The selection of the formwork system for high rise building affects the entire construction project duration and cost. The study reports the factors influencing the selection of different formwork system in the construction of high rise buildings through structural questionnaire survey from the client, contractor, consultant, and interviews with expert members. Total of 40 technical factors was identified from the literature and 220 filled questionnaires were received from the respondent. Relative Importance Index method is used to find the topmost factors affecting the selection of formwork system. Additionally, from factor analysis 22 factors were identified to have a correlation with one another. Regression analysis reveals that duration of the project, maintenance cost, adaptability, and safety have impact on formwork selection across time, cost and quality. These findings could potentially increase the construction company’s existing knowledge in relation to formwork selection.

Iron production’s waste materials include significant quantities of blast furnace slag (BFS) which could potentially be used as a substitute for natural aggregates in hot mix asphalt (HMA) used in highway projects. Although many of properties of slag are interesting, its porosity and absorption rate would lead to greater consumption of asphalt. For this study, a Portland cement (PC) paste was used to reduce the porosity of a BFS. This PC treated BFS (called BFS-C) was then used in an HMA to replace the coarse fraction of a natural aggregate. Marshall, Indirect Tensile Strength (ITS), resilient modulus and Cantabro tests were then carried out on different HMA mixtures that included BFS-C. Using BFS-C, HMA’s resistance under monotonic loading, stiffness under cyclic loading, and resistance to moisture damage increased remarkably. In addition, the Cantabro abrasion resistance of BFS-C improved was better than that of the HMA mixture produced with untreated BFS.

Experimental tests were carried out to assess the failure model of steel and basalt fiber reinforced concrete two-span beams. Experimental research was focused on observing the changes in behavior of tested elements in dependence on the ratio of shear reinforcement and type of fiber. The beams had varied stirrup spacing. The steel fiber content was 78.5 kg/m³ (1.0% by vol.) and basalt fiber content was 5.0 kg/m³ (0.19% by vol.). Concrete beams without fibers were also examined. Two-span beams with a cross-section of 120×300 mm and a length of 4150 mm were loaded in a five-point bending test. Shear or flexural capacity of tested members was recorded. The effectiveness of both sorts of fibers as shear reinforcement was assessed and the differences were discussed. It was shown that fibers control the cracking process and the values of deflections and strains. Fibers clearly enhance the shear capacity of reinforced concrete beams.

The main objective of the article is to present quantified and measurable risks likelihood appearance, impact and significance of inspected and monitored 48 commercial construction projects and their feasibility to be carried out. Original technical, financial and organisational feasibility studies in compliance with a rigorous Bank Investment Supervision requirements have been executed by the author in the period of 2005–2018. Methodology of construction project appraisal for financing and execution professional preparation have been laid out – technical documentation, arrangements, realisation. Analysis and assessment of Bank Investment Supervision consisted of project execution plan PEP, geotechnical and environmental conditions, permit design, agreements and decision impacts of local authorities, engineering contract for construction works, project insurance and performance bonds, schedule of execution tasks and their costs, payment plan, investment budget and project economical effectiveness, scope of monthly construction works execution assessed by Earned Value Method approach and handover procedure of construction project. An attempt was made to express numerically the relationship between risks impacts and their level of likelihood. Also, a method of associating the influence of projects risks impacts on the extent of the likelihood of project risk occurrence which makes possible to determine the direction and the strength of this relationship was presented. Finally, risks likelihood appearance, impact and significance variability of commercial construction projects within last two years of booming investment industry have been determined.

A “rock bridge”, defined as the closest distance between two joints in a rock mass, is an important feature affecting the jointed rock mass strength. Artificial jointed rock specimens with two parallel joint fractures were tested under uniaxial compression and numerical simulations were carried out to study the effects of the inclination of the rock bridge, the dip angle of the joint, rock bridge length, and the length of joints on the strength of the jointed rock mass. Research results show: (1) When the length of the joint fracture, the length of the rock bridge, and the inclination of the rock bridge stay unchanged, the uniaxial compressive strength of the specimen gradually increases as the inclination of the joint fracture increases from 0° to 90°. (2) When the length of the joint fracture, the length of the rock bridge, and the inclination of the joint fracture stay unchanged, the uniaxial compressive strength of the specimen shows variations in trends with the inclination of the rock bridge increasing from 30° to 150° (3). In the case when the joint is angled from the vertical loading direction, when the dip angle of the joint fracture, the inclination of the rock bridge, and the length of the rock bridge stay unchanged, the uniaxial compressive strength of the specimen gradually decreases with an increasing length of joint fracture. When the dip angle of the joint fracture, the inclination of the rock bridge, and the length of the joint fracture stay unchanged, the uniaxial compressive strength of the specimen does not show a clear trend with an increase of the length of the rock bridge.

This paper presents the results of the static work analysis of laminated veneer lumber (LVL) beams strengthened with carbon fabric sheets (CFRP). Tested specimens were 45mm wide, 100 mm high, and 1700 mm long. Two types of strengthening arrangements were assumed as follows: 1. One layer of sheet bonded to the bottom face; 2. U-shape half-wrapped reinforcement; both sides wrapped to half of the height of the cross-section. The reinforcement ratios were 0.22% and 0.72%, respectively. In both cases, the FRP reinforcement was bonded along the entire span of the element by means of epoxy resin. The reinforcement of the elements resulted in an increase in the bending strength by 30% and 35%, respectively, as well as an increase in the global modulus of elasticity in bending greater than 20% for both configurations (in comparison to the reference elements).

The growth in high-rise building construction has increased the need for hybrid reinforced concrete and steel structural systems. Columns in buildings are the most important elements because of their seismic resistance. Reinforced concrete (RC) columns and steel columns were used herein to form hybrid structural systems combining their distinct advantages. Eleven 3D building models subjected to earthquake excitation with reinforced concrete beams and slabs of 12 floors in height and with different distributions of mixed columns were analyzed by the SAP2000 software in order to investigate the most suitable distributions of a combination of reinforced concrete and steel columns. Top displacements and accelerations, base normal forces, base shear forces, and base bending moments were computed to evaluate the selected hybrid structural systems. The findings are helpful in evaluating the efficiency of the examined hybrid high-rise buildings in resisting earthquakes.

The diaphragm wall and the open caisson represent two main competitive technologies used in the construction of underground objects. In modern times, diaphragm walls are primarily applied for large-size objects, with open caissons being preferred in the case of small-sized ones. Currently, objects of this type are designed mainly for sewage treatment plants and detention reservoirs. Their construction involves highly labour-intensive processes. During the execution of works unforeseen negative effects are observed to occur. During the underground objects construction the most common phenomena are: deviations from the vertical (tilt), sagging, sinking below the designed level, cracking, scratches or leakage through the wall. The purpose of the paper is to classify undesired risk factors emerging in the process of underground objects construction and selection of the optimal technological and material solution for municipal facilities. The implementation of this task involved the selection of Multi-Criteria Decision Making methods, taking into account the cause-effect rating, as the mathematical apparatus. The Ratio Estimation in Magnitudes or deciBells to Rate Alternatives which are Non-DominaTed (REMBRANDT) method was applied. The research proved that it is possible to analytically assess unforeseen risk factors conducive to emergency situations during the implementation of underground objects, using the REMBRANDT method.

Construction projects are characterised by complexity in the technical, organisational and environmental sphere. The organisational complexity of such projects makes it necessary to manage relationships between actors who fulfil various functions. Formal organisational structures that have been developed for this purpose do not always reflect the actual relationships between construction project participants. In literature, scholars more and more often point to the need to identify and monitor such informal relationships and attempt to manage them in order to effectively carry out projects. Structural analysis of so-called self-organising networks of relationships between project participants is carried out on the basis of established structural measures by performing Social Network Analysis (SNA). In a situation when inappropriate communication between project participants relative to management staff expectations is detected, interventions meant to improve communication in such networks are possible. The goal of the article is proposing an optimisation-oriented approach to planning such interventions while taking various constraints, such as communication costs, into consideration. As a part of this optimisation, the authors proposed a method from the heuristic methods group. This solution will support decision-making in terms of intervening within an informal relationship structure. The method was presented on the example of an actual construction project involving the construction of a complex of housing buildings. the self-organising network structure was defined on the basis of a survey carried out among the project's participants and concerned communication between them over a four-week period. As a result of the structural network analysis, abnormalities in communication between project participants were detected. The optimisation method developed by the authors pointed to possibilities of improving communication effectiveness within this network. The effects of the analysis confirmed the application potential of the method that was presented.

The most important challenges in the construction field is to do the experimentation of the designing at real time. It leads to the wastage of the materials and time consuming process. In this paper, an artificial neural network based model for the verification of sigma section characteristics like shear centre and deflection are designed and verified. The physical properties like weight, depth, flange, lip, outer web, thickness, and area to bring shear centre are used in the model. Similarly, weight, purlin centres with allowable loading of different values used in the model for deflection verification. The overall average error rate as 1.278 percent to the shear centre and 2.967 percent to the deflection are achieved by the model successfully. The proposed model will act as supportive tool to the steel roof constructors, engineers, and designers who are involved in construction as well as in the section fabricators industry.

The model for estimating the whole life costs of the building life cycle that allows the quantification of the risk addition lets the investor to compare buildings at the initial stage of planning a construction project in terms of the following economic criteria: life cycle costs (LCC), whole life costs (WLC), life cycle equivalent annual costs (LCEAC) and cost addition for risk (ΔR_LCC). The subsequent stages of the model development have been described in numerous publications of the authors, while the aim of this paper is to check the accuracy of the model in the case of changing the parameters that may affect the results of calculations. The scope of the study includes: comparison of the results generated by the model with the solutions obtained in the life cycle net present value method (LCNPV) for time and financial input data, not burdened with the risk effect; the analysis of the variability of results due to changes in input data; analysis of the variability of results as a consequence of changing the sets of membership functions for input data and methods for defuzzification the result.

Small construction objects are often built by standard task teams. The problem is, how to allocate these teams to individual works? To solve the problem of allocation three methods have been developed. The first method allows to designate optimal allocation of teams to the individual works in deterministic conditions of implementation. As a criterion of the optimal allocation can be applied: “the minimization of time” or “the minimization of costs” of works execution. The second method has been developed analogously for both criteria but for stochastic conditions and for the stochastic data. The third method allows to appoint a compromise allocation of teams. In this case, the criteria “the minimization of time” and “the minimization of costs” are considered simultaneously. The method can be applied in deterministic or stochastic conditions of works implementation. The solutions of the allocation problems which have been described allow to designate the optimal allocation of task teams and to determine the schedule and cost of works execution.

Accordingly to recommendations set out by standards, degradation curves which will serve as a tool facilitating decision-making regarding renovation works ought to be developed. The article presents the proposal of a model for predicting the aging of a residential building. The proposed PRRD (Prediction of Reliability According to Rayleigh Distribution) model determines the performance characteristics of a building over the full period of its use. PRRD accounts for the life spans of individual building components. Additionally introduced in the model were supplements accounting for the intensity of changes in the building and its surroundings. The developed method of the non-linear degradation process of a building accounts for the role and weights of individual building components as well as the intensity of significant factors influencing the aging process. The presented methodology of the description of changes in the performance characteristics over the course of using a building will be a diagnostic process of predicting the technical state of a building. The proposed predictions can serve as the basis for making the right strategic decisions when planning renovation works in residential buildings.

The article presents the results of research, the aim of which was to determine the qualitative and quantitative structure of the causes of accidents that were a result of falling from scaffolding. An original methodology for the classification of accidents with regards to their causes was developed and was based on cluster analysis. An example of using the proposed methodology is provided. 187 post-accident protocols of occupational accidents involving construction scaffolding, which occurred between 2010 and 2017 in selected Polish voivodeships, were analyzed. Afterwards, the matrix of accident causes, for which the calculations were made, was created. Five subsets of accidents were obtained and the accidents were classified to a subset with similar causes.

Construction projects, even exemplarily planned and organized, bear a risk of unforeseen events and problems which can result in completion of the works after the deadline, that is delays. The construction of bridges is an inseparable part of road and rail projects and construction and expansion of the transport network. The paper aims at finding a relationship between the independent variables characterizing bridge projects and the delays during their implementation. Two alternative models were proposed to solve the problem: logit and probit. The data set comprising road and rail bridges built in Poland in the last 12 years (2005–2017) was used to build the models. The evaluation, quality and accuracy parameters of proposed models were determined in the final part of the paper.

Various trading strategies have been proposed that use estimates of the Hurst coefficient, which is an indicator of long-range dependence, for the calculation of buy and sell signals. This paper introduces frequency-domain tests for long-range dependence which do, in contrast to conventional procedures, not assume that the number of used periodogram ordinates grow with the length of the time series. These tests are applied to series of gold price returns and stock index returns in a rolling analysis. The results suggest that there is no long-range dependence, indicating that trading strategies based on fractal dynamics have no sound statistical basis.

The development of linear infrastructure increases the degree of fragmentation of natural areas and has a negative impact on biodiversity and the range of available ecosystem services. The basic competing land use model is expanded to include infrastructure development. The extended model leads to the conclusion that due to the dual impact of the infrastructure (lowering the value of ecosystem services and increasing the private rents to developed land), the size of the natural area in the long-term equilibrium will be lower compared to the basic model. The preservation of nature ceases to be profitable enough. Infrastructure also reduces the marginal costs of conversion and thus increasing the volume of natural land being converted at avery moment along the transition path. If the decisions on optimal management of natural areas and infrastructure development are undertaken together, the result is a lower density of the infrastructure network and a larger ecosystem area in the steady state.

In the paper we present and apply a Bayesian jump-diffusion model and stochastic volatility models with jumps. The problem of how to classify an observation as a result of a jump is addressed, under the Bayesian approach, by introducing latent variables. The empirical study is focused on the time series of gas forward contract prices and EUA futures prices. We analyse the frequency of jumps and relate the moments in which jumps occur to calendar effects or political and economic events and decisions. The calendar effects explain many jumps in gas contract prices. The single jump is identified in the EUA futures prices under the SV-type models. The jump is detected on the day the European Parliament voted against the European Commission’s proposal of backloading. The Bayesian results are compared with the outcomes of selected non-Bayesian techniques used for detecting jumps.

This paper presents results of evolutionary minimisation of peak-to-peak value of a multi-tone signal. The signal is the sum of multiple tones (channels) with constant amplitudes and frequencies combined with variable phases. An exemplary application is emergency broadcasting using widely used analogue broadcasting techniques: citizens band (CB) or VHF FM commercial broadcasting. The work presented illustrates a relatively simple problem, which, however, is characterised by large combinatorial complexity, so direct (exhaustive) search becomes completely impractical. The process of minimisation is based on genetic algorithm (GA), which proves its usability for given problem. The final result is a significant reduction of peak-to-peak level of given multi-tone signal, demonstrated by three real-life examples.

In the complex RLC network, apart from the currents flows arising from the normal laws of Kirchhoff, other distributions of current, resulting from certain optimization criteria, may also be received. This paper is the development of research on distribution that meets the condition of the minimum energy losses within the network called energy-optimal distribution. Optimal distribution is not reachable itself, but in order to trigger it off, it is necessary to introduce the control system in current-dependent voltage sources vector, entered into a mesh set of a complex RLC network. For energy-optimal controlling, to obtain the control operator, the inversion of R(s) operator is required. It is the matrix operator and the dispersive operator (it depends on frequency). Inversion of such operators is inconvenient because it is algorithmically complicated. To avoid this the operator R(s) is replaced by the R’ operator which is a matrix, but non-dispersive one (it does not depend on s). This type of control is called the suboptimal control. Therefore, it is important to make appropriate selection of the R’ operator and hence the suboptimal control. This article shows how to implement such control through the use of matrix operators of multiple differentiation or integration. The key aspect is the distribution of a single rational function H(s) in a series of ‘s’ or ‘s⁻¹’. The paper presents a new way of developing a given, stable rational transmittance with real coefficients in power series of ‘s/s⁻¹՚. The formulas to determine values of series coefficients (with ‘s/s⁻¹’) have been shown and the conditions for convergence of differential/integral operators given as series of ‘s/s⁻¹’ have been defined.

The aeronautical industry is a sector constantly looking for new materials and equipment because of its tendency to expand quickly. The Ti6Al4V titanium alloy is used frequently in the aeronautic, aerospace, automobile, chemical and medical industry because it presents high strength combined with low density (approximately 4.5 g/cm3), good creep resistance (up to 550°C), excellent corrosion resistance, high flexibility, good fatigue and biocompatibility. As a result of these properties, this titanium alloy is considered an excellent material for manufacturing structural parts in the aircraft industry for modern aeronautic structures, especially for airframes and aero-engines. But its use is also problematic because the Ti6Al4V titanium alloy manifests hydrogen embrittlement, by means of hydrides precipitation in the metal. The Ti6Al4V alloy becomes brittle and fractures because of hydrogen diffusion into metal and because titanium hydrides appear and create pressure from within the metal, thus generating corrosion. Because of titanium hydrides, the titanium alloy suffers from reduced ductility, tensile strength and toughness, which can result in fractures of aeronautical parts. This poses a very serious problem for aircrafts. In this paper, rapid hydrogen embrittlement is presented along with XRD, SEM and TEM analysis. Its goal is to detect the presence of titanium hydrides and to spot the initial cracks in the metallic material.

Two methods for calculating transport parameters in semiconductor superlattices by applying Green’s functions are compared in the paper. For one of the methods, the Wannier functions method, where computations in the complex space and Wannier functions base are required, the Hamiltonian matrix is small in size and its elements depend solely on the energy. For the real space method, as it operates in the floating point domain and uses the Hamiltonian containing the elements dependent both on energy and position, the Hamiltonian matrix is larger in size. The size makes the method computationally challenging. To find the consequences of choosing one of the methods, a direct comparison between the computations, obtained for both methods with the same input parameters, was undertaken. The differences between the results are shown and explained. Selected simulations allowed us to discuss advantages and disadvantages of both methods. The calculations include transport parameters such as the density of states and the occupation functions, with regard to scattering processes where the self-consistent Born approximation was used, as well as the spatial distribution of electron concentration for two superlattices structures. The numerical results are obtained within the non-equilibrium Green’s functions formalism by solving the Dyson and the Keldysh equations.

The article presents the analysis of the simulation test results for three variants of the power electronics used as interface between the power network and superconducting magnetic energy storage (SMES) with the following parameters: power of 250 kW, current of 500 A DC and voltage of 500 V DC. Three interface topologies were analyzed: two-level AC-DC and DC-DC converters; three-level systems and mixed systems combining a three-level active rectifier and a two-level DC-DC converter. The following criteria were considered: input and output current and voltage distortions, determined as THDi and THDu, power losses in power electronics components; cost of the semiconductor components for each topology and total cost of the interface. Results of the analysis showed that for high-power low-voltage and high-current power electronics systems, the most advantageous solution from a technical and economical perspective is a two-level interface configuration in relation to both AC-DC and DC-DC converters.

This paper presents mechanical fault detection in squirrel cage induction motors (SCIMs) by means of two recent techniques. More precisely, we have analyzed the rolling element bearing (REB) faults in SCIM. Rolling element bearing faults constitute a major problem among different faults which cause catastrophic damage to rotating machinery. Thus early detection of REB faults in SCIMs is of crucial importance. Vibration analysis is among the key concepts for mechanical vibrations of rotating electrical machines. Today, there is massive competition between researchers in the diagnosis field. They all have as their aim to replace the vibration analysis technique. Among them, stator current analysis has become one of the most important subjects in the fault detection field. Motor current signature analysis (MCSA) has become popular for detection and localization of numerous faults. It is generally based on fast Fourier transform (FFT) of the stator current signal. We have detailed the analysis by means of MCSA-FFT, which is based on the stator current spectrum. Another goal in this work is the use of the discrete wavelet transform (DWT) technique in order to detect REB faults. In addition, a new indicator based on the MCSA-DWT technique has been developed in this study. This new indicator has the advantage of expressing itself in the quantity and quality form. The acquisition data are presented and a comparative study is carried out between these recent techniques in order to ensure a final decision. The proposed subject is examined experimentally using a 3 kW squirrel cage induction motor test bed.