Life-Cycle Cost Analysis of a Low-Volume Road Bridge Alternative

Life-cycle cost models offer engineers a means to evaluate the anticipated long-term economic performance of prospective design and construction alternatives. Traditionally, only initial investment costs and past experience were used to economically evaluate possible bridge designs. A more logical approach requires that all short- and long-term costs be considered in relation to project location, purpose, and performance specifications. The primary objective of life-cycle cost analysis is to evaluate the total ownership cost of all suitable alternatives. Recent reports indicate that a significant number of the nation’s bridges are either structurally deficient or functionally obsolete. In Iowa, a large portion of these types of bridges are on the secondary road system and fall under the jurisdiction of county engineers. Typically, Iowa county engineers have limited resources. In response to this, a bridge-replacement system was developed that county engineers can design and build with limited staff. The system, which is made up of precast (PC) double T units, involves the fabrication of PC units that consist of two steel beams connected by a thin concrete deck. To illustrate that this bridge system may be an economically viable bridge-replacement alternative for use on low-volume county roads, a life-cycle cost analysis was completed for an actual replacement-repair-rehabilitation project. Various alternatives were economically analyzed and compared with the steel beam PC unit bridge alternative. This analysis indicates that, when lower-cost salvaged steel beams and county work forces are used, the steel beam PC unit bridge can be a viable low-volume road bridge alternative.