Role of structural engineers in face of natural disasters

7/28/2019 Role of structural engineers in face of natural disasters

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HOW CAN STRUCTURAL ENGINEERS CONTRIBUTE TOWARDS

DISASTER MITIGATION?

Early 19th century London was a public health disaster; river Thames was literally an open sewer.

Cholera epidemics - along with tuberculosis, typhoid, dysentery and smallpox -were the primary

cause of death. They were thought of as everyday risks of living; until some wise men and a CivilEngineer by the name of Joseph Bazalgatte brought to an end that stream of thought. The life of the

common man was brought to a new high as a consequence of this sanitary revolution. As those

people thought then, it is now the time for us to stop being complacent about disasters and aim high;

zero loss of life, minimum property damage from disasters. Yet again the role of engineers will be

of paramount importance.

Disaster Mitigation

As hard as it is to predict a disaster, it is

difficult to prevent disasters from happening.

Although we are slowly unraveling the

mysteries of nature, it never fails to surprise

us; 1958 flooding of Zambezi during

construction of Kariba dam, 2010

Christchurch earthquake, 2013 Russian

meteor shower. Each one of them surpassed

the worst possible scenario, setup by means

of human expertise, experience and

expectation. There is no denying the

possibility of our own township being hit by a

disaster, better yet the worst kind.

The United Nations is in the forefront in

calling for the safety of human lives and

property in the face of rapidly increasing odds

for the world to be hit by a major disaster-

breaking records ,among other things we'd

rather see unshattered. According to

them the aim is to achieve a

significant reduction in the loss of life

and material damage caused by

disaster.

Disaster Management Models

There are several disaster

management models which are

helpful in responding to disasters. The

traditional model represents a cyclic

process where it shows a pre-disaster

risk reduction phase and post-disaster

recovery phase. A second model

crunch/release model- identifies a disaster as

the situation where a hazard meets

vulnerability. Both these models areimportant in their own rightand are helpful

in understanding the role of structural

engineering in disaster mitigation.

Role of a structural engineer scope under

the traditional view

We cannot restrict the role of a Structural

Engineer to a section of disaster mitigation

we can contribute across the full spectrum ofdisaster management. Structural Engineers

have a role not only in designing disaster

resistant structures, but also in rescue efforts

in collapsed structures, immediate

rehabilitation of infrastructure and

reconstruction.

F igure 1: Traditi onal Model of D isaster Management


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Pre-disaster risk reduction activities are where

the contribution from structural engineers is

significant. Work in this could be better

guided by the crunch/release modelwhich

will be explained in the due cause of the text.

Role of the Structural Engineer in post-

disaster recovery phase is as much important

as any other professional role. Immediate

rescue efforts after a disaster will include

evacuation of people from unstable structures

-after an earthquake, landslide, tsunami, - or

accessing places with limited infrastructure

after a flood, tsunami.

Earthquakes and landslide produces unstable

structures and soil conditions. Immediate

rescue teams from military forces or fire

rescue are under risk in accessing such places

they put their lives in risk to rescue people

they do not even know. A Structural

Engineers input will be valuable in such

cases to take precautionary measures and

temporarily strengthen structures and

underlying soilif required. This can reduce

the risk on rescue personal and maybe even

increase the chance of survival of the trapped

people - by improving the safe access period

to structures. To do this Structural Engineers

should be trained to undertake quick visual

assessment of a partially damaged structure

and give an expert opinion.

It is also possible that roads are damaged or

flooded and the bridges have collapsed.

Providing alternative temporary access is of

utmost importance for rehabilitation after a

disaster- although Sri Lanka was one of the

hardest hit countries by 2004 Indian Ocean

Tsunami it recovered quickly, thanks largely

to the rapid bridge replacements and road

clearance. Provision of rapid access allows for

mobilization of medical and other basic

requirements to people hit by the disaster.

After the stages of immediate assistance the

hype about the disaster dials down, but the

lives have to continue. It is common - in

many developing countries - to see people in

relief camps, years after a disaster has struck.

Importance of bringing back the city to life -

as soon as practicable- can never be

overstated.

The reconstruction effort is threefold-

essential infrastructure, public facilities,

residencies. All these have to be completed

simultaneously. Rehabilitation ofinfrastructure may require renovation or

complete reconstruction. Structural Engineers

will be required to assess the requirement and

propose and carry out a structurally and

economically viable solution.

The residential structures pose a different

challenge. Although the short term

requirement is to bring the house up to a

standard that allows resettlement, in long termthe house may be required to be further

expanded- even to luxurious living standards.

So the structural engineer will be required to

look at the social aspects of the situation also.

Rapidly deployable permanent housing units

are a newly explored area. This would be a

significant step towards rapid rehabilitation.

F igur e 2: Road washed away during

flooding, limi ting access to disaster h it areas.


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Role of a structural engineercrunch and

release

The crunch and release model describes a

disaster as the situation where a fragile

situationstructural, natural, social,

economic or personal- meets a hazard

earthquake, high wind, flood or drought. Thus

the way to prevent a disaster is to release the

pressure- from the hazard and fragility- on the

element at riskphysical property, economy,

or society. This model identifies the built

environment as an element at risk. So it is in

ourStructural Engineershand to come up

with ways to reduce hazards and reduce

fragility of built environment.

Control of hazards is not an easy task at some

situationsearthquakes, cyclones - but for

some hazards it is a possibility -landslides,

floodsand there are some hazards which

can be avoided by appropriate land usage -

tsunamis, floods. It is important to note that

none of these mean complete elimination of

hazards.

The twobroader categories ofactivities

Structural Engineers can get involved in to

control hazards are,

a. Research -to get a broaderunderstanding of the mechanism of

hazards.

b. Eliminate any activity that supportscreating a hazarde.g. improper land

use will increase the possibility of a

flood event.

This second category should be looked intoas an integral part of designlike the

emphasis on environmental performance and

health and safety - but not as a separate line of

work.

Design of disaster resistant structuresas

obvious to anyone- would be fully under the

scope of Structural Engineering. Although

there is an economical consideration when

strengthening a structure to withstand adisaster force, there is no point in putting

peoples life at riskat the current point in

timewhen no one is certain of a place free

from disasters. Disaster resistancein some

peoples view- should be a compulsory

design consideration.

Further there is a certain portion of deaths

occurring not due to disaster itself, but due to

structures falling on. Along this line, research

has been done to retrofit masonry structures

in Middle Eastern countrieswhere

earthquake dislodges heavy masonry blocks

which are heavy enough to cause severe

damage to people. They have proposed to use

a Polypropylene net on either side of the

block workcovered by a finishing mortar-

to effectively hold the block work as a single

integral unit. It is Structural Engineersresponsibility to even predict such cases and

further reduce casualties.

A lot of research work is being done in the

area of vulnerability of structures due to

natural disasters. Data collected from

previous disaster situations provide data to

create vulnerability curveswhich set the

probability of a specified damage level (e.g.

non- structural damage, complete collapse) tostructure at different values of a demand

parameter related to the disaster in

F igure 3: Crunch Model of Disaster M iti gation


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consideration (e.g. ground acceleration,

tsunami wave height). These can be used to

come up with collapse mechanisms for

structures and design criterion and design

codes for disaster resistant structures. This

data are always insightful as disastersituations are always dynamic and it is very

much difficult to distinguish what caused the

collapse.

Structural Engineerthe human being

All those professional work of a structural

engineer -at the face of disaster- is in addition

to the social being he is. All of us have a

social responsibilityand a capacity to act so

to help out a person in need and not to put

them in harms way. Our ability to be a part

of a communityin essence- will push us to

act in a way that will help out our fellow

beings , be it professional work or -purely- an

'in the moment' act.

Figure 4: The Human Side in the Face of

Disaster

References:

Asian Disaster Preparedness Centre. Disaster

Risk Management & Mitigation. [online]

Available fromwww.wyf.org.my/DRM.pdf

[Accessed April 08 2013]

Coburn A.W, Spence R.J.S, Pomonis A.

Disaster Mitigation, 2nd ed.,

Nelson Lam. 2011.Built Infrastructure in

Extreme Events: Preparing Structural

Engineers to Take on The Tasks of Disaster

Mitigation. In Dissanayake R, Jayasinghe

M.T.R, Mendis P.A, Fernando S.

International Conference on Structural

Engineering, Construction and Management

2011. December 15 -17. Earls Regency Hotel,Kandy. p vii - xv

Sathiparan N. 2012. SSESL Monthly

Question Time.Retrofitting of Masonry

Buildings under Seismic Loading. May 29.

IESL Auditorium
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Role of structural engineers in face of natural disasters