Thanks for those ideas, Brian.
Chris
On 13 Apr 2013, at 13:09, "Brian Swale" <bj@xxxxxxxxxxxxxxx> wrote:
>> Why were bridges built like that? Do the roof and walls add to the
>> structural strength?
>>
>> It's surely not worth sheltering traffic for the short distance of the
>> crossing.
>
> Without seeing the image ( I obviously missed the link) and with much of my
> professional working life being in forestry, timber utilisation, and so on; I
> can
> think of at least two good reasons for covering timber bridges.
>
> 1) Where the timber is inherently of low natural durability and no
> preservative treatment is / was available, keeping the decking and structural
> timbers dry would extend their useful life a lot. There would of course also
> possibly be timber-eating insects as well though.
>
> 2) Where the decking / running surface is timber, it is very important in
> winter to keep the surface protected from radiation frost. Timber is a
> relatively good insulator and tends to not accumulate heat. So that in clear
> cold nights, even when it's not terribly cold, a layer of frost / ice will
> form on
> the timber surface.
> This is very slippery for traffic and contributes to bad accidents.
--
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