The Edmond Sun

June 10, 2013

Joplin tornado damage tied to poor construction practices

CNHI News Service

JOPLIN, Mo. — Damage to homes in the path of a destructive tornado two years ago would have been much less severe if better construction practices had been followed, a study released recently by the American Society of Civil Engineers concluded.

It did not take much wind to flatten houses in the Joplin tornado zone because so many were poorly constructed, the study concluded.

An investigative team of engineers sent to Joplin found that more than 83 percent of the damage on May 22, 2011, was caused by winds of 135 mph or less, which is equal to the maximum wind speed of an EF-2 tornado.

Only 4 percent of the damage could be linked to an EF-4 tornado, which can have winds speeds ranging from 168 to 199 mph. The ASCE investigators found no EF-5 level tornado damage to buildings at all.

The total path of the tornado was 22 miles. The team used sophisticated data collection methodology that documented damage and assessed the causes of failure to more than 150 buildings. More than 7,000 structures were destroyed or badly damaged by the tornado.

The engineers concluded that because the structures were so poorly built to withstand wind, flying debris from houses made damage in the tornado zone much worse.

Had the houses in the tornado zone been built with hurricane ties — metal clips that fasten the rafters and trusses to the exterior walls of a house — the damage would have been much less. It is one of the recommendations coming out of their analysis.

“The study team believes that a relatively large number of buildings could have survived in Joplin if they had been built to withstand hurricane winds,’’ said Bill Coulbourne, a member of the ASCE engineering team that came to Joplin.

“They would not survive the winds of an EF-4 or EF-5 tornado, but they could survive lower wind speeds by using hurricane ties and by strapping the house to the foundation.”