نشریه مهندسی عمران مدرس
سال بیست و دوم شماره 5 (آذر و دی 1401)

Given the varying water demand for various hours of the day from different seasons, the pressure of the water distribution network (WDN) will vary at different times. In the event of a decrease in demand, the network pressure increases, and the excess pressure leads to increase the leakage from old connections and small fractures. One of the ways to reduce leakage is the network pressure management and reduce excess pressure, which it can be achieved by the pressure reducing valves.‏ But the question is, how many pressure reducing valves and at which points of the water network should be installed. In the first part of this study, the optimal location of the pressure reducing valves (PRV's) was found by the combination of the binary genetic optimization algorithm (GA) and real differential evolution (DE) optimization algorithm. For this purpose, the GA proposes the potential locations (pipes) for the valve installation to the DE algorithm, and it attempts to eliminate surplus head in the WDN by making changes in the Hazen-William coefficient of proposed pipes and creating a head loss on the pipes. These changes should be in such a way that the WDN's constraints like the minimum allowable pressure to be respected. The related hybrid algorithm was coded in MATLAB software and connected to the Epanet software as a hydraulic solver. After determining the hydraulic model of the water network and the number of PRVs by the designer, the proposed code determines the optimal installation location of the PRVs in order to the reduction of network background leakage. In the next part of the study, after determining the optimal location of the PRVs, the optimal set-point of each PRVs has been determined. To this end, a single objective differential evolution algorithm is used. The design variable of the optimization algorithm is the outlet pressure of the installed PRVs and the permissible pressure ratio on both sides of PRVs considered as a new network constraint alongside the minimum allowable pressure. The objective function of this optimization problem is minimizing of WDN's background leakage. After validating of presented codes, they applied on a local WDN in the north of IRAN, Guilan, entitled Mehr Water Network. The covered area of this network is 144 acres and its daily average demand is 366 m3 per hour. The altitude difference of Mehr WDS is about 4 meters and it has 371 pipes with the length of 33 kilometers, 366 junctions, one reservoir and a pump station with 3 pumps. Results show that installing two pressure reducing valves in determined locations and control them with DE optimization algorithm can reduce the surplus head and background water leakage from 21.9% to 12.3% (about 41.3%) On a full day. It is noteworthy that this method can be used in Supervisory control and data acquisition (SCADA) in order to pressure management of WDNs and leakage reduction. A calibrated hydraulic model of WDN, current state of valves and pumps and demand multiplier (obtained from installed flow meters or estimated demand profile) are required as the input of the optimization code to determine the optimum output pressure (set-point) of PRVs in SCADA telecontrol system.

In smart cities, with using lots of new technologies, while creating appropriate facilities in routine urban life, infrastructure problems are investigated and the necessary measures are taken in a targeted and systematic manner to solve these problems. One of the most important technologies for managing infrastructure in smart cities is IT technology. GPS and smartphone sensors are other technologies that can be widely used in these cities. Streets, roads, and pavements are important infrastructures in any city and the future smart cities. Proper supervision, repair, and improvement of pavements, streets, and urban pathways are the main factor in reducing the cost of depreciation of vehicles and providing comfort and safety for citizens. On the other hand, if timely action is taken to restore and improve the pavement, huge costs of repair and reconstruction will be avoided, and this can significantly reduce the costs of urban management. The first step to achieving this goal is to identify the location of the roughness and distortion of the surface of the streets and urban pathways and the severity of these failures in the shortest possible time. In this paper, road surface roughnesses and failures have been studied using accelerometer sensors and GPS smartphone devices. Location and vertical acceleration data have been entered into GIS software and a quantitative index based on the values of vertical acceleration has been introduced to determine the quality of each section of urban road pavement. In this research, Androsensor software, which is a useful application for using smartphone sensors, has been used. This software is installed on two smartphones, Huawei, P30 Lite, and BlackBerry, Priv STV100. To collect the data, the smartphones were placed in a fixed position on the right and left sides of the car, on the dashboard. The collected data for analysis is transferred to the computer in Excel files. This research has been done in Kerman city and to collect data, different routes with specific failures have been selected. Data collection was performed in 81 pieces with a length of 500 meters and 24 pieces with a length of 200 meters (105 pieces, 45300 meters in total). By analyzing the vertical acceleration data and calculating some proposed indexes and comparing them, the best index has been selected. This index is classified into different ranges according to the field inspection of the pavement condition in the routes in this study, that each of which indicates the quality status of the pavement. Each of these intervals is introduced with a specific color, and by examining the index obtained in each route and the corresponding interval, the studied routes are marked with different colors on the map. Finally, it was found that the accelerometer sensors and GPS of smartphones can be used with low cost, high speed, and appropriate accuracy to check the surface of pavement of urban roads and grading the quality of the pavement. It also seems that in the smart cities of the future, which are based on IT technology, the use of user data, high accuracy in locating, and speed of action in prevention, the proposed method in this research can be used more favorably.

Today, in building structures, concrete shear walls are widely used due to their desirable ductility and high energy dissipation. The presence of openings in the concrete shear wall changes the behavior of the wall and also creates new members in the wall, so the presence of openings in the wall behavior is very effective. Among the components of shear wall are the base walls and interface beams. A connecting beam is a beam that connects two shear walls created by an opening. The base of the wall is the vertical part of the wall that is bounded between the opening and the edge. Therefore, in this study, the behavior of eccentrically open concrete shear walls that have been reinforced by steel sheets has been investigated. In this research, a sample of concrete shear wall with eccentric opening with the name of reference sample has been validated in ABAQUS software. According to the definition of ACI318-14, one wall base is in the dimensional range of the wall and the other is in the dimensional range of the wall base. The samples were reinforced using vertical, horizontal and diagonal steel sheets simultaneously (in RCSW15 to RCSW20 samples) and in them different parameters such as increasing bearing capacity, strength, hardness, ductility and energy dissipation were studied. . In the RCSW15 and RCSW16 models, only the reinforcement around the opening is done by vertical and horizontal steel sheets. In the RCSW17 sample, horizontal, vertical and diagonal sheets are used simultaneously. The RCSW18 uses horizontal and vertical sheets in the opening corner. In the RCSW19 model, horizontal and diagonal sheets are used to reduce strain on the heel of the wall. In the RCSW20 sample, reinforcement is performed by horizontal and vertical sheets in order to increase the bending and shear capacity. Sample loading is lateral and cyclic. Among the reinforced designs of RCSW20 sample, the best design was selected because this design increased the final strength of the structure by 127.3%, increased the maximum strength by 13.42% and increased the crack resistance by 22.53%. It also increased the amount of energy consumed by 16.8%.

Marl soils with their complex behavior can be found in different parts of the world, such as Spain, the United States, Italy, Britain, France, Canada, and the Gulf states. In Iran, also, Marls can be located in abundance in the marginal zones of the East Azerbaijan Province, Persian Gulf, Hormozgan, and Qeshm Island. Marl soils' engineering behavior and durability in dry and wet conditions are entirely different and cause challenges in construction projects. Marl-like soils are widely observed in different parts of the world. The behavioral characteristics of marl typically depend on the distribution and size of the particles and their plastic properties. Under dry conditions, the deformation of marl soil is due to the breakdown of particles and creating a new structure. However, when this type of soil is exposed to moisture, the aggregate bond will degrade and cause swelling in the soil and, at the same time, a change in its hardness and strength on the other hand, many polluting industries are located on marl soils. Usually, the pollution caused by these industries changes the pH and creates acidic and alkaline conditions in marl soils. Therefore, this study aims to study the effect of initial pH on the durability of marl soils from a microstructural perspective.

In this regard, marl soils with different initial pHs were prepared by adding 1 M sodium alkali hydroxide (NaOH) and hydrochloric acid (HCl). Changes in geotechnical and geoenvironmental characteristics were investigated by macrostructural experiments (Atterberg Limits, permeability, and unconfined compressive strength, durability, and water absorption testing) as well as microstructural experiments (Laser diffraction particle size analysis (PSA), X-ray diffraction (XRD), X-ray fluorescence (XRF), carbonate percentage determination and scanning electron microscopy (SEM) images) and the effect of initial soil pH change on marl engineering behavior was investigated.

One of the most important results of the present paper is the durability and stability of marl soils with initial pH ≤4 against moisture. Based on the SEM images and XRF analysis results, the formation of magnesium chloride in the structure of palygorskite and sepiolite has caused the stability of marl soils with initial pH≤ 4. Also, the initial strength of marl soil does not affect the durability of indentation.

While studying large-scale systems, non-local damping definition can beneficially model contact shear and long-range forces resulting from adjacent and non-adjacent elements in the set of interconnected dampers, damping patches and foundations which are modeled as non-local domains. If two or three dimensional systems are considered one dimensional (e.g. analyzing three dimensional beams based on Euler-Bernoulli, Rayleigh or Timoshenko Theories which simplifies the behavior of structures), the concept of non-local damping models arises to improve the accuracy of numerical results. Even though defining dissipative forces which are dependent on more parameters and quantities helpfully boost the validity of results compared to experimental cases in labs and three dimensional numerical analysis done by software, many researchers have widely employed viscous damping model to demonstrate damped behavior of the structures in the sake of simplicity. Actually viscous damping does not model accurately the dissipative behavior of real systems and practical structures often demonstrate some kind of viscoelasticity while vibration.  In the recent study, external damping force at any point in the domain is influenced by the past history of velocity and long-range interactions through convolution integral over proper kernel functions. As a consequence of applying Laplace transformation and using Galerkin method, the integro-partial differential equation of Rayleigh beam as a distributed parameter system turns to an ordinary differential equation governing a discrete system with finite degrees of freedom. Galerkin method is established based on error minimization of assumed mode method and despite Rayleigh and Rayleigh-Ritz methods can suitably analyze nonconservative systems including damped beams. Corresponding undamped mode shapes of Rayleigh beam which satisfy essential boundary conditions are chosen as the best admissible functions to expand the trial response of equation of motion. In order to get  continuous functions and finite weighted residual integral, the equation is presented in the weak form. Afterwards stiffness, damping and two types of mass matrices are determined with respect to generalized coordinates. To get scaled mode shapes the mass change method is considered to evaluate scaling factor, then the results are mass normalized. By equating dynamic stiffness matrix to zero and solving the resulting algebraic equation, complex and real eigenvalues are obtained which are respectively elastic and non-viscous modes in stable systems. It’s noteworthy to announce that contrasted with the viscously damped systems the degree of algebraic equation in the case of viscoelastic non-locally damped Rayleigh beam would generally be more than 2N (which N stands for total degrees of freedom). Accordingly eigenvectors are found based on Gaussian elimination method and null space of the dynamic stiffness matrix. Additionally, Neumann series expansion is developed to determine eigenvectors of vibrating systems effected by inertia. Finally, numerical results of Rayleigh and Euler-Bernoulli beams are compared. Very thin Rayleigh beams are verified and show great accuracy but when the thickness increases and inertial effect becomes bold, results of Rayleigh and Euler-Bernoulli beams are not matched anymore. Furthermore it’s understood from the graphs and tables that when the characteristic parameter of nonlocality and relaxation constant increase and tend to infinity, the nonlocal and non-viscous effects decline.

Cement production is responsible for consuming 13% of energy along with producing 7% of CO2 worldwide. Using supplementary cementitious materials (SCMs) such as pozzolans could be helpful in this regards, while it could potentially improve the properties of concrete. The results of previous investigations have illustrated the fact that pozzolans partially replacing cement as binaries (one pozzolan along with cement), resulted in the improvement of concrete's durability parameters in many cases. On the other hand, one of the main uses of pozzolans is in self-consolidating concrete (SCC), a special concrete that has gain attention and popularity in recent years due to its specific properties. Recent studies on SCC containing ternary (two pozzolans along with cement) blends revealed impressive improvements in the mechanical and specially durability properties, outperforming both binaries and non-pozzolanic mixes. This was attributed to the fact that using pozzolans resulted in great decrease in permeability caused by their filler effect along with transformation of CH to CSH or CASH. Also their high blain causes significant improvement in the pore structure of concrete. In this context, capillary pores increase in number, each with much lower volume and diameter compared to non-pozzolanic samples. Another consequence of using these materials is less porosity of the interfacial transition zone (ITZ). Overall, the numerous beneficial effects of using pozzolans in concrete is well-established, and this could promote the use of more pozzolans in concrete.   Nevertheless, there has few investigations concerning the effects of ternary mixes on the durability of SCC, and studying the properties of quadratics mixes (three pozzolans along with cement) has been rarely done. On this basis, the purpose of this research was to study the effects of using binary, ternary and quadratic blends on durability characteristics of SCC. In this regards, two natural pozzolan, namely trass and pumice, were used as cement replacements at 0, 10 and 20% levels in mixes containing 10% silica fume. Various tests on the fresh properties of SCC including slump flow as flow ability and J ring as filling ability test were performed. As for hardened concrete, the 28 day compressive strength, velocity of ultrasonic pulses in concrete, water absorption, depth of penetration of water under pressure, Surface Resistivity toward Chloride Ion Penetration and rapid chloride penetration (RCPT) tests were considered.The results showed that binaries, only in compressive strength and to some extent in pulse velocity performed better compared to ternaries and quadratics. Also, it was concluded that ternaries slightly outperformed quadratics in terms of compressive strength, pulse velocity, and water penetration tests, whereas quadratics generally had slight superiority over ternaries in terms of electrical resistivity and rapid chloride penetration. Overall, choosing the best performance for each test result, using ternaries and quadratics decreased compressive strength, pulse velocity, water absorption, water penetration and rapid chloride penetration by 5%, 3%, 15%, 61%, 71% respectively, while increased electrical resistivity by 55% compared to binary mixture. In addition, all mixtures had desirable, water absorption below 2% and binaries, ternaries and quadratics had similar results with no significant differences.

Chloride attack is one of the most destructive phenomena that has an adverse effect on concrete and steel materials in reinforced concrete structures. Corrosion of rebars and damage of concrete can significantly reduce the seismic capacity of these structures over time. Accordingly, it is necessary to model the deterioration of reinforced concrete sections before performing nonlinear analysis to evaluate their seismic behavior. In this regard, Instruction for Seismic Rehabilitation of Existing Buildings (code No. 360) recommends that in order to consider the corrosion effects of reinforced concrete sections, the moment-curvature relationships used in the definition of plastic joints are corrected by a fixed number called the knowledge factor. Due to the fact that the deterioration process of concrete structures under chemical attacks is time-dependent and also there are various uncertainties in modeling this phenomenon, it seems that considering the effects of corrosion with only one constant factor, is not enough and in this regard, more research needs to be done. In this regard, in the present paper, the seismic behavior of a reinforced concrete flexural frame with a lifetime of 50 years under chloride attack on the external aspects of the columns was studied. For this purpose, in the first step, chloride diffusion is modeled according to Fick's law and then the measure of damage in rebars and concrete was calculated using MATLAB software. In order to increase the modeling accuracy, a probabilistic framework based on Monte Carlo simulation was used to consider the uncertainties. In the next step, Moment-curvature curves of the sections were extracted using the results of deterioration modeling and were compared with those recommended by code No. 360. After that, the seismic behavior of the flexural frame was studied using static nonlinear analysis (Pushover) based on the moment-curvature results obtained from the present study and the recommendations of Code No. 360. A summary of the results obtained in this study can be expressed as follows: Corrosion due to chemical attacks can change the behavior of reinforced concrete members over time from deformation-control to force-control. For this reason, the type of failure mechanism of these structures changes from ductile to brittle. In correcting the moment-curvature diagrams of reinforced concrete flexural frame columns using the knowledge factor of Code No. 360, it is necessary to pay attention to the actual behavior of the member subject to corrosion. Using the method used in this research, it is possible to predict the actual behavior of concrete sections under the chloride attacks during the lifetime of the structure based on the modeling results of cross-sectional deterioration. For the studied moment frame, it was concluded that in the first half of the structure life, the use of a knowledge factor 0.75 to modify the curvature, is appropriate to correct the behavior of column sections subject to corrosion. But in the second half of the life of the structure, it is better to correct the moment-curvature relationship by applying the knowledge factor to the moment. In this study, the diameter of the rebars, ductility of steel, and the compressive strength of concrete were considered as indicators of damage due to chloride attacks. Based on statistical calculations, it was concluded that the determination of the reduction in diameter of rebars over time has a higher uncertainty than the other two parameters. Therefore, further research is needed to provide a suitable solution to more accurately estimate this parameter.

Nowadays, helical piles as tensile anchors are widely used in industry. A helical pile is consisted of one or several bearing plates which are attached to the central shaft. A helical pile is installed in the ground by applying a torque on the shaft top together with a thrust force. The main advantages are the ease and rapidity in the installation, instant loading after the installation and no use of soil drilling. In this research paper, the tensile bearing capacity of helical piles in sandy soils is investigated experimentally in small scale. In most cases, the geometry of the bearing places is circular. Considering other geometries such as square or hexagonal may reduce the materials used in the pile fabrication and also, the effect of bearing capacity is not known in the engineering practice. The main aims of this study are to find the effect of the plate geometry as well as the number of bearing plates on the bearing capacity. To do so, helical piles were made up of steel with one, two and three plates with circular, square and hexagonal shapes. The cross section area of all the plates are considered the same. The piles were installed in a reservoir filled with dry medium-dense Firoozkooh sand by rotating manually the pile top. The pile top was drawn vertically under a uplift force. The loading process was performed according to quick method explained in ASTM D3689 standard. Having obtained the variation of force against the pile displacement, the bearing capacity of the pile were assessed. Four different methods were considered here to assess the average bearing capacity by considering different criteria mentioned in the technical literature. As the first step to find the best match theatrical formula, the pile bearing capacity with single circular plate was studied. By investigating several formulas, it is found out that the formula presented by Veesaert and Clemence (1977) matches well with the experiment and thus, this formula was used hereafter in all the analytical investigations. By comparing the experimental results with theoretical formulations, it can be said that the shear cylinder is the dominant mechanism which was observed in all the multi-plate piles. The results also show that the geometry of the plates clearly influences on the tensile bearing capacity. The piles with hexagonal and circular plates have the greatest and the lowest capacity, respectively. Based on the results, a shape factor is defined for the pile with hexagonal plates. The shape factor of the piles with square plate is obtained 1.20 which is consistent with other previous studies. For the pile with hexagonal plate, the shape factor is assessed as 1.34. It is also shown that this bearing capacity is correspondent to an equivalent circumferential circular plate. By using the values of the shape factors (for both square and hexagonal) and the analytical method, the bearing capacity of the piles with two three plates were assessed. A good match is observed between the results of the experiment and analytical method. Again, the results implicitly confirm the dominancy of cylindrical shear mechanism. Results also show that the increase in the number of plates does not necessarily increase the bearing capacity, but it depends on the plate geometry. The reason can be explained by the differences in the perimeter of the helices and accordingly, the effective soil weight which is considered as the generated wedge against the uplift. This can be justified by the results of analytical methods.

Most seismic hazard assessments are usually performed only with consideration of the initial shock in the technical literature of structural and earthquake engineering. While the magnitude of aftershocks that occur after the main earthquake, may be enough strong to cause a lot of damage to the structures. Most aftershocks increase the structural damage caused by the main earthquake because of cumulative damage and increased vulnerability may seriously threaten the safety of residents. The structures are designed for solely a single earthquake – design earthquake –  based on the existing seismic design codes. For example, these codes did not provide specific values for the actual relative displacement under successive earthquakes to assess the structural damages. Therefore, considering the effect of multiple shocks consist of fore-shock and main-shock or main-shock and after-shock seems necessary. Moreover, the construction of a new building is not economic and requires a lot of time, which is not easily available to many communities. Hence, the design of structures considering the some capabilities such as replacement of damaged elements can improved significantly the performance of structures after severe successive earthquakes. However, most of the proposed structural systems are not generally repairable while replacing several damaged members under the earthquake, can be very economic and applicable. The linked column frame (LCF) as a relatively modern lateral bearing system, is a type of dual systems; the recent emergence of this structural system has reinforced the need for multiple seismic studies. For this reason, LCF is selected in this paper and the deflection amplification factor (Cd) for this system is evaluated under critical earthquakes with seismic sequences. This coefficient is calculated based on the linear displacements obtained from linear static analysis and actual values from nonlinear analysis. In this regard, 18 steel frames equipped by the linked column frame as lateral bearing system, with 3, 7, and 11 stories are designed based on the Iranian earthquake design code (Standard No. 2800, 4th version – 2014). These frames are implemented in Opensees software and have been subjected to linear static, linear, and nonlinear dynamic analyses using critical earthquakes with/ without seismic sequence phenomenon to calculate the deflection amplification factor (Cd) and Cd/R for each of them based on Uang methaod. In order to better investigation of the mentioned coefficient, the effect of various parameters such as the length of the connection beams as well as the flexural or shear behavior of the connection beams have been considered. Thus, after the evaluations, the findings indicate an increase in Cd and Cd / R values, for the linked column frame with the connected column exposed to successive earthquakes. The increase of this coefficient has been more in short-frame frames. So that the most increase which hase been related to the 3-story frame with shear behavior and 2-meter linked distance, is about 11 percentage under the successive earthquakes. Also, the average results which have been obtained from consecutive earthquakes reveal that the proposed values ​​for Cd coefficient in the technical literature are not sufficient, and larger values ​​have been demanded.

Proper and timely maintenance of concrete pavement plays a decisive role in increasing the life of these pavements. Joint plain concrete pavement is a type of concrete pavement used for roads. One of the important parts of this type of pavement is the joints created in it. The use of joints to provide conditions for expansion and contraction in concrete pavements and thus reduce stresses due to changes in weather conditions (temperature and humidity), friction, and facilitate the manufacturing process. Due to the fact that the joint in the joint plain concrete pavements is a weakened area for the conduction of cracks from unforeseen areas of the concrete slab to it, the entry of water and other materials into it causes penetration into the underlying layers of the slab to prevent penetration. Joint Sealants are used in these areas. Hot applied bitumen sealant is one of the most common sealants used in joints, which is based on bitumen. One of the key factors in the longevity of concrete pavement is the proper functioning of the joint and joint sealant. The adhesion and cohesion failures are two main damage types in the hot-applied bituminous joint sealants in concrete pavement joints. The mentioned failures are caused by the contraction of concrete pavement under the temperature drop and fluctuation as well as vertical displacement due to passing traffic load. The failure in joint sealant causes elimination of water proofing feature in joints leading to penetration of water into the sublayers. Subsequently, the presence of water in sublayers results in pumping of water under the concrete slab, which leads to other failures types, such as faulting, blow up, corner break. The resealing of joint sealant is the commonly used approach to repair the joints, which takes considerable costs, times and environmental consequences. In recent years, induction heating has attracted substantial attentions among the pavement engineers for innovative applications, specifically for induced healing. The researchers used this method in asphalt mixtures to heal cracks and microcracks. To make the electromagnetic radiations more effective, they used bipolar additives such as activated carbon and carbon black to raise the temperature of the asphalt mixture and cover the cracks and microcracks. In this study, the induction heating and induced healing of asphalt binder was carried out in reaping the joint sealant and to recover the cohesion-adhesion failures. To this end, a new testing setup and frame were designed to conduct the tensile test on hot-applied bituminous joint sealant. First, the sealant bitumen was placed between two concrete blocks, and then the specimens were conditioned at low temperatures (i.e. -10 °C, -20 °C, and -30 °C). After conditioning, the tensile under a displacement controlled loading test was carried out until failure point of joint sealant. Subsequently, the broken joint sealants were exposed to the electromagnetic radiation in a microwave machine to heat and heal the joint sealant. Then, the tensile test was again conducted on the specimen until failure point. The results showed that induced healing can recover and heal the joint sealant experienced cohesion-adhesion under contraction loading. This observation indicates that the induced heating is a potential technique to repair the joint sealants in jointed concrete pavements.

Using a Tuned Mass Damper (TMD) in a structure, is a reasonable solution for absorbing its movements caused by external forces. However, when designing a TMD on the grounds of passive control, it is a challenging task as this device can be tuned once and for a specified range of frequency. Employing more than one TMD is another option; although this will lead to higher cost and might increase the base shear of the structure. In this paper, to provide a wide range of frequency and mode shapes in the analysis, nine types of steel structures are designed, having the story number of 4, 8, and 12, respectively, and then subjected to 22 acceleration records of FEMA-P695; These records, are a suitable choice for generating statistical results as they provide a wide range of magnitudes. Three of these structures are uncontrolled, and the remaining are equipped with a TMD on their roof, being of 0.5% and 1% mass ratio and considering the first mode frequency for the TMD design. The design of the TMDs is carried out via Den Hartog's formula.Using incremental dynamic analysis (IDA), fragility curves are created with constant 0.1g steps for PGA intensity measure. In addition, for considering the uncertainties in the performance of the TMD and the structure due to the changes in frequency, a 10% error is applied for the first mode frequency in the nonlinear design of the structures. The maximum drift ratio is used as a damage measure due to its simplicity and comprehensive coverage. Multiple earthquake recordings and their statistical characteristics, such as mean, median, 16%, and 84% of the recorded amplitudes and their more robust components, are utilized to examine the IDA curves to eliminate any ambiguity about structure response. This paper presents its novelty by applying a statistical method for choosing the mass ratio of TMD, considering the possible real-world quantities for this parameter and a wide range of frequencies for the excitations; therefore, limiting the TMD stroke. Subsequently, verifying the linear and non-linear behavior of the model used in this paper is carried out by modeling a 40-story steel structure equipped with a TMD situated on its roof and tuned based on its first mode under the Kobe Earthquake. Furthermore, the displacement response of the 4, 8, and 12-story structures, being equipped with a single TMD of 0.5% and 1% mass ratio, respectively, are compared to their uncontrolled state by exposing them to the Landers earthquake.Results show that using TMD reduces the maximum drift ratio of the structures. Considering the first 16% of the acceleration records, as expected, a 12-story steel structure equipped with a TMD of 1% mass ratio on the roof, presents the best results of maximum drift improvement ratio of 2.54%. Moreover, for reducing computational effort, another alternative is applying a limited number of earthquakes to the structure. By using the median for the duration and PGAs of all FEMA-P695 data to estimate this earthquake record, the maximum drift improvement ratio is then 1.61% for the twelve-story structure resulting in decent numbers compared to the first method. Moreover, all types of the 4, 8, and 12-story structures (uncontrolled, controlled with a TMD of 0.5% mass ratio, and controlled with a TMD of 1% mass ratio) were subjected to the Kobe earthquake, and their average roof displacements were compared. Among these three types of structures, the 12-story structure was recorded to have the highest rate of maximum roof displacement compared to its uncontrolled state, being 3.47%.

Considerable age of numerous concrete structures and due to some reasons like changes in design philosophy, increase in applied loads, etc., have made strengthening and maintenance compulsory. Shear failure in reinforced concrete beams is frequently sudden and brittle. For this reason, efforts are made to avoid this type of failure by strengthening them, especially in structures that were made with engineering mistakes and damaged structures. Steel, fiber-reinforced polymers, and carbon fiber-reinforced polymers are used as conventional solutions, but these methods have some drawbacks. For instance, prestressing them is hardly applicable, and the prestressing force decreases over time. Therefore, nowadays, as an alternative, shape memory alloys (SMAs) are investigated as new strengthening methods owing to their unique features. Shape memory alloys are novel and smart material groups that have been considered in civil engineering for many purposes, including active and passive control of structures, dampers, and strengthening of structures like reinforced concrete structures and bridges, etc., due to unique features such as pseudo-elasticity and shape memory effect. They have the particular property of returning to their initial shape by heating which is called the shape memory effect. If the SMAs prevented from returning to their initial shape by using mechanical fixation, a prestress force develops owning to the shape memory effect property. NiTi or Nitinol has been used for damping applications in civil engineering, and it has been investigated in the literature. Iron-based shape memory alloys (Fe-SMAs) have attracted much attention in civil engineering applications due to their shape memory effect. Particularly for strengthening applications, iron-based shape memory alloys have some benefits such as wide transformation hysteresis, high elastic modulus, and lower cost compared to conventional NiTi alloys. The advantage of shape memory alloys over fiber-reinforced polymer is that they can be prestressed more easily than FRP, and the prestressing force will not reduce over time. In addition, it does not require any mechanical and hydraulic jacks. Prestressing these materials has some advantages in strengthening. For example, cracks and deformations can be reduced or at least prevented from further growing, and the stresses in internal stirrups are reduced. The usage of prestressing for shear strengthening is rare because it is very complex from a practical standpoint. This study aims to assess the behavior of RC beams strengthened in shear with iron-based shape memory alloys. For this purpose, based on experiments in the literature, T-beams with 5.2-meter long are investigated numerically by using finite-element analysis software, ABAQUS. Three-dimensional finite element models were developed using the concrete damage plasticity and were verified with experimental results. Comparison between the results from the FE models and experimental test results confirmed the accuracy of the proposed models. Furthermore, the effects of parameters such as shape memory alloy diameters, prestressing force, and shotcrete thickness on beams' shear behavior are also investigated. The results of the analysis indicate a notable increase in the final shear strength of the strengthened beams and a reduction in stirrups' stresses. The prestressing ability of shape memory alloys delays the yielding of stirrups and the appearance of shear cracks and reduces the thickness of the cracks.

In this research, the adequacy of the method recommended by the Iran highway asphalt pavement code (Code 234) for pavement design is investigated. Pavement design in Iran highway asphalt pavement code is in accordance with the ASHTO method. Design variables in this Code are considered as Deterministic and without probability distribution; while the Average Daily Traffic (ADT), the annual growth rate (r), and the variables related to resistance such as modulus of elasticity and thickness of each layer, despite the segmentation, have many changes along a route. As a result, pavements designed on this basis may have a shorter useful life than expected and be destroyed in less traffic or age than the initial design. Iran highway asphalt pavement code uses a method similar to First Order Second Moment (FOSM) to consider the reliability in pavement design. FOSM is an old and simple method. This method has low accuracy in calculating the confidence level, especially for nonlinear functions. There are more accurate methods such as First Order Reliability Method (FORM) and Sampling for reliability analysis that eliminate the disadvantages of the FOSM method and perform reliability analysis more accurately for nonlinear functions. Therefore, it is better to consider the uncertainty of the variables and use accurate reliability methods to calculate the level of pavement reliability. A reliability-based method is proposed to improve the pavement design based on the Iran highway asphalt pavement code. To compare the two methods, traffic data and pavement condition of the Qom-Salafchegan route were collected. At first, the variables were considered Deterministic and without probability distribution, and the overlay thickness was calculated at a confidence level of 80% based on code 234. Then the most appropriate probability distribution of variables was determined by the Anderson-Darling test. According to the thickness of the overlay obtained from the Iran highway asphalt pavement code, the confidence probability of each section was determined by the FORM and Sampling methods of reliability in the Rtx software and Monte Carlo simulation in the R programming language. Based on Code 234, the pavement reliability was approximately 20% higher than that of the proposed method. Furthermore, based on this code, the required overlay thickness was about half of that determined according to the proposed method with an equal reliability level, which leads to was destroyed less traffic and lifetime than the design value and needed repair again. In the following different reliability, methods are compared with each other. According to the sampling method with a higher probability of failure than the FORM method, the required overlay thickness is determined and therefore, leads to a more conservative overlay thickness. To evaluate the accuracy of Rtx software, a Monte Carlo simulation is performed in the R programming language. It was concluded that Rtx results in the overlay design at a lower reliability level than the R programming language. In the ASHTO method, the logarithm probability distribution of wt18 and w18 variables is considered normal. This hypothesis was rejected by performing the Anderson-Darling test on the collected data and these variables do not have a normal distribution.

In recent years the use of nano materials in engineering projects has significantly increased. In fact, the impact of nano materials as a component in composite materials is one of the new horizons in engineering science. On the other hand, existence of heavy metal contaminated soils is one of the common problems in geo-environmental projects all around the world. In the process of retention of heavy metals by clayey soils, the pH of soil solution plays a significant role. In fact, an increase in pH of soil pore fluid causes a noticeable increase in contaminant retention. On the other hand, the use of additives in soil can increase the contaminant retention as well. In comparison with other additives such as cement, polymers do not require a long curing conditions. In addition, they have a positive impact on permeability of compacted soil, in which their presence decrease the soil permeability. In spite of several researches on the interaction process of clay minerals and polymer, there are very limited researches on the interaction process of polymer-clay minerals-heavy metal contaminant. Therefore, the main objective of this paper is to investigate the role of polyacrylamide polymer in retention of heavy metals in bentonite. To achieve the above mentioned objective, at the first step, the buffering capacity of polymer treated bentonite samples were measured. In this series of experiments, different concentrations of nitric acid from 0.002 to 0.02 molar were prepared. Then, 4 grams of bentonite and bentonite treated with different concentrations of polymer were poured in centrifuged tubes. Then, 40 cc of nitric acid were added to each centrifuge tube. After equilibrium period, the pH of soil suspension was measured and reported. In the second step of this research, two different series of experiments were performed. In the first series of experiments of this research, bentonite treated by polymer were exposed to different concentrations of heavy metal contaminants. In the second series of experiments, contaminated bentonite samples were treated by different percentages of polymer. The contaminant retention of these samples was investigated by performance of sets of batch equilibrium experiments. The achieved results indicate that the polymer treated bentonite sample (with 3% polymer), after exposure to 200 cmol/kg-soil has shown 19% increase in contaminant retention in comparison to bentonite sample. However, the addition of 3% polymer to contaminated bentonite with 200 cmol/kg-soil lead nitrate has shown 72% increase in contaminant retention in comparison to contaminant retention of bentonite sample. Based on the achieved experimental results it is concluded that there are three phases in heavy metal contaminants in interaction process of bentonite-polymer-heavy metal. These phases include retention by double-layer of clay, the contaminant retention in micro pores of clay minerals which are solidified by polymer, and the contaminate retention capability of polymer. According to the achieved results, the solidification effect of polymer has more contribution to the contaminant retention than the polymer buffering capacity. This proves that post-solidification of contaminated bentonite is a practical method for efficient prevention of contaminant transport in clayey soils.

Estimation  of  the  load  carrying  capacity  of  pile  foundation  is  one  of  the  most  sought  after  research  areas  in geotechnical   engineering.   Static   equilibrium   and   other dynamic equations are used to predict  the  axial  load  capacity  of  pile.  The  prediction  of lateral  load  capacity  of  piles,  used  in  tall  and  offshore structures is more complex and requires solution of non-linear differential equations. The elastic analysis adopting Winkler   soil   model is   not suitable for the non-linear soil behavior.  Estimating the load capacity of such piles using experimental methods is always associated with error and makes the modeling result far from reality. Today, intelligent methods have shown a high capability in predicting and estimating unknown variables and can replace experimental and analytical methods. In this research, we tried to accurately predict the lateral load capacity of piles in clay soils by creating an intelligent hybrid model called optimized relevant vector regression with the artificial bee colony algorithm. The relevant vector regression is a probabilistic method based on Bayesian approach. The relevant vector regression does not need to predict the error/margin tradeoff parameter C, which can decrease the time and the kernel function, does not need to satisfy the Mercer condition. For those relevant vector regression advantages compared with the support vector regression approach, relevant vector regression model is successfully applied in regression prediction problems. In this method, relevant vector regression is used as a predictive model and artificial bee colony algorithm is used to optimize the parameters of relevant vector regression method. The artificial bee colony algorithm is a swarm based meta-heuristic algorithm for optimizing numerical problems. It was inspired by the intelligent foraging behavior of honey bees. The algorithm is specifically based on the model for the foraging behavior of honey bee colonies. The model consists of three essential components: employed and unemployed foraging bees, and food sources. The first two components, employed and unemployed foraging bees, search for rich food sources, which is the third component, close to their hive. The model also defines two leading modes of behavior which are necessary for self-organizing and collective intelligence: recruitment of foragers to rich food sources resulting in positive feedback and abandonment of poor sources by foragers causing negative feedback.  In artificial bee colony, a colony of artificial forager bees (agents) search for rich artificial food sources (good solutions for a given problem). To apply artificial bee colony, the considered optimization problem is first converted to the problem of finding the best parameter vector which minimizes an objective function. Then, the artificial bees randomly discover a population of initial solution vectors and then iteratively improve them by employing the strategies: moving towards better solutions by means of a neighbor search mechanism while abandoning poor solutions.In this modeling, the data used are related to a laboratory data set of small-scale pile load capacity. Various statistical indicators were used to evaluate the modeling accuracy. Finally, the results showed that the combined relevant vector regression with the artificial bee colony algorithm for test data with R2 = 0.975 and RMSE = 0.001, has a high ability to predict the lateral load capacity of spark plugs. In addition, the sensitivity analysis performed in this study showed that the variables of eccentricity of load and the length of pile are more important and effective compared to other parameters.