Analysis and modelling of the seismic behaviour of high ... - Ingegneria

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3. SEISMIC BEHAVIOUR OF BOLTED END PLATE BEAM-TO-COLUMN STEEL JOINTS i. When proper consideration is given to material selection and detailing, extended end plates show a cyclic performance adequate for seismic design. The considered joints exhibit a plastic rotation greater than 35 mrad; therefore, they can be classified as ductile in accordance to Eurocode 8 (2002). In detail, test results on isolated bolted Tee stubs as well complete extended end plate bolted joints have shown that the overall behaviour of the specimens under investigation is governed by the material endowed with the lowest strength, viz. the base metal, in which yielding occurs, effectively. In fact, the weld metal persists in the elastic regime while the contiguous zones are weakened owing to the sharp thermal treatments and to structural as well as shape discontinuities. ii. Component cyclic tests enable identification of the failure mode. Moreover, they allow the Code requirements on the rotational capacity of the joint to be checked. Moreover, the mechanical models provided by the Eurocodes to determine the stiffness and strength characteristics of the individual components showed little agreement with the experimental data. iii. A component model, which approximates the cyclic response of the joints on the basis of the responses of the elemental components, does not seem to possess sufficient accuracy. Conversely, the use of macro- components, incorporating some of the interaction effects among elemental components, appears to be more adequate. iv. The simulations relevant to isolated Tee stub and Complete Joint connections indicate that the numerical model with isotropic hardening rule is able to capture both the monotonic and the cyclic responses but is not able to reproduce properly stiffness and strength degradation. v. A number of parametric analyses have been performed by considering fractures initiating from weld-root defects by means of the onset cracking method. Conclusions drawn from the models indicate that: a. fracture driving force demands are reduced by using fillet welds matching the end plate material; b. welding-induced residual stresses increase the fracture demand; c. connections with σy/σu = 0.9 exhibit reduced fracture driving force demands but also limited plastic regions. The yield-to-ultimate strength reduction must comply with the requirements of plastic analysis. Besides, the study is currently concentrating on the damage evolution aspect both for the components and the joint. The availability of adequate damage assessment methods is a pre-requisite to the development of reliable hysteretic models for research as well for design purposes. 95
3. SEISMIC BEHAVIOUR OF BOLTED END PLATE BEAM-TO-COLUMN STEEL JOINTS 3.9 References 96 Adey B.T., Grondin G.Y. and Cheng J.J.R. (1998): Extended End Plate Moment Connections under Cyclic Loading. J. of Construct. Steel Res., Elsevier Applied Science, UK, 46:1-3, 435-436. AISC (1992): Seismic provisions for structural steel buildings, Chicago, USA. AISC (1997): Shape Material – ASTM A572 Gr. 50 with Special Requirements. Tech. Bull. N. 3, Chicago. Astaneh-Asl A. (1995): Seismic design of bolted steel moment-resisting frames. In Steel Tips, Structural Steel Education Council, Moraga, Calif., p. 82. ASTM E 813-89 (1989). Standard Test Method for J1c, a Measure of Fracture Toughness. Annual Book of ASTM Standards, Philadelphia; 646- 660. ASTM E 1290-93 (1993): Standard Test Method for Crack-Tip Opening Displacement (CTOD) Fracture Toughness Measurement. Philadelphia: Annual Book of ASTM Standards; 866-875. ATC (1992): Guidelines for cyclic seismic testing of components of steel structures for buildings. Rep. No. ATC-24, Applied Technology Council, Redwood City, CA. Bahaari M. R. and Sherbourne A.N. (2000): Behavior of eight-bolt large capacity end plate connections. Computers & Structures, Pergamon Press, UK, 77, 315-325. Barsom JM. and Rolfe ST. (1987): Fracture and Fatigue Control in Structures – Applications of Fracture Mechanics. Prentice-Hall. Bernuzzi C., Zandonini R. and Zanon P. (1996): Experimental analysis and modelling of semi-rigid steel joints under cyclic reversal loading. J. of Construct. Steel Res., Elsevier Applied Science, UK, 38:2, 95-123. Bertero V.V., Anderson J.C. and Krawinkler H. (1994): Performance of Steel Building Structures During the Northridge Earthquake. Rep. No. UCB/EERC-94/04. California: University of California, Berkeley. Bjorhovde R., Brozzetti J. and Colson A. (1988): Connections in Steel Structures: Behaviour, Strength & Design. Elsevier Applied Science, London, UK, 395. Bjorhovde R. et al. (1992): Connections in Steel Structures II: Behaviour, Strength & Design. AISC, Chicago, USA, 464.
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Dipartimento di Ingegneria Meccanic
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UNIVERSITÀ DEGLI STUDI DI TRENTO D
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Ai miei genitori
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INDEX 1 INTRODUCTION...............
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INDEX iii 4.10.3 Results of the PsD
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1.1 Introduction 1 1 INTRODUCTION I
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1. INTRODUCTION imposes precise con
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1. INTRODUCTION joints whilst 2D mo
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7 2 DUCTILITY AND SEISMIC RESPONSE
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2. DUCTILITY AND SEISMIC RESPONSE O
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3. SEISMIC BEHAVIOUR OF BOLTED END
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3. SEISMIC BEHAVIOUR OF BOLTED END
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5. SEISMIC BEHAVIOUR OF RC COLUMNS
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6. SUMMARY, CONCLUSIONS AND FUTURE
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