Issue 15

The paper presents a formula from which the bending moments within the columns of an interbraced column structure may be evaluated at any level of axial load and degree of out-of-straightness of the columns and for any number of columns and interlinking brace lines. Charts indicate the distribution of moments within a column and their magnitude variation. An example stress calculation is included. I.C. Medland

This paper considers the problem of premature instability of optimised space frames. As loads are increased, plastic hinges start forming in succession, resulting in the possible instability of the deteriorating frame before a plastic mechanism is reached. The problem is formulated, and a method of analysis, which provides a lower limit on the actual failure load, is presented. The analysis establishes the order in which the plastic hinges form, but avoids the repeated inversion of the frame stiffness matrix. The method developed is applied on two simple space frames. M. M. K. Khalifa

A Moiré fringe technique has been used to measure the in-plane strains in the web plate of a steel bridge girder above a bearing support. The new method is discussed in detail. The results of one set of readings, taken while the bridge was under construction, are presented and compared with the predictions of a finite element analysis. I.C. Brown, J. McKelvie, S.H. Perry and C.A. Walker

A major theoretical study has been undertaken into the behaviour of bridge panels under combinations of shear, compression, tension, and in-plane bending. Average stress-strain curves have been produced and have been used to derive interaction curves for all the combinations of loading types found in the web panels of box girder and other bridge types. The effect of geometric imperfection level, residual stress level, boundary restraint, and yield stress have been studied. J.E. Harding and R.E. Hobbs