鋼結構同心斜撐構架系統之靜態往覆載重實驗加載歷時評估

Abstract

目前規範中所採用的鋼結構靜態往覆加載實驗所施加的位移歷時，若直接施 加於鋼結構同心斜撐構架系統，實缺乏理論基礎。規範中的鋼結構靜態實驗加載 歷時，主要根據鋼結構抗彎構架系統的動力行為而決定，然而鋼結構抗彎構架系 統與同心斜撐構架系統在結構動力特性上有所差異，因此，用來決定同心斜撐構 架系統破壞行為及容量的靜態實驗加載歷時需要再重新研究探討。 本研究將選取一系列不同地震危害程度的地震歷時，分析同心斜撐構架系統 的非線性動力行為，歸納結構物在非線性動力分析中的破壞累積行為，並以靜態 往覆載重模擬類似的破壞累積行為，研究將提出適當的結構行為參數，用以表達 靜態實驗加載歷時。 所提出的加載歷時將以斜撐構件實驗及構架實驗驗證其破壞行為，第一年實 驗計畫規劃八組斜撐構件實驗，擬採用兩種斜撐長細比、四種靜態往覆載重加載 歷時，包括本研究分析將提出的方案，探討不同加載歷時對斜撐破壞行為的影 響。為了更進一步了解同心斜撐構架系統複雜的破壞行為，第二年實驗計畫規劃 兩組實尺寸斜撐構架實驗，探討同心斜撐構架系統在不同加載歷時作用下的構架 整體與局部破壞模式。實驗將配合有限元素分析以建立結構破壞行為與加載歷時 之關係。 研究目標將檢討現有靜態實驗往覆載重加載歷時，並提出適當歷時，以使類 似行為的結構系統與構件之靜態實驗結果，在評估結構破壞行為與容量時，更精 確且更具代表性。

Quasi-static cyclic testing has been a standard procedure to identify the performance of structural components and frame systems. The loading protocols are standardized in the provisions, where the universal quasi-static loading protocol for steel structures is based on the seismic responses of steel moment frame systems. However, different structural systems have different dynamic properties. The fundamental periods of steel concentrically braced frame (SCBF) system are usually shorter than those of steel moment frame systems, and the failure modes are also different for the two structural systems. As such, applying the universal quasi-static loading protocol to SCBF systems cannot accurately estimate the damage states of SCBF systems under seismic loading. Thus, it is essential to constitute a more representative quasi-static loading protocol for SCBF systems. This research will propose a quasi-static loading protocol for SCBF systems in terms of structural damage parameters, such as the cumulative plastic deformation, strain energy, etc. First, a series of ground motion records will be selected to represent various seismic hazard levels. The dynamic responses of SCBF systems to the ground motions will be summarized from non-linear dynamic analyses. A representative loading protocol will be proposed based on the analysis results, and then examined by component tests and frame tests. Eight brace components tests with two slenderness ratios and four different quasi-static loading protocols, including the proposed one from non-linear dynamic analyses, will be conducted in the first year of the proposed two-year research. The effects of quasi-static loading protocols on the brace components will be investigated. To further examine the complicated damage behavior of SCBF systems, two full-scale SCBF tests will be conducted in the following year. The global and local failure modes of the SCBF systems will be explored. The research will also employ finite-element analysis to help construct the relationship between the quasi-static loading protocols and the damage states of the structural systems. The research will investigate the current quasi-static loading protocols and propose a more appropriate loading protocol to present the failure modes of SCBF systems under seismic excitations properly. With the proposed loading protocol, engineers and researchers can estimate the performance and the capacity of the SCBF systems more accurately when conducting a quasi-static cyclic testing.