This article aims to highlight, through a comparative study, the efficiency of steel bracing systems used to reduce seismic vulnerabilities in existing buildings with reinforced concrete structures (reinforced concrete frames and reinforced concrete dual structures, general building structures including those used in transport infrastructure). In order to simplify the calculations, the analysis was reduced to the study of the behavior of resistance lines corresponding to four-, nine- and fifteen-level buildings with the same plane distribution. In order to obtain features similar to those of existing building elements, structures were initially loaded with seismic forces corresponding to code P13-63. The next step was to apply to previously dimensioned structures the seismic loads according to P100-3: 2008 in relation to P100-1: 2013, thus obtaining the deficiencies of the existing structures against the requirements of these norms. Correction of these strength and stiffness deficiencies was attempted by introducing X-shaped centric brace systems. The bracing systems used as consolidation methods are of three types: direct bracings stuck in the reinforced concrete frames and bracings of the indirect type, made of internal and external bracing steel frames. Structural calculations were made in the linear elastic field using the ETABS program.
The elastic couplings are frequently used in mechanical transmissions design, to take over the radial, axial and angular misalignments and also to take over the shocks and the overloads that could appear. In this paper is presenting some aspects about the construction of couplings with bolts using non-metallic elements, e.g. rubber, having different hardness, the elements involved in torque transmission, in this case elastic elements, having also different dimensions or forms, in the way to have a good elasticity and capacity of vibration absorbtion, determining theoretical static rigidity and experimental static rigidity of a new elastic coupling with cylindrical bolts and nonmetallic elements and compare of results for these values.