José L. Almazán

A macro-element model for inelastic building analysis

A three-dimensional model for approximate inelastic analysis of buildings is presented herein. The model is based on a single macro-element per building storey. The inelastic properties of the model are characterized by the so-called ultimate storey shear and torque (USST) surfaces. Different algorithms for the construction of these surfaces, as well as their applications in building modelling, are presented and discussed. Two alternative procedures are developed to integrate the force-deformation constitutive relationship of the macroelements. The first one follows the exact trajectory of the load path of the structure on the USST, and the second uses linear programming without ever forming the USST surface. The accuracy of the model and integration procedure is evaluated by means of the earthquake response of single-storey systems. The model and integration procedure developed is finally used to compute the inelastic response of a seven-storey R/C building. The results of this investigation show that the model proposed, although approximate, can be effective in estimating the inelastic deformation demand of a building. It also enables the engineer to capture and interpret important features of the three-dimensional inelastic response of a structure even before performing any inelastic dynamic analysis.

Experimental cyclic response assessment of partially grouted reinforced clay brick masonry walls

As part of an ongoing research project into the seismic response of partially grouted reinforced masonry (PG-RM) walls, this article presents the analysis of the experimental results of eight full-scale walls that were tested in laboratory under cyclic lateral loading. All walls tested were constructed using multi-perforated clay bricks and horizontally reinforced with ladder-type bed-joint reinforcement. Three design parameters were investigated in this research: wall aspect ratio, axial load level, and horizontal reinforcement ratio. The combined effect of these variables on shear response of the walls tested is analyzed and discussed. In addition, the accuracy of four shear expressions available in the literature is assessed against the experimental results obtained. The study has confirmed that a rise in the horizontal reinforcement ratio may lead to an increase in lateral capacity of PG-RM walls, although this effect would be more remarkable for square and slender walls. The results obtained also suggest that the influence of axial load level becomes more relevant as the aspect ratio decreases. In addition, moderate values of displacement ductility, ranging from 2.5 to 5.5, were estimated from a bilinear idealization. At the level of maximum lateral force, the average drift level for all walls tested in this experimental program ranged between 0.2 and 0.62%. Finally, the research also confirms the need to review the shear expressions currently available for the design and assessment of this type of walls.

Análisis experimental de la aislación sísmica de un estanque con líquido con interfaz de geosintéticos

Una interfaz compuesta por un geotextil no tejido de alta resistencia y un polimero de ultra alto peso molecular, colocados debajo de las fundaciones de una estructura, pueden proveer proteccion sismica. Esto se logra disipando la energia que se transmite hacia la superestructura a traves de un deslizamiento controlado entre estas dos superficies. Se prepararon ensayos dinamicos en una mesa vibradora y se ejecutaron en un estanque de almacenamiento con apoyo continuo, en condiciones con y sin liquido. Se utilizaron solicitaciones armonicas y sismicas en dos direcciones de analisis, para describir la respuesta dinamica del sistema. Los resultados mostraron que la interfaz de geosinteticos actua reduciendo notoriamente la aceleracion transmitida desde la mesa vibradora hacia el estanque, a la vez que un deslizamiento del mismo ocurrio a lo largo de la interfaz. Ademas, su implementacion en las fundaciones del estanque permitio registrar menores presiones de liquido en la pared interior del estanque, respecto de la condicion no aislada. Debido a esto se logra demostrar la factibilidad tecnica de este metodo de aislacion, perfilandolo como un sistema de proteccion sismica de costo reducido y de facil implementacion para ser utilizado en la reduccion de danos sismicos.