斜撐構件斷面補強之實驗行為研究

Abstract

鋼結構特殊同心斜撐構架系統在過去的地震中發生許多破壞現象，主要問題在於斜撐構件的耐震行為不佳導致結構系統耐震能力較差，由於斜撐構件在特殊同心斜撐構架中除了是提供側向勁度與強度的主要構件外，在結構系統進入非線性行為後，也扮演系統主要消能角色，因此在大地震下將有大量的非線性行為發生，其常見的缺點包括受壓之挫屈強度過低、低週疲勞壽命不足以至於過早發生斷裂而韌性不足，更甚者引起斜撐構件周圍之接合板與梁柱接頭的破壞，或引發梁、柱構件發生扭轉等不穩定的破壞現象。本研究擬採類似的概念，但維持傳統斜撐易設計易施工之特性，以簡易的方式改善斜撐構件之耐震行為，並將對斜撐構件進行靜態往覆加載實驗，用以探討不同加工方式對斜撐構件行為的影響，實驗規劃八組斜撐構件試體，斷面類型均為寬翼斷面，加工方式分為三類，分別為UR、W與F三類，UR為原斷面，W類是在斜撐中間段腹板上補強、翼板上切削，F類是在斜撐中間段翼板上補強。實驗後依據結果，探討各試體之遲滯行為、試體指標強度(降伏強度、挫屈強度與最大受拉強度)、能量消散關係、面外位移量與中間段(700mm)曲率等影響。研究結果顯示，F系列試體在變形量較小時，比其他試體具有較高的指標強度，但斜撐構件到斷裂時所累積能量不會明顯增加，而W系列試體在斜撐構件斷裂時所累積的能量則較多，因此能兼具提升斜撐構件指標強度與累積消能。

The damages of special concentrically braced frame (SCBF) system have been commonly observed in the past earthquakes. The primary failure occurred in the braces. Braces are not only the structural members in SCBF to provide lateral stiffness and strength but also one of the most important parts to dissipate energy by their extensive nonlinear behavior. Under cyclic deformation, the braces show a few disadvantages including low buckling strength in compression and low fatigue life which results in premature failure and lack of toughness for the braces. In some cases, the failure of braces also causes damages to the brace to framing connections leading to torsional instability of beams, columns and frames. In this research, we apply reinforcement to the conventional brace members by adding steel plates or reducing section areas to widen the energy dissipation range of the braces. This approach of reinforced brace section will reduce the strain range of the braces and therefore increase their fatigue life. Eight specimens have been tested and all of them are wide-flange section with three types of reinforcement options. The first type is unreinforced section (UR). The second type is the section with reduced flange width and reinforced web (W series). The third type is the section with reinforced flange (F series). Based on the test observations and data analyses, the performance parameters of different specimens including the hysteretic behavior, strength (yielding strength, buckling strength and maximum tensile strength), energy dissipation, out-of-plane displacement, curvature of mid segment (700mm), etc., have been discussed. The results show that series F increases the strength of the braces efficiently, but the energy dissipation capacity is not obviously increased. Differently, series W increase the strength of the braces less efficiently, but the energy dissipation capacity is obviously increased.