نشریه مهندسی عمران
سال پنجاه و سوم شماره 7 (مهر 1400)

Discharge over the ogee weir is related to the length of crest, upstream total head and discharge coefficient. Also discharge coefficient is influenced by several factors. In this study, some parameters that are affecting the discharge coefficient in ogee weir are investigated. These are: ogee weir upstream slope, apron elevation and downstream submergence. In this regard, some ogee weir physical models were fabricated. These models include: (1) ogee weir with vertical upstream face; (2) ogee weir with inclined upstream face (18, 33, and 45 degrees); (3) ogee weirs with downstream apron elevations (3, 5, 7, and 10 cm thickness) in free flow; and (4) ogee weir with vertical upstream slope in submerged flow condition. Results show that in all the ogee weirs, the discharge coefficient (C) increases with increasing (P/He), and then remain constant. The value of discharge coefficient decreases from 2.25 (in free flow) to 2.15 (in submerged flow). For a constant value of head over ogee weirs (He), the discharge coefficient decreases with increasing in downstream apron elevation and submergence. The relative discharge coefficient has constant trend at beginning with parameter (hd/He), then has decreasing trend. The threshold value for submergence (hd/He), is 0.75 in ogee weir in this study. With increasing relative submergence (hd/He) from 0.75 to 1, the relative discharge coefficient (Cs/C0) decreases from 0.88 to 0.24.

For most rock materials, there exists a coupling between inelastic deformations caused by crack displacements on micro-crack faces and damage evolution due to nucleation and growth of wing- and secondary-cracks. While rock material is subjected to dynamic loading, the interaction between micro-cracks plays an important role in materials behavior. The self-consistent homogenization scheme is implemented in this paper to consider micro-cracks interaction and determine the equivalent mechanical properties of micro-cracked rock deteriorated by damage evolution. The aim of this article is to develop a self-consistent based micromechanical damage model by taking into account the wing- and secondary-cracking mechanisms accompanied by inelastic strains caused by crack displacements under dynamic compressive loading. While stress intensity factors in tensile and in-plane shear modes at flaw tips exceed the material fracture toughness in modes I and II, respectively, wing- and secondary-cracks are sprouted and damage evolution occurs. For closed cracks, an appropriate criterion for the secondary-crack initiation is proposed in this paper. The developed model algorithm is programmed in the commercial finite difference software environment for numerical simulation of rock material to investigate the relationship between the macroscopic mechanical behavior and the microstructure. The fracture toughness parameters of the rock samples are experimentally determined.

Pile foundations are widely used to ensure the stability of structures subjected to seismic excitation. Numerous structures and foundations in soil-pile-structure systems have been destroyed during occurrence of earthquakes. Because of complexities involved in soil-pile interaction problems and the lack of precise methods, it is necessary to use numerical methods for analyzing soil-pile interaction problems. There are several factors affecting the dynamic response of a pile in soil-pile system. These factors can be divided into three main categories: geometrical factors, material properties, and load characteristics. Studying the effects and importance of these factors in the response of the pile will help geotechnical engineers to optimize their design. In this research, three-dimensional modeling has been developed using FLAC3D computer program, and the effects of various soil and pile properties on the dynamic behavior of a single pile in clayey soils are evaluated. One of the most important subjects in the numerical modeling of soil-pile system dynamic response is the constitutive model considered for the soil. This strongly affects the accuracy of results. In this study a softening model has been used for the behavior of the soil under dynamic loads.Sinusoidal harmonic loading has been applied to the model base as the acceleration time history, and the variations of bending moments, shear forces, and displacements along the pile are obtained for all analyses carried out in this study.The results show that kinematic interaction coefficient depends on the loading characteristics and in the high frequencies head pile response is lower than free field.

Maintenance and rehabilitation planning plays a pivotal role in the implementation of efficient pavement management system. The variables are generally considered deterministic to solve the problem. Nevertheless, this problem tackles with high level of uncertainty. For instance, the budget, as one of the essential criteria, is fluctuated owing to resource limitation, and policy alteration. If the budget is taken into account as deterministic, the result of problem may be considerably different from the absolute optimal solution to the problem. This investigation aims to solve maintenance and rehabilitation problem by consideration of a novel and powerful uncertainty approach. To this end, a multi-stage integer linear uncertainty model is introduced in order to find a solution, which is feasible and optimal in all of the uncertainty modes. The case study of this paper is a network including six pavements. The outcomes indicate that the proposed model is competent to consider budget fluctuation, and it introduces a solution that is optimal for all uncertainty scenarios. The comparison of deterministic and uncertainty models reveals that the number of preventative maintenance selected by uncertainty model is more than that of deterministic model. The number of preventative maintenance is increased from 36.67% to 40.91% if uncertainty is considered in the problem, and it can be postulated that the uncertainty model tries to allocate budget to more segments so as to reduce the likely negative impacts of budget fluctuation on the project.

Roads are considered as one of the most extensive civil infrastructures and national capitals of each country. Pavement maintenance and rehabilitation (M&R) management is one of the most important problems, which can help reducing further costs. Two issues are important in the field of road maintenance and rehabilitation management; first type of M&R option and then time of applying it. In this paper, we have attempted to combine prioritization, artificial intelligence and optimization methods to select the optimal option for maintenance and rehabilitation of pavement sections at any time interval. For this purpose, the analytical hierarchy process is used to prioritize the branches of the pavement network. In the next step, using the linear programming model, the probability of selecting maintenance and rehabilitation options for pavement sections is maximized considering several specific constraints. Fuzzy inference system is used to determine the probability of selecting each maintenance and rehabilitation option in pavement sections. A case study in Mahan (Kerman) is used to run the proposed model. Based on the results, it can be concluded that the proposed algorithm can consider different parameters and indices for pavement branches and sections. In addition, it offers different scenarios for selection of M&R options in a year. The model helps comparing various scenarios based on different budgets for each year. In all, the proposed algorithm facilitates the process of selecting M&R options in the different sections of a road network and provides a scientific approach to manage maintenance roads.

Chemical stabilization of weak subgrade soil is a viable and essential method of avoiding weak soil replacement problems with selected borrow pit in economically and environmentally point of view. Although the use of new materials such as polymers instead of traditional materials such as lime accelerates operations and reduces resource pressure, the environmental impact and long-term resistance in these methods are concerns for experts. Recently, according to the “Kyoto Environmental Protocol” recommendation on soil stabilization with geotechnical purposes, research on new biological methods of soil stabilization including "soil microbial stabilization" has been developed. In this study, the effect of clay subgrade stabilization with chemical and biological methods was investigated and compared through different experiments. Cationic polyelectrolyte as a liquid polymer and microbial induced calcium carbonate precipitation (MICP) were used to stabilize chemically and biologically respectively.In both methods, the specific dry weight of soil decreases and its optimum moisture content increases. Chemical stabilization increases Plastic Index and microbial stabilization decreases it. Both materials at low concentrations raise the pH for up to three days. Both materials increase uniaxial compressive strength and elasticity modulus of soil almost equally. In terms of project economy (time and cost), chemical stabilization with cationic polyelectrolyte and in terms of environmental issues, MICP method is suitable for the studied soil.

Simulating the flow in order for managing the water allocation in drought and wet periods is of great importance. According to the researches conducted during several decades in this regard, computational intelligence methods combined with wavelet are known to be effective. In this paper, Wavelet-Principal Component Analysis-Random Forest (WPCARF) hybrid approach is suggested to model daily flow of Polroud river. In the suggested model, first, hydrometric data is processed by wavelet transform and applied to the PCA algorithm along with meteorological data. Afterward, their output vectors were entered into the random forest network. The results have shown that the PCA algorithm can improve the performance accuracy and speed of the model, despite reducing the input vectors and simplifying them. Also, it can integrate a model with increased simulation time and input vectors uncertainty having a lower impact on model capability leading to a more uniform decreasing trend. Furthermore, preprocessing the data accompanied by PCA could enhance the agreement index by 5 and 8 percent during one and three days of the simulation and increase the model ability for more accurate simulation of river flow. On the other hand, results for the best proposed hybrid model during the one-day simulation time were R=0.911 and RMSE=7.095m3/S, while these values were R=0.817 and RMSE=8.681 m3/S in the best hybrid model for three-day simulation time. This indicates the adequate capacity of the suggested combined model for long-term simulation times.

RC slabs are the structural members responsible for carrying and transferring of loads. RC slabs need to be strengthened as the result of different reasons such as changing of function and corrosion of steel bars. The most widely utilized approach in strengthening these slabs has been the usage of steel plates. However, the concern in using these plates consists of their immense weight as well as their unreliability in being properly connected to the concrete slabs. This study focuses on using punched steel plates as a strengthening factor for concrete slabs since they have reduced weight and allow easier and more reliable connection. For the purpose of experiment, two-way RC slabs with the dimensions of 120 cm and the thickness of 8 cm are strengthened through punched steel Plates and are placed under semi-concentrated load. The effect of plates’ thickness, the arrangement and the area of the punched holes and the connection type in the performance of strengthening system are studied through load-displacement graphs, and are analyzed in ductility. The results have shown that the punched strengthening plates increase loading capacity, energy absorption and the ductility of the two-way slabs up to 62%, 253% and 220% respectively. Also, it is shown that the arrangement of the holes have a significant effect on the performance of the strengthening system. Failure state control show that the failure mode in using epoxy resin is the debonding of the steel plate, while in using expansive bolt is pull out of the bolt.

Nowadays, project management knowledge improvement and developing of management methods, decrease projects failure. Nevertheless many project's goals won't happen. One of the most important process affects project goals is project risk management. Identifying and managing of the risk triggers is an effective method of project risk management. Many years have passed since this concept was introduced but is so limited yet. This research endeavor to develop and make a better understanding on this concept as a main goal. Recognition and managing of this phenomenon help project risk management process. It makes the best decision for having the right time to adopt a strategy and ultimately it reduced the negative impact of risk taking on the project.The type of contract always play an effective role in creating risk. Therefore, in this study, it is selected to develop and analyse the concept of risk trigger phenomenon, in DB method which has many benefits and client's tendency and And in order to explain the status and importance of risk triggers, its relationship with a number of important risks has been analyzed qualitatively. For this purpose, through library studies, a table of common risks of these contracts and risk indicators from existing sources has been identified and compiled. Interviews with experts on risk, source and risk triggers relationships, in some important risk to study and validated results. Finally, a functional table of risk trigger is presented that is a great help to stakeholders in being prepared to respond better to risk triggers.

One of the kinds of structural floors system is consisting of profiled steel sheet and dry board which connected to each other by self-drilling and self-tapping screws. The aim of this research is study on the behavior of mentioned floor under explosion load. For this purpose, effect of various parameters such as: thickness of dry board and profiled steel sheet, kind of bry board, screw spacing, boundary conditions, floor dimensions, duplicate of mentioned surfaces, and also weight and distance of explosive material from the center of floor, on the nonlinear dynamic behavior of the mentioned floor is studied. This study is performed by using numerical finite element method taking advantage of ABAQUS software. The research results show by varying parameters such as: thickness and kind of bry board, dimensions and boundary conditions of floor, duplicate of main elements, and also distance and weight of explosive materials, significant changes in floor maximum displacement and strain energy is created, but varying of other above mentioned parameters not create significant changes in them. The profiled steel sheet and dry board reach to their yield stress under various structural conditions and floor loading, though in many cases, they not reach to their yield stress. The results of current research present great help to researchers and designers in identification effective and ineffective parameters on the behavior of studied floor under explosion load.

Today, with the increasing urban development, construction waste is a major problem for urban life. The city of Qazvin is no exception to this, and researching an optimum landfill site is an important necessity. The purpose of this research is to optimum site selection areas for landfill of Construction wastes using the geographic information system (GIS) in a boundary area of Qazvin county which taking into account the terms and conditions of organizations such as the Municipality, Waste Management and Environmental Protection Organization. In this study, 16 layers of information including geology, soil type and permeability, Landuse, climate, river distance, distance from protected areas, aspect, etc. in the boundary of Qazvin county were used. After producing the preliminary maps, the sub-criteria of each information layer are classified and evaluated and the values are converted to fuzzy values between zero and one. Then, Fuzzy Hierarchical Process (FAHP) method have been used to determine the absolute weight of each information layer and by integrating and overlapping weighted layers, to the landfill suitability map of construction landfill for Qazvin city is produced. According to the suitability map, sites for landfill were identified in five distinct zones and high-lying areas of the fifth zone (with value 9) were suggested as the best landfill site for a 40-year period. The results showed that northwest of Qazvin due to good soil type, suitable land use, distance from rivers, faults and access to communication road and dry climate could be the most suitable site for landfill.

Concrete pavements are widely used by pavement engineers due to their advantages over flexible pavements such as longer lifetime, good performance and durability, etc. However, concrete pavements represent some drawbacks such as shrinkage that increases the tensile stress in concrete, which may lead to cracking, warping, etc. Drying shrinkage is the most important type of shrinkage in concrete pavements. To prevent or reduce the amount of cracking, shrinkage reducing admixture (SRA) can be used. This admixture controls shrinkage by reducing water surface tensile in capillary tubes. In this study, the effect of shrinkage reducing admixture on the behavior of concrete used in concrete pavement was investigated. Slump, compressive strength, third-point flexural strength, electrical resistance, skid resistance, free shrinkage and restrained shrinkage by ring test were performed. Two water-cement ratios of 0.35 & 0.4 were used for mix design and the percentage of shrinkage reducing admixture used in mixtures was 2% by weight of cement. The results showed that the use of SRA had negligible effect on workability. Also, the use of SRA caused about 10% reduction in compressive and flexural strength and electrical resistance. Furthermore, a reduction of 10% and 20% was observed in free and restrained shrinkages, respectively, followed by a 40% reduction in crack width and more than one week delay in occurrence of first crack. Finally, no certain relationship was observed between using SRA and changing the skid resistance of concrete pavement.

In this research, lime and cement additives were used to stabilize clay and therefore to reduce the settlement in raft foundations. Lime and cement were mixed with clay and the effect of the use of these two additives on the stabilization of fine clay soil in the laboratory was investigated. Soil samples in normal state and in combination with different percentages of lime and cement equal to 3, 6 and 8 percent dry weight of soil for laboratory tests including Atterberg limits Test, Grading Test, Standard Compaction Test, Uniaxial Compressive Strength Test and California Bearing Ratio Test, and Also, Consolidated Undrained Triaxial Compression Strength Test (CU) and direct shear tests were used. The results show a decrease in the plasticity and maximum dry unit weight of soil and an increase in optimum moisture content, compressive strength, and also the California Bearing ratio of clay by adding these two materials. The cohesion and internal friction angle that obtained from Consolidated Undrained Triaxial Compression Strength tests (CU) and direct shear tests increase with increasing cement and lime percentages. After laboratory tests the effects of the use of soil improvement with depths of 1m, 2m, 4m, 6m, 8m and 10m using Plaxis software suggests that as the depth of improvement Increases, the amount of settlement decreases, which is a lot different from that of the plate loading test prior to improvement while the difference between the results obtained from Plaxis and plate loading test after improvement are negligible.

In this paper, seismic behavior of wide beams was investigated. First, code provisions and results of previous tests on reinforcement concrete wide beam-column connections were reviewed. After precise investigation of previous test results and in order to detailed study of behavior of wide joints, 4 specimens of exterior wide beam-column connections in scale of 3:5 were casted and tested under constant axial and cyclic lateral lateral loads. The specimens were designed and detailed in accordance with ACI 318-14 and ACI 352R-02. In tested specimens, differet geometries for columns (square, rectangular or circular) and spandre beams (wide or conventional) were considered. During the tsets, formation of full-width flexural plastic hinge of wide beams was observed in all the specimens without any shear or torsional failure. Energy absorption of specimens was relatively high and that is because of using stirrups at the joint area and axial loads apllied to columns. The width of spandrel beam and geometry of columns influenced the seismic performance of tested specimens. A comparison between experimental results and ACI provisions showed that dimentional limitations of ACI 318 on wide beams can be violated. Also, in wide joints with axial load ratio greater than 15%, the bond performance of column longitudinal bars is improved and ACI 352R provisions in this context can be relaxed.

In this study, natural frequency of single layer homogeneous and horizontal alloys under one-dimensional harmonic vibrations was studied. If the ground surface, the rock surface and the boundaries between the soil layer and the rock layer are considered horizontally, the lateral extent of the deposit has no influence on the response and in this case the soil layer may be considered as a semi-infinite and horizontal layer. In such cases, when the soil is affected by seismic excitation at the base, only shear deformations occur in the soil. The nonlinear soil behavior resulting from cyclic loading is investigated by free vibration modification in the properties of the dynamical deformation of the granular soil, such as damping ratio and normalized stiffness using a new approach to the dynamic equilibrium equation governing the behavior of a freedom-degree system. So, by deriving a nonlinear equation of motion, it is possible to solve this equation by the perturbation technique. Then the natural frequency of the system will be determined analytically. It was seen that the nonlinear natural frequency depends on the response amplitude and with increasing of amplitude it increases. In other words, the system behavior is of hardening type. The analytical method for determining the response of a freedom-degree system has good agreement with the numerical method of solving the free equation such as the Runge-Kutta method.

Bridges are a critical part of the urban and suburban transportation network, so they are supposed to be designed to sustain earthquake induced damages to be utilized after earthquake. Various parameters can affect the behavior and probability of failure of a bridge and the present work aims to evaluate the effects of changes in structural parameters on the probability of failure in isolated concrete bridges OpenSees software is used for simulating and analyzing 16 different bridge models. Incremental dynamic analysis is conducted using this software and IDA and fragility curves of models are derived and presented. The results show that the probability of failure decreases with the increase of the pier diameter, concrete compressive strength, yield strength of longitudinal rebars and diameter of longitudinal bars. Also increasing the stiffness of elastic isolator and decreasing confined diameter of pier results in increasing the probability of failure. Furthermore, results show that, the probability of failure is more sensitive on the variation of pier confined diameter, yield strength of longitudinal rebars, diameter of longitudinal bars and the stiffness of elastic isolators in comparison with the variation of concrete compressive strength.

Several factors affect the bearing the load of natural and engineered embankments and slopes including the crude oil leakage, leading to a severe decrease in resistance. This is especially important for oil-rich countries, such as Iran, which have several crude oil resources. The main purpose of this study is to investigate the load bearing the load (i.e. load versus settlement) and strain-stress behavior of crude oil contaminated sandy soils using California Bearing Ratio (CBR) Test. In this paper, 10 different types of sand with different characteristics used. At first, a series of CBR experiments performed for natural sands (i.e. clean sands) and then contaminated sands with 6% crude oil tested under similar conditions and densities to obtain the reduction in bearing the load of crude oil contaminated sands quantitatively. Experimental results showed that bearing the load of sand containing 6% of crude oil decreased at least 50% compared to clean sands and the stress-strain diagram of these contaminated soils would decrease significantly. Based on the results of investigation, it can be stated that particle shape(sharpness or roundness), coarse particle ratio,and finally the type of aggregation influences the resistance of crude oil contaminated sands. It was also found that standard Ottawa sand had 83% reduction in strength and sand with a coarse particle had 57% decrease in strength. Sand contaminated with crude oil experience a severe loss of bearing capacity,so in designing foundations and engineering structures, greater safety factors should be considered, where there is a risk of crude oil leakage.

The use of different soil improvement methods has always been accompanied by an assessment of the impact on strength parameters, costs and environmental impacts. Since new and eco-friendly methods are associated with a high initial cost, optimizing these methods in order to commercialize them is the priority of research projects. The use of biologic methods for soil improvement, despite its high environmental compatibility, has not been welcomed from the economic point of view in most parts of the world and is still being considered as an academic and not an executive method. Improvement of soil using calcium carbonate sedimentation is one of the most environmentally friendly biological methods. One of the most influential bacterial suspension parameters for calcium carbonate treatment is its culture medium, usually Nutrient Broth or Yeast Extract. An alternative culture medium is one of the ways to reduce the cost of biodiversity in the soil. In this research, the use of sugar beet molasses, which is a waste of sugar and sugar factories, has been investigated as a suitable culture medium for biological improvement along with other culture media. It can reduce the cost of producing a suitable culture medium by up to 500 times. The success of soil regeneration after bacterial cultivation has been evaluated in this study.

Experiences of previous earthquakes shows the effects of soil-structure interaction and behavior of beam-column connections on the seismic behavior of the building structures. In this research, seismic vulnerability assessment of RC precast Frames was investigated by consideration of the effect of soil-structure interaction and nonlinear behavior of beam-column connections. The RC precast building represented in this study, damaged in Bojnord earthquake 2017 and located on the soil type II of Iranian seismic design code. The soil-structure interaction 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 seismic vulnerability and performance of RC precast frames are evaluated using nonlinear static pushover, nonlinear dynamic time history analyses and incremental dynamic analyses (IDA). The numerical models are developed using OpenSees software by consideration of nonlinear behavior of the beam-column joint. The numerical results are shown the significant role of soil-structure interaction and beam-column connections on the seismic vulnerability and performance of RC precast buildings. In fact, seismic vulnerability of RC precast buildings are increased by considering soil-structure interaction and beam-column connections effects.

According to reports from past earthquakes around the world, the phenomenon of liquefaction is one of the main hazards of earthquakes that causes damage to structures and infrastructures. The risk of liquefaction and associated lateral spreading can be reduced by different ground improvement techniques, including the densification, solidification, vibro-compaction, drainage, explosive compaction, deep soil mixing, deep dynamic compaction, permeation grouting, jet grouting, pile-pinning and gravel drains or SCs. In this research, the effects of pile groups on reducing the potential for liquefaction during earthquakes are investigated parametrically, applying three-dimensional finite element (FE) simulations using OpenSees. Saturated Uniform and Stratified loose sand are subjected to two realistic destructive events with different characteristics. A multi-yield-surface plasticity model is considered for the dynamics analysis conducted in this study based on constitutive laws applicable to all types of soils. The objective of this study is to assess the effectiveness of the pile methods on the basis of several different factors, including area replacement ratio (Arr), piles diameter, number of piles, thickness and position of liquefiable soil, and earthquake characteristics. This parametric study evaluates the effect of each of these factors on soil acceleration, lateral displacement, and excess pore pressure. The results are shown, the responses of the saturated stratified sand strata are not only dependent on the thickness of the liquefiable layer but are also highly influenced by its position. The presence of a liquefiable layer at lower depths, although acting as an isolate relative to the acceleration, can increase lateral displacements.

Increasing the resistance of members or adding constraints to the structure does not jeopardize the overall safety of the structure. This can be proved under certain static loads by the safe theorem which is one of the fundamental theories of plastic analysis. Although this theorem has not proved in the condition of dynamic loads, its results are used in the everyday design under dynamic loads, so this paper attempts to numerically study these results under dynamic loads. Since the concept of mechanism and collapse cannot be investigated under transient loads, the level of ductility demand of structural components is considered to ensure the safety of the structure. For this purpose, the plastic rotation of the members was extracted after a minor variation in resistance and stiffness of the beams in a 2D-five-story steel moment frame by performing dynamic analysis. To compare ductility demand in dynamic analysis with criteria values, the evaluation was surveyed under nonlinear static analysis. The results analysis shows that with the increasing resistance, in most cases the ductility demand decreases, and in some cases the maximum increases by 7.3%. With increasing stiffness, the ductility demand has increased by a maximum of 16%.By comparing the results of dynamic and static analysis, it can be concluded that the required ductility in the dynamic analysis by increasing characteristics has been lower than the corresponding value in static analysis. Therefore, the increase in the partial stiffness and resistance of the beams under dynamic loads has not caused the structural collapse.

In this study, dynamic behavior of earth dams with clay core was analyzed using finite element method. The seismic responses of earth dams under main and wavelet-based decomposed earthquake records were investigated. Earthquake records were decomposed up to five stages by using wavelet de-noising method. The ratio of acceleration response spectrum to maximum acceleration, ratio of velocity response spectrum to maximum velocity, ratio of displacement response spectrum to maximum displacement, Fourier amplitude spectrum and time history of Arias intensity of earth dam crest under main and wavelet-based decomposed earthquake records were analyzed. The results demonstrate that the acceleration response spectrum ratio of dam crest under de-noised records up to 3rd level and the velocity and displacement spectrum ratios of dam crest up to 4th level has an acceptable accuracy in comparison to the responses under main earthquake records. Results of dynamic analysis indicate that Fourier Amplitude Spectra and Arias intensity of earth dam crest under de-noising based records up to 4th level are compatible with main earthquake records. The results indicate that the wavelet-based decomposed earthquake records can be a reliable alternative for main earthquake records in dynamic analysis of embankment dams.

In this research, dilation effect related to density and confining stresses during liquefaction on structural settlement is investigated using OpenSees. Therefore, a sand layer with different dilation angles and surface load is considered. The numerical model presented in this research, calculated the excess pore water pressure based on fully coupled effective stress analysis during seismic loading. Model parameters were selected and verified using the results of VELACS centrifuge tests. The results show that by increasing the dilation angle, the pore water pressure decreases and the liquefaction-induced settlements decrease. The decreasing trend of settlement with increasing dilation angle tends to a constant value, so that at high densities with increasing dilation angle, little changes in settlement is observed. Also, the dilation angle is calculated based on the preshear mean effective stresses and compared with the dilation angle caused by the stresses during liquefaction. The comparison shows that for relative densities less than 60%, the dilation angle obtained from preshear effective stress is more than the confinig stress based method during liquefaction.

This paper presents a new structural system for retaining walls. In civil works, in general, there is a trend to use the traditional reinforced concrete (RC) retaining walls to resist against the soil pressure. Despite their good resistance, RC retaining walls have some disadvantages such as need for huge temporary formworks, high dense reinforcing, low construction speed, etc. In the present work, composite wall with only one steel plate (steel – concrete) was proposed to cover the disadvantages of the RC walls. In this system, steel plate was utilized not only as tensile reinforcement but also as a permanent formwork for the concrete. In order to evaluate the efficiency of the proposed SC composite system, an experimental program that included six specimens was performed. In this experimental campaign, effects of different parameters such as length of shear connectors, use of compressive steel plate, concrete ultimate strength, distance between shear connectors and compressive steel reinforcement were investigated. The results showed that with proper design, the composite walls have very good and ductile behavior under out-of-plane loads. Furthermore, it was observed that even with large distance between the shear connectors, short length of the shear connectors etc., this system is capable to keep the flexural performance and shows the semi-ductile behavior. Furthermore, the design equations based on ACI code for calculating out-of-plate flexural and shear strength of SC composite walls are presented and compared to experimental database.

Local scour involves removal of material from around piers and abutments as the flow accelerates around the obstructed flow area. Various methods have been suggested for the control and reduction of local scour around the bridge piers and abutment. Using submerged vanes is one of these methods. Vanes change the regime of bed load movement that led to control place of deposition and erosion. The function of vanes to reduce scour around the bridge piers and sediment movement in the region of vanes due to down flow in front of them are affected by arrays of the vanes. In the present study, Different lay out of arrangements (Parallel rows, two parallel rows, and two zigzag rows) Flat Submerged vanes with the ratio of length to height at an angle of 20 degrees relative to the direction of flow on protection of local scour around abutment and piers group with rectangular debris were laboratory investigation. All experiments conducted in uniform flow with clear water were be done. The results showed that the zigzag arrangement of the two three rows had the greatest effect to protection of local scour around abutment. In this case, vane distance from abutment and the row spacing with the relative spacing is 0/5 and 1.(The distance of the vanes from the abutment was La and the distance of the rows was 2La) that reduced the scour depth by 81%.