Zarembski, Allan M.2022-05-022022-05-021993-10Zarembski, A. M., “Concrete vs. Wood Ties: Making the Economic Choice”, Conference on Maintaining Railway Track; Determining Cost and Allocating Resources, Arlington, VA, October 1993.https://udspace.udel.edu/handle/19716/30839Track components must satisfy two basic criteria for acceptance. The first criterion is a performance criterion, which addresses whether the component has sufficient "strength" to function and survive in the railway environment. The second criterion in the economic one, whether the cost of the component is economic with respect to other similar components or products. This second criterion comes into play only if the first is satisfied, i.e., the component or system must have adequate performance, before its relative economics is even considered. Only when that performance criterion is met, the economic criterion comes into play. One clear application of this approach is that of the cross- ties and fastener systems, specifically that of the concrete cross-tie as compared to the traditional wood cross-tie that has been used by railroads for over two hundred years. While concrete tie designs have been around for many years, it has only been in the last two decades that their performance has been deemed to be adequate to withstand the severe loading environment of North American freight operations. Once this performance criterion has been satisfied, i.e., once it has been established that the concrete cross-ties can function and survive in the heavy haul environment, then the economics of this alternate tie system enters into the consideration of railway engineers. Specifically, the relative economics or the concrete tie system must be compared with the existing conventional systems, wood ties with cut spikes. In addition, the relative economic of these systems would have to be compared with several other technically proven systems, such as wood ties with alternate (elastic) fastening systems. This economic comparison, however, is not a simple matter. Because different tie/fastener systems exhibit different lives, require different maintenance activities, and affect other maintenance activities differently, simple comparison of the initial or "first" cost is not adequate. Rather, a comprehensive comparison of the costs and benefits of the alternate systems over their entire service lives is required, i.e., a "life cycle" cost analysis. This is further complicated by the fact that component lives and behavior vary significantly as a function of track and traffic characteristics, as well as individual railroad practices. Thus, the relative economics of these alternate cross-tie systems is not fixed, but vary with many of the operating and maintenance parameters. One approach that has been effectively used to address these significant differences is the development of life cycle costing computer models that can be run on personal computers. This approach led to several such models, such as the SelecTie model developed by ZETA-TECH Associates, Inc. for the Railway Tie Association. Such a model is capable of incorporating a comprehensive analytical methodology and allow for the ready (and rapid) changing of key parameters and the "instantaneous" recalculation of the results. This approach has been found to ZETA-TECH Associates, Inc. 2 1993 be an effective means of carrying out economic benefit comparisons, particularly ~such life cycle benefit analyses. The basic analytical approach used in this methodology (and in the model itself) is a present worth analysis approach, in which all the costs associated with the two alternative systems are examined and compared in terms of a "present worth". Thus, any future costs or savings associated with the two systems are brought to the present, and the "worth" of these future costs calculated using an appropriate interest rate. (Thus, taking into account the time value of money.)Track componentsCross-tieCost analysisPresentation