Scheduled for completion by 2016, Pearl Harbor Memorial is a 10-lane bridge. One of the first extra-dosed cable-stayed bridges constructed in the U.S., it is the centerpiece of a $2.2 billion mega-project to reconstruct and widen 7.2 miles of I-95 in Connecticut between West Haven and Branford.
Polygon is proud to have worked with construction firm Cianbro/Middlesex JVIII (CMJVIII) to successfully control the movement of the bridge superstructure during two challenging integral pier cap placements.
The project involved the placement of two integrated pier caps encasing four girders spanning 230 feet over a roadway. In its final design condition, these pier caps lock the girders into the concrete thus restricting movement.
“Structural steel will elongate or contract with temperature changes. If this movement is not controlled while the concrete is being cured, the pier caps will crack,” said Aric Dreher, P.E., Superintendent with CMJVIII. “To minimize these movements, we had to devise a plan to maintain a set temperature range in each of the four girders. We had to hold these conditions before, during, and after placement for an estimated 72 hours.”
The state limited the allowable movement of the steel beams to a mere 2.5 millimeters. It was also required to maintain the steel temperatures at a range of 60 to 70 degrees Fahrenheit (°F).
Our team reviewed weather data to identify the climate control equipment needed. They then worked with CMJVIII to submit an extensive work plan to the bridge designer and state transportation officials for approval.
CMJVIII also hired Hippwrap, a company specializing in shrink-wrap abatement containment, to design a shrink-wrap system to encase the 230-foot bridge span. Once state officials and the bridge designer approved the plan, all parties – Polygon, Hippwrap, and Cianbro/Middlesex – met on-site frequently to ensure everyone was in sync.
The process then began. To hold the steel beams at 65°F for the allotted time, we recommended using eight 30-ton DX cooling units and two 20-ton DX cooling units. As well as customized air conditioners that deliver high-performance, efficient cooling using refrigerant technology and ExactAire remote monitoring system to measure conditions on an ongoing basis.
Work was done during the nighttime hours, the highway below the project area was closed temporarily, and five DX units were placed on both sides of the roadway. They were then ducted into containment. The concrete pour required intensive monitoring of both the temperature and movement of the steel – only 2.5 millimeters of movement was allowed as part of the control.
In total 20 monitoring points were installed along the bridge and recorded the steel temperatures in the containment. Five Polygon ExactAire systems were deployed with four measuring points each, and the sensors were placed in increments along the steel beams to evenly track the entire span.
“The hot August temperatures proved to be one of our biggest challenges. This schedule-sensitive operation was on our critical path for the project, and we could not afford to wait for the cooler fall temperatures. And at the end of the day, the proof was in the results. Polygon was very responsive to our needs and the equipment performed exceptionally,” said Dreher.
With the support of our team this Pearl Harbor Memorial bridge was completed a year earlier than expected with proper climate mitigation throughout the process.
The unique wrap solution allowed for safe installation without the steel beam expanding or contracting.