سازه های چند طبقه مقاوم در برابر زلزله Earthquake Resistant Multi Storey Structures

INTRODUCTION International annual Seismic Design Competition (SDC) held in USA requires the design of a 3D multi-story (from 15 to 28 story) structure that is subjected to several recorded (and scaled down) and artificially generated earthquakes [1]. No failure is a fundamental criterion for winning the competition. Current study is an extract of the theoretical and experimental job carried out by the TUCN team that qualified for the final phase (Seattle, February 2013) of the competition. For designing the building several aspects have been taken into consideration, such as architecture, the environment, financial costs (investment/maintenance), all of which were subordinated to fundamental principles of seismic design. The resulting structure has a two axis in plane symmetry, and it’s based on a bundle tube concept, consisting of four 3D substructures located in the four corners. Each substructure is made up of 3D one bay frame that creates an open space inside, allowing a large freedom of inside arrangement at every level. For the theoretical study of the structure in what regards its seismic response, several scaled down earthquakes have been used: Northridge 1990, El Centro 1940, DAVIS – artificially generated earthquake (ground acceleration=1.57g). The dynamic model considered for this structure is the classical lumped mass vertical cantilever. Computed parameters refer to natural period of vibrations T1, seismically induced response (lateral displacement and accelerations, base shear). The experimental studies focused on recording the seismic responses in lateral displacement and acceleration, objective that has been achieved using a laboratory shaking table [2] equipped with digital transducers and recorders. A highly acceptable accuracy could be noted of experimental and theoretical results. Obtained results constituted the bases of a beforehand compulsory assessments of seismic response at the final stage of the SDC For a more accurate modelling of real loading, dead loads that act upon the structure have been represented with steel bars, mounted upon the structure at H/10 distance between them and perpendicular placed towards earthquake action direction (Fig.1).