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I n t e r n a t i o n a l C o n f e r e n c e o n
Structural and Civil Engineering
Research
JET 2018
ISSN: 2319-9873
O c t o b e r 0 1 - 0 2 , 2 0 1 8
Am s t e r d a m , N e t h e r l a n d s
Civil Engineering 2018
Page 21
In past 20 years, several researchers have discussed the underlying assumptions
and limitations of the pushover analysis. It has been found that, if a unique
invariant force distribution proportional to the fundamental mode of vibration is
assumed, satisfactory predictions of seismic demands are mostly restricted to
regular in plane and in elevation low and medium-rise structures. Indeed, invariant
force distributions are notable to take into account the redistribution of inertia
forces due to yielding, and the associate change in the mode shape. Moreover,
force distribution and displacement pattern related to the fundamental period
of vibration do not account for the contribution of higher modes. To solve this
drawback, Chopra (2003) proposed a method called modal pushover analysis
(MPA), where the seismic demand due to the individual terms in the modal
expansion of the earthquake forces is determined by a non-linear pushover
analysis. To overcome the former limitations, and with the aims of bounding the
likely distribution of interstory drifts and local ductility demands, seismic codes
require that the analysis is performed enveloping the results obtained by using
two different seismic force patterns: a load pattern aiming at reproducing the
distribution of the seismic forces acting on the structure in the elastic state;
an uniform or an adaptive load pattern aiming at bounding or reproducing the
change in distribution of the seismic forces due to the progressive yielding of the
structure. Numerical analyses performed in the last two decades have shown that
the uniform load pattern is too conservative for the estimation of the response
parameters for the lower floors of buildings, while all the adaptive load patterns
proposed do not always succeed in providing a better estimation of the seismic
response. In this context, in the proposed paper, firstly two very simple load
distributions were proposed, one invariant and one adaptive. Each of the proposed
load distributions is effective in bounding the seismic response of the structure
without introducing the large overestimation of the seismic response. Regarding
irregular structures, a modified version of the modal pushover in which correlation
rule that takes into account the non-linear behaviour of structures is proposed. The
effectiveness of the proposed load distributions are proved by comparison with
the results provided by several lateral load distributions prescribed by international
codes.
Nonlinear seismic analysis for regular and
irregular structures
Piero Colajanni, S Pagnotta and G Testa
University of Palermo, Italy
Piero Colajanni et al., JET 2018 Volume: 7
Biography
Piero Colajanni is currently serving as an Associate Professor
of Structural Engineering at the DICAM, University of Palermo.
He has completed his Msc in Civil Engineering in 1990 and
PhD in Structural Engineering in 1995 from Palermo University.
He was a Visiting Assistant Professor at Florida Atlantic
University, Department of Mechanical Engineering in 1996
and a Researcher of Engineering and Solid Mechanics in 1997,
and an Associate Professor in Structural Engineering in 2001
at University of Messina. In 2013, he moved to University of
Palermo, where nowadays teaches building structural analysis
and design, and seismic design of buildings. He was Promoter
and President of the Scientific Committee of Master in Seismic
Engineering at University of Messina in 2003 and 2006. He
is the author of more than 150 papers on international and
national journals, and conference proceedings. His research
activities include in the fields of Structural Engineering and
Seismic Engineering, focused on procedure for seismic design,
vulnerability assessment and retrofitting of buildings, the use of
innovative devices and materials for seismic protection of new
and existing structure and design of hybrid steel truss concrete
beams.