STATE OF THE BRIDGES: Some truth

Bridge conditions are improving in the U.S., if only slightly

Bridges Article May 06, 2013
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Numbers do not lie, but what’s stopping some of them from speaking out of both sides of the mouth?


Not much, because anyone looking at the deficient data from the nation’s bridge list could see multiple sides to the story. Take the total number of structurally deficient bridges. According to the American Society of Civil Engineers (ASCE), it’s 66,749, or just about 11% of the entire bridge network. However, Bala Sivakumar, who is a lead author of a Transportation Research Board book titled “Innovative Bridge Designs for Rapid Renewal Toolkit,” believes the number is a bit smaller when you look at those spans that pose an actual safety risk to the motoring public.


“We came up with methodology on looking at bridges from a risk perspective,” the HNTB Corp. project manager told ROADS & BRIDGES. “It’s not enough to look at the bridge in terms of condition. We have to look at the true safety of the bridge and look at it from the risk perspective.”


Sivakumar has been practicing this way of thinking for the past four or five years now, and HNTB Corp. even created BridgeAdvise software that works with National Bridge Inventory data and other metrics to prioritize bridges based on risk instead of condition. Redundancy, amount of truck traffic, load ratings, the type of bridge and the impact to the overall system if the bridge is taken out are other factors put into play. This safety risk evaluation definitely would take numbers off the 66,749, but Sivakumar could not commit to how many because, among other things, “it depends on whether the state uses federal standards or their own.”


In its most recent report card, released in March, ASCE said the percentage of structurally deficient and functionally obsolete bridges, now making up just under 25% of the fleet, has gone down slightly. However, the number of bridges closed to traffic went from 2,816 in 2007 to 3,585 in 2012, and intensive efforts at the state level in Missouri (Safe and Sound Bridge program) and Pennsylvania to lower the number of decaying bridges are coming to a close.


Higher marks
So, is the nation in better shape when it comes to its elevated car carriers? The ASCE thinks so, but the improvement is slight. The 2013 ASCE report card elevates the bridge grade from a C in 2007 to a C+. Along with the minor drop in the number of deficient bridges, the progress report also shows the total percentage of postings on spans has lowered from 67,969 in 2007 to 60,971 in 2012, and the average age has gone from 43 years in 2009 to 42 years. Still, the FHWA figures more than 30% of the existing bridges have exceeded their 50-year design life, and federal funding continues to remain flat, meaning all the pressure of improving infrastructure falls on the state’s shoulders.


“You are starting to see a number of states coming up with the necessary funding,” Andy Herrmann, former president of ASCE, told ROADS & BRIDGES. “Two states [Virginia and Maryland] are putting up more money to fix roads and bridges, and I think 20 or more additional states are either starting to look at doing something like that. They have to do something.”


States are feeling better now than they have in the last few years, and it is leading to a steady stream of dollars for bridge work. According to the American Road & Transportation Builders Association (ARTBA), the amount of activity has been at record levels: $29 billion in 2012 and an expected $28 billion in 2013.


“If you want to look at how much state and local governments are investing in their own highway and bridge work, their overall tax revenues are one of the best indicators,” Alison Premo Black, chief economist for ARTBA, told ROADS & BRIDGES. “We have started to see a recovery in overall state and local tax revenues.”


And even though the curtain is dropping on the aggressive programs in Missouri and Pennsylvania, states like New York, which has owned about 10% of all U.S. bridge contracts over the last four years, Florida, Texas and California continue to churn out production, and now Oklahoma has entered the fold.


According to ROADS & BRIDGES’ annual survey on bridge conditions in the U.S., the situation has indeed improved—if only just a touch. In 2012, 16% said the number of functionally obsolete bridges in their area went down, and 21.9% said the same about structurally deficient bridges. This year, 23.7% said the structurally deficient bridges have improved, and 16.5% said it is better on the functionally obsolete side as well. Furthermore, just over 55% indicated that they would be able to do enough in bridge repair this year to keep their inventory in decent shape.


To assist states in their quest, ARTBA has created an analytic tool—BridgeDataPro—which contains the basics about each span listed in the NBI, such as the deficiency status and sufficiency rating, inspection frequency and the last inspection date. The web-based software also goes into the conditions of the deck, superstructure, substructure, guardrails and roadway alignment, and identifies work and repair needed and the cost involved.


“From an advocacy standpoint we think it is very important to have this information in a way people can understand it a little bit more,” said Premo Black. “It’s much more user friendly than the files you can download from the FHWA.”


More will be available in the coming months behind a deluxe version that will contain historical information about the bridges and a way for the user to map their unique search results.


“So it’s not just a pinpoint on a Google map,” Premo Black said. “It’s, ‘Here are the hundred bridges I am interested in across the country and this is where they are.’”


Accelerated is accelerating
Sivakumar has another tool that could become as common as the hammer to bridge engineers. He has been working with the FHWA to come up with a new way to load-rate bridges and just wrote the protocols for a response-based load rating system where gauges are strategically placed on various elements on a bridge for a span of about four months.


“Nothing is as accurate as a true response of the bridge,” Sivakumar remarked. “This could knock out about a third of the load-posted bridges.”


The first set of protocols was for steel bridges, and the same is now being done for concrete prestressed spans.


Accelerated bridge construction also is picking up across the country—and with it comes another software aid. HNTB Corp. has developed the ABC Toolkit, with the first demonstration project taking place in Iowa. A second project will go on in New York and involves the replacement of twin bridges on I-84. The new spans will be slid into place in one night. In September, the Franklin Avenue Arch Bridge over the Mississippi in Minneapolis will be rehabbed, and crews will replace the deck and spandrel caps. Again, ABC will be executed.


“I would say that the momentum [of ABC] has definitely picked up,” said Sivakumar. “Minnesota is rolling out a program, Michigan is rolling out a program, and we are working with PennDOT. I have been working in this area for five years, and in the last couple of years there is a greater appreciation for ABC.” R&B
 

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