含剪力接頭鋼構造梁之耐火性能研究

Abstract

鋼構造建築物受火害時，因鋼材為高熱傳導性材料，對其防火性能與行為的了解極為重要。先前火害研究著重於梁、柱等結構構件，於小梁的研究較少。小梁的功用不在於貢獻整體結構於極限狀態下側向的強度與勁度，主要承載樓版傳遞的垂直方向作用力。一般小梁以鉸接與大梁接合，為一簡支梁。小梁與樓版受火害時，將降低兩者的承載力，影響其防火時效的主要參數為載重比(即承受載重和極限強度的比值)與樓版厚度。因受到樓版與大梁束制的影響，小梁受高溫時因熱膨脹將承受軸壓力，冷却時產生軸向收縮將有軸拉力。此溫度荷載將對小梁剪力接頭之剪力板與螺栓造成額外的作用力，可能會造成破壞。小梁受火害行為的建立有其重要性，本研究擬透過火害實驗與分析加以探討此一情形。

The understanding of fire resistance and behavior of steel structural buildings in fire is highly important because the steel is a thermal conductive material. Previous research concentrates on the members of girders and columns, but the research on the beams is much less. The steel beams are designed to carry gravity force transferred from the floor, but not to provide the lateral strength and stiffness for the structures in an ultimate state. The steel beams are usually joined to the girder by a hinged joint, and the beams act as a simply supported beam. While the steel beam and floord expose to a fire, their load-carrying capacities will be decreased. The majord variables affecting their fire resistances are the load ratio (the raito of applied load to the ultimate strength in ambient temperature) and slab thickness. Due to the restraining effects of the slab and girders, the steel beam will be subjected to axial compression caused by the thermal elongation in temperature rise. However, the steel beams will be tensioned due to thermal contraction in the cooling phase. The temperature loading will result in additional forces on the shear tab and bolts in the shear connection, and these forces may cause failure of the steel beams. This research will be conducted experimentally and numerically and to establish the behavior of the steel beams exposed to elevated temperatures.