Current Practices and Guidelines for the Reuse of Bridge Foundations (2017) / Chapter Skim
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Pages 7-28
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7 chapter two Literature review Reuse of bridge foundations involves concepts from many disciplines. Accordingly, a relatively broad review of literature is necessary to appreciate the benefits and challenges of foundation reuse.
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8 Bridge Management U.S. transportation agencies use the NBI ratings to inform decisions regarding allocation of agency resources to maintain the inventory of agency bridges.
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9 building foundations, its review of and recommendations regarding the technical and administrative challenges of foundation reuse are also relevant to bridge foundations and to U.S. practice.
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10 one of the presentations from the TRB workshop introduced questions related to risk and responsibility arising in projects involving foundation reuse (Brown 2014)
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11 goal and challenge of existing foundation investigations. The scope of field explorations is generally intended to verify and supplement the information from historical records.
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12 measurements of signals that have passed through the ground and the foundation, whereas pile integrity test measurements only involved signals from within the foundation element. Borehole methods require drilling boreholes close to the existing foundation.
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13 Surface geophysical Methods Seismic methods include Seismic Reflection, Seismic Refraction, Spectral Analysis of Surface Waves, Multichannel Analysis of Surface Waves, and tomography. The methods generally involve interpreting features such as soil layer boundaries based on stiffness contrasts that influence seismic wave velocities.
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14 The contours clearly indicate the shaft locations and accurately identify shaft depth of up to 50 feet. That the geophones were installed next to the shafts, not in line with the shafts, is noteworthy since placement in line with the shafts would not be feasible for many bridges.
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15 Borehole geophysical Methods The Parallel Seismic method applies the same principles used in the pile integrity test methods; however, the collection of data in a borehole adjacent to the existing foundation addresses many of the limitations regarding depth and the effect of pile caps or other structures at the surface. As shown in Figure 6, the method involves striking the existing foundation and recording seismic waves in an adjacent borehole.
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16 process wherein air, water, and negatively charged ions oxidize steel, resulting in its degradation. In addition, corrosion of steel reinforcement is a primary concern regarding concrete durability, as discussed in the following section.
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17 The Leo Frigo case was not the first documented example of severely corroded steel piles. In 1988, Connecticut DoT began replacing the intersection of I-84 and I-91 in Hartford, intending to reuse the existing 30-year-old steel H-piles.
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18 Although these mechanisms are relevant to foundation concrete, it is important to note that documented cases of such threats affecting underground concrete are relatively limited. Mehta and Monteiro (2014)
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19 • Target Design Service Life -- The time period during which the bridge element, component, subsystem, or system is expected to provide the desired function with a specified level of maintenance established at the design or retrofit stage. • Design Life -- The period of time on which the statistical derivation of transient loads is based -- 75 years according to the current version of AASHTo LRFD Bridge Design Specifications" [LRFD (Load and Resistance Factor Design)
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20 The foundations deformation work of project R19B addresses a critical serviceability consideration in designing for service life; however, methods related to the deterioration component of service life are lacking. The same could be said for many bridge components, but is especially true for foundation elements, primarily because of the inherent condition assessment challenges.
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21 corrosion potential. Chloride ions remaining in the concrete are further from the reinforcing steel, providing further service life gains.
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22 • Static (or rational) analysis methods: The methods most often used to predict load capacity of new foundations (e.g., bearing capacity theory and settlement analysis for shallow foundations, methods for predicting unit side and unit tip resistance values for deep foundations)
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23 • Reserve capacity: For deep foundation elements tied into walls, pile caps, or rafts the effects of the adjoining structures were often neglected or considered conservatively in the original design. • Time-related capacity: The capacity of many foundations, particularly driven piles in cohesive soils, increases with time.
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24 FIGURE 12 RuFUS decision method for reuse of deep foundations (Source: Butcher et al.
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25 United Kingdom-based engineering consulting firm Arup developed the Sustainable project Appraisal Routine (SpeAR®) diagram for reuse evaluation (Strauss et al.
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26 fast 14 (Massachusetts dot) In the summer of 2011, the Massachusetts DoT (MassDoT)
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28 An additional challenge is an uncertain standard of care for consulting engineers involved in foundation reuse (Brown 2014)
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