MODARES CIVIL ENGINEERING JOURNAL
Year:2021 | Volume:21 | Issue:4|Papers Count:17

On the mechanics of solids, in many cases, the body is affected by mechanical force and heat load simultaneously. One of the most widely used and important parameters in the optimal design of engineering problems is the utilization of the sensitivity numbers respect to the values of its design variables. Sensitivity numbers or derivative of a function with respect to a design variable show how a dependent variable responds to the design variables changes. The present paper analyzes sensitivity in thermomechanical problems using the complex variables method (CVM). The most important drawback of past methods for the analysis of sensitivity values such as finite difference method (FDM) and semi-analytical method (SAM) is the dependence of the calculated values of sensitivity numbers on the step size, which leads to unreliable answers. Complex variables method is a new robust approach that uses a Taylor series extension in a complex space and which is not sensitive to step size, disturbance and given that during the computational process, subtraction of two numbers is almost equally avoided, so does not influence from error caused by removing meaningful figures that commonly occur in finite difference method due to subtracting of two near the number. As a result, it is possible to achieve accurate answers by choosing a small step size. Also, it has some potential advantages over other methods. At first order sensitivities using the complex variables method, the implementation is straightforward, only requiring a perturbation of the finite element mesh along the imaginary axis. Implementation of sensitivity using complex variables method requires complex variable finite element code such that complex nodal coordinates can be used to implement a perturbation in the shape of interest in the complex domain. All resulting finite element outputs such as temperature, displacements, strains, stresses, etc. become complex and accurate derivatives of all finite element outputs to the shape parameter of interest are available. So, unlike most methods, using the proposed method does not require calculations to select the appropriate change in step size. However, the value of the change in step size is not known in advance and changes from one problem to another. Therefore, it is necessary to repeat the simulation to ensure the results. The study found that the source of the rounding error was due to the rotation of the element, this also makes it difficult to use two methods, semi-analytical and finite difference. In this case, the use of CVM is not limited and can be achieved by effective answers without worrying about the small step size. In the present study, to examine how efficient and valid the proposed method is, how it works to solve several thermomechanical problems is described. The methodologies are demonstrated using two-dimensional finite element models. Obtained sensitivity derivatives are compared to the semi-analytical solution and also finite difference method and it is shown that the proposed method is effective and can predict the stable and accurate sensitivity results. The complex variable method presented in this study can be used to solve a wide range of engineering problems.

The Presence of defects in the compressive structural members may reduce their load-carrying capacity to a large extent. These defects may be in the form of cracks, corrosion, perforation, or dents existing on the smooth surface of the member. In most cases, the impact of an external object is the main cause of these damages. For example, tubular sections of offshore platforms which are mostly under axial loads, may be damaged with the collision of supply vessels. Similarly, the columns of bridges and buildings, may be hit by heavy moving vehicles. The Existence of the mentioned defects in compressive members with circular cross-sections may cause premature failure of these structural elements due to local buckling followed by the member's overall instability. Hence, the effect of these damages on the buckling strength of tubular columns, and the effect of different influencing parameters should be studied in depth. This study presents a parametric investigation on the axial load-carrying capacity of cylindrical columns damaged by a spherical indenter. For this purpose, the numerical models were generated in general purpose finite element software "Abaqus" and verified against results of two axial compression tests on intact and damaged thin-walled cylinders. The studied parameters included depth of the damage, shell slenderness ratio, location of the damage, length of the axial member, and radius of the indenter object. The analysis results showed that, the depth of the damage, shell slenderness ratio, and the damage location were the parameters affecting the buckling capacity of the damaged cylinders under axial load. The increase in damage depth or shell slenderness ratio decreased the buckling load of the member. On the contrary, the buckled shape of the members with different damage depth values or shell slenderness ratios was almost identical. The post-buckling behavior of the studied specimens was affected by the shell slenderness ratio, the damage location, and the length of the compressive member. As the shell slenderness ratio or length of the member increased, the member strength in the post-buckling range experienced more rapid reduction. Also, as the damage became closer to the one of supporting ends, the buckling ring at the farther support vanished while the buckling ring at the closer support became more critical, resulting in an increased strength reduction. The radius of the indenter object had a negligible effect on the buckling capacity and post-buckling behavior of the specimens. For samples with the same damage depth and different radius of the indenter object, the damage profile difference was very small. This small difference vanished during the buckling process, and the final deformation profile for the samples became almost identical. Finally, a regression analysis was conducted on the results of analyses considering the effect of different parameters, and two predictive equations were proposed to determine the buckling and residual capacity of the studied members as functions of influencing parameters. The evaluations performed to estimate the accuracy of the proposed equations showed that they have good accuracy and provide reliable predictions for design rechecking of damaged cylindrical members subjected to axial compression.

Buckling-restrained braced (BRB) frames are steadily replacing concentrically braced frames because they can yield without buckling when subjected to both tension and compression loads. Though BRB frames are being widely used in construction industry especially for building structures in high seismicity areas such as Iran, it is shown that at large strains, a considerable amount of permanent deformation is generated at the support connector between the brace and the frame. This drawback can be overcome by providing recentering capabilities to the braced frame system. By applying the concept of a recentering system to the design of BRB frames, we used braced frames that incorporate BRBs with superelastic shape memory alloy (SMA). Also, the use of SMA in the bracing system causes damping and reduction of residual deformation. BRBs are considered as lateral load-bearing systems due to their non-buckling in compression. But these braces also have disadvantages. Among these disadvantages is the creation of permanent deformation in the structure after the end of loading and also the costly replacement of these members after the failure and current of the steel core of these braces. Therefore, the application of SMA in BRB systems, given the specific characteristics of these alloys, can be an effective step in improving seismic responses. However, recent studies have shown that BRB frames are susceptible to residual deformations during earthquakes which makes them vulnerable to aftershock events. The effectiveness of SMA-BRBs in controlling the seismic response of a structure largely depends on the relative strength and stiffness of SMA bars and BRB core plates. The aim of the current study is to investigate the aftershock collapse capacity of BRB frames with and without SMAs. In this paper, seismic behavior of frames with BRB’, s and the effect of utilizing SMAs were studied. The selected models are three frames with 3, 6 and 9 story, which in different openings have BRBs in two states with and without applying shape memory alloys. These prototypes were modeled in OpenSees under nonlinear dynamic time history analyses. The results comparison was performed under three records including Main Shock-Aftershock Ground Motions. The results include comparing the seismic responses of structures with and without applying SMAs including maximum roof displacement, maximum interstory drift, maximum base shear, and maximum acceleration of roof and hysteresis curves in structures with BRBs and SMAs rods. The results showed that by employing SMAs rods, seismic responses including roof displacement, interstory drift and base shear have been significantly reduced. By reviewing the results, it is clear that improvements in the 6 and 9-story frames compared to the 3-story frame is more tangible. Also, the analysis results showed by equipping the frames with SMAs, the energy dissipation concentration pattern has been changed. In the case of frames without SMAs, due to the greater absorption of lateral force (larger base shear), the amount of energy dissipation of BRBs was higher. In these frames, energy loss was in the first stories and in frames with SMAs, the energy dissipation concentration was in the final stories. Using a SMA in these frames can reduce the cost of restoring and recovering of damaged systems and make more resilience building system.

High pressure and temperature in the earth's crust lead to fracture and microcracks in rocks. Direct access to earth crust rocks at great depths is very costly and, in most cases, impossible. The study of the condition of rocks at great depths is often done using indirect methods such as seismic waves. The results of these studies are compared with the results of laboratory studies of wave velocities in different rocks and the conditions of the rocks are simulated. At high depths, hydrostatic stress is applied to the rocks of the earth's crust, and tectonic, earthquake and other stresses cause it to be anisotropic. The primary purpose of this study is to investigate the change in compressive wave velocity due to the change in compressive stress in rocks. At first, a cylindrical core of different stones with a length to diameter ratio of 2 to 2. 5 is prepared according to the standard test method (ASTM D4543) and their dimensions and weight are determined. after measuring the unconfined compressive strength of cores according to the standard test method (ASTM D2938), the hydrostatic pressure of 50% to 95% of it is applied to the rock samples prepared from the earth. This pressure is applied to the cores by using the Hoek cell (for lateral pressure) and the axial load machine and using an ultrasonic device, determine the compressive wave velocity (ultrasonic pulse) is determined according to the standard test method (ASTM D2845) in the axial direction of the sample. Then, the wave velocity was measured by decreasing the lateral pressure (increasing deviatoric stress) in a stepwise manner and the wave velocity was measured at each step. In the following, comparative diagrams of compressive wave velocity (Vp) with density (ρ, d), uniaxial compressive strength (UCS) and the effect of hydrostatic stress (σ, hyd) and deviatoric stress (σ, dev) on P-wave velocity in each sample are drawn. The results show linear relationships between compressive wave velocity and the physical properties of rock samples. Also, the Pwave velocity at hydrostatic pressure is the highest and as the lateral pressure decreases (increasing the deviatoric stress), the velocity also decreases.

This paper presents a non-hydrostatic two-dimensional vertical (2DV) numerical model for the simulation of wave-porous structure problems. The flow in both porous and pure fluid regions is described by the extended Navier-Stokes equations, in which the resistance to flow through a porous medium is considered by including the additional terms of drag and inertia forces. The finite volume method (FVM) in an arbitrary Lagrangian-Eulerian (ALE) description is employed to discretize the flow and transport equations. A twostep fractional method has been deployed to solve the governing equations. In the first step, the momentum equations in the absence of pressure field were solved to compute an intermediate velocity. The second fractional step consisted of bringing the pressure terms back into the equations, and calculating the pressure field by solving the extended continuity equation and the momentum equations excluding advective and diffusive terms and drag force components. By substitution of the approximations of the pressure derivatives into momentum equations, and subject to the continuity constraint, the pressure Poisson equation was obtained. The solution of the pressure Poisson equation led to a linear system of equations in the form of a block tri-diagonal matrix with the pressures as unknowns. The second step was completed by computing the updated velocity values. In the present numerical model, two types of boundary conditions, namely Dirichlet and Neumann boundary conditions were adapted to solve the governing equations. The Dirichlet boundary condition was set to zero for normal velocities at impermeable bottom and the Neumann boundary condition was considered to be equal to zero for normal gradient of the tangential velocities at impermeable bed and also the left side of the computational domain. At open boundaries, where required, by setting the dynamic pressure equal to zero at the end of the numerical domain, a free exit for water was considered. The newly developed model in the absence of porous medium was verified by comparing the numerical simulations with the analytical solutions of a solitary wave propagation in a constant water depth. The newly developed model was then employed to simulate the solitary wave interaction with a permeable submerged breakwater. Based on the numerical results, when the solitary wave front reaches the offshore side of the submerged breakwater, due to the hydraulic jump formation, the flow is separated from the top of the obstacle and small clockwise vortices are generated at the leading edge of the breakwater. As the wave passes over the breakwater, the primary vortex grows in size and penetrates into the deeper layers of water. It was also seen that, due to the drag and inertia resistance forces of the porous medium, the velocity inside the permeable breakwater was noticeably smaller than that on the top of the breakwater. The comparisons between the numerical results and experimental measurements for time histories of water displacements, spatial distributions of free surface elevation, velocity fields and velocity profiles in both horizontal and vertical components, showed the capability of the newly developed model in predicting wave interaction with permeable submerged breakwater.

Groundwater is the most reliable source of supply for potable water and supports a wide array of economic and environmental services. There is a significant concern that groundwater levels are declining due to intense aquifer use. The sustainable management of groundwater resources requires good planning and concerted efforts. To manage groundwater resources, it is necessary to predict the groundwater levels and its fluctuations. The prediction groundwater level can guide water managers and engineers effectively. On the other hand, there are multifarious types of equipment for measuring levels of groundwater. Sophisticated water level loggers or divers can measure the groundwater level automatically. Sounding devices with acoustic and light signals are also used to check groundwater levels. The use of devices for measuring the level of groundwater is timeconsuming and costly. To reduce the time and cost of the groundwater level measuring process, many methods of Artificial Intelligence (AI) have been utilized for estimating the groundwater level. Among the AI methods, SVMs has great ability in predicting non-linear hydrological processes. Support vector machines (SVMs) is as an intelligent computational method for predicting hydrological processes. Recently, (SVMs) have been successfully applied in classification problems, regression and predicting,as techniques of machine learning, statistics and mathematical analysis. The SVM is based on the structural risk minimization (SRM), which can escape from various difficulties, such as the necessity of a large number of control parameters and a local minimum in artificial neural networks (ANNs). The weighted least squares support vector machines (WLSSVM) was first introduced by Suykens et al., and has proved to be much more robust in several fields, especially for noise mixed data, than least squares version of SVM (LSSVM). Their powerful scientific research provides motivation for employing WLSSVM method in estimating groundwater level. The accurate value of WLSSVM parameters (γ, , σ, ) effect on the estimation, these optimal parameters can be achieved optimization algorithms. Therefore, weighted least square support vector machine (WLS-SVM) model was coupled with particle swarm optimization (PSO) and gravitational search algorithm (GSA) as metaheuristic algorithms for estimating well water level. In this study, an attempt has been made to use the hybrid model with high accuracy to estimate the groundwater level. In order to estimate the groundwater level, ten wells data in Bagheyn plain of Kerman province is considered during ten-year time series. The estimated value obtained by the WLSSVM-PSO and WLSSVM-GSA models are compared with the observed value, and showed the estimated results have nearly coincidence with observed values. Numerical results show the merits of the suggested technique for groundwater level simulation. In order to verify the hybrid learning machine metaheuristic model, Mean Absolute Error (MAE), Root Mean Squared Error (RMSE), Average Absolute Error (AAE), and Model Efficiency (EF) are computed, and these statistical indicators stand on the good acceptable range, and find WLSSVM-GSA is more accurate than WLSSVM-PSO. The results demonstrate that the new hybrid WLSSVM-GSA model has high efficiency and accuracy with observed values, and the modelling method is an innovative and powerful idea in estimating well water level.

Fiber strands due to their flexibility, high aspect ratio, cross-section varieties and degree of crystallinity are adequately strong to be used as reinforcement in composites such as concrete. Newly introduced fiber reinforced concretes (FRC) are the cementitious materials that exhibit reinforcing features in all directions. FRCs due to their interesting properties are enormously favored by civil and structural engineers. Natural and synthetic fibers can be employed in concretes, shutcretes and mortars. The interface between the added fibers and the cementitious matrix fundamentally influences the properties of the FRCs. Fibers are classified into hydrophobic and hydrophilic. The former fibers have negligible moisture absorbent capacity while exhibiting acceptable mechanical properties. Hydrophobic fibers are incapable of forming adequate adhesion with cementitious matrix. Properties such as low weight, strength parity in wet or dry conditions and inertness in acid or alkaline environments are among the salient properties of polypropylene (PP) fibers. PP as a hydrophobic fiber has gained wide acceptance as concrete reinforcement. The hydrophobicity of fibers, such as PP, has been always been disadvantageous for the use of these fibers in concrete structures. Treatments such as chemical surface modification imparts hydrophilic property to PP fibers. Thus the modified PP fibers can successfully adhere to concrete matrix. In this research melt-spinning technology as the most widely used manufacturing technique for production of the PP fibers was used. Pure and grafted anhydride maleic PP granules were used to produce both hydrophobic and hydrophilic PP fibers. The produced fibers were characterized according to relevant standards prior to be added to concrete samples at identical fiber volume fraction. The results pointed to the positive effect of the induced hydrophilic properties in the fibers as far as the fiber-matrix adhesion was concerned. The ability of the chemically modified fibers to absorb water when wetted with the moisture present in the concrete, greatly improved the adhesion of the added fibers with the concrete matrix. The effect of hydrophilicity of PP fibers on mechanical properties of reinforced concrete was investigated by comparing concrete samples prepared by modified and unmodified fibers. Results showed that in comparison to control concrete sample, addition of modified hydrophilic fibers to concrete enhances compressive, tensile and flexural strength of concrete by 11%, 45% and 77% respectively. It was found that compressive, tensile and flexural strength of concrete samples containing the chemically modified fibers were respectively higher by 5%, 7% and 2% in comparison to the concrete samples containing unmodified hydrophobic fibers. Addition of fibers is more effective in enhancement of flexural strength of resultant concrete. This is due to the fiber bridging phenomena that prevent both crack formation and propagation. Addition of fibers also improves load bearing capacity of the resultant concrete, which in turn leads to enhancement of flexural strength of the concrete.

Due to the earthquake prone region in Iran and the need of strengthen structures against lateral loads which one of the important elements used in the structure are the shear walls. The use of concrete shear wall structural system, due to the hardness and maximum resistance, high energy absorption and the building movement control are suitable system against the lateral load of the building. If the shear wall and boundary elements are homogeneous, in other words they are similar, the problems are much less, but it happens that such structures are not made of one, for example, the type of the shear wall is concrete and the type of the boundary elements are steel or the opposite. One of the uses of concrete shear wall is its simultaneous use with steel frame, which consists of shear wall, boundary columns and level-level beams. The way of connecting these walls to boundary are very important. Therefore, knowing the behavior of these structures is important. In this research, the shear wall of the concrete type and its connection to steel frame will be studied and investigated. For this purpose, first a 10-floor structure along with a steel frame system with concrete shear wall was modeled in Etabs software, in order to determine the beam dimensions, columns, wall and the amount of the longitudinal and transverse reinforcements of the concrete shear wall. Then, a wall from the first floor is selected with boundary elements to be modeled in Abaquse software in 4 different types of boundary elements and how to connect the steel frame to the concrete wall and compare the resistance and the type of the wall failure under pushover load. The models which are made are as following: A_ Buried column in concrete shear wall. B_ Half-buried column in concrete shear wall. C_ Buried column in concrete shear wall by attaching the welding of transverse shear wall reinforcement to the column flange. D_Buried column in concrete shear wall by connecting bolt shear wall transverse reinforcement to the column flange. From the results of the analysis, can be concluded,the shear wall model with buried column and bolt connection of transverse reinforcement are shown that have more resistance than other models of connection, that the reason for this can be found in strong bolt connection, which makes the steel border element more involved in the tolerance of the seismic loads. Also, the model with the half-buried columns showed less resistance than the other models of connection, where the unconfinement in the boundary elements zone and less participation of the steel element in this condition can be known for this reason.

Side weirs are a type of hydraulic structures used for different purposes in water transition systems, water supply, flow diversion and flood control important. Side weir, is a key structure in transition of urban sewage,the advantage of this structure in urban sewage is the pretreatment of the diverted flow due to side weir height which is in environmental engineering. The flow on these structures is spatially varied flow type with decreasing discharge. Spatially varied flow is a type of steady flow with decreasing or increasing discharge along the channel. To analyze this flow, its necessary to know the velocity distribution and the values of the kinetic energy correction factor (α, ) and the momentum correction factor (β, ). However due to complexities concerned with this type of flow and experimental limitations there hasn't been enough study on the velocity distribution for this kind of flow. In this research the velocity distribution in a rectangular side weir has been investigated using a commercial software. Before performing the numerical analysis it's necessary to check the software's ability in modeling the 3D flow on the side weir. Experimental data of JaliliGhazizadeh (1994) has been used for verification. In these experiments side weir lengths 20, 30, 45, 75 (cm) and side weir heights 1, 10, 19 (cm) has been used while discharge in the main channel varied from 43 to 90 (lit/s). The simulation boundary conditions are volume flow rate discharge for upstream boundary, the "wall" for wall and "symmetry" boundary conditions for water surface. The only difference in boundary conditions for subcritical and supercritical flow is in downstream boundary condition which is "specified pressure" for supercritical flow and "specified velocity" for subcritical flow used respectively. Turbulence model is RNG in all simulations. Comparing the results shows that the software is capable of calculating the discharge passing the rectangular side weir with a good accuracy for both subcritical and supercritical flows. Therefore, based on obtained results we can conclude that the commercial software is capable of simulating 3D flow on rectangular side weir and the results obtained from performing analysis with this software can be cited. Velocity distribution, correction factors for kinetic energy and momentum were studied in detail. In the case of subcritical flow on the side weirs, water in the main channel and downstream area of the side weir has been observed to separate in the opposite direction of the main channels, there for it is important to study these areas. A noticeable point is that although large amounts of simulation points have (α, ) and (β, ) close to one, simulation results show that (α, ) and (β, ) cannot be considered equal to one for the whole cases. The variation of (α, ) and (β, ) in side weirs length in this research were ascending. Based on existing simulation results, new equation between (α, ) and (β, ) for subcritical and supercritical flow and quantification of separating area were proposed. Results of this research can help side weir designers to have a better understanding of the complex 3D flow on side weirs.

Successful implementation of active control technology requires an appropriate control algorithm to calculate the adaptive control force required by the actuators. Smart structures represent a new engineering approach that integrates the actions of digital sensors, actuators and control circuit elements into a single control system that can respond adaptively to environmental stochastic changes in a useful manner. The mathematical model of the system is an estimation of its actual dynamic behavior. In general, this difference can have a significant effect on the performance and stability of the control system. One of the important issues in active control algorithms is the evaluation of the control system's robustness to model uncertainties and the actuator saturation. In this paper, a Developed Robust Proportional Integral Derivative controller with uncertainties in the structural stiffness parameter, the sensing noise and saturation windup of the saturation is introduced. the PID control force is obtained in such a way that the infinity norm of the closed loop system transfer function from disturbance inputs to target outputs becomes minimal. By considering the parametric uncertainty in the structural stiffness parameters and multiplicative unstructured uncertainty and the windup phenomenon in the actuator model and existence of noise in the velocity sensor, PID control scheme has been developed in the form of state space. The PID control gains by taking advantage of the H∞,mixed sensitivity minimization criterion, are obtained simultaneously by considering the effects of all vibration modes of the building in such a way that the infinity norm of the closed loop transfer function from exogenous inputs to the controlled outputs becomes minimal. To demonstrate the robust performance and stability of the proposed algorithm, the results of numerical simulations on a 4-story structure equipped with an active tuned mass damper are used. The obtained results show the robust performance and stability of the proposed robust PID control scheme in comparison with conventional PID and linear quadratic regulator (LQR) control algorithms, both in time and frequency domains. According to the mean values of performance indices, in average 11 and 7% more reduction in J1, 7 and 5% in J2 and 10 and 6% in J3 in the proposed robust PID in comparison with the LQR and common PID for three models subjected to far field selected earthquake records. And in average 17 and 10% more reduction in J1, 12 and 8% in J2 and 11 and 8% in J3 in the proposed robust PID in comparison with the LQR and common PID for three models subjected to near field selected earthquake records. And J4 which related to amount of control effort, for the proposed robust PID, LQR and conventional PID are 1. 3e-2, 9. 1e-3 and 7. 9e-3 in average for the three models subjected to far field and 4e-2, 2. 4e-2 and 2. 7e-2 subjected to near field selected earthquake records. The obtained results show the robust performance and stability of the proposed controller in the presence of structural stiffness uncertainties, actuator saturation and measurement noise.

Because of having amazing mechanical physical properties including noise pollution reduction, quiet, reliability, most cost-effective, sustainable and lasting life, asphalt pavement system has been utilized for parking lots, roadways, airstrips by the most state and federal governments highly prefer asphalt pavement by many civil engineers. Generally, asphalt pavement is made up of sand, stone (aggregate), liquid (petroleum) asphalt and additives. Accordingly, the main objective of this article is to analyze the thermo-dynamic behavior of porous viscoelastic asphalt pavement system under a moving harmonic load based on the classical plate theory. The asphalt pavement system is modeled as a rectangular sandwich plate structure. Three states of porosity distribution pattern, i. e., uniform porosity, non-uniform symmetric porosity, non-uniform asymmetric porosity distributions are considered for porous asphalt layer which are supposed to vary along the in-plane and thickness directions. The equations of motion are extracted in accordance with Hamilton’, s variational principle and then solved using the expanded Fourier series. The accuracy and correctness of the extracted formulation are firmly demonstrated by comparing the data accessible in the literature and finite element simulation COMSOL Multiphysics®, . In this study, the dynamic response of the asphalt pavement system was evaluated analytically and numerically by considering the porous asphalt layer under the harmonic load at various velocities in a thermal environment. The classical theory of plates was used for the analytical modeling of the system. The dynamic equations were derived in view of the relations for porosity and thermal strain in the stress-strain matrices in combination with Hamilton’, s principle. With the aid of Fourier series expansions, and given the considered boundary conditions, the partial dynamic equations were transformed into differential dynamic equations. Furthermore, the dynamic response of the system was obtained using Laplace transform, which was then evaluated in terms of effective parameters. A finite element simulation software was also used to validate the results against the published articles. Parameter studies reveal the impacts of the velocity and the excitation frequency of the harmonic moving load, porosity distributions, and temperature changes on the dynamic response of the pavement system. According to the conducted studies thus far, the dynamic behavior of asphalt pavement system is inevitably affected by such outcomes. Furthermore, the results demonstrated that non-uniform symmetric porosity case is more suitable than the other two types of porosity, the temperature changes lead to a softer asphalt pavement system, with increasing porosity, the dynamic response of the system rises in all the cases of porosity distributions and the amplitude of nondimensional dynamic deflection is directly proportional to the frequency of excitation up to the resonance. It is seen that for a smaller velocity parameter in this case, i. e. 𝛼,= 0. 1, and with increasing frequency parameter, i. e. from 𝛽,= 0 to resonance 𝛽,= 1, higher dimensionless dynamic deflections are observed. However, a reversed behavior is displayed if the excitation frequency parameter surpasses the resonance. For 𝛽,≠,0 (moving harmonic load), and a predetermined excitation frequency, the number of oscillations is inversely proportionate to the velocity parameter. Accordingly, a twofold increase in the velocity parameter halves the number of oscillations as observed in the deflection time response.

Traffic Loading, environmental condition and pavement layers weakness properties affect pavement failure and deterioration. Fatigue cracking is one of the most significant and common type of pavement distresses which can effects on the pavement performance and durability. On the other hand, moisture susceptibility would intensify structural distresses and affect pavements serviceability life. Over the past decades, pavement researchers have taken different approaches to enhance rheological properties of bitumen and promote performance of asphalt mixtures. Application of additives such as Crumb Rubber (CR) in asphalt layers of pavements is one of the most economic approaches and would reduce environmental pollution issues. CR modification has been perceived to be a very reliable and effective additive in improving the performance and characteristics of asphalt pavements. The use of CR not only improves performance of asphalt mixtures by increasing fatigue life and rutting resistance of mixes but it reduces moisture susceptibility of mixes and bring about several environmental benefits. Despite the above mentioned advantages, mixing CR with bitumen in wet processing results in problems such as increased production cost, initial aging, and coagulation of rubber modified bitumen, as well as phase separation of the modified binder. In order to overcome the above problems, an innovative technique was developed to produce CRM mixtures in TMU Road Research Centre. This method, named Processed Crumb Rubber (PCR), was consisted of incorporating blending surface activate materials, CR and soft bitumen in order to produce processed rubber type granules. No need to high shear mixer, lower PCR-Bitumen mixing time, reduced coagulation problems in modified bitumen are some advantages of this new product. Since this material is new, extensive experimental research works are required to evaluate rheological properties of the PCR modified bitumen and performance of asphalt mixtures prepared with that. In this research, with producing reacted and activated crumb rubber modified bitumen, the moisture susceptibility and fatigue resistance of asphalt mixtures modified with CR (wet process) and PCR were investigated. In order to obtain performance of samples contain these two additives, Indirect Tensile Strength (ITS) under dry and wet conditions and Indirect Tensile Fatigue Test (ITFT) were applied. In addition, properties of the PCR modified specimens were compared with those of the wet-processed rubber modified bitumen. Moisture susceptibility testing results showed that the CR (modifying bitumen with wet processing) increased indirect tensile strength of samples as well as PCR in both dry and saturated conditions. However, because of surface activated minerals in PCR, specimens prepared using PCR had more ITS value in saturated conditions that result in better performance and lower moisture susceptibility. Finally, Tensile Strength Ratio (TSR) results showed that only asphalt mixtureS contains 20% of PCR and 20%CR reached the minimum TSR value (TSR≥,70). Fatigue life of samples was investigated under two stress level (250 and 400 kPa). Results showed that incorporation these two additives increased fatigue life of control mix. On the other hand, results indicated that as stress level increased, fatigue life of samples decreased but samples modified with PCR had better performance and more fatigue life up to 12 percent.

Extensive numerical and experimental studies of self-centered steel systems have been conducted by researchers in recent years. Despite this extensive research, their use is still not common enough due to differences in the performance of such structures. The need for skilled manpower and equipment to create post tensioning and installation of energy dissipating elements are among the factors that increase the cost of selfcentered structures compared to the implementation of structures with conventional welding connections. Due to the relatively high cost of retrofitting using post tensioned connections, the optimal use of such systems can be considered as a way to increase their use in seismic improvement. For this purpose, the seismic improvement of the steel moment frame by creating a self-centered system has been evaluated locally and only in some floors in this paper. In the evaluations performed in this research, the PF and PEF coefficients have been introduced and used. After performing two hundred and eighty five time history analyzes on nineteen three and six-story frames using Perform-3d software, it was observed that if the appropriate pattern of location of post tensioned connections is selected in the floors, a higher performance can be obtained compared to the frame performance with the post tensioned connections in all floors. However, the use of post tension connections in all floors has resulted in a performance improvement of only 0. 1% more than the t-4 frame. Among the eight three story frames evaluated in this study, the t-4 frame has been selected as the most appropriate improvement plan. The mentioned frame has resulted in a performance improvement of 23. 2% compared to the frame with welded connections in all floors. The t-4 frame has post tensioned connections in only two-thirds of the floors, indicating that for other frames in various seismic improvement projects, the evaluation of different modes can have appropriate economic consequences. Among the three story frames, the t-1 frame has improved the performance of the structure by 15. 3% by using post tension connection in only one floor. If this performance enhancement is sufficient for the frame, the t-1 frame can be a good choice. Also, in a retrofitting project, if the financial resources are not injected together, the initial upgrade of the frame can be done in the first step by converting the frame with welded connections to the t-1 frame. Then, after financing, it converted the t-1 frame to a 3st-PTED or t-4 frame and provided the highest performance. Among the eleven six story frames, the s-9 frame provides the highest performance and highest efficiency. The mentioned frame, using post tensioned connections in the first four floors, has caused a performance improvement of 30. 1% compared to the frame with common welded connections in all floors, which is even higher than the performance improvement of the 6st-PTED frame. In other words, the 6st-PTED frame, using post tensioned connections on all floors, results in a performance improvement of 23. 9%, which is less than the value for the s-9 frame.

Rotational friction dampers are a specific type of friction dampers which have several advantages. Dampers are used to improve the cyclic behavior of structures against forces caused by wind and earthquake. These types of dampers will cause energy dissipation by its rotating and rerotating. However, complete and comprehensive researches have not been performed on the effect of rotational friction dampers and their effect on the bearing capacity of steel frames. In this research, the behavior of concrete-filled steel tube (CFT) in two cases frame braced with rotational friction dampers and frame braced without rotational friction dampers is investigated. For verification, the results obtained from finite element method software, ABAQUS, were compared with that of experimental studies for test samples used in a building with a height of 300m in Osaka, Japan. The hysteresis curves of the modeled samples are in good agreement with the experimental results. In order to investigate the performance of steel composite frame (with CFTs) braced with rotational friction dampers towards to steel composite frame (with CFTs) braced without rotational friction dampers under the effect of three earthquake Far-field records, the structure was modeled, designed and analyzed in ETABS software. The use of bracing with rotational friction dampers has caused a decrease in the displacement of the roof’, s center of mass for each record mentioned above which modeled in ETABS software. It decreased by 13 to 49 % for 9 records and increased by 2 to 17 % for 2 records. The use of bracing along with rotational friction damper modeled in ABAQUS software under the effect of each record has caused a decrease in base shear. The extent of these reductions was different for each record mentioned above. In each record modeled in ETABS software, the base shear of the structure has not reduced similarly,however, in some cases, the base shear has increased. It had a decrease of 11 to 37% for 7 records and an increase of 3 to 26% for 4 records. Then a Single-storey frame with single-span With the same materials and specifications introduced in ETABS software in ABAQUS software Has been modeled. For lateral loading of columns, the lateral loading protocol based on ATC-24 and the instructions for using dampers in the design and reinforcement of buildings have been used. According to Regulation No. 766 of the Program and Budget Organization, the loading cycles introduced in ETABS software with a frequency of 1. 15T have been used in the ABAQUS Limited Components Software to move. The use of rotary braces and crankshafts in the ABAQUS limited component software under the influence of each of the discussed records has reduced the displacement of the structure relative to the structure without braces and without rotational friction dampers of the structure mentioned above was exerted under the record effect of the same earthquake in ABAQUS software The use of bracing along with rotational friction damper modeled in ABAQUS software under the effect of each record has caused a decrease in base shear. The amount of energy reduction for records understudy was not equal and varied from 8% to 34. 7%. The hysteresis curves of base shear of braced structures with and without dampers are well presented.

Water distribution networks are of the most important urban infrastructure for water supply. Given that water loss is currently a global concern, and water demand s increasing,this has made it necessary to manage demand and improve consumption patterns. One of the most important ways to manage consumption is to reduce unaccounted-for water. Leakage is one of the components of unaccounted-for water in the water supply networks. Also, due to population growth and water crisis in a large part of the world, the issue of leakage in urban water supply networks has become very important. Leakage in water distribution networks wastes energy and water resources, increasing damage to infrastructure, and contaminating drinking water. Water leakage in the water distribution systems (WDSs) varies between 5 to 55% of the total water. Therefore, leakage has an important effect on system performance. The importance of leakage can be found in issues such as water scarcity, optimal use of available resources and high costs of water treatment and distribution. In other words, in the discussion of water transmission and use, we are observing obvious and hidden waste, which is important in dry and semi-arid countries like Iran, so this need to minimize the amount of waste so that resources can be used optimally. In recent years, various solutions have been considered to reduce leakage by researchers and managers of the water industry,this includes hardware methods (acoustic procedures, flow measurements, etc. ) and software methods (neural network, genetic algorithm, EPANET, WATERGEMS, etc. ). In this paper, a software method is developed to facilitate leakage detection and eliminate uncertainty of hardware methods such as human and device errors. In other words, to reduce the cost and time of hardware methods, a simulation-modeling method is developed here based on harmonic search algorithm. For this purpose, EPANET hydraulic model and MATLAB environment have been used. Different scenarios for locating leaks and finding leakage sizes were investigated in two water supply networks. Scenarios include one leak and three simultaneous leaks in different parts of the networks. Also, the variability of nodal demands during the day and night was considered as an uncertainty parameter, and thus the coefficients of the consumption pattern during 24 hours were allocated to the nodes of both networks in EPANET software. After that, the main body of the Harmony Search Algorithm was written in MATLAB environment, and in accordance with each of the location and leakage scenarios, the Harmony Search Algorithm was developed. Algorithm parameters were also adjusted according to the type of scenario, the size of the studied network (number of nodes) and the number of variables to produce acceptable responses. The algorithm in MATLAB environment was linked to EPANET software. The developed model examined 14 different scenarios. The results show that the developed model has been successful in locating one leak, finding the size of the leak, and locating three leaks, respectively. In general, the model has had an acceptable performance in locating and finding the size of leakage during the day and night.

In this study, a statistical analysis of the prediction of compressive strength of self-compacting steel fiber reinforced concrete (SFRSCC) based on pull-off test results using linear and nonlinear regression models is presented. For this purpose, an extensive test program was performed including different amounts of cement and aggregate size along with steel fibers in the amounts of 0, 30, 50 and 80 kg / m3. Aluminum and steel discs with diameters of 50 mm and 70 mm with different thicknesses were used. In addition, the effect of partial core depth on pull-off resistance was investigated. The effects of SFRSCC properties and test parameters are included in the proposed equations as dimensionless variables. The results showed that both linear and nonlinear regression models have high potential as a reliable tool for predicting SFRSCC compressive strength based on pull-off experiments. In the multiple linear regression model for predicting SFRSCC compressive strength for aluminum disc, the most effective parameter is F / C factor and da / D factor has the least effect and for steel disc, the most effective parameter is F / C and the lowest effect is related. To the da / D factor. However, the most accurate results are obtained from nonlinear equations compared to linear models.

Granular materials in their natural state have an inter particle boning that is resulted from natural cementation. These bonds form a relatively strong structure in the soil mass that is called soil structure and consequently these types of material are called structured soils. Structured soils could also be produced artificially by cement or lime treatments. Volumetric compression and the stress-strain behavior of the structured materials after virgin yielding are highly nonlinear that cannot be expressed by a single line in semilogarithmic scale. The natural or artificial structure of the soil retains the void ratio of the soil in higher levels than the void ratio of the same soil in remolded state at the same stress levels. Increasing the stress level from the threshold stress of the virgin yielding initiates the crashing of the soil structure that results large amounts of volumetric strains with a small value of volumetric stiffness. Further crashing the structure of the soil and decreasing its void ratio increases the volumetric stiffness of the soil. Although this procedure is highly nonlinear, however it is a continuous phenomenon and can be formulated mathematically. Since the structure losing behavior of structured soils occurs between two known states, therefore, it could be explained based on the disturbed state concept (DSC). According to the DSC, the behavior of complex phenomena between two reference states could be described based on their behaviors in two reference states using an appropriate state function. The state function or interpolating function relates the response of the material at any level to its responses at two reference states. In this paper a constitutive model base on hierarchical single surface model (HISS) and the disturbed state concept was proposed to describe the stressstrain and the failure behavior of structured soils. The behavior of the soil at the beginning of the virgin yielding was considered as initial, relatively intact (RI), state and its behavior after fully crashed state was considered as fully adjusted (FA) state. The disturbance function derived based on the isotropic compression behavior of the material in the laboratory. A power form state function was proposed to describe the variation of the bulk modulus of the soil. The variable compression model was implemented in HISS model to capture the volumetric behavior of the structured soil. The proposed model verified based on the data from literature. The verification of the proposed constitutive model showed the ability of the model to predict the stress-strain and failure behavior of structured soils. The proposed model could be employed with any other constitutive models to introduce the effect of the structure destruction on the stress-strain and failure behavior of the soil. In the proposed model, if the initial and end modulus of elasticity are equal, the strain stress relationship is linear, and if the initial and final values of the modulus of elasticity are different, then the nonlinear stress-strain behavior is simulated. Hence the behavior of a wide range of materials can be predicted by this model. The proposed model could be utilized to predict the behavior natural structured soils, artificially cemented soils.