Rectangular Steel Tube Columns Research Articles

Experimental study and design method of embedded concrete-filled rectangular steel tube column base under cyclic load

Embedded column base has been widely used in concrete-filled steel tube (CFST) structures due to its high rigidity and good seismic performance. However, the strength analysis of the embedded CFST column base was not yet clear since there was little experimental research on it. In this paper, the experimental investigations of six embedded concrete-filled rectangular steel tube (CFRST) column bases under constant axial load and cyclic load were carried out to study the effects of embedded depth, improvement measures and axial compression ratios on the seismic performance of the column bases. The experimental results indicated that setting stiffeners, increasing the embedded depth or axial compression ratios could improve the seismic performance of the column base. In this experiment, the critical embedded depths of the columns with or without stiffeners were 0.7 and 1.5 times the column width B respectively. When the embedded depth was 0.7B, the contribution of anchor bolts to the moment resistance capacity of the column bases could reach up to 14.2%. Based on the analysis of the force transmission mechanism between the column and the concrete foundation in the embedded CFRST column base, a design method considering the contribution of different components to the moment resistance capacity of the CFRST column bases is proposed. The prediction results are in good agreement with the tested results and collected data, within ± 15% error. The parameter analysis based on the design method has revealed the influence patterns of various parameters on the moment resistance capacity of the column bases.

Experimental investigations on the compression capacity of rectangular steel tubular columns strengthened with intermittently welded angle steel

Many steel structure buildings in China were built from the 1970s to the 1980s, and they have been in service for decades. However, due to factors such as changes in their functionality, prolonged disrepair, and erosion of the surrounding environment. Studying the strengthening of many existing steel structures will become an important measure during the “reinforcement period.” Welding angle steel on the surface of steel columns for reinforcement is a commonly used method in practical engineering. However, the traditional continuous welding of angle steel to reinforce rectangular steel tube columns results in a relatively large welding workload on the construction site, extending the construction period and increasing the engineering cost, which cannot guarantee high welding quality. To reduce the workload of on-site welding and the cost of construction reinforcement, intermittent welding is proposed. This article designed 9 test specimens for axial and eccentric compression tests to obtain the failure modes, ultimate bearing capacity, and stress distribution of the cross-section of steel tube columns reinforced with different intermittent welding angle steels. The experimental results indicate that intermittent welding can replace continuous welding for the reinforcement of steel tube columns, significantly reducing on-site welding workload and fully utilizing the role of angle steel reinforcement. If the length of the intermittent welding is too large, local buckling will occur, thereby weakening the reinforcement effect of the angle steel. The existence of batten plates can improve the ultimate bearing capacity of intermittent welded angle steel tube columns. Comparative analysis was conducted using a finite element model, which revealed the force transfer mechanism and ultimate bearing capacity of intermittent welding angle steel reinforced steel tube columns. The optimal weld spacing and weld length for intermittent welding of angle steel to reinforce rectangular steel tube columns provide a theoretical reference for the design and application of practical reinforcement engineering.

Nonlinear Analysis on the Static and Cyclic Behaviors of UHPC Filled Rectangular Steel Tube Columns

Nonlinear Analysis on the Static and Cyclic Behaviors of UHPC Filled Rectangular Steel Tube Columns

A study of the mechanical behavior of rectangular steel tubular column strengthened using intermittent welding angle steel

From the perspective of the development of steel structures in China, the existing steel structure had experienced decades of service. However, due to the change of its functionality, and the erosion caused due to the surrounding environment, reinforcement of steel has become necessary. Thus, the research on reinforcement theory and methods of the existing steel structures has become an important measure in the “reinforcement period”. Steel angle welding on the surface of steel columns is a common method used in practical engineering. However, the traditional continuous welding angle steel reinforcement of rectangular steel pipe columns leads to a large amount of welding work on the construction site, thus prolonging the construction time and increase the project cost. Moreover, the quality of welding also cannot be guaranteed. Therefore, in order to reduce the cost of field welding and reinforcement of the construction project, intermittent welding is proposed in this work. In this paper, the finite element analysis of rectangular steel tube column models that were strengthened using different intermittent welded angle steel under axial and eccentric compression is discussed out and the results are compared with the experimental results for validation. Further, a large number of numerical models with different parameters are analyzed. From the analysis, the ultimate bearing capacity and the load transfer mechanism of the rectangular steel tube columns that were strengthened using intermittent angle steel under eccentric and axial compression are studied, and the optimal weld spacing and weld length are obtained. The results provide a theoretical base for future practical engineering applications.

Strength and Axial Behavior of Cellular Lightweight Concrete-Filled Steel Rectangular Tube Columns under Axial Compression

This paper presents the experimental results on the strength and axial behavior of rectangular steel tube columns filled with cellular lightweight concrete (CLC) under axial compression. A total of 24 specimens, including 6 reinforced cellular lightweight concrete (RCLC) columns and 18 cellular lightweight concrete-filled steel tube (CLCFT) columns are investigated. The nominal dimension of the rectangular columns are 150×75 mm in cross-section and 750 mm in height. The parameter used in all tests are the ultimate compressive strengths of the CLC, which are 15 MPa, 20 MPa and 25 MPa, and the wall thicknesses of steel tubes, which are 3.0 mm, 4.5 mm and 6.0 mm. All specimens are prepared and loaded concentrically in axial compression to failure. The results of these tests demonstrated that the CLCFT columns have a linear behavior up to the approximately 80-90% of their maximum compressive load. Then, the behavior of the columns is nonlinear. The nonlinear behaviors are due to the crushing of the concrete core and local wall buckling of the steel hollow tube. In addition, it is found that the CLCFT columns have high axial deformability at the failure when compared to the reference RCLC columns. Finally, by comparing the maximum compressive load of the test results with those obtained from the ACI composite design equation, the comparison results show that calculation formula in ACI code can be applied to compute the axial capacity of CLCFT columns under axial compression.

Force transmission mechanism of a new joint of concrete-filled rectangular steel tubular column under axial compression

In this study, a new joint of concrete-filled rectangular steel tube column was proposed and analyzed. The force transmission components include distribution beams and inner periphery ribs in the floor node area. The stress behavior of the new proposed concrete-filled rectangular steel tube column under axial compressive load was investigated. It was found that the force transmission components coordinate the force and deformation of external steel tube and internal concrete. This indicates that the steel tube and concrete can work together to bear external load. Our previous test results also show that arranging force transmission components in the floor node area can improve the mechanical behavior of a concrete-filled rectangular steel tube column. Finally, a design method of force transmission component distribution beam is proposed, which provides a reference for the structural designer to use the new concrete-filled rectangular steel tube joint in actual engineering.

각형강관 기둥-H형강 보 신형상 내진접합부의 실험적 평가

각형강관 기둥-H형강 보 신형상 내진접합부의 실험적 평가

Experimental and analytical investigation of transition steel connections in traditional-style buildings

This article examines experimentally the behavior of transition steel connections between smaller rectangular and larger circular tubes in traditional-style Chinese buildings. The steel connections were subjected to combined constant axial load and lateral cyclic displacements. Tests were carried out on four 2/3 scale connections extracted from a prototype with two upper column lengths (or slenderness) and two levels of axial force. The influence of axial compression ratio and slenderness ratio on the mechanical behavior of the connections was assessed by looking at hysteretic performance, backbone curves, characteristic loads and corresponding displacements, ductility, energy dissipation capacity, and stiffness degradation. Test results showed that the primary failure modes were cracking of welds or base metal around the welds, and local buckling of the flange at the base of the rectangular steel tube column. The hysteresis loops were full and showed moderate degradation, indicating very good seismic performance for these steel connections. When failure occurred, the interstory displacement angle was between 2.2% and 2.8%, and the equivalent viscous damping coefficient was about 0.26–0.29. Based on the experimental research, an idealized bilinear backbone curve model was developed considering both stiffness degradation and second order effects. This simplified model provides both a yield and an ultimate strength and deformation capacity that can be used in design.

Improved equivalent bracing model for seismic analysis of mid-rise CFS structures

An improved equivalent bracing model of cold-formed steel shear wall with concrete-filled rectangular steel tube column as reinforced end studs was proposed, for seismic analysis of mid-rise cold-formed steel structures. The model can consider end stud's compression buckling and beam-column joint's behavior. Elements and parameters of the model were described, comparisons between the model and pinned equivalent bracing model were performed. The results show that: (1) compression buckling can be simulated by setting an axial spring at the bottom of end stud; the reinforced end stud can be defined as a composite section, and the sectional properties can be determined according to the principle of equivalent flexural rigidity; the spring's axial stiffness can be determined by the shear capacity Fp of the wall and its corresponding deformation Δa; (2) beam-column joint's behavior can be simulated by rotational spring, which can be defined by pinching4 model after its constitutive relationship has been determined by experiments or the moment-rotation prediction model proposed in this study; (3) the shear behavior of the wall can be represented by equivalent diagonal braces with nonlinear springs whose restoring force properties can be defined by pinching4 model according to the load-displacement hysteretic curve obtained from full-scale cyclic loading test or numerical simulation etc.; (4) the model can predict actual seismic performance of mid-rise cold-formed steel structure more accurately than pinned equivalent bracing model; moreover, a wall's yield limit directly affects the response modification factor R, the model can thereby provide more reliable design objectives for the structure.

FRACTURE ANALYSIS OF RECTANGULAR COMPOSITE STEEL TUBES UNDER AXIAL LOADING USING ABAQUS/CAE 6.10-1

This research paper focuses on Fracture Analysis of Concrete Filled Rectangular Steel Tube Columns under Uniaxial Loading using ABQCUS/CAE 6.10-1 software was used for proper analytical modeling and also damage analysis of CFST columns were carried out. CFST column structure has high ductility , high load bearing capacity hence it has been widely used in civil engineering field. In this dissertation work,’ Fracture analysis has been carried out rectangular composite steel tubes under axial loading using ABAQUS. Cracked & uncracked modles have been developed using 8-noded 3Dsoild element for concrete & C3H8 element for steel modelling in ABAQUS 6.10-1 . At the outset, developed model is used to validate the results obtained by “ S.D. Bedage , Dr .D.N. Shinde “ of “ Comparative study of concrete filled steel tubes under axial compression” is the International journal of engineering research , vol.3.,issue.3., 2015. Experimental on rectangular axially loaded composite steel tubes were also carried out for different length , width of varying thickness. Ultimate load values obtained were compared with proposed cracked & uncracked fracture model using CTOD method. Further, all the experimental & ABAQUS results compared with ACI code, Euro code, BS code results. The results obtained by Euro codes were found to be inpar with the experimental & proposed ABAQUS values. For the proposed abaqus fracture model & experimental values, the % of error is in the range of 8-15%.

Reversed cyclic performance of cold-formed steel shear walls with reinforced end studs

To improve the shear performance of cold-formed steel (CFS) shear walls and to prevent a structure from collapsing due to compression buckling of the end studs, shear walls with concrete-filled rectangular steel tube columns as end studs were proposed. Cyclic loading tests on nine full-scale CFS shear walls with reinforced end studs were conducted concerning the influence of stud type, sheathing material and openings. The results showed that: (1) the walls' shear strength will be improved because the screws will be less able to tilt due to the concrete core in the reinforced end studs; (2) the walls' ductility may be improved by increasing stud thickness, but no meaningful difference in shear strength was observed when the interior stud section's type was replaced with a coupled C section; (3) compared to a wall that was individually sheathed with autoclaved lightweight concrete slabs on the external side, the shear strength could be increased by approximately 58.1% due to the addition of supplementary bolivian magnesium boards, which would be installed under the condition of an identical sheathing setup on the inner side; (4) the wall's shear capacity would be decreased due to an increase in the opening's size, and this shear capacity would also be impacted by the opening's position. Based on the experimental results and a bearing mechanism analysis of CFS shear walls with reinforced end studs, a simplified method for predicting the perforated walls' shear capacity was proposed, and the differences between the calculated and experimental results were within 8%.

Research on Concrete-Filled Rectangular Steel Tube Stiffeners and Axial Compression Bearing Capacity

Concrete-filled rectangular steel tube four sides restraint effect on the core concrete was weaker than the corner, which made the effect not significant. The paper studied a new kind of stiffening rib –PBL stiffener to strengthen restraint effect of concrete-filled rectangular steel tube , and evaluated its advantages compared with other stiffening ribs. 9 PBL stiffened concrete-filled rectangular steel tube columns under axial compressive load were tested. It also collected the test with other stiffened rids, such as straight ribs, binding bars, knee brace, steel reinforcement cage, steel bar stiffeners, saw tooth shaped stiffeners, stitching straight stiffeners and no rib concrete filled rectangular steel tube to compare. It evaluated increasing coefficient of bearing capacity by stiffening ribs. The results showed that: the PBL stiffeners and binding bar of concrete-filled rectangular steel tube bearing capacity was greater than other reinforcement measures by more than 20%; PBL stiffener could be a new prominent type of stiffener because of its excellent mechanical performance and simple construction.

Behaviour of Concrete Filled Rectangular Steel Tube Column

The Concrete Filled Steel Tube (CFST) member has many advantages compared with the conventional concrete structural member made of steel reinforcement. CFSTs are frequently used for columns, caissons and for piers, deep foundations because of their large compressive stiffness. The FEA modeling using ANSYS software is adopted to investigate the load versus lateral deflection behavior of the composite sections. The effects of steel tube thickness and strength of in-filled concrete tubes are examined. The size of the column is 140 x 160 x 1500 mm and the grades of concrete infill are M20, M30 and M40. The thickness of the tube is taken as 2 mm, 3 mm, 4 mm, 5 mm and 6 mm and, the D/t ratio varies from 26.67 to 80.00. Since past few decades, composite steel-concrete construction of column and girder is being used in the construction industry. These composite sections have the rigidity and formability of reinforced concrete with the strength and speed of construction associated with structure, thereby making them economical. The steel and the concrete element in a composite member complement each other ideally. Composite members consisting of rectangular steel tubes filled with concrete are extensively used in structures involving very large applied moments, particularly in zones of high seismic risk. Concrete Filled Tubes (CFTs) have been used as girder, beam and columns in frame structures. A steel hollow section in-filled with concrete has higher strength and larger stiffness than the conventional structural steel section and reinforced concrete. Composite column are structural members, which are mainly subjected to forces and end moments. The steel tube serves as a formwork for casting the concrete, which reduces the construction cost. No other reinforcement is needed since the tube itself act as a longitudinal and lateral reinforcements for the concrete core. The continuous provided to the concrete core by the steel tube enhances the core's strength and ductility. The concrete core delays bending and buckling of the steel tube, while steel tube prevents the concrete from spalling. Also concrete filled tube (CFT) columns are suitable for tall buildings in high seismic regions since concrete delays the local buckling of steel hollow sections and increases the ductility of the section significantly. While there is a large number of studies on the behaviour of CFT columns and beam-columns; there is relatively little research reported on the flexural behaviour of concrete-filled hollow structural steel column. The structural behavior of a CFT is governed by the member strength, reflecting the fact that the load resistance is dependent not only on the material properties but also on the geometric properties of the entire member. Tests on CFTs by Bridge showed that the concrete core only provides approximately 7.5% of the capacity in members under pure bending. Lu and Kennedy studied strength on twelve beams of concrete-filled Steel Square and Rectangular Hollow Sections for examining the effects of different depth to width ratios and different values of shear span to depth. The tests showed that the ultimate flexural strengths of the composite beams are increased by about 10% - 30% over that of bare steel sections, depending on the relative proportions of steel and concrete. Although composite columns of concrete and steel were rarely used from the end of World War II until the early 1970s (Viest et al. 1997, 1.13), research had started a long time before, at the beginning of the 20th century. Combining of these materials had a number of motivations; steel columns were often encased in concrete to protect them from fire, while concrete columns were combined with structural steel as reinforcement. The model is created for different width-to-wall thickness ratios (from 26.67 to 80.00) and different concrete cube strengths (27.8, 42, 51 MPa). It is found that in general, concrete filling of the steel tube enhances strength, ductility and energy absorption especially for thinner sections. Han proposed a mechanics model that can predict the behaviour of concrete-filled hollow structural sections. In this paper, CFTs with three different wall thicknesses (Table 1) are selected (D/t = 26.67 - 80.00). Three different grades of concrete in-fills are considered. An effort is made to find the relative contributions of the steel tube and the confined concrete core to the moment capacity and deformation of CFTs under flexure.

The Influence Factors Researching of Percentage of Load-Carrying Capacity Shared by Concrete for Large Section Concrete-Filled Rectangular Steel Tube Column

Through the analysis of the transmission mechanism—distribution beam for large section (side length>800mm) concrete-filled rectangular steel tube column by the theory of elastic foundation beam we can obtain, percentage of load-carrying capacity shared by concreteis related with vertical spring stiffness of the steel tube, rotational spring stiffness of the steel tube, the vertical spring stiffness of the core concreteand stiffness of the distribution beam. Through analysis of the relationship among percentage of load-carrying capacity shared by concreteand the impact factors, we can identify the main factors that affect the percentage of load-carrying capacity shared by concrete, to control the design of the distribution beam.

고강도콘크리트 충전 각형강관기둥의 내력평가에 관한 연구

두께가 얇은 강관을 사용한 CFT기둥은 강관의 국부좌굴에 대한 구속효과로 내력상승을 기대할 수 있으므로 폭두께비가 작은 강관 CFT기둥에 비해 경제성을 확보할 수 있다. 본 논문의 목적은 각형 CFT기둥에 대한 기존 설계식의 타당성을 입증하고, 내력 증대에 따른 강관 폭두께비의 사용성 한계를 확인하고자 하였다. 실험의 주요변수로는 강관의 폭두께비, 콘크리트 각 주의 높이 및 콘크리트 충전 유무로 하였다. 실험결과, 고강도 콘크리트를 충전한 박판의 각형강관기둥에서 충전콘크리트의 압축내력에 대한 강관의 구속효과가 크게 나타났으며, 비선형 해석에 따르면, 실험결과에 의한 내력은 전체 CFT단주 실험체에서 해석값보다 다소 크게 나타남을 알 수 있었다. The CFT columns used in thin-walled steel tubes can be more economical, because it was expected the increase of strength by restriction for the local buckling of steel tubes. The purpose of this paper is to review feasibility of existing design formula and verify the applicability limit of width-to-thickness ratio for increasing the strength of rectangular CFT columns. As the main parameters of experiments, width-to-thickness ratios of steel tube, height of rectangular concrete columns, and concrete filled or not. The strength of concrete are selected to 90MPa. From the test results, the confinement effect of steel tube on the compressive strength of infilled concrete is remarkably appeared in the thin-walled rectangular steel tube columns infilled wih high strength concrete. By the non-linear analysis, the axial strength from experiment result was given higher than analysis result for all CFT stub columns.

Numerical Simulation on Failure Process of Concrete-Filled Rectangular Steel Tube Column

Realistic Failure Process Analysis (RFPA3D) was used to simulate the concrete-filled rectangular steel tube columns which are subjected to axial loads. The ultimate bearing capacity and the load-strain figures were presented. The Numerical simulation results were verified by experimental data of the paper [5]. Meanwhile, the development process of crack in the specimen was described. The whole failure process of rectangular steel tube columns was reproduced. The failure principles of concrete-filled rectangular steel tube column were discussed deeply.