Improvements in Code and Dynamic Analyses of Buildings: Vibration Periods and Modal Damping Ratios

建筑物规范和动态分析的改进：振动周期和模态阻尼比

• 批准号: 9416265
• 负责人: Anil Chopra
• 金额: $ 8万
• 依托单位: University of California-Berkeley
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1994
• 资助国家: 美国
• 起止时间: 1994-09-01 至 1996-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9416265&HistoricalAwards=false
• 关键词: Improvements; Code; Dynamic; Analyses; Buildings

9416265 Chopra The objectives of this project are to "measure" two important properties--fundamental vibration period and modal damping ratios-of some forty buildings from their recorded motions during the Northridge earthquake and other recent earthquakes. These buildings, shaken strongly by ground motions with peak accelerations between 0.15g and 0.82g, would provide information directly relevant to earthquake resistant design of buildings in contrast to much of the existing data which are for smaller amplitudes of motion. The vibration properties will be identified from the recorded motions of the buildings using system identification procedures. These results from the Northridge earthquake and other recent earthquakes, combined with similar data available from the 1971 San Fernando earthquake, will create the most comprehensive database which can be easily updated after every major earthquake. This database will be used to evaluate and improve: (1) code formulas for estimating the fundamental vibration period used in calculating the design base shear and lateral forces; and (2) current recommendations for damping values used in dynamic analysis. The period formulas in the 1994 UBC and the 1990 SEAOC "blue book" were developed in 1975 as part of the ATC-3 project, based largely on motions of buildings recorded during the 1971 San Fernando earthquake. Similarly, the damping values used widely were originally recommended by Newmark and Hall in 1978. This project will culminate in: (1) formulas for estimating the fundamental vibration period of buildings using different materials--steel, R/C, masonry etc.--and various structural systems--moment resisting frames, shear walls etc.; and (2) recommendations for modal damping ratios for different categories of buildings, depending on response amplitude and, if appropriate, on mode number. This is a Northridge earthquake project. ***

9416265 Chopra这个项目的目标是“测量”两个重要的属性--基本振动周期和模态阻尼比--从北岭地震和其他最近的地震中记录的大约40个建筑物的运动。 这些建筑物，强烈震动的地面运动与峰值加速度之间的0.15 g和0.82 g，将提供直接相关的信息，抗震设计的建筑物相比，现有的数据是较小的运动幅度。 将使用系统识别程序从记录的建筑物运动中识别振动特性。这些来自北岭地震和最近其他地震的结果，加上1971年圣费尔南多地震的类似数据，将创建最全面的数据库，可以在每次大地震后轻松更新。 该数据库将用于评估和改进：（1）计算设计基底剪力和侧向力时使用的基本振动周期估算的规范公式;以及（2）动态分析中使用的阻尼值的当前建议。 1994年UBC和1990年SEAOC“蓝皮书”中的周期公式是在1975年作为ATC-3项目的一部分开发的，主要基于1971年圣费尔南多地震期间记录的建筑物运动。 同样，广泛使用的阻尼值最初是由Newmark和Hall在1978年推荐的。 本项目的最终成果是：（1）使用不同材料（钢、R/C、砌体等）的建筑物的基本振动周期的估算公式;以及各种结构体系--抗弯框架、剪力墙等;（2）根据响应幅度和振型数（如适用），对不同类别建筑物的模态阻尼比提出建议。 这是北岭地震项目。 ***