Modares Civil Engineering journal
Year:2019 | Volume:19 | Issue:4 |Papers Count:17

Construction of inclined piers has been observed in a great number of bridges worldwide today. With installation of the bridge piers on river path, the simple and steady flow pattern reaching the pier undergoes intense and complicated changes. Complicated vortex systems created around the pier dig around the pier a hole called a scour hole. Expansion of such a hole around the piers empties the foundations from beneath, leading to consequent destruction of the foundations and the bridge. Whereas, few studies have been conducted to address scour at inclined piers. This issue was investigated in light of the significance of severe damages caused by the scouring phenomenon, the construction of vertical-inclined piers and their untold effects specifically in meandering paths. In this study, the effect of different arrangements of inclined and vertical bridge piers (in convergent and divergent fashions), installed at the vane vertical to the flow, was analyzed along with the effect of flow conditions and the position of the pier groups at the 180 degree sharp bend on parameters such as the maximum scour depth, the maximum sedimentation level, the scour hole dimensions, etc. in the laboratory. To conduct the experiments, a channel consisting of a 180 degree sharp bend was utilized. Due to its 2-meter-long central curvature radius, it is classified as a sharp bend. The channel contains upstream and downstream straight ends respectively as long as 5 and 6. 5 meters. The experiments were carried out under clear water (where u/uc is equal to 0. 87), incipient motion (u/uc = 0. 98), and mobile bed (u/uc = 1. 03) conditions. Two vertical and four inclined piers formed the pier group. The diameter of the piers was selected 5 cm and their inclination angle was 21 degrees. The pier groups were placed at the 60, 90, and 120 degree positions of the bend. Results indicated that the maximum scour depth and level of sedimentation occurred at the 60 degree position under live bed conditions. These values were measured equal to 4. 2 and 3. 2 times the pier diameter. In every three position of the installation of the piers at the bend, the maximum scour depth occurred due to position of the convergent-vertical pier group. However, the maximum sedimentation level occurred in the case of positioning the divergent-vertical pier group. In both pier groups, the maximum scour depth occurred in the vicinity of the inclined pier near the outer bank in the first row. Changing the position of the piers from the 60 to 90 and 120 degree angles leads the maximum sedimentation level to occur at a distance closer to the vicinity of the pier group. Such a distance was obtained in those three positions to be respectively 42, 28, and 22 times the pier diameter on the average. In both pier groups, the minimum area of the scour hole occurred at the 120 degree position. Further, the maximum area was observed in the experiments on the 60 degree position. Shifting the flow regime from the clear flow to incipient motion resulted in an increase in the area of the scour hole. Such an increase is observed in every three position per both pier groups.

The aims of this research are mainly to obtain the collapse preventation (CP) seismic capacity of eccentric braced high rise steel moment resisting frames under near field earthquakes and evaluate the effects of fling step and forward directivity, using incremental dynamic analysis and capacity spectrum methods. Drift ratio θ and mode acceleration specrum with 5% damping Sa(T1, 5%) are selected as the appropriate damage measue (DM) and intensity measure (IM) respectively. Six eccentric steel braced frames with 3 bays and 15, 20 and 25 storeys with eccentricity of 1m and 2m are designed according to standards. The frames systems are equivalently taken as shear-flexural beams with representative lateral stiffness ratios. Twenty two earthquakes according to FEMAP695 are chosen which are divided in two groups, one with fling step effects and the other with forward directivity effects. Incremental dynamic analysis (IDA) is one of the efficient tools for estimating seismic capacity of frames. In this research, IDA is implemented for each of 6 frames using all 22 earthquakes. The frames are once subjected to multiple scaled 11 selected earthquakes with forward directivity effects, and once more they are subjected to other multiple scaled 11 selected earthquakes with fling step effects, and response parameters of frames are calculated using nonlinear dynamic analysis. Each IDA curve is ploted for Sa(T1, 5%) versus maximum inter story drift ratio θ . Spectral acceleration Sa(T1, 5%) is scaled until the collapse of the frames occure. IDA analysis results show that fling step and forward directivity characteristics of near field earthquakes have less effects on drift ratios compared with their effects on spectrum acceleration values. Frames under earthquakes with fling step reach CP point with lower acceleration spectrum values compared to those under earthquakes with forward directivity characteristics. Also IO and LS limit state spectrum values for frames under earthquakes with forward directivity effects are more than those values for frames under erthquakes with fling step effects. Collapse prevention (CP) points are also calculated using the capacity spectrum method. For this purpose, at first, mode shapes for elastic vibration of frames are calculated. Then each scaled shear force is distributed using the first mode of vibration and capacity curves are drawn using nonlinear static push over analysis. The push over capacity curve is then converted to capacity spectrum using first mode of vibration. Acceleration resposnse spectrum are drawn for each of 22 earthquakes using 5% damping and then converted to demand spectra. The demand spectra are then corrected for effective damping which is a value more than 5%. The corrected demand spectra for 11 near field earthquakes with fling step effects and those for other 11 earthquakes with forward directivity effects are then averaged. CP point for each frame is then obtaind from the point of conjuction of the averaged corrected demand spectra with those corresponding capacity spectra of frames. Results from capacity spectrum method show that CP values are less than thos CP values calculated from IDA analysis.

Rockfill materials are used in construction projects such as dam construction, road construction and so on. Due to the increasing use of these materials, experiments and studies have also been carried out on this material and usually, these studies have been carried out on strong rockfill materials. Today, the use of soft and weak rockfill materials has expanded because the economic and environmental issues. These marginal materials traditionally would not be used owing to their unfavorable engineering properties that is, low strength, high compressibility, and proneness to material degradation with time. Therefore, the use of soft rocks excavated on site as rockfill materials for high rockfill dams is still a controversial issue, as weathering takes place when the rock is exposed to an environment in which variations in air, temperature, and water content are involved. and still no comprehensive studies have been conducted on soft rockfill materials and need more information on the behavior of these materials in different conditions. One of the most important subject discussed in the rockfill materials is the particle breakage phenomena. Particle breakage index that quantifies the degree of particle breakage, can reflect the degree of particle crushing of material. To select weak rockfill materials, we visited the Nohob dam that is under construction and rockfill material in spillway excavation section is thrown away and it is not used in the construction of the dam. With considering that the dimensions of the usable rockfill material may be much larger than the dimensions of the laboratory equipment. Therefore, it is always a matter of scaling and matching the results of the laboratory and the field from the important items of rockfill materials. In this research, the behavior of weak rockfill materials has been studied in medium scale oedometer apparatus, in dry, wet and saturate conditions and also Los Angeles experiment is done. Based on the present study, the particle breakage increases with the addition of water and in saturate conditions, particle breakage also has a slight increase compared to wet conditions and for settlements and deformations of wet and dry specimens of materials show that wet specimens settlements are more than dry specimens.

Dynamic properties of soils at very small strain, i. e. small strain shear modulus (G0) and shear wave velocity (Vs), are used frequently in geotechnical applications. Many researchers have studied the effective factors on the small strain shear modulus in clean sands or sand-fine mixtures. However, less attention has been given to the dynamic properties of gravelly soils at small strain and they are poorly understood. Reviewing the technical literature, one may find it very interesting to study the impacts of non-plastic fine content on the small strain shear modulus of gravelly soils. A fundamental experimental study was designed to explore the influence of non-plastic fine content on the small strain shear modulus of gravel-sand-silt mixtures (common geomaterials in nature). Since gravel and silt mixtures with no sand particles are less common in nature, three types of sandy gravels with different sand-to-gravel ratios of 0. 25, 0. 43 and 0. 67 were selected as base gravelly soils. In order to isolate the impacts of the fine content, sand-to-gravel ratio was kept constant in each soil type. Various percentages of silt (0~45%) were carefully added to the base soil. Eighteen mixtures of sandy gravels with different silt contents were prepared. Bender Element tests were carried out under saturated conditions to determine the small strain shear velocity. Samples were prepared by the moist tamping method due to its advantages for making loose and homogeneous samples without creating any segregation of grains. Following the saturation process, specimens were subjected to three isotropic confining pressure levels of 50, 100, 150 kPa. The relative densities of the samples were carefully kept constant to avoid the density effect on the responses. To keep the densities of samples constant while varying the fine content percentages, the initial relative density (Dr before consolidation) was selected in a way to ensure that the target relative density (Dr after consolidation) was approximately 35% (i. e., Dr=32% ~ 38%). The appropriate initial relative densities for each mixture and for various effective confining pressures were obtained using iterative efforts. Laboratory results show that the maximum shear modulus increases in all mixtures when the effective confining pressure increases. The small strain shear modulus is significantly impacted by the percentage of non-plastic fine content and sand-to-gravel ratio of base gravelly soils. Increasing the percentage of silt and also the sand-to-gravel ratio causes the shear modulus to decrease constantly. The reduction (rate of which is different for mixtures and effective confining pressures) can be explained from the micromechanical perspective and the formation of strong and weak force chains through interparticle contacts. Finally, Hardin's general equation is fitted to experimental data and fitting parameters are found using regression analysis. Empirical relationships are presented to estimate the small strain shear modulus in each of those three types of soil. These correlations are a function of non-plastic fine content, void ratio and effective confining pressure of mixtures. The comparison between the estimated and the measured small strain shear modulus clearly indicates that the purposed equations yield good agreement with experimental data. Therefore, these equations can be used to predict the small strain shear modulus for different mixtures of gravel-sand-silt in many geotechnical applications such as soil improvement, evaluation of liquefaction potential and the design of dynamic foundations.

Soil pH is a measure of the acidity and alkalinity in soils, ranging from 0 to 14 that measured in a slurry of soil mixed with water. Soil pH normally falls between 3 and 10, with 7 being neutral, acid soils have a pH below 7 and alkaline soils have a pH above 7. Ultra-acidic soils have pH value less than 3. 5 and very strongly alkaline soils have pH value more than 9 which are rare. Extremes in acidity or alkalinity may affect mechanical behaviour physical properties of soil. Recently, the rapid development of cities and the industrial revolution have caused enormous environmental impacts and become a serious environmental problem. About 80% of the pollutants in the atmosphere, including suspended particles and gases, result from vehicular traffic and industrial activities. Precipitation acts as a significant natural cycle to clean up atmospheric pollutants such as gases and particles in the air. The major sources of acid water are strong presence of SO2 and NOx gases in the atmosphere. One of the most important effects of acid water is its effect on soil, including washing nutrient cations, releasing toxic elements, and acidifying the soil. Also, acid mine drainage and the contaminants associated with it, is a common occurrence in waste dumps of mining sites results in acidic conditions with a pH of less than 4 develop over time. On the other hand, mineral deposits, over liming in some parts of the land and the use of limestone to improve the different soil natural and control the pH in waste dumps leads to alkaline conditions (pH more than 7) at mine sites. One of the most important effects of air pollution is acid rain. The increasing expansion of cities, the rapid growth of urbanization and the industrial revolution have caused enormous environmental impacts in and around cities. Industrial activities, production of energy and fuel, the use of fertilizers and pesticides cause significant amounts of contaminants to the atmosphere. The entry of metal contaminants and acidifying compounds such as sulfur, nitrogen compounds or their reaction to the atmosphere in the rain will increase the acidity of the rain which can change the quality of atmospheric precipitation. In general, it can be stated that the meaning of acid rain is a rain that has a pH of less than 5. 5 which is a lower natural pH. In the current study, the effect of acid rain on the mechanical behavior and physical properties of lime stabilized sand with respect to the eastern regions of Isfahan has been investigated. At first, the various lime content was added to the soil and the specimens were tested after treatment and saturation under various pH values. The results show that adding lime increased the optimum moisture content, shear strength of the specimens, the cohesion and the friction angle of the soil. On the other hand, reducing the pH value results in continuously decreasing the shear strength parameters of the soil specimens. Finally, based on the scanning electron microscopy (SEM) image from the specimens, the effect of pH and lime content on the bonds between the sand grains was investigated.

Weirs are structures used to measure discharge and flow control in canals and dams. Economically, a significant part of the cost of building a dam is due to weirs. By investigating different types of weirs, researchers have concluded that the piano-key weirs have two major advantages over other weirs. One of the most important advantages of a piano-key weir is that this kind of weir needs less space to run and can have smaller dimensions. Another important advantage of this type of weir is the ability to transmit more water than other weirs, which can safely protect the dam. A review of previous studies suggests that some studies have been carried out in the field of piano-key weirs. But, there are not sufficient studies on the performance of these types of weirs in curved plans as well as their hydraulic performance improvement factors. The main objective of the present research is to investigate the factors that can improve the performance of curvilinear piano-key and increase their hydraulic efficiency. In order to verify the results of the numerical model, the Anderson (2011) laboratory model has been used. Numerical modeling has been done for 5 inflow discharges in FLOW3D software. In order to quantitatively compare the results of the numerical model with laboratory values, some error criteria including R2, MAE and RMSE have been used. The values of these parameters were 0. 9985, 0. 00804 and 0. 009521, respectively. Results showed that numerical model has acceptable adaptation to experimental results. In the next part of the paper, factors that can be effective in increasing the discharge capacity of the curvilinear piano-key weirs are investigated and analyzed based on the discharge coefficient curves and contours. In the first step, effect of crown shape on weir hydraulic performance was investigated and for this purpose three curvilinear piano-key weir models with rectangular, triangular and elliptical shapes were designed. Results showed that the weir with triangular crown had up to 60% higher discharge coefficient than the elliptical-crown weir and up to 65% more than the rectangular-crown weir. According to the general pattern of flow, in weirs with rectangular and elliptical crowns, the flowing flow clinging to trunk weir is discharged to downstream, while in weir with triangular crown, adhesion among flow and trunk of the weir is decreased. This factor increases discharge capacity of the weir with triangular crown in comparison to the other two weir types. In the next section, effect of existence or absence, as well as the geometric shape of the bundle, on the performance of these types of weirs was investigated. For this purpose, three weir models with cubic rectangular, half-cylindrical and prism bundles were designed and compared with a weir without bundle. Results showed that the bundle improved hydraulic performance of the weir. Also, for all the studied range of hydraulic heads, weir with half-cylindrical bundle had higher discharge capacity than the other weirs. The reason is that in the weir with half-cylindrical bundle, the sudden change in the angle of flow lines before collision with the bundle occurred further away from the end of the bundle, which caused flow entrance with less disturbance to the weir keys. Finally, the impact of a parapet wall on the weir operation was investigated. A 1. 3 cm high parapet wall was added to the weir crown. Results showed that addition of the parapet wall increased the water level in the weir crown area and resulted in decreasing the velocity of approaching flow to the weir structure. Reduction of the velocity decreases the possibility of flow blockage and the flow has more time to run away from the weir keys. The set of these factors cause the weir with parapet wall to have higher discharge capacity than weir without the parapet wall.

The number of scrap tires is increasing rapidly in both developed and developing countries due to the steady rise in the number of vehicles. Scrap tires accumulation in the environment causes several social, economical and environmental issues all around the world. Recent studies showed that this material can be considered as an alternative for some conventional materials in construction industries. Scrap tires are used as a whole or in processed pieces in geotechnical engineering to help reducing the disposal effects and improve mechanical characteristics of soils. It is becoming quite common to mix soils and processed rubber particles in different civil and geotechnical constructions like lightweight backfill, road subbase, embankment fills, slopes, asphalt construction, sound barriers, rail construction and foundation reinforcement. However, the employment of these mixtures in real scale projects requires a better understanding of the mechanical performance of the mixtures. The mechanical response of sand-rubber mixtures, initial fabric skeleton and interaction mechanism between constituents depend on several factors such as volume proportions of the mixtures, confinement stress and size ratio between constituent’ s grains. The idea of mixing sand and rubber particles with the same particle size distribution was employed in this study to minimize size contrast effect between the grains. Therefore, the mechanical behavior of the mixtures is only based on the volume proportions of the mixtures and internal mechanism between sand and rubber particles. To do so, drained triaxial compression and extension tests were conducted in conventional triaxial apparatus on sand-rubber mixtures. The triaxial samples were made using moist tamping method in three successive layers to avoid high segregation between rubber and sand particles. The effect of rubber particles was significant on drained mechanical response of sand-rubber mixtures. Peak strength reduction followed by axial strain increase corresponding to the peak strength were observed by increasing the rubber fractions of the mixtures. Consequently the initial elastic modulus of sand-rubber mixtures reduces by increasing the rubber proportions of the mixtures. The contribution of volume proportions of the rubber particles inside the mixtures was found to be significant on the deformation behavior of the mixtures. The volumetric response of sand-rubber mixtures shows that increasing the rubber proportions of the mixtures increases the compressibility tendency of the mixtures which reduces the dilatancy of the mixtures. The angle of friction and intercept cohesion reduces and increases by increasing the rubber fractions of sand-rubber mixtures which are consistent with what have been observed by the previous investigations in the literature. The critical state line parameters of the mixtures were highly dependent on rubber proportions of the mixtures as the slope of critical state line increases by increasing the rubber fraction of the mixtures. The radial strain of the mixtures decreases by increasing the rubber proportions of the mixtures which could be the effect of replacing sand particles by rubber particles in force chains. In general, the mechanical response of sand-rubber mixtures was mostly controlled by sand particles where FR ≤ 20% and by rubber particles where FR > 30%.

It is important in Hydraulic and river engineering to estimate the mean velocity and turbulence intensity to identify the presence of secondary currents, its shape and position. The flow of channels consists of three conponents of velocity, one component in the direction of flow and two components in the transverse direction of the channel. Due to the heterogeneity of the velocity fluctuations, a series of vortex vortices in the channel section to be formed which is called secondary currents cells. The secondary currents are dependent on factors such as bed roughness, channel slope and shear stress. The present study investigates the effect of bed roughness form on the pattern of secondary currents with numerical modeling in Flow-3D software by using RNG turbulent model. This research has been carried out according to the data of the Negara laboratory model carried out at the Hydraulic Laboratory of Singapore National University. In the results obtained from the mean velocity profile, the mean error for triangular roughness trough was 9. 94% and for roughness crest was 3. 71%. in the case of shear velocity, the error for triangular roughness was obtained at three cross sections x=4, x=5 and x=6 respectively 6. 58%, 6. 86% and 5. 67% which demonstrates the good fit of the numerical model results with the reference laboratory model. The flow conditions in the channel were designed and studied for three types (rectangular roughness, trapezoidal roughness with an internal angle of 80 degrees and trapezoidal roughness with an internal angle of 55 degrees) of roughness that are most used in hydraulic structures. The results of the study on the turbulence intensity, secondary currents and turbulence kinetic energy showed the effect of trapezoidal roughness with an internal angle of 55 degrees relative to the other two forms of roughness. The difference in the turbulence intensity in trapezoidal roughness with an internal angle of 55 degrees relative to a triangular roughness at a height of 0. 1 meter from the channel bed was obtained at about 4. 54%, which is affected by a sharp roughness. The location of the center of the contour nucleus begins in the depth of about 0. 2 meters, due to channel size B/H=1. 5 of less than 5, the channel is narrow and justifies the presence of vortices in the middle. On the other hand, the tendency of cells to the left and right walls of the canal is also affected by roughness geometry with also different from the deformation of the location of these cells. In trapezoidal roughness with an internal angle of 55 degrees, there is a tendency to both walls. The turbulence kinetic energy contour with the center of the nucleus begins at the roughness crest with an approximate value of 0. 0002 for all roughness, but its location is different in relation to the roughness geometry. In fact, the turbulence kinetic energy is the effect of oscillating velocity components that the existence of external rotations is the effect of the redistribution of energy by velocity tensor, which is responsible for the formation of secondary current cells.

Wind turbines are considered as an important element of the renewable energy structure. Offshore wind turbines are tending to be more efficient than onshore because wind speed and direction are more consistent. Monopiles are widely used for offshore wind turbines at present. They are always subjected to significant cyclic lateral loads due to wind and wave excitation. Monopiles are hollow cylindrical steel piles with a circular cross-section and a length to diameter ratio of less than 10 (L/D < 10). Currently, the design of monopiles is based on experiments performed on slender piles. Since monopiles behave rigidly, finding their action seems to be very necessary for accurate analysis and design of these structures. In order to better understand the performance of monopiles under static and cyclic lateral loads, a series of static and cyclic lateral load tests was conducted on a stainless steel monopile in the geotechnical centrifuge. The main goal of this study is the examination of accumulated lateral displacement of a monopile foundation for an offshore wind turbine with a large diameter subjected to wind and wave loads. In this article, the lateral responses of a large diameter monopile under one-way force-controlled cyclic lateral loads are described and accumulated permanent pile shaft lateral displacements caused by cyclic lateral loads are discussed. All tests were performed in beam centrifuge. Monopile was installed in Firoozkooh-161 sand in this study. The centrifuge tests were carried out at different cyclic load and magnitude ratios insights into the ongoing development of net stresses and bending moment. In this research, 4 Tests were designed and implemented to centrifuge modeling the action of monopiles in sandy soils. Tests were carried at physical modeling laboratory of the school of civil engineering at the University of Tehran. The first experiment was initially conducted to estimate the ultimate capacity of these piles, and then the obtained results compared to similar research findings. Three other experiments were carried out to evaluate their behavior affected by cyclic lateral load and to determine cumulative displacements and deformation state. Consequently, the results were finally compared with findings of other researchers, regulations, and relationships available related to other used piles (with a diameter less than 2 m) in geotechnical projects. Results of the study indicate that the use of available regulations and instructions in estimating the lateral load-bearing capacity of these piles was conservative. However, this fact can lead to the achievement of unreliable and upper-hand results. Thus, the existing relationships and regulations need to be changed to provide accurate results related to these piles. The major findings of this study are presented below:-The estimation of the monopile lateral bearing capacity is impossible with existing formulas, and this requires numerical or physical modeling.-The behavior of the monopile structure under lateral loading is rigid until the failure limit, so the failure mechanism of the monopiles will be similar to the short and rigid piles.-Cumulative lateral displacement of the monopile head is ascending in the number of cycles, and its rate in all cyclic tests is reducing.-The monopile has rotated around a point in the depth of 30 to 75 percent of the driving length.-The maximum bending moment value in all cycles has occurred in the depth of about 20% of the driving length.

An important goal of deviation of water flowing in a river is to control sediment and supply required water with minor sediment. This goal can be achieved using some sediment control structures, such as sill, spur dike and submerged vanes. These structures, however, can influence the flow pattern in a water intake, which induces scouring at downstream of the intake in main channel. For instance, generated helical motion due to secondary circulation induced by submerged vanes is the main cause of scouring at downstream of these structure. As for spur dikes, the generated helical motion is also the main cause of scouring in the main channel downstream, which occurs through increased flow velocity and curvilinear flow near the spur dikes. The induced scouring may impact the stability of coastal region near the channel/river that must be taken into account in designing process. In this study some experimental tests were carried out to understand the effect of sill, spur dike and submerged vanes on sediment control and scouring in the downstream of intake in the main channel. Four different cases were considered to be discussed; in the first case, there was no sediment control structure installed. In the second one, however, the effects of a sill with a height of one third of the flow depth at the entrance of the intake was evaluated. In the third case the effect of installing both sill and spur was studied. In this case, in addition to a sill installed at the intake entrance, an impermeable direct non-submerged spur, with a length of 1/4 of width of the main channel at upstream, was mounted on the opposite side of the intake at upstream of the main channel. In the fourth case, submerged vanes were added up to the two other mentioned structures earlier. The submerged vanes were put in two parallel rows in front of the intake in the main channel. All experimental tests were conducted in a flume equipped with a recirculating sediment system and a 90° lateral diversion channel. Three important parameters including the ratio of bed sediment transport into intake (Gr), the volume fraction of sediment deposited within intake (Vr), and the dimensions/volume/area of scouring at upstream in the main channel were evaluated in this study under three different discharge ratios of 0. 12, 0. 15 and 0. 18. The experimental results indicate that the mentioned parameters are mainly determined by the discharge ratio and the mechanism of sedimentation control. It can be noted that Gr increases with Qr, whereas Vr decreases as Qr raises up. It was also observed that all sediment control structures play an important role in sediment control at the intake entrance, although the influence of spur dike and submerged vanes is greater as compared with that of sill, which causes a significant reduction in Gr and Vr. It was also found that the dimensions/volume/area of scouring area at upstream in the main channel is mainly controlled by existence of those structures. Generally speaking, the dimensions/volume/area of scouring area is mainly controlled by the velocity of water in contact with the downstream bank of intake, Qr, the power of induced secondary flow by the submerged vanes and the spur dike, and the cumulative sediment in front of the intake due to existence of sill. It was also noticed that in some cases both the submerged vanes and the spur dike may result in scour increase. The dimensions/volume/area of scouring area demonstrated different behavior over different Qr ranges that could be described through this fact that these parameters are influenced by many causes simultaneously. To approximate Gr, Vr and dimensions/volume/area of scouring area in different situations, some relationships have been presented in this study. A comparison has also been made between the results obtained from the current study and those presented by other authors, based on which the most proper structure was chosen with respect to sediment control and scouring. Eventually, the third and fourth cases were found as the most desirable system able to control sediment more efficiently comparing to other cases.

A number of pavement condition assessment methods are used to perform pavement condition evaluation. Two of the most widely used methods are determination of “ International Roughness Index (IRI)” and “ Pavement Condition Index (PCI)” parameters. IRI is measured on roads using specific equipment that determine road roughness. In contrast, PCI is based on subjective rating of a number of pavement distresses. Road pavement structures very often could not reach their design service life as a result of several parameters affecting their performance. PCI decreases as a result of increased traffic loading. Aside from the impact of traffic loading, many other factors cause damage to pavements; namely, low construction quality, poor maintenance, flooding and water scouring. As a result of many factors causing damage to roads, road serviceability age uncertainties arise, so that the remaining life of a pavement service life will be difficult to predict. Determining the structural capacity and surface pavement condition of pavements play important roles in pavement evaluation. With this regard, it is important to find relationship between surface characteristics and structural capacity of pavements. Therefore, finding a reliable model for surface characteristics and structural capacity will be beneficial. Structural evaluation of pavements is carried out by non-destructive testing. FWD is one of the most important non-destructive testing of pavements, although performing that is costly and time-consuming. On the other hand, the remaining service life of pavements is one of the most important parameters for the structural assessment of pavements. This is essential for assessment of requirements, maintenance and rehabilitation, prioritization and budgeting purposes. The lack of precise evaluation of remaining service life of pavements is a crucial issue. In addition, lack of a proper performance prediction model is a major barrier to predict the remaining service life of pavements. The combined analysis of FWD testing results and PCI measurements can be known as an appropriate solution for determining RSL. With selecting a series of independent variables reliable correlation was found between RSL and independent variables. RSL can be used with other indexes and parameters that make their data capturing easier and less costly. In addition, using this model enabled finding correlation and interaction between different variables.

One of the common issues in the cast-in-situ reinforced concrete structures is creating a construction joint (cold joint) caused by an interruption or delay in the concreting operations. According to ACI 224. 3R-95, construction joints in columns are to be provided below the beam for lower story columns and above the floor slab for upper story columns. The cold joint is a weakness or defect in the concrete, which results in the non-integrity of the concrete. For this reason, the performance of concrete elements with the cold-joint is under the influence of that behavior. The seismic design procedure for in-situ construction generally considers that the connection of beam and column that frames into the joint is monolithic in nature. But in actual construction, it is not possible to cast columns of the multi-story frame in one go and therefore, a cold joint is inevitable in all the upper story columns immediately above the lower story slab. In this research, firstly, cold joint behavior is modeled. The model of concrete damage plasticity used for the modeling the concrete behavior and the surface-based cohesive behavior with the traction-separation response used for the modeling the cold-joint. The three-point bending beam specimens with the same compressive strengths of concrete on both sides of the cold-joint have been used to verify the opening mode behavior of the cold joint from the experimental results. Three different sizes of the beam were considered to ensure the validation of opening mode behavior for the cold joint. So, the push-off test specimens have been used to verify the shear-friction behavior of the cold joint from the experimental results. Three same specimens with same compressive strengths of concrete on both sides of the cold-joint and the different number of steel connectors crossing the interface surface of the push-off specimens were considered to ensure the validation of shear-friction behavior for the cold joint. Then, a single-story single-bay reinforced concrete frame is modeled. After ensuring the validity of the numerical model of the cold joint and frame, a reinforced concrete frame containing a cold joint is modeled on its columns at the below of the beam and the top of the foundation. Subsequently, in order to investigate seismic behavior, an In-plane monotonic loading, stroke-controlled pushover tests were performed once on a frame containing a cold joint and once again on the same frame but without a cold joint. From the result, prior to the yield point, there was no difference between the load-displacement curve of the monolithic frame and frame with cold joints. In the range between the yield point and the failure point in the frame, a relatively small difference was observed between the load-displacement curve of the monolithic frame and frame with cold joints. A significant effect on the frame behavior was achieved in monolithic frame and frame with cold joints in their ultimate displacement so that the ultimate displacement in the cold-joint state was reduced by about 30% compared to the monolithic one. In fact, the finding results showed that under monotonic loading, the existence of a cold joint hadn’ t any effect on the maximum lateral force of the frame, but reduced the ductility of it by about 30%.

Roads are one of the most important and valuable assets of countries, and remarkable amounts are spent annually to repair and restructure them. The pavements are divided into two main groups of flexible pavements (asphalt pavements) and rigid pavements (concrete pavements). In Iran, mainly used asphalt pavements, which were formerly about 90 years old. Therefore, there are many reasons why the most important of them, according to most experts, is the use of the country from abundant oil resources and low initial costs in the construction of this type of pavement. In recent years, with the entry of bitumen as one of the main components of the asphalt composition of the commodity exchange and consequently the increase in the cost of manufacturing and manufacturing asphalt, as well as the development of cement production plants in the country and the creation of carbon dioxide (CO2), a suitable platform for the development of geo-polymeric concrete pavements in competition with asphalt pavements and concrete cement has been provided. In addition to abbility of bearing and reducing the pressure caused by the vehicle wheels, the pavement layers should be durable against atmospheric and physical factors, including the natural elements of the freeze-thaw cycles, acids and sulfates. Th pavement must be able to withstand the durability and durability of the pavement and maintain its service over the lifetime specified. These destructive effects led to more attention to the optimal use of resources, pozzolanic materials, and waste. In this regard, the use of ground granulated blast furnace slag and Silica fume in various industries such as road construction and building have been considered as a solution, however, practical, accurate and effective steps have not been taken yet. This research tried to present the materials and experiments carried out and to summarize them in order to eliminate the obstacles and obtain the necessary results for the use of alkaline concrete (geo-polymeric) in the manufacture of durable concrete veneers in the pavement. The use of alkali-activated slag concrete with the replacement of Silica fume instead of silica in sodium silicate, in addition to the use of waste materials, enables the strength and durability of concrete pavement to be increased under freezing and thawing cycles, acid attacks and being sulfate. In this study, alkali-activated slag concrete with different percentages of Silica fume was studied using The experiments of compressive and bending strength, durability under freeze-thaw cycles, sulfuric acid, and magnesium sulfate attacks. The results showed that the replacement of 30% silica fume instead of silica in sodium silicate, increasing the compressive strength to 43. 8%, increasing the bending strength by 58. 9%, increased the durability under freezing and thawing cycles by 78. 2%, increasing durability against sodium sulfate to The rate of 57. 1%, increase the durability against magnesium sulfate by 54. 1%, and the reduction of pavement slab thickness by 20. 8% compared with concrete cement.

One of the oldest and most durable building materials used for a large number of ancient structures by mankind is the masonry material. The advantages of this material such as few maintenance costs of masonry building and beautiful sight view of this structure, as well as its proper resistance to fire, have caused to be the boost building materials nowadays. Although numerical analysis of the seismic behavior of masonry structures due to their geometrical and behavioral complexities is difficult, it is possible to accurately evaluate them by using an appropriate recently developed modeling method. In order to select the appropriate numerical method in addition to the accuracy of the results, the simplicity of the modeling and the necessary parameters to determine the behavioral characteristics of the masonry materials must also be considered. Two major modeling approaches for simulating the behavior of masonry members are micro-modeling (heterogeneous model) and macro-modeling (homogeneous model). In the micro-modeling approach, the failure mechanisms and cracking pattern are precisely determined; but because of the required specifications and details, it is considered as a sophisticated modeling approach. In this study, the main purpose is to develop a micro-modeling approach based on the discrete element method (i. e. rigid block and spring method) for simulating in-plane behavior of unreinforced brick masonry buildings. For modeling each brick masonry wall in this paper, the masonry unit is defined which is consisted of a rigid block in the transverse direction and four blocks in the horizontal direction with two different types of springs. This unit represents, in fact, two bricks and connecting mortar in real condition. According to the assumption of the rigid block and spring method, the properties of the normal and shear springs are considered independently. In this situation, it is not practically possible to accurately estimate the behavior of masonry member in shear dominated case. In order to model cracking in brick, the two-way crack hypothesis and for subsequent behavior in each masonry unit, the idea of fixed smeared crack approach is implemented in this research. The properties of the normal and shear springs, simulating behavior of the mortar and the brick-mortar interaction, are determined separately by estimating the cracking opening and shear displacement in the crack surface. The Mohr-Coulomb criterion is used to evaluate the behavior of mortar-brick interface. The computational algorithm and developed FORTRAN code are described and validated. Comparison of analytical and experimental results showed that by applying corrections to evaluate the stiffness of springs attached to the blocks and also the application of behavioral models introduced in this paper for the masonry material, it is possible to evaluate the different mechanisms of failure of the masonry building along with their cracking pattern. Therefore, an accurate evaluation of the structural responses can be obtained by applying the smeared crack approach in the modeling assumptions of the rigid block and spring method for different loading conditions. The lateral load-displacement diagrams of the masonry walls in analytical and numerical models illustrate the appropriate accuracy of the developed numerical models.

The precision and speed of numerical simulations of physical phenomena has led to their increasing use in designing and research applications. These precision and speed are owed to the improvements in numerical methods and significant advancements in computing power of CPUs and GPUs. Particle-based methods are some of the most recently developed numerical simulation methods. Development of these methods has been long delayed due to the need for a relatively high computational effort. Particle-based methods can be considered as a subset of Meshless Methods. In nonlinear computational methods, mathematical equations in the problem domain are estimated only by nodes, and contrary to the case about the nodes in FEM and FDM methods, there is no need for these nodes to be connected to each other by a mesh. If the nodes are particles that carry physical properties, such as mass and stiffness, and simulations proceed on the basis of updating trajectory and physical properties of particles, then the method is called a particle-based method. Particle-based methods include molecular dynamics (MD), Discrete Element Method (DEM), Smoothed Particle Hydrodynamics (SPH), and Lattice Boltzmann Method (LBM). The number of studies and computer codes developed based on these methods has grown dramatically over the past two decades. Among particle-based methods, DEM method is mainly used to model solid objects and fractures and in some cases it has been used to model granular materials like soil. While most of the applications of SPH method include numerical solution of the Navier-Stokes equations in fluid dynamic problems. Despite their differences, both DEM and SPH methods are particle-based methods and so there have been successful attempts to integrate them into a single application. In current study, a computer code called “ QUANTA” is introduced. In this software, the researchers have tried to integrate the SPH method with another particle-based method called Bonded Particle Method (BPM). BPM is based on DEM and was originally developed to model rock and soil mechanics phenomena. QUANTA is being developed with the goal of providing a tool to simulate two-dimensional solid, fluid, and multi-phased interactive environments for research purposes. In this software, the solid environment is modeled using the BPM algorithm and the fluid environment is modeled using the SPH algorithm by solving Navier-Stokes equations. Depending on the problem at hand, BPM and SPH particles interact with each other by equations based on momentum or pressure. The code is developed using Visual C ++ programming language and has the ability to perform parallel computations with a remarkable speed. To verify the software, a few simple and frequently used problems in the literature were chosen. A cantilever beam was modeled and loaded to verify BPM part of the software. Poiseuille and shear cavity problems were used to verify the SPH part. In order to verify the interaction of these two algorithms, a solid cylinder was modeled once in a wind tunnel travelling at supersonic speeds and then against the flow of a viscous fluid. According to the results of these numerical modellings, the software can be deemed successful in simulating the sample problems. While simulation with particle methods requires more computational effort than common methods such as finite element and finite difference, the particle-based and micromechanical nature of these methods and their ability to model large-scale deformations and complex behaviors has, in many cases, made them logical choices for simulation. As the next steps of this study, the authors are developing new equations for interaction of particles and equations of state to improve the software performance.

The use of high strength concrete (HSC) is increasing due to the expansion of the construction technology of these concretes. In structural engineering, concrete is known as a material with brittle behavior that the tensile strength of which is negligible compared to its compressive strength and show low resistance to crack propagation. Moreover, the concrete can be considered as a quasi-brittle material, which is due to the type of behavior related to the crack propagation and is also existed around the crack tip of fracture process zone (FPZ) that involves a set of microcracks. From the perspective of structural behavior, the size effect of the structure is one of the most important concepts provided by the fracture mechanics; therefore, it is important to provide an equation between concrete fracture properties such as fracture toughness (KIC) and fracture energy (Gf) and its correlation with the size effect mechanism. The fracture energy is one of the most important characteristics for analysis of fracture behavior in concrete, evidenced to be a concrete property, showing its strength to cracking and fracture toughness. Given that the fracture energy (Gf) is sufficient to calculate the fracture behavior evaluation for the brittle materials in range of linear fracture mechanics, for the quasi-brittle materials such as concrete, this is not a sufficient parameter due to the presence of microcracks in the fracture process zone, and the length of fracture process zone (Cf) is one of the important properties of fracture in the unlimited-size structures. For determining the fracture parameters of concrete, various methods have been proposed. One of the most important methods that is presented by Bazant is the size effect method (SEM). This research studies and analyzes the fracture behavior of high strength concrete (HSC) with various amounts of silica fume, along with a change in water to cementitious materials ratio (w/c) with SEM. In this experimental study, a total of 10 mixing designs have been tested. To investigate the effects of different w/c ratios in the range of HSC and the effect of silica fume, four w/c ratios of 0. 24, 0. 3, 0. 35 and 0. 4 Examined and in two w/c ratios of 0. 24 and 0. 35 a mix design for plain concrete without silica fume and three mix designs prepared with silica fume content of 5%, 10% and 15% by weight of cement. To determine the fracture characteristics of concrete, a total of 120 beams were tested. The results showed that by decreasing the w/c ratio from 0. 35 in the range of HSC, the value of initial fracture energy (Gf), the effective length of fracture processing zone (Cf) and the critical crack tip opening displacement (CTODc) decreased and on the other hand the brittleness number (β ) increased. Also, by increasing the amount of silica fume in the w/c ratios of 0. 35 and 0. 24, the fracture energy, the length of the fracture processing zone, the fracture toughness (KIC), the critical crack tip opening displacement reduced, and the brittleness number increased. Also, the results indicated that by using the fracture parameters obtained from the SEM, the maximum load on the high strength concrete specimen can be predicted correctly.

Sustainability studies, from the point of view of regional identification with the potential of failure in the soil, and from the point of view of designing the new engineering structures, are considered as important issues in geotechnical engineering and have always been a significant part of the references in this field. Subject is dedicated. In the meantime, instability analysis in classical geotechnical problems such as the back of the retaining wall, bearing capacity of foundation and slopes and landslides with a progressive failure mechanism, is considered as a challenging topic in this discussion. These issues are in the category of issues with large displacements and have always attracted the attention of many scholars in recent years. With advances in computer technology and computational techniques, numerical methods such as finite difference, finite element, and boundary components have been widely employed in analyzing engineering issues. In the meantime, the finite element method, due to the ability of that method to control issues with geometry and complex conditions and modeling the behavior of soil shape change, has increased significantly compared to other numerical methods. In conventional analyzes of soil slopes failure, resistance parameters are assumed to be stable even in large strains without change. However, during the rupture, soil resistance exhibits maximum and residual amounts, and its strength increases prematurely by increasing the plastic strain. In addition to changing soil resistance parameters in the progressive mechanism, the non-uniform nature of the soil also causes spatial variations of these parameters. Therefore, geotechnical systems should be considered in terms of the uncertainty of soil parameters values uncertainly using the concepts of statistics and probabilities. The simulation of a progressive failure is definite or non-deterministic only by applying numerical techniques such as finite element method that are able to simulate the development of deviant plastic strain. Although the finite element method is widely used in the analysis of sustainability issues, however, this approach is based on problems that are essentially related to gridding. In this research, a radial point interpolation method in combination with a random field was used to model the spatial variations of soil resistance properties and slope instability analysis. In order to consider the progressive failure of soil, elastoplastic method has been developed with the Coulomb Moore's behavioral model for applying strain softness. For probabilistic analysis, the random field is also used to determine the cohesion parameters and the friction angle as well as the plastic strain threshold based on their mean values and standard deviation. In order to investigate the application of the point interpolation method with randomized radial functions, a geotechnical earthwork with definite and non-deterministic geometry has been analyzed and its reliability coefficients has been investigated. Based on the analysis of the progressive failure modeling, it is concluded that the actual failure of the soil and the occurrence of continuous displacements occur simultaneously with the formation of a progressive mechanism of soil degradation and the arrival of the slipping path to the ground. In the following, probabilistic distribution functions of the coefficient of reliability were determined by probabilistic analysis and the production of random fields, and then the statistical parameters are calculated.