نشریه پژوهش های تجربی در مهندسی عمران
پیاپی 1 (بهار و تابستان 1393)

Routing is a process used to predict the temporal and spatial variations of a flood hydrograph as it moves through a river reach. The effects of storage and flow resistance within a river reach are reflected by changes in hydrograph shape and timing as the flood wave moves from upstream to downstream. Flood routing procedures may be classified as either hydrological or hydraulics. Hydrological methods use the principle of continuity and a relationship between discharge and temporary storage of excess volumes of water during the flood period. Hydraulic methods of routing involve the numerical solutions of the one dimensional Saint-Venant equations of gradually varied unsteady flow in open channels. In this study, firstly the developed hydraulic models were verified by field observations, secondly the posteriori investigation of channel bed slope, Manning’s roughness coefficient, inflow hydrograph shape factor, time to peak, space step, time step, weighting factor, and the different terms of Saint-Venant equations were studied through the comprehensive numerical experiments. The results indicate that the effects of input parameter errors on the output results are more significant in special situations, such as lower values of Manning’s roughness coefficient and/or a steeper bed slope on the characteristics of a design hydrograph, larger values of the skewness factor and/or time to peak on the channel characteristics, larger values of Manning’s roughness coefficient and/or the bed slope on the space step, and lower values of Manning’s roughness coefficient or a steeper bed slope on the time step and weighting factor.

In this research, horizontal dynamic response of foundation on homogeneous half-space was investigated using physical modeling. In order to carry out a comprehensive study on the effect of embedment depth ratio on horizontal impedance functions, 173 different tests in three series were conducted. In these tests, the embedment ratio of footing was increased from zero to 0.5 and finally reached to one by implementing the mentioned sand raining method. In each series of tests, the steady-state response of footing to horizontal vibrations was investigated. Using recorded data and related motion equations, foundation responses were analyzed. The obtained results were presented by graphs of horizontal impedance functions of square foundation on homogenous half-space against dimensionless frequency. Comparing horizontal impedance functions shows that an increase in embedment depth ratio resulting from amplifying impedance function coefficients up to dimensionless frequency of 3.5 Hz.

Most of the distress in flexible pavements is due to cracking and rutting. Propagation of cracks is divided into three modes. Mode I is opening the cracks, mode II is propagation of cracks through the overlay and mode III is breakage. Geogrids distribute the street and loads to adequate area and cause augmentation bearing capacity. This work surveys the function of carbon and glass fiber geogrids on delay of crack propagation in flexible pavements; by comparing laboratory and computer software (BISAR3.O andCIRCLY5.O) results. The research utilizes the beam fatigue test, gyratory compactor and indirect tensile test. Simulated– repeated loading with a frequency of 10 Hz simulate high speed traffic was applied to beam fatigue specimen. Evaluation of the results is work test as well as numerical calculation using the software yield comparable results and 25-40% tensile stresses can be absorbed as a result of carbon fiber Geogrids.

In this study the effect of infill masonry on vulnerability of reinforced concrete frames subjected to internal blast loading is investigated. To do so, several 3D reinforced concrete frames with infill which have been designed based on the Iran Concrete Code are subjected to internal blast loading and analyzed using finite element commercial software ABAQUS. Reinforced concrete is assumed to be plastic in behavior while elastic behavior is taken for infill masonry. The infill is modeled as continuum elements using homogenizing theory. It is found that infill masonry effect on the stiffness and elasticity of reinforced concrete frames so neglecting this effect loads to unrealistic assessment of dynamic analysis of in filled RC frames subjected to internal blast loading.

The most important problem in shallow tunnels excavated in soft ground of the urban areas is the surface settlement and its effect on the adjacent structures and facilities of the city, depending on the effects of the range of surface settlement profiles. This feature is clearly visible in Bimeh Station (A4-2) Line 4 of Tehran Metro. One method of supporting tunnel in this circumstance is using the umbrella arch method such as a pre-supporting. Due to the small radius and volume of grout injected into the umbrella arch method and manner of its implementation in field, a homogeneous area containing slurry and soil can be build up around the tunnel. To conduct laboratory studies, soil sampling and in-situ soil characteristics is used to achieve sample preparation. Shear and compressive strength tests were carried out according to the ASTM standards. The shear strength parameters of the soil samples (containing various percentages of silica in the slurry) were determined. The results are presented in tables and figures.

Geodetic methods and devices of surveying and photogrammetry cannot meet all the requirements for measuring displacement. Therefore, to collect information from local deformations, geotechnical devices are used inside the deformable objects. Devices such as extensometer, tilt meter, inverted pendulum, and other similar devices can be used to collect continuous data. Certainly, we can achieve to more reliable results in the detection and measurement of moving objects and structures by combining the results of geodetic and geotechnical measurements and comprehensive analysis of movement. In this paper, the results of geodetic measurements, such as precise measurements of length, angle and height have been compared with the results of observations of non-geodetic instruments.

In the current research, three coarse grained soils and four geo-grids of the same material but of different aperture size have been used. Experiments have been conducted using large direct shear box. Results have been employed to assess the effects of grain and aperture size on the shear strength of reinforced soils and comparing these results with the shear strength of unreinforced soils. The obtained results show that for a soil with a specific grain size distribution, there is a geo-grid with a specific aperture size which produces the maximum increase in shear strength. In addition, for each particular soil there is a specific aperture ratio that results in the highest shear strength. The maximum and the minimum interaction coefficients for all samples have been determined, which is an indication of the best and the worst soil–geogrid interaction.