Steel I-beams Research Articles

Performance Analysis of Castellated Steel I-Beam using FRP Stiffeners

Abstract: Castellated beams are now widely used for a variety of structural applications. Castellated beams are the ones which have perforations in their web part. However, these perforations increase stress concentration around the openings, and also get subjected to web post-buckling. To reduce these post-buckling failures and increase the load-carrying capacity, the castellated steel I-beams are provided with different types of stiffeners at various locations. In this paper, the behaviour of a hexagonal castellated steel I-beam (ISMB) under point loading is investigated using carbon fibre polymer (CFRP) strips as stiffeners. Two different types of CFRP strip stiffeners are provided in the transverse direction and around the openings of the castellated beam. The finite element analysis of these stiffeners has been carried out by using ABAQUS software. The results show that the use of CFRP stiffeners for castellated beams enhances load-carrying capacity up to 20% and reduces the deflection by 12% as compared to the control castellated beam. The use of transverse CFRP stiffener reduces the web buckling failure and increases the load carrying capacity effectively as compared to the stiffeners used along the openings. As a result, it is preferable to use transverse stiffeners instead of the stiffeners used along of the openings. Keywords: Abacus software, Castellated beam, CFRP, Openings, Transverse stiffeners

Impact Behavior of Composite Reinforced Concrete Beams with Pultruded I-GFRP Beam.

The present study experimentally and numerically investigated the impact behavior of composite reinforced concrete (RC) beams with the pultruded I-GFRP and I-steel beams. Eight specimens of two groups were cast in different configurations. The first group consisted of four specimens and was tested under static load to provide reference results for the second group. The four specimens in the second group were tested first under impact loading and then static loading to determine the residual static strengths of the impacted specimens. The test variables considered the type of encased I-section (steel and GFRP), presence of shear connectors, and drop height during impact tests. A mass of 42.5 kg was dropped on the top surface at the mid-span of the tested beams from five different heights: 250, 500, 1000, 1500, and 1900 mm. Moreover, nonlinear Finite Element (FE) models were developed and validated using the experimental data. Static loading was defined as a displacement-controlled loading and the impact loading was modeled as dynamic explicit analysis with different drop velocities. The validated models were used to conduct a parametric study to investigate the effect of the concrete compressive strength on the performance of the composite beams under static and impact loadings. For the composite specimen with steel I-sction, the maximum impact force was 190% greater than the reference specimen NR-I at a drop height of 1900 mm, whereas the maximum impact forces for the specimens composite specimens with GFRP I-sction without and with shear connectors were 19% and 77%, respectively, more significant than the reference beam at the same drop height. The high stiffness for the steel I-beams relative to the GFRP I-beam was the reason for this difference in behavior. The concrete compressive strength was more effective in improving the impact behavior of the composite specimens relative to those without GFRP I-beams.

Steel I-beam simulation for different stiffener patterns

Steel I-beam simulation for different stiffener patterns

NONLINEAR FINITE ELEMENT ANALYSIS OF MECHANICALLY ANCHORED REINFORCED STEEL I BEAMS

Aim: Steel structural elements can lose their strength in vehicle crashes, fire, fatigue, decay, humidity, etc. Consequently, their load-bearing capacities reduce considerably. A widely used strengthening method for steel beams is fiber-reinforced polymer strips or plates. One of the most important problems for this practice is sudden end-strip debonding due to the high normal and shear stress concentration. In this study, the structural behavior of deformed steel I-beams strengthened by carbon composites under bending was studied numerically. Using a commercial nonlinear finite element program (ABAQUS), a finite element model verified with the formerly executed experimental study was presented. To examine the effect of Mechanical Anchorage on large samples, a parametric study was carried out with the verified finite element model. In the parametric study, mainly three parameters were considered. Flange slenderness ratio (Bf/tf), web slenderness ratio (H/tw), and length to cross-sectional depth ratio (L/bf). Results derived from the nonlinear analysis revealed that the employment of the bolt anchorage increases the load capacity of the deformed elements and sustains the elements to resist more loads. However, the behavior and strengthening capacity of this practice is accordingly dependent on the flange slenderness ratio and web slenderness ratio of the proposed beam. Obtained results also indicate that the efficiency of mechanical anchorage in short-span beams is higher compared to the long-span beams.

Steel I-beam simulation for different stiffener patterns

Steel I-beam simulation for different stiffener patterns

The influence of mounted assembly process on the stress-strain state of the lattice dome frame

The aim of the research - analysis of the stress-strain state of spherical lattice dome structure during mounted assembly process. The dome has a metal frame consisting of six repeating sectors with triangular grid cells. The mesh dome has five tiers in height. The study is devoted to establishing the dependence of the stress-strain state of the fully assembled frame of the lattice dome on the method mounted assembly. Methods. A computer model of the frame of the lattice dome made of steel I-beams in its design configuration has been developed. On its basis, assembly models of an incomplete frame for different stages of installation are created. For all models of the lattice dome frame, computer calculations were performed for the effect of the load from the own weight of its bars. As a result of calculations deformations, internal forces and stresses in the frame bars were determined at all stages of assembly, which were compared with those for the design configuration scheme. Results. Diagrams of deformations, moments and stresses in the bars of the dome frame at all stages of mounted installation are obtained. Comparative diagrams of installation and design stresses in the bars of the lattice dome are presented. The assessment of the installation stress state of the frame is given, and their inevitability and influence on the initial stress state of the lattice dome are noted.

Lateral–torsional buckling behaviour of welded Q690 steel I-beams with double lateral restraints along the length

This paper presents experimental and numerical investigations of lateral–torsional buckling behaviour of welded Q690 steel I-beams with double lateral restraints along the length. In the experimental programme, 11 steel beams with different beam depths, load ratios and span ratios were tested under two concentrated point loads. Lateral–torsional buckling resistance of beams was obtained through experimental tests. Comparisons between experimental bending moments and calculated values suggest that existing design methods in different national codes cannot accurately predict the critical moments of beams in the selected range of slenderness. Besides, numerical models were also established and verified against test data. Parametric studies showed that the buckling factor of beams increased with increasing ratio of the middle span over the clear span and with increasing ratio of concentrated point loads on beams. It was also concluded from numerical results that the Chinese code and the American code are not safe when used for calculating the buckling factor of beams with intermediate slenderness, whereas Eurocode 3 is rather conservative. Comparisons between buckling factors of continuous and single beams also indicate that the buckling factor of beams can be substantially underestimated if only the beam segment in the middle span is considered by neglecting the restraints provided by adjacent beams. Finally, a modification factor was proposed for welded Q690 steel beams with unequal bending moments at the two ends, which can predict the buckling factor of beams with fairly good accuracy.

Mass, Direct Cost and Energy Life-Cycle Cost Optimization of Steel-Concrete Composite Floor Structures

This paper presents a study showing the optimization of the mass, direct (self-manufacturing) costs, and energy life-cycle costs of composite floor structures composed of a reinforced concrete slab and steel I-beams. In a multi-parametric study, mixed-integer non-linear programming (MINLP) optimizations are carried out for different design parameters, such as different loads, spans, concrete and steel classes, welded, IPE and HEA steel profiles, and different energy consumption cases. Different objective functions of the composite structure are defined for optimization, such as mass, direct cost, and energy life-cycle cost objective functions. Moreover, three different energy consumption cases are proposed for the energy life-cycle cost objective: an energy efficient case (50 kWh/m2), an energy inefficient case (100 kWh/m2), and a high energy consumption case (200 kWh/m2). In each optimization, the objective function of the structure is subjected to the design, load, resistance, and deflection (in)equality constraints defined in accordance with Eurocode specifications. The optimal results calculated with different criteria are then compared to obtain competitive composite designs. Comparative diagrams have been developed to determine the competitive spans of composite floor structures with three different types of steel I beam: those made of welded sections and those made of IPE or HEA sections, respectively. The paper also answers the question of how different objective functions affect the amount of the calculated costs and masses of the structures. It has been established that the higher (more wasteful) the energy consumption case is, the lower the obtained masses of the composite floor structures are. In cases with higher energy consumption, the energy life-cycle costs are several times higher than the costs determined in direct cost optimization. At the end of the paper, a recommended optimal design for a composite floor system is presented that has been developed on the multi-parametric energy life-cycle cost optimization, where the energy efficient case is considered. An engineer or researcher can use the recommendations presented here to find a suitable optimal composite structure design for a desired span and uniformly imposed load.

Анализ методов вибродиагностики металлических конструкций

Due to the constant machine complexity increasing as well as the requirements imposed on them, the issue of ensuring their reliability is becoming more and more urgent. The main part of any machine is supporting metal structure, which state determines the state of the machine as a whole. This determines the need to diagnose structures in order to prevent failures. At present, the methods of vibration diagnostics are being widely developed, as applied to objects of various industries. Scientists’ research is aimed at studying various types of defects, vibration parameters, methods for detecting defects and assessing the residual life. The article considers the main current trends in the development of vibration diagnostics methods. The sensitivity of the dynamic structure characteristics to the presence of a defect in the form of a crack has been investigated. A finite element analysis of a steel I-beam was performed for various cases of its fixation and crack location. The dependence of the natural frequencies and amplitude-frequency characteristics of the beam on the crack size has been analyzed. It is found that the presence of a defect has the greatest effect on the frequency response of the beam.

Design equations for buckling strength of steel I-beam under non-uniform heating condition

This paper presents a numerical study on lateral-torsional buckling strength of the simply supported beam under fire subjected to general loading conditions. The influence of length to height ratio and the non-uniform temperature distribution in the steel beam was considered to evaluate the buckling strength of the beam. The numerical simulations were carried out by utilizing a commercial finite element program, ABAQUS. The buckling strengths of steel beams using buckling design curves at elevated temperature of Eurocode 3 Part 1–2 were also generated and compared. The results showed that the buckling resistance of the steel beam under fire using Eurocode 3 can give unconservative values for beams subjected to positive moment and give very conservative values for beams subjected to negative moment. The new correction factor was proposed to take into account the effect of length to height ratio and non-uniform heating condition on buckling strength. The proposal equation was suggested to determine the lateral-torsional buckling capacity of the steel beam under fire and general loading conditions.

Load Rating of Al Halfaia Bridge over the Nile

This paper summarizes the results of applying load rating process that has been applied to Halfaya Bridge over the main Nile in Khartoum, Sudan. Load rating procedures have reviewed as per Manual of Bridge Evaluationof AASHTO Standards. Three levels of H/Y live loadings have been considered. AASHTO HL-93 is used for design load rating. For Legal load rating the Sudanese legal loads - as per Sudan National Highway Authorityare considered. Permit load rating process has been made using actual special heavy truck used in Sudan during the last 20 years .The rating process has been made on the assumption that the capacity of the main structural element of the bridge, which is Girder type II Composite Steel Ibeams, had been decreased with different percentage from 10%up to 20%, due to different factors. Suitable software, CSi Bridge, has been used for calculations and the results are presented. The paper predicted the load rating factors for the composite steel I-beams of the bridge- moment and shear wise- for considerable capacity loss in future .The paper also checked the deflection of the composite I-Girder .Results showed that deflection is the governing factor when stiffness is lost by 8%, but still the momentcapacity is the governing factor –design load rating –when the loss is 5%of the capacity. Suggested several recommendations to save such vital structure are given

Stability behavior of Steel–concrete Composite Beams subjected to hogging moment

The behavior of Steel–concrete Composite Beams (SCCB) under the action of hogging moment is not yet fully understood. In this condition, these structural elements may be subjected to local buckling or Lateral Distortional Buckling (LDB). LDB is a mode of stability in which the web must distort in order for the compression flange to displace and twist during buckling. The classic LDB standard procedures start from the determination of the elastic critical moment and subsequently use empirical curves to determine the LDB strength. However, investigations show that there is no consensus in determining the LDB elastic critical moment. In addition, studies indicate that the use of the same empirical curves obtained for the analysis of steel I-beams leads to the conservative results of the LDB strength in SCCB. In this context, this paper investigates the behavior of SCCB under the action of hogging moment through the development of buckling and post-buckling numerical analyses with the ABAQUS software. In the parametric study, the effects of the I-section, the unrestrained length, the reinforcing ratio, the concrete slab height and the slab topology were investigated. The investigations showed divergences between the elastic critical moment and ultimate moment when compared with classic procedures. In addition, the influence of the analyzed parameters is presented. These results can provide a reference for future research and specification reviews.

Experimental and Analytical Study of Horizontally Curved I-Girders Subjected to Equal End Moments

If bending and torsional moments are applied to an I-shaped beam member, the coupling of those two forces could reduce the bending moment capacity of that member. Therefore, the interaction between bending and torsional moments is an important issue for horizontally curved members that are always simultaneously subjected to bending and torsion. In this study, the behavior of the horizontally curved steel I-beam was investigated through numerical analysis. The ultimate state of sharply curved members that showed large displacement was defined in accordance with the stiffness reduction ratio to consist of strength curves. Based on the analysis results, interaction curves were established, and a strength equation was derived. The uniform torsional moment capacity, curvature, and slenderness parameters were considered in the equation, which were the main factors that affected the ultimate strength of curved members. The curvature effect was considered individually, so that the strength of the straight or curved girder could be estimated with a unified equation. To verify the accuracy of the suggested equation, experimental studies were also conducted. Consequently, the suggested equation shows very good agreement with the test results, and is expected to provide useful information for the design of curved members.

Lateral-torsional buckling of partially protected steel I-beams exposed to fire

This paper proposes a new model for thin-walled open profiles able to predict bending-torsion buckling of thermally restrained steel I beams with bi- and mono-symmetric cross-sections. Refined nonlinear kinematics accounts for the shifts of the centroid and shear centre generated by the thermal gradient. The eigenvalue problem derived from geometrically nonlinear balance equations is solved via power series and Newton-Raphson technique. Several examples are presented; the results are compared with those provided by Abaqus simulation and the literature.

Numerical Simulation of Some Steel Structural Elements with Uncertain Initial Porosity

The main research purpose of this work was to study the elasto-plastic responses of some fundamental steel structural elements exhibiting stochastic volumetric microvoids. The constitutive model of the steel material was consistent with the deterministic Gurson–Tvergaard–Needleman (GTN) porous plasticity model, where some of the microvoids parameters have additionally been defined as Gaussian random variables. The iterative stochastic finite element method implemented based on the-tenth order stochastic perturbation technique was utilized in numerical experiments. An interoperability of the computer algebra system MAPLE 2019 and the finite element method system ABAQUS was employed to study the influence of the initial microvoids f0 with uncertainty in the structural steel on the statistical scattering of the resulting stresses and deformations. The basic probabilistic characteristics of the structural response were computed and contrasted with statistical estimators inherent in the Monte–Carlo simulation and also with the results obtained from the semi-analytical probabilistic method. Reliability indices according to the first-order reliability method (FORM) were also calculated. Two numerical illustrations included the (i) tension test of the round cylindrical steel rebar and the (ii) bending test of the steel I-beam restrained at both its ends. Expectations and coefficients of variation of the structural responses confirmed here the importance of the microvoids for the stochastic elasto-plastic behavior of some basic engineering structures, where tensile stress plays an important role in designing procedures.

Fatigue crack arrest in steel beams using FRP composites

Previous studies have demonstrated the effectiveness of strengthening with pre-stressed carbon-fiber reinforced polymer (CFRP) composites to increase the lifetime of cracked steel members. In some cases, complete crack arrest has been observed. This study aims to present a method that can estimate the minimum required prestressing that would result in a complete crack arrest in steel I-beams. Analytical and numerical models based on linear elastic fracture mechanics (LEFM) were developed and verified using a set of experimental results. Three steel I-beams with different crack lengths were strengthened with pre-stressed CFRP composites and later tested under a high-cycle fatigue loading regime. It was shown that the pre-stressed CFRP composites could result in a crack closure mechanism, in which the crack surfaces remained closed even under large external loads. Furthermore, it was shown that by considering the stiffness of the CFRP in the analytical formulation, the amount of prestressing required to arrest the fatigue crack growth can be reduced.

NUMERICAL ANALYSIS OF SQUARE HOLLOW COLUMN-BEAM CONNECTIONS BY ABAQUS

In recent years, steel or composite beam-column connections have drawn increasing praise due to the rapid development of assembled steel structures. However, limited researches have paid attention to the analytical behavior of square hollow column-beam joints. This work presents a numerical study on the static and cyclic behavior of the connections between a square hollow steel column and I-beam. Finite element analytical modeling of the joint was performed considering complex contact interactions and material models. Six different connections were evaluated by using ABAQUS. The modeling techniques used in this work, including the mesh and element types, the material properties, and the contact elements, were validated by comparing the numerical results of a through plate connection model with the experimental study results. Good agreement between the test and analytical results was observed in terms of the failure modes and the hysteretic behavior. Based on numerical results, the failure mode, moment-rotation curves for the SHS column to steel beam connections were discussed.

Additional Cover

The cover image is based on the Research Article Guided Wave-based Damage Assessment on Welded Steel I-Beam under Ambient Temperature Variations by Xian Xu et al., https://doi.org/10.1002/stc.2696.

Numerical and Analytical Study of the Distribution of Concentrated Pressure in the Wall of a Steel I-beam

The theory of the strength of load-bearing structural elements made of steel I-beams suggests that the nature of the stress distribution in the element is known, including from the action of concentrated pressure. A concentrated load is often applied at the level of the upper girdle of the beams, and causes local stresses in the wall. The walls of steel I-beams, due to their insignificant thickness, are sensitive to local pressure. That is why it is necessary to accurately determine the most stressed sections of the wall and the intensity of local stresses. In this paper, we consider a test model of a steel I-beam with a span of 9 m, to the upper girdle of which a concentrated load of 200 kN is applied. The local stresses in the wall are determined by analytical and numerical methods. The numerical calculation of the beam model was performed in the SCAD Office computing complex. The beam is modeled from volumetric isoparametric finite elements. The length of the beam wall is divided by two-sided stiffeners into nine compartments, with a step of 1000 mm. A comparative analysis of the nature of the distribution of local stresses in the wall of a steel beam obtained by analytical and numerical calculations is presented. Recommendations are given on taking into account local stresses in the beam wall from the action of a concentrated load when calculating strength.

Flexural impact resistance of steel beams with rectangular web openings

This paper focuses on the flexural impact behaviour of steel I-beams with rectangular web openings. Published studies on impact resistance and design requirements of perforated steel beams are limited. To shed light such a topic, detailed non-linear three-dimensional finite element models (FEMs) were developed using ABAQUS. Rigorous validation process was employed to verify the FEMs built against published experimental tests in terms of force and displacement time histories. Reasonably good agreement was obtained between the numerical results and the corresponding experimental ones. Then, the validated FEMs were exploited to investigate the flexural impact resistance of perforated steel beams with rectangular openings. The factors examined in the current study were the area, depth, number and reinforcement of web openings under different impact velocities ranged between 2.214–7 m/s to provide comprehensive understanding on the flexural impact response of steel beams perforated with rectangular openings. It was observed that increasing the number of narrow web openings negligibly effected the flexural impact resistance of steel beams. Moreover, using wide openings significantly reduced the dynamic flexural resistance of such beams. Besides, slight effect on the flexural impact resistance and mid-span deflections were obtained if the depth of openings increased. Moreover, a considerable improvement was observed by providing perforated beams by horizontal steel reinforcement particularly for those with wide openings. The perforated steel beams showed similar mode of failure by generating four plastic hinges around the edges of an opening, which is the failure mode produced for perforated beams under quasi-static loading.