11.26: The seismic design of a building having a dual type structural system in Romania

Abstract

ABSTRACTThe March 4, 1977 earthquake was the last major seismic event that struck Romania. 1,600 persons were killed, over 11,000 were injured, and 33,000 buildings collapsed or were severely damaged. The great majority of these injuries were in masonry and reinforced concrete buildings. The few existing steel structures behaved very well during the earthquake, excepting the situation when inadequate structural concepts were met. Even if the number of steel buildings was not so high, steel was used especially for long span roofs of industrial buildings. Starting with that period, the design practice proved that steel is an excellent material for seismic‐resistant structures thanks to its performance in terms of strength and ductility. The bulk of the paper consists in presenting the design of a dual type structural system having in the horizontal plane the shape of the letter “Y” and in the vertical plane two basements, a ground floor and 14 stories. Trying to realize a building virtually immune to earthquake action the superstructure of the building, of composite type, was conceived to have two different parts: (a) a reinforced concrete structural subsystem formed by the three structural cores placed in the peaks of the equilateral triangle, their main role being that of assuring the lateral strength of the building to the seismic loads; (b) a steel structural subsystem, having a structural role mainly towards the gravity loads. The steel structural subsystem is placed in the central zone of the building and is connected to the three reinforced concrete cores placed in the peaks of the equilateral triangle. It consists of three moment resisting frames and composite type floor structures. The paper also contains information about the results of some in‐situ dynamic investigations performed after each stage during the construction, in order to validate the structural models of analysis and the contribution of the steel structural subsystem on the overall dynamic characteristics of the building.