Changing a layer of weak soil in deformed foundation with a compacted soil bed consisted of various strong materials (sand, gravel, pebble-gravel, production waste materials). Existing calculation methods and techniques to build compacted soil beds based on weak highly compressive soils do not meet up-to-date requirements. Calculation methods used the dimensions of compacted beds quite often appear to be overestimated, and this results in increase in costs and working hours needed to build artificial foundation. The paper presents the possibility of using reinforced soil beds as an efficient method to build artificial foundation based on weak soils.

The motion of strong earthquakes causes nonlinear deformation and damages to the structure. For structural systems of buildings, domestic and European (EC8) regulation apply algorithm of seismic design based on reference linear-elastic methods that are carried out in two phases. Phase I includes determination of dynamic characteristics of structure, which are then used in phase II for calculation of seismic effects. In this study, parametric analysis of influence of dynamic characteristics of structure was done on multiple numerical examples, according to domestic and EC8 regulations and comparison of results.

Experiences from previous earthquakes have shown that level of structural damages depends onground features where the structure is placed. Also, it is noted that reinforced concrete framestructures collapse due to the appearance of “weak floor”, especially when are founded on groundswith lower characteristics. In this paper, the seismic analysis of structure is presented on example ofthe six-storey RC frame structure, founded on different ground types. The seismic analysis isperformed in accordance with European regulations and still valid ex-Yugoslavian code PIOVSP'81.At the end of the paper, a comparison of the results was made, and corresponding conclusions werereached.

Experience from previous earthquakes have shown that wall structural systems experience less damage during earthquake compared to frame systems. Wall systems for functional and architectural reasons frequently have openings (windows, doors, elevators, esc.). Wall systems with regularly distributed openings represent efficient system for resisting earthquake loads. Coupling beams connecting the walls, if designed and detailed properly, increase seismic resistance of the building by distribution of inelastic deformations both vertically and in plan. Eurocode 8 introduced set of rules for design and detailing of coupled walls and coupling beams. In order to access performance of coupled walls and beams designed in accordance with EC8, linear and nonlinear analysis of 11 story building was performed. Linear elastic modelling was done using software for linear analysis. The walls and coupling beams were designed and detailed in accordance with the provisions of Eurocode 8, part 1. Nonlinear model and assessment of inelastic response was conducted using Perform 3d CSI software for nonlinear analysis. For the modelling of coupled walls, wall section with fibers is used. The confined constitutive relationship is used for concrete edge elements, and unconfined relationship for concrete for the rest part. The reinforcement constitutive model was defined with bi-linear curve. Coupling beams are modelled using frame elements with shear hinge elements. Deformation capacities of elements was defined in accordance with EC8 provisions. Considering that EC8 doesn’t provide provisions for deformation capacities of diagonally reinforced coupling beams, deformation capacities for these elements is defined in accordance with the provisions of ASCE 41-06 standard. Static nonlinear analysis is performed in accordance with EC8 provisions and deformation capacities of wall elements and coupling beams checked in accordance with the provisions EC8 part 1 and part 3, where applicable. Characteristic results are presented on the end of paper, with conclusions and recommendations.

Nonlinear analysis enables engineers to control various aspects of seismic behavior. Utilizing nonlinear analysis, engineers can directly determine inelastic deformations of elements (e.g. rotation), as well as deformations of the structure (inter-storey drift). In addition, nonlinear analysis can be used to check the bearing capacity of the elements that should remain in elastic region of deformations in order to prevent brittle failure. Subject of this paper is comparison of the results obtained from linear and non-linear seismic analysis of concrete frame structure designed and detailed according to principles of Eurocode 8 and capacity design method. Linear-elastic seismic analysis of multi-story frame structure was performed, with design and detailing of critical regions according to results and relevant requirements of Eurocode 8. Seismic analysis was performed for seismic zone which corresponds to PGA=0.36g (peak ground acceleration) according to EC8, and for ground type C. Assessment of structure performance during strong ground motions was performed with non-linear time history (dynamic) analysis using software PERFORM 3D (Nonlinear Analysis and Performance Assessment of 3D Structures). Non-linear dynamic analysis was performed for four groups of seven ground motion records that were chosen in order to comply with spectrum defined by Eurocode 8 for analyzed frame structure. Comparison of characteristic results is presented at the end of paper, with conclusions, recommendations and critical assessment of regulation.