GTSTRUDL Users Group 23rd Annual Meeting and Training Seminar Marriott Hotel Delray Beach - Florida, U.S.A. June 22-25, 2011 Structural Engineering Department Mechanical Engineering Department THE MODAL PROPERTIES OF THE ‘PALAZZO LOMBARDIA’ BUILDING, THE NEW SEAT FOR THE REGIONE LOMBARDIA IN MILAN: A COMPARISON BETWEEN NUMERICAL ANALYSIS AND EXPERIMENTAL RESULTS Elena Mola, PhD – ECSD Srl, Engineering Consulting and Structural Design, Milano Prof. Alfredo Cigada – Dept. Of Mech. Eng., Politecnico di Milano Prof. Franco Mola – Dept. Of Struct. Eng., Politecnico di Milano Gianfranco Stella, SE – CAD Data Consult Srl, Milano Prof. Marcello Vanali – Dept. Of Mech. Eng., Politecnico di Milano PALAZZO LOMBARDIA: THE ARCHITECTURAL DESIGN The Dynamic Behavior of the ‘Palazzo Lombardia’ Building: Comparison between Numerical Model and Experimental Results Ing. Gianfranco Stella Ing. Chiara Pozzuoli 2 PALAZZO LOMBARDIA: FACTS AND FIGURES Credits - - OWNER: Regione Lombardia CONSTRUCTION SUPERVISION: Infrastrutture Lombarde SpA ARCHITECTURAL DESIGN: Pei Cobb Freed & Partners Architects with Caputo Partnership and Sistema Duemila STRUCTURAL DESIGN: Prof. Ing. Franco Mola CONTRACTORS: ‘Consorzio Torre’: Impregilo, Cile, C. M. B., Consorzio, Cooperative Costruzioni, Costruzioni Giuseppe Montagna, Pessina Costruzioni, Sirti, Techint Infrastrutture CONSTRUCTION STARTED: October 2006 CONSTRUCTION ENDED: November 2009 Figures total surface of the construction area: 230.338sq total surface of the Complex: 30.000sq global built surfaces: 190.000sq public spaces: 4.500sq parking spaces: 35.150sq The Dynamic Behavior of the ‘Palazzo Lombardia’ Building: Comparison between Numerical Model and Experimental Results Ing. Gianfranco Stella Ing. Chiara Pozzuoli 3 PALAZZO LOMBARDIA: STRUCTURAL DESIGN HIGHLIGHTS a. The complex is made of five lower buildings (about 40m high, called Cores 2, 3, 4, 5 and 6), surrounding the high-rise Tower (Core 1), which, at 161.20m, is currently the tallest building in Italy b. The curvilinear, intersecting shapes of the buildings define an inner covered public ‘plaza’, having an area of about 4200m2, covered by a steel truss system supporting transparent Texlon ETFE (ethylene-co-tetrafluoroethylene) cushions c. The structural system is entirely made of reinforced concrete load bearing elements, except for the Auditorium area in Core 4 and the ‘Velarium’ on top of Core 1, a three-storey high belvedere area to be used for official public purposes and rented for private events. For the two parts structural steel was employed. The Dynamic Behavior of the ‘Palazzo Lombardia’ Building: Comparison between Numerical Model and Experimental Results Ing. Gianfranco Stella Ing. Chiara Pozzuoli 4 PALAZZO LOMBARDIA: STRUCTURAL DESIGN HIGHLIGHTS OF CORE 1 1. The load bearing elements of Core 1 are entirely made of reinforced concrete: the lateral load bearing capacity is fully provided by a central stairways core, whereas the vertical structural elements are circular columns with varying cross sections, with diameters ranging between 120cm and 65cm. 2. The slabs of Core 1 starting from the ground floor are 35cm thick, fully bi-directional reinforced concrete structural systems (‘bubbledecks’): the reduction of the weight is obtained by inserting high density polyethylene (PEHD) spheres with a diameter of 270mm in the slab The Dynamic Behavior of the ‘Palazzo Lombardia’ Building: Comparison between Numerical Model and Experimental Results Ing. Gianfranco Stella Ing. Chiara Pozzuoli 5 PALAZZO LOMBARDIA: STRUCTURAL DESIGN HIGHLIGHTS OF CORE 1 3. The structural system achieved by means of steel encasing for the vertical elements and light weight ‘bubbledeck’ slabs exhibits the behaviour of a continuous plate on point supports (the columns) and continuous support (the walls of the core).The encasing elements were thus holed so that slab rebar and concrete could pass through, thus making the column-to-slab joints completely effective in bearing lateral load induced moments. The Dynamic Behavior of the ‘Palazzo Lombardia’ Building: Comparison between Numerical Model and Experimental Results Ing. Gianfranco Stella Ing. Chiara Pozzuoli 6 PALAZZO LOMBARDIA: STRUCTURAL DESIGN HIGHLIGHTS OF CORE 1 3. The foundations of Core 1 is made of a slab with a thickness ranging between 2 and 4m. Under the slab, the ground was injected with compacting grout columns, having a diameter of 1.5m, spacing between 3 and 4m, and depth between 14 and 22 m. Self compacting concrete was used to cast the lower layer of the slab, then normal concrete was used for the remaining depth. The two layers were interconnected by means of vertical steel bars purposely distributed in the slab and joined by means of steel couplers. The Dynamic Behavior of the ‘Palazzo Lombardia’ Building: Comparison between Numerical Model and Experimental Results Ing. Gianfranco Stella Ing. Chiara Pozzuoli 7 PALAZZO LOMBARDIA: STRUCTURAL DESIGN HIGHLIGHTS OF CORE 1 3. The inner stairway core is a C55 reinforced concrete hollow core element with mean rebar content of 200 kg/m3 4. The most severe lateral load condition for its pre-dimensioning is wind loading, which induces a base shear 3.3 times higher than those induced by earthquake loading 5. The inner core takes up 65% of the total vertical loads and self-weight 6. The construction method used for the stairway core is the industrialized moving formwork The Dynamic Behavior of the ‘Palazzo Lombardia’ Building: Comparison between Numerical Model and Experimental Results Ing. Gianfranco Stella Ing. Chiara Pozzuoli 8 PALAZZO LOMBARDIA: NUMERICAL ANALYSES o Finite Element Model Features • A finite element model of Core 1 was implemented, using GT STRUDL®, a commercial software for structural analysis • In order to derive the modal features of the structure, a linear dynamic modal analysis was then carried out, in order to provide accurate numerical predictions of the modal response of the building, which would be compared to a series of dynamic excitation tests that were to be run on the ‘as-built’ structure as a pre-requisite for its final validation. • 52757 6-degrees-of-freedom joints • A total of 316542 degrees of freedom • 53910 shell elements • 9088 linear element (beams and columns) • 77171 load types, • 27 basic loading conditions and 5 loading combinations The Dynamic Behavior of the ‘Palazzo Lombardia’ Building: Comparison between Numerical Model and Experimental Results Ing. Gianfranco Stella Ing. Chiara Pozzuoli 9 PALAZZO LOMBARDIA: NUMERICAL ANALYSES • The so-called ‘bubble slabs’ (i.e. cast-in-situ RC slabs lightened by means of poliethylene spheres) were modelled by means of shell elements with an equivalent thickness to provide the correct flexural stiffness. o Modeling assumptions (1) 0.20 0.30 0.33 0.35 0.35 0.40 0.44 0.45 0.65 1.83 1.90 Z the ‘Palazzo Lombardia’ Building: The Dynamic Behavior of Comparison betweenY Numerical Model and Experimental Results X Ing. Gianfranco Stella Ing. Chiara Pozzuoli 10 PALAZZO LOMBARDIA: NUMERICAL ANALYSES •In order to investigate the sensitivity of the modal properties to the effective stiffness distribution in slabs, two different meshing options were implemented. •Called NO RIGID JOINTS ,the first mesh would not take into account the stiffening effect of the columns’ effective cross sections on the joints of the slabs mesh; • The second meshing option , called TOTAL RIGID JOINTS , would take into account the presence of the columns’ cross sections by means of an additional infinitely rigid constraint imposed to the joints of the mesh where each columns was present and in its immediate vicinity. This option has been abandoned. The Dynamic Behavior of the ‘Palazzo Lombardia’ Building: Comparison between Numerical Model and Experimental Results o Modeling assumptions (2) Ing. Gianfranco Stella Ing. Chiara Pozzuoli 11 • The tirdh meshing option , called RIGID JOINTS , would take into account the same effect assuming a different thickness of element rounding the joint on the axis of column. The Dynamic Behavior of the ‘Palazzo Lombardia’ Building: Comparison between Numerical Model and Experimental Results Ing. Gianfranco Stella Ing. Chiara Pozzuoli 12 PALAZZO LOMBARDIA: NUMERICAL ANALYSES o Modeling assumptions (3) • Modal dynamic analyses were carried out assuming linear elastic behaviour of materials • A mean value of the compressive strength was derived from the compressive strenght tests carried put on cubes during the construction on the different structural elements • For the different structural elements, by applying the Model Code 90 formulation, the corresponding elastic modulus was computed The Dynamic Behavior of the ‘Palazzo Lombardia’ Building: Comparison between Numerical Model and Experimental Results Ing. Gianfranco Stella Ing. Chiara Pozzuoli 13 PALAZZO LOMBARDIA: NUMERICAL ANALYSES o Modeling assumptions (4) •The results proved that the sensitivity of the first modal frequencies and eigenvector to this parameter was much lower than that to the refinement of the mesh •for the foundation properties, a subgrade coefficient value of 2.0x10-3 N/mm3 was assumed; this was the design value used in the pre-dimensioning analyses run separately on the foundations alone The Dynamic Behavior of the ‘Palazzo Lombardia’ Building: Comparison between Numerical Model and Experimental Results Ing. Gianfranco Stella Ing. Chiara Pozzuoli 14 PALAZZO LOMBARDIA: NUMERICAL ANALYSES o Modeling assumptions (4) • Modal frequencies and modal shapes also depend on the actual mass distribution •Since the experimental dynamic excitation tests would be run at the end of construction, but before the whole static permanent loading would be in place, it was necessary to make a computation of the actual masses present on the structure at the moment of testing. •For the final simulations it was assumed that a fraction of 20% of the permanent loading would be present. The Dynamic Behavior of the ‘Palazzo Lombardia’ Building: Comparison between Numerical Model and Experimental Results Ing. Gianfranco Stella Ing. Chiara Pozzuoli 15 PALAZZO LOMBARDIA: NUMERICAL ANALYSES o Modeling assumptions (3) • Modal frequencies and modal shapes also depend on the actual mass distribution •Since the experimental dynamic excitation tests would be run at the end of construction, but before the whole static permanent loading would be in place, it was necessary to make a computation of the actual masses present on the structure at the moment of testing. •For the final simulations it was assumed that a fraction of 20% of the permanent loading would be present. •Finally, as for the foundation properties, a subgrade coefficient value of 2.0x10-3 N/mm3 was assumed; this was the design value used in the pre-dimensioning analyses run separately on the foundations alone The Dynamic Behavior of the ‘Palazzo Lombardia’ Building: Comparison between Numerical Model and Experimental Results Ing. Gianfranco Stella Ing. Chiara Pozzuoli 16 THE DYNAMIC EXCITATION TESTS Introduction Pre-test: Ambient Vibrations Operational Modal Analysis to get a first experimental estimate of the natural frequencies and mode shapes Forced Vibrations tests Stepped sine excitation with varying resolution frequency, changed accordingly to the resonance positions known from OMA. The Dynamic Behavior of the ‘Palazzo Lombardia’ Building: Comparison between Numerical Model and Experimental Results Ing. Gianfranco Stella Ing. Chiara Pozzuoli 17 THE DYNAMIC EXCITATION TESTS: INTRODUCTION Mechanical Engineering Department Politecnico di Milano Dynamic tests at real scale are a valuable tool to refine and update numerical models Static numerical models need a further refinement to account for dynamic features Mass and stiffness distributions are given at a certain uncertainty level. Damping coefficients are hard to be estimated and affected by strong non-linear behaviors A check on both static and dynamic behavior can help narrowing these uncertainties A further goal of dynamic excitation testing, which is growing in importance, is trying to lay down the basis for a proper monitoring, as intended for Palazzo Lombardia The Dynamic Behavior of the ‘Palazzo Lombardia’ Building: Comparison between Numerical Model and Experimental Results Ing. Gianfranco Stella Ing. Chiara Pozzuoli 18 THE DYNAMIC EXCITATION TESTS: FEATURES The main problems in testing a skyscraper are: a proper forecast of the mode shapes, to fix sensors in the right positions the certainty to have a proper input to excite the structure The global response is dominated by the behaviour of Core 1, which can be approximated with a cantilever beam the numerical model provided an initial approximation of the expected vibration modes and frequencies To confirm the FEM results a PRE-SET of the structure subject to ambient vibrations was carried out (Operational Modal Analysis) The Dynamic Behavior of the ‘Palazzo Lombardia’ Building: Comparison between Numerical Model and Experimental Results Ing. Gianfranco Stella Ing. Chiara Pozzuoli 19 OPERATIONAL MODAL ANALYSIS Low noise Seismic Piezo accelerometers On the 38th floor This is a typical case of Operational Modal Analysis (OMA), as the input is roughly known. Unknown input: wind and traffic even if the signal to noise ratio is less favourable in this kind of tests, acquisition through the whole week has allowed an output quality improvement thanks to continuous averaging, especially selecting the periods with higher vibration levels The Dynamic Behavior of the ‘Palazzo Lombardia’ Building: Comparison between Numerical Model and Experimental Results Ing. Gianfranco Stella Ing. Chiara Pozzuoli 20 3 AMBIENT VIBRATIONS: PSD 24 HRS Weak axis: all the 3 y-sensors measure the same 0.33 Hz 1 Strong axis: all the 3 x-sensors measure the same 2 PSD -7 CRANE 10 Compatibility with torsion: 3y has the highest peak 0.42 Hz Ampiezza [(m/s 2)2 / Hz] 0.65 Hz 02 X 02 Y 01 X 01 Y 03 X 03Y higher amplitudes as the distance from the main core increases Uncertain area, small excitation, further investigation -8 10 Any contribution at higher frequencies is not so easy detectable, having peaks close to the transducers noise floor. -9 10 0.2 0.4 0.6 0.8 1 1.2 Frequenza [Hz] 1.4 The Dynamic Behavior of the ‘Palazzo Lombardia’ Building: Comparison between Numerical Model and Experimental Results 1.6 1.8 2 Ing. Gianfranco Stella Ing. Chiara Pozzuoli 21 THE IDENTIFIED MODES (VECTORS HAVE REAL LENGTHS) 0.42 Hz mode 0.33 Hz mode 3 1 3 1 2 2 CRANE CRANE 3 1 0.65 Hz mode 2 CRANE The Dynamic Behavior of the ‘Palazzo Lombardia’ Building: Comparison between Numerical Model and Experimental Results Ing. Gianfranco Stella Ing. Chiara Pozzuoli 22 COMPARISON WITH THE NUMERICAL MODEL Natural frequency NUMERICAL NO RIGID NODE Natural frequency EXPERIMENTAL (Ambient excitation) [Hz] [Hz] 0.33 0.37 0.55 1.11 1.21 0.33 0.42 0.65 1.28 1.36 Ratio EXP / NUM 1.01 1.13 1.17 1.15 1.12 It seems reasonable!! The Dynamic Behavior of the ‘Palazzo Lombardia’ Building: Comparison between Numerical Model and Experimental Results Ing. Gianfranco Stella Ing. Chiara Pozzuoli COMPARISON WITH THE NUMERICAL MODEL Natural frequency NUMERICAL RIGID NODE Natural frequency EXPERIMENTAL (Ambient excitation) [Hz] [Hz] 0.34 0.42 0.58 1.16 1.28 0.33 0.42 0.65 1.28 1.36 Ratio EXP / NUM 0.96 1.00 1.12 1.11 1.06 It seems reasonable!! The Dynamic Behavior of the ‘Palazzo Lombardia’ Building: Comparison between Numerical Model and Experimental Results Ing. Gianfranco Stella Ing. Chiara Pozzuoli 24 COMPARISON WITH THE NUMERICAL MODEL The Dynamic Behavior of the ‘Palazzo Lombardia’ Building: Comparison between Numerical Model and Experimental Results Ing. Gianfranco Stella Ing. Chiara Pozzuoli 25 FORCED VIBRATION TESTS Based on the numerical model results and on the first operational analysis The sensors were located on three different floor levels, the 21st, the 32nd and the top floor, the 38th, considered enough to point out the first vibration mode shapes. Each floor has been instrumented with 2-axis accelerometers in the horizontal plane, capable to identify flexural modes (strong and weak axis) and torsion modes. The Dynamic Behavior of the ‘Palazzo Lombardia’ Building: Comparison between Numerical Model and Experimental Results Ing. Gianfranco Stella Ing. Chiara Pozzuoli 26 SIDE VIEW: SENSORS POSITIONS 38 32 21 The Dynamic Behavior of the ‘Palazzo Lombardia’ Building: Comparison between Numerical Model and Experimental Results Ing. Gianfranco Stella Ing. Chiara Pozzuoli 27 TOP VIEW: FLEXURAL-STRONG AXIS 5 1 2 Flexural-strong axis 3 4 6 The Dynamic Behavior of the ‘Palazzo Lombardia’ Building: Comparison between Numerical Model and Experimental Results Ing. Gianfranco Stella Ing. Chiara Pozzuoli 28 TOP VIEW: FLEXURAL-WEAK AXIS 5 2 1 Flexural-weak axis 3 4 6 The Dynamic Behavior of the ‘Palazzo Lombardia’ Building: Comparison between Numerical Model and Experimental Results Ing. Gianfranco Stella Ing. Chiara Pozzuoli 29 TOP VIEW: TORSION 5 1 2 3 4 6 Torsion The Dynamic Behavior of the ‘Palazzo Lombardia’ Building: Comparison between Numerical Model and Experimental Results Ing. Gianfranco Stella Ing. Chiara Pozzuoli 30 THE DYNAMIC TESTS: ENVIRONMENTAL EXCITATION During the tests, a rather windy day has been analyzed separately from the rest, allowing for a spectrum detection with a best signal to noise ratio. It is observed, for the first flexural mode, an increase of the acceleration peaks at different heights, as expected, and coherent with a cantilever first mode. Further confirmation of the predicted mode shapes and frequencies The Dynamic Behavior of the ‘Palazzo Lombardia’ Building: Comparison between Numerical Model and Experimental Results Ing. Gianfranco Stella Ing. Chiara Pozzuoli 31 FORCED VIBRATIONS THE MAIN TROUBLE: THE INERTIAL EXCITER Problems in producing a meaningful force at low frequencies High energies at low frequencies: -Long strokes (2 m) -Big masses (1000 kg) The Dynamic Behavior of the ‘Palazzo Lombardia’ Building: Comparison between Numerical Model and Experimental Results Ing. Gianfranco Stella Ing. Chiara Pozzuoli 32 FORCED VIBRATIONS THE MAIN TROUBLE: THE INERTIAL EXCITER • The usual test is a stepped sine • We need to transmit high force levels at low frequencies • Assumed a sine wave the force is: F ma mx 2 F = transmitted force a = peak acceleration x = peak displacement 2 = circular frequency is very low (natural frequencies below 1 Hz) → we need long strokes and high mass to gain back the very low (also squared) The Dynamic Behavior of the ‘Palazzo Lombardia’ Building: Comparison between Numerical Model and Experimental Results Ing. Gianfranco Stella Ing. Chiara Pozzuoli 33 WE HAVE DECIDED TO USE A LINEAR MOTOR PROVIDED BY SIEMENS (A SHORT MAGLEV) The Dynamic Behavior of the ‘Palazzo Lombardia’ Building: Comparison between Numerical Model and Experimental Results Ing. Gianfranco Stella Ing. Chiara Pozzuoli 34 INPUT: EXCITATION- INERTIAL EXCITER The Dynamic Behavior of the ‘Palazzo Lombardia’ Building: Comparison between Numerical Model and Experimental Results Ing. Gianfranco Stella Ing. Chiara Pozzuoli 35 OUTPUT ACCELERATION - TIME The Dynamic Behavior of the ‘Palazzo Lombardia’ Building: Comparison between Numerical Model and Experimental Results Ing. Gianfranco Stella Ing. Chiara Pozzuoli 36 THE DYNAMIC TESTS: IMPOSED INPUT EXCITATION Measurements have been analyzed through a synchronous approach, reducing spectral leakage and allowing for a correct estimation of the natural frequency positions. A substantial confirmation of the ambient vibration tests is evident, even if this time data are evaluated with respect to the given input; Also meaningful phase information are added, testifying the presence of real resonances, with a much better signal to noise ratio Amplitude [(m/s2)/N] 2 x 10 Frequency response functions -6 1.5 P381X 1 P381Y 0.5 0 0.2 P382X 0.4 0.6 0.8 1 Frequency [Hz] 1.2 1.4 P38 1.6 2Y P383X P383Y 200 Phase [°] P384X 100 P384Y 0 -100 -200 0.2 The Dynamic Behavior of the ‘Palazzo Lombardia’ Building: Comparison between Numerical Model and Experimental Results 0.4 0.6 0.8 1 Frequency [Hz] 1.2 Ing. Gianfranco Stella Ing. Chiara Pozzuoli 1.4 1.6 37 EXPERIMENTAL AND NUMERICAL RESULTS: COMPARISON AND DISCUSSION The model that took into account the stiffening effects of the columns on the slab elements better predicted the modal frequencies, but both of them matched the measured values extremely well. The ‘rigid-joints’ model, as expected, improves the predicted frequencies, particularly in the weak direction (i.e. the second vibration mode). In both cases, though, the ratio of numerical vs experimental frequencies is included in a range of less than 10% on the first five modes (down to less than 5% on the first two modes), which is extremely good, and particularly impressive for a model with this complexity and such a high number of degrees of freedom. NO SLAB-TO-COLUMN JOINT CONSTRAINT CONSTRAINED SLAB-TO-COLUMN JOINTS With foundation mass Weight = 109533 T With foundation mass Weight = 109533 T Freq. cyc/sec Ratio Ratio Gap Freq. cyc/sec Ratio Ratio Gap MODE Meas. Num. meas/num num/meas % MODE Meas. Num. meas/num num/meas % 1 0.32 0.32 0.97 1.01 -0.93 1 0.32 0.34 0.95 1.05 -5.1 2 0.40 0.37 1.04 0.92 7.60 2 0.40 0.40 0.99 1.01 -1.0 3 0.63 0.55 1.13 0.87 13.22 3 0.63 0.57 1.11 0.90 10.0 4 1.25 1.09 1.13 0.87 12.83 4 1.25 1.12 1.11 0.90 10.2 5 1.35 1.19 1.11 0.89 11.42 5 1.35 1.24 1.08 0.92 7.5 The Dynamic Behavior of the ‘Palazzo Lombardia’ Building: Comparison between Numerical Model and Experimental Results Ing. Gianfranco Stella Ing. Chiara Pozzuoli 38 EXPERIMENTAL AND NUMERICAL RESULTS: COMPARISON AND DISCUSSION o As for the modal shapes, the eigen vectors exhibit full compatibility with the measured accelerations at the floors, both in direction, proportion and sign, which confirms a modal response dominated by the cantilever flexural mode along the strong axis (Mode 1, with almost 50% normalized participation factor), followed by a cantilever flexural mode along the weak axis (Mode 2, 42% normalized participation factor) and showing torsional effects only in higher modes (for example Mode 4, involving both X and Y directions with the same normalized participation factor, much lower than the first two). Mode 1 – Freq. 0.32 Hz o Mode 2 – Freq. 0.40 Hz The Dynamic Behavior of the ‘Palazzo Lombardia’ Building: Comparison between Numerical Model and Experimental Results o Mode 4 – Freq. 1.09 Hz Ing. Gianfranco Stella Ing. Chiara Pozzuoli 39 EXPERIMENTAL AND NUMERICAL RESULTS: COMPARISON AND DISCUSSION The reason why the comparison between experimentally and numerically derived modal frequencies yielded very good results are mostly but not only related to the structural configuration. The basic conceptual design configuration of the structure is based on the optimization of the stiffness ratio of the core vs that of the columns and on the reduction of differential lateral and vertical displacements of columns and core. The dynamic behavior of the structure is thus characterized by the first two modal shapes being almost totally uncoupled inflections along the two main stiffness axes, with no major torsional effects affecting the modal response and significant torsional effects being present only in higher modes. Also, the very strict quality control procedure carried out both on the materials and on the construction methods guaranteed that the mechanical properties assumed in the design and modeling phase would be the same in the ‘as built’ structure, meaning that the estimate of the structural stiffness made by the software, based on material properties, would be very accurate The Dynamic Behavior of the ‘Palazzo Lombardia’ Building: Comparison between Numerical Model and Experimental Results Ing. Gianfranco Stella Ing. Chiara Pozzuoli 40 DEVELOP OF PROJECT An interesting develop of investigation and refining of model is related to the value assumed for the elastic behavior of fondation soil assumed for the modal analysis. NNR-TD2.2 : NO RIGID JOINT - LESS RIGID SOIL NRI-TD2.2 : RIGID JOINT - LESS RIGID SOIL NRI-TD5.0: RIGID JOINT - MORE RIGID SOIL NRI-TD2.2 versus NNR-TD2.2 : better accuracy of 2^ frequency – affectect by slab-column stiffness NRI-TD5.0 versus NRI-TD2.2 : better accuracy of all frequency 12.7 % OF ACCURACY (frequencies) 14.0 12.0 10.6 10.0 10.0 8.0 9.6 9.9 9.1 6.0 11.2 10.0 11.610.9 7.7 8.3 6.8 4.0 2.8 2.0 2.6 0.0 SHAPES 1 2 The Dynamic Behavior of the ‘Palazzo Lombardia’ Building: Comparison between Numerical Model and Experimental Results 3 4 NNR-TD2.2 NRI-TD5.0 5 NRI-TD2.2 Ing. Gianfranco Stella Ing. Chiara Pozzuoli 41 CONCLUSIONS The set of dynamic excitation tests carried out on ‘Palazzo Lombardia’ proved to be an effective and reliable tool to validate the finite element modeling assumptions and the basic conceptual choices enforced in the design phase. The structural system exhibited a good response to dynamic excitation, governed by mostly uncoupled flexural deflection vibration modes, associated to low frequencies, making it less sensitive to potential earthquake excitations. The global numerical analysis model implemented in GT STRUDL proved to be well tuned, as for the basic parameters and assumptions and able to derive the modal properties of the structure with good accuracy. The experimental tests were also an additional method to enforce a final quality control on the materials and the construction method: they highlighted a good correspondence between the ‘as-designed’ structure and the ‘as-built’ one. The numerical analysis model, thus experimentally validated, can now be used as the basis for the planned continuous monitoring activity on the Tower. The Dynamic Behavior of the ‘Palazzo Lombardia’ Building: Comparison between Numerical Model and Experimental Results Ing. Gianfranco Stella Ing. Chiara Pozzuoli 42 ACKNOWLEDGEMENTS ‘Palazzo Lombardia’: Owner: Regione Lombardia Architectural Design: Pei Cobb Freed & Partners Architects (USA) with Caputo Partnership (ITA) and Sistema Duemila (ITA) - Architectural Project Supervisor: Arch. Henry N. Cobb Structural Design: Prof. Ing. Franco Mola - ECSD Srl – Engineering Consulting & Structural Design, Milano (ITA) Construction Supervisor: Infrastrutture Lombarde Spa General Contractor: Consorzio Torre Spa Leading Contractor: Impregilo Spa - President and General Manager: Ing. Gaetano Salonia Site Technical Manager: Ing. Vinicio Scerri Construction Site General Manager and Safety Supervisor: Ing. Guglielmo Fariello - CONSTRUCTION STARTED: October 2006 - CONSTRUCTION ENDED : November 2009 The Dynamic Behavior of the ‘Palazzo Lombardia’ Building: Comparison between Numerical Model and Experimental Results Ing. Gianfranco Stella Ing. Chiara Pozzuoli 43

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