Modares Civil Engineering journal
Year:2018 | Volume:18 | Issue:6 |Papers Count:17

Eccentrically braced frames (EBF) by covering the advantages of moment-resisting frames (MRF) and concentrically braced frames (CBF) have been used as seismic load resisting systems in buildings for more than two decades. In eccentrically braced frames (EBFs), the link beams transmit bracing forces through themselves into the columns and other bracings and, in the end, create dominant forces in the bracings. Link beams, similar to ductile fuses, in addition to avoiding bracing buckling, attract earthquake energies. In eccentrically braced system, failure and yielding should happen in the link beams, and other members of the structure must remain in elastic behaviour. On the other hand, link beams prevent transmitting of more forces to the other members by yielding, therefore, link beams are so important. Typically, the link beams, which are relied upon for energy dissipation through inelastic deformation, have had a wide-flange or I-shaped cross-section that requires lateral bracing to prevent lateral torsional buckling. This has limited the use of wide-flanges or I-shaped cross-sections in bridge piers and towers, as lateral bracing is difficult to provide in those situations. Tubular cross-sections of link beams have substantial torsional stability, making them less susceptible to lateral torsional buckling than I-shaped cross-sections in eccentrically braced frames, and may thus not require lateral bracing. Long link beams due to providing proper conditions for the openings performances have architectural advantages. Nevertheless, the behaviour of long link beams within sever seismic loads is not comparable to short link beams in stiffness, strength, rotation capacity and energy dissipation capacity, i. e. it is at lower level. Therefore, using long link beams is not recommended in buildings and particularly besides the columns. In this study, a method is presented for arraying the stiffeners of long tubular link beams to improve the behavior of long tubular link beams in eccentrically braced frames. Long link beams at the distance of 1. 5b from both ends of the link beams make flange buckling. Now if this distance strength by any way, the flange buckling delay and the rotation capacity of link beams are increased. For this purpose in this investigation, the stiffeners have been used in the middle of the flange vertically in this diatance and the link beam web has been considered as a stiffener that its distance from the middle stiffeners of link beam flange is 0. 5b. In long tubular link beams when the middle stiffeners of the link beam flange do not present, Tension-Field will not create and link beam flange will buckle because of moment. When the middle stiffeners of the link beam flange present at its both ends, then Tension-Field will be created. In this investigation, the formulas presented for determining the stiffener sizing of long tubular link beam flange. In this investigation, non-linear dynamic behavior for 6-stotories eccentrically braced frames with different two length of link beams (shear-flexural and flexural), tubular cross sections with two arraying of stiffeners under the influence of three records of far-fault and three records of near-fault are studied. The result of investigations indicates that flange stiffeners of long tubular link beams have important influence in decrease of displacement demand of eccentrically braced frames that approximately 19% for far fault earthquake records and 32% for near fault earthquake records.

Measuring total metal concentration of heavy metals cannot be a suitable indicator to evaluate their danger and human health risk. Their toxicity depends on their mobility and bioavailability. In the present study, sixty-five surface soil samples in the Bama zinc-lead mining and residential area were collected to assess metal bioavailability. Since the mine is near to the metropolitan area (Isfahan) and a village is located in vicinity of the mine, assessing potential adverse effects of the surface soil on human health is a crucial issue. Firstly, total concentration of metals, using acid digestion method (Pb, Zn, Cu, Mn, Fe and Cd) as well as L. O. I and carbonate contents were determined for precisely understanding on pollution condition. Enrichment factor was used to determine the accumulation or non-accumulation of metals at Bama mining area and its residential area, using Fe and Mn as references elements. Single extraction tests were conducted to reveal bioavailability and human bioaccessibility of metals, using EDTA and glycine as extractants. Moreover, Bioavailability risk assessment index (BRAI) was used to assess the risk of metal bioavailability/bioaccessibility. Based on BRAI, qualitative mapping of health risk distribution was presented, using ordinary kriging method. High concentrations and enrichment factor of Pb, Zn and Cd were determined at mining area. Their high concentrations in mining area may be due to Bama host rocks where significant contents of mentioned metals were accumulated. The amount of L. O. I was higher in mining area, indicating the ability of its soils to carry more polluted metals. Cu created no pollution and health risk due to its low total and bioavailable contents at study area. Based on single extraction methods, the absorption percent for the toxic metals were different. The highest percent of bioavailability and human bioaccessibility was allocated to Cd and the lowest was for Pb. Further, it was found that glycine extracted more amounts of metals in comparison with EDTA, Since pH is in lower values using glycine solution, greater amount of metals can be changed into solution forms due to acidic pH of glycine. So the single extraction test exhibited higher bioaccessible fraction of metals. Bioavailable and bioaccessible percent of toxic metals was higher in residential area as mineral soils are in poor condition. Pearson correlation coefficient showed that Pb, Zn, Cd and carbonate contents were highly correlated at residential area. This is expressing that the metals probably are bonded with carbonate at residential area, which may increase the possibility of their mobility and release under changing conditions. Based on EDTA extractant, BRAI index was calculated 3. 46 and 4. 2 for mining and residential area, respectively. Further, on the base of glycine extractant, result of BRAI was calculated 4. 2 and 4. 6 for mining and residential area, respectively. The calculated BRAI represent a high risk for human beings and plants in both the mining and residential areas. Moreover, results revealed that higher degree of bioavailability/bioaccessibility for the residential area in comparison with the mining area. It could be concluded the higher potential health hazard for the residence beside the mining area.

Nowadays, heavy metals are one of the greatest environmental problems. In scientific reports, many cases of poisonings due to the various metals such as Chromium, lead, Mercury, Cadmium, etc. which should be an important warning for control industrial pollution, be considered. This problem intensifies by development of great industries and increasing of pollutant and contaminant resources daily. Increasing of population and reduction of water resources detect importance of waste treatment and reuse of water resources. Studies on treatment of effluents containing heavy metals have showed that adsorption to be a highly effective technique for removing heavy metals from aqueous solutions. The aim of this research was to use of absorbent materials (kaolin clay) to remove chromium (VI) from the wastewater in discontinuous system According to the results, optimum conditions of chromium removal were, pH=5, primary concentration of pollutant: 1000(mg/l), fine grained weight of consumed kaolin in constructing concrete: 30%, equilibrium time: 360 minutes, absorbing capacity: 3. 06 mg/g absorbent. The results showed that by using kaolin in the concrete structure as one of the materials used in the mixing design from 5 to 30 percent, the absorption of heavy metal chromium by concrete samples increased up to 81%. It was observed that increasing the amount of kaolin used in the sample, could decrease the concrete compressive strength. In order to compensate for the reduction of compressive strength and also to increase other mechanical properties of concrete, polypropylene fibers were used which the effect of these fibers on increasing the compressive strength of concrete was Maximum of 7. 8%. Covering the concrete surface with kaolin absorbent can be an innovative and useful solution for increasing the rate of elimination of pollutant and contaminants, cost reduction and accelerating the absorption process. Absorbing capacity of chromium is 29. 5 mg/g absorbent in this condition respectively. Real waste sample are used for confirming the application of concrete in ordinary conditions of wastewater basin in accordance of optimum conditions of kinetics wastewater. Elimination rates of heavy metal of chromium were 90. 3% in optimum condition with real samples that has been got from industrial factory. Therefore, it could be concluded that modified concert presents a good potential for treatment of Cr in wastewater. Protecting the structures used in wastewater installations against chemical attacks and reducing maintenance and operation costs is an essential requirement. Usage of kaolin is not only important in terms of removing heavy metals in the wastewater, but also in terms of improving the durability and lifetime of concrete in harsh sewage conditions. Parameters such as short contact time, appropriate range for pH, acceptable absorption capacity, low cost and easy accessibility of the absorbent were the advantages of using Kaolin as an adsorbent to remove heavy metals (Chromium) from industial wastewater solution. However, further research should be applied for continuous removal of heavy metal in large-scale. According to the result, mixing Kaolin in the concrete could be used to increase the Durability and adsorption efficiency of Chromium.

The hydraulic jump takes place in both natural and manufactured systems. As it can be seen in streams, rivers and water distribution and irrigation networks formed downstream of hydraulic structures such as spillways, sluice gates, and drops. Generally, it is necessary to construct special structures downstream of flow in order to prevent damage caused by the high energy of water in supercritical velocities and also to dissipate the extra kinetic energy of hydraulic jumps. Stilling basin is one of these structures which is constructed downstream of spillways or waterfalls. Baffle blocks are often used to stabilize the jump, decrease its length and increase the energy dissipation. In order to make stilling basin with its dissipating equipment effective, the design should be in a way that the tailwater depth becomes greater than or equal to the sequent depth, otherwise, the jump doesn’ t occur completely and will be swept out of the basin, resulting in scour of the downstream channel. If the flow rates become more than the design discharge, the tailwater depth will be greater than the one required for a free hydraulic jump. These situations are common in low head hydraulic structures including low diversion dam spillways and gates. Under such conditions, the hydraulic jump will be submerged. For submerged hydraulic jumps with blocks, two different types of flow have been observed, the deflected surface jet regime (DSJ) and reattaching wall jet regime (RWJ). There was also a transition state in which the flow could be changed from one state to the other by some external disturbance. In this article, a numerical study was conducted to investigate the influence of some parameters, consist of block height and shape, Froude number and distance of blocks from the gate, on the performance of submerged hydraulic jumps with blocks as energy dissipators. 3D RANS simulations have been applied by Fluent software. RSM turbulence model was used which illustrated much precise results in verification. In total fifty-four models with different geometrical and hydraulic situation according to the four mentioned parameters have been created and the percentage of dissipating energy is presented in each case to find the most effective condition. It was observed that the Froude number is the most important factor in the study of dissipating energy; such that the percentage of dissipating energy increases almost ten percent per one unit raise in Froude number. Furthermore, the existence of a slope at the back of blocks does not have an effect on energy dissipating, but it can be implemented to avoid cavitation. In addition, the percentage of dissipating energy goes up as the blocks are mounted closer to the gate and also provided the condition which leads to the deflected surface jet regime. The more turbulence in the deflected surface jet regime makes the desirable condition in which baffle blocks perform more efficiently as energy dissipators in comparison to reattaching wall jet regime. Finally, it can be concluded that for effective energy dissipation, block dimensions and all conditions should be provided in a way to form submerged hydraulic jump as the deflected surface jet regime.

Reactive Powder Concrete (RPC) is a ultra-powerful concrete with superior physical and mechanical properties, which was registered in France in 1994. This concrete uses high cement factor, fine powdered materials, low water to cement ratio, and the use of superplasticizer with high compressive strength and very low permeability, high durability and abrasion resistance. the high amount of cement and microsilica used in this concrete not only increases the cost of production, but also increases the heat of hydration. On the other hand, cement production can have harmful effects on the environment. In the production of reactive powder concrete, fine-grained powder materials such as silica sand, microsilica, and quartz powder are used as materials. This concrete has a high compressive strength compared to conventional concrete, which has attracted much attention in recent years. With this type of concrete, the weight of the structure can be significantly reduced, and its important features include high compressive strength, low permeability, durability and abrasion resistance and high ductility that can absorb more energy during an earthquake. In this research, limestone powder was used instead of a part of silica sand. For this purpose, after obtaining optimal mixture ratios based on the compressive strength, consistency and diffusion diameter of flow table test, first, the limestone powder is considered as partial substitute of silica sand with percentages of 0, 10, 20, 30, and then in continuation, limestone powder is used as a substitute-additive with percentages and mixing ratios. Experiments conducted on these samples include testing the flow table, water absorption during curing and compressive strength at the age of 7, 28 and 90 days. The results of the experiments show that by increasing the limestone powder up to 20% replacement with silica sand, the compressive strength significantly increases, and also reduces the water absorption during of curing. The compressive strength of mixtures containing 20% limestone powder is 43% higher than the base concrete for 28-day samples. This increase in compressive strength for 7-day and 90-day samples is 39% and 42%, respectively. Water absorption during of curing for 28-day samples decreased by 19. 7%. In these experiments, it has been attempted to cure under normal environmental conditions (temperatures of 23 to 25 ° C without pressure) and also to be sufficiently fluid in condition of loose concrete or self compacting concrete, so it can easily be used in practical applications. For example, in connections with the number of overlapping reinforcements, ordinary concrete does not have the capacity to fill the very small spaces. In such connections we can use these mixtures. The cement content is 780kg. In order of cement content, it should be noted that the cement content of reactive powder concrete is about 700 to 1000 kg, and is used in mixtures up to 1200 kg. So here the cement content is moderate and the lower part of moderate. There is also no pressure and heat to be used in curing of concrete, and the amount of water and superplasticizer is somewhat higher than similar mixtures, so obtained fresh concrete is SCC. These conditions resulted in less compressive strengths than similar mixtures, but they are sufficiently strong for use in building projects, and even more so. The compressive strength of mixtures containing 20% limestone powder at 28 days of age reached 582 kg/cm2 and at 90 days of age, it reached648kg/cm2.

The procedures for measuring, mixing, transporting, and placing heavyweight concrete are similar to those used in conventional concrete construction; however, special expertise and thorough planning are necessary for the successful completion of this type of concrete. The use of heavyweight concrete in construction is a specialized field, Heavyweight concrete is used in counterweights of bascule and lift bridges, but it is generally used in radiation shielding structures to absorb gamma rays and differs from normal weight concrete by having a higher density and special compositions to improve its attenuation properties. When heavyweight shielding concrete is used to attenuate neutrons, sufficient material of light atomic weight, which produces hydrogen, should be included in the concrete mixture. Some aggregates are used because of their ability to retain water of crystallization at elevated temperatures, which ensures a source of hydrogen not necessarily available in heavyweight aggregate Cements would be suitable for conventional concrete and produce the required physical properties, are suitable for use in heavyweight concrete. Low-alkali cement should be used when alkali-reactive constituents are present in the aggregates and a moderate or low-heat cement should be used for massive members, To avoid high and rapid heat of hydration and resultant cracking, it is advisable not to use Type III cement or accelerators unless the concrete temperature is controlled by specially designed refrigeration systems. Thorough examination and evaluation of heavyweight aggregate sources are necessary to obtain material suitable for the type of shielding required. These sources are limited, and a material survey should be conducted to determine availability, chemical and physical qualities. The supplier’ s sources should be inspected to evaluate rock composition, abrasion resistance, and density since these properties may vary from one location to another within a deposit. The purchaser must realize that mineral ores are not as uniform as normal weight concrete aggregates and make appropriate allowances Limited resources and increasing use of concrete, particularly in the industrial production cause that the heavyconcrete be useful. In order to optimize production of heavyconcrete, the most basic parameters that must be changed is the mix design. Optimization of the concrete mixture design is a process of search for a mixture for which the sum of the costs of the ingredients is lowest, yet satisfying the required performance of concrete, such as workability strength and durability. For this purpose, heavy concrete mix design optimization model is firstly defined and then optimal mix design will be achieved, by using an optimization algorithm. The experimental data were utilized to carry out analysis of variance. To develop a polynomial regression model for compressive strength in terms of the five design factors ( cement, coarse aggregate, fine aggregate, water and density ) considered in this study The numerical results shows that the amounts of coarse aggregate and cement are simultaneously reduced and amount of the fine aggregate is increased in the optimum mix design. Considering mass production concrete in nuclear power plants, this optimal mix design methods and reduce the cost of concrete can greatly reduce the cost of construction.

The stage-discharge relationship is a type of resistance to flow evaluation that is used to determine the depth and hydraulic radius in open channels, if the flow discharge, channel cross-sectional shape and the properties of bed materials are specific. Wide channels as well as plane bed rivers, due to having the higher ratios of width to depth, b/h, they have specific hydraulic characteristics than that of the normal open channels. In this research work, the hydraulic characteristics of widening long and wide channels including flow pattern, stage-discharge relationship and flow resistance, by using a physical model of rigid boundary with 60m length, 1. 5m wide and a longitudinal chanel bed slope of 1 in 1000 (0. 001) that has b/h ratios range of 12 to 56 are experimentally investigated. The construction material of channel model is concrete bed and concrete block walls were used. To insulate the channel bed and walls, a thick layer under the concrete was also used. Due to its wide width and length, the physical model of this study has low scale effects and the obtained results are closer to the normal open channels as well as the plain bed rivers. Based on the values obtained for the Froude, Reynolds and Shear Reynolds numbers in model, it was found that the flow regime is subcritical and turbulent. According to the results of model, stage-discharge-Tailgate relationship is shown plotted and it is found that as the flow rate increases, the Tailgate height that required at the downstream end of the channel to produce a normal depth, increases. On the basis of normal depths obtained in a widen channel model, a reliable stage-discharge relationship is presented. The results show that this relationship has a higher coefficient than that of a natural channel stage-discharge relationship. Results, also reveals that between the calculated and measured Manning’ s roughness coefficient, n, in the wide channel model, a difference (about 10%) is observed. The results show that, for discharges greater than 35 lit/s, the measured Manning roughness coefficient, n is very close to the n values presented in literature. However, for the discharges less than 35 lit/s, the measured values of Manning’ s n is 15% higher than the amounts provided in literature. The results of the present research show that by increasing the ratio of hydraulic radius to the roughness height of the bed (Rh/ks), the Manning roughness, n, decreases linearly. Also, based on the results, it was found that by increasing flow depth, The Manning roughness, n, decreases and by increasing Reynolds number, Re, the Manning n decreases linearly. The results also show that in the wide channel model, the Manning roughness coefficient, n, decreases from 0. 022 to 0. 016 by increasing Froude number, Fr, from 0. 26 to 0. 4, In this research, the wide to depth ratio, b/h, was considered as the main independent variable in the determination of n, and using the coding, a reliable relation was obtained between them, which can be used for wide channels. According to the results, it is clear that with increasing b/h ratio, the Manning roughness coefficient, n, also increases, but this trend changes in b/h ratios larger than 43 and has a decreasing trend.

It is seldom possible that rock engineering structures found without joints, cracks, or discontinuities. On the other hand, the application range of these structures are steadily increasing in recent years and includes bridges, tunnels, slopes, underground gas storage and etcetera. Thereby, their impact is to be considered in the rock structure design. In the present study, it is intended to evaluate the effect of induced micro-cracks on the mechanical behavior of rock specimens. For this purpose, 24 cylindrical specimens of Granite were prepared and some of them heated up to 800 degrees Celsius to induce micro-crack in the specimens. In the next, uniaxial compression test for determination of stress-strain curve of heated and unheated specimens were performed based on International Society for Rock Mechanics (ISRM) suggested method on a cylindrical specimen with 110 mm and 54 mm in length and diameter, respectively. The tests were conducted using a load controlled testing machine and the loading rate was kept at 0. 5 MPa/Sec. Results of experimental tests indicate that mechanical properties of heated specimens change with increasing the temperature. For example elastic modulus, uniaxial compression strength, tensile strength of the fractured specimens is smaller than the intact ones and the strain corresponding to the failure increases with inducing the micro-cracks in the specimens. Also, it should be noted that tensile strength compared to the compression strength in more sensitive to thermal stress and induced micro-cracks. Therefore, brittleness index of the specimens (ratio of compression strength to tensile strength) decreases with increasing the fracture density. Further, induced micro-cracks influence on the failure pattern of specimens. The failure pattern of unheated specimen is axial splitting mode, while the failure pattern of heated specimen up to 800 degree Celsius changes to shear mode failure. In the next step, numerical modeling of the uniaxial compression test was provided to evaluate the reasons for changing of the failure pattern of heated specimens compared to the unheated ones. Numerical simulation was conducted using rock failure process analysis (RFPA) tool as a finite element code which has been developed on the basis of elastic damage model. The heterogeneity of rocks at a mesoscopic level is considered by assuming that the material properties follow the Weibull distribution. Elastic damage mechanics is used for describing the constitutive law of the meso-level element. The numerical models were adopted using mechanical properties of heated and unheated specimens extracted from laboratory tests. On the basis of numerical modeling results, it is found that in the specimen with induced micro-cracks, ratio of the number of shear cracks to tensile ones increases, under loading sequences. With increasing the fracture density in the specimens, the index of brittleness reduces and consequently the probability of nucleation and propagation of shear cracks, under uniaxial compression, increases. This is the main cause for changing of the type of specimen failure mode from axial splitting to shearing.

Because of the existence of concentrated forces and high bending moments at the junction of pile and raft in structure with a high load using the non-connected pile raft foundation can be an appropriate option for the foundation of the mentioned structures. In this system, the piles and the raft are not connected and a cushion is used between the piles and the raft to redistribute the forces. in this state, load transmit from raft to pile by the arching mechanism that forming in cushion layer. The behavior of pile raft because of the interactions such as: pile-pile, pile-soil, pile-raft and raft-soil is very complicated. The pile used in pile raft for two purpose: 1-reduce the settlement and 2-increase the bearing capacity. In this study, a series of experimental tests were conducted on a non-connected pile raft located on a sandy soil in order to investigate the effect of parameter such as cushion height (H) and pile spacing (S) in forms of non-dimensional form (H/B & S/D) on load-settlement behavior, pile bearing ratio and axial and frictional stress in center and corner piles. For this purpose, cases H/B= 0. 17, 0. 34, 0. 5 and S/D=2, 4, 6 were investigated. The axial stress in piles measured according to strain gauges that installed in the perimeter of piles. The results show that in three state S/D=2, 4, 6 optimum state occur in H/B=0. 34. With increase H/B, the forces applied in piles is decrease and then the pile bearing ratio is decrease. The maximum pile bearing ratio occur in H/B=0. 17 and the minimum occur in H/B=0. 5. In the low level of the load major of the load protected by raft that with increase the load level, pile bearing ratio increase and stable in a specified value. Because part of the load is transmitted to piles by the soil around the piles, the maximum force applied to the piles does not occur at the tip of the piles and a negative friction is formed in the upper part of the piles. In the upper part of the piles, the displacement of the soil is more than the displacement of the piles, resulting in the formation of a negative friction and the formation of a positive friction in the bottom of the piles. With increase the H/B, the value of negative friction increases and neutral axes (a location of piles that displacement of soil and pile are equal) move down. In various pile spacing (S/D=2, 4, 6) and in three states (H/B= 0. 17, 0. 34, 0. 5) maximum bearing pressure was observed in S/D= 4. In S/D=2 maximum interaction effect (pile-pile) and minimum confinement of sand and in S/D=6 minimum interaction effect (pile-pile) existed and confinement of sand has insignificant effect because of high pile spacing. In three states H/B= 0. 17, 0. 34, 0. 5 minimum pile bearing ratio in S/D=6 and maximum pile bearing ratio in S/D=4 were observed. Maximum negative friction in S/D=6 and minimum negative friction in S/D=4 were observed. In all states in corner piles negative friction is more than center piles.

Shallow foundation is one of the most common types of foundations used in mid– rise buildings in high seismic zones. The effects of soil-foundation-structure interactions are generally not significant in the structure with rigid bases, while the nonlinear behavior of soil and soil-structure interaction phenomenon cause various changes in the seismic response of structures with flexible bases. When a structure supported on shallow foundations is subjected to inertial loading due to earthquake ground motion, the foundation may undergo sliding, settling and rocking movements. If the capacity of the foundation is mobilized, the soil-foundation interface will dissipate significant amounts of vibrational energy, resulting in a reduction in structural force demand. This energy dissipation and force demand reduction may enhance the overall performance of the structure, if the settlement or bearing failure potential is considered. In this paper, the effect of soil and shallow foundation types, and variation of safety factor are studied to assess the seismic response of steel buildings. For this purpose, five stories special steel moment frames with two different soil types (II and IV) have been considered. The footing and strip shallow foundations have been designed for these buildings with safety factors of 2, 3 and 4. The finite element models are developed using OpenSees software. The structural members such as beams and columns are modeled by nonlinear beam– column elements and fiber sections. The soil– foundation interface is modeled using Beam-on-Nonlinear-Winkler foundation. In this procedure, an array of vertical q– z springs is used to capture vertical and rotational resistance of the foundation, while two springs, namely p– x and t– x, are placed horizontally to capture the passive and sliding resistance of the foundation, respectively. The constitutive relations for the q– z, p– x, and t– x springs are represented by nonlinear backbone curves that have been constructed from the pile-calibrated backbone curves developed by Boulanger. The independent p-x and t-x springs are connected to identical end nodes with zero distance between them. The seismic performance of these special steel moment frames with various foundation and soil type are evaluated using nonlinear static pushover and nonlinear dynamic time history analyses through seven far– fault ground motions. The numerical results for each case of soil-foundation-structure systems and rigid base conditions are then presented and compared in terms of maximum base shear and maximum inter– story drifts. These results are shown that in the soil type IV, the steel moment frames with the footing foundations have lower structural capacity and maximum base shears than structures with the the strip foundations or rigid bases, but the maximum inter-story drifts in the strip foundation bases are higher than others. It is also observed that by enhancing the safety factor, the structural capacity, the maximum base shear and the maximum inter-story drifts in the models with the footing foundations are increased, but changing in the safety factors do not influence in the structural response of models with the strip foundation. On the other hand, the safety factor and foundation types have not any effect on the structural capacity and the seismic responses of the structures that located on the soil type II.

Reinforced concrete shear walls are frequently used as lateral load resisting systems because of their ductile response and very good energy dissipation. When openings in RC shear walls are used due to architectural requirements, coupling beams are forming to connect two adjacent walls. The behavior of coupled shear walls is governed by coupling beams and they are the most vulnerable parts of coupled shear wall systems and were seriously damaged due to severe past earthquakes. To avoid construction difficulties and huge size of the RC coupling beams and better seismic performance an ductility, steel coupling beams in reinforced concrete shear walls have been mostly used during last years. Steel coupling beams connections to concrete shear walls are vulnerable and it is practically difficult and economically waste to repair damaged coupling beams, which would cause the building life cycle cost increasing. Therefore, it is necessary to transform traditional design approach to a design method in which some important parts would be replaceable rather than repairable. In this paper a building with special shear walls with steel coupling beams as lateral force resisting system is designed based on Iranian Standard 2800 and Iranian National Building Code. One of the 5th to 8th floor steel coupling beams section considered as fuse element and side beams and stiffeners of I-shaped beams designed based on eccentrically braced frames link beam criteria of Iranian National Building Code (part 10). Experimental specimen containing two RC shear walls that connected to each other with designed replaceable steel coupling beam in 1 to 3 scale is constructed and assembled in strong floor lab. For providing one degree of freedom movement of load wall four TBI Motion Company TRH65VE linear supports used. Cyclic displacement history of experiment calculated based on story drift and amplitudes of loading determined using Iranian Standard 2800 limit for story drift. Based on experimental results side beams remained in the border of elastic range and inelastic behavior of system concentrated in fuse element so the goal of system is satisfied. The side beam section is stronger and different with that was obtained from link beam criteria of Iranian National Building Code (part 10) because of available steel sheet size and since the side beam force is almost equal to elastic capacity of beam, the criteria for designing side beams is modified. Total system stiffness and fuse beam stiffness that obtained from experiment are fewer than analytical stiffness of system and fuse beam. Stiffness degradation of system occurs due to partially fixed performance of steel coupling beam connection to RC shear wall and micro cracks of wall in the connection zone. Different between real and analytical stiffness of system is very important and it is necessary to repeat the building design with modified stiffness and recalculate story drifts and distributed forces in structural elements. In this paper modifying method of stiffness is developed with moving fixed end point of steel coupling beam and increase of beam length. Effective fixed point of beam is defined by adding a portion of embedment length of steel beam in RC shear wall to both steel coupling beam ends.

By increasing the use of vehicles today, a large number of tires are produced daily, and on the other hand, the number of worn tires has risen and, given the fact that they are not environmentally friendly, and their recycling is not economical, the worn tires are observed in different parts of the earth in a sporadic or massive manner, this issue causing many environmental problems, including a potential fire hazard, a place for the accumulation and cultivation of insects and rodent organisms such as rats. One of the solutions used to remove worn tires is burning, that cause produce toxic gases and air pollution, and the black powder resulting from the burning of tires causes pollution of surface water and soils. In some cases worn tires are used to produce carbon black, which has a lower quality and higher cost than carbon produced from crumb rubber, therefore, it is necessary to find solutions for the use of recycled materials from tires, on the other hand, by increasing the use of concrete structures, including concrete pavement and use of this pavement in many new pavements, and noting that the primary sources of concrete production, including sand, are limited and exhausted, the need to use alternatives for these materials in concrete pavements is becoming increasingly important. So in this research to resolve the problems, the combination of rubber and recycled steel fibers from worn tires is used in concrete pavements, also it should be noted that the composition of the crumb rubber consists of rubbers with three different granules and crumb powder that made from a recycling factory for worn tires, and then the mechanical properties of the concrete made from the replacement of these materials, has been evaluated. In this research, 0, 5, 10, 15 and 20 percent of crumb rubber mix was used as a fine grained substitute for concrete pavement. Also, in another state, half percent of the steel fibers recovered from worn tires were added to these samples. The results of this study indicate that the compressive strength of samples with 5, 10, 15 and 20% crumb rubber in comparison with the control sample was reduced by 1. 6, 36. 9, 49. 9% and 63. 1%, and samples with 0, 5, 10, 15 and 20% crumb rubber and 0. 5% steel fibers, respectively, decreased by 0. 3, 11. 2, 33. 7, 5 / 41% and 44. 3% respectively. Therefore, it is observed that the compressive strength of concrete containing crumb rubber and steel fibers is better than specimens with crumb rubber. Also, by replacing 5%, 10%, 15% and 20% of crumb rubber in concrete, its indirect tensile strength would be reduced by 7. 5%, 15. 3%, 41. 4% and 31. 2%, and by adding 0. 5% of the steel fibers to the concrete by replacing 0, 5, 10, 15 and 20% of crumb rubber in concrete, Indirect tensile strength increased by 67. 8%, 46. 7%, 32. 4%, 17. 8% and 3. 5%, respectively, and it is concluded that the tensile strength of concrete increases due to the addition of steel fibers. Due to the increase in the amount of petroleum residue replacement.

Dams are among infrastructural and essential structures which are designed and implemented for storage of water for multi-purpose usage. One of the natural events that constantly threatens the sustainability of dams is the earthquake. Therefore, accurate modeling and investigation of dam behavior considering the effective parameters and interactions during earthquake is one of the principles of safety evaluation of dams. With the advancement of knowledge in the field of earthquake engineering and the development of more precise methods for estimating the intensity of possible earthquakes, The methods of analyzing and evaluating the seismicity of the structures have been improved and the effects of more parameters can be considered in assessing the risk of each structure. Considering the nonlinear behavior of materials and the effect of cracking and its extension in dams, as well as more precise expression of the forces involved in, and its analysis with more advanced methods, are included as the important achievements of earthquake engineering in this field in recent years. For nonlinear analysis of concrete dams, nonlinear behavior of these structures by choosing existing methods requires acquaintance with the functional nature of the materials. In the past, seismic analysis of concrete gravity dams was most often considered ideally by using two dimensional monoliths in design mechanisms, and earthquake effects were usually applied by defining an earthquake coefficient. But in recent years, more emphasis has been placed on linear time history analysis and the failure analysis of the concrete dams in three dimensional space. In the present study, the seismic response of a concrete arch-gravity dam under the influence of earthquake stimulation is investigated in a three dimensional finite element analysis. The effects of dam-reservoir-foundation interactions are considered, the nonlinear behavior of the concrete and also the different patterns of the arc radius of the dam are studied and the results are compared with the two dimensional analysis. Finally, the contribution of response of each of the sustainability factors to seismic stimulation is evaluated. In the present study, the seismic response of a concrete arch-gravity dams has been evaluated through three dimensional nonlinear incremental dynamic analysis (IDA). For this purpose, five different-radius arch-gravity dam-reservoir-foundation coupled systems are analyzed under a set of 7 proper three-component ground motions, each scaled to 10 increasing intensity levels. The effects of dam-reservoir-foundation interactions are considered and the nonlinear behavior of the concrete and also the different patterns of the arc radius of the dam are studied. A damage index (DI) has proposed so that the damage imposed to the dam body is calculated based on the obtain results from the IDA study. Crest displacement, tensile damage occurred in various zones of the dam body and energy dissipation are considered as damage measure (DM), then the performance and different limit-states of the dam structure are determined.

The study investigated the effect of combined loading on end-plate moment connection considering the interaction of bending moments, axial forces and twisting moments. In some cases, beam-to-column joints can be subjected to the simultaneous action of bending moments, axial forces and twisting moments. Current specifications for steel joints do not take into account the presence of axial forces (tension and / or compression) or twisting moments in the joints. Although the axial force or twisting moments that transferred from the beam is usually low, it may, in some situations attain values which can lead to a considerable effect on the connections behaviour and significantly reduce the joint flexural capacity. Unfortunately, few studies considering the bending moment versus axial force interactions have been reported and there aren’ t any reports considering bending moments versus twisting moments interactions or combination of all the mentioned cases of loads. The lack of knowledge for understanding the performance of end-plate moment connection under combined loads may lead to unreasonable or even unsafe design, so in this study a combination of different loads have been examined. Therefore two extended End-Plate connections with different behaviour modeled using finite element method of analysis. The interactions between connection components (bolts, members and endplate) were accurately modelled to simulate the actual behaviour of connections. Both material and geometric nonlinearities were considered. At first the behavior of these models are investigated in pure bending application and numerical results validated against experimental data. The suggested finite element models showed good agreement with experimental results. The level of axial forces in joints of structures can be significant and has a significant influence on characteristics of joints. Because of the existence of this force in the moment resisting frames, the combination of bending and axial force in beams should be considered. Structures under fire situations where the effects of beam thermal expansion and membrane action can induce significant axial forces in the connection is a common condition. The results show that even in small amount of axial force the mode of failure and moment capacity of connection can change. Axial tensile forces decrease the initial stiffness of connection and axial compressive forces increase the stiffness. In many applications beams are eccentrically loaded and as a result experience twisting loads in combination with bending. The interaction effects due to torsion acting in combination with bending can reduce the capacity of the beam and initial stiffness of connection. Finally axial forces were added to the previous models so they experienced a combination of axial force, bending and twisting moment. The results indicated that the level and direction of axial force significantly modified the connection response. It was observed that compression forces significantly decrease the bending capacity of the models and lateral-torsional buckling of beam occures in all models. Tension forces can reduce the effect of torsion and in many cases they caused the bolts ruptured. Moreover, interaction diagram for predicting the bending capacity considering interaction of bending, torsion and axial forces are proposed based on the results from finite element analysis.

In this paper, the Navier-Stokes and Laplace equations are solved using the Finite Element Method (FEM) based on complex Fourier elements. The FEM is considered by two types of shape functions: Lagrange shape functions and new complex Fourier functions. The proposed interpolation functions are derived using enrichment of complex Fourier radial basis functions in the form of exp(i r ). The present functions have properties of Gaussian and real Fourier radial basis functions. These useful properties have provided the robustness of the proposed method. Also, these functions have the simultaneously functions field such as trigonometric, exponential, and polynomial; while the classic Lagrange functions satisfied only polynomial functions field. In other words, these features provide an improvement in the solution accuracy with number of elements which are equal or lower than the ones used by the classic finite element method. Solving the Navier-Stokes and Laplace equations is the important challenge in the fluids mechanics problems. The most problems cannot be solved by the analytical methods. For this reason, the numerical methods are developed. Generally, the numerical methods are divided to two classes: the methods based on the mesh and meshless methods. In the first class, the computational domain are meshed and the governing equations are solved based them the finite element method, Finite Difference Method (FDM) and finite volume method (FVM) are placed in this category. While, in the second category methods, the computational domain is divided to moving particles. In these methods, there is no needed to any grid and the equations are solved on the particles. The smoothed particles hydrodynamic (SPH) method, Moving Particles Semi-implicit method and Discrete Least Squares Meshless method are in this class. The FEM is capable to solving the problems with complicated geometry. Also, the Neumann boundary conditions are applied properly. Generally, the numerical methods such as finite element and finite difference methods are based on the mesh for solving the equations. For obtaining the results with high accuracy, it is needed to have enough elements. On the other side, when the number of elements (or number of degrees of freedom) is enhanced, the CPU time and storage space are also increased. For this reason, in this paper, the complex Fourier shape functions have been developed, which using them, both the number of elements can be reduced and also the suitable results can be obtained. In the present paper, at first, the governing equations and boundary conditions are expressed. Then, the FEM formulation and solution procedure are stated. Next, the complex Fourier shape functions and their enrichment process are described. Finally, three benchmark numerical examples are used in solving the Navier-Stokes and Laplace equations for the application of the proposed functions in the finite element method. These tests include Couette flow, flow of a viscous lubricant in a slider bearing and steady state heat transfer in rectangular region. In order to show the efficiency and accuracy of the present method, the results of the proposed method are compared with the classic functions and also the analytical solutions. The results of this comparison indicate the high accuracy of the proposed method.

Several studies have been done on the rheological properties and setting time of cementitious materials and mixtures, but the relationship between these two important features has not been studied so far. In this research, the main purpose of the done experiments, is to evaluate the relationships between the rheological properties and setting time in self-consolidating concrete (SCC) mixtures. Rheology is the science of studying the materials deformation and flow and in general, in SCC mixtures, the most important variables are the rheological variables. The setting time is also one of the most important parameters existing in all kinds of concrete mixtures. It should be noted that from the past up to now different definitions have been presented for the time of setting in various sources. As a short definition, it can be said that the setting time is a period of time in which concrete changes from fluid phase to solid phase. In aspect of rheology evaluations, workability tests and rheometric experiments have been performed. Also in aspect of determining the setting time, the main method used to determine the time of setting is the electrical resistance measurement method (E. R. ). Despite there is a long time of using this method in determination the time of setting of concrete mixtures, there is no standard written for it. Therefore in this research said method and its results have also been brought under more precise verification and study (which can be referred to as a side purpose). For this purpose, the standard penetration resistance (P. R. ) method is used according to the ASTM C403. Based on the obtained results, it was found that the fault percentage of E. R. method in comparison with the standard P. R. method is about 5. 3% and 3. 59% in determining the initial and final setting time respectively which was minor and negligible differences. Therefore, it was found that the results obtained by electrical resistance method are reliable. Thus, by using the results obtained from the E. R. method, the existence or non-existence of relationships between the rheological properties and the setting time was studied. According to the obtained results, it was found that there are behavioral and numerical relationships between these two issues. Based on the results it was found that in the SCC mixtures with lower slump flow and longer T50, the setting time becomes shorter. This fact means that the lower willingness of flowability causes a decrease in setting time of self-consolidating concrete mixtures. In the section of rheometric studies of the SCC mixtures performed by the rheometer, it was found that there are also important relationships between the yield stress and the setting time. According to the achieved results, it was found that the higher yield stress led to occurrence of shorter setting time and in connection to this issue, some numerical relations were also introduced. Thus, in this research it has been endeavored to study the relationship between the setting time and rheology properties in SCC mixtures as much as possible and obviate the existing gaps.

Gravity dams are vital structures whose proper design and evaluation for stability are quite important. One of the effective forces on stability of concrete dams is the uplift force and its distribution below the dam base. Uplift pressure resulting from headwater and tail-water not only exists through dam cross sections and the dam base, but also within the foundation below the dam base. In many gravity dams uplift pressure is the major active force that must be included in the stability and stress analysis to ensure structural adequacy. There have been different methods employed since past to the present to assess and calculate the uplift load. In each of these methods, depending on the degree of simplification, the accuracy of the answers will be reduced. Due to the limitations of each of these methods, available numerical methods may be used nowadays to estimate the values of pore pressure within the porous medium. As far as seepage forces have a great effect on stability of gravity dams, understanding the seepage in rock masses has a great importance, because the gravity dams are generally built on rock foundations. The actual influential phenomenon encountered in saturated jointed rock media is the joints hydro-mechanical interaction effect. Finite element method as a general and systematic method is one of the most common numerical methods for solving engineering problems. Also, this method has significant application in hydraulic and hydrodynamic problems. In addition, the uplift load pattern and distribution according to common codes are influenced by some factors such as head and tail water, assuming a segmented linear load distribution below the dam. In this research, to investigate the sensitivity of the load pattern to dam height, a number of gravity dams of Pine Flat type with different heights and their foundations are modeled. An enhanced modeling approach is employed to estimate the equivalent uplift load distribution at the dam base for application in the standard finite element modeling procedures. Coupled p-u finite element analysis is performed accounting for the seepage and stress field simultaneously. Dam body is considered to be completely impervious. The foundation rock is assumed as homogeneous and uniform, in terms of elasticity and permeability. The stresses generated in the dam interface for each case of the coupled hydro-mechanical analysis is compared against that of the conventional load pattern according to the U. S. Army Corps of Engineers regulation for the same dam model. It was found that the error magnitude due to the conventional pattern has a direct relationship with the dam height. As the dam height increases, the amount of error of calculated stress increases. In particular, the error at the critical zones of the foundation such as at the dam heel, may raise even up to 40%. In the group of dams studied, the error increases even up to 12 times in respect to the expected error in the shorter dams. The deficiency could in some cases completely affect the safety of the dam. This research indicates the necessity of using more accurate methods of estimating uplift load under high gravity dams.