The Factor building (Fig. 1) houses the UCLA Center for the Health Sciences, taking up 0.4 acres of area. It is composed of approx. 198,000 sq. feet that make up laboratories, faculty offices, administrative offices, the School of Nursing, School of Medicine, auditoriums, and classrooms. The building consists of two stories below grade and is set back at the north end to avoid shoring and underpinning of the existing adjacent UCLA Life Sciences building at the northwest corner. The building is approximately rectangular (longer in the N-S direction than the E-W direction) and this contributes to the differing properties apparent in the orthogonal horizontal waveform recordings described later in this paper. See Building Location for map and geographical coordinates.

Factor building construction is steel frame type 1 as per the Uniform Building Code. Except for some concrete cassons, the structure is supported by concrete spread footing. The basement walls are reinforced concrete protected by waterproofing. The floor slabs are lightweight aggregate concrete conforming to ASTMC330 lightweight aggregates for structural concrete placed on metal decking. There is reinforcing steel conforming to ASTM A615 grade 60. The building has a clay brick veneer split 1.5_ thick secured with metal anchors attached to metal slots. There are six elevators: two geared passenger elevators serve floors 1-8 at 4000 lbs, two passenger elevators serve the basement-15th floors at 4000 lbs, and two are service elevators serving the basement-14th floors at 3000 lbs. The air conditioning system components are housed in equipment rooms on various floors. The machinery is mounted by means of isolation devices to minimize both vibration and acoustical disturbances.

Excavation of the soft soil below the site was required during building construction. During site preparation, a report on the site characteristics (see References for full report citation) found that the natural soils beneath the Factor building consist of silty sand, silt, clayey sand, clay, and sand. The natural soils are firm throughout. Existing fill soils, 1/3 to 3 m in thickness, consist of silt, sand, clay, and silty sand with some debris. Deeper and/or poorer quality fill probably occurs between locations. There is backfill adjacent to the existing buildings. Site investigation was done by drilling three borings to depths of 26 to 30 m below the existing grade. Fig. 2 shows a typical soil cross section for one of the borings. A downhole seismic survey was performed as part of the site investigation to determine P-wave and S-wave soil velocities (Fig. 3). P and S waves were recorded by a borehole seismometer with three orthogonal geophones. Layer thicknesses were determined from velocity data and known geometry. P-wave and S-wave velocities are ~150 m/s and ~300 m/s in the first few meters of the silty sandy soil.