Effects of near-fault ground motions on the nonlinear behaviour of reinforced concrete framed buildings

Abstract

The design provisions of current seismic codes are generally not very accurate for assessing effects of near-fault ground motions on reinforced concrete (r.c.) spatial frames, because only far-fault ground motions are considered in the seismic codes. Strong near-fault earthquakes are characterized by long-duration (horizontal) pulses and high values of the ratio a PGA of the peak value of the vertical acceleration, PGA V , to the analogous value of the horizontal acceleration, PGA H , which can become critical for girders and columns. In this work, six-and twelve-storey r.c. spatial frames are designed according to the provisions of the Italian seismic code, considering the horizontal seismic loads acting (besides the gravity loads) alone or in combination with the vertical ones. The nonlinear seismic analysis of the test structures is performed using a step-by-step procedure based on a two-parameter implicit integration scheme and an initial stress-like iterative procedure. A lumped plasticity model based on the Haar-Kàrmàn principle is adopted to model the inelastic behaviour of the frame members. For the numerical investigation, five near-fault ground motions with high values of the acceleration ratio a PGA are considered. Moreover, following recent seismological studies, which allow the extraction of the largest (horizontal) pulse from a near-fault ground motion, five pulse-type (horizontal) ground motions are selected by comparing the original ground motion with the residual motion after the pulse has been extracted. The results of the nonlinear dynamic analysis carried out on the test structures highlighted that horizontal and vertical components of near-fault ground motions may require additional consideration in the seismic codes.

Multicomponent nonlinear incremental dynamic analysis of r.c. spatial framed structures subjected to near-fault earthquakes

“…F12) framed structures are designed in line with the Italian seismic code (NTC08, [17]), considering the following design assumptions for the horizontal seismic loads: high-risk seismic region; medium subsoil (class B, subsoil parameter: SS=1.13); flat terrain (class T1, topographic parameter: ST=1). Criteria imposed by NTC08 for the variation of lateral stiffness and shear strength are not satisfied at all storeys, so that F6 and F12 structures have to be classified as irregular in elevation [18]. As a consequence, the ductility class B is considered, assuming qH=3.12 as behaviour factor for the horizontal seismic loads.…”

Seismic response control of building structures under pulse-type ground motions by active vibration controller

“…Near-field ground motions with directivity effects tend to have a high peak ground velocity (PGV)/peak ground acceleration (PGA) ratio, which significantly affects their response characteristics. 18 Mazza 19 elegantly highlighted that the effects of near-field ground motions should be considered through appropriate further code provisions. Ghowsi and Sahoo 20,21 presented the performance of novel buckling restrained braces (BRBs) in response reduction of structures under near-field ground motions.…”

Quantification of Energy-Related Parameters for Near-Fault Pulse-Like Seismic Ground Motions

“…Within this framework, several studies have been conducted in the past years to analyze the main features of pulse-like seismic ground motions as well as to estimate the corresponding pulse period value [5][6][7][8][9][10][11][12][13][14]. Several studies have been also conducted in order to examine the effects of near-fault pulse-like ground motions on the seismic response of structural systems [15][16][17][18][19][20]. In this regard, most studies have focused on the displacement and strength demand for elastic or inelastic structural systems subjected to near-fault pulse-like earthquakes [21][22][23][24][25][26].…”