D. Nigro | Università della Basilicata (original) (raw)
Papers by D. Nigro
Many existing R/C framed buildings in seismic areas are designed with no seismic criteria, consid... more Many existing R/C framed buildings in seismic areas are designed with no seismic criteria, considering only gravity loads. They are a significant percentage of existing structures and their strengthening is one of the most urgent problems for seismic risk mitigation. New passive control techniques are very effective and to assess their feasibility and effectiveness, an in-situ experimental investigation has been carried out on an existing two storey, one bay R/C building structure, designed for gravity loads only, with no transverse frame. The structure was upgraded in the transverse direction with four re-centring braces based on the super-elastic properties of NiTi shape memory alloys (SMA). Push-over and cyclic tests, as well as dynamic release tests, were carried out on the upgraded structure.
Applied Mechanics and Materials, 2014
Beam-column joints can play a key role on the seismic behavior of reinforced concrete buildings. ... more Beam-column joints can play a key role on the seismic behavior of reinforced concrete buildings. Until now studies and experimental investigations on this topic have been mainly focused on beam-column joints with stiff beams, i.e. beams with height larger than the thickness of the adjacent floor slab. However, especially in the European residential building stock, frame structures are often equipped with wide -therefore rather flexible -beams. However, not many studies have been devoted so far to this type of connection, therefore an experimental investigation on full scale beam-column joints with wide beam was planned at the University of Basilicata and is currently in progress. In the present paper the main results of two cyclic tests are reported and discussed specifically analyzing the role of the axial load applied to the column on the joint performances and damage mechanisms. Test results highlights that the axial load value has a significant influence of on deformation capacity and ductility behavior.
The 2005-2008 DPC-Reluis Project, funded by the Italian Department of Civil Protection (DPC), is ... more The 2005-2008 DPC-Reluis Project, funded by the Italian Department of Civil Protection (DPC), is made up of ten Research Lines (RL). RL 2 specifically focuses on the seismic performance of existing RC buildings and is, in turn, organised in nine different Tasks. In the paper, the design of the research activities being carried out within the Task 7 by the four involved Research Units (RU UNIBAS, RU UNIUD, RU UNISA, and RU UNINA) and some first results are reported. Main objective of Task 7 is to investigate on the experimental behaviour of beam-column joints without or with strengthening, thus providing a contribution to a more reliable evaluation of the seismic vulnerability of Reinforced Concrete existing buildings. To this purpose the main activities carried out are devoted to design and set up of wide experimental programs on beam-column joints and base column joints relevant to typical existing RC buildings having different Earthquake Resistant Design (ERD) level, to make a literature review of the state of the art on the subject, to perform numerical simulations based on some analytical models available in literature in order to fully understand the mechanical behaviour. Further, some results of the tests already carried out are reported, analysed and compared in order to understand the failure mechanism and evaluate the seismic performance of joints with and without ERD.
Journal of Earthquake Engineering, 2013
A wide experimental program on beam-column RC joints carried out in the framework of the DPC-Relu... more A wide experimental program on beam-column RC joints carried out in the framework of the DPC-Reluis Project (DPC: Department of Civil Protection, Reluis: Network of University Laboratories of Earthquake Engineering) is presented. All the experimental tests were performed at the Laboratory of Structures of the University of Basilicata, Potenza (Italy). The main objective of the experimental campaign is to study and compare the post-elastic behaviour of beam-column joints with different earthquake resistant design levels, indicating the role of some structural parameters such as the axial load value acting on the column, the beam dimensions, and the steel type, on the joint performances and failure mechanism. The analyses have mainly been devoted to improving the assessment procedures regarding existing buildings but also to verifying the prediction capability of the capacity models relevant to beam-column joints contained in literature and in the new seismic codes. Following a short description of the experimental methodologies used in other campaigns, the experimental program is presented, providing a detailed description of the specimens and of the testing set-up. This is followed by a report of the main results of the cyclic tests performed on the beam-column specimens which highlight the role played by axial load and seismic design level in determining the failure mechanism and the global response of the joints.
Il presente lavoro descrive i risultati di un'ampia sperimentazione su assemblaggi trave col... more Il presente lavoro descrive i risultati di un'ampia sperimentazione su assemblaggi trave colonna nell'ambito del progetto di ricerca DPC-Reluis 2005-2008, eseguita presso il Laboratorio di Strutture dell'Università degli Studi della Basilicata a Potenza. La sperimentazione rientra nel task denominato "Comportamento e rinforzo di nodi" che rappresenta uno dei nove task della linea di ricerca n. 2 dal titolo "Valutazione e riduzione della vulnerabilità di edifici esistenti in c.a.". Il programma completo prevede l'esecuzione di test ciclici quasi statici su nodi a T progettati secondo differenti livelli dell'azione sismica, ossia nodi non antisismici, antisismici per zona 2 ed antisismici per zona 4, dotati di trave a spessore o emergente. L'obiettivo della memoria è quello di mettere in luce l'influenza che alcuni parametri progettuali quali il livello di sforzo assiale applicato, i quantitativi di armatura, il tipo di trave, il ...
Nel lavoro viene presentato un ampio programma sperimentale su assemblaggi trave-colonna, in fase... more Nel lavoro viene presentato un ampio programma sperimentale su assemblaggi trave-colonna, in fase di esecuzione presso il Laboratorio di Strutture dell'Università della Basilicata a Potenza, nell'ambito del progetto di ricerca DPC-Reluis 2005-2008. Obiettivo principale della sperimentazione è quello di studiare e confrontare il comportamento in fase post elastica di nodi trave-colonna con differenti livelli di progettazione antisismica, valutando il ruolo
The mechanical properties of elastomers can change significantly due to air temperature variation... more The mechanical properties of elastomers can change significantly due to air temperature variations. In particular, prolonged exposure to subzero temperatures can result in rubber crystallization, with a considerable increase in the shear stiffness of the material. As a result, the seismic response of structures with elastomeric isolators can be strongly influenced by air temperature. Current seismic codes, indeed, require an upper and lower bound analysis, using suitable modification factors, to account for the changes in the cyclic behavior of elastomeric isolators due to air temperature variations. In this study, the sensitivity of the cyclic behavior of elastomeric isolators to air temperature variations is investigated based on the experimental results of an extensive test program on six different elastomeric compounds for seismic isolators, characterized by a shear modulus ranging from 0.5 to 1.2 MPa at 100% shear strain and 20 • C. The cyclic tests have been performed on small-size specimens, subjected to shear strain amplitudes and frequency of loading typical for elastomeric seismic isolators, at seven different air temperatures, ranging from 40 to −20 • C. The effects of rubber crystallization due to prolonged exposure to low-temperatures have been also investigated. A finite element model for the evaluation of the temperature contour map inside a full-size elastomeric isolator exposed to low air temperatures has been also developed. In the paper, the experimental outcomes are compared with the modification factors provided by the current seismic codes to account for the temperature effects on the mechanical properties of elastomeric isolators.
More reliable assessment procedures of existing RC buildings are currently available, and have be... more More reliable assessment procedures of existing RC buildings are currently available, and have been introduced in the Italian and European codes reporting new rules for seismic design and analysis. However, further studies are necessary in order to upgrade such procedures and, specifically, obtain more detailed information on the behaviour of beam-column joints, whose role on the global behaviour of framed RC buildings can be crucial. Until now studies on this issue have been mainly devoted to joint specimens with rigid beams, however joint specimens having flat (flexible) beams are widely used in the European residential RC buildings. To this purpose, given the lack of knowledge, an experimental investigation on full scale beam-column joints with flat beam has been planned and is currently in progress. In the present paper the first results of four tests are reported and discussed.
Brazilian Journal of Medical and Biological Research
The responses to noradrenaline (NA) and acetylcholine (ACh) of aortae and microvessels were compa... more The responses to noradrenaline (NA) and acetylcholine (ACh) of aortae and microvessels were compared in control and DOCA-salt hypertensive rats. Macro- and microvessels from hypertensive rats showed an increased response to NA and a decreased response to ACh (an endothelium-dependent vasodilator). Unlike ACh, sodium nitroprusside (an endothelium-independent agent), was equally effective in evoking a vasodilator response from aortae and microvessels of hypertensive rats. These data suggest that the impaired response to ACh and the increased response to NA in DOCA-salt hypertension may result from an alteration of endothelial cell function.
Revista brasileira de pesquisas médicas e biológicas
Introduction Cardiac surgery with cardiopulmonary bypass (CPB) is a recognized trigger of systemi... more Introduction Cardiac surgery with cardiopulmonary bypass (CPB) is a recognized trigger of systemic inflammatory response, usually related to postoperative acute lung injury (ALI). As an attempt to dampen inflammatory response, steroids have been perioperatively administered to patients. Macrophage migration inhibitory factor (MIF), a regulator of the endotoxin receptor, is implicated in the pathogenesis of ALI. We have previously detected peak circulating levels of MIF, 6 hours post CPB. Experimental data have shown that steroids may induce MIF secretion by mononuclear cells. This study aims to correlate levels of MIF assayed 6 hours post CPB to the intensity of postoperative pulmonary dysfunction, analysing the impact of perioperative steroid administration.
Many existing R/C framed buildings in seismic areas are designed with no seismic criteria, consid... more Many existing R/C framed buildings in seismic areas are designed with no seismic criteria, considering only gravity loads. They are a significant percentage of existing structures and their strengthening is one of the most urgent problems for seismic risk mitigation. New passive control techniques are very effective and to assess their feasibility and effectiveness, an in-situ experimental investigation has been carried out on an existing two storey, one bay R/C building structure, designed for gravity loads only, with no transverse frame. The structure was upgraded in the transverse direction with four re-centring braces based on the super-elastic properties of NiTi shape memory alloys (SMA). Push-over and cyclic tests, as well as dynamic release tests, were carried out on the upgraded structure.
Applied Mechanics and Materials, 2014
Beam-column joints can play a key role on the seismic behavior of reinforced concrete buildings. ... more Beam-column joints can play a key role on the seismic behavior of reinforced concrete buildings. Until now studies and experimental investigations on this topic have been mainly focused on beam-column joints with stiff beams, i.e. beams with height larger than the thickness of the adjacent floor slab. However, especially in the European residential building stock, frame structures are often equipped with wide -therefore rather flexible -beams. However, not many studies have been devoted so far to this type of connection, therefore an experimental investigation on full scale beam-column joints with wide beam was planned at the University of Basilicata and is currently in progress. In the present paper the main results of two cyclic tests are reported and discussed specifically analyzing the role of the axial load applied to the column on the joint performances and damage mechanisms. Test results highlights that the axial load value has a significant influence of on deformation capacity and ductility behavior.
The 2005-2008 DPC-Reluis Project, funded by the Italian Department of Civil Protection (DPC), is ... more The 2005-2008 DPC-Reluis Project, funded by the Italian Department of Civil Protection (DPC), is made up of ten Research Lines (RL). RL 2 specifically focuses on the seismic performance of existing RC buildings and is, in turn, organised in nine different Tasks. In the paper, the design of the research activities being carried out within the Task 7 by the four involved Research Units (RU UNIBAS, RU UNIUD, RU UNISA, and RU UNINA) and some first results are reported. Main objective of Task 7 is to investigate on the experimental behaviour of beam-column joints without or with strengthening, thus providing a contribution to a more reliable evaluation of the seismic vulnerability of Reinforced Concrete existing buildings. To this purpose the main activities carried out are devoted to design and set up of wide experimental programs on beam-column joints and base column joints relevant to typical existing RC buildings having different Earthquake Resistant Design (ERD) level, to make a literature review of the state of the art on the subject, to perform numerical simulations based on some analytical models available in literature in order to fully understand the mechanical behaviour. Further, some results of the tests already carried out are reported, analysed and compared in order to understand the failure mechanism and evaluate the seismic performance of joints with and without ERD.
Journal of Earthquake Engineering, 2013
A wide experimental program on beam-column RC joints carried out in the framework of the DPC-Relu... more A wide experimental program on beam-column RC joints carried out in the framework of the DPC-Reluis Project (DPC: Department of Civil Protection, Reluis: Network of University Laboratories of Earthquake Engineering) is presented. All the experimental tests were performed at the Laboratory of Structures of the University of Basilicata, Potenza (Italy). The main objective of the experimental campaign is to study and compare the post-elastic behaviour of beam-column joints with different earthquake resistant design levels, indicating the role of some structural parameters such as the axial load value acting on the column, the beam dimensions, and the steel type, on the joint performances and failure mechanism. The analyses have mainly been devoted to improving the assessment procedures regarding existing buildings but also to verifying the prediction capability of the capacity models relevant to beam-column joints contained in literature and in the new seismic codes. Following a short description of the experimental methodologies used in other campaigns, the experimental program is presented, providing a detailed description of the specimens and of the testing set-up. This is followed by a report of the main results of the cyclic tests performed on the beam-column specimens which highlight the role played by axial load and seismic design level in determining the failure mechanism and the global response of the joints.
Il presente lavoro descrive i risultati di un'ampia sperimentazione su assemblaggi trave col... more Il presente lavoro descrive i risultati di un'ampia sperimentazione su assemblaggi trave colonna nell'ambito del progetto di ricerca DPC-Reluis 2005-2008, eseguita presso il Laboratorio di Strutture dell'Università degli Studi della Basilicata a Potenza. La sperimentazione rientra nel task denominato "Comportamento e rinforzo di nodi" che rappresenta uno dei nove task della linea di ricerca n. 2 dal titolo "Valutazione e riduzione della vulnerabilità di edifici esistenti in c.a.". Il programma completo prevede l'esecuzione di test ciclici quasi statici su nodi a T progettati secondo differenti livelli dell'azione sismica, ossia nodi non antisismici, antisismici per zona 2 ed antisismici per zona 4, dotati di trave a spessore o emergente. L'obiettivo della memoria è quello di mettere in luce l'influenza che alcuni parametri progettuali quali il livello di sforzo assiale applicato, i quantitativi di armatura, il tipo di trave, il ...
Nel lavoro viene presentato un ampio programma sperimentale su assemblaggi trave-colonna, in fase... more Nel lavoro viene presentato un ampio programma sperimentale su assemblaggi trave-colonna, in fase di esecuzione presso il Laboratorio di Strutture dell'Università della Basilicata a Potenza, nell'ambito del progetto di ricerca DPC-Reluis 2005-2008. Obiettivo principale della sperimentazione è quello di studiare e confrontare il comportamento in fase post elastica di nodi trave-colonna con differenti livelli di progettazione antisismica, valutando il ruolo
The mechanical properties of elastomers can change significantly due to air temperature variation... more The mechanical properties of elastomers can change significantly due to air temperature variations. In particular, prolonged exposure to subzero temperatures can result in rubber crystallization, with a considerable increase in the shear stiffness of the material. As a result, the seismic response of structures with elastomeric isolators can be strongly influenced by air temperature. Current seismic codes, indeed, require an upper and lower bound analysis, using suitable modification factors, to account for the changes in the cyclic behavior of elastomeric isolators due to air temperature variations. In this study, the sensitivity of the cyclic behavior of elastomeric isolators to air temperature variations is investigated based on the experimental results of an extensive test program on six different elastomeric compounds for seismic isolators, characterized by a shear modulus ranging from 0.5 to 1.2 MPa at 100% shear strain and 20 • C. The cyclic tests have been performed on small-size specimens, subjected to shear strain amplitudes and frequency of loading typical for elastomeric seismic isolators, at seven different air temperatures, ranging from 40 to −20 • C. The effects of rubber crystallization due to prolonged exposure to low-temperatures have been also investigated. A finite element model for the evaluation of the temperature contour map inside a full-size elastomeric isolator exposed to low air temperatures has been also developed. In the paper, the experimental outcomes are compared with the modification factors provided by the current seismic codes to account for the temperature effects on the mechanical properties of elastomeric isolators.
More reliable assessment procedures of existing RC buildings are currently available, and have be... more More reliable assessment procedures of existing RC buildings are currently available, and have been introduced in the Italian and European codes reporting new rules for seismic design and analysis. However, further studies are necessary in order to upgrade such procedures and, specifically, obtain more detailed information on the behaviour of beam-column joints, whose role on the global behaviour of framed RC buildings can be crucial. Until now studies on this issue have been mainly devoted to joint specimens with rigid beams, however joint specimens having flat (flexible) beams are widely used in the European residential RC buildings. To this purpose, given the lack of knowledge, an experimental investigation on full scale beam-column joints with flat beam has been planned and is currently in progress. In the present paper the first results of four tests are reported and discussed.
Brazilian Journal of Medical and Biological Research
The responses to noradrenaline (NA) and acetylcholine (ACh) of aortae and microvessels were compa... more The responses to noradrenaline (NA) and acetylcholine (ACh) of aortae and microvessels were compared in control and DOCA-salt hypertensive rats. Macro- and microvessels from hypertensive rats showed an increased response to NA and a decreased response to ACh (an endothelium-dependent vasodilator). Unlike ACh, sodium nitroprusside (an endothelium-independent agent), was equally effective in evoking a vasodilator response from aortae and microvessels of hypertensive rats. These data suggest that the impaired response to ACh and the increased response to NA in DOCA-salt hypertension may result from an alteration of endothelial cell function.
Revista brasileira de pesquisas médicas e biológicas
Introduction Cardiac surgery with cardiopulmonary bypass (CPB) is a recognized trigger of systemi... more Introduction Cardiac surgery with cardiopulmonary bypass (CPB) is a recognized trigger of systemic inflammatory response, usually related to postoperative acute lung injury (ALI). As an attempt to dampen inflammatory response, steroids have been perioperatively administered to patients. Macrophage migration inhibitory factor (MIF), a regulator of the endotoxin receptor, is implicated in the pathogenesis of ALI. We have previously detected peak circulating levels of MIF, 6 hours post CPB. Experimental data have shown that steroids may induce MIF secretion by mononuclear cells. This study aims to correlate levels of MIF assayed 6 hours post CPB to the intensity of postoperative pulmonary dysfunction, analysing the impact of perioperative steroid administration.