Design of Transverse Stiffeners in Plate Girders with Corrugated Web

This study reports investigations into the effect of relative flexural stiffness of intermediate stiffeners γ on the failure zone location in the corrugated web. The study also aimed at obtaining stiffness criterion for intermediate stiffeners that depends on the magnitude of the plate geometry parameter α. To achieve the goals of the study, experimental investigations were conducted into load displacement paths of four exemplary SIN girders. They were simply supported girders, made to full scale, and composed of pre-assembled units. The phenomena occurring in the experiment were represented using the Finite Element Method. For FEM numerical analysis of girders with intermediate stiffeners, models with the web height of 1000, 1250 and 1500 mm, made from 2; 2.5 and 3 mm thick corrugated sheet metal were used. Due to the analysis of 52 girder numerical models, it was possible to propose the stiffness criterion of intermediate stiffeners. The criterion was based on the assessment of shear buckling strength of the corrugated web. Using the regression method, dimensionless coefficients of the stiffener stiffness ks dependent on the optimum stiffness γ were determined. Based on estimated coefficients of the stiffener stiffness ks, the absolute minimum stiffness of intermediate stiffeners Ismin used in corrugated web plate girders was calculated. It was demonstrated that the use of an intermediate stiffener, the stiffness of which is greater than Ismin , additionally leads to a change in the location of the site of the web shear buckling.

Application of ring beam stiffness criterion for discretely supported shells under global shear and bending

Silos in the form of a cylindrical metal shell are commonly elevated to provide access to the space beneath. In general, a few discrete column supports at evenly spaced intervals are commonly utilized. The presence of discrete supports results in circumferential non-uniformity in the axial compressive stress above the support. Depending on the size of the structure, several different support arrangements may be chosen. A stiff ring beam is utilized in larger silos to transfer and evenly distribute the discrete forces from the supports into the cylindrical shell wall. A stiffness criterion was developed by Rotter to assess the degree of non-uniformity in axial compressive stresses around the circumference. The stiffness criterion is based on the relative stiffnesses of the ring beam and the cylindrical shell and was verified for loading conditions that produce circumferentially uniform axial stresses around the circumference. A study has been undertaken to investigate the applicability of the stiffness criterion to cylindrical shells under global shear and bending. Pursuant to this goal, extensive finite element analyses were conducted where different ring beam and cylindrical shell combinations are subjected to global shearing and bending actions. The results revealed that the stiffness criterion can be extended to shells under this loading condition. The degree of non-uniformity in axial stresses is quantified and presented as simple formulas that can be readily adopted by design standards.

An Energetic Criterion for Dynamic Instability of Structures Under Arbitrary Excitations

An energetic criterion for identifying the global dynamic instability of structures subjected to any kind of excitations is proposed in the paper. The concept of dynamic stability for structures is firstly interpreted and distinguished from the stability concept in the Lyapunov sense. It is demonstrated that the dynamic instability depends not only on the properties of the structure, but also relates to the change of external excitations on the structure, which distinguishes the essence of dynamic instability from the pseudo static stiffness criterion. This background leads to a novel energetic criterion with which the first passage of the variation of intrinsic energy over the input energy manifests the dynamic instability of structures. The proposed criterion has been extensively tested and verified in the numerical examples, with its advantages clearly illustrated.

Structure Topology Optimization of the Spindle Box of a Machining Center

To meet the need of high precision and speed, the movable parts of a high speed machining center should be as light as possible with high stiffness, which can be realized effectively via structure topology optimization. In this paper, structure topology optimization of the spindle box of a type of machining center was carried out based on the software of OptiStruct of HyperWorks. In the course of design, a stiffness criterion was put forward to deal with the uncertainty of cutting load on a machining center. And based on the criterion, the load boundary condition of the spindle box model was defined. And a clear structure was finaly obtained in the postprocessor of OptiStruct.