Thermal break strategies for cladding systems in building structures - - PowerPoint PPT Presentation

Thermal break strategies for cladding systems in building structures

Kara Peterman, Ph.D., Postdoctoral Research Associate Department of Civil and Environmental Engineering, Northeastern University Julieta Moradei, Undergraduate Research Assistant Department of Civil and Environmental Engineering, Northeastern University James D’Aloisio, P.E., SECB, LEED AP BD+C, Principal Klepper, Hahn & Hyatt Mark D. Webster, P.E., SECB, LEED AP BD+C, Senior Staff II – Structures Simpson Gumpertz & Heger, Inc. Jerome F. Hajjar, Ph.D., P.E., CDM Smith Professor and Department Chair Department of Civil and Environmental Engineering, Northeastern University

SPONSORS & INDUSTRY PARTNERS

FUNDING SOURCES IN-KIND FUNDING

THERMAL BRIDGES & BREAKS

MITIGATION STRATEGIES 1. Add a thermally improved shim (FRP, steel foam, stainless steel).

• Takes advantage of intermittent spacing
• Easy to install
• Structurally promising

2. Replace structural steel member with thermally improved member (FRP).

• Available member sizes not large

enough

• May not be structurally effective for

these applications 3. Coat structural steel member in paint, foam, etc.

• Reductions in thermal transmissivity

minimal (<5%)

• Energy still lost at connections

4. Use a manufactured thermal break assembly. CHALLENGES

• Thermal breaks must not compromise structural

integrity of unmitigated system

• FRP-to-steel connections are not validated in

the experimental literature

• FRP-to-FRP and FRP-to-steel connections are

not clearly approved for structural use within national design specifications related to structural steel This project aims to design, test, and computationally validate structural connections that include thermal breaks

CLADDING DETAILS

Thermal break is installed at or beneath end plate, as in roof post detail

Model Name ( - ) Bolt Type ( - ) U-Value (BTU/h*ft2*°F) Model Name ( - ) Shim Material ( - ) Bolt Type ( - ) U-Value (BTU/h*ft2*° F) ∆ U-Value (BTU/h*ft2*°F) %-Reduction Shelf Angle Unmitigated 2.5 Inch_S1_V2 A304-SH 0.138 Shelf Angle Mitigated 2.5 Inch_S8_V3 Vinylester shim A325 0.082 0.056 40.41 Shelf Angle Unmitigated 2.5 Inch_S1_V2 A304-SH 0.138 Shelf Angle FRP 2.5 Inch_S19 FRP angle A304-SH 0.072 0.066 47.94 Shelf Angle Unmitigated 5 Inch_S4_V2 A304-SH 0.112 Shelf Angle Mitigated 5 Inch_S14.1_V3 Vinylester shim A325 0.056 0.056 50.22 Shelf Angle Unmitigated 5 Inch_S4_V2 A304-SH 0.112 Shelf Angle Mitigated 5 Inch_S14.2_V3 Vinylester shim A304-SH 0.053 0.060 53.16 Shelf Angle Unmitigated 5 Inch_S4_V2 A304-SH 0.112 Shelf Angle Mitigated 5 Inch_S17_V3 Proprietary 1 shim A304-SH 0.051 0.061 54.32 Shelf Angle Unmitigated 5 Inch_S4_V2 A304-SH 0.112 Shelf Angle Mitigated 5 Inch_S18.1_V3 Proprietary 2 shim A304-SH 0.052 0.061 54.05 Shelf Angle Unmitigated 5 Inch_S4_V2 A304-SH 0.112 Shelf Angle Mitigated 5 Inch_S18.2_V3 Stainless tube shim A304-SH 0.059 0.054 47.73 Comparison Unmitiagated Model Mitigated Model

SHELF ANGLE: THERMAL MODELING

Unmitigated Model

CREEP TESTING

• As many of these mitigation strategies involve use of a bearing shim in a steel

bolted connection, it is necessary to discern the behavior of these shims under compression (termed flatwise compression) for prolonged loads

• Existing ASTM standards for FRP materials subjected include standards for

tension or compression in the direction of the grain

• Prior creep testing exists on FRP materials in tension and compression along the

grain, and for FRP materials in flexure

• No applicable ASTM standard exists for determining creep properties of materials

under flatwise compression.

• Relevant ASTM standards are combined to create a new testing procedure.
• ASTM D7337 outlines the procedure for testing polymers under tensile prolonged loads
• Flatwise compression testing (monotonic testing, not creep testing) is established in ASTM C365 for

testing sandwich panels

• D4762 for general testing of polymer matrix composite materials (creep not specified)

PROLONGED BEARING COMPRESSION TESTING OF FRP MATERIALS (CREEP)

tf, time to failure (hr) material specimen σapp/σmax Fapp (kip) <100 >100 >101 >102 >103 vinylester 3c 0.8 21.28 0.628

• 1c

0.8 20.98

• 2.79
• 2c

0.8 20.93

• 3.30
• 5c

0.758 20.78

• 6.23
• 6c

0.75 20.10

• 13.4
• 4c

0.7 19.11

• 132
• polyurethane

1c 0.9 54.68 0.127

• 2c

0.9 54.45 0.785

• 3c

0.9 54.01

• 6.09
• 4c

0.8 44.03

• 36.9
• 5c

0.78 43.46

• 500+
• phenolic

8c 0.875 12.85

• 125+
• 3c

0.85 12.31

• 1.92
• 7c

0.85 12.49

• 9.63
• 5c

0.84 12.58

• 73.0
• 2c

0.8 12.11

• 231
• proprietary 1

2c 0.85 27.84

• 3.08
• 1c

0.8 28.15

• 16.7
• 3c

0.78 27.16

• 146
• proprietary 2

1c 0.8 26.76 0.214

• 2c

0.7 22.49

• 2.27
• 6c

0.69 21.63

• 6.68
• 5c

0.65 21.13

• 85.4
• CREEP TEST MATRIX (IN PROGRESS)

CONNECTION TESTING

DOUBLE LAP SPLICE BOLTED CONNECTIONS WITH NON-STEEL FILLS

• Steel-to-FRP connections and FRP fills in steel-to-steel connections are not currently

approved for structural use.

• Connection tests are necessary to determine reduction factor for non-steel fills.
• Tests are monotonic to failure. Anticipated failure mode is bolt shear.
• Connection type:

− 5/8” dia. A325 bolts − 1/2” dia. A325 bolts − 5/8” dia. A304-SH bolts (strain-hardened stainless steel bolts) − Snug tight connections − Standard holes − Carbon and stainless steel bolts considered

• Tested variables:

− Shim material − Shim thickness − Bolt material − Effect of multiple plies

Combined with the aforementioned creep testing, these tests aim to determine whether “soft materials” such as fiber reinforced polymers can be used as fills in steel connections with snug-tight bolts, and if so, how to design for this condition.

Rig Thicknesses Test Name Shim Type Shim Thickness Bolt Dia. (in) Bolt Spec Hole Size Top Bottom C1S no shim

• 5/8

A325 11/16 4" 4" C1 no shim

• 5/8

A325 13/16 4" 4" C2 no shim

• 5/8

A304 SH1 11/16 4" 4" C3 no shim

• 1/2

A325 9/16 4" 4" C4 polyurethane 1/4" 5/8 A325 11/16 3.5" 4" C5 vinylester 1/4" 5/8 A325 11/16 3.5" 4" C6 phenolic 1/4" 5/8 A325 11/16 3.5" 4" C7 proprietary 1 1/4" 5/8 A325 11/16 3.5" 4" C8 proprietary 2 1/4" 5/8 A325 11/16 3.5" 4" C9 vinylester 2x1/2" multiple plies 5/8 A325 11/16 2" 4" C10 vinylester 1" 5/8 A325 11/16 2" 4" C11 vinylester 1" 5/8 A304 SH1 11/16 2" 4" C12 vinylester 1" 1/2 A325 9/16 2" 4" C13 vinylester 2x1" multiple plies 5/8 A325 11/16 4" 8" C14 vinylester 2x1" multiple plies 5/8 A304 SH1 11/16 4" 8" C15 vinylester 2x1" multiple plies 1/2 A325 9/16 4" 8" C16S vinylester 3x1" multiple plies 5/8 A325 11/16 2" 8" C16 vinylester 3x1" multiple plies 5/8 A325 13/16 2" 8" C17 vinylester 3x1" multiple plies 5/8 A304 SH1 11/16 2" 8" C18 vinylester 3x1" multiple plies 1/2 A325 9/16 2" 8"

*holes are standard holes (bolt dia. + 1/16")

CONNECTION TESTING

The top rig is replaced after each test, while the bottom base remains installed for every set of tests as shown. The top rig is always 2 inches or thicker. Shims < 1 inch, 4 inch base is used Shims > 1 inch, 8 inch base is used

CONNECTION TESTING

¼” shims 1” shims (2) 1” shims (3) 1” shims

CONNECTION TESTING

No shims ¼” shims 1” shims 2” shims 3” shims

• While bolt material, number of plies, and shim material do affect results, performance is best

characterized by shim thickness

• Thick shims (1 - 3”) result in ~10-20% reduction in strength and a ~70-80% reduction in

stiffness (consistent with results in steel fill connection testing)

• Thin shims (1/4”) do not have a significant impact on stiffness or strength, but do permit

additional bolt elongation in the initial loading region.

5/8” dia. 1/2” dia.

No shims ¼” shims 1” shims 2” shims 3” shims

¼” shim test 2” shim test - delamination 2” shim test – delamination and bolt bearing

CONNECTION TESTING

SHELF ANGLE: DESIGN METHODOLOGY

GOAL: examine structural performance of thermal bridge mitigation strategies DESIGN PARADIGM

• Designed: Examine designed connection details to determine progression
• f failure for a typical constructed shelf angle.
• Over-Designed: Isolate mitigation component (shim, FRP angle, etc.) such

that connections and supporting structure do not fail first. STRENGTH OF CONNECTION ELEMENTS (WEAKEST TO STRONGEST) Designed specimens Over-designed specimens

• 1. Connection (bolt)
• 1. Shelf angle (if steel)
• 2. Shelf angle (if steel)
• 2. Mitigation component
• 3. Mitigation component (shim or angle)
• 3. Connection (bolt or weld)
• 4. Supporting structure
• 4. Supporting structure

Mitigation Strategy Specimen Information Test Name Specimen Type Type Material Thick (in) Length Section Bolt/Stud Spec Bolt Dia. (in)* S1 designed

• 42

L6x4x5/16 A325 0.625 S2 designed

• 42

L6x4x5/16 A304-SH 0.75 S3

• ver-designed
• 42

L6x4x5/16 A325 1 S4 designed

• 42

L7x4x3/8 A325 0.625 S5 designed

• 42

L7x4x3/8 A304-SH 0.75 S6

• ver-designed
• 42

L7x4x3/8 A325 1 S7

• ver-designed

shim vinylester 1.5 42 L6x4x5/16 A325 1 S8 designed shim vinylester 1.5 42 L6x4x5/16 A325 0.625 S9

• ver-designed

shim polyurethane 1.5 42 L6x4x5/16 A325 1 S10

• ver-designed

shim phenolic 1.5 42 L6x4x5/16 A325 1 S11

• ver-designed

shim proprietary 1 1.5 42 L6x4x5/16 A325 1 S12

• ver-designed

shim proprietary 2 1.5 42 L6x4x5/16 A325 1 S13

• ver-designed

shim vinylester 3 42 L7x4x3/8 A325 1 S14 designed shim vinylester 3 42 L7x4x3/8 A325 0.625 S15

• ver-designed

shim polyurethane 3 42 L7x4x3/8 A325 1 S16

• ver-designed

shim phenolic 3 42 L7x4x3/8 A325 1 S17

• ver-designed

shim proprietary 1 3 42 L7x4x3/8 A325 1 S18

• ver-designed

shim proprietary 2 3 42 L7x4x3/8 A325 1 S19

• ver-designed

FRP angle vinylester

• 42

FRP L6x4x1/2 A325 1 S20

• ver-designed

tube shim carbon steel HSS3x3x3/8 42 L7x4x3/8 A325 1 S21

• ver-designed

steel shim carbon steel 3 42 L7x4x3/8 A325 1

*holes are standard holes (bolt diamter + 1/16 inch)

SHELF ANGLE: TEST MATRIX

SHELF ANGLE: TEST RIG

Shelf angle specimen shown in green Load beam in brown

CLIMATE ZONE 7 RESULTS

• Mitigated specimens stiffer in initial stiffness region (up to 0.1” displacement) than

unmitigated specimens

• Due to change in M/V ratio, shimmed specimens benefit from decrease in moment

arm; shims compress and eventually fail in bearing/crushing/delamination. Strong shims (steel, HSS, some FRP) do not fail, and the angle eventually fractures.

Steel shims provide upper bound Unmitigated details provide lower bound

Delamination during test on top of shim Crushing, delamination, hole ovalization, bolt deformation Delamination in FRP angle Shelf angle fracture

ROOF POST & CANOPY BEAM: DESIGN METHODOLOGY

GOAL: examine structural performance of thermal bridge mitigation strategies DESIGN PARADIGM

• Isolate failure to post/beam in “overdesigned” specimens, and to base plate

and anchor rods in “designed” specimens. Welds between post/beam and base plate are intended not to fail (CJP weld). STRENGTH OF CONNECTION ELEMENTS (WEAKEST TO STRONGEST) Designed specimens Over-designed specimens

• 1. Anchor rod/base plate
• 1. Post/beam
• 2. Post/beam
• 2. Mitigation component
• 3. Mitigation component (shim)
• 3. Anchor rod/base plate
• 4. Weld
• 4. Weld

CONCLUSIONS

• Thermal bridging is important to address for steel structures
• Preliminary results indicate that FRP shims provide an effective thermal break
• Likely to be able to address structural performance and integrity of steel

connections with FRP in the plies of the steel connection:

• Design loads are likely to be low enough (or may be limited to be low

enough) that creep is not an issue

• Decrease of strength due to thick FRP shims may be addressed in design

provisions

• Shelf-angle geometry tends to increase strength compared to unmitigated

solution

• Ongoing research will consider additional configurations such as roof posts

and canopy beams

THANK YOU!

INDUSTRY ADVISORY PANEL (IAP)

Fiona Aldous Associate Principal Wiss, Janney, Elstner Associates, Inc. Glenn Barefoot Vice President of Business Development and Marketing Strongwell Craig D. Blanchett Principal LeMessurier Associates John P. Busel Executive Director American Composites Manufacturing Association Rodney Gibble Principal Rodney D. Gibble Consulting Engineers Robert Haley President ArmadilloNV Adam Kimble Head of Schӧck North America Schӧck USA, Inc. Robert Kistler Principal The Façade Group Adrian Lane Senior Product Engineer Owens Corning Andrea Love Building Scientist Payette Alex McGowan Vice-President, Technical Services Levelton Consultants, Ltd. Steve Moore Project Manager Fabreeka International, Inc. Larry Muir Director, Steel Solutions Center American Institute of Steel Construction Rick Pauer Applications Polynt Composites USA Inc. Mark Perniconi Executive Director Charles Pankow Foundation Thomas Schlafly Director of Research American Institute of Steel Construction Tabitha Stine Director of Technical Marketing American Institute of Steel Construction Dustin Troutman Director of Marketing and Product Development Creative Pultrusions, Inc. OTHER PROJECT PERSONNEL

Sean O'Brien

Associate Principal Simpson Gumpertz & Heger Inc.

James Parker

Senior Principal & Division Head, Structural Engineering Simpson Gumpertz & Heger Inc.

Mehdi Zarghamee Senior Principal

Simpson Gumpertz & Heger Inc.