I-shaped Steel Research Articles

Verification of the Ramberg-Osgood Material Model for the Fire Design of Steel Members

Abstract In this paper, the modified Ramberg-Osgood constitutive equations for calculating the stress-strain of steel at elevated temperatures using the parameters determined based on the transient state tensile test results achieved at the Helsinki University of Technology are verified. This is done by numerically comparing the global and local buckling capacities of I-shaped steel members incorporating the modified Ramberg-Osgood model along with the material model given in the fire section of Eurocode EN1993-1-2. For this purpose, a numerical model using the ABAQUS software was developed. Then, nonlinear analyses with imperfections (GMNIA) were performed to compare the buckling capacities of the steel columns and beams of four different hot-rolled cross-sections (IPE160, IPE180, HE100B, HE500B), made of steel grade S355, at three different temperatures (400°C, 500°C, 600°C). The results showed that adopting the modified Ramberg-Osgood model can lead to the same buckling capacities resulting when using the EN1993-1-2 material model for steel temperatures of less than 400°C. However, adopting this model for 600°C overestimates the buckling capacities in most cases.

Flexural behavior of U-shaped steel-concrete composite beams under positive bending

The use of cold-formed U-shaped steel and concrete composite beams has increased with the advantage of permanent steel form as a load-resisting element. In this study, a new type of U-shaped steel-concrete composite beam with a bolt connection was proposed. Four-point flexural tests of full-scale specimens were performed to evaluate the flexural behavior of the composite beams under a positive bending moment. The main test parameters were the types of U-shaped steel sections and location of the neutral axis at ultimate strength. The U-shaped composite beams under positive bending behaved similarly to the composite beams with an I-shaped steel section. The strain compatibility method is recommended to evaluate the positive flexural strength of the composite beams. In addition, the effective flexural rigidity was proposed to capture the increasing trend of the flexural stiffness ratio according to the shear span-to-depth ratio.

Axial compressive behaviour of concrete encased extended I-shaped steel composite stub columns with less reinforcement

A novel concrete encased extended I-shaped steel composite (EI-CES) column with less reinforcement for prefabricated structures is proposed. Eight EI-CES stub columns with one covered by concrete fireproof board, and two bare extended I-shaped steel stub columns, are tested under axial compression loads. The effects of stirrup spacing, stirrup form, proportion of steel sectional area, and concrete compressive strength on the axial compressive behaviour of composite columns are studied by test and finite element analysis. According to the results, the concrete cover with less reinforcement can prevent internal steel instability under axial compression. 25 mm thickness of concrete cover can satisfy the load-carrying capacity and serviceability requirements for the composite column. The premature spalling of concrete cover can be prevented by installing fireproof board, reducing stirrup spacing, and using closed stirrups. The proportion of steel sectional area in composite columns increasing from 7.5 % to 9.6 % has no effect on the maximum material full-utilization coefficient, but can reduce premature concrete cracks and improve the residual strength of EI-CES columns. The concrete compressive strength in composite columns decreasing from C50 to C30 can improve the maximum material full-utilization coefficient and residual strength. The composite columns have excellent post-peak deformability. A formula for the axial resistance of EI-CES columns is proposed and validated.

Overall stability capacity design of T-shaped irregularly concrete-filled steel tube columns considering axial compression and any directional moments

A slender T-shaped irregularly concrete-filled steel tube column (T-ICFSTC) may be subjected to overall instability failure under combined axial load and moment. But current research is not available about a complete design of T-ICFSTCs subjected to axial compression and any direction bending moments because of a complicated parameter study involved in the analysis. This paper investigates the overall stability capacity performance and design prediction of the T-ICFSTCs that are formed by I-shaped steel, U-shaped steel and several cell infilled concrete. First, the finite element model for analyzing the overall instability performance and failure is established and verified by the previously experimental tests carried out by the authours. Then, the overall stability capacity of T-ICFSTC around its symmetric axis is investigated numerically and accordingly design formulas of φy-λny are established. In particular, interaction influence between initial imperfection direction and applied bending moment direction is studied, thus resulting in a critical initial imperfection direction relatively to applied bending direction. Sequently, the load-bearing capacity and performance under any direction bending moments are explored numerically and the normalized design curves reflecting interaction of N-M and Mx-My at their limit states are formulated by fitting the FE results of examples. Finally, a complete set of overall stability prediction formulas of T-ICFSTCs under combined axial load and any directional bending moment are established and the results obtained agree well with FE numerical investigation results.

Analysis of the explosion resistance of an I-shaped steel‒concrete composite structure under contact explosion

Reinforced concrete and steel structures are commonly used in bridge construction; thus, researchers have conducted relatively comprehensive analyses of their dynamic responses and damage mechanisms under blast loads. However, for a new type of I-shaped steel‒concrete composite structure with various structural performance advantages, there remains a lack of effective experiments and analyses of damage modes. In this paper, three I-shaped steel‒concrete composite specimens are designed and fabricated, and explosion experiments under different explosion scenarios are performed. The experimental results show that under the support of an I-shaped steel plate, the structure has a strong ability to withstand the blast load. The concrete damage area on the rear blast surface is small, and the I-shaped steel plate does not yield under a small explosive equivalent. Based on the experimental results, the dynamic response and failure behavior of the I-shaped steel‒concrete composite structure are numerically evaluated using Autodyn explicit dynamic analysis software. By considering different working conditions and by taking the deformation and damaged areas of the structure as the damage index, the key explosion resistance factors of the structure under contact explosion are studied. Some important structural parameters greatly influence the explosion resistance of the structure, including the thickness of the I-shaped steel plate; however, increasing the strength of concrete does not significantly improve the explosion resistance of the composite structure.

Cyclic and monotonic behaviour of steel-reinforced concrete-filled steel tubular columns

Steel-reinforced concrete-filled steel tubular (SRCFST) column, exhibits high strength and superior fire resistance, is a type of composite members developed by configuring the steel section in conventional concrete-filled steel tubular (CFST) column. In this paper, the cyclic behaviour of SRCFST columns was experimentally investigated. Twenty columns with cross and I-shaped steel sections under cyclic loading were tested. The effects of the axial load ratio and steel section type on the failure modes, lateral load–displacement curves, and seismic performance were investigated. The test results demonstrate that columns with circular cross-sections, which experience severe local buckling and fracture of the steel tube, exhibit superior cyclic performance compared with those with square cross-sections. The steel section type has a negligible influence on the seismic behaviour of the columns. As the axial load ratio increases, the ductility factor and ultimate load of the columns decrease moderately. A finite element (FE) model was developed to investigate the full-range behaviour of the columns under monotonic loading. Finally, design methods were proposed for calculating the lateral capacity of SRCFST columns with circular and square cross-sections.

Optimum design of prestressed steel beams via genetic algorithm

The objective of this article is to present an optimization problem formulation to reduce the total structural cost of prestressed doubly-symmetric and monosymmetric I-shaped steel simply supported beams with straight tendons. The optimization problem was implemented via MATLAB’s native Genetic Algorithm. The validation and evaluation processes adopted two examples from literature. The design method follows the Brazilian standard NBR 8800:2008 for the Ultimate and Serviceability Limit States. The best result was found for a monosymmetric case by up to 20.00% and 25.70%. Saving in material weight and installation of tendons, without exceeding the security limits, was also effective. Furthermore, the results presented an efficient alternative for structural engineering, providing a significant model for similar analyzes.

Utilizing Low Yield Point Steel to Improve the Behavior of the I-Shaped Shear Links as Dampers

Concentrically braced frame (CBF) systems are susceptible to buckling (which causes a decrease in energy absorption), although this system has considerable lateral stiffness and strength. To over this shortcoming, researchers have suggested the use of I-shaped steel dampers as a practical idea that prevents buckling and increases the energy absorption but reduces the stiffness of the system. To increase the stiffness of the damper, the thickness of the web or the thickness of the flange can be increased, but by increasing their thickness the shear capacity of the damper also increases. Nevertheless, with the increase in the capacity of the damper, the forces created in the elements outside the damper will also increase, which is usually not a suitable solution. Therefore, in this paper, the use of the low yield point for the web plate of an I-shaped damper is proposed to compensate for it. Accordingly, its behavior is investigated parametrically and numerically and also requires equations to design the system proposed. Results indicated that utilizing an LYP damper improves the behavior of the system in the case of energy absorption, stiffness, and strength. Comparing the LYP damper and the conventional I-shaped damper (made of A36 steel) reveals that both dampers pertain to stable hysteresis loops without any degradation, which confirms the capability of the I-shaped damper to dissipate seismic energy. Although the flange plate properties contribute to the load-bearing of the damper, the A36 damper is more affected by the flange plate than the LYP damper that is concluded for LYP dampers the flange plate contribution in the shear strength of the damper is ignorable at the beginning of imposed loading.

Experimental and numerical study of T-shaped irregularly concrete-filled steel tube columns under combined axial loads and moments

T-shaped irregularly concrete-filled steel tube column (T-ICFSTC) is formed by I-shaped steel, U-shaped steel and infilled concrete. The I-shaped steel and U-shaped steel are welded together to form a multi-cell CFST column. The T-ICFSTCs can be used in the corner of T-shaped intersection location of two walls in the buildings, which can avoid the exposure of the columns and increase the available area of the indoor space. The overall flexural stability performance of the T-ICFSTCs under axial loads and moments may still be an important problem in engineering design. This paper studies the overall flexural stability performance of the T-ICFSTCs under combined axial loads and moments. Firstly, the experiments of two T-ICFSTC specimens under eccentric loading with eccentric distance of 100 mm and opposite eccentric directions were carried out. Subsequently, the refined finite element (FE) models and the simplified finite element (FE) models are established and verified by the experimental results. The simplified FE models use beam elements (B31) and have higher calculation efficiency than the refined FE models, and are adopted for the numerical investigation of the T-ICFSTCs. Finally, based on the simplified FE model verified by the experimental results, the parametric analysis of the overall flexural stability capacity of the T-ICFSTCs under axial loads and unidirectional moments is carried out. The parameters studied include the height of the T-ICFSTCs, several geometric parameters of the cross section and the strength of material. Based on the results of numerical investigations, a preliminary design formula of the overall flexural stability capacity of the T-ICFSTCs under axial loads and unidirectional moments is proposed. This paper provides reference for engineering design of the T-ICFSTCs and the foundation to establish a complete design formula of the T-ICFSTCs under axial loads and unidirectional moments.

Closed-form relationships of flexural moment–curvature-axial force for I-shaped steel sections

Closed-form relationships of flexural moment–curvature-axial force for I-shaped steel sections

Time-Dependent Reliability Assessment of a Continuous I-shaped Steel Beam Considering Corrosion Effects

Among other fields, climate change has a great influence on metal corrosion that reduces the durability and reliability of steel structures. A time-dependent reliability analysis includes time-dependent climate scenarios and deterioration processes as well as random variables, material properties, and dimensions. The extent of corrosion damage is calculated by tracking the evolution of the corrosion process using Monte Carlo simulations. The current paper presents a time-dependent reliability assessment of a continuous I-shaped steel beam, considering the corrosion effects of climate change in Vietnam. The results showed that the safety probability of a continuous steel beam considering metal corrosion from the pristine to 100 years reduces from 96.77% to 63.08%. These findings can be used to assess and provide a cost-technical analysis of climate adaptation measures.

A hybrid IMSE-FE-BE method coupled with RSM for vibro-acoustic analysis and optimization of an I-shaped steel beam damped with constrained layer damping

In this paper, a method for calculating vibration and noise from the I-shaped steel beam damped with constrained layer damping (CLD) was proposed based on iterative modal strain energy (IMSE) method and finite element (FE)-boundary element method (BEM). Then, a series of hammer tests were carried out to obtain the typical vibro-acoustic response samples of a CLD-damped beam. It is shown that the calculated noise and vibration agreed well with the measured results, indicating that the proposed method is effective and accurate. Then, the response surface methodology (RSM) was used to analyze the influence of CLD-structural parameters on the sound radiation characteristics and natural frequency of the damped beam. With the objective of minimizing the acoustic radiation power, a program for finding the optimal CLD-structural parameters was developed based on interior penalty function method (IPFM). Finally, the acoustic response comparisons between the original bare beam and the optimized CLD-damped beam were performed. It shows that the overall sound power level was decreased from 98.12 dB to 80.47 dB, and the overall sound pressure level at measuring point S3-3 was reduced from 78.86 dB to 61.07 dB, demonstrating that the optimization of CLD-structural parameters can significantly improve the acoustic performance of CLD-structures.

Critical study of steel beams with web openings

ABSTRACT In this study, experimental and numerical approaches are adopted to comprehensively investigate the flexural strength capacity and failure modes of I-shaped steel members with various web openings geometry. To validate the results, the finite element models are established using ABAQUS with the same configurations as the test specimens. Based on the experimental and numerical investigation it is observed that, the web openings not only weaken the practical section but also destroy its continuity. The common mode of failure observed in beams with web openings is excessive bending, Vierendeel mechanism and web post buckling. When the opening ratio exceeds 0.75, the openings greatly affect the stability of the components, which results in reduction in strength capacity of perforated beams. In contrast, when the opening ratio is less than 0.5, the openings have negligible impact on the stability and strength component. The web openings also have a significant impact on the bearing strength of the members when the provided web post width is less than 200 mm. In contrast, when the web post width exceeded 200 mm, the web opening ratio had only a small effect on the member bearing capacity. The response of the perforated beams was presented in terms of load-deflection and moment-deflection curves. .

Low-cycle fatigue performance and damage sequence investigation of I-shaped steel braced systems and braced frames

Simulations of 12 braced systems (I-shaped steel (Q355B) brace with the gusset plate connection) and 5 braced frames (single diagonal) are conducted. The results show that the low-cycle fatigue life of the braced system and the braced frame is determined by the minimum value of the fatigue life between the gusset plate connection and the brace. For the gusset plate connection, small value of clearance distance and large value of loading amplitude lead to small fatigue life. The ability for ductility property and energy dissipation of the braced system is optimal when the fatigue life of the gusset plate connection and brace is similar. The critical plane method (LZH model) and ductile damage method are applied to predict the fatigue life and investigate the fatigue damage of the specimens. These two methods have good applicability not only on fatigue life prediction but also the damage sequence of each component (including the gusset plate connection and the brace). Based on experimental data from related literature, fatigue parameters that are used in life prediction methods of steel Q355B (including the base metal and welding material) are calibrated.

Control of Early-Age Cracking in Super-Long Mass Concrete Structures

The early-age cracking problem in concrete has long been recognised by civil engineers and scientists because it can jeopardise the intended serviceability of concrete structures. However, the effects of various crack control methods are different. This paper carried out field monitoring on a super-long wall with different crack control measures and compared the temperature and strain development process of the wall. In the middle of the super-long wall, the pipe cooling method reduced the hydration heat of concrete by 13 °C via a vertical pipe arrangement, but the wall could reach the maximum tensile strain earlier than with the other methods. By embedding an I-shaped steel plate in the induced joint method, a structurally stiff mutation zone was generated, and the maximum strain was generated at the induced seam web. By calculating and setting a reasonable construction length, the alternative bay construction method reduced the internal tensile strain of the structure. The early-age cracking of super-long mass concrete structures is affected more by restrained shrinkage than by temperature, so it is difficult to control early-age cracking by addressing only one factor.

Shear performance of assembled shear connectors for timber–concrete composite beams

This paper presents three types of assembled shear connectors consisting of a steel component anchored to timber by screws and glued-in rods (GiRs) for timber-concrete composite (TCC) beams. Single-shear tests were carried out to evaluate the shear performance of the proposed shear connectors. The test results showed that the anchors bent obviously and finally failed in “single-hinge” and “double-hinge” yield modes under lateral load. The timber surrounding the anchors was obviously crushed, and cracks in concrete were also observed during testing. The shear connectors with I-shaped steel anchored by GiRs exhibited the highest shear capacity of 158.92 kN. The folded steel plate shear connectors with GiRs and screws showed the highest slip modulus (38.41 kN/mm), and the highest ductility with an average coefficient of 29.6, respectively. In general, the shear connectors anchored with GiRs showed better shear performance compared to the screwed shear connectors. Finally, numerical simulation results indicated that the simulated load–slip curves were generally in good agreement with the test curves. The anchor diameter and strength and the frictional coefficient between anchors and the wall of the holes in timber have significantly influenced the shear performance of the proposed shear connectors.

Structural Performance and Engineering Application of a Long Lasting Weathering Steel Composite Bridge with Tubular Flanges

A study of the structural performance and engineering application of a long lasting composite bridge with tubular steel flanges was carried out. The flexural, shear and torsional resistance of high-performance composite girders with tubular flanges were analysed comparatively based on tests and finite element simulation. Based on the research and design rules achieved above, the first two typical composite girder bridges with rectangular tubular flanges using high-performance weathering steel have been constructed in China. The structural performances were compared of a composite girder bridge with tubular flanges and a composite girder bridge adopting traditional I-shaped steel girders. A long-term performance evaluation was conducted for a weathering steel composite bridge with tubular flanges, which included an in situ inspection and rating assessment of the patina and life cycle cost evaluation of the whole bridge. Learned from the application experience and evaluation results, weathering steel composite girder bridges with tubular flanges revealed superior long lasting structural performance including improved torsional stiffness and resistance, fewer web stiffeners and cross beams, fast construction, and easy and less maintenance during the in-service stage.

Experimental research on seismic damage of cross-shaped CFST column to steel beam joints

The special-shaped (L-shaped, T-shaped and cross-shaped) concrete-filled steel tubular (CFST) columns have been applied in many building structures, and they are usually connected with either I-shaped or box steel beams. This paper presents an investigation on the seismic damage of the cross-shaped CFST column to I-shaped steel beam joints. Five specimens with a scale of 1/2 were performed and tested under various loading schemes. The failure pattern, load-displacement curves, energy dissipation capacity, cyclic strength degradation, the maximum principal strain of the joint panel zone, and beam-column rotation are analyzed. The experimental results reveal that the failure pattern of the joints is mainly the shear failure of the joint panel zone and fracture of the beam end. There is no noticeable pinch effect on the hysteretic curves, and the joints have good energy dissipation capacity with the equivalent viscous damping coefficient of 0.299–0.377. The shear bearing capacity improves with the growth of depth to width ratio. When the depth to width ratio exceeds the value of 3, the seismic damage of the joints develops more rapidly, and the joints are more prone to damage during the earthquake. The seismic damage of the joint panel zone web is severer than the joint panel zone limb during the loading. Based on the Park-Ang damage model, the seismic damage of specimens is analyzed. Furthermore, the parameter analysis was conducted based on the finite element analysis. The influence of axial compression ratio and the concrete strength was analyzed.

Research on Mechanical Properties of U-Shaped Retractable Gangue Prevention Structure of Gob-Side Entry by Roof Cutting and Pressure Releasing in Deep Mining

Abstract In recent years, as a new type of gob-side entry retaining method, roadway automatically formed by roof cutting and pressure releasing (RAFRCPR) has been widely used in China. Under the condition of deep mining, the deformation of the gangue rib of the automatically formed gob-side entry retaining is difficult to control, and it is difficult for the traditional I-shaped steel to provide the needed support. To effectively control the deformation of the gangue rib, a new type of U-shaped retractable gangue prevention structure (URGPS) with high lateral support strength and axial compressible dynamic absorption energy is proposed. Based on the geological conditions of the 21304-working face in the Chengjiao coal mine in Henan, the mechanical characteristics of URGPS and the causes of its local instability are analyzed in detail employing theoretical analysis, laboratory tests, and numerical simulation. A reasonable bolt tightening force, overlap length, and lap combination form of the URGPS are determined according to the actual situation of the project site. Engineering practice shows that a URGPS that was applied to control the deformation of the gangue rib in deep roof-cutting roadway was effective.

Mixed-mode fatigue crack growth analysis of I-shaped steel girders with trapezoidal corrugated-webs

In bridge industry, the composite box-girder with corrugated steel webs and concrete flanges is quite a common practice over recent years. However, this innovation encounters fatigue-sensitive details not fully investigated, especially in the research area of mixed-mode fatigue crack growth. This study addresses the mixed-mode fatigue crack growth analysis of an I-shaped corrugated web girder associated with the represented web-to-flange detail. A linear elastic fracture mechanics (LEFM) based numerical framework was established to simulate the mixed-mode crack propagation. For comparison, a semi-analytical weight function framework was also introduced to predict the pure Mode-I crack propagation life of the same detail. Experimental results of a full-scale inclined corrugated web girder were employed to evaluate these two proposed frameworks. A parametric study was presented based on the proposed frameworks to investigate the effect of initial crack depth and crack shape on fatigue crack propagation life. By comparing the simulation results with test results, the applicability of the proposed LEFM-based numerical framework to the simulation of mixed-mode fatigue crack propagation behaviour in corrugated web girders was discussed.