A Simple Method for Calculating the Shear Deformation of Reinforced Concrete Elements in the Elastic and Plastic Domains

This paper proposes a simple method for calculating the shear deformation and the shear capacity of reinforced and prestressed concrete elements containing shear reinforcement. This new approach considers that, for large deformations, concrete elements follow compatibility conditions based on displacements of the composite material subjected to shearing forces. The result is a beam, inspired by the Timoshenko-Ehrenfest beam theory, which considers a new hypothesis regarding shearing deformation, informed by the behavior of the shear reinforcement. The new method is compared with previous approaches, allowing us to assess the technological advances of the new proposal. The new method is easy to implement and provides information about the shearing deformation (in the elastic and plastic domains) and the shearing capacity of concrete beamcolumn elements. A detailed example is developed, in which all the components of the shear deformation are evaluated, and the simplification of the new method is analyzed in comparison with other more comprehensive methods in the elastic domainUniversidad de Granada/ CBU

Fragility Curves for Historical Structures with Degradation Factors Obtained from 3D Photogrammetry

The influence of the effects of the degradation of materials on the seismic fragility of Cultural Heritage buildings in Granada (Spain) is investigated. The degradation of the material, which mainly happens at the lower levels of the façades, is obtained by using 3D photogrammetry data. Fragility curves for three cultural heritage constructions in Granada are calculated by using FE nonlinear dynamic analyses for both non-deteriorated and deteriorated geometries. The Finite Elements (FE) models, based on the macro-modelling technique, are subjected to ground motions for the city of Granada, which were selected by considering Probabilistic Seismic Hazard Analysis (PSHA) methodology with their probability of occurrence. The response of each model is analyzed for different seismic Intensity Measure (IM) levels, which, in this study, correspond to average pseudoacceleration. The procedure is applied to three monuments in Granada that were built with two different constructions materials: calcarenite and rammed earth. The damage mechanisms considered are roof displacement or maximum compressive principal stress, depending on each case. The results show that the restoration works that have been carried out has prevented structural failures in the rammed earth construction studied, and that, during future seismic events, special attention must be paid to the level of compressive strengh reached in the Santa Pudia calcarenite used at the San Jerónimo monastery.European Union's Framework Programme for Research and Innovation (Horizon 2020)Spanish Government (Ministerio de Ciencia, Innovacion y Universidades) as part of the Research Projects 821054RTI2018-101841-B-C21 RTI2018-101841-B-C2

Mechanical characterization and elastic stiffness degradation of unstabilized rammed earth

Rammed earth is attracting renewed interest due to its sustainability. In this work, a mechanical characterization of unstabilized rammed earth is presented. Compressive strength, Young’s modulus, and Poisson’s ratio were determined, with the first of these being the most representative mechanical property of rammed earth. Stress – strain curves were obtained from uniaxial compression tests. Creep is of great importance in the long-term assessment of historical buildings and in the design of new ones. Samples of rammed earth were subjected to a constant load for 15 days to study their creep behavior. In order to simulate the long-term behavior of the material, different rheological models were fitted to the experimental results. The instantaneous deformation of rammed earth samples caused by a sudden additional load (maintaining a previous service load level) was also studied. This is the first time that this phenomenon, called elastic stiffness degradation, has been studied for rammed earth material.European Union Framework Programme for Research and Innovation 82105

Influence of the level of connectivity on the members of the Octahedron and X-Octahedron families of tensegrities

Tensegrity structures based on topological patterns have been developed greatly in recent years. Tensegrities obtained from the same pattern are said to belong to a family. Two examples of tensegrity families are the Octahedron and the X-Octahedron, whose members are composed of rhombic and X-rhombic cells, respectively, which are collected in three groups. The general connectivity pattern of both families consists of three levels of connectivity. This work analyzes the influence of the reduction of the level of connectivity on the members of both families. The connection graphs corresponding to different levels of connectivity are defined based on the new concept of “twin tensegrities”. Analytical computations have been performed to determine the force:length ratios that satisfy equilibrium, stability, and super-stability conditions. In addition, the mathematical sequence that follows the ratio between the force:length ratio of struts and cables of the X-Octahedron family that leads to a super-stable equilibrium configuration is presented. The new tensegrities obtained in this work also belong to the Octahedron and X-Octahedron families and could have promising engineering applications such as modular constructions.Funding for open access charge: Universidad de Málaga / CBU

Designing compression structures by topological mapping

Congreso celebrado en la Escuela de Arquitectura de la Universidad de Sevilla desde el 24 hasta el 26 de junio de 2015.The Force Density Method has been traditionally employed to seek the equilibrium shape of tension structures. Recently, the use of a process based on topology has been introduced to provide a first network in which the Force Density Method can be applied. Compression-only structures such as vaults and domes can also be modelled by means of the former approach if this is modified to get a design process similar to the Gaudí’s one based on hanging models. The conjunction of Topological Mapping and the Forced Density Method is first explained in the form-finding process of tension structures and, later on, the modifications to that approach are introduced so that an iterative procedure is obtained to get equilibrium shapes of compression-only structures. The versatility of this novel approach is presented by means of the analysis of some representative examples

Bayesian assessment of surface recession patterns in brick buildings with critical factors identification

The deterioration of built heritage is a major concern for many countries. In the specific caseof brick heritage buildings, degradation depends on several factors such as the chemical andmineralogical composition and the porosity of the bricks, floor insulation and exposure toenvironmental conditions. This paper applies a probabilistic Bayesian approach to identi-fying the pattern of recession of the brick walls using digital photogrammetry data. Twocases studies are presented corresponding to two buildings classified as Assets of CulturalInterest by the Spanish Ministry of Culture. The analysis of physico-chemical factors andphotogrammetric descriptions allow a holistic understanding of the deterioration processto be developed. The degradation patterns and degradation velocities obtained are used forthe structural assessment of the buildings. The comparison of the degradation patterns ofboth buildings considering their individual features allows the most critical factors in thedegradation process of brick walls to be identified.El deterioro del patrimonio construido es una gran preocupación para muchos países. En el caso específico de los edificios patrimoniales de ladrillo, la degradación depende de varios factores como la composición química y mineralógica y la porosidad de los ladrillos, el aislamiento del suelo y la exposición a las condiciones ambientales. Este artículo aplica un enfoque probabilístico bayesiano para identificar el patrón de recesión de las paredes de ladrillo utilizando datos de fotogrametría digital. Se presentan dos casos de estudio correspondientes a dos edificios catalogados como Bienes de Interés Cultural por el Ministerio de Cultura español. El análisis de los factores físico-químicos y las descripciones fotogramétricas permiten desarrollar una comprensión holística del proceso de deterioro. Los patrones de degradación y las velocidades de degradación obtenidos se utilizan para la evaluación estructural de los edificios. La comparación de los patrones de degradación de ambos edificios considerando sus características individuales permite identificar los factores más críticos en el proceso de degradación de las paredes de ladrillo.Spanish Government RTI2018-101841-B-C21 RTI2018-101841-B-C2

Mechanical characterization and elastic stiffness degradation of unstabilized rammed earth

Rammed earth is attracting renewed interest due to its sustainability. In this work, a mechanical characterization of unstabilized rammed earth is presented. Compressive strength, Young’s modulus, and Poisson’s ratio were determined, with the first of these being the most representative mechanical property of rammed earth. Stress – strain curves were obtained from uniaxial compression tests. Creep is of great importance in the long-term assessment of historical buildings and in the design of new ones. Samples of rammed earth were subjected to a constant load for 15 days to study their creep behavior. In order to simulate the long-term behavior of the material, different rheological models were fitted to the experimental results. The instantaneous deformation of rammed earth samples caused by a sudden additional load (maintaining a previous service load level) was also studied. This is the first time that this phenomenon, called elastic stiffness degradation, has been studied for rammed earth material

An approximate procedure for a general analytical expression of the Prandtl membrane analogy in linear elastic pure torsion

Artículo en revisiónFor pure torsion in linear elasticity, if the shape of cross-section is defined by a closed-form analytical expression satisfying certain conditions, the shear stress in each of the principal Cartesian directions can be obtained by the derivation of the stress function, whose analytical expression can be obtained from the Prandtl analogy. In this paper, a general methodology to obtain an approximate analytical expression of the Prandtl membrane is presented. The proposed methodology uses two variable quadratic piecewise functions to define the Prandtl membrane. This approximate procedure can be applied to any cross-section shape, and it has been proved be especially suitable for steel shapes, for which the proposed method leads to values close to the ones obtained with more precise methods. Several examples are presented

The octahedron family: a source of tensegrity structures

A tensegrity family is a group of tensegrity structures that share a common connectivity pattern. In the case that just two values of the force density or force:length ratio are adopted (one for cables and another for struts), the members of the octahedron family are: the octahedron, the expanded octahedron and the double-expanded octahedron. In this work a higher number of possible force:length ratio values have been considered in order to find new members of the family. The values of the force:length ratios which satisfy the super-stability conditions have been computed analytically. New super-stable tensegrity forms of the octahedron family have been obtained. Results show that all of them are members of the octahedron family having as folded forms all the lower members of the family. Finally, based on topological rules, it has been proved that the double-expanded octahedron can be defined from a truncated cube