NCHRP 18-14: Evaluation and Repair Procedures for Precast

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					                                     A Survey conducted for:

NCHRP 18-14: Evaluation and Repair Procedures for Precast/Prestressed
     Concrete Girders with Longitudinal Cracking in the Web
Dear Colleagues:

The objective of NCHRP Project 18-14 is to establish procedures for the acceptance, repair, or
rejection of precast/prestressed concrete girders with longitudinal web cracking. This survey is the
first step in a information collection task to guide the project. Your response will be
incorporated into a database, where all information will be kept confidential and will be used
for this research project only. The entities to be surveyed include state DOTs, other owner
agencies, selected bridge consultants, and precast concrete producers. The success of this
project depends upon your participation in this survey and your candid responses will be
greatly appreciated. You will be provided with a summary of the survey results when it is
available. Thank you very much for sparing time from your busy schedule.

Please return this form to: mtadros@mail.unomaha.edu, by fax: (402) 554-3288, or by
surface mail to: Department of Civil Engineering, Peter Kiewit Institute, 1110 South 67th
Street, Omaha, NE 68182-0178. If you have any suggestions or comments, please contact
Dr. Maher Tadros at (402) 554-4842 (office) or (402) 216-6222 (cell). Thank you.

Sincerely,

Maher K. Tadros, Principal Investigator
Professor of Civil Engineering, University of Nebraska-Lincoln
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                    Note: this survey will take about 10 minutes to complete

1. What is your business affiliation?
   XO State DOT              O Consultant            O Precast concrete producer              O
Researcher
   O Other: please specify ___________________________________


2. Approximately how many linear feet of precast/prestressed concrete bridge girders do you
   design, fabricate, or construct annually?
   O Hundreds            O Thousands            X O 10s of thousands              O Other:
_____________


3. What type of precast/prestressed bridge girders do you oversee, design or produce?


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   XO I girders and bulb tees      XO Box girders        O Other (specify):
________________
4. Have you observed longitudinal or diagonal cracks in the web in the end zones of
   precast/prestressed concrete girders? Generally end zone is defined as the region at the
   girder end, equal in length to approximately the member depth.
   O No – end of survey, thank you for your time.
   XO Yes – please proceed to the next question


5. On which type of girder:Primarily Bulb-T Sections


   How frequently (specify percentage of cracked girders): 5 to 10 per cent




6. Do you have special end zone reinforcement details that you are willing to share with the
   research team?
   O No
   XO Yes
   If yes, please send to us by e-mail, fax or surface mail. Thanks.


7. Do you maintain records of girders with end zone cracking?
   XO No
   O Yes


8. What are your current criteria for determining extent of end cracking?
   O No established criteria
      O Crack width (specify): Generally we follow the new PCI “Manual                         Formatted: Right




      O Crack length (specify): For Evaluation and Repair of Precast, Prestressed


      O Number of cracks (specify):      Concrete Bridge Products”




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9. Do you use an instrument to determine extent of end cracking?
   XO Naked eyes        O Magnifying scope           O Impact echo O Ultrasound
   OX Crack comparators                O      Other methods (specify):


10. Do you have established criteria for deciding when to repair cracks?
    O No established criteria
    OX Yes (specify): PCI “Manual for the Evaluation and Repair of Precast, Prestressed
   Concrete Bridge Products”




11. What commercial products and procedures do you use to repair end zone cracking?
       Epoxy injection of cracks and pre-packaged quick setting concrete with latex
   modifiers for bond for minor spalls. For large repairs, the concrete mix used in
   manufacturing the beam, itself, is used.




12. Do you believe the repair product will restore the tensile strength of the girder across the
repaired cracks?
   O No
   O Yes
   O Partially (to what level): Our expectation is that properly injected cracks can sustain
   tension to the allowable design limit 6 sq root f’c


13. Do you believe that it is necessary to restore the tensile strength of the girder across the
   crack?
   XO No
   O Yes



                                                 3
O If yes, why:




14. What criteria do you use to reject a cracked bridge girder from a precast concrete
producer?
      If we feel that a beam cannot be repaired to satisfy the rigors of everyday service for
   its design life, we will reject it. However, rejections are very rare.




15. Which strand release process do you specify/use?
     O Hydraulic release (jack down) of all strands in one step
     O Hydraulic release of individual strands
     O Flame cutting of individual strands
     XO Other (specify): _We do not specify, however all precast suppliers for Tennessee
contractors use flame cutting_
____________________________________________________


15. Please specify the strand diameter you commonly specify?
       OX 0.5 in.; in the following products
___Any____________________________________
       OX 0.6 in.; in the following products
_Any______________________________________
       O Other (specify):


16. What do you believe contributes to end zone cracking?
    O Strand size                             OX Detensioning (prestress transfer method)
    OX Lifting method and insert location          O Concrete strength
    OX Strand distribution                         O Other (specify): __________________




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   Please elaborate: _We are by no means certain of the cause, or causes, otherwise we
   would craft our designs and specifications to minimize or eliminate these
   cracks._____________________________________________________




17. Additional comments: ___________________________________________________




Name of the respondent:Edward P. Wasserman

Title:                    Civil Engineering Director – Structures Division

Company/Agency:           Tennessee Department of Transportation

Address:                  Suite 1100, James K. Polk Bldg.
                          Nashville, TN 37243-0339                                       Formatted: Indent: First line: 0.5"




Phone number:             615-741-3351

Fax number:               615-532-7745

E-mail:                   ed.wasserman@state.tn.us


                                     Thank You




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