Doka’s Top 50 Forming System Speeds Bridge Project
📅 Tue November 27, 2007 - West Edition
Highway 1, the fabled road that runs along California’s coastline, makes for some dramatic scenery — and at times, dangerous road conditions. The aptly named Devil’s Slide region is one of the more treacherous stretches of the highway, and it’s often the scene of rock slides and road closures. After a particularly debilitating incident in 1995 (the section of Highway 1 between Pacifica and Monterrey was closed for 158 days, racking up $3 million in repair costs), the California Department of Transportation (Caltrans) realized it was time to come up with a permanent solution.
That solution — a bypass consisting of two tunnels bored into San Pedro Mountain and a 1,000-foot bridge spanning the valley north of the tunnels — is currently under construction on Highway 1. Construction on the $272-million project began in August 2006, with work on the twin bridges preceding construction of the tunnels. The balanced cantilever design of the bridges consists of two sets of twin piers, from which concrete box sections are being constructed outward in an attempt to preserve the environmentally sensitive valley below. Aesthetic details such as tapered piers and curved struts will allow the structure to blend in with the surrounding environment.
To help build the bridge, general contractor Disney Construction relied on Doka USA’s Top 50 forming equipment, which is designed to provide easy and efficient forming sequences for large-area projects. Doka also supplied custom fabricated parts to handle the geometric conditions and proper fitness of the formwork. The Doka system was used in conjunction with a launch traveler from a different supplier.
Because the ambitious construction schedule called for casting steps weekly, the versatility and efficiency of the Top 50 system was especially valuable. The system can be configured to meet the unique demands of individual projects, and for the bridge’s fast-paced schedule, that meant designing the system for fast and safe stripping of the formwork, after which the interior forms were immediately reconfigured and rapidly re-set into the next casting.
The Top 50 system’s ability to adapt to any type of architectural requirement, form facing, formwork pressure tie-hole pattern also came in handy on this project. The unusual geometry on this bridge design, including a radial curve with a varying cross slope from 2 to 10 percent, as well as a super-elevated bridge deck, made detailing each pour crucial for maintaining proper control.
In addition, because the bridge didn’t feature the typical wings that most cantilever bridge designs do, attaching formwork to the previous casting required additional anchorage points. Doka’s ability to conform standard components to the unusual design of the bridge and adapt to quickly changing conditions made the transitions from pour to pour simple.
The amount of planning, attention to detail and on-site expertise that Doka was able to provide to the contractor also went a long way in helping to get this major project off the ground. Doka provided the contractor with detailed drawings, and a Doka representative was on-site to provide expertise and guidance during the initial erection. The project’s success was largely dependent on good coordination and communication between Doka, the contractor, the traveler supplier, the bridge designer and the project’s consulting engineers. Multiple meetings and discussions were held to control and maintain accurate, fast, safe and efficient construction of the bridge.
Rick Disney, president of Disney Construction, stated “Doka’s performance on our project was exceptional. They delivered a great product, which included detailed shop drawings with an eye for detail. In addition, the pre-assembly and on-site support was a great benefit in getting the project started properly. We look forward to partnering with them on future projects.”
Thanks to the dedication of the entire team, the $40-million bridge is on track to be completed in the summer of 2008. It will have to languish without traffic for a few more years, though, until tunnel construction is complete in 2011. Once the Devil’s Slide bypass is in use, the old section of highway, along with 70 acres of state-owned land, will be set aside for public access and recreational use, ensuring that those who travel Highway 1 in the future will be able to enjoy both the beauty of unparalleled scenery and the security of safe roads.
For more information, call 877/365-2872 or visit www.dokausa.com.