VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

VULNERABILITY ASSESSMENT AND DAMAGE
PREDICTION OF REINFORCED CONCRETE
BUILDINGS AGAINST NON-SEISMIC HAZARDS
WELCOME TO OUR
PRESENTATION ON

PRESENTED BY:
ENGR. JOHANA SHARMIN
ENGR. SOUPTIK BARMAN TIRTHA
AND
ENGR. KAZI WALIUL HASAN
Date: 20th July, 2016
T H I S P R E S E N T A T I O N I S C O M P L E T E L Y B A S E D
O N M A N U A L O F P W D A N D J I C A P R E P A R E D
U N D E R T H E P R O J E C T F O R C N C R P .

CONTENTS
INTRODUCTION
VULNERABILITY ASSESSMENT
NON-SEISMIC NATURAL HAZARDS
BUILDING ELEMENTS
POTENTIAL DAMAGE DUE TO NON SEISMIC FORCES
VULNERABILITY ASSESSMENT GUIDELINES (CYCLONE)
VULNERABILITY AND DAMAGE PREDICTION OF BUILDING
ENVELOPE BY ‘WIND DAMAGE BAND’ MODEL
STRENGTH EVALUATION OF MWFRS
LOAD COMBINATION
WIND LOAD ANALYSIS
ILLUSTRATIVE EXAMPLE
INUNDATION DEPTH DUE TO STORM SURGE AND TSUNAMI
BUILDING DAMAGE ASSESSMENT DUE TO FLOOD, TIDAL SURGE AND
TSUNAMI
MITIGATION MEASURES

• The purpose of this manual is to establish a
method of vulnerability assessment of RCC
building against non-seismic natural hazards
so that an appropriate cost effective scheme of
retrofitting may be designed for improved
resistance to non-seismic natural disaster.

• Vulnerability assessment of buildings other
than RCC frame structure with in-filled walls
is not within the scope of this manual and is
limited to only non-seismic natural hazards.
• Assessment and load calculation of tornado,
landslide and lightning and thunderstorm are
not considered in this manual.

• A systematic examination of a building or
structure through which crucial components
of the structure or building are defined,
identified and assessed that may be at risk
against natural disaster like earthquake,
cyclone, flood, tsunami, cyclone/tsunami
induced storm/ tidal surge etc.
• It also determines appropriate procedure or
countermeasures and evaluates their actual
effectiveness in reducing or removing the risk
after they are put into use.

Define Project
Form planning group
Identify and describe probable hazards
Define and classify major components of the structure/ building
Assign relative level of important to the components
Identify potential risk to each component
Describe effects
Set a strategy to deal with most serious potential problem first followed
by natural sequence
Define ways to minimize consequence
Recommend action
Implement action

NON SEISMIC NATURAL HAZARDS
Cyclone
Flood
Cyclone induced
storm surge
Tornado
Tsunami
Lighting and
Thunderstorm
Landslide

CYCLONE
• In the Atlantic ocean and Eastern Pacific tropical cyclones are
known as- hurricanes.
• In the Western Pacific ocean- typhoons
• In the Indian ocean- cyclones
• Cyclones are normally straight line wind event. Wind speeds range
from very low to very high. High winds associated within tense low
pressure can last for days at a given location.

CYCLONE
• A tropical cyclone needs
warm ocean temperature (at
least 28 degree Celsius) in
order to form.
• Heat is drawn up from the
oceans creating heat engine.
• Tall convective tower of
clouds are formed within the
storm as warm ocean water
evaporates.
• As the air rises higher it cools
and condenses releasing latent
heat which causes even more
clouds to form and feed the
storm.

CYCLONE
• The coastal regions of
Bangladesh are subject to
damaging cyclones almost
every year.
• They generally occur in
early summer (April-May)
or late rainy season
(October-November).
• Cyclones originate from
low atmospheric pressures
over the Bay of Bengal.

WIND INTENSITY SCALES
• Five types of Wind Intensity Scales:
▫ Beaufort Scale (B- Scale)- 1805 and 1921
▫ TORRO Tornado Intensity Scale (T-Scale)- Purely wind speed scale
▫ Fujita Scale or Enhanced Fujita Scale (F or EF)- Rates the strength of
tornadoes based on the damage they cause
▫ The Saffir-Simpson Hurricane Wind Scale
▫ Integrated Kinetic Energy Scale
• Relation between B-scale, T-scale and wind velocity:
▫ B=2(T+4) and conversely, T=(B/2-4)
B 8 10 12 14 16 18 20 22 24 26 28 30
T 0 1 2 3 4 5 6 7 8 9 10 11
v m/s 19.00 26.50 34.80 43.80 53.60 64.00 75.00 86.40 98.40 111.00
124.0
0
137.5
0
v
mph
42.40 59.40 78.00 98.00
120.0
0
143.4
0
168.0
0
193.2
1
220.1
4
248.2
2
277.3
9
307.6
5
v
km/h
68.43 95.63
125.3
4
157.8
0
192.9
3
230.2
3
269.6
1
311.5
0
354.4
3
399.6
3
446.5
9
495.3
2

• Integrated Kinetic Energy (IKE)
▫ A new scale patented by US Government in 2007 designated to
better convey the destructive power from both hurricane wind
and storm surge.
▫ It has the ability to more accurately predict
 How big the hurricane is
 How strong it is
 What the storm surge may be
so that the emergency management officials can make an
informed decision on whether to evacuate people before the
hurricane gets close to landfall.
▫ The IKE scale measures in a continuous scale from 0-5.99.

Table: Nomenclature of cyclone in Bangladesh
Nomenclature
Wind speed
km/h
Wind speed
mph
Wind speed m/s
Depression Up to 51 Up to 31.7 Up to 14.17
Deep Depression 52-61 32.3-37.90 14.44-16.94
Cyclonic Storm 62-88 38.5-54.65 17.22-24.44
Severe Cyclonic Storm 89-117 55.28-72.67 24.72-32.50
Severe Cyclonic Storm of hurricane
intensity
>117 >72.67 >32.50
• Bangladesh also uses a 1 to 10 scale to classify tropical cyclones with 10 being
the most severe.
• Alert stage: Signal No. I, II and III
• Warning Stage: Signal No. IV
• Disaster Stage: Signal No. V, VI, VII and VIII, IX, and X
• The most severe cyclones of recent memory since 1970 are November ‘70
(v=222km/h) and April ‘91 (v= 235km/h).

FLOOD
• Bangladesh is in the low-
laying Ganges-Brahmaputra
river delta, with many
tributaries flowing into the
Bay of Bengal.
• About 75% of Bangladesh is
less than 10m (33 feet)
above sea level and 80% is
flood plain.
• It is believed that about 10%
of the land shall be under
water, if the sea levels were
to rise 1 m (3.3 feet).

TYPES OF FLOODS
• Monsoon Flood
▫ From the major rivers generally rises slowly and the period of rise and
fall may extend from 10 to 20 days or more.
• Flash Flood
▫ In the eastern and northern rivers is characterized by a sharp rise
followed by a relatively rapid recession, often causing high flow
velocities that damage crops and property.
• Local Flood
▫ Due to high localized rainfall of long duration in the monsoon season
often generate water volume in excess of the local drainage capacity.
• Floods due to storm surges
▫ These cyclones predominate during the post monsoon (October-
November) and pre-monsoon (April-June) period.

CYCLONE INDUCED STORM SURGE
• A tidal surge is the bulge of
water that washes onto shore
during a storm, measured as a
difference between the height of
storm tide and the predicted
astronomical tide.
• It is driven by wind and low
atmospheric pressure and is
influenced by waves, tides and
uneven bathymetric and
topographic surface.
• Storm surge can reach height of
12m near the center of Category
5 hurricane and fan out across
several hundred miles of coast
line.

RELATION BETWEEN WIND VELOCITY, STORM SURGE AND
LIMIT OF INUNDATION IN COASTAL AREAS OF BANGLADESH
Wind
velocity
(km/h)
Storm
surge
height (m)
Wind
velocity
(mph)
Storm
surge
height (ft)
Limit of
inundation
from
coastline
(km)
Limit of
inundation
from
coastline
(miles)
85 1.5 52.80 4.92 1.0 0.62
115 2.5 71.43 8.2 1.0 0.62
135 3.0 83.90 9.84 1.5 0.93
165 3.5 102.50 11.48 2.0 1.24
195 4.8 121.12 5.74 4.0 2.48
225 6.0 140.00 19.68 4.5 2.8
235 6.5 146.00 21.32 5.0 3.11
260 7.8 161.50 25.58 5.5 3.42

TORNADO
• A tornado is a powerful column of winds spiraling around a centre of low
atmospheric pressure. It looks like a large black funnel hanging down from a
storm cloud.
• Most tornados have wind speeds less than 177 km/h (110 mph), are
approximately 80 m across, travel several km, lasts less than 20 mins before
dissipating.
• Tornado falls under the category of ‘Extraordinary events’ and ASCE7
considered probability of occurrence of extraordinary events as 10^-6 through
10^-4 per year or greater.

TSUNAMI
• The term tsunami comes from the Japanese, composed of the two kanji ‘tsu’
meaning harbour and ‘nami’ meaning wave.
• The principal generation mechanism of a tsunami is the displacement of a
substantial volume of water or perturbation of sea.
• Tsunami can be generated when thrust faults associated with plate boundaries
move abruptly, resulting in water displacement.

LIGHTNING AND THUNDERSTORM
• Lightning
▫ A massive electrostatic discharge
between electrically charged regions
within clouds, or between a cloud and
the Earth’s surface.
▫ Lighting occurs approximately 40-50
times a second worldwide, resulting
in nearly 1.4 billion flashes per year.
▫ Lighting primarily occurs when warm
air is mixed with colder air masses
resulting in atmospheric disturbances
necessary for polarizing the
atmosphere.
▫ Objects struck by lightning
experience heat and magnetic forces
of great magnitude.

• Three primary types: from a cloud to itself ( intra-cloud or IC), from
one cloud to another cloud (CC), and finally between a cloud to the
ground (CG).

• Thunderstorm
▫ It is a form of turbulent weather
characterized by the presence of
lighting and acoustic effect on
the Earth’s atmosphere.
▫ Thunderstorm result from the
rapid upward movement of
warm, moist air.
▫ Damage that results from
thunderstorms is mainly
inflicted by downburst winds,
large hailstones, and flash
flooding caused by heavy
precipitation.
▫ The effect of thunderstorm on
RC building is insignificant.

LANDSLIDE
• The term landslide describes downhill earth movements that can move slowly
and cause damage gradually, or move rapidly, destroying property and taking
lives suddenly and unexpectedly.
• Most landslides are caused by natural forces or events, such as heavy rain and
snowmelt, shaking due to earthquakes, volcanic eruptions and gravity.
• Landslides are typically associated wet periods of heavy rainfall or rapid
snowmelt and tend to worsen the effects of flooding.
• This hazard is not directly related to reinforced concrete buildings.

BUILDING ELEMENTS
Structural Elements
• Foundation
• Column
• Slab
• Beam
• Shear Walls
Non Structural Elements
• Stairways, Doorways, Windows, Partitions, Glass, Cornices,
False ceiling, Facades, Pipes, Wall claddings, Lighting
fixtures etc.
Building Contents
• Furniture, Appliances, Electronics, Equipments, Air-
conditioners, Stored items etc.

POTENTIAL DAMAGES DUE TO WIND (CYCLONE)
• Major causes of damage:
Low quality of
construction
Inappropriate
techniques and
utilization of low
resistance
materials
Failure of doors
and windows due
to wind pressure
Excessive
openings in the
building envelope
Location of the
building
General
roughness of the
surrounding
terrain
Height of the
building above
ground
Height of the
building more
than surrounding
structures and
vegetation
Configuration of
the building
Surrounding
topography

POTENTIAL DAMAGES DUE TO WIND (CYCLONE)
• Structural damage:
Collapse of structural
elements or the entire
building along with damage
to the building envelope
Water infiltration into the
building exterior wall
Leakage between door and
frame, frame and wall and
threshold and door

POTENTIAL DAMAGES DUE TO FLOOD
• A building may face the following hazards due to flood:
Lateral
hydrostatic and
buoyant forces
Hydrodynamic
forces
Impact load
caused by
floating debris
Erosion and
scour
Geotechnical
considerations
Contamination
Breaking waves
with floating
debris

POTENTIAL DAMAGES DUE TO FLOOD
• Due to mentioned flood related hazards the building shall face
the following problems:
Settlement of
Foundation
Scouring of
wall base
Debris impact
Impact of storm
surge wave

POTENTIAL DAMAGES DUE TO CYCLONE
INDUCED STORM SURGE
• Bangladesh coastline including islands are densely populated and
many regions lie less than 3 m (10 ft).
• Currents created by tides combine with the waves severely erode
beaches and coastal highways.
• Buildings that survive cyclone winds can be damaged if their
foundations are undermined and weakened by erosions.
• Impact of water borne debris and logs may seriously damage a
building or structure in their path.

POTENTIAL DAMAGES DUE TO TSUNAMI
• Difficulty of tsunami is that it cannot be precisely predicted, even
if the magnitude and location of an earthquake is known.
• Smashing force of a wall of water travelling at high speed
destroys everything in its path.
• A series of wave trains with periods ranging from minutes to
hours arrive when tsunami strikes.
• Wave heights as high as 10m (33ft) can be generated by a large
event.
• A wave of only 0.9m (3 ft) high, 3.2 km long and 1600 km wide
contains 10 billion tons of water. A 3.0 m (10 ft) wave shall
produce water velocity of approximately 20m/s.

POTENTIAL DAMAGES DUE TO TORNADO
• Because of extreme high pressure and missile loads that
tornados can induce, specially building envelope may face
serious damage due to tornado.
• Most buildings experience significant building envelope
damage and damage to interior partitions and ceilings if
they are in the path of a strong or violent tornado (F4 and
F5).
• As wind speed rapidly decreases with increase distance
from the center of tornado, a building on the periphery of a
strong or violent tornado could be subjected to moderate to
high wind speed depending upon the distance from the
center of the tornado.

VULNERABILITY ASSESSMENT GUIDELINES
(CYCLONE)
• This covers the guidelines for survey and inspection of the
building for assessment of degree of vulnerability against
cyclone.
• Standard pro forma prepared for survey and inspection shall
establish
▫ Building typology, configuration, weaknesses in structural system
and elements, inadequacy in the material strength and method of
construction
so that an appropriate cost effective scheme of retrofitting may
be designed for improved cyclone resistance and thus decreasing
vulnerability to any future non-seismic natural disaster like
cyclone.

VULNERABILITY ASSESSMENT GUIDELINES
(CYCLONE)
• Guidelines for filling standard pro forma for field survey of
building
▫ The pro forma has been prepared on the basis of a questionnaire
presented in checklist from through which detailed information can
be gathered regarding
 Building configuration, structural system, member sizes, architectural
details, construction material and building environment
▫ The pro forma contains basically two types of questions.
 In the first set, multiple options are given and the surveyors have to
provide a tick on the respective box.
 In other set of questions, the answer is to be provided in definite
quantitative terms on the basis of actual measurement or information at
site in the box provided.

VULNERABILITY ASSESSMENT GUIDELINES (CYCLONE)
• Standard Pro forma for Vulnerability Assessment of Building
▫ Pro forma A :
 statistical information of the building for the purpose of characterization
of the building typology
 Information about structural system, member sizes, connection details
for examining the cyclone resistance of the existing building and to
retrofit them
▫ Pro forma B:
 Summary of information about building envelope collected from Pro
forma A for examining the cyclone resistance of building envelope
▫ Pro forma C:
 Information collected from Pro forma A about structural system and its
components for performing structural strength analysis

VULNERABILITY AND DAMAGE PREDICTION OF
BUILDING ENVELOPE BY ‘WIND DAMAGE BAND’ MODEL
• The amount of damage is defined as the ratio of replacement cost of damaged
building components (due to wind pressure and wind borne missiles) to the
replacement cost of the building.
• It is necessary that a wind damage prediction model satisfies the following
criteria:
▫ The model should be capable of predicting the actual amount of damage to a building
▫ There should have some proportionality relationship between the model predictions of
damage degrees to individual buildings based upon their relative wind performance
characteristic.
• The first criterion is the desired output, upon which several decisions are ultimately
based. The second criterion enables a check to be made on the precision of the model
prediction.

• Wind Damage Band:
▫ The procedure for wind damage prediction of individual building based on the
concept of wind damage bands for building occupancy classes. Wind damage bands
define the damage degree ranges bounded by a lower and upper damage threshold
for given intensities of the wind hazard.
▫ The upper boundary damage band for a class of building represents the wind
damage function of the least wind resistant building in the building class, while the
lower boundary represents the damage function of the most wind resistant building
in the building class.
▫ For individual buildings the damage degree due to the wind pressure and wind-
borne missile is given by:

•RRI= a measure of the building’s
damage resistance relative to other
buildings
•RRI very close to 1 indicates a
building whose features and
components offer very little
resistance to wind damage, while
RRI very close to zero represents a
building whose features and
components offer very high
resistance to wind damage.

STRENGTH EVALUATION OF MAIN WIND FORCE
RESISTING SYSTEM
• Basic Requirements
• Nominal and
factored loads
in load
combination
1
• Adequate
stiffness
2 • Self
restraining
forces
arising
3
• Load
effects
4 • Resist forces
due to
earthquake
and wind.
5

RESISTING SYSTEM
• Special Requirements for Coastal Saline Areas
Minimum live
load of 4.8 kN/m2
(100 lb/ft2)
No reduction in
live load
Denseness of
concrete
Clear cover to
reinforcement
Effect of chloride
on concrete
Minimum strength
of concrete shall
be 24 Mpa
No artificial
coarse aggregate
Fine aggregate
shall be 100%
coarse
Saline water
strictly prohibited

RESISTING SYSTEM
• Steps for Non-Seismic Structural Strength Evaluation
Select the
building to be
analyzed
Identify
appropriate
structural
system
Determine
risk category
Collect information
related to type of
materials used & their
strength, design criteria
etc.
Determine
basic wind
speed
Determine wind
load parameters
Select
appropriate
lateral force
procedure
Select gravity,
live and wind
loads
Calculate
velocity
pressure
Calculate wind
pressure

RESISTING SYSTEM
• Steps for Non-Seismic Structural Strength Evaluation
Calculate forces
acting on
MWFRS
Collect test core-
concrete
Study story drift
limitations
Design &
evaluate elements
of MWFRS
Compare
capacity of
existing MWFRS
Evaluate
overturning
effects
Verify structure’s
continuous load
path
Comment on the safety of
individual members of MWFRS
against wind load combination

RESISTING SYSTEM
• The evaluation method depends on:
▫ Structural framing system
▫ Information known about its existing condition
▫ Logistic and economic consideration
• Two methods of strength evaluation of existing structures:
▫ Analytic evaluation based on member dimensions and material properties
▫ Load test (if member dimensions and material properties are not possible to
determine)
• If the dimensions and material properties are available then:
▫ Dimension of structural elements shall be established at critical sections.
▫ Location and size of the reinforcing bars shall be determined by measurement.
▫ Concrete strength shall be based on the results of cylinder tests.
▫ The number of core tests may depend on the size of the structure and sensitivity of
the structural safety to concrete strength.

RESISTING SYSTEM
• Basic parameters in determining wind loads:
• Earthquakes and wind load need not be assumed to act simultaneously. In
some instances, forces due to wind might exceed those due to earthquake,
while ductility requirements might be determined by earthquake load.
Basic wind
speed
Wind
directionality
factor
Building
exposure
category
Importance
factor
Topographic
factor
Gust effect
factor
Enclosure
classification
Internal
pressure
coefficient
External
pressure
coefficient

STRENGTH EVALUATION OF MAIN WIND FORCE RESISTING
SYSTEM
• Coastal areas subjected to flooding can be designated into two categories:
▫ Coastal A-zone (Risk area)
▫ Coastal High Hazard Area (V-zone) (High risk area)
• Coastal A-zones lie landward of V-zones. Coastal A-zones are subjected to the
effects of waves, high velocity flows, and erosion, although not to the extent
those V-zones are.
• In order for a coastal A-zone to be present, two conditions are required:
▫ A still water flood depth greater than or equal to 0.61m.
▫ Breaking wave heights greater than or equal to 0.46m.
▫ Forces generated by the impact of flood borne debris.
• Coastal V-zones extend from offshore to the inland limit of a primary frontal
dune along an open coast.
• Generally speaking, A-zones are designated where wave less than 0.9m (3ft)
is expected. V-zones are designated where wave height greater than 0.9m (3ft)
is expected.

LOAD COMBINATION
• Combining factored loads using strength design (BNBC15 and
ASCE7-5):
1. 1.4 (D+F)
2. 1.2(D+F+T)+1.6(L+H)+0.5(Lr or R)
3. 1.2D+1.6 (Lr or R)+ (1.0L or 0.8W)
4. 1.2D+1.6W+1.0L+0.5 (Lr or R)
5. 1.2D+1.0E+1.0L
6. 0.9D+1.6W+1.6H
7. 0.9D+1.0E+1.6H
• Load combination including flood load
▫ In V-Zones or coastal A-zones, 1.6W in combinations (4) and (6) shall be
replaced by 1.6W+2.0Fa.
▫ In non-coastal A-zones, 1.6W in combination (4) and (6) shall be replaced
by 0.8W+1.0Fa.

LOAD COMBINATION
• Combining nominal loads using allowable stress design:
1. D
2. D+L
3. D+F
4. D+H+F+L+T
5. D+H+F+ (Lr or R)
6. D+H+F+0.75 (L+T) +0.75 (Lr or R)
7. D+H+F+ (W or 0.7E)
8. D+H+F+ 0.75 (W or 0.7E) +0.75L+0.75 (Lr or L)
9. D+L+ (W or 0.7E)
10. 0.6D+W+H
11. 0.6D+0.7E+H
• Load combination including flood load
▫ In coastal zones vulnerable to tidal surge 1.5Fa shall be added to other loads in
combination (7), (8), (9) and (10) and E shall be set equal to zero in (7), (8) and (9).
▫ In non- coastal zone, 0.75Fa shall be added to combination (7), (8), (9) and (10) and
E shall be set equal to zero in (7), (8) and (9).

WIND LOAD ANALYSIS
• METHOD 1- SIMPLIFIED PROCEDURE:
▫ It can be used for determining wind forces on low rise enclosed building
with flat, gabled or hipped roof, provided it satisfied the requirements
below.
▫ Main wind force resisting system:
 The building is a simple diaphragm building (no structural separation).
 The building is a low rise building that complies with the following conditions:
 Mean roof height h is less than or equal to 18.3m (60.0ft)
 Mean roof height h does not exceed least horizontal dimension
 The building does not comply with requirements for open or partially enclosed
buildings.
 Open building: a building having each wall at least 80 percent open.
 Partially Enclosed building:

WIND LOAD ANALYSIS
• METHOD 1- SIMPLIFIED PROCEDURE:
 The building is a regular-shaped building having no unusual geometrical
irregularity in spatial form.
 The building is not a flexible (slender) building and has a fundamental
natural frequency greater than or equal to 1Hz.
 The has an approximately symmetrical cross section in each direction
with either a flat roof or a gable or hip roof with θ≤45˚.
 The building does not have response characteristics.
▫ Components and claddings
 The mean roof height h≤18.3m (60.0ft).
 The building is enclosed, a regular shape building and does not have
response characteristics as defined earlier.
 The building has either a flat roof, a gable roof with θ≤45˚ or a hip roof
with θ≤27˚.

WIND LOAD ANALYSIS
▫ Design procedure
▫ Design of Main Wind-force Resisting System
 Ps, the combination of windward and leeward net pressure,
▫ Design of Components and Claddings
 Pnet, net design wind pressure,
Basic wind
speed, V
(Table 1)
Importance
factor, I (Table
2)
Exposure
category
Height and
exposure
adjustment
coefficient λ
(Table 4)

WIND LOAD ANALYSIS
• METHOD 2- ANALYTICAL PROCEDURE
▫ A building whose design wind loads are determined in
accordance with this section shall meet all of the following
conditions:
 The building is a regular shaped building having no unusual geometrical
irregularity in spatial form.
 The building does not have response characteristics.

WIND LOAD ANALYSIS
• METHOD 2- ANALYTICAL PROCEDURE
▫ Design Procedure:
Basic wind
speed, V
(Table 1)
Wind
directionality
factor (Table
5)
Importance
factor, I
(Table 2)
Exposure
category
Velocity
exposure
coefficient (Kz
or Kh)
Topographic
factor, Kzt
Gust effect
factor, G or
Gf
Enclosure
classification
Internal
pressure
coefficient,
Gcpi (Table 9)
External
pressure
coefficient,
Cp or GCpf
Velocity
pressure qz
or qh
Design
load p or F

TABLE 1: BASIC WIND SPEED (3-SECOND GUST SPEED)
FOR SELECTED LOCATIONS OF BANGLADESH
Location
Basic Wind Speed
m/s Km/h Mph
Angorpota 47.8 172.10 106.88
Bagerhat 77.5 279.0 173.30
Bandarban 62.5 225 140
Barguna 80.0 288.0 179.0
Barisal 78.7 283.32 176.0
Bhola 69.5 250.2 155.4
Bogra 61.9 222.84 138.40
Brahmanbaria 56.7 204.12 126.78
Chandpur 50.6 182.16 113.14
Chapai
Nowabgonj
41.4 149.04 92.57
Location
Basic Wind Speed
m/s Km/h Mph
Chittagong 80.0 288.0 179.0
Chuadanga 61.9 222.84 138.40
Comilla 61.4 221.04 137.30
Cox’s Bazar 80.0 288.0 179.0
Dahagram 47.8 172.10 106.88
Dhaka 65.7 236.52 146.90
Dinajpur 41.4 149.04 92.57
Faridpur 63.1 227.16 141.10
Feni 64.1 230.76 143.33
Gaibanda 65.6 236.16 146.68
Gazipur 66.5 239.40 148.70

Location
Basic Wind Speed
m/s Km/h Mph
Gopalgonj 74.5 268.20 166.58
Habigonj 54.2 195.12 121.20
Hatiya 80.0 288.0 179.0
Ishurdi 69.5 250.20 155.40
Joypurhat 56.7 204.12 126.78
Jamalpur 56.7 204.12 126.78
Jessore 64.1 230.76 143.33
Jhalokathi 80.0 288.0 179.0
Jhenidah 65.0 234.0 145.34
Khagrachari 56.7 204.0 126.78
Khulna 73.3 263.88 163.90
Location
Basic Wind Speed
m/s Km/h Mph
Kutubdia 80.0 288.0 179.0
Kishorgonj 64.7 232.92 144.67
Kurigram 65.6 236.16 146.68
Kushtia 66.9 240.84 149.59
Lakshmipur 51.2 184.32 114.48
Lalmonirhat 63.7 229.32 142.43
Madaripur 68.1 245.16 152.27
Magura 65.0 234.0 145.34
Manikgonj 58.2 209.52 130.14
Meherpur 58.2 209.52 130.14
Maheshkhali 80.0 288.0 179.0

Location
Basic Wind Speed
m/s Km/h Mph
Moulovibazar 53.0 190.8 118.51
Munshigonj 57.1 205.56 127.68
Mymensingh 67.4 242.64 150.71
Naogoan 55.2 198.72 123.43
Norail 68.6 246.96 153.40
Narayanganj 61.1 220.0 136.62
Narshinghdi 59.7 214.92 133.49
Natore 61.9 222.84 138.41
Netrokona 65.6 236.16 146.68
Nilphamari 44.7 160.92 100.00
Noakhali 57.1 205.56 127.68
Location
Basic Wind Speed
m/s Km/h Mph
Pabna 63.1 227.16 141.10
Panchagorh 41.4 149.04 92.57
Patuakhali 80.0 288.0 179.0
Pirojpur 80.0 288.0 179.0
Rajbari 59.1 212.76 132.15
Rajshahi 49.2 177.12 110.00
Rangamati 56.7 204.12 126.78
Rangpur 65.3 235.08 146.01
Satkhira 57.6 207.36 128.80
Shariatpur 61.9 222.84 138.41
Sherpur 62.5 225.00 139.75

Location
Basic Wind Speed
m/s Km/h Mph
Sirajgonj 50.6 182.16 113.14
Srimongol 50.6 182.16 113.14
St. Martin
Island
80.0 288.0 179.0
Sunamgonj 61.1 220.0 136.62
Sylhet 61.1 220.0 136.62
Sandwip 80.0 288.0 179.00
Tangail 50.6 182.16 113.14
Teknaf 80.0 288.0 179.00
Thakurgaon 41.1 147.96 91.90

TABLE 2: OCCUPANCY CATEGORIES OF BUILDINGS AND OTHER
STRUCTURES FOR FLOOD, SURGE, WIND AND EARTHQUAKE LOADS

TABLE 3: IMPORTANCE FACTOR, I (WIND LOADS)
Category or
Importance Class
Non-cyclone Prone
Regions and Cyclone
Prone Regions with V=
38-44m/s
Cyclone Prone Regions
with V>44m/s
I 0.87 0.77
II 1.00 1.00
III 1.15 1.15
IV 1.15 1.15

TABLE 4: HEIGHT AND EXPOSURE ADJUSTMENT
COEFFICIENT, λ
Adjustment Factor For Building Height and Exposure, λ
Mean roof height Exposure
ft meter A B C
15 4.6 1.00 1.21 1.47
20 6.0 1.00 1.29 1.55
25 7.6 1.00 1.35 1.61
30 9.1 1.00 1.40 1.66
35 10.7 1.05 1.45 1.70
40 12.2 1.09 1.49 1.74
45 13.7 1.12 1.53 1.78
50 15.2 1.16 1.56 1.81
55 16.8 1.19 1.59 1.84
60 18.3 1.22 1.62 1.87

TABLE 5: WIND DIRECTIONALITY FACTOR, Kd
Structure Type Directionality Factor, Kd
Buildings
Main Wind-force-resisting system
Components and cladding
0.85
0.85
Arched roofs 0.85
Chimneys, tanks, similar structure
Square
Hexagonal
Round
0.96
0.95
0.95
Solid signs 0.85
Open Signs & Lattice Frame work 0.85
Trussed towers
Triangular, square, rectangular
All other cross sections
0.85
0.95

SURFACE ROUGHNESS CATEGORIES AND EXPOSURE
CATEGORIES
• Surface roughness categories
▫ Surface roughness A: urban and suburban areas,
wooded areas or other terrain with numerous closely
spaced obstructions having the size of single family
dwellings or larger
▫ Surface roughness B: open terrain with scattered
obstructions having heights generally less than 9.1m.
This category includes flat open country, grasslands,
and all water surfaces in cyclone prone regions.
▫ Surface roughness C: flat, unobstructed areas and water
surfaces outside cyclone prone areas.

SURFACE ROUGHNESS CATEGORIES AND EXPOSURE
CATEGORIES
• Exposure Categories
▫ Exposure A (Exposure B of ASCE):

GUST EFFECT FACTOR, G or Gf
• Frequency determination
▫ The approximate building natural frequency, na shall be
permitted to be calculated for concrete buildings meeting the
following requirements:
 The building height is less than or equal to 91m (300ft).
 The building height is less than 4 times its effective length Leff
 The effecting length Leff in m (ft.) in the direction under consideration
shall be determined from the eqn.
• Natural Period and Frequency
▫ It is important to distinguish between the building period (Ta)
with site period or with the period of earthquake (T=1/n).

TABLE 6: VALUES OF APPROXIMATE PERIOD
PARAMETERS Ct AND x
Structure Type
Ct
x
SI Fps
Moment resisting frame system in which the frames
resist 100% of required seismic force and are not
enclosed or adjoined by components that are more rigid
and will prevent the frames from deflecting when
subject to seismic force:
Steel moment-resisting frame
Concrete moment resisting frame
0.0724
0.0466
0.028
0.016
0.8
0.9
Eccentrically braced steel frame 0.0731 0.03 0.75
All other structural system 0.0488 0.02 0.75
▫ But in the commentary of ASCE 07-5, it has been suggested that the above
expressions are based on recommendations for earthquake design. For wind
design applications, these values may be unconservative.

TABLE 7: COMPARATIVE VALUES OF FREQUENCY OF
BUILDING FOR DIFFERENT EQUATIONS
Equation (fps) Equation(SI)
N1 (Example
values)
Type
Ta = Ct hn
x
n1 = 1/Ta
Ta = Ct hn
x
n1 = 1/Ta
0.70
1.17
Flexible in E-W
Rigid in N-S
Ta = 0.1N
n1 = 1/ Ta
Ta = 0.1N
n1 = 1/ Ta
0.83 Flexible
n1 = 43.5/ H0.9 n1 = 14.3/ H0.9 0.48 Flexible
n1 = 100/H (avg
value)
n1 = 75/H (lower
bound value)
n1 = 30.49/H (avg
value)
n1 = 22.86/H
(lower bound
value)
0.68
0.51
Flexible
Flexible
fn1 = 150/H fn1 = 45.73/H 1.014 Rigid
n1 = 220/H n1 = 67/H 1.49 Rigid

• For rigid structures having a fundamental frequency greater than or equal
to 1Hz, the gust effect factor shall be taken as 0.85 or calculated by the
eqn:

TABLE 8: TERRAIN EXPOSURE CONSTANTS IN SI AND
FPS SYSTEM
Expo
sure
α zg (m)
zg
(ft)
â b ά Б c l (m)
l
(ft)
є
zmin
(m)
zmin
(ft)
A 7.0 365.76 1200 1/7 0.84 ¼.0 0.45 0.30 97.54 320 1/3.0 9.14 30
B 9.5 274.32 900 1/9.5 1.0 1/6.5 0.65 0.20 152.4 500 1/5.0 4.57 15
C 11.5 213.36 700 1/11.5 1.07 1/9.0 0.80 0.15 198.12 650 1/8.0 2.13 7

• For flexible or dynamically sensitive structures are those
which satisfy any one of the following conditions:
▫ A slender building or structure having a height exceeding five times the
least horizontal dimension.
▫ A building or structure that has a fundamental natural frequency less
than 1Hz.

ENCLOSURE CLASSIFICATION
• General
▫ All buildings shall be classified as enclosed, partially enclosed or open
• Openings
▫ A determination shall be made of the amount if openings in the building
envelope to determine the enclosure classification
• Wind borne debris
▫ Glazing in building located in wind-borne debris regions shall be
protected with an impact resistant covering or be impact resistant
glazing.
• Multiple classification
▫ If a building by definition complies with both the “open” and “partially
enclosed” definitions, it shall be classified as “open” building. A
building that does not comply with either the “open” or “partially
enclosed” definitions shall be classified as “enclosed” building.

TOPOGRAPHIC EFFECT
• Wind speed-up over Hill, Ridges and Escarpments
▫ The hill ridge or escarpment is isolated and unobstructed upwind by
other similar topographic features of comparable heights for 100 times
the height of the topographic feature (100H) or 3.22 km (2.0 miles,
whichever is less.
▫ The structure is located in the upper one-half of a hill or ridge or near
the crest of an escarpment.
▫ H/Lh ≥ 0.2
▫ H is greater than or equal to 4.5 m (15 ft) for exposure B and C and 18.0
m (60.0 ft) for exposure A.
• Topographic factor, Kzt

TABLE 9:INTERNAL PRESSURE COEFFICIENT GCpi
Enclosure Classification Gcpi
Open Building 0.00
Partially Enclosed Building
+0.55
-0.55
Enclosed Building
+0.18
-0.18
• Plus and minus signs signify pressure acting toward and away from internal
surfaces respectively.
• Values of Gcpi shall be used with qz or qh
• Two cases shall be considered to determine the critical load requirement for the
appropriate condition:
• A positive value of GCpi applied to all internal surfaces
• A negative value of Gcpi applied to all internal surfaces

TABLE 10: EXTERNAL PRESSURE CO-EFFICIENT, Cp OF
WALLS AND ROOF FOR ENCLOSED, PARTIALLY
ENCLOSED BUILDING
Wall Pressure Coefficient, Cp
Surface L/B Cp Use with
Windward wall All values 0.8 qz
Leeward wall
0-1 -0.5
qh2 -0.3
>4 -0.2
Side wall All values -0.7 qh

TABLE 10: EXTERNAL PRESSURE CO-EFFICIENT, Cp OF
WALLS AND ROOF FOR ENCLOSED, PARTIALLY
ENCLOSED BUILDING
Wind
Direction
Roof pressure coefficient Cp for use with qh
Windward Leeward
Angle, θ (degrees) Angle, θ (degrees)
normal to
ridge for
θ≥10◦
h/L 10 15 20 25 30 35 45 >60 10 15 >20
≤0.25
-0.7
-0.18
-0.5
0.0
-0.3
0.2
-0.2
0.3
-0.2
0.3
0.0
0.4
0.4 0.01θ -0.3 -0.5 -0.6
0.5
-0.9
-0.18
-0.7
-0.18
-0.4
0.0
-0.3
0.2
-0.2
0.2
-0.2
0.3
0.0
0.4
0.01θ
-0.5 -0.5 -0.6
≥1.0
-1.3
-0.18
-1.0
-0.18
-0.7
-0.18
-0.5
0.0
-0.3
0.2
-0.2
0.2
0.0
0.3
0.01θ
-0.7 -0.6 -0.6

TABLE 10: EXTERNAL PRESSURE CO-EFFICIENT, Cp OF WALLS
AND ROOF FOR ENCLOSED, PARTIALLY ENCLOSED BUILDING
Wind
Direction
h/L
Horizontal
distance from
windward
edge
Cp
•Value is provided for
interpolation purposes
• Value can be reduced
linearly with area over
which it is applicable as
follows
Normal to
ridge for
θ<10 and
parallel to
ridge for all θ
≤0.5
O to h/2 -0.9,-0.18
h/2 to h -0.9,-0.18
H to 2h -0.5,-0.18
>2h -0.3,-0.18
≥1.0
0 to h/2 -1.3,-0.18
Area (sqft)
Reduction
factor
≤100
(9.3sqm)
1.0
> h/2 -0.7, -0.18
200
(23.2sqm)
0.9
≥1000
(92.9sqm)
0.8

VELOCITY PRESSURE EXPOSURE COEFFICIENT KZ

TABLE 11: VELOCITY PRESSURE EXPOSURE COEFFICIENT Kh
AND KZ
Height above ground level Exposure
m ft A B C
0-4.6 0-15 0.57 0.85 1.03
6.1 20 0.62 0.90 1.08
7.6 25 0.66 0.94 1.12
9.1 30 0.70 0.98 1.16
12.2 40 0.76 1.04 1.22
15.2 50 0.81 1.09 1.27
18.3 60 0.85 1.13 1.31
21.3 70 0.89 1.17 1.34
24.4 80 0.93 1.21 1.38
27.4 90 0.96 1.24 1.40
30.5 100 0.99 1.26 1.43
36.6 120 1.04 1.31 1.52

TABLE 11: VELOCITY PRESSURE EXPOSURE COEFFICIENT Kh
AND KZ
Height above ground level Exposure
m ft A B C
42.7 140 1.09 1.36 1.52
48.8 160 1.13 1.39 1.55
54.9 180 1.17 1.43 1.58
61.0 200 1.20 1.46 1.61
76.2 250 1.28 1.53 1.68
91.4 300 1.35 1.59 1.73
106.7 350 1.41 1.64 1.78
121.9 400 1.47 1.69 1.82
137.2 450 1.52 1.73 1.86
152.4 500 1.56 1.77 1.89

VELOCITY PRESSURE, qz
DESIGN WIND LOADS ON ENCLOSED AND PARTIALLY
ENCLOSED BUILDING
• Sign convention
▫ Positive pressure acts towards the surface and negative pressure
acts away from the surface.
• Critical load conditions
▫ Values of external and internal pressures shall be combined
algebraically to determine the most critical load.
• Tributary areas greater than 65m2 (700 sft.)
▫ Components and cladding elements with tributary areas greater
than 65m2 shall be permitted to be designed using the provisions
of MWFRS.

DESIGN OF MAIN WIND-FORCE RESISTING SYSTEM
• Rigid buildings of all heights
• Flexible Buildings
• Parapets
• Design Wind Load Cases
• Components and Claddings
▫ Low rise building & building with h≤18.3m (60ft)
▫ Buildings with h> 18.3m (60ft)

ILLUSTRATIVE EXAMPLE OF A HYPOTHETICAL
BUILDING BASED ON CNCRP-JICA MANUAL

INUNDATION DEPTH DUE TO STORM SURGE AND
TSUNAMI IN COASTAL AREAS
• Introduction
▫ Bangladesh has approximately 710 km (441 miles) coastline.
▫ 13 coastal districts vulnerable to strong tidal surge, wind action,
high waves and tropical cyclones and tsunami:
 Satkhira
 Khulna
 Bagerhat
 Perojpur
 Barisal
 Barguna
 Patuakhali
 Bhola
 Lakshmipur
 Noakhali
 Feni
 Chittagong
 Cox’s Bazar
50 upazillas/ thanas are considered to be
exposed directly to vulnerability from natural
disaster.
All these areas are comparatively low in
elevation
Of these areas, about 62% of the lands
have an elevation of up to 3 meters (10ft)
and 86% up to 5 meters (16.40 ft) from mean
sea level.

• Risk zone and high risk area
▫ Multipurpose Cyclone Shelter Programme (MPCSP) has
delineated the coastal belt of Bangladesh into two zones
based on the possible extent of the inland intrusion of the
cyclone storm surge.
 Risk zone (RZ) and
 High Risk Area (HRA)
• Inundation depth due to storm surge:
▫ IWM, while calculating inundation depth due to cyclone,
has considered the following climate change sceneries for
2050:
 Sea level rise of 0.5m (1.64 ft)
 10% increase in maximum wind speed of cyclone

• Comparison of Inundation depths due to storm surge and
tsunami
▫ Inundation depth is higher due to tidal surge than tsunami.
▫ As the maximum water velocity in relation to depth of water is
double for tsunami compared to tidal surge, the hydrodynamic
force, debris impact force shall be same for tsunami in
comparison to tidal surge for half the water depth.
▫ For tidal surge water rises gradually with the increase of intensity
of wind velocity, whereas water forces due to tsunami is
somewhat sudden and surge volume of receding water draining
off the land has the devastating power of carrying almost
everything with it.
▫ So even with half the inundation depth compared to tidal surge,
the damage and destruction due to tsunami may be much more.

BUILDING DAMAGE ASSESSMENT DUE TO FLOOD,
TIDAL SURGE AND TSUNAMI
• Introduction
▫ Flood actions include
 Hydrostatic force
 Hydrodynamic force
 Impact force
 Breaking wave force
 Time-dependent local soil scour
▫ The assessment (a stochastic methodology) is based on
both flood water depth and flood water velocity. The
methodology focuses on the vulnerability of reinforced
concrete frame building with infill concrete block
walls.

• Introduction
▫ Expected flood damage (EFD):
▫ Buildings are considered a total loss when EFD reaches
60%. This threshold indicates that the cost of repairing
the building is equal to the value of replacing it.
▫ Buildings located particularly in coastal areas are
frequently affected by high winds in addition to the
flood action.
▫ Although tsunami and storm surge are very different
events, the effects on the buildings or infrastructures of
the low-lying coastal zones can be very similar.

Load Cases and Forces for Different Flooding Conditions
Riverine
Flood
•Slow rise of water allowing
infiltration of water into the
building.
•Flood water level equal at both
sides of external wall
•Hydrodynamic force due to water
velocity on the outside of external
column/wall
•No hydrostatic force
•Flash flood
•High velocity water
Hydrostatic as well as
hydrodynamic force
Storm Surge
Depth of still water increments
gradually & flooding of coastal area
occurs hours before system landfall
•Hydrodynamic force due to storm
surge
Breaking wave reaches the building
located at the coast line
•Breaking wave force
Possibility of carrying debris Debris impact force
Tsunami
High velocity current with turbulent
bores
Hydrostatic as well as
hydrodynamic forces
Possibility of breaking waves with
direct impact on building
Breaking wave force
Possibility of carrying debris either
from sea or from coast as broken
buildings or tree trunks
Debris impact force

• Flood Forces and Loads
▫ Flood depth (d):
▫ Design Flood Elevation (DFE):
▫ Flood proofing design depth:
▫ Hydrostatic forces:
 The pressure exerted by still and slow moving water (velocity less
than 3.0m/sec) is called hydrostatic pressure.
 During any point of flood water contact with a structure, hydrostatic
pressures are equal in all direction and always act in perpendicular
direction to the surface on which they are applied.
 Pressure increases linearly with depth
 Four types:
 Lateral hydrostatic force
 Combined water and saturated soil pressure
 Equivalent hydrostatic pressure due to low velocity of water
 Vertical buoyancy hydrostatic pressure

FLOOD DEPTH AND DESIGN FLOOD DEPTH

DIAGRAM OF HYDROSTATIC PRESSURE

▫ Hydrodynamic Forces:
 Low velocity hydrodynamic forces
 Where flood water velocities do not exceed 3m/s (10ft/s).
 In this case, the hydrodynamic effects of moving water shall
be permitted to be converted to an equivalent hydrostatic
loads by increasing the DFE for design purpose by an
equivalent surcharge depth, dh.
 High velocity hydrodynamic forces
 for special structures and conditions and for velocity greater
than 3m/s, the basic eqn for hydrodynamic pressure is,

HYDORDYNAMIC AND IMPACT FORCES

CONVERSION OF EQUIVALENT HEAD TO EQUIVALENT HYDROSTATIC FORCE

▫ Hydrodynamic Forces:
 Complexities:
▫ One of the complexities when calculating forces generated by a
storm surge is determining the flood water velocity.
▫ Both the direction and velocity of flood water vary drastically
throughout the course of a storm system.
▫ FEMA (2000) recommended that flood water velocities due to
storm surge should be assumed to lie between specific lower and
upper bounds.
▫ For tsunami, the upper bound eqn is,

▫ Debris Impact Forces:
 It is related to isolated occurrences of typically sized debris or
floating objects striking the building.
 Magnitude of impact load due to a floating object:
 With the coefficients set equal to 1, the eqn reduces to
▫ Breaking Wave Force:
 Two wave forces:
 Breaking waves on columns/piles:
 Breaking waves on walls:

• Components of Buildings Affected by Flood:
▫ Foundation
▫ Reinforced concrete frame
▫ Infill external brick/ block wall
▫ Doors and windows
▫ Utility services, building contents and finishes
• Flood Damage Computation
▫ EFD defined as the expected value of flood damages, is then computed
per building unit by considering the aggregated damage to all five
building components.

MITIGATION MEASURES AGAINST NON-SEISMIC
NATURAL HAZARDS
• Planning and Site Consideration
▫ As far as possible, the building shall be on good ground.
▫ Regular plan shapes are preferred.
▫ For individual building, a circular or polygonal plan is
preferred over rectangular or square plans.
▫ Ornamental architecture involving horizontal or vertical
cantilever projections, facets etc should be avoided.
▫ Building should not be located in low-lying areas as cyclones
are invariably associated with flood & tidal surge.
▫ Long walls having lengths in access of about 3.5m shall be
provided with cross walls.
▫ In hilly regions, construction along ridges should be avoided.
▫ It is always preferable to locate the facility on a site in
Exposure A. Also where possible, avoid locating a building on
an escarpment or upper half of a hill.
▫ Trees in excess of 150mm in diameter, poles or tower should
not be placed near office or shelter buildings.

MITIGATION MEASURES AGAINST NON-
SEISMIC NATURAL HAZARDS
• Inspection, Periodic Maintenance, Repair and
Replacement
▫ It is important to understand that, over time, a facility’s
wind-resistance will degrade due to exposure to weather
unless it is periodically maintained and repaired.
• Exterior Doors
▫ Door assembly should be of sufficient strength to resist
negative and positive wind pressure.
▫ When corrosion is problematic, anodized aluminium or
galvanized doors and frames and stainless steel hardware
are recommended.
• Wall Opening
▫ Opening just below roof level is avoided.
▫ Percent of the total opening in the cross-section of any
wind resisting walls shall be less than 50% of the width of
the wall.

NATURAL HAZARDS
• Glass Paneling
▫ A wooden board may be securely fixed outside
all large size glass panels as and when cyclone/
wind storm warning is issued.
▫ Provide well-designed glass panels.
▫ Recourse may be taken to reduce the panel size
to smaller dimension.
▫ Glass panes can be strengthened by pasting thin
plastic film or paper strips.
▫ To prevent damage to glass panels from wind
borne missiles, a metallic fabric/ mesh may be
provided outside the large panels.

NATURAL HAZARDS
• Design Considerations
▫ Basic wind speed
▫ Pressure and Force
▫ Load Effects
▫ Wind Direction
▫ Resistance to Corrosion
• Causes of Damage Propagation
▫ Lack of general awareness among engineers that
structural integrity against collapse is important enough
to be regularly considered in design.
▫ In attempting to achieve economy in structure through
greater speed of erection and less site labor, systems may
be built with minimum continuity.
▫ Un-reinforced or lightly reinforced load bearing walls in
multistory structure may also have inadequate continuity
and joint rigidity.

NATURAL HAZARDS
• General Structural Integrity
▫ Good plan layout
▫ Integrated tie system
▫ Change direction of span of floor slab
▫ A part of the detailed design effort
▫ Ductile detailing
▫ Load bearing interior partition
• Durability
▫ Special attention needs to be given to specification of
adequate protection to ferrous metals.
▫ Where termites are problematic, it is recommended that
the soil be treated with a germicide.
▫ When corrosion is problematic, anodized aluminium or
galvanized doors and frames and stainless steel hardware
are recommended.

NATURAL HAZARDS
• Non load bearing walls
▫ Although masonry walls are not indented to carry gravity loads,
they must be designed to resist the positive and negative wind
loads in order to avoid collapse.
• Lighting protection system
▫ It is important to adequately design the attachment of the
lightning protection system and it should be firmly fixed with the
roof system.
• Elevator Pent House
▫ Proper waterproofing membrane should be provided in external
doors and windows of elevator penthouse or machine room.
• Protection of Utility System
▫ If the lowest floor is above DFE, utility system components can
be protected from flood damage by locating them anywhere on
or above the lowest floor of the structure.

NATURAL HAZARDS
• Mitigation Measures for Tornado
▫ Safe room can be located anywhere in the house or even
outside.
▫ Safe room must be designed for wind speeds up to 112m/s
▫ Exposure B and exposure C
▫ Partially enclosed
▫ Structurally isolated from the main structure of the house
▫ Securely anchored to the foundation
▫ All components must be designed and tested to resist the
specified wind forces and prevent perforation by wind-
borne debris.
▫ Adequate ventilation
▫ Constructed in accordance with the perspective design of
the FEMA 320

NATURAL HAZARDS
• Mitigation Measures for Tsunami
▫ Elevate the structure above the ground floor with deeper
foundation and open ground floor
▫ The columns should be firmly fixed to the foundation, also
braced to each other.
▫ As much as possible, leave vegetations and reefs intact.
▫ Do not build building at low level on the shore line at the
top of a smooth shallow beach.
▫ Buildings should not be close together in a way that makes
a wider dam.
▫ Construct small sea walls parallel to the sea shore.
▫ Construct multi level buildings within the inundation zone
▫ Orient the building at an angle to the shore line.
▫ Construct building with reinforced concrete structures.

VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

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VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH