The St Croix Crossing Bridge is an extradosed bridge, which is something of a cross between a segmental box girder and cable-stayed bridge. The scale of the massive concrete segments can be seen in the picture above in comparison to the barge the segments are sitting on and some of the equipment in the background.
Construction of drilled shafts continues as the superstructure begins to emerge over the skyline between Elizabeth, NJ and Staten Island, NY. The new bridge will be a dual-span 1,983-ft long cable-stayed bridge with approach spans of over 2,500 ft on each side. The bridge is supported on over 200 drilled shaft foundations ranging in diameter from 4.5 ft to 10 ft and socketed into Passaic Formation siltstone.
The GBR is a Public-Private Partnership (P3) that represents a major milestone for the PANYNJ in its distinguished history of bridge building in the greater New York City metropolitan area. The existing Goethals Bridge along with the Outerbridge Crossing and the Bayonne Bridge comprise the three Port Authority bridges connecting Staten Island with New Jersey. The Goethals Bridge and the Outerbridge Crossing are cantilever truss structures and both opened on the same day in 1928. They were designed by J.A.L. Waddell under the supervision of the eminent engineer Othmar H. Ammann (1879-1965), who was the designer of many other iconic bridges in the NY City area including the Bayonne Bridge (1931), the George Washington Bridge (1931), and the Verrazano Narrows Bridge (1964). The designer of record for the replacement Goethals Bridge is Parsons Corporation, which is the successor firm of Robinson & Steinman, whose principal David B. Steinman was also a notable NY area bridge designer and a contemporary and rival of O.H. Ammann.
Each main pylon tower of the GBR is supported on a group of six 9-ft diameter drilled shafts and each anchor pier is supported by two 10-ft diameter shafts. Approach piers are two-column bents with each column supported on a rock-socketed drilled shaft.
DBA is the foundation design engineer of record and this project provides an example of how rock-socketed drilled shafts can provide a reliable and cost-effective means of supporting a major bridge by taking advantage of the high resistances that can be achieved. Key factors involved in taking advantage of rock sockets for this project were: (1) load testing to demonstrate high axial resistances (>30 ksf side resistance and >300 ksf base resistance), (2) utilization of all relevant construction QC/QA tools to ensure that rock sockets are constructed in a manner that is consistent with construction of the load-tested shafts that provide the basis of the design, (3) close collaboration between all members of the design-build team, and (4) adequate subsurface characterization, especially a thorough characterization of rock characteristics and their effect on socket resistances. Load testing for this project demonstrates that side and base resistances can be used in combination to design rock socketed shafts for axial loading. This approach avoids the use of unnecessarily deep sockets, thereby minimizing the associated construction risks and costs.
DBA is on the design-build team that is replacing the Goethals Bridge for the Port Authority of New York and New Jersey (PANYNJ). We are not able to post much about the project or our involvement due to security agreements. However, the PANYNJ has a public website for the project (http://www.panynj.gov/bridges-tunnels/goethals-bridge-replacement.html) that has several webcams. As is the case with most big projects these days, the webcams are a common feature and show some great views of the project.
To give you an idea of what the project involves, here is a summary from the PANYNJ site:
The replacement bridge will be located directly south of the existing bridge and will provide:
Three 12-foot-wide lanes in each direction replacing the current two narrow 10-foot-wide lanes
A 12-foot-wide outer shoulder and a 5-foot-wide inner shoulder in each direction
A 10-foot-wide sidewalk/bikeway along the northern edge of the New Jersey-bound roadway
Improved safety conditions and performance reliability by meeting current geometric design, structural integrity, security and seismic standards, and reduces life-cycle cost
A central corridor between the eastbound and westbound roadway decks, sufficient to accommodate potential transit service
State-of-the-art smart bridge technology
The project also includes the demolition of the existing bridge upon completion of the replacement bridge.
The design-build team Tappan Zee Constructors that is building the Tappan Zee Bridge is installing the over 200-ft long steel pipe piles using a relatively simple concept to mitigate vibration impacts on fish – a bubble curtain. Such curtains have become more common as an approach to mitigate potential impacts (pardon the pun) on aquatic life when large piles are driven over water. The vibrations from the hammer impact on the pile during driving are reduced or dampened by a curtain of bubbles generated around the pile by compressed air. An item in the December 26th ASCE Smart Brief linked an article in The Journal News (White Plains, NY) highlighting the use of the curtain on the Tappan Zee project.
A rubber-looking sleeve covered the hammer where it met the pile, dampening some of the noise in the air. Underwater, however, it was a curtain of bubbles serving as the aquatic equivalent of earplugs for fish and other creatures in the Hudson River.
Aluminum rings are slid over the pilings like the rings on a shower curtain rod before any banging starts. Air pumped into the rings produces a sheath of bubbles in the water around the pile. The froth generated in the water is called a bubble curtain.
“Bubble curtains are designed to protect the fish in the area from the noise generated by the hammer impact below the water level,” said Walter Reichert, project manager for Tappan Zee Constructors. “This divides the water into basically two sections. It greatly reduces the sound waves.”
History was made on Sept. 7, 2013when state and local officials cut the ribbon on the new Hurricane Deck Bridge during a ceremony held in the center of the new structure. The bridge officially opened to traffic in the late evening on Monday, Sept. 9. The original bridge is now closed and will be prepared for demolition during the remainder of 2013. Final demolition will take place in the spring of 2014.
NCHRP Synthesis 429 – Geotechnical Information Practices in Design-Build Projects is a report on the current practices of allocating and managing geotechnical risk through the use (or lack of!) geotechnical information in transportation project bid documents. Even though design-build as a delivery process for projects has been around for a while now, the allocation of risk due to subsurface conditions is an issue still treated with a variety of approaches.
Those of us who have been in this industry for a while know that a thorough geotechnical investigation reduces both cost risk and construction/schedule risk. Design-build is an effective method for accelerating project construction and delivery; however, the acceleration of the schedule puts more pressure on the geotechnical design since “geotechnical investigation and design is usually the first design package that must be completed and geotechnical uncertainty is usually high at the time of DB contract award.”
Because geotechnical investigation and design is usually the first design package that must be completed and geotechnical uncertainty is usually high at the time of DB contract award, the design-builder’s geotechnical designers are under pressure to complete their work and enable foundation and other subsurface construction to commence. Successfully managing the geotechnical risk in a DB project is imperative to achieving the requisite level of quality in the finished product. The purpose of this synthesis is to benchmark the state of the practice regarding the use of geotechnical information in DB solicitation documents and contracts. The high level federal encouragement through EDC for state DOTs to accelerate project delivery by using DB elevates the need to manage geotechnical risk while expediting geotechnical design to a critical project success factor, and makes the results of this synthesis both timely and valuable.
As is the case with NCHRP synthesis reports, the authors conducted a literature review, conducted a survey of state DOTs and other agencies, and developed some conclusions that include effective practices for managing geotechnical risk.
The synthesis was based on a comprehensive literature review; a survey of U.S. DOTs, which received responses from 42 states (response rate = 84%); a content analysis of DB solicitation documents from 26 states; a content analysis of DB policy documents/guidelines from 12 state DOTs and 5 federal agencies; and interviews of 11 DB contractors whose markets encompass more than 30 states. The synthesis also furnishes three legal case studies (Colorado, Illinois, and Virginia) on cogent geotechnical issues and four geotechnical engineering case studies (Hawaii, Minnesota, Missouri, and Montana) that illustrate the methods transportation agencies use to deal with geotechnical issues on DB projects. Conclusions were drawn from the intersection of independent sources of information from the survey, case studies, and literature.
Some of the effective practices highlighted include the use of confidential Alternative Technical Concepts (ATC) during pre-bid, explicit differing site conditions (DSC) clauses that clearly quantify the design-build team’s risk and the threshold above which the DOT assumes the risk, the use of qualified personnel, and timely review schedules for geotechnical design items early in the project.
Our (DBA) experience in design-build has seen the range from effective practices to poor practices. This report provides a great summary of many of the effective practices we have found to be beneficial and that help reduce conflicts and delays. We can’t completely eliminate geotechnical risk, but it can be effectively and equitably managed.
The W. 7th Street bridge is a gateway between downtown Fort Worth and its cultural district. TxDOT designed the bridge with six arch spans across the Trinity River to improve safety, pedestrian access and add to the architectural redevelopment under way in this corridor. The project will widen and reconstruct the four-lane bridge with 10-foot sidewalks. It is the world’s first pre-cast network arch bridge.
ENR had an article in early June about the unique bridge (requires subscription to ENR):
Very carefully, of course! (You knew that was coming!)
DBA has had the pleasure of consulting with Sundt Construction on their effort to replace the West 7th Street Bridge over the Trinity River in Fort Worth, Texas. Our role has been to provide geotechnical consulting for the heavy lifts of the arches, as well as a VE design on a secant wall.
The aging Seventh Street Bridge, a popular east-west thoroughfare that connects downtown to the Cultural District, is due to be reconstructed.
The original span was built in 1913 and was expanded in 1953 when the Trinity River was rerouted and the surrounding levees were built. Although the bridge has been determined safe to use, beams, girders and the deck of the 1913 section are deteriorating.
To reduce the impact of closing the bridge, Sundt has installed new drilled shaft foundations on either side of the existing bridge. The twelve, 163-foot long, 300-ton concrete arches were fabricated off-site on the west side of the river. Large trailer dollies with 120 wheels move the arches from the yard to the site. Large cranes from Burkhalter (heavy lift and transport specialist) pick the arches from the dollies on the existing bridge and set them on the new foundations. The bridge is closed or partially closed during each lift. Once all of the arches are in place, the bridge will be closed to demolish the existing structure and build the new deck between the pairs of arches. The compete closure is supposed to last only 150 days.
Here is a time lapse video of the first arch being set:
The first arches were set over the weekend of May 11-12. Here are some links to video and articles:
Nearly 1,000 project teams submitted their best work to ENR’s regional "Best Projects" competitions. For each of the nine regions, our editors assembled an independent panel of industry judges to home in on the winners in 19 categories. The winners of the regional contests moved on to the national competition. A different set of industry judges examined the projects to distinguish the "Best of the Best" in teamwork, success in overcoming challenges, innovation and quality. This year, a new award honors the safest project, judged by industry safety experts in both the regional and national competitions. Also, ENR’s editorial staff chose one special project as the "Editors’ Choice" to represent the pinnacle of design and construction excellence.
The Audubon Bridge won the Editor’s Choice – the editorial staff’s selection of the “pinnacle of design and construction excellence”. Congratulations to everyone at Audubon Bridge Constructors (Flatiron, Granite and Parsons), Louisiana DOTD, and all who worked on the project!