Knee bracing vs full-length shear bracing for small timber shelters in typhoon prone areas

[rddd]

Currently working in the Philippines constructing very small temporary timber shelters, after last year's super typhoon damaged or destroyed just over a million houses. The typical floor plan of these temporary shelters is 4m x 6m.

There is a guidance note produced locally which is provided to all agencies constructing these lightweight timber shelters. It outlines rules of thumb and simple techniques for 'building back safer' in this context.

Regarding lateral bracing for walls, the guidance note advises against knee bracing. It instead recommends cross bracing in both directions, from the top corners of the wall, to a 'strong point' at the floor beam/bottom plate connection in the centre position of the wall.

I'm interested to hear feedback on the advice given that knee bracing is inferior and/or ineffective in this case. Your advice will be much appreciated and help to expand this debate in-country. Many thanks in advance.

 

[JAE]

Knee bracing induces bending in the columns and beams to which it attaches. That requires much heavier columns and beams to resist that bending.

Both work for wind loads - the full bracing is just much more efficient and effective.

Also, with knee braces, you would have much higher lateral deflections but with a little timber shelter that probably doesn't mean much.

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[msquared48]

Agree with JAE here.

Mike McCann, PE, SE (WA)

 

[KootK]

Full height bracing will also reduce the demand in your connections significantly. Connections are often the weak link.

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[woodman88]

I remember working with a Hawaii Structural Engineer on some small temporary shelters built with 2x lumber and truss plates. He had a big note that the engineering was only good for so long and that the structures were to be taken down before such and such date. I wonder how long they were actually used.

Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.