vulnerability assessment and damage mitigation for rcc buildings due to non seismic hazards in...

116
VULNERABILITY ASSESSMENT AND DAMAGE PREDICTION OF REINFORCED CONCRETE BUILDINGS AGAINST NON-SEISMIC HAZARDS WELCOME TO OUR PRESENTATION ON

Upload: johana-sharmin

Post on 16-Feb-2017

243 views

Category:

Engineering


2 download

TRANSCRIPT

Page 1: 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

Page 2: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

PRESENTED BY:ENGR. JOHANA SHARMINENGR. SOUPTIK BARMAN

TIRTHAAND

ENGR. KAZI WALIUL HASAN

Date: 20th July, 2016

THIS PRESENTATION IS COMPLETELY BASED ON MANUAL OF PWD AND J ICA PREPARED UNDER THE PROJECT FOR

CNCRP.

Page 3: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

CONTENTSINTRODUCTION

VULNERABILITY ASSESSMENTNON-SEISMIC NATURAL HAZARDS

BUILDING ELEMENTSPOTENTIAL DAMAGE DUE TO NON SEISMIC FORCES

VULNERABILITY ASSESSMENT GUIDELINES (CYCLONE)VULNERABILITY AND DAMAGE PREDICTION OF BUILDING

ENVELOPE BY ‘WIND DAMAGE BAND’ MODELSTRENGTH EVALUATION OF MWFRS

LOAD COMBINATIONWIND LOAD ANALYSIS

ILLUSTRATIVE EXAMPLEINUNDATION DEPTH DUE TO STORM SURGE AND TSUNAMI

BUILDING DAMAGE ASSESSMENT DUE TO FLOOD, TIDAL SURGE AND TSUNAMI

MITIGATION MEASURES

Page 4: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

SCOPE AND PURPOSE

•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.

Page 5: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

LIMITATIONS

•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.

Page 6: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

VULNERABILITY ASSESSMENT•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.

Page 7: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

STEPS OF VULNERABILITY ASSESSMENT

Define Project

Form planning group

Identify and describe probable hazardsDefine and classify major components of the structure/

buildingAssign relative level of important to the components

Identify potential risk to each component

Describe effectsSet a strategy to deal with most serious potential problem first

followed by natural sequenceDefine ways to minimize consequence

Recommend action

Implement action

Page 8: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

NON SEISMIC NATURAL HAZARDS

Cyclone

Flood

Cyclone induced storm surge

Tornado

Tsunami

Lighting and

Thunderstorm

Landslide

Page 9: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

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.

Page 10: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

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.

Page 11: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

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.

Page 12: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

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 98.40 111.00 124.00

137.50

v mph 42.40 59.40 78.00 98.00 120.0

0143.4

0168.0

0193.2

1220.1

4248.2

2277.3

9307.6

5

v km/h 68.43 95.63 125.3

4157.8

0192.9

3230.2

3269.6

1311.5

0354.4

3399.6

3446.5

9495.3

2

Page 13: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

WIND INTENSITY SCALES

Page 14: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

WIND INTENSITY SCALES

Page 15: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

WIND INTENSITY SCALES

Page 16: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

WIND INTENSITY SCALES• 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 beso 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.

Page 17: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

WIND INTENSITY SCALESTable: 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 14.17Deep Depression 52-61 32.3-37.90 14.44-16.94Cyclonic Storm 62-88 38.5-54.65 17.22-24.44

Severe Cyclonic Storm 89-117 55.28-72.67 24.72-32.50Severe 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).

Page 18: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

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).

Page 19: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

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.

Page 20: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH
Page 21: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH
Page 22: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

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.

Page 23: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

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 0.62115 2.5 71.43 8.2 1.0 0.62135 3.0 83.90 9.84 1.5 0.93

165 3.5 102.50 11.48 2.0 1.24195 4.8 121.12 5.74 4.0 2.48225 6.0 140.00 19.68 4.5 2.8235 6.5 146.00 21.32 5.0 3.11260 7.8 161.50 25.58 5.5 3.42

Page 24: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

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.

Page 25: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH
Page 26: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

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.

Page 27: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH
Page 28: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH
Page 29: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH
Page 30: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

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.

Page 31: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

LIGHTNING AND THUNDERSTORM• 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).

Page 32: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

LIGHTNING AND THUNDERSTORM• 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.

Page 33: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

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.

Page 34: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

BUILDING ELEMENTSStructural 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.

Page 35: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

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 envelopeLocation 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

Page 36: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

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

Page 37: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

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 consideration

s

Contamination

Breaking waves with

floating debris

Page 38: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

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

Page 39: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

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.

Page 40: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

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.

Page 41: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

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.

Page 42: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

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.

Page 43: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

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.

Page 44: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

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

Page 45: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

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.

Page 46: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

VULNERABILITY AND DAMAGE PREDICTION OF BUILDING ENVELOPE BY ‘WIND DAMAGE BAND’

MODEL• 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:

Page 47: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

VULNERABILITY AND DAMAGE PREDICTION OF BUILDING ENVELOPE BY ‘WIND DAMAGE BAND’

MODEL• Wind Damage Band:

Page 48: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

VULNERABILITY AND DAMAGE PREDICTION OF BUILDING ENVELOPE BY ‘WIND DAMAGE BAND’

MODEL• Wind Damage Band:

•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.

Microsoft Office Excel Worksheet

Page 49: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

STRENGTH EVALUATION OF MAIN WIND FORCE RESISTING SYSTEM

• Basic Requirements

• Nominal and factored loads in load combination

1

• Adequate stiffness

2

• Resist forces due to earthquake and wind.

5

Page 50: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

STRENGTH EVALUATION OF MAIN WIND FORCE 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

Page 51: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

STRENGTH EVALUATION OF MAIN WIND FORCE 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

Page 52: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

STRENGTH EVALUATION OF MAIN WIND FORCE 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

Page 53: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

STRENGTH EVALUATION OF MAIN WIND FORCE 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.

Page 54: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

STRENGTH EVALUATION OF MAIN WIND FORCE 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

Page 55: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

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.

Page 56: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

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+1.0L6. 0.9D+1.6W+1.6H7. 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.

Page 57: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

LOAD COMBINATION• Combining nominal loads using allowable stress design:

1. D2. D+L3. D+F4. D+H+F+L+T5. 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+H11. 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).

Page 58: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

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:

Page 59: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

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˚.

Page 60: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

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)

Page 61: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

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.

Page 62: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

WIND LOAD ANALYSIS• METHOD 2- ANALYTICAL PROCEDURE

▫Design Procedure:Basic wind speed, V (Table 1)

Wind directionali

ty 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 classificati

onInternal pressure

coefficient, Gcpi (Table

9)

External pressure

coefficient, Cp or GCpf

Velocity pressure qz or qh

Design load p or F

Page 63: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

TABLE 1: BASIC WIND SPEED (3-SECOND GUST SPEED) FOR SELECTED LOCATIONS OF

BANGLADESH Location

Basic Wind Speedm/s Km/h Mph

Angorpota 47.8 172.10 106.88Bagerhat 77.5 279.0 173.30

Bandarban 62.5 225 140Barguna 80.0 288.0 179.0Barisal 78.7 283.32 176.0Bhola 69.5 250.2 155.4Bogra 61.9 222.84 138.40

Brahmanbaria 56.7 204.12 126.78Chandpur 50.6 182.16 113.14

Chapai Nowabgonj 41.4 149.04 92.57

LocationBasic Wind Speed

m/s Km/h Mph

Chittagong 80.0 288.0 179.0Chuadanga 61.9 222.84 138.40

Comilla 61.4 221.04 137.30Cox’s Bazar 80.0 288.0 179.0Dahagram 47.8 172.10 106.88

Dhaka 65.7 236.52 146.90Dinajpur 41.4 149.04 92.57Faridpur 63.1 227.16 141.10

Feni 64.1 230.76 143.33Gaibanda 65.6 236.16 146.68Gazipur 66.5 239.40 148.70

Page 64: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

TABLE 1: BASIC WIND SPEED (3-SECOND GUST SPEED) FOR SELECTED LOCATIONS OF

BANGLADESH Location

Basic Wind Speedm/s Km/h Mph

Gopalgonj 74.5 268.20 166.58Habigonj 54.2 195.12 121.20

Hatiya 80.0 288.0 179.0Ishurdi 69.5 250.20 155.40

Joypurhat 56.7 204.12 126.78Jamalpur 56.7 204.12 126.78Jessore 64.1 230.76 143.33

Jhalokathi 80.0 288.0 179.0Jhenidah 65.0 234.0 145.34

Khagrachari 56.7 204.0 126.78Khulna 73.3 263.88 163.90

LocationBasic Wind Speed

m/s Km/h Mph

Kutubdia 80.0 288.0 179.0Kishorgonj 64.7 232.92 144.67Kurigram 65.6 236.16 146.68Kushtia 66.9 240.84 149.59

Lakshmipur 51.2 184.32 114.48Lalmonirhat 63.7 229.32 142.43Madaripur 68.1 245.16 152.27

Magura 65.0 234.0 145.34Manikgonj 58.2 209.52 130.14Meherpur 58.2 209.52 130.14

Maheshkhali 80.0 288.0 179.0

Page 65: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

TABLE 1: BASIC WIND SPEED (3-SECOND GUST SPEED) FOR SELECTED LOCATIONS OF

BANGLADESH Location

Basic Wind Speedm/s Km/h Mph

Moulovibazar 53.0 190.8 118.51Munshigonj 57.1 205.56 127.68Mymensingh 67.4 242.64 150.71

Naogoan 55.2 198.72 123.43Norail 68.6 246.96 153.40

Narayanganj 61.1 220.0 136.62Narshinghdi 59.7 214.92 133.49

Natore 61.9 222.84 138.41Netrokona 65.6 236.16 146.68Nilphamari 44.7 160.92 100.00Noakhali 57.1 205.56 127.68

LocationBasic Wind Speed

m/s Km/h Mph

Pabna 63.1 227.16 141.10Panchagorh 41.4 149.04 92.57Patuakhali 80.0 288.0 179.0Pirojpur 80.0 288.0 179.0Rajbari 59.1 212.76 132.15

Rajshahi 49.2 177.12 110.00Rangamati 56.7 204.12 126.78Rangpur 65.3 235.08 146.01Satkhira 57.6 207.36 128.80

Shariatpur 61.9 222.84 138.41Sherpur 62.5 225.00 139.75

Page 66: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

TABLE 1: BASIC WIND SPEED (3-SECOND GUST SPEED) FOR SELECTED LOCATIONS OF

BANGLADESH Location

Basic Wind Speedm/s Km/h Mph

Sirajgonj 50.6 182.16 113.14Srimongol 50.6 182.16 113.14St. Martin

Island 80.0 288.0 179.0

Sunamgonj 61.1 220.0 136.62Sylhet 61.1 220.0 136.62

Sandwip 80.0 288.0 179.00Tangail 50.6 182.16 113.14Teknaf 80.0 288.0 179.00

Thakurgaon 41.1 147.96 91.90

Page 67: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

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

EARTHQUAKE LOADS

Page 68: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

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 0.77II 1.00 1.00III 1.15 1.15IV 1.15 1.15

Page 69: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

TABLE 4: HEIGHT AND EXPOSURE ADJUSTMENT COEFFICIENT, λ

Adjustment Factor For Building Height and Exposure, λMean 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

Page 70: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

TABLE 5: WIND DIRECTIONALITY FACTOR, KdStructure Type Directionality Factor, Kd

BuildingsMain Wind-force-resisting system

Components and cladding

0.850.85

Arched roofs 0.85Chimneys, tanks, similar structure

SquareHexagonal

Round

0.960.950.95

Solid signs 0.85

Open Signs & Lattice Frame work 0.85Trussed towers

Triangular, square, rectangularAll other cross sections

0.850.95

Page 71: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

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.

Page 72: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

SURFACE ROUGHNESS CATEGORIES AND EXPOSURE CATEGORIES

•Exposure Categories▫Exposure A (Exposure B of ASCE):

Page 73: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

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).

Page 74: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

TABLE 6: VALUES OF APPROXIMATE PERIOD PARAMETERS Ct AND xStructure Type

Ct xSI 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 frame0.07240.0466

0.0280.016

0.80.9

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.

Page 75: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

TABLE 7: COMPARATIVE VALUES OF FREQUENCY OF BUILDING FOR DIFFERENT

EQUATIONSEquation (fps) Equation(SI) N1 (Example

values) Type

Ta = Ct hnx

n1 = 1/Ta

Ta = Ct hnx

n1 = 1/Ta

0.701.17

Flexible in E-WRigid in N-S

Ta = 0.1Nn1 = 1/ Ta

Ta = 0.1Nn1 = 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)

0.680.51

FlexibleFlexible

fn1 = 150/H fn1 = 45.73/H 1.014 Rigidn1 = 220/H n1 = 67/H 1.49 Rigid

Page 76: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

GUST EFFECT FACTOR, G or Gf• 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:

Page 77: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

TABLE 8: TERRAIN EXPOSURE CONSTANTS IN SI AND FPS SYSTEM

Exposure 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

Page 78: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

GUST EFFECT FACTOR, G or Gf• 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.

Page 79: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

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.

Page 80: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

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

Page 81: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

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

Page 82: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

TABLE 10: EXTERNAL PRESSURE CO-EFFICIENT, Cp OF WALLS AND ROOF FOR ENCLOSED,

PARTIALLY ENCLOSED BUILDINGWall Pressure Coefficient, Cp

Surface L/B Cp Use withWindward wall All values 0.8 qz

Leeward wall0-1 -0.5

qh2 -0.3>4 -0.2

Side wall All values -0.7 qh

Page 83: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

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

-0.50.0

-0.30.2

-0.20.3

-0.20.3

0.00.4 0.4 0.01θ -0.3 -0.5 -0.6

0.5 -0.9-0.18

-0.7-0.18

-0.40.0

-0.30.2

-0.20.2

-0.20.3

0.00.4

0.01θ -0.5 -0.5 -0.6

≥1.0 -1.3-0.18

-1.0-0.18

-0.7-0.18

-0.50.0

-0.30.2

-0.20.2

0.00.3

0.01θ -0.7 -0.6 -0.6

Page 84: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

TABLE 10: EXTERNAL PRESSURE CO-EFFICIENT, Cp OF WALLS AND ROOF FOR ENCLOSED, PARTIALLY

ENCLOSED BUILDINGWind

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,-0.18h/2 to h -0.9,-0.18H to 2h -0.5,-0.18

>2h -0.3,-0.18

≥1.0

0 to h/2 -1.3,-0.18Area (sqft) Reduction

factor≤100

(9.3sqm) 1.0

> h/2 -0.7, -0.18

200 (23.2sqm) 0.9

≥1000 (92.9sqm) 0.8

Page 85: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

VELOCITY PRESSURE EXPOSURE COEFFICIENT KZ

Page 86: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

TABLE 11: VELOCITY PRESSURE EXPOSURE COEFFICIENT Kh AND KZ

Height above ground level Exposure

m ft A B C0-4.6 0-15 0.57 0.85 1.036.1 20 0.62 0.90 1.087.6 25 0.66 0.94 1.129.1 30 0.70 0.98 1.16

12.2 40 0.76 1.04 1.2215.2 50 0.81 1.09 1.2718.3 60 0.85 1.13 1.3121.3 70 0.89 1.17 1.3424.4 80 0.93 1.21 1.3827.4 90 0.96 1.24 1.4030.5 100 0.99 1.26 1.4336.6 120 1.04 1.31 1.52

Page 87: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

TABLE 11: VELOCITY PRESSURE EXPOSURE COEFFICIENT Kh AND KZ

Height above ground level Exposure

m ft A B C42.7 140 1.09 1.36 1.5248.8 160 1.13 1.39 1.5554.9 180 1.17 1.43 1.5861.0 200 1.20 1.46 1.6176.2 250 1.28 1.53 1.6891.4 300 1.35 1.59 1.73106.7 350 1.41 1.64 1.78121.9 400 1.47 1.69 1.82137.2 450 1.52 1.73 1.86152.4 500 1.56 1.77 1.89

Page 88: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

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.

Page 89: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

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)

Page 90: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

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

Page 91: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

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

Page 92: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

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

Microsoft Office Excel Worksheet

Microsoft Office Word 97 - 2003 Document

Microsoft Office Excel Worksheet

Microsoft Office Excel Worksheet

Page 93: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

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 elevationOf 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.

Page 94: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

INUNDATION DEPTH DUE TO STORM SURGE AND TSUNAMI IN COASTAL AREAS

• 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

Page 95: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

INUNDATION DEPTH DUE TO STORM SURGE AND TSUNAMI IN COASTAL AREAS

• 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.

Page 96: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

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.

Page 97: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

BUILDING DAMAGE ASSESSMENT DUE TO FLOOD, TIDAL SURGE AND TSUNAMI

• 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.

Page 98: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

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

• No hydrostatic forceBreaking wave reaches the building

located at the coast line• Breaking wave force• No hydrostatic 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 trunksDebris impact force

Page 99: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

BUILDING DAMAGE ASSESSMENT DUE TO FLOOD, TIDAL SURGE AND TSUNAMI

• 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

Page 100: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

BUILDING DAMAGE ASSESSMENT DUE TO FLOOD, TIDAL SURGE AND TSUNAMI

FLOOD DEPTH AND DESIGN FLOOD DEPTH

Page 101: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

BUILDING DAMAGE ASSESSMENT DUE TO FLOOD, TIDAL SURGE AND TSUNAMI

DIAGRAM OF HYDROSTATIC PRESSURE

Page 102: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

BUILDING DAMAGE ASSESSMENT DUE TO FLOOD, TIDAL SURGE AND TSUNAMI

•Flood Forces and Loads▫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,

Page 103: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

BUILDING DAMAGE ASSESSMENT DUE TO FLOOD, TIDAL SURGE AND TSUNAMI

HYDORDYNAMIC AND IMPACT FORCES

Page 104: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

BUILDING DAMAGE ASSESSMENT DUE TO FLOOD, TIDAL SURGE AND TSUNAMI

CONVERSION OF EQUIVALENT HEAD TO EQUIVALENT HYDROSTATIC FORCE

Page 105: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

BUILDING DAMAGE ASSESSMENT DUE TO FLOOD, TIDAL SURGE AND TSUNAMI

• Flood Forces and Loads▫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,

Microsoft Office Excel 97-2003 Worksheet

Page 106: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

BUILDING DAMAGE ASSESSMENT DUE TO FLOOD, TIDAL SURGE AND TSUNAMI

• Flood Forces and Loads▫ 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:

Microsoft Office Excel Worksheet

Page 107: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

BUILDING DAMAGE ASSESSMENT DUE TO FLOOD, TIDAL SURGE AND TSUNAMI

• 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.

Page 108: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

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.

Page 109: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

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.

Page 110: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

MITIGATION MEASURES AGAINST NON-SEISMIC 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.

Page 111: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

MITIGATION MEASURES AGAINST NON-SEISMIC 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.

Page 112: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

MITIGATION MEASURES AGAINST NON-SEISMIC 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.

Page 113: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

MITIGATION MEASURES AGAINST NON-SEISMIC 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.

Page 114: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

MITIGATION MEASURES AGAINST NON-SEISMIC 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

Page 115: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

MITIGATION MEASURES AGAINST NON-SEISMIC 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.

Page 116: VULNERABILITY ASSESSMENT AND DAMAGE MITIGATION FOR RCC BUILDINGS DUE TO NON SEISMIC HAZARDS IN BANGLADESH

THANK YOU ALL