Current Issue : July - September Volume : 2013 Issue Number : 3 Articles : 6 Articles
An accurate assessment of the fatigue life of hot mix asphalt (HMA) mixtures depends on the criteria used in the fatigue analysis.\r\nIn the past, various studies have been conducted on crack initiation and crack propagation of the HMA mixtures. Most of these\r\nstudies were focused on the beam samples with or without a sawed crack at the bottom. ?is paper presents and discusses two\r\ndifferent fatigue life criteria for two-dimensional problems represented by cylindrical samples. One criterion is based on the rate\r\nof accumulation of the tensile horizontal plastic deformation (HPD) as a function of the number of load repetitions. ?e second\r\ncriterion is based on fracture mechanics, stress intensity factor, and the rate of crack growth with respect to the number of load\r\nrepetitions. It was found that, because of three-dimensional nature of the crack growth in cylindrical samples, the Paris� law was\r\nviolated. It is shown that the rate of crack growth criterion provides higher values of fatigue life relative to the rate of accumulation\r\nof HPD criterion. Although a trend could be established among the fatigue lives obtained by using the two criteria, it was found\r\nthat the fatigue lives obtained from the rate of accumulation of HPD were consistent and based on the actual measurement of HPD\r\nfor HMA mixtures....
During the last years, in many developed countries, administrations and private companies have devoted considerable amounts\r\nof money to obtain mapping data using airborne LiDAR. For many civil activities, we can take advantage of it, since those data\r\nare available with no cost. Some important questions arise: Are those data good enough to be used for determining the heights\r\nof the civil constructions with the accuracy we need in some civil work? What accuracy can we expect when using low-density\r\nLiDAR data (0.5 pts/m2)? In order to answer those questions, we have developed a speci??c methodology based on establishing a\r\nset of control points on the top of several constructions and calculating the elevation of each one using postprocessing GPS. ?ose\r\nresults have been taken as correct values and the comparison between those values and the elevations obtained, assigning values\r\nto the control points by the interpolation of the LiDAR dataset, has been carried out. ?is paper shows the results obtained using\r\nlow-density airborne LiDAR data and the accuracy obtained. Results have shown that LiDAR can be accurate enough (10ââ?¬â??25 cm)\r\nto determine the height of civil constructions and apply those data in many civil engineering activities....
Capillary rise is an important cause of deterioration for plaster in building. This phenomenon has been studied by the tensiometric\r\nexperimental technique. Structural and hydric characteristics of plaster have been determined.Decane, a perfectly impregnate fluid,\r\nhas been used to calculate the porous constant characteristic called ???? and other structural parameters like pore radius and specific\r\nsurface. Evaluation of the sensibility of plaster for water has been evaluated in a second time. The angle constant and the capillary\r\nmoisture content have been determined. A comparison between results for plaster and composite plaster with fiber has been done.\r\nThe addition of glass and hemp fiber does not have important effect on hydric properties (angle constant), but we have observed\r\ninfluence on structural charecteristics (pore radius, porosity, and degree of heterogeneity)....
Uncertainties in predictive models for concrete structures performance can influence adversely the timing of management\r\nactivities. A methodology has been developed that uses data obtained through proactive health monitoring to increase the\r\nconfidence in predicted performance by reducing the associated uncertainties. Due to temporal and spatial variations associated\r\nwith climatic changes, exposure conditions, workmanship, and concrete quality, the actual performance could vary at different\r\nlocations of the member. In this respect, the use of multiple sensors may be beneficial, notwithstanding cost and other constraints.\r\nTwo distinct cases are identified for which an updating methodology based on data from multiple sensors needs to be developed.\r\nIn the first case the interest lies in improving the performance prediction for an entire member (or a structure) incorporating\r\nspatial and temporal effects. For this purpose, the member is divided into small zones with the assumption that a sensor can\r\nbe located in each zone. In the second case, the objective is to minimise uncertainties in performance prediction, or to increase\r\nthe redundancy of health monitoring systems, at critical locations. The development of updating methodologies for the abovementioned\r\nscenarios is described in this paper. Its implications on the management activities, for example, establishing the timing\r\nof principal inspections, are evaluated and discussed....
Timely rehabilitation and preservation of pavement systems are imperative to maximize benefits in terms of driver�s comfort and\r\nsafety. However, the effectiveness of any treatment largely depends on the time of treatment and triggers governed by treatment\r\nperformance models. This paper presents the development of rutting model for overlay treatment of composite pavement in the\r\nState of Louisiana. Various factors affecting the rutting of overlay treatment were identified. Regression analysis was conducted, and\r\nrut prediction model is generated. In order to better predict the pavement service life, the existing condition of the pavement was\r\nalso utilized through the model.The developedmodels provided a good agreement between the measured and predicted rut values.\r\nIt was found that the predictions were significantly improved, when existing pavement condition was incorporated.The resulting\r\nrutting model could be used as a good pavement management tool for timely pavement maintenance and rehabilitation actions to\r\nmaximize LADOTD benefits and driver�s comfort and safety...
This paper describes the design of a novel semi-prefabricated LVL-concrete composite floor that has been developed in New\r\nZealand. In this solution, the floor units made from LVL joists and plywood are prefabricated in the factory and transported to the\r\nbuilding site. The units are then lifted onto the supports and connected to the main frames of the building and to the adjacent units.\r\nFinally, a concrete topping is poured on top of the units in order to form a continuous slab connecting all the units. Rectangular\r\nnotches cut from the LVL joists and reinforced with coach screws provide the composite action between the concrete slab and the\r\nLVL joists. This system proved to be an effective modular solution that ensures rapid construction. A design procedure based on the\r\nuse of the effective flexural stiffness method, also known as the ââ?¬Å?gamma methodââ?¬Â is proposed for the design of the composite floor\r\nat ultimate and serviceability limit states, in the short and long term. By comparison with the experimental results, it is shown\r\nthat the proposed method leads to conservative design. A step-by-step design worked example of this novel semi-prefabricated\r\ncomposite floor concludes the paper...
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