Study on prevention of overturning failure of concrete masonry garden walls during an earthquake

本研究的主要目的是研究混凝土砌块花园墙的抗震性能，并提出一种加固方法，以防止抗震能力较差的砌块花园墙在强震中发生倾覆破坏。在这项研究中，对下列砖墙进行了实地调查：a)1995年Hyogoken-Nanbu地震中幸存下来的1220堵砖墙；b)1997年鹿儿岛地震中受损或未损坏的79堵砖墙；c)大分市现有的1032堵砖墙；d)神户、鹿儿岛和大田的34堵加固砖墙。此外，调查人员还使用了1995年Hyogoken-Nanbu地震后大约两周调查的236堵砖墙的调查结果，并将地震破坏与砖墙的结构细节、结构细节进行了比较研究表明，竖向配筋、钢筋混凝土基础和相交墙体对墙体的抗震安全起着非常重要的作用。针对大分市现有墙体抗震性能较差的现状，根据现场调查结果，对抗震性能较差的墙体进行了加固处理。结果表明，将砌块墙体与相交墙体连接起来对提高其抗震性能是非常有效的，这种加固方法可以应用于各种既有砌块墙体。最后，提出了采用相贯墙体和钢柱加固的设计方法。

Main objective of this research is to investigate the seismic resistance of concrete block masonry garden walls and to propose a strengthening method for preventing the masonry garden walls with poor seismic resistance from overturning failure during severe earthquakes. In this research, field investigations of the following masonry garden walls were conducted:a) A total of 1220 masonry walls survived during the 1995 Hyogoken-nanbu earthquake.b) A total of 79 masonry walls damaged or undamaged during the 1997 Kagoshimaken-hokuseibu earthquake.c) A total of 1032 existing masonry walls in Oita City.d) A total of 34 strengthened masonry walls in Kobe, Kagoshima and Oita.In addition, the investigation results of 236 masonry walls which were surveyed by the investigators about two weeks after the occurrence of the 1995 Hyogoken-nanbu earthquake were also used in this research.By comparing earthquake damage to the masonry walls with their structural details, it was indicated that vertical reinforcing bars, reinforced concrete foundations and intersecting walls play very important roles for seismic safety of the masonry walls. The investigation results of the masonry walls in Oita City showed that the seismic resistance of most existing walls is very poor.Based on the results of field investigations, strengthening methods for masonry walls with poor seismic resistance were examined. As a result, it was concluded that connecting masonry walls to intersecting walls is very effective for increasing their seismic resistance and this type of strengthening method can be applied to various existing masonry walls. Finally, a design method for strengthening by using the intersecting walls and steel pillars is proposed.