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Epoxy Used in the D Street Portal

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Anchor creep testing in the laboratory. Standardized testing methods for adhesive anchors ... Anchor Creep Testing in the Laboratory ... – PowerPoint PPT presentation

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Title: Epoxy Used in the D Street Portal


1
Epoxy Used in the D Street Portal
  • Carl Schultheisz

2
Topics Addressed
  • Epoxy fundamentals
  • Anchor creep testing in the tunnel
  • Anchor creep testing in the laboratory
  • Standardized testing methods for adhesive anchors

3
Epoxy Fundamentals
  • Epoxy covers a wide range of materials
  • Solid epoxy is formed by a chemical reaction
    between two components
  • Epoxy resin
  • Hardener
  • Resin and hardener molecules link to form long
    chains
  • Crosslinks result in a network that limits motion

4
Epoxy Fundamentals
  • Under constant load, molecular rearrangement
    allows epoxy to deform continuously in a process
    called creep
  • The rate of creep and the amount of creep depend
    on molecular structure, crosslink density, and
    temperature
  • Under small loads, deformation is linear and
    reversible
  • With increasing load or longer times, deformation
    becomes nonlinear and irreversible, leading to
    fracture and damage accumulation

5
Epoxy Fundamentals
  • Rate of creep is accelerated at higher
    temperatures
  • Time-temperature superposition data from
    short-term tests at increasingly higher
    temperatures are combined to predict the
    long-term creep behavior
  • Tests applied to Fast Set and Standard Set
    epoxies from Powers Fasteners

6
Fast Set
Increasing anchor displacement
Standard Set
Data courtesy of NIST
7
Epoxy Fundamentals
  • Compared to Standard Set epoxy, Fast Set epoxy
    forms a poor network with a much lower crosslink
    density
  • Fast Set epoxy is therefore expected to creep at
    a higher rate and by a larger amount

8
Anchor Creep Testing in the Tunnel
  • 11 tests total, for up to 3 months
  • Loads of 1000, 2000, and 3000 pounds
  • 3 failures
  • All anchors showed continuous displacement
    throughout the test (up to 0.14 inch)

9
Anchor Creep Testing in the Laboratory
  • Eliminate unknown installation and load histories
  • 1000, 2000, 3000, and 4000 pounds
  • 82 days, 2 replicates
  • Fast Set and Standard Set epoxies

10
Anchor Creep Testing in the Laboratory
Anchors loaded at 4000 pounds
Fast Set
Standard Set
Figure courtesy of FHWA TFHRC
11
Anchor Creep Testing in the Laboratory
Anchors installed with Fast Set
4,000 lbs
3,000 lbs
2,000 lbs
1,000 lbs
Figure courtesy of FHWA TFHRC
12
Anchor Creep Testing in the Laboratory
  • Fast Set epoxy showed significant displacement at
    all load levels
  • Standard Set epoxy showed minimal displacement
    throughout the test
  • Fast Set anchors loaded at 4000 pounds pulled out
    completely
  • The ceiling collapse was primarily the result of
    the poor creep resistance of the Fast Set epoxy

13
Standardized Testing Methods
  • No FHWA or AASHTO standards for adhesive anchors
  • Adhesive anchor standards (including creep) in
    International Code Council - Evaluation Service
    (ICC ES) Acceptance Criteria AC 58
  • Without the creep test, adhesive is limited to
    short-term loading only
  • AC 58 creep test is optional

14
Standardized Testing Methods
  • ICC-ES AC 58 creep test is relatively rigorous
    useful as a screening tool
  • 1995-96 - Standard Set and Fast Set tested for
    creep per AC 58
  • Standard Set epoxy passed
  • Fast Set epoxy failed
  • Fast Set failing the creep test should have
    precluded its use in 1999 to support the ceiling

15
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