INFLUENCE OF THERMAL CYCLES ON THERMO-ACTIVATED STRUCTURES CONSTRUCTION TECHNOLOGY ARTICLE RESEARCH Kenzo-Jorge Hosokawa-Menéndez, Alfonso Cobo-Escamilla, María- Isabel Prieto-Barrio, Inmaculada Martínez-Pérez Concrete Technology Pag. 1 / 12 Publicaciones DYNA SL -- c) Mazarredo nº69 - 4º -- 48009-BILBAO (SPAIN) Tel +34 944 237 566 – www.revistadyna.com - email: dyna@revistadyna.com INFLUENCE OF THERMAL CYCLES ON THERMO-ACTIVATED STRUCTURES Kenzo-Jorge Hosokawa-Menéndez, Alfonso Cobo-Escamilla, María-Isabel Prieto-Barrio, Inmaculada Martínez-Pérez Universidad Politécnica de Madrid. Escuela Técnica Superior de Edificación. Avda. Juan de Herrera, nº 6 – 28040 Madrid. Tfno: +34 913367613. mariaisabel.prieto@upm.es Received:15/Jun/2017-- Reviewed: 20/Jun/2017-- Accepted: 16/Oct/2017--DOI: http://dx.doi.org/10.6036/8494 ABSTRACT: 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. Keywords:  concrete, temperature-related & thermal effects, thermo-active structures, compression test, splitting tensile test, flexural test RESUMEN: En el presente trabajo se estudia el comportamiento del hormigón cuando se encuentra sometido a ciclos de temperatura, imitando así el proceso de carga y descarga térmica de las estructuras termo-activadas a lo largo de su periodo de servicio. Se han fabricado probetas cilíndricas para estudiar el comportamiento a compresión y tracción y probetas prismáticas para realizar los ensayos a flexión. Del análisis de resultados se puede concluir que en las estructuras termoactivas sometidas a ciclos térmicos, la variación de temperatura influye en la evolución de las propiedades mecánicas del hormigón, no manteniéndose constantes a lo largo del tiempo. Así mismo, se hace necesario una mayor cantidad de armadura de compresión y la reformulación de los métodos de cálculo planteados en la instrucción de hormigón EHE, con el fin de realizar el cálculo de este tipo de estructuras del lado de la seguridad, tanto a nivel de tensiones como de deformaciones. Palabras clave: hormigón, ciclos de temperatura, estructuras termoactivas, ensayo compresión, ensayo tracción indirecta, ensayo flexión 1.- INTRODUCTION Buildings are one of the largest consumers of natural resources, and represent a significant part of the emissions of greenhouse gases affecting climate change. Globally, the lifecycle of buildings accounts for about 32 % of the total energy consumption and 20 % of the greenhouse gas emission [1]. Therefore, there is a growing awareness of the important role that certain changes carried out from an energy efficiency perspective can play in reducing the environmental effects [2]. Construction structural elements, such as slabs, structural floors and piles, which also store energy with a dynamic- thermal behavior, are exploited to provide cooling by absorbing the energy of the internal environment, or heating, by releasing stored energy. This, in turn, prevents the use of air conditioning by conventional means and promotes cooling by using energy accumulated on the ground, from groundwater and from outdoor air [3]. The researches dealing with studies of thermo-active structures behavior can be classified into three groups: geotechnical behavior of thermo-active piles [4,5]; thermo-mechanical behavior of thermo-active piles monitoring the results obtained from the tests to real scale and later modeling these behaviors [6-9]; and finally, the dynamic thermal behavior of thermo-active slabs [10]. Mechanical properties of concrete vary depending on temperature. Schneider [11,12] appreciated a negative evolution of the concrete compressive stress in a range between 0 ºC and 120 °C. DeJong and Ulm noted that the main reason for