Disaster Mitigationin Health Facilities:

Wind EffectsStructural Issues

Disaster Mitigationin Health Facilities:

Wind EffectsStructural Issues

22

Hurricane paths in the Hurricane paths in the Caribbean Region during 1998Caribbean Region during 1998

33

Hurricane Georges’ path - 1998Hurricane Georges’ path - 1998

44

Hurricane Mitch’s path - 1998Hurricane Mitch’s path - 1998

55

Floods are a very important Floods are a very important consequence of hurricanesconsequence of hurricanes

66

Natural hazards impact in Natural hazards impact in health facilities (1981 - 2001)health facilities (1981 - 2001)Natural hazards impact in Natural hazards impact in health facilities (1981 - 2001)health facilities (1981 - 2001)

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.

77

Hospitals are specially Hospitals are specially vulnerable to natural hazardsvulnerable to natural hazardsHospitals are specially Hospitals are specially vulnerable to natural hazardsvulnerable 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 The ingredients a hurricane a hurricane

needsneeds

•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

99

Hurricane stages during its path Hurricane stages during its path towards the Caribbean Region towards the Caribbean Region

9

Tropical Disturbance

Tropical Disturbance

Tropical Depression

Tropical Depression

Tropical

Storm

Tropical

Storm

HurricaneHurricane

1010

Anemogram of Hurricane Anemogram of Hurricane Georges - 1998Georges - 1998

1111

Saffir-Simpson scale Saffir-Simpson scale for hurricane categoriesfor hurricane categories

Category Velocity1 minute

(km/hr)

Pressure(mb)

Damages

1 120 - 150 > 980 Minimum

2 150 – 175 965 – 980 Moderate

3 175 – 210 945 - 965 Extensive

4 210 – 250 920 - 945 Extreme

5 > 250 < 920 Catastrophic

1212

Hurricanes categories in the Hurricanes categories in the North Atlantic and the North Atlantic and the Caribbean Region 1944-2001Caribbean Region 1944-2001

1313

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

1414

Turbulent flow on high-rise Turbulent flow on high-rise buildings due to upwind buildings due to upwind obstructionsobstructions

1515

Wind velocity increase due to Wind velocity increase due to large openings at lower floorslarge openings at lower floorsWind velocity increase due to Wind velocity increase due to large openings at lower floorslarge openings at lower floors

1616

Wind flow on gabled roof Wind flow on gabled roof buildings showing buildings showing turbulenceturbulence on leeward roof on leeward roof and wallsand walls

Wind flow on gabled roof Wind flow on gabled roof buildings showing buildings showing turbulenceturbulence on leeward roof on leeward roof and wallsand walls

1717

Wind’s basic pressureWind’s basic pressure

221 Vq

Dynamic part of Dynamic part of Bernoulli’s basic Bernoulli’s basic equationequation

1818

Standard Identification

ISO International Standard Organization

CUBiC Caribbean Uniform Building Code

ENV Eurocode

DRBC Dominican Republic Building Code

AIJ Japan Standard

AS Australian Standard

BNSCP Barbados Standard

Different international Different international design standardsdesign standards

1919

Different calculations for design Different calculations for design wind speeds and dynamic wind speeds and dynamic pressurespressures

AS1170.2-89

BNSCP28

AIJ

DRBC-03

ENV 1991-2-4

CUBiC

ISO 4354

Building Pressure/Force

PressureSpeedStandard

2ref21

ref Vq

V

V

gusts3V

V

dynfigexpref CCCqW

zplae,pe qKKKCP

peqCP

221

ref Vq

221

ref Vq

2dztz2

1z IVKKKq

2H2

1h Uq

2z2

1h Vq

232121 SSVSq

0,refalttemdirref CCCCV

REEUU gfgH

itscat,zz MMMVV

pihpz GCqGCqp

peeexprefe CZCqW

dynCfigexpref CCqW

AGCqW ffhf

2020

Building Shape/Type

ISO 4354

CUBiC ENV 1991

DRBC2003

AIJ AS1170.2

BNS CP28

Stepped Roofs no no no yes no no yes

Free-standing walls yes yes yes yes no yes no

Multispan canopies no no yes yes no no no

Arched roofs yes yes yes yes yes yes yes

Domes no no yes no yes no no

Silos and tanks yes yes yes yes no yes no

Circular sections yes yes yes yes yes yes yes

Polygonal sections no no yes no no yes yes

Lattice towers yes yes yes yes no yes yes

Spheres no yes yes no no no yes

Signs yes yes yes yes yes yes yes

Building types in seven Building types in seven international wind international wind standardsstandards

2121

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

2222

NotationNotation FactorFactor What does it mean?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 IConverts a 50-year return period into a 100-year return period recommended for hospitals

ExposureRepresents 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

dK

zK

ztK

Meaning of factors in Meaning of factors in ASCE-7ASCE-7

2323

NotationNotation FactorFactor What does it mean?What does it mean?

3-sec gust GRepresents 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 p Represents the design pressure

Design force FRepresents the net force on open structures

pC

piC

Meaning of factors in Meaning of factors in ASCE-7ASCE-7

2424

Effects of terrain Effects of terrain roughness and roughness and height on wind height on wind speedsspeeds

2525

Effects of exposure and Effects of exposure and altitudealtitude

Exposure B

0

100

200

300

400

0 10 20 30 40 50

Exposure C

0

100

200

300

400

0 10 20 30 40 50

Case 1 Case 2Case 1 and 2

Case 1 Case 2Case 1 and 2

≤ 5 .70 .57 .85 32 1.03 1.03 1.30

6 .70 .62 .90 34 1.07 1.07 1.34

8 .70 .67 .96 36 1.10 1.10 1.37

10 .72 .72 1.00 38 1.14 1.14 1.4

12 .76 .76 1.04 40 1.17 1.17 1.43

14 .79 .79 1.07 42 1.20 1.20 1.46

16 .82 .82 1.11 44 1.23 1.23 1.48

18 .85 ..85 1.13 46 1.25 1.25 1.51

20 .88 .88 1.16 48 1.28 1.28 1.53

22 .90 .90 1.18 50 1.30 1.30 1.55

24 .92 .92 1.20 52 1.32 1.32 1.57

26 .93 .93 1.21 54 1.35 1.35 1.59

28 .96 .96 1.24 56 1.37 1.37 1.61

30 .98 .98 1.26 58 1.39 1.39 1.63

Height Z (m) B C Height Z (m) B C

Exposure Exposure

Exposure Coefficients KExposure Coefficients Kzz K Khh

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

2727

Topographic effect showing Topographic effect showing wind velocity increasewind velocity increase

2828

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

10 m

80Vs

100Vg

60

gV100

g

120sV

Vs

V

100gV

40

100

Open sea Wind ward Speed up over Sheltered leeward

coast

Speed up

Coast hill crest

2929

Different ways of Different ways of measuring wind velocitymeasuring wind velocity

Average timeAverage time Wind velocityWind velocity

1 Hour 120 113 91 79

10 minutes 127 120 96 84

Fastest mile 158 149 120 105

3 second gust 181 171 137 120

3030

N

0 1 2 3 4 5knotsmphkphm/s

Storm Category25 50 75 100 125

25 50 75 100 125 150

50 100 150 200 250

10 20 30 40 50 60 70

9 N

89

.5 W

23 N5

9 W

Wind velocities in the Wind velocities in the Caribbean for a return period Caribbean for a return period of 100 yearsof 100 years

3131

2dztz2

1 IVKKKq

Modified basic pressure-Modified basic pressure-

ASCE-7ASCE-7

Modified basic pressure in Modified basic pressure in ASCE-7 to accommodate local ASCE-7 to accommodate local parametersparameters

3232

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

3333

Different types of forces Different types of forces acting on structural acting on structural elementselements

Different types of forces Different types of forces acting on structural acting on structural elementselements

3434

Wind can induce torsional Wind can induce torsional effects on structural steeleffects on structural steel

3535

Design pressure on primary Design pressure on primary systems (structural)systems (structural)

Rigid primary systemsRigid primary systems

Flexible primary systemsFlexible primary systems

p = q GCp - qh (GCpi)

p = qGf Cp - qh (GCpi)

3636

Pressure coefficients on Pressure coefficients on high- rise buildingshigh- rise buildings

- 0.6

- 0.7

- 0.6

- 0.6

- 0.6

0.4

0.40.40.30.3

0.3

0.6

0.5

0.7

- 0.5- 0.5

- 0.6

- 0.50.8

0.9

- 0.6

- 0.6

- 0.5

- 0.6

SIDE FRONT BACK WIN

D

WIND

ROOF

Pressure varieswithheight(Wind ward)

Pressurekeeps constantwith height(Leeward)

3737

Design pressure diagram Design pressure diagram on gabled roof buildingon gabled roof building

3838

Total destruction of Princess Total destruction of Princess Margaret Hospital in JamaicaMargaret Hospital in Jamaica

3939

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

4040

Failure of steel beams supportFailure of steel beams support

4141

Timber roof split due to Timber roof split due to strong hurricane windsstrong hurricane winds

4242

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

4343

Construction close to the sea Construction close to the sea shore might result in great shore might result in great losseslosses

Construction close to the sea Construction close to the sea shore might result in great shore might result in great losseslosses

4444

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

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

4545

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

4646

Pressure increase due to Pressure increase due to wind on overhanging roofswind on overhanging roofs

Win

d w

ard

Leew

ard

Roof

SECTION

4747

Protection effect of Protection effect of hospital buildinghospital building

A favorable location of adjacent buildings can decrease the hurricane effects by reducing the wind loads

4848

Unfavorable location of Unfavorable location of buildings adjacent to a hospitalbuildings adjacent to a hospital

A bad location of nearby buildings might induce increase of wind loads

4949

Bridge base erosion as a Bridge base erosion as a consequence of river flow consequence of river flow increaseincrease

5050

Landslide obstructing Landslide obstructing highway accesshighway access

5151

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

11.64

3.88

-226.90

-180.22

-246.68

Net pressure Perpendicular to ridge

Internal pressure (+)

5252

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

11.64

3.88

-306.03

20.94

38.01

44.21

-226.90 -187.34

-203.16

Net pressure Parallel to ridge

Internal pressure (+)

5353

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

5454

Wind load path on Wind load path on pitched-roof buildingspitched-roof buildings

5555

Structural steel frame collapsed Structural steel frame collapsed

due to strong windsdue to strong winds

5656

Hurricane design philosophy Hurricane design philosophy for hospitalsfor hospitalsHurricane design philosophy Hurricane design philosophy for hospitalsfor 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.

5757

Vulnerability assessment Vulnerability assessment objectivesobjectivesVulnerability assessment Vulnerability assessment objectivesobjectives

Available Available methodologiesmethodologies

Qualitative Qualitative methodsmethods

Quantitative Quantitative methodsmethods

To evaluate the To evaluate the likelihood of a likelihood of a structure suffering structure suffering damage due to the damage due to the effects of a effects of a hurricane, and to hurricane, and to characterize the characterize the possible damagepossible damage

ObjectiveObjective

5858

Qualitative methodsQualitative methods

Qualitative methods for Qualitative methods for vulnerability assessmentsvulnerability assessmentsQualitative methods for Qualitative methods for vulnerability assessmentsvulnerability 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

5959

Quantitative methodsQuantitative methods

Quantitative methods for Quantitative methods for vulnerability assessmentsvulnerability assessmentsQuantitative methods for Quantitative methods for vulnerability assessmentsvulnerability assessments

The goal is to determine the levels of resistance The goal is to determine the levels of resistance of the structure by means of an analysis similar to of the structure by means of an analysis similar to that used in new buildings and incorporating that used in new buildings and incorporating nonstructural elementsnonstructural elements..

6060

The goal is to ensure that the health care facility The goal is to ensure that the health care facility will continue to function after a hurricane, by will continue to function after a hurricane, by reinforcing existing components or incorporating reinforcing existing components or incorporating additional structural components to improve the additional structural components to improve the levels of strength and stiffness. levels of strength and stiffness.

The retrofitting measures should not interfere with The retrofitting measures should not interfere with the operation of the hospital during the process.the operation of the hospital during the process.

Structural retrofittingStructural retrofittingStructural retrofittingStructural retrofitting

6161

Detail of stud to concrete Detail of stud to concrete footing connectionfooting connection

Galvanized strap

min

. d

ep

th

3'-

0"

Groundsurface

Concrete base

Concrete pier

Double base plate

Stud

Stud to concrete connection

6262

Stud and top plate connectionStud and top plate connection

Stud & top plate connection

Galvanized plate

Double top plate

Stud

6363

Rafters and top plates should be Rafters and top plates should be anchored with galvanized strapsanchored with galvanized straps

Galvanized hurricane

Double top plate

Rafter

strap

Rafter & top plate connection

6464

Anchorage of timber Anchorage of timber beams to concrete beamsbeams to concrete beams

Beam

Timber rafter connection to concrete

of rafter

Galvanized hurricanestraps either side

Rafter

Use of galvanized hurricane straps is recommended

6565

Anchorage details between Anchorage details between steel joist and masonry wallssteel joist and masonry wallsAnchorage details between Anchorage details between steel joist and masonry wallssteel joist and masonry walls

6666

Interaction between structural Interaction between structural and nonstructural elementsand nonstructural elementsInteraction between structural Interaction between structural and nonstructural elementsand nonstructural elements

6767

Considerations for infilling Considerations for infilling masonry partitionsmasonry partitionsConsiderations for infilling Considerations for infilling masonry partitionsmasonry partitions

If the infilling If the infilling masonry wall acts as masonry wall acts as part of the part of the structural system, it structural system, it will undergo great will undergo great deformations and deformations and failuresfailures

6868

Reinforcement Reinforcement method: addition of method: addition of (interior or exterior) (interior or exterior) wallswalls

Reinforcement Reinforcement method: addition of method: addition of (interior or exterior) (interior or exterior) wallswalls

6969

Retrofitted wall in Retrofitted wall in children’s children’s hospital in Santo hospital in Santo DomingoDomingo

7070

Details of Details of retrofitted wall retrofitted wall sectionssections

7171

Construction method Construction method details of retrofitted details of retrofitted wallwall

7272

Front view of Front view of retrofitted wallretrofitted wall

7373

Lateral view of Lateral view of retrofitted wallretrofitted wall

7474

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) 567-9271Fax: (809) 566-3200danielc@intec.edu.dowww.intec.edu.do

Grupo de Estabilidad Estructural (Ge2) / INTECAve Los Próceres, GaláApdo 349-2Santo Domingo, Dominican Republic