Abstract
A theoretical research project is undertaken to develop integrated analysis and design tools for long span composite beams in modern high-rise buildings, and it aims to develop non-linear finite element models for practical design of composite beams. As the first paper in the series, this paper presents the development study as well as the calibration exercise of the proposed finite element models for simply supported composite beams. Other practical issues such as continuous composite beams, the provision of web openings for passage of building services, the partial continuity offered by the connections to columns as well as the behaviour of both unprotected and protected composite beams under fires will be reported separately. In this paper, details of the finite elements and the material models for both steel and reinforced concrete are first described, and finite element studies of composite beams with full details of test data are then presented. It should be noted that in the proposed finite element models, both steel beams and concrete slabs are modelled with two dimensional plane stress elements whose widths are assigned to be equal to the widths of concrete flanges, and the flange widths and the web thicknesses of steel beams as appropriate. Moreover, each shear connector is modelled with one horizontal spring and one vertical spring to simulate its longitudinal shear and pull-out actions based on measured load-slippage curves of push-out tests of shear connectors. The numerical results are then carefully analyzed and compared with the corresponding test results in terms of load mid-span deflection curves as well as load end-slippage curves. Other deformation characteristics of the composite beams such as stress and strain distributions across the composite cross-sections as well as distributions of shear forces and slippages in shear connectors along the beam spans are also examined in details. It is shown that the numerical results of the composite beams compare well with the test data in terms of various load-deformation characteristics along the entire deformation ranges. Hence, the proposed analysis and design tools are considered to be simple and yet effective for composite beams with practical geometrical dimensions and arrangements. Structural engineers are strongly encouraged to employ the models in their practical work to exploit the full advantages offered by composite construction.
Key Words
composite beams; finite element models; integrated analysis and design; bending; shear; degree of shear connection.
Address
Department of Civil and Structural Engineering, The Hong Kong Polytechnic University, Hong Kong SAR, China
Abstract
Structures in seismic regions are designed to dissipate seismic energy input through inelastic deformations. Structural or component failure occurs when the hysteretic energy demand for a structure or component subject to an earthquake ground motion (EQGM) exceeds its hysteretic energy dissipation capacity. This paper presents a study on identifying the hysteretic energy demand and distribution throughout the height of regular steel moment resisting frames (SMRFs) subject to severe EQGMs. For this purpose, non-linear dynamic time history (NDTH) analyses were carried out on regular low-, medium-, and high-rise steel SMRFs. An ensemble of ninety EQGMs recorded on different soil types was used in the study. The results show that the hysteretic energy demand decreases from the bottom stories to the upper stories and for high-rise structures, most of the hysteretic energy is dissipated by the bottom stories. The decrease is quite significant, especially, for medium- and high-rise structures.
Key Words
energy input; hysteretic energy; steel frames; non-linear analysis.
Address
Bulent Akbas; Department of Earthquake and Structural Science, Gebze Institute of Technology, 41400 Gebze-Kocaeli, TurkeyrnJay Shen; Department of Civil and Architectural Engineering, Illinois Institute of Technology, 60616-3793 Chicago, IL, USArnHakan Temiz; Department of Earthquake and Structural Science, Gebze Institute of Technology, 41400 Gebze-Kocaeli, Turkey
Abstract
The present paper summarizes the experimental research carried out at the \"Politehnica\" University of Timisoara, Romania, with the scope of investigating the influence of different column webstiffening solutions on the performance of beam-to-column joints of Moment Resisting Steel Frames. Theresponse parameters, such as resistance, rigidity and ductility were examined. Five different types of panel
web stiffening were compared with regard to a reference test. A quasi-linear relationship between the moment
capacity and the total shear area of the web panel was observed from the experimental tests while the initial
rigidity increased non-proportionally with the same area. Comparisons are presented of the experimental tests
with the mathematical model developed by Krawinkler and with the model stipulated in Eurocode 3 Part 1.8. These comparisons showed a generally good agreement in the case of moment capacity, while the computed rigidities were always greater than the experimental rigidities.
Key Words
column web panel; supplementary plate; rigidity; shear resistance; moment capacity; seismic codes.
Address
The \"Politehnica\" University of Timisoara, Romania
Abstract
This paper deals with the dynamic behaviour of cold-formed steel hollow frames with different connection stiffnesses. An analytical model of a semi-rigid frame was developed to study the influence of connection stiffnesses on the fundamental frequency and dynamic response of the frames. The flexibilities of the connections are modeled by rotational springs. Neglect of semi-rigidity leads to an artificial stiffening of frames resulting in shorter fundamental period, which in turn results in a significant error in the evaluation of dynamic loads. In the seismic design of structures, of all the principal modes, the fundamental mode of translational vibration is the most critical. Hence, experiments were conducted to study the influence of the connection stiffnesses on the fundamental mode of translational vibration of the steel hollow frames. From the experimental study it was found that the fundamental frequency of the frames lie in the semi-rigid region. From the theoretical investigation it was found that the flexibly connected frames subjected to lateral loads exhibit larger deflection as compared to rigidly connected frames.
Key Words
steel hollow frames; cold-formed; semi-rigid; dynamic response; fundamental frequency.
Address
P. S. Joanna; Civil Engineering, Hindustan College of Engineering, Chennai, IndiarnG. M. Samuel Knight; Civil Engineering, Anna University, Chennai, IndiarnA. Rajaraman; Department of Civil Engineering, I.I.T., Madras, India
Abstract
H-shaped welded steel column members are fabricated by welding together pre-cut flanges and the web. Modern fabricators are increasingly using plasma-cutting technique instead of traditional flame cutting. Different fabrication techniques result in different degrees of geometric imperfections and residual stresses, which can have considerable influence on the strength of steel columns. This paper presents the experimental investigation based temperature profiles, geometric imperfections, and built-in residual stresses in plasma cut-welded H-shaped steel column members and in similar flame cut-welded H-shaped steel columns. Temperature measurements were taken during and immediately after the cutting operations and the welding operations. The geometric imperfections were established at closely spaced grid locations on the original plates, after cutting plates into plate strips, and after welding plate strips into columns. Geometric imperfections associated with plasma cut element and members were found to be less than those of the corresponding elements and members made by flame cutting. The
Key Words
plasma cutting; flame cutting; plasma cut-welded H-shaped steel columns; experimental; measurements; imperfections; temperature profiles; geometric imperfections; residual stresses.
Address
P. Arasaratnam and K. S. Sivakumaran; Centre for Effective Design of Structures, Department of Civil Engineering, McMaster University, Hamilton, Ontario, Canada, L8S 4L7rnKim J. R. Rasmussen; Centre for Advanced Structural Engineering, Department of Civil Engineering, The University of Sydney, Sydney, NSW 2006, Australia
