中文摘要：

雷击起火对古建安全存在较大影响,主要分析了直接雷击引起古建木材着火的原因和途径,推导了计算古建引下线温升的公式,并和IEC62305给出的公式做了对比分析.结果显示：当引下线直径大于8mm时两公式计算结果基本一致,后者计算温升数值较前者高,在古建温升计算中选择前者更合理.引下线直径对温升影响较明显,雷电流大小对温升影响相对较小,引下线长度对温升无影响.同等条件下,不同材料的引下线温升从大到小顺序依次为钢、铝、铜.引下线搭接处过渡阻值对温升影响非常明显,当过渡阻值偏大时更易引起古建着火.引下线断开时,可能出现雷电放电火花引起古建着火.针对古建雷击易起火途径给出了相应的防护对策,其定量分析结果可为古建防雷提供一些参考.

英文摘要：

Lightning fires have huge influence on the security of ancient timber buildings.The causes and ways for ignition of ancient timber buildings from direct lightning stroke have mainly been analyzed in this paper.The formulas of temperature rise of down-conductor on ancient buildings were deduced and the comparative analyses with the formula from IEC62305 were performed.The results show that the two calculation results are basically consistent when the down-conductor is more than 8mm in diameter.On the whole,the latter calculation result of temperature rising is higher than the former.The former should be more reasonable in the temperature rise calculation on ancient buildings.The diameter of the round steel down-conductor has more obvious influence on the temperature rise,but the lightning current intensity has small influence on the temperature rise while the down-conductor length has no influence on temperature rise.Under the same conditions,the descending order of temperature rise of the down-conductor with different materials is as follows：steel,aluminum,and copper.The transition resistance of the down-conductor has obvious influence on the temperature rise.When the transition resistance of the down-conductor is too large,the fire disaster will be more easily caused at ancient building.When the down-conductor is disconnected,the spark fire of igniting ancient buildings will be likely caused by lightning.The corresponding protection countermeasures were put forward according to the fire approaches The results of quantitative analysis from this paper could provide some reference for lightning protection of ancient architecture.