Sharif Digital Repository

The behavior of soil-structure interface plays an important role in the static and dynamic analysis of soil-structure systems. Development of new materials such as polymer concrete requires an understanding of the behavior and their interaction with other materials. In this investigation, the interface behavior between polymer concrete and ordinary concrete with sand was studied using interface direct shear tests. In order to find optimum content of epoxy resin for polymer concrete, a series of tensile and compressive tests were conducted. To study the mechanical properties of concretes-sand interfaces behavior two series of interface direct shear tests were conducted at three different... 

The understanding of the mechanical behavior of engineering materials and their interfaces plays an important role in the prediction, analysis, and desing of engineering systems. Considering the important role of understanding and describing the behavior of materials and systems, this thesis is devided into three sections: 1) Modeling the behavior of polymer concrete under uniaxial compression, 2) Modeling the behavior of various light- and normal- weight concretes under uniaxial and triaxial compression, and 3) Modeling the behaivor of interfaces between polymer concrete and normal concrete with sand. In this context, various constitutive models were investigated and compared together,... 

In order to enhance the behavior of structures during an earthquake, various system have been proposed and used in recent years. The main purpose of these systems is to provide enough deuctility to dissipate the input energy of the earthquake. Buckling restrained braces are used extensively in seismic-restraint structures due to their sutiable cyclic behavior. They consist of a core energy dissipation and external restraining component. The purpose of this study is to improve the behavior of BRBs using FRP strips as a restraining component. In this study ABAQUS is used to model analyze the structure. Concrete Damage Plasticity (CPD) is used to model concrete, Hashin model used for FRP strips... 

Understanding and defining mechanical behavior of engineering materials play an important role in the prediction of material response as well as analysis and design of engineering structures. In this investigation, polymer concrete (PC) with three different epoxy resin contents, ordinary cement concrete (OCC), lightweight concrete (LWC) and lime-mortar soil (LMS) have been studied under uniaxial and triaxial compression tests to determine their mechanical behavior by measuring axial stress-strain and volumetric strain versus axial strain curves. According to the results, PC showed higher strength, ductility and energy absorption than that of OCC and LWC. Nowadays, waste tire rubber is used... 

This study has investigated the effects of different environmental conditions on the bond at the interface between two fiber reinforced polymer (FRP) layers. A total of 945 single lap splice coupons with three bond length were made using wet lay-up technic. There were used three unidirectional fabrics and one type of epoxy resin. A Uniaxial tensile test was performed on samples after 2, 4, 12, 20, 28, 36 and 48 weeks of exposure. Also series of test were conducted in order to determine the minimum lap splice length of single splice FRP samples. The experimental results indicated reduction of bond strength in glass specimens that was 17 % after 48 weeks of exposure while for same amount of... 

Ground granulated blast furnace slag (GGBFS) based alkali-activated concrete (GAAC) is one of the eco-friendly alternatives of traditional concrete, which uses industrial byproducts instead of ordinary Portland cement (OPC). Besides environmental benefits, substituting OPC concrete with GAAC has some economic advantages, while it successfully meets the concrete structural requirements in both mechanical and durability characteristics. Despite this fact, employing GAAC in the construction industry has been limited due to a lack of standard mix design code.This study aims to develop an accurate prediction model for the compressive strength of GAAC by employing the most appropriate machine... 

In recent decades, particle composite materials have a wide range of applications in engineering. Particle composites are a group of heterogeneous materials with different length scales and are characterized by particles that are randomly distributed in a matrix phase. Geopolymer concrete is a special type of concrete that its binder is made by reacting alumina and silicate carriers with an activating agent and in recent years with the expansion of its use has reduced the amount of cement consumption. In addition to the many advantages of geopolymer concrete, it has disadvantages in terms of setting time. That is why the use of cement has been proposed as a solution to the problem. This... 

Alkali-activated fly ash-slag (AAFS) is a new type of sustainable construction material widely studied in recent years for its desirable mechanical properties and low environmental impacts. In this study, the effects of the slag incorporation from 10 to 30% of fly ash are investigated on the strength, pore structure, and transport properties of the AAFS with various levels of fly ash replacements with slag. The unconfined compression and ultrasonic pulse velocity tests were performed to evaluate the mechanical properties of the AAFS concrete. Microstructural and mineralogical changes were studied by porosity, N2-adsorption/desorption, and SEM/EDX tests. Additionally, transport properties... 

Nowadays, construction with earthen materials has become more widespread due to their advantages: low construction cost, low embodied energy, application of green materials, and recyclability. Rammed earth (RE) as a sustainable construction has been used worldwide for decades. They are built in many countries such as Australia, China, India, and many parts of Africa and Europe. The rammed earth materials are cheap, accessible, and green and provide good thermal buffering. Stabilizers such as cement and lime with high embodied energy are frequently used in rammed earth construction to enhance materials' mechanical properties and durability. Stabilizers in RE materials could affect the energy... 

The behavior of construction materials at high temperatures has been an important aspect of researches in recent years. The first part of the current research aims to non-destructively monitor the formation and growth of damage at geopolymer concrete (GPC) after being exposed to high temperatures using linear and nonlinear ultrasonic techniques. Ultrasonic waveform and pulse velocity (UPV) tests were conducted on the specimens before and after exposure to the temperatures. Nonlinear wave signals were processed in phase-space domain for qualitative health monitoring of GPC. Furthermore, feature extraction was applied to phase-plane attractors using fractal dimension for quantitative... 

Selecting a suitable material is crucial for repairing the old concrete structures and joining precast panels of bridges, especially the bond strength between the substrate concrete and the overlay material. In this regard, this research focused on high-performance alkali-activated slag concrete (HPASC) as a new concrete used as an overlay on ordinary Portland cement concrete (OPCC) as a block of old concrete. Approximately four hundred bi-surface shear (BSS) tests were performed to evaluate the interface properties of OPCC and HPASC. HPASC specimens were designed with different NaOH molarity, silica fume (SF) content, steel fiber content, age of repair material, and proportion of grooved... 

In this thesis, supervised and unsupervised deep learning-based frameworks were proposed for distributed damage detection and quantification in concrete using sinusoidal ultrasonic response signals. Before the main study on ultrasonic-based concrete damage assessment, a preliminary study was performed on deep learning-based concrete compressive strength prediction. In this study, convolutional neural networks were utilized to predict the compressive strength of concrete through its mix proportions. The Genetic algorithm was employed to find the optimum number of filters in each convolutional layer of the convolutional neural networks. The proposed framework demonstrated high accuracy in... 

This study aims to evaluate the seismic behavior of geotextile-reinforced soil retaining walls by using incremental dynamic analysis and endurance time analysis methods. Five different wall models with variables of length and the modulus of elasticity of reinforcements have been constructed in the ABAQUS finite element software. In this study, the soil behavior and the interaction between the soil and reinforcement are modeled using a fully plastic linear elastic behavior model based on the Mohr-Coulomb yield criterion. Despite reinforced retaining walls' numerous benefits and extensive use, there is an obvious need for more precise design and a better knowledge of these structures' static... 

This study investigates the reliability analysis of mechanically stabilized earth (MSE) wall and takes into account the uncertainty associated in the mechanical properties of soil and geogrid, the magnetude of surcharge load and the soil-geosynthetic interface friction angle. In addition, the effect of number, length and place of the geogrid layers on the performance of this wall has been evaluated. The failure modes related to external stability, internal stability and horizontal displacement of the wall were considerd. In order to determine the probabilistic characteristics and the probability distribution function of soil and soil-geosynthetic interface friction angle, direct shear test... 

Polymer concrete is well-known for the quick repair of concrete structures and pavement. Many concrete structures such as bridges, offshore, and pavements are under cyclic loads when they are exposed to different environmental conditions during their lifespan. However, there are relatively few studies on the durability of Polymer concrete. The durability and fatigue performance of these structures are significant issues that should be considered. This study aims to investigate the long-term environmental effects on the mechanical properties of Polymer concrete. Therefore, polymer and ordinary cement concrete specimens were prepared and exposed to four chemical solutions with pH values of... 

In cold climates, structures are exposed to low temperatures during winter, which is one of the primary factors contributing to the deterioration of mortar and concrete. The destructive effect of freeze-thaw cycles on concrete is the main cause of concrete failure in cold regions. Frost damage in concrete is a complex physical phenomenon that begins with the internal microstructure of concrete. This damage occurs when water fills the voids of porous material and then freezes and expands. A prerequisite for improving the resistance to frost and extending the useful life of concrete is understanding the damage mechanism and the performance evolution model in a thawing and freezing environment.... 

Research on the impact of high temperatures on the mechanical properties of concrete is crucial for fireproof design, safety assessments, and repairing fire-damaged structures. However, there is a lack of research on the effects of water re-curing on thermally damaged concrete. This study aims to explore how high temperatures and water re-curing affect the compressive behavior of concrete with varying percentages of rice husk ash (0, 4, 8, 10, and 12%). The compressive behavior was assessed by analyzing stress-strain responses and parameters such as compressive strength, modulus of elasticity, strain at peak stress, ultimate strain, absorbed energy, failure mode, and visual observations.... 

This study seeks to compare the effect of curing conditions in the sea, coast, and middle of the island environment on five mix designs of alkali-activated concrete (AAC) based on ground granulated blast furnace slag (GGBFS) and fly ash (FA) and the effect of the ratio of sodium silicate (SS) to sodium hydroxide (SH) and alkali activated solutions (AAMS) to the binder on mechanical properties. The compressive strength and load-deflection test was conducted to obtain uniaxial compressive strengths (UCS), modulus of elasticity ("E" _"S" ), elastic and ultimate strain, and dissipated energy. The most significant decrease in strength was observed in the coastal area and the sea. Also, the... 

releasing substantial quantity of carbon dioxide to the atmosphere due to the production of OPC concrete is believed to be one of the most important environmental concerns. It is reported that the global cement industry contributes around 2.8 billion tons of the greenhouse gas emissions annually. geopolymer concrete is an efficient and effective alternative to OPC for reducing air pollution and preventing environmental damage which is utilized in construction industry. Despite the phenomenal research carried out in the field of GPC , There is no standard mix design procedure for this novel concrete. In this study a neural network is to predict the compressive strength of fly ash based... 

In recent years, many engineers and researchers have identified one of their primary concerns as finding economically viable construction methods that promote sustainable development and are environmentally friendly. Compacted earth structures have recently gained attention among engineers and researchers due to the mentioned advantages. The discussion regarding their durability and acceptance as construction materials is crucial. A better understanding of compacted earth from a mechanical and structural perspective allows overcoming its disadvantages. Numerous studies have extensively investigated the durability of stabilized compacted earth materials through various experiments. To date,...