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MacKiewicz P.,Instytut Inzynierii Ladowej Politechniki Wroclawskiej | Krawczyk B.,Instytut Inzynierii Ladowej Politechniki Wroclawskiej
Roads and Bridges - Drogi i Mosty | Year: 2015

The most popular methods used for evaluation of subgrade bearing capacity with light weight deflectometer (LWD) assume linear-elastic behaviour of material. In these methods the input data used for identification of subgrade parameters are limited to initial loading cycles. Change of material parameters occurring under repetitive loading is not taken into consideration. Due to the characteristics of road building materials, including in particular granular materials, omitting the compaction resulting from repetitive loading is considered a rough approximation. Actually the subgrade parameters do change after each load application. It is generally accepted that after the third loading cycle (3rd drop) final degree of compaction is achieved and, as such, the vertical deflections obtained at the fourth, fifth and sixth cycles provide a representative measure of the subgrade parameters (calculated as an average of the three measurements). This paper presents the results of research carried out to verify the above-mentioned assumption by measuring subgrade displacements according to LWD test, followed by comparing the measurement results against numerically identified moduli of the respective layers. The authors have demonstrated that the identified subgrade parameters vary depending on the number of loading cycles (drops) in LWD test. Identification of subgrade parameters was carried out with 3D-FEM (Finite Element Method). © 2015, Instytut Badawczy Drog i Mostow. All Rights reserved. Source


Mackiewicz P.,Instytut Inzynierii Ladowej Politechniki Wroclawskiej | Krawczyk B.,Instytut Inzynierii Ladowej Politechniki Wroclawskiej
Roads and Bridges - Drogi i Mosty | Year: 2015

Achieving the required bearing capacity of a road subgrade during VSS static plate measurements is very often problematic in the contemporary road engineering execution. The problems arise during the test due to passing over a viscous-plastic characteristics of material. The fact remains that only elastic properties of material are being analyzed in the commonly applied measurement practice which does not give a full picture of tested subgrade, especially in case of a subgrade with a limited bearing capacity. Therefore the authors examined the impact of loading and unloading times in the VSS test on registered vertical deflections and the estimated bearing capacity of the examined subgrade. Consequently, the appropriate calculations not only have acknowledged the viscous-plastic component of displacements, but also have disclosed some significant differences in results of deflections, and values of primary and secondary moduli, depending on the time of testing. Moreover, the drawn up 3D model using the Finite Element Method (FEM) has been verified in real field testing. © 2015, Instytut Badawczy Drog i Mostow. All Rights reserved. Source


Krawczyk B.,Instytut Inzynierii Ladowej Politechniki Wroclawskiej | Szydlo A.,Instytut Inzynierii Ladowej Politechniki Wroclawskiej
Road and Bridges - Drogi i Mosty | Year: 2013

Frequently FWD measurement results of vertical displacements of the same object differ to a considerable degree. Varying measurement results of displacements (making the subsequent base for the identification of elasticity moduli of relevant pavement structure layers) may not be directly averaged since they would build up a false picture ofthe tested section. The reliable identification method for homogenous sections of pavement structure based on measurement results of FWD tested vertical displacements, with the use of some basic properties of the exponential function, was described in this paper. The applied identification algorithms were analysed and their limitations were pointed out. The effectiveness of the elaborated method was verified on a real pavement section with four different structures. Source


Zwolski J.,Instytut Inzynierii Ladowej Politechniki Wroclawskiej | Bien J.,Instytut Inzynierii Ladowej Politechniki Wroclawskiej | Kuzawa M.,Instytut Inzynierii Ladowej Politechniki Wroclawskiej | Rawa P.,Instytut Inzynierii Ladowej Politechniki Wroclawskiej
Road and Bridges - Drogi i Mosty | Year: 2013

Dynamic load tests performed before commissioning a bridge generally have three main goals: to determine the response of tested structures to dynamic loads, to define the dynamic characteristics of the bridge used in the assessment of its condition changes during the operation and to optimize design methods by using the results of experimental studies. In this paper the main attention was focused on the use of experimental data to determine the Dynamic Amplification Factors (DAF) for concrete box girders and deck directly loaded by road vehicles. Applied methodology of dynamic tests of the Re{ogonek}dziński Bridge access ramp as well as the procedure of DAF calculation are presented. Results of experimental tests are compared with recommendations of design codes and improved procedure of DAF calculation for concrete box griders of road bridges is proposed. Source

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