Papers by Keyword: Local Buckling

Abstract: In steel building structures, local buckling and/or fracture of columns could occur during strong ground motions, furthermore complete collapse might be induced due to the column strength degradation. In this paper, cold press-formed square tube columns are targeted, and numerical model being able to trace precisely degradation behavior is proposed. In order to take account of both local buckling and fracture with low computational costs, multi-spring model which consists of some uni-axial springs is adopted. Axial force-deformation relationships of uni-axial springs are provided on flat area and corner area of square tube severally, and are separated into skeleton part and hysteresis part. All parameters on force-deformation relationship are identified based on finite element analysis results of short columns under monotonic or cyclic axial loading. Comparing between analysis results by multi-spring models and past cyclic loading test results or finite element analysis results, it is clarified that degradation behavior of cold press-formed square steel tube columns can be traced with high accuracy.

Abstract: From lessons learned after the 2011 Tohoku earthquake, it is clear that the quick procurement of an emergency public shelter and restoration of the city function are very important in the event of a disaster. This paper focuses on effects of the seismic repair to the residual out-of-plane deformations in local buckling region of steel column. The major findings obtained from the test are summarized as follows: (1) the RA repair method brought the strength recovery from the residual strength and the maximum strength is larger than the original one; (2) RF and RW repair methods also brought the strength recovery from the residual strength, however, the maximum strength is roughly same to the plastic moment of the original column.

Abstract: When a buckling-restrained brace (BRB) is composed of a flat steel core encased in a rectangular steel tube with infill mortar, the flat steel core develops high-mode buckling waves within the spaces occupied by compressible debonding layers when BRB is in compression. The wave crests and troughs collide with mortar and then acting outward forces on restrainer. The steel tube wall may bulge out if the restrainer is too weak to sustain the outward forces and the BRB may lose its compression carrying capability. The outward force can be estimated according to steel core high-mode buckling wavelength and the debonding layer thickness. The restrainer capacity in resisting outward forces can be estimated by using the upper bound theory in plastic analysis. The results of 39 BRB tests were compared in order to evaluate the effectiveness of steel tube capacity estimation methods. 24 BRBs exhibiting local bulging failure suggested that the steel tube capacity can be estimated by assuming the bulged wall as a wedge shape with five of its boundary developing flexural strength. The proposed estimation is conservative and can be adopted for BRB design in preventing local bulging failure for severe seismic services.

Abstract: In many developed countries, concrete filled steel tubular arch bridges are being constructed for roads and railway lines. The CFST arch bridges use steel tubular arches with self consolidating concrete pumped inside and the steel tube provides confinement to the concrete infill. Also, these concrete filled steel tubes have enhanced ductility, better seismic performance, aesthetic quality, lesser consumption of materials and self weight, speedy construction and small vibrations according to studies conducted earlier. Due to the presence of steel tube, local buckling of arch is delayed and reduces the ingress of moisture when exposed to harsh environmental conditions. This paper aims to find the seismic performance of CFST arch bridges in terms of seismic output and deformation when compared to conventional bridges being currently constructed.

Abstract: Aluminium plates containing a single hole or multiple holes in a row are recently becoming very popular among architects and consultant engineers in many constructional applications, due to their reduced weight, as well as facilitating ventilation and light penetration of the buildings. However, there are still uncertainties concerning their structural behaviour, preventing them from wider utilization. In the present paper, local buckling phenomenon of perforated aluminium plates has been studied using the finite element method. For the purposes of the research work, plates with simply supported edges in the out-of-plane direction and subjected to uniaxial compression are examined. In view of perforations, circular cut-outs and the total cut-out size has been varied between 5 and 40% of the total plate area. Moreover, different perforation patterns have been investigated, from a single, central cut-out to a more refined pattern consisting of up to 25 holes equally distributed over the plate. Regarding the material characteristics, several aluminium alloys are considered and compared to steel grade A36 on plates of different slenderness. For each case the critical (Euler) buckling load and the ultimate resistance has been determined.A study into the boundary conditions of the plate showed that the restrictions at the edges parallel to the load direction have a large influence on the critical buckling load. Restraining the top or bottom edge does not significantly influence the resistance of the plate.The results showed that the ultimate resistance of aluminium plates containing multiple holes occurs at considerably larger out-of-plane displacement as that of full plates. For very large total cut-out, a plate containing a central hole has a larger resistance than a plate with equal cut-out percentage but with multiple holes. The strength and deformation in the post-critical regime, i.e. the difference between the critical buckling load and the ultimate resistance, differs significantly for different number of holes and cut-out percentage.

Abstract: Deflections at the serviceability limit state are often decisive in the design of aluminium structures due to the low elastic modulus. Where design is based on deflections, it may not be necessary to calculate the resistance exactly and simple conservative methods are sufficient. The proposed method may be used to generate a quick, approximate and safe solution, perhaps for the purpose of initial member sizing, with the opportunity to refine the calculation for final design. Another reason for the simple method is enhancing ease of use of Eurocode 9.The principal of the proposed method is to eliminate calculation of effective cross-sections by reducing the elastic resistance with the reduction factor for the most slender part of the cross-section or the factor for HAZ softening whichever is less. This means that you don’t need to define the cross-section class. The disadvantage is that you don’t utilize the plastic reserve for class 1 and 2 cross-sections, nor the redistribution of stresses in the post-buckling range of class 4 cross-sections or sections with HAZ. The procedure is similar to the method with permissible stresses familiar to most engineers.

Abstract: At present, the relevant researches of Glulam columns in China are mainly restricted to short columns. In order to study the mechanical properties of long columns under axial loading, an experimental study on five different slenderness ratios of Larch Glulam columns was carried out. With slenderness ratio changing, the variations of experimental data such as axial strain, lateral deflection at mid-height, ultimate bearing capacity, and peak strain were comparatively analyzed. The failure pattern and failure mechanism of long columns were discussed. The results indicate that the ultimate bearing capacity of Larch Glulam columns gradually decreases as the slenderness radio increases and the failure mode is gradually converted from strength failure to instability failure. The ultimate load reduction factor is obtained by regression analysis based on the experiment results of Larch Glulam short columns. The basis for design and application of Larch Glulam columns are provided.

Abstract: There are situations in the thin-walled steel girders with box intersection, in which the internal wall of compression flange is elastically restrained in the webs of section and along its length occurs the change of normal stresses. Such a wall was modelled, as a bilateral elastically restrained internal plate variably loaded at the length. Explicit formulation of neural formula on buckling coefficient of internal plate at non-linear distribution of longitudinal stress was discussed in this paper. A few structures of neural networks (NN) were envisaged in order to obtain the best of the numerical effectiveness of the final formula. The results noted from the literature were used for the evaluation of neural prediction of coefficient.

Abstract: Nowadays cold bent steel thermal сold-bent С-profile is widely used in building construction but we still have some little studied questions in the fields of thermal conductivity, air permeability, resistibility and corrosion behavior of the profile. Cold-bent notched С-profile is used for interior exterior panel members. Lengthwise notches made chequerwise in the profile walls increase the distance of heat flow and decrease heat conductivity and eliminate cold bridges that is why the profile is called “thermal profile”. Cold-bent profile made by cold bending requires alternate approach when engineering structures are designed and maintained. The approach means thin walls’ and the profile special form’ impact on the bearing capacity and stability of the structures should be taken into account. In spite of the wide use of cold-bent notched C-profile in building frameworks, we see lack of information on how the notches influence the bearing capacity and stability of structures. There are no official normative documents on calculation and designing of cold-bent notched profile structures. We carry out theoretical and experimental investigations on global buckling and bearing capacity of steel members of C-shaped notched profiles of different cross-sections area. We carry out theoretical and experimental investigations on heat current passing through the thermal profile structure is held with the use of testing bed.

Abstract: This paper presents analytical studies using Eigenvalue buckling analysis in the Finite Element Method to determine shear buckling and subsequently determine shear resistance of thin plated member with trapezoidal corrugated web. The result is compared with experimental results. It is found that the proposed equations give good agreement to the experimental results. However, the buckling coefficient k is still not generate a good shear stress based on its slenderness ratio h_w/t_w.