- Volume:3 Issue: 3, 2013
- تاریخ انتشار: 1392/07/12
- تعداد عناوین: 6
Assessment of Tunnel Excavation on Surface SettlementPages 1-5The expansion of underground structures is important in urban areas with high population density. In most large cities in the world, urban development is spreading along the structures. These structures are generally located at shallow depth; therefore study of shallow tunnels in urban areas is critical for development. During the excavation of tunnels in urban areas, creating the asymmetric settlement of surface structures caused by changing stresses in the area due to the construction of underground structures is an issue to be regarded. In this research, the surface structure is considered as an overburden incurred on the tunnel, to assess the effects of tunnel excavation on the asymmetric settlement in the buildings to be built. For this purpose, a baseline model considered and the effect of the tunnel location are assessed into the existing buildings. Studies show the significant impact of the Location of tunnel on surface structures settlement than construction. The article is designed to provide the criteria can be generalized to all tunnels. The paper has tried to compare different modes of tunnel placement to get the best condition for the tunnel to the surface buildings, regarding the rate of asymmetry settlement foundation of Buildings Achieved.Keywords: TBM, Surface buildings, asymmetric settlement
The Behavior of Type of RC Column-to-Steel Beam Connections and Scrutiny Of Behavior CoefficientsPages 7-10(RCS) frames which are systems that dwell of concrete columns and steel beams , by optimizing the act of compressive strength of concrete and bending strength of steel due to not only a decrease in building weight in comparison to concrete structures but also having a better action in long spans frames .
In this paper for analysis RCS behavior, a category of nonlinear Push Over analyses were achieved on typical low to mid-rise RCS buildings. 1,2,3,4 and 5 span frames with span length of 6 meters in 1 to 5 stories were elected for this project.
The systems were controlled by using FEMA-273 and ATC-40 codes.Keywords: Hybrid RCS frame system, Composite structures, nonlinear Push Over analyses
Statistical Evaluation of Induced Seismicity at the Karkheh Dam, IranPages 11-16Karkheh Dam is the largest dam in Iran with a capacity of about 7.4×109 cubic meters and height of 127 meters. Since the first impoundment, increasing in seismic activity in the dam area has been observed that indicates the possible occurrence of reservoir-induced seismicity (RIS).In the present work, a preliminary evaluation is conducted firstly in order to investigate these observations. Based on the assessment of the number of earthquakes occurred in equal time periods before and after reservoir impoundment and their focal depths, it is concluded that RIS is happening in the dam site. Secondly, a cross-correlation method is applied in order to find the relationship between water level fluctuations and the variations of seismic activities. This analysis confirms a strong relationship between fluctuation of the water level and the number of seismicity events in the dam area.Keywords: Reservoir, induced Seismicity (RIS), Karkheh Dam, Dam impoundment, Cross, Correlation method
Earth Pressure behind an Integral Bridge Abutment and Comparison with that behind a Conventional Bridge Abutment under Traffic LoadsPages 17-29Integral bridges are gaining increased popularity because of both economic and fast construction associated with the omission of bearing supports and expansion joints. In the present study the cyclic earth pressure behind integral bridge abutments under traffic surcharges are investigated and compared with that induced behind the abutment of conventional bridges (with isolated deck and abutment) under the same surcharges. A numerical modeling has been developed to evaluate the dynamic earth pressure using the FLAC package. The model was calibrated by direct measurement of earth pressure behind a physical model developed in soil mechanics laboratory to study the behavior of retaining walls.The induced earth pressures under static and cyclic conditions are evaluated and the pressure distribution behind the wall as well as the point of application of the total thrust was determined. The results have shown significant changes happen in both quantity and distribution of earth pressure behind the abutment when using integral bridges. The details of findings and their causes will be discussed in the next sections.Keywords: Integral abutment, Isolated abutment, Earth pressure, Cyclic surcharge, Numerical model, Integral bridge
A Study of the Wave Propagation Velocity in Granular Soils Using Discrete Element Method (DEM)Pages 31-35In the present paper, discrete element method (DEM) is used to study wave propagation phenomenon in granular soils. The effect of factors such as coefficient of friction, frequency, normal stiffness and soil gradation on the wave velocity is studied. Using the wall motion based on the sinusoidal function is the method of loading used in this simulation, through which the pressure wave is transferred to particles. Simulations results are well consistent with the results of experiments conducted by other researchers. In addition, the results obtained are shown as graphs to study the effectiveness of each parameter. According to the results, the coefficient of friction and normal stiffness have a greater effect on the wave velocity.Keywords: Granular Soils
Investigation of Liquefaction Mechanism and Displacement in Buried Sand LayersPages 37-44One of the most important reasons for damages during earthquakes is the liquefaction of loose and saturated sand soils. However, in many regions with proper soil specifications, the large settlements have been observed in the ground surface. Loose sand layers buried in fine soils are one of the cases which may result in these problems and as a weak point during earthquake can cause this phenomenon. In this paper, the behaviour of buried sand layer affected by cyclic loading and its deformation during liquefaction has been studied and investigated using FDM. Then, the results have been compared with those of other investigators. Based on comparisons, the deformation of liquefied layer resulted in current study is in a good agreement with experimental methods proposed by Seed-Tokimatsu and Ishihara-Yoshimine.Keywords: Liquefaction, Displacement, Sand Layers