Bridges for Service Life Beyond 100 Years: Service Limit State Design (2014) / Chapter Skim
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41.1 Objectives of Project R19B The request for proposal for SHRP 2 Project R19B stated the following objectives: • Develop new design codes that incorporate a rational approach based on service limit states (SLSs) for durability and performance of bridge systems, subsystems, components, and details that are critical to reaching the expected service life and assuring an actual life beyond 100 years.
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5 1.2 Scope 1.2.1 Original Scope As originally scoped, the project was broken into two phases containing the tasks described below. Phase 1 Task 1 Conduct a review of the literature to review and identify current practices of using SLS principles for determining structural service life approaches.
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61.2.2 Revised Scope for Tasks 5 and 6 Task 5 was completed. Members of the INC were selected and approved.
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7 • Task 10. Modjeski and Masters took the lead, working primarily with the University of Delaware.
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8achieve a determined life with a specific level of certainty because the tools and data to accomplish this calibration were not available to the AASHTO LRFD code writers. The current AASHTO LRFD SLSs include limits on the following: • Live load deflection of structures; • Cracking of reinforced-concrete components; • Tensile stresses in prestressed concrete components; • Compressive stresses in prestressed concrete components; • Permanent deformations of compact steel components; • Slip of slip-critical friction bolted connections; and • Settlement of shallow and deep foundations, among others.
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9 Various aspects of deformations that should be considered in the design of bridges include • The effect of uneven settlement between various support elements; • The rotation and horizontal movements of the foundation system affecting movements at the bridge-seat level; and • Serviceability problems near a bridge abutment, in particular the ubiquitous "bump at the end of the bridge" that affects joint serviceability and abutment performance. The cumulative effect of these deformations may generate uneven deformations and stresses across a bridge system and its subsystems.
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10 Rostam (2005) describes two overarching strategies for addressing durability: • Strategy A, avoidance (such as use of corrosion-resistant rebar)
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11 sulfates in the mix; usually these sulfates are in the water, but they may be in the aggregate. Sulfate attack debonds the aggregate and creates expansive pressure leading to crack or delimitation.
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12 could be considered an SLS for some bridges) could be quite different from that which affects deflection, vibrations, concrete cracking, and so forth.
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13 Performance Committee. In addition, one of the coprincipal investigators has been associated with LTBPP virtually throughout the project and is now technical director of the project.
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