طراحي لرزه اي سازه ها با استفاده از "روش ضريب رفتار

Introduction of “Modified Response Modification Factor

در حال حاضر، در طراحي لرزهاي سازهها از دو روش نيرويي و تغييرمكاني استفاده مي شود. اخيراً محققان با تركيب اجزاي دو روش نيرويي و تغييرمكاني، روش سومي با عنوان روش طراحي لرزهاي مركب معرفي كردهاند. هدف از ارايه اين مقال ه، است كه از تركيب روش نيرويي استاندارد 2800 و روش « روش ضريب رفتار اصلاحشده » معرفي يك روش مركب جديد با نام تغييرمكاني نشريه 360 حاصل مي شود. در اين روش، ضريب رفتار با مشاهده رفتار واقعي سازه و بهره گيري از تحليل استاتيكي غيرخطي (تحليل پوشاور) تعيين ميگردد. براي ارزيابي روش پيشنهادي، دو قاب فولادي 5 و 7 طبقه، به دو روش نيرويي استاندارد 2800 و روش مركب ضريب رفتار اصلاح شده، طراحي شده و پاسخ هاي مختلف آنها مورد مقايسه قرار گرفته است. به دليل اينكه در بسط تيوري روش مركب پيشنهادي، از معايب روشهاي نيرويي و تغييرمكاني پرهيز شده است، پاسخ هاي لرزه اي همچون برش پايه طرح و تغييرمكان غيرارتجاعي سازه در اين روش با دقت بيشتري تعيين مي شود.

The traditional procedure for seismic design of building structures has been generally termed the force-based design (FBD) method. In the FBD method, the elastic seismic force acting on the structure is calculated first with the aid of a design acceleration response spectrum. This elastic force is then divided by a reduction factor called behavior factor R, representing the ductility and overstrength capacities of the structures. The implementation of FBD in seismic codes, does not clearly define the performance level. Furthermore, this method assumes the constant behavior factor values for the structures with the similar types of the lateral load resisting systems and do not take into account structure numeral properties same as the influence of the number of stories. These are some disadvantages of the FBD method that have been referred in many researches. So recently, procedures have been developed to substitute for this method. The design procedure would be more rational if the performance of the structure was quantified through a target value of deformation treated as an input variable in the design procedure. This target value of deformation can be assigned to different performance objectives and is the starting point for the development of the rather new displacement-based seismic design (DBD) method and is described in the some guidelines and publications as a performance-based seismic design method. The third and newest seismic design method is called the hybrid force/displacement-based design (HBD) method that adopts the seismic design philosophy based on both the resistance and the performance. The HFD method combines the best elements of the FBD and DBD methods and tries to avoid those ones, which are usually thought of as disadvantages. This research proposes a new hybrid force/displacement-based seismic design method that is named the modified behavior factor (MBF) method. The MBF method combines the FBD method of the Iranian Earthquake Resistance Design Code (Standard No. 2800) and the DBD method of the Iranian Instruction for Seismic Rehabilitation of Existing Buildings (Publication No. 360). Two 5 and 7 story frames with three bays have been seismicallydesigned by the MBF and the FBD methods and the results of them have been compared. The seismic responses of the MBF method are more precise than the responses of the FBD method.