Numerical methods in bridge structure analysis - Computational Analysis and Design of Bridge Structures - page 57

Numerical methods in
bridge structure analysis
3.1 INtroductIoN
Numerical methods, such as the finite element method (FEM), are fun-
damental to bridge structure analysis. When analyzing or designing a
bridge, different modern computer programs may be used. A deep under-
standing of the principles of the underlying methods to analyzing or
designing a bridge is essential to properly conduct bridge analysis and
design and is particularly important in building an appropriate computer
model representing a bridge for different types of analyses. In this chap-
ter, the principles of FEM, the automatic time incremental creep analysis
method, and the influence line/surface live loading method are introduced
to provide the basis for computational applications in bridge analysis
and design.
FEM was first introduced in 1960s and is widely adopted in bridge engi-
neering as the primary structural analysis approach. As modern computer
science has advanced since the end of the twentieth century, FEM's appli-
cation to bridge structure analyses, including its pre- and postprocessing
techniques, has also greatly developed. FEM plays a critical role in mod-
ern bridges' analyses and designs. Although many generic FEM packages
and more bridge-specific analysis systems are available and engineers or
researchers do not need to develop a FEM package by themselves, a general
understanding of FEM's principles, procedures, and its limitations will help
to master its applications, including model preparation, result procession,
and error identification.
Creep and shrinkage behaviors are part of the nature of concrete
material. Most of these behaviors occur during the early stages, and there is
less development as concrete ages. Therefore, their total effects are limited.
However, the amount of both displacements and internal force redistribution
due to creep and shrinkage has to be analyzed in certain concrete bridges,
especially those built in multiple stages, or prestressed concrete bridges
(Bažant et al. 2011). Dischinger and effective Young's modulus methods,
as shown in Chapter 4, are commonly used in concrete creep analyses.
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