Structural Engineering Slide Library

Set B: Arch Structures

This set of slides covers many of the important aspects of arches as used in the design of buildings and bridges. It includes the following general topics:

• Masonry arches: historic
• Masonry arches: 18th and 19th century
• Three-hinged arches: bridges
• Three-hinged arches: roof structures
• Two-hinged arches
• Tied arches: bridges
• Tied arches: buildings
• Fixed arches: historic
• Fixed arches: modern
• Various arch structures

As arch construction is one of the oldest means of spanning rivers and forming the roofs of large buildings, it is appropriate that this set should start with illustrations of a number of historic arches, including Roman and Medieval. It was inevitable that the arch form should dominate the early history of building as without the availability of a material capable of taking significant tensile stresses, a predominantly compressive system was the only means of forming large spans -- hence early structural and architectural forms were primarily based on columns, arches, and domes.

With the coming of steel and the ability to cast in concrete, there was a revolution in arch design with a dramatic increase in possible span. A good example of this change can be seen by comparing two slides, B17 and B67, both taken from the same place near Bregenz, Austria. Slide B17, taken upstream, shows a masonry multi-span railway viaduct built in a manner very similar to the Roman aqueducts. Slide B67, taken downstream from the same location, shows the change brought about by the advent of reinforced concrete. Now the valley could be spanned with a single arch as the reinforced concrete rib could withstand tensile stresses due to bending.

As the behavior of an arch is strongly influenced by its boundary conditions (as in the case of beam structures) particular attention is paid to the manner in which the arches are supported, and slides of many support details are included.