Tom 28 (2020): Zeszyt 1 (March 2020)

The experimental investigation involved stabilizing an expansive soil using lime, amending the stabilization process with varying doses of coconut shell powder (CSP), and studying the effects of the amendment on the strength, index properties, mineralogy, and microstructure of the stabilized soil. The optimum lime content (OLC) for the maximum strength gain of the stabilized soil was determined by performing unconfined compressive strength (UCS) tests. The stabilization process was amended with four different proportions of CSP, and the UCSs of the amended specimens were evaluated and compared. The spent UCS samples were crushed and pulverized to perform index property tests as well as mineralogical (XRD) and micro-structural (SEM) tests. The results of the investigation revealed that amending the lime stabilization process with CSP yielded positive results only at a low dosage of 0.25%. It is concluded that materials of an organic origin such as CSP need to be adopted in low dosages to reap beneficial effects in the stabilization process.

Most of the existing models for analyzing unconfined flows in hillslope aquifers are based on the Boussinesq (1877) equation. In the development of these models, the assumption of negligible bed-normal velocity was employed, thus restricting their application to shallow groundwater-flow situations. On the basis of a non-hydrostatic pressure approach, a ground-water-flow model that considers the effects of the vertical curvature of the flow streamlines and the three-dimensional geometry of the underlying bedrock was proposed. A dissipative two-four finite-difference scheme was utilized to discretize and solve the model equation. The applicability of the model was assessed by conducting numerical experiments on transient unconfined flows in convergent- and divergent-type hillslope aquifers with non-uniform bedrock slopes. The numerical results for the phreatic-surface profiles and outflow discharges were compared to the experimental data, and a good agreement was obtained. The results of the comparison attested that the dynamics of the hillslope drainage processes were accurately portrayed by the proposed model. This study highlights the necessity of considering the effects of the plan shape and the profile curvature of complex hillslopes in order to improve the overall performance of the computational model.

This article proposes to contribute to the discussion on environmental product declarations for buildings. Using a simple life-cycle analysis of a low-energy detached house and CO2-equivalent emissions as a comparative unit, the case study presented illustrates the problems with the initial input data related to embodied energy and a definition of the criteria for an assessment of the environmental quality of buildings. The actual case study compares the expected energy demand of a detached house in the course of its service life and the energy input (embodied energy) necessary for its assembly and for the manufacture of the individual building products. The operation of the building during its service life is described using a computer-aided building performance simulation. The input data related to the embodied energy are based on information from classical works on life cycle analyses. In addition, the article discusses the limits of building envelope improvements in terms of the thickness of thermal insulation and also stresses the increasing significance of embodied energy in the environmental assessment of buildings.

The presented paper deals with an analysis of the reliability of a diagnostic method of air permeability through building openings (windows, doors, glass walls) by the application of infrared thermography. A test sample of a plastic double casement window was experimentally tested for air permeability and watertightness in a large pressure chamber. Different levels of the tightness were adjusted between the casement and frame part of the window. Additionally, the window test sample was measured in the large climate chamber with variant air pressure differences. Moreover, the surface temperatures were measured on the window by thermocouples and subsequently compared with images directly taken by infrared thermography. The effect of the increased air infiltration can be detected by infrared thermography but cannot quantify the overall air permeability of the window. The distribution of the exterior window surface temperature is influenced by several factors which should be taken into consideration in the final assessment of the window.

A detailed analysis of concrete structures requires knowledge of the mechanical properties of the materials used. In the case of a non-linear analysis, the scope of the information needed is even greater. In particular, the tensile strength and fracture-mechanical parameters are required for the concrete. Prospective approaches that could increase the informative value of detailed analyses include the use of stochastic modelling. It particularly enables the definition of the effects of individual input parameters on the load capacity, failure mode, and general behaviour of the structure. The presented paper aims at a detailed analysis of a reinforced-concrete beam without shear reinforcement, which is based on a complex set of laboratory tests and non-linear analyses with a sensitivity study. The laboratory program includes different types of laboratory tests. Selected and missing material parameters of the concrete are calculated according to recommendations in scientific papers and the valid standards. The results are compared and discussed.

A current trend is to reduce the energy performance of buildings by using alternative sources for heating and cooling. One of the most promising, and so far unprecedented sources of heating and cooling, is the use of energy from the earth using the thermally-activated foundation piles of a building, the so-called energy piles. The paper deals with an overview and comparison of computer-aided analytical models of energy piles. The individual analytical models are compared (categorized) from the point of view of their physical complexity, computational costs, and thus their usability for the purpose of optimizing energy-pile equipment or assessing the long-term energy efficiency of an energy pile field. Selected mathematical models were algorithmized, and the results obtained were compared with a more robust numerical solution performed using CalA 4 software.

The structural integrity of precast concrete structures mainly depends on the connections between the precast structural elements. The purpose of a connection is to transfer loads, restrain movement, and/or to provide stability to a component or an entire structure. Therefore, the design of connections is one of the most important aspects in the design of precast concrete structures. All the connections should be designed according to the valid codes. All precasters have developed connection details over the years that suit their particular production and erection preferences. It is common that the structural engineer shows the internal forces and connection locations, and the manufacturer’s engineering department provides the final design and details of the connections. This paper describes basic types of connections and joints used in precast concrete structures