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

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4. SEISMIC RESPONSE OF PARTIAL-STRENGTH COMPOSITE JOINTS • The first one calculates the value of the behaviour factor as the ratio between the p.g.a. at the ultimate limit state, and the p.g.a. at the first yielding of the structure. q dyna pga pga u y ( 4.38 ) • The second one uses the results obtained from the non-linear static analysis (pushover curve) and determines the value of the behaviour factor by means the following formula: q stat ( 4.39 ) where µk represents the ductility factor, while Ω is the overstrength factor (Eurocode 8, 2002). The two obtained values are reported in Table 4.8. One may observe that the results are in a good agreement with the design behaviour factor q = 6 proposed by the Eurocode 8 (2002). Nevertheless, in the same Table the calculated design overstrength factor Ωd is reported. This parameter is obtained by using the formula pga a con pga pga q y g d d d d 0,40 6 where p.g.a.d is the design value of the base acceleration. p.g.a.y p.g.a.u Dynamic analysis Pushover analysis 0.25g 1.54g Overstrength factor Ω α1 αu Ω = α1 /α1 µd Ductility factor µd 0.459 1.164 2.533 3.11 qdyna 6.16 qstat 7.89 p.g.a.d 0.07g p.g.a.y 0.25g Ωd 3.75 Table 4.8. Values of the behaviour factor obtained from the analyses ( 4.40 ) 159
4. SEISMIC RESPONSE OF PARTIAL-STRENGTH COMPOSITE JOINTS The possible factors that have influenced the overestimation of the design overstrength factor should be: • the partial safety factors used during the design of the structure; • the design action amplification for accidental torsional effects; • the interstorey drift limits that should be satisfied in the design; • the difference between the design strength and the actual strength value of the 160 materials; 4.10 Pseudo-Dynamic tests on the prototype structure It is worthwhile to emphasize that quasi-static cyclic loading tests are no doubt the most effective tests to acquire data on the capacity of the structure, such as the maximum resistance and ductility. Nonetheless, to evaluate the performance of the structure in terms of complex hysteretic behaviour under earthquake-like loading pseudo-dynamic tests (PsD) are needed. Pre-test analyses of the specimen and post-test comparisons will be performed. Basing on the Performance Based Seismic Engineering (PBSE) method, the values of the peak ground acceleration (PGA) employed for the pseudo-dynamic tests were chosen, as reported in Table 4.9. PsD Tests PGA [g] OBJECTIVES 1 0,10 Elastic Test 2 0,25 Serviceability Limit State: SLS 3 1,40 Ultimate Limit State: ULS (joints’ maximum rotation equal to 35 mrad) 4 1,80 Collapse Limit State CLS Table 4.9. Values of the PGA’s for the pseudo-dynamic tests 1. Snap back PsD test with a value of acceleration equal to 0.1g was performed to measure dynamic elastic properties of the frame, viz. eigenvalues, eigenvectors and equivalent viscous damping as well as to verify the precision of the PsD algorithm. 2. The objective of the second test was to lead the structure to the elastic limit, so as provided by the EC8 for the structural Serviceability Limit State. As a result, the basic vertical- and lateral force resisting system of the structure substantially retain original strength and stiffness. Only limited structural
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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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4. SEISMIC RESPONSE OF PARTIAL-STRE
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5. SEISMIC BEHAVIOUR OF RC COLUMNS
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6. SUMMARY, CONCLUSIONS AND FUTURE
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Analysis and modelling of the seismic behaviour of high ... - Ingegneria

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