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

本研究的主要目的是对混凝土砌块砌体园林墙的抗震性能进行研究，提出一种防止抗震性能较差的砌体园林墙在强震中发生倾覆破坏的加固方法。在本研究中，对以下砖石园林墙进行了实地调查：a)在1995年的小古根-南部地震中，共有1220座砖石墙幸存下来。b)在1997年鹿儿岛根-北武地震中，共有79座砖石墙受损或未受损。c)大分市现有的砖石墙共有1032座。d)神户、鹿儿岛和大分共有34座加固砖墙。此外，本研究还利用了1995年小古根-南部地震发生后约两周内调查人员对236面砖石墙的调查结果。通过对砌体墙的地震损伤与结构细节的比较，表明竖向钢筋、钢筋混凝土基础和交叉墙对砌体墙的地震安全起着非常重要的作用。对大分市砖石砌筑墙体的调查结果表明，大部分既有墙体的抗震性能很差。根据现场调查结果，对抗震性能较差的砌体墙体的加固方法进行了探讨。结果表明，砌体墙与相交墙连接是提高砌体墙抗震性能的有效方法，这种加固方法可以应用于现有的各种砌体墙。最后，提出了采用交墙加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.