Papers by Vincenzo Bianco
Proceedings of the 6th International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering (COMPDYN 2015), 2017
This paper presents a study of a reconstruction hypothesis of collapsed masonry vaults with archa... more This paper presents a study of a reconstruction hypothesis of collapsed masonry vaults with archaeological value, by taking advantage of the features of frictional bearings, either flat or curvilinear. Such study finds a natural application to the case of the "Galleria delle Volte Crollate", which is a collapsed rubble masonry barrel vault, dating back to the I century BC and placed in the Roman Forum, in Italy. The proposed intervention strategy is based on the need to fulfill both philological and structural criteria. As to the former, the solution has to reconstruct the original geometry, while suggesting the historical memory of the occurred collapse. As to the latter, both geometrical and tribological features of the isolation system have to be designed in order to fulfill both static and seismic ultimate limit states. This design can be carried out by means of a parametric study. In fact, based on the case-study herein dealt with, parametric studies are conducted in order to single out the values of the parameters corresponding to the optimal solution. Non-linear dynamical analyses with sitespectrum compatible accelerograms are performed by means of the commercial Finite Element software SAP2000 ®. The innovative aspects of the proposed solutions are highlighted along with limits and possible further developments.
Multibody Kinematics of the Double Concave Curved Surface Sliders: From Supposed Compliant Sliding to Suspected Stick-Slip
Practice Periodical on Structural Design and Construction
AbstractThe double-concave curved-surface slider isolators are tribological systems composed of t... more AbstractThe double-concave curved-surface slider isolators are tribological systems composed of the assemblage of three rigid bodies that include two concave spherical plates and a straight cylinde...
Mechanical Modelling of Friction Pendulum Isolation Devices
Even though different versions of the Friction Pendulum Devices (FPD) can be found on the market ... more Even though different versions of the Friction Pendulum Devices (FPD) can be found on the market and their effectiveness has been extensively proven by means of numerous experimental campaigns carried out worldwide, many aspects concerning their mechanical behaviour still need to be clarified. These aspects concern, among others: (1) the sequence of sliding on the several concave surfaces, (2) the influence of temperature on the frictional properties of the coupling surfaces, (3) the possibility of the stick-slip phenomenon, (4) the possibility of impact-induced failure of some components, (5) the geometric compatibility, and so on. These aspects are less clear the larger the number of concave surfaces of which the device is composed. This paper presents a new way of modelling the mechanical behaviour of the FPDs, by fulfilling: (1) geometric compatibility, (2) kinematical compatibility, (3) dynamical equilibrium, and (4) thermo-mechanical coupling.
Fine-Tuning of Modelling Strategy to Simulate Thermo-Mechanical Behaviour of Double Friction Pendulum Seismic Isolators Ust Estimator
NED University Journal of Research, 2019
The use of friction pendulum devices has recently attracted the attention of both academic and pr... more The use of friction pendulum devices has recently attracted the attention of both academic and professional engineers for the protection of structures in seismic areas. Although the effectiveness of these has been shown by the experimental testing carried out worldwide, many aspects still need to be investigated for further improvement and optimisation. A thermo-mechanical model of a double friction pendulum device (based on the most recent modelling techniques adopted in multibody dynamics) is presented in this paper. The proposed model is based on the observation that sliding may not take place as ideally as is indicated in the literature. On the contrary, the fulfilment of geometrical compatibility between the constitutive bodies (during an earthquake) suggests a very peculiar dynamic behaviour composed of a continuous alternation of sticking and slipping phases. The thermo-mechanical model of a double friction pendulum device (based on the most recent modelling techniques adopte...
Archives of Civil and Mechanical Engineering, 2019
Thermomechanical models of flat, single and double friction pendulum bearings
Friction pendulums are relatively new and cheaper seismic isolators that is increasingly attracti... more Friction pendulums are relatively new and cheaper seismic isolators that is increasingly attracting the interest of both the technical and scientific communities as an alternative to the already widely adopted elastomeric ones. Even if its effectiveness has been extensively proved, many aspects concerning the behavior under seismic action still need to be clarified. One of these is the effect of the heat developed by friction during the sliding of the surfaces in contact, which could significantly influence the superficial properties of the sliding surfaces and, consequently, the overall performance of the isolating system, due to eventual recoupling of the structure with the ground shaking. The most commonly used methods to compute the temperature rises during motion are based on the solution of heat conduction problems on a semi-infinite body under intermittent heat pulses and therefore require the computation of convolution integrals. In this work a very simple alternative for the computation of the temperature changes during motion induced by frictional heating is proposed, on the basis of suitable thermo-mechanical rheological elements. The effectiveness of the modeling is then validated through the numerical simulation of some experimental tests carried out both on flat bearings and friction pendulums
Proceedings of the 6th International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering (COMPDYN 2015), 2017
Friction Pendulum Devices (FPDs) are strongly attracting the attention of both Academic and Techn... more Friction Pendulum Devices (FPDs) are strongly attracting the attention of both Academic and Technical Communities of Engineers concerned with the development of strategies for the protection of structures against earthquakes. Several versions of such devices can be found on the market, ranging from the Single, to the Double and up to the so-called Triple Friction Pendulum. Those devices are characterized by an increasing number of kinematic pairs and corresponding sliding plates. Even though their effectiveness has extensively been proven by means of numerous experimental campaigns carried out worldwide, it seems that many aspects concerning their mechanical behavior still need to be clarified. These aspects concern, among others: 1) the sequence of sliding on the several concave surfaces, 2) the influence of temperature on the frictional properties of the coupling surfaces, 3) the possibility of alternation of mechanical sticking and slipping phases, 4) the possibility of impact-induced rupture of some components, and so on. Those aspects are less clear the larger the number of concave surfaces the device is composed of. With the aim to contribute to a better understating of the mechanical behavior of the multiple friction pendulum devices, a new mechanical interpretation of their behavior was formulated and the relevant model was developed. Such model is based on a rigorous, though simplified, mechanical approach. Starting from the analysis of a double pendulum device, which comprises two stainless steel concave plates facing each other and a convex-faced pad coated with polytetrafluoroethylene (PTFE), the mechanical model envisages the decomposition of each time-instant of the dynamic time-history in two phases. For each phase the device is modelled by an open kinematic chain of rigid bodies differently constrained between each other. Moreover, the model is based on the fulfillment of 1) geometric compatibility, 2) kinematic compatibility, 3) dynamical equilibrium and 4) thermo-mechanical coupling.
Buildings, 2021
In seismic risk estimation, among the different types of fragility curves used (judgement-based, ... more In seismic risk estimation, among the different types of fragility curves used (judgement-based, mechanical, empirical/observational, hybrid), the mechanical ones have the twofold advantage of allowing a better control over the basic parameters and of representing a validation test of the consistency of empirical/observational ones. In this study, fragility curves of RC frames with column-driven failures are obtained from a simplified analytical pushover method implemented in a simple spreadsheet, thus allowing the user to perform a large number of analyses. More importantly, the proposed method introduces the concept that Limit States at the structural level are obtained consequent to the attainment of the same Limit States at the local level, in the columns’ sections. This avoids using additional criteria, such as interstorey drift thresholds. This simple analytical model allows for rapid development of fragility curves, for any Limit State, of different building typologies identi...
The adoption of Friction Pendulum Devices (FPD), as a cheaper alternative to the elastomeric bear... more The adoption of Friction Pendulum Devices (FPD), as a cheaper alternative to the elastomeric bearings, has caught the attention of both academic and technical communities, in the last decades. Even though different versions of such devices can be found on the market and their effectiveness has been extensively proven by means of numerous experimental campaigns carried out worldwide, many aspects concerning their mechanical behaviour still need to be clarified. These aspects concern, among others: 1) sequence of sliding on the several concave surfaces, 2) influence of temperature on the frictional properties of the coupling surfaces, 3) possibility of mechanical stick-slip phenomena, 4) possibility of impact-induced failure of some components, 5) geometric compatibility, and so on. Those aspects are less clear the larger the number of concave surfaces the device is composed of. This paper presents a new way of modelling the mechanical behaviour of the FPDs, by fulfilling 1) geometric...
Buildings, 2021
This paper deals with the design of the seismic rehabilitation of a case-study building located i... more This paper deals with the design of the seismic rehabilitation of a case-study building located in Florence, Italy. The particular reinforced concrete building hosts an important operational center of the main company that manages the Italian highway network. It is composed of the juxtaposition of three reinforced concrete edifices standing out from a common basement. The design of the interventions for the seismic rehabilitation of this case study posed different challenges, some even in contrast with each other. The main design challenge was to reach the seismic retrofitting, due to the strategic role of the activities hosted herein, safeguarding as much as possible the peculiarity of the architectural elements. Moreover, the design was made harder by the presence of existing thermal joints between adjacent edifices which were inadequate to prevent the latter from pounding upon each other during an earthquake. This outcome yielded the need to intervene by enlarging the gap between...
Energy-based method to design hysteretic bracings for the seismic rehabilitation of low-to-medium rise RC frames
Bulletin of Earthquake Engineering, 2021
In this study an energy-based method for the design of passive Energy Dissipative Bracing (EDB) s... more In this study an energy-based method for the design of passive Energy Dissipative Bracing (EDB) systems is presented, as a retrofit technique for existing reinforced concrete buildings. A comprehensive literature overview concerning the design of hysteretic bracing systems based on various design philosophies, such as force-, displacement- or energy-based, is provided. The proposed method is suitable for low to medium height buildings which exhibit shear-type behaviour. The procedure is based on the principle of optimum strength distribution that enables the distribution of damage/energy and avoids its concentration at a single storey. Initially the design strength of EDB system at the base is determined and subsequently the strength of storeys above is evaluated through a shear coefficient obtained from numerical analysis. The efficiency of the proposed method is verified by performing non-linear static and non-linear dynamic analysis of three reinforced concrete frames designed with obsolete codes of pre-1980s. Furthermore, the results of the proposed method are compared with two other procedures selected in the literature. The validity of each procedure is discussed based on the results of non-linear static and non-linear dynamic analyses.
Pounding Response Spectra of Bridge Decks
Applied Mechanics and Materials, 2016
Pounding-induced damage to structures, either buildings or bridges, is systematically observed af... more Pounding-induced damage to structures, either buildings or bridges, is systematically observed after significant earthquakes. This has emphasized the necessity of accounting for this phenomenon either in the design of new bridges or the seismic assessment of existing bridges. For this reason, practitioners concerned with bridge structures should be provided with concise computational tools to correctly quantify the effects due to pounding. One such tool is represented by pounding spectra, which were already introduced a couple of decades ago. This work presents a proposal of simplified equations for pounding-related displacement spectra. The first part of this paper presents the computational aspects arising when modeling such complex phenomenon. The second part presents the results of numerical analyses, in terms of displacement spectra. The third part presents a set of simple expressions to allow practitioners easily evaluate pounding-related effects in terms of displacement ampli...
Advances in FRP Composites in Civil Engineering, 2011
The need to provide a rational explanation to the observed peculiar failure mode affecting the be... more The need to provide a rational explanation to the observed peculiar failure mode affecting the behaviour, at ultimate, of a Reinforced Concrete (RC) beam strengthened in shear by Near Surface Mounted (NSM) Fibre Reinforced Polymer (FRP) strips, led the authors to develop a comprehensive numerical model for simulating the NSM shear strength contribution to RC beams throughout the entire loading process as function of the Critical Diagonal Crack (CDC) opening angle. That model was respectful of equilibrium, kinematic compatibility and constitutive laws. Despite its high level of prediction accuracy, taking into account all of the possible failure modes, as well as the interaction among adjacent strips, that model resulted relatively complex to be easily implemented in a practitioners-addressed building regulations code. Yet, it can be conveniently simplified into a more user-friendly and closed-form design formula. Crucial point of that simplification is the development of a reliable constitutive analytical law providing the single strip strength as function of the imposed end slip. This paper presents the modelling strategy adopted to determine that constitutive law, as well as its final analytical expression.
Journal of Structural Engineering, 2011
This paper presents a closed-form procedure to evaluate the shear strength contribution provided ... more This paper presents a closed-form procedure to evaluate the shear strength contribution provided to a Reinforced Concrete (RC) beam by a system of Near Surface Mounted (NSM) Fiber Reinforced Polymer (FRP) strips. This procedure is based on the evaluation of: a) the constitutive law of the average-available-bond-length NSM FRP strip effectively crossing the shear crack and b) the maximum effective capacity it can attain during the loading process of the strengthened beam. Due to complex phenomena, such as: a) interaction between forces transferred through bond to the surrounding concrete and the concrete fracture, and b) interaction among adjacent strips, the NSM FRP strip constitutive law is largely different than the linear elastic one characterizing the FRP behavior in tension. Once the constitutive law of the average-available-bond-length NSM strip is reliably known, its maximum effective capacity can be determined by imposing a coherent kinematic mechanism. The self-contained and ready-to-implement set of analytical equations and logical operations is presented along with the main underlying physical-mechanical principles and assumptions. The formulation proposed is appraised against some of the most recent experimental results, and its predictions are also compared with those obtained by a recently developed more sophisticated model.
Engineering Structures, 2012
This paper presents the results of a parametric study carried out with a a mechanical model recen... more This paper presents the results of a parametric study carried out with a a mechanical model recently developed to simulate the shear strength contribution provided by a system of Near Surface Mounted (NSM) Fiber Reinforced Polymer (FRP) strips applied to a Reinforced Concrete (RC) beam. That model, developed fulfilling equilibrium, kinematic compatibility and constitutive laws of both materials, concrete and FRP, and local bond between themselves, takes into consideration the possibility that the NSM strips may fail due to: loss of bond (debonding), concrete semi-conical tensile fracture or strip tensile rupture. The model also takes into consideration: a) interaction between progressive force transferred by bond to the surrounding concrete and its tensile fracture and b) bi-directional interaction among adjacent strips placed on the two sides of the strengthened beam cross-section web. In the first part of the paper attention is focused on the bond-based behavior of a single NSM FRP strip mounted on a concrete prism. The influence of each geometrical-mechanical parameter on the peak force transferable through bond stresses to the surrounding concrete, excluding the possibility of either concrete fracture and strip rupture, is analyzed. In the second part of the paper attention is focused on the comprehensive behavior of a single NSM FRP strip mounted on a concrete prism. The influence of each geometrical-mechanical parameter on the peak force transferable to the surrounding concrete, also including the possibility of both concrete fracture and strip rupture, is analyzed. The third part of the paper is devoted at assessing the influence of each geometrical-mechanical parameter on the maximum shear strength contribution provided by a system of NSM FRP strips applied to a RC beam. The results of these studies are presented along with the main findings.
Composites Part B: Engineering, 2014
This paper presents the closing step of a synthesis process aiming at deriving, from a previously... more This paper presents the closing step of a synthesis process aiming at deriving, from a previously developed more complex model, a simple design formula to evaluate the shear strength contribution provided by a system of Near Surface Mounted (NSM) Fiber Reinforced Polymer (FRP) strips to a Reinforced Concrete (RC) beam. The self-contained and ready-to-implement set of analytical equations and logical operations is presented along with the main underlying physical-mechanical principles and assumptions. The formulation proposed is appraised against some of the most recent experimental results and its predictions are also compared with those obtained by the two previous and more sophisticated versions of the same modeling strategy. Monte Carlo simulations are carried out in order to appraise the sensitivity of the NSM shear strength contribution prediction to the value assumed by the input parameters.
Shear strengthening of RC beams by means of FRP strips glued by a structural adhesive into thin s... more Shear strengthening of RC beams by means of FRP strips glued by a structural adhesive into thin shallow slits cut in the cover of the web lateral faces, is becoming a popular technique. Nonetheless, many aspects related to the mechanical behaviour and relevant failure modes still need to be clarified. A recent experimental-analytical investigation has demonstrated that, besides debonding and tensile rupture of the strip, the semi-conical tensile fracture of concrete surrounding the strip should be considered among the possible failure modes. A comprehensive analytical model for predicting the NSM strips contribution to the shear strength of RC beams was also developed. Despite its consistency with experimental results, that model had room for improvements. The upgraded version of that analytical model is herein presented and appraised on the basis of some among the most recent experimental results. This appraisal shows the high level of accuracy and potentialities of that modelling strategy arise.
The occurrence of a failure mode, different from debonding, consisting on the detachment, from th... more The occurrence of a failure mode, different from debonding, consisting on the detachment, from the beam core, of "two concrete lateral walls" containing the glued laminates, highlights the paramount importance of concrete mechanical properties on the effectiveness of NSM shear strengthening technique. A new mechanical-analytical interpretation of the phenomenon affecting the ultimate behaviour of RC beams NSM-strengthened in shear is presented along with the main findings. This approach takes into account the possibility that the shear strengthening contribution of the NSM laminates can be limited by the three following failure modes: debonding, concrete tensile fracture and laminates' tensile rupture. The interaction between laminates can be also accounted for. The proposed mechanical interpretation of the NSM laminates behaviour can be extended to NSM rods.
Shear strength contribution provided by concrete f V Ultimate shear strength contribution provide... more Shear strength contribution provided by concrete f V Ultimate shear strength contribution provided by the FRP system fi V Ultimate shear strength contribution provided by th i-th element , f k V NSM shear strength contribution in correspondence of the k-th configuration , DM f k V NSM CFRP laminate ultimate shear resistance according to the Debonding Model in the k-th configuration p fi V Ultimate force that can be resisted by the i-th element parallely to its axis , p fi k V Shear strength contribution provided by the i-th laminate of the k-th configuration parallely to its orientation , p cf fi V Ultimate force that can be resisted by the i-th element parallely to its axis due to concrete tensile fracture , p db fi V Ultimate force that can be resisted by the i-th element parallely to its axis due to debonding , p spl fi V Adhesive splitting-based component of the i-th laminate shear strength contribution parallely to its orientation , p tr fi V Ultimate force that can be resisted by the i-th element parallely to its axis due to tensile rupture of the element itself ,max DM f V Analytical maximum contribution to the overall shear resistance by NSM laminates according to the DM ,min DM f V Analytical minimum contribution to the overall shear resistance by NSM laminates according to the DM exp f V Experiemntal contribution to the overall shear resistance by NSM laminates ,max PM f V Analytical maximum contribution to the overall shear resistance by NSM laminates according to the PM ,min PM f V Analytical minimum contribution to the overall shear resistance by NSM laminates according to the PM p k V Matrix of the shear strength contributions, for the k-th configutation, ascribed to each i-th laminate parallely to their orientation s V Shear strength contribution provided by the existing steel stirrups R V Ultimate shear resistance of the RC element Rd V Design shear resistance of the strengthened RC element , Rd c V Concrete contribution to the design shear resistance of the strengthened RC element , Rd s V Stirrups contribution to the design shear resistance of the strengthened RC element , Rd f V FRP contribution to the design shear resistance of the strengthened RC element ,max Rd V Maximum value of design shear resistance of the strengthened RC element Sd V Design shear force 1 f V NSM FRP shear strength contribution according to debonding (after De Lorenzis) 2 f V NSM FRP shear strength contribution according to aggregate interlock saving (after De b Minor semi-axis of the i-th semi-ellipse in the generic k-th configuration d Section effective depth c b Width of the concrete specimen f b Width of the cross section of the adopted FRP element w b RC beam cross section web width Shear Strengthening of RC beams by means of NSM laminates: experimental evidence and predictive models
Proceedings of the 6th International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering (COMPDYN 2015), 2017
Most of the existing Reinforced Concrete (RC) buildings in Italy were built according to obsolete... more Most of the existing Reinforced Concrete (RC) buildings in Italy were built according to obsolete regulations that were not enough aware of issues related to seismic design so that they need to be upgraded by pursuing either amelioration or full seismic rehabilitation. In doing that, the first step is to figure out what is, based on the results of the initial analysis of the structure in its ante-operam version, the best overall dissipative mechanism that could be obtained by a number of suitable and economically convenient local interventions. The choice of the overall dissipative mechanism strongly affects the amount of reinforcement to be adopted for the beam-column joints. For new buildings, the current adopted capacity design philosophy pursues an overall beam-sway mechanism in which plastic hinges first form in beams and at last at the base of the columns. On the contrary, for existing ones, often very irregular and gravity-load-dominated, pursuing such overall mechanism may result either uneconomic or even extremely difficult to implement due to the amount of reinforcement to be inserted in the joints. In such cases, an overall dissipative mechanism allowing, at some extent, columns flexural plasticization should be accepted and clearly identified in advance. Anyway, such approach needs to be addressed properly in order to avoid the formation of column-sways at one story only that would result very dangerous due to the excessive demand of plastic rotations on the resulting hinges. This paper presents two simple models that may help the designer in dealing with the operations above. The former is a model that allows to understand if, given the existing RC building case-study, either the beam-sway or a hybrid beam-column-sway mechanism should be conveniently pursued during the design of the retrofitting intervention. The latter is a model that allows to design a hybrid beam-column-sway overall mechanism involving a suitable number of stories such as to guarantee a uniform and reasonable demand of plastic rotations in the involved columns.
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Papers by Vincenzo Bianco