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COOPERATIVE RESEARCH PROGRAMS NEWS Load and Resistance Factor Design: Minimum Flexural Reinforcement Requirements According to the American Association of State Highway and Trans- portation Officialsâ (AASHTOâs) Load and Resistance Factor Design (LRFD) Bridge Design Specifications, minimum reinforcement pro- visions provide flexural capacity greater than the cracking moment, reducing the probability of brittle failure. In pretensioned or post- tensioned concrete flexural members, however, increased nominal capacity of a member can result in an increase in its cracking moment. The current minimum reinforcement requirement for posttensioned members is difficult to satisfy, makes the design process iterative, and may lead to less efficient design. Iowa State University has received a $550,000, 38-month con- tract [National Cooperative Highway Research Program (NCHRP) Project 12-94, FY 2013] to propose revisions to the AASHTO LRFD Bridge Design Specifications minimum flexural reinforcement pro- visions. For more information, contact Waseem Dekelbab, 202-334-1409, wdekelbab@nas.edu. Connecting Adjacent Precast Concrete Box Beam Bridges A recurring problem in bridges constructed with adjacent precast prestressed concrete box beams is cracking in the longitudinal grouted joints between adjacent beams. This leads to reflective cracks in the asphalt wearing surface or concrete deck. The crack- ing appears to be initiated by stress; once cracking has occurred, chloride-laden water can penetrate the cracks and cause corrosion. NCHRP Synthesis 39 reported the practices used by state highway agencies for the connection details between adjacent box beams. These include partial- or full-depth grouted keyways, keyways grouted before or after transverse posttensioning, grout materials, posttensioned or nontensioned transverse ties, applied transverse posttensioning forces, and cast-in-place concrete decks or no decks. Some states were successful in reducing longitudinal cracking, but others were not. Iowa State University has received a $450,000, 39-month con- tract (NCHRP Project 12-95, FY 2013) to develop guidelines for the design and construction of connection details to eliminate cracking and leakage in the longitudinal joints between adjacent boxes. For more information, contact Waseem Dekelbab, 202-334-1409, wdekelbab@nas.edu. Measuring Pavement Roughness on Low-Speed and Urban Roads State highway agencies use pavement smoothnessâor roughnessâ as a gauge to monitor network condition, assess construction qual- ity, or optimize investments in preservation, rehabilitation, and reconstruction. States use the International Roughness Index (IRI), which is calculated as the mechanical response of a generic quarter-car, traveling at 50 mph, to the elevation pro- file of the roadway, to measure highway performance. When used on urban roadways, how- ever, the IRI interprets features such as drainage provisions, sudden grade changes, and crowned intersecting streets as roughness and produces varied calculations when run at slower speeds. Changes in travel speed, as well as stops or near-stops, can further distort or invalidate the measured elevation profile. The University of Michigan, Ann Arbor, has received a $450,000, 24-month contract (NCHRP Project 10-93, FY 2013) to identify or develop a means for measuring, characterizing, and reporting pave- ment roughness on low-speed and urban roads. For more information, contact Amir N. Hanna, 202-334-1432, ahanna@nas.edu. TR N EW S 28 8 SE PT EM BE Râ O CT O BE R 20 13 50 TRB HIGHLIGHTS P H O TO : N IC O LE S C H N EID ER, P ED ESTR IA N A N D B IC Y C LE IN FO R M A TIO N C EN TER An NCHRP project will develop a means of measuring the pave - ment roughness of urban roads. RESEARCH TAKES OFFâThe Airport Cooperative Research Program (ACRP) Oversight Committee met July 14â15 at the National Academy of Sciences building in Washington, D.C., to select projects for the Fiscal Year (FY) 2014 program. The more than 25 projects chosen include research into severe weather impacts, airport wayfinding for the elderly and persons with disabilities, noise modeling, and the Next Generation Air Transportation System. P H O TO : M IC H A EL R . S A LA M O N E, TR B
TR N EW S 288 SEPTEM BERâO CTO BER 2013 51 SECOND STRATEGIC HIGHWAY RESEARCH PROGRAM NEWS Operations Center of Excellence Incorporates SHRP 2 Research L I N D A S . M A S O N In September, representatives from theAmerican Association of State Highway and Transportation Officials, the Intelligent Transportation Society of America, and the Institute of Transportation Engineers, Inc., signed a memorandum of understanding that outlines a strategy for a National Oper- ations Center of Excellence. The center will provide technical leadership and dissemi- nation of best practices, research, and professional education and training to prac- titioners, policymakers, and researchers, and will incorporate products developed in the Reliability focus area of the second Strategic Highway Research Program (SHRP 2) as its core elements. SHRP 2 products, such as the Enhanced Knowledge Transfer System, support effec- tive transportation system management and operations to relieve congestion and improve safety and reliability. SHRP 2 Reli- ability work, which addressed fundamental barriers to progress and the causes of traffic congestion and unreliable travel times, now will be integrated into a substantial body of knowledge in systems operations and man- agement to improve highway system per- formance. A business plan for the Center is in development. Mason is Communications Officer, Second Strategic Highway Research Program. (Left to right:) Intelligent Transportation Society of America President and CEO Scott Belcher, AASHTO Executive Director Bud Wright, and Institute of Transportation Engineers, Inc., Executive Director and CEO Thomas Brahms after signing a memorandum to create the National Operations Center of Excellence. BUILDING A CONFERENCEâMembers of the committee for the 11th International Conf - erence on Low-Volume Roads gathered at the National Academiesâ Keck Center, July 19 in Wash - ington, D.C., to organize a program on research, practice, and technology transfer for low-volume roads. The conference goal is to foster collabo - ration and to increase the technical literature addressing the engi - neering and management problems unique to low- volume roads and roadway systems. Conference Explores Multimodal Transportation Systems The 2013 Barge and Rail Symposium, cosponsored by TRB, show- cased innovative research on multimodal transportation to improve the speed and reliability of freight moving over the U.S. inland water- way and rail systems and to enhance the sustainability and long-term viability of multimodal freight networks. The inaugural symposium convened representatives from industry, government, and academia, August 14â16, in Louisville, Kentucky. Sessions addressed such critical topics as finding new ways to leverage knowledge about transportations systemsâ interactions and interdependencies to streamline freight movement. Other presen- tations examined the steps needed to bolster multimodal efficiency. Participants also visited the Kentucky Railway Museum, McAlpine Locks and Dam, the Falls of the Ohio, and American Commercial Linesâ Jeffboat Manufacturing facility. Conference cosponsors included the Multimodal Transportation and Infrastructure Consortium, the Kentucky Transportation Cen- ter, American Commercial Lines, Genesee & Wyoming, Global Transportation Consultancy LLC, Patriot Rail, and the University of Louisville. For more information, contact Candice Wallace (candice.wal- lace@uky.edu) or Amy I. Terry (amy.terry@uky.edu) at the Kentucky Transportation Center, University of Kentucky.