Effect of Building Height on the Seismic Behavior of Steel Framed Structures

Northridge-USA and Kobe-Japan earthquakes in mid 1990s caused numerous structural damages to 3, 6 and 12 story buildings, in relation to structural design and framing type. Hence, this research was aimed at studying the effect of structural framing type and building height on seismic behavior of steel structures. Equivalent Static Analysis (ESA) were carried out using ETABS software to analyze 6, 12 and 20 story Moment Resisting Frame (MRF) and Concentric Braced Frame (CBF) buildings, with regular and irregular plan and elevations. Eurocodes 3 and 8 were used for the design of 77 different building models considering soil and earthquake parameters for Lebanon. In addition selective models of both frame types were also analyzed using Response Spectrum (RS) and Nonlinear Static Pushover Analysis (NSPA). Considering the lateral displacements obtained it was found that generally up to story 15 moment frames have more displacements than braced frames with similar structure. However, for taller structures the situation was reversed and braced frames achieved more displacements than moment frames. Introducing belts at top and middle or top story only of 20 story braced framed structure generally reduced its lateral displacement in both directions except in y-direction only up to 14 floors. Pushover analysis results showed that moment framed 6 and 12 story regular buildings performed better than similar braced frame ones, and the case was vice versa for 20 story regular buildings. Keywords: Earthquake, Moment Resisting Frame, Concentric Braced Frame, Irregularity, Displacement, Height Effect, Equivalent Static, Response Spectrum, Nonlinear Static Pushover.