garden furniture wood splitting

[seneca]

I've noticed that some of the timbers on my arbour and arch are splitting. It's mostly on the vertical pillars - around 10cm square - where cracks have formed. They are not down the full length of wood, just sections of around 1-2 ft in length. How can prevent further splitting, or the cracks widening and potential collapsing of my furniture. It's due for painting, so I thought I would maybe put a few screws in and try to force the splits to close. Are there another ideas?

 

[big-all]

if the splits are along the grain they wont effect the strength unduly unless it has a twisted grain that dosnt follow along the timbers length or large dead knots
but highly unlikly in verticals in any case as the strength off the wood in compresion is greatest!!

is a picture possible

 

[seneca]

I really think i need to get a camera, as my powers of description aren't up to much and a picture is worth a 1000 words (my long winded descriptions!)

Anyway, the splits are along the grain (always down the verticals) and are a few mm wide and don't appear that deep. So will a screw across the spilt not help? How about filling the crack with some kind of exterior filler? Will that prevent the slpit getting water inside it? Trickky chap wood. I think the splits occurred over winter. Will warmer weather cause the splits to close? (in which case maybe some flexible sealant?)