Hagia Sophia: New Types of Structural Evidence Author(s): Robert L. van Nice Reviewed work(s): Source: Journal of the Society of Architectural Historians, Vol. 7, No. 3/4 (Jul. - Dec., 1948), pp. 5-9 Published by: University of California Press on behalf of the Society of Architectural Historians Stable URL: http://www.jstor.org/stable/987423 . Accessed: 01/05/2012 19:36 Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at . http://www.jstor.org/page/info/about/policies/terms.jsp JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected]. University of California Press and Society of Architectural Historians are collaborating with JSTOR to digitize, preserve and extend access to Journal of the Society of Architectural Historians. http://www.jstor.org Hagia Sophia: New Types of Structural Evidence* ROBERT L. VAN NICE Historically and architecturally Justinian's great of the more interesting types of evidence and their church of Hagia Sophia is unparalleled among implications, it may be useful to review in general mediaeval monuments. Completed in A. D. 537 the reasons which establish Hagia Sophia as a key and dedicated to the Orthodox ritual, it was sacked monument in the history of architecture. in 1204 by Venetians of the Fourth Crusade and This vast domed basilica (Plate 1, Fig. 1), com- became for fifty-seven years a Roman Catholic parable in height to a modern building of fifteen church; at the capture of Constantinople in 1453 stories, was brought to successful completion in less it was converted to Moslem rites and for nearly five than six years, between A. D. 532 and 537, by Jus- hundred years thereafter served as a mosque; in tinian's architects Anthemius and Isidorus. Fol- 1935 it was made a State Museum of the Turkish lawing injury from an earthquake in the previous Republic. Thus, as the center of prescribed re- year, the initial dome collapsed in 558. Jus- ligions of the three empires with which its fate tinian entrusted its reconstruction to Isidorus the has been intimately connected, the history of Hagia Younger, nephew of the first Isidorus, who is re- Sophia is well documented. But for lack of oppor- ported to have raised the crown of the new dome tunity in the past to examine the building freely, approximately 6.25m., thereby reducing its lateral what information is available in documentary thrusts as compared with those of the first, flatter sources cannot be correlated with details of the ex- dome. This second dome, which was completed isting structure. before 563 and parts of which remain today, has The purpose of the following remarks is not to been injured subsequently by earthquakes on two attempt a solution of any of the varied architec- occasions: In 986 a segment was injured when the tural problems inherent in, or ascribed to, Hagia western arch gave way, and repairs were accom- Sophia; it is to explain briefly and informally some plished by 994 under supervision of Trdat, an Ar- types of evidence which have not hitherto been menian architect; in 1347 a segment came down brought to bear on these problems. The material when the eastern arch collapsed and restorations presented herewith was assembled during an ex- were finished by 1354 under direction of Astras, tended structural investigation initiated in 1937 Faciolatus and Giovanni Peralta. These damages by William Emerson, former Dean of the School which, according to the accepted history, are the of Architecture at the Massachusetts Institute of only instances of major injury incurred by the Technology, sustained and supervised by him, and structure, illustrate why Hagia Sophia merits our aimed at identifying the original form of Hagia closest attention. The present dome, constructed Sophia at the time of its completion in A. D. 537. in the sixth century upon supports designed for In a strict sense this has not been an archaeological an earlier dome of unknown form, incorporates re- undertaking, for it involves neither excavation nor pairs of undetermined extent which date from the re-examination of documents. On the other hand it tenth and fourteenth centuries. Further, the sys- has the advantage, thanks to the friendly collabora- tem of support for the dome, which is not altogether tion of scientists at M.I.T., of offering data inter- logical, raises questions of unusual structural in- preted according to the most advanced technical terest. knowledge of the moment. Before describing some The rapidity of Hagia Sophia's successful con- struction ranks it among the great engineering *Presented at the Symposium on Medieval Architecture at Oberlin feats of all a even more remarkable in College, October 16-17, 1948. time, speed 6 SOCIETY OF ARCHITECTURAL HISTORIANS view of certain novel structural devices employed cisely dated periods at intervals of four hundred in it. Pendentives of immense size, once thought years throughout the Byzantine epoch. Because of to have been invented and simultaneously to have the part played by physical forces in disasters that reached their fullest development here, were car- have befallen the building, an attempt to explain its ried beyond the farthest limits of previous experi- complex form must take into account certain struc- ence. These spherical triangles rise within a square tural principles. formed four arches which the im- by equal convey Since the stability of any structure depends ulti- that the dome is carried on a pression regular geo- mately upon the character of its foundations, it metrical But while the four visible arches figure. was imperative at the outset of our investigation which to the dome are appear carry apparently to gauge foundation conditions beneath Hagia those which the dome are alike, actually support Sophia. This question has more than technical in- of two kinds and are in turn different supported by terest, for it touches upon one of the most colorful structural devices. legends attached to the building: The belief that The eastern and western arches, which span the cisterns of great size are enclosed within its sub- nave transversely, are thin at their crowns, open structures. In the absence of permission to exca- beneath, and braced by semidomes of equal diame- vate, inspection of wells, drains and tunnels lying ter; these are working arches. The arches of simi- beneath the western half of the nave and nartheces lar span, which are visible along the sides of the was our only available source of information. nave, are not primary supports of the dome but Though data obtained in this manner are not final, are applied to the faces of the working arches; their implications provide a useful point of de- the latter are flush with the tympana and there- parture for assessing the structure. fore invisible from the nave. The northern and The well which has often been cited as an en- southern structural arches, as compared with the trance to the supposed cisterns proved on examina- eastern and are shorter in thicker western, span, tion to be a shaft cut from natural rock, the sur- the broader on and through crown, soffit, unsup- face of which, it is now clear, lies from 1.0 to 2.0m. buttresses built at ported except by (Plate I, Fig. 2) below present floor level. The proximity of this angles their be- right against springings. Hence, natural rock to the existing floor excludes the pos- cause of this dual of the lateral system support, sibility that large cisterns were built into the origi- thrusts of the which are radial and in dome, equal nal structure and suggests that the main piers and all are countered on two sides semi- directions, by buttresses are built on rock. According to an domes and on the other two buttresses which do by analysis made by Prof. Frederick K. Morris, a not lie in line with the forces are intended to they geologist at M.I.T., the rock is a relatively weak oppose. Devonian layer. Pressures exerted on it by the The surpassing interest that ingenious design supports of the dome, which were estimated by and an eventful history give to Hagia Sophia may Prof. E. N. Gelotte from sources available before be summed up as follows: Despite the embodiment the start of work in the building, are in the order of an untested and somewhat illogical principle of of magnitude of 105 tons per square meter. With support for the dome, the church was successfully these facts in hand, Prof. Morris and Dr. Karl erected with unprecedented speed at a scale of size Terzaghi, soil mechanics expert at Harvard, ar- and magnificence unrivalled for several centuries; rived at two significant conclusions: First, the it has suffered serious injury from three earth- estimated pressures are sufficient to cause subsi- quakes and has survived innumerable others; it has dence in the Devonian layer; and, second, damage endured the effects of time, decay and intermittent caused by earthquakes to buildings of Hagia neglect; yet it comes down to us after 1400 years of Sophia's size which stand on rock results from the constant use, not as a lifeless ruin, but with struc- vibration in phase of large structural members and ture intact and forces still in action. It is conse- not from dislocation of their foundations. These quently more than a mediaeval monument of un- principles, as will later become apparent, are in- paralleled historical interest; it is, in effect, a vast dispensable to an understanding of Hagia Sophia's and living laboratory for studying the best tech- past history and present condition.