايط ساخت‌گاهي و ضوابط آيين نامه ‌يي طراحي لرزه‌يي ايران، پارامترهاي: نوع خاك، تقسيم‌بندي مناطق لرزه‌يي، ضريب بازتاب ساختمان، طيف طراحي، زمان تناوب ساختمان ها و ضريب توزيع نيروي جانبي در ارتفاع در دو آيين نامه با يكديگر مقايسه و نتايج اين بررسي و تطبيق پارامترها در پروسه‌ي پيشنهادي لحاظ شده است. به‌منظور ارزيابي پروسه‌ي پيشنهادي، چند مدل سازه‌يي در نظر گرفته شده و نتايج حاصل از پروسه‌ي پيشنهادي با نتايج تحليل هاي تاريخچه‌ي زماني غيرخطي مقايسه شده است. نتايج تحليل ها بيان‌گر تخمين مناسب و قابل اطمينان مقادير پاسخ حاصل از روش پيشنهادي بوده است. به‌علاوه با توجه به نتايج، درنظرگرفتن ضرايبي براي لحاظ‌كردن اثرات حوزه‌ي نزديك در آيين‌نامه‌ي ايران ضروري به نظر مي‌رسد.

The base isolation system is a method developed to protect structures against earthquake excitations, which is designed and implemented based on seismic codes. The aim of this study is the development of a procedure in Iran for the seismic design of buildings using an isolation system. For this purpose, the Japanese Code for the design of base isolated buildings is considered the basis of the proposed procedure. The Building Standard Law of Japan and related Enforcement Order and Notifications have been substantially revised since the year 2000 to introduce a performance-based regulatory and deregulation system for building control systems. The verification procedures of seismic performance in the new code are, in essence, a blend of the equivalent single-degree-of-freedom modeling of a building and the site-dependent response spectrum concepts, which make possible prediction of maximum structural response against earthquake motions without using time history analysis. Simplified design procedures, based on the equivalent linear method for seismically isolated buildings, have been issued from the Ministry of Construction. To develop the procedure, we compared the Japanese and Iranian (Standard 2800) codes from different points of view. For example, parameters of soil type, seismic zone, design spectrum, fundamental period and distribution of seismic load in height are compared. By considering both codes, the procedure for seismic design of buildings with an isolation system in Iran is developed. Then, for evaluation of the procedure, several structural models were considered, and results are compared with results of nonlinear time history analyses. Based on analyses results, the responses of the structure models at near field were higher than far field excitations, by two times. In both far and near field records, base displacement responses (at the level of base isolation) were higher than base shear responses. In all models, the response of structures based on the proposed procedure was reliable. Also, it is necessary to consider factors for near field effects in the Iranian seismic code.