Earthquake Engineering Research - HKU Libraries - The University ...

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excitation. Also, the software was built following the object-oriented (OO) programming
paradigm by using Or computer language.
To trace and simulate the overall behavior of the structures subjected to earthquake
excitation, various types of non-linear finite element analysis for reinforced concrete
frame structures have been pursued and investigated over the last thirty years. Most of
them can be divided into three categories: local models (microscopic or macroscopic
finite element models), global models (member models), and semi-local models (fiber
element models) (Miramontes et al. 1996, Meyer et al. 1991).
Semi-local models stand between global models and local models (Miramontes et al.
1996). A simplified kinematic hypothesis was adopted and equations of equilibrium are
solved only for nodal points, like global models. By employing a cyclic constitutive
relationship of the constituent materials, stress and strain were calculated at local level
and consequently no hysteretic model at section or member level was needed, like local
models. Fiber models exploited in this research fall into the category of semi-local
models and have been investigated by many researchers (Taucer et al. 1991, Rubianobenavides
1998). Despite many merits, fiber models had been considered to be too
expensive for practical structural analysis. As personal computers have been getting
cheaper and more computationally efficient, however, fiber models may become a
rational and feasible tool for practical structural analysis. In this research, force-based
finite fiber elements for RC frame structures and its applications were investigated.
In addition to the precise nonlinear FE analysis of the overall structural responses,
larger-scaled quick estimation of critical structural responses are convenient tools for preearthquake
damage evaluation and emergent post-earthquake repair. In this research, the
application of artificial neural networks (ANN") to estimate the critical structural
responses was explored. The application of multiplayer perceptron (MLP) networks was
studied and an augmented form of MLP was proposed to improve the modeling accuracy
of classical MLP.
CYCLIC STRESS-STRAIN RELATIONSHIP OF REINFORCED CONCRETE
MATERIALS
Reinforced concrete is actually a composite material, in which its constituent
materials, reinforcing steel and concrete, are subjected to quite a different loading
condition than that of the tests for the individual materials. Hence, another approach to
the investigation of RC materials is to derive the average (smeared) behavior of steel and
concrete of reinforced concrete directly from experiments on larger reinforced concrete
specimens, such as the tests on panel element conducted at the University of Houston
(Hsu 1993, Mansour et al. 2001). Such constitutive relations can be defined as reinforced
concrete material models (Meyer et al. 1991).
This study was aimed at analyzing RC/PC frame structures subjected to cyclic static
loading or dynamic earthquake excitation. With this goal, five material models (Jeng
2002) were employed for the finite element analysis to attain sufficient accuracy and to
maintain computational efficiency as well. The first four models are shown in Figs. 1 to 4.