Steel H-section Columns Research Articles

Buckling and Critical Temperature Prediction Formulas of Restrained H-Section Steel Columns in Fire

Buckling and Critical Temperature Prediction Formulas of Restrained H-Section Steel Columns in Fire

Selection of 110 kV Prefabricated Steel Substations Considering Seismic Vulnerability in China

Prefabricated modular substations are expected to become the mainstream construction type for substations in China. However, there is a lack of scientific basis for structural selection and seismic performance evaluation. Taking a 110 kV substation as an example, this study compares the construction cost of cast-in situ reinforced concrete (RC) substations and prefabricated steel (PS) ones. Two types of PS structures are considered: one with H-section steel columns and the other with box-section steel columns. A seismic vulnerability analysis is performed to compare the probability distribution of various damage states of substation building structures under different seismic damage levels. Results indicate that the construction cost of PS structures is approximately 27.9% higher than that of cast-in situ concrete. When using H-section steel columns, there is a significant difference in the flexural stiffness in two horizontal directions, resulting in reduced seismic performance in the weak-axis direction. The construction cost of using box-section steel columns is slightly higher than that of the H-section steel case, but its seismic performance is significantly improved. Although the probability of slight and moderate damage states for the box-section steel column scheme is generally higher than that of the cast-in situ RC scheme, the probability of collapse is reduced. Thus, box-section steel columns are recommended for prefabricated modular substation building structures.

Axial compressive behavior of corroded H-shaped steel columns

The unpredictability of corrosion in steel structures, especially in H-section columns, is a topic that has received limited research attention. Using Monte Carlo simulation (MCS) and finite element analysis (FEA), this study investigates the effect of random pitting corrosion on H-section steel columns' ultimate bearing capacity under axial compression. In this study, MCS was employed to address the random distribution of pitting corrosion. The reliability of MCS and FEA was validated through existing literature on compression tests of H-shaped steel columns. To comprehensively assess the detrimental effects of pitting corrosion, a total of 3650 models of H-shaped columns, each exhibiting different pitting corrosion characteristics, were subjected to analysis. These models incorporated three corrosion parameters (volume loss rate, size, and depth) and two geometric parameters (slenderness and section size). A nonlinear buckling analysis was carried out to investigate the ultimate bearing capacity of the columns. The findings indicate that a volume loss rate of 20% can cause a decrease in the column's ultimate bearing capacity by approximately 50%. Furthermore, the study reveals that at equal volume loss rates, corrosion depth and slenderness significantly influence the reduction factor, while corrosion size and section size exert a minimal impact. As a result, this paper introduces a probabilistic assessment method for estimating the reduction factor in ultimate bearing capacity for H-section steel columns. Notably, with every 10% increase in the volume loss rate, the mean reduction factor in the ultimate bearing capacity decreases by approximately 0.12.

Local–overall buckling behavior of corroded intermediate compression-bending H-section steel columns

The primary aim of this paper is to assess the impact of corrosion damage on intermediate H-section steel columns subjected to combined compression and bending about the strong axis. The study conducted a comprehensive investigation into the corrosion-induced transition in the buckling behavior of steel columns through experimental and numerical analyses. Six H-section Q355 steel intermediate columns were designed, with five undergoing an artificial spray-accelerated corrosion process. The three-dimensional scanning technology was employed to quantify the general corrosion and corrosion pits. Eccentric compression tests were carried out on intermediate H-section steel columns to investigate the effect of the different corrosion levels on the failure mode and load-displacement curves, as well as to determine local buckling load based on the load-strain curves. The test results showed that the corrosion characteristic parameters of each cross-section of the steel column exhibited irregularity and variation in all locations, reflecting the heterogeneity of corrosion. The density of corrosion pits exhibited a decreasing trend with increased corrosion duration. Corrosion remarkably reduced both the ultimate carrying capacity and local buckling capacity, with the most severely corroded specimen exhibiting an average cross-sectional area loss rate of 37 %, resulting in a 43 % and 51 % reduction in ultimate load and buckling load compared to the uncorroded specimen. Furthermore, the corrosion features substantially influenced the failure mode, resulting in a transition from overall buckling to local buckling or local-global interaction buckling. A numerical methodology was developed to incorporate the actual surface morphology of corrosion, and the reliability of the modeling method was validated through comparison with experimental results, further revealing the failure mechanism of corroded intermediate H-section steel columns under compression and bending about the strong axis.

Experimental investigation on H-section members with large width-thickness ratios under traverse impact

Experimental work of 12 axially pre-loaded H section columns with large width-thickness ratios under transverse impact load were carried out. The boundary conditions of the specimens were fixed at one end and sliding at another end and the impact position was 1/3 from the bottom of the column. In the test, the main parameters affecting the impact resistance of the members including web thickness, flange thickness, impact energy and axial pressure were studied. Then a finite element analysis FEA model was established to predict the impact behavior of H section members, in which the strain rate effects was considered. Test data of impact force and total deflection from the author were used to verify the accuracy of the FEA model and general good results were achieved. Results demonstrate that increasing the axial load exerts a negative effect on the impulse from impact load and extension of the impact duration. Under certain impact energy, the impact force in plateau stage of impact process was mainly affected by the flange thickness and the peak stage impact forces was mainly affected by the web thickness. Web was main component on the impact resistance of H-section steel column as over 70% of the impact energy was absorbed. Results provide new information on the impact response of H section columns with large width-thickness ratios and the effects of controlling parameters to form an extensive database.

Life-cycle assessment and prediction on ultimate capacity of corroded Q690 steel columns with H-section under bi-directional cyclic loading

The structures or structural members made of high-strength steel may have time-varying mechanical properties in whole life-cycle due to the ageing effects. In particular, the corroded steel structures in high-seismicity regions could have unexpected failure modes when subjected multi-directional excitations. Therefore, in this study, the mechanical properties of Q690 steel H-section columns during the life-cycle under bi-directional cyclic loads are investigated. Firstly, a refined finite element (FE) model is built, which takes the time-varying of corrosion characteristics into consideration. Then, the degradations of mechanical property and failure mechanisms of steel columns with different design parameters at whole life-cycle are analysed by the FE models. Finally, a quantitative calculation method of ultimate resistance and damage index of steel columns considering ageing effects is proposed. The findings demonstrate that several factors affect the ultimate strength of steel columns during the life-cycle stage, with the axial compression ratio and flange width-thickness ratio having the greatest impacts on the ultimate capacity. The ageing effect decreases the plastic flow capacity of steel columns, increases the stress concentration, and induces the failure mode transition from plastic flow to buckling failure. The ageing effect may be accurately estimated by the suggested calculation method for the ultimate capacity and damage index of steel columns at the life-cycle stage. The findings of this study highlight the significance of taking into account the ageing effects of steel columns in the seismic design.

Simplified constitutive model of austenitic stainless steel at high temperatures

Based on completed experimental data and constitutive models, we proposed the simplified constitutive model of austenitic S30408 (AISI304) stainless steel at high temperatures. According to continuous trial calculation and analysis fined that the simplified constitutive model can be divided into two segments. In the first segment, the Ramberg-Osgood model (R–O model) was adopted, while the second segment was represented using a straight-line expression. Next, simplified constitutive model was obtained by nonlinear fitting using Matlab. Based on this, FEA models were created, incorporating the simplified constitutive model, refined constitutive model, and constitutive model fitted based on experimental data from other literature. Using the sequential therm-mechanical coupling analysis method, the FEA of the fire-resistant performance of three specimens including simply supported stainless steel rectangular beam, restrained rectangular stainless steel column and restrained stainless steel H-section columns, was carried out and compared. The conclusions drawn were as follows: For members at low temperatures, when the strain value is small, the deformation and force calculated using simplified constitutive model is not much different from that using the constitutive model fitted based on experimental results. For members at high temperatures, when the strain value is large, the deformation and force calculated using simplified constitutive model deviates from that using the constitutive model fitted based on experimental results, but deviation is within an acceptable range. Therefore, the simplified constitutive model demonstrates both feasibility and accuracy, making it suitable for calculating the fire resistance of specimens.

Buckling and critical temperatures of restrained H-section steel columns in fire considering dynamic effect

In this paper, a parametric analysis on the buckling and critical temperatures of restrained H-section steel columns in fire, considering the dynamic effect, is presented. The developed finite element model of steel columns was verified by test results. Then, the buckling and critical temperatures of steel columns, obtained by static and explicit dynamic analyses, were compared. Moreover, the effects of rotational and axial restraint stiffness ratios, as well as load ratios, were studied. It was found that as the rotational restraint stiffness ratio increased, the buckling and critical temperatures both rose, and the rotational restraint stiffness ratio affected the critical temperature more than the buckling temperature. Besides, when the axial restraint stiffness ratio and load ratio rose, the buckling and critical temperatures dropped significantly. Finally, by combining the findings of the research and existing calculation formulas in literatures, new simplified formulas for buckling and critical temperatures were proposed, respectively. The prediction results of the proposed calculation formulas agreed well with the parametric analysis results. The proposed formulas were further verified by test data. According to the comparative results, the proposed formulas could well predict the buckling and critical temperatures of steel columns in fire.

Experimental study on a steel self-centering rocking column with SMA slip friction dampers

This paper investigates the cyclic behavior of a steel self-centering (SC) rocking column. The steel SC rocking column consists of an H-section steel column and a pair of shape memory alloy (SMA) slip-friction dampers (SMASFDs). As the kernel part, the SMASFDs enhance SC capability of the rocking column and dissipate the input energy. The working principle of the rocking column is first described, along with the analytical equations that govern the behavior under loading cycles, which are validated by experimental data. The component tests were conducted on the NiTi SMA bar and the slip-friction mechanism, separately. And then, the cyclic loading tests were conducted on a 1:2-scaled rocking column specimen. The considered axial force ratio included 0, 0.1 and 0.2. During the entire experimental procedure, the SMA bars were neither repaired nor replaced. It is found that up to a drift ratio of 7 %, the rocking column maintained stable flag-shaped hysteresis, which is characterized by excellent SC capability and satisfactory damping capacity. The testing results also indicated that increasing axial force ratio effectively increased the strength and stiffness of the rocking column, whereas it reduced the post-decompression stiffness due to the P-Δ effect. Finally, the numerical models were established in ABAQUS and OpenSees, both of which were verified by the experimental data, and a parametric study was carried out.

Buckling and post-buckling analysis of restrained non-uniform columns in fire

This paper investigates the buckling and post-buckling behavior of restrained non-uniform columns in fire where the temperature surrounding the column varies along the longitudinal direction. The material properties of the column are considered to be temperature-dependent (TD). First, according to the convective–radiative condition on the surfaces of the column, a dimensionally reduced nonlinear heat transfer equation is proposed and is solved by the differential quadrature (DQ) method. Then, considering the geometric imperfection, the nonlinear governing equation is derived based on the von-Kármán theory when the column is subjected to an axial compression load at the column end. An improved DQ method is applied to the buckling and post-buckling analysis of the non-uniform column under the fire. Considering the yield strength of material at elevated temperature, the ultimate load of the column is obtained. A tapered H-section steel column surrounded by localized fire is taken as an example. The present results are verified by comparing with those in the literature and those obtained from the finite element (FE) method. The parameter analysis reveals the temperature distribution, the buckling and post-buckling behavior of the tapered column in the localized fire.

Damage evaluation of axial-loaded H-section steel columns during and after impact loading

The H-section steel members are usually employed as the key load-bearing elements in industrial buildings, which are vulnerable to the vehicle or crane-load collision. This paper presents the performance of H-section steel columns exposed to impact loading, including the course of impact and post-impact stages. A total of 12H-section steel columns were fabricated and tested to obtain failure patterns, impact forces and mid-height deflections as well as post-impact residual load carrying capacities. Additionally, finite element (FE) models were established and were calibrated with testing data. The calibrated models were then employed to conduct further numerical simulation and parametric study to reveal damage mechanism. Results demonstrated that the axial loading reduced the impact resistance significantly. The global deflection and the local indentation in the impact zone were found to result in reduction of the load-bearing capacity. Moreover, based on the post-impact deformations, an empirical equation was proposed to estimate the residual load carrying capacity of H-section steel columns, which can be used for rapid evaluation of damage after impact.

Influence of rotational restraints on response of H-section steel columns under fire

In this paper, a parametric investigation on the influence of rotational restraints on the response of H-section steel columns under fire was conducted through a validated numerical model. Nine rotational restraint stiffness ratios (βR) were considered, from 0.0001 to 10.0. Other considered parameters include the slenderness ratio, axial restraint stiffness ratio, and load ratio. The analysis results showed that there are three failure scenarios of the columns with βR increases from 0.0001 to 10.0. Specifically, in failure scenario I, the failures are all dynamic failures; in failure scenario II, the failures change from dynamic failure to quasi-static failure; and in failure scenario III, the failures are all quasi-static failures. The occurrence of the failure scenarios is related to the slenderness ratio, axial restraint stiffness ratio, and load ratio. The dynamic effects of the columns in failure scenario I decrease first and then increase with the increase of βR. The dynamic effects of the columns in failure scenario II decrease with the increase of βR until the failure type of the columns change to quasi-static failure. For the above failure scenarios, there is a critical value of βR (namely βR,cr), after reaching which the influence of βR on the response of the columns becomes negligible. The value of βR,cr is less than 2.0 in general, and depends on the slenderness ratio, axial restraint stiffness ratio, and load ratio. The failure scenarios and βR,cr values of the H-section columns are the same with box-section columns for most of the cases.

Buckling behaviour of Q460GJ welded H-section columns subjected to minor axis under axial compression

To study the overall buckling behavior of Q460GJ steel columns around the minor principal axis under axial compression, experimental investigations were carried out on 8 pin-ended H-section steel columns. The main parameter of the specimens is slenderness λ, ranging from 36 to 86. Besides, material properties, initial geometrical imperfections and residual stresses of the specimens were measured. During the loading process, horizontal displacements at the mid-span of the specimens and the strain development were monitored. All the specimens failed with overall buckling and the bearing capacity was obtained. Moreover, a finite element model that considered initial geometric imperfections and residual stress was established and verified, and numerical studies were followed. The buckling factor φ - nondimensional slenderness λn relationship is compared with that in current design specifications. The curve “c” in the Chinese standard GB50017-2017 and curve “c” in Eurocode 3 are recommended to evaluate the overall buckling resistance of 460GJ welded H-section columns under axial compression conservatively.

Seismic Performance of Welded Stainless Steel H-Section Columns under Cyclic Horizontal Loading

This study investigated the seismic performance of welded stainless steel H-section columns. Ten columns were tested under cyclic horizontal load; their seismic performance was analyzed according to their hysteresis curves, degree of plasticity, and energy dissipation capacity. The test results obtained were used to validate the developed finite-element (FE) model, which was later utilized in parametric studies. In the tests, it was found that the final failure form of all test columns was local buckling. Slenderness of the component plates and axial load ratio were the governing factors which affected the development of plasticity within the cross sections, the energy dissipation density, and the ductility coefficient. The cross-section classification in the relevant European code is discussed in this paper. Based on numerical data, a ductility-based design approach is proposed, which can provide a reference for the seismic design of welded stainless steel H-section columns.

Damage evaluation of H-section steel columns under impulsive blast loads via gene expression programming

Increasing terrorist attacks towards ordinary or strategic buildings and soft targets represent one of the major impetus to improve existing methods of design for blast-resistant structures. When a building undergoes an extreme dynamic event such as blast or impact, local damage of its key structural components (i.e., the columns) may lead to severe failure and even collapse of the entire building. Consequently, the availability of simplified, time efficient and reliable methods of analysis can be relevant for design. In this paper, H-section steel columns subjected to blast loads are numerically investigated, so as to derive practical formulations for damage evaluation assessment. The strategy is based on parametric Finite Element (FE) models (with up to 5600 configurations), validated towards experiments and, used as an extensive data bank, for further elaboration via Gene Expression Programming. Analytical formulations are in fact proposed for calculating some relevant parameters of design, such as (a) the initial and (b) the residual axial capacity of the examined columns. The collected results show that the proposed formulations can offer a good level of accuracy and high calculation efficiency for blast loaded H-section steel columns. In addition, an expression is proposed to relate the damage index (based residual axial capacity) to the conventional displacement/rotational index. Sensitivity analyses and some calculation examples are finally presented, to further investigate the potential of the approach for design purposes.

Experimental investigation on the fire resistance of restrained stainless steel H-section columns

To investigate the failure mechanism of restrained stainless steel H-section columns under axial compression during fire exposure, the mechanical properties of S30408 (EN1.4301) austenitic stainless steel at normal and elevated temperatures were obtained by the tensile tests, and 7 restrained stainless steel H-section columns under axial compression were tested in fire. By high temperature steady-state test, the elastic modulus, ultimate strength, yield strength and stress-strain curve under different temperatures were obtained. Comparing on the mechanical properties of stainless steel at normal and elevated temperatures, the mechanical property reduction factors under different temperatures were proposed. The influences of axial/rotational restraint stiffness ratio, load ratio and slenderness ratio on the fire resistance were analysed. The failure modes, temperature curves, axial displacement curves, mid-span lateral displacement curves, buckling temperatures and critical temperatures of the specimens were presented. The result shows that axial/rotational restraint stiffness ratio, load ratio and slenderness ratio all have great influences on the fire resistance of restrained stainless steel H-section columns under axial compression.

Flexural buckling behaviour of 690 MPa high strength steel H-section columns

The paper describes a numerical study on columns fabricated from high strength steel (HSS) plates with nominal yield stress of 690 MPa. The study comprised 4 benchmark models validated by testing data and 144H-section parametric study models. The benchmark models were firstly created and validated against testing data for the accuracy. A full-scale parametric study was carried out to investigate effect of flange width/thickness ratio (α), web height/thickness ratio (β), geometrical imperfection (D) and residual stress (R) on overall buckling behaviour of the columns. The purpose of the study was to understand the relationship between section geometry, imperfections and column strength fabricated by welding from 690 MPa high strength steel plates. The H-section HSS columns were studied in this paper for the buckling behaviour along the minor axis in which direction those columns have smaller stiffnesses.It is shown that all those factors can be classified into three groups according to their impact on column strength (expressed with strength reduction factor χ): favourable factor (α), adverse factor (β and D) and uncertain factor (R). α and χ are positively correlated: χ increases at different rates as α increases. It is an effective way to increase α to improve column strength when α is a small value. χ decreases with the increase of β at very low rate and the effect of β on χ is not very obvious. D could produce more pronounced deterioration effect on ultimate strength of columns with higher α. The effect of residual stress (R) on H-section column strength is related with α: for the columns with higher α value, higher residual stress could produce more serious strength reduction effect. Residual stress does not always have negative effect on χ. It could produce beneficial effect on the ultimate strength of high strength steel H-section columns as long as α is reasonably small.The paper also shows a comparison of analysis results with existing standards including Eurocode 3 and GB50017-2017. For Eurocode 3, curve a0 can accurately predict χ with λ¯ when D = 0.03%. When D = 0.20%, curve b gives the best-fit prediction.

Degradation Model and Evaluation Criteria for the Seismic Behavior of Corrosion H-section Steel Column

The cross section would be reduced and the material properties of the steel structure would be deteriorated under the corrosion environment, which will have different effects on the earthquake resistant behavior. This paper takes corroded H-steel column as the research object. Firstly, the influence on the failure mode, bearing capacity, hysteretic properties, ductility and hysteretic energy is analyzed from specific factors which consist of different width-to-thickness on flange, different height-to-thickness on web and different axial compression ratios by FEA. The results show that, the area of the hysteresis loop diminishes gradually, the bearing capacity decrease clearly, the accumulative energy dissipation and ductility coefficient decreased continuously, and the degradation laws of buckling load, peak load, hysteretic energy and ductility coefficient of corroded H-steel columns are thereby established. When the thickness of flange decreased by 30%, the peak load decreased by 32% and hysteretic energy decreased by 77%. However, the peak load decreased by 14% and hysteretic energy decreased by 40% when the thickness of web decreased by 30%. When the axial compression ratio is 0.6, and the mass loss ratio of corroded H-steel columns reached 22%, the peak load and hysteretic energy decreased by 28% and 51% respectively. Secondly, the hysteretic model of load-displacement of corroded H-steel members under cyclic loading is proposed based on the simulation results and the degradation model of characteristic point of skeleton line was given. Finally, the evaluation criteria are proposed based on the seismic performance objectives, and the classification of failure types as well as the overall performance evaluation of corroded steel members are carried out.

Experimental and Numerical Investigation of Steel Beam-to-CFST Column Frame-Thin Steel Plate Shear Walls with Cross Stiffness

Steel plate shear wall (SPSW) systems have been used increasingly in medium- and high-rise buildings in recent decades. Two major issues in the slender-web SPSW are the buckling of H-section steel column base and significant pinching in hysteretic curves. As a solution, SPSW using concrete-filled steel tubular (CFST) column and cross stiffeners was proposed in this paper. Cyclic tests of two specimens of 1/3 scaled steel beam-to-CFST column frame-thin SPSW with cross stiffeners or without stiffeners were conducted. Based on the verified finite element method, parametric investigations considering the effect of the flexural rigidity of CFST column, width-to-height aspect ratio, height-to-thickness ratio of infill steel plate and relative rigidity of cross stiffener were carried out. Findings show that SPSW using CFST column exhibited favorable ductility behavior with no sudden loss of lateral bearing capacity. Adding stiffeners to SPSWs relieves the pinching effect of hysteretic curves and reduces the maximum lateral displacement substantially. With stiffeners, the average yield load and the peak load of SPSWs were approximately 15% and 9% higher than that of the unstiffened specimens. Moreover, a flexural rigidity of CFST column of at least 2.5 and a stiffener rigidity of 30–50 were recommended to provide an economical and approving lateral bearing capacity.

Fire resistance design method for restrained stainless steel H-section columns under axial compression

Considering the material and geometric nonlinearity of restrained axially-compressed stainless steel H-section columns, this paper investigates their behavioural responses during fire exposure via the coupled thermo-mechanical analysis method and finite element models that were established by using ABAQUS. 7 restrained stainless steel H-section columns under axial compression were tested in the ISO-834 standard fire. A numerical simulation analysis was carried out, and the validity and feasibility of the finite element analysis model was proven by the test results. On this basis, a parameter-influencing analysis was performed to determine the main influencing factors of the fire resistance of a restrained axially-compressed stainless steel H-section column. The result shows that the load ratio n, slenderness ratio λ, axial restraint stiffness ratio βl and rotational restraint stiffness ratio βr are the key factors. Based on existing experimental studies and numerical simulations, an equivalent method of rotational restraint at the ends of a stainless steel column in fire is tentatively presented. A simplified formula, based on the effective length coefficient μθ of restrained axially-compressed stainless steel H-section columns, for calculating the critical temperature is proposed.