The historic Ben Sawyer Bridge was built in 1945 to carry locals and visitors between the east cooper barrier islands of Sullivan’s Island and Isle of Palms with Mount Pleasant and the rest of the Charleston area. For years, it was the only vehicular access for both Sullivan’s Island and the neighboring Isle of Palms. The Isle of Palms Connector was completed in 1993 and provided additional access to both Sullivan’s Island and the Isle of Palms.
The Ben Sawyer Bridge drew significant national attention when Hurricane Hugo came ashore in the Charleston area in 1989. The storm essentially picked up and rotated the swing span, leaving it tilted at a 45-degree angle, which created one of the lasting images of the hurricane’s devastation. The swing span was lifted back into place on October 5, 1989. One lane of the bridge was re-opened to traffic on October 8, 1989.
Traffic Congestion Traditional construction requires a 12-month, 11-mile detour through the Isle of Palms and Mt. Pleasant. ABC requires a 10-day detour. ABC avoids approximately 12 months of additional traffic congestion in both the Town of Mt. Pleasant and the Isle of Palms. ABC reduces crash potential. ABC reduces motor user costs. ABC provides much greater access to both Sullivan’s Island and the Isle of Palms.
Quality of Work ABC improves the quality of work by constructing the swing span in an off-site controlled atmosphere. The use of ABC further improves the quality by having the majority of the swing span’s electrical and mechanical components installed off-site as well. Preliminary functional testing can be completed off-site without interference of the motoring public. Marine Traffic ABC has much less impact to the intra-coastal waterway and its’ users.
Project Duration – 540 days Liquidated Damages - $2,900/day over 540 Days DBE Goal – 5% 5-Year project warranty Warranty Bond ($5 Million) Professional Liability Insurance ($3 Million)
Duration – 10 days for Total Closure Closure Restrictions – Prohibited between April 1 st and October 1 st. Prohibited between December 15 th and January 3 rd. Incentive Pay - $2,500/hour up to 48 hours. Disincentive - $2,500/hour over 10 days with no cap. Swing Span fully operational
April 29, 2010 cracks in the webs of steel plate girders were found by the District 4 Bridge Inspection Team at I-77 NB and SB over S-12-56 in Chester County Bridge Maintenance Office verified the severity of this condition, which did not exist as of the previous normal inspections 2 years ago It is believed that the primary causes for the cracked girders on I-77 are the following: thin web plates (<1/2”), these were 3/8” diaphragm and stiffener web plates were only welded to the web and top flange thus causing an inordinate amount of torsion to be carried more directly by the web 22 Weld No weld Diaphragm s offset due to skew
Other factors contributing to the cracking were: bridge skew torsional fatigue and possible overall fatigue possible overheating of the steel substrate due to multiple weld passes on the web to flange connection during fabrication material mechanical properties (to be verified by testing) construction loadings during I-77 construction could have reduced the fatigue life Emergency Declaration was approved by SCDOT Secretary of Transportation Limehouse on May 3, 2010 met two qualified bridge contractors on site May 4, who were given information that required the contractors to bid on temporarily shoring and replacing both steel plate girder main spans District 4 closed the ramps and overpass/S-12-56 on May 5, 2010 and began work to improve the on and off ramps which were used for the detour Bids were received on May 10, 2010 and an accelerated contract cost and schedule was negotiated on May 11, 2010 with the project low bidder, United Contractors 23
Temporary shoring was installed beginning May 12, 2010 to allow traffic to continue using the bridges until closed for work 24 Temporary Shoring
Bridges were closed on June 7, 2010 and demolition of the main spans began. New girders were set beginning June 11, 2010 25
Interstate Rehabilitation of I-385, approximately 15 miles, with 10” of high strength concrete Raising of 6 overpass bridges Bridge replacement of fly-over bridge that connects I-26 westbound to I-385 northbound Shoulder widening with roller compacted concrete I-385 northbound detoured; construction duration condensed from 3 years to 7 ½ months
Northbound Detour Relatively low ADT (17,600 to 21,900) within project corridor Existing pavement width (32’) insufficient to stage or run head to head traffic Parallel interstate in close proximity for detour traffic (15 mi./15 min.) Good network of regional primary routes for local traffic Detour Benefits Safety increased by separating motorists from construction operations Construction operations streamlined with closure; allowed pavement of full width PCC up to one mile per day (weather permitting) Estimated $34.6 million in savings compared to traditional construction staging over multiple years
Affected businesses, elected officials, and state trucking association contacted months prior to closure Brochures and maps were distributed at local Rest Areas and project website was established with detour information Contractor was required to hold Public Information Meeting prior to closure Pre-construction and mid-construction partnering meetings Contract had $25,000 daily incentives not to exceed $750,000 and $50,000 daily liquidated damages with no cap beginning August 16, 2010
Bridge jackings were let in separate contract and completed prior to I-385 northbound closure Project let five months in advance of closure date for prep work and material fabrication (fly-over bridge superstructure) All excavation was converted to Site Excavation Concrete paving machine guided by laser total station with an automatic dowel inserter Leica Scan Station 2 survey scanner used to verify cross- slope correction