Construction on the tower bridge in London started in 1886 and took eight years to complete. During the construction of the bridge, 432 workers were employed by five major contractors. Two massive piers, containing over 70,000 tons of concrete, were sunk into the river bed to support the construction. Over 11,000 tons of steel provided the framework for the towers and walkways. Above is the sketch of the bridge with three equations.


A logarithmic spiral, equiangular spiral or growth spiral is a special kind of spiral curve which often appears in nature. Circular staircases, the chambers of the nautilus shell, and a low pressure area are all arranged in an approximate logarithmic spiral. Learn more about logs in Intermediate Algebra/Algebra ll.

The London bridge is a combined bascule and suspension bridge. This design was London's soluiton to their river crossing problem. The architect Sir John Barry, devised the idea of a 800 foot length that opened with two towers each 213 feet high, built on piers. The central span of 200 feet between the towers was split into two equal bascules or leaves, which could be raised to an angle of 83 degrees to allow river traffic to pass. The bascules, weighing over 1,000 tons each, were counterbalanced to minimize the force required and allow raising in five minutes.

The two side-spans are suspension bridges, with the suspension rods anchored both at the abutments and through rods contained within the bridge's upper walkway.