The interaction parameters between soil and reinforcement at their interface play a critical role in influencing the mechanical behavior of reinforced soil systems. In this research, the effect of the size of soil grains and the stiffness of the reinforcement on the pull out resistance of the reinforcement from the soil has been investigated in a laboratory. The pullout resistance of three types of reinforcements with different stiffness in three types of soil with different grain sizes has been investigated. The amount of penetration of solid soil grains into the reinforcement increases by reducing the stiffness of the reinforcement and increasing the size of the diameter of the soil grains. For each specific vertical stress level, the greater the penetration of solid soil grains into the reinforcement, the higher the pull out strength of that reinforcement. The results show that with the increase in the diameter of the solid grains of the soil, the pullout resistance of the reinforcement has also increased, but this increase has been more significant in the case of the reinforcement with lower stiffness compared to the reinforcement with higher stiffness. Also the difference in pullout resistance of three reinforcements with different stiffness in fine-grained soil was less than the difference in the pullout resistance of three reinforcements in coarse-grained soil, which indicates the simultaneous effect of reinforcement stiffness and soil grain size on pullout resistance.

Real-time hybrid simulation (RTHS) is a form of testing where physical component of structure communicate with numerical model which simulate the behavior of the rest of the structure. Interface forces between the experimental and computational substructure are imposed by actuator. Resulting displacement and velocity of the experimental substructure are fed back to the computational engine to determine the interface forces applied to the computational and experimental substructures for the next time step. In this thesis, the RTHS technique is used to conduct experiments with a numerically simulated structure and physically tested tuned liquid damper (TLD). One very important factor which causes instability in RTHS is the actuator inability to perform the commands from the simulator in real-time. In RTHS, an actuator dynamic is approximated by a pure time-delay, and the time-delay in the closed loop system causes inaccuracy results or even instability. Therefore, Delayed Differential Equation (DDE) is used to determine the critical time-delays depending on the TLD parameters. Then, the compound stability condition is investigated for a general case and the results show that the mass ratio has lower limit for low delays and upper limit for high delays to remain stable. As frequency and amplitude ratios increases, margin of stability for mass ratio increases.

The importance of developing passive defense systems, requires the study and analysis of structures in this area due to surface explosions. Due to the localization of the explosion phenomenon and the effects and environmental characteristics and existing obstacles, this phenomenon has special complexities. In this research, using the finite element method and with LS-Dyna, the nonlinear behavior of the walls of concrete structures reinforced with GFRP in a war shelter against The charge due to the impact of the surface blast wave is simulated and investigated in a more precise three-dimensional space. In this study, the explosive load, abutment conditions, wall dimensions, fiber material and characteristics of the materials used are considered the same and the effect of different reinforcement modes with GFRP sheet and their thickness in these modes is investigated. First, the stress distribution in the walls of the reference concrete structure was calculated and the critical areas of the structure were identified. Then, the response of the walls of the reinforcement structure in the critical area with different thicknesses is compared with each other and with the reference structure and the effect of using this reinforcement method for the walls of the structure against surface explosion loading is determined. Finally, the amount of displacement and stress distribution for different geometric locations of GFRP sheets is calculated and due to the extraction of the optimal state of reinforcement against full coverage of the walls of the structure, the use of this method in this method is considered appropriate..

Tuned Mass Damper (TMD) is amongst the simplest and, the most usable passive control tools, to improve the behavior of various structures. However, factors such as the characteristics of the soil beneath the structure and the presence of an adjacent structure could also affect the performance of that. This study investigates the effects of using a TMD in two 20-story steel moment frames with two different aspect ratios on the seismic response of them in fixed and flexible base and considers the adjacency of two structures, known as Structure-Soil-Structure Interaction (SSSI). To apply the effects of SSSI, reduced stiffness matrix of the foundation-soil-foundation system, considering as a plane strain problem, is obtained through analysis of a finite element model in Abaqus and is applied to the 2D models of end frame of the structures using a set of springs and a newly developed element in OpenSEES. Furthermore, the particle swarm optimization (PSO) algorithm is used to optimize the design parameter of TMD. The average results obtained from time history analysis under ten far-field seismic records specifies that, exploiting a TMD with parameters optimized in a 20-story structure in both fixed-base case and considering SSSI, can reduce the seismic responses in the form of the average of maximum drift and displacement. However, the SSSI effect can changes the responses of structures equipped with dampers; in such a way that, in high-rise structures with a higher value of the height to dimension ratio (thinner structure), the response of structures is increased.

This study is focused on the treatment and reuse of agricultural drainage water using permeable reactive barriers (PRBs). To construct the physical model, a cubic iron tank with dimensions of 1×1×1 is used. Drainage pipes with a standard diameter of 16 mm are installed at a depth of 20 cm. To determine the depth of the static level, piezometer tubes are used in the model. After permeability tests and evaluating the obtained results as well as considering the availability of materials, the mixture weight ratios of the materials in PRB are selected as follows: 25% sand, 25% anthracite, 20% zeolite, 20% iron borings, and 10% poplar wood sawdust. The permeability coefficient of the PRB with this mixture after complete saturation over 24 hours is equal to 0.0322 cm/s. An initial nitrate concentration of 100 mg/liter is considered for the column to obtain the break through curve of the synthetic wastewater. It takes 15 minutes to detect the nitrate breakthrough. The breakthrough curve is considered a normal curve, and the only unknown of the problem, i.e., the longitudinal diffusion coefficient (D_L), is obtained by trial and error as 1.5×〖10〗^(-7) m^2⁄s, which is an acceptable value. The Peclet number for the proposed PRB is 14.344, which indicates the identical effects of the dispersion and diffusion processes. In this study, the drainage filter, which includes PRB and sandy loam soil, is able to eliminate nitrate by 99.44% after 24 days.

Incorporation of crumb rubber (CR) among ballast aggregate is characterized as an advantageous way to considerably lessen the degradation rate of granular particles. Meanwhile, there is an uncertainty about the proper drainage performance of mixture whenever the ballast aggregate is further degraded. The present study evaluates the drainage capability of degraded ballast aggregate in which disparate percentages and sizes of discarded granulated rubber particles are incorporated. To provide degraded aggregate, the impact loading test under controlled condition is implemented on fresh railway ballast. Afterwards, the large-scale constant head permeability test is carried out on prepared mixtures of degraded aggregate and CR particles. The results confirm that the effect of CR size on drainage potential of degraded ballast combined with discarded CR particles is more than the influence of CR percentage. Also, the nonlinear trend line observed between the applied hydraulic gradient and the water flow velocity approaches to the conventional linear trend line represented by Darcy’s law whenever the smaller-sized CR particles are incorporated into the most degraded ballast aggregate. As expected, higher level of degradation of aggregate decreases the hydraulic conductivity of ballast specimen, meanwhile the permeability is yet considerably more than the acceptable limit even for specimens subjected to significant level of degradation combined with the smaller-sized crumb rubber particles.

The hydromechanical behavior of unsaturated soils depends on their state of stress. In recent years, the use of effective stress as a fundamental variable converting a multiphase medium to a continuum has appealed researchers’ attention. The determination of effective stress needs estimation of the so-called effective stress parameter, which is a function of other physical variables and essential parameters such as those of the soil water retention curve (SWRC). In the current study, multigene genetic programming (MGGP) has been employed to predict a relationship for the effective stress parameter of soils. The input variables are: the net stress, suction, slope of the soil water retention curve, air entry value, residual and saturated water contents. The comparison of the performance and accuracy of the obtained equation with the available equations as well as the values of effective stress parameter obtained from experimental tests indicate the reasonable adequacy and accuracy of the proposed equation. For this purpose, 101 datapoints of effective stress parameter from literature were gathered and used. The high coefficient of determination obtained for the proposed equation, namely, 0.94, confirmed its reasonable accuracy.Parametric study revealed that an increase in the ratio of net stress to the air entry value will lead to an increase in the effective stress parameter for the same suction levels. However, a decrease in the effective stress parameter values was observed with the increase in the SWRC slope, and with the decrease in the ratio of residual to saturated water content.

Seismic analysis of foundations rested on saturated porous media can be performed using several methods. Some of these methods are very accurate such as boundary element method, complex finite element method and scaled boundary finite element method, and some others, such as the cone model method, are simple and practical and have appropriate and acceptable accuracy. Using the cone model method, the soil mass is modeled with incomplete cones and the propagation of waves in these cones is followed until the wave is sufficiently damped and its effect on the foundation response is becomes negligible. In this paper, the application of the cone model method has been investigated in determining the dynamic stiffness of foundations resting on different soil conditions by taking into account the effect of pore water (two-phase approach). A special attention is carried out to obtain the system of differential equations governing horizontal and torsional vibrations in a porous medium, taking into account the effect of soil dilation. Also, the effect of different parameters such as soil layer thickness, porosity, permeability coefficient has been investigated on the dynamic response of foundations under shear and torsional vibrations. The results show that the cone model formulas can provide a good level of accuracy and high computational efficiency for predicting the horizontal and torsional vibrations of foundations resting on saturated porous media.

Some excavations need to be designed for a long time or sometimes they are left for a long time. Stabilization of most of excavations has been done using anchors. Field surveys of these excavations show that in some cases, deformation of the excavations increases over time, and locking force of anchors decreases, leading to dangers. Therefore, it is very important to know the long-term behavior of stabilization systems by an anchor and reducing the anchor load. The main purpose of this study is to evaluate the changes in anchor load in excavations. Numerical modeling of the long-term behavior of soils has many complexities and may not correspond to reality. Therefore, in this study, data on the long-term behavior of an excavation project in Tehran were collected and then numerical modeling in finite difference software was used to study the long-term behavior of this system. Also, using the back analysis method, the input creep variables of the rheological model of the time function in the numerical model were determined and used. Comparison of the results of this research and field survey results confirms the time function behavior of the numerical model performed in software. The results of this research show that in an anchor installed in the middle depth of the excavation project, a 7% reduction in load occurs one year after prestressing. Also, during the creep time, the maximum horizontal deformation of the excavation walls increases by 13% during one year.

The use of self-compacting concrete types is increasing day by day, and understanding its rheological behavior is a high priority in the use of this type of concrete. In this study, the rheological properties of fiber-reinforced ultra-high performance self-compacting concrete (UHPSCC) were predicted by ANN-GA (Genetic Algorithm hybrid with Artificial Neural Network) and RBF-NN (Radial Function Neural Network), and its output was compared with laboratory results. The purpose of this study is to evaluate the making of UHPSCC with durable and to achieve an artificial neural network that can more accurately predict the rheology properties of this type of concrete. Rheology properties of self-compacting concrete include tests related to fresh concrete, including; Slump flow (D), slump flow (T50), V-funnel flow, and L-box test were performed. Experimental results indicate high compressive and tensile strength and rheological properties placement within the acceptable EFNARC range. Estimation and prediction of the two neural networks studied from the rheological properties of this type of concrete show the acceptable accuracy of prediction of both neural networks. Between these two artificial neural networks, the prediction accuracy of ANN-GA is higher.