Overview of building codes and CUBiC. Discussion of wind loading in St Lucia. Tony Gibbs

Transcription

1 Overview of building codes and CUBiC National adoptions in the Eastern Caribbean Discussion of wind loading in St Lucia Consulting Engineers Partnership Ltd 1

2 Codes = laws and regulations Standards = technical provisions History pre CCEO 1969 the formation of the CCEO Timber Earthquakes Wind Masonry GAPE APETT BAPE JIE 2

3 History The early 1970s Three conferences in Jamaica 1978 The First Caribbean Earthquake Engineering Conference in Trinidad History 1979 The Caribbean Disaster Preparedness Conference in St Lucia The conception of CUBiC 3

4 History 1979 The CARICOM Council of Ministers of Health 1980 Disaster Preparedness Conference in Dominican Republic (CUBiC project formulation) History 1980 Funding meeting in Washington CUBiC project preparation CUBiC project execution 4

5 Contents Part 1 Administration and Enforcement of the Code Part 2 Structural Design Requirements Part 3 Occupancy, Fire Safety and Public Health Requirements Part 4 Services, Equipment and Systems (Not Included in Present CUBiC) Part 5Small Buildings Contents Part 2 Section 1 Section 2 Section 3 Section 4 Section 5 Section 6 Section 7 Section 8 Structural Design Requirements Dead Load and Gravity Live Load Wind Load Earthquake Load Block Masonry Foundations (not Included in Present CUBiC) Reinforced and Prestressed Concrete Structural Steel Structural Timber 5

6 Earthquake Loads and Design Provisions o o o Historical observations of successes and failures Equivalent static forces Dynamic analysis 6

7 History 1967 Caracas Earthquake 1971 Key, Tomblin, Imbert 1974 Antigua Earthquake 1969 SEAOC 1979 First Caribbean Conference on Earthquake Engineering Principia Mechanica 1997 Cariaco and Tobago Tb Earthquakes 2003 Dominican Republic Earthquake EUCENTRE SRC Study 2010 Haiti Earthquake 1967 Caracas Earthquake: soils, non structural infill, overturning 7

8 Photo: David Key 8

9 Photo: Photo: The 09 July 1997 Cariaco Earthquake north-east of Venezuela Photo: Photo: The 09 July 1997 Cariaco Earthquake north-east of Venezuela 9

10 The 22 Sep 2003 Earthquake north of Hispañola The 22 Sep 2003 Earthquake north of Hispañola Photo: Daniel Comarazamy 10

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13 NATIONAL CATHEDRAL Photo: GADR 13

14 World Bank ECCR Workshop in St Vincent 26 January 2012 Photo: Julian Jackson Fuel Port 14

15 Fuel Port 15

16 Design Philosophy Protect lives rather than property Structures designed in conformance with the provisions and principles i set forth hin CUBiC:Part 2:Section 3 2S i should, in general, be able to: 1 resist minor earthquakes without damage; 2 resist moderate earthquakes without structural damage, but with some non structural damage; 3 resist major earthquakes, of the intensity of severity of the strongest experienced in (the target area), without collapse, but with some structural as well as non structural damage. 16

17 Concrete Behavior A sp f yh A sp d s f yh A sp Confinement from spiral or circular hoop Forces acting on 1/2 spiral or circular hoop Confinement from square hoop Column with spiral reinforcement 17

18 Column with inadequate ties Wind Loads and Design Provisions 18

19 CP3 Chapter V:Part mph 1 minute average (= 93 mph or 41 m/s 3 second gust) Rudimentary procedures South Florida Building Code 1960s 120 mph fastest mile (= 137 mph or 61 m/s 3 second gust) Rudimentary procedures 19

20 The Council of Caribbean Engineering Organisations (CCEO) 1969 gave a mandate to the Barbados Association of Professional Engineers (BAPE) to prepare a wind load standard, AR Matthews, HC Shellard Wind Loads for Structural t Design 1970 including HC Shellard HC Shellard Extreme Winds in the Commonwealth Caribbean 20

21 Our first modern standard Based on the approach of the 1972 edition of the British Standard CP 3:Chapter V:Part 2 (also the guide for the 1970s Australian standard and the Brazilian standard) Over 80 pages: o procedures o extensive range of pressure and force coefficients i o several appendices of explanatory background to the procedures the suitable textbook of fundamentals Basic wind speed V (3 second, 33 ft, 50 year, open terrain) Topographic factor S1 Terrain roughness, height, size S2 Importance S3 Design wind speed VS = V x S1 x S2 x S3 Pressures derived from VS 21

22 Durst-Deacon 22

23 Suggested Basic Wind Speeds (mph, 3s) for Some Commonwealth Caribbean Countries 1970 Jamaica 120 (= 54 m/s) BVI 120 (= 54 m/s) Leeward Islands 120 (= 54 m/s) St Lucia, St Vincent 120 (= 54 m/s) Barbados 120 (=54 m/s) Grenada, Tobago 100 (= 45 m/s) Trinidad 90 (= 40 m/s) Guyana 50 (= 22 m/s) 23

24 1981 Revision of Wind Loads for Structural Design (3s) CCEO BAPE NCST OAS HE Browne BA Rocheford Procedures for aerodynamically sensitive structures (< 1Hz) Jamaica 56 m/s (= 125 mph) BVI 64 m/s (= 143 mph) Leeward Islands 64 m/s (= 143 mph) St Lucia, Dominica 58 m/s (= 130 mph) Barbados, St Vincent 58 m/s (= 130 mph) Grenada, Tobago 50 m/s (= 112 mph) Trinidad 45 m/s (= 101 mph) Guyana 22 m/s (= 49 mph) BA Rocheford (Caribbean Meteorological Institute) 1984 Revision of Wind Speeds 10 minute Belize Centre 29.0 m/s (= 65 mph) [= 93 mph 3s] Jamaica N 37.0 m/s (= 83 mph) [= 119 mph 3s] Jamaica S 41.0 m/s (= 92 mph) [= 132 mph 3s] St Kitts 44.5 m/s (= 100 mph) [= 143 mph 3s] Antigua 46.0 m/s (= 103 mph) [= 147 mph 3s] Dominica 41.0 m/s (= 92 mph) [= 132 mph 3s] St Lucia 43.0 m/s (= 96 mph) [= 137 mph 3s] Barbados 42.0 m/s (= 94 mph) [= 134 mph 3s] Tobago 31.5 m/s (= 70 mph) [= 100 mph 3s] Trinidad Central 27.5 m/s (= 62 mph) [= 89 mph 3s] 24

25 The Caribbean Uniform Building Code (CUBiC:1985) The Boundary Layer Wind Tunnel Laboratory (University of Western Ontario) Davenport Surry Georgiou Simulation of hurricane wind climate using: o drop in barometric pressure; o radius of the ring to maximum wind speeds; o translation speed; o angle of its track; o position of the point of interest relative to the centre of the storm. 25

26 CUBiC:1985 (forerunner of ISO 4354:1997) UWO BLWTL o o Reference pressures (10 minute average wind speeds adjustments for height and ground roughness; shape and size; dynamic response: w = (q ref )(C exp )(C shp )(C dyn ) CUBiC Part 2 Section 2 26

27 Maximum Wind Speeds (50 year return) 23 N 89.5 W 59 W CDMP knots mph kph m/s 9 N Storm Category Wind Speeds

28 Ir P C van Staalduinen and Dr Ir C P W Geurts TNO (Netherlands Organisation for Applied Scientific Research) Hurricane Hazard in the Netherlands Antilles

29 1999: CARICOM decision to adopt and adapt the I codes of the ICC 2000: The I codes adopt by reference the wind load provisions of the ASCE : PAHO executed a project, funded by USAID for the preparation ofthe Caribbean Application Document (CAD) for ASCE 7 05 Ch 6. The trend for Caribbean standards is to adopt and adapt the ASCE 7 approach (Dominican Republic, new CUBiC, Cayman, Bahamas) 29

30 Wind Hazard Maps for the Caribbean Basin (3 second mph at 33ft) Overall region and individual islands April 2008 Principal researcher Applied Research Associates (Peter Vickery) Regional coordinator (CEP International Ltd) Executing agency Pan American Health Organisation (Dana van Alphen) Funding agency United States Agency for International Development (Tim Callaghan and Julie Leonard) Caribbean Basin Wind Hazard Maps: a series of overall, regional, wind hazard maps using uniform, state of the art approaches covering all of the Caribbean islandsandthe Caribbeancoastal areasof South and Central America. 30

31 Contour plots of modelled minimum central pressures (mbar) 50 year return period. Contours represent the minimum pressure anywhere within 250 km of a point 50 Year Wind Speeds for Caribbean

32 100 Year Wind Speeds for Caribbean Year Wind Speeds for Caribbean

33 1700 Year Wind Speeds for Caribbean

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37 Location Return period (years) Peak gust wind speeds (mph) in flat open terrain as a function of return period for selected locations in the Caribbean Trinidad (S) Trinidad (N) Isla Margarita Grenada Bonaire Curacao Aruba Barbados Saint Vincent Saint Lucia Martinique Dominica Guadeloupe Montserrat St. Kitts and Nevis Antigua and Barbuda Saint Martin/Sint Maarten Anguilla US Virgin Islands British Virgin Islands Grand Cayman Little Cayman/Cayman Brac Turks & Caicos (Grand Turk) Turks & Caicos (Providenciales) Eleuthera Andros New Providence (Nassau) Great Abaco Grand Bahama (Freeport) Belmopan miles per hour Wind Load Factor Non-Hurricane Hurricane Return Period (Years) Wind load factor (V T /V 50 ) 2 for Hurricane and Non Hurricane Wind Speeds plotted vs return period 37

38 Wind Load Factor Non-Hurricane Hurricane Return Period (Years) Contour plots of (V 700 /V 50 ) 2 38

39 World Bank ECCR Workshop in St Vincent 26 January Contour plots of importance factor for ASCE category III and IV structures defined by I=(V 1700 /V 700 ) 2 o o o o ASCE 7Basic Wind Speed, V 3 sec, 33 ft height, Exposure C, 50 years For same level of safety in the Caribbean a pseudo 50 year wind speed = V 700/ 1.6 must be used instead of the real V 50. Alternatively the real V 50 could be used with an upward adjustments to the Load Factors and Importance Factors. Alternatively, the Basic Wind Speed could be taken y, p as V 700 for Category II buildings and V 1700 for Categories III and IV buildings, with the Load Factor and Importance Factor = 1. This last approach will be simpler in a regional context. 39

40 The 700 year Return Period: 1 50 year return period for non hurricane areas 2 Load factor = Failure load produced by 50 year wind speed x Use 700 year wind with load factor of 1 Load Combinations (factored loads using strength design) 1: 1.4(D + F) 2: 1.2(D + F + T ) + 1.6(L + H) + 0.5(Lr or S or R) 3: 1.2D + 1.6(Lr or S or R) + (L or 0.8W) 3a: 1.2D + 1.6(Lr or R) + (L or 0.8W700/1.6) 4: 1.2D + 1.6W + L + 0.5(Lr or S or R) 4a: 1.2D + 1.0W700 + L + 0.5(Lr or R) 5: 1.2D + 1.0E + L + 0.2S 6: 0.9D + 1.6W + 1.6H 6a: 0.9D + 1.0W H 7: 0.9D + 1.0E + 1.6H 40

41 SYMBOLS AND NOTATION D = dead load Di = weight of ice E = earthquake load F = load due to fluids with well defined pressures and maximum heights Fa = flood load H = load due to lateral earth pressure, ground water pressure, or pressure of bulk materials L = live load Lr = roof live load R = rain load S = snow load T = self straining force W = wind load Wi = wind on ice determined in accordance with Chapter 10 Load Combinations (nominal loads using allowable stress design) 1: D + F 2: D + H + F + L + T 3: D + H + F + (Lr or S or R) 4: D + H + F (L + T ) (Lr or S or R) 5: D + H + F + (W or 0.7E) 5a: D + H + F + (W700/1.6 or 0.7E) 6: D+H+F+0.75(W or 0.7E)+0.75L+0.75(Lr 0 0 5( or S or R) 6a: D+H+F+0.75(W700/1.6 or 0.7E)+0.75L+0.75(Lr or R) 7: 0.6D + W + H 7a: 0.6D + W700/1.6 + H 8: 0.6D + 0.7E + H 41

42 ASCE 7 was written for the USA which h has a mixture it of hurricaneprone regions and non hurricane regions. The CAD will eliminate all references to non hurricane regions. ASCE 7 allows three methods for determining i wind dforces on structures: Method 1: Simplified (tables & limited use) Method 2: Analytical (almost all cases) Method 3: Wind Tunnel (unusual cases) 42

43 Method 1: Simplified The building must be: 1. a simple diaphragm building; 2. a low rise building; 3. enclosed and conform to the wind borne debris provisions; 4. a regular shaped building or structure; 5. not classified as a flexible building; 6. not assessed as having unfavourable aerodynamic characteristics and not having an unfavourable site location; 7. of a structure with no expansion joints or separations; 8. not subject to unfavourable topographic effects; 9. of an approximately symmetrical cross section. Method 2: Analytical The Design Procedure requires the following steps: 1. basic wind speed V and wind directionality factor K d 2. importancefactor I 3. exposure category or exposure categories and velocity pressure exposure coefficient K z or K h 4. topographic factor K zt 5. gust effect factor G or G f, 6. enclosure classification 7. Internal pressure coefficient Gc pi 8. External pressure coefficients C p or GC pf, or force coefficients C f 9. Velocity pressure q z or q h, 10. Design wind load p or F 43

44 o o o A lengthy process but, ASCE 7 provides most of the answers in tables and figures. A growing reliance on proprietary software for the use of computers in the determination of wind forces The negative effect of reducing the understanding of engineers in the fundamentals of wind forces on structures more likely that gross errors would occur There is debate over the wind directionality factor K d where it is applied to round chimneys and similar shaped structures. (See Rolando Vega s paper.) 44

45 The penalties in the form of increased loads for buildings without impactresistant glazing or impact resistant, permanently installed shutters are severe. This should provide significant impetus for owners, designers and builders to incorporate impact resistant windows or shutters in buildings. o o o Topographic effects are very important in most Caribbean countries. This issue receives attention in ASCE 7. Wind speed up is recognised over hills, ridges, and escarpments. Valleys are missing. 45

46 Photo: UWO BLWTL Sketch showing effects of topography on wind velocity on a hilly island V g 100 Speed up V s 120 V g 100 V g 100 Vg 100 V m s V s Open sea Winward Speed up over Sheltered leeward Coast hill crest coast 46

47 Winds N Probability 1% / year, 100-Year Return Time Antigua 1. St. John s Downtown East side of town 47 m/s 51 m/s 2. Parham Desalinization plant 50 m/s Wt Waterfront tby town 47 m/s Hill above town 53 m/s 3. English and Falmouth Harbours Nelson s Dockyard 48 m/s Falmouth SE 41 m/s Falmouth NW 52 m/s 4. Jolly Harbour Channel entrance Inner boat basin Beach front 45 m/s 44 m/s 45 m/s W Ross Wagenseil for PGDM April W Directory Topo. Map 10yr 25yr 50yr 100yr Wind Wave Surge AR RC-MINUTES KILOMETERS N MILES Storm Category knots mph m/s N Wind Speeds 3 PGDM May Min Max Winds N CDMP 100-Year Return Time 72 W Dominican Republic 68 W DEGREES MILES KIL LOMETERS N 17.5 N Ross Wagenseil for CDMP January Storm Category knots mph kph m/s Wind Speeds Return to Directory Wind Wave Surge 10yr 25yr 50yr 100yr West Basin Mid- Basin Caribbean East Basin 47

48 Risk Management Solutions Topographic effect showing wind velocity increase z z z V(z) x (windward) V(z) H/2 H speed up x (leeward) z V(z) x (windward) V(z) H/2 H speed up x (leeward) L m H/2 L m H/2 Hill Escarpment 48

49 Pre-Ivan photograph by Brooks La Touche Pre Ivan photograph by Brooks La Touche 49

50 Photo: The National Stadium Method 3 Wind Tunnel Procedure o o Wind tunnel testing is no longer unknown in the design of Caribbean buildings. Used for: overall loads on the main wind force resisting systems; pressures on external cladding; pedestrian conditions adjacent to buildings. 50

51 Present Standards and Codes CUBiC and national codes Barbados Belize OECS (9 states) Bahamas South Florida Building Code Cayman Southern Building Code Congress International TCI hybrid (USA and CUBiC) Guyana (?) Jamaica (IBC) Trinidad & Tobago (in preparation) 51

52 The New CUBiC (or CUBiS) to be based on the IBC CUBiS countries: Barbados Belize Guyana Jamaica Trinidad & Tobago OECS (9 states) Othersimilar countries Bahamas SFBC >> IBC Cayman SBCCI >> IBC TCI hybrid >> IBC Dominican Republic >> IBC approach Components (agreed by CCEO & CARICOM in March 1999) 1 Caribbean Application Document (CAD) based on IBC 2 Caribbean Residential Design Standards 3 Model Laws and Regulations 52

53 Components 1 Caribbean Application Document (CAD) based on IBC a Use IBC 200? (The soon to be published version is 2006.) b Delete clauses?? c Amend clauses?? by replacing them with d Add clauses as follows: Components 2 Caribbean Residential i lstandards d a b c Not necessarily based on IRC 200? Consistent with the CAD Prescriptive and necessarily more conservative than CAD 53

54 Components 3 ModelLaws and Regulations a Each Caribbean state may wish to have its own laws and regulations. b It would be desirable if there were similarities of approach and content. Country Standards Laws Enforcement Status Anguilla Y Y Y Antigua Y Y Y? Bahamas Y Y Y Barbados Y N N Belize Y N N BVI Y Y Y? Cayman Y Y Y Dominica Y Y? N Grenada Y Y Y? Guyana N N N Jamaica Y Y Y Montserrat Y Y Y St Kitts Y Y Y? St Lucia Y N N St Vincent Y N N TCI Y Y Y Trinidad N Y Y 54

55 AMO = Atlantic multi decadal oscillations 55

56 NAtl = North Atlantic The Impact of Climate Change on Design Wind Speeds in Saint Lucia 2008 Peter J. Vickery 56

57 Percentage Increase in Basic Wind Speed in Lucia vs. Percentage Increase in Annual Rates of Category 4 and 5 Hurricanes 15% Increase in Basic Wind Speed 10% 5% Category II Buildings Category III and IV Buildings 113 0% 0% 50% 100% 150% 200% 250% 300% 350% Projections According to Curry et al. (2007), there could be an average of three to four Category4 and 5 hurricanes per year by 2025in the Atlantic Basin. This represents a 210 to 280 percent increase in the number of Category 4 and 5 hurricanes compared to the long term ( ) average of 1.4 Category 4 and 5 hurricanes per year. If this were the case, the basic wind speeds for Category II buildings in Saint Lucia should be increased by about 12 to 14 percent, and the basic wind speeds for Category III and IV buildings should be increase by about 10 percent. Note that the increases in the basic wind speeds assume that the hurricane hazard remains elevated for the expected life of the building