The use of approximate methods of seismic assessment of structures

Abstract

Greece is an earthquake prone area, which is also exposed to coastal environment. Most existing buildings present common characteristics, concerning quality of the materials and environmental conditions [1].The vulnerability of these structures is exteriorized under powerful seismic loads. This is because they were designed, according to older regulations, primarily to bear vertical loads and secondarily to bear horizontal loads, an indicative sign of the absence of anti-seismic design. Designing and evaluation of the seismic performance of existing structures is a really complex issue, because structural degradation phenomenon is related to both corrosion damage of steel reinforcement on RC structures and high vulnerability of masonry. Precisely, the inadequate seismic performance of masonry structures, which is recorded under intense earthquakes, is attributed to the characteristics of masonry and to the ageing phenomena of the materials. For the seismic inspection of masonry structures, both EC2 and OASP can be used [3], although there is often a great misunderstanding concerning the range of the maximum permissible interventions, the financial inability and modern perceptions of redesigning [2]. On the other hand, in the case of RC structures, there is no prediction –concerning the corrosion factor- included in the international regulations and standards. In the current study is presented an experimental procedure, concerning a RC column before and after corrosion. An estimation concerning the drop of its mechanical performance has taken place, indicating the importance of the corrosion factor. Additionally, an existing monumental masonry tower building, was subjected to seismic evaluation [4]. Both OASP and EC2 inspection methods were used. The results pointed out that, for medium–intensity earthquakes, both analytical and approximate methods are respectable and reliable.