Disaster Mitigation in Health Facilities: Wind Effects Structural Issues Disaster Mitigation in Health Facilities: Wind Effects Structural Issues

2 Hurricane paths in the Caribbean Region during 1998

3 Hurricane Georges’ path

4 Hurricane Mitch’s path

5 Floods are a very important consequence of hurricanes

6 Natural hazards impact in health facilities ( ) According to the Pan American Health Organization, between 1981 and 2001 more than 100 hospitals and 650 health centers suffered serious damages as a result of natural disasters. The Economic Commission for Latin America and the Caribbean (ECLAC) reported direct economic losses of US$ 3,120 million. This could be compared to an extreme situation in which 20 countries in the region had each suffered the loss of 6 major hospitals and 25 health centers.

7 Hospitals are specially vulnerable to natural hazards  The occupancy rate is constant, 24 hours a day, year-round. It is almost impossible to evacuate a hospital in the event of an emergency.  The survival of some patients depends on the proper operation of the equipment and the continuity of basic services.  Hospitals are highly dependent on public utilities (water, electricity, communications, etc.) which are often interrupted by the effects of a disaster.  In emergencies and disasters, health facilities are essential and must continue to function after the event has taken place.

The ingredients a hurricane needs Warm water – above 80ºF Converging winds Unstable air Humid air being pulled into the storm(up to about 18,000 ft) Pre-existing winds coming from nearly the same direction An upper atmosphere high-pressure area helps pump away air rising in the storm

9 Hurricane stages during its path towards the Caribbean Region 9 Tropical Disturbance Tropical Depression Tropical Storm Tropical Storm Hurricane

10 Anemogram of Hurricane Georges

11 Saffir-Simpson scale for hurricane categories CategoryVelocity 1 minute (km/hr) Pressure (mb) Damages > 980Minimum 2150 – – 980Moderate 3175 – Extensive 4210 – Extreme 5> 250< 920Catastrophic

12 Hurricanes categories in the North Atlantic and the Caribbean Region

13 Turbulent flow of wind on longitudinal and transverse sides of high-rise buildings

14 Turbulent flow on high-rise buildings due to upwind obstructions

15 Wind velocity increase due to large openings at lower floors

16 Wind flow on gabled roof buildings showing turbulence on leeward roof and walls

17 Wind’s basic pressure Dynamic part of Bernoulli’s basic equation

18 StandardIdentification ISOInternational Standard Organization CUBiCCaribbean Uniform Building Code ENVEurocode DRBCDominican Republic Building Code AIJJapan Standard ASAustralian Standard BNSCPBarbados Standard Different international design standards

19 Different calculations for design wind speeds and dynamic pressures AS BNSCP28 AIJ DRBC-03 ENV CUBiC ISO 4354 Building Pressure/Force PressureSpeedStandard

20 Building Shape/Type ISO 4354 CUBiCENV 1991 DRBC 2003 AIJAS BNS CP28 Stepped Roofsno yesno yes Free-standing wallsyes noyesno Multispan canopiesno yes no Arched roofsyes Domesno yesnoyesno Silos and tanksyes noyesno Circular sectionsyes Polygonal sectionsno yesno yes Lattice towersyes noyes Spheresnoyes no yes Signsyes Building types in seven international wind standards

21 The trend for international standards is to adopt and adapt the ASCE-7 approach for primary systems.

22 NotationFactor What does it mean? Directionality Takes into account the probability that the maximum wind has the same direction as that of the maximum pressure Importance I Converts a 50-year return period into a 100-year return period recommended for hospitals Exposure Represents the wind velocity at a ‘z’ height above the ground Topography Takes into account the fact that the structure may be located on top of a hill or on an escarpment, increasing the wind velocity Meaning of factors in ASCE-7

23 NotationFactor What does it mean? 3-sec gust G Represents the turbulence-structure interaction and the dynamic amplification of the wind External pressure coefficient Estimates the wind pressure on the building, external walls Internal pressure coefficient Reflects the internal pressure due to wall opening quantity and sizes Design pressure pRepresents the design pressure Design force F Represents the net force on open structures Meaning of factors in ASCE-7

24 Effects of terrain roughness and height on wind speeds

25 Effects of exposure and altitude

Case 1Case 2 Case 1 and 2 Case 1Case 2 Case 1 and 2 ≤ Height Z (m) B C BC Exposure Exposure Coefficients K z K h Exposure type B C NOTE: 1.Case 1 shall be used for all primary systems in buildings with height ‘h’ less than 18 m and for secondary systems of any type of structure 2.Case 2 shall be used for all primary systems of any other structure not indicated in case 1 3.For values of Z not shown, linear interpolation shall be permitted

27 Topographic effect showing wind velocity increase

28 Sketch showing effects of topography on wind velocity on a hilly island

29 Different ways of measuring wind velocity Average time Wind velocity 1 Hour minutes Fastest mile second gust

30 N knots mph kph m/s Storm Category N 89.5 W 23 N 59 W Wind velocities in the Caribbean for a return period of 100 years

31 Modified basic pressure- ASCE-7 Modified basic pressure in ASCE-7 to accommodate local parameters

32 A high percentage of wall openings are dangerous for a health facility

33 Different types of forces acting on structural elements

34 Wind can induce torsional effects on structural steel

35 Design pressure on primary systems (structural) Rigid primary systems Flexible primary systems p = q GC p - q h (GC pi ) p = qG f C p - q h (GC pi )

36 Pressure coefficients on high- rise buildings

37 Design pressure diagram on gabled roof building

38 Total destruction of Princess Margaret Hospital in Jamaica

39 Absence of an appropriate anchorage led to the overturning of a clinic

40 Failure of steel beams support

41 Timber roof split due to strong hurricane winds

42 In health facilities, a connection between structural elements and the roof must be adequate

43 Construction close to the sea shore might result in great losses

44 When there is a lack of symmetry among resisting elements, wind will induce torsional effects

45 Hipped roofs with slope from 20 to 30 degrees interact better with the wind forces

46 Pressure increase due to wind on overhanging roofs

47 Protection effect of hospital building A favorable location of adjacent buildings can decrease the hurricane effects by reducing the wind loads

48 Unfavorable location of buildings adjacent to a hospital A bad location of nearby buildings might induce increase of wind loads

49 Bridge base erosion as a consequence of river flow increase

50 Landslide obstructing highway access

51 Pressure sketch for wind perpendicular to the ridge on a pitched-roof industrial building

52 Pressure sketch for wind parallel to the ridge on a pitched-roof industrial building

53 Flat-slab systems without capitals present little resistance against lateral forces. Their use on hospitals should be avoided

54 Wind load path on pitched-roof buildings

55 Structural steel frame collapsed due to strong winds

56 Hurricane design philosophy for hospitals The hospital structure must be designed and built in such a way that it:  withstands, without any damage, the design hurricane event;  withstands, with minor and easily repaired damage, hurricanes greater than the design event.

57 Vulnerability assessment objectives Available methodologies Available methodologies  Qualitative methods  Quantitative methods To evaluate the likelihood of a structure suffering damage due to the effects of a hurricane, and to characterize the possible damage Objective

58 Qualitative methods Qualitative methods for vulnerability assessments They assess quickly and simply the structural safety conditions of the building, taking into account the following parameters: The age of the building The state of conservation and maintenance The characteristics of the materials used The number of stories The architectural plan

59 Quantitative methods Quantitative methods for vulnerability assessments The goal is to determine the levels of resistance of the structure by means of an analysis similar to that used in new buildings and incorporating nonstructural elements.

60  The goal is to ensure that the health care facility will continue to function after a hurricane, by reinforcing existing components or incorporating additional structural components to improve the levels of strength and stiffness.  The retrofitting measures should not interfere with the operation of the hospital during the process. Structural retrofitting

61 Detail of stud to concrete footing connection Galvanized strap min. depth 3'-0" Ground surface Concrete base Concrete pier Double base plate Stud Stud to concrete connection

62 Stud and top plate connection

63 Rafters and top plates should be anchored with galvanized straps

64 Anchorage of timber beams to concrete beams Use of galvanized hurricane straps is recommended

65 Anchorage details between steel joist and masonry walls

66 Interaction between structural and nonstructural elements

67 Considerations for infilling masonry partitions If the infilling masonry wall acts as part of the structural system, it will undergo great deformations and failures

68 Reinforcement method: addition of (interior or exterior) walls

69 Retrofitted wall in children’s hospital in Santo Domingo

70 Details of retrofitted wall sections

71 Construction method details of retrofitted wall

72 Front view of retrofitted wall

73 Lateral view of retrofitted wall

 Pan American Health Organization 2005 These slides have been made possible through the financial support of the Disaster Preparedness Program of the European Commission Humanitarian Aid Department (DIPECHO III). Ph: (809) Fax: (809) Grupo de Estabilidad Estructural (Ge 2 ) / INTEC Ave Los Próceres, Galá Apdo Santo Domingo, Dominican Republic