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30 ering SMA technology for use in ABC. TRL values are given in Table 32. Self-Propelled Modular Transporters SPMTs are computer-controlled platform vehicles that can move prefabricated bridge superstructures weighing up to several thousand tons with precision to within a fraction of an inch. They consist of a load-bearing platform with many pairs of steered wheels, each pair with its own hydraulic jack. The platform may be raised or lowered as necessary to follow a certain travel path. This technology is used to lift and trans- Figure 20. Stress-strain behavior of SMA and steel. port existing bridge superstructures from bridges requiring replacement. The technology can also be used to transport new bridge superstructures from temporary substructures Performance and time savings evaluation. At this point at a bridge staging area along a designated travel path to be in their development, SMA bars have worse performance placed in the final bridge position, minimizing road closure and take more construction time than conventional CIP con- time (Figure 21). SPMTs provide large amounts of flexibility, struction with mild steel. From the seismic performance per- can move loads in multiple directions with a high degree of spective, the material behavior is very attractive: energy accuracy, all within a span of hours rather than months required dissipation with minimal residual strains, high strain capacity, by conventional bridge construction methods. high corrosion resistance, and good low and high cycle fatigue The Utah DOT used SPMTs for their "Innovate 80" proj- properties. However, the difficulties with constructability, the ect to replace 13 bridge structures. UDOT is endeavoring to high material cost, and the additional time required to splice make ABC the standard for bridge construction, so SPMTs SMA bars suggest that the technology is not ready for use in are being employed to assist in accomplishing that goal. See ABC. The scores for this connection type are shown in Table the UDOT website for the ABC SPMT Process Manual and 29 and Table 30 as connection 2. Design Guide (2009a) for more information regarding engi- neering and construction using SPMTs. Technology readiness. SMA bars are a relatively new When SPMTs are used for rapid installation of bridge technology in structural engineering. Only a handful of replacement projects, the traveling public experiences fewer studies and tests have examined the material's advantages hours interrupted by construction and spends less time in and disadvantages for use in lateral force resisting systems. work zones. In addition, workers have less exposure to traffic SMA bars have not been experimentally tested for use in hazards. Typically bridges requiring transport using SPMTs precast bridge elements. Experimental testing of a con- are simply supported beam and slab spans. Constructing the structible SMA connection detail with prefabricated bridge entire bridge superstructure away from the bridge site can substructure elements needs to be completed before consid- allow longer cure times prior to loading for all concrete com- Table 32. Technology readiness level evaluation for emerging technologies. Technology Readiness Level (TRL) % of Development Complete TRL Description 0-25 25-50 50-75 75-100 1 Concept exists 2 Static strength predictable 3 Non-seismic deployment 4 Analyzed for seismic loading 5 Seismic testing of components 6 Seismic testing of subassemblies 7 Design and construction guidelines 8 Deployment in seismic area 9 Adequate performance in earthquake