International Journal of Steel 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.

A test program was considered to clarify the cyclic characteristics of eight full-scale unstiffened extended end-plates with variable parameters and one SidePlate moment connection. All specimens were subjected to 2010 AISC seismic provision loading protocol where flexural strengths were identified at each interstorey drift angle. The results showed that all unstiffened extended end-plate failed to develop full inelastic capacity of connected beams and plastic hinges mainly appeared in the connection’s components. On the other hand, the SidePlate moment connection had the capacity to develop adequate interstorey drift angles up to 0.06 rad, indicating that this type of connection possesses sufficient stiffness and strength to be classified as a rigid and full-strength connection. The results also showed that SidePlate possesses considerably more energy dissipation capacity and an equivalent hysteretic damping ratio compared to unstiffened extended end-plate specimens, especially at higher interstorey drift angles.

It is known that the effects of corrosion on fatigue originate from two major sources: stress concentration due to corrosion discontinuities (CNF factor) and stress amplification due to loosing net section (NAF factor). In order to account for these effects, a performance function is developed which takes CNF and NAF factors into account and considers both random and time-dependent nature of the involved parameters. In order to consider real fatigue and environmental conditions, the available CNF-y and y-t functions are extended employing α and φ factors, respectively. In addition, some recommendations have been made to establish corrosion pattern of different steel sections. The final output of the methodology is development of a reliability-based procedure to establish time-dependent deterioration profile of a structural member, which assists in decision-making with regard to maintenance activities. The proposed methodology has been applied to Neka Bridge, a railway bridge in northern Iran, which is presented in Part II.

To study the dynamic response characteristics and failure process of single-layer spherical reticulated shells under impact loads at different loading points, impact dynamic analysis and experimental study are conducted on the K6 single-layer reticulated shell structure. First, the basic theory of numerical calculation and the model parameters are described. Then, dynamic response analysis under impact load is done by choosing different impact points. Finally, the impact test is performed on a large-scale shell model, dynamic response data of key members and nodes of shell structure are obtained, and the shell deformation and destruction process is recorded by a high-speed camera. The results show that the structural dynamic response gradually increases farther from the base point under the same impact force. The nearer the impact point is, the earlier the response occurs, and the larger the corresponding amplitude will be. The apex is the most unfavorable impact loading point, and the member at the apex should be strengthened for impact resistant design of the reticulated shell. The transmission time of the impact dynamic response from the impact site to the entire reticulated shell is short.