Innovative Bridge Designs for Rapid Renewal (2014) / Chapter Skim
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8C h a p t e r 2 research tasks The research effort was organized according to the following 14 tasks: Task 1: Conduct an international and national literature search of published and unpublished material about innovative bridge technologies pertinent to rapid highway renewal. Task 2: Conduct multiple focus groups to identify existing obstacles in the design and construction processes that inhibit optimum use of rapid renewal technologies.
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9Task 1: Conduct an international and national literature search of published and unpublished material on innovative bridge technologies pertinent to rapid highway renewal. The literature review consisted of gathering published data from various sources including academic journals, conference proceedings, trade publications, research reports, and similar outlets on many topics related to this project.
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10 representatives from all regions of the country participated in the focus group conference calls. Task 3: Develop new bridge designs that are more compatible with these innovative construction techniques and technologies.
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11 and further evaluations. The purpose of these evaluations was to recommend ABC concepts and techniques that could be advanced to standard plans and field trials in Phase III.
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12 the research and incorporated the ABC standards. The US-6 bridge, which crosses Keg Creek near Council Bluffs, Iowa, is representative in size and length of a large majority of bridges across the United States, was identified and replaced as a demonstration bridge using prefabricated elements and modular systems.
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13 designed and fabricated in less time, and then installed on site in minutes or hours using innovative construction equipment. The products should accommodate the future reuse of these systems.
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14 ABC practices and to identify obstacles currently inhibiting ABC use for a greater number of bridge replacements. No meaningful response from the precaster surveys was obtained; thus, only the owner and contractor surveys are included.
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15 the speed with which bridge projects are delivered. When asked why ABC techniques were used, the criterion most likely to be considered "very important" or "important" was traffic disruption mitigation, at 98%.
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16 they can do to engage the contractor during the design phase, which makes ABC more difficult. Some states have used CM/GC contracting to improve this early communication without going to design-build.
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17 placement using self-propelled modular transporters (SPMTs) (Figure 2.1)
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18 • As simple to erect as possible 44 Fewer workers on site; 44 Fewer fresh-concrete operations; 44 No falsework structures required; 44 Simpler geometry; and 44 Bearings or seismic I/D systems instead of pier continuity. ABC should demonstrate flexibility and scalability in all three aspects of renewal, which are 1.
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19 • When designing, consideration should be given for structures to be moved, for acceptable deformation limits during movement. Overall, there is a need for better specifications.
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20 • Reduced exposure of traveling public to construction activities. • Less time curing concrete in the field.
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21 Design Concept D-2: Hybrid Drilled Shaft/Micropile Foundation System Concept Description The intent is to develop a high-capacity drilled shaft foundation system that eliminates the need for large lifting equipment and complex rigging, handling, and fabrication. Micropile foundation systems have a number of key advantages for ABC.
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22 A key benefit of this approach is that a significant length of the drilled shaft in soil is replaced by micropiles. By using a much shorter drilled shaft length, significant time and logistics savings accrue in excavation, reinforcement placement, and concreting.
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23 One of the goals of this research project is to produce preengineered plans for precast piers that can be readily implemented by state DOTs with minimal additional effort. The intent is to provide standardized details that are applicable to both seismic and non-seismic regions.
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24 provide cost savings by shortening the bridge length. But they can also provide benefits because they can accelerate the construction schedule, require smaller equipment to construct, can tolerate significant settlements, and allow for the mitigation of settlement before placement of the bridge.
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25 For taller piers (see Figure 2.9) , which have been constructed up to 200 ft in height, the SPER piers are constructed using an inner and outer form that provides a large hollow space and provides considerable material and weight savings.
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26 strengths of 18,000 psi to 30,000 psi can be achieved, depending on the mixing and curing process. The material has an extremely low permeability and is highly durable due to the almost non-existing intrusion of chloride-laden water.
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27 Source: Keierleber et al.
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28 of a UHPC waffle slab, could be used as either a short-span bridge or, in a slightly modified configuration, as a fast-track deck replacement system for a girder bridge. Advantages UHPC offers a number of advantages for accelerated construction: • Extremely high strength-to-weight ratio.
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29 • Ductile connections and similar details can be developed for seismic applications. • Easy transportation and erection on site.
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30 Advantages Steel/composite superstructures have great potential for economy and for ABC as described below: • They are lighter primary structural members than precast, prestressed girder structures. This allows for longer spans and larger building blocks to be prefabricated in the shop.
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31 trying to take advantage of the low cost, versatility, and compressive strength that concrete as a building material has to offer. To achieve the same quality as conventional construction, a superior knowledge of the behavior of these materials, separately as well as when combined to form an efficient composite material, is usually required.
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32 lack of proper posttensioning. For spans up to approximately 100 ft, the system can be simplified considerably by using solid slab sections that are match cast and posttensioned for extremely high durability and low cost.
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33 • Segments designed for transportation and erection stresses. This is an issue only for full spans in the channel bridge option.
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34 shipping the segments in pieces, splicing on site, and using a temporary launching truss for erection, as discussed in the section on Construction Concept C-2.) • Design for sections that can be transported in pieces and spliced on site before erection to extend spans to 200 ft and beyond.
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35 system, shimming the bearings of the deck sections may be necessary. Preservation Strategy and Use of Asphalt Overlay • The combination of high-performance concrete and highquality construction will provide a long service life for these systems.
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36 strength over the course of the next few days until over 10 ksi of strength is achieved in about 3 days. No special curing is needed for the joint material (though steam curing is beneficial when applied)
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37 widespread use in Texas, will increase the U beams' availability with local and regional fabricators and drive down the cost associated with designing, detailing, and fabricating the units. A system that can span 115 ft has already been successfully completed in Texas, where precast shell columns and complete superstructures were erected in as little as 4 days.
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38 Design Concept D-12: Space Frame Bridge Superstructures Concept Description The steel tubular space frame is a lightweight structure that has seen significant growth, primarily in the building industry, as shown Figure 2.24. Today there are numerous manufacturers of steel space frames.
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39 posttensioning system can be installed by the contractor without specialty equipment or labor quickly and easily. Eliminating the CIP joints accelerates the schedule considerably.
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40 Advantages Full-depth precast deck panels offer a number of significant advantages in the ABC environment: • Accelerated erection. • High-quality plant production with tighter production tolerances.
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41 • Thin steel pipes provide to concrete filling 44 Falsework and formwork during filling; 44 Well-distributed reinforcement; 44 High transverse confinement for enhanced ductility; and 44 Protection from aggressive agents for improved durability. • Concrete filling provides to thin steel pipes 44 Additional compressive strength and stiffness; 44 Control of local buckling without any need for stiffeners; and 44 Enhanced ductility.
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42 Concept ND-1a: Two Girder Systems Concept Description The two girder system typically takes full advantage of the load distribution characteristics of a two-way slab, and engages both girders in an efficient manner regardless of how the load is applied to the superstructure. In the design of any bridge, the ideal load fraction for which each girder is designed can be added to the load fraction for which all the other girders are designed, the sum of which should never be any larger than the actual live load that is applied to the bridge.
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43 • Composite concrete top and bottom flanges. • Construction in situ under controlled conditions.
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44 Concept ND-1c: Segmental Composite Bridges Concept Description The Boulonnais bridge was constructed with conventional segmental technology, except that it incorporated a tubular steel space frame, as illustrated in Figure 2.34, in lieu of conventional precast webs. This space frame reduced weight and facilitated delivery and erection.
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45 FRP composites offer many advantage for building bridges, such as the following: • Reduced weight: The reduced dead weight of the deck allows the bridge to carry an increased traffic load. • Decreased effects from environment: FRPs do not rust and are not affected by salts and other contaminants.
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46 Application for ABC Construction The ADDCs can be delivered to the site in various configurations (shipped on flatbed trucks or towed using mountable axles) , with delivery options weighed by contractors on the basis of project criteria.
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47 Figure 2.36. ADDC used for different span configurations.
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48 Figure 2.37. ADDC used to remove and replace exterior portions of a structure.
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49 Figure 2.38. ADDC used to remove and replace center portion of a structure.
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50 Figure 2.39. ADDC used to remove first half of a narrow structure.
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51 Figure 2.40. ADDC used to remove second half of a narrow structure.
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52 Figure 2.41. ADDC rigged with multiple axles to reduce loads on structure.
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53 Figure 2.42. ADDC is transportable on urban and rural highways.
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54 Figure 2.43. ADDC is adjustable for multiple span lengths.
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55 Construction Concept C-2: Launched Temporary Truss Bridge Concept Description Launched temporary truss bridges (LTTBs) offer new, modularized, lightweight equipment that can be used for rapid construction with minimal disruption to activities and environment below the structure.
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56 with delivery options weighed by contractors on a projectby-project basis. Once at the site, LTTBs will be erected and launched.
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57 Figure 2.45. LTTB used for different span configurations.
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58 Figure 2.46. LTTB used to deliver girders across spans.
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59 Figure 2.47. LTTB is transportable on urban and rural highways.
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60 Figure 2.48. LTTB is adjustable for multiple span lengths.
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61 Figure 2.51. Launched prestressed bridge.
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62 anchor blocks may be used for the prestressing tendons. The internal form of the box girder is launched with the bridge and extracted backwards into the new reinforcement cage.
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63 • <1% dynamic friction. • 79 tons sliding force.
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64 However, the total cost of a tunnel is not measured only in terms of volume of concrete, excavated material, and so forth. When the ground above and adjacent to the tunnels includes rail tracks, roads, services, or other facilities, it is necessary to consider the cost of the disruption to the service provided by these facilities to obtain a true indication of the total cost of the tunnel.
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65 Figure 2.55. Tunnel jacking, typical longitudinal section, Example B
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66 Figure 2.56. Section view along jacking plane.
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67 Figure 2.57. Typical pilot tunnel configuration and sliding surface detail.
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68 method for installing culverts without severe disruption to the overlying rail service. The development from pipe jacking to tunnel jacking was made in the 1960s, when circular pipe jacked sections were found to be either too small or were inefficient for their intended purpose.
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69 forward by the amount of excavation. Often the shield's cutting edges will remain embedded in the ground to enhance stability of the tunnel face and to limit ground movements and resulting settlement, although in favorable ground conditions it can be possible to excavate a little ahead of the shield, particularly any internal shield dividers.
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