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- 검색키워드
- 저자 : George N. Stamatopoulos (검색결과 6 건)
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George N. Stamatopoulos 한국강구조학회 2017 International Journal of Steel Structures Vol.17 No.2
The objective of this article is to demonstrate a comprehensive procedure for the estimation of the fatigue life of the component centre-beam-to-support-beam (CB/SB) bolted yoke connection. In this procedure, all the aspects are included such as fatigue vehicle loading, cycles per truck passage, lifetime average daily truck volume, fatigue classification of the detail and determination of fatigue infinite life. A typical single support beam (SSB) steel modular beam expansion joint (MBEJ) was modelled as 3D space frame. Moreover, three F.E. sub-models were created for the simulation of the (CB/SB) bolted yoke connection with preloaded bolts M16, M20 and M22 respectively. The Fatigue Load Model 2 (FLM2), recommended in EN 1991-2:4.6.4 for infinite fatigue life was chosen for the fatigue verification of the bolted yoke connection detail, assumed to be travelling at 90 km/h over the expansion joint. The 3D space frame was analysed by using Time-history dynamic analysis and thereafter, the calculated outputs were introduced in the F.E. sub-models. From the analysis of the sub-models the stress ranges were obtained and the fatigue evaluation of the yoke joint was performed. The investigation shown that poor detailing at the connection between the centre-beam-to-support-beam (CB/SB) bolted yoke connection is susceptible with reference to fatigue. Finally, important conclusions were extracted for both the behaviour of the entire modular joint and the fatigue life of the bolted yoke detail.
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Non-preloaded Bolted Ring Flange Connections Subjected to Static Loads
George N. Stamatopoulos 한국강구조학회 2014 International Journal of Steel Structures Vol.14 No.2
The ultimate behaviour of bolted connections in tubular members, such as chimneys, is studied and the interaction M-Ncurves are plotted, taking into account the main parameters of the problem. The proposed methodology is based on aclassification of failure patterns of the L-stub main component (segmental behaviour) under compressive or axial tensile forces,considering non-preloaded bolts. Besides, the results of the theoretical analysis of the main L-shape component ultimatebehaviour are compared with the corresponding obtained through finite element analysis of the constructed 3D models. Extending the local behaviour of the individual L-shape segments along the ring flange, the ultimate bearing capacity is derived,for each level of axial force, through a proposed analytical procedure and the corresponding interaction M-N curves areobtained. The parameters considered are the size and thickness of the flange and the tubular shell, the size and the location ofthe bolts, the quality of the materials and the amount of the applied axial load on the tubular element.
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Assessment of Strength and Measures to Upgrade a Telecommunication Steel Tower
George N. Stamatopoulos 한국강구조학회 2013 International Journal of Steel Structures Vol.13 No.2
The present paper deals with the analytical study of an existing telecommunication tower to assess the strength of the current configuration for additional reflectors, according to the owner’s decision. The evaluation of the capacity of the tower for the loads of the reflectors and antennas, as well as for the wind, ice and seismic loads, as specified by current design codes, was performed using a finite element model. Besides, after the owner’s recent decision to add new reflectors, the required strengthening was estimated and the measures to upgrade were also provided.
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Influence of the Flexible Supports on the Buckling Loads of Steel Frames
George N. Stamatopoulos 한국강구조학회 2015 International Journal of Steel Structures Vol.15 No.3
The partial constraint supports of steel-frames affects the structural stiffness and the buckling loads as well. To incorporate the effect of semi-rigid supports’ flexibility on column stability, the supports of a two-bar typical plane frame are modeled as nonlinear rotational and translational springs. Employing an energy approach with nonlinear kinematic relations, the system of equilibrium equations of the frame, which incorporates the effect of the nonlinear supports’ flexibility, is derived. The solution of the system is successfully obtained through an iterative procedure, by employing the Newton-Raphson numerical scheme, and the buckling loads are calculated. From the results of the analysis it is seen that, when the value of the non-dimensionalized rotational spring of the column base lies between two specific limits, the effect of the flexible supports on the buckling response of the frame should be always considered. Finally, the procedure of the nonlinear stability analysis proposed herein is illustrated by a representative example.
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Contribution of the Flexible Supports to the distribution of the Internal forces in Steel Frames
George N. Stamatopoulos 한국강구조학회 2012 International Journal of Steel Structures Vol.12 No.3
In this paper, the contribution of the flexible supports to the overall frame response and internal forces distribution is examined. Two types of a two-bar typical frame are considered, subjected to vertical uniformly distributed load q on the beam and concentrated load P at the top of the column. In the first frame under examination, the free end of the beam is pinned,while in the second frame the free end of the beam is horizontally sliding, representing the cases of nonsway and sway mode respectively. To incorporate the effect of semi-rigid supports’ flexibility, the column base support is simulated with nonlinear springs, representing the moment-rotation (M-θ ) behaviour and the foundation rotational and tranlational stiffnesses as well. The non-linear equilibrium systems of both nonsway and sway frames in their deformed state are formulated, and the internal forces and the rotations and displacements of the joints are obtained. From the obtained distribution of the internal forces that act in the members of the frames examined, it could be concluded that the influence of the flexible supports should be always taken into account in design practice, since this consideration leads to important economy and to a more realistic determination of the safety of structures.
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Seismic Response of Steel Frames Considering the Hysteretic Behaviour of the Semi-rigid Supports
George N. Stamatopoulos 한국강구조학회 2014 International Journal of Steel Structures Vol.14 No.3
The influence of the steel column base plate semi-rigid behaviour on the seismic behaviour of steel frames was examined. In order to evaluate this influence, three typical frames with different types of semi-rigid column base connections weremodeled. The investigation of the seismic behaviour of these frames was performed with the implementation of nonlineardynamic analyses using a recorded ground motion of the fault normal component of the 1995 Aigion earthquake in Greece. The analyses were performed using a sequence of hysteretic curves corresponding to the axial load levels during the processevaluation, including the base plate flexibility related phenomena of joint materials’ yielding (base plate, anchor bolts andconcrete). The direct comparison of the response analyses results, in terms of variation of the fundamental periods, the peakdisplacements, the column base bending moments and shear forces and the plastic hinges sequence, indicated that the columnbase flexibility strongly affects the seismic response of the frames and therefore should be always considered.
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