按加拿大抗震规范设计的框架的可靠度及其应用
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摘要
NBCC加拿大建筑规范(1995版)近来更新为2005版。它在抗震方面做了很大修正,并说明了基本原理。但是,两种版本均没有按抗震规定定量评估结构的可靠度,也没有提出能校准地震作用(假如有)设计值的目标可靠度。以按规范设计的6种抗弯框架为例,进行了结构的可靠度评估。该评估采用延性方法,将结果与用美国SAC工程中采用的方法所得的结果进行比较,二者所得的可靠度吻合较好。依据NBCC两种版本设计的框架的可靠度没有变化。举例说明了能校准地震作用设计值并获得目标可靠度的延性方法的使用过程,考虑了初始损伤和倒塌。结果表明:延性因子,抗震设计水平取决于考虑初始损伤或倒塌的目标可靠度。
The 2005 edition of the National Building Code of Canada (NBCC) that replaces the 1995 edition of the NBCC has been released recently. The new edition incorporated many changes to the seismic provisions. The rationale behind these changes is documented in the literature. However, a quantitative assessment of the implied reliability level of the designed structures according to the seismic provisions in the new and previous editions of the NBCC is lacking, and the target reliability levels used to calibrate the new seismic design loads, if any, is not spelled out. In this study, a reliability assessment of six steel moment resisting frames designed according to these codes is carried out. The assessment uses a ductility-based procedure and the obtained results are compared with those obtained using the procedure developed for use in the SAC project. The estimated reliabilities for the designed frames using both procedures are in good agreement. In addition, the reliability levels for frames designed in accordance with the new and previous editions of the NBCC are consistent. Use of the ductility-based procedure for calibrating seismic design loads to meet specified target reliability levels considering both incipient damage and incipient collapse are illustrated. The results suggest that, depending on the displacement ductility capacity factor, the seismic design level could be governed by the considered target reliability levels for the incipient damage or incipient collapse.
The 2005 edition of the National Building Code of Canada (NBCC) that replaces the 1995 edition of the NBCC has been released recently. The new edition incorporated many changes to the seismic provisions. The rationale behind these changes is documented in the literature. However, a quantitative assessment of the implied reliability level of the designed structures according to the seismic provisions in the new and previous editions of the NBCC is lacking, and the target reliability levels used to calibrate the new seismic design loads, if any, is not spelled out. In this study, a reliability assessment of six steel moment resisting frames designed according to these codes is carried out. The assessment uses a ductility-based procedure and the obtained results are compared with those obtained using the procedure developed for use in the SAC project. The estimated reliabilities for the designed frames using both procedures are in good agreement. In addition, the reliability levels for frames designed in accordance with the new and previous editions of the NBCC are consistent. Use of the ductility-based procedure for calibrating seismic design loads to meet specified target reliability levels considering both incipient damage and incipient collapse are illustrated. The results suggest that, depending on the displacement ductility capacity factor, the seismic design level could be governed by the considered target reliability levels for the incipient damage or incipient collapse.
引文
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