Iskanje po katalogu digitalne knjižnice

Opis: The unstable economic conditions that have been in place in the Slovenian and international construction markets reveal the problem of a disproportionate increase in the prices of construction materials and energy products. Such increases will therefore result in higher costs of construction services, which would ultimately affect the total value of the construction project. These events in turn bring uncertainty to the construction project and would negatively impact the business of construction companies and investors. Legal and construction practices have so far developed various ways to regulate contract changes arising due to unforeseen market conditions. The present paper offers a contribution to the contract price change solution during the construction phase. The introduction first presents the measures and guidelines that deal with the differences in contract prices in Slovenia and some other countries. Then, various methods of calculating price differences that have emerged in current Slovenian practice are described. As a result, a proposal for a hybrid method of monthly price difference calculation is presented. The hybrid method represents a balanced solution resulting from the unforeseen increase in construction material prices on the market and is applicable to all construction projects. The three methods, i.e., a calculation method, a method based on the GZS-ZGIGM index, and a hybrid method, are applied to a real example of a public contract. The calculation of the price valorisation, represented as an index of the recognised price increases of contract works, is carried out. The results are compared, and further solutions are proposed.
Ključne besede: connstruction contract, construction market, contract price, price index
Objavljeno v DKUM: 03.03.2025; Ogledov: 0; Prenosov: 0
Celotno besedilo (498,47 KB)
Gradivo ima več datotek! Več...

Ključne besede: construction industry, sustainable building, environmental protection, optimization
Objavljeno v DKUM: 19.09.2024; Ogledov: 0; Prenosov: 342
Celotno besedilo (158,71 KB)
Gradivo ima več datotek! Več...

Opis: Mobile cranes represent conventional construction machinery that is indispensable for the erection of most prefabricated buildings, especially those containing heavy components. However, it is also common knowledge that the engagement of these machines has a significant influence on the environment, various social aspects of the construction process, and its economic benefits. Optimal positioning of the mobile crane on the construction site, primarily driven by the contractor’s interest to perform assembly operations with expensive machinery as effectively as possible, considerably reduces not only the costs of engaging such a machine but indirectly also its negative impacts on construction sustainability. This paper discusses an exact nonlinear model for the optimization task. The optimization model consists of a cost objective function that is subject to various duration and positioning constraints for the mobile crane, including bounds on its degrees of freedom of movement and stop positions. Because the model formulation includes discontinuous and non-smooth expressions, nonlinear programming with discontinuous derivatives (DNLP) was employed to ensure the optimal solution was reached. The model provides the mobile crane operator with exact key information that enables the complete and optimal assembly of the building structure under consideration. Additionally, the information gained on the optimal distribution of the mobile crane rental period to assembly operations allows for a detailed duration analysis of the entire process of building structure erection, which can be used for its further improvement. An application example is given in this study to demonstrate the advantages of the proposed approach.
Ključne besede: construction sustainability, mobile crane, nonlinear programming with discontinuous derivatives, optimization, positioning
Objavljeno v DKUM: 18.12.2023; Ogledov: 403; Prenosov: 27
Datoteka (877,26 KB)
Gradivo ima več datotek! Več...

Opis: This paper presents the design of geosynthetic reinforced flexible pavements and their modification by incorporating waste materials into bonded and unbonded layers of the pavement structure. The optimal design of flexible pavements was achieved by minimizing the construction cost of the pavement. The incorporation of waste materials into the pavement structure affects the material properties. Therefore, along with the traffic load, the effects of the material properties of the asphalt concrete, base layer, sub-base layer, and subgrade were analyzed in terms of pavement structure costs and CO2 emissions of materials used in pavement construction. In addition, a comparison was made between pavements with and without geosynthetic reinforcement in terms of design, optimum construction cost, and CO2 emissions. The use of geosynthetics is even more effective in pavement structures that contain waste materials in an unbound layer, both in terms of cost and CO2 emissions. The minimum value of the California Bearing Ratio of the subgrade was determined at which the use of geosynthetic reinforcement for pavement structure with and without the inclusion of waste materials is economically and sustainably justified. The use of geosynthetics could result in a 15% reduction in pavement structure cost and a 9% reduction in CO2 emissions due to the reduced thickness of unbound layers. In addition, reducing the CBR of the unbound layer from 100% to 30% due to the inclusion of waste materials implies a cost increase of up to 13%. While the present study is based on an empirical pavement design method in which pavement thickness is limited by the pavement thickness index, the same minimum thicknesses are obtained in the optimization process regardless of whether the objective function is the minimum construction cost or minimum CO2 emissions.
Ključne besede: pavement design, waste materials, optimization, minimum construction cost, CO2 emissions, geosynthetics, waste management
Objavljeno v DKUM: 18.09.2023; Ogledov: 644; Prenosov: 56
Celotno besedilo (6,20 MB)
Gradivo ima več datotek! Več...

Opis: Construction engineers typically avoid the use of expansive soils as construction materials because they are usually difficult to work on and can cause structural failure. This research work investigates how the application of sawdust to tropical clay and bentonite influences their geotechnical properties in order to determine their suitability for use as landfill-liner materials for the effective containment of toxic substances from landfills. X-ray diffractometry, X-ray fluorescence spectroscopy and scanning electron microscopy were used to determine the mineralogical composition, oxide composition and microstructure, respectively, of the clay and the bentonite. A series of laboratory tests were conducted to determine the specific gravity, Atterberg limits, compaction, unconfined compressive strength and permeability characteristics of the clay and the bentonite for varying proportions of sawdust application. Generally, increasing the percentage of sawdust caused a reduction in its specific gravity, maximum dry unit weight and unconfined compressive strength, while it caused an increase in the optimum moisture content and permeability of the modified clay and bentonite. The clay and bentonite both have a sufficiently low permeability that satisfies the hydraulic conductivity requirement for use as clay liners. Eight percent sawdust application to a clay having similar properties as that in this study is recommended as an economic way of modifying it – with the potential of improving its adsorbent property – for use in landfill-liner systems in order to prevent the toxic substances leaching from the landfills, thereby protecting the environment and public health.
Ključne besede: geotechnical properties, hydraulic barrier, landfill, construction, soil improvement, sustainability
Objavljeno v DKUM: 18.06.2018; Ogledov: 1112; Prenosov: 155
Celotno besedilo (766,16 KB)
Gradivo ima več datotek! Več...