marco corradi | University of Perugia (original) (raw)

Papers by marco corradi

Proceedings of the Twelfth International Conference on Computational Structures Technology, 2014

ABSTRACT Uncertainty in the strength of natural material, such as timber, is considerably higher ... more ABSTRACT Uncertainty in the strength of natural material, such as timber, is considerably higher than man-made construction materials which are produced through controlled and precise manufacturing processes. Adopting a classical deterministic design approach, designer usually employs high factor of safety to incorporate this material strength uncertainty in design; an approach that can lead to overdesigned structures with unpredictable performance. This paper, firstly, presents the evaluation of the performance of classical design method against nondeterministic design technique. The nondeterministic design is carried out with Monte Carlo technique in order to estimate failure rates corresponding to the adopted factors of safety utilised in the classical design. It is shown that increase in factor of safety does not necessarily yield a reliable design. Secondly, two methods of reinforcement, namely, Fibre Reinforced Polymers (FRP) and Steel Reinforced Polymers (SRP), are investigated in this study. The uncertainty in the strength of reinforced timber is also quantified and modelled. It is shown that reinforcement of timber has a two-fold effect on its strength, namely, enhanced strength and reduced uncertainties, directly leading to reduction in the overall cost of the structure.

Proceedings of the Twelfth International Conference on Computational Structures Technology, 2014

ABSTRACT This paper presents the results of a systematic study on the effects of the cross-arm si... more ABSTRACT This paper presents the results of a systematic study on the effects of the cross-arm size (cross sectional diameter and thickness) and the cable stay cross sectional diameter on the maximum load carrying capacity of single cross-arm prestressed stayed column system. Due to the addition of cross-arms and prestressed cables, the traditional slenderness ratio definition for ordinary unstayed columns is not applicable for this type of structural system. Therefore, the effects of the cross sectional size of the additional cross-arm and stay on the load bearing capacity are studied for different lengths and cross sectional size of the main column. Nine different combinations of column length (short, intermediate and long) and column cross-section size (small, medium and large) are investigated. It is shown that the column cross section size has a negligible effect on the maximum load carrying capacity while the effect is much more significant with varying column length. An enhancement ratio, i.e. the ratio of maximum load carrying capacity of the stayed column to the critical buckling load of unstayed column is also presented. It is shown that optimum cross-arm and stay size leading to the maximum achievable enhancement ratio and maximum load bearing capacity is independent of the size of the column. The enhancement ratio varies from about 14 with a corresponding 27.9 % added volume (material) to about 40 with a corresponding 15% added volume (material) with increasing column length.

Composites Part B: Engineering, 2005

This paper presents a study on the reinforcement of existing wood elements under bending loads th... more This paper presents a study on the reinforcement of existing wood elements under bending loads through the use of FRP materials. An analytical investigation was first conducted on the behavior of a generic FRP-reinforced wood section. This study, in turn, led to a numerical procedure based on non-linear wood properties, suitable for application in the design of FRP reinforcement of old, pre-existing wood beams under varying configurations of intervention layouts and materials. An experimental programme based on a four-point bending test configuration is proposed to characterize the stiffness, ductility and strength response of FRP-wood beams. Mechanical tests on the reinforced wood showed that external bonding of FRP materials may produce increases in flexural stiffness and capacity. The FRP composite material was made of High Tensile Carbon monodirectional reinforcing fabrics embedded in an epoxy resin matrix. This reinforcing method can be applied without necessitating the removal of the overhanging part of the pre-existing wood structure, thus maintaining the original historical structure. In addition, a beam non-linear model was proposed to predict ultimate load. At the end of this paper results of the experimental programme are presented and used for comparison with the numerical procedure. q

Construction and Building Materials, 2005

This paper presents the results of a real-scale experimental work regarding innovative seismic re... more This paper presents the results of a real-scale experimental work regarding innovative seismic retrofitting technique for masonry walls and vaults by epoxy-bonded composite strengthenings. Palazzo Elmi-Pandolfi in Foligno (Italy), an historical building dated 1600 that was seriously damaged in the earthquake of 1997, has been repaired and retrofitted including carbon FRP (CFRP) strengthenings, whose effectiveness has been evaluated through dynamic and static tests.

Journal of Materials in Civil Engineering, 2014

ABSTRACT In the last decades, a number of technical solutions for the improvement of structural c... more ABSTRACT In the last decades, a number of technical solutions for the improvement of structural connections using new materials between masonry wall panels have been the subject of several studies. In this context, the increasing interest in titanium could be attributed to its high specific resistances and chemical stability. The emphasis of this study is therefore the understanding of the bond behavior between lime-based mortars and titanium-based reinforcing rods. Experimental results showed that the titanium-lime bond is characterized by low bond strength. With the aim of increasing bond stresses, different surface treatments were investigated based on chemical and mechanical interlocking. The effect of these treatments and the general problems related to masonry reinforcing techniques have been discussed.

Composites Part B: Engineering, 2007

High-performance fibers are being widely researched for repair and rehabilitation in civil engine... more High-performance fibers are being widely researched for repair and rehabilitation in civil engineering structures. The potential benefits, liabilities, and architectural considerations regarding the use of high-performance fibers for reinforcing wood beams are discussed. An experimental program based on a four-and three-point bending test configuration is proposed to characterize the stiffness and strength response of wood beams reinforced with pultruded GFRP (glass fibers reinforced polymers) elements. Improving wood mechanical characteristics through the use of fiber reinforced polymers often involves the use of adhesives, generally epoxy resins. For this reason mechanical, calorimetric and thermo-gravimetric analyses were performed on the resin utilized and bonding effectiveness was studied. Mechanical tests carried out on full-scale wood beams showed that the reinforcement with GFRP beams may produce strong increases in flexural stiffness and capacity. In addition, an analytical investigation based on a simple linear analysis was conducted to predict ultimate load. At the end of this paper results of the experimental program are presented and used for comparison with the analytical procedure.

Proceedings of the Tenth International Conference on Computational Structures Technology, 2010

This paper aims to comparise and illustrate the behaviour of two different FRP intradossal applic... more This paper aims to comparise and illustrate the behaviour of two different FRP intradossal applications made of sheets or pultruded elements, in order to show all those situations that can compromise these upgrading works, leading to local collapse mechanism, which correspond to the debonding of FRP reinforcement from the substrate. In order to avoid such problems the use of CFRP pultruded plates rather than strips or sheets is analyzed and illustrated. The paper presents preliminary results of experimental research on solid brick masonry arches strengthened at their intrados with GFRP sheets or CFRP pultruded plates. The results have pointed out the enhancement in capacity of the strengthened arches and the influence on the ultimate strength and failure mechanism of the different types of FRP (sheets and plates) reinforcements applied at arch intrados.

The paper addresses the problem of evaluation of strength of masonry walls, within the context of... more The paper addresses the problem of evaluation of strength of masonry walls, within the context of seismic assessment of existing buildings. In-plane behaviour of full scale stone and brick masonry panels has been studied under monotonic diagonal-compression and shear-compression loading in quasi-static test facility. The experimental research was carried out in Abruzzi and Umbria since the 1990s, and it represents an important database for mechanical characterization of some widely used masonry walls in these seismic regions. The monotonic shear-compression and diagonal compression tests were performed under load control and experimental data have provided information about in-plane behaviour of unreinforced masonry (URM) walls. Failure modes, shear strength, displacement capacity and post-peak performance are discussed. A presentation is also given of the results of a F.E. investigation for shear strength evaluation of masonry walls. F.E. modeling non-linear procedure (available in...

This paper presents the results of a series of tests carried out on masonry tile arches reinforce... more This paper presents the results of a series of tests carried out on masonry tile arches reinforced with an innovative technique by means of GFRP (Glass Fiber Reinforced Plastics) mesh inserted into an inorganic matrix. The innovative technique here illustrated is the result of historical evolution of an ancient system of reinforcing tiled vaults from ancient Spanish construction tradition. Such technique involves the lamination of flat rectangular tiles or thin bricks into thin vaults known as boveda tabicada. Since the use of modern technologies may improve the mechanical properties of traditional materials, the core of the proposed strengthening system seeks to combine the advantageous compressive strength of masonry units with the excellent tensile properties of composite materials. In detail, it is possible to obtain reinforced masonry arches by overlapping different layers of thin bricks and GFRP laminates, embedded within lime mortar, so that the entire assembly acts as a sing...

The application of Steel fiber Reinforced Polymer (SRP) as a means of increasing the capacity of ... more The application of Steel fiber Reinforced Polymer (SRP) as a means of increasing the capacity of masonry columns is investigated in this study. The behavior of 27 solid-brick specimens that are externally wrapped by SRP sheets in low volumetric ratios is presented. The specimens are subjected to axial monotonic load until failure occurs. Two widely used types of masonry columns of differing square cross-sections were tested in compression (square and octagonal cross-sections). Octagonal cross-section masonry columns are common in many historical constructions and no data are present in bibliography on their mechanical behavior. Three different configurations of the reinforcing system were investigated: SRP sheets are applied as external reinforcement along the perimeter of the masonry columns in the form of continuous and discontinuous wrap, respectively. To elaborate, in the first case the confinement was provided by a continuous laminate; whereas in the second and third case the c...

This paper is an answer to the need of finding the optimal solution for the throttling system in ... more This paper is an answer to the need of finding the optimal solution for the throttling system in refrigerating machines using CO2 as working fluid; such a solution must combine reliability, low installation cost and high energy efficiency. To this purpose, different expansion ...

Advanced Materials Research, 2013

The innovative technique here illustrated is the result of historical evolution of ancient system... more The innovative technique here illustrated is the result of historical evolution of ancient systems of hooping and is conditioned by design criteria that take into account the structural life in the respect of existing elements. It consists in the application of small diameter stainless steel cords able to provide overlapping hoops at every course over the entire height of the column. Three series of uniaxial compression
tests, with a total of 19 specimens, were conducted on model brick masonry columns with these variables: cross-section geometry, amount and scheme of confining reinforcement. Laboratory outcomes have shown how the investigated confining systems are able to provide significant gains in terms
of compressive strength (values of the confined-tounconfined
strength ratio ranging between 1.45 and 3.00 have been obtained). Test results have been finally used to assess the reliability of the existing design equations suggested by Italian National Research Council for design of FRP strengthening of
masonry columns.

Bulletin of Earthquake Engineering, 2015

ABSTRACT It is known that the mechanical behavior of masonry material depends on many factors, su... more ABSTRACT It is known that the mechanical behavior of masonry material depends on many factors, such as compressive or shear strength of components (mortar and blocks), blocks shape, volumetric ratio between components and wall texture, that is the result of applying a series of construction devices which form the ‘‘rule of art’’. Taking into account the complexity of the problem due to the great number of variables, a fair assessment of the load carrying capacity of masonries can be made only with in situ test. Being in situ test a semi-destructive methods, not always viable, a numerical estimate of the mechanical parameters of the walls can be made on the basis of a qualitative criteria evaluation. The method here proposed, called Masonry Quality Index (MQI) method, consists in evaluating the presence, the partial presence, or the absence of certain parameters that define the ‘‘rule of the art’’, namely a set of construction devices that, if executed during the construction of a wall, provides a good behavior and ensure the compactness and the monolithicity.

Key Engineering Materials, 2014

ABSTRACT In this study, an effort was made to develop an experimental protocol to study the effec... more ABSTRACT In this study, an effort was made to develop an experimental protocol to study the effects of accelerated ageing on composite materials based on bamboo and steel fibers. The physicomechanical properties of different types of steel and bamboo fibers were investigated. Specimens were subjected to environmental agents. Mechanical and physical tests were used to measure the retained properties and to observe the causes of damage and strength reduction. The experimental data showed that resin properties may strongly influence the durability of FRP reinforcement, environmental combined cycles did not take to significant damage of conditioned specimens; steel fibers are sensitive to alkaline attack when resin does not provide adequate protection to fibers.

Key Engineering Materials, 2014

ABSTRACT In this study, an effort was made to develop an experimental protocol to study the effec... more ABSTRACT In this study, an effort was made to develop an experimental protocol to study the effects of accelerated ageing on GFRP (Glass Fiber-Reinforced Polymer) grids. The physic-mechanical properties of different types of glass FRP grids were investigated. GFRP specimens were subjected to environmental agents including freeze-thaw, high relative humidity, high temperature. Mechanical and physical tests were used to measure the retained properties and to observe the causes of damage and strength reduction. The experimental data showed that resin properties may strongly influence the durability of FRP reinforcement, environmental combined cycles did not take to significant damage of conditioned specimens; GFRP grids are sensitive to alkaline attack when resin does not provide adequate protection to fibers.

Key Engineering Materials, 2014

ABSTRACT The innovative technique here illustrated is the result of historical evolution of ancie... more ABSTRACT The innovative technique here illustrated is the result of historical evolution of ancient systems of hooping and is conditioned by design criteria that take into account the structural life in the respect of existing elements. It consists in the application of small diameter cords able to provide overlapping hoops at every course over the entire height of the column. Three series of uniaxial compression tests, with a total of 22 specimens, were conducted on model brick masonry columns with these variables: cross-section geometry, amount and scheme of confining reinforcement. Laboratory outcomes have shown how the investigated confining systems are able to provide significant gains in terms of compressive strength. Test results have been finally used to assess the reliability of the existing design equations suggested by Italian National Research Council for design of FRP strengthening of masonry columns.

Proceedings of the Twelfth International Conference on Computational Structures Technology, 2014

Composites Part B: Engineering, 2005

Construction and Building Materials, 2005

Journal of Materials in Civil Engineering, 2014

Composites Part B: Engineering, 2007

Proceedings of the Tenth International Conference on Computational Structures Technology, 2010

Advanced Materials Research, 2013

Bulletin of Earthquake Engineering, 2015

Key Engineering Materials, 2014

ABSTRACT In this study, an effort was made to develop an experimental protocol to study the effec... more ABSTRACT In this study, an effort was made to develop an experimental protocol to study the effects of accelerated ageing on GFRP (Glass Fiber-Reinforced Polymer) grids. The physic-mechanical properties of different types of glass FRP grids were investigated. GFRP specimens were subjected to environmental agents including freeze-thaw, high relative humidity, high temperature. Mechanical and physical tests were used to measure the retained properties and to observe the causes of damage and strength reduction. The experimental data showed that resin properties may strongly influence the durability of FRP reinforcement, environmental combined cycles did not take to significant damage of conditioned specimens; GFRP grids are sensitive to alkaline attack when resin does not provide adequate protection to fibers.

Key Engineering Materials, 2014