International Concrete Abstracts Portal

SP-164 (V2) Although bearing and joint systems comprise only a small percentage of the construction cost of highways, buildings, and bridges (1 percent, typically), their importance to the functioning of those structures is vastly greater. For without adequate engineering effort in design of these vital elements to account for the many, sometimes conflicting, requirements of loading and/or movement, the integrity of the entire structure may be compromised. Our increased understanding of seismic activity has made us more aware of the wider area of this activity as the greater demand placed on support and joint systems. This Fourth (quinquennial) World Congress on Joint Sealing 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. As with the first two Congresses, this is V.2 of a two-volume set. V.1 contains 22 papers, plus the abstracts ofpapers presented at the Third Congress.

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.

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 seismic performance of high type steel bridge bearings of both the fixed and expansion/rocker type were investigated. Simple seismic retrofit strategies were proposed and investigated experimentally. It was shown that by retrofitting existing high type steel bridge bearings, it is possible to provide sufficient strength and displacement capability to withstand substantial ground shaking. The weak link in the chain of force transmission may thus become the anchor bolts and/or the reinforced concrete pedestal. To understand the influence of the reinforced concrete pedestal and mild steel anchorage on the overall behavior of a high type fixed bearing assembly, a full scale reinforced concrete cap beam with pedestals was constructed. The rest results demonstrate the importance of considering the flexibility and strength of the concrete pedestal-anchor bolt system. As a retrofit method for the damaged reinforced concrete pedestal, a steel jacketing retrofit wrapped around the damaged reinforced concrete pedestal and bearing was investigated. Once retrofitted, it is shown that essentially elastic behavior may be expected in an earthquake.

Most engineering professionals have been educated and trained to appreciate and use a scientific orientation in their specialty. Scientific orientation means an orientation or habit of mind that continually compels and provokes one to reexamine, evaluate, and improve his or her symbolic representations of reality. However, for some situations and in certain circumstances, some professionals, either through neglect or inattention, base their beliefs, decisions, practices, and policies on idealizations that have a tenuous relationship to reality. Consequently, some of their actions are based on flawed assumptions, assumptions that are partly responsible for their questionable decisions and the poor performance of their designs. This is especially true when considering inadequacies that are everywhere evident in the design and construction of bridge deck joints and bearings. This paper describes and discusses a number of flawed assumptions, assumptions made by technicians, novice engineers, supervisory engineers, design administrators, and entire transportation agencies. It urges a greater awareness of reality as the most effective way to appreciate the disparity between the ideal and the real. Such an appreciation will lead to an improvement in basic assumptions, to an improvement in the performance of individuals responsible for design, and ultimately to an improvement in the performance and durability of the structures produced for transportation systems.