Analysis of trussed bents by moment distribution

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1948
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Virginia Polytechnic Institute
Abstract

The analysis of trussed bents can be very satisfactorily executed by using the Cross method of moment distribution in conjunction with a method of distributing thrust. The use of such a method as this may be realized when we think of the contrasting time element involved in the solution of the problem by this method and the older method of least work. In the case of the first method, the problem may be solved, once the distribution constants are known, in a matter of minutes. The least work process may take hours, and not infrequently, days.

It was the purpose of this thesis to determine what effect the fixed end thrust in trusses has on the solution of the problem by distributing moments. The results of this investigation empathetically warn us that when we are dealing with fixed supports, we must consider these thrusts, whereas, when we are concerned with a trussed bent that has only hinged supports, the effect of the thrust may be neglected.

It is the opinion of the writer that, whereas, the effect of the thrusts in parallel chord trusses may not be of such great influence on the final results, the truss sections which approach the shape of an arch (Fink roof truss with knee bracing, for instance) will be seriously affected, whether the supports or hinged or fixed.

This method of analysis would be very greatly benefitted if some future investigator would strive to develop a tool which would make for more rapid convergences in the distribution process, and would develop tables which could be used for finding carry-over and stiffness factors and fixed-end moments and thrust for different truss sections.

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