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CONTENTS
Volume 1, Number 2, June 2001
 

Abstract
The Millennium Tower is situated to the north of the center of Vienna. With a height of 202 mrnit is the highest building in Austria. Realization was improved by new methods. The tower is a typicalrnexample of mixed building technology, combining composite frames with a concrete core. Specialrnattention has been paid to the moment connections between the slim floors and the column tubes resultingrnin a drastically reduced construction time and thin slabs. The semi-continuity has been considered in therndesign at ultimate and serviceability limit states.

Key Words
structural engineering; tower block; beam-to-column joints; connections; semi-rigid; semicontinuous;rnmixed building technology.

Address
IStHM, Institute of Steel, Timber and Mixed Building Technology, University of Innsbruck, Technikerstrasse 13, A-6020 Innsbruck, Austria

Abstract
The design of tall buildings has recently provided many challenges to structural engineers.rnOne such challenge is to minimise the cross-sectional dimensions of columns to ensure greater floorrnspace in a building is attainable. This has both an economic and aesthetics benefit in buildings, whichrnrequire structural engineering solutions. The use of high strength steel in tall buildings has the ability tornachieve these benefits as the material provides a higher strength to cross-section ratio. However as thernstrength of the steel is increased the buckling characteristics become more dominant with slendernessrnlimits for both local and global buckling becoming more significant. To arrest the problems associatedrnwith buckling of high strength steel, concrete filling and encasement can be utilised as it has the affect ofrnchanging the buckling mode, which increases the strength and stiffness of the member. This paperrndescribes an experimental program undertaken for both encased and concrete filled composite columns,rnwhich were designed to be stocky in nature and thus fail by strength alone. The columns were designedrnto consider the strength in axial compression and were fabricated from high strength steel plate. Inrnaddition to the encased and concrete filled columns, unencased columns and hollow columns were alsornfabricated and tested to act as calibration specimens. A model for the axial strength was suggested andrnthis is shown to compare well with the test results. Finally aspects of further research are addressed inrnthis paper which include considering the effects of slender columns which may fail by globalrninstabilities.

Key Words
columns; composite construction; high strength steel; steel structures; tall buildings.

Address
School of Civil & Environmental Engineering, The University of New South Wales, Sydney, NSW, 2052, Australia

Abstract
Most of the portal frames are designed these days by the application of plastic analysis, withrnthe normal assumption being made that the column bases are pinned. However, the couple produced by therncompression action of the inner column flange and the tension in the holding down bolts will inevitablyrngenerate some moment resistance and rotational stiffness. Full-scale portal frame tests conducted during arnprevious research program had suggested that this moment can be as much as 20% of the moment ofrnresistance of the column. The size of this moment of resistance is particularly important for the design ofrnthe tensile capacity of the holding down bolts and also the bearing resistance of the foundation. The presentrnresearch program is aiming at defining this moment of resistance in simple design terms so that it could bernincluded in the design of the frame. The investigation also included the study of the semi-rigid behaviour ofrnthe column base/foundation, which, to a certain extent, affects the overall loading capacity and stiffness ofrnthe portal frames. A series of column bases with various details were tested and were used to calibrate arnfinite element model which is able to simulate the action of the holding down bolts, the effect of thernconcrete foundation and the deformation of the base plate.

Key Words
column base; holding down bolts; flexibility; portal frame.

Address
Manchester School of Engineering, University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom

Abstract
In order to investigate the effect of the loading rate on the mechanical behavior of SRCrnshearwalls, we conducted the lateral loading tests on the 1/3 scale model shearwalls whose edge columnsrnwere reinforced by H-shaped steel. The specimens were subjected to the reversed cyclic lateral load under arnvariable axial load. The two types of loading rate, 0.01 cm/sec for the static loading and 1 cm/sec for therndynamic loading were adopted. The failure mode in all specimens was the sliding shear of the in-filled wallrnpanel. The edge columns did not fail in shear. The initial lateral stiffness and lateral load carrying capacityrnof the shearwalls subjected to the dynamic loading were about 10% larger than those subjected to the staticrnloading. The effects of the arrangement of the H-shaped steel on the lateral load carrying capacity and thernlateral load-displacement hysteresis response were not significant.

Key Words
shear wall; loading rate; SRC edge column; sliding shear failure.

Address
Fumiya Esaki, Department of Architecture, Faculty of Engineering, Kyushu Kyoritsu University, 1-8 Jiyugaoka, Yahatanishi-ku, Kitakyushu-City, Fukuoka, 807-8585, JapanrnMasayuki Ono, Department of Architecture, Kyushu School of Engineering, Kinki University, 11-6 Kayanomori, Iizuka-City, Fukuoka, 820-8555, Japan

Abstract
This paper presents a simplified approach for the design of semi-continuous composite beamsrnin braced frames, where specific attention is given to the effect of joint rotational stiffness. A simplerncomposite beam model is proposed incorporating the effects of semi-rigid end connections and the nonprismaticrnproperties of a ?racked?steel-concrete beam. This beam model is extended to a sub-frame inrnwhich the restraining effects from the adjoining members are considered. Parametric studies are performedrnon several sub-frame models and the results are used to show that it is possible to correlate the amount ofrnmoment redistribution of semi-continuous beam within the sub-frame using an equivalent stiffness of thernconnection. Deflection equations are derived for semi-continuous composite beams subjected to variousrnloading and parametric studies on beam vibrations are conducted. The proposed method may be appliedrnusing a simple computer or spreadsheet program.

Key Words
semi-rigid connections; connection stiffness; moment capacity; sub-frame analysis; plastic hinge; non-prismatic; composite beam; moment redistribution.

Address
J.Y. Richard Liew?and K.L. Looi, Department of Civil Engineering, National University of Singapore, Blk E1A, #07-03, 1 Engineering Drive 2, Singapore 117576rnBrian Uy, School of Civil and Environmental Engineering, The University of New South Wales, Sydney, NSW, 2052, Australia

Abstract
The strengthening of reinforced concrete structures using externally bonded steel or advancedrnfibre reinforced plastic (FRP) composites is becoming increasingly common. A key factor affecting thernbehaviour and reliability of such strengthened structures is the bond strength between the steel or FRP platernand the concrete substrate. Several different experimental set-ups have previously been used to determinernbond strength. This paper presents a careful finite element analysis of the stress distributions in these testrnset-ups. Results show that stress distributions can be significantly different for different set-ups, for similarrnmaterials and geometry.

Key Words
bond strength; bond test; concrete; finite element method; FRP; shear test; steel plate; strengthening; test method.

Address
J.F. Chen, School of the Built Environment, Nottingham University, University Park, Nottingham NG7 2RD, U.K.rnZ.J. Yang?and G.D. Holt, Built Environment Research Unit, School of Engineering and the Built Environment,rnWolverhampton University, Wolverhampton WV1 1SB, U.K.

Abstract
The analysis of steel-concrete composite joints presents some particular aspects that increaserntheir complexity when compared to bare steel joints. In particular, the influence of slab reinforcement andrncolumn concrete encasement clearly change the moment-rotation response of the joint. Starting from anrnenergy approach developed in the context of steel joints, an extension to composite joints is presented inrnthis paper that is able to provide closed-form analytical solutions. In addition, the possibility of tri-linear orrnnon-linear component behaviour is also incorporated in the model, enabling adequate treatment of therninfluence of cracked concrete in tension and the softening response of the column web in compression.rnThis methodology is validated through comparison with experimental tests carried out at the University ofrnCoimbra.

Key Words
component method; composite joints; moment resistance; stiffness; non-linear equivalent elastic models.

Address
L. Simoes da Silva, Departamento de Engenharia Civil, Universidade de Coimbra Polo II, Pinhal de Marrocos, 3030 Coimbra, PortugalrnAna M. Girao Coelho, Departamento de Engenharia Civil, Instituto Superior de Engenharia de CoimbrarnQuinta da Nora, Apartado 10057, 3031-601 Coimbra, PortugalrnRui A.D. Simoes, Departamento de Engenharia Civil, Universidade de Coimbra Polo II, Pinhal de Marrocos, 3030 Coimbra, Portugal


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