Is the Gateway Arch a Parabola?

The Gateway Arch, or Gateway to the West, is part of the Jefferson National Expansion Memorial in St. Louis, Missouri.

Built as a monument to the westward expansion of the United States, the arch has become the iconic image of St. Louis. It typifies "the pioneer spirit of the men and women who won the West, and those of a latter day to strive on other frontiers". At 630 feet (192 m), it is the tallest man-made monument in the United States, and Missouri's tallest accessible building. Located on the west bank of the Mississippi River.

Why do they use the parabola shape for bridges ?

The arch helps transfer force to the outside of the bridge so that the abutments can support it.

Comparing our parabola to the photo, we can see (especially near the waterline at the bottom) the shape of the arch is not really a parabola at all. The designer of the Gateway Arch, Eero Saarinen, knew that a parabola was not the best shape for such an arch. An arch shape that is often used is the catenary. The Gateway Arch is also the largest architectural structure designed as a weighted or flattened catenary arch.

So, the Gateway Arch is not a parabola. It is a catenary arch!!!

Gateshead Millennium Bridge in Newcastle

Blinking eye bridge

The bridge takes its place at the end of a line of distinguished bridges across the River Tyne, including the Tyne Bridge and Robert Stephenson's High Level Bridge.
Linking Gateshead with Newcastle via Gateshead Quays (described as one of the best places in Europe by Tony Blair) and Newcastle's Quayside, the bridge not only serves a functional purpose as the River Tyne's only foot and cycle bridge, but its grace and engineering attract people from all over the world. 

The 130m long deck is parabolic in elevation and of steel box section that tapers in plan towards the centre of the deck. It carries a pedestrian footway that varies from 3m to 5m in width as well as a 2.5m cantilevered cycleway. 

The main arch is also parabolic in shape and tapers both in plan and elevation.

Six 450mm diameter Hydraulic rams (three on each side, each powered by a 55kW electric motor) rotate the bridge back on large bearings to allow small ships and boats (up to 25m tall) to pass underneath. The bridge takes as little as 4.5 minutes to rotate through the full 40° from closed to open, depending on wind speed. Its appearance during this manoeuvre has led to it being nicknamed the "Blinking Eye Bridge".

Arches

Arcs all around the world

More PowerPoint presentations from KF