نشریه مهندسی عمران مدرس
سال شانزدهم شماره 4 (زمستان 1395)

Precast segmental construction methods can decrease bridge construction costs by reducing construction time while maintaining quality control. In addition, the absence of scaffold can minimize traffic congestion and environmental impact. Because of these great advantages of using the precast segmental bridges, their usage is increasing in the world, but it is limited in high seismicity areas due to lack of sufficient knowledge about the dynamic response under seismic loads. According to the precast construction of these types of bridges and their post-tensioning contact on segment joints, it is expected that under earthquake excitation specialy vertical earthquake, superstructure behavior is affected by joints operation in the presence of long-term loads. This issue is very probable in non-continuous post-tensioned bridges. This study is trying to investigate the effects of vertical earthquake on the superstructure of the bridges in near-fault regions by studying a sample model and obtaining structure response including joints response and their openings, force-displacement response of the system, stress and strain in concrete and cables and the level of nonlinearity of them.
Recent research has shown that segment joints can undergo very large rotations that open up gaps in the superstructure and The primary seismic concerns regarding segmental construction are focused on the behavior of joints between segments as no mild reinforcement crosses such as joints. The lack of reinforcement across segment joints allows to an increased rate of construction, yet creates inherent regions of weakness that act as crack initiators and can result in large localized rotations. According to phase I experiment results by Megally et al. [1-3] which are concentrated in regions of high moment and low shear (i.e. near midspan), models were created using the computer software OpenSees V2.4.4 and using detailed 2D nonlinear time history analysis under a suite of ten near-field earthquake records to quantify effect of vertical motion on the joint response. The prototype bridge structure used for this study is single-cell box girder bridge that consist of a 50m span, sixteen 3m segments long with unbonded tendons constructed with the span by span construction method. The segments of the superstructure are modelled using linear elastic frame type members except for a region at the ends of each segment which is discretized into several axial non-linear zerolength springs. The springs are connected to the ends of the superstructure beam elements through rigid body links. Results indicate that the vertical components of earthquake can affect the response of these bridges and segment-to-segment joints opening are very probable particularly at the mid-span joints and superstructure can collapse under upward acceleration demand because of concentrate greater part of concrete on top flange and lack of tension material on top of joints or sliding on elastomer caused by decrease of effective weight. the joint compressive strain remained way below the concrete spalling limit state minimizing the damage and stiffness reduction of the superstructure; the cables remained in the elastic range and closed all joints after earthquake even high seismic intensity levels and the residual vertical displacements were negligible.

Despite several studies and researches already carried out on secondary consolidation in fine-grain soils, there is no consensus among researchers about the changes of the coefficient of secondary consolidation versus stress. The present research specifically aims to discuss the trend of these changes in soils having double porosity and undergoing stress. The behavior of kaolin has been investigated un this work. Samples with a double porosity structure have been compacted. In order to make sure of the preparation procedure as well as the existence of double porosity in them, prosimetry experiments were also carried out by mercury intrusion method which finally confirmed the existence of double porosity structure in the samples. The samples were put in a consolidation apparatus. Saturation was done in two ways; the first group samples were saturated and then loaded. In the second group, the samples were loaded and then saturated under a constant load. The results indicate that the order of saturation process has no effect on the porosity of the samples after they have been saturated (Collapse). Over the long time of measuring the secondary changes in soil volume, the samples were put under a constant load, and value of increase in settlement versus time after the completion of initial consolidation was measured. The experimental data shows that in the stress range of 100 to around 300 kPa, the coefficient of secondary consolidation has had an increasing trend reaching its maximum and has descended after passing the 300 kPa. This result is in compliance with the past researchers’ results trend. So, given that the soil used by the past researchers has been of simple-porosity type, it can be inferred from the results of the present research that double porosity structure has no effect on trend of changes in secondary consolidation coefficient. The main purpose of this research is to present experimental data on the changes of coefficient of secondary consolidation under stress in an aggregated soil,. One-dimensional consolidation tests were performed and analyzed. The effect of net stress and initial porosity on changes in secondary consolidation coefficient was also studied. The paper is divided into four major parts; after the first part of the paper, introduction, the second part presents details of the experimental plan including characteristics of the soil under study, sample preparing technique, and experiment procedure (method of applying loads). Results and their interpretation are discussed in the third part, and finally, the main findings of the research are summarized in the fourth section. The tests indicated that path of collapse of structure and transposition of loading and saturation processes have no effect on porosity of sample after collapse at a certain stress value, and end of the primary consolidation line is a unique line.

One of the challenging tasks for civil engineers is to mitigate the response of structures that are subjected to dynamic loads in order to prevent possible damages that may cause human and enormous economic losses.To minimize vibration, reduction of the external disturbance to a system is always preferred, but in many cases, this may not be possible. Modification of the system to avoid resonance may entail significant redesign. Furthermore, it would be difficult to be applied to existing structures. Thus, vibration control devices, which can be simply attached to the existing system to reduce the vibration without drastically altering the original system, have been developed. Passive tuned mass damper (TMD), whose concept was presented more than a century ago, is undoubtedly a simple, inexpensive and reliable means to suppress unfavorable vibrations of structures but the very narrow band of suppression frequency, the ineffective reduction of non-stationary vibration, and the sensitivity problem due to detuning are the inherent limitations of the passive TMDs. TMDs are usually tuned to the first natural frequency of the structures. Since TMD parameters are constant during the life cycle of the structure, it is important to adjust them properly to achieve a favorable performance. Optimal values of TMD parameters for structures with non-linear behavior require non-linear dynamic analyses. There are many analytical and empirical relations to identify these parameters obtained by structure simplification and loading. In this paper, genetic algorithm (GA) is employed to find optimum TMD parameters for vibration control of the College Bridge in Tehran. With the length of 372 m, this steel bridge has 14 spans. The bridge is modeled in OpenSees environment. Verification of the finite element modelling is performed by comparing the results of the dynamic analyses under four earthquake records by those of another model created in SAP2000 software. In order to mitigate its vibrations, 11 TMDs are considered to be installed on the bridge. The aim of GA is to minimize the displacement of the tallest pier of the bridge in order to decrease the maximum displacement of the structure subject to earthquake excitations. Based on the analyses conducted for near-field and far-field earthquakes, it was concluded that employing GA considerably reduces convergence rate to achieve optimum TMD parameters. To evaluate the performance of a control system during severe earthquakes, incremental dynamic analyses (IDA) for maximum peak ground accelaration (PGA) of 0.1g to 1.0g was conducted. The longitudinal root mean square and maximum displacement of the tallest pier in uncontrolled and controlled cases are obtained and compared. The results of IDA analyses show that for low PGA values, TMDs by themselves absorb and dissipate a large portion of the input energy because in this case the piers remain elastic. However, for higher values of PGA, piers also dissipate some portion of input energy by entering nonlinear region. The percentage of response reduction for different earthquakes are not the same because each earthquake has its own frequency content. According to the numerical analyses for the mass ratio as 4%, the longitudinal displacement and reduced RMS displacement of the largest pier of bridge by tuned mass damper for El-Centro, Kern-County, Kobe and Northridge earthquakes are 24.9 and 34.3, 43.5 and 38.7, 30.6 and 40.4, 13.6 and 28.1 respectively.

In open channels, the distribution of velocity, shear stress and other related quantities such as the diffusion and dispersion coefficients and thus all transport processes are three-dimensional, according to the three-dimensional convection and diffusion principles. Determining the velocity distribution- as a key parameter for estimating other hydraulic parameters- has always been the subject of attention. Velocity distribution in the inner region of the flow (y0.2D). The log-Wake law is of the most accepted laws for velocity distribution in wide open channels, this law modifies the logarithmic law by adding a Wake function; but in case of narrow open channels, the log-Wake law deviates from the measured data near the free surface. Because the profile by the log-Wake law depicts the velocity which increases with the increase of distance from the bed monotonically and is not able to show the velocity negative gradient near the free surface which happens in narrow open channels. In narrow open channels, the three dimensional structure of the flow and the transport momentum from the side walls to the central zone due to strong secondary currents, causes the maximum velocity to occur below the water surface which is called velocity-dip phenomenon. The velocity dip phenomenon was first reported more than a century ago. Since that time, numerous investigations have been conducted by many researchers in order to propose new models to be able to not only describe the dip phenomenon and negative gradient of velocity near the free surface, but also to predict the position of the maximum velocity accurately and fit the experimental data throughout the whole flow depth.
This paper introduces an analytical model based on Reynolds Averaged Navier Stokes (RANS) equations and an eddy viscosity distribution, to estimate velocity distribution in turbulent fully developed flows. The proposed model is suitable for both narrow and wide open channels, and is capable of predicting the dip phenomenon. The results by the model verified with data measured in several rectangular lab channels and data collected from an actual sewer channel. Since the proposed equation for velocity distribution is dependent of Coles Wake parameter (Π), the effect of this parameter on level of accuracy and description of velocity profile as well as prediction of dip phenomenon and location of maximum velocity has been studied. Many researchers proposed different values for Coles parameter, and it seems there is no universal constant value for this parameter. In this study, the value of Coles parameter was proposed by fitting the data from different channels, based on the least error calculated in predicting the velocity profiles by the proposed model. The results show that the profiles by the model agree well with experimental data and predict the velocity-dip phenomenon; also the model provides little errors compared to measured data in the channels, which is representative of high level of accuracy in defining velocity distribution profile of the flow. The value of Coles parameter estimated for channel-sewer was less than that for lab channels.

With regard to the increase of computing power in the past decade, finite element methods have been used to obtain the graphs of rotational moment curves which reflect non-linear effect in connections response. Using finite element methods the effect of different parameters on connections behavior can be investigated. In this study, several common semi-rigid connections are modeled and their behavioral properties are briefly reviewed and then providing the details related to a new semi-fixed connection, its behavioral properties like its hardness, ultimate capacity and ductility is investigated and is compared to other modeled connections.
In this study, to perform non-linear analyses of connection, finite element software Abaqus is used. One capability of this software is different analyses like non-linear analysis which is very applicable. In this modeling, it has been tried to have inter-component interactions according to reality as much as possible. Bolted connections are modeled exactly and the interaction among the bolt surface and hole is modeled as a hard friction with friction coefficient 0.3 with the ability of separating after loading. Also, fillet welds are modeled as a prism with triangular section. Where a groove weld is applied, since the strength in this type of welding is like base metal, two connection parts are stuck together. To mesh the element, C3D8R element is used.
To modeling the behavior of high strength bolts A10.9, the polyline elasto-plastic stress-strain curve has been used. The force is applied to samples according to the loading protocol presented by ATC-SAC which in fact is a replacement of real earthquakes.
The proposed connection n1 has the most rigidity values among semi-rigid connections. Reducing the number of connection bolts has more reducing impact on connection rigidity value, so that with the half thickness of upper and lower sheets, rigidity rate is reduced only 9%, but with the half number of bolts, rigidity rate is reduced about 64%. Also the connection n3 have lowest rigidity rate and its rigidity amount is in the class of bolted connection in seat angle to web angle.
In connections with high strength, the connection strength is highly related to girder strength and during creating plastic joint, this joint is formed in girder, while in connections with low strength, joint is formed in connection so it can be said that except joint connection state which are not applied in flexural resisting frames, four modes of rigid connection with high strength, semi-rigid connection with high strength, rigid connection with low strength and semi-rigid connection with low strength can be used in flexural resisting structures.
Connection ductility is a key parameter for semi-rigid connections in which deformations are concentrated in connection members.
Results show that the used mechanism in this connection has the ability of covering different classes of strength with the changes such as reducing the number of bolts or reducing the thickness of upper and lower sheets. Also this connection has the ability of absorbing energy and tolerating many deformations compared to other semi-rigid connections with same-class strength.

One of the connections which is designed based on the concept of weakening the beam is Reduced Beam Section (RBS) connection. The 1994 Northridge earthquake caused widespread damage to moment-resisting frames. Various brittle fractures were found in beam-to-column welded moment connections. So far numerous efforts have been made to find a better connection configuration to improve the behavior of the post-Northridge moment connections. The improvements are mainly based on the connection reinforcement or the weakening of the beam section. These methods are intended to force the plastic hinge to form away from the column face and consequently increasing the connection ductility. The reduced beam section (RBS) protects a welded SMRF connection detail by forcing the plastic hinge in a beam to form away from the column face. Traditionally, welded SMRF connection design requires using a strong column-weak beam combination, which means that any instability in the frame would result from plastic hinging in the beams rather than the columns. With maximum moments occurring at the beam-column interface in moment frames under lateral loading, the plastic hinges will form at the column face, placing high strain demand on the weldment. An elastic-plastic fiber model is presented herein to analyze the column tip load vs. RBS contribution to total story drift curve. Isolation of RBS material behavior requires that the rest of the material in the frame is treated as rigid forcing all of the deformation into the RBS. Considering the advantages of RBS moment connections and lack of knowledge of the performance of this connection with respect to Indian profiles led to a study on this topic. The objective of this study was to investigate experimentally the cyclic behaviour of welded moment connections with and without RBS. The idea of weakening the beam near the end of the beam is achieved by trimming some parts of the beam flange near the column face forcing the formation of plastic hinge in this region. The RBS area acts as a fuse. In this study, cyclic performance of the Reduced Beam Section connection is studied in a numerical environment by using ABAQUS software. The investigated connection is a single-sided beam-to-column assembly. The cyclic load is applied at the tip of the beam. Length of the beam is a half of determined span in a designed building. Pinned boundary condition is applied at the top and bottom of the column and out of plane displacement of the beam is restricted. No weld fracture was observed in RBS connection while there was a crack observed near beam bottom flange weld for connection without RBS. A reduction in material and labour cost is possible due to elimination of continuity/doubler plates for RBS moment connection. The loading protocol proposed by AISC is used for cyclic loading. In parametric study of this connection, the effects of changing dimensions of reduced area are investigated. The results reveal that the moment capacity of RBS connection is less than the moment capacity of a corresponding intact section connection but no plastic hinge is formed in intact section connection.

The scope of this study is to investigation of the rehabilitation of concrete beam column joints retrofitted by use of carbon-fibre-reinforced plastics (CFRPs) to achieve a safe, economic and practicable level of seismic damage. This paper investigates analytically the efficiency of the strengthening technique at improving the seismic behaviour of damaged structures. 4 beam-column connections are tested under reversed cyclic load. The connections have none-seismic detailing of rebars, i.e. no transverse rebar and seismic stirrups are used in the joint core and beam and column critical end zones, respectively. The joints are damaged in different levels and then retrofitted by carbon fibre reinforced materials (CFRP sheets). The strengthened joints were tested again to reach the ultimate drift capacity. The experimental results show that the beam column joints could be retrofitted by external bonding of FRP sheets until a limited level. This level determined for tested joint approximately equal to 1.5% story drift. The specimens initially damaged until 1% and 1.5% drifts showed the capacity increase up tp 5% and 3%, respectively. If the damage level is higher than this repair-ability level, other rehabilitation methods may be useful. Then, to simulate the behaviour of joints, a numerical model was developed in the OpenSees framework version 2.4.0. The tested joints such as reference joint and retrofitted joints are analyzed by Opensees nonlinear software. The open source Opensees software has several models for concrete and reinforcement rebar materials possible for considering reloading / unloading stiffness deterioration and hysteretic energy dissipation during reversed cyclic loads. Also nonlinear beam-column elements with spread or concentrated plasticity make this nonlinear software capable for high accurate simulation. The analytical models are used to assess the efficiency of the CFRP rehabilitation to set an optimum level of damage that the seismic behavior parameters could be compensated, safely, economically and practicable. The results of joint analysis are compared with experimental behavior of specimens. The hysteresis curves of the modeled beam column joints had a high level of accuracy in terms of stiffness degradation, moment carrying capacity, capacity degradation and energy dissipation. So, the model is calibrated for each level of damage intensities. The results showed that the model had a good accuracy in terms of load carrying capacity, secant stiffness, energy dissipation and joint ductility and the error was less than 10% between analytical and experimental results. Then, the effct of some variables such as column axial load and existence of transverse slab connected to the beam was analytically investigated. The results showed that increasing the axial load on the column increased the load carrying capacity and stiffness from 5% to 12% (related to initial damage intensity of the joint), but it had negligible effect on dissipated energy. Also modeling of transeverse slab revealed an increasing effect on the capacity, stiffness and energy. The positive effect was higher in absence of gravity loads on the slab. So, existence of transeverse slab with gravity load had negative effect on secant stiffness in specimens with initial damage higher than 1.5% story drift.

Rigid Body-Spring Models (RBSM) are a kind of discrete models which are developed mainly for the simulation of quasi-brittle materials ranging from ceramic, concrete, and masonry, to rock and soil. In this approach, material domain is discretized to a set of rigid cells interconnected through a set of translational and rotational springs located at cell interfaces. These cells are constructed over a set of points (seeds) distributed regularly or randomly over the domain. When it comes to heterogeneous materials, the seeds may be located in accord to the geometry and distribution of inclusions. For two-dimensional problems, each rigid cell has normally two translational and one rotational degrees of freedom (DOFs). The springs may be distributed along the interface or lumped at a point called contact/computational point (CP) and activated by the relative movement of connecting cells. As a fundamental issues, before being applicable for the simulation of inelastic behavior of materials, the kinematics of an RBSM and also the force-displacement relations of its springs should be defined in such a way that the model can adequately predict the elastic behavior of continuum at both macro and micro scales. Our review of the literature shows that except one of the RBSMs, used in the current paper for comparison, others suffer from some shortcomings which result in their inaccurate elastic predictions. In the aforementioned model, cells are convex polygons generated by the Voronoi diagram of seeds (cell nucleus) and the spring set of an interface is comprised of two translational (normal and tangential) and one rotational springs located at the midpoint of the interface. Our study shows that, although this RBSM presents generally a reliable predictions, however, there exists some kind of scattering in the predicted micro strain and stress distributions. Accordingly, with the aim of eliminating the observed scatters, this paper borrows the interpolation functions of the conventional finite element method and presents a new kinematic formulation for the RBSM. In the new model, called FE-RBSM, a Delaunay tessellation is constructed over cell nuclei. This results in a network of triangular elements which can be considered as 3-node constant strain triangular finite elements. Two translational DOFs at each nucleus and two CPs per interface with normal and tangential springs are assumed. Next the triangles including the CPs are determined. Finally, the normal, tangential, and lateral strains of each CP are calculated by projecting the constant strain tensor of the associated triangle on the corresponding interface. In order to examine the efficiency and accuracy of the proposed FE-RBSM formulation, two kinds of numerical analyses including constant and variable stress fields are employed. For the case of constant stress field, a 100mm square sample is analyzed in uniaxial tension and pure shear. Besides, for the case of variable stress field, a 300mm square sample including a 10mm diameter hole at its centroid is analyzed in uniaxial and biaxial tension. Also, a 300mm diameter circle sample is analyzed under splitting compression. The results are compared with those of the selected RBSM and also the analytical solutions. They show that, compared to the RBSM, the FE-RBSM can better predict the macro elastic properties and also gives scatter-free microstress fields.

Different reasons cause traffic oscillation such as: sudden speed drop of leader vehicle. Stop and go traffic commonly observed in congested freeway traffic result in traffic oscillation. When follower driver of platoon receives the last released wave of downstream to upstream in the traffic oscillation, driver makes different reactions proportional to released wave. They result in forming different behavioral patterns and behavior diversion from equilibrium driver. Follower vehicle drivers of platoon make different reactions to receiving wave based on behavior patterns. In this paper, this study employs vehicle trajectory data from Next Generation Simulation (NGSIM) program. Platoons of vehicles identified through a traffic disturbance classify in deceleration and acceleration phase based on driver behavior and hysteresis in traffic oscillation. Driver behavior in deceleration phase lead to congestion classify into four behavioral patterns: under reaction, under constant reaction, over reaction, over constant reaction based on maneuvering errors of follower driver. And also, in acceleration phase based on traffic hysteresis it classifies into two categories: aggressive and timid behavior. In this search, we can study only three driver behaviors: Over Reaction-Timid, Over Constant Reaction-Timid, Under Reaction-Timid because of vehicle trajectories data failure. When follower vehicle in traffic oscillation receives the last deceleration wave lead to congestion, follower vehicle deviates with equilibrium behavior, Newell trajectory, based on driver behavioral patterns. Every car-following model is used to explain the dependency of the follower vehicle trajectory, and its position at time t, to leader vehicle. According to fig.4, if leader vehicle (n-1), moves with constant speed (v), the follower vehicle must move with constant speed (v), too. Spacing between follower and leader vehicles at the time (t) can be changed, but if the freeway was homogenous, the spacing must be constant at approximately Sn; however, it can be varied for different types of vehicles. In this case, all the vehicles are considered as the same type. According to fig 5.a, in the Newell`s model, when a leader vehicle changes its speed from v to v`, the disturbance wave by speed of d^i/τ^i , will be sent to follower vehicle. This process results in an increase in acceleration of follower vehicle. In this model, di, τi are considered constant and independent of speed. According to fig.5.b, these characteristics result in linear relationship between speed and spacing s^i=d^iτ^iv. Next, neural network models are developed to analyze the relationship between the microscopic parameters and time of two phases. Neural Networks are kinds of mathematical models characterized by a huge parametric space and flexible structure, and also, inspired by human brain neurons. In this article Multi-Layer Perception (MLP) related to free-Forward neural network is used by following the backward error propagation regulation, including 3 different Layers, namely, input layer, hidden layer and output layer. In comparison to more complex neural network structures, the advantage of Multi-Layer perception is its procedure according to universal function approximation. Although by choosing the suitable active Multi-Layer perception function, the direct relationship with the statistical equal model is available, Multi-Layer perception with the active mathematical function may be considered as a general sample of mathematical regression model. There is some progress in different methods that enable the neural network to identify the impacts of input on the changes of output, more precisely, i.e., information measurement theory, partial derivative and etc. Based on three behavior patterns, analysis results present that are most effective two parameters: deceleration wave lead to congestion and stop phase time. increasing deceleration wave results in reducing time between two phases based on over reaction-timid, and results in increasing it based on under reaction-timid and pattern and over constant up reaction – timid. And also, results of stop phase lead to congestion present based on three behavior patterns that increasing stop phase results in increasing time between two phases.

Structural damage identification can be considered as the main step in Structural Health Monitoring (SHM). We can find many different methods which use structural dynamic responses for damage prognosis. Although some of them are concentrated on solving an inverse problem for damage identification, others suggest a direct procedure for defect detection. Despite the good performance of these methods in damage identification, researchers are attempting to find efficient and simple methods for damage identification with high level of accuracy. This paper presents a reference-free method for structural damage identification under earthquake excitation. Damages are defined as some changes in the special instants during an earthquake occurrence and structural time history responses are used as an input signal for discrete wavelet analysis. Finally the “detail coefficients” are inspected for determining the damage characteristics, such as the appearance, the time sequence, and the location of damage(s). Although the peak values in the detail coefficients can show the existence and time sequence of damage, for determining damage location we should inspect these peaks for finding the maximum value. As a result, the associated element with a signal which has maximum peak, can be considered as the damaged element. The applicability of the presented method is demonstrated by studying three numerical examples. First example is devoted for damage identification in a four-story shear frame. It is assumed that we have equipped all of the stories by sensors for recording structural responses. Three different damage scenarios with single and multiple damage cases under two samples of earthquake records, namely El-Centro (1940), and Northridge (1994) earthquakes, are studied. In addition, we study the effect of using different wavelet mother functions and different input signals, such as displacement and velocity responses. All of the obtained results emphasize the applicability of the presented method in damage identification. In second example, we consider a concrete simple beam with ten elements by simulating two different damage scenarios. In this case, we inspect the applicability of the method by considering only the transitional degrees of freedom (DOF) as the equipped DOFs by sensors. This can be interpreted as using limited number of sensors. In addition we use the displacement time histories for damage identification. For having a clear strategy in damage localization, we propose two rules for judging about elements’ health which are based on seeking maximum values of the wavelet coefficients in the damaged instants. Obtained results show the good performance of the presented method in finding time sequence of damage occurrence and damage location. In the third example, we investigate the applicability of the presented method in the presence of complex models of damages by defining bilinear stiffness reduction. In this case, although damage can cause some reduction in the effective stiffness of damaged structure, this reduction is different in positive and negative displacements. Two different damage scenarios are simulated on a single DOF structure under different excitations, namely earthquake excitations and generated White Noise excitation. Obtained results reveal the robustness of the presented method in damage prognosis in the presence of complex damage models.

Aromatic aldehydes are toxic compounds present in different waste-waters coming from the chemical and petrochemical industries. Their environmental fate may end up by their occurrence in the ground water through the infiltration/deep percolation processes of rain and snow water. Therefore, this kind of substances is contained not only in various industrial wastewaters, but occasionally also in drinking water. Hence, the degradation of such compounds in water and wastewater is still of special interest for many researchers. Benzaldehyde is an aromatic aldehydes used chiefly as a precursor to other organic compounds, ranging from pharmaceuticals to plastic additives and it has been classified as a hazardous substance by the United States Environmental Protection Agency. As a result, the use of alternative treatment technologies, aiming to mineralize or transform refractory molecules into others which could be further biodegraded, is a matter of great concern. Among them, advanced oxidation processes (AOPs) have already been used for the treatment of water and wastewater containing recalcitrant organic compounds such as pesticides, surfactants, colouring matters, pharmaceuticals and endocrine disrupting chemicals. Moreover, they have been successfully used as pretreatment methods in order to reduce the concentrations of toxic organic compounds that inhibit biological wastewater treatment processes. The main mechanism of AOPs function is the generation of highly reactive free radicals. Hydroxyl radicals (HO•) are effective in destroying organic chemicals because they are reactive electrophiles (electron preferring) that react rapidly and nonselective with nearly all electron-rich organic compounds. They have an oxidation potential of 2.33 ev and exhibit faster rates of oxidation reactions comparing to conventional oxidants such as O3. The diverse methods used for generating these radicals are photo catalysis and sonochemistry methods. A new alternative sonochemistry approach offers a solution for combating the persistent water and wastewater organic pollutants. Sonochemical degradation could be used for organic pollutant removal in aqueous solutions. The advantages of using ultrasound irradiation are the simplicity of its use , the ultrasound does not require additional chemicals, and it can be used for treatment of turbid solutions. In this research, ultrasonic/H2O2 advanced oxidation process has been studied for degradation of aqueous solution of benzaldehyde. The effect of key parameters such as ultrasonic frequency, ultrasonic amplitude, time, pH of solution and initial concentration of the benzaldehyde on the removing rate of benzaldehyde are investigated. Different concentrations of benzaldehyde and H2O2 were prepared and the solutions were exposed to ultrasonic treatment (UP 400S model). The experiments was carried out in a batch reactor for 60 min and each 5 min an aliquot was taken from the solutions. Absorbance of sampling solutions was recorded by UV-Vis spectrophotometer of Hack (DR 5000-15 V model). The results show that, the removal rate increases with the increase of time, ultrasonic frequency and amplitude and decreases with the increase of solution pH, H2O2 and benzaldehyde concentrations. As data shown, the degradation of benzaldehyde in ultrasonic/ H2O2 process best fitted by pseudo first order kinetic. It can be conclude the combined of ultrasonic/ H2O2 led to 91% degradation of benzaldehyde after 60 min.

Structures such as side orifices, side weirs, and side sluice gates are known as flow diversion structures. Side orifices are flow diversion structures which have wide application in hydraulic and environmental Engineering. This flow diversion structure has been extensively used in irrigation and drainage networks, wastewater treatment plants, sedimentation tanks, etc. Therefore, Study of the characteristics and flow pattern such as flow velocity components and free surface adjacent to the side orifice is important. In this paper, the flow over a sharp-crested rectangular side orifice in an open channel was simulated by FLOW-3D software. RNG turbulence model was used to apply the Navier-Stokes equations and the VOF method was used to model the free surface profile changes. In the present study, at first, the results related to the side orifice discharge and flow patterns obtained from numerical simulation were compared with experimental data. In this study, some experimental data of Hussian et al (2011) were used for model verification. In this study, the discharges through the orifice resulted from the present numerical simulation and the experimental research, along with the relative errors are reported. All relative error quantities were about 8-9%, thus there was relatively good agreement between numerical and experimental results. Therefore, the numerical model can be employed as a powerful tool for studying flow through side orifices in open channels. Then the effects of height of the side orifice crest on the flow velocity components and free surface adjacent to the side orifice was investigated. The results indicated that the discharge ratio, ratio of the discharge through the side orifice to the inlet discharge of the main channel increases with decreasing heights of the side orifice crest. Maximum and minimum longitudinal velocity for all heights of the side orifice crest was occurred at the beginning and end of the side orifice, respectively. By decreasing the height of the side orifice crest, maximum and minimum longitudinal velocity increases and decreases, respectively. By decreasing the height of the side orifice crest, the longitudinal velocity in the vicinity of the side orifice is negative because of the reverse flow formed in this area. Examining the lateral velocity component variation showed that this component increased with decreasing height of the orifice crest. That is why the discharge through the side orifice increased with decreasing height of the orifice crest. At height 2.2 cm of the orifice crest, the flow direction is upward then in all cases vertical velocities in the orifice length are positive. In the other hand, at height 6.7 cm of the orifice crest, the flow direction is downward then in all cases vertical velocities in the orifice length are negative. Also, the absolute value of the vertical velocity increases with by decreasing the height of the side orifice crest because more flow is diverted to the side orifice with decreasing the height of the side orifice crest. Also, increasing height of the orifice crest caused significant changes in the free surface profiles especially in the vicinity of the side orifice.

Urban runoffs usually contain a large variety of pollutants such as heavy metals, organic compounds, nutrients, solids, and de-icing agents. These are normally accumulated on impervious urban surfaces over time. Hence, the runoff itself becomes a wastewater that could create substantial degradation of water quality in receiving area. There are many alternative management strategies for treating these contaminants. Most of the approved stormwater management measures are difficult to be implemented on a wide scale (due to infrastructure and space/cost constraints). Permeable pavement is one of the urban runoff management methods that are widely used in order to reduce storm runoff flow and volume, and minimize pollution conveyance to receiving waters. Pervious pavement systems consist of a permeable pavement surface layer and one or more underlying aggregate layers designed to temporarily store storm-water. Runoff treatment using three aggregate layers, namely steel slag, limestone and silica aggregates were applied both as filter and pavement base layers. The research was conducted at laboratory scale and in continuous mode. All the experiments were conducted in cylindrical reactors of 0.6 m height and 0.2 m diameter. Each column was filled up to an average depth of 0.5m (0.1 m for filter layer and 0.4 m for the base layer). In order to determine the lifespan of the media, synthetic runoff in successive cycles was injected into the column continuously. Results from the study showed that the base and the filter layers of the permeable pavement can reduce the total range of runoff pollutants effectively with high removal percentages. In all experiments the rate of pollutant removal at the initial time of reaction was faster. However, these were gradually decreased and after 120 hours approximately the maximum removal efficiency was achieved. Comparing the effects of the three aggregates types, the steel slag aggregates exhibited better performance. The treatment process showed that the maximum removal of COD, phosphate and total solids from runoff in 3 hours, were 61, 59 and 70 percent respectively. These were increased to 98, 96 and 99 percent after 120 hours. In addition, the total capacity of slag aggregates for removing COD, P-PO4 and TS parameters were estimated to be 3.43, 0.21 and 22.10 g/Kg respectively. The testing results indicated that after the slag aggregates, limestone materials showed a high ability to remove pollutants from runoff waters as compared with the silica aggregates. The kinetic study resulted that the pseudo-second order kinetics equation, compared with the pseudo-first order and intra-particle diffusion models, described better the removal of organic compound absorption (COD removal) from the storm water. In this study the rate constant of the reaction (K) for the COD removal via steel slag, limestone and silica aggregates were estimated to be 0.31, 0.31 and 0.30 g mg−1 min−1 respectively. The correlation coefficients (R2) under different conditions were also calculated to exceed 97%. Since steel slag is a byproduct of steel production factories, its application as a road-building material, would be an appropriate alternative pavement layer in protecting the environment and conserving the natural resources.

Additional dampers TADAS are a kind of passive control systems which can be used in seismic design or retrofit of structures. In this study, behavior of TADAS dampers in large deformation has been examined and some of the possible errors in its design are expressed. It is shown that how the lack of attention can result in damage to the structure and reduce the ability of energy dissipation in the damper. To investigate this issue, TADAS damper with all its details was simulated in ABAQUS finite element software. TADAS damper made up of several components, these components include the upper plate, the lower plate, triangular plates, rods rollers (pins) and connection plates. Damper modeling in ABAQUS determined that in a large deformation, the damper stiffness strongly and suddenly increases. It is examined that this sudden changes in damper characteristics is mainly due to the collision of the damper pin and the upper wall of its slot. This sharp increase could lead to adverse responses and even help to the destruction of the structures. In this paper, two suggestions are presented to prevent this situation. These suggestions include increasing the slot height and putting pins in the lowest point than slot bottom during damper installation. Assuming uniform curvature over the damper plates, a relationship has been proposed to predict the amount of the large displacement corresponding to the high stiffness of the damper. Using this relationship can get awareness of the occurrence or non-occurrence of increasing stiffness of the damper in the various classes of structures. It can also be used as a design tool for selecting the proper height of the damper slots.Also, a frame equipped with TADAS damper is constructed and get under cyclic loading to large deformation. This frame was simulated in ABAQUS and its behavior was compared with laboratory sample. This comparison indicates that there is a good agreement between laboratory and software results. From laboratory and software models it became clear that the frame equipped with TADAS damper even in large deformation has stable and acceptable behavior, but two very important defects are observed in the frame. One of these defects is buckling of braces despite their design based on the toleration of the maximum capacity of damper. This buckling has occurred due to the rotation of beam-to-column connections. To prevent damper from degradation, it must be considered in the design process as far as the large deformations is concerned. As per the design codes, damper’s retainer system TADAS (Chevron braces) should not be damaged and/or buckled. The second defect is related to the looseness of damper’s pins and the looseness of damper’s connection bolts inside their slots. It will be shown that how this looseness causes a delay in the performance of damper and will increase the possibility that the damper plays a lesser role during earthquake. Therefore, the looseness in pins and bolts must be properly prevented. In this study, 10 bolts with 24 mm diameter were used to the connecting damper to floor-beams and Chevron braces.

Based on ASTM E1823 standard, fatigue phenomenon is the process of permanent, progressive and localized structural change which occurs to a material point subjected to strains and stresses of variable amplitudes which produce cracks which lead to total failure after a certain number of cycles.
During an earthquake fatigue failure can occur at loads much lower than tensile or yield strengths of material. Therefore material behavior under cyclic loading is an important design criterion.
Fatigue data are obtained from the experiments and are shown in S-N curves which represent stress or strain amplitude versus number of cycles. All fatigue ranges can be included generally in three categories. Ultra Low Cycle Fatigue (ULCF), Low Cycle Fatigue (LCF), and High Cycle Fatigue (HCF). HCF is recognized with low strain amplitude and high frequency, and LCF is a material deterioration which is described as high plastic strain amplitude and low frequency. ULCF involves a few cycles (less than 20) of large plastic strains. ULCF is of great importance for structural and earthquake engineers, because fatigue failure in structural members occurs generally in less than 10 cycles during a seismic event. Fatigue fracture in moment connections, or gusset plates and brace members are examples for ULCF or ductile fracture.
Fatigue life is expressed as the total number of stress cycles required for a fatigue crack to initiate and grow large enough to produce fatigue failure. Currently, two major methods are available for fatigue life prediction of structures. One type is based on material fatigue life curves (e.g., S–N curves or ε–N curves) and a damage accumulation rule. The other is based on fracture mechanics and crack growth analysis.
The Manson–Coffin law is the most widely used procedure to predict material failure under LCF and ULCF. But last researches showed that Manson–Coffin relation overestimates fatigue life in ULCF domain.
Miner’s rule is one of the most widely used cumulative damage models for failures caused by fatigue.
The rainflow method is a method for counting fatigue cycles from a time history. The counting of each load cycle and the relative damage produced must be done with extreme accuracy and care. Rainflow counting has been shown to be most effective. The rainflow method allows the application of Miner's rule in order to assess the fatigue life of a structure.
In this paper low cycle fatigue performance of restrained buckling braced frames with diagonal, V-shaped and chevron configurations are investigated. Last researches and experimental tests results of BRBs usually show very stable hysteresis behavior with an excellent low cycle fatigue life.
In this study For modeling the low cycle fatigue phenomenon, the “fatigue material” model in OpenSees is used. The fatigue material uses a modified rainflow cycle counting algorithm to accumulate damage in a material using Miner’s Rule. Once the Fatigue material model reaches a damage level of 1.0, the force (or stress) of the material becomes zero and the material is destructed completely.
By obtaining the hysteretic loops and also the cumulative damage charts of diagonal, V-shaped and chevron buckling restrained braced frames, the hysteretic behavior and fatigue life of them are evaluated. Buckling restrained braces in three configurations of concentrically braced frames, exhibited stable hysteretic behavior up to failure. Considering area of the hysteretic loops and low cycle fatigue life, V-shaped buckling restrained braced frame showed better low cycle fatigue performance.

Damage detection of structures is an important issue for maintaining structural safety and integrity. In order to evaluate the condition of structures, many structural health monitoring (SHM) techniques have been proposed over the last decades. Major approaches of SHM are non-destructive in nature and are widely used for damage detection in engineering structures such as aerospace, civil and marine structures. The existence of damage in a structure may be traced by comparing the response of time-domain wave traveling in the structure at its present state with a base-line response. A difference from the base-line response is correlated to the damage location through estimation of time of arrival of the new peaks (scattered waves). Thus, by employing the wave based methods, presence of damage in a structure is detected by inspecting at the wave parameters affected by the damage. The wave parameters that are commonly used for damage detection are the parameters representing attenuation, reflection and mode conversion of waves due to damage. Although detection of flaws is extremely important for many industrial applications, current approaches are severely restricted to specific flaws, simple geometries and homogeneous materials. In addition, the computational burden is very large due to the inverse nature of the problems where one solves many forward and backward problems. For instance, conventional ultrasonic methods measure the time difference of returning waves reflected from a crack; however, for laminated composite plates, the ultrasonic wave would be partially reflected at the interface of two layers where no crack actually exists, and partially continues to propagate further where it eventually is reflected back by the true crack. Numerical methods employed in crack detection algorithms require the solution of inverse problems in which the spatial problem is often discretized in space using finite elements in association with an optimization scheme. The solution of these problems is not unique, and sometimes the optimization algorithm may converge to local minima which are not the real optimal solution. Moreover, they often require hundreds of iterations to converge considering the algorithm used in the process. On the other hand, an accurate detection of cracks requires the re-meshing of the finite element domain at each iteration of the optimization. This is a severe limitation to any numerical approach when the conventional finite element method is employed for crack modeling, as the re-meshing of a domain is often not a trivial task. This paper investigates crack detection of two-dimensional (2D) structures using the extended finite element method (XFEM) along with particle swarm optimization (PSO) algorithm. The XFEM is utilized to model the cracked structure as a forward problem, while the PSO is employed for finding crack location as an optimization scheme. The XFEM is a robust tool for analysis of structures having discontinuities without re-meshing. Therefore, it is an efficient tool for an iterative process. Also, the PSO is a well-known non-gradient based method which is suitable for this inverse problem. The problem is formulated such that the PSO algorithm searches crack coordinates in order to detect the existing crack by minimizing an error function based upon sensor measurements. This problem is a non-destructive evaluation of a structure. Three benchmark numerical examples are solved to demonstrate capability and accuracy of the XFEM and the PSO for crack detection of 2D domains.

Spillways and bottom outlets are the common hydraulic structures in dam engineering to convey excess water from the reservoir toward the downstream river. Economy and operation are the major factors affecting the type of spillway and its’ crest shape to avoid unfavorable hydraulic phenomena. An appropriate spillway crest results in increasing the discharge coefficient and distributing a uniform pressure inside the conveying conduits. One of the most common types of spillways in dam engineering is shaft spillways with morning glory inlet. Generation of swirling flow at the entrance of the shaft spillways and entraining air into the conduits is an unfavorable phenomenon. Air-entrainment into the system leads to different depressing effects on system operation including reduction of the discharge coefficient and can cause severe damages. To control the swirling flow phenomenon one way is the application of anti-vortex devices. Applying certain shape of inlets e.g. installing a Daisy (Marguerite)-shape inlet over the shaft entrance is another alternation to avoid the swirling flow effects thereby to increase the discharge coefficient. Marguerite-shape inlet has been used in different existing dam projects. Marguerite inlet is a unique inlet compared to other shapes of spillway crests for a constant head. This is in part due to spatially varied flow inside the marguerite inlet which makes it capable of passing greater discharge. Although different types of dam spillways have been the subject of different investigations, there is a lack of study on these types of spillways.
In this study, the effects of Daisy (Marguerite)-shape inlet on free-flow through shaft spillways have been investigated based on model experimentation. Dimensional analysis has been used to determine the effective dimensionless parameters. Experiments were conducted in a cylindrical model of 2 m diameter with two shafts of 10 and 12.5 cm diameters on the tank bottom. The tests have been performed based on a wide range of geometric and hydraulic parameters to study the effects of each dimensionless parameter on flow hydraulics. Finally, applying SPSS software and nonlinear regression analyses empirical correlations were obtained for estimating the discharge coefficient and the threshold depth of orifice flow over Daisy-shape inlets. To validate these correlations, the normalized root-mean-square error (NRMSE), the weighted quadratic deviation (WQD) and the coefficient of determination R2 were applied. Contrary to R2, both NRMSE and WQD must be small to have the best correlations.
Spillways and bottom outlets are the common hydraulic structures in dam engineering to convey excess water from the reservoir toward the downstream river. Economy and operation are the major factors affecting the type of spillway and its’ crest shape to avoid unfavorable hydraulic phenomena. An appropriate spillway crest results in increasing the discharge coefficient and distributing a uniform pressure inside the conveying conduits. One of the most common types of spillways in dam engineering is shaft spillways with morning glory inlet. Generation of swirling flow at the entrance of the shaft spillways and entraining air into the conduits is an unfavorable phenomenon. Air-entrainment into the system leads to different depressing effects on system operation including reduction of the discharge coefficient and can cause severe damages.

The lack of accessibility of high quality materials and the increased costs associated with the use of these materials will finally demand engineers to use local soils. In such cases, ground improvement performed reasonably in many conditions. Ground improvement can be defined as the procedure of increasing shear strength parameters and decreasing the permeability and compressibility of the soil. Different methods can be used to improve the geotechnical properties of the problematic soils such as loose sand that one of them is using additives. The stabilization of soils with cement is an attractive technique due to economic and environmental issues and avoiding the use of borrow materials from elsewhere. Cementation of sand results in increased brittle behavior as peak compression strength increases. The compressive strength of artificially cemented soils has been studied in the past by several investigators.A number of studies have also reported on the influence fiber, glass, fly ash, silica fume and nono particle on the mechanical behavior of cemented sands .However, to the author’s knowledge, there has been a little effort devoted to the research on the use of pozzolans such as natural zeolite as an addictive material to the cemented sands. Natural zeolite, an extender, has been investigated for use as cement and concrete improver by some researchers.
It is widely known and well emphasized that the cemented sand is one of economic and environmental topics in soil stabilization. In some instances, a blend of sand, cement and other materials such as fiber, glass, nano particle and zeolite can commercially available and effectively used in soil stabilization in road construction. In this investigation, zeolite and its effect on unconfined compression studied as one of addictive material to cement. Therefore, cilinopiolite kind of zeolite, Neka cement type II and Babolsar sand are used. A total number of 144 unconfined compression tests were carried out on 24 combination type of cement and zeolite include different cement percentages 2, 4, 6 and 8 percent of total dry weight of samples and replacement percent’s of 0, 10, 30, 50, 70 and 90 zeolite with cement based on 50,70 and 85% relative densities in7 and 28 days curing times. Results show that in 28 day curing time, by replacement percentage of 30 zeolite material by cement, the unconfined strength increased 20 to80% in comparison with cemented samples by increasing shear strain. For higher cement content and less compacted blends, these improvement rates are more. At the end, a power function fits presented to relate unconfined compressive strength (UCS) and zeolite-cement-soil parameters (porosity (n) and voids/ polynomial model of cement and zeolite voids).It is widely known and well emphasized that the cemented sand is one of economic and environmental topics in soil stabilization. In some instances, a blend of sand, cement and other materials such as fiber, glass, nano particle and zeolite can commercially available and effectively used in soil stabilization in road construction. In this investigation, zeolite and its effect on unconfined compression studied as one of addictive material to cement. Therefore, cilinopiolite kind of zeolite, Neka cement type II and Babolsar sand are used. A total number of 144 unconfined compression tests were carried out on 24 combination type of cement and zeolite include different cement percentages 2, 4, 6 and 8 percent of total dry weight of samples and replacement percent’s of 0, 10, 30, 50, 70 and 90 zeolite with cement based on 50,70 and 85% relative densities in7 and 28 days curing times. Results show that in 28 day curing time, by replacement percentage of 30 zeolite material by cement, the unconfined strength increased 20 to80% in comparison with cemented samples by increasing shear strain. For higher cement content and less compacted blends, these improvement rates are more. At the end, a power function fits presented to relate unconfined compressive strength (UCS) and zeolite-cement-soil parameters (porosity (n) and voids/ polynomial model of cement and zeolite voids).

In this paper, the effect of soil-structure interaction is investigated on the maximum drift demand and probabilistic seismic confidence level of geometric vertically irregular steel buildings. A series of vertically irregular steel building with different setback ratios were designed based on the regulations in the earliest version of Iranian seismic design code. Foundation design of the structures was accomplished with the assumption of sandy soil with shear wave velocity of 200m/s under the strip footings. Three dimensional model of nonlinear soil-structure system was built in OpenSees. Concentrated plastic hinges were used at the end of frame members to model the nonlinear behavior of these elements. Soil-foundation system of the structures was modeled with Beam on Nonlinear Winkler Foundation (BNWF) approach. In this method, a series of nonlinear springs are used to model the soil behavior under the dynamic excitation. The seismic analysis of the structures was performed under the simultaneous action of orthogonal components of real ground motions. An ensemble of twenty ground motions that have a reasonable response spectrum matching with the design spectrum was chosen for the time history analysis. Incremental dynamic analysis (IDA) was accomplished to estimate the structural performance of the regular and vertically irregular setback buildings from the earlier linear behavior to the nonlinear phase and up to the global instability of the structures. Based on the results, the median IDA curve of fixed and flexible base buildings was evaluated. Four common performance objectives namely Immediate Occupancy (IO), Life Safety (LS), Collapse prevention (CP) and Global Instability (GI) were specified on the median IDA curve of each fixed and flexible base structure. Following the performance-based earthquake engineering framework, the confidence level of meeting a specific performance level was evaluated at each limit state. Based on the given results, curves were generated to specify the confidence level of meeting a specific performance level for a range of earthquake intensities and corresponding maximum inter story drift ratio. The performance based confidence level of flexible base setback buildings was compared to that of the fixed base structures at five seismic hazard levels. The seismic hazard of earthquakes was chosen to cover a wide range of return period from 25 years to 4975 years. It is observed that all the fixed and flexible base buildings have the ability to continue their immediate occupancy with the confidence level of 100% under the excitation of earthquakes with low to medium hazard levels (i.e. with the return period of 25 to 43 years that know as the service level). However, as the level of seismic hazard increases the difference between the confidence level of flexible base structure and the fixed base ones increases. Depend on the position and ratio of the setback, 40 to 60% of reduction is observed in the performance based confidence level of flexible base structures. Meanwhile, demand evaluation of structures at each hazard level shows that soil-structure interaction increases the maximum drift demand in structures. Based on the given results, it is observed that up to 35% increase of maximum drift happens in vertically irregular structures with flexible foundation.

The destruction of the bridges because of the erosion of the bed is a question that if is not addressed properly it can’t be compensated. The aim of this research reviews the scour around the twin bridge piers affected by parameter of time and its role in the bed topography. In this research, the equilibrium time test was done to determine the equilibrium time. After that a test without the establishment of bridge pier was done. The aim of this test is to know the effect of steep bend flume to the bed topography and scour pattern. The next tests were done at 20, 50 and 100 percent of the relative equilibrium time with the establishment of the twin bridge piers. The experiments were performed at the Advance Hydraulic Laboratory of Persian Gulf University of Bushehr in Iran. The channel used in this study has 1 m wide and bend routh with the 180 degrees angle flume with the relative curvature of 2. The upstream routh has the length of 6.5 m and the downstream path is 5 m long. The condition was clear water in all test and live bed using sediment with average diameter of 1 millimeter and standard deviation equals to 1.3. Flow rate was fixed at 70 litter per second with depth of 18 centimeter at straight upstream rought. The piers had the diameter of 5 centimeter and making the angle of 21 degrees with the vertical axis and also placed at the perpendicular plane to the flow stream. Due to maximum scouring at 60 degree of the flume in preliminary tests without the establishment of the piers, for the rest of the tests the piers were installed at 60 degrees angle of the channel bend. At the end of each test channel was gradually drained and after drying the bed topography was harvested with the use of laser device called bed topographer with the accuracy of 1 millimeter. For the best result according to the test more than 4500 points were measured. The most important results achieved is that by the relative equilibrium time the second scour hole is 12 percent deeper than the main scour hole around the piers. In addition the second scour hole is created at the 123 degrees along the outer wall of the flume. Studying the parameter of time indicated that at the beginning of the experiment the second pier which is closer to the outer wall has more scouring depth , but after the relative balance time of 20 percent both pier has the same scouring rate. Reducing the time of the test by 100% to 50% of the relative equilibrium time reduces the maximum scouring depth of the main hole by 20 percent. In all test a scour hole at the middle of the channel bend was seen which deeper at 50 percent of the equilibrium time compared to the 100 and 20 percent of the relative equilibrium time. Advanced discussion and analysis about the results achieved from the tips are outlined in this paper.

Increasing pollution levels due to rapid industrialization and urbanization are now causes of major concern in industrializing countries. Petroleum and chemical processes are responsible for many emissions both into the air. Equipment leaks in chemical and petroleum processing industries are responsible for significant amount of emissions. Even if each individual leak is generally small, it is the largest source of emissions of volatile organic compounds (VOCs) from petroleum industries and chemical manufacturing facilities. Styrene and Acrylonitrile are two major components in the streams of ABS plant of Tabriz Petrochemical Complex which is expected to be released to the atmosphere through various sources such as equipment leaks and tank venting. In the first step of this study the major sources of pollutants emission in the ABS plant were identified considering the PDF and PID of the plant. Then the emission rate of each source was estimated using the emission factors presented by USEPA. An emissions factor is a representative value that attempts to relate the quantity of a pollutant released to the atmosphere with an activity associated with the release of that pollutant. Emission factors are powerful tools for policy makers as they can be used to relate emissions and concentrations. In the last step, the estimated emission rates were used as the input of Industrial Source Complex Short-Term Version 3 (ISCST3) model to predict the ground level concentration of Styrene and Acrylonitrile around the ABS plant. The ISCST3 is steady-state Gaussian plume model which can be used to assess pollutant concentrations from a wide variety of sources associated with an industrial complex. The model is generally applicable for near-field (within 10 km) impact assessment of air pollutant in meteorologically and topographically uncomplex conditions. Among the 54 pumps, 23 compressors and other equipments of the plant, 11 pumps, 8 compressors and 6 storage tanks were identified as the emission sources of considered pollutants. The emission rates of pumps and compressors were estimated using the emission factors presented in AP-42 document of USEPA. The emission estimation of Styrene and Acrylonitrile from six storage tanks has been done using USEPA standard regulatory storage tanks emission model (TANKS 4.0.9a). The emission software program TANKS is developed using emission factors presented in AP-42. The results showed that the compressors are the significant sources of considered pollutants which release about 586 g/day Styrene and 2506 g/day Acrylonitrile to the atmosphere. The emission rate of Styrene and Acrylonitrile from pumps were estimated 36 g/day and 94 g/day, respectively. The results of using TANKS model indicated that Styrene and Acrylonitrile emission rates are 7 g/day and 22 g/day, respectively. The estimated emission rates were used as the input of ISCST3 model to find the ground level concentrations of considered pollutants around ABS plant. The results showed that the maximum level of Styrene was 646 µg/m3 which is below the Reference Concentration (Rfc). In the case of Acrylonitrile the maximum level of estimated concentration was 272 µg/m3 which is higher than Rfc. The implementation of a leak detection and repair (LDAR) program or modifying/replacing leaking equipment with “leakless” components were recommended to reduce the emissions from equipment leaks of ABS plant.