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Excess stormwater runoff is a serious problem in a large number of urban areas, causing flooding, water pollution, groundwater recharge deficits, and ecological damage to urban streams. Solutions currently proposed to deal with this problem often involve large centralized infrastructure and high expense. Phase II of the Environmental Protection Agency's stormwater regulation is now requiring smaller communities nationwide to make important decisions about the potentially expensive management of excess stormwater runoff. This paper builds on research investigating the use of economic incentives to promote dispersed placement of smaller-scale best management practices (BMPs) for water detention to control excess runoff. We estimate a hedonic price function for houses in the area of a pilot project, and include the estimated part worth of yard area as our lower bound for opportunity cost in the cost function of the residential BMPs. We then show the effects of the inclusion of opportunity cost on two potentially useful incentive-based policy instruments available to communities. DOI: 10.1061/(ASCE)0733-9496(2006) 132:2(89) CE Database subject headings: Stormwater management; Runoff; Urban areas; Ecology; Floods; Water pollution.

Storm-water flow from an impervious surface can lead to stream degradation, habitat alteration, low base flows, and increased toxic loadings from nonpoint sources, a problem that has resisted traditional command and control regulatory approaches. We explore the thesis that a well-designed, tradable runoff allowance system can create economic incentives for landowners to employ low-cost runoff management practices to reduce excess stormwater flow to more ecologically sound levels. Attributes such as percent impervious surface, soil type, and so on, determine a given land parcel's runoff potential and management alternatives and, by extension, its allowance requirements. Using a small watershed in Cincinnati, Ohio, as a case study, we show that a tradable runoff allowance system carries promise as a low-cost method for attaining reductions in storm-water runoff. DOI: 10.1061/(ASCE)0733-9496(2003)129:5(409) CE Database subject headings: Stormwater management; Storm runoff; Pollution control.

Alkali-silica reaction (ASR) is a persistent issue and has evaded eradication for nearly 80 years. The problem stems from a lack of standardized testing of aggregates. Cases occur when changes in material properties lead to potentially reactive aggregates reacting with higher alkali cements. A research program was established at the University of Arkansas to investigate cases of ASR, which occurred in combination with previously inert aggregates. In addition, locally available fly ashes were evaluated to determine replacement rates required to minimize the risk of ASR. A field monitoring program was established to evaluate deterioration mechanisms and mitigation measures. A concrete barrier wall located near the University of Arkansas was diagnosed with ASR that had considerable variation in the damage between sections of the wall. Deterioration ranges from minimal visible deterioration to severe damage or complete failure. The testing program reveals that certain aggregates that were previously deemed safe for use in concrete reacted deleteriously when other material properties changed. [ABSTRACT FROM AUTHOR]

Northwest Arkansas Regional Airport (International Air Transport Association Code, XNA) opened in 1998. XNA is a regional airport serving the northwest Arkansas area. Alkali silica reaction (ASR) was detected at XNA's runway 16/34 in 2002, and in 2012 the runway was closed for replacement. The airport includes a single runway; therefore, runway replacement required the construction of a temporary alternate landing surface (ALS). Consequently, costs related to the premature runway replacement were substantial. XNA is experiencing significant pavement distress caused by ASR. Therefore, in addition to the runway, taxiways and apron areas will require replacement. The article reviews ASR, causes of ASR at XNA, and a preliminary investigation to develop a remediation approach to ASR at XNA. For ASR remediation, the authors are investigating various surface sealants for their effectiveness to retard ASR, to provide XNA operators additional time before future pavement replacement is warranted. [ABSTRACT FROM AUTHOR]

Transfer length is a significant parameter in the design of pretensioned concrete members. The estimation of transfer length is typically achieved by measuring concrete strain or strand slip at the member ends. The end slip method is simple and requires little effort, but relies on an empirical formula with an undetermined coefficient (α), which relates to the bond stress distribution.Many studies have proposed appropriate a coefficients; however, the variability in estimating the a coefficient exists between studies depending on the chosen empirical fit. This study gives an estimation of the a coefficient using α probabilistic approach called the maximum likelihood (ML) method. Approximately 600 data points of transfer lengths and strand end slips were measured for 25 pretensioned concrete beams. Strand end slips were measured at release and at 3, 5, 7, 14, and 28 days. Concrete strains were measured at the same period of time using a detachable mechanical strain (DEMEC) gauge to determine the transfer lengths. An estimated a coefficient of 2.61 maximized the likelihood of the observed sample of the measured transfer lengths and end slips. [ABSTRACT FROM AUTHOR]

Prestressing strands are commonly used in pretensioned prestressed concrete bridge construction. Transfer length is an important parameter for structural design. This paper presents a comparative study on strand transfer length provisions from Eurocode 2 and North American practice, and identifies similarities and differences between both models. A database of measured transfer lengths according to several authors has been compiled and compared with predictions according to code provisions. The intervals of predictions are smaller than those corresponding to the experimental results, and they are smaller when code provisions are more simplified. The interval from Eurocode 2 is greater than that from American Concrete Institute (ACI) code 318, which, in turn, is greater than the interval from AASHTO. The number of underestimated cases is lower for Eurocode 2 because of the higher predicted values, but situations in which a short transfer length is unfavorable are neglected by all models because they are not good predictions of shorter measured transfer lengths. When a transfer length estimation criterion is based on an allowable free end slip, more cases are excluded from the ACI code 318 provisions. [ABSTRACT FROM AUTHOR]

Air transportation has an overall outstanding safety record. However, accidents do occur. If an aircraft is unable to stop within the runway length, the incident is described as an overrun. To provide passenger safety during an overrun, the Federal Aviation Administration (FAA) requires airports to have a 305 m (1000 ft) runway safety area. At airports that are unable to satisfy this requirement, because of either natural or man-made barriers, the FAA allows the use of a shorter runway safety area with a properly designed arrestor bed. A sensitivity analysis is presented in this paper to investigate critical parameters in the design of an engineered-materials arrestor system (EMAS). A single arrestor-bed configuration is used as a base case for considering a low-density concrete EMAS material. Five aircraft types are considered, ranging from 51,700 kg (114,000 lbs) to 322,100 kg (710,000 lbs) maximum-certificated takeoff weight. These aircraft types include aircraft with various landing-gear configurations. Earlier studies by the authors showed, on the basis of an analysis using B727 and B747 aircraft, that aircraft stopping distance is most sensitive to aircraft weight. This paper investigates a larger suite of aircraft types with a range of weight and main-gear configuration. Stopping distance in this study reflects a critical scenario of zero reverse thrust and minimal tire-pavement friction. In addition to the base-case analysis, additional studies are included to illustrate the dependency of stopping distance on arrestor-material compressive strength and arrestor-bed configuration. [ABSTRACT FROM AUTHOR]