鋼板補強方管鋼斜撐構件之實驗行為研究

Abstract

一般傳統同心斜撐構架主要是藉由斜撐構件提供側向的勁度與強度，斜撐構件可抵抗大部分作用於結構系統上之側向力，並在結構進入非線性階段後扮演結構主要的消能角色，然而以過往的經驗來看，同心斜撐構架在較大的地震力作用下仍有許多破壞的情況發生，常見的原因有斜撐構件的受壓挫屈強度過低、低週疲勞壽命不足導致斜撐提早斷裂以及降伏後的韌性變形能力過小等，甚至進一步造成接合角隅板或梁柱接頭的部分發生破壞，因此對於改善以上斜撐構件的缺點仍有進一步研究的空間。本研究以方管斜撐為研究對象，透過在斜撐上銲接鋼板的方式，希望能提高斜撐構件的低週疲勞壽命，並改善斜撐構件的韌性，增加傳統斜撐構件的消能能力，此外由於已有研究證實低降伏強度鋼為一良好的消能材料，因此本研究中也探討利用低降伏強度鋼補強斜撐構件的效果。 本研究設計八組斜撐並進行靜態往覆加載實驗來探討不同的加勁補強方式對斜撐構件行為的影響，試體主要可分為UR、F與W三大類，UR為原斷面，F類為在斜撐左右兩側銲接補強鋼板，而W類為在斜撐上下兩側銲接補強鋼板。根據實驗的結果分別探討各試體之遲滯行為、指標強度（降伏強度、最大受拉強度、挫屈強度）、累積消能關係以及中間段(900 mm)曲率等現象，而研究結果顯示，F類以及W類的補強方式皆可有效增加降伏及挫屈強度，並且能有效分散挫屈行為集中的狀況，其中F類試體若補強板的寬度超出斜撐寬度，則能發揮類似H型鋼之翼板功能，可以有效增加斜撐構件降伏後的韌性變形容量。

Brace members provide efficient lateral stiffness and strength in concentrically braced frame (CBF). Being the primary members to resist most of the structural lateral forces, the braces also dissipate energy by their nonlinear behavior. However, under severe earthquakes, it is common that the braces damage in CBFs. One of the most common reasons that the braces rupture is their insufficient low-cycle fatigue life which results in premature failure and lacking of ductility. Furthermore, the damage of braces possibly causes the damage of gusset plates, beam-to-column connections or structural components in the vicinity. To improve the typical failure modes of the braces, this research applies reinforced steel plates to the square hollow steel braces as a reinforcement option. This research also takes the advantage of low yield point steel (LYS100) to increase the ductility as well as the energy dissipation capacity of the reinforced steel plates. Test plan includes eight specimens under static cyclic loading. The specimens are categorized into three types, namely UR, F series and W series. UR represents the specimen with unreinforced section. F series are the specimens with the section reinforced on the right and left sides. W series are the specimens with the section reinforced on the top and bottom sides. According to the test results, the performance parameters of different specimens including the hysteretic behavior, nominal strength (yielding strength, maximum tensile strength and buckling strength), energy dissipation capacity and curvature of mid segment (900 mm), etc., have been discussed. The results show that the reinforcement strategies in both F series and W series are able to enhance the yielding strength and buckling strength of the braces. These strategies also slightly reduce the deformation concentration when brace buckles. Among the specimens, one of the most efficient options is to reinforce the brace with steel plates which is wider than the square hollow section and attached to the right and left sides of the cross section (F Series). This option is able to increase the ductility and the energy dissipation capacity of the braces.