Abstract: Due to the numerous advantages of steel corrugated
web girders, its application field is growing for bridges as well as for
buildings. The global stability behavior of such girders is
significantly larger than those of conventional I-girders with flat web,
thus the application of the structural steel material can be
significantly reduced. Design codes and specifications do not provide
clear and complete rules or recommendations for the determination of
the lateral torsional buckling (LTB) resistance of corrugated web
girders. Therefore, the authors made a thorough investigation
regarding the LTB resistance of the corrugated web girders. Finite
element (FE) simulations have been performed to develop new
design formulas for the determination of the LTB resistance of
trapezoidally corrugated web girders. FE model is developed
considering geometrical and material nonlinear analysis using
equivalent geometric imperfections (GMNI analysis). The equivalent
geometric imperfections involve the initial geometric imperfections
and residual stresses coming from rolling, welding and flame cutting.
Imperfection sensitivity analysis was performed to determine the
necessary magnitudes regarding only the first eigenmodes shape
imperfections. By the help of the validated FE model, an extended
parametric study is carried out to investigate the LTB resistance for
different trapezoidal corrugation profiles. First, the critical moment of
a specific girder was calculated by FE model. The critical moments
from the FE calculations are compared to the previous analytical
calculation proposals. Then, nonlinear analysis was carried out to
determine the ultimate resistance. Due to the numerical
investigations, new proposals are developed for the determination of
the LTB resistance of trapezoidally corrugated web girders through a
modification factor on the design method related to the conventional
flat web girders.
Abstract: The objective of this research is to investigate the
advantages of using large-diameter 0.7 inch prestressing strands in
pretention applications. The advantages of large-diameter strands are
mainly beneficial in the heavy construction applications. Bridges and
tunnels are subjected to a higher daily traffic with an exponential
increase in trucks ultimate weight, which raise the demand for higher
structural capacity of bridges and tunnels. In this research, precast
prestressed I-girders were considered as a case study. Flexure
capacities of girders fabricated using 0.7 inch strands and different
concrete strengths were calculated and compared to capacities of 0.6
inch strands girders fabricated using equivalent concrete strength.
The effect of bridge deck concrete strength on composite deck-girder
section capacity was investigated due to its possible effect on final
section capacity. Finally, a comparison was made to compare the
bridge cross-section of girders designed using regular 0.6 inch strands
and the large-diameter 0.7 inch. The research findings showed that
structural advantages of 0.7 inch strands allow for using fewer bridge
girders, reduced material quantity, and light-weight members. The
structural advantages of 0.7 inch strands are maximized when high
strength concrete (HSC) are used in girder fabrication, and concrete
of minimum 5ksi compressive strength is used in pouring bridge
decks. The use of 0.7 inch strands in bridge industry can partially
contribute to the improvement of bridge conditions, minimize
construction cost, and reduce the construction duration of the project.
Abstract: The National Bridge Inventory (NBI) includes more
than 600,000 bridges within the United States of America.
Prestressed concrete girder bridges represent one of the most widely
used bridge systems. The majority of these girder bridges were
constructed using 0.5 and 0.6 inch diameter strands. The main
impediments to using larger strand diameters are: 1) lack of prestress
bed capacities, 2) lack of structural knowledge regarding the transfer
and development length of larger strands, and 3) the possibility of
developing wider end zone cracks upon strand release.
This paper presents a study about using 0.7 inch strands in girder
fabrication. Transfer and development length were evaluated, and
girders were fabricated using 0.7 inch strands at different spacings.
Results showed that 0.7 inch strands can be used at 2.0 inch spacing
without violating the AASHTO LRFD Specifications, while attaining
superior performance in shear and flexure.