The Forbidden City. Image from en.paralympic.beijing2008.cn
Summer palace. Image from architecture.about.com
¨The dominant architectural feature of the great halls and palaces of the Forbidden City is the traditional Chinese curved roof. The curved line was made possible by the use of a roof support system more flexible than the rigid, triangulated truss employed in Europe. The Chinese used a beam frame system in which progressively shorter crossbeams, separated by struts, supported longitudinal beams known as purlins. The rafters of the roof rested on the purlins. By varying the relative lengths of the crossbeams and thus the position of the purlins, curved roofs could be produced from short, straight rafters.
The Chinese beam support system could just as easily have been used to build straight roofs, and the British architect Andrew Boyd, who asserts that ¨structure does not dictate architectural form,´ attributes the curved roof to aesthetic choice. That great popularizer of Chinese culture Lin Yutang points out that one of the basic tenets of Chinese calligraphy is the ¨interplay of rigid straight lines and curving forms,¨ and he suggests that in the Peking palaces the curving roofs form a harmonious whole with the straight lines of the base and pillars, producing a combination of grace and strength.¨
Chinese writing. Image from akuindeed.com
The Forbidden City. By Roderick MacFarquhar and Editors of the Newsweek book division. P. 93-94. New York. 1972.