Alfonso Cobo Escamilla

INFLUENCIA DE LOS CICLOS TÉRMICOS EN EL COMPORTAMIENTO MECÁNICO DEL HORMIGÓN DE ESTRUCTURAS TERMOACTIVADAS

This article examines the behavior of concrete when subjected to thermal cycles, thus, imitating the process of thermal loading and unloading in thermo-activated structures, throughout their in-use period. Cylindrical specimens have been performed to study the behavior to compression and tensile strength, and prismatic specimens were performed to flexural test strength. The analysis of results shows that in thermo-active structures subjected to thermal cycles, temperature variation influences on the evolution of concrete mechanical properties, not staying constant over time. Likewise, a greater amount of reinforcement to withstand compression is necessary, as well as the reformulation of calculation methods outlined in the concrete standard EHE, so that analysis of this type of structures can be performed on the safe side, regarding both stresses and strains.nnKeywords: ? concrete, temperature-related & thermal effects, thermo-active structures, compression test, splitting tensile test, flexural test

INFLUENCIA DE LA ADICIÓN DE FIBRAS EN LAS PROPIEDADES DE LOS MORTEROS DE CAL HIDRÁULICA

The influence of carbon and basalt fibres addition on hydraulic lime mortars mechanical properties and durability has been studied. The objective is to evaluate the possible use in restoration of architectural heritage, as an alternative to Portland cement because of the pathological processes that the latter causes. To assess the effect, the obtained results have been compared with two reference mortars: hydraulic lime with no additions and basalt fibres. The amount of fibres to be incorporated is questioned in the first phase. The tests performed show that the incorporation of 1% of fibres (volume) in the mortars, improves their behaviour under bending and compression loads. Additionally, the fibres increase the ductility of the reinforced mortar, almost doubling the effect that causes the addition of basalt fibres. Finally, the durability studies show the increase in ductility caused by the addition of carbon fibres, despite the logic decrease experienced after the ageing tests.nnKeywords: Hydraulic lime, mortar, carbon fibre, basalt fibre, ductility, durability

ESTUDIO EXPERIMENTAL DE VIGAS MULTICAPA DE HORMIGÓN LIGERO Y HORMIGÓN CONVENCIONAL

Lightweight concrete (LWC) has advantages over conventional concrete (CC). For the same strength value, LWC has a lower weight so the load over the structure is reduced. However, CC produces shorter deflections for the same load. The combined use of both materials could optimize the best behavior of each.nThe goal of this paper is to study experimentally the multilayer LWC and CC beam behaviour. It is compared against monolithic LWC and CC beams.nKeywords: Lightweight concrete, multilayer beam

EVOLUCIÓN CON LA EDAD DE LAS PROPIEDADES MECÁNICAS DE HORMIGONES AUTOCOMPACTANTES REFORZADOS CON FIBRAS DE ACERO SOMETIDOS A COMPRESIÓN

En este trabajo se estudia el efecto de la edad sobre propiedades relacionadas con la resistencia a compresion de hormigones autocompactantes reforzados con fibras de acero (HACRFA). Se ha trabajado sobre una amasada de HACRFA con la que se han fabricado 15 probetas cilindricas de 15cm de diametro y 30cm de altura y 15 probetas cubicas de 15cm de lado. Tres especimenes de cada probeta se han ensayado a compresion a las edades de 7, 14, 28, 90 y 365 dias. Los resultados permiten obtener funciones que relacionan con la edad las siguientes propiedades: resistencia a compresion, valor del coeficiente de paso, modulo de elasticidad longitudinal y coeficiente de Poisson. Palabras clave: HACRFA, Compresion, Poisson, HAC, HRFA

Static load behavior and energy absorption of safety guardrails for construction works

One of the requirements which must be met by the temporary edge protection systems (TEPS) is to stop a worker who walks, stumbles, falls and knocks against the system. The effect of the worker’s crash with the protection system is a dynamic type stress applied as an impact. The capacity of the system to withstand the impact depends on its ductility and its ability to absorb energy. The area enclosed by the load-displacement graph of a TEPS when the load is statically applied is an indicator of its ductility and its ability to absorb energy. In Europe, the EN 13374 standard specifies the requirements to be fulfilled by the TEPS. For systems placed in floor slabs with a slope smaller than 10° (class A systems), the standard indicates that the testing should be performed using static loads. In this work, TEPS manufactured from steel, wood, injected plastic, and composites have been tested with the static loads test system specified in the EN 13374 standard for assessing class A systems. Subsequently, the areas enclosed in the load-displacement diagram have been tested and have been compared with the estimated values of impact energy.