ASCE Met Section Spring Seminar - Session 4

Thursday, May 28 - 5:00-6:30PM

Transforming the I-81 Viaduct: Design and Construction of the Community Grid

Speaker: Kian-Siang Chau, PE, SE, PMP, LEED AP BD+C, DBIA

The I-81 Viaduct Project in Syracuse, New York is a major transportation infrastructure program undertaken by the New York State Department of Transportation (NYSDOT) to replace the aging elevated interstate viaduct through downtown Syracuse with a Community Grid transportation network. The program includes numerous bridge rehabilitations and replacements, retaining walls, and staged construction schemes within a constrained urban corridor.

This presentation focuses on structural engineering challenges associated with the design and delivery of multiple bridge, retaining wall, and underground utility elements. These include bridge structures and retaining wall systems designed under significant geometric, geotechnical, and constructability constraints. The discussion will highlight the structural engineering considerations that informed bridge type selection, including the use of fixed-frame abutments, multicolumn bents with integral steel caps, jointless abutment systems, and optimized superstructure configurations to accommodate roadway geometric constraints while improving long-term durability and maintainability. The presentation will also discuss the structural design of support-of-excavation systems required for major underground utility construction and relocation.

Foundation design in complex subsurface conditions will also be discussed, including the use of deep foundation systems to address variable soil and rock profiles while accommodating existing infrastructure and utility conflicts. Additional topics include structural considerations for staged demolition and construction adjacent to active traffic, the design of retaining wall systems within limited right-of-way, and coordination between structural elements and major utility relocations.

The presentation will also describe how structural design parameters developed under these contracts were incorporated into contract documents to support both design-build and design-bid-build procurement processes. Lessons learned illustrate key structural engineering strategies for delivering bridge and transportation infrastructure within a complex urban megaproject environment.

Thursday, May 28 - 7:00-8:00PM

Post-Tensioning Preservation and Rehabilitation of the I-526 Wando River Bridge

Since the discovery of a ruptured 1,010-foot external post-tensioning tendon in 2016, the I-526 Wando River Bridge has undergone an extensive program of evaluation, rehabilitation, strengthening, and durabilityupgrades. The rupture, caused by corrosion accelerated by grout voids and water infiltration, prompted theSouth Carolina Department of Transportation to initiate a comprehensive assessment of the bridge’sexternal post-tensioning system and implement repairs to restore redundancy and extend service life.

The initial investigation utilized advanced inspection and testing techniques, including magnetic flux leakagescanning, capacitive probe testing, grout material evaluation, and borescope inspections of externaltendons. Rehabilitation measures included multiple tendon replacements, installation of supplementaltendons, and segment joint strengthening using steel frame systems. In spans where tendons could not beremoved or replaced, an expandable supplemental post-tensioning system utilizing post-installed anchorsand deviators was developed and constructed. Time-dependent staged construction analyses and detailedthree-dimensional finite element models supported evaluation of existing conditions and design of thestrengthening solutions.

Building on the experience from the initial repairs, subsequent work has focused on improving long-termdurability and structural performance. Recent upgrades include impregnation of external tendons withcorrosion inhibitors to mitigate future deterioration, carbon fiber reinforced polymer (CFRP) strengthening ofbox girder webs to increase shear capacity, and installation of five new external tendons using innovativedetailing and construction techniques, including the first application of un-ducted post-tensioning tendonson a bridge in the United States.

This presentation summarizes nearly a decade of investigation, repair, and durability enhancement on amajor post-tensioned segmental bridge, highlighting innovativ

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Host or Publisher ASCE SEI Metropolitan Section