Purpose The purpose of this paper is cost optimization of project schedules under constrained resources and alternative production processes (APPs). Design/methodology/approach The model contains a cost objective function, generalized precedence relationship constraints, activity duration and start time constraints, lag/lead time constraints, execution mode (EM) constraints, project duration constraints, working time unit assignment constraints and resource constraints. The mixed-integer nonlinear programming (MINLP) superstructure of discrete solutions covers time–cost–resource options related to various EMs for project activities as well as variants for production process implementation. Findings The proposed model provides the exact optimal output data for project management, such as network diagrams, Gantt charts, histograms and S-curves. In contrast to classic scheduling approaches, here the optimal project structure is obtained as a model-endogenous decision. The project planner is thus enabled to achieve optimization of the production process simultaneously with resource-constrained scheduling of activities in discrete time units and at a minimum total cost. Practical implications A set of application examples are addressed on an actual construction project to display the advantages of proposed model. Originality/value The unique value this paper contributes to the body of knowledge reflects through the proposed MINLP model, which is capable of performing the exact cost optimization of production process (where presence and number of activities including their mutual relations are dealt as feasible alternatives, meaning not as fixed parameters) simultaneously with the associated resource-constrained project scheduling, whereby that is achieved within a uniform procedure.
COBISS.SI-ID: 22484502
The trend of renewing buildings and providing new housing, public and other areas without using new building lots is becoming increasingly important. A frequent situation in building renewal is the change of the category of use, which can in certain cases require the consideration of higher imposed loads for the floor elements that are often of the timber floor type, and result in necessary strengthening procedures. Often, strengthening methods impair the original appearance of the timber floor. An example of such a procedure is the usage of tensile strengthening elements made from steel or various polymers. If the strengthening element is glued to the timber joist, the procedure is not reversible anymore and is therefore unfavorable for timber floors of historical or architectural importance. This article proposes an improvement of the strengthening technique with cross-laminated timber (CLT) panels. The usage of a glass strip as an additional reinforcement is discussed and evaluated with a practical example. The proposed approach enables the usage of thinner CLT panels, thus still achieving a considerable increase of the timber floor load-bearing capacity. The essential feature of the suggested approach is the preservation of the original appearance and simultaneous strengthening of the timber floor.
COBISS.SI-ID: 22480918
We present an optimal cost and design prediction of an underground gas storage (UGS) system, which is proposed to be constructed from one or more lined rock caverns. The adaptive network based fuzzy inference system ANFISUGS was generated to predict minimal investment costs and optimal UGS design. Since a safe and impermeable UGS system requires a rigorous calculation, three steps were proposed to solve this task: the first is solving the geotechnical engineering problem for different UGS designs, the second is the cost/design optimization of the UGS structures, and the last is the generation of an ANFIS system for optimal cost and design prediction of the UGS. While the geotechnical problem was solved with a series of finite element analyses in order to define special geotechnical constraints to be put into the optimization models, a parameter non-linear programming (NLP) optimization approach was used for a variety of different UGS design parameters. The ANFISUGS system was then constructed on the basis of data sets defined from previous NLP optimization results. A case study demonstrates the effectiveness and the prediction capability of the proposed ANFISUGS system.
COBISS.SI-ID: 21866262
The construction sector accounts for a major part of European energy stock, so enhancing the energy performance of building is becoming more and more important. The improvement of the energy performance of building can be achieved through passive design measures and these have to be made in early design phases. Among them is the position and size of glazing in buildings. The study focuses on different deviations of the main glazed façade of a single-family building from the south and how this affects the energy flows through the glazing. The study was conducted for different European climates that are classified Cfb according to the Köppen-Geiger classification, namely Ljubljana, Budapest, Munich and Stockholm. The calculations were made for the orientations: WSW, SW, SSW, S, SSE, SE, ESE and for different U-values and g-values of the glazing. For each orientation and glazing properties type the optimal share of glazing (AGAW) was calculated. The optimal share of the glazing of the main façade for the climate of Ljubljana is between 38 and 42% of the façade, depending on the glass properties of the triple glazing windows. By tilting the main façade, the optimal share of glazing decreases, for example between 0 and 20% of glazing for the ESE orientation or between 0 and 24% for the WSW orientation. The optimal glazing areas remained very similar for Budapest and it is also possible to forecast the optimal areas for climates that have different cooling and heating requirements but similar solar gains for separate orientations (Stockholm and Munich). This means that the results are also applicable for other places that are classified as Cfb according to the Köppen-Geiger classification.
COBISS.SI-ID: 22483222
This paper will present a new concept of cable cars with central entry and exit. First, existing systems of cable cars and their properties will be presented and advantages of the new concept will be explained. The new concept utilizes solution geometry as the basis of the idea. 3D computer graphic tools were used for the design. In the second part of the article, the geometric procedure of the design of the rope flow curve in the station is presented. This is necessary in order to stop the cabin steadily in the central position. If the station is designed in such a way that passengers enter and exit on a stationary platform separate from the device, the capacities of the device can be large. In this case, passengers entering and exiting do not interfere with the other passengers who are traveling with the cable car on the line.
COBISS.SI-ID: 22589718