Vertical, horizontal or diagonal cracks after an earthquake? Here's what’s dangerous

A structural engineer on Wednesday said the direction of cracks in a building will indicate if a structure may collapse after an earthquake.

In an interview on GMA News’ News To Go, Ruel Ramirez, principal structural engineer of RBRA and Associates, an engineering consultancy firm, said there are two types of cracks that may be seen after an earthquake hits a structure—shear cracks and flexural cracks.

Shear cracks are diagonal cracks while flexural cracks are vertical or horizontal cracks.

According to Ramirez, shear cracks are dangerous.

“Kapag meron kang shear crack, brittle failure 'yan. Meaning, it will not give you a warning. The building will just collapse immediately,” he said.

Unlike shear cracks, horizontal and vertical cracks are safe, Ramirez said.

“Kapag ang cracks sa poste mo ay horizontal, kapag ang cracks sa poste mo ay vertical, ang ibig sabihin noon flexural cracks…Okay lang 'yun,” he said.

“Parang metal. 'Yung metal kapag hinila mo puwedeng mag-elongate muna siya bago maputol. Pero 'pag ang metal shinear out mo 'yan, it will just collapse,” Ramirez added.

On Monday, a 6.1-magnitude earthquake hit central Luzon which caused damage to several buildings including Chuzon Supermarket in Porac, Pampanga. The supermarket collapsed, pinning five people to death and trapping others.

Meanwhile, Ramirez advised builders to go beyond the standards set by the Building Code in constructing structures to ensure their durability despite earthquakes. —Joviland Rita/KG, GMA News