Some Engineering Aspects of Ancient Structures

Abstract

Large monumental constructions were a prominent feature in ancient Sri Lanka. Construction materials and techniques used in the past can be of significant interest to the modern engineer. The evolution of brick sizes during four ancient periods of Sri Lanka spanning from 375 B.C to 1350 A.D. was studied by using recorded data of bricks found on ancient construction sites. The calculated ratios and the relationships indicate that the length was relatively significant in the reduction of the brick sizes while breadth and thickness changed roughly in proportion to the length at a lower rate. The effect of ground condition, i.e. rock, strong soil and weak soil; and the effect of pedestals on a solid hemispherical dome type Stupa were analysed using SAP2000. It was found that a stupa, if unrestrained along its horizontal directions, could experience tension being developed at the centre when built on a weak soil. Also, when constructed on poor ground conditions a pedestal reduces the compressive stresses at the base. However, the pedestal causes higher hoop and radial tensile stresses closer to the top and bottom of the outer surface of the dome. Vaulted structures in Sri Lanka exhibit approximately similar span to wall thickness ratios, thus indicating the possibility of the design being governed by the geometry of the structure. Also the development of stresses in vaulted structures indicates that the maximum vertical stress is compressive at the base, while the maximum tensile stress is at the crown intrados.