Special-shaped Columns Research Articles

A Comparative Study of L-shaped Multi-storey Building using Rectangular and Special Shaped Columns

A Comparative Study of L-shaped Multi-storey Building using Rectangular and Special Shaped Columns

Residual stress model of welded steel L-shaped and T- shaped sections

Steel special-shaped columns, incorporating L, T, or cross-shaped sections, have gained increasing application in modern multi-story and high-rise buildings owing to their benefits in optimizing space utilization and enhancing structural performance. However, the welding manufacturing process induces residual stresses in these steel special-shaped columns, which can adversely affect the stability of the column components. This study conducted experimental research on the residual stress distribution in L-shaped and T-shaped steel columns using the sectioning method, which reveals the residual stress distribution patterns in the two types of steel special-shaped columns. By comparing and analyzing the experimental results with the existing residual stress model for welded sections, a residual stress distribution model for welded L-shaped and T-shaped steel columns is proposed, which fulfills stress self-balanced and is validated through numerical simulation methods. Subsequently, the proposed residual stress distribution model was applied in the numerical analysis of buckling in steel special-shaped columns. The effectiveness and necessity of considering this residual stress distribution model into the stability analysis of steel special-shaped columns are demonstrated by comparing the results with column stability test. The proposed residual stress distribution model significantly enhances the numerical accuracy for steel special-shaped columns, providing a theoretical basis for the stability analysis of such columns.

Study on optimisation of seismic performance of special-shaped column structure in residential buildings based on BIM technology

Study on optimisation of seismic performance of special-shaped column structure in residential buildings based on BIM technology

Design method of axial compression stability for cross-section corrugated plate steel special-shaped column

Obtaining a larger moment of inertia and overall stability with smaller material input, which is an effective way to improve the bearing capacity and reduce the self-weight of structural columns. This paper proposes a cross-section corrugated plate steel special-shaped column (CCSC), which is based on the optimization design idea of steel profiled-shaped column section, combined with the comprehensive consideration of the overall stability of steel structure column members, material use efficiency and building interior space utilization rate. The new CCSC is composed of three parts: core square steel pipe, corrugated plate, and flange plate. The high-out-of-plane stiffness characteristic of corrugated plate is utilized to improve the section rotation radius. The three parts above are coordinated to resist lateral load. The square steel pipe and flange plate are the main vertical bearing plates. The new special-shaped column can obtain a larger moment of inertia and overall stability with a smaller material input, thus improving the bearing capacity. Through the combination of theoretical analysis and numerical simulation, the overall stability of the axial compression of CCSC are analyzed, and the instability modes and failure modes of CCSC are revealed. The design method and suggestions for the stability of CCSC under axial compression are put forward. Then, the overall stability design and application suggestion based on conventional square steel tube is given. The results show that the stability design method of CCSC under axial compression can effectively judge the instability mode of CCSC and obtain the ultimate bearing capacity of the whole member. Compared with square steel tube columns with regularized slenderness ratio greater than 0.8 in structural design, the CCSC has obvious advantages in overall stability and steel consumption.

Analysis on the Seismic Behavior of RC Frame with Different Special-shaped Columns at the Bottom

In order to study the seismic behavior of the bottom large-bay frame with different special-shaped columns, the numerical models of the special-shaped columns frame with ordinary, dark and square columns at the bottom are established using the finite element analysis in ANSYS. The three type special-shaped Frame are performed with nonlinear time-history dynamic method under earthquakes. The dynamic characteristics and seismic response of the three type RC Frame are conducted. The weak parts and the development of the plastic hinges on the end of beams and columns are discussed. The results show that the special-shaped frame with bottom square columns can overcome the weak phenomenon at the bottom, and provide outstanding seismic performance compare with the other two frames.The seismic behavior of the special-shaped columns frame with dark columns is better than the normal special-shaped columns, however it can not effectively overcome the weak parts of the bottom floor. The results can provide a theoretical basis for the engineering application of the frame with special-shaped columns.

Experimental Study of Ultimate Bearing Capacity of Axial Compression of L-type Steel Column

The L-type steel column studied here is a special-shaped column composed of a square steel pipe and two of T-shaped steel, which are connected by weld. Because the columns have better properties than ordinary steel columns, it may be wildly used in residential steel structures. Therefore, it is quite valuable to study the bearing capacity and stability of the new steel columns. Three of specimens of the column are tested, and behaviour of deformation, distribution of displacements and stresses, and bearing capacity are presented. Effect of related factors on property of the steel column are discussed. It is concluded that the local buckling happened before finally failure of the column, which is sensitive to geometric defects.

Influence of openings on the punching shear behaviour of concrete slabs supported on special-shaped columns

Punching shear of special-shaped columns supporting reinforced concrete two-way slabs has been addressed in design codes since the late 1970s. While these provisions have existed for over 40 years their basis is unclear as previous studies related to the punching shear behaviour of irregular column geometries, such as L, T, and cruciform shapes, are limited. In this paper, the punching shear behaviour of L, T and cruciform slab-column connections, with or without slab openings near the connection, under concentric vertical loading is studied using a three-dimensional nonlinear finite element model (FEM) implemented in Abaqus/Explicit. The nonlinear FEM, based on the concrete damaged plasticity model, is used to study the influence of both the opening size and location on the punching shear behaviour of special-shaped (irregular) slab-column connections of various sizes. Based on the FEA results, the ideal location for openings around special-shaped slab-column connections (SS-SCCs) is between the column flanges. This location minimizes their negative influence on concentric punching capacity and is also beneficial architecturally. Finally, the accuracy of the ACI 318–19 punching shear provisions is evaluated. Based on the FEA results modifications to the existing provisions are necessary, particularly to account for the location of openings around special-shaped slab-column connections.

Seismic behavior of wide-limb special-shaped columns composed of concrete-filled steel tubes

To study the seismic performance of wide-limb L-shaped columns composed of concrete-filled steel tubes (W-LCFST columns), five specimens were fabricated and tested under quasi-static cyclic loading. The W-LCFST column was composed of a center mono column, two side mono columns, and vertical connecting steel plates. The mono column was made of steel tube and an infill of concrete. The cavity between the vertical connecting plates was also filled with concrete. The test focused on the parameters including vertical connecting plates with headed studs or perfobond leiste (PBL) stiffeners inside and the sectional dimension of the side mono column. The ultimate failure mode, force-displacement curves, ductility, strength degradation, stiffness degradation, energy dissipation capacity, and strain distribution under different influence factors were discussed. The results showed that all specimens exhibited buckling and fracture failure at the bottom of the W-LCFST column. Increasing the width of the side mono column can increase the initial stiffness. Compared with the headed studs, the PBL stiffeners had a better effect on preventing large-area buckling of the vertical connecting plates and improving the peak bearing capacity and stiffness. Based on the limit state theory, the calculation method of the sectional flexural capacity of the W-LCFST column was established. Additionally, the accuracy of predicting the compression and bending capacity of the W-LCFST column under positive and negative loads by Standard CECS159–2004 was analyzed, and the recommended correction value was also given.

Mechanical properties and automatic design method for rural residences with hinged frames and cold-formed thin-walled stiffened walls

At present, the overall construction quality of rural residences is still relatively poor, and the seismic performance of their structural systems is insufficient. In this study, quasi-static tests were carried out on three cold-formed thin-walled stiffened steel plate wall (CFSW) specimens infilled in a single-span two-story 1/2 scale hinged special-shaped column frame. The seismic performance of each specimen was evaluated by comparing the bearing capacity, ductility, stiffness degradation, energy dissipation capacity, and strain. The results show that the filling of concrete and gypsum in the column helps improve the bearing capacity of the structure but has no notable effect on the stiffness. The brittle failure phenomenon in the filled concrete specimens is obvious, and those specimens either without filler or whose columns are filled with gypsum show better ductility and energy dissipation capacities. A finite element (FE) model was established and validated, and the influence of parameters such as the connection method between the wall and frame, the shear-span ratio of the wall, the thickness of the stiffened wall, and the number of hat-section cold-formed steel (HCFS) stiffeners upon the structural system was analyzed. In combination with the test and the FE analysis results, the calculation method for horizontal bearing capacity of CFSW restrained by HCFS stiffeners and engineering design suggestions were put forward. In addition, an automatic program for the forward generation of the CFSW was designed, and the application of the system in practical engineering was verified using Midas software.

Investigation on axial resistance of steel reinforced concrete cross-shaped columns exposed to high temperature

Steel reinforced concrete (SRC) special-shaped columns have the advantages of high spatial utilization, flexible layout and good economic benefits, which are used in high-rise buildings. However, this composite structure has the disadvantages of high steel content and large fire area, which makes it easier to suffer damage in fire, and even cause the collapse of buildings. This paper presents mechanical properties of SRC cross-shaped columns exposed to high temperature. Seven SRC cross-shaped column specimens were analyzed. Temperature field distribution, failure mode, deformation and fire resistance of specimens were obtained under different axial compression ratios (0.4, 0.6) and eccentricity (0, 40, 60, 80 mm). The results showed that: (1) All specimens were in a condition of compression failure and section steel had partial bending failure with the concrete falling off. (2) The larger eccentricity and axial compression ratio were, the earlier cracks appeared, and the more cracks appeared, the more serious concrete shedding of specimen were. Moreover, the cracks were concentrated especially on the side of loading point (i.e., two sides close to the point where the applied load is located), and the cracks are adjacent to the support of specimen, which appear in the whole length of specimen. (3) Axial compression ratio had a significant influence on fire resistance of SRC cross-shaped columns, and influence of eccentricity on fire resistance was generally little compared with axial compression ratio. The fire resistance declined by 43.48–69.14% as axial compression ratio increased from 0.4 to 0.6. Fire resistance declined by 5.45–45.31% as eccentricity increased from 0 to 80 mm, and it was significantly reduced by 28.12–45.31% when axial compression ratio was 0.6. Finally, fire resistance calculation method of SRC cross-shaped column was obtained, which provided reference for fire resistance design of SRC structure.

Experimental Study and Finite Element Calculation of the Behavior of Special T-Shaped Composite Columns with Concrete-Filled Square Steel Tubulars under Eccentric Loads

Special T-shaped composite columns with concrete-filled square steel tubulars have good restraint on internal concrete, are convenient to process, have a high bearing capacity and good mechanical properties, and can increase the aesthetics of the building and the utilization rate of indoor space. Theoretical analysis, experimental study, and numerical simulation of the eccentric compression performance of the special-shaped column are carried out. Taking the specimen length, eccentric distance, and eccentric direction as test parameters, nine specimens with different slenderness ratios were designed to carry out eccentric compression tests. The eccentric compression performance was numerically simulated and analyzed by the general finite element software ABAQUS. The results show that the short column mainly suffers section strength failure, while the middle and long columns mainly suffer bending instability failure without torsional deformation. The degree of influence of the test parameters decreases in turn according to the eccentric distance, eccentric direction, and length of the specimen; there is no weld cracking phenomenon, and the square steel pipes can work together. The finite element calculation results are in good agreement with the experimental and theoretical values.

Experimental study on seismic behaviors of prefabricated embedded concrete-filled steel tube special-shaped column exterior frame

The new type of prefabricated embedded concrete-filled steel tube (CFST) special-shaped column structure delivers green and environmentally-friendly strengths and high space. In this study, a full-scale frame test piece with one frame façade, two stories and two spans are designed and fabricated for purposes of exploring the seismic performance and node connection safety of filled built-in steel tube concrete-filled special-shaped column, and low cyclic load testing is implemented. The bearing characteristics, deformation capacity, energy-dissipating capacity, ductility and stiffness degradation of the test piece are analyzed. The results showed that the failure mechanism is typical beam hinge mechanism. The fabricated beam-column and column-column connection nodes in this paper are safe and reliable. The hysteretic curve of fabricated embedded CFST special-shaped column is full, the ductility and energy dissipation capacity of fabricated embedded CFST special-shaped column are better than such indexes of ordinary reinforced concrete special-shaped column. The inter-story displacement angle is 1/32 when the test piece is damaged, being significantly higher than the limit value of elastic-plastic inter-story displacement angle of 1/50 under strong earthquake. The precast embedded steel-reinforced concrete special-shaped column structure is only required to be connected with steel ribs to significantly improve the construction speed and quality, delivering great economy.

Study on the Mechanical Behavior of Composite Special-Shaped Columns under Compression-Bending Without End Rotation Constraints

Study on the Mechanical Behavior of Composite Special-Shaped Columns under Compression-Bending Without End Rotation Constraints

Stress Analysis of Concrete Materials Based on Finite Element Analysis

China’s construction industry standard “technical code for concrete special-shaped column structure” has been implemented since 2006, and the use of special-shaped walls in the actual construction of buildings is more common. The cross-section wall can effectively reduce the protruding angle of the building, thereby expanding the effective building area of the room, reducing the proportion of the building components themselves, and making the structure layout of the building more beautiful. In order to analyze the dynamic characteristics of eccentrically compressed prestressed concrete beams, the finite element simulation of different reinforcement parameters, longitudinal reinforcement diameter, and reinforcement ratio was constructed. Through comparison, the load flexibility curve change law of concrete stress cloud and reinforcement stress cloud under various working conditions and the influence change law of test mold are studied, and the influence change law of dynamic characteristics under the above four conditions and unidirectional bias pressure is clarified.

Investigation of the punching shear behaviors of reinforced concrete slab–steel reinforced concrete L-shaped column connections

To study the punching behaviors of reinforced concrete (RC) slab–steel reinforced concrete (SRC) L-shaped column connections, four slab–column connection tests were designed and completed, and a new punching shear resistance measure proposed. The test variables were column section shape, slab thickness and column cap. The test results show that the failure mode of L-shaped column was mainly two-way shear. Meanwhile, increasing slab thickness and installing column cap can effectively improve the ultimate bearing capacity of the slab–column connection. The punching angles formed by the punching cone and horizontal direction at the final failure of the connection were between 23.5° and 49.5°. In addition, a numerical simulation analysis was carried out using ABAQUS software, and the effects of various parameters on the performance of slab–column connections were studied. It was found that the change of column section shape will lead to more complex shear stress distribution and stress concentration phenomenon. However, the punching capacity of the special-shaped column was higher than that of the equivalent square column with the same section area. As a new punching shear resistance measure, inverted T-shaped steel can effectively improve the ultimate bearing capacity of the connections. In addition, when the ratio of slab thickness to web width of inverted T-shaped steel was less than 0.75, the failure mode of the connection changed from brittle punching failure to flexural failure.

Yield-Line solutions for flexural failure of flat slabs on columns of different shapes

There are two failure modes of slab–column connections, flexural and punching shear. However, when the tensile reinforcement ratio in the slab is low, the failure mode of the slab is difficult to distinguish, because the slab may fail in flexural before the punching shear failure occurs. To study the flexural failure of flat slabs on special-shaped columns (cruciform, L-shaped, T-shaped), the ultimate bearing capacity of slab–special-shaped column connections considering corner lever effect under vertical concentrated load was deduced and predicted by using yield-line theory. The correctness of the theoretical solution was verified by comparison with the experimental results. In addition, the effects of column section shape, column limb length to thickness ratio (c2/c1) and reinforcement ratio on flexural capacity were studied. The results show that the column section shape and the c2/c1 have little influence on the flexural capacity of the slab, but the reinforcement ratio will change the failure mode of the slab-column connections. When the reinforcement ratio was less than 0.8%, the failure mode of slab–special-shaped column connections was main flexural failure..

The analysis on the seismic behavior of L-shaped prefabricated special-shaped CFST with rectangular multi-cell columns

In this paper, a prefabricated special-shaped concrete-filled steel tube (CFST) with rectangular multi-cell column has been subjected to low cyclic reversed loading experiment and finite element (FE) parameter analysis. A total of three full-scale L-shaped specimens were tested under constant axial compression load and transverse cyclic load. The main variable in the experiment was the direction of loading. The results show that the failure mode of the special-shaped column specimen is compression-bending failure. Within 300 mm of the bottom of the column, the steel tube bulges or even cracks, the concrete powder fells and fails to exit the work. Among them, the L-135° specimen has the highest peak bearing capacity while the L-0° specimen has better ductility. The main variables of FE parametric analysis are axial compression ratio, concrete grade, steel tube thickness and loading angle. The analysis results show that the lower axial compression ratio and higher concrete grade are conducive to the improvement of bearing capacity. As the thickness of the steel tube increases, the peak bearing capacity and displacement of the specimen increases but the ductility decreases. The special-shaped column model has better seismic behavior when loaded along various loading angles. The peak bearing capacity of the special-shaped column specimen loaded at 135° is consistent with the test results and compared with the L-45° specimen, its bearing capacity is increased by up to 62.04%, which has better comprehensive seismic behavior.

Experimental and numerical study of fire performance of L-shaped concrete-filled steel tubular columns under eccentric compression

Six special-shaped columns composed of concrete-filled steel tubes (CFST) were designed and tested based on the ISO-834 temperature curve to access their fire performance under eccentric loads. Key test variables include the types of stiffener, load eccentricity, as well as load angle, and the failure modes, temperature distribution, and deformation of specimens were analyzed. The test outcomes indicate that the L-shaped CFST columns’ fire resistance declines as the load eccentricity rises, but its decrease amplitude narrows under a relatively high eccentricity. Besides, the impact exerted by the load angle on the columns’ fire resistance is also significant. A Finite Element Analysis (FEA) method was carried out afterward and compared with the test outcomes. Moreover, an extensive parametric analysis containing 2008 FEA models was developed to study the impact of major parameters on the L-shaped CFST columns’ fire resistance, namely load ratio (n), slenderness ratio (λ), column limb width (B), column limb depth-to-width ratio (D/B), load eccentricity ratio (e/r0), steel ratio (αs), steel strength (fy), concrete strength (fck), and load angle (θ). The analysis results imply that the parameter of load ratio (n) remarkably affects the columns’ fire resistance, while the other parameters exert a certain impact on the fire resistance when n < 0.5. Given the test and analysis, a simplified calculation approach for the fire resistance of L-shaped CFST columns is designed.

Investigation on buckling behavior of T-shaped box-T section columns under axial load

Special-shaped columns (i.e., L-shaped, T-shaped, and cross-shaped) present the main advantages of avoiding column protrusion and enlarging the indoor space, and they also have large stiffness and strength in the direction of their longer sections. However, there is a lack of systematic research of the buckling performance of T-shaped column. In this paper, T-shaped box-T section columns, composed of one cold-formed box section and several T-sections, were concerned. The elastic buckling analysis of T-shaped box-T section columns was firstly conducted, and it is recommended to set stiffeners to restrain the distortional buckling of the first order buckling modes of the columns. Based on the elastic buckling analysis, 10 T-shaped box-T section columns with one stiffener were tested under axial load. The measured material properties, geometries, initial imperfections, failure modes, ultimate capacities, and loading histories of the specimens were reported and employed to validate the finite element (FE) models. The plane section assumption was confirmed for T-shaped box-T section columns based on the records of the strain gauges and the FE results. FE analysis was carried out to investigate the effects of initial geometric imperfections, residual stress, and stiffeners on the buckling performances of T-shaped box-T section columns. Totally 880 FE results of the pin-ended columns were employed to evaluate the design curves of the current specifications GB 50017-2017, EN 1993-1-1, and ANSI/AISC 360-16, and new design curves were also proposed.

Seismic Performances of SRC Special-Shaped Columns and RC Beam Joints Under Double-Direction Low-Cyclic Reversed Loading

Steel-reinforced concrete (SRC) special-shaped column and beam frame structure is a special structural form that can meet the requirements of high bearing capacity and satisfy the esthetic requirement of buildings. In this study, a new joint design approach is adopted to focus on the seismic behavior of SRC special-shaped column and reinforced concrete (RC) beam joints under low-cyclic double-directional reactions through pseudo-static tests with a controlled stirrup distance. The joints of SRC specimens were compared with those of RC specimens by controlling the area of steel and reinforcement, and hysteresis cycle skeleton curves and load and strain hysteresis cycles were analyzed. The specimen with profiled steel was found to have better energy dissipation capacity. The energy dissipation capacity and stiffness degradation of the nodes were analyzed. The test results showed that the energy dissipation capacity of the SRC joints was better than that of the conventional concrete column joints, and the stiffness degradation of RC joints was more significant than that of SRC joints.