Structural Analysis of Laminated Glass

Transcription

1 Structural Analysis of Laminated Glass Malvinder Singh Rooprai - M.E. ( Structures) Tech. Consultant ( AP Region) PVB Division, Kuraray India World of Facades, Hong Kong 12th June, 2018

2 Laminated Glass under Flexural Loads 20 June 2018 Trosifol Business 2

3 Polymer Mechanical Properties Polyvinyl Butyral (PVB) Large strain behavior Viscoelasticity (VE) Characterization of VE Key values for PVB Ionoplast (SentryGlas ) Large strain behavior Key property values for Ionoplast interlayer Comparison of PVB and Ionoplast Interlayer 20 June 2018 Trosifol Business 3

4 Durability of Mechanical Properties Investigate changes in beam stiffness with time and/or weathering Various aging conditions: Ageing under natural weathering in Florida for 7 years Ambient temperature cycling 4 C to 45 C Ambient humidity 25 % RH to 90 % RH Rain showers and thunderstorms No reduction in Ionoplast stiffness properties Also passed Florida Dade Co. (USA) tensile property retention requirements Beam Stiffness, k (N/mm) Three-Point Bend Test "Long" Beam, L = 510 mm 0 45 Mins 95 Mins 12 Hour 7 Years Laminate Age, t 20 June 2018 Trosifol Business 4

5 PVB Vs Ionoplast: Comparison SentryGlas chemistry shifts glass transition to higher temperatures Elasto-plastic versus hyperelastic 20 June 2018 Trosifol Business 5

6 PVB Vs Ionoplast: Comparison 35 SentryGlas chemistry shifts glass transition to higher temperatures. Elasto-plastic versus hyperelastic. Increased toughness: area under curve (5x). Engineering Stress, (MPa) SentryGlas(R) Plus (0.1 /s) PVB - Butacite(R) (0.1 /s) Engineering Strain, (%) 20 June 2018 Trosifol Business 6

7 Bond Strength Elevated Temp (50ºC) This study is an attempt to compare the bond strengths for SentryGlas and Trosifol ES with glass at room temperatures and Elevated Temperatures measured through Compressive Shear Strength on un-aged samples. Weathering is kept deliberately out of the scope of this study as there is lack of consensus on correlation between accelerated weathering conditions in a lab and real time natural weathering conditions. 20 June 2018 Trosifol Business 7

8 Compressive Shear Strength Test Results 20 June 2018 Trosifol Business 8

9 Analysis Approaches in Various Standards 1. European Standard pr EN & pr EN DIBT Technical Approval for SentryGlas with Shear Bond 3. ASTM E Structural Use of Glass 2018, Hong Kong 5. Full Finite FEM Analysis An Engineer wants to analyse a shop front glazing panel of height 2.0 Mts, simply supported at the top and bottom edges, that can sustain a wind pressure of 1.5 KPa location having maximum temperature of 35 Celsius Comparative Analysis as per above standards June 2018 Trosifol Business 9

10 European Standards pr EN & pr EN European Standard for Determining Load Resistance of Glass against lateral loads pr EN European Standard for Determination of interlayer mechanical properties Classifies the interlayers into stiffness families ( 0,1,2) based on their Young s Modulus Attempts to avoid a characterisation of interlayers by the properties of individual products 20 June 2018 Trosifol Business 10

11 European Standards pr EN & Step 2 : Classification into Stiffness families (0,1,2) based on their Young s Modulus IONOPLAST Standard PVB Acoustic PVB 20 June 2018 Trosifol Business 11

12 European Standards pr EN & ω for Different Stiffness Families and load Types 20 June 2018 Trosifol Business 12

13 European Standards pr EN & Effective Thickness for Calculating Deflection Effective Thickness for Calculating Stress 20 June 2018 Trosifol Business 13

14 DIBT General Technical Approval Product approval for laminated glass having SentryGlas 5000 interlayer with SHEAR BOND Very detailed quality control requirements for interlayer manufacturer and laminator - Moisture - Adhesion ( Pummel, Pull Test) Recommends Shear Modulus values for different load scenarios. To be used in FEM calculations No Analytical approach 20 June 2018 Trosifol Business 14

15 DIBT General Technical Approval Recommended Shear Modulus Values for Various Load Scenarios 20 June 2018 Trosifol Business 15

16 Effective Thickness Method ASTM E 1300 Globally, it was the first Standard to adopt Effective Thickness Method in 2009 Engineers have to rely on Shear Modulus data from interlayer manufacturer 20 June 2018 Trosifol Business 16

17 Laminate Effective Thickness (after Wölfel) Laminate effective thickness to use with analytic solution Effective thickness for deflection - a h h ΓI ef ; w s Effective thickness for stress - h h 1; ef ; 2; ef ; h 1 h h 2 h 3 ef ; w 2Γhs;2 h 3 ef ; w 2Γhs;1 h ) s 0.5( h1 h2 h v h h s;1 s;2 hsh1 h1 h hsh2 h h I s Γ h h h h s;2 2 s; G interlayer shear modulus (temperature/load duration) EI s h v 2 a 2 Ghs G measure of shear transfer (0 > 1) 20 June 2018 Trosifol Business 17

18 Structural Use of Glass General recommendation for designing laminated glass without composite action Composite action is acceptable but with some caveats Maximum degree of composite action λ( Lamda) to be not more than 70% of the stiffness of an equivalent monolithic glass of thickness equal to sum of thicknesses of individual panes The 4 point bend tests should confirm that the interlayers have the capacity to adhere the two or more panes rigidly such that they form a monolithic body. 20 June 2018 Trosifol Business 18

19 Structural Use of Glass Four Point Bend Test for Degree of Composite Action Glass Beam 360 x 1100 mm (5 Specimens) 50 ± 3 C is Test Temperature Loading Rate 2.0 ± 0.4 MPa / sec. Stress Control! Test to failure. Failure Load is recorded Load Vs Deflection Plot Extraction of Equivalent Stiffness Load/Deflection = W/Δ Determine Equivalent Thickness = t eqv. Determine λ test 20 June 2018 Trosifol Business 19

20 Structural Use of Glass Determination of t eqv and λ test through Four Point Bend Test Typical Load Vs Deflection Plot λ test should be always June 2018 Trosifol Business 20

21 Full FEA of the Shop Front Glazing Panel An Engineer wants to find out the effective thickness of a mm thick laminated glass (8mm mm Ionoplast + 8mm ) with shop front glazing panel of height 2.0 Mts, simply supported at the top and bottom edges, that can sustain a wind pressure of 1.5 KPa location having maximum temperature of 35º C h 1 = h 2 = 7. 7 mm, G for Ionoplast ºC, 3 sec load = 100 MPa 2000 FEA in MEPLA Software 20 June 2018 Trosifol Business 21

22 Summary of Comparative Analysis Country Standard/ Tech Approval pr EN pr EN Deflection Principal Stress mm MPa DIBT Tech Approval mm MPa ASTM E mm MPa SUG mm MPa Full FEA in Mepla mm MPa 20 June 2018 Trosifol Business 22

23 Summary of Analysis with Various Standards Deflection Stress Europe DIBT ASTM SUG 2018 FEA 20 June 2018 Trosifol Business 23

24 Façade Resiliency against Cyclone / Typhoon SUG 2018 is the most stringent code yet it does not address impact resistance of glass facades due to wind borne debris. No missile impact test criterion unlike ASTM E 1886 and Australian Standards AS Small Missile Impact, 2 gm Steel 39.6 m/sec for Height > 9.1 Mts - Large Missile Impact, 4 Kg Timer mass ( 50 x 20m/sec < 9.1 Mts Criteria for post impact pressure cycling, makes ASTM standards very comprehensive 20 June 2018 Trosifol Business 24

25 Designing Laminated Glass Fins for Buckling AS 1288 & SUG 2018 addresses buckling Sub-sections provide formulas for calculating the critical elastic value for beams with and without intermediate buckling restraints The critical elastic value for beams that are continuously restrained against lateral displacement According to AS 1288, the ultimate limit state design moment for a particular structural situation is not to exceed the critical elastic buckling moment (M CR ) divided by a safety factor of Code only addresses monolithic glass How do we address laminates? 20 June 2018 Trosifol Business 25

26 Critical Lateral Buckling Moment Comparison (Dr. Luible) Describe critical buckling moment in terms of: Elastic Modulus of Material (Glass), Moment of Inertia, span, Shear Modulus of interlayer, support condition, loading type How can we visualize this information? 20 June 2018 Trosifol Business 26

27 Critical Lateral Buckling Moment Comparison (Dr. Luible) Same Construction Depth Comparison Fin Type 19 mm Monolithic Glass Fin 10mm PVB + 10 mm 10 mm SentryGlas + 10 mm Span/Height (mm) ASTM Minimum Thickness (mm) Fin Depth (mm) Critical Lateral Torsional Buckling Moment % Comparison of Depths knm 100% knm 151% knm 93% Fin depth is 10% shallower for Ionoplast than monolithic, and 40 % shallower than that of PVB

28 Load (kn) FEA Modeling RIKS Analysis Finite Element Analysis 25 Load vs. Deflection RIKS Analysis 20 Post-Buckling Region Critical Load Critical Load FEA 13.58mm Imperfection FEA 6mm Imperfection Lateral Displacment (mm) 20 June 2018 Trosifol Business 28

29 Load (kn) Finite Element Analysis Load vs. Deflection RIKS Analysis FEA Modeling RIKS Analysis 10mm + SG + 10mm 20C 1min Load Duration Critical Buckling Loads Dr. Luible 17.1 KN AS KN FEA Eigenvalue 16.9 KN RIKS See Graph Critical Load FEA 13.58mm Imperfection FEA 6mm Imperfection Lateral Displacment (mm) 20 June 2018 Trosifol Business 29

30 Finite Element Analysis FEA Modeling RIKS Analysis 20 June 2018 Trosifol Business 30

31 Torsional Glass Fin Test Program Fin is grabbed at the top edge of the center, with load applied axially 20 June 2018 Trosifol Business 31

32 Load (kn) Test Results: Buckling Capacity of Ionoplast & PVB Laminated Fins 25 Load vs. Displacement of 500mm Deep Fin 10mm+10mm Laminated Glass PVB Eigenvalue PVB RIKS Analysis PVB Test Data SG RIKS Analysis SG Eigenvalue SG Test Data Lateral Displacment at Bottom of Fin (mm)

33 Summary Ionoplast Interlayers enhance the structural performance of Laminated glass in both pre breakage and post breakage conditions Ionoplast Interlayers have the highest stability compared to other interlayers. Ionoplast Interlayers retain a considerably high bond strength at elevated temperatures. With SUG 2018, Hong Kong joins the league of other country standards accepting composite action for structural analysis of laminated glass. Its analysis approach is the most stringent. ASTM E 1300 is the most lineant. FEA for Glass Fins is complex. Analytical Approach for laminated glass fins is missing in all the global standards including SUG Interlayer properties have a significant impact on the buckling capacity of laminated glass fins. Dr. Luible s work may be adopted by glass standards for information of engineers 20 June 2018 Trosifol Business 33

34 THANK YOU!! 20 June 2018 Trosifol Business 34

35 D I S C L A I M E R June 20, 2018 Trosifol Business 35

36 D I S C L A I M E R Trosifol, SentryGlas and Butacite are registered trademarks of Kuraray Co., Ltd. and its affiliates. The information, recommendations and details given in this document have been compiled with care and to our best knowledge and belief. They do not entail an assurance of properties above and beyond the product specification. The user of our products is responsible for ensuring that the product is suitable for the intended use and conforms to all relevant regulations. Kuraray Co., Ltd. and its affiliates do not accept any guarantee or liability for any errors, inaccuracies or omissions in this document. June 20, 2018 Trosifol Business 36