The Khaju Bridge is located in the historic city of Isfahan, Iran, spanning across the Zayandeh River. Built on the foundations of an ancient bridge in 1667 it is an archetypical model of a Roman Arch bridge. It has a semicircular structure with abutments on each end that bear the weight and pressure of the arches. The arches shift the weight from the bridge deck to the support structure with the compression forces bring pushed outward along the curve of the arch toward the abutments. The two-storey Khaju Bridge with a length of approximately 132 meters and a width of 14 meters is constructed entirely from stone and brick.
The pedestrianised lower level of the bridge comprises vaulted spaces within the arches, which not only provide public circulation routes but also microclimatic conditions. The vaults and arches work in accordance with evaporative cooling and turbulent air flows to produce a cool climatic condition, producing a more comfortable internal environment within the pedestrian passageway. The upper storey has a 7.5 meter wide road running through its centre with arched spaces and pedestrian passageways either side. In total the bridge has 23 arches that intersect with 21 larger, and 26 smaller inlet and outlet channels.
Khaju not only forms a crossing point across the Zayandeh River, but it also performs as a social focal point, a dam and sluice gates. On the eastern side of the bridge there is a high sill, which collects the water when the sluice gates are closed. This provides a basin from which irrigation water for the surrounding area is drawn off in a series of channels via sluice gates. As a mechanism to control large flood-flows and diffuse hydraulic energy 18 low-flow deep channels each equipped with sluice gates operate along the bridge weir. The channels have stepped cascades to enhance the effect of the flood control, which are situated on the western side of the bridge. The stepped cascades also form social meeting points where people often gathered to do their laundry or meet with one-another, enjoying the coolness of the flowing water.
An octagonal pavilion is set in the centre of the bridge that now houses an art gallery and teahouses. In the 17th century the Shah Abbas and his courtiers would often sit and admire the views from within the pavilion as the bridge provided a haven from the heat of the desert. Original paintings and beautiful tile work are still visible on the bridge today, reflecting its legacy of opulence and importance.
Today, even though there are drought problems, the Khaju Bridge has withstood the tests of time. Structurally sound, the bridge is still in working order even though it is around 350 years old. The bridge has continued to function as a point for recreation, social exchange and culture, while providing transportation and agricultural infrastructure as well as a flood control interface. The longevity and consistent structural stability of the Khaju Bridge illustrates the effectiveness and sophistication of the design and engineering which was involved with its construction. The combination of environmental and climatic conditioning alongside auxiliary social functions epitomizes the overall success of the bridge as an urban heterogeneous piece of architecture and infrastructure.
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