現在，土壁の壁倍率は建築基準法施行令で定める0.5である．昭和56年建設省告示第1100号が平成15年国土交通省告示第1543号(以下，告示と呼ぶ)で改正され，そこで定める仕様とすれば土壁の壁倍率を1.0や1.5とすることができる.一方，本論で対象とした1990年以降1〗〜42)の実験結果では壁倍率は0.5を超えており，土壁の耐カ壁としての性能を再評価できる可能性がある．ただし，実験された土壁の仕様は様々に異なっているため，評価にあたっては，土壁における仕様規定の定め方を含む検討が必要である．%This paper discusses the coefficient of effective wall-length of mud wall examined statistically using the data in cyclic loading tests reported in late years. The coefficient of effective wall-length is called“Kabe-bairitsu”in Japan. The Kabe-bairitsu of Japanese mud wall is 0.5 in the Enforcement Ordinance of the Building Standards Law. The 135 experimental data of mud wall is gathered in the paper published from 1990 to 2015. The mud wall taken here is plastered in both sides and the width of 1.8 meters. The experimental condition is not necessarily same. The decision factor of the Kabe-bairitsu of mud wall was the yield strength P_y or the product of ultimate strength P_u by 0.2/D_s. More than 95％ of Kabe-bairitsu of 135 experimental mud walls were beyond 1.0. With disregard to the conditions of experiments and the specification of specimens, the average Kabe-bairitsu of 135 mud walls was 2.2 and the coefficient of variation was 0.25. Even if the dispersion is considered, the Kabe-bairitsu of Japanese mud wall seems to be more than 1.0 or 1.5.
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