Box Columns Research Articles

Vibration and damping of composite sandwich box column with viscoelastic/electrorheological fluid core and performance comparison

In this paper, vibration and damping of composite sandwich box column containing viscoelastic layer (VEL) or electrorheological fluid (ER) core with constraining layer and their performance comparison is carried out. The finite element based modal strain energy method is used for predicting the modal loss factor and frequency of laminated composite box columns with integral viscoelastic/ER fluid layers. Effects of core thickness, orientation of the fiber in the base plate and constraining layer, applied voltage and stacking sequence on the vibration behavior of composite sandwich box column for clamped-free boundary condition are studied in the paper. The performance comparison of vicsoelastic layer damping and ER layer damping is also investigated.

Ultimate strain of stiffened steel box sections under bending moment and axial force fluctuations

The influence of axial force fluctuations on the ductility of short steel cylinders has been previously reported by the authors, together with a proposal for a design formula that takes this influence into account. The present paper describes a similar investigation for stiffened short steel box columns. Elastoplastic large-displacement analysis of parametric short steel box columns is carried out and the bending behavior under constant and fluctuating axial forces is compared. The maximum value of axial force fluctuation is taken to be the same as the axial force magnitude in the constant axial force case. It is found that ductile capacity corresponding to the post-peak region of the bending behavior is improved to different degrees depending on the magnitude and amount of fluctuation of the axial force, a finding that is similar to that for short steel cylinders. Design formulae for failure strain taking this improvement into account are proposed for two different limit states and their validity is demonstrated through numerical analysis.

VIBRATION AND DAMPING STUDIES ON A HOLLOW SANDWICH BOX COLUMN WITH A VISCOELASTIC/ELECTRORHEOLOGICAL/MAGNETORHEOLOGICAL FLUID CORE LAYER BY THE FINITE ELEMENT METHOD

In this paper, the vibration and damping of a hollow sandwich box column containing a viscoelastic layer (VEL) or an electrorheological (ER) or magnetorheological (MR) fluid core with a constraining layer are analyzed and a comparison of performance is made. The hollow sandwich box column comprises two skin plates and a VEL/ER/MR fluid core layer. The finite element method is used to study the vibration and damping behaviors of the column. The natural frequencies and modal loss factors are obtained by solving the complex eigenvalue problem. The modal dampings and natural frequencies of the column are calculated for various electric as well as magnetic fields and their performance is compared with that of the viscoelastic core layer for the clamped-free boundary condition. Effects of core thickness, electric voltage and magnetic field on the vibration behavior of the sandwich box column are investigated.

Modeling the Cyclic Flexural and Shear Response of the R. C. Hollow Box Columns of an Existing Viaduct

The cyclic response of R.C. hollow box columns, constructed as part of a typical single-column bent viaduct, built in the 1970’s in Central Europe, was studied both experimentally and analytically. Moderate displacement ductility capacity (between 3 and 4) was observed regardless of the column construction details, which are nowadays considered inappropriate for seismic regions. Standard analytical flexural models correlated with the experimental results quite well. Shear strength was estimated using the two methods included in the EC8 standards, as well as the method developed at the University of California, San Diego. Quite different results were obtained. The most accurate was the third method.

A design model for stainless steel box columns in fire

A study of stainless steel cold-rolled box columns at elevated temperatures is presented, which is a part of an on-going RFCS project “Stainless Steel in Fire”, 2004–2007. Experimental results of six, class 4, stub columns at elevated temperature, tested by Ala-Outinen [Members with Class 4 cross-sections in fire: Work package 3, ECSC project stainless steel in fire. Contract no. RFS-CR-04048, Espoo, Finland; 2005], were used to evaluate the finite element (FE) model. The FE analysis obtained using the commercially available software, ABAQUS, shows that the critical temperature was closely predicted. Further, a parametric study was performed using the same numerical model. This was a basis to check the quality of prediction of a newly proposed improvement for design rules of class 4 cross-sections in fire according to EN 1993-1-4 [Eurocode 3 - Design of steel structures — Part 1-4: General rules — Supplementary rules for stainless steels, CEN; 2006] and EN 1993-1-2 [Eurocode 3: Design of steel structures — Part 1.2: General rules — Structural fire design, CEN; 2005].

Cyclic response characteristics of retrofitted moment resisting connections

Experimental studies were conducted in order to investigate the behavior of the weld in steel moment resisting connections. A total of forty seven reduced-scale subassembly model specimens were tested that represent welded moment resisting connections of the beam to box column. These specimens were used to study the following aspects in fabrication and retrofitting of moment resisting connections: Complete joint penetration (CJP) groove weld behavior, transversely loaded fillet weld behavior, grinding and rewelding influence on weld behavior, reinforcing of connection with T -stiffener and rib plates, strain rate effect on weld and material characteristics and electrode toughness effect on weld behavior. Following test result interpretations, five full-scale moment resisting connections of beam to box column were fabricated and tested. These models included one specimen fabricated with details of an outdated connection, two specimens with an improved CJP groove weld detail, and two specimens retrofitted by T -stiffeners. Each specimen was subjected to a standard quasi-static cyclic load pattern. Overall, the improved and retrofitted specimens performed well, achieving total (elastic plus plastic) story drift ratios of at least 4% radians in magnitude before experiencing 20% strength degradation.

Progressive collapse analysis of thin-walled box columns

Box columns are often used as main strength members of various types of thin-walled structures such as ships, ship-shaped offshore structures, and aerospace structures. Until and after the ultimate limit state is reached, box columns exhibit highly nonlinear structural behavior in terms of geometrical and material aspects. In particular, the effects of local buckling, global buckling, and their interaction play a significant role in the resulting consequences of box columns under extreme actions. In order to calculate the maximum load-carrying capacity of box columns, it is thus highly required to perform the progressive collapse analysis to take into account progressive failures of individual components and their interacting effects. The aim of the present study is to demonstrate a method that is useful for the progressive collapse analysis of thin-walled box columns in terms of computational efficiency and accuracy. Theoretical outline of the method is addressed. Short, medium and long box columns in length are studied in terms of interacting effects between local component failure modes and global system failure modes. The effect of unloaded edge conditions of individual plate elements is also studied. A comparison of the method with more refined nonlinear finite element method computations is made.

Seismic Performance of Pre-Northridge Welded Steel Moment Connections to Built-Up Box Columns

Results of experimental and analytical investigations of the seismic response of fully restrained steel moment connections between deep W-shape beams and deep and square built-up box columns are presented. Prototype beam-column connections were selected from the steel moment-resisting frames in a building built before the 1994 Northridge earthquake. Two full-size, single sided, pre- Northridge box column connection assemblage specimens were fabricated using the prototype connection data. Pretest analyses showed that the responses of box column connections can be substantially different from W-shape column connections. Both specimens were tested using a standard connection prequalification test protocol and each failed by brittle fracture in the complete joint penetration CJP welds of the beam flanges at connection drift angles less than 0.8% rad. The pre-Northridge beam flange CJP welds are likely to fail in a brittle manner regardless of the type of column cross section. ABAQUS finite-element models of the specimens were validated using the test results. The locations of the cracks in the beam flange CJP welds coincide with the region of high axial stresses, which varies depending on the column type, presence of continuity plates, and thickness of box-column plates.

Finite-element buckling and vibration analysis of functionally graded box columns in thermal environments

In the current paper, buckling and vibration behaviours of thin-walled box columns in a thermal environment made of functionally graded materials are investigated, using finite-element method based on classical laminated plate theory. The four node thin-plate element with five degrees of freedom is employed in the study. The box column is considered as assemblages of plates, and a continuously graded variation in composition of the ceramic and metal phases across the plate wall thickness in terms of a simple power law distribution is implemented. The effects of temperature dependent material properties on the critical buckling and the free vibration response are studied. The analysis is carried out under thermal environment for clamped—clamped boundary condition and results are presented.

Design of high strength steel columns at elevated temperatures

The main objective of this paper is to study the behaviour and design of high strength steel columns at elevated temperatures using finite element analysis. In this study, equations predicting the yield strength and elastic modulus of high strength steel and mild steel at elevated temperatures are proposed. In addition, stress–strain curve model for high strength steel and mild steel materials at elevated temperatures is also proposed. The numerical analysis was performed on high strength steel columns over a range of column lengths for various temperatures. The nonlinear finite element model was verified against experimental results of columns at normal room and elevated temperatures. The effects of initial local and overall geometrical imperfections have been taken into consideration in the analysis. The material properties and stress–strain curves at elevated temperatures used in the finite element model were obtained from the proposed equations based on the material tests. Two series of box and I-section columns were studied using the finite element analysis to investigate the strength and behaviour of high strength steel columns at elevated temperatures. Both fixed-ended stub columns and pin-ended slender columns were considered. The column strengths predicted from the finite element analysis were compared with the design strengths predicted using the American, European and Australian specifications for hot-rolled steel columns at elevated temperatures by substituting the reduced material properties. In addition, the direct strength method, which was developed for the design of cold-formed steel columns at normal room temperature, was also used in this study to predict the high strength steel column strengths at elevated temperatures. The suitability of these design rules for high strength steel columns at elevated temperatures is assessed. Generally, it is shown that the American and European specifications as well as the direct strength method conservatively predicted the column strengths of high strength steel at elevated temperatures. The European Code predictions are slightly more conservative than the American Specification and the direct strength method predictions.

Explicit local buckling analysis of rotationally restrained composite plates under uniaxial compression

A variational formulation of the Ritz method is used to establish an eigenvalue problem for the local buckling behavior of composite plates elastically restrained along their four edges (the RRRR plates) and subjected to compression along one axis, and the explicit solution in terms of the rotational restraint stiffness ( k ) is presented. Based on the different boundary and loading conditions, the explicit local buckling solution for the rotationally restrained plates is further simplified to several special cases (e.g., the SSSS, SSCC, CCSS, SSRR, RRSS, CCRR, and RRCC plates) with a combination of simply supported ( S ) , clamped ( C ) , and/or rotationally restrained ( R ) edge conditions. The unique deformation shape function combining the harmonic and polynomial functions is proposed by considering the effect of elastic rotational restraint stiffness ( k ) along the four edges of the orthotropic plate. The explicit local buckling solutions of the RRSS and SSRR cases are validated with the exact transcendental solutions. A parametric study is conducted to evaluate the influences of the rotational restraint stiffness ( k ) and the aspect ratio ( γ ) on the local buckling stress resultants of various rotationally restrained plates. The applicability of the explicit solutions of restrained composite plates is illustrated in the discrete plate analysis of two composite structures: short thin-walled composite columns and honeycomb sandwich cores. The local buckling strength values of plate panels in short FRP box columns and core walls between the top and bottom face sheets of sandwich are predicted, and they are in excellent agreement with the numerical finite element solutions and experimental results. The simplicity of the “explicit” local buckling solution of elastically restrained composite plates facilitates analysis, design, and optimization of composite structures.

Flexural–torsional performance of thin-walled steel hollow box columns subjected to a cyclic eccentric load

This paper investigates the seismic performance of steel hollow box sections. The test results obtained from the combined load tests were used to define the relationship among member performance, sectional aspect ratios and the load combinations. It was found from the comparisons that the flexural strength of members decreased when the torsion magnitude was increased. It was also observed that the reduction in flexural strength increased when the sectional aspect ratio was increased. An empirical expression for estimating member performance under three-dimensional loads is proposed for design references.

繰返し載荷を受ける角形鋼柱の変形能力に及ぼす局部座屈の影響

This paper presents a numerical study on the effects of the width-to-thickness ratio, axial force ratio, and slenderness ratio on local buckling and strength deterioration of steel box columns subjected to cyclic loading. The maximum strength experienced during cyclic loading, and the strengths remaining after prescribed rotation angles are examined. The following observations are notable: 1) The maximum strength increases with a larger axial force ratio, but serious strength degradation is present due to local buckling; 2) The strength degradation is affected significantly by the width- to-thickness ratio, but the effect of the slenderness ratio is minor; 3) The width-to-thickness requirements stipulated in the present Japanese seismic design codes are not necessarily sufficient for columns sustain large cyclic loading up to 0.03rad in rotation.

Strength of Concrete-Filled Steel Box Columns with Buckling Effects

This paper studies the ultimate strength and ductility of short concrete-filled thin-walled steel box columns with local buckling effects using a nonlinear fibre element analysis technique. New effective width formulas for determining the ultimate strengths of steel plates with geometric imperfections and residual stresses in concrete-filled thin-walled steel box columns are incorporated in the fibre element analysis program to account for the effects of local buckling. The progressive local and post-local buckling is simulated by gradually redistributing the normal stresses within the steel box. Performance indices are employed to quantitatively evaluate the section and ductility performance of composite columns. The effects of local buckling, steel ratios and steel yield strengths on the strength and ductility of concrete-filled steel box columns are investigated. It is demonstrated that local buckling significantly reduces the ultimate strength of thin-walled high-strength steel box columns filled with concrete. The 4% limit on the steel ratio or the 0.2 limit on the steel contribution ratio imposed on composite column sections in current design codes leads to the use of very slender steel plates in concrete-filled steel box columns. It is suggested that the section performance index of concrete-filled steel box columns should be as high as 0.5 for a better structural performance. The use of high strength steels in concrete-filled steel box columns significantly increases the ultimate strengths of the columns but reduces their ductility.

冷間プレス成形角形鋼管柱(BCP325)の載荷加熱実験挙動の数値解析

A numerical simulation of the fire resistance test of large steel columns is presented. The experimental investigation into the fire resistance properties of axially loaded large steel box columns were described in Ref.(1,2) by authors. In this paper, a procedure for a one-dimensional finite element of nonlinear numerical analysis was applied to simulate thermal deformation, which is described as an elastic-plastic-creep, of steel columns as they are subjected to high temperatures. And the results of the calculations clearly show that numerical analysis can be used to provide accurate predictions of the deformation characteristics of columns at high temperatures, when an appropriate mechanical model and creep strain data of steel materials at high temperature are used.

Change of Weld Residual Stresses due to Loss of Material

The loss of material due to corrosion sometimes has a large influence on the change of weld residual stresses and residual deflections of steel structures. A new finite-element method is proposed that can take into account the effects of the volume change of material. By the use of this new method, it is expected that the change of weld residual stresses and residual deflections due to loss of material can be evaluated, if only the distributions of the residual stresses and residual deflections at the initial state as well as the corrosion profiles are known in advance. In order to confirm the validity of the proposed method, an experiment is carried out to measure the change of weld residual stresses and residual deflections by mechanically forming a groove on the surface of a welded steel box column that mimics a local corrosion loss pattern. From the experiment, it is observed that the change of the weld residual stresses and residual deflections caused by the groove is well predicted by the proposed analysis method as long as the corresponding initial values of the box column without groove are known in advance.

Strength and ductility evaluation of steel bridge piers with linearly tapered plates

Important issues on the application of linearly tapered steel plates to highway bridge piers are discussed in this paper based on extensive experimental work. The factors that affect the seismic resisting performance of tapered plate steel columns were examined. The main factors considered are: (1) types of tapering mold line (outer, central, and inside tapering); (2) tapering ratio (or the slope of thickness change); (3) stiffeners’ rigidity; and (4) tapered stiffeners. To this end, four groups of specimens were tested under cyclic lateral loads and constant axial load. The columns with the outside taper plates were found to have the best strength and ductility characteristics among the three types of mold lines. In the case of different tapering ratios, the largest ductility was observed in the specimens with the tapering ratio slightly less than or equal to unity. The stiffeners’ rigidity ratio of around 3.0 was found to give the best ductility performance in columns with both constant thickness and varying thickness stiffeners. The test results were compared with a recently proposed design equation for limit strain of box columns with tapered plates. Finally, finite element analyses were performed and comparisons between the test and the analyses’ results of several test specimens are presented.

Effect of the moment transfer efficiency of a beam web on deformation capacity at box column-to-H beam connections

This paper investigates the effect of moment transfer efficiency of a beam web on deformation capacity at beam-to-column connections. Non-linear finite element analysis of five connection models was conducted. Analytical results showed that the moment transfer efficiency of the connection with a box column was poor when compared to a connection with an H-column; this was due to the out-of-plane deformation of the column flange. Based on previous test data, analytical results were compared with experimental results. Analytical and experimental results showed that the deformation capacity of the connection with a box column decreased due to the poor moment transfer efficiency of a beam web, followed by strain concentration at the beam flange.

기존 용접형 철골 박스기둥 접합부의 내진성능

본 연구에서는 1994년 미국 노스리지 지진 이전에 건설된 기존 철골 건물의 용접형 철골 박스기둥과 보 접합부의 내진성능을 반복재하 실험에 의해 평가하였다. 실험결과에 의하면 노스리지 지진 이전 접합상세를 갖는 박스기둥과 보 접합부에서도 H-형강 기둥과 보 접합부 실험결과와 유사하게 취성파단이 발생하였다. 하지만, 박스기둥과 보 접합부에서의 플랜지 응력전달 경로가 H-형강 기둥과 보 접합부에서의 것과 상당한 차이가 있고 또한 박스기둥의 형상에 따라 균열 전파의 형태가 다를 수 있다는 것이 밝혀졌다. 따라서 용접형 철골 박스기둥과 보 접합부의 내진성능을 향상시키기 위해서는 H-형강 기둥과 보 접합부에 대한 기존 연구결과를 그대로 적용하기보다는 박스기둥에 적합한 접합부의 보강상세 개발이 요구된다. In this study the seismic performance of welded steel moment connections to built-up box columns in the existing building built before 1994 Northridge earthquake was evaluated by cyclic tests. According to the test results, the pre-Northridge steel moment connections to the box columns also suffered from brittle fracture similar to that in the H-shaped column connections. However, the flange force transfer mechanism of the box column connections was substantially different from that of the H-shaped column connections, and the patterns of crack propagation may be changed due to the shape of the box column. Therefore, it is required to develop proper details for the box column connections instead of using the research results for H-shaped column connections in order to enhance the seismic performance the connections.

Optimum seismic design of a multi-storey steel frame

An interior three-storey frame structure with a column and 4 beams in each floor is investigated. The vertical and horizontal (seismic) forces, normal forces and bending moments as well as elastic interstorey drifts are calculated. The welded box columns and rolled I-section beams are designed for minimum weight and cost. The beam-to-column connections are selected from a number of structural versions improved for seismic resistance. The fabrication costs are calculated in detail. Design constraints relate to interstorey drifts and to the stability of column parts and beams loaded by compression and bending. Calculations show that, after a connection type is selected, the fabrication cost has little effect on the optimum design, since it varies proportionally with the mass according to the present calculating method. Thus, the minimum weight design gives suitable results.