Investigation on core-walls of tall buildings subjected to torsion

by Leung, King-wai

(Uncorrected OCR) Abstract of thesis entitled 'Investigation on Core-walls of Tall

Buildings sub;ected to Torsion'

submitted by LEUNG King Wai. B.Sco(Engo). H.K.

for the degree of Master of Philosophy

at the University of Hong Kong in J_u ?.. n_e ...? ___.l_9;...;7_4 ?. o _

ABSTRACT

This thesis is concerned primarily with the development of an analytical method for core-walls of tall buildings subject to torsional loads. A review of existing methods is presented, and a new approach to the problem based on transfer matrix method

is put forth.

The proposed method consists of treating each storey as a

member segment and e~pressing the angular rotation, rate of twist, bimoment and torque as transfer functions in form of a state vector. Member transfer matrices are derived from Vlasov's equation of torsion, and nodal transfer matrices are obtained from equations

of equilibrium and compatibility. Contributions from cross beams are represented by beam factors S that appear in the nodal matrices. Using these transfer matrices, together with external load vectors at every floor level, a transfer relationship between state vectors at any two levels can be set up. The whole structure becomes determinate when boundary conditions are superimposed. Further .simplification of the transfer relationship is possible for uniform

free-standing cores.

Experimental results obtained from a l6-storey perspex model

have been used to check against theoretical calculations. Two examples are selected from recent publications to serve as a comparison between the proposed method and other analytical methods.

The flexibility parameter a and beam factor S are used to describe the warping rigidity of a core. Results indicate that an increase of a reduces the bimoment, but amplifies the rotation and

the rate of twist, while on the other hand, an increase of B causes a reduction in the deformations as well as in the bimoment.

Based on values of a and B , several dimensionless coefficients are defined, which can be compiled into charts for practical design purposes. An account of the design procedure is

also given.