Volume 15 (2020): Edizione 1 (September 2020)

The importance of the retaining structures is crucial in geotechnical engineering and the accurate determination of static and seismic earth pressures and natural frequency is important for study the dynamic behavior of these structures. Usually analytical formulas which do not consider the earth pressures behind retaining structure are used. An analytical model for predicting the natural frequency of retaining structures including the earth pressures by failure wedges is proposed in the present analysis. The model considers the effect of Coulomb and Mononobe Okabe failure wedges. Backfill material is considered in the analysis as cohesionless. The failure wedge is an important factor which should be considered in determining the natural frequency of retaining structures. As the weight of failure wedge increases the natural frequency decreases significantly. The current model is validated using several analytical models reported in the literature of the earlier researcher.

This paper presents experimental results of the study of falling water film evaporation from water wall. The contribution is divided into several parts. The introduction is devoted to the theoretical part of the use, then the prototype of the water wall is presented and its most important parts are described. In order to verify the humidification performance of the water wall, experimental verification under laboratory conditions (climate chamber) was chosen. One task for the definition of water wall evaporation potential is to determine and develop the measuring system, which is clearly defined in article. The present document describes the methodology and boundary conditions during experiments. Plate heat exchanger ensured a water temperature in the system approximately 23 °C hot during all measurements. A total of 4 measurements were performed at different air temperatures and relative humidity. The results showed that at different temperatures and relative humidity of air, the water wall has a different humidification performance.

This paper could be considered as a general overview of current examples of realization, research, in architecture which could be called parasitic. Also, as an outline of possible new perspectives on current issues through the biomimicry design philosophy. The aim was also to clearly articulate the intent of the research I am dealing with while opening up a discourse on the subject.

Short-term heavy rains are one the most important rains from a meteorological, hydrological, and also technical point of view. When designing rainwater drainage systems or rainwater management systems, the intensity of short-term rains is used as a design parameter, because of short-term rains usually reach the highest intensity. This paper is focused on analysis of short-term heavy rains occurrence in the last 15 years in 3 rainfall stations in eastern Slovakia. The data used in analysis are automatically collected 10-minute precipitation totals at rainfall stations Poprad, Kamenica nad Cirochou and Košice.

In recent times, extremely dry seasons have been occurring more and more often in the eastern Slovakia, alternating with extremely wet seasons like torrential floods from extreme rainfall. Trend of reconnaissance drought index (RDI) and streamflow drought index (SDI) was evaluated in the paper using the Mann-Kendall test. The indices were evaluated at six climatic and river stations in the eastern Slovakia. The Mann-Kendal test results showed that the trend in the SDI index is not significant in 5 stations and only in one station the trend is significant. In the RDI index the trend is not significant in four stations and the trend is significant in two stationshe abstract is to indicate the subject of the paper, how the author proposes to develop the subject and its overall objective, aim or outcome.

Currently, the consumption of blended cements is increasing all over the world. This is due to environmental, technical and economic reasons. Among the additives mixed with ordinary Portland cement, ground granulated blast furnace slag and fly ash are of particular significance. However, some regions may lack standard additives, and vice versa, may be rich in natural pozzolans. This paper is focused on the perlite as a natural pozzolanic material which is locally available. This study presents the results of the application of perlite as a component of blended cements in different proportions, representing binary and ternary compositions, and compares it with standard additives (fly ash and ground granulated blast furnace slag). The time development of both compressive and flexural strength, including results of 2, 7, 28 and 90-day testing, is analyzed. Perlite binders show acceptable time development of strengths, which is comparable to conventional blended binders based on ground granulated blast furnace slag and fly ash and do not constitute a technological barrier. With a higher dose of perlite, the time increase in flexural strength is slower, but the rate of increase in compressive strength does not change substantially. Flexural strength of 4.1–6.2 MPa and compressive strength of 18.8–38.5 MPa are sufficient for a number of practical applications and are expected to meet the required limits. An improvement of strengths in the later period (90 days) was also confirmed.

Together with the natural environment, the built, artificial environment represents a barrier to the wind fluxes. Especially in the densely built cities, the wind flow pattern and the wind speed are considerably altered by buildings, which can lead to zones of an accelerated wind and turbulent flow. Incorporating the wind into the early conceptual stage of architectural design, this reciprocal interaction of the built environment and the wind fluxes can be analyzed and controlled to create zones of calmer wind around buildings. Presently, building envelopes are designed to withstand extreme load cases, which, however, demands thicker and bulkier structures. The subject of this study is a proposal and investigation of a lightweight, adaptive building envelope, which is able of a local, passive morphing in the wind. This local shape change leads to creating a textured, dimpled building surface; the final shape depends on the wind direction and force. The wind-induced dimpled surface influences the wind flow around the building, as well as surface wind pressure acting on the building, and the drag force. The analysis of three fundamental building shapes using the CFD (Computational Fluid Dynamics) simulation is performed for the variants with and without the proposed adaptive envelope. Concluding from the wind simulations, the wind flow can be decelerated, the turbulence reduced, and calmer zones around buildings can be created, by certain conditions. Moreover, the envelope, morphing with the instant wind force, can contribute to the reduction of the surface wind suction on buildings. Strikingly, the dimpled geometry of the wind-adaptive envelope can decrease the wind drag force by up to 28.4 %, which is again dependent on the global form, as well as the initial wind speed.

An occurrence of indoor particulate matters largely depends on outdoor pollution and its transportation indoors as well as on the presence of indoor pollution sources. Pollutants can flow from outdoor to indoor or indoor to outdoor under various conditions e.g. contribution of indoor pollutants to outdoor (in rural location with biomass fuel used for cooking) or outdoor to indoor in urban locations. This study aims to carry out an experimental investigation of particulate matter (PM) concentrations, temperature, humidity and air velocity during three days in winter season in Košice-Sever, Slovakia. Values of outdoor PM₁₀ concentrations ranged from 12.58 μg/m³ to 6,627.51 μg/m³. Extremely high concentrations of PM₁₀ were found near the traffic. Outdoor mean value of PM_2.5 (21.82 μg/m³) did not exceed a permissible value of 25 μg/m³. Overloads by PM₁₀ concentrations denote almost 108% and 2,270%. The indoor/outdoor (I/O) ratio was <1 for all fractions of particulate matters.

The building industry has been one of the fast-growing sectors in Rwanda, and multiple residential houses with amazing pitched roofs are being implemented in different cities. As the country is very hilly, the influence of wind loads on the buildings is high and therefore the selection step of roof slopes needs to be carefully undertaken, in order to ensure not only the structure safety, but also the economy. Available international and national guidelines give details about safety and functionality requirements, but don’t talk much about economic aspect, and this was the purpose of the given study. Using a well elaborated methodology, the influence of the roof slope on its cost was checked, and it was established that the slope’s increase of one degree would raise the roof cost by 3.6%. Therefore, during the roof slope selection and design process, economic requirements need more attention.

The exact concentration of the stress generated by the presence of a cavity is a problem of great significance in Mining and Civil Engineering. An interesting stress concentration problem is the biaxial one. A numerical analysis of stress around a cylindrical hole in an infinite elastic medium under opposite biaxial loading was investigated. This far-field loading is equivalent to a pure shear loading on planes rotated 45°. Analysis consisted of two-dimensional finite-difference computations carried out with the Fast Lagrangian of Continua (FLAC) code. The Stress Concentration Factor (SFC) is evaluated numerically and compared with the existing solution. Predicted results of stress distribution around the hole were found in good agreement with the analytic theory.

This paper presents an experimental investigation on the post-repair flexural response of mortars with and without damage. In order to improve the mechanical properties of the damaged mortars, which were subjected to different loads ranging between 40 % and 90 %, the mortars specimens were reinforced and repaired using two different composite materials, the first with only epoxy resin, while the second consisted of a mixture of epoxy resin and glass fiber. The results show a significant improvement in the stiffness damaged. Therefore, the reinforced specimens by a layer of resin on the lower side surface increased the bending strength by 58 %, when compared to those control samples. The reinforcement using composite resin-fiber of glass exhibited considerable increases in the safety of constructions. The SEM images of damaged samples with and without repair, revealed the impact of reinforced glass fibers-mortar on the matrix-mortar by improving theirs mechanical performances.

The purpose of this work is to assess the steel fiber distribution effect on physical and mechanical properties of self-compacting mortar. An experimental study was conducted to see the fiber distribution during the implementation of self-compacting mortars that are fluid and on mechanical behavior in bending tensile strength. A method of placing self-compacting mortar in the molds has been developed to highlight the distribution of fibers in the cementitious matrix. The mortars are placed in prismatic molds in three layers. The amount of steel fibers differs from one layer to another. A total quantity of 90 kg /m³ was distributed in prismatic molds of dimensions 40x40x160 mm³. Straight and hooked ends steel fibers were used. The characteristics of mortars containing both types of fibers in the fresh and hardened state were measured and compared to those of self-compacting mortar without fibers. The pouring by layer allowed us to deduce that the distribution of metallic fibers has a significant effect on the hardened properties of the mortar. Indeed, the mechanical strength of the fiber-reinforced mortar depends on the nature and distribution of fibers in the cementitious matrix (mortar). A gain in bending tensile strength of 71.83% was recorded for self-compacting mortars elaborated with hooked end fibers and 52.11% for those containing straight steel fibers. Indeed, mortars containing entirely the same dosage of steel fibers (90 kg/m³) have a bending tensile strength that varies according to the fibers dosage by layers. Mortar samples with higher fiber content in the lower layer have a higher bending tensile strength than other samples with a higher fiber layer in the middle or layer above. However, it should be noted that steel fibers with hooks are much more effective than those without hooks. Indeed, the effect of fiber distribution is more significant for fibers without hooks because the hooks can slow down the movement of the fibers during the pouring of the mortar. The variation of the dosages per layer generated a difference in the deflection values for the mortars. The deflection is much higher for fiber-reinforced mortars (with hooks) compared to fiber-reinforced mortars without hooks.