Column Section Research Articles

Eccentric compressive performance and design of asymmetric steel columns with complex edges

Box-type houses often use asymmetric cold-formed thin-walled steel columns with complex edges to meet structural requirements. However, there is a need to clarify the mechanical properties of eccentric loading in this section of the steel column. This study conducted eccentric compression tests on 24 asymmetric cold-formed thin-walled steel columns with complex edges, clarifying the specimens' ultimate load-bearing capacity and buckling mode. The results showed that the resistance to pressure provided by the corner was higher than that provided by the two crimped edges. Subsequently, a finite element model was established, and its accuracy was verified by comparing it with experimental results. Finally, based on the formula for calculating the nominal axial strength in AISI, the direct strength method formula for the stable bearing capacity of asymmetric cold-formed thin-walled steel columns with complex edges under in-plane eccentric compression was proposed. This method takes into account the local-global interactive buckling and distortional-global interactive buckling. The comparison between the theoretical calculation results and numerical simulation results demonstrated that the design method proposed in this study is effective and conservative. It can provide a reference for future engineering applications.

Thermally coupled distillation columns without vapor transfer – Current state and further needs

Reducing the energy requirements is one essential pillar in the effort to reduce the carbon footprint of the energy intensive chemical industry. Thermal coupling of distillation columns and the equipment-integrated implementation in dividing wall columns can be considered a mature and established technology to reduce the energy demand of distillation sequences. Despite the widespread investigations and applications, the vaporous transfer stream between thermally linked columns or vapor split in the dividing wall column is associated with certain limitations. Some of these can effectively be overcome by adding an additional column section with reboiler or condenser to the thermally linked column, converting the bidirectional transfer of liquid and vapor to a unidirectional liquid transfer, which mandates additional investment, but provides an additional degree of freedom and retains the energy saving potential of the thermally coupled sequence. Although these so-called Liquid-Only-Transfer (LOT) sequences have been introduced almost 25 years ago, the process concept is receiving an increasing interest in recent years, with specific focus on conceptual design and control studies. The current review provides a methodological overview on synthesis, design and control studies for LOT-sequences, considering zeotropic and azeotropic distillation processes. It analyzes the advantages and challenges of this interesting process concept and highlights research areas and questions that still require additional attention.

Design of cold-formed high strength steel irregular octagonal hollow section columns

This paper presents experimental numerical investigations on the structural behaviour of cold-formed high strength steel irregular octagonal hollow section (OctHS) columns with both non-slender and slender cross-sections. An experimental programme, including material tests, measurements of initial global geometric imperfection, and pin-ended column tests, was first conducted. The key findings from the experimental programme are presented and discussed. Following the validation against the experimental results, the proposed finite element modelling methodology was established to replicate the test observations, and then was adopted to generate a boarder range of numerical results through parametric studies. The collected experimental and numerical data were used to evaluate the applicability of current structural steel design methods on the column buckling strength for irregular OctHS columns. Assessment results demonstrate that the design method adopted in Chinese code can provide accurate prediction, whilst modified design method adopted in Eurocode 3, considering the effect of steel grade on the column strength, has been proposed and shown to greatly enhance the prediction accuracy with improved consistency. The corresponding assessments on the design approaches adopted in American and Australian codes were also discussed.

Numerical and Theoretical Studies on Axial Compression Performance of Modular Steel Tubular Columns Grouped with Shear-Key Connectors

Shear-keyed inter-modular connections (IMCs) are integral components of high-rise modular steel structures (MSSs), providing robust interconnectivity to support grouped tubular columns across modules, thereby introducing column discontinuities and distinctive structural behavior. This study conducted a comprehensive numerical assessment and theoretical analysis of the axial compression behavior of grouped tubular columns based on a validated finite element model (FEM), which captured the member-to-structural level behavior of steel hollow section (SHS) columns and accommodated geometric imperfections. An FEM was initially developed and validated using 28 axial compression tests documented in the literature, comprising 15 tests on cold-formed and 13 on hot-rolled steel hollow section (SHS) columns. The primary parameters explored in tests included material properties (stainless/carbon), processing methods (cold-formed/hot-rolled), cross-section sizes (D/B), cross-sectional or member slenderness ratios (D/tc, B/tc, or Lc/r), and the number of columns (1, 7, and 11). A comprehensive parametric numerical study involving 103 grouped tubular column FEMs then investigated the influence of initial imperfection, shear-key height (Lt), thickness (tt), steel tube length (D), width (B), thickness (tc), and height (Lc) alongside the effects of space between tube and key, and the gap between tubes. The results indicated that the load-shortening behavior of the grouped columns consists of linear elastic, inelastic, and recession stages. The failure modes observed primarily displayed an S-shaped pair of inward and outward local buckling on the outer sides and double S-shaped local buckling on the interior sides. The buckling arose near the shear key or at 1/4 or 1/2 of the column height. None of the considered models experienced global buckling. Increasing tt, Lt, tc, D, or B enhances strength and stiffness, while Lc or Lc/r linearly affects stiffness and ductility. The columns’ nominal axial strength was reduced because of the shear keys, which decreased compression yielding and caused localized elastic buckling. Subsequently, the theoretical analysis revealed that the design codes do not capture this behavior, and thus, their capacity estimate yields inaccurate findings. This discrepancy renders existing code prediction equations, including those from Indian (IS800), New Zealand (NZS400), European (EC3:1-1), Canadian (CSA S16), American (AISC360-16), and Chinese (GB50017) standards, as well as the model proposed by Li et al., non-conservative. To assure conservative results, the paper recommended modification of existing standards and proposed prediction equations based on a fourth-order differential equation that describes the actual behavior of modular steel columns grouped with shear keys. The proposed design approach accurately predicted the axial compression capacity of modular steel-grouped columns, proving conservative yet effective. This provides valuable data that could transform design and construction techniques for MSSs, extending to various column and IMC forms through adaptable design parameters. This enhancement in structural performance and safety significantly contributes to the advancement of modular construction practices.

OPTIMIZATION OF STEEL PROFILE DIMENSIONS AND BOLT CONNECTIONS IN INTAKE STRUCTURES FOR ENHANCED STRUCTURAL INTEGRITY

Intake structures are facilities for clean water supply situated along riverbanks. These structures are reinforced concrete with pile foundations, and the intake structure comprises a profiled steel frame serving as the upper column-beam framework. The implementation of steel structures demands a high level of precision, particularly in designing connections between sectional steel beams and columns. This study, therefore, aims to determine the optimal dimensions for steel profiles by referring to the design of bolt connections as specified in SNI 1729-2020, particularly for steel beam columns subjected to pump loads and load combinations. The analysis concludes that all three material types meet the safety criteria, with a structural ratio value of ≤ 1 and structural deflection within the allowable limits. Additionally, after assessing the steel column and beam sections' capacity to bear pump loads, it was determined that the optimal bolt connection involved 8 bolts of 24 mm diameter. The ideal supplementary steel plate connection required a plate thickness of 13 mm.

Experimental study on compressive capacity of stainless steel S35657 columns with welded box section and I-section under axial compression

Compared with conventional stainless steel, a new type of stainless steel, S35657, has broad application prospects owing to its advantages of high strength and low production costs. In this study, the compressive capacity of stainless steel S35657 columns was investigated. A total of 13 specimens were designed and tested, including 4 box section specimens and 9 I-section specimens (4 buckling around the major axis and 5 buckling around the minor axis). Complementary chemical composition analyses, material tensile tests, residual stress measurements, and initial geometric imperfection measurements were also conducted. The mechanical properties of the material, as well as its residual stress distribution model, failure mode, load-displacement curve, and compressive capacity, were reported and analyzed. For box section columns, when the slenderness ratio increased from 29 to 55.2, the compressive capacity of the column decreased by 27.6 %. The accuracy and safety of design methods specified in European standard EN 1993–1–4, American specification ASCE-8–02, and Chinese specification CECS 410 were assessed based on the test results. The result shows that EN 1993–1–4 is overly conservative in its compressive capacity calculations, whereas ASCE-8–02 overestimates the compressive capacity with a higher level of scatter exhibited. The methods of CECS 410 for predicting the compressive capacity of welded stainless steel S35657 columns are more accurate compared with the methods of EN 1993–1–4 and ASCE-8–02.

Global stability capacity of partially encased composite columns with cruciform-shaped section under axial compression

This paper undertakes a test investigation and finite element (FE) analysis of the stability behavior of partially encased composite (PEC) columns with cruciform-shaped sections. Two PEC column specimens with the same geometric size were tested under axial compression loading, and the difference between the specimens is that the main steel components (MSCs) made of solid-web steel and castellated steel, respectively. The test results show that the two columns exhibited similar failure modes: concrete crushing and global flexural instability. Furthermore,the capacities of both columns were found to be smaller than the corresponding theoretical axial capacities of the composite column section. The test and FE results show that the bearing capacity of the PEC columns with solid-web MSCs is higher than that of the PEC columns with castellated MSCs. The size of the web openings exerts a considerable detrimental impact on the compressive capacity of the PEC column, while the shape and spacing of the openings have little influence on the capacity. In addition, design equations were proposed to predict the stability capacity of the cruciform-shaped section PEC column with both solid-web MSCs and castellated MSCs, in the equations, the castellated MSCs were simplified as the lattice columns with batten plates.

Novel application of X-ray characterisation techniques in froth flotation for the study of bubble clusters

Froth flotation is commonly used to upgrade minerals. Bubbles are used to carry valuable particles out of a slurry into the froth phase to a launder. The pursue of energy saving in grinding has led to the emergence of coarse flotation technologies. Evidence points to the crucial role of bubble clusters to lift coarse particles effectively. However, little is known about their formation and behaviour except from what can be gathered from the photographic method. This study demonstrates the capability of X-ray computed tomography (X-ray CT) to study the morphology of bubble clusters. The method is able to distinguish individual particles and how they are positioned on bubbles. In addition, X-ray particle image velocimetry (X-ray PIV) was initially employed on a 2-phase system (air and water) to determine its suitability for tracking bubbles and eventually bubble clusters. X-ray PIV could effectively be used to track the mean velocity of bubbles in all sections of a foam column. It was possible to estimate the composition (i.e., liquid holdup) within the column. It is believed that both methodologies will provide insights into the morphology of bubble clusters as well as their behaviour in the pulp, in the froth, and at the pulp/froth interface.

PERANCANGAN APLIKASI PERHITUNGAN KUAT NOMINAL KOLOM BETON BERTULANG BERBASIS APLIKASI ANDROID

Nowadays, the use of applications which is to analyze or to design in civil engineering are necessary. Besides being able to solve the analysis and design problem, the use of applications is an effective for computational time problems compared to manual calculations. Column is one of the most crucial elements in a building construction where the role of the column is to support and distribute the loads on the building structure. In general, in designing a column, column interaction diagram with a certain cross section is made and compare the capacity of the column sections (Pn and Mn) from the column interaction diagram with the required strength values (Pu and Mu). Android is an operating system on smartphones and is popular nowadays. The aim of this research is to develop an Android-based application using Android Studio with Java programming language to create a column interaction diagram of several types of columns, i.e. square column with 4 (four) side reinforcement, square column with reinforcement on 2 (two) sides, and circular columns. The results obtained from the developed application are compared with manual calculations (reference). The difference of result obtained is less than 1% which means that there is no significant comparison between the designed application and manual calculations (reference). Therefore, the developed application can be practically used as an alternative in designing columns.

Pin-ended stainless steel equal-leg angle section members under compression and major-axis bending: Experimentation, FE modelling and design

The behaviour and design of cylindrically-pinned stainless steel equal-leg angle section members under compression and compression combined with strong-axis bending are investigated herein. An experimental investigation, including material testing, initial geometric imperfection measurements and physical tests on hot-rolled stainless steel equal-leg angle section members is first presented. Numerical models are developed by means of shell finite element modelling formulated within ABAQUS and validated against experimental data. A numerical parametric study is then presented considering both hot-rolled and cold-formed stainless steel equal-leg angle section columns alongside beam–columns with a wide range of cross-section and member geometries. Finally, new design proposals for cylindrically-pinned stainless steel equal-leg angle section members under compression and compression plus major-axis bending are developed and verified against the results of physical experiments and numerical simulations. The proposed design rules are shown to offer substantially more accurate and consistent resistance predictions compared to existing codified design rules. The reliability of the new design provisions, with a recommended partial safety factor γM1=1.1, is verified following the EN 1990 procedure.

Design cost minimization of a reinforced concrete column section using overnew swarm-based optimization algorithms

It is very tiresome for a practiser to detect the best feasible sizing design of structural members including reinforced concrete columns that is a highly nonlinear and complicated structural engineering optimization problem. This is due to such a design is practically conducted via conventional trial-and-error computing methods in which resistance to external loads, cost efficiency, and aesthetic factors, etc. have to be considered. This study focuses on minimizing the design cost of primarily proposed reinforced concrete column design problem via three overnew swarm-based optimizers such as Coati Optimization Algorithm, Fox Optimizer and Pelican Optimization Algorithm (POA) that are firstly utilized for this purpose. In this regard, the type of steel rebar distribution, the characteristic strength of the concrete, the height and width of the column section, and the number and diameter of the rebars are treated as discrete design variables of the newly proposed complex reinforced concrete column design cost optimization problem. In solution, the design requirements specified in practice code provisions should also be met. Here, Turkish Building Earthquake Code 2018 specifications are considered as practice structural design constraints. Consequently, the algorithmic performances of three overnew swarm-based metaheuristic optimization algorithms are compared and evaluated in detail. Amongst them, the POA shows most fruitful algorithmic design solution performance.

Vibration Control of Wind Turbines through a Novel Reduced Column Section Approach: Numerical Application to the Onshore Wind Turbine in Sassoferrato, Italy

Vibration Control of Wind Turbines through a Novel Reduced Column Section Approach: Numerical Application to the Onshore Wind Turbine in Sassoferrato, Italy

Study on explosion impact pressure and damage distribution law of rock powder segmented charge

The charge structure is the critical to determine the bench blasting effect of rock slope. Through theoretical calculation, model testing, and numerical simulation, a formula for calculating the stress attenuation of the axial hole wall of the segmented charging structure is proposed. Moreover, the influence mechanism of the explosive ratio and interval packing length on the internal damage distribution of the concrete of concrete specimens under a segmented charging structure of the cuttings is described. Finally, the research results are applied to the mining of a rock slope in southwest China. The research results reveal the following: 1) The pressure at the charge section is highest when the rock debris interval charge is used, and with the increase in the charge section distance, the pressure markedly decreases—sharply first before stabilizing. In the upper filling interval charge section, the minimum pressure corresponded to approximately the midway point of the filling section, and the stress distribution on the axial hole wall is concave: high at both ends and low in the middle. 2) The ratio of the upper and lower sections of the explosive column determines the form of blasting damage, and the range of blasting damage increases first and then decreases with the increase in the length of the rock debris in the interval section. 3) The field test shows that compared with the traditional blasting charge structure, the optimized segmented charge structure can reduce the blasting block rate by 13.1%. 4) Using the optimized charge structure, the explosive unit consumption can be decreased from 0.27 kg/m3 to 0.24 kg/m3, which improves the economic benefits of mining and construction of related mines.

Experimental and numerical investigations of the impact resistance of socket and pocket connections for precast bridge columns

This study investigates the dynamic performance of precast bridge columns under pendulum impact testing, including socket connection, pocket connection, and cast-in-place (CIP) columns. The study focuses on comparing the impact behavior of CIP and precast columns regarding failure modes, impact force-time, and deflection-time histories. Furthermore, the mechanism by which the socket or pocket connection configurations affect the impact resistance of the precast columns is discussed. The results indicate that the development of cracks in the precast and CIP columns is consistent under the same impact conditions. Notably, the shear resistance mechanisms and failure modes vary significantly at the bottom of the two columns. For the precast specimens, substantial local damage occurs at the connections with consecutive impacts. Specifically, punching shear failure is observed at the pocket connections, whereas the connection sections of the socket columns may pull out from the grooves. Local damage to the column-footing connections reduces the global stiffness of precast columns, leading to higher deformation, greater residual displacements, and lower impact forces than those of CIP columns. A simplified finite element modelling method is proposed to simulate the characteristics of precast column connections, and its accuracy is verified using the test results. The numerical findings show that increasing the friction coefficient at the connection interface promotes the formation of diagonal compression struts within the connection, effectively resisting impact loads and preventing excessive shear stress produced by sliding at the interface. Furthermore, amplifying the minimum embedment depth of the socket-connected precast column to 1.0 D is recommended to ensure safe performance under impact loading.

The Seismic Performance of Self-Centering Ribbed Floor Flat-Beam Frame Joints

To achieve rapid post-earthquake repair of self-centering ribbed floor flat-beam frame structures, a ductile hybrid joint consisting of dog-bone-shaped, weakened, energy-dissipating steel bars connected to the upper and lower column sections through high-strength threads is proposed based on the damage control design concept. By moving the ductile energy-dissipating zone out to the locally weakened section of the energy-dissipating steel bars and the locally unbonded prestressed steel bars in the core area, the residual deformation was limited and the seismic performance improved. Based on the working principle of hybrid joints, low cycle loading tests were conducted on two joint specimens to analyze the influence of lateral prestress on the seismic performance of the hybrid joints. Numerical modeling methods were used to compare the position of the energy-dissipating steel bars in the composite layer and the friction performance of the joints. The research results indicated that the hybrid joint had stable load bearing, deformation, and energy dissipation capabilities, with damage being primarily concentrated in the energy-dissipating steel bars. Even at an inter-story displacement angle of 5.5%, the upper and lower column segments remained elastic. After unloading, the connection seam at the joint was closed, and the self-centering performance was good. When the inter-story displacement angle reached 5.5%, the lateral prestress increased from 150 kN to 250 kN, the ultimate bearing capacity of the joint increased by 16.3%, and the cumulative energy consumption increased by 30.0%. The influence of the friction coefficient of the joint surface on the structural performance was set at a threshold of 0.7. When it was less than the threshold, the ultimate bearing capacity and initial stiffness of the joint increased with the increase in the friction coefficient. After reaching the threshold, the increase in the ultimate bearing capacity of the joint slowed down, and the rate of stiffness degradation gradually accelerated. This joint showed excellent seismic performance and can thus achieve post-earthquake repair of structures.

Development of component stiffness equations for thread-fixed one-side bolt connections to an enclosed rectangular hollow section column under tension

Development of component stiffness equations for thread-fixed one-side bolt connections to an enclosed rectangular hollow section column under tension

Analysis of Pedestrian Steel Bridge Subjected the Seismic Load And Wind Load Using Damper at Different Span

A Pedestrian steel truss bridge model was created by using structural analysis by software. With the similar loading and support condition the 3D model was analyzed for different span like 20m, 25m,30m the basic emphasis has been given decreases the response of structure member by providing damper at different span I section Girder, steel plate thickness. Steel girder and M40 grade of concrete is used for column section in Etab software. The dynamic loading caused by moving pedestrian and earthquake and wind load, Excessive vibration in footbridges usually occurs when they are subjected to rhythmic dynamic loads caused by human activities like walking and running. In order to mitigate the human induced vibrations in footbridges, an increase in the damping ratio is often suggested as the most economical approach. Tuned mass dampers have been widely used for this purpose, however, their installation and maintenance costs are high. This has encouraged researchers to examine the efficiency of the other types of dampers. Viscoelastic dampers have been successfully employed for vibration mitigation of structures against wind and earthquake loads.

Energy-based equations for distortional buckling of Zed and rack section columns

This paper develops energy-based equations for symmetric distortional buckling in columns with Zed and rack sections. Using the Rayleigh quotient method, two sets of displacement functions are assumed for each cross-section type and closed-form expressions depending on geometrical parameters of the cross-sections are obtained for critical length and buckling stress. Additionally the proposed deformed shapes allow a closed-form derivation of the warping profile of the cross-sections. A parametric study is conducted to compare the derived expressions to GBTUL numerical results for a wide range of cross-section geometries. The average results σcr,proposed/σcr,GBTUL of the study are 0.995 ± 0.005 for Zed sections and 0.988 ± 0.025 for rack sections. Therefore the proposed equations may be applied in practical design of axially compressed thin-walled cold-formed members as an alternative to computational tools.

Seismic Design Procedure for Low-Rise Cold-Formed Steel–Special Bolted Moment Frames

In 2007, the American Iron and Steel Institute (AISI) established a standard for cold-formed steel–special bolted moment frames (CFS-SBMFs). This structural system is designed to resist seismic forces. The CFS-SBMF system employs double-channel beams and square hollow structural section (HSS) columns that are bolted together to create a sturdy and robust structural frame. However, the CFS-SBMF system is only suitable for constructing one-storey buildings, and ASCE 7 prohibits its use in buildings with a height of over one storey. This study was conducted to expand the use of CFS-SBMFs to the construction of multi-storey low-rise buildings. Firstly, a new moment connection detail is proposed, and a design procedure is proposed to ensure that bolted connections, instead of beams or columns, have the ductility to withstand seismic forces. Secondly, the proposed design procedure for bolted connections was verified through full-scale cyclic testing. Finally, a comprehensive evaluation was undertaken to evaluate the proposed structural system’s performance under seismic excitation. The evaluation included nonlinear dynamic analysis and incremental dynamic analysis (IDA) according to FEMA P695, which provided a detailed understanding of the seismic design factors (SDFs) in multi-storey low-rise CFS-SBMF buildings.

Bearing Behavior of Engineered Cementitious Composite and Ultra-High-Performance Concrete Filled-In Double Steel Tubular Composite Columns Subjected to Eccentrical Load

To study the eccentric compression mechanical properties of ECC and UHPC filled-in double steel tubular (EUFDST) composite columns, 35 full-scale EUCFDST composite column specimens were designed by ABAQUS software with the slenderness ratio (λ), UHPC cylinder compressive strength (fcu), inner and outer steel tubular strength (fy1, fy2), inner and outer steel tubular thickness (t1, t2), inner and outer steel tubular diameter ratio (Ω), eccentricity (e), and fiber content (γ) as the main parameters. By comparison with the simulation of the existing test, the correctness of the finite element modeling is verified. The parameter analysis of 35 full-scale EUFDST composite columns was carried out to obtain the eccentric load-mid-span deflection curve of the specimens. The failure mechanism, ductility coefficient, and stiffness degradation of the composite columns under different parameters were analyzed, and the section of the composite column was verified to satisfy the plane section assumption. The variation trend of maximum load-bearing capacity and the ductility of composite columns under different parameter conditions was obtained. By introducing the eccentricity correction coefficient and slenderness ratio correction coefficient, the calculation equation of the eccentric maximum load-bearing capacity of EUCFDST composite columns is statistically regressed, which provides a basis for the practical use of these columns.