STUDIES IN DESIGN ASPECTS OF TRANSFER BEAMS FOR HIGH-RISE BUILDINGS

Abstract

Lateral loads due to wind or earthquake generate drift in highrise buildings. Such drifts not only make it inconvenient to the users but may also lead to premature failure of the building. Hence, it is imperative upon the designer to make the highrise buildings stiff against lateral sway. This is why many vertical and lateral structural systems have come into picture to control drifts. One of these systems is to provide a large number of closely spaced columns all along the periphery of the building. This provides a lot of structural stiffness to the building but makes it problematic to the free flow of people and goods at the entrance level. This problem has been solved by locating columns at large spacings at ground floor level and at closer spacings at upper floor levels. It makes it essential to provide a beam at the interface of the columns at ground floor level and the columns at upper floor levels. The depth of the beam becomes enormously high due to heavy concentrated loads. Such a beam is referred to as Transfer Beam. Quite often such beams are supported at such a spacing that span-to-depth ratio comes in the range of 2.5 or less. Structurally such beams are referred to as deep beam. These beams show different structural characteristics than the normal beams. Here, shear becomes a predominant factor of design contrary to the shallow beams where flexure is the governing factor of design. Thus, it is pertinent to study the structural behaviour and design considerations of such beams. In this dissertation, attempts have been made to study the design characteristics of transfer beams. It also includes the comparative study of different codal provisions such as ACI Code, CEB-FIP Model Code, CIRIA Guide 2, Canadian Code and IS Code. It also elaborates the truss model of design. A computer program has been developed for design of deep beam based on the American Code, ACI 318-95 for shear, and CEB-FIP Model Code for flexure. Parameteric studies have been carried out using the developed computer program to arrive at relevant conclusions regarding the deep beam. Seven beams have been analysed and designed by truss model method and results have been compared with the results obtained by codal method. Computer program has been written in the programming language 'C'.