Journal of Applied Engineering (JOAE), 2(3), March-2014 (Volume-II, Issue-III) 35 Study of the Conditions on Reinforced Concrete Structures with More Than 50 Years of Exploitation Miroslav Todorov University of Architecture, Civil Engineering and Geodesy (UACEG) 1 Hristo Smirnenski Blvd, Sofia 1046, Bulgaria Abstract: Reinforced concrete structures in the mass practice of construction have been used for more than a century. This fact presents challenges for the construction engineer, requiring study of the conditions and assessment of efficiency of the constructions. Especially relevant is the question what is the bearing capacity of the elements and how reliable is the future exploitation of the construction as a whole. In Bulgaria the reinforced concrete has been used since the beginning of 20th century. The first structural concrete was used by the Italian Arnoldo Zocchi in 1903 for the creation of monument of the Emperor Alexander the Second. During the first three-four decades of the 20th century (the second period) the reinforced concrete structures are successfully implemented in housing and community construction. Most of the community and housing buildings of this period already have reinforced concrete bearing skeleton. The third main period of use of steel reinforced concrete constructions is after the World War II. During this period the practice of mass usage of prefabricated steel reinforced concrete constructions is enforced in the Eastern block. Nowadays a big part of the buildings of the Bulgarian industries consists of monolithic and prefabricated reinforced concrete constructions. The results of 70-80 years of exploitation of these buildings and the requirements, enforced by the modern new functions create new tasks for the structures. All these features of the buildings require from the construction engineer knowledge of the study and use of different technological methods of reconstruction. Keywords: Concrete, Reinforcement, Long term of Exploitation I. INTRODUCTION The study of existing reinforced concrete constructions is an extremely interesting task from engineering point of view. The study of defects and damages of the construction represent the history of the functioning of the construction for prolonged period of time. This experience is invaluable. The collection of data about the quality of the materials, evaluation of the defects and damages creates an opportunity to evaluate the spatial functioning of the construction together with the ground base. In this mechanism usually take part materials with different mechanical behavior - elastic and elastoplastic. The study of the properties of the materials is an important phase and gives an idea about their changes in the conditions of their natural environment. This study uses known and modified techniques for evaluation of the overall condition of the structure. The structures from the first three decades of the 20th century offer a series of challenges during reconstruction. These buildings are subjected to partial and complete reconstructions more and more often. The reconstructive solutions vary from partial demolition to implantation of new skeleton in the existing substance. All these features require construction engineer's knowledge of study and use of different technological methods of reconstruction, such as:  Knowledge of geodesic and photogrammetric methods;  Knowledge in the sphere of different technological processes, concomitant with the ongoing exploitation of the structures;  Knowledge in the sphere of construction materials and construction chemistry. Nondestructive and destructive methods of testing;  Digital methods of analysis and prediction of the behavior of the construction. Mechanical models used in analytical technologies;  Follow up of the constructions functionality through the developing in it defects and damages. The defects and damages, developed in the constructions are means of verification and creation of veritable calculation ISSN: 2348-4802