ASPIRE is a quarterly magazine published by PCI in cooperation with the associations of the National Concrete Bridge Council. The editorial content focuses on the latest technology and key issues in the Concrete Bridge Industry.
Issue link: http://www.aspiremagazinebyengineers.com/i/306858
Completed Bristol Bridge carrying NH 3A over the Newfound River used partial-depth deck panels. 48 | ASPIRE , Winter 2009 S TAT E D esigning and constructing economical and durable highway bridges has always been a challenge for state transportation agencies. Conflicting needs such as system expansion for safety and capacity versus system preservation and maintenance compete for dollars. Shrinking state transportation budgets compound the problems at the same time that increasing numbers of highway users overburden our aging infrastructure. State and federal agencies nationwide have worked individually and collectively to develop design concepts and materials to address these needs. The New Hampshire Department of Transportation (NHDOT) continues to be involved in developing solutions to some of the problems facing the public transportation community in the twenty- first century. Over the past 15 years or so, many NHDOT bridge projects have built on the success of previous projects and details. Initial efforts concentrated on the development of standards for high performance concrete (HPC) for bridge decks. In turn, this technology was applied to other structural elements. Through support from PCI Northeast (PCINE), the New England bulb- tee (NEBT) girder utilizing HPC was developed as an economical standard precast, prestressed concrete bridge member. Details were developed for partial- and full-depth precast, prestressed concrete deck panels that also utilized HPC, again learning from previous successes and challenges. This article presents several of the many NHDOT bridge projects that make use of proven HPC and precast, prestressed concrete technologies. Although comparatively small in scope, these projects demonstrate the effectiveness, efficiency, and economy of precast concrete systems and details for bridge rehabilitation and construction. Concrete Bridges in New Hampshire by Mark W. Richardson, David L. Scott, and Jason A. Tremblay, New Hampshire Department of Transportation Bristol – NH Route 104 over Newfound River Built in 1995, this 65-ft-long single-span bridge was NHDOT's first use of HPC. The five AASHTO Type III girders were spaced at 12 ft 6 in. and used a specified compressive strength of 8000 psi at 28 days. This was the highest ever specified in a NHDOT design. The wide girder spacing necessitated an HPC deck with a specified 28-day strength of 6000 psi, which is significantly higher than NHDOT's typical 4000 psi deck concrete. The selected deck mix design was based on research performed by the University of New Hampshire. This research involved casting deck slabs from three unique concrete mixes and then subjecting those slabs to truck loading at the entrance to a landfill. Bristol – NH Route 3A over Newfound River Based on the success of the first Bristol project, NHDOT constructed a second HPC project in 1999. This project utilized four NEBT girders spaced at 11 ft 6 in. to achieve the 60-ft-long span. To avoid the expensive deck falsework prices of the first project, partial-depth precast deck panels were used. These were then topped with an HPC concrete overlay.