Analysis and modelling of the seismic behaviour of high ... - Ingegneria
Analysis and modelling of the seismic behaviour of high ... - Ingegneria
Analysis and modelling of the seismic behaviour of high ... - Ingegneria
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6. SUMMARY, CONCLUSIONS AND FUTURE PERSPECTIVES<br />
c. connections with σy/σu = 0.9 exhibit reduced fracture driving force<br />
dem<strong>and</strong>s but also limited plastic regions. The yield-to-ultimate strength<br />
reduction must comply with <strong>the</strong> requirements <strong>of</strong> plastic analysis.<br />
Besides, <strong>the</strong> study is currently concentrating on <strong>the</strong> damage evolution aspect both<br />
for <strong>the</strong> components <strong>and</strong> <strong>the</strong> joint. The availability <strong>of</strong> adequate damage assessment<br />
methods is a pre-requisite to <strong>the</strong> development <strong>of</strong> reliable hysteretic models for<br />
research as well for design purposes. The confirmation <strong>of</strong> <strong>the</strong> above-mentioned<br />
conclusions to <strong>the</strong> complete joints tested deserves fur<strong>the</strong>r studies.<br />
6.2.2 Seismic response <strong>of</strong> partial-strength composite joints<br />
The objective <strong>of</strong> this study was <strong>the</strong> investigation <strong>of</strong> <strong>the</strong> <strong>seismic</strong> performance <strong>of</strong> a<br />
realistic size moment resisting frame structure <strong>of</strong> <strong>high</strong> ductility class according to<br />
Eurocode 8 (2002) under various levels <strong>of</strong> earthquake. Dissipative elements were<br />
conceived to be partial strength beam-to-column joints <strong>and</strong> column base joints at<br />
later stages. Some full-scale substructures, representing <strong>the</strong> interior <strong>and</strong> exterior<br />
joints, have been subjected to monotonic <strong>and</strong> cyclic tests at <strong>the</strong> Laboratory for<br />
Materials <strong>and</strong> Structures Testing <strong>of</strong> <strong>the</strong> University <strong>of</strong> Pisa in Italy. Experimental<br />
results <strong>and</strong> three-dimensional finite element analysis <strong>of</strong> composite substructures<br />
has allowed <strong>the</strong> composite joints to be calibrated; <strong>and</strong> some inelastic phenomena<br />
characterizing <strong>the</strong>ir <strong>behaviour</strong>, such as <strong>the</strong> distribution <strong>of</strong> longitudinal stresses in<br />
<strong>the</strong> composite slab around <strong>the</strong> composite columns <strong>and</strong> <strong>the</strong> distribution <strong>of</strong> stresses<br />
in <strong>the</strong> column web panel <strong>and</strong> flanges to be understood. Moreover, analyses have<br />
demonstrated <strong>the</strong> adequacy <strong>of</strong> three-dimensional finite element models based on<br />
<strong>the</strong> smeared crack approach. The parametric analyses conducted both on exterior<br />
<strong>and</strong> interior joints have revealed that <strong>the</strong> full activation <strong>of</strong> Mechanisms 1 <strong>and</strong> 2 in<br />
<strong>the</strong> concrete slab causes a stiffening <strong>and</strong> streng<strong>the</strong>ning <strong>of</strong> joints. This represents<br />
<strong>the</strong> most favourable design situation also due to a substantial increase <strong>of</strong> <strong>the</strong><br />
effective breadth. None<strong>the</strong>less, <strong>the</strong> aforementioned mechanisms have not <strong>the</strong><br />
same stiffness, exhibiting Mechanism 1 a greater stiffness than Mechanism 2.<br />
Therefore, it is not easy to benefit from <strong>the</strong> strength <strong>of</strong> both mechanisms. For <strong>the</strong><br />
exterior joint <strong>the</strong> full activation <strong>of</strong> Mechanism 2 is <strong>the</strong> mot favourable design<br />
situation, while for <strong>the</strong> interior joint Mechanism 1 seems to be more effective, owing<br />
to <strong>the</strong> interaction phenomena between <strong>the</strong> two parts <strong>of</strong> <strong>the</strong> composite slab. The<br />
quantification <strong>of</strong> <strong>the</strong> stiffness corresponding to <strong>the</strong> activation <strong>of</strong> Mechanism 1 <strong>and</strong><br />
<strong>of</strong> Mechanism 2 analysed in <strong>the</strong> parametric study performed in this work clearly<br />
imposes fur<strong>the</strong>r study. Simulation <strong>and</strong> implementation in FE codes <strong>of</strong> <strong>the</strong><br />
deteriorating <strong>behaviour</strong> <strong>of</strong> dissipative components <strong>of</strong> <strong>the</strong> joints, by means <strong>of</strong> robust<br />
hysteretic models, deserves fur<strong>the</strong>r studies.<br />
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