M. Piazza - Academia.edu (original) (raw)

Papers by M. Piazza

The applicability of the Direct Displacement-Based Design (DBD) procedure is strictly related to ... more The applicability of the Direct Displacement-Based Design (DBD) procedure is strictly related to a priori evaluation of the design displacement and the matching Equivalent Viscous Damping (EVD) of the structure. In this paper we propose analytical models of these design parameters, at the ultimate limit state, for wooden structures built with engineered joints. Experimental results show that the plastic resources and dissipative capabilities of timber structures under earthquake conditions are ensured by the connections between the members. Therefore, the formulation of the design DBD parameters is based on the mechanical model of the single connector and assumes the inelastic deformation of the structure to be concentrated at the joints. The expected non-linear response of the connections can be either ductile or brittle. However, through an appropriate choice of the geometry and strength characteristics of the materials, in the design process we can control the expected ductile behavior of joints. Blank line 10 pt

Journal of Earthquake Engineering, 2011

Proceedings of the VI International Conference on Structural Analysis of Historic Construction, SAHC08, 2-4 July 2008, Bath, United Kingdom, 2008

An accurate geometric and mechanical evaluation of two king-post trusses, based in grading result... more An accurate geometric and mechanical evaluation of two king-post trusses, based in grading results with data gathered from NDT as well as from mechanical evaluation, followed by full-scale tests were performed. The trusses were reassembled in laboratory and submitted to a series of cyclic tests under symmetric and asymmetric loading. Strengthening techniques evaluated in precedents research steps were used in a second phase of the carrying tests.

The structural behaviour of an existing masonry building, when subjected to seismic action, is af... more The structural behaviour of an existing masonry building, when subjected to seismic action, is affected by the inplane mechanical properties of the floors and roofs. The goal of the present paper is to investigate the influence of the diaphragms properties (and therefore the influence of the different refurbishment techniques) on the global seismic behaviour of simple e regular masonry buildings. For this purpose a simplified elastic no-tension (ENT) method for modelling masonry structures have been proposed and adopted in order to perform pushover non linear analysis in function of different parameters of the building. According to the ENT method, at every step all the elements which are outside a Rankine failure surface are eliminated, and the analysis is repeated with an updated geometry of the model: a "globally nonlinear" behaviour is therefore determined through a series of linear analyses. The results of the pushover analyses show a lesser influence on the on the maximum level of the load and on the maximum displacement of the floor stiffness in case of URM buildings endowed with regularity and symmetry of the geometry.

Proceedings of the VI International Conference on Structural Analysis of Historic Construction, SAHC08, 2-4 July 2008, Bath, United Kingdom, 2008

The structural behaviour of an existing masonry building subjected to seismic action, is strongly... more The structural behaviour of an existing masonry building subjected to seismic action, is strongly affected by the in-plane stiffness of the floors, and by the connections between the horizontal diaphragms and the masonry walls. The aim of the research is to experimentally evaluate the behaviour of timber floor refurbished using different techniques, with special regard to the in-plane stiffness. The size adopted for the specimens (5 m span, 4 m width), is similar to the ordinary dimensions of timber floors in historical buildings in Italy. Taking into account the size of the specimens, and the need to determine the in-plane strength and stiffness of the floor, a special test setup has been designed and adopted in order to allow the free in-plane deformation of the floor itself subjected to lateral load: the load configuration applied to the floor simulates the effect of seismic action on the floor. The experimental phase of the research aims to calibrate engineered models that can be used for studying existing structures.

Structural Engineering International, 2008

Abstract: Ductility, which is the capability of a structure to deform significantly beyond the el... more Abstract: Ductility, which is the capability of a structure to deform significantly beyond the elastic limit without brittle failure, is a fundamental property which can be an important requirement in many instances. In particular, the behaviour of structures under seismic ...

Architectural Engineering 2003, 2003

The reported research aims to provide means to improve the performances of timber structures, par... more The reported research aims to provide means to improve the performances of timber structures, particularly when brittle behavior of timber elements can represent an obstacle in adopting timber structures. Several technological approach solutions are under investigation within the frame of a threeyear national research project: the first solution analyzed is the mixed glulam beam manufactured coupling laminations of different wood species, featuring a better performance as far the global ductile behavior is concerned. A numerical iterative approach has been adopted to determine the moment-curvature relationship in the plastic field up to failure. The tests performed so far confirm the expected behavior on the basis of the numerical analysis. NOMENCLATURE

Advanced Materials Research, 2010

In this paper an investigation campaign, carried out in occasion of the restoration of a timber f... more In this paper an investigation campaign, carried out in occasion of the restoration of a timber floor in the Belasi Castle (Trentino, Italy), is reported. In order to validate a testing procedure for the calibration and control of an innovative wood-wood strengthening technique, results of tests performed in situ on the structural elements, in both the original and the repaired condition, have been compared with those obtained in laboratory on some dismantled beams. For the characterization of the material decay, both local mechanical and global vibrational testing have been carried out. For the mechanical characterization of the beams, before and after repair, direct static bending tests have been performed, with distributed loads, on site, and according to standard four-points loading schemes, in laboratory.

Journal of Earthquake Engineering, 2013

ABSTRACT An analytical model is proposed to estimate the seismic displacement capacity, at servic... more ABSTRACT An analytical model is proposed to estimate the seismic displacement capacity, at serviceability and ultimate limit states, of timber portal frame structures with dowelled joints. The predictions from the simplified formula are compared with the results of numerical analyses carried out on a sample of representative cases. These cases result from a simulated design procedure, consistent with Eurocode 8, and are generated via Monte Carlo sampling, with varying sizes, materials and load conditions and also uncertainties in these parameters. Based on the outcome of the analysis we propose a set of practical formulas which allow prediction of the displacement with a given percentile of overestimates. In addition, it is shown that these equations for displacement capacity can be used to generate fragility curves for performance-based earthquake engineering applications. Prescription of an overstrength factor in code provisions is recommended to avoid brittle failure.

Construction and Building Materials, 2010

The aim of this paper is to propose a method for calculating the load-bearing capacity and stiffn... more The aim of this paper is to propose a method for calculating the load-bearing capacity and stiffness of screws placed in an inclined position with respect to the shear plane and subjected to shear–compression load, to shear–tension load or to a combination due to ...

Apresentam-se os principais resultados de uma campanha experimental sobre ligações tradicionais d... more Apresentam-se os principais resultados de uma campanha experimental sobre ligações tradicionais de madeira. Através de ensaios monotónicos e cíclicos, analisaram-se ligações originais (não reforçadas) e estudaram-se três soluções típicas de reforço, nomeadamente, soluções com recurso a: braçadeira, esquadro e varões. Com base nestes resultados experimentais foi implementado e calibrado um modelo simplificado para a simulação do comportamento histerético das ligações entre elementos estruturais nas asnas tradicionais de madeira.

Different strengthening solutions with metal elements have been experimentally evaluated with tes... more Different strengthening solutions with metal elements have been experimentally evaluated with tests on full-scale connections. Attention has been focused on the birdsmouth joints, due to its common use in practice. Even if unstrengthened, these types of connections reveal significant moment resistance. Experimental results show that structural response of birdsmouth connections under cyclic loading cannot be represented by common constraint models, like perfect hinges or rigid joints, but with semi-rigid and friction based models. Thus, the rotational behaviour of the birdsmouth joints is analysed.

Cd-Rom Proceedings of 12th …, 2007

Construction and Building Materials, 2010

The misunderstanding of the overall behaviour of traditional timber trusses can result in incorre... more The misunderstanding of the overall behaviour of traditional timber trusses can result in incorrect strengthening interventions or, frequently, on their replacement. Timber roof structures need a more concise knowledge of the real behaviour to determine internal loads and control the load transfer. For that, laboratory tests on scaled or full-scale specimens of members, connections and trusses are needed. In this paper, an accurate geometric and mechanical evaluation of the timber elements of two King-post timber trusses, based on grading results with data gathered from non-destructive tests (NDT), including mechanical evaluation of the modulus of elasticity in bending (MoE), followed by full-scale carrying tests were performed. The trusses were reassembled in laboratory and submitted to a series of symmetric and non-symmetric cyclic tests, according to the Limit States. Strengthening techniques evaluated in precedent research steps were used in a second phase of the load-carrying tests.

A series of monotonic and cyclic tests on unstrengthened full-scale specimens were performed in o... more A series of monotonic and cyclic tests on unstrengthened full-scale specimens were performed in order to characterize the original behavior of connections representative of traditional timber trusses. Subsequently, connections strengthened with metal devices were tested under monotonic and cyclic loading. Tests on assembled connections were preceded by accurate material characterization, in terms of the mechanical properties of the timber elements used for all full-scale models. The experimental study was complemented by a numerical analysis using FEM, through parametric studies that followed the models calibration process.

Nondestructive Testing of Materials and Structures, 2011

In this paper the combined use of high resolution images of wood texture and non destructive imag... more In this paper the combined use of high resolution images of wood texture and non destructive imaging of internal defects of wood is proposed for the characterization of structural timber on site. Experimental results are presented, based on the integrated use of digital photogrammetry, ultrasonic tomography and image analysis techniques. The implemented methodology aims at investigating the exploitation of some digital imaging techniques as complementary tools to be used during visual inspection.

Proceedings of the VI International Conference on Structural Analysis of Historic Construction, SAHC08, 2-4 July 2008, Bath, United Kingdom, 2008

In-situ cyclic tests on an existing traditional timber truss were performed. The main goal of the... more In-situ cyclic tests on an existing traditional timber truss were performed. The main goal of the tests was to evaluate the overall behavior of the timber truss under symmetric and non-symmetric loading. Moreover, the influence of the location of point loads application, without and with eccentricity relatively to joints, was assessed. The carrying tests were preceded by a visual and non-destructive inspection aiming to collect geometric data and to assess the decay level. The field tests results of a queen-post truss are presented and analyzed. A numerical model was developed to reproduce the test results.

New concepts, applications and challenges, 2013

ABSTRACT In this work we propose and calibrate a formulation for evaluating the ultimate displace... more ABSTRACT In this work we propose and calibrate a formulation for evaluating the ultimate displacement of glued laminated timber portals, in view of application of a direct Displacement Based Design (DBD) method. The case study investigated is an industrial wood-framed warehouse with two-hinged frames where the post-beam connections are semi-rigid moment-resisting joints with dowel-type fasteners. A necessary condition for applying the DBD method is that it be somehow possible to estimate a priori the target displacement d of the portal, regardless of the geometrical dimensions of members and connections. A first version of this expression was proposed by the authors in 2006. Here, we now validate and refine the original formulation , using Monte Carlo simulations. A total number of one thousand different case studies was generated, assuming geometrical dimensions, joint configuration, and mechanical properties of materials as random variables. We defined a statistical procedure for selecting the geometrical dimensions of the members simulating the logical path commonly followed by the designer. In a similar way, we selected distributions of the mechanical properties reproducing the actual variability of the materials (glulam and steel) available on the market. For each sampling, the ultimate displacement of the structure was calculated using non linear static pushover analysis. The finite element model used takes into account the exact geometry of the members and connections and considers two possible failure mechanisms: ductile embedding of the dowel connections and brittle bending failure of the timber members. The analysis of the outcomes lets us conclude that: in order to prevent brittle failure it is appropriate to introduce in the design provisions an overstrength factor (the value suggested is 1.2); the original formulation produces slight systematic errors in displacement prediction that can be eliminated by inserting appropriate correction coefficients; the displacement capacity is influenced by the gravity loads, to a small extent, and this effect can be taken into account using an additional correction term.

The applicability of the Direct Displacement-Based Design (DBD) procedure is strictly related to ... more The applicability of the Direct Displacement-Based Design (DBD) procedure is strictly related to a priori evaluation of the design displacement and the matching Equivalent Viscous Damping (EVD) of the structure. In this paper we propose analytical models of these design parameters, at the ultimate limit state, for wooden structures built with engineered joints. Experimental results show that the plastic resources and dissipative capabilities of timber structures under earthquake conditions are ensured by the connections between the members. Therefore, the formulation of the design DBD parameters is based on the mechanical model of the single connector and assumes the inelastic deformation of the structure to be concentrated at the joints. The expected non-linear response of the connections can be either ductile or brittle. However, through an appropriate choice of the geometry and strength characteristics of the materials, in the design process we can control the expected ductile behavior of joints. Blank line 10 pt

Journal of Earthquake Engineering, 2011

Proceedings of the VI International Conference on Structural Analysis of Historic Construction, SAHC08, 2-4 July 2008, Bath, United Kingdom, 2008

An accurate geometric and mechanical evaluation of two king-post trusses, based in grading result... more An accurate geometric and mechanical evaluation of two king-post trusses, based in grading results with data gathered from NDT as well as from mechanical evaluation, followed by full-scale tests were performed. The trusses were reassembled in laboratory and submitted to a series of cyclic tests under symmetric and asymmetric loading. Strengthening techniques evaluated in precedents research steps were used in a second phase of the carrying tests.

The structural behaviour of an existing masonry building, when subjected to seismic action, is af... more The structural behaviour of an existing masonry building, when subjected to seismic action, is affected by the inplane mechanical properties of the floors and roofs. The goal of the present paper is to investigate the influence of the diaphragms properties (and therefore the influence of the different refurbishment techniques) on the global seismic behaviour of simple e regular masonry buildings. For this purpose a simplified elastic no-tension (ENT) method for modelling masonry structures have been proposed and adopted in order to perform pushover non linear analysis in function of different parameters of the building. According to the ENT method, at every step all the elements which are outside a Rankine failure surface are eliminated, and the analysis is repeated with an updated geometry of the model: a "globally nonlinear" behaviour is therefore determined through a series of linear analyses. The results of the pushover analyses show a lesser influence on the on the maximum level of the load and on the maximum displacement of the floor stiffness in case of URM buildings endowed with regularity and symmetry of the geometry.

Proceedings of the VI International Conference on Structural Analysis of Historic Construction, SAHC08, 2-4 July 2008, Bath, United Kingdom, 2008

The structural behaviour of an existing masonry building subjected to seismic action, is strongly... more The structural behaviour of an existing masonry building subjected to seismic action, is strongly affected by the in-plane stiffness of the floors, and by the connections between the horizontal diaphragms and the masonry walls. The aim of the research is to experimentally evaluate the behaviour of timber floor refurbished using different techniques, with special regard to the in-plane stiffness. The size adopted for the specimens (5 m span, 4 m width), is similar to the ordinary dimensions of timber floors in historical buildings in Italy. Taking into account the size of the specimens, and the need to determine the in-plane strength and stiffness of the floor, a special test setup has been designed and adopted in order to allow the free in-plane deformation of the floor itself subjected to lateral load: the load configuration applied to the floor simulates the effect of seismic action on the floor. The experimental phase of the research aims to calibrate engineered models that can be used for studying existing structures.

Structural Engineering International, 2008

Abstract: Ductility, which is the capability of a structure to deform significantly beyond the el... more Abstract: Ductility, which is the capability of a structure to deform significantly beyond the elastic limit without brittle failure, is a fundamental property which can be an important requirement in many instances. In particular, the behaviour of structures under seismic ...

Architectural Engineering 2003, 2003

The reported research aims to provide means to improve the performances of timber structures, par... more The reported research aims to provide means to improve the performances of timber structures, particularly when brittle behavior of timber elements can represent an obstacle in adopting timber structures. Several technological approach solutions are under investigation within the frame of a threeyear national research project: the first solution analyzed is the mixed glulam beam manufactured coupling laminations of different wood species, featuring a better performance as far the global ductile behavior is concerned. A numerical iterative approach has been adopted to determine the moment-curvature relationship in the plastic field up to failure. The tests performed so far confirm the expected behavior on the basis of the numerical analysis. NOMENCLATURE

Advanced Materials Research, 2010

In this paper an investigation campaign, carried out in occasion of the restoration of a timber f... more In this paper an investigation campaign, carried out in occasion of the restoration of a timber floor in the Belasi Castle (Trentino, Italy), is reported. In order to validate a testing procedure for the calibration and control of an innovative wood-wood strengthening technique, results of tests performed in situ on the structural elements, in both the original and the repaired condition, have been compared with those obtained in laboratory on some dismantled beams. For the characterization of the material decay, both local mechanical and global vibrational testing have been carried out. For the mechanical characterization of the beams, before and after repair, direct static bending tests have been performed, with distributed loads, on site, and according to standard four-points loading schemes, in laboratory.

Journal of Earthquake Engineering, 2013

ABSTRACT An analytical model is proposed to estimate the seismic displacement capacity, at servic... more ABSTRACT An analytical model is proposed to estimate the seismic displacement capacity, at serviceability and ultimate limit states, of timber portal frame structures with dowelled joints. The predictions from the simplified formula are compared with the results of numerical analyses carried out on a sample of representative cases. These cases result from a simulated design procedure, consistent with Eurocode 8, and are generated via Monte Carlo sampling, with varying sizes, materials and load conditions and also uncertainties in these parameters. Based on the outcome of the analysis we propose a set of practical formulas which allow prediction of the displacement with a given percentile of overestimates. In addition, it is shown that these equations for displacement capacity can be used to generate fragility curves for performance-based earthquake engineering applications. Prescription of an overstrength factor in code provisions is recommended to avoid brittle failure.

Construction and Building Materials, 2010

The aim of this paper is to propose a method for calculating the load-bearing capacity and stiffn... more The aim of this paper is to propose a method for calculating the load-bearing capacity and stiffness of screws placed in an inclined position with respect to the shear plane and subjected to shear–compression load, to shear–tension load or to a combination due to ...

Apresentam-se os principais resultados de uma campanha experimental sobre ligações tradicionais d... more Apresentam-se os principais resultados de uma campanha experimental sobre ligações tradicionais de madeira. Através de ensaios monotónicos e cíclicos, analisaram-se ligações originais (não reforçadas) e estudaram-se três soluções típicas de reforço, nomeadamente, soluções com recurso a: braçadeira, esquadro e varões. Com base nestes resultados experimentais foi implementado e calibrado um modelo simplificado para a simulação do comportamento histerético das ligações entre elementos estruturais nas asnas tradicionais de madeira.

Different strengthening solutions with metal elements have been experimentally evaluated with tes... more Different strengthening solutions with metal elements have been experimentally evaluated with tests on full-scale connections. Attention has been focused on the birdsmouth joints, due to its common use in practice. Even if unstrengthened, these types of connections reveal significant moment resistance. Experimental results show that structural response of birdsmouth connections under cyclic loading cannot be represented by common constraint models, like perfect hinges or rigid joints, but with semi-rigid and friction based models. Thus, the rotational behaviour of the birdsmouth joints is analysed.

Cd-Rom Proceedings of 12th …, 2007

Construction and Building Materials, 2010

The misunderstanding of the overall behaviour of traditional timber trusses can result in incorre... more The misunderstanding of the overall behaviour of traditional timber trusses can result in incorrect strengthening interventions or, frequently, on their replacement. Timber roof structures need a more concise knowledge of the real behaviour to determine internal loads and control the load transfer. For that, laboratory tests on scaled or full-scale specimens of members, connections and trusses are needed. In this paper, an accurate geometric and mechanical evaluation of the timber elements of two King-post timber trusses, based on grading results with data gathered from non-destructive tests (NDT), including mechanical evaluation of the modulus of elasticity in bending (MoE), followed by full-scale carrying tests were performed. The trusses were reassembled in laboratory and submitted to a series of symmetric and non-symmetric cyclic tests, according to the Limit States. Strengthening techniques evaluated in precedent research steps were used in a second phase of the load-carrying tests.

A series of monotonic and cyclic tests on unstrengthened full-scale specimens were performed in o... more A series of monotonic and cyclic tests on unstrengthened full-scale specimens were performed in order to characterize the original behavior of connections representative of traditional timber trusses. Subsequently, connections strengthened with metal devices were tested under monotonic and cyclic loading. Tests on assembled connections were preceded by accurate material characterization, in terms of the mechanical properties of the timber elements used for all full-scale models. The experimental study was complemented by a numerical analysis using FEM, through parametric studies that followed the models calibration process.

Nondestructive Testing of Materials and Structures, 2011

In this paper the combined use of high resolution images of wood texture and non destructive imag... more In this paper the combined use of high resolution images of wood texture and non destructive imaging of internal defects of wood is proposed for the characterization of structural timber on site. Experimental results are presented, based on the integrated use of digital photogrammetry, ultrasonic tomography and image analysis techniques. The implemented methodology aims at investigating the exploitation of some digital imaging techniques as complementary tools to be used during visual inspection.

Proceedings of the VI International Conference on Structural Analysis of Historic Construction, SAHC08, 2-4 July 2008, Bath, United Kingdom, 2008

In-situ cyclic tests on an existing traditional timber truss were performed. The main goal of the... more In-situ cyclic tests on an existing traditional timber truss were performed. The main goal of the tests was to evaluate the overall behavior of the timber truss under symmetric and non-symmetric loading. Moreover, the influence of the location of point loads application, without and with eccentricity relatively to joints, was assessed. The carrying tests were preceded by a visual and non-destructive inspection aiming to collect geometric data and to assess the decay level. The field tests results of a queen-post truss are presented and analyzed. A numerical model was developed to reproduce the test results.

New concepts, applications and challenges, 2013

ABSTRACT In this work we propose and calibrate a formulation for evaluating the ultimate displace... more ABSTRACT In this work we propose and calibrate a formulation for evaluating the ultimate displacement of glued laminated timber portals, in view of application of a direct Displacement Based Design (DBD) method. The case study investigated is an industrial wood-framed warehouse with two-hinged frames where the post-beam connections are semi-rigid moment-resisting joints with dowel-type fasteners. A necessary condition for applying the DBD method is that it be somehow possible to estimate a priori the target displacement d of the portal, regardless of the geometrical dimensions of members and connections. A first version of this expression was proposed by the authors in 2006. Here, we now validate and refine the original formulation , using Monte Carlo simulations. A total number of one thousand different case studies was generated, assuming geometrical dimensions, joint configuration, and mechanical properties of materials as random variables. We defined a statistical procedure for selecting the geometrical dimensions of the members simulating the logical path commonly followed by the designer. In a similar way, we selected distributions of the mechanical properties reproducing the actual variability of the materials (glulam and steel) available on the market. For each sampling, the ultimate displacement of the structure was calculated using non linear static pushover analysis. The finite element model used takes into account the exact geometry of the members and connections and considers two possible failure mechanisms: ductile embedding of the dowel connections and brittle bending failure of the timber members. The analysis of the outcomes lets us conclude that: in order to prevent brittle failure it is appropriate to introduce in the design provisions an overstrength factor (the value suggested is 1.2); the original formulation produces slight systematic errors in displacement prediction that can be eliminated by inserting appropriate correction coefficients; the displacement capacity is influenced by the gravity loads, to a small extent, and this effect can be taken into account using an additional correction term.