نشریه مهندسی عمران
سال پنجاه و سوم شماره 5 (امرداد 1400)

The triangular in plan sharp-crested weirs do not have a direct and straight edge and are in good agreement with the broken line. The aim of the present study is to provide an equation for discharge coefficient (Cd) for these types of weirs. Cd is between 0.53-0.88 based on the observed data. For =15 degrees Cd has highest value and thus weir can convey maximum discharge. Using laboratory data based on h/p and α parameters, a regression equation was presented. The results of the regression equation were compared with the results of the numerical model (Ansys Fluent) and the results showed the high precision of this equation. Ansys Fluent software works based on finite volume method. The numerical simulation is 3D. In addition, the performance of MR-Linear and MR-nonlinear regression models on the application of the stage-discharge equation the triangular in plan sharp-crested weirs were investigated and indicated that the result of this equations is very similar to results of the experimental data. The results also showed that due to the angle of the triangular in plan sharp-crested weirs, the Cd is increased from 1 to 8 % to the suppressed weir. In a situation where the head on the crest of these weirs is low, they will show better performance.

In developing countries due to economic and social problems, resource and budget constraints, high risk in the construction industry, and other constraints, governments are unable to implement projects alone. The use of private-sector partnerships in recent years by governments and urban managers has been one of the most effective ways to further develop cities. However, many developing countries, including Iran, have always faced challenges in attracting private sector participation in urban infrastructure investment. Therefore, the present study aims to evaluate the barriers that governments and urban managers may face in attracting private capital. A qualitative method was used to do this. In this study, a structured questionnaire was used to collect information. A total of 60 experts' opinions were obtained from public and private sectors to identify and evaluate the barriers to private sector participation in urban projects. The barriers identified in attracting private sector participation were divided into three general categories, namely technical and organizational barriers, financial and economic barriers, and political and legal barriers. The results of the questionnaire were analyzed by SPSS software. According to the results, technical and organizational barriers are of the utmost importance in attracting private sector participation. Financial and economic barriers and political and legal barriers, respectively, were assigned the next degree of importance in attracting private sector participation, according to expert opinions.

The bridge pier scour is one of the major causes of bridge destruction worldwide. In spite of extensive research in this field, the study of this topic has always been of interest to researchers and it is necessary to study different methods to counter it. The collar is a simple and inexpensive structure for protection against bridge pier scour. In this study, the effect of collar size and height on bridge pier scour and determination of the best collar performance conditions in steady and unsteady flow conditions were investigated. The experiments used three different collar sizes and three different mounting heights relative to the substrate surface. After calculating the percentage of scour reduction in all test cases and comparing them, Investigation of time evolution diagram of scour hole and comparison of maximum depth of scour created in different states, It was found that increasing the size of the collar and decreasing the height of the collar installation relative to the substrate surface resulted in a further decrease in the depth of the bridge pier scour and this changes was more evident in the unsteady flow state. Also by comparing the two variables of size and height of collar installation, it was found that the height of collar with dimensionless ratio H/D=0.5 in steady and unsteady flow had the best performance and the greatest effect in reduction scour around bridge pier.

Economic concerns and environmental issues have led to increased use of recycled materials in cementitious mortars. In fact, to mitigate the adverse effects of cement, it can be partially replaced with recycled materials. In this paper, cement was partially replaced with iron, rubber, glass and eggshell powders (IP, RP, GP and EP) by 7, 14, 21 and 28% and then, compressive and tensile strength, water absorption and microstructure of the specimens were assessed. The strength tests, as well as microstructure analysis, were conducted at the age of 28-day and the water absorption was tested at the ages of 7, 28, 56 and 90 days. Based on the results, use of all powders by 14%, enhances the compressive strength up to 14%. Moreover, it was found that up to replacement ratio of 28%, the tensile strength is greater than that of the control specimen although, in the case of 7% admixtures, maximum tensile strength is achieved. In addition, water absorption of the specimens containing GP and EP up to 35% replacement ratio, is less than that of the other specimens, which was well observed in the SEM analyses.

Floods, as one of the natural disasters, cause irreparable damages to urban infrastructures, agricultural lands, and natural resources. Therefore, access to comprehensive information on effecting factors the extent of flood damage can be useful in estimating the extent of damage. Therefore, the aim of this study was to create a database of Effective parameters on flood destruction power using case study of Landsat-7 satellite images with ETM+ sensor and ASTER DEM data using decision tree data mining method. In this study, environmental parameters such as canopy, natural slope, and slope direction were considered in order to evaluate flood degradation power in the study area and the decision tree model was created using these criteria. Finally, based on these parameters, the number of changed pixels (after the flood) in the study area is 692361 which indicates 62312.49 hectares of degraded land in the study area. According to the findings of the present study, lands with low canopy characteristics, namely normalized differential vegetation index (NDVI) between 0.2 to 0.4, low slope 0 to 45 degrees and Southern slope direction caused the most damage caused by floods. Also, areas with dense NDVI, high slope, and northern slope orientation have preventative influence on floods-caused-damages. Finally, it can be concluded that the decision tree, as data mining method is capable of yeilding better accuracy and quality in determining the effective parameters in estimating flood destruction power by increasing the input variables.

Reinforced concrete shear walls are the most common used lateral resistance systems in steel and concrete structures, especially Mid-rise and High-rise structures. Investigates on buildings has also shown the proper functioning of these walls in controlling structural and non-structural damage and limiting the inter-story drift. Due to this fact, strengthening of concrete shear walls and studying the seismic behavior of them, can be important. Rehabilitating of these structural elements will have a significant effect on improving the structural response and behavior of the initial structure. Using the FRP composite sheets is one of the practical methods for strengthening of these types of walls. In this regard, it is necessary to know about these elements and how those effect on the seismic behavior of concrete shear walls. Literature review has shown inadequate study of the behavior of high-rise shear walls which strengthening with FRP rather than short walls. Due to this lack of studies, in this research the seismic behavior of high-rise shear walls which is rehabilitated with FRP layers has been studied. The main purpose of this study is on numerical modelling of sample shear walls –with Finite Elements Method (FEM) - and evaluate their seismic responses. Mid-rise and High-rise concrete shear walls have been modeled and analyzed using ABAQUS. These types of shear walls' behavior have been investigated with two types of strengthening layers (CFRP & GFRP) and two different arrangements. The results show increased in load capacity, ductility and energy absorption of sample walls rehabilitated with FRP layers.

The rigid base proximity (such as stiff rock) under a relatively thin sand stratum and employing a 3D reinforcement (e.g. geocell) can tend to significant improvement in the bearing pressure of shallow footings. In this study, the behavior of circular footings located on unreinforced and geocell-reinforced thin sand layer was investigated. The simultaneous or individual effect of footing dimensions, sand layer thickness, and geocell reinforcement on the bearing pressure and settlement was studied by conducting large-scale model tests. The influence of soil layer thickness on footing behavior was elucidated by considering optimum dimensions and location for geocell reinforcement. Based on the results, improvement in the bearing capacity and settlement reduction for both unreinforced and reinforced footing bed was seen when the sand layer thickness is lower than two times of the footing width. Additionally, the effectiveness depth of the rigid base for both cases was obtained two times of footing width. The combination of geocell reinforcement and rigid base as lateral and vertical confinement factors, led to increase in the bearing capacity and settlement reduction at the failure point up to 45% and 53%, respectively. The tests results were served to define new factors extending classical bearing capacity equations for footings located on thin soil at reinforced and unreinforced cases. The comparision of this study’s achievement with the previous investigations confirmed their good agreement.

Some factors such as soil mass settlement, earthquake activities, and hydraulic failure causing tensile forces in the earth's structures and, consequently, cracks creatoin and development of water leakage from cracks. In this study, in order to reduce possible damage caused by cracking and its extension to the erosion of internal structures, the effects of nano-clay on the self-healing properties of clayey soils have been investigated. In this study, the effect of nano-clay additive, pressure and time elapsed on crack restoration in clay was evaluated. In order to perform experiments, two types of cracks with thicknesses of 0.5 and 1 mm with a depth of 50 mm created in the samples and the montmorillonite nano-clay was used as an additive. Twelve tests with different percentage of nano-clay, without pressure and at pressures of 50 to 500 kPa in two steps after the cracking (first day) and 24 hours after the creation of crack (second day) was performed for samples with a thickness of 0.5 and 1 mm. The flow rate is measured in all tests and was the basis for judging the impact of each factor. The results show that when the cracked sample is made with one millimeter, under non-pressure conditions, in about 60 minutes, approximately 500 ml of water passes through the crack. However, when the sample contains 2 and 5% nano-clay, the amount of water passing through the crack within 60 minutes, would be 40 and 5 ml, respectively.

The use of crumb rubber to modify the binders has been the interest of researchers for many years. It has been proven that the use of asphalt mixtures containing crumb rubber is leading to improve performance and increase the durability of asphalt pavement. However, increasing the viscosity of rubber modified binder which increases mixing and compaction temperature of asphalt mixture, known as one of the disadvantages of using crumb rubber. So, there is a good concept for using warm mix additives to besides improving the performance of asphalt mixture, reduce energy consumption and environmental pollution also be considered. On the other hand, binder has an important role in investigation of the performance of the asphalt mixture. It is also time-consuming and costly to evaluate the properties of asphalt mixtures. Evaluating the performance characteristics of the binder helps in understanding the performance of asphalt mixtures against various types of damage. The main objective of this study is to investigate the effect of organic warm mix additives (waxes) on the rutting performance of rubber modified binder by using the Multiple Creep Stress Recovery test. Because, it was found that the MCSR test results have a good correlation to rutting than SHRP criteria. The results of this study show that the use of polypropylene wax in addition to increase rutting resistance of rubber modified binder also will lead to increase in pavement traffic level by one degree. Despite of this, slack wax reduces rutting resistance of rubber binder by increasing the Jnr parameter.

The presence of organic matter in soil reduces its compressive and shear strength. It is, therefore, not suitable for construction projects. Soil strength can be enhanced by various methods. Stabilization and reinforcement are two common ways of improving soil strength parameters. In this study, the effect of polypropylene fibers on stabilized soil was investigated. For this purpose, lime and xanthan gum biopolymer were used as stabilizers, and soil was reinforced with polypropylene fibers. The experiments were performed using 1 and 3% lime, 1 and 1.5% xanthan gum biopolymer and 0.5% polypropylene fibers (by dry weight). To investigate the effect of these materials on soil strength, uniaxial compression strength and indirect tensile strength tests were conducted. The processing time of the samples was 7 and 21 days. The results showed that the addition of lime, xanthan gum biopolymer and polypropylene fibers can increase the compression strength of soil. Increasing the processing time can also increase the strength of stabilized soil, and addition of fibers leads to the improvement of soil ductility. The maximum tensile strength was observed in the sample stabilized with xanthan gum biopolymer. In the soil sample with 1% lime, the addition of fibers could increase the soil tensile strength. The results suggest that soil strength parameters can considerably be improved if xanthan gum is replaced with lime. In addition, this material is environment-friendly.

This article addresses the question of how the use of helical piles will improve the uplift capacity and displacement. Shahriar sand has been used with the relative density of 70% and the compression operation has been performed using hammering. The universal Zwick/Roell Z160 apparatus has been employed for tensile. With regard to the dimensions of the apparatus, the sand container was designed and physical modeling of the helical pile has carried out using dimensional analysis and nondimensionalization by Buckingham π theorem. After fabricating of the pile sample with pitch of 13, 20 and 25 mm, the behavior of simple and helical piles were investigated and the effect of pitch was examined. The maximum uplift capacity and its associated displacement were extracted and analyzed. The results show that the maximum uplift capacity of helical piles with pitch of 13, 20 and 25 mm in comparison with the simple pile increased 453.57%, 518.66% and 436.24%, respectively. When the ratio of the pitch/central shaft diameter is between 1 and 1.5, the tensile capacity is improved by the generated friction and the weight of sand on the blade as a resisting factor. By increasing the ratio of S/d to 1.92 the blade torsional angle increases and the sand weight on the blades decreases. Therefore, the uplift capacity is reduced compared to the previous two. The outputs show that the displacements of helical piles are approximately equal.

Excavation of tunnels can cause the earth to move, which is significant in the static and dynamic response of structures. In this study, the effect of a tunnel excavation in Tehran city on the dynamic and static response of structures in three section has been investigated. In the first part, PLAXIS software calculates the following two step session before and after excavating. The second part of PLAXIS also performs dynamic analysis for both stages and the following acceleration response is calculated. The purpose of the second part is to investigate the impact of excavating on acceleration response and its use in SAP 2000 software as input for structural analysis. In the third part, structure in modeled in SAP 2000 software and the results of the first part of the displacements of footing are applied and by using accelerating response, the structure`s nonlinear dynamic analysis is performed in two stages (PLAXIS output). The results of the analysis show that the tunnel excavation has increased the subsidence of foundation subsurface and the highest subsidence is in 6th model (Operation stage), which is 1.2 times the average of the previous one. The excavation has increased and the impact of the supporting structures during the execution phase compared to the operation stage where the concrete side walls are executed, has been effective in reducing the subsidence by 4% and maximizing the acceleration below 1.5 times and also in the structures the displacement increased by 1.25 times compared to the pre excavation phase response.

In this paper, a new meta-heuristic optimization method called the Jump of Circles Optimization Method is introduced. In any optimization problem, an answer zone is defined in which the optimization algorithms search the space to find the optimal answer. The method presented in this paper, uses two important pillars in searching the answer zone. The first pillar is to use the geometric principles. The Jump of Circles, uses the circle with decreasing radius. The second pillar is to use the meta-heuristic application. In meta-heuristic algorithms, the search points distribute randomly and jump in answer zone. In the proposed method, the center of the searching circle jumps and sits on the optimal point of each step. The proposed algorithm solves the optimization problem in two phases. The first phase is optimal area exploration and the second phase is exploiting the exploration. Finally, the most optimal point that will be obtained from the two phases, is the optimal answer of the problem. This paper focuses on engineering problems. So, to check the proposed method, three truss benchmark problems is solved. In addition, the Keane's bumpy function is solved using the Jump of Circles Optimization Method. The answer obtained from the proposed method are compared with some conventional methods and are presented in the paper. The superiority of the proposed method is observed clearly.

Damage detection is a topic of great importance for structural health monitoring. Many varieties of structural damage can be detected by examining changes in structural response in terms of stiffness. Wavelet transform is a powerful mathematical tool for the processing and time-frequency analysis of transient signals and has great potential to be used in structural damage detection. In FRP-strengthened reinforced concrete and steel sections, stiffness changes can be caused by cracking, yielding of steel components, crushing of concrete, or rupture of FRP panels. With the help of wavelet transform, it is possible to use the continuous measurements of the response to bend or torsional loading to estimate the capacity of the cross section corresponding to the stiffness changes. In this paper, bending of FRP-reinforced steel beams filled by concrete under bending and CFRP-reinforced concrete beams under pure torsion is evaluated. The results show that the location of the damage appears as perturbations in the diagram of discrete wavelet coefficients, which indicate the time of cracking, yielding of steel, crushing of concrete in the compression zone, and rupture of FRP. Therefore, a wavelet transform-based data processing procedure can be used to estimate the cracking and yielding capacities of the beams subjected to torsion, the yielding capacity of the steel and the ultimate capacity of the beams subjected to bending. The results demonstrate a high level of agreement between the estimates obtained from the discrete wavelet transform method and the examined experimental and numerical data.

In this study, the performance and efficiency of cable in control of local scour around the pier of the rectangular bridge has been investigated by changing the flow collision angle. In this study, three types of piers, namely: 1.round corner rectangular without cables, 2.round corner rectangular with cable with 10 % of pier diameter with a 15-degree twist angle of cable (second type pier), 3.round corner rectangular with cable with 15 % of pier diameter with a 12-degree twist angle of cable (third type pier), were used with four different flow collision angles, including 0, 5, 10, and 15 degrees.The purpose of this study is wrapping the cable around the pier and changing the flow collision angle from the downstream flow water and then its effect for the reduction of the depth of the final scour measure. In this experimental study, the effect of flow angles on the pier was investigated, so that the first type pier under zero degrees angle was compared with the second and third types parallel to the flow direction. The maximum scour depth in experiments was achieved at the 15-degree angle with the flow direction, and the effect of the cable in reducing the scour depth in this angle for type-2 and type-3 piers was 10% and 22%, respectively. Also, for type-2 piers, in experiments under 5, 10, and 15-degree angles with the flow direction, the scour depth was increased by 3%, 21%, and 37%.

In this paper, a new nonlinear static (pushover) analysis method is presented to evaluate the displacement-based demands of steel moment resisting frames (MRFs) at the collapse prevention performance level. In this method, the modal pushover responses are integrated using modal combination coefficients, which are calculated from optimization procedures. Two metaheuristic algorithms, including particle swarm optimization and colliding bodies optimization, are utilized in for this purpose. In the proposed procedure, the collapse prevention performance level is obtained by a new suggested criterion, which is based on the onset of severe local damages at the structure. This criterion corresponds to occur backward shape in the story capacity curves. The modal combination coefficients are obtained from incremental dynamic analysis (IDA) results of 5, 9, and 11 story steel moment resisting frames. The optimized modal pushover (OMPA) method is applied to two 9 and 12 story steel MRF buildings. The results show that the proposed method is easy to implement and is accurate enough to evaluate the displacement-based responses at the CP performance level.

In this study, the macro modeling of masonry structures is used based on homogenous models, and an equivalent planar-frame model based analytical method is proposed for the purpose of masonry structures assessment. The equivalent frame model is a simple applicable approach which is almost accurate and time saving. Also, it holds proper convergence compared to the exact analytical and experimental methods. In the formulation of beam column elements, distribution of nonlinearity is chosen. Nonlinear constitutive model is simulated in the cross-sections and length-sections by the usage of fiber elements. For the consideration of shear behavior, bed joint sliding mode of failure and diagonal tension mode, smeared crack approach based interface element is developed in the Matlab framework. To consider seismic assessment of masonry walls, constitutive models is considered according to Instruction for Seismic Rehabilitation of Existing Buildings (No. 36) through a subroutine in main program. The accuracy of suggested approach is verified through comparison of experimental results and existing analytical methods.The comparison of experimental results with numerical results shows a good agreement.

Ali Abad Plain of Qom Province, located in the center of Iran, is among the areas recently affected by subsidence phenomenon due to water overexploitation. In this research, using the differential radar interferometry and Sentinel-1 images, vertical land deformation was monitored for an 18-month period from March 2015 to September 2016. The results showed a maximum subsidence of 240 mm. Moreover, it was found that subsidence in this plain is a progressive and continuous phenomenon with an almost constant spatial distribution. Next, groundwater table fluctuations were measured in Saveh Plain for a 14-years period ranging from September 2002 to September 2016. The results showed a maximum water table decline of -44 m. Comparing the ground deformation map with groundwater level fluctuation map revealed a direct relation between spatial distribution and ground deformation intensity and groundwater drop. In addition, comparing the alluvium thickness variations with ground deformation indicates that the alluvium thickness of the Ali Abad Plain varies from 20 m in its eastern part to 300 m in the western and central areas. The results do not show any significant relation between these two parameters in the study area. Moreover, it was found that layering type and the presence of thick fine-grained formations are among other factors affecting the intensity and rate of subsidence in the plain.

Effect of feeding rate of crushing product was investigated on product particles size distribution by fractal dimension. particle size distribution was calculated according to the cumulative weight of the particles relative to particles size. A comparison between results obtained by Rosin-Rammler distribution and ones obtained by fractal geometry was made by root mean square error (RMSE). Comminution of ore was performed by three jaw, cone and roll crushers, each fed by rates of 0.5, 1, 1.5, 2, 3, 4 and 4.5 kilogram per minute. Fractal dimension of products for jaw, cone and roll crushers were (from 2.18 to 2.32), (from 2.12 to 2.27), and (from 2.30 to 2.43) respectively. Smallness of fractal dimension by cone crusher is due to particles uniformity. Bigness of fractal dimension of roll crusher is due to limited range of particles granulation. Limitation range of particle granulation causes uniformity of product weight distribution. A 2 mm opening sieve was selected as a passing target sieve. Results show that by increasing feeding rate, amount of material passing through of target sieve is decreased. The RMSE obtained by fractal geometry for jaw, cone and roll crushers were (between 8.01 to 8.60), (between 3.50 to 4.17) and (between 0.83 to 2.62) respectively. These ones obtained by Rosin-Rammler distribution were (between 8.11 to 8.60), (between 4.50 to 4.93) and (between 3.91 to 7.91) respectively. A comparison of results obtained by these two methods reveals that fractal geometry is a better way to particle size distributions description.

Due to the thickness and low weight of the parts made of glass reinforced concrete, it is impossible to use reinforcement in the manufacture of these products. For this purpose, glass fibers are used to improve the concrete behavior under tensile and flexural loads and to increase the toughness. Glass fiber reinforced concrete can be used to make parts in different shapes and designs.This paper uses glass fibers and pozzolanic materials with different percentages. In order to investigate the flexural strength and toughness indices of concrete produced by pre-mixing and spraying methods, 15 mixing designs containing different percentages of glass fibers and pozzolanic materials in pre-mixed method and 14 mixing designs with spraying method have been tested. All mixing schemes were also tested at 350, 650 and 1000 ° C and the results were analyzed by scanning electron microscope (SEM). The use of pozzolanic materials in specimens reinforced with glass fiber improves the modulus of rupture. The modulus of rupture in the presence of heat and in the event of a fire is greatly reduced, which is a better performance for controlling this reduction process. Also, the flexural strength of high-temperature samples (1000 ° C) can be significantly increased by using methaquoline at different percentages of 10 and 15%.

In this paper, the seismic response of base-isolated and fixed-base concrete structures with soil-structure-interaction effect was investigated. The structures with 4, 8, and 12 stories with lead rubber bearing isolators on three types of soils including soft, medium, and firm soils as well as on rigid foundation modeled using OpenSees software v 2.5.0. The ACI 318-02 code was used to design of RC intermediate moment frames. The incremental dynamic analysis was performed to determine the structural response under six near field and six far-field earthquakes recorded with the same seismic parameters but with different stations. The inter-story drift ratio and failure probability for each level of damage (slight, moderate, extensive and complete) were calculated and the fragility curves for maximum inter-story drift in different levels of PGA were drawn. The results indicated that considering the soil-structure-interaction decreased the structural damage on both isolated and fixed base structures. Softening the soil under isolated structures resulted in increasing the median fragility acceleration in each level of damage. Furthermore, considering the soil-structure-interaction effect in the low-rise to medium-rise structures (4 and 8 story buildings) has a more significant effect on median fragility accelerations than high-rise buildings. While, the effect of the base shear on the 12-story frame was more considerable.

In the current study, it was tried to determine the mechanism of the tracer penetration through the depth of the river beds to investigate the self-purification nature of the rivers. For this purpose, experimental tests were carried out, and an analytical solution was developed. The electrical conductivity sensors and sodium chloride tracer (as a conservative contaminant) were operated in the operations. Also, for the derivation of the analytical equation, a conceptual model was presented based on the hybrid cells in series model. Then, by imposing the mass conservation to each cell of depth column, the governing differential equation was obtained and solved. Next, the results were evaluated by the framework of the developed equation. Moreover, the applicability of the new model was checked and confirmed by the recreation of the breakthrough curves. The time parameters of the new model were extracted. Then, their variation by the other parameters was queried. It is observed that the sum of temporal parameters (α,T_1,T_2) have a reverse relationship with the vertical dispersion coefficient. On the other hand, its value has been raised by an increment of the bed depth. Furthermore, the product of void scale and the pore velocity has been used for calculation of the vertical dispersion coefficient. Also, the magnitudes of the pore velocity and dispersivity were commuted. It is revealed that by the increase of the bed depth, the mentioned parameters were decreased.

Portland cement production has caused problems such as air pollution, energy consumption, loss of natural resources, exacerbation of greenhouse effects and global warming which have some economic issues. The use of pozzolans in the production of concrete decrease the negative points of the above mentioned problems and improves the mechanical properties and durability of the concrete in long run. In this paper, the effects of Taftan natural pumice powder and silica fume are investigated on the mechanical and durability properties of concrete. For this purpose, 18 concrete mixes were considered for two water to cementitious materials ratios of 0.4 and 0.45. Taftan natural pumice was replaced for Portland cement at 0, 10 and 20 percents and silica fume at 0, 7 and 10 percents. The results showed that using Taftan natural pumice improves the mechanical and durability properties of concrete. After 90 days the highest values of compressive strength, tensile strengths and sulfate resistance of mixes containing 10% Taftan natural pumice, 10% silica fume and mixes containing 20% Taftan natural pumice, 10% silica fume were achieved. For these mixes the capillary absorption and electrical resistance results were better comparing to the other mixes, too. On the other hand, the use of the Taftan natural pumice instead of a percentage of Portland cement has reduced the cost of production concrete.

In this study, a new method is presented to solve the geometry and sizing optimization problems of truss structures using an effective hybrid of cellular automata (CA) and gravitational search algorithm (GSA), which is named CA-GSA method. The basic of the GSA is the Newtonian Gravity and Motion laws. Due to the direct effect of all objects on each other and the lack of attention to elitist selection, this algorithm converges to a local optimum point. In this study, with the help of the CA method, masses are distributed in a finite cellular network, and each cell is only related to its neighbors. In the CA-GSA method, the laws of gravity and motion of masses in the GSA method are defined as the relationship factor of each cell to its neighboring ones. Therefore, the applied force on each mass is obtained from the resultant force of its top neighboring masses. The definition of these top neighboring masses and their applied force on the central mass add memory and elitist selection to the GSA algorithm, respectively. Another advantage of the new method is to update the cellular network after any local evolution, which makes it possible to achieve the optimal point using fewer analyzes. To investigate the usefulness of the proposed method, the CA-GSA method was used to solve the geometry and sizing optimization problems of four benchmark truss structures. The results of CA-GSA show the superiority and power of this algorithm in comparison with the methods introduced in the literature.

Permeability is one of the most effective parameters on concrete durability. Therefore, in this paper penetration of water into concrete is studied. Although most of the researchers have considered the coefficient of permeability obtained from one dimensional Darcy’s equation, in the present paper due to movement of water in all directions, two-dimensional diffusion equation which defines penetration of fluid into a porous material has been used for first time. For this purpose, cubic concrete specimens with different W/C ratios were prepared and their permeability was measured using “Cylindrical chamber” method. In this method, applied pressures and durations of water penetration were varied. The two-dimensional equation considered, was solved using Laplace and Henkel transformations and the obtained results were compared with the “Cylindrical chamber” results. Comparison of the theoretical and experimental results showed that the average respective percentage errors calculated for the estimation of wet curve, maximum penetration depth, average penetration depth and wet surface were 23.07, 13.64, 21.41 and 1.66. The coefficients of determination between pressure magnititude and duration of water penetration, considering the variables of maximum penetration depth, average penetration depth, wet surface, penetrated volume and optimum diffusion coefficients were seen to be higher than 0.95. Furthermore, no reliable correlation was observed between the optimum diffusion coefficients and the mentioned variables.

Ski-jump bucket spillway is one of the energy dissipation structures applied at downstream of spillways or bottom outlets. In this study, the effect of the convergence angle of the ski-jump bucket on the flow energy dissipation was experimentally investigated and the results were compared with the conventional bucket model. For this purpose, four convergence angles of 10, 20, 30 and 40 degrees were created using deflectors in the bucket. The effect of adding a dividing wall, in two modes of bucket splitter wall (BSW) and full separator wall (FSW), on the conventional and convergent buckets were investigated. The results showed that the flip buckets dissipated about 60 to 65 percent of their energy. At a 20-degree convergence angle, the energy dissipation of the flow increased by about 5 percent, however, at a 30-degree convergence angle, the energy dissipation decreased by about 15 percent. In general, the energy dissipation decreases by increasing the flow discharge. Adding a dividing wall to the bucket does not have a significant effect on energy dissipation, although adding a separator wall to a converged bucket eliminates the effect of reduction in the energy dissipation due to convergence of the bucket. By mounting the dividing wall on the bucket, a local disturbance is created in the flow pattern, however, the resulting loss is not significant compared to the energy dissipation caused by the jet colliding with the bottom of the stilling basin. Whereas full separator wall (FSW) divides the bucket into two parts and it doesn't cause major disruption to the flow pattern.