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BE OUR GUEST: Walls will tumble down


Grenville Phillips II

BE OUR GUEST: Walls  will tumble down

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Following the earth tremor on Tuesday, the CBC Evening News broadcast the advice that people should remain in the building during an earthquake. This advice assumes that the building will be stable during an earthquake. This critical assumption should have been verified before offering such advice.
     Allow me to assess this assumption by examining two ancillary issues.
The first issue is the absence of adequate shear walls. The Barbados National Building Code specifies that houses must have adequate shear walls in order to resist earthquake forces. Shear walls contain no door or window openings from foundation to roof, and should be on all four sides of a house. Shear walls should be 3m (10ft) wide.
 If 3m is inconvenient, then two 2.2m (6.5ft) wide walls on each side are permitted.
Regrettably, of the thousands of houses constructed since the publication of the code 21 years ago, perhaps only five of them have the required shear walls. It should be noted that it costs no additional money to achieve this safe level of building stability.
The second issue is the unsafe bending of steel reinforcement.
Building contractors normally bend steel reinforcement to the point of failure, and then use this damaged material to connect structural elements (like walls and slabs) together. Buildings that relying on these weak connections are expected to fail during an earthquake.
During the earthquake in Kashmir (Indian subcontinent) in 2005, male students jumped through the windows and ran through the doors of their school and survived.  
When they cleared the rubble of the collapsed school, they found the bodies of the girls huddled near the middle of the classroom. The assumption that buildings are built to be stable during earthquakes is false.
The advice that I give to my son is to run out of the building as fast as possible at the start of any movement.
On a related matter:?following earth tremors in L’Aquila, Italy, in 2009, six earth scientists reassured residents that a large earthquare was “unlikely”. Then a 6.3 magnitude earthquake devasted the city, resulting in 309 deaths. The scientists were subsequently convicted of manslaughter. Geologist (Andre)?Brathwaite is advised to be very careful with his public reasssurances.
Grenville Phillips II is a chartered structural engineer and the president of Walbrent College.

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