The influence that general contractors and subcontractors have on the operation of a company is immense. Keeping this in mind, the authors have decided to develop and algorithm based on the analysis of partnering relations between construction companies that would select the best possible construction company for the purposes of cooperation. This algorithm, developed for a given construction company, is meant to support its decision-making system in the field of the selection of another construction company to cooperate with. The author has made references to earlier research, in which she had used the ELECTRE III method, and in which she bad analysed the possibility of applying the BIPOLAR method in order to solve the problem of the selection of a construction company to develop partnering relations with. The author provided an example of the calculations performed for a selection of construction companies.
This article aims to identify potential risk factors affecting the implementation and synchronisation of surveying and construction works during building and operation of roads. The task was executed on the basis of literature studies and experience. The article is an introduction to the research that has been conducted by the authors on the reasonably precise index of factors which one may deal with during the implementation of facilities of this type. The raised issue is crucial for financial and time reasons, but what is important in the roads construction - also for social ones, as prolonged traffic disruption adversely affects the environment.
Thin-walled bars currently applied in metal construction engineering belong to a group of members, the cross-section resistance of which is affected by the phenomena of local or distortional stability loss. This results from the fact that the cross-section of such a bar consists of slender-plate elements. The study presents the method of calculating the resistance of the cross-section susceptible to local buckling which is based on the loss of stability of the weakest plate (wall). The "Critical Plate" (CP) was identified by comparing critical stress in cross-section component plates under a given stress condition. Then, the CP showing the lowest critical stress was modelled, depending on boundary conditions, as an internal or cantilever element elastically restrained in the restraining plate (RP). Longitudinal stress distribution was accounted for by means of a constant, linear or non-linear (acc. the second degree parabola) function. For the critical buckling stress, as calculated above, the local critical resistance of the cross-section was determined, which sets a limit on the validity of the Vlasov theory. In order to determine the design ultimate resistance of the cross-section, the effective width theory was applied, while taking into consideration the assumptions specified in the study. The application of the Critical Plate Method (CPM) was presented in the examples. Analytical calculation results were compared with selected experimental findings. lt was demonstrated that taking into consideration the CP elastic restraint and longitudinal stress variation results in a more accurate representation of thin-walled element behaviour in the engineering computational model
Decision-making processes, including the ones related to ill-structured problems, are of considerable significance in the area of construction projects. Computer-aided inference under such conditions requires the employment of specific methods and tools (non-algorithmic ones), the best recognized and successfully used in practice represented by expert systems. The knowledge indispensable for such systems to perform inference is most frequently acquired directly from experts (through a dialogue: a domain expert - a knowledge engineer) and from various source documents. Little is known, however, about the possibility of automating knowledge acquisition in this area and as a result, in practice it is scarcely ever used. lt has to be noted that in numerous areas of management more and more attention is paid to the issue of acquiring knowledge from available data. What is known and successfully employed in the practice of aiding the decision-making is the different methods and tools. The paper attempts to select methods for knowledge discovery in data and presents possible ways of representing the acquired knowledge as well as sample tools (including programming ones), allowing for the use of this knowledge in the area under consideration.
Planning a construction project, the investor frequently faces the choice of the option of the planned investment. Assessment of options is difficult due to the complex nature of construction projects. Various methods of multicriteria evaluation are successfully applied in the assessment and analysis of options. For those methods to work, a handful of information must be prepared beforehand. Among others, it is necessary to establish the assessment criteria and determine their weight for specific cases. This stage is implemented in cooperation with experts. The results of evaluations, obtained on the basis of the experts' opinions, must be processed and prepared. The paper will discuss one possible option for assessing the experts' opinion.
The paper presents selected aspects of dynamic numerical simulations of an orthotropic steel railway bridge loaded by high-speed trains. The model of moving loads was adopted in accordance with the models set out in the applicable standards. The current European code requirements are referred in which the computer calculations of the dynamic response of the structure are the basis for assessing the suitability of the structure to carry high-speed rail traffic ( v > 160 km/h ). In this research the calculations are based on the author's method of generating traffic roads in Abaqus FEM environment. lt is emphasized in the paper that in most commercial FEM codes (including Abaqus), moving loads are not implemented in modules responsible for defining of loads. The author's approach to this issue allowed to obtain results confirming its adequacy. In the longer term, the authors will develop a plan to adapt this algorithm in order to generale traftic loads on bridges discretized as spatial and plane numerical models.
The need to modify conventional pavement rises due to high maintenance cost of the highway systems. With the continuously increased consumption, a large amount of waste glass materials is generated annually in the world. This paper aims to study the performance of pavement asphalt in which a fractional aggregate is replaced with crushed glass. In this paper, some important properties of asphalt mix, including stability, flow, specific gravity and air voids are investigated. The original sample is prepared without adding glass for different percentages of bitumen. Other samples are prepared by adding crushed glass to the mix with 5%, 10%, and 15% by aggregate weight. The results show that the properties of glass-asphalt mixture are improved in comparison with normal asphalt pavement. lt is concluded that the use of waste glass in asphalt pavement is desirable.
Self-curing concrete SC is a concrete type that can be cured without using any external curing regimes. It can perform by several methods such as using lightweight aggregate or chemical agents. In this research chemical curing agent is used to produce SC. This paper reports the results of a research study conducted to evaluate the effect of sulfates on the performance of self-curing concrete compared to ordinary concrete. Samples are immersed in sodium sulfate Na2S04 solution of 4% concentration. Results are measured in terms of compressive strength, tensile strength, flexural strength and mass loss. It was found that the rate of strength loss is noticed at ordinary concrete compared to SC concrete. Sulfate resistance is improved when using self-curing concrete. This improvement appears to be dependent on using a chemical curing agent.
This paper presents application of optical microscope for evaluation of microtexture changes of coarse aggregate during simulated polishing in laboratory. Observations of the apparent changes on surfaces of seven different aggregates are presented. Simulation polishing of aggregate was performed in accordance with PN-EN 1097-8:2009. lmages of the aggregate surface were taken with the optical microscope in the reflection mode in particular stages of polishing. Digital images were analyzed. Standard deviation was determined on the basis of the histogram of intensities from digital images of the surfaces of aggregate grains which was assurned as the measure of changes in microtexture during simulated polishing (namely the σh parameter). Statistical analysis has shown that the changes of the σh parameter between the particular stages of polishing confirm certain trends related to the petrographic characteristic of the rocks. Aggregates which included minerals of similar hardness (granodiorite, dolomile, basalt) were more prone to polishing than gabbro and postglacial. Regeneration of the microtexture, the recovery to its original asperity, occurred in the case of quartz sandstone and steelmaking slag.
We propose a method of constructing multisector-multiregion input-output tables, based on the standard multisector tables and the tools of spatial econometrics. Voivodship-level (NUTS-2) and subregion-level data (NUTS-3) on sectoral value added is used to fit a spatial model, based on a modification of the Durbin model. The structural coefficients are calibrated, based on I-O multipliers, while the spatial weight matrices are estimated as parsimoniously parametrised functions of physical distance and limited supply in certain regions. We incorporate additional restrictions to derive proportions in which every cross-sectoral flow should be interpolated into cross-regional flow matrix. All calculations are based on publicly available data. The method is illustrated with an example of regional economic impact assessment for a generic construction company located in Eastern Poland.
The model considered in the paper is defined as VAR with the prior distribution for parameters generated by the dynamic stochastic general equilibrium (DSGE) model. The degree of economic restrictions in the DSGE-VAR model is controlled by the weighting parameter. In the paper there is investigated the impact of the weighting parameter prior specifications for the posterior shape of impulse response functions (IRFs). In case of conditional models the paths of IRFs highly depend on the value of the weighting parameter that is set arbitrary. When considering full estimation with different prior types, means and gradual change in the dispersion the posterior time paths of IRFs are similar in models with high values of the marginal data density.
The aim of this paper was to estimate the gender wage gap in Poland and in the 16 NUTS2 Polish regions in 2010, and to verify the predictions of the spatial monopsony model for Poland with a newly created, harmonized database for wages of individuals in Poland. According to the model, the unexplained part of the gender wage gap, identified with wage discrimination, tend to be lower in regions with more competition between employers. The results of the analyses performed in this paper show that in more urbanized regions the average wages are higher than in the rural ones. In each of the 16 NUTS2 Polish regions, women earn less than men. Raw differences in wages between men and women are largest in the most urbanized regions but a significant part of the differences in those regions can be explained by differences in workers’ characteristics, especially by different sectoral structure of employment. The part of the gender wage gap which remains unexplained, and in the literature is commonly attached to discrimination, is the highest in rural regions of Eastern Poland in line with the predictions of the spatial monopsony model.