Resolution of Collapse Mechanism of Timber Space Frames Subjected to Excessive Snow Load and Practical Formulation to Predict their Critical Performance.

1. 通过对历年大雪季节木质建筑破坏情况的调查，发现木质建筑的整体倒塌主要发生在木结构结构陈旧和雪荷载过大的情况下。此外，本研究的问卷调查结果表明，由于缺乏人力、设备和智慧来清除屋顶上的积雪，最近我们生活方式的变化容易导致我们的房屋承受过多的雪负荷。通过对杉木榫卯简支柱各种屈曲试验数据的分析，建立了房屋柱屈曲荷载的预测方程。对于简支细长柱，屈曲荷载可用欧拉方程计算，对于大柱，可用修正的Johnson方程计算。3 .对于典型的雪区木结构房屋框架模型，通过参数化分析研究墙体体积及其布置方式对屈曲荷载或相关倒塌模式的影响，结果表明，导致其全部倒塌的条件仅限于一些无承重墙或几乎破旧的裸骨架。通过对典型的日式屋架的竖向荷载试验及有限元分析，明确了屋架的倒塌是由于屋架梁的弯曲断裂或屋架梁节点的拉伸断裂造成的。最后，在总结上述重要成果的基础上，提出了过度屋面雪荷载作用下木结构房屋极限承载力预测的原则和框架。

1. Based on the survey of damages of wooden buildings in past seasons of heavy snow, it was found that the total collapse of such buildings occurred when they were made of decrepit timber-frames and also when they suffered excessive snow load. In addition, answers to questionnaires in this study showed that the recent change in our lifestyles was liable to result to excessive snow loads to our houses due to the lack of human power, equipments, and wisdoms for the removal of snow from the roofs.2. An equation to predict the buckling load of columns in houses was formulated through the data analysis of various buckling tests of Japanese cedar simple columns with tenon joints. The buckling load can be estimated by the Euler equation for slender columns with simple supports and by the modified Johnson equation for large ones.3. For the typical frame models of wooden houses in snowy regions, the parametric analytical study to examine the effects of wall volume and their arrangements on the buckling loads or their relevant collapse modes showed that the condition that causes their total collapse was restricted to some bare-like skeletons such as those with little bearing walls or with almost decrepit ones.4. The vertical loading test of a typical Japanese-style roof truss and its relevant finite element analysis clarified that the roof truss will collapse either by the bending break of its beam or by the tensile break of a joint of the beam.5. Finally, the principle and the framework to predict the ultimate capability of timber frame houses subjected to an excessive roof snow load are proposed by summing up the above important results.