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CONTENTS
Volume 1, Number 1, March 2001
 

Abstract
Due to aesthetic, economic, and structural performance, the use of structural hollowrnsections as columns in both continuous moment resisting and nominally pinned construction is attractive.rnConnecting the beams to these sections is somewhat problematic as there is no access to the interior ofrnthe section to allow for the tightening of a standard bolt. Therefore, bolts that may be tightened fromrnone side, i.e., blind bolts, have been developed to facilitate the use of site bolting for this arrangement.rnThis paper critically reviews available information concerning blind bolting technology, especially thernperformance of fasteners in shear, tension, and moment resisting connections. Also provided is anrnexplanation of the way in which the results have been incorporated into design guidance covering thernparticular case of nominally pinned connections. For moment resisting connections, it is concluded thatrnwhilst the principle has been adequately demonstrated, sufficient data are currently not available tornpermit the provision of authoritative design guidance. In addition, inherent flexibilities in the connectionsrnmean that performance equivalent to full strength and rigid is unlikely to be achievable: a semicontinuousrnapproach to frame design will therefore be necessary.

Key Words
blind bolts; bolts; fasteners; hollow sections; joints; simple connections; moment connections;rnstructural design; tubular construction.

Address
T. C. Barnett?and W. Tizani, School of Civil Engineering, The University of Nottingham, University Park, Nottingham NG7 2RD, U.K.rnD. A. Nethercot, Department of Civil and Environmental Engineering, Imperial College of Science, Technology and Medicine, London SW7 2BU, U.K.

Abstract
The Rosette-joining system is a completely new press-joining method for cold-formed steelrnstructures. One Rosette-joint has a shear capacity equal to that of approximately four screws or rivets.rnThe Rosette thin-walled steel truss system presents a new fully integrated prefabricated alternative tornlight-weight roof truss structures. The trusses are built up on special industrial production lines fromrnmodified top hat sections used as top and bottom chords and channel sections used as webs which arernjoined together with the Rosette press-joining technique to form a completed structure easy to transportrnand install. A single web section is used when sufficient but can be strengthened by double-nesting twornseparate sections or by using two lateral profiles where greater compressive axial forces are met. Anrnindividual joint in the truss can be strengthened by introducing a hollow bolt into the joint hole. Thernbolt gives the connection capacity a boost of approximately 20%. A series of laboratory tests havernbeen carried out in order to verify the Rosette truss system in practice. In addition to compression testsrnon individual sections of different lengths, tests have also been done on small structural assemblies andrnon actual full-scale trusses of a span of 10 metres. Design calculations have been performed on selectedrnroof truss geometries based on the test results, FE-analysis and on the Eurocode 3 and U.S.(AISI)rndesign codes.

Key Words
Rosette-joint; truss testing; light-weight steel; roof truss; cold-formed steel; steel sheet joining.

Address
Laboratory of Steel Structures, Department of Civil and Environmental Engineering Helsinki University of Technology, P.O. Box 2100, FIN-02015 HUT, Finland

Abstract
In this paper an experimental study is performed on end-plate type joints. The testrnarrangement represents a column-base joint of a steel frame. Altogether six specimens were tested, eachrnof them subjected to cyclic loading. The specimens were carefully designed by performing detailedrnpreliminary calculations so that they would present typical behaviour types of end-plate joints. On thernbasis of the experimentally established moment-rotation relationship, the cyclic characteristics of eachrnspecimen have been calculated and compared to one another. The results are evaluated, qualitative andrnquantitative conclusions are drawn.

Key Words
experimental testing; bolted connections; joints; cyclic behaviour; hysteresis loops;rnfailure mode; beam-column joints.

Address
Sandor Adany, Department of Structural Mechanics, Budapest University of Technology and Economics, HungaryrnLuis Calado, DECivil, Instituto Superior Tecnico, Lisbon, PortugalrnLaszlo Dunai, Department of Steel Structures, Budapest University of Technology and Economics, Hungary

Abstract
A series of tests on concrete-filled SHS (Square Hollow Section) stub columns (twenty),rncolumns (eight) and beam-columns (twenty one) were carried out. The main parameters varied in therntests are (1) Confinement factor ( x) from 1.08 to 5.64, (2) concrete compression strength from 10.7MParnto 36.6MPa, (3) tube width to thickness ratio from 20.5 to 36.5. (4) load eccentricity (e) from 15 mm torn80 mm and (5) column slenderness ( l) from 45 to 75. A mechanics model is developed in this paperrnfor concrete-filled SHS stub columns, columns and beam-columns. A unified theory is described where arnconfinement factor ( x) is introduced to describe the composite action between the steel tube and filledrnconcrete. The predicted load versus axial strain relationship is in good agreement with stub column testrnresults. Simplified models are derived for section capacities and modulus in different stages of therncomposite sections. The predicted beam-column strength is compared with that of 331 beam-columnrntests with a wide range of parameters. A good agreement is obtained. The predicted load versus midspanrndeflection relationship for beam-columns is in good agreement with test results. A simplified modelrnis developed for calculating the member capacity of concrete-filled SHS columns. Comparisons are madernwith predicted columns strengths using the existing codes such as LRFD (AISC 1994), AIJ (1997), andrnEC4 (1996). Simplified interaction curves are derived for concrete-filled beam-columns.

Key Words
composite actions; concrete-filled tubes; mechanics model; steel hollow sections; stub columns;columns; beam-columns; constraining factor; section capacity; member capacity.

Address
Lin-Hai Han, College of Civil Engineering and Architecture, Fuzhou University, Gongye Road 523, Fuzhou, Fujian Province, 350002, ChinarnXiao-Ling Zhao, Department of Civil Engineering, Monash University, Clayton, VIC 3168, AustraliarnZhong Tao, College of Civil Engineering and Architecture, Fuzhou University, Gongye Road 523, Fuzhou, Fujian Province, 350002, China

Abstract
Actual buckling curves are always characterised by the erosion of ideal buckling curves. Inrncase of compact sections this erosion is due to the imperfections, while for thin-walled members, arnsupplementary erosion is induced by the phenomenon of coupled instabilities. The ECBL approach-rnErosion of Critical Bifurcation Load - represents a practical and convenient tool to characterise therninstability behaviour of thin-walled members. The present state-of-art paper describes the theoreticalrnbackground of this method and the applications to cold-formed steel sections in compression andrnbending. Special attention is paid to the evaluation methods of erosion coefficient and to their validation.rnThe ECBL approach can be also used to the plastic-elastic interactive buckling of thin-walled members,rnand the paper provides significant results on this line.

Key Words
thin-walled steel sections; local buckling; overall buckling; critical load; coupled instabilities;rnimperfections; erosion; coupling range; buckling curves; local plastic mechanism.

Address
Department of Steel Structures and Structural Mechanics, Civil Engineering and Architecture Faculty,?olitehnica?University of Timisoara, Stadion 1, RO-1900, Timisoara, Romania

Abstract
Architectural steel structures with visible tension and compression members are becomingrnmore prevalent as a popular form of construction that reflects the nature of the resistance to the appliedrnloads. These members require the use of structural steel pins at their ends to ensure either axial tensionrnor axial compression in the members. Structural pins have been used as a means of connection forrncenturies and it would appear that their behaviour is relatively well understood. However, the rules forrnthe design of pins vary quite considerably from code to code and this has caused some confusionrnamongst consulting structural engineers operating internationally. To provide some insight into thisrnproblem, a comprehensive testing program has been carried to examine the influence of parameters suchrnas pin diameter, material properties of the pin, thickness of the loading plates, material properties of thernloading plates and the distance of the pin to the edge of the loading plates. The modes of failure havernbeen carefully examined. Based on this study, modifications to current design procedures are proposedrnthat properly take into account the different possible modes of failure.

Key Words
bearing; design; failure; pins; shear; steel structures; strength; tests.

Address
School of Engineering and Industrial Design, University of Western Sydney, PO Box 10, Kingswood, NSW 2747, Australia

Abstract
This paper presents an effective, reliable and accurate method for prediction of structuralrnbehaviour of steel frames at elevated temperature. The refined plastic hinge method, which has beenrnused successfully in the second-order elasto-plastic analysis of steel frames at ambient conditions, isrnadopted here to allow for time-independent fire effects. In contrast to the existing rigorous finiternelement programs, the present method uses the advanced analysis technique that provides a simplernand reliable means for practical study of the behaviour of steel frames at elevated temperature by arnlimiting stress model. The present method is validated against other test and numerical results.

Key Words
elastic-plastic analysis; plastic hinge analysis; steel frames; elevated temperature; fire.

Address
Department of Civil and Structural Engineering, The Hong Kong Polytechnic University, Hong Kong SAR, Hong Kong

Abstract
Overpressurization can occur due to the ignition of flammable vapors existing insidernaboveground oil storage tanks. Such accidents could happen more frequently than other types ofrnaccident. In the tank design, when the internal pressure increases, the sidewall-to-roof joint isrnexpected to fail before failure occurs in the sidewall-to-bottom joint. This design concept is the socalledrn?rangible roof joint?introduced in API Standard 650. The major failure mode is bifurcationrnbuckling in this case. This paper presents the bifurcation buckling pressures in both joints underrninternal pressure. Elastic and elastic-plastic axisymmetric shell finite element analysis was performedrninvolving large deformation in the prebuckling state. Results show that API Standard 650 does notrnevaluate the frangible roof joint design conservatively in small diameter tanks.

Key Words
finite element method; axisymmetric shell; structural analysis; bifurcation buckling;rnelastic-plastic problem; large deformation; oil storage tank; internal pressure; frangible roof design.

Address
Formerly Koyo Iron Works & Construction Company Tokyo, Japan

Abstract
An experimental study was conducted to evaluate the effects of loading sequence andrnlateral bracing on the behavior of reduced beam section (RBS) steel moment frame connections. Fourrnfull-scale moment connections were cyclically tested-two with a standard loading history and thernother two with a near-fault loading history. All specimens reached at least 0.03 radian of plasticrnrotation without brittle fracture of the beam flange groove welds. Two specimens tested with the nearfaultrnloading protocol reached at least 0.05 radian of plastic rotation, and both experienced smallerrnbuckling amplitudes at comparable drift levels. Energy dissipation capacities were insensitive to therntypes of loading protocol used. Adding a lateral bracing near the RBS region produced a higherrnplastic rotation; the strength degradation and buckling amplitude were reduced. A non-linear finiternelement analysis of a one-and-a-half-bay beam-column subassembly was also conducted to study thernsystem restraint effect. The study showed that the axial restraint of the beam could significantlyrnreduce the strength degradation and buckling amplitude at higher deformation levels.

Key Words
Northridge earthquake; reduced beam section (RBS) moment connection; steelrnmoment connection; near-fault ground motion; loading protocol; lateral bracing, system restraint.

Address
Qi-Song ?ent?Yu, Degenkolb Engineers, San Francisco, CA 94104, U.S.A.rnChia-Ming Uang, Department of Structural Engineering, University of California, San Diego, La Jolla, CA 92093-0085, U.S.A.


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