Portal frame

About: Portal frame is a research topic. Over the lifetime, 1778 publications have been published within this topic receiving 7210 citations.

Five-shaft linkage numerically controlled machining center

Abstract: The invention discloses a five-axle linkage digital-control processing centre which comprises a lathe bed (10) and a portal frame (30), wherein the portal frame (30) comprises a left portal upright post (32), a right portal upright post (32) and a fixing portal crossbeam (35), and the front part of each portal upright post (32) is provided with a direct driving type double-shaft precise rotating table (20) which enables a working table (26) to simultaneously rotate round an A shaft and a C shaft. Furthermore, the portal frame (30) is provided with a crossbeam (40) which can move along the Y direction, the front part of the crossbeam (40) is provided with a slide carriage (50) which can move along the X direction, the front part of the slide carriage (50) is provided with a main shaft box (60) which can move along the Z direction, the main shaft box (60) is provided with a main shaft installing hole (66) used for installing a main shaft (70), and a tool magazine (80) is arranged in a cavity positioned between the lathe bed (10) and the portal frame (30). The invention has novel structure, small occupied area, space saving, low cost and stable operation and property. Besides, a motion shaft of a machine tool has high dynamic property, regulating property, positioning precision and repeated positioning precision.

Nonlinear Behavior of Structural Plane Frames

Abstract: The deformations that occur in an actual structural frame may significantly influence the joints’ equations of equilibrium and hence the theoretical load-carrying capacity. The finite deflection theory is introduced to deal with the influence of finite displacements on the behavior of structural frames. The method is applied to rigid-jointed pitched roof portal frame and the results are presented in the form of nondimensional graphs. The bowing functions (b\D1\N and b\D2\N) and stability functions (s and c) influence significantly the behavior of this type of frame at high load parameter which indicates their importance for the estimation of the theoretical load-carrying capacity. The classical phenomenon of elastic critical load needs to be reconsidered since the load-deflection curve does not produce the buckling phenomenon. In general, the nonlinear behavior of structural frames as influenced by instability, bowing and finite deflections are studied. A relaxation method has been developed for solving the problem because direct solution is not possible.

Post-buckling analysis of thin-walled steel frames using generalised beam theory (GBT)

Abstract: This paper presents the development and illustrates the application of a beam finite element based on the generalised beam theory (GBT) and intended to analyse the local, distortional and global post-buckling behaviour of thin-walled steel frames. After briefly reviewing the main concepts and procedures required to obtain the GBT system of non-linear equilibrium equations, the paper describes the steps involved in the numerical implementation (incremental-iterative strategy) of a non-linear beam finite element that incorporates the influence of the frame joint behaviour. Next, one uses evidence gathered from shell finite element simulations to establish kinematic constraint conditions ensuring displacement compatibility at frame joints connecting two non-aligned plain/lipped channel members. Finally, the application and capabilities of the proposed GBT-based beam finite element formulation are illustrated by presenting and discussing numerical results concerning the post-buckling behaviour of two “L-shaped” frames and a symmetric portal frame. For validation purposes, most GBT-based results are compared with values yielded by beam and shell finite element analyses carried out in the code A nsys.