Field Vibration Testing & Analyses of an Existing RC Building

缺乏足够高的空间分辨率数据集，从现场测试的全尺寸结构在动态加载条件下显着限制了地震工程师的能力，以提高他们的理解的结构和岩土系统的抗震性能。例如，对重大地震事件后高度非线性结构响应的现场观测，已经得到了大量定性观测的支持。在过去的几十年里，来自建筑物的仪器记录一直是一种无价的资源;然而，（每个结构约12个是常见的分配）太低而不能实现系统或组件响应的详细评估。加州大学洛杉矶分校的土木工程系正在开发设备，以大大提高强迫-振动测试是NSFNetwork for Earthquake Engineering Simulation（NEES）计划的一部分。该项目名为结构性能的现场测试和监测，于2000年1月启动，并持续到2004年9月。正在采购的现场测试设备包括最先进的振动源（线性惯性和偏心质量振动器）、传感器和无线数据采集系统（加速度计、LVDT、光纤仪表读出装置、数字化仪、路由器、工作站）、CPT卡车和现场土壤振动传感器以及网络设备（数据集中器、卫星上行站），以便能够进行实时数据采集、处理和在万维网上广播实验结果。本项目只涉及设备的采购和集成;通过与UCLA/NEES项目的一个以建筑师为基础的实施咨询委员会（IAB）的合作，洛杉矶的一座四层办公楼被确定为受迫振动测试的候选建筑。这座建筑之所以受到普遍关注，是因为（1）它有一个非常常见的结构体系，由周边弯矩框架和内部后张板柱框架组成，（2）它在北岭地震中受到严重破坏，导致它被遗弃。以往基于分析的建筑物震后研究一般都无法解释的破坏。业主计划拆除结构;然而，由于各种原因，将不会这样做约两年，并已授予PI进行测试的许可。拟议的研究包括强迫振动测试的建设使用NEES设备以及详细的系统识别和数值模拟研究。地震类型和谐波力历史将被施加到屋顶水平的建筑物上，并记录波形，以评估完整的结构系统响应、结构部件行为（例如，板柱连接和桩帽），以及非结构部件的响应（例如，隔板、管道系统）以及这些部件对系统响应的影响。将使用密集的仪器阵列，其中包括加速度计、位移传感器和应变计。将安装无线局域网以采集和记录波形数据。从测试中产生的详细数据集将提供有价值的洞察这种常见类型的结构系统的性能和性能差的主题建筑在北岭地震的原因.测试还将为NEES计划提供关于设备使用协议和数据存档模型的宝贵经验。在本供资期内获得有关这些问题的经验特别有用，因为NEES设备的开发工作正在进行中，所吸取的经验教训可以在NEES系统于2004年上线之前加以实施。与这项建议的及时性有关的另一个事实是，这座重要的建筑将在两年内被夷为平地。

The lack of adequately high spatial resolution data sets from field testing of full-scale structures underdynamic loading conditions significantly limits the ability of earthquake engineers to improve theirunderstanding of the seismic performance of structural and geotechnical systems. For example, fieldobservations of highly nonlinear structural response following major seismic events have been largelysupported with qualitative observations. Instrument recordings from buildings have been an invaluableresource over the past few decades; however, the density of instruments (with ~12 per structure being acommon allocation) is too low to enable detailed evaluations of system or component responses.To address this shortcoming, the Civil Engineering Department at UCLA is in the process of developingequipment to substantially enhance field testing capabilities for forced-vibration testing as part of the NSFNetwork for Earthquake Engineering Simulation (NEES) program. The project, entitled Field Testingand Monitoring of Structural Performancece, was initiated in January 2000 and continues throughSeptember 2004. Field testing equipment being purchased consists of state-of-the-art vibration sources(linear inertial and eccentric mass shakers), sensors and a wireless data acquisition system(accelerometers, LVDTs, fiber optic gage readout unit, digitizers, routers, workstations), a CPT truck andin situ soil vibration sensors, and networking equipment (data concentrator, satellite uplink station) toallow for real-time data acquisition, processing, and world wide web broadcasting of experimental results.The project involves only purchase and integration of the equipment; no specific research activities arebeing conducted with the project funds.Through collaboration with a practitioner-based Implementation Advisory Board (IAB) for theUCLA/NEES project, a four-story office building in Los Angeles has been identified as a candidate forforced vibration testing. The building is of general interest because (1) it has a very common structuralsystem consisting of a perimeter moment frame and an interior post-tensioned slab-column frame, and (2)it was significantly damaged during the Northridge earthquake, causing it to be abandoned. Previousanalysis-based post-earthquake studies of the building have generally been unable to explain the observeddamage. The owners plan to demolish the structure; however, for a variety of reasons, will not do so forapproximately two years and have granted the PIs permission to conduct testing.The proposed research involves forced vibration testing of the building using the NEES equipment aswell as detailed system identification and numerical modeling studies. Both earthquake-type andharmonic force histories will be applied to the building at the roof level, and waveforms will be recordedto enable evaluations of the complete structural system response, structural component behavior (e.g.,slab-column connections and pile caps), and the response of non-structural components (e.g., partitions,piping systems) as well as the influence of these components on the system response. A denseinstrumentation array will be utilized that will include accelerometers, displacement transducers, andstrain gauges. A wireless local area network will be installed to acquire and record waveform data,. Thedetailed data set generated from the tests will provide valuable insight into the performance of thiscommon type of structural system and the reasons for the poor performance of the subject building duringthe Northridge earthquake. The testing will also provide invaluable experience to the NEES program withrespect to equipment use protocols and data archiving models. Gaining experience on these issues withinthe present funding period is particularly useful as the NEES equipment development work is ongoing,and lessons learned can be implemented prior to the NEES system going online in 2004. Also relevant tothe timeliness of this proposal is the fact that this important building will be razed in two years.