Journal of Performance of Constructed Facilities

This paper deals with minimizing the cost of protective coating maintenance for steel bridges. Coating maintenance for steel bridges is of major significance and is reviewed here in some detail with respect to problems, causes, remedial techniques, and associated costs. One of two analysis methods under investigation to minimize the cost of coating maintenance for steel bridges is presented in this paper. This first method, featured in the bridge corrosion cost model, performs a life-cycle cost analysis using equivalent annual costs to compare the three maintenance strategies: spot repair, overcoat, and recoat. The strategy that provides the minimum equivalent annual cost is considered to be optimal. A computer application, which will be presented in a later paper, has been developed to reduce the manual work required to implement the procedures described in the bridge corrosion cost model. Presentation of the second analysis method will follow in the near future.

This second of two papers studying the minimization of the cost of coating maintenance for steel bridges deals with two main topics: the computer implementation of a life-cycle cost analysis (developed in the first paper) in a spreadsheet environment using equivalent annual costs to compare three single maintenance strategies—spot repair, overcoat, and recoat; and the development of a coating maintenance model using the dynamic programming approach that can optimize combinations of maintenance procedures for minimum cost. The flexibility of the life-cycle cost spreadsheet implementation allows the user to adjust key parameters in order to account for variability in costs and environmental conditions between different regions in British Columbia. The program can be easily adapted for different climatic conditions. In addition, an on-line “Help” feature is provided to reduce the time needed to operate the program. The computer application and demonstrative example are described here and the source code is available on request. The second evolved coating maintenance model using the dynamic programming approach presented here minimizes the sum of the costs resulting from a sequence of rehabilitation choices (a combination of maintenance strategies). It is a more flexible analysis technique than the equivalent annual cost approach and can determine the optimal sequence of rehabilitation activities over the service life of the structure. The procedures developed in this analysis can be easily converted into algorithms for possible computer applications. Based on results from a preliminary analysis of in-service bridges with good coating condition assessments using the life-cycle cost and dynamic programming approaches, spot repair is the most cost-effective rehabilitation method. Overcoating is the second most effective strategy and recoating is usually the most expensive solution. However, the difficulty in obtaining adequate deterioration and cost functions for the coating systems will significantly reduce the accuracy of these analysis techniques. Therefore, a uniform data-collection system should be implemented so that a database will be available for these models.

To try to improve the feedback that currently exists in the building industry, an effort was made to set up a feedback service based on building problems in Canada. The concepts for an effective feedback service are described in this paper. A field trial of such a feedback service was carried out by the National Research Council and Canada Mortgage and Housing Corporation. The experience of the field trial shows that such a service has considerable potential, but that it must be carefully planned and designed in cooperation with all segments of the building industry.

Masonry buildings represent the earlier building tradition in Egypt. The majority of the older building stock is of unreinforced masonry, some of which is worth preserving as part of the cultural heritage. Deterioration of the elements of such buildings are due to aging and environmental effects, lack of proper maintenance, as well as natural hazards. This paper reports on the structural integrity of a large masonry building damaged by the October 1992 Dahshour earthquake near Cario, Egypt. Analysis of the structure highlighted several elements that helped improve the overall behavior and control the extent of cracking. Although damage was mainly due to the seismic loading, some of the damage was not earthquake-related. Damage assessment of the building indicated typical damage to unreinforced masonry structures. Several retrofit techniques are studied and the one thought to be most suitable is presented.

Floor trusses are often used as primary load-carrying members in a bridge superstructure. Load is typically transferred to the floor truss from the concrete deck through the stringers. The floor truss can be supported by two or more plate girders or a pair of tied arches. Several assumptions are often made about the structural behavior of floor trusses in bridge superstructures to simplify the design process. This paper analyzes the validity of several of these assumptions based on field measurements. The measurements were made on three floor trusses in a tied-arch span over the Mobile River on I-65. The measurements were made as part of a larger research project conducted for the Alabama Department of Transportation. Floor trusses were instrumented with strain gauges and strain was recorded as test trucks of known weight either stopped over the floor trusses (static tests) or were driven across the span (dynamic tests) as well as when trucks in the normal traffic flow crossed the span (random tests). In addition, the results from a simple planar computer model of a floor truss were compared to the field measurements. The assumptions were found to be conservative and reasonable with the exception of one.