نشریه مهندسی عمران مدرس
سال بیستم شماره 4 (مهر و آبان 1399)

Given that terrorist operations have increased in recent decades, it is therefore necessary to confront the dangers of this phenomenon. The explosions can cause severe damage to buildings and cause the progressive and complete destruction of these structures. Blast stresses are one of the most destructive loads which a structure may experience. Many of the existing structures are vulnerable to loads caused by the blast wave, so their resistance to such loads should be investigated to identify critical points of structures. In the meantime, bridges are considered as the vital available structures for terrorist operations, but with respect to their importance, solutions must be provided to reduce the vulnerability of bridges subjected to explosive loads. This paper investigates the behavior of bridge under blast loads in different weights and distances. Several experiments samples have been modeled and analyzed under blast loads for validating the results at finite element ABAQUS software, and the analyses showed that this software is able to predict the behavior of studied systems under blast loads. In this case, a bridge that has been located in Tehran, Shahid Saniechr('39') Khani bridge, was chosen and investigated by utilizing ABAQUS. This bridge was subjected to blast loading substance, TNT, in different weights of 45.4, 100, and 150 kg and in different distances of 0.5, 1.2, 1.83, 2.54, and 3.83 meters from the center area of the bridge’s slab. Additionally, a new system U-boot named was added to the initial model for investigating its influences under blast loading.  To conclude, firstly, increasing the amount of exploding substance (in a fixed distance from the center of the slab) cause an increase in the slab displacement and subsequently the damage in the slab is being increased. Secondly, increasing the exploding substance from the center of the slab and assuming a fixed weight for it in both first and second cases showed that increase in the amount of distance could lead to decreasing the displacement in slab and subsequently the damages decreases. Finally, adding the U-boot system leads to incredible improvement in the whole model in comparison with the initial one.

Two-way slabs are one of the common structural systems. The benefits of such systems have led to extensive use of them in building construction. However, these systems are prone to pushing shear problem which causes sudden failure. There are lots of equations to predict punching shear of slabs. The main proportion of the existing equations are based on statistical results from previous experimental studies. However, these equations are approximate and have large errors. Therefore, more exact and reliable equations that can estimate punching shear capacity are desirable. The aim of this study is to propose an applicable method to predict punching shear in thin and thick slabs using artificial intelligence. For this reason Genetic Programming (GP) and Biogeography-Based Programming (BBP) are employed to find a relationship between punching shear and the corresponding effective parameters. GP that is inspired by natural genetic process, searches for an optimum population among the various probable ones. Two main operations of GP are crossover and mutation which make it possible to form new generations with better finesses. Unlike the GP, BBP is a Biogeography-Based Optimization (BBO) technique which is inspired by the geographical distribution in an ecosystem. BBP employs principles of biogeography to create computer programs. First, 267 experimental data is collected from the past studies. Next, using the aforementioned algorithms, a relationship to predict punching shear is proposed. To evaluate the error of prediction, several error functions including RMSE, MAE, MAPE, R, and OBJ are utilized. Matlab software is used to build the models of prediction. 10 different models are built and the one with the minimum error is selected. Based on the results, GP3 and BBP9 models could reach the best fitness. These models contain 3 sub-trees that use operators of plus, minus, multiplication, division, ln, sin, power 2, power 5 power 0.5, power 0.33, power 0.2, and power 0.25. Overall, the final tree includes several variables and integers, the variables are inputs of column dimension, effective depth, rebar ratio, compressive strength of concrete, and yielding strength of the rebars, and the output of punching shear capacity. The results of modeling are compared with recommended values of the ACI318 and EC2 codes. Comparison shows that code equations are scattered and therefore are not very reliable. Maximum error for both model and code equations occurs when the yielding strength of the rebars is low. Minimum estimation is related to GP and ACI codes with the ratio of 0.485 and 0.52, respectively which is due to very low thickness of the slab (41 to 55 mm). The maximum estimated shear belongs to ACI code in which the estimated value is two times the real one. Also, standard deviation of ACI values is about two times the others. Among the code equations, EC2 values yield more accurate results. However, GP and BBP models give much less mean error. Also, standard deviation of these methods is less than code values. In total, results show that the methods based on artificial intelligence are able to estimate pushing shear with around 2% error, compared to existing code equations which give 14-28% error.

Nowadays, protecting various structures including commercial, medical, industrial, and residential infrastructures against fire is a very complex issue. High heat causes microstructural changes and decreases compressive strength of the concrete containing conventional portland cement, but geopolymers as the third generation of cement due to amorphous structure and aluminosilicate 3D networks lead to more stable behavior under high heat conditions considering the conventional concrete. Calcium silicate hydrate (C-S-H) and calcium aluminosilicate hydrate (C-A-S-H) nanostructures are products of the hydration and geopolymerization processes that play an important role in increasing the strength of conventional and geopolymeric concrete, But heat, either in transient or steady state, changes the mechanical properties and microstructure of the concrete. Hence for a deeper understanding of the behavior of C-S-H and C-A-S-H nanostructures affected by high temperatures, geopolymer concrete has been compared with conventional concrete. In this regard, about 300 samples were cured in the humidity bath for 1, 3, 7, 14, and 28 days. All samples were then put in of 25, 50, 100, 200, 300, 500, 700, and 900°C temperatures for 2 hours. Length and weight change percentages, compressive strength, and ultrasonic and cracking behavior tests were performed on all samples. Images from the scanning electron microscope (SEM) and the energy-dispersive X-ray (EDX) analysis were also used to evaluate the microstructural behavior of samples in various temperatures. According to the results, the strength of both types of concrete decreases with increasing temperature. By increasing the temperature to more than 700 °C, the geopolymer concrete structure has transformed to a porous and semi-stable ceramic structure. This change in the ceramic structure has made a difference in the high heat compressive strength of geopolymer concrete vs. conventional concrete. The compressive strength of 28-day aged geopolymer concrete and conventional concrete samples at 900 °C was 7.35 and 4.31 MPa, respectively.

Electrokinetics is known as a common method for improvement of soil engineering properties and contaminant removal from soils. In carbonated soils due to the soil buffering capacity, the acid front does not form through the soil sample. Therefore, the soil improvement usually caused by hydrogen ion effect will not occur. Consequently, a reduction in electrokinetics efficiency happens. One of the methods to overcome this problem is the application of enhancement methods. In this paper the influence of enhancement by the use of calcium chloride solution on two mechanisms of electrolysis and electro osmosis in electrokinetics remediation of carbonated clay is experimentally investigated. For this purpose, an un enhancement and enhance electrokinetics process with 0.2, and 0.5 molar concentrations of calcium chloride has been applied on  carbonated natural clay  samples. The calcium chloride solutions were added to anode reservoir. The achieved results of this paper indicate that due to the noticeable percentages of carbonate calcium in soil sample, not only the pH of soil in electrokinetics process has not decrease, but also because of alkaline condition of soil sample due to the presence of calcium carbonate and calcium chloride solution, the pH of soil has increased. Furthermore, in enhancement electrokinetics with calcium chloride, the presence of calcium ions and an increase in electro migration process have caused an increase in efficiency of electro osmosis. For this reason, the volumetric flow rate of enhanced electrokinetics experiments with 0.5 molar calcium chloride has been almost 250% more than that of for un-enhanced experiments.

Heeled concrete walls (T-Wall) are used for privacy, protection and some form of blockage. These walls can be built precast or cast in place and can be designed according to the possible loads such as blast loads, earthquakes, winds and so on. Also, the use of fiber concrete to absorb more energy and durability can be a good solution in the construction of such walls. Resistance, stability, and possibility of overturning of these walls due to the blast load and depth of buried walls are those that should be controlled by the designer. In addition to all the controls mentioned, one of the important issues is to optimize the cost of construction and consumables, so comparing reinforced concrete use with fiber reinforced concrete is of interest. In this study, six types of walls are considered: Type 1 and 2 walls with 3 m height and 2.5 m width, Type 3 and 4 walls with 4 m height and 2 m width and Type 5 and 6 walls with 5 m height and are 1.6 meters wide. Which, the walls of Type 5 and 6 are non-prismatic and are one meter buried in soil. In addition, type 1, 3 and 5 walls are made of fiber reinforced concrete and type 2, 4 and 6 walls are reinforced concrete. The purpose of this study is to investigate the resistance of concrete prefabricated walls against the impact and explosion. During an explosion, there is an explosive wave that spreads from the center of the explosion. Waves spreading at a later time are much faster than the speed of the initial waves. When a structure is exposed to the wave front, its surface pressure rises and reaches its maximum value in a very short time. This pressure affects the structure on all sides rapidly. This wave is a combination of high-pressure shock that emits outward from the center of the explosion and decreases as a function of the time and place of the explosion. The energy released by the explosion affects the structure in two ways. The first effect is the blast pressure, which is the key factor in determining the structural response, and the second effect is the dynamic pressure or the secondary pressure, which at high speed results in the debris being thrown around. Therefore, the most important parameter of an explosion is the forward blast pressure, the amount of which depends on the type of explosive and the weight of explosion. Hence, in order to find the above parameters, the 6 types of discussed wall modeled in Abacus software by CDP method. Also, the earthquake loading with different acceleration is applied to the walls and lateral displacements of them are calculated by using linear time history analysis with SAP2000 software. Finally, the performance level of walls under loads has been evaluated according to the national building earthquake loading criteria and 21th national building regulations. The results of the present study show that; the use of fibers has a positive effect on improving the performance level of prefabricated walls against dynamic loads such as explosion and earthquake.

Ingredients in agricultural pesticides are a group of chemicals and synthetics that are widely used in the industry. The constant entry of these substances into water resources produces very high levels of pollution, which poses a threat to aquatic environments and their organisms. Among the pesticides used in agriculture are organophosphorus, carbamate and pyrithioide pesticides. Organophosphorus and carbamates have the highest levels of consumption to deal with plant pests. In this study, the photocatalyst was synthesized by ball mills method. In this method, oxide and iron oxide nanoparticles were rotated in half steel compartment (40.5 g of oxide and 80 g of iron oxide) for 12 hours in a high-energy satellite mill at 300 rpm. The weight ratio of the catalyst to 10 mm spheres is 1:20 and for each 15 min rotation, 5 min rest and a total of 16 h cyclical rotation was performed in the device to complete the nanocomposite synthesis process. Heat treatment was carried out for 1 hour by a muffle furnace at 700 ° C. Also, this nanocomposite were characterized with the analysis of XRD, XRF, DRS and FTIR. The XRD analysis showed the hexagonal structure of nanocomposite with using of Debay-Scherer relationship, the crystals size of ZnO/α-Fe2O3 nanocomposite was calculated about 10.66 nm. SEM images showed the Fe2O3 nanoparticle Placement between ZnO nanoparticle. Result of DRS revealed that band gaps of the ZnO and Balmiled iron oxide and heated was 1.878 eV. By FTIR analysis, peaks of Zn-O and Fe-O were observed in the nanocomposite. According to EDX analysis for the weight values of Zn and Fe and O of ZnO/α-Fe2O3 nanocomposite was 5.30% and 55.8%. According to XRF analysis, the weight values of Zn and Fe in ZnO/α-Fe2O3 nanocomposites were 77.33% and 61.13%, respectively. The photocatalytic activity of the synthesized ZnO/α-Fe2O3 nanocomposite under UV irradiation was analyzed by two 8 watts UVC lamps for mineralization of organic carbamate pollutants from agricultural wastewater. In this design ZnO/α-Fe2O3 nanocomposite concentration, pH and radiation time were considered as effective quantitative variables and the type of catalyst consumed as effective qualitative variables. Reaction rate reached best at 0.0043 min-1 in the best conditions, including modified oxide and catalyst concentration of 1 gr/l and two 8W UV lamps and pH = 8 for 3 hours.

Due to the lack of access to the data of three rotational components of earthquakes, seismic analysis of new buildings as well as assessment of the vulnerability of existing structures are usually carried out only by applying the translational components of earthquakes. Iranian Standard 2800 proposed an accidental eccentricity for considering the earthquake rotational component effect in the seismic analysis of building structures. The present investigation is focused on the effects of earthquake rotational excitation on the seismic response of buildings having various dynamic properties which situated on a rigid foundation. In addition, adequacy of the accidental eccentricity of 5% recommended by seismic design code for inclusion of the earthquake rotational component impact in the non-linear time history analysis of buildings is studied, as well. To achieve this, a large number of one-story torsionally stiff and flexible building models with a wide range of lateral vibration periods (T=0.05 to 2sec) and three different values of inherent eccentricity of 0, 15 and 25% were modeled. These models were once excited by the translational components of ground motions and once again by both translational and rotational components of ground motions. The building models were re-analyzed after applying the 5% accidental eccentricity based on the procedure presented by Standard 2800 (shifting the center of mass in the negative and positive directions by 0.05 of the plan dimension). For conducting the non-linear time history analyses, a number of earthquakes were selected and the rotational records for these events were generated by use of an indirect single station method based on the seismic wave propagation in an elastic and homogeneous medium. In total, over than 2600 nonlinear dynamic analyses have been conducted in this numerical research. In order to determine the role of earthquake rotational excitation in the seismic behavior of  buildings, the variations of displacement response for the left and right sides of diaphragm and the torsion of diaphragm about the mass center due to the effect of rotational component were evaluated. By comparing the results obtained in this study, it is found that the rotational component has a substantial influence on the structural responses, which this effect is a function of the fundamental dynamic characteristics of system such as uncoupled rotational to translational frequency ratio, lateral vibration period and irregularity. The displacement of diaphragm can be increased up to 50% when the rotational component of ground motion is included in the seismic load combinations. Decreasing the frequency ratio leads to increase of the rotational component effect for the stiff buildings with short periods, while in the other cases reduces the growth of displacement due to the rotational component. Furthermore, results indicate that the accidental eccentricity of 5% cannot increase the seismic responses as much as the earthquake rotational motion, and leads to unreal and underestimate results for the most of lateral vibration periods. Thus, the current Standard 2800 approach cannot be considered as an appropriate alternative for considering the accidental torsion induced by the rotational component of ground motion, and it seems that this approach needs to be re-evaluated.

Concrete-encased concrete-filled steel tube (CFST) has been presented to integrate reinforced concrete (RC) and CFSTs that have been used increasingly in high-rise buildings and bridges in the world. Concrete-encased CFST exhibits higher confinement of the concrete core, high stiffness and strength, better durability and ductility, small sectional size, higher fire resistance due to the protection of the outer RC encasement compared to CFST, avoidance of local buckling and corrosion of steel tube, and easier connection with steel RC beams. On account of the insufficient research and the unknown behavior of these beam types, in this research, prestressed concrete-encased CFST (PCE-CFST) beams that incorporate CFST in the compression zone to improve the strength of concrete, and prestressed strands in the tension zone to control cracks in reinforced concrete (RC) beams are numerically investigated. The objective of this study is the finite element analysis of parameters that are not feasible to be examined through experimental specimens. Hence, the experimental study has been done to validate the nonlinear finite element modeling and a full-scale model is constructed to explore the flexural behavior of the cross-section. The model is then developed to include parameters such as the longitudinal rebar ratio, prestressed strand ratio, core concrete ratio, and the steel tube ratio indices. Based on findings, a good agreement was observed in the moment-deflection diagrams and the failure modes between the experimental and numerical results. Then the model was developed and 9 PCE-CFST beams is modeled by finite element software of ABAQUS to investigation of longitudinal rebar ratio (0.0257, 0.00856, 0.00286), prestressed strand ratio (0.00228, 0.00912, 0.000569), core concrete ratio (0.0206, 0.07799, 0.0281), and the steel tube ratio (0.01385, 0.00615, 0.000385) indices. The beam specimens were subjected to four-point loading and the parameters of bearing capacity, moment-deflection curve, energy absorption, ductility, failure mode, bending stiffness were investigated. Examination of indices revealed that as the prestressed strand ratio increases, displacement ductility, flexural stiffness and ultimate moment increase by 1.47, 1.06 and 3.22 times, respectively. Further, the elastic and entire absorbed energy of cross-section escalate by 1.04 and 3.22 times respectively, with increasing prestressed strand ratio. Likewise, by increasing the index of longitudinal rebar ratio, flexural stiffness and ultimate moment are 1.18 and 1.22 folded, respectively. In addition, the elastic absorbed energy is increased by 2.85 times as the longitudinal rebar ratio increased. As the ratios of core concrete and steel tube increase, the flexural stiffness is reduced by 5% and 6%, respectively. While, by increasing the core concrete and steel tube ratios, the ultimate moment grow by 1.05 and 1.29 times, respectively. The only effective index on the cross-section ductility and the entire absorbed energy is the prestressed strand ratio. The longitudinal rebar ratio has also the greatest increasing impact on the flexural stiffness and the elastic absorbed energy. Moreover, the core concrete ratio has the least effect (less than 10%) on the flexural stiffness. The prestressed strand and core concrete indices have respectively the highest and lowest escalating effects on the ultimate moment. As a consequence, an increase in the prestressed strand and longitudinal rebar ratios lead to a rise in the flexural stiffness and ultimate moment. On the contrary, an increase in the steel tube and core concrete ratios, decrease the flexural stiffness and gives a marginal increase to the ultimate moment. It was also unveiled that the failure mode of full-scale beams is flexural, and shear crack and shear capacity govern the behavior of PCE-CFST beams with shear span-to-depth ratios of less than 2. As shear span-to-depth ratio increases, that is, the shear failure mode shifts to flexural, flexural stiffness decreases, yet the ultimate bending moment increases. Additionally, a strut-and-tie model was proposed to describe the load transfer mechanism of PCE-CFST beams.

distribution systems to a wide range of consumers, and therefore constitute the basic infrastructure in each city. The main objective of this research is to identify and prioritize critical and critical assets of water supply facilities including reservoirs, transmission and distribution networks, refineries, dams, tanks, wells, rivers, based on economic value criteria , Functional and unique value through the AHP hierarchical compilation method and Risk Analysis and Management for Critical Asset Protection )RAMCAP(.Based on the combined method of Amir Kabir Dam, Taleghan Dam, Lotyan dam, Lar dam, Mamlo dam, Nimrod Dam, Ziarat dam, Shahid Ghafour Dam, wells, springs, rivers, No. 1 treatment plant (Jalaliyeh), No. 2 treatment plant (No. 3 and No. 4), No. 5, No. 5, No. 6, No. 7 (Sohanak), Seahqeraniyeh Sewage Treatment Plant, Municipality Sewage Treatment Plant, Zargand Sewage Treatment Plant, Gheitariyya Sewage Treatment Plant, Ghods Town Sewage Treatment Plant, Shosh Sewage Treatment Plant , Ekbatan sewage treatment plant, pumping stations, storage tanks, water distribution network B Rsany system were critical of Tehran. Based on the defined economic value criteria, the value of the Letian dam and the Amir Kabir dam and Taleghan Dam respectively were 0.1477, 0.1359 and 0.1109, respectively, in the first to third positions, respectively, and the distribution network and reservoirs were ranked respectively 24 and 25 were assigned 0.0046 and 50.004, respectively.

Pullout resistance of cement-grouted soil nails is a key factor affecting the safety conditions of retaining walls, slopes and excavations. Hence, survey of resistence of pullout nail is the one of the most important parameters in designing of nailing functions. This parameter depend on critical factors including: instalation method, overburden press, grouting pressure, degree of saturation of the soil, the roughness of nail surface, changes of lengh & diameter of nail, the shear strengh of the soil and etc. Sometimes, used soil nail layers affected by cyclic loads due of traffic passing, train and so on. Hence the research aimed to study influence of this kind loadings on resistence of nail post-cyclic pullout and affective factors on it. The study pointed to apply slopes and nailed retaining walls next to traffic loads and rail-roads. Several studies conducted; according to, vary factors influence on nail pullout behavior that buried into soil. Key studies carried out in form of impression of static loading on nail pullout resistance including: overburden stress, grouting stress, impression of an addition to grouting, nail geometry, nail spaces, using spiral nails, comparison laboratory results of pullout set with direct shear test in interface grouted-nail to earn identical ratio and etc. yet, it not examineted cyclic loading impression on post-cyclic pullout resistance in nails. The study just focus on geogrid. For the first time, this research provide impression of cyclic loading on post-cyclic pullout resistance in nails. This research used nail pullout set; able to apply static and cyclic loads in conditions of force or displacement controling with differ frequencies and sinus shape of cyclic wave. This search used the notes of specifications of pullout set; also, sampling due to test and tables of done tests. In this research examined affection of variation of static, cyclic load rate. Resistance of post-cyclic pullout nail generally is more to static pullout resistance; even though , more affections of cyclic loading lead to decrease of resistance; also, obserued in the cyclic part developing in displacement.

In structural monitoring, modal parameters extracted from vibration data are commonly used to gain some information about the condition of bridges. However, even small amount of uncertainty in extracted modal parameters has a considerable erroneous impact on different processes of structural monitoring, including structural model updating and damage detection. Accordingly, in this research effects of different data processing methods and types of vibration tests such as ambient vibration and free vibration, on extracted modal parameters, have been studied. In this regard, four methods including Covariance based Stochastic Subspace Identification (Cov-SSI), Eigensystem Realization Algorithm (ERA), Frequency Domain Decomposition (FDD), and Analytical Mode Decomposition - Hilbert (AMD-Hilbert) have been used to estimate modal parameters. SSI and ERA are parametric methods in time domain in which mathematical bases are similar. FDD and AMD-Hilbert are non-parametric methods which work in frequency and time-frequency domain, respectively. SSI and FDD methods were used for ambient vibration test data and ERA was used for free vibration test records, while AMD-Hilbert method was applied for both free and ambient vibration data. In this article, vibration data of six points were measured from a girder of Gisha Bridge using three Molecular-electronic seismometer sensors, roved in three different setups. One sensor was chosen as reference and its position was fixed among different setups. Data of this sensor were later used for merging different setups results. Therefore, to extract modal parameters multi-setup merging approaches were inevitably used. The measurements were done in vertical direction which leads to identifying vertical bending modes. Ambient vibration responses were measured while the bridge was excited by wind and traffic under the bridge. Free vibration responses were measured after making an impact on the girder.  Two approaches were considered for merging. In the first approach setups were analyzed separately and their final results were combined together and in the second one, merging was done before the process of system identification which eliminates any need to analyze multiple times. A numerical model was also simulated to compare with the field results. Filtering of the recorded data was done before beginning of the system identification process to remove the drift and sudden changes in the signals. Data processing on ambient vibration responses resulted in the first three vertical bending modes which are compatible among all methods, to some extent. In addition, the first two vertical bending modes were identified from free vibration data. Similarity of the mode shapes between different methods were assessed using MAC criterion. Compatible results between these two types of test and numerical model, verifies the results. It is seen that FDD and SSI methods obtained more stable and reliable modal parameters among different setups. Results indicate more modes were identified for ambient vibration data compared to free vibration data. Since, in free response of the structure the first modes are more dominant, lower number of modes could be identified. Considering the non-stationary condition of the conducted vibration tests, the results indicate that the post-processing multi-setup merging approach works better than the pre-processing multi-setup merging approach.

Actually, after drilling a borehole, some materials would be eliminated from the original rock mass. The exhumed materials no longer can carry the stresses transferred to the rock surrounding the borehole. The process represents a stress concentration in the rock around the borehole. The so-called borehole breakout failure results from an enhancement in shear stress on the borehole wall because of the excavation-induced increase of the hoop stress surrounding the wall. Vertical borehole breakouts generated via un-equal horizontal in-situ stresses are usually focused in two opposed areas along the least horizontal in-situ stress. Excavation cause loss of balance stresses around the borehole and also cause compressive stress concentration on the walls. Changes in stresses around the borehole may cause formation damage. This status results in other modes of borehole instability such as collapsing of the wall due to shearing failure. Breakout phenomenon (collapsed walls under shear failure) will occur by increased shear stress at the borehole wall which by itself is due to an increase in hoop stress on the wall. In this paper, the goal is to compare four failure criteria including, Mohr-Coulomb, Hoek-Brown, Griffith and Fairhurst to estimate the depth and angular width of the borehole wall in damaged zone, where the stresses are heterogeneous. The results show that damaged zone, undamaged zone and boundary curve of failure around the borehole, can be obtained using the function of failure criteria (F) in σ1-σ3 plane. The more that the area under the curves of these criteria would be in σ1-σ3 plane, the less damaged zone will occur around the borehole.  For instance, the area under the curve for Griffith criteria in σ1-σ3 plane, is less than the area of other criteria. So damaged area in Griffith criteria is more than 3 other criteria. Angular width obtained from Hoek-Brown criterion, Mohr-Coulomb criterion and Fairhrust criterion (unlike Griffith) coincide, because these 3 criteria cut the σ1 axis with the same width in σ1-σ3 plane. Also, with the constant value for difference of in-situ stresses (σd=σH-σh), depth of the failure in minimum in-situ stress direction is more in Griffith and Fairhrust criteria in compare with 2 other criteria. By comparing the failure criteria, it has been observed that, with an increase in in-situ stresses ratio (σH/σh), the results of Griffith and Fairhrust criteria are more close to experimental results in compare with 2 other criteria (Hoek-Brown and Mohr-Coulomb).

Some events such as scour and deposition in rivers may endanger the stability of the outer bank’s bend and reduce the navigable width of them. So far, different techniques have been developed to control this phenomena such as bottom vanes, submerged groynes, bandal-like structures. In the present study, the influences of non-phase hydraulic jet usage on bed scouring and deposition in a 90 bend has been investigated experimentally. Experiments were conducted in a experimental channel to measure the variations of bed topography under a clear water condition. The90 bend is connected to an upstream straight reach 5 m long and a downstream straight reach 3 m long. The channel was rectangular having 70c m width and 280cm radius of bend to centerline. (R/B=4; where R=radius and B=flume width). Four Froude number values including 0.37, 0.41, 0.45 and 0.47 with a constant flow depth of 11cm under clear water condition were used for each test. Bed topography was measured with a laser meter and contour lines were plotted with the Tec plot360software. The scour geometry in a bend depends on channel geometry (channel width, channel , radius and bed slope), flow conditions (depth and discharge or velocity), non-phase hydraulic jet characteristics (length, angle with bank, location in bend), sediment properties (specific gravity, grain size), and fluid parameters (density and viscosity). Therefore, by Using the Buckingham theory and after eliminated the parameters with constant values, the important parameters were q/Q, D/h , Fr and α.Three-dimensional (3D) velocity components were measured using the electromagnetic velocity meter JFE ALEC model ACM3-RS in tests with and without an installed non-phase hydraulic jet. The sampling rate was 20 Hz and time of sampling was 60 seconds. So the minimum 1200 data were collected for each point and their mean was used for determine the 3D flow pattern. The results showed that with installing non-phase hydraulic jet, the maximum scour depth is reduced as much as 77%, 82.7% for Froude numbers equal to 0.37 and 0.41, respectively. It was also found that generally the scour depth occurs away from the outer bank and it was shifted toward the middle parts of the section in the main experiments, which can positively result in the increase in the navigable width and also sediment deposition was observed at the outer bank in some experiment. The results show that non-phase hydraulic jet significantly modified bed topography and reduced the maximum scour depth in outer bank. In this paper to evaluate the effect of space between porous tube and outer bank , three different space (D=0,2.5 and 8 cm) were used. It was found that by decreasing the space between outer bank and porous tube the amount of scour decreases and the maximum scour depth reduced as much as 87.9%, 54.5% and 15.15% for space equal to 0, 2.5 and 8 cm, respectively and it is most efficient when it placed on outer bank. Maximum scour was usually saw near the outer bank, and attributed to the maximum stream wise velocities that occur near the toe of the bank , also the analysis of data have shown that the presence of non-phase hydraulic jet caused uniformity in the velocity distribution at upstream and the high velocity zone moved toward the center of the channel and inner wall. The installing a non-phase hydraulic jet on the outer bank of bend, by its rising velocities, generated a secondary flow that rotates in the sense opposite to the curvature-induced secondary flow. The jet-induced secondary flow cell causes an inwards shift of the cores of maximum streamwise velocity and maximum vertical velocity impinging on the bed, that both of them play an important role in the cour in the outer bank.

Beam–column connections in reinforced concrete (RC) structures play an important role when the frame is subjected to seismic loading. The overall stability of the structure and the formation of the optimal energy absorption mechanism in the beam plastic hinge zone depends on the role of the beam-column joints. The non-seismic detailing in the joint panel area can cause a partial or total collapse of the structure. Beam-column connections with non-seismic detailing in buildings with moment resisting lateral load bearing systems, are the major cause of post-earthquake damage. The optimal shape and energy absorption of the moment frame structure is dependent on the design and perfect execution of the beam-column connections. In the beam-column connections, the lack of positive reinforcement of the beam in the joint area and non-extension of the column stirrup in the joint area are common defects of the joints in accordance with new regulations. Researchers have provided a lot of experimental studies on beam–column connections, while experimental studies are usually costly and time consuming, and can be restricted by the test facilities and space. The behaviour of the RC beam–column joint is very complex and several parameters such as axial load ratio, reinforcement detailing, concrete strength have significant influences on its seismic performance, it is impractical to fully investigate all parameters through a limited number of experimental tests. Finite element modelling using ABAQUS software platform can provide an opportunity to study the various parameters governing the monotonic and cyclic behaviour of the beam–column joints. In this study, by examining several parameters in the finite element model of the RC Beam–column connections in ABAQUS software, such as specifications of strain-hardening for steel, bushinger effects, concrete damaged plasticity (CDP) in tensile and compression, concrete confinement effects, presence of lateral beam, and also bond-slip of reinforcing bars was investigated and leads to provides recommendations for finite element modelling of the RC frames. For this purpose, the behaviours of the seismically and the non-seismically detailed beam–column joints under monotonic and cyclic lateral loading were evaluated in different conditions of the presence of lateral beam. The finite element models with seismic and non-seismic detail were considered and validate with laboratory tests by considering sliding effect of longitudinal beam reinforcement using modified steel stress-strain curve. Then, the effect of different lateral beam conditions around the joint was considered. The results showed well that the finite element model is more consistent with the experimental results when considering the slip effects of the longitudinal beam reinforcement. Also comparing the results of the models with the different lateral beam conditions showed that confining the non-seismic joints can increase the joint strength against lateral loads. The general behaviour mode for the seismically detailed specimen was flexural yielding in the beam at the column face whereas for the non-seismically detailed specimens joint shear failure occurred generally before the beam section reached its ultimate flexural strength. The finite element model of beam-column joint specimens was calibrated by test results and good agreement was found between the experimental and numerical hysteretic behaviour. The model was able to capture the modes of failure, peak load and initial stiffness of the tested specimens.