Structure of a reliable calculation model of road pavement-subsoil system

Każda konstrukcja powinna być tak zaprojektowana i wykonana, aby zapewniała trwałość przez cały zamierzony okres użytkowania. Wymóg uznaje się za spełniony, jeśli konstrukcja przez zamierzony okres użytkowania spełnia swoje role w zakresie nośności, użytkowalności i stabilności bez znacznego zmniejszenia swojej roli i bez nadmiernych, nieoczekiwanych kosztów. Wiąże się to z koniecznością przewidywania odpowiedzi obiektu budowlanego w danych warunkach obciążenia w całym okresie jej użytkowania, co jest także zgodne z planowanym podejściem BIM. W tym celu coraz częściej wykorzystuje się analizy numeryczne przy użyciu metod elementów skończonych MES. Jednak numeryczny model obliczeniowy MES może być zbudowany w różny sposób. W pracy przedstawiono wpływ geometrii modelu, doboru wielkości siatki dyskretyzującej oraz doboru odpowiedniego modelu (3D) lub (2D) na odpowiedź modelu obliczeniowego układu nawierzchnia-podłoże gruntowe. Przez pojęcie modelowania przestrzennego (3D) rozumie się modelowanie rzeczywistych zagadnień inżynierskich w pełnej przestrzeni (3D) oraz jako modelowanie uproszczone z wykorzystaniem osiowej symetrii (OS).Each structure should in turn be designed and built to show sufficient durability for the intended period of use. This requirement is met if, throughout its intended lifetime, the structure fulfils its roles regarding load-bearing capacity, serviceability limits and stability without a significant decrease in its role and without excessive, unexpected costs. This is associated with the need to predict the response of an engineering structure to given loads throughout its life. This is consistent with the approach BIM. Thus it becomes increasingly common to employ numerical analyses using the finite elements method (FEM). However, a numerical calculation model FEM may be constructed in different ways. This paper presents the impact of the model’s geometry, the choice of a discretization mesh and the choice of 3D or 2D model on the response of a road pavement-subsoil system calculation model. 3-dimensional modelling was carried out in this paper as full modelling of actual engineering problems in 3-dimensional space, and in the form of simplified modelling using axial symmetry

Mechanical Characterization of Lightweight Foamed Concrete

Foamed concrete shows excellent physical characteristics such as low self weight, relatively high strength and superb thermal and acoustic insulation properties. It allows for minimal consumption of aggregate, and by replacement of a part of cement by fly ash, it contributes to the waste utilization principles. For many years, the application of foamed concrete has been limited to backfill of retaining walls, insulation of foundations and roof tiles sound insulation. However, during the last few years, foamed concrete has become a promising material for structural purposes. A series of tests was carried out to examine mechanical properties of foamed concrete mixes without fly ash and with fly ash content. In addition, the influence of 25 cycles of freezing and thawing on the compressive strength was investigated. The apparent density of hardened foamed concrete is strongly correlated with the foam content in the mix. An increase of the density of foamed concrete results in a decrease of flexural strength. For the same densities, the compressive strength obtained for mixes containing fly ash is approximately 20% lower in comparison to the specimens without fly ash. Specimens subjected to 25 freeze-thaw cycles show approximately 15% lower compressive strengths compared to the untreated specimens

Description of Limit States in the Subsurface Layer of Loosened Subsoil in View of Critical State Soil Mechanics

The article aims to present an effective numerical method for the behaviour analysis and safety assessment of a subsurface layer of subsoil in the existing or predicted states of mining and post-mining deformations. Based on our own analytical record, using the equations of the Modified Cam-Clay model, the description of limit states in the subsurface layer of subsoil was validated, making it consistent with in situ observations. The said effect was demonstrated by comparing numerical analyses of the subsoil layer subjected to the limit state, using the Modified Cam-Clay (MCC) model and the Coulomb-Mohr model (C-M). The article also presents the applicability potential of the numerical analysis of the loosened subsoil layer for the assessment of protection elements (e.g., geo-matresses) used under linear structures in the areas subjected to mining and post-mining impacts

Characteristics of Recycled Polypropylene Fibers as an Addition to Concrete Fabrication Based on Portland Cement

High-performance concrete has low tensile strength and brittle failure. In order to improve these properties of unreinforced concrete, the effects of adding recycled polypropylene fibers on the mechanical properties of concrete were investigated. The polypropylene fibers used were made from recycled plastic packaging for environmental reasons (long degradation time). The compressive, flexural and split tensile strengths after 1, 7, 14 and 28 days were tested. Moreover, the initial and final binding times were determined. This experimental work has included three different contents (0.5, 1.0 and 1.5 wt.% of cement) for two types of recycled polypropylene fibers. The addition of fibers improves the properties of concrete. The highest values of mechanical properties were obtained for concrete with 1.0% of polypropylene fibers for each type of fiber. The obtained effect of an increase in mechanical properties with the addition of recycled fibers compared to unreinforced concrete is unexpected and unparalleled for polypropylene fiber-reinforced concrete (69.7% and 39.4% increase in compressive strength for green polypropylene fiber (PPG) and white polypropylene fiber (PPW) respectively, 276.0% and 162.4% increase in flexural strength for PPG and PPW respectively, and 269.4% and 254.2% increase in split tensile strength for PPG and PPW respectively)

An Assessment of the Thermal Behavior of Envelope Surface Coatings with Different Colors

Contemporary solar power engineering enables the conceptual interlocking of the shape of a building object with its location, structural design, and external envelope, as well as applied materials. Suitably selected solutions involving the structure, shape, construction, and location of a building can significantly improve the thermal balance of rooms in a building. Particularly valuable and warranted are studies involving various solutions for building partitions contributing to a considerable improvement in the thermal balance of a building. This article presents the results of research on temperature changes on the surface of the external part of a partition coated with layers of different colors. For the lightest coating (white), both the average temperature obtained on the and the maximum temperature obtained on the surface were the lowest. With the darker coatings, these temperatures were both higher. The back analyses that were performed indicated lower and higher absorption coefficients, respectively, for the coating compared with the base value for the red coating. Additionally, it was demonstrated that the average surface roughness (Ra) after tests in a natural environment decreased by 12.1% for the base (red) coating. For the grey and white samples, a more than two-fold increase in roughness was reported, of 198.6% and 202.0%, respectively. The SEM analysis indicated material loss and discoloration on the sample surfaces

Calculation of Building Heat Losses through Slab-on-Ground Structures Based on Soil Temperature Measured In Situ

The article aims to assess the effects of soil temperature measured in situ on the heat loss analyses of a building. Numerical analyses and in situ measurements of soil temperature profiles for real conditions under a residential building (profile I) in Poland and under the area outside the building (profile II) were performed. Based on the measurement results, a proprietary geometric model of the partition was proposed. The heat flux and heat flow results obtained for reliable models are 4.9% and 6.9% higher compared to a model based on a typical meteorological year for the wall–foundation system and 10.0% and 10.1% higher for the slab-on-ground structure for profile I. The adoption of temperatures from the area outside the building as the boundary condition (profile II) results in greater differences between the obtained results. The difference in heat flow obtained in the numerical analyses for profiles I and II is about 2 W/m2, both for the wall–foundation system and for the slab-on-ground structure calculations. The adoption of temperatures for the ground outside the building led to overestimation in the heat flux calculations, this being due to lower temperatures in these particular layers of the ground

Physical and Mechanical Properties of Polypropylene Fibre-Reinforced Cement–Glass Composite

In accordance with the principles of sustainable development, environmentally friendly, low-emission, and energy-intensive materials and technologies, as well as waste management, should be used. Concrete production is responsible for significant energy consumption and CO2 production; therefore, it is necessary to look for new solutions in which components are replaced by other materials, preferably recycled. A positive way is to use glass waste. In order to determine the effect of a significant glass cullet content on the properties of concrete, glass powder was used as a filler and 100% glass aggregate. The cement–glass composite has low tensile strength and brittle failure. In order to improve tensile strength, the effects of adding polypropylene fibres on the mechanical properties of the composite were investigated. With the addition of 300, 600, 900, 1200, and 1500 g/m3 of fibres, which corresponds to 0.0625%, 0.1250%, 0.1875%, 0.2500%, and 0.3125% of cement mass, respectively, flexural strength increased compared with the base sample by 4.1%, 8.2%, 14.3%, 20.4%, and 26.5%, respectively, while the increase in splitting strength was 35%, 45%, 115%, 135%, and 185%, respectively. Moreover, with the addition of fibres, a decrease in slump by 25.9%, 39.7%, 48.3%, 56.9%, and 65.5%, respectively, compared with the reference specimen was determined

Physical and Mechanical Properties of Polypropylene Fibre-Reinforced Cement–Glass Composite

In accordance with the principles of sustainable development, environmentally friendly, low-emission, and energy-intensive materials and technologies, as well as waste management, should be used. Concrete production is responsible for significant energy consumption and CO2 production; therefore, it is necessary to look for new solutions in which components are replaced by other materials, preferably recycled. A positive way is to use glass waste. In order to determine the effect of a significant glass cullet content on the properties of concrete, glass powder was used as a filler and 100% glass aggregate. The cement–glass composite has low tensile strength and brittle failure. In order to improve tensile strength, the effects of adding polypropylene fibres on the mechanical properties of the composite were investigated. With the addition of 300, 600, 900, 1200, and 1500 g/m3 of fibres, which corresponds to 0.0625%, 0.1250%, 0.1875%, 0.2500%, and 0.3125% of cement mass, respectively, flexural strength increased compared with the base sample by 4.1%, 8.2%, 14.3%, 20.4%, and 26.5%, respectively, while the increase in splitting strength was 35%, 45%, 115%, 135%, and 185%, respectively. Moreover, with the addition of fibres, a decrease in slump by 25.9%, 39.7%, 48.3%, 56.9%, and 65.5%, respectively, compared with the reference specimen was determined