A rural road just west of Cotton Valley may not seem a place for innovation, but state highway La. 160 at Webster/ Bossier parish line features Department of Transportation and Development's first jointless bridge.
"At DOTD, we are always striving to implement innovative methods to enhance our infrastructure, while maintaining our commitment to being effective stewards of tax dollars," said DOTD Secretary Sherri H. LeBas, P.E.
According to DOTD spokesperson Susan Stafford, construction on the $5.4 million structure began on October 24, 2010. It replaces a 50-year-old bridge spanning Caney Creek and Bodcau Bayou and serves as one of the primary means north of I-20/U.S. 80 to cross the Bodcau flood basin.
Approximately 850 motorists cross the bridge daily, many serving agricultural and commercial needs.
"DOTD bridge construction typically involves simple span flat deck bridges that use mechanical joints to allow for bridge deck movement, concrete contraction and expansion, temperature variations and girder deflection," said Stafford in an email to Minden Press-Herald.
"This type of joint system should provide smooth rideability, low noise level and wear resistance. However, factors such as increased traffic loads, traffic volumes and normal bridge movement can adversely impact the bridge expansion joint system," she continued.
Conventional bridges are more costly to maintain because joints commonly leak when exposed to rain and snow. These leaks cause corrosion and degrade concrete structures, which shortens the overall life of a typical bridge.
Also, loading on conventional bridges stresses the joints, giving them multiple points of potential structural failure.
Jointless bridges have a contiguous deck spanning the bridge, leaving no joints for fluid to enter. They also have a more even load distribution across the entire length of the bridge, removing potential points of failure.
They have been proven to be more cost-effective than conventional bridges because they require less maintenance and have a longer expected service life, according to Stafford.
"A jointless bridge can accomplish the following objectives: (1) Long-term serviceability; (2) minimal maintenance requirements; (3) economical construction; and (4) improved overall performance," she said.
According to Stafford, there are more than 13,000 bridges in the state, approximately 8,000 state-owned and 5,000 locally-owned. The local DOTD district maintains approximately 1,200 bridges throughout seven parishes.
"Over the last five years, DOTD has demonstrated a commitment to improving the infrastructure in Louisiana by investing more than $741 million in bridge preservation and/or replacement projects," Stafford said.
"Additionally, within the next two years, we expect to take bids on an estimated $521 million in bridge projects."
Up-to-date travel information is available by dialing 511 or by visiting www.511la.org. Out-of-state travelers can call 1-888-ROAD-511 (1-888-762-3511).