Lateral earth pressure on retaining walls is a widely researched classical problem in geotechnical engineering. This study investigates the active lateral earth pressure on a circular retaining wall using the stress characteristics method in the presence of soil-wall adhesion and friction. A computer code was developed for determining the lateral pressure of soil on the wall as well as the lateral pressure coefficients upon receiving the required input parameters. The principle of superposition was implemented to determine the lateral earth pressure coefficients. The effects of the soil-wall adhesion and friction angle on the lateral earth pressure were studied under active conditions. Moreover, the effects of these parameters on the characteristics network and failure region were demonstrated. The results showed that the coefficient of lateral earth pressure due to cohesion increased with increasing adhesion at the soil-wall boundary.

This paper presents a novel approach to solve the double-track railway rescheduling problem, when an incident occurs into one of the block sections of the railway. The approach restricts the effects of an incident to a specific time, based on which the trains are divided into rescheduled and unchanged ones, so that the latter retain their original time-table after the incident. The main contribution of this approach is the simultaneous consideration of three rescheduling policies: cancelling, delaying and re-ordering. A mixed-integer optimization model is developed to find optimal conflict-free time-table compatible with the proposed approach. The objective function minimizes two cost parts: the cost of deviation from the primary time-table and the cost of train cancellation. The model is solved by CPLEX 11 software which automatically generates the optimal solution of a problem. Also, a meta-heuristic solution method based on simulated annealing algorithm is proposed for tackling the large-scale problems. The results of an experimental analysis on two double-track railways of the Iranian network show an appropriate capability of the model and solution method for handling the simultaneous train rescheduling. The results indicate that the proposed solution method can provide good solutions in much shorter time, compared with the time taken to solve the mathematical model by CPLEX software.

Investigating the seismic amplification of incident waves induced by subsurface cavities and characterizing its patterns for the ground surface are important in seismology, geophysics and earthquake engineering both in theory and practical application. Nowadays, it has been established that the seismic ground response above subsurface structures can be different from the free-field motion during earthquakes. In this regard, this research studied preliminary results of a numerical parametric study on the seismic response of the ground surface above subsurface cavity. Basically, this study is applied to get new idea to move a step forward in site response analysis which can be used in the seismic microzonation of areas located above underground spaces. For analysis purposes, a numerical time-domain analysis is performed by utilizing a robust numerical algorithm working based on the boundary element method. It is observed that the amplification of the ground surface underlain by a shallow elliptical cavity is increased in long periods. Some preliminary simple relationships and tables are presented which could be used while introducing simple preliminary ideas for modification of the standard design spectra in building codes and seismic microzonation studies.

In this paper using the eigenvalues and eigenvectors symmetric block diagonal matrices with infinite dimension and numerical method of finite difference a closed form solution for exact solving of Laplace equation is presented. Moreover, the method of this paper has applications in different states of boundary conditions like Newman, Dirichlet and other mixed boundary conditions. Moreover, with the method of this paper, a mathematical model for the exact solution of the Poisson equation is derived. Since these equations have many applications in engineering problems, in each part examples like water seepage problem through the soil and torsion of prismatic bars are presented. Finally the method is provided for torsion problem of prismatic bars with non-circular and non-rectangular cross sections by using of conformal mapping.

In this article, general procedures for vulnerability assessment and retrofitting of a generic seismically designed bridge are outlined and the bridge’s damage criteria for blast resistance are explained. The generic concrete bridge is modeled and analyzed with the finite element technique implemented in ANSYS LS-DYNA environment and explosion threats are categorized into three main levels. Uncoupled dynamic technique is adopted to apply the blast loads on the bridge structure, damage and performance levels are resulted based on quantitatively verified damage mechanisms for the bridge members. The results show that, amongst different loading scenarios, the explosions that happen under deck are more critical comparing to blasts initiating from over deck sources. Furthermore, two retrofitting methods 1) concrete filled steel tube (CFST) and 2) concrete jacket are applied on the bridge columns. The program AUTODYN is used with coupled dynamic analysis of a column to compare the effectiveness of each method. Afterward, more efficient method for a column is applied to the whole bridge and its efficiency is revaluated. It is shown that CFST can decrease concrete spall, scabbing, rotation, displacements and shear forces more than the concrete jacket. Considering the proposed damage and performance levels, the bridge retrofitted with CFST reacts with lower damage level and higher performance level to blast loads.

In this study, the relative performance of two soils as a sustainable natural material in retaining the selected heavy metal ions, cadmium (Cd²⁺) and nickel (Ni²⁺), from aqueous solutions has been evaluated. Red earth soil (RS) and black cotton soil (BCS) originating from India, were selected and batch equilibrium tests including sorption kinetics and leaching studies were conducted. The experimental data was used to plot sorption isotherms, Langmuir isotherm was found to be more suitable than Freundlich isotherm for both the soils. Monolayer sorption capacity was calculated from Langmuir isotherm. Kinetic data was fitted on four models namely pseudo first order, second order, Elovich and intraparticle diffusion. Correlation coefficients obtained by all models fitted well in the following ranking: Elovich>Intraparticle diffusion > Pseudo second order> Pseudo first order. Based on extensive experimental data, it is concluded that the ranking on sorption was of the order Cd > Ni for both the soils and BCS exhibited relatively higher retention levels compared to RS.  It is further concluded that, BCS can be used as a substitute to filter material, RS a substitute to main liner material in attenuating Cd²⁺ and Ni²⁺ from an industrial landfill leachate.

Complex nature of diagonal tension accompanied by formation of new cracks as well as closing and propagating preexisting cracks has deterred researchers to achieve an analytical and mathematical procedure for accurate predicting shear behavior of reinforced concrete, and there is the lack of a unique theory accepted universally. Shear behavior of reinforced concrete is studied in this paper based on recently developed constitutive laws for normal strength concrete and mild steel bars using nonlinear finite element method. The salient feature of these stress-strain relations is to account the interactive effects of concrete and embedded bars on each other in a smeared rotating crack approach. Implementing the considered constitutive laws into an efficient secant-stiffness based finite element algorithm, a procedure for nonlinear analysis of reinforced concrete is achieved. The resulted procedure is capable of predicting load-deformation behavior, cracking pattern, and failure mode of reinforced concrete. Corroboration with data from shear-critical beam test specimens with a wide range of properties showed the model to predict responses with a good accuracy. The results were also compared with those from the well-known theory of modified compression field and its extension called disturbed stress field model which revealed the present study to provide more accurate predictions. 

Steel bridges play a very important role in every country’s transportation system. To ensure that bridges perform reliably, engineers monitor their performance which is referred to as Structural Health Monitoring (SHM). An important element of SHM includes the prediction of service life. There is ample historical evidence that bridge damage is pervasive and their life time is decreasing. To manage costs and safety, service life prediction of bridges is necessary. We present a statistical method to predict service life for steel bridges. A nonparametric statistical model based on the bootstrap method for stress analysis for fatigue life prediction of steel girder bridges is proposed. The bootstrap provides a simple approach for reproduction of the probability distribution of measured strain data. The bootstrap is sensitive to the number of events in the verification sample (data), thus we introduce a stable survival distribution function (SDF). An index is presented in this paper for inferring the service life of steel bridges, which can be known as the Life Index (µ). The life index function shows variation of the age of steel bridges under daily traffic loads. A regression model is developed which relates the service life of steel bridges using a bridge life index based on measured operational strain time histories. The predicted remaining service life derived from the model can contribute to effective management of steel bridges. The proposed method assists bridge engineers, bridge owners, and state officials in objective assessment of deteriorated bridges for retrofit or replacement of deteriorated bridges. Timely repair and retrofit increase the safety levels in bridges and decrease costs.

A least squares based meshfree method is used in the numerical simulation of a turbulent flow. The proposed approach is integral free, vectorized and enjoying sparse positive definite matrices. Here the standard k-ε model is employed to model the turbulent flow. A matrix formulation is illustrated that simply can be extended for other turbulence models. Two bench mark problems are solved and results are compared with the literature.

Engineering design usually requires considering multiple variances in a design and integrating them appropriately in order to achieve the most desirable alternative. This consideration takes particular importance in the constructional projects of civil engineering. However, frequently, the structural designer’s considerations in civil engineering teams contrast the stylish and creative novelties of architectures. Then, we should take up new methodologies to yield appropriate alternatives which meet artistic aspects of design and simultaneously satisfy the structural designer’s demands. Consequently, the process of design should incorporate the multi-fold aspects of engineer’s requirements and their personal preference. So, in this study, we preset a systematic approach, so-called desirability based design, to perform a directed multi-objective optimal design considering various aspects of a design, based on soft-computing methods. Fuzzy logic integrated with genetic algorithm is employed to build a decision-making fuzzy system based on expert knowledge. It will be employed to conduct the designing process. Illustrative examples show practicality and efficiency of the presented methodology in structural design of several space structures.

Tuned mass dampers are common solutions for passive control of bridge responses against dynamic loads. The present work concerns non-uniform support excitation of earthquakes as the dynamic loading source and studies TMD performance in controlling consequent vertical response of simply supported steel bridges. Charged system search as a recent meta-heuristic is successfully utilized to optimize TMD parameters whereas the dynamic response is evaluated via rigorous step-by-step time-history finite element analysis. As another issue, superiority of multiple TMD’s over single TMD is investigated for the present problem after unifying their parameters via optimization. Treating a bridge model as the case study under a number of real-world recorded earthquakes, the error of uniform support excitation under such a non-uniform case is evaluated. Superior efficiency of the utilized charged system search over popular genetic algorithm is observed for this problem. The results also revealed that how advantageous is the application of optimally designed multiple TMD in controlling dynamic vibration modes of such a distributed mass structure

From practical point of view, optimum design of structures under time variable loadings faces many challenges. Issues such as time-dependent behavior of constraints and the computational costs of the gradients could be mentioned. In order to prevent such difficulties, in this paper, response spectrum method has been utilized instead of applying direct time history method. Additionally, seismic design of structures is defined as a design for a specific response spectra not for an individual acceleration time history. Furthermore, here, in order to guarantee the global optimal designs, the obtained results from gradient-based method are compared with those from the discrete optimization technique (Genetic algorithm). As well, the P-Delta effects are considered in a seismic analysis. In addition, many practical constraints according to the Iranian national building code (NBC) are included in the optimization problem. The developed MATLAB based computer program is utilized to solve the numerical examples of low, intermediate and relatively high-rise braced and un-braced steel frames.

Microtremor measurement is a precise and applicable technique for evaluating structural dynamic characteristics and vulnerability index of historical buildings. In this research a historical citadel in Iran has been considered. Karim Khan Citadel (Arg-e Karim Khan) is a huge masonry structure which has been built in the 17th century in Shiraz, Iran. The plan of this building has a rectangular shape and has a circular tower in each corner. The height of each three story circular tower is 14 m and the height of walls between each two towers is 12 m. One of these towers has been swerved and for preventing its collapse, concrete was injected to the foundation of this tower. To study seismic behavior and vulnerability of the swerved tower and compare it with other straight tower, microtremor measurements were performed. Measurements were done on the center of each tower and its basement simultaneously. For determining natural frequency and damping ratio of each tower, Floor Spectral Ratio (FSR) and Random Decrement Method (RDM) were used, respectively. Results show that the natural frequency and damping ratio of the swerved tower are 1.9 Hz and 1.55 % while dynamic parameters of the straight tower are 2.12 Hz and 3.86 %, respectively. Also the towers frequencies are very different to the site frequency (4.18 Hz), therefore the resonance phenomenon isn’t probable. In addition, the vulnerability indexes of the swerved and straight towers were calculated 131.31 and 76.9, respectively, which shows that the swerved tower is more vulnerable.

Sliding foundations is a technique to suppress seismic loads applied to structures. There are many studies showing that sliding foundations are efficient specially for low rise buildings, however most of them have ignored the effects of vertical components of the earthquake records on the behavior of such bases. This paper focuses on influences of sliding foundations on seismic behavior of low rise buildings, for real cases. For this purpose, vertical component of earthquakes are considered as well as inherent properties of foundation material such as coefficient of Restitution (COR). Furthermore, variation of friction coefficient during the earthquake is considered. COR is utilized to consider bouncing of the structure after separation of the foundation, occurred for extreme downward vertical accelerations (greater than gravitational acceleration). Variation of friction coefficient is considered based on a new study, showing that the coefficient of friction depends on instantaneous amplitude and frequency of the vertical excitation. The obtained results show that vertical component of earthquake affects the behavior of the sliding base substantially. It is also demonstrated that providing material for the sliding base with higher COR is advantageous in decreasing structural acceleration response. Furthermore, the coefficient of friction is really lower than the regularly assumed values and therefore, leads to smaller structural acceleration response but mostly greater residual displacements.

Dividing open channels are varied types of open channel structures used to provide water for irrigation channels, agriculture and wastewater networks. In the present study the mean velocity is calculated in different dividing angles within the branches channel through the use of artificial Neural Network (ANN) and coputational fluid dynamices (CFD) models. First the ANSYS-CFX model is used to simulate the flow pattern within the branch with a 90° angle. The results of the CFX model correspond fairly well to the results of the experimental model with Mean Absolute Percentage Error (MAPE) of 5%. After verifying, two CFX model are generated in 30° and 60° angle in different width ratios of 0.6, 0.8, 1, 1.2, and 1.4, and the mean velocities are obtained by flowmeter. Following that ANN model trained and tested through the use of a set of experimental and CFX datas. The comparison showed that the ANN model has an acceptable level of accuracy in predicting the dividing open channel mean flow velocity with mean value R2 of 0.93. Comparing the results indicated that ANN model with the MAPE of 1.8% performs better in 0.8 m width ratio. Also, in this width ratio the MAPE are equal to 1.58, 1.87, and 2.04 % in 30°, 60°, and 90° deviation angles respectively and therefore the model performs better in 30° angle.

The motorcycle is considered as one of the most applicable transportation modes for different types of trips in Iran. According to the report by Iran Police Department in 2011, almost 25% of all crash fatalities are related to the motorcycle riders and their passengers. The objective of this study is to identify the most important factors that contribute to the fault of motorcyclists involved in crashes. This is done by using the Classification And Regression Trees (CART) model to differentiate between at-fault and not-at-fault cases. The results show that the most important factor in determining at-fault probability of motorcyclists is the collision type. According to this fact, the probability of rear-end collision is the highest, while the probability of side collisions is the lowest. The importance of other factors is variable considering the collision type. In the case of rear-end collisions, the passengers characteristics and the age of the rider are the most important factors. However, in the case of side collisions, lighting condition and area type (in both urban and rural roads) are the most important. Finally, it is suggested that, training of riders can reduce rear-end collisions as well as installing systems that warn drivers when they are close enough to motorcycles in side collisions.

This paper investigates the frequency response method for waterhammer phenomenon in piping networks. The unsteady flow governing equations are solved in time domain using the method of characteristics. They are also solved in frequency domain using the transfer matrix method. For the pipe network under consideration, critical transient excitation scenarios are identified. For each scenario, the frequency responses of the system as well as the time history of the transient pressures at the network nodes are calculated. The model is applied against a real pipe network and the results of the transfer matrix method are compared with those of the method of characteristics. It is concluded that the frequency response method not only presents a very fast algorithm for analyzing pipe systems but also, has an acceptable accuracy compared to the method of characteristics. The frequency response method requires linearization in some terms of the governing equations. Instead of that, it needs no computational discretization and interpolation necessary in time-space domains when using the method of characteristics.

Construction industries are the most dangerous worksites with high risk of occupational accident and bodily injuries, which ranges from mild to very severe cases. The aim of this study was to explore the causal factors of accident severity rate (ASR), in 13 of the biggest Iranian construction industries. In this analytical cross-sectional study, the data of registered accidents from 2009 until 2013 were obtained from an official database. Data of HSE risk management systems and HSE training were also gathered from comprehensive accident investigation reports. Data analysis and regression modeling were done using SPSS statistical software (version 22). The mean and SD of ASR of studied construction worksites was 257.52±1098.95. The results show that the system associated with HSE and HSE risk management established only 41.8 and 18.4%, respectively. The results of multiple linear regression indicated that some individual and organizational factors (IOFs), HSE training factors (HTFs), and Risk Management System factors (RMSFs) were significantly associated with ASR (p<0.05). The study revealed the causal factors of ASR. Hence, these findings can be applied in the design and implementation of a comprehensive HSE risk management system to reduce ASR.

Traffic simulation is a powerful tool for analyzing and solving several transportation issues and traffic problems. However, all traffic micro-simulation models require a suitable car-following model to show the real situation in the best way possible. Several car-following models have been proposed. An obvious disadvantage of the former models is the great number of parameters which are difficult to calibrate. Moreover, any change in these parameters creates considerable disturbances. In this paper, a car-following model was proposed using the Epsilon -Support Vector Regression method whose output is the acceleration of the following car. Radial Basis Function was used as the kernel of the ε-SVR method, and the model parameters were tuned using the Grid Search method. The best values for the parameters were obtained. Furthermore, linear scaling in the interval [-1, 1] was used for both the training and testing input data, and the method was proven to more accurate than the case where no scaling was used. Accordingly, a car-following model with the mean squared error equal to 0.005 and the squared correlation coefficient equal to 0.98 was proposed using the function estimation method through the ε-SVR method. Finally, the ε-SVR output was compared with the results of the well-known car-following models, including Helly linear model, the GHR model, and the Gipps model. It was shown that, when using the scaling and parameters tuning techniques, the proposed method was more accurate compared to all three of those models. Moreover, a function fitting Artificial Neural Network was ran for this purpose and the outputs showed that the result of the ε-SVR method is better than that of the function fitting method by the proposed ANN. Implementing a microscopic validation of the proposed model showed that it can be used in the drivers’ assistance devices and other purposes of Intelligent Transportation Systems.

During the entire life cycle of a pavement, highway agencies are expected to maintain adequate surface frictional properties to facilitate traction between car tires and pavement surface. Traditionally the repair method for a friction-deficient pavement surface is the application of a new surfacing layer. The monitoring and remedying practice is important however, it is a passive approach toward the problem. A more proactive approach would be to test the hot mix asphalt in the laboratory during its initial mix design stage to ensure that aggregate combinations used in the asphalt pavement will provide adequate friction over the life of the pavement. Toward this objective the polishing behavior of laboratory-prepared HMA specimens made of eight different job mix formulas has been studied in terms of friction values. In addition, a robust statistical analysis of the obtained surface friction values has also been carried out in an attempt to verify the success in developing this new asphalt polisher that is used to simulate the tire-pavement interaction. Furthermore, polishing behavior (i.e., polishing trend, rate of friction loss and absolute and percent values of decrease) were all fully investigated to capture surface frictional deterioration of HMA specimens. In conclusion, the new asphalt polisher showed a good degree of repeatability. Additionally, it has been concluded that the decrease in polish number is maximum during the first hour of polishing. With the passage of time the drop in friction decreases and stabilizes.