FIRST I must say how grateful I am for the honour you have done me by electing me to the chair of the Wales and Monmouthshire Branch of the Institution this year. I can but endeavour to live up to the standards set by my predecessors. F. V. M. Bell
The paper describes a new method for the analysis ofsimply supported interconnected bridge girders. Thetransverse system is considered to be a uniform mediumof total moment of inertia equal to that of the actual transverse system and a differential equation including terms due to rotation and twist is written down for each longitudinal. These equations are solved by harmonic analysis and distribution coefficients are derived giving the amplitudes cf the harmonics of the bending moment or deflection curve for each girder. The theory presented allows for any degree of torsicnal stiffness of the longitudinals and in the most general case the dlstribution coefficients are functions of three dimensionless parameters; the first is a measure of the transverse stiffness of the bridge, the second of the torsional stiffness and the third expresses the ratio of the inertias of the outer to the inner longitudinals. For design purposes the cases of zero and infinite torsional stiffness are of greatest interest, but intermediate cases can be obtained by use of an interpolation function. An alternative and wry simple method is developed for zero torsional stiffness and the calculation of transverse moments is also dealt with. A number of comparisons with experimental results are quoted and the application to the design of steel and concrete bridges is demonstrated. Leslie G. Jaeger and Arnold W. Hendry