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An Investigation on Transversely Prestressed Concrete Bridge Decks

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Title: An Investigation on Transversely Prestressed Concrete Bridge Decks


1
An Investigation on Transversely Prestressed
Concrete Bridge Decks
  • J. Paul Smith

2
Objective
  • Study of transverse post-tensioning of concrete
    bridge decks as an alternative to improve
    durability.

3
Types of Bridges in Indiana
4
Scope
  • Develop design specifications applicable to
  • Slab bridges
  • Slab-on-Girder bridges

5
Problem Statement

q F/L
s?
Assumption Linear behavior
6
Specimen for Experimental Phase of Texas Study
Location of strain gages
1.2ksi
0.6ksi
1.2ksi
7
(No Transcript)
8
Comparison of Analytical (SAP2000) Experimental
(Texas Study) Results
Modeling Type
Top Stresses
3D(III)
3D(II)
3D(I)
2D
14
14
14
16
m
42
38
38
40
Max
m mean(ss/sexp)-1x100
Max Max(ss/sexp)-1x100
9
Analysis using ANSYS 5.7
  • Alternative modeling
  • Use brick and shell elements

10
SAP2000 vs. ANSYS 5.7(Texas Model)

11
Variables of Interest
  • Girders (spacing, stiffness)
  • Diaphragms (spacing, stiffness, location)
  • Boundary conditions
  • Post-tensioning spacing
  • Slab thickness

12
Base Case
22 in.
13
Preliminary Evaluation of Variables (2D Modeling)
  • Base Case

14
Preliminary Evaluation of Variables (2D Modeling)
  • Effect of Girder Spacing

a) Half Spacing
b) Quarter Spacing
15
Preliminary Evaluation of Variables (2D Modeling)
  • Effect of Girder (No diaphragms)

a) Concrete girders
b) Steel girders
16
Preliminary Evaluation of Variables (2D Modeling)
  • Effect of Diaphragms

Top half diaphragms present
Bottom half diaphragms no present
17
Preliminary Evaluation of Variables (2D Modeling)
  • Effect of boundary conditions

18
Preliminary Evaluation of Variables (2D Modeling)
  • Effect of Post-tensioning Spacing

a) Forces at every other node
b) Forces every four nodes
_at_ 4
_at_ 8
19
Preliminary Evaluation of Variables (2D Modeling)
  • Effect of Slab Thickness

8 slab
6 slab
20
Preliminary Identification of Relevant Variables
(2D Modeling)
  • Diaphragms (stiffness, location, spacing)
  • Boundary conditions
  • Post-tensioning spacing

21
Effect of Diaphragms
  • Distribution of transverse stresses is mainly
    affected by diaphragm size and location.

22
Notation
Normalized stress ss/q
y
x
23
Effect of Diaphragm Size
y
y
Stripe 1
Stripe 2
24
Effect of Diaphragm Location(Exterior Diaphragms
Only)
y
y
Stripe 2
Stripe 1
25
Minimum Stress vs. Diaphragm Position
26
Effective Width of T Beam vs. Top Stress
Beff
27
Diaphragm Location vs. Effective Width
28
Conclusions at this Stage
  • Distribution of transverse stresses mainly
    influenced by
  • Diaphragm axial stiffness and position
  • Boundary conditions
  • Influence of diaphragm position Rationalized
    using T-beam analogy
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