Friction Pendulum bearings have been extensively tested for different environmental conditions and loadings applicable to bridges. Data are presented from various test programs, spanning six years, and including several hundred shake table and compression-shear tests. Shake table tests of bridge models were used to verify dynamic performance of the seismic isolation system. Results are reported for models of bridge decks mounted on flexible piers and rigid abutment supports, and for various types of ground motions. including standard Caltrans ground motion spectra and near fault pulse motions. Comparisons between experimental results and dynamic analysis results are presented. Compression-shear test results are reported for the effects of temperature variations from minus 20°F to 90°F. 20,000 cycles of thermal movements, simulated aging. scragging, compression overloads, and tension loads. The test results show the effect of these factors on the properties of the bearing. Results for bearing ultimate strength and factors of safety are shown. The implications for the design and application of seismic isolation to bridges are discussed. Stable and predictable responses are observed over a wide range of conditions and loadings, lending support and confidence for the application of seismic isolation to reduce earthquake hazards for bridges.

SP-164(V1) The Fourth World Congress on Joint Sealants and Bearing Systems in Concrete Structures will enhance the general understanding of these systems and introduce entirely new concepts developed to cater to the latest seismic code requirements. This conference was held in Sacramento, California on September 29 through October 3, 1996.

To assist bridge engineers in the State of Florida in selecting expansion joint systems, the Florida Department of Transportation/Structural Research Center (FDOT/SRC) concluded a two year bridge expansion joint evaluation program. This program consists of three components: I) Performance Evaluation, 2) Load Test Evaluation, and 3) Installation & Maintenance Evaluation. The test elements include seals. compression seal joints, strip seal joints, and buried joint systems. Twelve (12) joint suppliers volunteered to participate in the program. A total of seventeen (17) joints (or seals) were installed in eight (8) bridges on I-95 in Saint Lucie County, District IV. All bridges in the test program have prestressed concrete AASHTO girders and concrete deck slabs. All the bridges had armored compression seals at the end bents. In general, the test joint systems or seals were installed at the end bent joints (replacing the original material). The original design joint opening at 70 "F was one inch (1") for the end bent joints. Using criteria recommended by FDOT engineers and the Structures Design Guidelines, the SRC evaluated the test expansion joint sealants or systems. This paper presents the results of the test program. Also, it provides guidance concerning the selection of expansion joint systems for both new and existing bridges.

The design of a bridge deck joint must be able to withstand the wear and impact of heavy traffic loads, and resistant to roadway oils and chemicals, debris, ultraviolet rays, and other environmental factors. Failure of a joint system can occur from a debonding of the nosing and substrate; a delamination of material layers; severe wearing, cracking or spalling of the nosing; or improper aterial mixing and joint installation. Loose steel armor retainers and leaking joint seals also cause joint system failures. A large scale accelerated testing facility designed and constructed at the University of Central Florida has tested over twenty different bridge deck joints for wear, abrasion, impact loading, and leakage. Many of the aforementioned failure criteria were observed during the course of testing. The testing program also established a simulated life expectancy for each joint system as a result of its performance under full-scale live loading, during a five week test period. This method of testing proved to be a timely, feasible alternative to live bridge applications and monitoring procedures. Test results indicated several areas of deficiency common to many of the joint components and systems and promoted further development of some of these products to enhance their performance.

The Greater Buffalo International Airport improvement program being planned and constructed by the Niagara Frontier Transportation Authority includes a new elevated departure viaduct. The overall length of this structure will be 1439 feet consisting of a 14 span main structure of 502'., two approaches at 115' each, and two mechanically stabilized earth embankments at 340' and 367'(Figures 1 and 2). The main span deck is 67' wide which will accommodate two parking lanes, and two traffic lanes designed to AASHTO HS-20 loading criteria and a sidewalk. The deck consists of precast prestressed concrete slab units placed perpendicular to the traffic flow and cantilevered 13' on one end to support the sidewalk. Cast-in-place longitudinal beams support the precast slabs and cast-in-place transverse beams are located at each column to stiffen the structural frame. The longitudinal beams are supported by two rows of columns. Each pair of columns is on a radial alignment approximately 52' apart (Figures 3 and 4). The preliminary analysis with conventional bearings resulted in high seismic forces on the columns and footings due to the very heavy superstructure. In an effort to reduce these forces, isolation bearings were evaluated. These bearings will be required to minimize displacements due to the close proximity of adjacent structures. In addition, the engineers were looking for a device that was a low height design which would function in cold weather. A sliding isolation system was selected with a positive restraint design which restores the structure to its original pre-quake position. This system was developed based on research conducted at the National Center for Earthquake Engineering Research located at the State University of New York at Buffalo (NCEER-91-0027). The use of sliding isolation on this structure resulted in significant force reductions while minimizing seismic displacement. The fact that all bearings are engaged in seismic resistance and energy dissipation resulted in mitigating seismic forces to a non-governing level.