IABSE Symposium, Guimarães 2019: Towards a Resilient Built Environment Risk and Asset Management
A growing interest concerning the seismic risk assessment at urban scale has been observed. In It... more A growing interest concerning the seismic risk assessment at urban scale has been observed. In Italy, recent earthquakes highlighted the vulnerability of the built environment causing severe damage and a high number of casualties. In addition, historical city centres are part of the cultural heritage and their preservation is deemed necessary. For these reasons, understanding how to assess urban systems behaviour is crucial. A major step in this direction is the definition of the Emergency Limit Condition (ELC), by the Civil Protection Department. More recently, a theoretical framework with four additional urban limit conditions has been proposed. This paper tries to take a step forward in this direction by assigning specific performance goals to defined urban limit conditions. These goals are linked to different level of damage and functionality loss of buildings and infrastructures and the possible short-to-long term effects on the population and economy.
This paper discusses the main results of a full-scale shaking table test campaign carried out und... more This paper discusses the main results of a full-scale shaking table test campaign carried out under the auspices of the EU funded research project SERA, whose objective is to investigate the seismic performance of three-leaf masonry walls with weak lime-mortar joints. These masonry walls are widely found in seismic prone regions in the Mediterranean area, thus assessing their behaviour under dynamic actions is an important pre-requisite for the seismic vulnerability evaluation of a plethora of historical centres. The first part of the paper presents a preliminary study on the mechanical properties of the wall component materials that was carried out through an ad-hoc experimental campaign. The outcomes are of particular interest for the characterization of the mortar and of the infill materials, that were designed to reproduce the low strength that is typically found in old masonry buildings. The design of the masonry wall that was tested and the test set-up are presented next. The ...
This paper discusses the main results of a full-scale shaking table test campaign carried out und... more This paper discusses the main results of a full-scale shaking table test campaign carried out under the auspices of the EU funded research project SERA, whose objective is to investigate the seismic performance of three-leaf masonry walls with weak lime-mortar joints. These masonry walls are widely found in seismic prone regions in the Mediterranean area, thus assessing their behaviour under dynamic actions is an important pre-requisite for the seismic vulnerability evaluation of a plethora of historical centres. The first part of the paper presents a preliminary study on the mechanical properties of the wall component materials that was carried out through an ad-hoc experimental campaign. The outcomes are of particular interest for the characterization of the mortar and of the infill materials, that were designed to reproduce the low strength that is typically found in old masonry buildings. The design of the masonry wall that was tested and the test set-up are presented next. The ...
The maximum seismic response of torsionally coupled plan asymmetric structures can be rationally ... more The maximum seismic response of torsionally coupled plan asymmetric structures can be rationally visualized and computed through a Mohr Circle Response Spectrum Analysis (MCRSA). This is done combining the graphic modal properties of the torsional dynamic equations of motion with the structural earthquake demand in terms of a displacement spectrum as a function of the modal eigenvalues S D (ω 2). A compact representation of the modal properties and of the response envelope is built and visualized in the Mohr plane. The maximum modal responses are then combined using a graphic adaptation of the SRSS and CCQ combination rules based on the elastic response spectrum. This Graphic Dynamic rule proves to be an effective response prediction tool, and is particularly suited to estimate the response of seismic base isolation systems.
Abstract Older infilled frame R/C structures have several deficiencies as compared to seismic cod... more Abstract Older infilled frame R/C structures have several deficiencies as compared to seismic code-conforming structures, inherent to the behavior of the structural elements and interaction between structural and nonstructural components, which should be accounted for an accurate performance assessment. In order to investigate the importance of incorporating the contribution of the infills (typically considered as non-structural members) and their interaction with non-ductile columns in a building structural model, a comprehensive performance based earthquake assessment over a range of hazard levels is carried out through Nonlinear static and Incremental Dynamic Analyses of a 2D frame model incorporating: (1) fiber section axial force–moment interaction, (2) cracking and crushing of the infills and (3) infills-induced shear failure of columns. The analyses are performed on three different common structural configurations: (A) bare frame, (B) uniformly infilled frame, and (C) partially infilled frame (pilotis frame). Results show the importance of correctly accounting for shear failure of columns when modeling the infill–frame interaction, and the influence of the inelastic shear law, opening placement, type of infills, and choice of infill constitutive model.
This paper discusses the importance of modeling soil-pile interaction in the response of reinforc... more This paper discusses the importance of modeling soil-pile interaction in the response of reinforced concrete piles. A displacement-based, reinforced concrete beam-column fiber model with distributed lateral deformable supports is presented first. The formulation is general and applies to both monotonic and cyclic loads. The proposed model is simple, computationally efficient and capable of representing the salient features of the soil-pile interaction, including dragging force and gap formation along the pile-soil interfaces as well as hysteretic responses of piles and surrounding soils. Two applications are presented to illustrate the model characteristics, to show the model capabilities, and to discuss the importance of modeling pile-soil system. The first application deals with a single end-bearing pile embedded in a cohesionless soil. The proposed beam-column model is used to investigate the effects of model parameters on the pile-soil response, including pile length, pile diame...
Seismic risk in the form of impending disaster has been seen from past records that moderate-to-l... more Seismic risk in the form of impending disaster has been seen from past records that moderate-to-large earthquakes have caused the loss of life and property in all parts of Nepal. Despite the availability of new data, and methodological improvements, the available seismic hazard map of Nepal is about two decades old. So an updated seismic hazard model at the country level is imperative and logical. The seismic hazard and risk model constitute important tools for framing public policies toward land-use planning, building regulations, insurance, and emergency preparedness. In fact, the reliable estimation of seismic hazard and risk eventually minimizes social and economic disruption caused by earthquakes. In this frame of reference, the seismic risk assessment at a country level is elementary in reducing potential losses stemming from future earthquakes. Thus, this study investigates structural vulnerability, seismic risk, and the resulting possible economic losses owing to future earthquakes in Nepal. To this end, seismic risk assessment in Nepal is done using an existing probabilistic seismic hazard, a newly developed structural vulnerability, and recently released exposure data. The OpenQuake-engine, the open-source platform for seismic hazard and risk assessment from the Global Earthquake Model initiative, was used to calculate the seismic hazard and risk in Nepal. The seismic hazard and mean economic loss map were formulated for the 1, 2, 5, and 10 % probability of exceedance in 50 years. Finally, the distribution of building damage and corresponding economic losses due to the recurrence of the historical 1934 earthquake was presented in this study.
ABSTRACT Infills can have a significant influence on the stiffness, strength, ductility, and othe... more ABSTRACT Infills can have a significant influence on the stiffness, strength, ductility, and other key modelling parameters of non-ductile R/C frames, thus resulting in very different response evaluation. They are quite often neglected in linear or nonlinear models because of the modelling complexity and increase in computational effort. To investigate the infill effects on the response of a sample 2D frame, three different structural configurations are analyzed using the diagonal strut scheme proposed by ASCE41/FEMA356: a) bare frame, b) partially infilled frame (pilotis frame) and c) uniformly infilled frame. These configurations are analyzed through Static Pushover Analyses, and Incremental Dynamic Analyses spanning a wide range of hazard levels under a suite of 14 natural ground motions. Results from the nonlinear analyses provide information on the interaction of the concentric/eccentric infill strut modelling arrangements with the inelastic flexural and shear behavior of the frame elements, and their impact on the global and local responses.
The use of Nonlinear Dynamic Analyses is coupled to the demands produced by earthquakes of differ... more The use of Nonlinear Dynamic Analyses is coupled to the demands produced by earthquakes of different intensities. The uncertainties associated with the demands are highly dependent on the variable adopted as the intensity measure (IM). This generates the need to compare different IMs and in particular the dispersion of the demand measure in relation to each IM. For this purpose correlations between maximum inter-story drift demand of nine reinforced concrete Multiple Degree of Freedom tridimensional structures and a number of widely used ground motion intensity parameters have been investigated. To determine the optimum parameter to be used as the IM, two additional intensity parameters are analyzed, the spectral acceleration corresponding to the cracked and non-linear period of each structure, S a (T crack) and S a (T *), respectively. The results showed that these two IMs have the best correlation with the deformation demand and their use produces a lower variability of structural response.
The hysteretic behavior of reinforced concrete elements depends in large measure on the interacti... more The hysteretic behavior of reinforced concrete elements depends in large measure on the interaction between reinforcing steel and concrete through bond. This paper presents a new finite element for reinforcing bars anchored in concrete. The novel aspect of the element is the use of force instead of displacement interpolation functions. The force interpolation functions satisfy equilibrium in a strict sense and ensure the numerical stability of the results, even in the presence of significant strength loss and softening, as might be the case for reinforcing bars with insufficient anchorage length. Another novel aspect of the element formulation is its implementation in a general purpose finite element analysis program that is based on the stiffness method of analysis. Correlation studies with available experimental data demonstrate the ability of the proposed model to simulate the bond deterioration and eventual pull-out of anchored reinforcing bars under severe inelastic excursions.
... 8. FF Taucer, E. Spacone and FC Filippou, A fiber beam-column element for seismic response an... more ... 8. FF Taucer, E. Spacone and FC Filippou, A fiber beam-column element for seismic response analysis of reinforced concrete structures. In: (4th Edn. ... In: (4th Edn. ed.),TheFinite Element Method Vol. 1, McGraw-Hill, London (1989). 10. ...
This paper presents an effective and accurate computational strategy for unreinforced brick mason... more This paper presents an effective and accurate computational strategy for unreinforced brick masonry structures. Mesoscale descriptions allow a realistic representation of the nonlinear structural behaviour of URM, but can pose prohibitive computational demands for large-scale problems. To overcome this drawback, the computational strategy presented in the paper employs the domain partitioning approach, which is coupled with an accurate mesoscale finite element model. This allows the effective parallelisation of the nonlinear structural analysis simulation, where significant speed-up can be achieved in the nonlinear analysis of large masonry structures. The potential and effectiveness of the proposed computational strategy are shown through numerical examples, where full-scale masonry structures are considered.
IABSE Symposium, Guimarães 2019: Towards a Resilient Built Environment Risk and Asset Management
A growing interest concerning the seismic risk assessment at urban scale has been observed. In It... more A growing interest concerning the seismic risk assessment at urban scale has been observed. In Italy, recent earthquakes highlighted the vulnerability of the built environment causing severe damage and a high number of casualties. In addition, historical city centres are part of the cultural heritage and their preservation is deemed necessary. For these reasons, understanding how to assess urban systems behaviour is crucial. A major step in this direction is the definition of the Emergency Limit Condition (ELC), by the Civil Protection Department. More recently, a theoretical framework with four additional urban limit conditions has been proposed. This paper tries to take a step forward in this direction by assigning specific performance goals to defined urban limit conditions. These goals are linked to different level of damage and functionality loss of buildings and infrastructures and the possible short-to-long term effects on the population and economy.
This paper discusses the main results of a full-scale shaking table test campaign carried out und... more This paper discusses the main results of a full-scale shaking table test campaign carried out under the auspices of the EU funded research project SERA, whose objective is to investigate the seismic performance of three-leaf masonry walls with weak lime-mortar joints. These masonry walls are widely found in seismic prone regions in the Mediterranean area, thus assessing their behaviour under dynamic actions is an important pre-requisite for the seismic vulnerability evaluation of a plethora of historical centres. The first part of the paper presents a preliminary study on the mechanical properties of the wall component materials that was carried out through an ad-hoc experimental campaign. The outcomes are of particular interest for the characterization of the mortar and of the infill materials, that were designed to reproduce the low strength that is typically found in old masonry buildings. The design of the masonry wall that was tested and the test set-up are presented next. The ...
This paper discusses the main results of a full-scale shaking table test campaign carried out und... more This paper discusses the main results of a full-scale shaking table test campaign carried out under the auspices of the EU funded research project SERA, whose objective is to investigate the seismic performance of three-leaf masonry walls with weak lime-mortar joints. These masonry walls are widely found in seismic prone regions in the Mediterranean area, thus assessing their behaviour under dynamic actions is an important pre-requisite for the seismic vulnerability evaluation of a plethora of historical centres. The first part of the paper presents a preliminary study on the mechanical properties of the wall component materials that was carried out through an ad-hoc experimental campaign. The outcomes are of particular interest for the characterization of the mortar and of the infill materials, that were designed to reproduce the low strength that is typically found in old masonry buildings. The design of the masonry wall that was tested and the test set-up are presented next. The ...
The maximum seismic response of torsionally coupled plan asymmetric structures can be rationally ... more The maximum seismic response of torsionally coupled plan asymmetric structures can be rationally visualized and computed through a Mohr Circle Response Spectrum Analysis (MCRSA). This is done combining the graphic modal properties of the torsional dynamic equations of motion with the structural earthquake demand in terms of a displacement spectrum as a function of the modal eigenvalues S D (ω 2). A compact representation of the modal properties and of the response envelope is built and visualized in the Mohr plane. The maximum modal responses are then combined using a graphic adaptation of the SRSS and CCQ combination rules based on the elastic response spectrum. This Graphic Dynamic rule proves to be an effective response prediction tool, and is particularly suited to estimate the response of seismic base isolation systems.
Abstract Older infilled frame R/C structures have several deficiencies as compared to seismic cod... more Abstract Older infilled frame R/C structures have several deficiencies as compared to seismic code-conforming structures, inherent to the behavior of the structural elements and interaction between structural and nonstructural components, which should be accounted for an accurate performance assessment. In order to investigate the importance of incorporating the contribution of the infills (typically considered as non-structural members) and their interaction with non-ductile columns in a building structural model, a comprehensive performance based earthquake assessment over a range of hazard levels is carried out through Nonlinear static and Incremental Dynamic Analyses of a 2D frame model incorporating: (1) fiber section axial force–moment interaction, (2) cracking and crushing of the infills and (3) infills-induced shear failure of columns. The analyses are performed on three different common structural configurations: (A) bare frame, (B) uniformly infilled frame, and (C) partially infilled frame (pilotis frame). Results show the importance of correctly accounting for shear failure of columns when modeling the infill–frame interaction, and the influence of the inelastic shear law, opening placement, type of infills, and choice of infill constitutive model.
This paper discusses the importance of modeling soil-pile interaction in the response of reinforc... more This paper discusses the importance of modeling soil-pile interaction in the response of reinforced concrete piles. A displacement-based, reinforced concrete beam-column fiber model with distributed lateral deformable supports is presented first. The formulation is general and applies to both monotonic and cyclic loads. The proposed model is simple, computationally efficient and capable of representing the salient features of the soil-pile interaction, including dragging force and gap formation along the pile-soil interfaces as well as hysteretic responses of piles and surrounding soils. Two applications are presented to illustrate the model characteristics, to show the model capabilities, and to discuss the importance of modeling pile-soil system. The first application deals with a single end-bearing pile embedded in a cohesionless soil. The proposed beam-column model is used to investigate the effects of model parameters on the pile-soil response, including pile length, pile diame...
Seismic risk in the form of impending disaster has been seen from past records that moderate-to-l... more Seismic risk in the form of impending disaster has been seen from past records that moderate-to-large earthquakes have caused the loss of life and property in all parts of Nepal. Despite the availability of new data, and methodological improvements, the available seismic hazard map of Nepal is about two decades old. So an updated seismic hazard model at the country level is imperative and logical. The seismic hazard and risk model constitute important tools for framing public policies toward land-use planning, building regulations, insurance, and emergency preparedness. In fact, the reliable estimation of seismic hazard and risk eventually minimizes social and economic disruption caused by earthquakes. In this frame of reference, the seismic risk assessment at a country level is elementary in reducing potential losses stemming from future earthquakes. Thus, this study investigates structural vulnerability, seismic risk, and the resulting possible economic losses owing to future earthquakes in Nepal. To this end, seismic risk assessment in Nepal is done using an existing probabilistic seismic hazard, a newly developed structural vulnerability, and recently released exposure data. The OpenQuake-engine, the open-source platform for seismic hazard and risk assessment from the Global Earthquake Model initiative, was used to calculate the seismic hazard and risk in Nepal. The seismic hazard and mean economic loss map were formulated for the 1, 2, 5, and 10 % probability of exceedance in 50 years. Finally, the distribution of building damage and corresponding economic losses due to the recurrence of the historical 1934 earthquake was presented in this study.
ABSTRACT Infills can have a significant influence on the stiffness, strength, ductility, and othe... more ABSTRACT Infills can have a significant influence on the stiffness, strength, ductility, and other key modelling parameters of non-ductile R/C frames, thus resulting in very different response evaluation. They are quite often neglected in linear or nonlinear models because of the modelling complexity and increase in computational effort. To investigate the infill effects on the response of a sample 2D frame, three different structural configurations are analyzed using the diagonal strut scheme proposed by ASCE41/FEMA356: a) bare frame, b) partially infilled frame (pilotis frame) and c) uniformly infilled frame. These configurations are analyzed through Static Pushover Analyses, and Incremental Dynamic Analyses spanning a wide range of hazard levels under a suite of 14 natural ground motions. Results from the nonlinear analyses provide information on the interaction of the concentric/eccentric infill strut modelling arrangements with the inelastic flexural and shear behavior of the frame elements, and their impact on the global and local responses.
The use of Nonlinear Dynamic Analyses is coupled to the demands produced by earthquakes of differ... more The use of Nonlinear Dynamic Analyses is coupled to the demands produced by earthquakes of different intensities. The uncertainties associated with the demands are highly dependent on the variable adopted as the intensity measure (IM). This generates the need to compare different IMs and in particular the dispersion of the demand measure in relation to each IM. For this purpose correlations between maximum inter-story drift demand of nine reinforced concrete Multiple Degree of Freedom tridimensional structures and a number of widely used ground motion intensity parameters have been investigated. To determine the optimum parameter to be used as the IM, two additional intensity parameters are analyzed, the spectral acceleration corresponding to the cracked and non-linear period of each structure, S a (T crack) and S a (T *), respectively. The results showed that these two IMs have the best correlation with the deformation demand and their use produces a lower variability of structural response.
The hysteretic behavior of reinforced concrete elements depends in large measure on the interacti... more The hysteretic behavior of reinforced concrete elements depends in large measure on the interaction between reinforcing steel and concrete through bond. This paper presents a new finite element for reinforcing bars anchored in concrete. The novel aspect of the element is the use of force instead of displacement interpolation functions. The force interpolation functions satisfy equilibrium in a strict sense and ensure the numerical stability of the results, even in the presence of significant strength loss and softening, as might be the case for reinforcing bars with insufficient anchorage length. Another novel aspect of the element formulation is its implementation in a general purpose finite element analysis program that is based on the stiffness method of analysis. Correlation studies with available experimental data demonstrate the ability of the proposed model to simulate the bond deterioration and eventual pull-out of anchored reinforcing bars under severe inelastic excursions.
... 8. FF Taucer, E. Spacone and FC Filippou, A fiber beam-column element for seismic response an... more ... 8. FF Taucer, E. Spacone and FC Filippou, A fiber beam-column element for seismic response analysis of reinforced concrete structures. In: (4th Edn. ... In: (4th Edn. ed.),TheFinite Element Method Vol. 1, McGraw-Hill, London (1989). 10. ...
This paper presents an effective and accurate computational strategy for unreinforced brick mason... more This paper presents an effective and accurate computational strategy for unreinforced brick masonry structures. Mesoscale descriptions allow a realistic representation of the nonlinear structural behaviour of URM, but can pose prohibitive computational demands for large-scale problems. To overcome this drawback, the computational strategy presented in the paper employs the domain partitioning approach, which is coupled with an accurate mesoscale finite element model. This allows the effective parallelisation of the nonlinear structural analysis simulation, where significant speed-up can be achieved in the nonlinear analysis of large masonry structures. The potential and effectiveness of the proposed computational strategy are shown through numerical examples, where full-scale masonry structures are considered.
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