Stanko Ćorić

Energy certification of new buildings was introduced in the Republic of Serbia as a mandatory procedure in 2012. In addition to civil engineers, eligibility to take the professional examination and issue Energy Performance Certificates (EPCs) is granted to architects, mechanical engineers, and electrical engineers who have completed at least 300 ECTS credits during their university studies. To date, more than 20,000 Energy Performance Certificates have been issued in the country. This paper analyzes the role and representation of civil engineers in the building energy certification process. Particular attention is given to the current legislative initiative, which is expected to make the certification procedure more complex and increase the scope of work for licensed engineers. Therefore, the paper highlights the importance of preserving the equal role of civil engineers in the energy certification process, particularly in light of the forthcoming legislative amendments.

The application of micropiles in geotechnics is a modern method for constructing and rebuilding foundations/structures and increasing stability of landslides/slopes too. In a case when vertical micropiles are used, for landslide stabilization, they are loaded by horizontal (lateral) forces. The lateral pressures of soil which act on micropiles may be determined by Ito-Matsui method. This method takes account three-dimensional effects of surrounding soil and it is assumed that plastic state satisfying the Mohr-Coulomb's failure criterion occurs around the micropiles. Landslide stabilization by vertical micropiles is a very complex task and is based on the interaction between landslide and stabilizing micropiles. In accordance to that, it includes simultaneous stability analyses of landslide and micropiles.

Green roofs are considered to be one of the optimal tools for saving energy and protecting the environment in developed countries. In this paper, an analysis of the possible application of green roofs on existing residential buildings with flat roofs is presented. In the economic analysis, models of existing buildings in Belgrade, with two different types of green roofs, are studied. A key indicator of investment profitability in this investigation is the net present value (NPV) of the green roof project. Besides the private economic impact, other aspects of green roof applications, significant for sustainable development, have been highlighted. The values of the reductions in the annual energy needed for heating and cooling are compared for different scenarios. A maximum energy saving of 22% in the heating season is determined in the building energy simulation program for the model with an intensive green roof. Life cycle profit analysis was based on the probabilistic approach. The corresponding variance-based sensitivity analysis determined the impact of various parameters on the final result. In all models, the first order sensitivity index, which measures the impact of the number of residential units on the NPV, ranges from 12.2% to 63.6%. Sensitivity analysis showed that the benefit of property value increase has the highest influence on the calculated NPV in scenarios that account for this benefit. The obtained results in those scenarios indicate that the most probable NPV at the end of the life cycle is EUR 43/m² and EUR 82/m² for extensive and intensive green roofs, respectively.

This paper considers the phenomenon of the instability of steel plane frame structures in the elastic–plastic domain. The numerical analysis uses finite element method, where the corresponding stiffness matrices are based upon the trigonometric and hyperbolic interpolation functions of normal forces. The tangent modulus concept is applied when buckling occurs in the plastic range. Thus, the stiffness matrices for nonlinear material behavior are also derived. The procedure for determining effective length factors of compressed columns, which implies a global stability analysis of entire frames, is established too. It means that the proposed approach is based on the assumption that the collapse of the structure occurs when the most loaded columns reach their stability limit. So, the presented procedure enables the calculation of the real critical load of plane frame structures in the elastic–plastic domain and determines the corresponding effective length factors.

Zbornik radova Gra?evinskog fakulteta Subotica, Journal of Faculty of Civil Engineering

Zbornik radova Građevinskog fakulteta Subotica, Journal of Faculty of Civil Engineering

Pile foundations are frequently loaded by horizontal forces. In such cases, it is important to calculate lateral capacity of vertical piles. It is governed by the strength of the surrounding soil i.e. geotechnical capacity or pile strength parameters i.e. structural capacity of a pile. In this paper, geotechnical capacity is analysed first, and then the Rankine's, Broms' and Brinch-Hansen's methods for calculating ultimate bearing capacity of a single pile under lateral loads are presented. In accordance with complex geological conditions, which are very often in Serbia, Brinch-Hansen's method has an advantage over the other two methods. It can be applied both to uniform and layered soils under drained or undrained conditions. This is highly important for foundation of structures and landslide's remedial measures, too. Accordingly, load capacity calculation of a pile group is presented as well. In the case of homogenous surrounding soil, deformations of laterally loaded piles may be determined by elastic analysis. However, in the case of complex geological conditions, these deformations may be calculated by the concept of coefficient of subgrade reaction or by p-y curves, too. Finally, numerical analysis for calculation of geotechnical capacity and pile head displacement of laterally loaded piles for foundation of Clinker Bin in Beocin is presented.

In this paper the phenomenon of instability of frames in elasto-plastic domain was investigated. Numerical analysis was performed by the finite element method. Stiffness matrices were derived using the trigonometric shape functions related to exact solution of the differential equation of bending according to the second order theory. When the buckling of structure occurs in plastic domain, it is necessary to replace the constant modulus of elasticity E with the tangent modulus Et. Tangent modulus is stress dependent function and takes into account the changes of the member stiffness in the inelastic range. For the purposes of numerical investigation in this analysis, part of the computer program ALIN was created in a way that this program now can be used for elastic and elasto-plastic stability analysis of frame structures. This program is developed in the C++ programming language. Using this program, it is possible to calculate the critical load of frames in the elastic and inelastic domain. In this analysis, the algorithm for the calculation of buckling lengths of compressed columns of the frames was also established. The algorithm is based on the calculation of the global stability analysis of frame structures. Results obtained using this algorithm were compared with the approximate solutions from the European (EC3) and national (JUS) standards for the steel structures. By the given procedure in this paper it is possible to follow the behavior of the plane frames in plastic domain and to calculate the real critical load in that domain.