Monday, 18 July 2011

Another Bridge

Very little has happened outside recently.  Since getting back after a week away on holiday the weather has not been conducive to concreting and mortaring.
I have designed the next bridge which will be a 1.25m under arched girder bridge.  It proved to be a little more difficult than I had anticipated as I didn't know how to calculate the radius of the arch, but a Google search led me to which provided the following information.

Given an arc or segment with known width and height:
Segment of a circle.  A horizontal base line with an arc on the top.  Its height is H and width of the base W
The formula for the radius is:
Circle.  One vertical line through the center, one horizontal across the upper part, each half labelled 'a'
        Vertical line labeled B in top part, c in bottomwhere:
W  is the length of the chord defining the base of the arc
H  is the height measured at the midpoint of the arc's base.

I've started cutting the aluminium which was left over from the last bridge, but work has now stopped until I can get more supplies.

The plan for the next bridge

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