Theoretical Ultimate Load Research Articles

Posttensioned and Shaped Hexagonal Grid Dome: Test and Analysis

This paper presents the results of an ultimate load test and analysis of a post tensioned and shaped hexagonal grid dome. The hexagonal grid dome is one type of the recently proposed posttensioned and shaped single chorded space trusses which are constructed by means of posttensioning. The dome is first assembled as a planar layout on the ground, and then is deformed into its final space shape by a posttensioning operation. After shape formation, the dome is loaded to failure in order to determine the ultimate load. Finite-element analyses that correlate experimental forces in individual members, and prestress forces caused by posttensioning, have been made in an attempt to predict the ultimate load of the posttensioned and shaped dome. Comparison between theory and experiment shows that the test dome did not reach the theoretical ultimate load, and that the posttensioning had some effect on the ultimate load capacity. The nonlinear finite-element method based on the experimental results can be helpful to predict the ultimate load of posttensioned and shaped domes.

Tolerances of initial deflections of steel plates and strength of I cross-section in compression and bending

A further step towards the strength-based assessment of fabrication tolerances of steel plates is attempted. The procedure presented derives from the idea that the strength reduction of an I cross-section due to initial deflection should not exceed, irrespective of the web-plate slenderness and of the type of loading, the maximum strength reduction for the case of uniform compression. Thus, despite the degrading influence of initial deflections, any I cross-section could be exploited up to a certain percentage of the strength of the cross-section with an initially flat web plate.The theoretical ultimate loads are calculated using the large deflection theory of thin elastic plates. Employing the so called ‘energy measure’ of imperfections a less conservative correspondence between the predominant single mode initial deflection, adopted for specifying the tolerances, and of the most dangerous one — corresponding to the initial buckling mode of the plate — applied in calculations of strength, is established.The application of the approach to the case of an unstiffened steel plate girder of I cross-section shows that the currently applied tolerances may be substantially relaxed.

Nonlinear analyses of thin-walled channel section columns

The paper presents a detailed comparison of nonlinear analyses of thin-walled channel section columns with tests. The columns are analysed as beam-columns having nonlinear constitutive relationships. The constitutive relationships are obtained firstly, by assuming elastic material behaviour and allowing local buckling of both flanges and web, and secondly, by assuming elastic-plastic material behaviour and confining local buckling deformations to the web. Based on the comparison, including theoretical and experimental load-shortening and load-deflection curves, it is concluded that the nonlinear theory generally closely agrees with the tests. The paper also investigates the applicability of combining an elastic nonlinear analysis with a spatial plastic mechanism analysis to describe the structural behaviour both before and after the ultimate load. The question of when this combination can be expected to accurately describe the column behaviour over the full loading range is discussed. A separate section compares theoretical ultimate loads with test strengths. The nonlinear analyses employed in the paper provide ultimate loads which agree with the test strengths to within 2% on average where primary local buckling occurs in the web of the channels, and 11% on average where primary local buckling occurs in the flanges of the channels.

Résultats d'essais sur des assemblages soudés excentriques en flexion

The development, by Butler and Kulak, of equations for the calculation of fillet weld resistance with relation to the angle of load application has improved the understanding of the limit states behavior of welded connections. For the design of welded connections subjected to shear and moment, Dawe and Kulak developed a method of analysis based on the principle of instantaneous center of rotation, which accounts for the actual load–deformation characteristics of the weld. Due to its complexity, the method of Dawe and Kulak requires the use of a computer. In order to make the method more attractive to the designer, Neis suggested some simplifying assumptions and at the same time criticized the work done by Dawe and Kulak. In the discussions that followed the publication of his results, various researchers expressed diverging opinions on several matters related to the theories.Since the proposed methods were based on the results of only 8 laboratory tests done by Dawe and Kulak, we have carried out a series of 24 tests. The results of these tests were compared with the theoretical ultimate loads obtained from the methods of Dawe and Kulak and Neis, and demonstrate that the proposed methods are adequate as long as they are used within certain limits and respect certain conditions.

L‐Shaped Column Design for Biaxial Eccentricity

Rational shape for the load contours in L‐shaped columns is proposed using the inverse method of analysis. Determination of the ultimate loads from the appropriate interaction curves derived from the shape of load contours is shown. An alternate and simple method based on the concept of an equivalent square or rectangular column is proposed to determine the theoretical ultimate loads using the interaction diagrams in square or rectangular columns. Theoretical loads computed by the two proposed methods are compared with the test results of 45 columns.

THE BEHAVIOUR UP TO FAILURE OF PRESTRESSED CONCRETE BOX BEAMS OF DEFOR -MABLE CROSS-SECTION SUBJECTED TO ECCENTRIC LOAD.

Keywords UNIVERSIDAD NACIONAL DE TUCUMAN ARGENTIN, HERIOT WATT UNIVERSITY BEHAVIOUR, FAILURES, PRESTRESSED, CONCRETE, BOX, BEAMS, DEFORMATION, LOADS, ECCENTRIC, TESTS, THICKNESS, WEBS, CRACKS, DIFFERENCES, PROPAGATION, BENDING, TORSION, SHEAR, DEFLECTION, ROTATION, FLEXURAL, TORSIONAL, DISTORTIONAL, STIFFNESS, STRAIN, LONGITUDINAL, TRANSVERSE, STRESS, ULTIMATE, COLLAPSE, MECHANISMS, EXPERIMENTAL, TRUSSES, SPACE, SPECIMENS, MODELS, INITIAL... Show All