Performance and Safety of Current Versus Bi-Level Design Procedures-Impact of Northridge Earthquake

我国9415726条温楼设计规程一直以一定重现期设计地震下的生命安全为目标。它基本上是一种单层设计。从最近的地震，特别是北岭地震中学到的一个宝贵的教训是，损失和经济损失可能与生命安全一样重要。在日本和新西兰等地震活动频繁的其他国家，已经使用了针对不止一级地震的设计，其中明确考虑了可使用性和极限状态。从北岭地震和最近在南加州发生的其他地震中收集的大量数据为我们提供了一个机会，让我们认真审视当前程序与替代双水平程序的安全性和性能。研究项目是在这里进行的，具体目标如下：(1)评估和比较按照现行程序和替代程序设计的建筑物的性能和安全性。(2)评估上述设计程序的长期风险影响，发展上述设计程序的策略含意，并制订策略，以制订更合理、风险一致的守则程序。为了实现上述目标，有必要进行以下工作：(I)分析要更新的北岭数据、地震风险和当前结构性能可靠性评估中使用的场地特定地震动模型，其中考虑了对震源、路径和场地特征的依赖。(2)根据1991年UBC和洛杉矶地区选定地点的替代双层程序设计低层(12层以下)钢和钢筋混凝土建筑。(3)对建筑进行动力响应分析，比较两种设计的响应行为和响应统计。(4)使用最新的地震风险和地面运动模型，根据这两个程序对设计进行长期风险分析，并比较风险影响。(V)找出替代设计程序与现行设计程序的优缺点，并提出今后守则需要改进的地方。本研究将为这一在国内外研究和实践中具有深远意义的重要问题提供有益的启示。这是北岭地震项目。

9415726 Wen Building design procedures in this country have been aiming at life safety under a design earthquake of a given return period. It is basically a single-level design. A valuable lesson learned from recent earthquakes, in particular the Northridge earthquake, is that damage and economical loss may be just as an important issue as life safety. Design for more than one level of earthquake has been used in other countries of high seismicity such as Japan and New Zealand in which serviceability and ultimate limit states are explicitly considered. The extensive data collected from the Northridge and other recent earthquakes in Southern California provide and opportunity for us to take a critical look at the safety and performance of the current procedures versus alternative bi-level procedures. The research projects is under taken here with the following specific objectives: (1) To evaluate and compare the performance and safety of buildings designed in accordance with the current and alternative procedures. (2) To evaluate the long- term risk implications of the above design procedures and develop strategy implication of the above design procedures and develop strategy for formulating more rational, risk-consistent code procedures. To achieve the above objectives the following tasks are necessary; (i) Analysis of Northridge data to update, the seismic risk and the site specific ground motion models used in current reliability evaluation of structural performance in which dependence on seismic source, path, and site characteristics is considered. (ii) Design of low-rise (under 12 stories) steel and reinforce concrete buildings according to the 1991 UBC and alternative bi-level procedures at selected sites in the Los Angeles area. (iii) Perform dynamic response analyses of the building and compare response behaviors and response statistics of these two designs. (iv) Perform long-term risk analysis of designs according to the two procedures us ing the updated seismic risk and ground motion models and compare risk implications. (v) Identify advantages and shortcomings of alternative versus current design procedures and suggest areas for improvement in future codes. The research conducted will provide insight to this important problem which has a profound implication in research as well as practice in US and abroad. This is a Northridge Earthquake Project.