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Special Interest
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Configuration. The Van Nuys building testbed is a 7-story, 66,000 sf (6,200 m2) hotel located in California's San Fernando Valley, northwest of downtown Los Angeles. The hotel was designed in 1965 according to the 1964 Los Angeles City Building Code, and built in 1966. In plan, the building is rectangular, 63 ft by 150 ft, 3 bays by 8 bays, 7 stories tall. The long direction is oriented east-west. The building is approximately 65 ft tall: the first story is 13 ft, 6 in; stories 2 through 6 are 8 ft, 6-½ in; the 7th story is 8 ft. The ground floor, as it existed prior to the 1994 Northridge earthquake, contains a lobby, dining room, tavern, banquet room, and various hotel support services. Upper floors are arranged with 22 hotel suites accessed via a central corridor running the longitudinal axis of the building. The building is owned by a private investor as income property. Structural system. The structural system is a reinforced concrete moment-frame with flat-plate slabs of 8 to 10-in thickness. Reinforcing steel lacks ductile detailing. Prior to the 1994 Northridge earthquake, lateral resistance was provided primarily by the perimeter moment-frames, with some stiffness and strength provided by the interior gravity frames. The building is founded on reinforced-concrete drilled piers, 32 to 37 ft long, in groups of one to four per pilecap. Past eathquake damage. The building was strongly shaken and damaged in the 1971 San Fernando and 1994 Northridge earthquakes. Repair after Northridge involved a change of structural system that will not be addressed by the present study. Elements of the Methodology Tested Here PEER researchers working on the Van Nuys testbed are focusing on estimating structural and architectural damage, collapse potential, repair cost, and repair duration. Other aspects of the PEER methodology, such as contents damage and post-earthquake operability, are the focus of the UC Science Building testbed. The performance estimation will entail evaluating the seismic hazard (including creation of a set of ground-motion time histories at three hazard levels), evaluation of engineering demand (deformations, accelerations, and member forces), evaluation of structural and architectural damage, and evaluation of repair costs and repair durations. Intensity measures. Seismic intensity will be measured initially in terms of spectral acceleration (Sa). PEER researchers will also test alternative intensity measures (IM). The objective is to identify an IM that is more strongly correlated with performance, and whose occurrence rates can be readily calculated. That is, the new IM should reduce uncertainty on facility performance, conditioned on hazard level. We will elucidate and illustrate a methodology for calculating the probability (or possibly occurrence rate) p[IM]. Engineering demand parameters. PEER researchers will attempt to identify a limited set of engineering demand parameters (EDP) that are indicative of overall structural response, for use in simplifying design. It is hoped that a single parameter (or perhaps a small set) such as peak transient drift at the top of the structure, will correlate strongly enough with performance that structural designers will not need to explicitly evaluate damage and loss, but merely demonstrate that EDP is less than some allowable level, associated with the desired level of performance. We will elucidate and illustrate a methodology for calculating the conditional probability p[EDP|IM], and given this and p[IM], the marginal probability p[EDP]. Damage measures. PEER researchers will create or compile fragility functions for the major damageable structural and architectural components of the building. Fragility functions give the probability of a facility component reaching or exceeding an undesirable performance level, as a function of excitation. PEER researchers will categorize all the building components into a limited, clearly defined taxonomic system; define relevant physical damage measures (DM) for each category; and create fragility functions for each damage state, p[DM|EDP]. Given this an p[EDP], we will elucidate and illustrate the calculation of p[DM]. Decision variables. These decision variables (DV) measure overall facility performance in terms most relevant to facility stakeholders. For the building owner, DV is most likely to include uncertain future repair cost, and may include repair duration, fatality risk, and other parameters. We will elucidate and illustrate a methodology for calculating p[DV|DM] and, given p[DM], the calculation of p[DV]. Resources provided here. This reader can find here geotechnical studies, hazard information, historic accelerometer recordings, design documents, photos of the building and its equipment, and a combined report exercising the PEER methodology on the Van Nuys testbed. For testbed researchers, please see the Contacts page.
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