The influence of frequency normalisation of FWD pavement measurements on backcalculated values of stiffness moduli

Backcalculation is commonly used for determining stiffness moduli of pavement courses and its subgrade based on in situ deflection tests. However, the in situ test results are dependent on the frequency domain, which in turn has a significant influence on the backcalculation results. In this paper, one of the methods for normalising the frequency of load and displacement functions obtained from a dynamic impulse generated by a falling weight deflectometer (FWD) test is verified. The assessment of the method is carried out based on backcalculation results of pavement deflection tests induced by both the dynamic and static loads and an independent numerical experiment. The analysis carried out in this paper shows that the normalisation of vertical displacements and pavement loads to the values corresponding to the frequency of 0 Hz improves the accuracy of the backcalculation results. It can be concluded that the frequency normalisation procedure is an effective way for standardising the boundary conditions in the backcalculation of flexible pavements

Back analysis of the multilayer cylindrical HMA samples – height reduction method

Although the complex modulus is one of the most basic properties used in pavement analysis and design, its accurate measurement for existing pavement layers has always been a challenging task. When samples cut out from the pavement asphalt layers are used for the hot mix asphalt (HMA) complex modulus tests, they are performed separately for each layer. This paper describes an original method for determining the complex moduli of individual asphalt layers. The new idea is tested by applying uniaxial loading–unloading cycle tests to the HMA specimens combined of multiple layers. It was observed that changing the thickness ratios in samples' layers, allows obtaining the sets of load and displacement values (F, u), which effectively enlarge the database needed for the back analysis. For now, the conducted analysis presented in the paper focused on numerical modelling of HMA specimens. The simulated numerical testing conditions were based on viscoelastic parameters of asphalt concrete samples whose values were determined in real laboratory tests. In the case of noisy results of laboratory test simulations with a stochastic Gaussian process, by applying multiple cuts and changing sample's height, the determined values of stiffness moduli of the individual layers do not vary from the reference values by more than 10%

Backcalculation of pavements incorporating Grouted Macadam technology

Applying cement grout with a high compressive strength to a porous layer made of asphalt concrete results in a pavement with the properties of an intermediate type that combines the characteristics of both flexible and rigid pavements. This solution is known as Grouted Macadam (GM). Despite a wide range of test results on the GM pavements presented in the literature, there are very few advanced modelling solutions formulated in the scope of bearing capacity measured in situ be means of a Falling Weight Deflectometer. This paper turns out that the seemingly small frequency of loading (≈20 Hz) generated during pavement deflection measurements using a Falling Weight Deflectometer-like device, has a significant impact on the backcalculation results of GM pavements. The study shows that, introducing frequency normalisation of both the pavement loading and vertical displacements to the backcalculation, can limit the statistical scatter of backcalculation results by close to a half in comparison with the classical backcalculation procedure

Chemical Composition of Seed Oils Recovered from Different Pear (Pyrus communis L.) Cultivars

Lipophilic bioactive compounds in oils recovered from the seeds of eight pear (Pyrus communis L.) cultivars were studied. Oil yield in pear seeds ranged between 16.3 and 31.5 % (w/w) dw. The main fatty acids were palmitic acid (6.13–8.52 %), oleic acid (27.39–38.17 %) and linoleic acid (50.73–63.78 %), all three representing 96–99 % of the total detected fatty acids. The range of total tocochromanols was between 120.5 and 216.1 mg/100 g of oil. Independent of the cultivar, the γ-tocopherol was the main tocochromanol and constituted approximately 88 %. The contents of the carotenoids and squalene were between 0.69–2.99 and 25.5–40.8 mg/100 g of oil, respectively. The β-sitosterol constituted 83.4–87.6 % of total sterols contents, which ranged between 276.4 and 600.1 mg/100 g of oil. Three significant correlations were found between oil yield and total contents of sterols (r = −0.893), tocochromanols (r = −0.955) and carotenoids (r = −0.685) in pear seed oils

Filtration of dynamic effects in pavement during measurement with FWD deflectometer

Artykuł dotyczy metody filtracji efektów dynamicznych wywołanych impulsowym uderzeniem spadającej masy na nawierzchnię, w celu oceny wpływu metody wymuszenia obciążenia nawierzchni charakterystycznej dla urządzeń typu FWD. Na podstawie eksperymentu numerycznego, który można zweryfikować, podano propozycję normalizacji częstotliwości funkcji obciążenia i przemieszczeń, które stanowią rzeczywistą odpowiedź nawierzchni obciążonej w sposób dynamiczny. Uzyskane tym sposobem quasistatyczne wartości mogą być w dalszej kolejności wykorzystane do obliczeń zarówno trwałości zmęczeniowych, jak i porównania wyników ugięciomierzami dynamicznymi FWD.The paper relates to filtration of dynamic effects caused by impulse strike of mass falling on the pavement, i.e. evaluation of the results of pavement load application characteristic for FWD apparatus. On the base of digital experiment, which is verifiable, proposal of frequency standardization in function of loading and dislocation was specified. This is real answer of pavement loaded in dynamic way. Quasi-static values, received in that way, may be later used to calculation of fatigue values and comparison of various FWD measurement

Issues of the linear normalization of the pavement deflection values under the overloads

Artykuł stanowi przegląd elementów oceny liniowości układu warstwowego, jaki tworzy nawierzchnia jezdni i jej podłoże. Do porównania wybrano trzy skrajne typy konstrukcji: nową nawierzchnię o podwyższonym module sztywności, nawierzchnię półsztywną po okresie 30-letniej eksploatacji oraz typową podatną nawierzchnię jezdni poddaną zabiegowi remontu. Przedstawione w artykule studium wpływu obciążeń ponadnormatywnych na liniową normalizację ugięć nawierzchni jezdni wykazało, że w zakresie obciążeń siłą do 90 kN, wartość błędów względnych nie jest większa niż umowna granica 10%.The article is an overview of the elements of linearity assessment of the system that is formed by the pavement and its subgrade. For comparing, three extreme types of pavement structures models were selected: new one made of high modulus asphalt concrete, 30-year old semi-rigid pavement and typical flexible pavement after being repaired. The presented studies on the impact of the overloads on the linear normalization of pavement surface deflections showed, that the range of pavement loads below 90 kN force makes that the relative error is less than the conventionally accepted limit of 10%