مدل‌سازي و بررسي رفتار اتصالات با مقطع كاهش‌يافته در تيرهاي دوبل ايراني

Modeling and Assessment of Reduced Beam Sections in Moment Resistant Connections of Iranian Double I-Beams

اتصالات مقاوم خمشي فولادي، به‌منزله‌ي فراگيرترين اتصال موجود در عرصه‌ي سازه هاي فولادي، بي ترديد نقش موثري در نيل به اهداف مقاوم سازي، قابليت اعتماد و صرفه‌ي اقتصادي در ساختمان هاي موجود دارند. براساس اين اهميت، بعد از زلزله ي نورثريج، ابداع اتصال RBS به عنوان نقطه ي عطفي در اتصالات مقاوم خمشي فولادي محسوب مي ‌شود. در اين مطالعه به بررسي رفتار لرزه ‌يي و نوع برش اتصال RBS با تضعيف بال و اتصال جديد AW-RBS با تضعيف جان در تيرهاي دوبل پرداخته شده است. اين بررسي ها با نرم افزار اجزا محدود ABAQUS انجام شده است. نمونه هاي مختلفي تحت بارگذاري چرخه ‌يي قرار گرفته و از لحاظ شكل پذيري، قابليت جذب انرژي، رفتار خميري مقطع تضعيف‌شده، سختي و مقاومت ارزيابي شده است. در ميان اتصالات بررسي‌شده‌، اتصال AW-RBS با كمينه‌ي افت مقاومت و سختي، 08/0 چرخش كل طبقه را تحمل كرده و نمونه ها با جذب انرژي و شكل پذيري بالا عملكرد بسيار خوبي در بارگذاري چرخه‌يي نشان داده‌اند.

Today, steel moment resistance connections are the most common type of connection widely used in steel structures, and they certainly play a significant role in retrofitting, reliability and economic benefits. Their use also improves the quality and useful life cycle of buildings. Considering their basic importance, and after the Northridge earthquake, the invention of RBS connections was a turning point in resistant steel moment connections. In RBS connections, a reduction of the beam flange at the end of the beam causes the plastic modules of the section to be reduced and the plastic hinge of the beam to be far from the column. This research observes the seismic behavior of the RBS connection, with a reduced section of the flange and a new AW-RBS with a reduced section of the web in a double section beam, which is particularly applicable in Iran. Double sections of I-beams have high torsional stiffness and are used in steel moment resistance frames. The seismic behavior of these frames needs to be investigated when conjugated with high performance AW-RBS connections. These observations are undertaken using ABACUS nonlinear finite element software. Experimental data from the literature were used for verification of our modeling in the finite element method. Many models were put under cyclic loads and ductility, and energy absorption and plastic behavior in the reduced section were studied. Parameter studies were included as the shape of cutting in the beam flange and the height of the web in double beams. Results from the studied connections show that AW-RBS has the least resistance and stiffness decrease; 8% has been cut off the rotation of the story and the models have acceptable behavior in cyclic loads. In double beam sections, the existence of two webs as folded plates in the reduced region causes the delay of lateral buckling and lateral torsional buckling, which makes the workability of the connection increase.