I-shaped Steel Beams Research Articles

Accordion effect of prestressed steel beams with corrugated webs

Various types of composite members have been developed to utilize the combined advantages of existing reinforced concrete and steel structures, and to actively improve ductility and serviceability of structural members. One of them is the hybrid-type steel beam, in which the prestressing method is applied to a steel beam. Introducing prestress to the existing I-shaped steel beam, however, results in a very low prestress efficiency due to the large axial stiffness of the section. On the other hand, if corrugated webs are used, the prestress introduced to the main flexural-resistant elements—the upper and lower flanges—gets larger due to the accordion effect, so that it is very advantageous not only in terms of serviceability, but also of achieving the improved flexural strength. Most previous studies on steel members with corrugated webs, however, have focused on the shear buckling strength of the corrugated webs, and few studies have been conducted on the accordion effect of the corrugated webbed beam to which prestress is introduced. Therefore, this research proposed two rational and theoretical models to quantitatively estimate the accordion effect, which is induced by the introduction of prestress to corrugated webbed steel beams, and performed experiments on two steel beams with corrugated webs and one with typical wide flange section. The experimental results showed that the prestressing efficiency of steel beams with corrugated webs increased more significantly than that of the steel beam with a typical web, and it is verified that the proposed methods are very simple and provide good agreements with the experimental results.

Mechanical Properties of Reinforced Steel Beams Influenced by the Degree of Unloading

Several I-shaped steel beams reinforced by CFRP are unloaded at different levels and the mechanical properties are analyzed and compared. Five forms of I-shaped steel beam (beam without reinforced; reinforced beam in condition of non-unloading; reinforced beam in condition of 50% unloaded; reinforced beam in condition of 75% unloaded; reinforced beam in condition of completely unloaded) are analyzed and compared. Conclusions are made that the stiffness and yielding load of I-shaped steel beams reinforced by CFRP are improved and the bearing capacity is improved for certain degree when the beams are unloaded.

Modeling and damage detection for cracked I-shaped steel beams

This paper presents the results of a study to show how the development of a crack alters the structural behavior of I-shaped steel beams and how this can be used to evaluate nondestructive evaluation techniques. The approach is based on changes in the dynamic behavior. An approximate finite element model for a cracked beam with I-shaped cross-section is developed based on a simplified fracture model. The model is then used to review different damage cases. Damage detection techniques are studied to determine their ability to identify the existence of the crack and to identify its location. The techniques studied are the coordinate modal assurance criterion, the modal flexibility, and the state and the slope arrays.

An experimental study of connections between I-beams and concrete filled steel tubular columns

Frame composed of concrete-filled steel tubular columns and I-shaped steel beam has been researched in order to development reasonable connection details. The present paper describes the results of an experimental program in four different connection details. The connection details considered include through-bolt between I-shaped steel beams and concrete-filled steel tubular columns and two details of welded connections. One of the welded connection details is stiffened by angles welded in the interior of the profile wall at the beam flange level. The specimens were tested in a cruciform loading arrangement with variable monotonic loading on the beams and constant compressive load on the column. For through-bolt details, the contribution of friction and bearing were investigated by embedding some of the bolts in the concrete. The results of the tests show that through-bolt connection details are very ductility and the bearing is not important to the behavior of these moment connections. The angles welded in the interior of the profile wall increase the strength and stiffness of the welded connection detail. In addition, the behavior curves of these connections are compared and some interesting conclusions are drawn. The results are summarized for the strength and stiffness of each connection.

Modelling of solidification structure of continuous cast steel

An analytical model of macro-micro type for predicting the microstructure of continuous cast steel is presented in this paper. The macroscopic part is based on a finite element model to solve the nonlinear heat conduction equation. The microscopic part consists of a solute diffusion model to predict undercooling, followed by a dendrite growth model to predict columnar dendritic features. The geometry of the model corresponds to an I-shaped steel beam blank that is continuously cast to near-net shape. Good agreement is found between the predicted and the measured secondary dendrite arm spacing in an actual continuous cast I-shaped steel beam blank.

Inelastic Local and Lateral Buckling in Design Codes

The flexural requirements for plastic design of I-shaped steel sections in international codes of practice are inconsistent and provide misleading emphasis on local buckling as the primary strain-weakening effect. The loss of ductility due to simulated axial force occurring simultaneously with inelastic bending is also underestimated in these codes. A model is described to assess the maximum moment and available inelastic rotation prior to strain weakening due to the interactive local flange and web buckling and lateral-torsional buckling. The results of 44 tests on I-shaped steel beams under pure flexure and 14 tests on similar specimens under combined bending and simulated axial force are also described. The rotation capacities measured in these tests are examined in terms of standard local and lateral buckling parameters as well as the proposed model. The relative importance of the different parameters is assessed and the effectiveness of the theoretical model is demonstrated in the analysis of these e...

Combined flexure and torsion of I-shaped steel beams

Design standards provide little information for the design of I-shaped steel beams not loaded through the shear centre and therefore subjected to combined flexure and torsion. In particular, methods for determining the ultimate capacity, as is required in limit states design standards, are not presented. The literature on elastic analysis is extensive, but only limited experimental and analytical work has been conducted in the inelastic region. No comprehensive design procedures, applicable to limit states design standards, have been developed.From four tests conducted on cantilever beams, with varying moment–torque ratios, it is established that the torsional behaviour has two distinct phases, with the second dominated by second-order geometric effects. This second phase is nonutilizable because the added torsional restraint developed is path dependent and, if deflections had been restricted, would not have been significant. Based on the first-phase behaviour, a normal and shearing stress distribution on the cross section is proposed. From this, a moment–torque ultimate strength interaction diagram is developed, applicable to a number of different end and loading conditions. This ultimate limit state interaction diagram and serviceability limit states, based on first yield and on distortion limitations, provide a comprehensive design approach for these members. Key words: beams, bending moment, flexure, inelastic, interaction diagram, I-shaped, limit states, serviceability, steel, torsion, torque, ultimate.