| Popis: |
This work is an investigation, both theoretically and experimentally, of the behaviour of r.c. arches at the ultimate load. A brief review of past contributions in this field is followed by the theoretical investigations. These open with the derivation of an expression for the simple collapse load Wsc of an arch. Wsc causes arch collapse with (n + 1) hinges considering bending only neglecting the effects of axial force and deformation. To determine it is necessary to know the hinge positions, methods of doing this graphically and by partial differention are shown. The effect of axial force on Wsc is next considered. It is shown that the application of a certain amount of axial force to a typical r.c. section can increase the ultimate M.O.R. of the section. A graphical moment distribution process is demonstrated using the elastic structural relationship between moment and thrust at each hinge section and the physical ultimate M.O.R. ~ axial force hinge section curve. This operation produces a simple collapse load modified for axial force. In deriving Wsc and Wac the arch is assumed undeformed. The effects of bending deformation on is next considered. To achieve this the deflected shape of the complete arch is determined in one analysis. This is done by a graphical method for use in the elastic and in-elastic ranges. Three methods are given to determine the effects of deformation on W AC. A collapse load W ACD modified for the effects of axial force and deformation is thus obtained. The effects of axial forces on deformations are then considered. The effects of pre-stressing and abutment spreading on the collapse load are next discussed. Three methods to determine W ACD are next presented. The fourth criteria for r.c. collapse design, i.e. that the strain at the hinge points must be within a defined limit is then examined. The rotation required for collapse under W ACD is found by the d IK method. The rotations available in r.c. members are discussed and approximate rules proposed to determine the rotation available. Use of stirrups to increase the available rotation is considered. A discussion of the material and section properties assumed in the previous 'structural' sections ends the theoretical work. The practical investigations follow. These are split into three parts (a) the Large Arch Tests - a report on the six parabolic fixed-ended arches tested, (b) Small Arch Tests - a report on the small model arches testes, (c) Analysis of arches tested by Jain. The thesis concludes with general conclusions and recommendations for design practice. |
