International Journal of Steel Structures

Bracing is the one of the best-known means of seismic retrofitting. Buckling restrained brace (BRB) is a certain type of brace with great efficiency against lateral loading. This paper presents the results of a finite element analysis on a BRB in which casing has no concrete infill. The core segment of this brace is similar to the conventional BRB, but it has a different buckling restraining system. The aim of this paper was to perform a parametric seismic study on the effect of a gap and also the effect of friction between the core and the casing and to evaluate the buckling behavior of these braces in response to changes in the initial shape of the bracing system. The results show that the flexural stiffness of the casing system, regardless of size of the gap, can significantly affect the buckling behavior of bracing.

Two conventional methods, the nominal stress method and the hot spot stress method, are examined for the fatigue assessment of a steel box girder bridge while considering the effect of the modeling options on the estimated fatigue life. Two analytical models, a simplified global analytical model and a refined local finite element analytical model, are developed for the evaluation of the stress ranges induced by a fatigue truck. The field tests are conducted for validating the analytical models as well as for direct fatigue assessment via an ambient vibration test. The local modeling options that are examined are the inclusion of the fillet weld itself in the refined analytical model and the mitigation of the concentrated stress at the web plate, considering stress dispersion over the width of the attachment. The fatigue life is estimated for three different nonexceedance probabilities, considering different partial factors according to the accuracy of the analysis method as well as the reliability of the estimated fatigue loading for a specific bridge site. Through a comparative analysis, the potential differences in estimated fatigue lives according to the assessment methods and the modeling options are quantitatively discussed.

This paper presents a comparative study on the composite structure of Corrugated Steel Plate (CSP) with normal and rubberized concrete. One CSP-normal-concrete plate and two CSP arch structures composited with different concretes are established. A theoretical section-property deduction is derived, which demonstrated that the flexural rigidity of such composite structure increased notably. Static and dynamic mechanical experiments are also conducted. Experimental results agree with expectations, and the measured results on plate structures verified the effectiveness of the analytical and numerical solutions. Comparing the deflection of two composite arches shows that the rubberized concrete composite arch has smaller flexural and compressive stiffnesses, resulting in larger deflection. The rubberized concrete composite arch has higher steel stress, lower concrete stress and better energy-dissipating capacity compared with the normal concrete composite arch. Therefore, the CSP-rubberized concrete composite structure is more suitable for anti-shock and earthquake-resistant structures.

In this paper, both experimental and analytical investigations are presented for the evaluation of yield moment capacity of the extended end plate connections under pure flexural loading. Four point loading system is adopted to simulate the pure bending condition. For the experimental study a beam–beam splice connection is made by joining hollow tubular sections (HTS) using bolted end plate connections. The parameters varied for the experimental investigation are cross sectional dimensions of HTS, thickness of end plate, diameter of bolt and thickness of weld. In the analytical study, yield line theory is used for the prediction of yield moment equations of the connection for a particular modes of failure. Finally, the proposed analytical equations are validated by comparing the analytical results with the experimental results. It is found that the experimental results are in proximity with the analytical results.

Stress concentration factors (SCF) of steel tubular T/Y-joints strengthened with different types of fiber reinforces polymer (FRP) materials were studied thoroughly under the action of in-plane bending (IPB) and out-of-plane bending (OPB) moments. A comprehensive FE study was carried out through examining different elements for steel substrate and FRP material along with the corresponding contact modeling to attain reliable results substantiated by existing SCF experiments. Shell-to-Solid contact using the node-sharing technique showed the best performance in conformity with the SCF experimental results. Such benchmark modeling was substantiated with additional verifications against the available experimental data on SCFs in T, Y, and K connections. Numerous FE models were then developed to put the most affecting FRP and joint parameters into perspective, while previous studies lack addressing all in one go. It was found that the geometry of the connection has a significant influence on the level of FRP effectiveness. For instance, the sensitivity of SCF in a Y-joint to FRP strengthening is less than a T-joint with similar geometry, due to the different brace-to-chord angles. Justified with analytical interpretations, cumulative effects of all parameters were carefully evaluated to derive SCF formulas for FRP strengthened tubular T/Y-joints under both IPB and OPB moments. Their accuracy and applicability were checked with the well-known statistical indices, and it was seen that the correlation of coefficients was higher than 95%. Moreover, the proposed SCF formulas meet all the acceptance criteria of the Fatigue Guidance Review Panel.

A new-type of orthotropic steel-concrete composite bridge deck system was developed, by casting the concrete overlay on the top of the orthotropic steel deck ribbed with T-shape steel members. To study its mechanical behavior (in terms of failure mode, load-deflection relationship, concrete crack initiation and propagation, strength, stiffness and so on), two new-type orthotropic steel-concrete composite bridge decks with different section dimensions were experimentally investigated and two reference decks (reinforced concrete deck and orthotropic steel deck) were also involved in the research for comparison. For the two new-type orthotropic steel-concrete composite decks, the average value of ultimate loads per width is 885.7kN, which is 2.35 and 1.61 times of that of the concrete and steel reference decks with almost the same section height. Experimental results proved that the composite deck can effectively control the crack initiation and propagation in the concrete and postpone the yielding of the steel bars and steel plates, due to the composite action between the concrete overlay and the underlying steel plate. Furthermore, the Finite Element (FE) model of the orthotropic steel-concrete composite deck was developed and validated by test results. A parametric study is conducted regarding to the stiffness of shear studs. With the validated FE model, stress distribution in the underlying steel plate and T-shape stiffeners and development of concrete cracking in the concrete overlay were characterized at different load levels.

Most of previous studies on fire resistance of restrained steel beams neglected creep effect due to lack of suitable creep model. This paper presents a finite element model (FEM) for accessing the fire resistance of restrained high strength Q460 steel beams by taking high temperature Norton creep model of steel into consideration. The validation of the established model is verified by comparing the axial force and deflection of restrained beams obtained by finite element analysis with test results. In order to explore the creep effect on fire response of restrained Q460 steel beams, the thermal axial force and deflection of the beams are also analyzed excluding creep effect. Results from comparison infer that creep plays a crucial role in fire response of restrained steel beam and neglecting the effect of creep may lead to unsafe design. A set of parametric studies are accomplished by using the calibrated FEM to evaluate the governed factors influencing fire response of restrained Q460 steel beams. The parametric studies indicate that load level, rotational restraint stiffness, span–depth ratio, heating rate and temperature distribution pattern are key factors in determining fire resistance of restrained Q460 steel beam. A simplified design approach to determine the moment capacity of restrained Q460 steel beams is proposed based on the parametric studies by considering creep effect.