Donatello Cardone | Università della Basilicata (original) (raw)

Papers by Donatello Cardone

Monetary losses induced by earthquakes in Reinforced Concrete (RC) buildings are mainly due to da... more Monetary losses induced by earthquakes in Reinforced Concrete (RC) buildings are mainly due to damage to non-structural elements (infills, partitions, finishes, etc.). In this study, alternative retrofit strategies for reducing monetary losses in RC frame buildings are examined. They include local strengthening of infills (and partitions) and seismic isolation. The Expected Annual Loss (EAL) of a number of RC frame buildings, pre-and post-rehabilitation, is evaluated, following the time-based assessment approach proposed in the FEMA P-58 guidelines. The break-even time of each retrofit intervention is then computed, considering the initial cost of the intervention and the expected benefit in terms of EAL reduction.

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Past earthquakes have shown that seismic events may incur large economic losses in buildings. FEM... more Past earthquakes have shown that seismic events may incur large economic losses in buildings. FEMA P-58 provides engineers a practical tool for the performance seismic assessment of buildings.
In this study, FEMA P-58 is applied to a typical Italian pre-1970 reinforced concrete frame building, characterized by plain rebars as steel reinforcement and masonry infills and partitions. Given that
suitable tools for these buildings are missing in FEMA P-58, in the first part of the paper, specific fragility curves and loss functions are presented. In the second part, building performance is evaluated following a time-based assessment approach. Finally, expected economic losses in form of repair costs are derived.

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SUMMARY Performance-based earthquake engineering procedures have now developed to the point that ... more SUMMARY Performance-based earthquake engineering procedures have now developed to the point that it is possible to evaluate a range of possible decision variables, including the expected annual monetary loss (EAL). Quantification of the EAL is considered to be particularly useful because it could assist with the identification of effective design and retrofit measures that consider seismic performance over a range of intensity levels. Recognizing, however, that existing procedures for the evaluation of EAL tends to be quite time consuming, this paper builds on a recent proposal to use simplified limit state loss versus intensity relationships to compute EAL via a closed-form equation, without the need to compile an inventory of damageable components and with freedom in the choice of structural analysis method. Various developments to the simplified approach are made in this paper to allow consideration of loss thresholds, non-uniform damage distributions and the impact of differences in seismic performance in orthogonal directions. In addition, means of accounting for uncertainties in the simplified EAL assessment are described. The work has focused on the assessment of EAL for reinforced concrete frame buildings with details representative of construction practice adopted in Italy in the 1950s through to the early 1970s. By comparing loss assessment results obtained using a refined methodology with those obtained using the new guidelines developed here for two case study buildings, it is concluded that the simplified approach works well. Future research should therefore aim to further validate the approach and extend it to other building typologies and construction eras.

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Fragility and loss functions are developed to predict damage and economic losses due to earthquak... more Fragility and loss functions are developed to predict damage and economic losses due to earthquake loading in Reinforced Concrete (RC) structural components with smooth rebars. The attention is focused on external/internal beam-column joints and ductile/brittle weak columns, designed for gravity loads only, using low-strength concrete and plain steel reinforcing bars. First, a number of damage states are proposed and linked deterministically with commonly employed methods of repair and related activities. Results from previous experimental studies are used to develop empirical relationships between damage states and engineering demand parameters, such as interstory and column drift ratios. Probability distributions are fit to the empirical data and the associated statistical parameters are evaluated using statistical methods. Repair costs for damaged RC components are then estimated based on detailed quantity survey of a number of pre-70 RC buildings, using Italian costing manuals. Finally, loss functions are derived to predict the level of monetary losses to individual RC components as a function of the experienced response demand.

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Masonry infills, commonly found in frame buildings throughout Europe and other parts of the world... more Masonry infills, commonly found in frame buildings throughout Europe and other parts of the world, have performed poorly in past earthquakes, with infill damage endangering lives, causing disruption and significant monetary losses. To characterize the performance of masonry infills, commonly classified as non-structural elements, an extensive set of experimental test data is collected and examined in this work in order to develop fragility functions for the in-plane performance of masonry infills. The collected data stems from testing conducted in Europe, the Middle East and the United States and includes solid and hollow clay brick or concrete block infills, constructed to be in contact within either reinforced concrete or steel framing. The results indicate that infill masonry can exhibit first signs of damage at drifts as low as 0.2% but may not suffer complete failure until drifts as high as 2.0%. Furthermore, it is shown that masonry fragility changes significantly according to the type of infill masonry. Subsequently, a short discussion is provided to highlight the potential use of the infill fragility information within non-linear analysis models of masonry infill. Finally, repair cost estimates for infills in Italy are computed using costing-manuals and are compared with cost estimates obtained through consultation with a number of Italian building contractors, with examination of both the median and dispersion in repair costs. It is anticipated that the results of this work will be particularly useful for advanced performance-based earthquake engineering assessments of buildings with masonry infill, providing new information on the in-plane fragility, repair costs and non-linear modelling of masonry infills.

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SUMMARY Two families of passive seismic control devices exploiting the peculiar properties of sha... more SUMMARY Two families of passive seismic control devices exploiting the peculiar properties of shape memory alloy (SMA) kernel components have been implemented and tested within the MANSIDE project (Memory Alloys for New Seismic Isolation and Energy Dissipation Devices). They are special braces for framed structures and isolation devices for buildings and bridges. Their most important feature is their extreme versatility, i.e. the possibility to obtain a wide range of cyclic behaviour * from supplemental and fully re-centring to highly dissipating * by simply varying the number and/or the characteristics of the SMA components. Other remarkable properties are their extraordinary fatigue resistance under large strain cycles and their great durability and reliability in the long run. In this paper, the working mechanisms of the SMA based devices are outlined and the experimental tests carried out to verify the above-mentioned properties are extensively described.

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The results of cyclic tensile tests on superelastic NiTi shape memory alloy (SMA) wires are prese... more The results of cyclic tensile tests on superelastic NiTi shape memory alloy (SMA) wires are presented and discussed. The tests were carried out within a large experimental test programme for the MANSIDE Project, with the scope of verifying the suitability of SMA superelastic wires as kernel components for seismic protection devices. The mechanical behaviour is described by means of four fundamental quantities, namely: secant stii-ness, energy loss per cycle, equivalent damping and residual strain. The sensitivity to temperature and strain rate, as well as the innuence of strain amplitude and the eeects due to repeated cyclic deformation, are analysed in detail. The experimental results show that the characteristics of the superelastic wires are well suited for seismic applications, as both the recentring and the energy dissipating features of the devices can be easily obtained. Moreover, the innuence of the investigated parameters, within their usual range of variation in seismic protection devices, is compatible with the use of superelastic wires for practical applications. ? 2001 Published by Elsevier Science Ltd.

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The mechanical behaviour of several specimens of nickel–titanium shape memory alloy (SMA) has bee... more The mechanical behaviour of several specimens of nickel–titanium shape memory alloy (SMA) has been deeply investigated through a large experimental test program and numerical simulations, in view of their possible use as kernel components for seismic protection devices. The SMA specimens were diierent in shape (wires and bars with diierent diameter), physical characteristics (alloy composition, thermomechanical treatment and material phase) and stress mode (tension, torsion, bending and shear). The experimental tests were carried out by applying repeated cyclic deformations. Strain rate, strain amplitude, temperature and number of cycles were considered as test parameters, and their values were selected taking into account the typical range of interest for seismic applications. The aim of the experimental program was to examine the performances of the SMA elements under the working conditions they should be subjected to in a feasible seismic device, under repeated earthquake-like excitations. In this paper, the most important outcomes of the torsion tests are described and analysed in terms of three fundamental mechanical quantities: secant stiiness, energy loss and equivalent damping. The experimental results show that SMA bars subjected to torsion, especially the martensitic ones, have great potential for their use in seismic devices due to their considerable energy dissipation capacity and outstanding fatigue resistance. ?

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The objective of the prgent work is to mine advantages and drawbacks of different types of isolat... more The objective of the prgent work is to mine advantages and drawbacks of different
types of isolation systems, when seismic isolation is used as a protection strategy against
damage to internal equipment and contents. The starting point of the study is the big
experimental program of table tests on reduced-scale R/C structural models, carried
out within the MANSIDE (Memory Alloys for New Seismic Isolation DEvices) project.
Seven identical 133-scaled, bstorey frames were tested, including two fixed-base models
and four base-isolated models with different isolation systems, namely: (1) rubber
isolators, (2) steel-hysteretic system and (3), re-centring SMA (Shape Memory Alloy)
system. In this study the internal equipment is regarded as an elastic single degree of
freedom, with 2% equivalent viscous damping. Therefore, the capability of fixed-base
and base-isolated models with different isolation systems to protect light secondary systems
is evaluated by comparing the floor response spectra obtained from the storey
accelerations recorded during shaking table tests. Three different PGA's are considered,
about 0.15g, 0.39 and 0.59, respectively. All the shaking table tests are also simulated
with an accurate numerical mnodel, to validate and better understand the experimental
results. It is found that each type of isolation system reduces considerably the seis
mic effects on internal equipments in wide frequency regions. However, tuning effects
may arise in specific frequency ranges, corresponding to ,the first mode in structures
equipped with quasi-elastic (rubber) isolation systems, and to higher modes in structures
equipped with elast-plastic (steel) and nonlinear re-centering (SMA) isolation
systems

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An extensive program of shaking table tests on 1/4-scale three-dimensional R/C frames was jointly... more An extensive program of shaking table tests on 1/4-scale three-dimensional R/C frames
was jointly carried out by the Department of Structure, Soil Mechanics and Engineering
Geology (DiSGG) of the University of Basihcata, Italy, and the National Laboratory
of Civil Engineering (LNEC), Portugal. It was aimed at evaluating the effectiveness of
passive control bracing systems for the seismic retrofit of R/C frames designed for gravity
loads only. Two different types of braces were considered, one based on the hysteretic
behaviour of steel elements, the other on the superelastic properties of Shape Memory
Alloys (SMA). Different protection strategies were pursued, in order to fully exploit the
high energy dissipation capacity of steel-based devices, on one hand, and the supplemental
re-centring capacity of SMA-based devices, on the other hand. The experimental
results confirmed the great potentials of both strategies and of the associated devices in
limiting structural damage. The retrofitted model was subjected to table accelerations
as high as three times the acceleration leading the unprotected model to collapse, with
no significant damage to structural elements. Moreover, the re-centring capability of the
SMA-based bracing system was able to recover the undeforrned shape of the frame, when
it was in a near-collapse condition. In this paper the experimenta1 behaviour of the non
protected and of the protected structural models are described and compared

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The widespread use of sliding bearings for the seismic isolation of structures requires detailed ... more The widespread use of sliding bearings for the seismic isolation of structures requires detailed knowledge of their behavior and improved modeling capability under seismic conditions. The paper summarizes the results of a large experimental investigation on steel–PTFE interfaces, aimed at evaluating the effects of sliding velocity, contact pressure, air temperature and state of lubrication on the mechanical behavior of steel-PTFE sliding bearings. Based on the experimental outcomes, two different mathematical models have been calibrated, which are capable of accounting for the investigated parameters in the evaluation of the sliding friction coefficient. The first model is basically an extension of the model proposed by Constantinou et al. (1990) Journal of Earthquake Engineering, 116(2), 455–472, while the second model is derived from the one proposed by Chang et al. (1990) Journal of Engineering Mechanics, 116, 2749–2763. Expressions of the model parameters as a function of bearing pressure and air temperature are presented for lubricated and non-lubricated sliding surfaces. Predicted and experimental results are finally compared.

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The fatigue resistance of Ni–Ti shape memory alloy (SMA)-martensite bars in bending subjected to ... more The fatigue resistance of Ni–Ti shape memory alloy (SMA)-martensite bars in bending subjected to large deformation cycles has been experimentally evaluated. Firstly, fatigue tests under constant displacement amplitude have been carried out, at two different frequencies of loading. Then, the cumulative fatigue damage and fatigue life prediction of specimens loaded under variable load conditions have been investigated. Finally, the effect of low-cycle-fatigue (LCF) and plastic deformations on subsequent high-cycle-fatigue (HCF) has been studied. The experimental results point out that the frequency of loading (i.e. temperature) significantly affects the fatigue life of the specimens. The damage accumulation process seems to follow the ''Miner'' linear damage theory for low-to-high (L–H) loading sequences, while the same does not hold for high-to-low (H–L) loading sequences. Surprisingly, a small fraction of LCF life consumption seems to enhance the subsequent HCF limits.

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An extensive experimental program of shaking table tests on reduced-scale structural models was c... more An extensive experimental program of shaking table tests on reduced-scale structural models was carried out within the activities of the MANSIDE project, for the development of new seismic isolation and energy dissipation devices based on shape memory alloys (SMAs). The aim of the experimental program was to compare the behaviour of structures endowed with innovative SMA-based devices to the behaviour of conventional structures and of structures endowed with currently used passive control systems. This paper presents a comprehensive overview of the main results of the shaking table tests carried out on the models with and without special braces. Two diierent types of energy dissipating and re-centring braces have been considered to enhance the seismic performances of the tested model. They are based on the hysteretic properties of steel elements and on the superelastic properties of SMAs, respectively. The addition of passive control braces in the reinforced concrete frame resulted in signiÿcant beneÿts on the overall seismic behaviour. The seismic intensity producing structural collapse was considerably raised, interstorey drifts and shear forces in columns were drastically reduced.

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This paper describes the conceptual design, the engineering process and the implementation of an ... more This paper describes the conceptual design, the engineering process and the implementation of an impact resisting structure for volcanic shelter. Basically, the designed shelter consists of two homologous reinforced concrete shells, interconnected by suitable flexible and highly dissipative devices, which absorb and dissipate the impact energy. The shelter has been purposely designed to resist, without damage, an impact with a 150 kg mass rock, colliding with the surface of the external shell at approximately 62 m/s. The characteristics of the shelter and the process followed in its design and implementation are illustrated. Particular attention is addressed to the mechanical behaviour of the impact absorbing devices. The numerical modelling of the impact phenomenon and of the shelter structure is illustrated. Finally, the results of accurate non-linear dynamic simulation analyses for safety verifications are discussed.

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Shape Memory Alloys (SMAs) have great potential for the use in the field of civil engineering. Th... more Shape Memory Alloys (SMAs) have great potential for the use in the field of civil engineering. The authors of this manuscript have been involved, from 1996, in several experimental and theoretical studies of the application of SMAs in civil engineering, for national and international research projects. This paper provides an overview of the main results achieved, consisting in the conceptual design, implementation and testing of three families of SMA-based devices, namely: (i) special braces for framed structures, (ii) seismic isolation devices for buildings and bridges and (iii) smart ties for arches and vaults. The main advantage of using SMA-based devices in the seismic protection of structures comes from the double-flag shape of their hysteresis loops, which implies three favourable features, i.e.: self-centring capability, good energy dissipation capability and high stiffness at small displacements. The main advantage of SMArt ties comes from the thermal behaviour of SMA superelastic wires, which is opposite to that of steel rod. This implies a strong reduction of the force changes caused by variations of air temperature.

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Two full-scale isolation re-centring devices, embodying NiTi Shape Memory Alloy elements, were de... more Two full-scale isolation re-centring devices, embodying NiTi Shape Memory Alloy elements,
were designed and manufactured as the final product of a European research
project for the exploitation of SMA's in the seismic protection of structures (MANSIDE
Project). The devices were subjected to several experimental tests aimed at verifying
the feasibility and evaluating the mechanical properties of ShIA-based devices for the
passive seismic protection of buildings and bridges. In order to fully chd the applicability
of SMA-based isolation systems in real situations, the two devices were temporarily
installed in a small base-isolated building, at Rapolla, Southern Italy, which was subjected
to several in situ release tests. The complete SMA-based isolation system consisted
of the SMA re-centring devices and steel-PTFE lubricated sliding bearings. The release
tests were carried out by moving the superstructure and then suddenly releasing it.
Numerical seismic simulation analyses have also been carried out to evaluate the effects
of the variations of the mechanical characteristics of the isolation systems, including
those due to temperature, on the seismic behaviour of the building. Based on these
results, a proposal for the improvement of the performances of ShIA based isolation
systems is made and verified by numerical simulations.

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This paper presents the results of a series of experimental tests, aimed at investigating the imp... more This paper presents the results of a series of experimental tests, aimed at investigating the impact and dynamic response of a volcanic shelter. Similar shelters are to be installed in the Stromboli island (Aeolian archipelago, Sicily, Italy), to protect human lives from the pyroclastic eruptions of the volcano. Basically, the Shelter consists of two homologous reinforced concrete shells, interconnected by rubber-based special devices, which absorb and dissipate most of the impact energy. The Shelter has been specifically designed to resist, without damage, an impact with a 150 kg mass rock, knocking the surface of the external shell at 62.5 m/s speed. The experimental tests were carried out on a 1:2-scale model, using a testing apparatus purposely realised to simulate impact conditions comparable with those considered in the design. Impact energy and mass ratio between projectile and reinforced concrete shell were assumed as main experimental parameters and varied during the tests. A finite element model of the Shelter was also implemented and direct-integration time-history analyses were performed, to validate the experimental results. Reference to the Hertz's law was made to simulate the impact between the two bodies. The experimental tests proved the ability of the Shelter to resist impacts without damage. Acceptable agreement between numerical predictions and experimental results was found.

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The effectiveness of seismic isolation in protecting structural and non-structural elements from ... more The effectiveness of seismic isolation in protecting structural and non-structural elements from damage has been assessed in an extensive programme of shaking-table tests, carried out on four identical 1/3.3-scale, two-dimensional, reinforced concrete (R/C) frames. Four different isolation systems were considered, namely: (i) rubber-based, (ii) steel-based, (iii) shape memory alloy (SMA)-based and (iv) hybrid, i.e. based on both SMA and steel components, isolation systems. This paper presents a comprehensive overview of the main results of the experimental tests on base-isolated models, whose structural response is described through: (i) maximum base displacements; (ii) maximum interstorey drifts; (iii) maximum storey accelerations and (iv) maximum storey shear forces. The evolution of the fundamental frequency of vibration of the R/C frame during the tests is also described. The beneficial effects of using base isolation resulted in no or slight damage, under strong earthquakes, to both structural and non-structural members, as well as to the internal content of the building. The comparison with the experimental results obtained in shaking-table tests on similar fixed-base models emphasizes these positive aspects. Finally, advantages and drawbacks related to the use of each isolation system are discussed in the paper.

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Three different isolation systems (IS's) for bridges and viaducts are considered in the present s... more Three different isolation systems (IS's) for bridges and viaducts are considered in the present study. All of them are made of steel-PTFE sliding bearings (SB) to support the weight of the deck and auxiliary devices, based on different technologies and materials (i.e. rubber, steel and shape memory alloys), to provide re-centring and/or additional energy dissipating capability. An extensive numerical investigation has been carried out in order to (i) assess the reliability of different design approaches, (ii) compare the response of different types of IS's, (iii) evaluate the sensitivity of the structural response to friction variability due to bearing pressure, air temperature and state of lubrication and (iv) identify the response variations caused by changes in the ground motion, bridge and isolation characteristics. The nonlinear time-history analyses have been carried out using a simplified pier-deck model, where the pier is modelled as an elastic cantilever beam and the mass of the deck is connected to the pier through suitable nonlinear elements, simulating the behaviour of the IS. Both artificial and natural seismic excitations have been used in the nonlinear dynamic analyses.

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Three different Nonlinear Static Methods (NSM’s), based on pushover analysis, are applied to a 3-... more Three different Nonlinear Static Methods (NSM’s), based on pushover analysis, are applied to a 3-story,
2-bay, RC frame. They are (i) the Capacity Spectrum Method (CSM), described in ATC-40, (ii) the
Displacement Coefficient Method (DCM), presented in FEMA-273 and further developed in FEMA
356, and (iii) the N2 Method, implemented in the Eurocode 8. Pushover analyses are conducted with
DRAIN-3DX by using four different lateral force distributions, according to the acceleration profile
assumed along the height of the structure: uniform, triangular, modal-proportional, and multimodal
fully adaptive. In the numerical model, RC members are modeled as fiber elements.
The numerical predictions of each method are compared to the experimental results of the
shaking table tests carried out on two similar 1:3.3-scale structural models, with and without
infilled masonry panels, respectively. The comparison is made in terms of maximum story displacements,
interstory drifts, and shear forces. All the NSM’s are found to predict with adequate accuracy
the maximum seismic response of the structure, provided that the associated parameters are properly
estimated. The lateral load pattern, instead, is found to little affect the accuracy of the results
for the three-story model considered, even if collapse occurs with a soft story mechanism.

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