英语翻译IntroductionMost codes provide minimum safety requiremen

英语翻译
Introduction
Most codes provide minimum safety requirements and limit
themselves to a minimum safety standard by specifying that minimum
requirement which has historically protected life and they
do not evaluate the structure performance after the onset of damage.
Performance-based seismic design 1PBSD2 is a different
safety paradigm that has recently emerged from the Federal
Emergency Management Agency and is receiving much attention.
PBSD is a methodology that allows engineers to consider spending
more resources to achieve quantifiably higher performance,
thereby reducing risk 1FEMA-3492.Hence,the seismic structural
performance of critical structures such as dams,nuclear containment
vessels,and offshore structures,could be improved through
appropriate nonlinear analysis provided that a suitable model can
be used.For most concrete structures,their “Achilles heel” is the
low tensile strength; this problem is further compounded when
they are also subjected to the cyclic load generated by a seismic
excitation.
In dams,for instance,the main 1if not only2 source of material
nonlinearity is the jointed nature of lift joints,cracks,rock joints,
expansion joint,or the concrete–rock interfaces.Despite their different
origin,all these discontinuities can be generically characterized
as “joint” to be modeled through a single generalized
formulation 1Puntel 20042.On a smaller scale,there are numerous
instances of unreinforced cracks such as old reinforced concrete
beams with no shear reinforcement,cracks radiating from an anchor,
or cracks caused by a corroding rebar 1Hansen and Saouma
19992.
Joint models abound in the literature and have reached levels
of significant sophistication and maturity,especially when examined
through the prisms of fracture mechanics,plasticity,or damage
mechanics.However,most of them are inherently developed
under the assumption of monotonic loading conditions,thus disregarding
specific features of reversed cyclic loading; in some
cases this can lead to gross mistakes such as unsafe overestimation
of joint opening.This deficiency is partly explained by the
comparatively small number of test data and by the concurrent
lack of experimentally derived relationships.
As such,this paper addresses the scarcity in relevant tests.
First,a complex experimental setup will be described,and results
reported.Then,a model previously developed by the writers
1Puntel et al.20062 will be refined to account for the test results
obtained.Finally,the numerical response of both the existing and
updated joint models will be compared with the experimental one