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Articles by M. Labibzadeh
Total Records ( 7 ) for M. Labibzadeh
  M. Labibzadeh and S. A. Sadrnejad
  Among the various numerical simulating models of plane concrete, the micro-planes models have an excellent position. These models are not as complicated as microscopic models such as discrete particles models and do not have the shortcomings of macroscopic models based on the stress or strain invariants. The object of this study is the application of author's recently developed micro-planes damage based model of plane concrete through a 3D finite elements code to show it's abilities in crack/damage analysis of actual concrete structures such as concrete double curvature arch dams. The proposed code not only able to predict the crack line, but also determine which combination of loading conditions occurs on damaged micro-planes. Validity of the proposed code is investigated through a few standard benchmark examples.
  M. Labibzadeh and S. A. Sadrnejad
  The constitutive equations for the mechanical behavior of concrete capable of seeing damage effects or crack growth procedure under loading/unloading/reloading was developed upon microplane framework. The proposed damage formulation has been built on the basis of five fundamental types of stress/strain combinations, which essentially may occur on any of microplanes. Model verification under different loading/unloading/reloading stress/strain paths has been examined. The proposed model is capable of presenting pre-failure history of stress/strain progress on different predefined sampling planes through material. Many of mechanical behavior aspects happen during plasticity such as induced anisotropy, rotation of principal stress/strain axes, localization of stress/strain and even failure mechanism are predicted upon a simple rational way and can be presented.
  M. Labibzadeh , S. A. Sadrnejad and M. Naisipour
  In recent years, the material behavior dependence of laboratory concrete specimens built with the same concrete mixture under the same load conditions to their geometrical sizes is well established. This phenomenon which is observed not only in concrete but also in most quasi-brittle materials such as rock, ceramic or composite materials is now called as size effect. Many of the existing structural analyzing codes are not able to consider this important feature of concrete structures especially under compressive loadings. However we know that the main purpose of concrete application in structural members is to resist compression. The aim of this study is to show the ability of author's recently developed 3D finite elements code equipped with the proposed author's newly micro-planes damage based model for considering of compressive size effect of plane concrete. To do so, two different sizes of cubic concrete specimens are modeled with mentioned code under the uniaxial compressive test and their fracture mechanisms, pre-peak and post-peak strain-stress paths are investigated. Obtained results reveal the good coincidence with experimental evidences. In fact, the combination of proposed micro-planes damage based model and developed presented 3D finite elements technique creates a powerful numerical tool to capture and predict precisely strain localization and fracture mechanism in the specimens and consequently to assess properly the compressive size effect of plane concrete in analysis and design.
  S.A. Sadrnejad and M. Labibzadeh
  The analysis of large structures mostly requires a complete three dimensional finite element discretization. Stability of such structures includes not only the stability of structure itself but also that of foundation as well as interconnection elements. The general instability of a structure may be affected by two aspects, firstly, an inappropriate preliminary classical design of the structure and inadequate control over the geometry and quality of the materials used for construction. Secondary, the foundation rock and abutments may contain a number of faults and joints which may be unfavorable to stability of the structure. Therefore it is necessary to consider appropriately the influence of interaction between the structure, foundation and abutments under static and dynamic loads. from construction point of view some of the structures such arch dams are divided into vertical blocks, which are separated by vertical joints which are grouted at the later stage .Since the behavior of such and many other structures whose have contraction joints under static and dynamic loads depends largely on those joints, therefore, the presence of structural codes that can recommend the appropriate specifications on modeling these joints, seems to be necessary. The present study contribution deals with the development of three dimensional finite element software including interfacial behavior of joints between different substructures and interaction behavior of structure and foundation to evaluate the safety of the structure subjected to static and dynamic loads. The developed software is verified upon different points of view and the results are in agreement with experiments.
  M. Labibzadeh
  An oil well in Darquain region of Khuzestan province in Iran was selected as a case study and contemporary changes in pressure and temperature according to real inside borehole conditions of this well have been simulated in curing the class G cement samples in the laboratory. The mentioned cement usually used for cementing the annulus between casing and rock formation in the oil well early age tensile strength of the samples were measured via Brazilian tension test in order to perform more precisely predicting tensile cracking of cement sheath. It is worth to mention that in this study no special additives used in cement slurry mixture in order to evaluate only the effects of environmental conditions in curing the cement samples. Results of laboratory tests showed that with the rise of the pressure and temperature up to 150°F and 1500 psi, earl age tensile strength is growing slightly while after that it experiences a decreasing treatment.
  M. Labibzadeh , S.A. Sadrnejad and A. Khajehdezfuly
  In this study, the simulation of the thermal behavior of an arch dam which is subjected to the environmental thermal action during service, the method of solution adopted as well as the evaluation of the different parameters will be described in detail. The case study is a double curvature concrete arch dam (Karun-1 dam) with 200 m height in the Southwest of Iran which is modeled by the powerful scientific ABAQUS software. The ABAQUS program has the ability to transfer heat within the body of the dam with high accuracy, the main challenge of previous researches in the field of thermal analysis of arch dams. In addition to thermal loads, in this study, the effects of hydrostatic pressure and weight of the dam and reservoir-dam-foundation interaction also have been considered and it became distinct that the thermal effects on dam displacements, stresses and strains are significant and would not be neglected.
  M. Labibzadeh and A. Khajehdezfuly
  In this study, effect of vertical contraction joints on the Karun-1 arch concrete dam safety certainly under effect of thermal loads was looked over by means of the relatively 3D finite elements exact simulation of the geometric, material behavior and boundary conditions of the dam using ABAQUS package. This software has good potentials for modeling three dimensional heat transfer thorough dam volume. Arch, cantilever and principal stress tensors as well as displacement vectors were selected as stability indexes safety control and deeply examined. It was revealed that the contraction joints have significant effects in the thermo-static response of the dam and if any of two important factors e.g., contraction joints or thermal effects are not considered in Kurun-1 dam processing, the significant errors in computing displacements and stresses and consequently in dam stability qualification can be occurred.
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