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Effectiveness of Waterproofing Membranes for Precast Prestressed Concrete Adjacent Box-Beam Bridges
Başlık:
Effectiveness of Waterproofing Membranes for Precast Prestressed Concrete Adjacent Box-Beam Bridges
Yazar:
Almonbhi, Ali, author.
ISBN:
9780438097544
Yazar Ek Girişi:
Fiziksel Tanımlama:
1 electronic resource (236 pages)
Genel Not:
Source: Dissertation Abstracts International, Volume: 79-10(E), Section: B.
Advisors: Anil Patnaik Committee members: Ala Abbas, Dr.; Yilmaz Sozer, Dr.; Jun Ye, Dr.; Ping Yi, Dr.
Özet:
Bridge designs frequently employ precast concrete box beams, with adjacent beams connected using grouted keyways. Failure at these joints leads to water leakage and corrosion in reinforcing bars/strands, resulting in severe damage to concrete elements and reducing the bridge's lifespan. This dissertation investigates the causes for the ineffectiveness of waterproofing membranes in preventing leakage at joints of adjacent box beams.
Testing of five commercially available waterproofing membranes showed low tensile and shear strength and high deformability, with membranes exhibiting large elongation and no leakage. Adhesion tests showed limited peel strength. Different practices such as use of primer, sealant, and direct heat were also investigated. Sealant provided better bonding than primer, and heating yielded no improvement in bond strength. All membranes showed low punching resistance but could resist loads up to 1,200 lb in wheel load tests without being damaged.
Prestress losses were calculated for construction scenarios for concrete box beams of ages varying from 7 to 180 days at time of deck placement. The difference in prestress losses have an inverse relationship with concrete age at the time of deck placement, while an inverse relationship exists between the age of concrete of prestressed box beams at the time of deck placement and the differential deflections. Spans having different lengths were found to have a proportional relationship to the difference in prestress losses and differential deflections. While differential prestress losses at different concrete ages contribute to joint cracks between adjacent box beams, losses may not be sufficient to rupture the membranes. The maximum differential deflection between adjacent box beams with different concrete ages may cause cracking in the keyways but is likely to be negligible compared to the ability of the membrane to stretch.
In visits to an existing bridge and a new bridge underconstruction, deficiencies were noted in the implementation of waterproofing membranes: inadequate specifications and ineffective inspection, absence of membranes on portions of the existing bridge, and protrusions/debris on the concrete deck of the new bridge prior to membrane installation. This study recommends that waterproofing membranes continue to be used in bridges and provides suggestions to improve their implementation.
Notlar:
School code: 0003
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