A model for early construction cost prediction is useful for all construction project participants. This paper presents a combination of process‐based and data‐driven model for construction cost prediction in early project phases. Bromilow’s “time‐cost” model is used as process‐based model and general regression neural network (GRNN) as data‐driven model. GRNN gave the most accurate prediction among three prediction models using neural networks which were applied, with the mean absolute percentage error (MAPE) of about 0.73% and the coefficient of determination R² of 99.55%. The correlation coefficient between the predicted and the actual values is 0.998. The model is designed as an integral part of the cost predicting system (CPS), whose role is to estimate project costs in the early stages. The obtained results are used as Cost Model (CM) input being both part of the Decision Support System (DSS) and part of the wider Building Management Information System (BMIS). The model can be useful for all project participants to predict construction cost in early project stage, especially in the phases of bidding and contracting when many factors, which can determine the construction project implementation, are yet unknown.

Additional temperature stresses in continuously welded rails (CWRs) are caused by track/bridge interaction (TBI) due to thermal actions. Exceeding permissible stresses in CWRs on the bridge can lead to track buckling or rail cracking, compromising the safety of railway traffic. The main aim of the conducted study is to determine the effects of the key parameters such as rail cross-sectional area, track longitudinal resistance, bridge expansion length, and longitudinal stiffness of the fixed bridge support on the reduction of additional temperature stresses in CWRs on steel truss railway bridges. To quantify the effects of these parameters, two steel railway bridges with CWRs and the maximum expansion lengths according to UIC Code 774-3 were analyzed: (1) simply supported truss bridge with expansion length of 60 m and (2) continuous truss bridge with expansion lengths of 2 × 60 m. According to the obtained results, the track longitudinal resistance had the most significant impact on additional temperature stresses in CWRs, leading to their reduction of up to 72%. The bridge expansion length and the rail cross-sectional area led to reductions of up to 25% and up to 18%, respectively. Considering the deformation criteria of TBI, the longitudinal stiffness of the fixed bridge support had a minor effect on the reduction of additional temperature stresses in CWRs.

Due to increased activities in civil engineering, and especially in the transport infrastructure, and thus an increase in the use of additional construction materials, innovative solutions are needed in finding alternative materials for the preservation of natural resources. One of the solutions for preserving natural building materials is the application of recycled material, which will also meet the required standards in civil engineering. In the transport infrastructure, there is a great opportunity for the use of recycled material, starting from the subbase, through the embankment and all the way to the superstructure and the concrete structures. One of the recycled materials that can be used in construction is fly ash. Fly ash is the most promising waste material when it comes to the wide range of applications in construction. Fly ash is obtained by burning coal in thermal power plants to produce electricity. Due to variations in the composition and characteristics of fly ash, several divisions and classifications have been created. One of the main classifications is according to the American standard ASTM C 618-05 where it is divided into class C and class F fly ash. This research aims to investigate the application of fly ash for subgrade stabilization and to determine the difference from a financial and environmental perspective for the application of fly ash compared to natural stone aggregate. The main research was carried out in connection with the increased use of natural stone aggregate, which appeared as a need during the rehabilitation of state road R1206, section Karpalak - Zelino. Apart from the use of large quantities of stone aggregate for the stabilization of the subgrade, it also had an impact on the financial framework for the realization of the road project. In Macedonia, an analysis of the chemical composition of 4 samples of fly ash obtained in REC Bitola was carried out. From the obtained results, it can be concluded that it belongs to the classification of F-class fly ash and with the use of an activator (lime or cement) it can be used in the stabilization of the subgrade.

Decision making is the study of identifying and choosing alternatives to find the best solution based on different factors and considering the decision makers expectations. Every decision is made within a decision environment, which is defined as the collection of informations, alternatives, values and preferences available at the time when the decision must be made. The difficult point in decision - making is the multiplicity of the criteria set for judging the alternatives. The objectives are usually conflicting and, in most of the cases, different groups of decision - makers are involved in the process. To facilitate this type of analysis, a family of tools referred to as Multi - criteria decision - making methods gained ground due to the need to have a formalized method to assist decision - making in situations involving multiple criteria. This paper presents a methodology for route selecting in the planning and designing of railways based on the multiple criteria decision making. The need for applying multi criteria analysis in the decision making process for studying and designing a transport infrastructure project is also conditioned by the characteristics of the infrastructure that has the title of the public good (many interested subjects for it) and in order to minimize the problems and risks which are related to the elaboration of such projects. The proposed methodology provides a complete and systematic solution to this problem. Result of the methodology is the most suitable route in accordance with the adopted criteria and existing constraints. The developed methodology is based on three different methods for multiple criteria decision making, Weighted Sum Model - WSM, AHP method (Analytic Hierarchy Process) and VIKOR method. Evaluation is performed in section of railway route of two alternatives on the Corridor 10, on the section from station Dracevo (Skopje) and station Veles. The results confirm validity and usefulness of this methodology. Alternative I is new corridor on the left side of the Vardar Valley, with a minimal radius R = 1.500m. the route passes through the villages Oreshani, Taor and Katlanovo. The track is designed for speed of 160km/h. Alternative II is a new corridor near variant I, except for the section between the chainage km16 to km29, with a minimum radius R = 800m, in order to minimize earthworks as well as the length of the objects (bridges, viaducts, tunnels) wherever possible. The track is designed according to the speed of 120km / h.

The concept of risk analysis and management has a big impact and application in various branches of society. Today in civil engineering, especially in infrastructure projects this concept represents a serious matter that should not be avoided or delayed. There are different approaches and definitions for a risk, but it is important every problem to be reviewed separately. In tunneling the uncertainties and risks are always present, so appropriate measures and management should be considered and implemented.