International Concrete Abstracts Portal

Central to the design of the Intermountain Power Project (IPP) mechanical cooling towers was the ability to configure connections between precast concrete members so that large horizontal seismic forces could be transferred between beams and girders and between girders and columns. Complicating the task of connection design were substantial thermal loads and severe environmental conditions. To solve these and related design questions, a testing program was undertaken using «-scale models of certain key joints in the structure. This paper presents a description of the testing program, a brief description of the structural system in which the joints were located, and the results and conclusions of the tests. Principal among the conclusions is the recognition that embedded metal pins used to transfer forces between discrete members must not only be carefully detailed, but they also must accommodate substantial elastic deformation at the joint if failure below acceptable force levels is to be avoided. In the IPP, this was accomplished by the introduction of a confined viscoelastic medium surrounding the pin. This simple addition to the joint configuration increased the force transferred through the connection by a factor of 2.5 to 3 while limiting deformation to acceptable values.

The background and development of the specialized equipment required for the proper preparation and installation of hot-applied joint sealants is reviewed. The need to use specially designed melter-applicators is embellished. Many of the disastrous field problems resulting from failure to use approved equipment, as well as the appropriate sealant, are discussed in detail. The evaluation of field preparation and application equipment for hot-applied joint fillers and sealants is set forth, from hand pots and so-called tar of roofers' kettles to agitation, recirculation, and extrusion systems of today's melter-applicators. The required specialized laboratory test equipment is also discussed as is the correlation of test results with respect to field installation temperature parameters. Attention is also given to the proper selection of different types of sealants by basic constituents for compatibility with pavement type and previously used sealants and fillers.

The principal cause of deterioration to the superstructure and substructure are the expansion joint systems. Bridge engineers and maintenance personnel have long advocated longer spans with fewer and maintenance-free expansion joints. With longer spans, expansion joints have become greater. In 1978, the New York State Department of Transportation invited manufacturers of six different types of modular expansion systems to install their devices on a new structure crossing the Hudson River at Troy, N.Y. This paper is an up-to-date condition survey of the performance conducted on a regular basis of the six different modular expansion joints.

The neoprene compression seal has now been used commercially in construction projects, including highways and bridges, for more than 20 years. It continues to be today's top method of sealing contraction and expansion joints in highways and bridges, as measured by the footages used annually. Through the years, there has been continued refinement of the specifications covering this type of sealing so that for practical purposes performance is assured when these specifications are followed. The degree of sophistication inherent in the development of this type of seal exceeds most rubber-like products. Enough time has now elapsed that data on field performance can be related back to the design parameters that were monitored by accelerated laboratory tests and that have been proven correct. The paper reviews the problems encountered in arriving at a proper seal design, the problems of field installation, and the correlation of accelerated laboratory testing to field results. Included also are remarks concerning the adoption of various special compression seals to specific applications.

A research and development session was held at the conclusion of the Second World Congress on Joint Sealing and Bearing Systems for the purpose of identifying the outstanding issues. This paper provides a summary of the proceedings of the session. Needed work on joints and bearings was identified within the following subject areas: bearings, bridges, base isolation, materials, movements, buildings, and pavements. The session concluded by endorsing the concept of a Joint and Bearings Research Council to act as a liaison group between all segments of the industry.