Residual Life Prediction of Historic Timber Truss Based on Strength Degeneracy Model
Residual Life Prediction of Historic Timber Truss Based on Strength Degeneracy Model
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发表时间：
2008
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通讯作者：
Wang Xue-liang
中科院分区：
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作者：
Wang Xue-liang
为了得到木结构的长期抗力与时间的关系，必须考虑荷载-历时效应、含水率和温度变化、腐朽和白蚁侵袭等因素etc.in。基于Gerhards损伤累积模型，推导了木构件在恒载作用下的强度退化模型，并以一个100- 200 m长的木结构为例，分析了荷载-历时效应对木构件长期抗力的影响。结果表明，木构件的长期抗力随时间的变化规律与荷载-历时效应有关。在不考虑其他因素变化的情况下，采用强度退化模型，对一根10年历史的木桁架在恒定荷载作用下进行了分析结果表明，在恒载作用下，结构木材的荷载-历时效应是有限的，构件的破坏是由大变形引起的，减小大变形和应力水平是减小荷载-历时效应的有效方法;虽然桁架的剩余寿命约为30年，但由于木材腐朽、白蚁侵袭、干缩裂缝以及地震、飓风等关键性脉动，桁架的抗力也会降低，因此桁架已处于危险状态，需要进行维修加固。
These factors must be considered such as load-duration effect,moisture content and temperature change,decay and termite attack etc.in order to obtain the relation between the long-term resistance of the historic timber structure and time.The strength degeneracy model of timber member was deduced under constant load based on the Gerhards damage accumulation model.Then the load-duration effect on the resistance of a 100-years historic timber truss under constant load was analyzed by the strength degeneracy model without regard to the other factors’ change during the service life.Finally the strength degeneracy model was used to predict the residual life of the truss.The results indicates that the load-duration effect on the structural lumber under constant load is limited,and that it is large deformation that induces the member’s damage,and the effective method to decrease the load-duration effect is to reduce the large deformation and stress level;although its residual life is about 30 years the truss has been in danger and should be repaired and strengthened because timber decay,termite attack,dry shrinkage crack and some critical pulses such as earthquake and hurricane also decrease the truss’s resistance.