查看更多>>摘要：Data collected from Arizona Department of Transportation customers during the SR-51 project were examined. During the $75 million project, approximately 10 mi of SR-51 between 1-10 and SR-101 was renovated to include new high-occupancy-vehicle lanes and rubberized asphalt. Communication was measured by customers' (e.g., motorists' as well as local residents' and businesses') utilization of four direct communication channels (e.g., construction signage) and four indirect communication channels (e.g., television programming). Satisfaction was measured by a composite score based on customer satisfaction with traffic, dust, noise, signage, and information during the construction process. Almost all respondents relied on at least one channel for construction communication, and almost 80% of respondents reported using between one and three channels. The most frequently used channel was construction signs (55.9%), and the least frequently used channel was e-mail alerts (1.5%). Fewer than 4% of the respondents did not use any communication channel. Direct communication channels resulted in higher customer satisfaction than did indirect communication channels. Construction bulletins contributed the most to customer satisfaction, followed by the project website. Neither television nor radio contributed to customer satisfaction. As sources of project communication, neighbors and friends had a strong but negative effect on customer satisfaction.
查看更多>>摘要：A practical model for scheduling and cost optimization of highway construction is presented in this paper. The model's objective is to minimize total construction cost while respecting the time and resource constraints of a project. For flexibility, the model allows each activity to have three alternative construction methods, from cheap and slow to fast and expensive. At the core of the model is an innovative scheduling algorithm for crew assignments along the various highway sections so that work continuity is maintained. The model is designed to be flexible enough to allow nontypical sections as well as variable sequence of work among the sections. For cost optimization, the model uses a nontraditional optimization technique, genetic algorithms. Details of the model formulation are presented in this paper along with its implementation in a simple-to-use computer system. To demonstrate the capabilities of the system, a realistic example is given of a highway project that is fast-tracked by using two crews working simultaneously from opposite sides. The example shows the usefulness of the system for what-if analysis, schedule optimization, and legible presentation of detailed crew assignments and activities' progress speeds. Extensions of the model to incorporate project control features are then highlighted.
查看更多>>摘要：Most of California's highway infrastructure was built between 1955 and 1970. These pavements had 20-year design lives, and many now require frequent maintenance. In 1998, the California Department of Transportation (Caltrans) launched the Long-Life Pavement Rehabilitation Strategies (LLPRS) program to rebuild approximately 2,800 lane kilometers of high-traffic-volume urban freeway in the 78,000-lane kilometer state highway network over a 10-year period. Priorities identified for the successful implementation of LLPRS projects are the selection of construction schedules and the development of traffic management plans that minimize road user and agency costs. This paper presents a construction simulation program called CA4PRS (Construction Analysis for Pavement Rehabilitation Strategies). The program was developed as a scheduling and production analysis tool for LLPRS projects for use during the planning and design stages. CA4PRS estimates the optimized distance and duration of highway rehabilitation projects. It takes into account the constraints of scheduling interfaces, pavement design, lane closure tactics, and contractor logistics. As a knowledge-based computer system on a Microsoft Access database, it uses Monte Carlo simulation, critical path method analysis, and linear scheduling. CA4PRS is designed to help highway agencies and paving contractors make construction schedule decisions that balance rehabilitation productivity, traffic inconvenience, and agency cost. Application of the CA4PRS model to urban freeway rehabilitation projects in California, including the I-10 Pomona, I-710 Long Beach, and I-15 Devore projects, has demonstrated its value in saving millions of dollars for both Caltrans and road users.
查看更多>>摘要：Staff at the North Carolina Department of Transportation (NCDOT) have close control over each highway construction project until the con-. struction contract is let; thereafter, the contractor manages the pace of work, which dictates the flow of payments. These payments make up about one-third of all NCDOT expenditures, so reliable forecasts are ' important in programming and in cash management. With no other means to predict the pace of construction through the duration of the contract, NCDOT must rely on statistical analyses of past payments to forecast future payments to contractors. Dye Management Group, Inc., which was retained by NCDOT to implement cash management strategies at the department, designed two statistical models of payments to contractors: the first to estimate payments on individual contracts, or the "payout curve," and the second to estimate total payments made under all contracts in a month. The parameters in both models were initially estimated with data from 4,128 payments made under 336 highway construction contracts completed between August 2000 and June 2002. The first model achieved an adjusted R~2 of .93. Although it was useful to engineers in managing individual projects, the model required awkward specifications of seasonal effects to forecast aggregate cash flows. Seasonally was simply accommodated in the second model, which achieved an adjusted R~2 of .92. Dye Management Group and NCDOT have operated the second model for more than 2 years and, with a database that has grown to more than 11,000 monthly payments, have consistently achieved mean absolute percentages of error under 10%.
查看更多>>摘要：It is rare that a state highway agency (SHA) uses only a single quality characteristic to determine the pay factor for a lot. This paper deals with two specific types of risk associated with the use of multiple quality characteristics: remove and replace provisions and the effect on pay factor determination if the quality characteristics are correlated. First, computer simulation studies showed that typical acceptance plan provisions that call for lot removal and replacement at a given quality level, such as a percentage of material within specification limits of 60 or 50, can place much greater risk on the contractor when they apply to multiple characteristics. An approach to correct this problem was developed. Next, a total of 1,742 sets of asphalt content (AC), air voids (AV), and voids in the mineral aggregates (VMA) test results were analyzed for correlations. VMA values were positively correlated with both AV and AC values. Additional simulation studies showed that while this correlation does not affect the long-term average pay factor for a lot, it increases the variability in the individual lot composite pay factors. The positive correlation also increases the weighting of AV and AC in a composite pay equation. The use of multiple quality characteristics for determining the pay factor for a lot introduces sources of risk that are not present when only one characteristic is used. Any SHA that uses multiple pay factors should consider performing the types of remove and replace and correlation analyses presented in this paper.
Gregory A. SholarGale C. PageJames A. MusselmanPatrick B. Upshaw...
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查看更多>>摘要：The Florida Department of Transportation adopted a percent within limits approach in July 2002 for the acceptance and payment of all hot-mix asphalt. Contractor test data, after being verified by the department, are used to calculate payment. Acceptance and payment for dense-graded Superpave~® mixtures are based on the following five asphalt material properties: roadway density, percent air voids, asphalt binder content, percent passing the No. 8 sieve, and percent passing the No. 200 sieve. Acceptance and payment for open-graded friction course mixtures are based on the following four asphalt material properties: asphalt binder content, percent passing the 3/8-in. sieve, percent passing the No. 4 sieve, and percent passing the No. 8 sieve. Contractor test data from recently completed construction projects were used to develop representative standard deviations of the asphalt material properties used for payment and acceptance. These standard deviations were then used to develop tolerance values for the percent within limits system. A system has been developed to handle acceptance and payment of small quantity LOTs (two or fewer sublots) within the same specification. In lieu of the department sampling and testing numerous independent samples and performing F-and t-tests to validate the contractor's results, an alternative verification and resolution system has been developed.
查看更多>>摘要：The West Sandusky Street Bridge over I-75 in Findlay, Ohio, consisted of a single 170-ft-span hybrid steel plate girder bridge with a concrete deck. To minimize closure times on West Sandusky Street and reduce traffic delays on I-75 during the bridge's replacement, full-width, full-depth precast concrete deck panels were proposed for the bridge deck construction. The precast deck panels are posttensioned both longitudinally and transversely to minimize cracking and improve durability and are constructed with shear stud pockets to allow for the installation of shear studs after erection and posttensioning. During detail design, a finite element analysis of the bridge deck was carried out to determine the required level of prestress in the deck. A time-dependent analysis was subsequently completed to determine the long-term creep effects and posttensioning losses, including the effects of restraint from the steel girders. A sensitivity analysis determined the optimum curing time required before stressing the longitudinal posttensioning tendons and grouting the shear pockets. The steel plate girders were designed for the long-term creep effects due to the posttensioning of the deck, which imposed additional axial loads and moments on the steel girders. The replacement deck panels were fabricated before bridge demolition and road closure. Bridge construction was completed in fall 2004.
查看更多>>摘要：The effects of multiple damage-heat straightening repair cycles (i.e., multiple cycles of damage followed by heat straightening repair) on the fundamental structural properties of typical bridge steels ASTM A36, A588, and A7 were evaluated. The damage and repair parameters considered in the study are the damage strain (ε_d), the restraining stress (σ_r), and the number of multiple damage-repair cycles (N_r). The effects of these parameters on the following structural properties were evaluated: elastic modulus, yield stress, ultimate stress, percent elongation, surface hardness, and fracture toughness. Seventy-five laboratory-scale specimens made from A36, A588, or A7 steel were subjected to multiple damage-repair cycles, and their effects on the structural properties were evaluated. The results indicate that multiple damage-repair cycles have a small influence (±15%) on the elastic modulus, yield stress, and ultimate stress. However, the percent elongation and fracture toughness of the damaged-repaired steel are influenced significantly. On the basis of reductions in the percent elongation and fracture toughness, it is recommended that A7 and A36 steel be limited to three damage-heat straightening repair cycles. A588 steel can be subjected to five damage-heat straightening repair cycles.
查看更多>>摘要：Ground-penetrating radar (GPR) is a nondestructive investigation tool that is usually used in flexible pavement evaluation to estimate the thicknesses of the various layers composing the pavement. GPR is also used in flexible pavements to detect subsurface distresses, such as moisture accumulation and air voids. For rigid pavements and bridge decks, GPR is used to measure the thickness of the concrete slab and detect the location of reinforcing bars (rebar). Rebar detection is typically achieved, in this case, when an experienced operator finds the rebar's classic parabolic signature in the GPR data. This paper presents image-processing techniques that can be used to detect the rebar parabolic signature automatically in GPR data collected from rigid pavements with a high-frequency ground-coupled antenna. After detection of the rebar, the reflected parabolic shape is fit to a theoretical reflection model to estimate the pavement's dielectric constant and the rebar depth. The algorithms were validated on GPR data collected from a known continuously reinforced concrete pavement section. The technique showed an average error of 2.6% on the estimated rebar cover depth.
查看更多>>摘要：This paper presents the results of an evaluation of the effectiveness of an innovative process for installing dowel bars in construction joints without drilling. The procedure involves inserting plastic sleeves with the same outside dimensions as the drilled holes into plastic concrete to create the holes for installation of the dowel bar, rather than drilling. The plastic sleeves are later removed, and the dowel bars are inserted in the holes left behind. To avoid any deleterious effects, the technique must produce dowel bar alignments that are comparable with those of the bars installed under the conventional method and must not cause any other problems. A field test was conducted to evaluate the viability of the new technique. The evaluation is based on the key factors that determine the engineering feasibility of the new procedure, which include dowel bar alignment, consolidation of concrete around the plastic sleeves, and the impact of the insertion techniques on pavement surface profile. The test results showed that the plastic sleeves can produce dowel bar alignments that are comparable with or better than those produced by the conventional drilling method, without any deleterious effects.
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