José Manuel Gordo

APPROXIMATE METHOD TO EVALUATE THE HULL GIRDER COLLAPSE STRENGTH

Abstract A method to estimate the ultimate moment based on a simplified approach to represent the collapse strength of beam columns is presented. Comparisons with experimental results of box girders, small scale models of box girders and a 113 frigate model are performed. Also, a comparison with results of other approximate methods and finite elements codes is made.

Compressive strength of rectangular plates under biaxial load and lateral pressure

Abstract Equations are derived to assess the strength of plates subjected to biaxial compressive loads, including the effect of initial distortions and residual stresses. These equations are then extended to the case of simultaneous lateral pressure loads. In calibrating the proposed methods and in assessing their model uncertainty published results of experiments and of numerical calculations have been used. The proposed methods were shown to be unbiased as regards plate slenderness and aspect ratio. The model uncertainty of each method was quantified and thus can be used to derive design formulations with the desired level of safety.

Design methods for stiffened plates under predominantly uniaxial compression

The performance of three methods to design stiffened panels under predominantly in-plane uniaxial compressive loading is compared by referring to numerical and experimental results. The prediction of the tripping of the stiffeners is also included in the design method in order to complement its scope of application. Experiments on stiffened plates under compression and lateral pressure are also compared with the methods of strength prediction. A method is proposed in order to decrease the bias and uncertainty as results from the data set considered.

Experimental evaluation of the behaviour of a mild steel box girder under bending moment

An experimental evaluation of a mild steel box girder subjected to a pure bending moment is presented. The moment–curvature curves are presented allowing for the analysis of elastic–plastic behaviour until collapse, the evaluation of the ultimate bending moment and post-collapse behaviour. The residual stress relief during loading and unloading path is also analysed. The results are compared with a test on a similar box girder made of high-tensile steel. The effects of residual stresses on the behaviour of the box girder are analysed using a progressive collapse method for structures under longitudinal bending moment.

Collapse strength of rectangular plates under transverse compression

Abstract This paper presents a proposal for a new design equation to predict the collapse, strength of plates under transverse compression both with restrained and unrestrained boundary conditions. The equation is developed from and calibrated with experimental and numerical results which allows an assessment of the uncertainty involved in its application. Finally, the proposed equation is compared with the predictions of a non-linear finite element code, which was used to verify in a systematic fashion the effect of changing some of the governing parameters.

Elasto-plastic Behaviour of Plates Subjected to Heat Loads

Abstract The collapse of steel plates subjected to thermal loads representative of fire conditions is analysed taking into account the temperature dependence of the steel properties. A brief description of the temperature dependence of steel properties is provided as well as the approach taken to account for their change during the heating process in the numerical algorithm. A series of calculations of load temperature curves is performed for plates of different aspect ratio, slenderness, initial imperfections and boundary conditions in order to established how they affect the temperature and the collapse load of the plates. It was observed that the maximum load carrying capacity of the plates is often reached at temperatures ranging from 100°C to 200°C, a situation in which the yield stress of the material has not decreased too much yet. The effect of the elastic support of the plates is important until collapse is reached, but afterwards it can be ignored.

Compressive Tests on Long Continuous Stiffened Panels

Results are presented of 8 tests on long stiffened panels under axial compression until collapse. The specime ns are three bay panels with associated plate made of very high tensile steel S690. Four different configurations are considered for the stiffeners, which are made of mild or high tensile steel for bar stiffeners and mild steel for ‘L’ and ‘U’ stiffener s. The influence of the stiffener’s geometry on the ultimate strengt h of the stiffened panels under compression is analyzed. Thi s series of experiments belong to an extended series of tests t hat include short and intermediate panels which allows analyzin g the effect of space framing on the strength of stiffened panel s.

Design equations for plates subjected to heat loads and lateral pressure

A brief description is presented of the strength behaviour of rectangular plates subjected to fire-induced intense heat loads of such a magnitude as to degrade the mechanical properties of the material. Design curves are proposed to predict the collapse of the plates under the biaxial state of stress induced by heat loads. Interaction curves are also derived for the case of plates that are initially subjected to lateral pressure and later to intense heat loads.

Effect of Initial Imperfections on the Strength of Restrained Plates

Most common studies on the strength of plates under compressive longitudinal loading are related to pla tes having unrestrained edges which lead to a zero net load in the transverse direction. In ships, the framing system and the continuity of the plating in the transverse directi on tend to induce rather different boundary conditions on the ‘unloaded’ edges, which results in a completely different stat e of stresses when the external loads are applied. This is due to the surge of a significant level of induced membrane stresses in the direction perpendicular to loading. In this work, the behavior of long restrained plate s under compressive axial loading is analyzed and compared with the one of plates having other boundary conditions. The finite element method is applied for the nonlinear analysi s of the plates using a commercial package. 56 cases are con sidered corresponding to different levels of plate slendern ess which ranges between 0.35 and 3.46 covering the practical range of structural plates used in the shipbuilding industry . Various shapes of initial imperfections are considered in o rder to establish the minimum level of resistance. Also the influence of the magnitude of the distortions associated to each mode is discussed. The study conducted to the establishment of the minimum compressive strength of restrained plates a nd it defines the expected range of strength’s variation due to the magnitude level of distortions. The biaxial axial state of stresses resulting from these boundary conditions is characterized and its dependence from the plate’s slenderness is quantified for the most common type of the hull plating.

EXPERIMENTAL EVALUATION OF THE ULTIMATE BENDING MOMENT OF A THIN BOX GIRDER

The results of a four points bending test on a box girder are presented. The experiment is part of series of tests with similar configuration but different thickness and span between frames. The present work refers to the slenderest plate box girder with a plate’s thickness of 2 mm but with a short span between frames. The experiment includes initial loading cycles allowing for residual stresses relief. The moment curvature relationship is established for a large range of curvature. The ultimate bending moment of the box is evaluated and compared with the first yield moment and the plastic moment allowing the evaluation of the efficiency of the structure. The post buckling behavior and collapse mode are characterized. Comparison of the experiment with a progressive collapse method is made taking into consideration the effect of residual stresses on envelop of the moment curvature curve of the structure.Copyright