The Experts below are selected from a list of 213 Experts worldwide ranked by ideXlab platform
Francesco Portioli - One of the best experts on this subject based on the ideXlab platform.
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INVITED: A simple contact model for dynamic analysis of Masonry Block structures using mathematical programming
2018Co-Authors: Francesco Portioli, Elias G. DimitrakopoulosAbstract:A simple contact model is presented in this paper for dynamic analysis of Masonry Block structures using mathematical programming. Masonry structures are represented as 2D assemblages of rigid Blocks interacting at no-tension, frictional interfaces with infinite compressive strength. To represent interaction at interfaces a point-based contact model is used, with static variables located at the vertices of each interface. Non-penetration conditions at contact points are formulated using gap functions and complementarity conditions to ensure that contact forces occur only if the gap is closed. The equations of motion are discretized with respect to time using the theta method and are expressed at the displacement level. The contact dynamic problem is formulated as force-based problem under the assumption of associative flow rule for displacement rates at contact points. The formulation of the variational problem associated to dynamics of the Block assemblages gives rise to a quadratic mathematical programming problem. To evaluate the accuracy and computational efficiency of the implemented formulation, applications to numerical case studies from the literature are presented. The case studies comprise a rigid Block under free rocking motion and earthquake excitation. A bi-Block structure under free rocking motion is also investigated for validation. Finally, the wall panels analysed by Ferris and Tin-Loi using limit analysis are considered to compare failure mechanism and magnitudes of lateral loads promoting the collapse.
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Contact Dynamics of Masonry Block Structures Using Mathematical Programming
Journal of Earthquake Engineering, 2016Co-Authors: Francesco Portioli, Lucrezia CasciniAbstract:A simple variational formulation for contact dynamics is adopted to investigate the dynamic behavior of planar Masonry Block structures subjected to seismic events. The numerical model is a two-dimensional assemblage of rigid Blocks interacting at potential contact points located at the vertices of the interfaces. A no-tension and associative frictional behavior with infinite compressive strength is considered for joints. The dynamic contact problem is formulated as a quadratic programming problem (QP) and an iterative procedure is implemented for time integration. Applications to analytical and numerical case studies are presented for validation. Comparisons with the experimental results of a Masonry wall under free rocking motion and of a small scale panel with opening subjected to in-plane loads are also carried out to evaluate the accuracy and the computational efficiency of the formulation adopted.
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assessment of Masonry structures subjected to foundation settlements using rigid Block limit analysis
Engineering Structures, 2016Co-Authors: Francesco Portioli, Lucrezia CasciniAbstract:Abstract In this paper, a three-dimensional rigid body model is implemented to investigate the behaviour of Masonry Block structures subjected to foundation settlements. The structural behaviour is investigated formulating a limit analysis problem for the calculation of the base reaction and the associated failure mode once the settlement is introduced in the model. The structural model is an assemblage of rigid Blocks which interact at contact interfaces. The latter are modelled as concave-contacts, using contact points located at the corners of the interface to represent interactions. A no-tension and non-associative frictional behaviour with infinite compressive strength is considered for joints. The limit analysis problem is formulated as a second order cone programming problem (SOCP) and an iterative procedure is adopted to take into account non-associative frictional behaviour. A computer program has been developed for applications of the proposed procedure. Two simple numerical examples are presented with the aim to verify the obtained results against analytical solutions. Applications to a set of experimental tests and to a 3D building model are introduced for validation and to evaluate the computational efficiency of the model. Finally a dissipation index is defined in order to give a quantitative estimation of the consequences related to the foundation settlement.
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Experimental tests on the limit states of dry-jointed tuff Blocks
Materials and Structures, 2016Co-Authors: Claudia Casapulla, Francesco PortioliAbstract:A proper definition of the yield domains governing the frictional behaviour at contact interfaces is generally required to perform the limit analysis of 3D dry-jointed Masonry Block structures. However, the modelling of the actual behaviour of frictional contact interfaces under simultaneous normal and shear forces, torsion and bending moments is a topic still poorly studied, especially from the experimental point of view. In this paper the single contact interface of a system composed of two dry-jointed tuff Blocks under different loading conditions is experimentally investigated. The programme includes several sets of tests based on different eccentricities of the vertical and horizontal loading implying pure strengths and interactions among shear, torsion and bending moments. The results of each set are then compared with those obtained by a recently proposed numerical model for 3D Masonry Block assemblages, based on the assumptions of infinite strength in compression, tension and shear for Blocks and no-tension and frictional behaviour at their contact. The comparison is useful, on the one hand, as a further validation the efficacy of the previously proposed yield domains in order to be used in 3D limit analysis formulations and, on the other, to highlight which yield domains need to be better represented.
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an efficient solution procedure for crushing failure in 3d limit analysis of Masonry Block structures with non associative frictional joints
International Journal of Solids and Structures, 2015Co-Authors: Francesco Portioli, Claudia Casapulla, Lucrezia CasciniAbstract:Abstract A formulation for limit analysis of three-dimensional Masonry structures modelled as rigid Block assemblages is presented. A concave contact model is adopted for interfaces, using contact points located at the corners of the interface to represent interactions. A no-tension and non-associative frictional behaviour with limited compressive strength is considered for joints. The limit analysis problem is formulated as a second order cone programming problem (SOCP) and an iterative procedure is proposed to model crushing failure and to take into account non-associative frictional behaviour. Applications to numerical case studies are presented for validation. Finally, the accuracy and the computational efficiency of the proposed formulation are evaluated by a comparison with the results of a full scale experimental sub-assemblage of a Masonry pier-spandrel system.
M E Rahman - One of the best experts on this subject based on the ideXlab platform.
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THE COMPRESSIVE STRENGTH CHARACTERISTICS OF THE Masonry Block FROM THE OIL PALM SHELL
2020Co-Authors: Agus Setyo Muntohar, M E Rahman, Taman TirtoAbstract:Indonesia and Malaysia is the two largest producer of palm oil. However, one significant problem in the processing of palm oil is the large amounts of waste produced and this is one of the main contributors to the nation’s pollution pro blem. This paper presents the investigation of the use of oil palm shell waste as Masonry Block ma terials. The study was focused on the compressive strength and the durability. The masonr y Block was made by mixing the portland cement, sand, and oil palm shell waste. The specime n size was 220 mm in length x 110 mm in width x 80 mm thickness. The test results showed th at the maximum strength was obtained by mixing proportion of 1 PC : 1 sand : 1 OPS. Additio n a large amount of OPS was lowering the compressive strength. Overall results indicated tha t the shellcrete complied the specification standard for lightweight to medium concrete buildin g brick which was suitable for load bearing purposes.
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Performance of Masonry Blocks incorporating Palm Oil Fuel Ash
Journal of Cleaner Production, 2014Co-Authors: M E Rahman, Agus Setyo Muntohar, Ang Lye Boon, Nafeez Hashem Tanim, Vikram PakrashiAbstract:This paper presents an experimental study on the development of Masonry Block with Palm Oil Fuel Ash (POFA) as a partial replacement to cement whilst maintaining satisfactory properties of Masonry Block. The dosages of POFA are limited to 0%, 20%, 40% and 60% by mass of the total cementitious material in the Masonry Block. The experiments on Masonry Block investigate the compressive strength and the breaking load for mechanical properties and water absorption and efflorescence for its durability. The compressive strength and the breaking load of the Masonry Blocks reduce with increasing percentage of POFA replacement. However, it satisfies the requirements of Class 1 and Class 2 load-bearing Masonry Block according to Malaysian Standard MS76:1972. In terms of durability of the Masonry Block, water absorption for all the Masonry Blocks satisfies the requirement of ASTM C55-11 and there is no any sign of efflorescence on all the Masonry Blocks. POFA based Masonry Block are also found to be cheaper than the cement sand Masonry Blocks. The experimental studies indicate that POFA based Masonry Block has a significant potential for application in the construction industry.
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lightweight Masonry Block from oil palm kernel shell
Construction and Building Materials, 2014Co-Authors: Agus Setyo Muntohar, M E RahmanAbstract:A large amount of waste produced in the processing of palm oil is one of the main contributors to the environmental problem. This paper presents an experimental study on the development of the shellcrete Masonry Block that made of oil palm kernel. The study was focused on the physical, compressive strength and flexural strength of shellcrete. The eco-efficiency of the shellcrete was also evaluated by measuring the carbon footprint. The shellcrete was made by mixing the Portland cement (PC), sand, and oil palm kernel shell (PKS). A control specimen made of PC and sand mixture (sandcrete) was also prepared. The specimen size was 220 mm length, 110 mm width and 80 mm in thickness. The maximum strength obtained was 22 MPa by mixing proportion of 1 PC:1 Sand:1 PKS, but the recommended mix proportion of the shellcrete for building materials was 1 PC:1 Sand:2 PKS as an optimum mix design for eco-friendly shellcrete.
Agus Setyo Muntohar - One of the best experts on this subject based on the ideXlab platform.
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THE COMPRESSIVE STRENGTH CHARACTERISTICS OF THE Masonry Block FROM THE OIL PALM SHELL
2020Co-Authors: Agus Setyo Muntohar, M E Rahman, Taman TirtoAbstract:Indonesia and Malaysia is the two largest producer of palm oil. However, one significant problem in the processing of palm oil is the large amounts of waste produced and this is one of the main contributors to the nation’s pollution pro blem. This paper presents the investigation of the use of oil palm shell waste as Masonry Block ma terials. The study was focused on the compressive strength and the durability. The masonr y Block was made by mixing the portland cement, sand, and oil palm shell waste. The specime n size was 220 mm in length x 110 mm in width x 80 mm thickness. The test results showed th at the maximum strength was obtained by mixing proportion of 1 PC : 1 sand : 1 OPS. Additio n a large amount of OPS was lowering the compressive strength. Overall results indicated tha t the shellcrete complied the specification standard for lightweight to medium concrete buildin g brick which was suitable for load bearing purposes.
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Performance of Masonry Blocks incorporating Palm Oil Fuel Ash
Journal of Cleaner Production, 2014Co-Authors: M E Rahman, Agus Setyo Muntohar, Ang Lye Boon, Nafeez Hashem Tanim, Vikram PakrashiAbstract:This paper presents an experimental study on the development of Masonry Block with Palm Oil Fuel Ash (POFA) as a partial replacement to cement whilst maintaining satisfactory properties of Masonry Block. The dosages of POFA are limited to 0%, 20%, 40% and 60% by mass of the total cementitious material in the Masonry Block. The experiments on Masonry Block investigate the compressive strength and the breaking load for mechanical properties and water absorption and efflorescence for its durability. The compressive strength and the breaking load of the Masonry Blocks reduce with increasing percentage of POFA replacement. However, it satisfies the requirements of Class 1 and Class 2 load-bearing Masonry Block according to Malaysian Standard MS76:1972. In terms of durability of the Masonry Block, water absorption for all the Masonry Blocks satisfies the requirement of ASTM C55-11 and there is no any sign of efflorescence on all the Masonry Blocks. POFA based Masonry Block are also found to be cheaper than the cement sand Masonry Blocks. The experimental studies indicate that POFA based Masonry Block has a significant potential for application in the construction industry.
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lightweight Masonry Block from oil palm kernel shell
Construction and Building Materials, 2014Co-Authors: Agus Setyo Muntohar, M E RahmanAbstract:A large amount of waste produced in the processing of palm oil is one of the main contributors to the environmental problem. This paper presents an experimental study on the development of the shellcrete Masonry Block that made of oil palm kernel. The study was focused on the physical, compressive strength and flexural strength of shellcrete. The eco-efficiency of the shellcrete was also evaluated by measuring the carbon footprint. The shellcrete was made by mixing the Portland cement (PC), sand, and oil palm kernel shell (PKS). A control specimen made of PC and sand mixture (sandcrete) was also prepared. The specimen size was 220 mm length, 110 mm width and 80 mm in thickness. The maximum strength obtained was 22 MPa by mixing proportion of 1 PC:1 Sand:1 PKS, but the recommended mix proportion of the shellcrete for building materials was 1 PC:1 Sand:2 PKS as an optimum mix design for eco-friendly shellcrete.
Claudia Casapulla - One of the best experts on this subject based on the ideXlab platform.
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Formulating the in-plane frictional resistances and collapse mechanisms for multi-storey Masonry Block walls
Frattura ed Integrità Strutturale, 2018Co-Authors: Luca Umberto Argiento, Alessandra Maione, Claudia CasapullaAbstract:In this paper a macro-Block model accounting for frictional resistances is presented to assess the lateral strength of a multi-storey Masonry Block wall. The kinematic approach of limit analysis is used to define the load factor causing the onset of rocking-sliding mechanism under in-plane horizontal loading. A dry frictional contact condition is assumed at the rigid Block interfaces, according to the Coulomb's law with non-associated flow rule. The key aspect of the proposed approach is the introduction of a criterion to evaluate the contribution of the actual frictional resistances depending on the inclination angle of the crack line. An accurate assessment of the frictional resistances is also obtained by distinguishing two different contributions (the wall own weight and additional vertical loads) and their application points. Hence, a sensitivity analysis is performed with respect to the overloading condition, the friction coefficient, and geometrical parameters such as the shape ratios of the wall and the unit Block and the number of rows. The analytical results of the proposed model are also validated against results from other existing macro and micro-Block modelling approaches in terms of load factor. The comparison confirms the reliability of the proposed model that allows, with similar results, great simplification of the computational effort with respect to micro-Block models.
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Experimental tests on the limit states of dry-jointed tuff Blocks
Materials and Structures, 2016Co-Authors: Claudia Casapulla, Francesco PortioliAbstract:A proper definition of the yield domains governing the frictional behaviour at contact interfaces is generally required to perform the limit analysis of 3D dry-jointed Masonry Block structures. However, the modelling of the actual behaviour of frictional contact interfaces under simultaneous normal and shear forces, torsion and bending moments is a topic still poorly studied, especially from the experimental point of view. In this paper the single contact interface of a system composed of two dry-jointed tuff Blocks under different loading conditions is experimentally investigated. The programme includes several sets of tests based on different eccentricities of the vertical and horizontal loading implying pure strengths and interactions among shear, torsion and bending moments. The results of each set are then compared with those obtained by a recently proposed numerical model for 3D Masonry Block assemblages, based on the assumptions of infinite strength in compression, tension and shear for Blocks and no-tension and frictional behaviour at their contact. The comparison is useful, on the one hand, as a further validation the efficacy of the previously proposed yield domains in order to be used in 3D limit analysis formulations and, on the other, to highlight which yield domains need to be better represented.
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an efficient solution procedure for crushing failure in 3d limit analysis of Masonry Block structures with non associative frictional joints
International Journal of Solids and Structures, 2015Co-Authors: Francesco Portioli, Claudia Casapulla, Lucrezia CasciniAbstract:Abstract A formulation for limit analysis of three-dimensional Masonry structures modelled as rigid Block assemblages is presented. A concave contact model is adopted for interfaces, using contact points located at the corners of the interface to represent interactions. A no-tension and non-associative frictional behaviour with limited compressive strength is considered for joints. The limit analysis problem is formulated as a second order cone programming problem (SOCP) and an iterative procedure is proposed to model crushing failure and to take into account non-associative frictional behaviour. Applications to numerical case studies are presented for validation. Finally, the accuracy and the computational efficiency of the proposed formulation are evaluated by a comparison with the results of a full scale experimental sub-assemblage of a Masonry pier-spandrel system.
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experimental and analytical investigation on the frictional contact behavior of 3d Masonry Block assemblages
Construction and Building Materials, 2015Co-Authors: Claudia Casapulla, Francesco PortioliAbstract:Abstract Crucial to the limit analysis of 3D dry-jointed Masonry Block structures is a proper description of the constitutive laws that govern the frictional contact behavior. In this paper an extensive experimental investigation is carried out on a stack of two dry-jointed tuff Blocks subjected to different loading conditions implying interactions among shear, torsion and bending moments. The results of each set are then compared with those obtained by the analytical model of two overlapped rigid Blocks, under the assumptions of infinite compressive, shear and tensile strength for Blocks and no-tension and frictional behavior at their contact. The non-linear yield functions are treated as piecewise linearizations in order to provide simplified expressions for mathematical programming in limit analysis formulations. Lastly, a simple example of 3D Block assemblage with associative frictional contacts is analyzed using linear programming (LP) formulation to show the computational efficiency related to the developed yield functions.
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limit analysis of Masonry walls by rigid Block modelling with cracking units and cohesive joints using linear programming
Engineering Structures, 2013Co-Authors: Francesco Portioli, Lucrezia Cascini, Claudia Casapulla, Mario DanielloAbstract:Abstract In this paper a rigid Block model with cracking units and cohesive joints is developed for limit analysis of Masonry structures using linear programming. The model is applicable to in-plane loaded unreinforced Masonry Block walls with regular textures and provides as output failure loads and collapse mechanisms. A simplified micro-modelling approach is adopted, based on the discretization of Masonry units into triangular Blocks separated by contact interfaces. Tensionless contact interfaces are used to model dry joints and cohesive contacts are introduced for mortar joints and internal unit interfaces. Failure modes at contact interfaces involve cracking, crushing and sliding. An iterative solution procedure is used to model non-associative flow rule in sliding and to take into account no-tension behaviour of cohesive joints in case of cracking. The modelling approach is validated and applied to different structural examples from the literature, including unconfined and confined Masonry panels and a Masonry beam. To show the accuracy of the proposed model and the improvement of the predicted response, the obtained results are compared with experimental tests and with the outcomes of standard rigid Block models using a single Block per Masonry unit and tensionless interfaces.
Lucrezia Cascini - One of the best experts on this subject based on the ideXlab platform.
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Contact Dynamics of Masonry Block Structures Using Mathematical Programming
Journal of Earthquake Engineering, 2016Co-Authors: Francesco Portioli, Lucrezia CasciniAbstract:A simple variational formulation for contact dynamics is adopted to investigate the dynamic behavior of planar Masonry Block structures subjected to seismic events. The numerical model is a two-dimensional assemblage of rigid Blocks interacting at potential contact points located at the vertices of the interfaces. A no-tension and associative frictional behavior with infinite compressive strength is considered for joints. The dynamic contact problem is formulated as a quadratic programming problem (QP) and an iterative procedure is implemented for time integration. Applications to analytical and numerical case studies are presented for validation. Comparisons with the experimental results of a Masonry wall under free rocking motion and of a small scale panel with opening subjected to in-plane loads are also carried out to evaluate the accuracy and the computational efficiency of the formulation adopted.
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assessment of Masonry structures subjected to foundation settlements using rigid Block limit analysis
Engineering Structures, 2016Co-Authors: Francesco Portioli, Lucrezia CasciniAbstract:Abstract In this paper, a three-dimensional rigid body model is implemented to investigate the behaviour of Masonry Block structures subjected to foundation settlements. The structural behaviour is investigated formulating a limit analysis problem for the calculation of the base reaction and the associated failure mode once the settlement is introduced in the model. The structural model is an assemblage of rigid Blocks which interact at contact interfaces. The latter are modelled as concave-contacts, using contact points located at the corners of the interface to represent interactions. A no-tension and non-associative frictional behaviour with infinite compressive strength is considered for joints. The limit analysis problem is formulated as a second order cone programming problem (SOCP) and an iterative procedure is adopted to take into account non-associative frictional behaviour. A computer program has been developed for applications of the proposed procedure. Two simple numerical examples are presented with the aim to verify the obtained results against analytical solutions. Applications to a set of experimental tests and to a 3D building model are introduced for validation and to evaluate the computational efficiency of the model. Finally a dissipation index is defined in order to give a quantitative estimation of the consequences related to the foundation settlement.
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an efficient solution procedure for crushing failure in 3d limit analysis of Masonry Block structures with non associative frictional joints
International Journal of Solids and Structures, 2015Co-Authors: Francesco Portioli, Claudia Casapulla, Lucrezia CasciniAbstract:Abstract A formulation for limit analysis of three-dimensional Masonry structures modelled as rigid Block assemblages is presented. A concave contact model is adopted for interfaces, using contact points located at the corners of the interface to represent interactions. A no-tension and non-associative frictional behaviour with limited compressive strength is considered for joints. The limit analysis problem is formulated as a second order cone programming problem (SOCP) and an iterative procedure is proposed to model crushing failure and to take into account non-associative frictional behaviour. Applications to numerical case studies are presented for validation. Finally, the accuracy and the computational efficiency of the proposed formulation are evaluated by a comparison with the results of a full scale experimental sub-assemblage of a Masonry pier-spandrel system.
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limit analysis of Masonry walls by rigid Block modelling with cracking units and cohesive joints using linear programming
Engineering Structures, 2013Co-Authors: Francesco Portioli, Lucrezia Cascini, Claudia Casapulla, Mario DanielloAbstract:Abstract In this paper a rigid Block model with cracking units and cohesive joints is developed for limit analysis of Masonry structures using linear programming. The model is applicable to in-plane loaded unreinforced Masonry Block walls with regular textures and provides as output failure loads and collapse mechanisms. A simplified micro-modelling approach is adopted, based on the discretization of Masonry units into triangular Blocks separated by contact interfaces. Tensionless contact interfaces are used to model dry joints and cohesive contacts are introduced for mortar joints and internal unit interfaces. Failure modes at contact interfaces involve cracking, crushing and sliding. An iterative solution procedure is used to model non-associative flow rule in sliding and to take into account no-tension behaviour of cohesive joints in case of cracking. The modelling approach is validated and applied to different structural examples from the literature, including unconfined and confined Masonry panels and a Masonry beam. To show the accuracy of the proposed model and the improvement of the predicted response, the obtained results are compared with experimental tests and with the outcomes of standard rigid Block models using a single Block per Masonry unit and tensionless interfaces.