Structure & Structural Problems | Hagia Sophia | Briefing | Professor Ousterhout

Hagia Sophia | Structure & Structural Problems
Professor Ousterhout

The lack of bilaterally symmetrical buttressing is clarified by contrasting longitudinal and transverse sections. Further problems were encountered due to the plastic flow of the mortar resulting in a shifting of walls and vaults and the settling of the foundations that occurred before the building was complete.

A major problem is presented by the grand scale. The dome is 100 feet in diameter and rises 180 feet above the floor. The first dome, probably 20 feet lower than the present dome, collapsed and was reconstructed. As a result, questions persist about the form of the first dome. It was probably a pendentive dome since the reconstruction employed a dome on pendentives. For both, the critical issue was the meeting point of the four great arches at the base of the dome. Note that for additional strength, lead was used instead of mortar at the springing of the arches and vaults; bipedales in the arches, cornices form tension rings. These points are not braced on the north and south. See studies in Mark and ‚akmak.

		Istanbul, Hagia Sophia, Interior view of the dome (Note the irregularity of the circumfrence.)