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Abstract

Currently, significant development of methods supporting decision making under uncertainty conditions is observed. One of such methods includes Bayesian networks used in many fields of economy and science. The paper presents the use of the Bayesian network method in civil engineering problems with particular emphasis on construction engineering projects. In addition to the existing examples of the use of the method cited, the authors’ method for the risk estimation of additional works is presented.

Abstract

The microstructural evaluation of complex cementitious materials has been made possible by the microscopic imaging tools such as Scanning Electron Microscope (SEM) and X-Ray Microanalysis. Particularly, the application of concrete SEM imaging and digital image analysis have become common in the analysis and mapping of concrete technology. In this study, six samples of two-dimensional (2D) SEM images were spatially resampled to produce Geo-referenced SEM sample images. Subsequently, they were analyzed and the intensity histogram plot was produced to facilitate visual interpretation. The consecutive digital image analysis performed was the enhancement and noise removal process using two filtering methods i.e. median and adaptive box filter. The filtered resampled images, then undergone the unsupervised K-Means classification process to collectively separate each individual pixel corresponds to the spectral data. By spatial segmentation of K-Means algorithms, the cluster groups generated were carefully reviewed before proceeding to the final analysis. From the resulting data, the mapping of the spatial distribution of k-cluster and the quantification of micro-cracks (voids) were performed. The results of the SEM images (1st - 4th sample) showed a higher percentage of k-cluster data indicating a good correlation with the major elemental composition of EDX analysis, namely Oxide (O), Silicon (Si) and Carbon (C). Meanwhile, the subjective visual assessment of the image (5th and 6th sample) has confirmed the micro-crack developments on the concrete SEM images upon which the crack density was 3.02 % and 1.30 %, respectively.

Abstract

This experimental study aimed to use the ultrasonic pulse velocity method (UPV) in order to investigate the effect of rubber tire waste content and transducers’ diameters and frequencies on the evolution of ultrasonic velocities in time and to elucidate the correlations between UPV and the properties of various concrete mixtures. The incorporation of this waste involved volume substitution (0, 5, 10, 15 and 20%) of fine aggregates (sand) by rubber waste (RW) granulates. The dry unit weight, porosity, compressive and flexural strengths, and velocity of ultrasonic waves with different transducers - which presents the non-destructive technique - were evaluated. Rubberized concrete mixtures showed increases in porosity with lower dry unit weight compared to the control concrete. Compressive strength, flexural strength and ultrasonic velocity obtained by all transducers decreases with increasing RW content. These decreases are not influenced by the curing age of concretes. Decreases in the diameter and frequency of transducers caused reductions in ultrasonic velocity. These reductions are not influenced by the volume replacement of sand by RW. Correlations showed that ultrasonic velocity represents a reliable non-destructive technique for measuring the properties of rubberized concretes.

Abstract

Mortars are subjected to severe external stresses such as freezing, thawing, and drying during their lifetime. These stresses can lead to a loss of adhesion between the support and the mortar. The strength of the substrates with respect to their ability to receive a coating (mortar) is characterized in particular by the value of minimum tear resistance of the surface to be coated. In this work, the use of a non-destructive method which is both fast and easy to implement is employed to evaluate this support-mortar adhesion. The first method is based on the measurement of the velocities of the surface ultrasonic waves and the second by tearing tests using a specific dynamometer. The determination of the adhesion strength concerned two different supports (concrete beam and masonry block) coated with two types of mortar (a prepared cement mortar and a ready-to-use mortar) with two different thicknesses for each mortar (1 and 2 cm, respectively). The results of the two methods are then correlated for an estimation of the adhesion of the mortars.

Abstract

This paper presents the stress-strain behaviour of Natural Banana microfibre reinforced Lightweight Concrete (LWC) prisms under axial compression. The compressive strength of masonry is obtained by testing stack bonded prisms under compression normal to its bed joint. LWC blocks of cross-sectional dimensions 200 mm x 150 mm were used to construct the prism with an overall height of 630 mm. Three series of specimens were cast; (a) prism without Banana fibre (control), (b) prism with Banana microfibres, (c) prism with Banana microfibres sandwiched with Glass Fibre Reinforced Polymer (GFRP) sheets. Natural Banana fibres were used as structural fibre reinforcement at different volume fractions (VF). The results indicate that the presence of fibres helps to improve the strength, stiffness, and ductility of LWC stack bonded prisms under compression. The test results also indicate that banana fibre reinforcement provides an improved crack bridging mechanism at both micro and macro levels. The GFRP sandwiched prism specimens exhibited excellent ductility and load-carrying capacity resulting from improved plastic deformation tolerance under compression and bonding between the LWC block and GFRP sheet.

Abstract

The article presents an analysis of the possibilities of shaping long - span structures using the expressive force of glued laminated timber related to its natural origin. Changes that arose in the 20th century and at the beginning of the 21st century under the influence of new technological possibilities in the field of woodworking, as well as radical changes in the doctrine of environmental protection, also changed the position of timber as an innovative construction material. Recent developments are considered groundbreaking. Timber is used both in large span structures as well as for the construction of multi-storey buildings, which opens the door for shaping new architectural forms. The principles of girder modelling and features related to timber symbolism were presented.

Abstract

The article discusses selected issues concerning the influence of ecophysiographic determinants on functional-spatial and socio-economic development in rural areas. Ecological, economic and social processes that have been taking place for the past few decades are examined in the context of the development of local self-governments and transformation of economic processes into market oriented economy following socioeconomic changes in Poland. The process of intense urbanization of the countryside is a common phenomenon that occurs specifically in rural areas that are within the impact zone of a big city. It is caused by i.a. human migration into rural areas as well as by development of areas of business activation. These tendencies, which occur both in the social and economic context, greatly affect ecological processes. Expansion of land development and the ensuing further development of necessary technical infrastructure give rise to numerous problems in natural environment. Ecophysiographic determinants play a vital role in the pursuit of sustainable development of the countryside in the aspect of threats that result from excessive urbanization of rural areas. The author discusses these issues on the example of a study of the village of Lubasz in the wielkopolskie voivodeship.

Abstract

High effectiveness of organic pollutants and nutrients removal is achieved in biological wastewater treatments plants – in case of proper exploitation of these objects. Nitrogen and phosphorus transformation or removal depends on many physic – chemical and biochemical conditions, deposit and environmental factors. A rule for treating wastewater consists in decomposition of organic compounds included in wastewater in water-soil environment. Removing contaminations is performed as a result of sorption of contaminations, bio-chemical oxidation-reduction reactions and biological activity of soil microorganisms and hydrophyte flora. The research has been carried out in the constructed wetland in Małyszyn (1300 EP). The treatment plant operates in horizontal system, with under-surface flow of wastewater.

Abstract

The aim of the paper is to verify and present methodology for ultimate tensile resistance prediction in steel angle tension members connected to gusset plates with one row of bolts. After a description of the experimental investigations, the next step was to build numerical models. The subjects of the experiments consisted of single plate specimens with drilled holes and angles connected to gusset plates with 1, 2, 3, or 4 bolts. Close attention was given to choosing the appropriate material model, which takes into account the influence of microstructural damage and the process of ductile fracture initiation and propagation. The porous Gurson-Tvergaard-Needleman material model was analysed and the paper focuses on hierarchical validation of numerical models of steel angle bolted connections, which will then be used for parametric studies.

Abstract

Diagnostics and mitigation of excessive moisture effects are some of the most frequent problems in historical buildings. In this article, an attempt was made to measure the moisture content of construction elements in the historical tenement house in Gubin. It is the largest town in the Krosno Poviat, in the area of the Lubuskie Voivodeship. The town suffered from military actions during World War II whereby approximately 90% of its urban development was destroyed. The tenement house at 14A, Śląska Street is one of the more well-preserved buildings, made in the classicist style with characteristic historical features. The whole history of the building is unknown but there are freemasonry symbols on the elevation, and probably the Military Police had its headquarters there after 1945.