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 CHALLENGES thermally improved member (FRP). • Thermal breaks must not compromise structural • Available member sizes not large integrity of unmitigated system enough • May not be structurally effective for these applications • FRP-to-steel connections are not validated in the experimental literature 3. Coat structural steel member in paint, foam, etc. • FRP-to-FRP and FRP-to-steel connections are • Reductions in thermal transmissivity not clearly approved for structural use within minimal (<5%) national design specifications related to • Energy still lost at connections structural steel 4. Use a manufactured thermal break This project aims to design, test, and assembly. computationally validate structural connections that include thermal breaks

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

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

CREEP TESTING PROLONGED BEARING COMPRESSION TESTING OF FRP MATERIALS (CREEP) • 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)

CREEP TEST MATRIX (IN PROGRESS) t f , time to failure (hr) <10 0 >10 0 >10 1 >10 2 >10 3 σ app / σ max material specimen F app (kip) 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 - -

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

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

CONNECTION TESTING • 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. No shims ¼” shims 1” shims 2” shims 3” shims No shims ¼” shims 1” shims 2” shims 3” shims 5/8” dia. 1/2” dia.

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

SHELF ANGLE: DESIGN METHODOLOGY GOAL: examine structural performance of thermal bridge mitigation strategies DESIGN PARADIGM • Designed: Examine designed connection details to determine progression of 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