جستجوی مقالات مرتبط با کلیدواژه « مدل سازی سه بعدی » در نشریات گروه « عمران »

The surface texture depth is an important indicator for evaluating the skid resistance capabilities and providing suitable surface drainage conditions for asphalt pavement, which has a direct effect on the safety and comfort of road users. Texture evaluation is one of the main goals of the pavement management system. Three-dimensional evaluation is the most accurate method of measuring pavement texture characteristics. In this paper, a three-dimensional automatic device based on a hybrid imaging technique is presented. In this device, a system consisting of two-dimensional digital cameras is designed to provide the required image data. The proposed system has a tool for reducing surface friction. This system also makes it possible to evaluate the texture in rainy conditions. Based on the two-dimensional images taken from the pavement surface, the three-dimensional models of the pavement texture are presented. A method for calculating the mean texture depth is presented. Measuring the depth of pavement texture in different directions is a the capability of this method, which makes it possible to uniformly evaluate the depth of the texture in different directions and find the critical direction for texture drainage capacity. The proposed system has been used to measure the depth of texture in different sections of pavement and the results in have been compared with the results of the standard sand patch method. This comparison shows a high correlation between the results of the proposed method and the standard pavement texture evaluation method.

Two of the important issues in the construction of structures located in seismic coastal areas are the study of the potential of liquefaction phenomenon in saturated sandy soils and seismic structure-foundation-soil interaction (SSFSI). Control of structure damage on the liquefiable soil and large deformations of soil due to seismic loading and, also, the other responses such as: the accelerations at top of the structure/foundation and excess pore water pressure related of this phenomenon are very important. The phenomenon of liquefaction happens due to the occurrence of an earthquake and due to the lack of sufficient opportunity for drainage of excess pore water pressure. One of the effective and useful mitigation methods to control of the liquefaction phenomenon is the usage of dense granular column (DGC) in appropriate dimensions and distances on the ground susceptible to liquefaction. The role of the DGC in controlling the liquefaction phenomenon are follow as: firstly, the DGC is made of materials that are more permeable to sandy soils and cause the excess pore water pressure to be dissipate faster, and secondly, DGC increases the stiffness of the system, which proportionally reduces the excess water pore pressure due to the dilative behavior. To reduce the risks of liquefaction, it is necessary to fully understand its consequences. These consequences depend on permanent soil displacements, structural performance, structural characteristics, foundation and structure dimensions, soil conditions of the structure site, type of loading and earthquake intensity. The presence of the structure and impact of SSFSI affects the intensity of liquefaction and static and dynamic stresses in the soil. Most prior studies (e.g., physical, numerical, or analytical models), ignore the existence of the structure or consider the effect of soil-structure interaction (SSI) on the liquefiable soil layer as an equivalent model. Hitherto, the essence and extend of these interactions are not sufficiently understood. These methods can not properly assess the damage caused by liquefaction; Therefore, these methods cannot be used in the design of structures resistant to liquefaction. Therefore, to accurately study the effect of liquefaction, a method and model is needed that can fully consider the soil, foundation, and structure so that it can be used to correctly estimate the amount of subsidence and displacement of the structure. In this study, to evaluate the seismicity and the mitigation effect of DGCs, using OpenSees finite element software, modeling of DGCs and surrounding soils without structure and models with 5, 10 and 15 storey structures were performed. The three-dimensional soil and DGCs modeled in the software are placed under different earthquakes and the effects of structural layers on the lateral displacement, excess pore water pressure, response of acceleration spectrum, drift and shear force of stories are investigated. The liquefiable soil is modelled through the pressure-dependent multi yield surface soil constitutive law (PDMY02) applied in OpenSees. The results of this study are shown the positive effect of DGC on the reduction of lateral displacement components of soil and structure, foundation subsidence and excess water pore pressure. Also, the presence of the structure on the soil and the increase of its floors have increased the mentioned components except for lateral displacement of soil.

In this paper, the seismic response of the surface in the presence of a circular underground lined tunnel subjected to vertical incident P/SV and SH-waves were obtained. In this regard, the three-dimensional (3D) finite element method (FEM) approach in the framework of ABAQUS numerical software was used for preparing the model. At first, a brief presentation of FEM formulation as well as solving a validation example was carried out. Then, by considering some key parameters such as tunnel depth, and the impedance ratio of the lining, the response of the ground surface was sensitized. In the following, a comparative study was performed between the responses of 3D-FEM and 2D half-plane boundary element method (2D-BEM). The results showed that the mentioned parameters are very effective in the formation of different patterns of ground motion. Furthermore, a slight increase of amplitudes is observed in the responses of the 3D approach compared to 2D modeling. The results of the present study can be used to complete the accuracy of existing seismic codes around the subject of micro-zonation of the site in the presence of subsurface openings as well.

Rockfill dams that are made by dumping and compacting rockfill materials are known as one of the most economical and safe dams. The main mechanical characteristics of rockfill depend on particle breakage. Particle breakage occurs when the stress levels are high enough or when the size of the particles is high enough as the rockfill particles. Particle breakage causes a change in grain size distribution of the media and causes a change in the mechanical properties of the granular media. Particle breakage is widely studied experimentally by classical laboratory tests, which need large and expensive equipment that is rarely available. Although numerical methods that are based on the continuum mechanics, such as finite element method, have been developed to be able to account for discontinuities; nevertheless, the internal discrete structure of the rockfill cannot be considered and physically modeled in this way. In addition, the fact is that these methods are not capable to simulate particle breakage to predict the mechanical properties of the rockfill materials. Discrete Element Method (DEM) can overcome these problems. In this research, discrete tri-dimensional modeling of rockfill behavior considering the particle breakage using DEM is studied. Particle breakage is modeled by a bonded particle model and, to consider particle breakage, a mechanical threshold criterion combined with a contact density of particles and a probabilistic criterion is used. PFC3D code and programming in FISH language were performed by investigating the resistance and deformation behavior. In addition, the effects of particle breakage during the tests were considered by providing a failure criterion. The model is compared with the experimental tests on Purulia rockfill dam materials, and the obtained results show good concordance with the obtained experimental results. Finally, the model and the presented failure criteria, whilst it has a simple computational procedure and high accuracy, were validated.

Utilizing of fiberglass nail in the face of tunnel is one of the economical and effective pre-support methods for increasing stability and control of settlement in weak grounds and tunnels with extended level and increase of ground mechanical strength. In this study, by taking advantage of 3D modeling of fiberglass nail which is effective in reduction of deformation, settlement, the direct modeling of nail in the 3D finite element and material with equivalent section. This study has covered effects of nail density, the overburden to depth of tunnel ratio. The method of strength reduction for analyzing the safety factor of tunnel has been considered. The result of 3D numerical analysis with limit equilibrium methods (LEM) for determining safety factor has been compared. The comparison of LEM and finite element method revealed that using of nail fiberglass and increases the range of safety factor between 5% to 75% and 1.25 to 2 in terms of overburden to diameter ratio. This increase of nail is dependent on density and overburden. While, with increase to advance length, the amount of vertical displacement would rise in both method, although these measures have no effects in horizontal displacement. In addition to that, using of nail in the tunnel face has caused the amount of vertical displacement between 20 to 35 percent and in the horizontal displacement between 50 to 60 percent of decrease has happened.

Having a 3-Dimensional model of high-rise buildings can be used in disaster management such as fire cases to reduce casualties. The fundamental dilemma in 3D building modeling is the unavailability of suitable data sources. However, available cadastral 2D maps could be used as low-cost and attainable resources for 3D building modeling. Smoke will be a great threat to people's health during a fire in a building and its movement and diffusion in different parts of the building are affected by the architectural design of the building. Computer simulation can be utilized to investigate smoke movement and its emanated toxic gases under various scenarios which can play a significant role in decision making during a fires incident event to reduce human casualties. In this research, at first, 2D cadastral maps of a high-rise building located at Tehran were utilized to produce a 3D model of building with adequate details in CityEngine. Next, smoke emission in the building was simulated under seven scenarios, using PyroSim software. The two-dimensional data of apartment separation is readily available and at the lowest cost. Using some tools and techniques in spatial information systems, making it possible to utilize this data to implement a three-dimensional model of a building with details to simulate the spread of smoke from fires. The process adopted in this study made it possible to use a two-dimensional floor plan to produce a three-dimensional model of the building at the LoD4. The results confirm the appropriateness of the constructed 3D model to simulate smoke emission under various scenarios in the high-rise building. This result shows the effect and importance of smoke transfer routes, both inside and outside the building, on the emission of toxic gases. The results show that ensuring that the ducts are closed is one of the factors controlling the spread of smoke to other floors. Flue gutters and ducts are among the most important routes for emitting smoke in high-rise buildings. The simulation results of Scenario 4 show that 40 seconds after the start of the fire, the toxic fumes spread through the stairs at all top floors of the building. Although data from 2D cadastral maps can be used to create a three-dimensional model of a building, these data have shortcomings. The part related to the texture of the map features is faced with a lack of information such as the thickness of the walls, the type of used materials, the exact location of the components (doors and windows) on the walls, and so on. These factors affect the smoke emission simulation results. As a result, development of a three-dimensional model of the building containing more detailed information about the specifications and materials used in the walls and various parts of the building needs to be considered in future research. The smoke emission simulation results can also be used in a variety of applications, including emergency evacuation modeling in the event of a fire in a building, along with the inclusion of other information such as number and physical characteristics of residents in different parts of the building.