March 03, 2014
T.Y. Lin International Collaborates with Ohio Universities to Develop New Instrumentation Program for Measuring Bridge Pier Displacement
T.Y. Lin International (TYLI), a globally recognized full-service infrastructure consulting firm, announces that TYLI, as part of the construction engineering and inspection (CEI) team with Omnipro Services, LLC, and in collaboration with the State of Ohio’s University of Cincinnati, Ohio University and University of Toledo, as well as the bridge’s designer-of-record HNTB Corporation, has developed a construction monitoring instrumentation program for the Ohio Department of Transportation’s Jeremiah Morrow Replacement Bridges project. The findings for the new program, which measures the displacement of bridge piers, were presented by TYLI, university researchers, and construction engineers at the Transportation Research Board’s (TRB) 93rd Annual Meeting in Washington, D.C. this past January. The findings will be published in TRB’s Transportation Research Record (TRR).
The innovative instrumentation program employs the use of gravity-referenced tiltmeters to monitor vertical tilt and slope of the tall concrete piers. While other projects have used similar measuring systems following bridge construction, the Jeremiah Morrow Replacement Bridges project utilized an uncommon approach.
“Many bridges include instrumentation for long-term health monitoring but neglect to ‘turn on’ the system during construction. This is a missed opportunity to collect potentially valuable data during construction,” said Karen Cormier, P.E., TYLI Senior Bridge Engineer. “On the Jeremiah Morrow Replacement Bridges project, the team saw the opportunity to build an instrumentation program to be used exclusively for monitoring behavior during construction. T.Y. Lin International’s extensive experience with bridge health monitoring systems was valuable in the design of the system, as well as in the interpretation and understanding of the produced data.”
The benefits of the instrumentation program were realized early on in the project. For the construction of the first structure, the new southbound span, the instrumentation program provided a continuous stream of data, giving engineers ready access to both construction loading and temperature-driven measurements. Via wireless data acquisition designed by the university team, numerical as well as graphic output was available on a continuous basis from a web-based data system. Because data could be quickly evaluated, engineers and construction managers were enabled to make critical decisions during complex stages of construction and to track results.
The new instrumentation program proved to be a highly accurate and cost-effective system for measuring displacement of the bridges’ tall piers using measured tilt. By analyzing data from a large array of tiltmeters on the southbound structure, the project team was able to quickly determine, without impacting the contractor’s progress, that the displacement at the top of the piers was within the desired range during planned horizontal jacking procedures.
When construction on the new northbound structure commences, the tiltmeters once employed on the southbound replacement bridge will be transferred to the northbound structure to monitor deflections. Traditional survey methods were also used to confirm tiltmeter measurement during the first phase of the program for the southbound bridge; consistent information was collected using both methods of measurement. For the northbound structure, tiltmeter monitoring as well as classical survey methods will be expanded to collect additional data in an effort to further understand thermal effects of sun on the tall columns, rather than only as parallel confirmation.
“The benefits of the instrumentation program for the Jeremiah Morrow Replacement Bridges include confirmation of predicted behavior, assessment of construction deflection, and real-time readings of displacement due to environmental and construction-induced loading,” said Cormier. “Going forward, the team is very pleased to have the opportunity to share the findings with the bridge construction community at-large.”
About the Jeremiah Morrow Replacement Bridges:
The Jeremiah Morrow Bridge is a pair of bridges that span Ohio’s Little Miami River and carry busy Interstate 71, a major corridor connecting two of the State’s largest and most populous cities, Cincinnati and Columbus. In June 2010, a six-year project was launched to replace the parallel continuous truss bridges, which were constructed in 1964. It was also determined that traffic flow had to be maintained on the older bridge during construction of the replacement structures.
The dramatic, new six-span twin crossings will be post-tensioned, single-cell, segmental cast-in-place concrete box girder structures. They are being built with the balanced cantilever method of construction and supported by concrete piers that are anchored in the river valley below. Featuring decks that span 239 feet above the valley floor, the new Jeremiah Morrow Bridge will be the tallest bridge in Ohio. Both the southbound and northbound spans will measure 2,240 feet long and 52 feet wide. The design includes widened shoulders and breakdown/maintenance lanes, and enables reconfiguration for three lanes when the decision is made to widen Interstate 71. The new Jeremiah Morrow Replacement Bridges project is scheduled for completion in 2016.