磚造古蹟及歷史建築物主要依賴砌築牆體抵抗地震力，牆體開裂後在面外地震力作用下，因構造本身缺乏韌性，經常產生無預警之傾倒。本文主要利用低降伏鋼其低降伏強度、高伸長率及塑性變形能力之特性，對磚造牆體進行面外補強以控制面外崩塌之發生，並藉由監測開裂處補強材料降伏時機而達預警功能。
本研究共計五道試體進行水平面外加載試驗，試體分為兩類型，分別為底部束制單向撓曲基本試體(47cm×154cm×23cm)與三邊束制鋼板補強具開口部牆體(383cm×133cm×11cm)。三道單向撓曲基本試體探討低降伏鋼板補強後受撓曲應力構件之行為。另兩道鋼板補強具開口部牆體，經由試驗記錄牆體之加載-面外變形關係、極限載重及破壞模式，並與文獻中無補強具開口部牆體相互比較，以討論補強前後牆體在性能上之提升。
經由試驗之探討，本研究獲得以下四點結論：
1. 低降伏鋼板補強後牆體初始剛度不變，破壞行為分三階段：(1)磚試體初始開裂，其破壞模式與無補強試體相同(2)鋼板與砌體介面於開裂區域脫膠(3)鋼板於開槽易降伏區受拉降伏伸長，並使試體開裂後強度可持續上升，但在設計上需注意受壓側之壓碎與劈裂問題。
2. 單向撓曲基本試體初始開裂載重較未補強試體提升25%-48%，極限加載提升115%-184%。本試驗採用0.42、0.8kgf/cm2兩種不同軸壓針對補強試體進行試驗，相較於本試驗砌體平均抗彎強度11.53 kgf/cm2，對試體撓曲應力強度貢獻僅為其4%，實際案例之灰縫強度較弱，軸壓之貢獻將較本文為大。
3. 具開口部牆體補強後可提升牆體強度與韌性，並使牆體整體強度較一致，初始開裂強度提升85%-99%，極限加載提升44%-56%，試體達極限加載後，仍可維持極限加載80%以上，變位角可持續增加至50/1000以上。
4. 鋼板開槽段之拉張應變建議以1/1000作為預警性基準，當此狀況發生，代表鋼板進入降伏階段，牆體開口角隅及窗臺可能產生細微開裂，此時便能進行必要之詳細檢測與適當修復工作。

The masonry wall subjected to the out-of-plane seismic loadings and the cracks have occurred, the lack of ductility leads the walls to immediate collapses without forewarning. This study focuses on retrofitting the wall structures to prevent them from tumbling down by using the low-yield point steel (LYS), which carries the characteristics of low yielding strength but exceptional ability of elongation and plastic deformation. Furthermore, when the out-of-plane bending causes the development of the wall cracks and yielding of the LYS, it can also be monitored and detected. Thus, the collapsing damage of the wall can be predicted and repaired in advance.
In this study, Three vertical flexure specimen in the first group are restrained only on the bottom edge, while two of those in the second group are with openings and restraints on three edges of the bottom and two vertical perimeters. The width, height and thickness of the specimens in the first group are 47cm, 154cm, and 23cm, and those of the second group are 383cm, 133cm, and 11cm, respectively. The out-of-plane force-deformation relationship, ultimate strength, and damage models of the wall specimens were investigated. The performances of the wall specimens before and after retrofitted by LYS were also compared to determine its effectiveness on improving the seismic capacity of the wall specimens with openings.
From the testing results, this thesis yields four significant conclusions as following:
Compared to non-retrofitted specimens, applying the low-yield point steel into the wall specimens didn’t change the initial stiffness of the wall specimens. And the behavior of the retrofitted specimens can be divided into three stages of: (1) firstly, the cracks occurred in the bricks (2) the ungluing occurred between the bricks and the LYS plate at the crack zones, and (3) the yielding and elongation of the LYS plate at the segment with slots provided the post-crack strengths of the specimens.
The cracking and ultimate strengths of the retrofitted specimens in the first group were raised 25~48% and 115~184%, respectively, compared to those of the non-retrofitted ones. For the wall specimens with openings, the LYS rose both of their ultimate strength and ductility. The cracking strength and ultimate strengths were raised 85~99% and 44~56%, respectively. The retrofitted wall specimens could resist 80% of the ultimate loading in the post-ultimate strength stage until the drift level reached 0.05.
It is recommended as the threshold of the forewarning when the tensile strain of the LYS plate at the segment with slots reaches 0.001. It indicates that, at this stage, the LYS plates have yielded yet the cracks may have occurred at the bottom and corners of the openings. Therefore, the wall should undergo detailed inspections and the appropriate repair can then be conducted.

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