ارائه مدل خرابي هيسترزيس براي سيستم ديوار برشي فولادي

ديوار برشي فولادي به علت مقاومت پس‍كمانشي بالا، شكل‌پذيري قابل‌توجه، مشخصه‌‌‌هاي هيسترزيس پايدار و سختي اوليه زياد، در حال حاضر به­عنوان يك سيستم باربر جانبي مناسب در نظر گرفته مي‌‌شود. جهت بررسي جامع عملكرد ديوار برشي فولادي، نياز به ارزيابي و پيش‌بيني رفتار غيرخطي آن و مدل‌هاي هيسترزيس تحليلي كه قابليت در نظر گرفتن همه‌ي مودهاي زوال را داشته باشند، مي‌باشد. يكي از مدل‌هاي هيسترزيس تحليلي جامع، مدل ايبارا-كراوينكلر زوال اصلاح شده‌ است. براي تعيين پارامترهاي مدل، ابتدا 60 عدد ديوار برشي فولادي يك طبقه با اتصال تير به ستون به صورت مفصلي و همچنين با ضخامت ورق مياني و طول دهانه مختلف با دو نوع فولاد مورد استفاده براي ورق مياني، به صورت عددي مدل‌سازي و تحليل شدند. با استفاده از نتايج تحليل، پارامترهاي مدل زوال واسنجي شده و سپس با استفاده از مشخصات هندسي و مقاومتي تأثيرگذار بر روي اين پارامترها، با تحليل وايازش (رگرسيون)، روابطي جهت تعيين پارامترهاي مدل براي ديوار برشي فولادي پيشنهاد شد. با توجه به نتايج، پارامترهاي اصلي تأثيرگذار بر روي ظرفيت برشي و سختي قبل و بعد از نقطه­ي تسليم، ضخامت ورق مياني و نوع فولاد استفاده شده براي آن و نسبت طول دهانه به ارتفاع ديوار برشي فولادي هستند كه نسبت طول دهانه به ارتفاع ديوار موثرتر است.

Nowadays, Steel Plate Shear Wall (SPSW) is considered as a suitable alternative to conventional lateral load resisting systems that used for earthquake resistant design of structures, because of high post buckling strength, significant ductility, stable hysteresis characteristics and high initial stiffness. Also, steel plate shear wall has lighter weight of structures, increased floor area, quicker speed of construction, significant economically affordable and high quality control compared to a traditional reinforced concrete shear walls. Study on behavior of steel plate shear wall began in 1970s with the aim of providing an easy method for the analysis and design. The initial experimental and analytical research clarified varies aspects of seismic behavior of steel plate shear wall, but it is still unknown, because of its complex behavior and design. Although some researches on steel plate shear wall has been done since the early 1980s, the appropriate performance of structures that had steel plate shear wall as lateral load resisting systems in the Northridge, USA (1994) and Kobe, Japan (1995) earthquakes caused researchers and working engineers to investigate and implement the steel plate shear wall system to a greater extent. Analytical and experimental research works and studies, provided primarily in Canadian, US and UK universities on steel plate shear wall considered different facets of the seismic behavior of steel plate shear wall and flourished the essential procedures for its application as an effective lateral load resisting system. However, in order to investigate the performance of steel plate shear wall comprehensively, wide range of nonlinear behavior has to be assessed and predicted and it requires hysteresis models that are capable to consider all deterioration modes. One of the comprehensive analytical hysteresis models is the modified Ibarra-Krawinkler (IK) deterioration model that provides four deterioration models including basic strength deterioration, post-cap strength deterioration, unloading stiffness deterioration and accelerated reloading stiffness deterioration for systems with bilinear, peak oriented and pinching behavior. In this study, by calibrating the modified Ibarra-Krawinkler deterioration model parameters for steel plate shear walls with different properties, some equations are proposed to determine modified Ibarra- Krawinkler deterioration model parameters. First, one of the experimental specimens was modeled and analyzed in ABAQUS software and accuracy of results was measured. Then, 60 number of pinned joints-one story steel plate shear walls with different infill plate thickness and bay length, using two types of steel for infill plate are numerically modeled and analyzed by ABAQUS software. Also, the height of steel plate shear walls was kept constant equal to 3500 mm. Using OpenSees software numerical analysis results, the modified Ibarra-Krawinkler deterioration model parameters are calibrated. Then, by identifying the effective and pertinent factors, some statistical equations are suggested. According to the results, effective parameters on lateral load resisting capacity, elastic stiffness and post capping stiffness were thickness of infill plate and its steel type and ratio of bay length to height of steel plate shear wall. Also according to the results, ratio of bay length to height of steel plate shear wall had more influence on modified Ibarra-Krawinkler deterioration model parameters.