Experimentally Determined Continuous Displacement Influence Lines for Bridges

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Experimentally Determined Continuous Displacement
Influence Lines for Bridges

• Jun Huang, Ph.D.
• Bechtel Corporation
• Harry Tripp Shenton, Ph.D.
• Center for Innovative Bridge Engineering
• Dept. of Civil and Environmental Engineering
• University of Delaware
• Newark, Delaware
• December 12, 2009

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Outline of the Presentation

• Introduction
• Continuous Displacement Influence Line
  Methodology Based on Least Square Method
• Field Verification
• Summary and conclusions

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Introduction---Displacement Influence Line

• Theoretical Influence Line - Uses
• Qualitative - determine position of live loads
  that will lead to maximum effects
• Quantitative - calculate maximum response
  directly by making use of Ils
• Experimentally Derived Additional Uses
• Experimentally derived stiffness model
• Displacement based load rating
• Condition assessment/health monitoring

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Introduction---Experimental Displacement
Influence Line

• Prior studies in Experimental IL
• Stress IL of a transverse bar in an reinforced
  bridge deck by Alampall and Fu .
• Turer Turer, 1997 proposed the unit IL
  decomposition method.
• A matrix equation for calculating the strain
  influence ordinates was presented by Obrien
  Obrien, etc., 2006.
• The experimental IL test by Hirachan Hirachan,
  2006.
• Hunt examined the realities of the field
  identification of strain ILs for typical
  steel-stringer bridges Hunt, 2000.

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Continuous Displacement Influence Line Method
(CDIL)

• Over-Determined Problem
• Theoretical DIL for a SS Beam
• Two-Axle Truck Passing a SS Beam
• Subdomain Analysis
• Field verification

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CDIL---Over-Determined Problem
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CDIL---Over-Determined Problem
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CDIL---Theoretical DIL for a SS Beam
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CDIL--- Two-Axle Truck Passing a SS Beam
and
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Possible truck locations
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CDIL---Subdomain Analysis
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CDIL---Subdomain Analysis
Final CDIL expressions in terms of the unknown
coefficients Ci
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CDIL---Subdomain Analysis
m measured load position (xi) deflection (yi)
data pairs from the load test
n1 data points in the first phase
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CDIL---Subdomain Analysis
n2 data points in the second phase
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CDIL---Subdomain Analysis
n3 data points in the third phase
etc..
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CDIL--- Formulate the over-determined problem
All together (system of m equations in 6
unknowns)
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CDIL--- Solve for the unknown coefficients
Reduce to Normal equations
Solve for the unknown coefficients Ci back
substitute to obtain the experimentally
determined CDIL
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CDIL---Field verification

• Methodology was tested/demonstrated on three
  different bridges.

Bridge 7R
Bridge 2-063
Bridge 1-911S
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CDIL---Field verification (B 1-911S)

• Bridge 1-911S is on southbound Delaware SR 1.
• Built in 2003 and in very good condition.
• Six W36X210 rolled I beams spaced apart 9.
• The span length----65. inner-to-inter
  width---48 8 1/2 thick. deck

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CDIL---Field verification (B 1-911S)
Deflection measurement
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CDIL---Field verification (B 1-911S)
Response at different locations for similar load
pass
Deflection measurement
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CDIL---Field verification (B 1-911S)
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CDIL---Field verification (B 1-911S)
Response at same location for different load
passes
Deflection measurement
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CDIL---Field verification (B 1-911S)
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CDIL---Field verification (B 1-911S)
Comparison between the Measured Data and the
Predicted Data by the Experimental Unit DIL at
T11 for Pass 1
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CDIL---Field verification (B 1-911S)
Predicted response at T11 in Pass 1 made using
the Experimental DIL determined from T11 in Pass
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CDIL--- Observations from the Test Results

• Based on the results from three different bridges
  the methodology has been demonstrated and works
  well.
• Experimental DILs at one position, obtained from
  different load passes, are very consistent,
  comparable.
• 3. Experimental DILs at different positions,
  obtained from the same load pass, are consistent.

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Summary and Conclusions

• Method developed for determining experimentally
  derived displacement influence lines for bridges,
  based on results of a controlled load test
• Uses Least-Squares fit between theoretical DIL
  and measured data
• Verified using results of tests of three
  different bridges
• Results are consistent and comparable
• Applications in load rating, modeling, condition
  assessment
• Technique will be challenging for more complex
  structures/bridges

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Thank You! Question?