بررسي آزمايشگاهي تاثير ديافراگم محيطي و ورق ميان‌گذر در اتصال تركيبي المان‌‌هاي سازه‌يي فلزي و بتني

Experimental Investigation of Perimeter Diaphragm and Internal Plate Effects on Hybrid Connections of Steel and Concrete Structural Elements

يكي از راهكارهاي ارايه‌شده جهت بهبود رفتار اتصالات سازه‌هاي بتني در زلزله و رفع مشكلات عديده‌ي آن‌ها نظير ازدحام آرماتور، مهار آرماتور، و ... ، استفاده از تير فولادي به جاي تير بتني است. در اين پژوهش يك اتصال بتني به عنوان اتصال مرجع استاندارد و 3 اتصال تركيبي تير فلزي به ستون بتني شامل: 1) اتصال با ديافراگم‌هاي محيطي و ورق‌هاي ميان‌گذر، 2) اتصال با ديافراگم‌هاي محيطي و برش‌گيرهاي داخلي، و 3) اتصال تركيبي پس‌تنيده، ساخته شده و تحت بارگذاري چرخه‌يي مورد آزمايش قرار گرفته‌اند. در كليه‌ي اتصالات تركيبي مورد بررسي، ستون بتني در ناحيه‌ي اتصال توسط غلافي فولادي محصور شده است. با مركب‌كردن اتصال، مقاومت بيشينه‌ي نمونه‌هاي تركيبي با ديافراگم و ورق ميان‌گذر، با ديافراگم و برش‌گير و اتصال پس‌تنيده نسبت به نمونه‌ي بتني مرجع به ترتيب به ميزان 39 ، 389، و 156 درصد افزايش يافته است. همچنين افزايش شكل‌پذيري اتصالات تركيبي با ديافراگم محيطي و ورق ميان‌گذر و اتصال تركيبي با برش‌گير نسبت به نمونه‌ي بتني به ترتيب به ميزان 118 و 25 درصد مشاهده شده است.

For several years, hybrid structures such as CFT and RCS have been studied and their good performance has been proved. By applying the benefits of concrete and steel together in hybrid systems, a connection with good performance is achieved. Composite structures have been widely used in the construction of buildings due to their excellent static and earthquake resistant properties, such as high strength, high ductility, and large energy dissipation capacity. In this paper, an experimental investigation of the perimeter diaphragm and internal plate effects on a hybrid connection of steel beam to concrete column has been conducted. So, a concrete connection and three composite connections were constructed and tested under cyclic loading. A concrete connection was the standard reference connection and the following three connections were proposed as composite connections of steel beam to concrete column: perimeter diaphragm and internal plates, perimeter diaphragm and inner shearheads, and post tensioned composite. In all these composite connections, the concrete column in the panel zone has been confined with a steel sheath. The perimeter diaphragm makes the plastic hinge form at a distance from the connection bay and column edge, and the connection elements remain in an elastic state. The results indicated that composing the connection created an increase in loading capacity and energy dissipation. An increase in the ductility of composite connections with the perimeter diaphragm in comparison with the reference concrete connection was also observed. By composing the connection, the maximum strength of specimens with a diaphragm and internal plates, the connection with diaphragm and shearheads, and the post tensioned connection, in comparison with the reference specimen, was increased 239,389,156 percent, respectively. Also, the ductility increase of specimens with diaphragm and internal plates, and with shearheads, in comparison with the concrete specimen, was 118.25 percent.