Factors to be considered for the study of a derrick boom can be given as follows: 1. Lifting load, 2. Axial force, 3. End morment acting near the top of the boom which is caused by the brackets to rig the purchese blocks and derrick head span block, 4. Self weight of the boom, 5. Tapering of the boom, 6. Ratio of effective mast hight and boom length, (See Fig. 4) 7. Angle between boom centre line and horizontal plane, 8. Effect of additional weights, i.e., weight of blocks, hook and wires etc., Standard statical strength calculation is usually made on the "Swinging", however "Burtoning" is so often used for most of cargoes. In this paper stresses arisen in the boom working in the "Burtoning" condition are studied statically as well on the dynamical effect of the lifting load for the case of "Swinging" when the winch drum is suddenly braked. JIS (Japanese Industrial Standard) Boom are designed based on approximate formulae for stresses and buckling loads obtained by the use of Galerkin's method for the sake of the simplicity of the calculations. In this paper the accuracies and the results of using these formulae are checked by comparing the sufficiently accurate and successive numerical solutions of the equation of the tapered boom subjected bending with compression by use of Digital Computer OKITAC 5090A. Results of the calcutations for JIS derrick booms are shown in figures and tables. Scantlings of JIS Booms are expected to change slightly for simultaneous fulfilment of JIS and AB Requirements for designing of booms, if the yield point of material of boom is taken as 23kg/mm^2.
