Sharif Digital Repository

Natural teeth are connected to alveolar bone by periodontal ligaments ( PDL). PDL in addition to supporting tooth have the damping effect on transferring load from tooth to the surrounding bone. The most common replacement for a complete tooth loss is the use of Osseointegrated dental implants. The healthy bone remodeling and full bonding between bone and titanium surface of the implant is subjected to a successful osseointegration. The lack of PDLs in the structure of implant-bone system could lead to the failure of implant’s components due to overloading or to the impact loads. The aim of this study is to use viscoelastic material in the structure of dental implants to compensate for the... 

It is very common to use moment frame system in earthquake-prone areas in the two main directions of buildings. This system is very popular among architects due to the creation of unobstructed openings between the columns and the possibility of using openings in them.The column is one of the main components in the design of orthogonal moment frame systems and plays an important role in the performance of this system. The columns that are in the two main directions of the intersection of two moment frame systems, due to the existence of the 30-100 rule in seismic design regulations, must be able to withstand 100% of the design earthquake force in one direction and 30% of the same force in the... 

This study deals with the monotonic behavior of reinforced concrete membranes. In the first step, small reinforced concrete membrane panels were studied. Examining the available test results on reinforced concrete panels, a new set of stress-strain relations for normal strength concrete and mild steel bars embedded in concrete. The salient features of the proposed constitutive laws are: 1) considering the effect of reinforcement ratio on average stress-strain relationships of cracked concrete; and 2) considering the gradual reduction of average stiffness of steel bars embedded in concrete. Equilibrium, compatibility, and constitutive relationships were incorporated into an algorithm to... 

Geopolymer concrete is one of the most environmentally friendly concretes that does not have any pollutants harmful to the environment. By-products that are normally harmful to the environment can be used in manufacturing this product, therefore, the use of this concrete is known as the first concrete replacement in the world. In order to use geopolymer concrete, it is necessary to an essential to know the mechanical information of these materials.In this study, the mechanical behavior of geopolymer concrete for fly ash and slag in terms of its stress and strain uniaxial loading and triaxial loading at , and15MPa pressures for three concrete mixing design are investigated.Then the... 

In the last decades, noticeable experimental and analytical investigations have been carried out on cast-in-place Reinforced Concrete column to Steel beam (RCS) connections, however rarely have been conducted on the precast RCS. In this reaserch, test results of five half-scale interior precast RCS connections with variable joint configurations are presented. The steel beams were connected to the precast column, using face bearing plates, embedded in the connection zone. The flanges of beams were strengthened with respect to scaled section, in order to increase the load transfer to the joint. All samples were loaded under reversed displacement controlled condition. The failure mode, joint... 

Understanding mechanical behavior of engineering materials plays an important role in prediction of material response and helps to analysis and design of engineering structures. In this thesis, behavior of polymer concrete (PC) with three different epoxy resin ratios, ordinary cement concrete (OCC), lightweight concrete (LWC), lime mortar soil (LMS), four various types of sandstone and granite was investigated under uniaxial and triaxial compression. In order to predict the mechanical behavior of aforementioned brittle materials, their behavior was simulated in terms of axial stress and volumetric strain versus axial strain. For computation of volumetric deformation and softening behavior,... 

This thesis aims to introduce a numerical method for investigating the appropriate arrangement of visco-pseudo-elastic dampers applicable to shell and plate structures under large deformation. These passive dampers are considered as viscoelastic layers and discrete shape memory alloy (SMA) wires in which this combination improves their overall efficiency and reduces their drawbacks. Also, the main advantages of these dampers are discussed during some illustrative problems. The current finite element formulation is based on an incremental updated Lagrangian (UL) approach along with the Newmark's integration technique. In the layerwise shell element, the Mindlin-Reissner theory is adopted in... 

Geomechanics has an immense impact on petroleum engineering and applies to the most aspects of petroleum extraction, from exploration and drilling to production and even reservoir abandonment. Studying the mechanical behavior of rocks in hydrocarbon reservoirs and overburden layers will lead to better characterization of mechanical state of the environment. Therefore, a solid understanding of rock mechanical behavior can play a crucial role in reducing operational issues of oil and gas extraction in different phases and prevent extra cost and time consumption. To illustrate, studies of wellbore stability and integrity, casing burst and collapse, drilling optimization, sand production,... 

In this paper, a machine learning-based atomistic-continuum multi-scale scheme is introduced to model the materials' geometrically and materially nonlinear behavior. The kinematic and energetic consistency principles are employed to link the atomistic and continuum scales. In order to establish the kinematic consistency principle, the periodic boundary condition is implemented for the atomistic RVE. The Ni-based superalloy, including 0 to 3% porosity, is considered for the models. Several parameter analysis is done to distinguish the proper atomistic RVE to be used in multi-scale models. The data set, including the stress-strain samples, is generated through molecular dynamics analysis...