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29
Conference Proceeding Paper, Computing in Civil and However, at least one presentation (no paper available) has
Building Engineering, pp. 17031710. implications for superstructure design. This study is de-
scribed below.
This proceeding consists of papers presented at the Fifth
International Conference on Computing in Civil and Build- Ibrahim, A. M. M., et al. (2005) Torsional Analysis and De-
ing Engineering held in Anaheim, California, June 79, 1993. sign of Curved Bridges with Single Columns - LFD vs. LRFD
The proceedings cover five major areas of concern: (1) com- Approach, Paper presented at the Western Bridge Engi-
puting in construction, (2) geographic information systems, neers Conference, Portland, OR.
(3) expert systems and artificial intelligence, (4) computing
in structures, and (5) computing in transportation. Within This unpublished study compared torsional superstruc-
these broad topics are subjects such as (1) computer analysis ture design of a curved concrete box-girder bridge subjected
of cable-stayed bridges; (2) artificial intelligence in highway to seismic loading using the Load Factor Design approach
CAD systems; (3) automated systems for construction bidding; currently used by Caltrans and the AASHTO LRFD method.
(4) effect of automation on construction changes; (5) optimal Torsion is induced in the superstructure not only by curva-
seismic design of structures; and (6) CAD instruction for civil ture, but also by column plastic hinging of the single column
engineering students. The book also presents several papers bent during an earthquake. Caltrans practice is to design the
discussing different aspects of multimedia information sys- superstructure in bridges with monolithic columns to remain
tems and geographic information systems. elastic. In this case, the limitation on seismically induced tor-
sional forces resulting from column yielding causes a redis-
tribution of superstructure forces in the box-girder.
Vehicular Impact
Vehicular impact in curved bridges is different than in
Design Optimization
straight bridges. A paper addressing this subject is discussed
below. Several combinations of slab and web width can be selected
to resist the applied loads. Although design optimization is
Rabizadeh, R. O., and Shore, S. (1975) "Dynamic Analysis generally not the subject of design specifications, at least one
of Curved Box-Girder Bridges," Journal of the Structural paper reviewed addressed this issue.
Division, ASCE, Vol. 101, No. 9, pp. 18991912.
Ozakea, M., and Tavsi, N. (2003) "Analysis and Shape
The finite element technique is used for the forced vibration Optimization of Variable Thickness Box-Girder Bridges in
analysis of horizontally curved box-girder bridges. Annular Curved Platform," Electronic Journal of Structural Engi-
plates and cylindrical shell elements are used to discretize the neering International, Vol. 3, Queensland, Australia.
slab, bottom flanges, and webs. Rectangular plate elements and
pin-jointed bar elements are used for diaphragm discretization. This paper deals with the development of reliable and effi-
The applied time varying forcing function used in this analysis cient computational tools to analyze and find optimum shapes
represents a vehicle that is simulated by two sets of concentrated of box-girder bridges in curved planforms in which the strain
forces with components in both the radial and transverse direc- energy or the weight of the structure is minimized subject to
tion. The position of these concentrated forces is moved at a certain constraints. The finite strip method is used to determine
constant radial velocity in circumferential paths on the bridge. the stresses and displacements based on Mindlin-Reissner
The effect of centrifugal forces is considered and the effect of shell theory. An automated analysis and optimization proce-
damping of the bridge is neglected in the analysis. The mass dure is adopted which integrates finite strip analysis, para-
condensation technique is used to reduce the number of cou- metric cubic spline geometry definition, automatic mesh
pled differential equations obtained from the finite element generation, sensitivity analysis, and mathematical program-
method. The resulting differential equations are solved by the ming methods. It is concluded that the finite strip method
linear acceleration method. Several bridges with practical offers an accurate and inexpensive tool for the optimization
geometries are analyzed and impact factors are calculated. of box-girder bridges having regular prismatic-type geome-
try with diaphragm ends and in curved planform.
Seismic Response
Detailing
Several papers and reports have addressed the seismic re-
sponse of curved box-girder bridges. Most of these deal with The detailing of prestressed concrete in bridges is addressed
substructure response and are beyond the scope of this study. by several agencies that commonly use this structural form.
