Construction Cost: $75M; Dates of Service: 04/2022 – 07/2022
The project involved the construction of a steel arch suspension bridge over I80 for pedestrians and bicyclists, and the reconfigurations of street traffics from convergence of frontage roads, freeway ramps, and Gilman Street. The suspension pedestrian overcrossing consists of east and west reinforced concrete box girder ramps, and the middle portion consisting of two post-tensioned edge beams and intermediate reinforced concrete floor beams at hangar points connected by hangar cables to the two steel arch ribs anchored to two elliptical bent caps on both sides.
Analyzer’s responsibilities included:
- Computing soffit and deck grades for the east and west ramps.
- Computing hangar elevations for the cable hangar inserts compensating for structure deflections during various construction stages.
- Responding to contractor’s requests for information.
- Reviewing and authorizing structures submittals.
- Supervising 2 field inspectors.
- Coordinating and inspecting mitigation for 2 CIDH piles with issues of blocked inspection tubes from dropped rebar cages and casings.
- Attending status meeting with Alameda Corridor Transportation Authority and Caltrans to resolve contract and construction issues.
- Liaise with consultant designers to resolve issues on deck profile and construction of hangars and steel arches.
- Liaise with Caltrans Foundation Testing Branch to expedite acceptance of anomalous CIDH piles which stalled the project at one point.
- Liaise with Caltrans Falsework engineer to resolve falsework grading, design and construction issues.
Value Added
- Working with Caltrans Foundation Testing Branch and consultant Geotech engineer to resolve issues on anomalous CIDH piles and blocked inspection tubes which threatened to stall the project. During CIDH construction for the retaining wall of West Ramp Approach, contractor inadvertently dropped the rebar cages for 2 CIDH piles resulting in blocked inspection tubes, twisted rebar cages, distorted holes and anomalous concrete. Analyzer coordinated and inspected the coring given the challenging conditions above. Analyzer made the determination to cut through rebars in various structurally non-critical regions in order for coring to proceed to pile tip. A few attempts were made to change the locations of the cores because the cores went outside of the pile due to the pile slant. Decision was made to core based on the slant of the pile and the coring was performed successfully to pile tip. Based on the core information, a decision was made to mitigation the piles by Caltrans approved standard mitigation of using hydroblasting and pressure grouting, and I inspected the pile mitigation and subsequently had the piles accepted by Caltrans and Designers without having to redesign and replace the anomalous piles which would seriously impact the project schedule and cost.
- Working with Designers to resolve issues of grades during the construction stages of hangars and steel arches and the impact on deck profiles and aesthetics. Because the bridge superstructure was poured in 2 stages, stem and soffit first, and then the deck, the deck grade and camber are complicated by the changes in dead load deflections of bridge girders and falsework, and their interactions. To further compound the issue, the suspension hangars were initially cast in the stem and soffit pour, and it was deemed crucial to compute the initial hangar grades accurately so that they would be installed within tolerances to the supporting steel arches with further changes in elevations from deck pours. Analyzer performed extensive calculations for the initial hangar grades.