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Experts Gather to Discuss Wind Effects

June 13, 2016

Researchers from around the world gathered last week to discuss how best to analyze the construct tall buildings, bridges, and other non-streamlined bodies to stand up to high winds at the 8th Inter­na­tional Col­lo­quium on Bluff Body Aero­dy­namics and Appli­ca­tions.


Source: News @ Northeastern

June 1 marked the offi­cial start of the 2016 Atlantic hur­ri­cane season, but Hur­ri­cane Alex and Trop­ical Storm Bonnie couldn’t wait: Alex hit early in Jan­uary, and Bonnie fol­lowed in May.

Luca Caracoglia, asso­ciate pro­fessor in the Depart­ment of Civil and Envi­ron­mental Engi­neering, knows the havoc such high winds and crashing rain can wreak on tall build­ings, bridges, chim­neys, and other non-​​streamlined, or “bluff,” bodies.

Last week, he brought his exper­tise in struc­tural dynamics and wind engi­neering to bear as chairman and co-​​host of the Eighth Inter­na­tional Col­lo­quium on Bluff Body Aero­dy­namics and Appli­ca­tions. Over four days, more than 200 engi­neering experts from around the world con­vened at North­eastern to dis­cuss how to best ana­lyze and struc­ture these square, cir­cular, and oblong bodies to with­stand tur­bu­lent air­flows and respond with more resilience to struc­tural oscil­la­tions and vibra­tions, among other topics.. Chris Letch­ford, pro­fessor at Rens­se­laer Poly­technic Insti­tute and pres­i­dent of the Amer­ican Asso­ci­a­tion for Wind Engi­neering (AAWE), served as co-​​chairman.

White­caps in the air

A bluff body, when immersed in an air­flow, expe­ri­ences a wake and a recir­cu­la­tion region forms behind it,” explains Caracoglia, who spe­cial­izes in sev­eral areas, including tall build­ings, the wind-​​induced dynamic insta­bility of long-​​span bridge decks and wind-​​turbine blades, and stay-​​cable aero­dy­namics and vibration.

Pic­ture the recir­cu­lating white­caps behind a ship coursing through the water, but here it’s whipped air inter­acting with a building like Boston’s 200 Clarendon—formerly John Han­cock Tower—whose win­dows hur­tled to the street during high winds in the 1970s, or the Tacoma Nar­rows Bridge, in Wash­ington state, which col­lapsed due to wind-​​induced vibra­tions in 1940. Con­struc­tion workers, observing the bridge’s ver­tical looping before the col­lapse, dubbed it “Gal­loping Gertie.”

June 8, 2016 - BOSTON, MA. -  Luca Caracoglia, Associate Professor in the Department of Civil and Environmental Engineering, gives open remarks during the 8th International Colloquium on Bluff Body Aerodynamics and Applications held in the Curry Student Center Ballroom at Northeastern University on June 8, 2016. Photo by Matthew Modoono/Northeastern University

Luca Caracoglia, asso­ciate pro­fessor, delivers opening remarks at the inter­na­tional col­lo­quium. Photo by Matthew Modoono/​Northeastern University

It’s a structure’s shape that deter­mines its response to severe winds,” says Caracoglia. Bluff bodies, with their cor­ners, edges, and spread, are par­tic­u­larly vul­ner­able to wind velocity fluc­tu­a­tions. “Broadly, in our research we are inves­ti­gating what char­ac­ter­is­tics to change to reduce the vibra­tions and other responses that can make these struc­tures unsafe.”

In par­tic­ular, Caracoglia focuses on devel­oping numer­ical method­olo­gies to sim­u­late how tall build­ings will respond to high winds. The aim is to pro­vide engi­neers and designers with the means to deter­mine which spec­i­fi­ca­tions respond best as they plan to con­struct and ren­o­vate the structures.

In a recent paper, he and doc­toral can­di­date Wei Cui out­lined a method­ology that went beyond ana­lyzing the struc­tural per­for­mance of tall build­ings in hur­ri­cane con­di­tions to assess the life­time costs, including repairs and main­te­nance, such build­ings would sus­tain because of damage from the winds. Focusing on the Atlantic coast­line, the researchers con­sid­ered how cli­mate warming over time would affect hur­ri­cane fre­quency and inten­sity to cal­cu­late future wind speeds in the area. They used a 180-​​meter tall building in Miami as a bench­mark, and con­firmed that the method­ology was trans­ferrable by run­ning sim­u­la­tions using vari­ables from sev­eral other cities along the Atlantic coastline.

We wanted to assess how the main­te­nance cost, con­se­quent to damage from strong storms, can accu­mu­late over time,” says Caracoglia. “Even­tu­ally this method­ology can be used to infer how to make the most cost-​​efficient deci­sions regarding design for future tall build­ings in areas likely to be hit by hur­ri­canes and other severe weather.”

The col­lo­quium

The col­lo­quium, which was attended by expe­ri­enced researchers and tal­ented grad­uate stu­dents, com­prised a blend of fun­da­mental work and prac­tical appli­ca­tions and addressed both com­pu­ta­tional and wind-​​tunnel studies.

It is held every four years under the umbrella of the Inter­na­tional Asso­ci­a­tion for Wind Engi­neering (IAWE). The IAWE, AAWE, and sev­eral industry spon­sors pro­vided funds to sup­port the travel of more than 30 stu­dents who attended the col­lo­quium and pre­sented their work.