WHAT HAVE BEEN ACCOMPLISHED:
JMEC has been Prime Design Consultant for the seismic retrofit of the Marsh Drive Bridge over Walnut Creek per the Caltrans LAPM. Work performed including field visits, structural and civil design, geotechnical investigation, design reports, working with permitting agencies, preparation of construction documents and construction cost estimating.
The 325-ft reinforced concrete slab bridge has 10 spans with typical span length of about 36-ft. The original bridge built in 1938 was subsequently lengthened in 1965 as part of the creek widening project. The existing expansion joints and the concrete pile extensions are most vulnerable to fail under seismic condition.
JMEC performed seismic evaluation and retrofit design based on Caltrans seismic design criteria and displacement ductility of support members. Provisions for future bridge widening was included in the bent cap and foundation retrofit design. The retrofit solutions essentially underpinned the existing bridge by installing CISS piles and strengthening existing cap beams. The retrofit measures included:
JMEC has been Prime Design Consultant for the seismic retrofit of the Marsh Drive Bridge over Walnut Creek per the Caltrans LAPM. Work performed including field visits, structural and civil design, geotechnical investigation, design reports, working with permitting agencies, preparation of construction documents and construction cost estimating.
The 325-ft reinforced concrete slab bridge has 10 spans with typical span length of about 36-ft. The original bridge built in 1938 was subsequently lengthened in 1965 as part of the creek widening project. The existing expansion joints and the concrete pile extensions are most vulnerable to fail under seismic condition.
JMEC performed seismic evaluation and retrofit design based on Caltrans seismic design criteria and displacement ductility of support members. Provisions for future bridge widening was included in the bent cap and foundation retrofit design. The retrofit solutions essentially underpinned the existing bridge by installing CISS piles and strengthening existing cap beams. The retrofit measures included:
- Add 36-in diameter CISS piles and strengthen cap beams
- Add cable restrainers and shear keys at expansion joints
- Construct wider cap beams and provide longer CISS piles for future bridge widening
Project Role: Prime Design Consultant
Clients: City of Concord
Clients: City of Concord
Special Issues: Original hydraulic evaluation and sedimentation analyses performed by Caltrans have indicated that the impacts of the seismic retrofits on the stream flow are small. Later studies in 2010 performed by the Contra Costa County Flood Control District using the USACE (US Army Corps of Engineers) updated hydraulic model has found that the impacts cannot be ignored and mitigation should be considered. The bridge was later replaced to minimize hydraulic impacts and to improve creek flow at Lower Walnut Creek.
Schedule: Construction was completed in 2022
Schedule: Construction was completed in 2022
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165 Lennon Lane, Suite 106, Walnut Creek, CA 94598
Tel: (925) 944-8999 Fax: (925) 944-9998
165 Lennon Lane, Suite 106, Walnut Creek, CA 94598
Tel: (925) 944-8999 Fax: (925) 944-9998
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