Damaged models for the static and dynamic analysis of stone masonry
Stone masonry is one of the oldest type of constructions in the world due to the natural and free availability of stones and the easy construction. The walls are basically used to transfer vertical loads to the foundation and are the principal resistant elements to horizontal actions. Since stone masonry has a brittle behaviour, unfortunately every time an earthquake occurs there is a lot of damage, collapse and causalities. Recently, some researchers have performed experimental tests to improve the knowledge of the stone masonry (e.g. diagonal compression, monotonic, cyclic and dynamic tests). However, there is still the necessity to reproduce the seismic behaviour by using numerical approaches as finite element and discrete element methods. In this work a simplified procedure to reproduce a diagonal compression and a shear compression test of a rubble stone masonry is proposed within the finite element method. Since the bond between stones is the most influence part in the seismic behaviour of the complete masonry, the procedure here represents the stone units as rigid bodies and the mortar by a plasticity material with compression and tension degradation. This methodology allows to reduce degrees of freedom in the numerical models and to save computation time, reproducing the experimental tests with good accuracy in terms of capacity and failure pattern.
Stone masonry is one of the oldest type of constructions in the world due to the natural and free availability of stones and the easy construction. The walls are basically used to transfer vertical loads to the foundation and are the principal resistant elements to horizontal actions. Since stone masonry has a brittle behaviour, unfortunately every time an earthquake occurs there is a lot of damage, collapse and causalities. Recently, some researchers have performed experimental tests to improve the knowledge of the stone masonry (e.g. diagonal compression, monotonic, cyclic and dynamic tests). However, there is still the necessity to reproduce the seismic behaviour by using numerical approaches as finite element and discrete element methods. In this work a simplified procedure to reproduce a diagonal compression and a shear compression test of a rubble stone masonry is proposed within the finite element method. Since the bond between stones is the most influence part in the seismic behaviour of the complete masonry, the procedure here represents the stone units as rigid bodies and the mortar by a plasticity material with compression and tension degradation. This methodology allows to reduce degrees of freedom in the numerical models and to save computation time, reproducing the experimental tests with good accuracy in terms of capacity and failure pattern.
Selection of input accelerograms through 1D stochastic analyses of the ground response at the basement of San Felice church, Poggio Picenze (Italy)
The amplification of the ground motion at the surface is greatly influenced by the geotechnical characteristics of the soil formations below the ground surface. Traditionally, analyses of the ground response are deterministic, which means no consideration of the aleatory nature of geotechnical parameters of soil layers like density, shear wave velocity, etc. A fully stochastic procedure for estimating the site amplification of ground motion allows taking into account the record-to-record variability in an input ground motion and the uncertainty in dynamic soil properties and in the definition of the soil model. In particular, their effect on response spectra at the ground surface can be evaluated.
In this work the soil profile below the San Felice Martire church, at Poggio Picenze, has been studied basically on geologic observations and drilling and geophysical tests. The dynamic properties were obtained by literature and by the test results. Amplification effects at the site under investigation have been estimated using fully stochastic site response analyses and for the object motion 7 real records compatible to the Italian code-based spectrum referred to 475-year return period. The results in terms of accelerograms and acceleration response spectrum (with the associated dispersion) indicated a clear amplification of the input motion at the basement of San Felice Martire church due to the characteristics of the soil profile.
The amplification of the ground motion at the surface is greatly influenced by the geotechnical characteristics of the soil formations below the ground surface. Traditionally, analyses of the ground response are deterministic, which means no consideration of the aleatory nature of geotechnical parameters of soil layers like density, shear wave velocity, etc. A fully stochastic procedure for estimating the site amplification of ground motion allows taking into account the record-to-record variability in an input ground motion and the uncertainty in dynamic soil properties and in the definition of the soil model. In particular, their effect on response spectra at the ground surface can be evaluated.
In this work the soil profile below the San Felice Martire church, at Poggio Picenze, has been studied basically on geologic observations and drilling and geophysical tests. The dynamic properties were obtained by literature and by the test results. Amplification effects at the site under investigation have been estimated using fully stochastic site response analyses and for the object motion 7 real records compatible to the Italian code-based spectrum referred to 475-year return period. The results in terms of accelerograms and acceleration response spectrum (with the associated dispersion) indicated a clear amplification of the input motion at the basement of San Felice Martire church due to the characteristics of the soil profile.
Non-linear dynamic analysis of a full-scaled unreinforced adobe module
In a preliminary numerical analysis of an adobe wall (see research below), the material properties of the adobe masonry were calibrated to represent the wall in-plane seismic behaviour. In this work, the analyses were extended to the numerical study of a full-scale adobe module, dynamically tested on a shake table. The adobe material was modelled as brittle. The inelastic part of the constitutive model was represented in tension by a softening curve and in compression by a hardening/softening behaviour, thus the fracture energy in both are key issues in the modelling process. A finite element model that relies on a homogenous continuum approach was used in Abaqus/Explicit. The damage evolution in the numerical simulation represented fairly well the experimental crack pattern, for both in-plane and out-of-plane actions. Overall, the calibrated material properties and the explicit solution scheme are good tools for analysing the seismic capacity of unreinforced adobe structures.
Download: Chapter 1&2, Chapter 3, Chapter 4&5, Chapter 6, Chapter 7, Chapter 8&Appendix
Download: Chapter 1&2, Chapter 3, Chapter 4&5, Chapter 6, Chapter 7, Chapter 8&Appendix
Finite element modelling of the cyclic in-plane response of an adobe wall
The lack of a complete experimental data for the material properties of the adobe material allows in this paper to calibrate them numerically. The calibration process has been done based on the results of a quasi-static cyclic in-plane test carried out at the Pontificia Universidad Católica del Perú (PUCP) on a typical Peruvian adobe wall. Micro and macro modelling approaches are used in nonlinear finite element codes. As a first step, just a monotonic load is considered for the numerical modelling. Then, the cyclic in-plane response is reproduced by introducing some damage factors into the material. The proposed material parameters for numerical modelling predict well the in-plane seismic capacity and the cyclic damage pattern development of the adobe walls. The results of this work establish a benchmark for the numerical analysis of adobe walls within a finite element method.
To download the complete research, please send an email to [email protected]
To download the complete research, please send an email to [email protected]
Displacement-Based Fragility Curves for Seismic Assessment of Adobe Buildings in Cusco, Peru
The seismic vulnerability of single-story adobe dwellings located in Cusco, Peru, is studied based on a mechanics-based procedure, which considers the analysis of in-plane and out-of-plane failure mechanisms of walls. The capacity of each dwelling is expressed as a function of its displacement capacity and period of vibration and is evaluated for different limit states to damage. The seismic demand has been obtained from several displacement response spectral shapes.
From the comparison of the capacity with the demand, probabilities of limit state exceedance have been obtained for different PGA values. The results indicate that fragility curves in terms of PGA are strongly influenced by the response spectrum shape; however, this is not the case for the derivation of fragility curves in terms of limit state spectral displacement. Finally, fragility curves for dwellings located in Pisco, Peru, were computed and the probabilities of limit state exceedance were compared with the data obtained from the 2007 Peruvian earthquake.
From the comparison of the capacity with the demand, probabilities of limit state exceedance have been obtained for different PGA values. The results indicate that fragility curves in terms of PGA are strongly influenced by the response spectrum shape; however, this is not the case for the derivation of fragility curves in terms of limit state spectral displacement. Finally, fragility curves for dwellings located in Pisco, Peru, were computed and the probabilities of limit state exceedance were compared with the data obtained from the 2007 Peruvian earthquake.
Booklet of construction and maintenance of confined masonry houses
The preferred housing construction material in Peru is confined masonry, which is considered “noble material”. Unfortunately, due to the difficult economic situation, many Peruvians do not have the possibility of hiring professionals to build their houses and resort to informal construction. In most of the urban areas many confined masonry houses are built by masons without proper technical training. As a result, most of these buildings have architectural, construction and structural problems and are seismically vulnerable.
A research project started in 2001 at the Catholic University of Peru (PUCP) to study the problem of informal masonry construction in the areas of highest seismic risk in the country. The objectives of the project were to survey a number of informal confined masonry houses in several Peruvian cities located in seismic zones, to determine and quantify their main structural and architectural problems, and to estimate their seismic vulnerability and risk. Then, the information obtained would be used to develop technical guidelines for seismic resistant confined masonry construction and the guidelines would be published in a booklet aimed mainly at informal masons.
A research project started in 2001 at the Catholic University of Peru (PUCP) to study the problem of informal masonry construction in the areas of highest seismic risk in the country. The objectives of the project were to survey a number of informal confined masonry houses in several Peruvian cities located in seismic zones, to determine and quantify their main structural and architectural problems, and to estimate their seismic vulnerability and risk. Then, the information obtained would be used to develop technical guidelines for seismic resistant confined masonry construction and the guidelines would be published in a booklet aimed mainly at informal masons.
Other researches
- Advanced non-linear analysis of structures, code: 225-2011. University of Gabriele d’Annunzio Pescara-Chieti, Engineering Department. 2012.
- Evaluation of damage on earthen buildings and monuments due to Pisco earthquake. Team lead. Catholic University of Peru. 2007.
- Reparation of cracks in Historic Adobe Buildings in Seismic Areas, preliminary studies. Research Assistant. DAI-PUCP. 2006.
- Seismic Analysis of reinforced adobe modules using polymer mesh. Research Assistant. DAI-PUCP. 2006.
- Reinforcement of adobe buildings using industrial materials: Dynamic tests. Research Assistant. DAI-PUCP. 2005.
- Seismic Vulnerability of informal dwellings built in the highland of Peru. Research Assistant. PUCP SENCICO. 2004-2005.
- Developing Technical Recommendations to Improve the Seismic Safety of Informal Masonry Dwellings in the Peruvian Coast. Research Assistant. DAI-PUCP, SENCICO. 2003-2004.