SMIP 2004 Seminar

Criteria and guidelines being utilized to form a Design Ground Motion Library (DGML) are summarized in this paper. The DGML is being formed as an electronic library of selected recorded acceleration time histories considered to be suitable for use by engineering practitioners for the time history dynamic analysis of various facility types in California and other parts of the Western United States (WUS). The broad criterion governing selection of records is that the records be representative of ranges of design earthquakes and ground motions expected for the WUS seismic environment. Separate sets of records are being developed for different ranges of earthquake magnitude and earthquake source-to-site distance, for soil and rock site conditions, and for different period ranges of significance for different types of structures. Ground motion characteristics that are used in criteria for record selection include measures of response spectral shape characteristics and, for near-source record sets, pulsive characteristics of ground motion caused by rupture directivity effects.

The San Simeon earthquake occurred on a previously unknown blind thrust fault. No surface rupture associated with the earthquake has been identified. It was recorded at more than 100 strong motion stations out to distances of over 300 km with relatively few stations at less than 50 km distance. The biggest acceleration of 0.48 g was recorded at the Templeton hospital 38 km SE of the epicenter. Data demonstrates strong directivity effect in the direction of rupture propagation. Combined inversion of GPS and seismic waveform data allowed constructing a finite-source model of the earthquake.

This paper presents measured and analysis time-history results of the heavily instrumented 10-span North Connector Bridge (53-2795F) at the 5/14 Interchange, subjected to the M7.1 Hector Mine earthquake. Relatively simple spine and more detailed shell element models were developed. Measured base motions were used as input for the finite element models, with absolute and relative superstructure displacement time-histories compared to measured responses. Results show that 5% equivalent viscous damping is realistic, as is the concrete strength of 5 ksi. It was found that the rotational mass inertia of the superstructure is an important quantity for spine models of single-column-bent bridges.

The objective of this investigation is to evaluate the FEMA-356 Nonlinear Static Procedure (NSP), the Sum-Difference procedure, and the Modal Pushover Analysis (MPA) procedure using recorded motions of buildings that were damaged during the 1994 Northridge earthquake. It is found the FEMA-356 NSP and the Sum-Difference procedures typically underestimates the drifts in upper stories and overestimates them in lower stories. The MPA procedure provides estimates of drifts that are better compared to the FEMA-356 NSP and the Sum-Difference procedure. In particular, the MPA procedure is able to capture the effects of higher modes.

The CSMIP-3DV software system illustrates more than ever that seismic instrumentation of buildings is vital for learning from performance of buildings during earthquakes, enhancing engineering practice, and further development of seismic code provisions. The state-of-the-art features of CSMIP-3DV, for the first time, make it possible to evaluate seismic performance of dozens of buildings over many earthquakes in a systematic, consistent, and user-friendly manner. It is anticipated that by the end of the year 2004 CSMIP-3DV users will be able to investigate more than 80 instrumented buildings. Soon thereafter, the entire collection of more than 180 instrumented buildings will be implemented in CSMIP-3DV.

This paper discusses a new computer program for visualizing the animated measured response of bridge structures subjected to earthquakes. A graphical display allows the bridge to be viewed from any angle with any level of perspective and magnification to deformations. Panning and zooming are also available. Bridge behavior is measured at various locations on the structure as part to the Strong Motion Instrumentation Program. Between measured locations the bridge response is determined from spline functions consistent with structural behavior and boundary conditions. Time-history plots are also available which allow any quantity to be plotted against any other quantity, providing a powerful tool for visualizing data.

The new east span of the San Francisco-Oakland Bay Bridge is under construction now. It is the most expensive public works project in California’s history. The bridge is designed to provide a high level of seismic performance. Even after a major earthquake, the bridge is intended to provide full service almost immediately and should sustain only repairable damage to structure. During the construction, a total of 199 strong-motion sensors will be installed at key structural members along the bridge. This paper presents various structural systems used along the bridge and discusses the instrumentation plans.

The Community Hospital in Templeton is a 1-story wood frame structure built in 1977 and instrumented by the California Strong Motion Instrumentation Program in 1994 as part of California's Hospital Instrumentation Project. During the M6.5 San Simeon Earthquake of December 22, 2003, maximum horizontal accelerations of 0.5 g and 1.3 g were recorded at the ground floor level and the roof, respectively. The hospital did not suffer structural or nonstructural damage during the earthquake despite the strong ground shaking. This paper presents analysis results of the recorded response data and building performance observed after the earthquake. Some factors that can be attributed to the good performance of this hospital during the San Simeon earthquake are also discussed.

Structural evaluation, in 1974, of the historic California State Capitol identified a number of deficiencies in the 100-year old unreinforced masonry structure with respect to the seismic hazard at the site. Extensive structural and functional rehabilitation of the building was performed while retaining the historic exterior of the building and the interior rotunda. The preliminary structural design was in accordance with the California State Building Code, Title 24. The results of a site-specific seismicity study by the California Department of Transportation were utilized to perform soil-structure interaction analyses to obtain ground motion at the foundation level. Linear dynamic analyses with t his motion provided close correlation with the preliminary design.