That's a good explanation, except that wooden bridges have proliferated worldwide while covering them seems quite limited. If weather protection for the bridge structure was the issue then bridge covering would be universal, it's reasonable to think, but it is uncommon except where heavy snow falls. However, pedestrian comfort is usually the only justification for footbridges to be covered.
Here in Australia are many wooden bridges of great age, often over a century old, that have survived uncovered with basic maintenance, giving the lie to Wikipedia's claim that, "Wooden bridges tended to deteriorate rapidly from exposure to the elements, having a useful lifespan of only nine years. Covering them protected their structural members, thus extending their life to 80 years or more." The Straight Dope writer unfairly debunks snow protection by claiming that it's the weathering effect of snow that's being argued. AFAIK and have read, it's the WEIGHT of the snow, not it's weathering nature, that bridge covering seeks to deter. A bridge deck, being flat, could pile up with a destructive weight of snow faster than it could be cleared. In a severe blizzard, with everyone confined indoors, a bridge could collapse under the load of snow before the storm cleared and the snow plough could arrived to remove the burden. Putting a pitched roof above the deck prevented snow from piling up. Simple as that. Regards, Anthony > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of > Derby Chang > Sent: Sunday, 19 October 2008 8:09 AM > To: Pentax-Discuss Mail List > Subject: Re: PESO: Covered Bridge > > > A Straight Dope classic > http://www.straightdope.com/columns/read/1136/why-are-covered-bridges-covere d > > Nice series too, Jack > > D > > -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
