The Scientific Journal of Riga Technical University
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Assessment of Pavement Structural Strength by the Falling Weight Deflectometer
No full textThe main objective of the research project was to derive the equation for calculating the pavement equivalent E-modulus on the basis of the Falling Weight Deflectometer (FWD) deflection measurement data to be used in the Estonian Pavement Management System (EPMS) for network and project level analysis so, that the determined values are comparable with the Estonian flexible pavement design procedure 2001-52. In 1999, 32 and in 2001 additional 19 FWD test sites were chosen on actual pavement structures to perform FWD measurements annually, once or twice per month from early spring until late autumn. FWD measurement data were analysed mathematically and the results were compared with the Estonian flexible pavement design procedure. The research project results in the following:The quantitative methodology for evaluating the qualitative characteristics of the pavement is determined on the basis of the Cobb-Douglas equation, taking into account at a time practically an unlimited number of factors influencing the pavement structural condition.The relationship between the pavement equivalent elastic modulus calculated according to the Estonian flexible pavement design procedure 2001-52 and based on the FWD measured deflection is determined. The equation for calculating of the pavement equivalent E-modulus on the basis of the FWD deflection data to be used in the EPMS is derived.The correction factors for the pavement equivalent E-modulus, taking into account the month of the FWD measurement performance, moisture conditions and road embankment height at the FWD test site, are mathematically based on statistical data determined for Estonian conditions
Development Level of Analysis for Road Cost Models
No full textThe importance of accurate estimates during the early stages of infrastructure projects has been widely recognised for many years. In an early estimation there is a compromise between the amounts of information available and accuracy of estimation. In this paper three levels of analysis were proposed such as regional, country and project levels for road cost models in order to provide an efficient data usage. The data for our research were obtained from the World Bank’s ROCKS database, which contains unit costs for road projects from over 80 developing countries
Research and Evaluation of Lithuanian Asphalt Concrete Road Pavements Reinforced by Geosynthetics
No full textThe paper focuses on the main functions of geosynthetics in asphalt concrete structures; it also offers results of the research into asphalt concrete pavements reinforced by geosynthetics. The present investigation also includes evaluation of the impact of geosynthetics. The analysis has helped identify the reological parameters whose values are related directly to geosynthetics. The regressive equations help calculate the depth of ruts, if the elasticity modulus and the viscosity of asphalt concrete are given. The statistical analysis supports the validity of the equations. The conclusions at the end of the paper refer to the reliability of geosynthetics used in asphalt concrete pavements
Condition Monitoring of Bituminous Pavements Subjected to Repeated Dynamic Aircraft Loading
No full textThe Heavy Weight Deflectometer (HWD) is one of the most commonly used devices for monitoring the structural condition of airport pavement infrastructure systems on a routine basis in a rapid and non-destructive manner. The HWD measures pavement surface response (ie deflections) to an applied dynamic load that simulates a moving wheel of an aircraft at moderate speeds. The pavement surface deflection basins obtained by the HWD tests is frequently used as an indicator of the load-bearing capacity of the pavement. These tests were conducted on flexible test pavements at the US Federal Aviation Administration’s National Airport Pavement Test Facility (NAPTF) at various times to monitor the effect of simulated Boeing 777 and Boeing 747 aircraft gear trafficking on pavement structural condition. Multi-Depth Deflectometers (MDDs) installed within the pavement sections recorded the load-induced displacements in the pavement and in the subgrade. In this paper, the variations in HWD surface deflections acquired at different stages of NAPTF trafficking are compared with the MDD resilient displacements obtained under multiple-wheel heavy aircraft gear trafficking as well as with the periodic rut depth measurements. The results demonstrate the usefulness of routinely collected HWD surface deflection basins for reliable evaluating the structural performance of airport flexible pavements
Principles of Rational Dislocation of Road Infrastructure Objects on the Main and National Roads
No full textLithuania has a rather good network of motor roads facilitating transportation of passengers and cargoes. Development of tourism and transit transport requires a rational distribution of hotels, motels, restaurants, cafes, staging posts, filling stations etc. Being now a member of the EU, Lithuania must undertake to improve the network of roads so as to meet the international requirements. Seeking to convert Lithuania into a country of travel, transit and transportation, the roads must be improved to provide all necessary services. The state of pavement, characterised by the indices of cracking and evenness, is an important factor of travelling comfort and safety. Roadsides service objects represent other factors which influence the flows of travellers. Basing on analysis of West European and Russian experience, we recommend to classify the objects and complexes of roadside service and infrastructure into categories A, B, C, D, E, F, and G depending on the rest time and to arrange them according to the model presented in the article. Having evaluated the questionnaire data and actual distribution of service complexes by the Lithuanian main roads, the authors recommend to space the service objects and complexes at suggested rational distances. The recommendations for improving the roads and their infrastructure represent the novelty of the present work. They will contribute to travelling comfort and contribute to providing the services necessary for travellers and drivers
Relationship of Road Pavement Deformation Moduli, Determined by Different Methods
No full textDeformations, caused by the axle loads of moving vehicles, are one of the main causes for pavement degradation. Measurement of elastic deflections is the best way to identify this effect. Currently, pavement deflections are most widely measured by the Falling Weight Deflectometer (FWD). Lithuanian standard LST 1360.5 "Soils for the motor roads" defines the measurement of deformations by static testing equipment at the top of each structural pavement layer. Based on the FWD-measured deflections at pavement surface, it is possible to calculate deformation moduli of structural pavement layers. In Lithuania deformation moduli are calculated by the ELMOD (Evaluation of Layer Moduli and Overlay Design) software. The results of experimental investigation of deformations of structural pavement layers by static and dynamic devices showed that the structural strength of road pavement, measured by the FWD, is close to the strength, measured by a static testing device. There is a linear relationship between E moduli, determined by static and dynamic methods. Investigation shows that the Falling Weight Deflectometer is suitable to determine the structural strength of investigated road pavements. However, more detailed investigations are necessary to identify the suitability of FWD to determine the structural strength of the other types of road pavement structures
Discrete Analysis Method for Suspension Bridges
No full textIn the calculation of suspension bridges, the geometrically non-linear behaviour of the parabolic cable is the main problem. The linear methods of analysis suit only for small spans. A geometrically non-linear continual model is especially useful for classical loading cases - a uniformly distributed load on the whole or a half span. But the modern traffic models consist of concentrated and uniformly distributed loads. The discrete model of a suspension bridge allows us to apply all kinds of loads, such as distributed or concentrated ones. The simplest suspension bridge consists of a geometrically non- linear cable, connected by hangers with an elastic linear stiffening girder. Depending on the load case, the hangers may be unequally loaded; thus the cable may also be loaded by unequal concentrated forces. The assumptions of the discrete method described here are: linear elastic strain-stress dependence on the material and absence of horizontal displacements of hangers. Hangers elongation is taken into account. Some comparative numerical examples are presented