اعتبارسنجي روش تحليل استاتيكي غيرخطي براي محاسبه‌ي تغييرمكان هاي لرزه ‌يي سازه هاي ديوار نگهبان ميخ‌كوبي شده

Verification of a Static Nonlinear Analysis Method for Estimation of Soil-Nailed Retaining Walls Seismic Deformations

در اين پژوهش، روش جديدي ارايه شده است كه با تركيب تحليل استاتيكي غيرخطي مدل كامل و تحليل ديناميكي يك سازه‌ي دو درجه‌ي آزادي قادر است تغييرمكان‌هاي ديوارهاي ميخ‌كوبي‌شده را در معرض تحريكات زمين‌لرزه محاسبه كند. دو منحني ظرفيت به‌دست‌آمده از تحليل هاي استاتيكي غيرخطي در برنامه‌ي تحليل سيستم دو درجه‌ي آزادي به عنوان اطلاعات ورودي استفاده و تحليل هاي استاتيكي غيرخطي با اعمال يك الگوي بار عمودي در پشت بلوك مسلح و روي سطح آزاد مدل چند درجه‌ي آزادي انجام شده است. نتايج تحليل هاي استاتيكي غيرخطي به‌صورت وضعيت نقاط خميري ارايه و با مكانيزم گسيختگي لرزه‌يي مقايسه و تطابق قابل قبولي بين نتايج روش پيشنهادي براي محاسبه‌ي تغييرمكان لرزه‌يي و روش تحليل ديناميكي كامل مشاهده شده است، در حالي كه روش پيشنهادي زمان تحليل را كاهش مي دهد. همچنين با توجه به نتايج حاصل، يك ابزار جديد تركيبي عددي و آزمايشگاهي براي ارزيابي آثار زلزله در سازه هاي ديوار نگهبان ميخ‌كوبي‌شده پيشنهاد شده است.

In recent years, due to the growing demand for high-rise structures, the use of soil-nailed walls has become increasingly common, particularly as a basement to provide sufficient parking space. However, the main concern when using soil-nailed cuts in high-seismicity regions is the performance of soil-nailed excavations during seismic loading. It is necessary to study the seismic performance of nailed structures for optimum design and it is useful to study displacement seismic design with a focus on displacement, instead of force, as the direct performance or damage indicator, to achieve these objectives. A method is proposed to evaluate the seismic deformation of soil reinforced structures using a combination of nonlinear static analysis of MDOF models and dynamic analysis of a 2DOF system. A computer program for dynamic analysis of nonlinear 2DOF systems was developed, in which seismic deformations of soil reinforced structures can be calculated. Two force-displacement relations, obtained from nonlinear static analysis, describe the characteristics of the whole structure and are used as the nonlinear stiffness of the 2DOF springs. Nonlinear static analysis was performed by applying a vertical load pattern behind the reinforced block and on the surface of the multi-degree of freedom model. Contours of the horizontal displacement and plastic strain from static nonlinear analyses are compared with the seismic failure mechanism of soil-nailed structures. Deformation of the soil nailed walls obtained from full dynamic analysis was used as a reference solution to ascertain the accuracy of the results given by the proposed method. Two soil-nailed structures were considered as case studies. 1940 El Centro and 1989 Loma Prieta were used to excite the models. A reasonable match was found between the results of the proposed method and fully dynamic analysis of the problem. The proposed method may be used effectively to perform a broad suite of parametric studies at the design stage. The above procedure can also provide a hybrid experimental and numerical tool for earthquake impact assessment of soil-reinforced retaining structures.