International Concrete Abstracts Portal

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.

A suitable design of deck joints and bearings in highway bridges should take into account the environmental conditions existing in the location of the bridge. Several authors state that the influence of the thermal effects should never be un derestimated in the design of joints and bearing systems and point out the existence of damages-in bridges due to environmental thermal effects. This paper presents a general method for the prediction of thermal movements in highway bridges located in Spain. It provides design recommendations which allow accurate prediction of thermal movements, depending on the location of the bridge, the longitudinal type of the bridge deck, the cross section type and other factors which significantly affect the thermal response of the bridge. Lastly, the influence of the temperature of settlement of the deck joints is also considered, in order to determine precisely the thermal movements in highway bridges. Such method can be developed and applied to other countries.

Describes a mathematical model for the seismic elastic response of base isolated buildings as a function of the superstructure dynamic properties when this is assumed fixed at the base, and of the same superstructure when this is assumed to behave as a rigid body with a single degree of freedom when mounted on base isolators. The expressions derived in this paper provide the period and damping of the isolated building, the magnitude of the seismic story forces, the base shear, and the base displacement. The expressions are simple and can be readily cast into building code format. The derived expressions are compared to the 1994 Uniform Building Code (UBC); a case study suggests improvement of currently recommended procedures by the UBC is feasible.

Bridge expansion joint systems perform three primary functions. The first function is to provide the designed and desired expansion/contraction movement while handling all necessary harsh climatic and traffic conditions. The second function is to provide a watertight joint to eliminate water and chlorides from gaining access to the deck and bridge substructure. The third function is to provide a smooth riding surface to eliminate undesirable stresses from traffic loading. Materials commonly used in the manufacture of expansion joint systems include steel, aluminum, and neoprene. Improvements in technology and new design methods have resulted in several innovative nonmetallic, nonrubber bridge expansion joints. The mini-plug system consists of three main components: a mild steel plate to bridge the expansion gap, 1/2 to 3/4 in. mixed double crushed granite aggregate, and a special two component polymer binder material. This system has the advantages of an asphaltic plug type joint, small movement range, smooth and flat to the existing surface, while reducing the required blockout width and eliminating most of the required equipment. This system is installed at ambient temperatures. The major advantage of this system is its capability of installation in small (6 to 12 in.) blockouts, substantially reducing material requirements. This also reduces construction time and results in less disruption of the riding surface.

In this study, sponsored by the Texas Department of Transportation, bearing performance was analyzed on the basis of elastomer hardness, shape factor, reinforcing shim orientation, degree of taper, and compressive stress level. Emphasis was placed on comparing the behavior of flat versus tapered pads. Experimentation included shear, compressive, and rotational stiffness tests; shear and compression fatigue loading; long term compressive loading; and tests to determine compressive stress limits. Bearings were intentionally loaded nonuniformly to define safe limits for bearing/girder slope mismatches. Research showed that tapered bearings performed as well as flat bearings and that manufacturing tapered bearings with steel shims oriented parallel to one another, rather than radially, is advantageous. Bearings made from lower hardness elastomers displayed several advantages over those made from harder material, particularly, a greater ability to accommodate girder end rotations. More highly reinforced bearings performed better in compression fatigue tests and easily accommodated compressive stresses well over 7.0 MPa (1000 psi).