Numerical modelling of in-plane behaviour of adobe walls

Some tests for material characterization of adobe blocks and adobe masonry have been carried out in universities and laboratories around the world. However, the number of tests is quite limited in comparison with those carried out with other structural materials, such as masonry or reinforced concrete, and even those tests just refers to elastic properties. The results of adobe tests (i.e. compression strength, elasticity modulus, shear strength, etc.), as well as the results of cyclic and dynamic tests on adobe masonry components and small buildings show that the mechanical properties of adobe masonry and the seismic performance of adobe constructions highly depend on the type of soil used for the production of units and mortar. Basic properties, such as elasticity modulus, can have significant variation from one soil type to another. The state-of-the-art for the numerical modelling of unreinforced masonry point to three main approaches: macro-modelling, simplified micro-modelling and detailed micro-modelling. In all three approaches, the use of elastic and inelastic parameters is required. For adobe masonry, the lack of knowledge concerning some of the material properties makes numerical modelling more difficult. In the proposed work, the mechanical properties of the typical adobe masonry in Peru have been calibrated based on a cyclic in-plane test carried out on an adobe wall at the Catholic University of Peru (PUCP). The mechanical parameters calibration and the modelling results of the in-plane behaviour of the adobe wall are presented. Macro-modelling and simplified micro-modelling strategies are used in finite element software with an implicit solution strategy. The results of this work represent the first step for the numerical modelling of the seismic behaviour of adobe constructions

The use of continuum models for analyzing adobe structures

As it is known, the adobe structures have a high seismic vulnerability principally due to the low material strength and sometimes due to the inadequate structural configuration. One way for understanding the seismic behaviour of these structures is by experimental tests. However, those are costly and sometimes not easy to make. An alternative for this is the analysis of adobe structures by numerical tools with the possibility to make parametric studies for understanding the behaviour of different geometrical configurations. In a previous work, some adobe material parameters have been calibrated based on a cyclic in-plane test. In this paper, that work was extended to a numerical modelling of the non-linear dynamic behaviour of an adobe module experimentally tested at the Pontificia Universidad Católica del Perú. For this, a continuum model in the finite element program Abaqus/Explicit, was used to represent the adobe masonry as a homogeneous and isotropic material

Estudio experimental del Sistema de Albañilería Integral en la construcción de viviendas sismorresistentes. Experimental study of the Integral Masonry System in the construction of earthquake resistant houses

This paper presents the application of the Integral Masonry System (IMS) to the construction of earthquake resistant houses and its experimental study. To verify the security of this new type of building in seismic areas of the third world two prototypes have been tested, one with adobe and the other with hollow brick. In both cases it’s a two-story 6x6x6 m3 house built to scale 1/2. The tests are carried out at the Laboratory of Antiseismic Structures of the Department of Engineering, Pontifical Catholic University of Peru in Lima, in collaboration with the UPM (Technical University of Madrid). This article shows the design process of the prototypes to test, including the sizing of the reinforcements, the characteristics of the tests and the results obtained. These results show that the IMS with adobe or brick remains stable with no significant cracks faced with a severe earthquake, with an estimated acceleration of 1.8 g. Este artículo presenta una aplicación del Sistema de Albañilería Integral (SAI) a la construcción de viviendas sismorresistentes y su estudio experimental. Para verificar su seguridad para su construcción en zonas sísmicas del tercer mundo se han ensayado dos prototipos, uno con adobe, y otro con ladrillo hueco. Se trata de una vivienda de 6x6x6 m3 y dos plantas que se construyen a escala 1/2. Los ensayos se realizaron en el Laboratorio de Estructuras Antisísmicas del Departamento de Ingeniería de la Pontificia Católica Universidad del Perú (PUCP) de Lima en colaboración con la UPM (Universidad Politécnica de Madrid). Este artículo muestra el proceso de diseño de los prototipos a ensayar, incluido el dimensionado de los refuerzos, las características de los ensayos y los resultados obtenidos. Estos resultados muestran que el SAI con adobe o ladrillo permanece estable sin grietas significativas ante un sismo severo, con una aceleración estimada de 1,8 g

Seismic Stability Analysis of Inca Earthen Walls

In many places around the world there still exist statues, walls and columns which, despite being located in areas of high seismicity, are still standing and in good conditions after several hundred years. Although Peru is located on a zone of high seismicity, some preColumbian walls are still standing after having withstood many intense earthquakes. The remarkably stable dynamic response of these structures when rocking freely due to horizontal ground motions has been extensively studied [1] [2]. The aim of the project presented in this article is to evaluate the probability of seismic overturning of Inca monuments (XVth century CE) during future strong earthquakes. The Wiracocha temple walls located near Cusco and the Inca trail walls that cross the PUCP campus in Lima were selected for this study. Both earthen walls were modelled as free-standing rigid blocks which could rotate around the corners at their base. A set of synthetic ground acceleration signals were then generated according to the seismicity and ground conditions of both sites. The artificial ground acceleration records were scaled to the uniform hazard spectrum of Peru for return periods of 500, 1000 and 2500 years and different moment magnitudes [3][4]. The rocking time history response of each wall due to these ground motions was then numerically computed and plotted in order to assess the seismic risk due to overturning of these important earthen monuments. The main conclusion is that these walls will most probably remain standing for many more centuries

Construcción sismorresistente en tierra: la gran experiencia contemporánea de la Pontificia Universidad Católica del Perú

In many developing countries the most common alternative for dwelling construction is building with earth because the material is abundant and cheap. The quality of most traditional earthen construction is very low, because it is done informally, with little or no technical assistance. In seismic areas where earthen construction is common, every time an earthquake occurs, many dwellings collapse, causing considerable economic losses and tragic injuries and deaths. The professional and academic communities in some seismic countries have not remained indifferent to this important problem. Researchers at the Catholic University of Peru (PUCP) have been investigating on the construction of earthen buildings in seismic areas for about 40 years and have obtained invaluable results. This article describes the evolution of the knowledge generated at PUCP of reinforced earth, a material composed of earth and compatible reinforcements, with which it is possible to build seismic-resistant constructions.En muchos países en vías de desarrollo la alternativa de vivienda más común es la construcción con tierra, pues el material es abundante y barato. La construcción tradicional de viviendas de tierra se realiza informalmente, sin asesoría técnica. Por ello, la calidad de estas construcciones es generalmente muy baja. En zonas sísmicas donde se construye con tierra, cada vez que ocurre un terremoto colapsan muchas construcciones de este material, causando considerables pérdidas económicas y lamentables pérdidas de vidas. Las comunidades académicas y profesionales de algunos países sísmicos no han permanecido impasibles frente a esta grave situación. En el Perú, investigadores de la Pontificia Universidad Católica del Perú (PUCP) han venido investigando la construcción con tierra en áreas sísmicas desde hace cerca 40 años y han obtenido invalorables resultados. Este artículo describe la evolución del conocimiento generado en la PUCP del material tierra armada, compuesto por tierra y refuerzos compatibles, que permite lograr construcciones sismorresistentes

Experimental investigation on the bond behavior of a compatible TRM-based solution for rammed earth heritage

Despite the current awareness of the high seismic risk of earthen structures, little has been done so far to develop proper strengthening solutions for the rammed earth heritage. Based on the effectiveness of TRM for masonry buildings, the strengthening of rammed earth walls with externally bonded fibers using earth-based mortar is being proposed as a compatible solution. In this context, the investigation of bond behavior was conducted by means of direct tensile tests, pull-out tests and single lap-shear tests. The specimens were prepared using earth-based mortars and two different types of meshes (glass and nylon) while considering different-bonded lengths. The direct tensile tests on TRM coupons showed the high capacity of the nylon mesh in transferring stresses after cracking of the mortar. The pull-out tests highlighted that in the case of glass fiber mesh, the bond was granted by friction, while the mechanical anchorage promoted by the transversal yarns granted the bond of the nylon mesh. Finally, the single lap-shear tests showed that the adopted earth-based mortar seems to limit the performance of the strengthening.This work was supported by the Fundacao para a Ciencia e a Tecnologia [PTDC/ECM-EST/2777/2014, SFRH/BD/131006/2017, SFRH/BPD/97082/2013]

Expression of AMPA and NMDA receptor subunits in the cervical spinal cord of wobbler mice

BACKGROUND: The localisation of AMPA and NMDA receptor subunits was studied in a model of degeneration of cervical spinal motoneurons, the wobbler mouse. Cervical regions from early or late symptomatic wobbler mice (4 or 12 weeks of age) were compared to lumbar tracts (unaffected) and to those of healthy mice. RESULTS: No differences were found in the distribution of AMPA and NMDA receptor subunits at both ages. Western blots analysis showed a trend of reduction in AMPA and NMDA receptor subunits, mainly GluR1 and NR2A, exclusively in the cervical region of late symptomatic mice in the triton-insoluble post-synaptic fraction but not whole homogenates. Colocalisation experiments evidenced the expression of GluR1 and NR2A receptors in activated astrocytes from the cervical spinal cord of wobbler mice, GluR2 did not colocalise with GFAP positive cells. No differences were found in the expression of AMPA and NMDA receptor subunits in the lumbar tract of wobbler mice, where neither motoneuron loss nor reactive gliosis occurs. CONCLUSION: In late symptomatic wobbler mice altered levels of GluR1 and NR2A receptor subunits may be a consequence of motoneuron loss rather than an early feature of motoneuron vulnerability