516 Copyright © All rights are reserved by Mojtaba Labibzadeh. Trends in Civil Engineering and its Architecture Research article ISSN: 2637-4668 Long-Term effects of Environment on Seismic Performance of Dez Concrete Arch Dam Mojtaba Labibzadeh 1 *, Alireza Firouzi 2 and Hamid R. Ghafouri 3 1 Associate Professor of Structural Engineering, Faculty of Civil Engineering and Architecture, Shahid Chamran University of Ahvaz, Iran 2 MSc Student of Structural Engineering, Faculty of Civil Engineering and Architecture, Shahid Chamran University of Ahvaz, Iran 3 Professor of Hydraulic Engineering, Faculty of Civil Engineering and Architecture, Shahid Chamran University of Ahvaz, Iran *Corresponding author: Mojtaba Labibzadeh, Associate Professor of Structural Engineering, Faculty of Civil Engineering and Architecture, Shahid Chamran University of Ahvaz, Iran Received: August 13, 2020 Published: September 04, 2020 DOI: 10.32474/TCEIA.2020.04.000176 Introduction Much of the hydraulic structures like arch concrete dams are rapidly approaching, or in some cases have already passed their original design life. It is not surprising to say that these old concrete structures which some of their surfaces are submerged in the water for a long time, experience more degradation in their mechanical features than those structures which remain in dry environmental conditions along their operational life Dam Safety Technology Development Program 2005 [1]. This phenomenon may probably be the result of, to some extent, the effects of saturation of micro voids in the concrete mass Wittmann [2]; Pihlajavaara [3,4]) or/ and to some extent of the chemical dissolution reactions that occur in the wet concrete parts Kuhl et al. [5]; Nguyen et al. [6]. Abstract In the first part of this paper, the degradation of the mechanical properties of the mass concrete of the Dez concrete arch dam under the long-term effects of its environment as well as its loading history has been investigated using an innovate inverse analysis method. For performing that inverse analysis, an objective function was defined and then it was attempted to minimize that. That function was defined as the sum of the squared differences between the displacements obtained from a developed enhanced FE model in the ABAQUS standard software by the authors in the current study for each assumed set of the degraded mechanical properties of the dam as input variables and those obtained from the inverse pendulum’s records of the dam. For the sake of the generality of the problem, in performing such FE analyses, it was assumed that the behavior of the concrete material of the Dez dam has transformed gradually from initial homogeneous and isotropic undamaged behavior to the heterogeneous and orthotropic deteriorated behavior under the long-term effects of the environment as well as load agencies. Hence, the vertical sections of the dam were divided into nine and six subsections along the thickness and height directions of the dam, respectively. In each subsection, a transversely isotropic degraded elastic constitutive law was considered for characterizing the concrete long-term deterioration phenomenon. Obtained results revealed that the long-term deterioration of the mass concrete of the Dez dam is in fact a heterogeneous and anisotropic process because that the magnitude of the above mentioned defined objective function was obtained smaller than the corresponding value in the previous study of the authors which was performed based on the homogeneous and isotropic damage evolution assumptions. Core test results from the mass concrete of the dam reported by a consulting engineer company confirmed the concrete degradation predicted by the proposed model. After that, the behavior of this dam against an earthquake excitation was investigated considering the above-mentioned degradation of its mechanical properties and the obtained results were compared with its corresponding behavior considering its initial un-damaged mechanical properties for the mass concrete. Comparisons revealed considerable growth in the enveloped tensile stresses which can change the initial assumed safety margin design factors of the dam and necessitates the re-evaluating of the dam stability. Keywords: Concrete; Thermal inverse analysis; Heterogeneous; Transversely isotropic; Long-term damage; Arch dam; Seismic response