Carlos Graciano

Resistance of longitudinally stiffened I-girders subjected to concentrated loads

Abstract This paper presents a design procedure for the determination of the ultimate resistance of longitudinally stiffened girder webs to concentrated loads. The influence from the longitudinal stiffener is considered in the slenderness parameter λ , through the buckling coefficient k f . This procedure is harmonized with other design procedures currently used for describing buckling problems in steel structures. An expression is developed for the buckling coefficient based on finite element analysis. The interaction between the web plate with flanges and a longitudinal stiffener was considered in the analysis. The ultimate strength according to the design procedure presented herein and the results are compared with available experimental results. The interaction with bending is also investigated.

Nonlinear FE analysis of longitudinally stiffened girder webs under patch loading

Abstract The ultimate load behavior of longitudinally stiffened girder webs under patch loading is studied here by means of a nonlinear finite element analysis. Large-deflection effects and initial shape imperfections are taken into account. The influence of the slenderness of the directly loaded web panel on the patch loading capacity is studied in depth, together with the size of the loaded flange. In addition, the influence of stiffener rigidity is also analyzed. This study was aimed at finding an optimum position of longitudinal stiffeners for patch loading. Currently, designers use the value recommended for bending, i.e. one-fifth of girder depth. The results presented here show that a stiffener located closer than one-tenth of the girder depth significantly increases the load carrying capacity of the plate girder due to a decrease in the slenderness ratio of the web panel between the loaded flange and the longitudinal stiffener.

Failure mechanism of slender girder webs with a longitudinal stiffener under patch loading

The failure mechanism of slender girder webs stiffened by a single longitudinal stiffener under patch loading is addressed. Experimental results have shown that failure is due to crippling in the web panel formed between the loaded flange and the stiffener. This mechanism is similar to the one for unstiffened webs, which is characterized by the presence of elastoplastic deformations in the compression flange (plastic hinges) and in the web (yield lines). A longitudinal stiffener with normal position, b1<0.3hw, and rigidity restricts the size of the buckle in the upper web panel, and in some cases the distance between the outermost plastic hinges in the loaded flange is reduced. Based on the upper bound theorem of plastic collapse an expression for the patch loading resistance of webs stiffened by a single horizontal stiffener is presented. Theoretical predictions are in good agreement with experimental results.

Critical buckling of longitudinally stiffened webs subjected to compressive edge loads

The resistance of steel plate girders subjected to concentrated load can be described using a strength curve, which includes a gradual transition from yielding to buckling depending on the slenderness ratio of the web. The slenderness is a function of the ratio of the yield resistance to the critical buckling load. This paper describes a methodology for the determination of buckling coefficients for longitudinally stiffened plate girders subjected to partial edge loading or concentrated loads. After an extensive parametric analysis, the optimum parameters that govern the change from a global buckling mode to a more local buckling mode were found. As in similar buckling problems, the results show that the location and the relative flexural/torsional rigidity of the stiffener are relevant parameters that govern the final buckling shape. Finally an expression for the buckling coefficient used to determine the critical buckling load for longitudinally stiffened girder webs is presented.

Ultimate resistance of longitudinally stiffened webs subjected to patch loading

Longitudinal stiffening increases the ultimate resistance of slender girder webs subjected to patch loading when the stiffener is placed rather close to the loaded flange. In the past, some attempts have been made to quantify this influence, however none of these formulae have been successfully implemented due to poor correlation between predictions and experimental results. This paper describes a methodology to determine the ultimate resistance of longitudinally stiffened girder webs subjected to patch loading. The methodology accounts for the influence of: (a) the relative position of the stiffener, (b) the ratio of flange-to-web thickness, and (c) the ratio between the yield strength of the flange and the web. Finally, theoretical predictions show good agreement with experimental results.

Recent Patents on Expanded Metal

Expanded metal has been widely used around the world. This paper is aimed at presenting latest advances in the use of expanded metal in engineering. Currently, expanded metal is mainly used in the construction industry as furniture, fences or protection purposes. Hundreds of patents can be found in the literature regarding possible applications for expanded metal. These applications fall into four main areas: furniture, construction, biomechanics, and energy absorption systems. When expanding the metal, the material undergoes slits and stretching modifying the mechanical properties of the base metal, hence enhancing the material strength. Additionally, there is a reduction of the weight per unit of area, which is an asset when designing lightweight structures. Waste material from the manufacturing process is almost none, since the base metal is cut and stretched to the final form. Recently, expanded metal sheets are used in architecture to create modern, efficient and elegant buildings that are also energy-efficient, open and transparent. The relevant patents on expanded metals are discussed.

ENERGY ABSORPTION CHARACTERISTICS OF COILED EXPANDED METAL TUBES UNDER AXIAL COMPRESSION

THIS PAPER PRESENTS AN EXPERIMENTAL INVESTIGATION ON THE AXIAL CRUSHING OF COILED EXPANDED METAL TUBES SUBJECTED TO COMPRESSIVE LOADING. THE INVESTIGATION AIMS AT COMPARING THE ENERGY ABSORPTION CHARACTERISTICS BETWEEN TUBES FABRICATED WITH COILED EXPANDED METAL MESHES AND SOLID PLATES. THEN, A SERIES OF QUASI-STATIC AXIAL CRUSHING TESTS WERE PERFORMED TO OBTAIN THE STRUCTURAL PERFORMANCE ON COILED TUBES, AND THEN COMPARE THESE WITH ROUND AND SQUARE SOLID TUBES. COILED TUBES WERE FABRICATED USING CIRCULAR AND SQUARE GEOMETRIES, AS WELL AS VARIOUS CELL ORIENTATIONS. THE RESULTS SHOWED THAT CELL ORIENTATION ENHANCE THE ENERGY ABSORPTION RESPONSE OF THE COLLIDED TUBES. REGARDING THESE RESPONSES IN COMPARISON TO THOSE OF SOLID TUBES, THE RESULTS SHOWED THAT FOR COILED AND SOLID TUBES WITH THE SAME WEIGHT, THE ENERGY ABSORPTION CAPACITY OF THE FORMER IS MUCH LESSER THAN THE LATTER.

AXIAL CRUSHING OF CONCENTRIC EXPANDED METAL TUBES UNDER IMPACT LOADING

THIS PAPER INVESTIGATES THE AXIAL CRUSHING RESPONSE OF CONCENTRIC EXPANDED METAL TUBES UNDER IMPACT LOADING. THE STUDY IN CONDUCTED BY MEANS OF NONLINEAR FINITE ELEMENT SIMULATIONS, CONSIDERING THE SPEED OF DEFORMATION AND THE SIZE OF THE EXPANDED METAL CELLS. IN THE ANALYSIS, TWO TUBES ARE PLACED CONCENTRICALLY AND THEN AXIALLY CRUSHED WITH AN IMPACT MASS AT VARIOUS SPEED LEVELS. CRUSHING LOAD-DISPLACEMENT RESPONSES ARE ANALYZED TO INVESTIGATE THE INFLUENCE OF THE SIZE OF THE MESH AND THE IMPACT SPEED. THE RESULTS SHOW THAT SPECIMENS WITH THE SAME MESH SIZES INCREASES THEIR CRUSHING LENGTH WITH INCREASING SPEED. FINALLY THE MAIN OUTCOME OF THIS INVESTIGATION IS TO ADD TO THE STATE OF KNOWLEDGE INFORMATION CONCERNING THE USE OF EXPANDED METAL MESHES IN IMPACT ATTENUATION DEVICES.