Improving the Efficiency of Structures Using Mechanics Concepts

Abstract

The efficiency of a structure defines the relationship between its performance and cost.Studies of structural efficiency will inevitably lead to improved structural performanceand/or reduced material consumption. There are various routes to achieve more efficientstructures, and the use of mechanics/structural concepts provides one important option.These concepts are valid for a broad range of structures, easy to understand and play adecisive role in a conceptual or scheme design stage which is the most influential stagefor determining structural efficiency. However, there are few systematic studies ofstructural efficiency from the perspective of mechanics concepts. This provides therationale for exploring mechanics concepts to improve the efficiency of structures.Three effective concepts are used as a basis for this study, that more direct force paths,smaller internal forces and more uniform force/stress distribution lead to a stiffer ormore efficient structure. These concepts can only be realized in particular types ofstructure through taking appropriate measures. Therefore, this thesis aims to improvestructural efficiency by making good use of some existing measures, developing newmeasures, providing a theoretical basis to some effective measures and abstractinggeneral principles from some available measures based on the three concepts.The following items are investigated in this thesis:1. For two existing approaches searching for efficient structural forms, the intuitive useand mathematical realisation (evolutionary structural optimization (ESO)) ofstructural concepts, their complementary characters are first identified which inspirea comparative study of the solutions. Through this study, the efficient profiles of amid-span loaded thick beam and effective bracing arrangements for laterally bracedframes are revealed; governing concepts affecting structural efficiency in particularconditions are discussed; and some design measures for designing efficient structuralforms in the two groups of cases are presented.2. As new measures, design criteria for effective bracing systems in simple and tallframes are developed, based on the concepts of direct force paths and small internalforces. The criteria are shown to be effective as a two-stage design procedure, withthe arrangement of braced panels followed by that of bracing member orientation.3. A theoretical study of an existing beam stiffening measure using external tendons isconducted, focusing on the stiffness and natural frequencies of a stiffened beam. Itprovides quantitative estimation of the stiffening effect and theoretical evaluation ofthe governing factors and optimal profile for designing the profiled tendons.4. The effective measures leading to the high efficiency of the Raleigh Arena areidentified and studied. The efficiency of the Arena is evaluated quantitatively usingnumerical methods. The concept of smaller internal forces can be abstracted fromone physical measure used in the Arena.

Date of Award	1 Aug 2012
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Tianjian Ji (Supervisor)