TORI—CONICAL SHELL FOUNDATION FOR TOWER SHAPED STRUCTURES

Abstract

With the increase in height and complexity of structures, foundation design is becoming rather complex. The problem of providing economical, yet structurally safe foundation systems can be solved to a large extent by providing shell foundations. The present study attempts to.present a parameterit study of Tori-conical Shell Foundation System. It is believed to be very efficient in character for tower like structures. It is an economical alternative, to annular foundation usually adopted for water towers and chimneys. Tori-conical shell foundation becomes more relevant when the foundation soil is weak with low bearing capacity. The membrane analysis of the Pori-conical shell foundation has been carried out by assuming uniform soil pressure distribu-tion. The preliminary design has been done by ensuring that statics is satisfied and the not horizontal thrust is directed towards the axis of the tower. The complexity of the problem is tackled by the use of Finite Element Method. This method also enables the inclusion of soil structure interaction with varrying soil modulli. The relevant parameters are varied so as to present a comprehensive picture of the behaviour- of Tbriconical shell foundation. The results are presented in the form of computer drawn stress con-tours and deformed profiles. The behaviour of the four cones ' analysed for their major contributions alongwith the soil reactions. The inner and outer middle cones connected to the shaft transmit the loads to the soil and cones acting as toes at inner most and outer most portions. The middle cones pri-marily carry the load through membrane action and the variation of axial thrust, and hoop force are plotted for varying soil modulii. The variation of bending moment and normal shears are important near the junction for which adequate basis for design has been established. The toe cones are basically subjected to bending and are useful for carrying unbalanced horizontal forces. Their utility is obvious for resisting the lateral loads. Finally a design procedures based on realistic Soil-structure interaction has been presented for the use of designers.