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Chiara Pozzuoli, RWDI, London (UK) “The Art of Shaping the Building Envelope for a Wind- and Climate-Aware design”

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The Future Envelope 12
Interreg IT-AU FACEcamp project
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Conference on Building Envelopes
20-21 May 2019, NOI Techpark, Bolzano (Italy)
"It’s all about performances".

Published in: Technology
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Chiara Pozzuoli, RWDI, London (UK) “The Art of Shaping the Building Envelope for a Wind- and Climate-Aware design”

  1. 1. The Future Envelope 12 It’s all about performances The Art of Shaping the Building Envelope for a Wind- and Climate-Aware design Chiara Pozzuoli RWDI www.interreg.net FACEcamp final event | Bolzano, 20-21 May 2019 FACEcamp is funded by European Regional Development Fund and Interreg V-A Italy-Austria 2014-2020.
  2. 2. Chiara Pozzuoli, PhD Qualification • Senior Project Manager (EU, ME) • Chartered Structural Engineer, Italy • Member, Scientific Committee, Interuniversity Research Centre for Building Aerodynamics and Wind Engineering (CRIACIV) • Registered Professional Engineer, Civil and Environmental Engineering Sector, Section A, Ordine degli Ingegneri della Provincia di Perugia, Italy Education • Doctor of Philosophy, Università di Firenze, Italy and Technische Universität Braunschweig, Germany, 2012 • Master of Science (Structural Engineering), Università degli Studi di Perugia, Italy, 2007 • Bachelor of Science (Civil Engineering), Università degli Studi di Perugia, Italy, 2005 Employment • 2015-Present Project Manager, RWDI • 2011-2015 Wind Engineering Specialist, Structural Dynamics and Seismic Engineering Consultant, ECSD S.r.l. • 2009-2011 Civil Structural Engineer, Generale Prefabbricati SpA The Future Envelope 12 final event 20-21 May 2019, Bolzano
  3. 3. A Global Presence The Future Envelope 12 final event 20-21 May 2019, Bolzano
  4. 4. Global Experience The Future Envelope 12 final event 20-21 May 2019, Bolzano
  5. 5. Services Offered • Air Quality • Ventilation • Noise & Acoustics • Vibration • Sustainable Design • Energy • Wind Loads • Comfort • Solar • Snow, Sand & Rain • Regulatory Permitting (ECA) The Future Envelope 12 final event 20-21 May 2019, Bolzano Design Solutions
  6. 6. • Gain an appreciation for the aerodynamic and meteorological variables involved in wind engineering • Gain an understanding of wind-induced phenomena that cause high wind loads and serviceability issues • Discuss various shaping strategies • Understanding the wind action on cladding elements • Wind tunnel testing vs CFD • Special problems • Other environmental effects on the building envelope • Glare • Thermal performance • Rainwater • Icing Presentation Objectives The Future Envelope 12 final event 20-21 May 2019, Bolzano
  7. 7. The Future Envelope 12 final event 20-21 May 2019, Bolzano Wind is often a primary consideration for high rise buildings
  8. 8. Shaping to Calm Pedestrian Level Winds Strong upper level winds are directed to grade level by taller buildings. Podium/setbac k at street level blocks the accelerated flow Large Scale mitigation – Early in Design Process! The Future Envelope 12 final event 20-21 May 2019, Bolzano
  9. 9. The Future Envelope 12 final event 20-21 May 2019, Bolzano Challenges with Response of tall buildings to wind
  10. 10. Response of a Typical Tall Building - Drag -4.0E+09 -2.0E+09 0.0E+00 2.0E+09 4.0E+09 BaseOverturningMoment(N-m) 10 60 110 160 210 260 310 360 Wind Direction (degrees) Mx Wind Direction (degrees) BaseOverturningMomentDrag Loads include mean and dynamic component Peak MaximumMean Peak Minimum DRAG WIND DirectionofLoading Plan • Code analytical methods tend to focus on drag loading which is adequate for many typical high-rise buildings. In these cases, wind tunnel testing often produces reductions in design loads due to shape factors, wind climate, surroundings, etc. The Future Envelope 12 final event 20-21 May 2019, Bolzano
  11. 11. -4.0E+09 -2.0E+09 0.0E+00 2.0E+09 4.0E+09 BaseOverturningMoment(N-m) 10 60 110 160 210 260 310 360 Wind Direction (degrees) Mx Wind Direction (degrees) BaseOverturningMomentAcross-wind response where mean loads are negligible Peak MaximumMean Peak Minimum DirectionofLoading Plan WIND • For a slender tall building with almost uniform cross-section, the wind loads can be governed by across-wind response due to vortex shedding. Wind tunnel testing is best way to identify these responses which impact strength and serviceability. LIFT The Future Envelope 12 final event 20-21 May 2019, Bolzano Response of a Typical Tall Building – Lift (Across Wind)
  12. 12. Across-Wind Loading (Vortex Shedding) Directions of fluctuating force WIND The Future Envelope 12 final event 20-21 May 2019, Bolzano b U SN =
  13. 13. What is the benefit of shape optimization ? -4.0E+09 -2.0E+09 0.0E+00 2.0E+09 4.0E+09 BaseOverturningMoment(N-m) 10 60 110 160 210 260 310 360 Wind Direction (degrees) Mx Wind Direction (degrees) BaseOverturningMoment Peak MaximumMean Peak Minimum DirectionofLoading Plan WIND • These responses tend to be more difficult to predict than the drag responses as they are very sensitive to shape, among other variables. Therefore, wind response can be significantly reduced by shape optimization. The Future Envelope 12 final event 20-21 May 2019, Bolzano
  14. 14. • Wind climate • Immediate Surroundings and Upwind Terrain Conditions • Detailed structural properties (mass and stiffness designed by structural engineer) • Damping (inherent and/or supplementary) • Aerodynamic shape Wind Tunnel Testing - What do we learn in the wind tunnel? The Future Envelope 12 final event 20-21 May 2019, Bolzano
  15. 15. Aerodynamic Response Wind Climate Model Combination of Response and Directionality Influence of the Wind Climate Peak response aligned with prevailing winds Peak response aligned with less frequent winds The Future Envelope 12 final event 20-21 May 2019, Bolzano
  16. 16. Influence of Surroundings Direction of LoadingDrag response • Code Analytical methods mostly address drag loading only • Lift is larger in both cases but ratio of lift / drag less in more built-up surroundings DRAG LIFT The Future Envelope 12 final event 20-21 May 2019, Bolzano
  17. 17. Influence of Shape Shaping Strategies • Tapering and setbacks • Varying cross-section shape • Spoilers • Porosity or openings The Future Envelope 12 final event 20-21 May 2019, Bolzano
  18. 18. “We virtually designed [the tower] in a wind tunnel” Bill Baker of Skidmore Owings & Merrill Discussing the Burj Dubai Project The Future Envelope 12 final event 20-21 May 2019, Bolzano
  19. 19. Burj Khalifa: Changing Cross Section, Orientation & Taper. Lower impact wind direction Higher impact wind direction NORTH The Future Envelope 12 final event 20-21 May 2019, Bolzano
  20. 20. 2020 Tapered Box 100 o Configuration 110 o Configuration 120 o Configuration 180 o Configuration SHANGHAI TOWER, CHINA - Final Configuration The Future Envelope 12 final event 20-21 May 2019, Bolzano
  21. 21. Benefits of Optimization due to Twist and Building Orientation: Comparison of Base Overturning Moments = + ( ) ( . )Max Min2 2 0 6Ref.Resultant Reference Configuration Test Date My (N-m) Ratio Mx (N-m) Ratio Ref. Resultant Ratio Base (Tapered Box) 08/22/2008 5.45E+10 100% 4.98E+10 100% 6.22E+10 100% 100o (107o ) 07/28/2008 4.53E+10 83% 4.19E+10 84% 5.18E+10 83% 110 o (118 o ) 08/22/2008 3.97E+10 73% 4.31E+10 87% 4.92E+10 79% 180 o (193 o ) 07/28/2008 3.39E+10 62% 3.65E+10 73% 4.18E+10 67% 120 o (129 o ) - 0° Rot. 12/12/2008 3.69E+10 68% 3.79E+10 76% 4.39E+10 71% 110 o (118 o ) - 30° Rot. 09/29/2008 3.92E+10 72% 3.60E+10 72% 4.48E+10 72% 120o - 40° Rot. 09/29/2008 3.57E+10 66% 3.53E+10 71% 4.15E+10 67% Assume the same structural properties for all configurations (Vr=52m/s, 100-yr wind, damping=2.0%) 0° Rot. – Original 110° Shape Footprint Position 30° Rot. – Optimal Orientation of 110° Shape 40° Rot. – Optimal Orientation of 120° Shape Final Configuration 50 Million Dollars of savings on the structure The Future Envelope 12 final event 20-21 May 2019, Bolzano
  22. 22. “Softened” corners The Future Envelope 12 final event 20-21 May 2019, Bolzano Sensitivity to Corner Details
  23. 23. Image: Copyright DBOX for CIM Group and Macklowe Properties 432 Park Avenue New York City Architect: Rafael Vinoly Structural: WSP The Future Envelope 12 final event 20-21 May 2019, Bolzano
  24. 24. 432 Park Avenue: Exploration of Openings Initial wind tunnel model of 432 Park Avenue which included a worst case baseline 432 Park Avenue with double story openings at five levels The Future Envelope 12 final event 20-21 May 2019, Bolzano
  25. 25. Cladding Damage from Hurricane Wilma Majority of insured losses are from cladding failures Wind loads on façades The Future Envelope 12 final event 20-21 May 2019, Bolzano Methodologies to asses the wind loads on the façade: • Desk Based Approach • CFD • Wind Tunnel Study
  26. 26. The Future Envelope 12 final event 20-21 May 2019, Bolzano Desk Studies
  27. 27. The Future Envelope 12 final event 20-21 May 2019, Bolzano CFD
  28. 28. • Steady state analysis is most commonly undertaken as it is relatively cheap/quick • Reasonable simulation of mean conditions • Misses the gusts which are important • Can significantly over/under predict pressures • Does not always capture localised effects The Future Envelope 12 final event 20-21 May 2019, Bolzano Wind Tunnel Vs CFD • Transient simulation captures both means and gusts • A sufficiently long simulation gives results similar to wind tunnel • Significantly more time consuming than steady state and wind tunnel • Not cost effective to simulate more than 4-12 wind directions (wind tunnel usually test 18-36)
  29. 29. • Wind loads may be difficult to predict because: • Complex building shape • Interference effects of neighbouring buildings • Flexible building • Complex terrain • Lack of resolution provided by building codes • Computational programs (CFD) are not sufficient The Future Envelope 12 final event 20-21 May 2019, Bolzano Why Would we Conduct an Experiment?
  30. 30. Wind loads on façades Wind tunnel testing Pressure taps inside model Schematic representation of cladding pressures The Future Envelope 12 final event 20-21 May 2019, Bolzano
  31. 31. • System where a second skin is placed in front of a inner skin • There is a gap between the skins that can vary from 100 mm to a couple of metres • The gap is often ventilated • Provides a number of benefits • Thermal • Sound • Shading Double Skin Facades The Future Envelope 12 final event 20-21 May 2019, Bolzano
  32. 32. • Knowing the proportion of the pressure carried by each skin is important for the design • There are limited guidelines and codes of practices. • Research is still ongoing • The pressures are highly dependent on the detailing Horizontal Seal Horizontal Seal Horizontal Vent Double Skin Facades The Future Envelope 12 final event 20-21 May 2019, Bolzano
  33. 33. • For single-surface elements exposed to wind on opposite sides, such as glass parapets, signs and canopies, the differential pressure is important for design • This net pressure can be determined by measuring the instantaneous pressure difference across the element in the wind tunnel • This pressure is often higher than those acting on the nearby elements of the façade which enclose an internal volume Tap on rear surface Tap on front surface Parapets, Signs etc. The Future Envelope 12 final event 20-21 May 2019, Bolzano
  34. 34. There are a number of non wind related issues that are important for the design of the building envelope • Glare • Thermal performance • Falling snow and ice • Icing • Rainwater Runoff The Future Envelope 12 final event 20-21 May 2019, Bolzano Non Wind Related Issues
  35. 35. Issues: - Ground-Based uses Vehicular Traffic both Private and Public - Airborne travel - Aircraft - Problems with Automated systems; - Impacts on neighbours - Can impact over significant distances - Limited criteria for determining an impact Prevention: - Textured façade materials, or in less sensitive areas - Early assessment is easily accomplished, and can be quickly repeated - Assessments can be high-level or detailed as appropriate - Mitigating post-construction is apparent, and costly both physically and in terms of building perception The Future Envelope 12 final event 20-21 May 2019, Bolzano Glare
  36. 36. Issues - Increased load on heating/cooling systems - Construction Cost vs Operational Costs - Difficult to Achieve benefits in dense urban areas - Impacts on automated systems Prevention - Façade materials, performances and composition; - Early assessment is easily accomplished, and can be quickly repeated - Assessments can be high-level or detailed as appropriate - Mitigating post-construction is costly to a building operator/owner The Future Envelope 12 final event 20-21 May 2019, Bolzano Thermal Performance
  37. 37. The Future Envelope 12 final event 20-21 May 2019, Bolzano Issue: - Increased rooftop/sloped surface loads - Danger to pedestrians - Impacts on building performance - Can be short or long-term, dependent on climate - Most issues are post-construction mitigation Prevention - Management of the risks - Favourable design can reduce/eliminate concerns - Establishing robust monitoring and prevention processes Falling Snow and Ice
  38. 38. The Future Envelope 12 final event 20-21 May 2019, Bolzano Issue • Generally a short-term problem • Usually during significant events • Affects pedestrian comfort, usually not users of the building itself • Effects are complex, typically unexpected • Usually post-construction concern • Drive for naturally ventilated spaces Prevention - Favourable design can reduce/eliminate concerns (orientation, form); - Consideration of wind driven aspects, not just drainage - Compliance or exceedance of appropriate code/requirements Rainwater Runoff
  39. 39. The Future Envelope 12 final event 20-21 May 2019, Bolzano Stack effect
  40. 40. The Future Envelope 12 final event 20-21 May 2019, Bolzano Smoke Management Systems
  41. 41. The Future Envelope 12 final event 20-21 May 2019, Bolzano Problem Sources • Fume hood stacks • Incinerators • Boilers • Emergency generators • Cooling Towers • Kitchen exhaust • Loading docks • Road traffic • Garbage • Emissions from neighbours Building Air Quality
  42. 42. Conclusions and summary • A climate-aware design of building forms requires the understanding of aerodynamic and environmental issues • Wind-induced phenomena can cause high wind loads and serviceability issues which can compromise the usability of the external spaces and the comfort of building occupants • Various shaping strategies can be effective to enhance the aerodynamic and environmental performances • Other environmental effects have also a great potential to impact neighbours and they can be looked at holistically for high- performance developments The Future Envelope 12 final event 20-21 May 2019, Bolzano
  43. 43. Thank you for your attention! www.interreg.net Chiara Pozzuoli RWDI Chiara.Pozzuoli@rwdi.com FACEcamp is funded by European Regional Development Fund and Interreg V-A Italy-Austria 2014-2020.

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