Modares Civil Engineering journal
Year:2016 | Volume:16 | Issue:5 (SUPPLEMENT)|Papers Count:21

Precast segmental construction methods can decrease bridge construction costs by reducing construction time while the quality control criteria are satisfied. In addition, the absence of scaffold can minimize traffic congestion and environmental impacts. Because of these great advantages, application of precast segmental bridges is increasing in the world. However, lack of reliable knowledge about the dynamic response of these bridges under seismic loads has limited their application in high seismicity areas. Combination of the precast construction with the post-tensioning contact on segment joints, may result in expecting a defeated behavior of superstructure due to earthquake excitation. This may happen especially in case of vertical components, which may harm the joints operation in the presence of long-term loads. This issue is very probable in non-continuous post-tensioned bridges. The present paper aims to investigate the effects of vertical earthquake on bridge superstructure in near-fault regions by studying a sample model and obtaining structural response including joints response and their openings, force-displacement response of the system, stress and strain in concrete and cables, and their level of nonlinearity.The research shows that segment joints can undergo very large rotations that open up gaps in the superstructure; Whereas, primary seismic concerns - regarding segmental construction - focus on the behavior of the joints between segments, and no mild reinforcement crosses trough them. The lack of reinforcement across segment joints may result in an increased rate of construction. Yet, it creates inherent regions of weakness that are susceptible to facing crack initiation and large localized rotations. At the first step of numerical modeling, specimens studied by Megally et al. [1-3] were modeled in OpenSees V2.4.4. The specimens discussed the regions with high moment and low shear (i.e. near mid-span). Using detailed 2D nonlinear time history analysis under a suite of ten near-field earthquake records, the effects of vertical motion on the joint response are quantifies. The prototype bridge structure - selected for this study- is a single-cell box girder bridge with a 50m span, consisted of sixteen 3-meters-long segments with non-bonded tendons constructed trough a span-by-span construction method. Segments of the superstructure are modelled using linear elastic frame type members, except for a region at the end of each segment which is discretized into several axial non-linear zero length springs. The springs are connected to the ends of the superstructure beam elements through rigid body links. Results indicate that vertical components of earthquake can affect the response of these bridges, and segment-to-segment joints opening is very probable particularly at the midspan joints. Thus, superstructure may collapse under upward acceleration component due to the presence of the greater part of concrete on top flange and lack of tensile material on top of joints, or even the occurrence of sliding in elastomer caused by the decrease in effective weight. The joint compressive strain remains below the concrete spalling limit state, minimizing the damage and stiffness reduction of the superstructure. The cables remain in the elastic range and all joints are closed after the earthquake, even in high seismic intensity levels, and the residual vertical displacements are negligible.

Despite several existing researches on the secondary consolidation of fine grained soils, there is no consensus among researchers about the main reasons for variations of the coefficient of secondary consolidation versus stress. The present research specifically aims to discuss the general trend of this parameter in soils with double porosity structure. This paper studies the commercial kaolin. After adding the required moisture to the soil and allowing the moisture equalization, samples of kaolin are statically compacted into the desired dry density. The density of the compacted kaolin is considered to be low enough to obtain an initial open and double porosity structure. In order to make sure about the compaction procedure -as well as the existence of double porosity structure, prosimetry experiments including mercury intrusion and BET experiments are carried out. The results of prosimetry experiments confirm the existence of double porosity structure in the samples. Furthermore the results of water retention analysis of soil prove the double porosity structure of compacted soil samples. The water retention curves show a stepwise trend which is a consequence of bimodal distribution of pore size. Moreover, the water retention curves show that the structure changes into single structure at high vertical stresses. In other words, the vertical stress causes the closure of macro pores. For further investigations, samples are put in conventional oedometer apparatus. Saturation is carried out in two ways: the first group of samples are saturated before being loaded; In the second group, the samples are initially loaded at compaction water content and then are saturated under a constant load. The results indicate that the history of stress before the collapse, transposition of loading and saturation processes does not affect the porosity of the samples after saturation (Collapse upon wetting). In other words the porosity after collapse is only related to the effective stress at saturation state. This may validate the idea which states “normal consolidation line of saturated samples is a unique line and is not substantially dependent on the stress path and history”. This idea simplifies the procedure of modeling the behavior of collapsible soils. Over a long period of time required for measuring the secondary changes in soil volume, the samples are put under a constant load, and the amount of settlement versus time is measured after the completion of primary consolidation. The coefficient of secondary consolidation is reported for all states of vertical stresses. Recorded experimental results show that in the stress range of 100 to around 300 kPa, the coefficient of secondary consolidation exhibits an increasing trend with respect to stress; where it reaches its maximum at 300 kPa and starts its descending trend. This is in compliance with the same results of earlier researches. Consequently, given that the soil studied in earlier researches has been of single porosity structure, present research shows that the double porosity structure does not considerably affect the general trend of changes in secondary consolidation coefficient. Furthermore this is in contrast with some theories that express the relation between the secondary deformations and double porosity structure of soil. Therefore, it could be stated that it is required to clarify the reasons of secondary deformations of soils more precisely.

One of the challenging tasks for civil engineers is to mitigate the vibrationof structures due to dynamic loads in order to prevent possible damages and human and economic losses. By reducing the external disturbance on a system, response of the system can be reduced. However, this may not be possible in all cases. On the other side, modification of a system to prevent occurrence of resonance may require significant redesigning. Furthermore, this would be difficult to be applied on existing structures. Therefore, using vibration control devices was introduced as a reliable and simple method. These devices are simply attached to existing systems to reduce the vibration of the structure without altering the original system drastically. Passive tuned mass damper (TMD) -introduced more than a century ago- is undoubtedly a simple, inexpensive and reliable mean to suppress unfavorable vibrations of structures. However, very narrow band of suppression frequency, ineffective reduction of non-stationary vibration, and sensitivity problem due to detuning are inherent limitations of the passive TMDs. These dampers are usually tuned to the first natural frequency of the structures. TMD parameters are constant during the life cycle of the structure, therefore it is important to adjust them properly to achieve a favorable performance. Optimal values for TMD parameters in structures with non-linear behavior are determined by non-linear dynamic analysis. There are many analytical and empirical relations to identify these parameters throughsimplified modeling. 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 model is performed by comparing the results of the dynamic analysis under four earthquake records by those of alternative model created in SAP2000. In order to mitigate vibration of this bridge, 11 TMDs are considered to be installed on the bridge. The aim of the GA approach is to minimize the displacement of tallest pier of the bridge in order to decrease the maximum displacement of the structure subjected to earthquake excitations. Based on the analyses conducted for near-field and far-field earthquakes, it was concluded that employing GA will considerably reducesthe convergence rate of achieving optimum TMD parameters. To evaluate the performance of the control system during severe earthquakes, Incremental Dynamic Analysis (IDA) is conducted for the maximum Peak Ground Acceleration (PGA) of 0.1g to 1.0g. The longitudinal root mean square and maximum displacement of the tallest pier in uncontrolled and controlled cases are obtained and compared. The results show that for low PGA values, TMDs absorb and dissipate a large portion of the input energy, and the piers remain elastic in this case. However, for higher values of PGA, piers also dissipate a 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. Numerical analyses for the mass ratio of 4% for TMDs show that the reduction percentage of longitudinal and RMS displacement of the largest pier with tuned mass damper are 24.9 and 34.3, 43.5 and 38.7, 30.6 and 40.4, and 13.6 and 28.1 for El-Centro, Kern-County, Kobe and Northridge earthquakes, respectively.

Determining the velocity distribution -as a key parameter for estimating other hydraulic parameters- has been always of interest. Velocity distribution in the inner region of the flow (y<0.2D where y is the vertical distance from the bed and D is the flow depth) is well described by the logarithmic law. However, this law deviates from the experimental data in the outer region (y>0.2D). The log-Wake law is among the most accepted laws for determining the velocity distribution in wide open channels. The law modifies the logarithmic law by adding a Wake function; but in the case of narrow open channels, it deviates from the measured data near the free surface. Distribution profile derived by the log-Wake law depicts the velocity which increases monotonically with increase of the distance from the bed. Thus, it is not capable to show the negative gradient of velocity 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- will cause the maximum velocity to occur below the water surface. This is called velocity-dip phenomenon which -for the first time- is reported more than a century ago. Since that time, numerous investigations have been conducted by many researchers in order to propose new models; not only for describing the dip phenomenon and negative gradient of velocity near the free surface, but also to predict the position of the maximum velocity accurately and to converge 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 numerical results are verified with experimental data measured in several rectangular lab channels and data collected from an actual sewer channel. Since the proposed equation for velocity distribution is dependent on Coles Wake parameter (Π), the effect of this parameter has been studied on the level of accuracy and description of velocity profile as well as prediction of dip phenomenon and location of maximum velocity. Many researchers have proposed different values for Coles Wake parameter. Thus, seemingly there is no universal constant value for this parameter. In this study, the value of Coles Wake parameter is proposed using 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 derived by the model agreeably match with experimental data, and predict the velocity-dip phenomenon. The model also contains few errors in comparison with the data measured in the channels. This shows a high level of accuracy in defining velocity distribution profile of the flow. The value of Coles Wake parameter estimated for channel-sewer is 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. Providing the details related to a new semi-fixed connection, its behavioral properties including hardness, ultimate capacity and ductility are investigated and compared with other modeled connections.To perform non-linear analyses of connection, the finite element software of Abaqus is used in this study. The main concern in this modeling is to have inter-component interactions with the most consistency with real specifications. Bolted connections and the exact interaction between the bolt surface and the hole are modeled as a hard friction, with friction coefficient of 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, two connection parts are stuck together, because the strength in this type of welding is like base metal. To mesh the element, C3D8R element is used. The behavior of high strength bolts A10.9, is modeled with the poly-line elasto-plastic stress-strain curve. The force is applied to samples according to the loading protocol presented by ATC-SAC, which in fact expresses real earthquakes.The proposed connection n1 has the most rigidity values among studied semi-rigid connections. Reducing the number of connection bolts decreases the connection rigidity value. With the half thickness for upper and lower plates, rigidity rate is reduced only 9%; Where half of the considered bolts are used, rigidity rate is reduced by 64%. Connection n3 has the lowest rigidity rate and its rigidity value is in the class of bolted connection in the seat angle to web angle.In high strength connections, the connection strength is highly related to girder strength, where the plastic joint is formed in girder. Connections with low strength will have the plastic joint in connection. Thus, they are not applicable 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 mechanisms discussed for the connections of this research have 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 plates. Also this connection has the ability to absorb energy.

Structural design for huge seismic events must explicitly consider the influences of response after the elastic range. The special moment frame (SMF) steel structures are designed such that the frame beam–column joists are able to absorb substantial energy through large rotational deformation. In this way, a major contribution occurs in the displacement ductility capacity of the system. One of the connections which is designed based on the concept of weakening the beam is the Reduced Beam Section (RBS) connection. The beam is weakened near its end, by trimming some parts of the flanges near the column face. In this way, the formation of the plastic hinge forcefully occurs in this region, because the RBS area acts as a fuse. Recent experimental results on RBS steel moment connections revealed that these connections tend to perform poorly by the early brittle fracture of the beam flange at the weld access hole. The measured strain data imply that the higher probability of base metal fracture in bolted web joints is -partly- related to the increased demand on the beam flanges. This demand is created due to the slippage of web bolt and the actual load transfer mechanism which is different from the one expected in connection design. Improvement methods include: using a better welding material and controlled welding process, using haunches at the beam-column interface (primarily intended for retrofitting of damaged frames), using cover plates on the beam flanges at the beam-column interface, and using a reduced beam section (RBS) at a prescribed distance from the column face. The RBS appears to be the most economic method and is already being used by structural engineers for welded SMRF structures in seismic zones. In this study, cyclic performance of RBS connection is studied in the numerical environment of ABAQUS. The investigated connection is a half-scale single-sided beam-to-column assembly. The cyclic load is applied at the tip of the beam. Pinned boundary condition is applied at the top and bottom of the column and is restricted out of plane displacement of the beam. The loading protocol proposed by AISC is used for cyclic loading. In parametric study of this connection, the effects of changing dimensions of the reduced area are investigated. Although the model gives reasonable predictions for the material deformation in the RBS, the designer must consider the material limit states, as this model does not predict local buckling or fracture in the RBS. Results reveal that the moment capacity of RBS connection is less than the moment capacity of a corresponding intact section connection. However, no plastic hinge is formed in intact section connection.

The scope of this study is to investigate the rehabilitation of concrete beam-column joints retrofitted by carbon-fiber-reinforced plastics (CFRPs), to achieve a safe and economic level of seismic damage. This paper, efficiency investigates the mentioned strengthening technique in improving the seismic behavior of damaged structures, analytically and experimentally. Four beam-column connections are tested under reversed cyclic loading. No specific seismic detail is used for connections, i.e. no transverse rebar and seismic stirrups are used in critical end zones of joint core, beam and column. Joints are damaged in different levels. Thereafter, they are retrofitted by carbon fiber 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 wrapping of FRP sheets until a limited level. This level is approximately equal to 1.5% story drift for tested joints. Specimens which were initially damaged with reference to 1% and 1.5% drifts showed an increase in their capacity up to 5% and 3%, respectively. This is called the repair-ability level and for the cases with higher damage levels, other rehabilitation methods may be useful.In order to simulate the behavior of joints, a numerical model was developed in the OpenSees framework version 2.4.0. The tested joints including reference joint and retrofitted joints are analyzed by nonlinear tools of the software. The software was selected regarding the available models for concrete and reinforcement rebar materials, which are enhanced with the consideration of reloading/unloading stiffness deterioration and hysteretic energy dissipation during reversed cyclic loads. Nonlinear beam-column elements with spread or concentrated plasticity can be evaluated in this software with accurate simulation. The analytical models are used to assess the efficiency of the CFRP rehabilitation to predict an optimum level of damage that the seismic behavior parameters could be compensated, safely and economically. 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. Thus, the model is calibrated for each level of damage intensities. 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 reported less than 10% comparing analytical and experimental results. Effect of other variables such as column axial load and the existence of transverse slab connected to the beam was analytically investigated. Results showed that increasing the axial load on the column results in increase in the load carrying capacity and stiffness from 5% to 12% (depending on the initial damage intensity of the joint). However, it had negligible effect on dissipated energy. On the other side, transverse slab modeling revealed an increase in the capacity, stiffness and energy. The positive effect was higher in the absence of gravity loads on the slab. Thus, the existence of transverse slab with gravity load had negative effect on secant stiffness in specimens with initial damage higher than 1.5% of story drift.

Rigid Body-Spring Models (RBSMs) 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 gives scatter-free microstress fields.

Stop-and-go traffic is frequently observed in congested freeways and is usually developed by a large traffic volume in commuting time by a lane block coming from incidents or road works, lane change maneuvers, sudden speed drop, and rubbernecking behavior. Traffic oscillation results in negative effects such as increasing fuel consumption and safety hazards. Speed drop of leader vehicle results in stop and go traffic in platoon from downstream to upstream. Follower vehicle drivers of platoon make different reactions to the receiving wave based on their behavior patterns. In this paper, behavioral patterns of follower driver are classified based on asymmetric microscopic driving behavior theory and traffic hysteresis in NGSIM trajectories. Vehicle trajectory data from Next Generation Simulation (NGSIM) program was also employed. Platoons of vehicles identified through a traffic disturbance were classified into deceleration and acceleration phases based on drivers’ behaviors and hysteresis in traffic oscillation. Drivers’ behaviors in the deceleration phase led to the classification of congestion into four behavioral patterns, based on the maneuvering errors of the follower driver, namely under reaction, under constant reaction, over reaction, and over constant reaction. Moreover, in the acceleration phase, traffic hysteresis was classified into two different categories: aggressive and timid behaviors. The two parameters of last deceleration wave which led to congestion i.e., d t, are calculated based on Newell’s car following model. The time of the two phases, stop and congestion phases, are identified based on follower vehicle trajectory. In order to calculate the time of the two mentioned phases, two points are identified in this paper: point of receiving the stop wave leading to congestion and point of entering congestion. As there are many parameters and errors of raw trajectory data, it is not important to illustrate target function, which is the main reason for developing the behavioral patterns. Effective parameters of behavior diversion in stop-and-go traffic are identified and analyzed at the microscopic level based on artificial neural networks (ANNS). Artificial neural network is a computational model, consisted of a large parameter space and an adaptable structure, which is inspired by the structure and functional aspects of biological neural networks. Artificial neural network is constructed based on learning various functions with actual and discontinuous vector values. It is created based on connecting several processors which relate input groups to the output by artificial neurons. A neural network consists of an interconnected groups of artificial neurons with activation functions, and processes information using a connectionist approach to computation. Neurons relate input and output groups to each other. Multi-layer perceptron (MLP) - used in this paper - belongs to the feed-forward artificial neural networks which are usually trained via the error back-propagation learning rule. Neural network models are developed to analyze the relationship between the microscopic parameters and the duration of the two phases. In this research, Crystal Ball software is used, as it can define the sensitivity analysis of behavioral diversion based on independent variables at the microscopic level. The software is linked to artificial neural networks in MATLAB using Excel software, so that, sensitivity analysis of the dependent variables to the independent variables can be performed by uniform probability. Based on three behavior patterns, the analyses results show that the two most effective parameters are the deceleration wave leading to congestion and the stop phase duration. Increasing the deceleration wave results in reducing the time between the two phases based on “over reaction-timid”, and its increase based on “under reaction-timid” and “pattern and over constant up reaction – timid”. In addition, results of stop phase leading to congestion, based on three behavior patterns, show that increasing the stop phase duration results in an increase in the time between the two phases.

Structural damage identification can be considered as the main step in Structural Health Monitoring (SHM). There are 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 by 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 determination of the damage characteristics including 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, these peak values must be inspected for determining the damage location and finding the maximum value. As a result, the element associated with a signal which has the maximum peak value, can be considered as the damaged element. Applicability of the presented method is demonstrated by studying three numerical examples. The first is devoted to damage identification in a four-story shear frame. It is assumed that all of the stories are equipped by sensors for recording structural responses. Three different damage scenarios with single and multiple damage cases are studied under two samples of earthquake records, namely El-Centro (1940), and Northridge (1994) earthquakes. In addition, the effects of using different wavelet mother functions and different input signals, such as displacement and velocity responses, are investigated in this research. Obtained results emphasize on the applicability of the presented method in damage identification. In the second example, a simple concrete beam is considered with ten elements for simulating two different damage scenarios. In this case, applicability of the method is inspected 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, the displacement time histories are used for damage identification. In order to reach a clear strategy in damage localization, two rules are proposed for judging about elements’ health. The rules are based on seeking maximum values of the wavelet coefficients in the damaged instants. Obtained results show the reliable performance of the presented method in finding time sequence of damage occurrence and damage location. In the third example, applicability of the presented method is investigated in the presence of complex damage models by defining bilinear stiffness reduction. Although the damage can cause some reduction in the effective stiffness of damaged structures of this case, the 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 among which side orifices have wide application in hydraulic and environmental Engineering. These flow diversion structures have been extensively used in irrigation and drainage networks, wastewater treatment plants, sedimentation tanks, etc. Therefore, Studying the pattern and characteristics of the flow -such as flow velocity components and free surface- adjacent to the side orifice would be important. In this paper, the flow over a sharp-crested rectangular side orifice in an open channel is simulated by FLOW-3D software. RNG k-e turbulence model is used to apply the Navier-Stokes equations and the VOF method is used to model the free surface profile changes. In the present study, the side orifice discharge and flow patterns are obtained by numerical simulation and are compared with experimental data of Hussian et al (2011) for model verification. The amount of the discharges through the orifice (both predicted by the present numerical simulation and recorded by the experimental research) are reported along with the relative errors which are about 8-9%. This shows 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.The effects of the side orifice crest's height (H) on the flow velocity components and free surface adjacent to the side orifice are also investigated. Results indicate that the discharge ratio (ratio of the discharge through the side orifice to the inlet discharge of the main channel) is increased with decreasing the height of the side orifice crest. Maximum and minimum values for longitudinal component of the velocity -for all heights of the side orifice crest- is reported at the beginning and end of the side orifice, respectively. By decreasing the height of the side orifice crest, these maximum and minimum values are respectively increased and decreased. Decreasing the height of the side orifice crest, the longitudinal component of the velocity in the vicinity of the side orifice is negative because of the reverse flow formed in this area. Examining the variation of lateral velocity component shows that this component is increased with decreasing the height of orifice crest. That is why the amount of discharge through the side orifice is increased with decreasing the height of orifice crest.The flow direction is upward at the height level of 0.25H; therefore, vertical component of velocity trough the orifice length is positive in all cases. On the other hand, the flow direction is downward at the height level 0.75H; thus, vertical component of velocity trough the orifice length is negative in all cases. Absolute value of the vertical velocity is increased by decreasing the height of the side orifice crest (H) because more flow is diverted to the side orifice. By increasing the height of orifice crest significant changes are reported 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 stories 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 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 that leads 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 the 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 the 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. Previous 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 health 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. 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. Thus, presence of damage in a structure is detected by inspecting at the wave parameters affected by the damage. The commonly used wave parameters are those 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.

Vertical shaft spillways have been widely used in a number of dam projects since the late 19th century around the world. Although a number of studies oriented to the shape of the inlet of shaft spillways including bell mouth inlet, there are lack of research studies regarding to the improved inlet shape of these hydraulic structures. A brief review of the former studies shows that most of those have focused on the bell mouth inlet to enhance the flow field thereby increasing the discharge capacity using complementary structural elements such as; anti-vortex plates, trash racks etc. Improving the hydraulic performance of different types of spillways was a major objective of several studies, resulting in different forms of spillway crests such as; piano key weirs and Daisy (Marguerite) shape inlets. Daisy (Marguerite) shape inlets which are the subject of the present study have been applied in some dam projects. Applying certain shape of inlets e.g. installing a Daisy (Marguerite) shape inlet over the shaft entrance is an alternation to avoid the swirling flow effects thereby to increase the shaft spillway discharge coefficient. Marguerite shape inlet has been used in different existing dam projects. Marguerite inlet is a unique inlet to increase the discharge coefficient compared to the other shapes of spillway crests. This is in part due to generation of spatially varied flow inside the Marguerite inlet blades, which makes it capable to pass greater flow discharges. Although different types of dam spillways have been the subject of different investigations, there is a lack of study on Marguerite-shape spillways.In this study, the effects of a Daisy (Marguerite) shape inlet on radial or crest control flow regime through shaft spillways have been investigated based on model experimentation. For the case of symmetry location of a vertical shaft spillway in the dam reservoirs, radial flow around the spillway should be considered to analyze the hydraulic performance of these spillways. Dimensional analysis has been used to determine the effective dimensionless parameters. Experimental study was conducted in a hydraulic model of vertical shaft spillway equipped with the Marguerite-shape inlets. Tests were performed in a circular cylinder of 2 meter diameter and 1 m high. The flow discharges through models of Marguerite spillways with different geometries (including; the length, the height and the number of blades) were ranged until a crest control flow was established. Tests were performed based on a wide range of geometric and hydraulic parameters to study as well as to evaluate the effects of each dimensionless parameter on flow hydraulic characteristics. To create a crest control flow condition, the flow was entered the main reservoir throughout a pipe inlet installed under the floor of the reservoir. Three-dimensional flow velocities were measured by an ADV installed over the reservoir with Frequency of 200 Hz. The water free-surface profile was measured using piezometers installed under the reservoir floor.Applying nonlinear regression analyses, empirical correlations were obtained for estimating the discharge coefficient and the threshold depth of orifice flow over Daisy (Marguerite) shape inlets.

Abstract: Soil stabilization with cement has for many years been a ground improvement technique for some engineering applications such as construction of stabilized bases under pavements, canal lining and engineered fills. This reliable and simple soil improvement technique can provide great advantages including increasing shear strength parameters and avoiding the use of borrow materials from elsewhere. The compressive strength of artificially cemented soils has been studied by many researchers. On the other hand, using additive fiber, glass, fly ash, silica fume and nano particle in cement stabilization industry has several advantages. There are few studies about the effect of natural zeolite as an additive material on the cemented sand. Natural zeolite, an extender, has been investigated for use as cement and concrete improver by some researchers. In this study, the use of a natural zeolite additive, as a potential improver of cemented sand is investigated. Natural zeolite contains large quantities of reactive SiO2 and Al2O3. Similar to other pozzolanic materials, zeolite substitution can improve the strength of cement by pozzolanic reaction with Ca (OH)2, can prevent undesirable expansion due to alkali- aggregate reaction, reduce the porosity of the blended cement paste and improve the interfacial microstructure properties between the blended cement paste. It has been observed that pozzolanic activity of natural zeolite is higher than that of fly ash but lower than that of silica fume. It was concluded that the clinoptilolite blend decreases the specific gravity of cements. There are several investigations about the relationship between unconfined compressive strength (qu) and voids/cement ratio of cemented sand. However, existing equations based on voids/cement ratio cannot estimate qu values of zeolite cemented sand mixtures properly. In this research, a series of laboratory tests have been performed to investigate the mechanical characteristics of zeolite cemented sand. The effect of zeolite, cement and porosity on behavior is evaluated in term of qu. Therefore, cilinopiolite kind of zeolite, Neka cement type II and Babolsar sand are used in this study. 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 in 7 and 28 days curing times. Results show qu and failure properties improvements of cement sand specimens when cement replaced by zeolite at optimum proportions of 30% after 28 days due to pozzolanic reaction. For 28 day curing time, by replacement percentage of 30 zeolite material by cement, the unconfined strength increased 20 to 80% in comparison with cemented samples by increasing shear strain. For higher cement content and less compacted blends, these improvement rates are more. The addition of zeolite to the cement sand mixture can makes increase strain at failure, and reduce brittle behavior. At the end, a power function fits presented to relate qu 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 drift demand and probabilistic seismic confidence level of geometric vertically irregular steel buildings. A series of vertically irregular steel buildings (known as setback buildings) with different setback ratios were designed based on the regulations in the current edition of Iranian seismic design code (Standard 2800). Foundation design of the structures was accomplished with the assumption of sandy soil with shear wave velocity of 200m/s under the footings. The three dimensional model of nonlinear soil-structure system was built in Open System for Earthquake Engineering Simulation (OpenSees). Concentrated plastic hinges at the end of frame elements were used to model the nonlinear behavior of these elements. Soil-foundation system of the structures was modeled with the Beam on Nonlinear Winkler Foundation (BNWF) approach. In this approach, a series of nonlinear springs are used to model the soil behavior under the dynamic excitation. Simplicity and efficiency of this modeling approach make it popular in soil structure interaction problems. The seismic analysis of the structures was performed under the simultaneous action of orthogonal components of real ground motions. Twenty earthquake records were used for this porpose. The selection of earthquake ground motions was accomplished based on appropriate specifications of earthquake components like magnitude, shear wave velocity, the distance from faults, and etc. Incremental dynamic analysis (IDA) was accomplished to estimate the structural performance of the regular and vertically irregular setback buildings from the linear phase of behavior to the nonlinear phase and up to the global instability of the structures. Based on the results, the median IDA curve was evaluated. This curve was used to estimate the structural performance objectives. 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 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 results, curves were generated to specify the confidence level of meeting a specific performance level for the 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 selected hazard levels have the return periods from 25 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 earthquakes with low to medium hazard levels (i.e. with the return period of 43 years). 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% reduction is observed in the performance based confidence level of flexible base structures. Meanwhile, 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 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/d Acrylonitrile to the atmosphere. The emission rate of Styrene and Acrylonitrile from pumps were estimated 36 g/d and 94 g/d, respectively. The results of using TANKS model indicated that Styrene and Acrylonitrile emission rates are 7 g/d and 22 g/d, 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 mg/m3 which is below the Reference Concentration (Rfc). In the case of Acrylonitrile the maximum level of estimated concentration was 272 mg/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.