جستجوی مقالات مرتبط با کلیدواژه "analytical method" در نشریات گروه "عمران"

Human civilizations have always depended on freshwater to form, develop and fulfillment of various needs. With increasing urbanization, not only has the need for freshwater not diminished, but also some new technologies and industries have increased water consumption, and the pollution of water sources has increased significantly. Since groundwater resources are far from surface pollution and have their natural remediation ability, protection and remediation have not been given sufficient and appropriate attention. This issue and the overexploitation of aquifers have resulted in the quantitative and qualitative balance of groundwater resources being unsustainable. These issues show that further research is needed on various aspects of groundwater remediation. By developing the equations for water movement in porous media and analyzing them, it is possible to simulate groundwater flow. In this study, the double-well pumping system has been investigated analytically as one of the effective methods for aquifer remediation. In this system, pumping wells provide a return to natural conditions by draining polluted water and preventing it from spreading in the aquifer. For this purpose, the equations of the groundwater potential function and the stream function were determined for two pumping wells near a permanent stream. In other words, the real part of the complex potential equation represents the potential function and its imaginary part specifies the stream function; using the image well theory, the effect of the stream was also applied in the problem relations. By determining the coordinates of the stagnation points, the capture zone of the multi-well system was delineated in various configurations and the amount of stream withdrawal was also calculated. The capture zone describes the behavior and capability of the multi-well system by indicating the capture domain of discharge wells for different distances and different pumping rates. Three configurations of the remediation system are presented for two types of critical pumping rates. Under these conditions, it is possible to control the capture zone without intercepting the stream boundary and creating gaps in the extraction region at different distances of the wells with certain pumping rates. At the first critical pumping rate, the capture zone of the double-well system is tangent to the permanent stream boundary, and at a pumping rate below this threshold, groundwater pollution does not reach the surface waters. At the second critical pumping rate, capture zones of two wells merge together. Indeed, in discharges less than this critical rate, there is a distance (gap) between capture zones of the wells and pollution can enter the surface water through this gap. Also, the distance between two wells was determined in the state that both types of critical pumping rate are equal. This case shows a state of capture zone whose boundary is tangent to the stream boundary, and the capture zones of two wells are merged together. In the mentioned state, the dimensionless distance between two pumping wells (the distance between the two wells divided by their distance from the stream boundary) and the dimensionless critical pumping rate are equal to 2×0.58 and 0.33, respectively.

Calculating the failure probability of structural problems with linear boundary condition functions is usually done at a low level and by first-order methods due to simple concepts and the need for few calculations. These methods are only suitable for providing an estimate of the probability of structural failure, and especially when the function expressing the performance of the structure is linear, they are accurate in providing the final answer. But when the limit function is nonlinear, due to inherent problems in this method, they are unable to accurately estimate the safety level of the structure. For such problems, it is necessary to use accurate methods of estimating the probability of failure, such as simulation methods. The use of concepts in the first and second order methods of reliability along with the use of an optimization algorithm will reduce the volume of calculations, but this factor causes assumptions and simplifications, derivation of functions and estimating the sensitivity of failure probability is also a part of the structure design process. It can be proven that for many design problems with nonlinear boundary condition function, the answer provided by these methods will not satisfy the probabilistic constraints of the problem, or the answer provided is not the most economical design option. Also, many existing methods in this group are unable to provide answers for problems with low failure probability, especially when the variables of the problem have non-normal density functions. Therefore, the present study has investigated the performance of these methods in dealing with various structural problems, and the strengths and weaknesses of each method are discussed. Three different issues have been studied in this research with seven analytical and simulation method, to achieve this goal. The first problem is to verify the results. In this case, the failure probability of a reinforced concrete beam was calculated by the Monte Carlo Simulation (MCS) and compared with the results obtained from the precise gradient method used in previous studies. The results of this problem showed a 0.5% error in the results, indicating the accuracy of the responses. The existence of very small differences between the results obtained from Monte Carlo and the results of previous researchers in estimating the integral of failure probability related to the discussed problems, indicates the high accuracy of the Monte Carlo method, and it is possible to use the results obtained from Monte Carlo as a suitable criterion in the analysis of these problems. used to compare the results. Also, analysis of two problems including three-span steel beam, two-degree-of-freedom seismic system using seven methods including MCS, SS, IS, LS, WSM, FORM and SORM were also put on the agenda. The results indicate that SS has high accuracy in solving nonlinear and complex problems. WSM has shown a significant decrease in the number of function calls. The LS method has a great performance in calculating the reliability of problems with a low failure probability. Therefore, in general, it can be stated that the first-order method (FORM) is the simplest safety estimation method (with low accuracy for non-linear functions) and simulation methods are the most accurate methods (with conceptual complexity or high calculations).

During the progressive collapse of structures, reinforced concrete (RC) beams must sustain large displacements which are not considered in usual design procedures. Regarding the extensive studies during the recent years, compressive arching and catenary actions are introduced as the main resistance mechanisms against progressive collapse. Despite the extensive studies, there is still a running debate on reliable estimation of the capacities and ultimate resistance of RC members against progressive collapse. Thus, in the present study, a simple and practical analytical method is developed to estimate the ultimate compressive arching capacity of RC beams under large displacements due to progressive collapse. The proposed method is developed based on the membrane action in RC slabs and analytical calculation of lateral stiffness of the structural system. Despite the available methods in the literature, the ultimate arching capacity of RC beams is obtained based on a single-stage procedure. The capability of the introduced method is evaluated utilizing a comprehensive laboratory database, including 99 experimental studies in the technical literature. According to the performed evaluations, the proposed method provides a reliable framework to estimate the arching capacity of reinforced concrete beams in large displacements. Any change in failure mode from flexural action to shear mechanism and increasing the rigidity of the connections leading to an improvement in lateral stiffness could reduce the accuracy of the proposed method.

The purpose of this paper is to investigate analytically the fully grouted rock bolt interaction with grout and rock in pullout test and to determine the load-displacement curve of the bolt head (beginning of the bonded section). Usually, the pullout test output is only the load-displacement curve. This paper discusses how to use this curve to determine the bolt-grout-rock interaction. For modeling bolt-grout interface behavior, coupling (compete for bonding), partial decoupling, decoupling with the residual shear strength, and complete decoupling have been considered. With increasing the applied load, two possible cases including complete pullout and bolt shank yielding are considered. Based on experimental results, a model for the shear stress along a fully grouted bolt is assumed. According to this model, the distribution of axial stress in the bolt and displacement of the bolt head is determined. It is also assumed that the bolt is sufficiently long, which is usually used in underground excavations. Based on the presented analytical method, the bolt head load-displacement curve is determined by assuming input parameters. This curve is compared with a pullout test result.

In order to increase the productivity of extraction of hydrocarbons reservoirs, the well is usually drilled in the direction of the minimum horizontal in situ stress and hydraulic fractures simultaneously initiate and propagate perpendicular/transverse to the wellbore. The last decade, more than 10,000 horizontal wells per year have been bored and hydraulically fractured, with up to a hundred hydraulic fractures placed in the horizontal segment of the well. The well is therefor stimulated in stages, with one stage consisting of a single pumping operation aimed at initiating and propagating simultaneously typically between3-8 cracks spaced about 10–30 m apart. When, the fluid pressure is applied on the surface of the fracture, the crack can propagate in the medium, but the pressure, induced from fluid injection, may have a negative influence on the extension of adjacent cracks which is stated as shadow or interaction stress. Certainly, an accurate estimation of interaction/shadow stress between the cracks leads to a more optimal design. In this research, the effect of the interaction between the hydraulic cracks with respect to the spacing and the number of cracks on the each other and considering position of the fractures are evaluated using the enhanced pseudo traction method. The results are shown that inner-fractures are further affected from shadow stress compared to outer-fractures. On the other hand as distance of hydraulic fractures increases, shadow stresses decrease. In the last, the results can be useful in determining the optimum number and spacing of cracks in the design of hydraulic fractures.

In this paper, a detailed analytic solution of the 1-D heat equation is presented to determine the distribution of temperature within a steel section integrated into a concrete slab, known as composite slim-floor beams (CoSFB). At first, the previous studies about the thermo-mechanical behavior of the slim-floor beams in the scale of experimental campaigns and numerical modeling have been investigated. Then, an analytical method, function of space and time, is suggested to determine the temperature distribution within the SFB section. Therefore, a steel section integrated into a concrete slab which is subjected to a time-dependent heat flux according to the standard fire curve will be examined. The proposed method is an analytical solution of the general form of the heat equation for transient conduction that simplified in order to calculate the load bearing resistance of SFB. This non-homogeneous differential equation is solved by applying the method of variation of parameters, setting up a homogenous problem and applying the separation of variables to get the homogeneous system. Hence, according to the results of FE modeling, the method has been based on assumptions to retain the accuracy of the calculations as well as to reduce the complications in the analytical method. At last, the results of the simplified analytical solution are compared with the numerical simulation, which confirms the logical process. Contrary to numerical methods, the newly proposed method can pragmatically be solved the heat equation with the moving boundary.

The available analytical and finite element methods set the values of elastic modulus of nanocomposites more than the values obtained from the test. In this thesis, a new linear and continuous analysis method is used to determine the best and most similar value of elastic modulus for polymer nanocomposites to laboratory value is provided. For this purpose, the governing elasticity equations in polar coordinates have been solved for nanocomposite representative volume element (RVE) with shear-lag model by assuming perfect bond condition between CNT and matrix. Then, using the finite element modeling with Ansys software, elastic modulus of connectivity states of almost complete and half break between the two phases are calculated and finally the proposed new model that is modeling with spring in the states of almost complete connectivity and half break between the two phases are provided and elastic modulus is calculated. In this method, shear stress is also offering a new relationship between CNT and matrix areas that have been. To ensure the validity of the results of presented model to determine the elastic modulus, the obtained results are compared with laboratory method results of other researchers that in all cases the proposed elastic modulus is much closer to laboratory sample and finite element models and good agreement

Design of support system is One of the most important issues in tunnels design. Therefore, in order to safe design of support system, determination of internal loads has a special importance. In this paper, analytical and numerical methods were used to determine of internal loads, and in 2D and 3D states, the results of these methods were compared with the assumption of no slip and full slip conditions. Findings prove that in different sections of support system, the axial force obtained from full slip condition is more uniform than that of no slip condition, and the bending moment of full slip condition is higher than that of no slip condition. According to results, an increase in stiffness contrast between support system and ground results in an increase in the internal loads. Moreover, by increasing of the tunnel radius, the bending moment decreases and axial force increases.

G‌e‌o‌s‌y‌n‌t‌h‌e‌t‌i‌c m‌a‌t‌e‌r‌i‌a‌l‌s, s‌u‌c‌h a‌s g‌e‌o‌t‌e‌x‌t‌i‌l‌e, g‌e‌o‌g‌r‌i‌d‌e a‌n‌d g‌e‌o‌c‌e‌l‌l (a‌s 3D-i‌n‌c‌l‌u‌s‌i‌o‌n r‌e‌i‌n‌f‌o‌r‌c‌e‌m‌e‌n‌t‌s), h‌a‌v‌e b‌e‌e‌n w‌i‌d‌e‌l‌y u‌s‌e‌d i‌n g‌e‌o‌t‌e‌c‌h‌n‌i‌c‌a‌l e‌n‌g‌i‌n‌e‌e‌r‌i‌n‌g a‌p‌p‌l‌i‌c‌a‌t‌i‌o‌n‌s f‌o‌r, e.g., r‌o‌a‌d c‌o‌n‌s‌t‌r‌u‌c‌t‌i‌o‌n l‌a‌y‌e‌r‌s, s‌t‌a‌b‌l‌e e‌m‌b‌a‌n‌k‌m‌e‌n‌t‌s o‌v‌e‌r s‌o‌f‌t s‌o‌i‌l, l‌o‌n‌g‌e‌r-l‌a‌s‌t‌i‌n‌g r‌o‌a‌d c‌o‌n‌s‌t‌r‌u‌c‌t‌i‌o‌n l‌a‌y‌e‌r‌s a‌n‌d e‌x‌p‌e‌d‌i‌e‌n‌t a‌c‌c‌e‌s‌s o‌v‌e‌r s‌o‌f‌t g‌r‌o‌u‌n‌d. A‌n a‌d‌d‌i‌t‌i‌o‌n‌a‌l, p‌o‌s‌s‌i‌b‌l‌e, u‌s‌e w‌o‌u‌l‌d b‌e t‌o i‌m‌p‌r‌o‌v‌e t‌h‌e b‌e‌a‌r‌i‌n‌g c‌a‌p‌a‌c‌i‌t‌y o‌f f‌o‌o‌t‌i‌n‌g‌s. A‌l‌t‌h‌o‌u‌g‌h a‌n‌a‌l‌y‌t‌i‌c‌a‌l s‌o‌l‌u‌t‌i‌o‌n‌s o‌n t‌h‌e b‌e‌a‌r‌i‌n‌g c‌a‌p‌a‌c‌i‌t‌y o‌f p‌l‌a‌n‌a‌r r‌e‌i‌n‌f‌o‌r‌c‌e‌m‌e‌n‌t‌s h‌a‌v‌e o‌f‌t‌e‌n b‌e‌e‌n s‌t‌u‌d‌i‌e‌d, t‌h‌e‌r‌e i‌s a m‌a‌j‌o‌r l‌a‌c‌k o‌f s‌t‌u‌d‌y i‌n‌t‌o t‌h‌e b‌e‌a‌r‌i‌n‌g c‌a‌p‌a‌c‌i‌t‌y o‌f f‌o‌o‌t‌i‌n‌g‌s w‌h‌e‌n s‌u‌p‌p‌o‌r‌t‌e‌d o‌n g‌e‌o‌c‌e‌l‌l-r‌e‌i‌n‌f‌o‌r‌c‌e‌d s‌o‌i‌l. T‌h‌u‌s, a‌c‌c‌o‌r‌d‌i‌n‌g t‌o t‌h‌e w‌i‌d‌e‌s‌p‌r‌e‌a‌d u‌s‌e o‌f g‌e‌o‌c‌e‌l‌l-r‌e‌i‌n‌f‌o‌r‌c‌e‌d b‌e‌d‌s, p‌r‌o‌v‌i‌d‌i‌n‌g a‌n a‌n‌a‌l‌y‌t‌i‌c‌a‌l a‌p‌p‌r‌o‌a‌c‌h t‌o t‌h‌e d‌e‌s‌i‌g‌n o‌f s‌h‌a‌l‌l‌o‌w f‌o‌u‌n‌d‌a‌t‌i‌o‌n‌s a‌n‌d t‌o e‌x‌p‌l‌a‌i‌n t‌h‌e‌i‌r s‌t‌r‌e‌s‌s s‌e‌t‌t‌l‌e‌m‌e‌n‌t b‌e‌h‌a‌v‌i‌o‌r c‌o‌u‌l‌d b‌e v‌e‌r‌y u‌s‌e‌f‌u‌l. D‌u‌e t‌o t‌h‌e t‌h‌r‌e‌e-d‌i‌m‌e‌n‌s‌i‌o‌n‌a‌l m‌e‌c‌h‌a‌n‌i‌s‌m o‌f a g‌e‌o‌c‌e‌l‌l, t‌h‌e c‌e‌l‌l w‌a‌l‌l‌s o‌f g‌e‌o‌c‌e‌l‌l r‌e‌i‌n‌f‌o‌r‌c‌e‌m‌e‌n‌t k‌e‌e‌p t‌h‌e e‌n‌c‌a‌p‌s‌u‌l‌a‌t‌e‌d s‌o‌i‌l f‌r‌o‌m b‌e‌i‌n‌g d‌i‌s‌p‌l‌a‌c‌e‌d f‌r‌o‌m t‌h‌e a‌p‌p‌l‌i‌e‌d l‌o‌a‌d b‌y c‌o‌n‌f‌i‌n‌i‌n‌g t‌h‌e m‌a‌t‌e‌r‌i‌a‌l t‌h‌r‌o‌u‌g‌h t‌h‌e h‌o‌o‌p a‌c‌t‌i‌o‌n o‌f a c‌e‌l‌l, t‌h‌e‌r‌e‌b‌y i‌n‌c‌r‌e‌a‌s‌i‌n‌g t‌h‌e s‌h‌e‌a‌r s‌t‌r‌e‌n‌g‌t‌h o‌f t‌h‌e c‌o‌m‌p‌o‌s‌i‌t‌e s‌y‌s‌t‌e‌m. T‌h‌i‌s p‌a‌p‌e‌r p‌r‌e‌s‌e‌n‌t‌s a n‌e‌w a‌n‌a‌l‌y‌t‌i‌c‌a‌l m‌e‌t‌h‌o‌d, b‌a‌s‌e‌d o‌n t‌h‌e t‌h‌e‌o‌r‌y o‌f p‌a‌v‌e‌m‌e‌n‌t l‌a‌y‌e‌r‌s a‌n‌d t‌h‌e t‌h‌e‌o‌r‌y o‌f m‌u‌l‌t‌i-l‌a‌y‌e‌r‌e‌d s‌o‌i‌l‌s, f‌o‌r e‌s‌t‌i‌m‌a‌t‌i‌n‌g t‌h‌e p‌r‌e‌s‌s‌u‌r‌e-s‌e‌t‌t‌l‌e‌m‌e‌n‌t r‌e‌s‌p‌o‌n‌s‌e o‌f c‌i‌r‌c‌u‌l‌a‌r f‌o‌o‌t‌i‌n‌g‌s r‌e‌s‌t‌i‌n‌g o‌n a r‌e‌i‌n‌f‌o‌r‌c‌e‌d s‌a‌n‌d b‌e‌d w‌i‌t‌h a s‌i‌n‌g‌l‌e l‌a‌y‌e‌r o‌f g‌e‌o‌c‌e‌l‌l. T‌h‌e e‌l‌a‌s‌t‌i‌c m‌o‌d‌u‌l‌u‌s o‌f t‌h‌e u‌n‌r‌e‌i‌n‌f‌o‌r‌c‌e‌d l‌a‌y‌e‌r‌s a‌n‌d g‌e‌o‌c‌e‌l‌l r‌e‌i‌n‌f‌o‌r‌c‌e‌d s‌o‌i‌l l‌a‌y‌e‌r (g‌e‌o‌c‌e‌l‌l a‌n‌d s‌o‌i‌l i‌n‌s‌i‌d‌e t‌h‌e g‌e‌o‌c‌e‌l‌l p‌o‌c‌k‌e‌t‌s) a‌s a c‌o‌m‌p‌o‌s‌i‌t‌e m‌a‌t‌e‌r‌i‌a‌l, w‌a‌s e‌v‌a‌l‌u‌a‌t‌e‌d b‌y a‌n e‌q‌u‌i‌v‌a‌l‌e‌n‌t c‌o‌m‌p‌o‌s‌i‌t‌e m‌a‌t‌e‌r‌i‌a‌l, w‌h‌i‌c‌h w‌a‌s d‌e‌v‌e‌l‌o‌p‌e‌d f‌r‌o‌m t‌r‌i‌a‌x‌i‌a‌l c‌o‌m‌p‌r‌e‌s‌s‌i‌o‌n t‌e‌s‌t‌s o‌n u‌n‌r‌e‌i‌n‌f‌o‌r‌c‌e‌d a‌n‌d g‌e‌o‌c‌e‌l‌l-r‌e‌i‌n‌f‌o‌r‌c‌e‌d s‌o‌i‌l s‌a‌m‌p‌l‌e‌s. C‌o‌m‌p‌a‌r‌i‌s‌o‌n‌s o‌f t‌h‌e p‌r‌e‌s‌e‌n‌t a‌n‌a‌l‌y‌t‌i‌c‌a‌l r‌e‌s‌u‌l‌t‌s w‌i‌t‌h p‌l‌a‌t‌e l‌o‌a‌d t‌e‌s‌t r‌e‌s‌u‌l‌t‌s s‌h‌o‌w f‌a‌v‌o‌r‌a‌b‌l‌e a‌g‌r‌e‌e‌m‌e‌n‌t, a‌n‌d t‌h‌u‌s, i‌n‌d‌i‌c‌a‌t‌e t‌h‌e a‌c‌c‌u‌r‌a‌c‌y a‌n‌d a‌p‌p‌r‌o‌p‌r‌i‌a‌t‌e p‌e‌r‌f‌o‌r‌m‌a‌n‌c‌e o‌f t‌h‌i‌s m‌e‌t‌h‌o‌d. A‌l‌s‌o, p‌a‌r‌a‌m‌e‌t‌r‌i‌c s‌t‌u‌d‌i‌e‌s a‌r‌e c‌a‌r‌r‌i‌e‌d o‌u‌t t‌o i‌n‌v‌e‌s‌t‌i‌g‌a‌t‌e t‌h‌e i‌n‌f‌l‌u‌e‌n‌c‌e o‌f t‌h‌e d‌i‌m‌e‌n‌s‌i‌o‌n‌l‌e‌s‌s s‌o‌i‌l s‌t‌i‌f‌f‌n‌e‌s‌s m‌o‌d‌u‌l‌u‌s, s‌t‌i‌f‌f‌n‌e‌s‌s g‌e‌o‌t‌e‌x‌t‌i‌l‌e u‌s‌e‌d i‌n c‌o‌n‌s‌t‌r‌u‌c‌t‌i‌n‌g t‌h‌e g‌e‌o‌c‌e‌l‌l, t‌h‌e h‌e‌i‌g‌h‌t o‌f t‌h‌e g‌e‌o‌c‌e‌l‌l l‌a‌y‌e‌r a‌n‌d d‌i‌a‌m‌e‌t‌e‌r p‌l‌a‌t‌e l‌o‌a‌d‌i‌n‌g, o‌n t‌h‌e p‌r‌e‌s‌s‌u‌r‌e s‌e‌t‌t‌l‌e‌m‌e‌n‌t v‌a‌r‌i‌a‌t‌i‌o‌n‌s o‌f t‌h‌e f‌o‌o‌t‌i‌n‌g.

Dams as one of the most important structures are always exposed to various hazards such as earthquake. As dam failure may lead to financial damages and fatalities, it should be designed with most economical and accurate methods. An earthquake causes hydrodynamic pressure waves exerting on the dam. This is one of the important factors in design of dams that are always considered by consulting engineers. Helmholtz equation is the governing relation on the propagation of hydrodynamic pressure waves in dam reservoirs during an earthquake. In order to solve the Helmholtz equation to calculate hydrodynamic pressures on dams, the reservoir’s boundary conditions (BCs) should be taken exactly into account. The BCs include (a) the interface boundary of dam and reservoir (as initial zone of reservoir excitation), (b) bottom boundary (with partial absorption of wave energy by accumulated sediments), (c) upstream boundary (with radiation of another part of the wave energy from the reservoir), and (d) formation of surface waves in the upper boundary of the reservoir. The purpose of present study is to model the mentioned physical phenomena in the frequency domain, using a new semi-analytical method, called Decoupled Equations Method (DEM). In the DEM, only the domain boundaries are discretized by specific high-order non-isoparametric elements. The main features used for modeling of geometry and physics of the problem consists of: (1) high-order Chebyshev polynomials as mapping functions, (2) special shape functions of 2n_η+1 degree polynomials for (n_η+1)-node elements, (3) Clenshaw-Curtis quadrature, and (4) integral forms produced by weighted residual method. By using these features and their properties, coefficient matrices of the system of governing equations become diagonal. This means that the governing partial differential equation for each degree of freedom (DOF) becomes independent from other DOFs of the domain to be analyzed. Therefore, this reduction in space dimensions of the main problem may significantly reduce computational costs in comparison with other available numerical methods. In this study, for the first time in order to provide a solution by low costs to calculate the hydrodynamic pressure distribution on the gravity dams, the relations of reservoir’s BCs are derived in local coordinates by using of the DEM and, the process of applying derived equations is then expressed into the solution of Helmholtz equation. To verify this method, an example of this field is solved by using the DEM, where dam and its rigid foundation are excited by horizontal harmonic vibration. The obtained responses from the solution of this example indicates that the present method for modeling of the potential problems with natural boundary conditions under earthquake excitations, by considering propagation of hydrodynamic waves in the reservoir, show acceptable accuracy and feasibility in comparison with the available analytical solution. The results of the DEM should be developed for more general condition of dam-reservoir interaction, which include flexible concrete gravity dams with inclined dam-reservoir interaction boundary conditions along with partial absorption of wave energy by accumulated sediments. These features are being followed by the authors, and will be disseminated in new papers soon.

In this project, swelling strain and stress caused by tunnel excavation is determined. Two main parts of the performed analysis is mentioned here. First, swelling differential equation is solved by analytical method and the swelling quantities related to tunnel environment is calculated. Then in the second part, the amount of stresses of the tunnel environment caused by tunnel excavation is evaluated. Calculations of this part are processed by a finite element method that use isoperimetric element to model the tunnel. MATLAB code is used to process numerical model of the second part.