Applied Research Associates, Inc. (ARA) is developing a high-speed Rolling Wheel Deflectometer(RWD) under SBIR/FHWA-sponsored research. The current RWD consists of a dual-wheel, single-axle semitrailerequipped with four spot laser mounted on an aluminum beam beneath the trailer. Three láser are usedto measure the unloaded pavement surface, and the fourth laser, placed near the center of the dual tires,measures within the deflection basin under an 18-kip single axle load. The RWD has been assembled, andpreliminary field runs have been made on thin and thick AC pavement sections. The RWD results have beencompared to Falling Weight Deflectometer (FWD) and accelerometer-determined deflections on the samepavement sections and have produced encouraging results, although with some limitations. Several neededimprovement were identified. Future plans for the RWD include system upgrade, further field testing over awider variety of pavement types and conditions, demonstrations, including comparisons to instrumented testpavements, and eventually the manufacture of a production-level device.
In this research, the most important properties of HPC were analyzed. The study was focused on HPC with specified28 days compressive cylindrical strengths between 60 to 110 MPa and made with locally available materials: RapidHardening Portland Blast Furnace Slag Cement, siliceous aggregates and commercial admixtures. Compressive andflexural strength, elastic modulus, abrassion resistance and shrinkage properties were analyzed and modeled usinginnovative methods. Laboratory test results showed that it is possible to develop a general model for compressive strengthcombining a hyperbolic equation for strength evolution and an exponential equation for mix design parameters. It was alsoconcluded that the measured moduli of elasticity are lower than the predicted values by ACI 363 and ACI 318 equations,and that the square root of the compressive strength did not turn out to be a good predictor of the flexural strength, for theused materials. Furthermore, it was concluded that the ASTM C944-99 abrassion test is not very effective to measureabrassion resistance of HPC, due to the high variability of results. Strain measurements showed that autogenous shrinkageis a significant part of the total shrinkage. It was shown that the FIB 2000 model is adequate to predict shrinkage of HPC,but some coefficients must be updated to local conditions. An updating method for shrinkage models was successfullyapplied
The aim of this work was to demonstrate the compressive strength of a compound of organic originwhich contains ligneous fibres from mahogany (Swietenia machrophylla). These ligneous fibres were mixed,in the first sample, with Portland cement, and in the other sample with Portland cement and pulverizedlimestone. Both meant to be used as constructive elements. The work consisted, based on the former strengthparameter, of the analysis of two ten-sample groups; one of them dried, the other one humid, both of themwere made of the two above mentioned different kinds of mixtures. The results are shown in two graphs ofeach of the groups; humid or dried. It could then be seen that the humid compounds made out of fibres andcement only, were the ones that reached the highest values. These values then demonstrate the possibility ofobtaining an alternative/alternating material of organic origin capable of being used in housing construction.The acquiring of the raw material/for which aids in the handling of the forest/ wouldn’t mess with the forest.
This work describes a housing quality certification system. This system was developed in a cooperative approachbetween the university and a group of construction companies. The major characteristics of the certification system arepresented briefly and a discussion about the impact that applications of the certification system to several buildingprojects have had upon quality. One of the main conclusions so far is the fact that the application of this certification systemhas proven very effective in producing quality improvements on site due to the generation of objective measures ofperformance.
This paper presents the results obtained for the behavior of corrosion in reinforced concrete beams, by resorting to measurements of corrosion potentials (ASTM C876) and Electrochemical Noise. These beams are exposed to oistened and drying cycles with 3.5 % sodium sulfate (Na 2SO4 ) and sodium chloride (NaCl). The purpose was settle an alternative in the evaluation of the reinforced concrete structures, using the electrochemical noise technique that is not perturvative to the system in study, and it provides more information than Polarization Resistance technique that is the only that at the moment is applied in the evaluation of reinforced concrete structures using commercial instruments. The evaluation was affected in beams of 20 x 20x 80 cm., reinforced with bars of 3/8 and stirrups of ¼" to each 20 cm, which were divided in four areas of 20 cm each one, having two protected areas and two naked areas, this with the purpose of having very defined the susceptible areas to suffer corrosion. The corrosion potential, in most of the beams presented an uncertainty of the phenomenon of corrosion, for both means, in accordance with the approach of evaluation that stable ASTM C876 and the rate corrosion of the exposed beams in sodium chloride presented a degree of moderate corrosion. While the exposed beams in sodium sulfate had rate corrosion more high in some cases, changing moderate to a very high corrosion degree. This investigation allows to establish thermodynamics and kinetic corrosion parameters without altering the system steelconcrete. It is feasible carry out mensurations with the techniques used in structures in service (bridges, jetties, buildings, etc.).
Construction schedules are critical to the success of construction projects, as they define the sequence, rhythm and duration of productive processes. However, the traditional construction schedules have not adequately coped with the variable nature of these processes that are reflected in interferences, delays and higher costs to attain a project efficiently. Even though there exist techniques based on Lean Production, such as, for instance, Last Planner which reduces the variability to reasonable levels, many projects either do not apply these techniques or there exist variability that is not controlled as yet. This investigation aims at using Schedule Buffers as a complementary strategy to protect from the production processes variability in the construction projects and also describes the main aspects of a Methodology of Management of Schedule Buffers in Repetitive Projects. This article addreses a number of issues: the problem of variability in construction, the main control techniques and construction schedules, the major investigations on Buffers in construction, and the conceptual aspects of a Methodology of Management of Schedule Buffers in Repetitive Projects. Existing literature show that there do exist any analytic models that permit determining optimum sizes of Buffers, nor methodologies to manage them appropriately. There is no conceptual structure that integrates the diverse types of Buffers that can be used in construction, so as to compare and evaluate their use (either jointly or separately). The use of optimumsized Buffers will facilitate the development of a construction schedule with a greater predictive capacity, as well as, an appropriate management of them will improve the production flow in site in the projects. This work is the preliminary development of a doctoral investigation supported by the Centro de Excelencia en Gestión de Producción, GEPUC, of the Pontificia Universidad Católica de Chile.
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