Capacity Of Steel Beams Research Articles

Numerical study on buckling capacity of steel H-beams under non-uniform temperature distribution

PurposeThe strength and stiffness of steel deteriorate rapidly at elevated temperatures. Thus, the characteristics of steel structures exposed to fire have been concerned in recent years. Most studies on the fire response of steel structures were conducted at uniformly distributed temperatures. This study aims to evaluate the buckling capacity of steel H-beams subjected to different loading conditions under non-uniform heating.Design/methodology/approachA numerical investigation was conducted employing finite element analysis software, ABAQUS. A comparison between the numerical analysis results and the experimental data from previous studies was conducted to verify the beam model. Simply supported beams were loaded with several loading conditions including one end moment, end equal moments, uniformly distributed load and concentrated load at midspan. The effects of initial imperfections were considered. The buckling capacities of steel beams under fire using the existing fire design code and the previous study were also generated and compared.FindingsThe results showed that the length-to-height ratio and loading conditions have a great effect on the buckling resistance of steel beams under fire. The capacity of steel beams under non-uniform temperature distribution using the existing fire design code and the previous study can give unconservative values or too conservative values depending on loading conditions. The maximum differences of unconservative and conservative values are −44.5 and 129.2% for beams subjected to end equal moments and one end moment, respectively.Originality/valueThis study provides the buckling characteristics of steel beams under non-uniform temperature considering the influences of initial imperfections, length-to-height ratios, and loading conditions. This study will be beneficial for structural engineers in properly evaluating structures under non-uniform heating conditions.

Study on the flexural behavior of corroded built-up cold-formed thin-walled steel beams

Eight cold-formed thin-walled steel beams were performed to investigate the effect of corrosion damage on the flexural behavior of steel beams. The relationships between failure modes or load-displacement curves and corrosion degree of steel beams were investigated. A series of parametric analysis with more than forty finite element models were also performed with different corrosion degrees, types and locations. The results showed that the reduction of cross-section thickness as well as corrosion pits on the surface would lead to a decline in the stiffness and flexural capacity of steel beams, and gradually intensified with the corrosion degree. The yield load, ultimate load and critical buckling load of the corroded specimen IV-B46-4 decreased by 22.2%, 26% and 45%, respectively. The failure modes of steel beams changed from strength failure to stability failure or brittle fracture with the corrosion degree increasing. In addition, thickness damage and corrosion pits at different locations caused the degradation of flexural capacity, the worst of which was the thickness damage of compression zone. Finally, the method for calculating flexural capacity of corroded cold-formed thin-walled steel beams was also proposed based on experimental investigation and numerical analysis results.

Effectiveness of CFRP composites on compression flange of structural I-beam

Purpose This study aims to use carbon fiber-reinforced polymer (CFRP) laminates to strengthen the compression flange of structural I-beam so as to avoid local failure of compression flange and to take a load to its full capacity. Light weight beam (LB) 100 at 5.1 kg/m and LB 115 at 8.1 kg/m are used for this purpose. The compression flange of a beam is well prepared to ensure a rust-free surface so as to achieve proper bonding between the flange and fiber sheet to avoid de-bonding at the time of testing. A flange of the beam is strengthened using CFRP sheets applied to it with the help of adhesive. The beam with CFRP is cured in air for 48 h before testing. Experiments are performed in a loading frame of 100 T capacity. Results show that the load carrying capacity of the strengthened beam increased by 25-30 per cent compared to the control beam (non-strengthened), and the local failure of the compression flange due to the applied load is totally avoided. The elastic behavior of the strengthened beam is also increased compared to the non-strengthened beam, which gives a higher yield point. Design/methodology/approach Different methods exist for strengthening various structures. Use of CFRP appears to be an excellent solution. Vast research has been conducted on the use of CFRP for strengthening and retrofitting of steel structures. The load carrying capacities of steel beams can be increased by strengthening their compression flange by using CFRP and avoiding the local failure of beams at early stages. Findings The load carrying capacity of a beam strengthened with CFRP increased by 25-30 per cent compared to the non-strengthened beam. In addition, the elastic behavior of the strengthened beam is also improved. Originality/value The compression flange of the steel beam is strengthened using different layers of CFRP strips to avoid the local failure, and its deflection is observed using linear variable deformation transducer.

21.08: Evaluation of steel buildings by means of non‐destructive testing methods

ABSTRACTNon‐destructive testing (NDT) methods have become increasingly attractive for verification of existing steel infrastructure including buildings. However destructive testing is still state of the art combined with load condition monitoring and yield limit determination of the steel elements incorporated in buildings.In many of the existing buildings, the characteristics of the steels used are often not known anymore. A statement of the residual load‐bearing capacity such as of incorporated steel beams within a building can be made if there is a means to determine it reliably. This opportunity principally exists via micromagnetic as well as ultrasonic measurements to be shown here. Magnetism even allows the yield strength of ferromagnetic steel beams to be determined. An ultimate limit state design can be proven by real material characteristics where model uncertainties have been excluded and not by selected minimum values only.If the residual load‐bearing capacity of steel beams cannot be guaranteed today, higher static loads can only be transferred by strengthening measures, such as welding or bolting additional parts. However, if the true loading as well as material condition could be determined those measures might be avoidable. A means on how to do this is by ultrasonic measurement since the propagation speed of ultrasonic waves in a steel is influenced by its strain and stress conditions. Acousto‐elastic characteristics show the correlation between the propagation of speed and the current state of stress. Those characteristics have therefore been determined on beams in lab tests and compared to strain gauge measurements, where the acoustic wave speeds have been determined first as a speed without the influence of load, before loaded conditions were considered.Material texture due to rolling processes plays a significant role in steel structures too. It has a ten times higher influence on the ultrasonic measurements than stresses due to loading have. Hence a clear separation between texture and stress related influences is therefore essential. Particularly since all those measurement results may further be exposed to significant scatter, statements regarding confidence bands of the determined stresses have to be made. This therefore includes statistical tests that will provide the respective reliability required for the concept to be competitive. The respective NDT techniques combined with suitable stochastic methods are shown below.

Evaluation of the increased load bearing capacity of steel beams strengthened with pre-stressed FRP laminates

We analyse the problem of a simply supported steel beam subjected to uniformly distributed load, strengthened with a pre-stressed fibre-reinforced polymer (FRP) laminate. We assume that the laminate is first put into tension, then bonded to the beam bottom surface, and finally fixed at both its ends by suitable connections. The beam and laminate are modelled according to classical beam theory. The adhesive is modelled as a cohesive interface with a piecewise linear constitutive law defined over three intervals (elastic response, softening response, debonding). The model is described by a set of differential equations with suitable boundary conditions. An analytical solution to the problem is determined, including explicit expressions for the internal forces and interfacial stresses. As an application, we consider the standard IPE series for the steel beam and the Sika® CarboDur® system for the adhesive and laminate. For each considered cross section, we first carry out a preliminary design of the unstrengthened steel beam. Then, we imagine to apply the FRP strengthening and calculate the loads corresponding to the elastic limit states in the steel beam, adhesive, and laminate. Lastly, we take into account the ultimate limit state corresponding to the plasticisation of the mid-span steel cross section and evaluate the increased load bearing capacity of the strengthened beam. KEYWORDS. Steel beam; FRP strengthening; Adhesive; Beam theory; Cohesive-zone model; Analytical solution; Pre-stressing; Ultimate limit state; Load bearing capacity.

On the plastic moment-shear interaction curves of steel sections under fire

Purpose Different approaches, originally developed for ambient conditions, exist in current codes and standards for incorporating the effect of moment–shear (M–V) interaction on the plastic-carrying capacity of wide-flanged (WF) steel sections. There is a lack of experimental and theoretical studies that address this issue under fire conditions. Design/methodology/approach The current paper presents a numerical study investigating the effect of fire exposure on the plastic M–V capacity curves of doubly symmetrical, WF, hot-rolled steel sections. Validated high-fidelity finite element (FE) models constructed via ANSYS are used to study the effect M–V interaction on the plastic capacity of WF sections. Also, a simplified plastic sectional analysis, intended to be used by engineering practitioners, is proposed for generating the plastic M–V interaction curves. Findings The study shows that the fire-induced non-uniform heating of the section plates affects the shape of the plastic M–V interaction capacity curves. Comparison of different methods against FE results shows that the method specified in the Eurocode is very conservative at room-temperature, but it turns out to be barely sufficiently conservative under fire conditions. Originality/value It is well noted that lack of fire tests on the M–V interaction, including the stability of the plates of steel sections under fire, make it difficult to reach a definite assessment on the effect of M–V interaction on the bearing capacity of steel beams.

Analysis on Residual Capacity of Steel after High Temperature

Steel material is very sensitive to temperature, the physical and mechanical properties at high temperature are distinct with those at room temperature. Taking steel beams as the research objects, based on EUROCODE3 for the steel properties at high temperature, this paper established numerical models and analyzed the carrying capacity of steel beams under different temperatures. According to the analysis, it is concluded that the higher the temperature, the lower the subsequent carrying capacity of the steel beam, and the formulas between them are defined by fitting the data.

The Performance of Steel Beams in the High Temperature

To study the performance of steel at elevated temperatures, the stress and deformation of steel beam were analyzed under high temperature in this paper. During the analysis, the properties of steel material must be defined firstly, which are the decisive factor affecting the carrying capacity of steel beam. The mechanical and physical properties of steel at high temperatures were accessed accordance to the provisions of the European specification in analysis. The finite element program ANSYS was used to analyze the constraints steel beam, which subjected to the uniformly line loads, then the steel beam was heated up continuously, and the mechanical properties and deformation of the steel beam was analyzed at different temperatures. The regularity of mid-span deflection changing with temperature was concluded, so as the variation of axial stress at both ends of the steel beam.

Buckling capacity of uniformly corroded steel members in terms of exposure time

Most of steel structures in various industries are subjected to corrosion due to environmental exposure. Corrosion damage is a serious problem for these structures which may reduce their carrying capacity. These aging structures require maintenance and in many cases, replacement. The goal of this research is to consider the effects of corrosion by developing a model that estimates corrosion loss as a function of exposure time. The model is formulated based on average measured thickness data collected from three severely corroded I-beams (nearly 30 years old). Since corrosion is a time-dependent parameter. Analyses were performed to calculate the lateral buckling capacity of steel beam in terms of exposure time. Minimum curves have been developed for assessment of the remaining lateral buckling capacity of ordinary I-beams based on the loss of thicknesses in terms of exposure time. These minimum curves can be used by practicing engineers for better estimates on the service life of corrosion damaged steel beams.

Effect of Partial loss of Spray-on Protection on the Load Capacity of Steel Beams during a Standard Fire

Spray-on fire protection is widely used in protecting building members, such as beams, against fire. As this protective coating may be damaged during the service life of the beams, it is essential that the effect of this damage on the fire resistance of a steel beam be understood. A numerical study has been conducted to investigate the reduction in the cross-section moment capacity of protected steel beams exposed to the ISO 834 standard fire due to partial loss of spray-on fire protection. Hot-rolled I-shape steel beams according to CAN/CSA—G40.20/ G40.21-98 specifications are used in this study. Results of the study indicate that the reduction of cross-section moment capacity due to the partial loss of protection strongly depends on the area of the protection damage. The reduction of cross-section moment capacity is also affected by several other factors, such as damage shape, damage location, damage penetration, and the weight and depth of the steel section.

Experimental and analytical investigation of steel beams rehabilitated using GFRP sheets

【Aging and deterioration of existing steel structures necessitate the development of simple and efficient rehabilitation techniques. The current study investigates a methodology to enhance the flexural capacity of steel beams by bonding Glass Fibre Reinforced Plastic (GFRP) sheets to their flanges. A heavy duty adhesive, tested in a previous study is used to bond the steel and the GFRP sheet. In addition to its ease of application, the GFRP sheet provides a protective layer that prevents future corrosion of the steel section. The study reports the results of bending tests conducted on a W-shaped steel beam before and after rehabilitation using GFRP sheets. Enhancement in the moment capacity of the beam due to bonding GFRP sheet is determined from the test results. A closed form analytical model that can predict the yield moment as well as the stresses induced in the adhesive and the GFRP sheets of rehabilitated steel beam is developed. A detailed finite element analysis for the tested specimens is also conducted in this paper. The steel web and flanges as well as the GFRP sheets are simulated using three-dimensional brick elements. The shear and peel stiffness of the adhesive are modeled as equivalent linear spring systems. The analytical and experimental results indicate that a significant enhancement in the ultimate capacity of the steel beam is achieved using the proposed technique. The finite element analysis is employed to describe in detail the profile of stresses and strains that develop in the rehabilitated steel beam.】

Interactive buckling model for the prediction of the rotation capacity of steel beams

Interactive buckling model for the prediction of the rotation capacity of steel beams

Differential Settlements and Inelastic Response in Steel Bridge Beams

A proposed method for mitigation of pavement faults at bridge abutments (the “bump at the end of the bridge”) is the use of shallow foundations. Abutments on shallow foundations are expected to settle compatibly with embankments and thus to minimize pavement faults. Allowing bridge abutments to settle may reduce faults, but it creates a demand for tolerance of different settlement in bridge superstructures. Current guidelines for tolerable differential settlement of bridges are empirical only, and the application of elastic analysis of bridge superstructures to determine tolerance of settlement has not produced satisfactory results. Inelastic analysis of steel bridge beams was applied to the computation of tolerable differential settlement. Tests of inelastic rotation capacity of steel beams were reviewed and compared with the results of inelastic analyses. A model of tolerable inelastic rotation capacity in steel beams is proposed.