Journal of Civil Engineering and Materials Application
Volume:3 Issue: 1, Winter 2019

In this paper, the reliability of T-stub pre-stressed connections is investigated using the numerical model. The T-stub connection is considered as a bolted one usually in the semi-rigid range. By selecting a test specimen, the T-stub bolted connection is initially simulated in the Abaqus finite element software to determine software validation and the modeling method used in this research. Then, the structural elements, loading, materials and type of analysis used in the test are introduced and 52 samples of T-stub connection controlled with construction and design constraints are determined to specify a series of targeted data through the changes in the geometric configuration and material strength of the T-stub connection elements. Finally, by performing nonlinear analyses in Abaqus finite element software and determining the limit state function of maximum tensile load of bolts in terms of random variables such as the bolt diameter, width and thickness of section flange, width and thickness of section at two performance levels, namely yielding and failure of web plate, the reliability is analyzed by Monte Carlo statistical method. The results of the probability of failure (PF) were zero for all samples under both performance levels. This is because the requirement for the failure mode not being occurred in the web of T-stub connection was observed when selecting the specimens. Therefore, the determined T-stub connection specimens are of strong bolted type and hence, the probability of failure (PF) becomes zero, which is the probability of the bolt being yielded in the unthreaded section after the web plate is yielded, and the failure of bolt in the threaded section after the failure of the web plate.

Although the increasing expansion of traffic in cities has increased economic and welfare benefits, it has, on the contrary, increased the number and severity of traffic accidents. Reducing the number of victims and injuries caused by road accidents in any common moral-value system is urgent and inevitable. In this way finding effective factors on the severity of road injuries can be considered as an effective step towards achieving the values. Finding effective factors on severity of injuries, with emphasis on statistical efficacy of effective policy-making factors, will be used as an appropriate tool in the middle level of road safety management. Accident prediction results using MATLAB software in selected roads showed that although this model, by choosing the appropriate calibration factor and using the appropriate parameters and high precision, can produce good outputs, but the results are less accurate than the MLP. The statistical analysis of the observed values ​​and the predicted crash values ​​showed that their differences were not statistically significant at the 5% confidence level, and their results could be used to predict crashes and determine future conditions.

Tunnel excavation on soil lands may leads to horizontal and vertical displacements around the tunnel. The displacements can reach the ground surface and cause damages to existing structures on the ground. Hence it is so important to estimate the ground settlement induced by excavation, particularly in urban environments. In this study, the effect of longitudinal distance between two tunnel faces on ground surface settlement is examined during the excavation of twin tunnels. Accordingly, the ground settlement is measured for the states where the distance between tunnel faces is 0D, 0.5D, 1D, 1.5D and 2D. The most important results suggest that creating a longitudinal distance (lagging) between the faces of twin tunnels during excavation operations causes changes in surface ground settlement. The maximum surface ground settlement along the width and length of tunnels decreases as the distance between two tunnel faces increases.

Today hydraulic reservoir structures are one of the most significant structures over the world and, on the other hand, have become of great importance because of current droughts, particularly in the Middle East. Concrete dams are noteworthy superstructures amongst these structures and their construction and maintenance involve intensive research. In this study, the effect of bed stiffness on a concrete gravity dam is examined under far- and near-fault ground motions. This study is conducted through the numerical modeling of Pine Flat concrete dam as a case study via Abaqus software, the import of 6 far- and near-field accelerograms and the investigation into the effect of 3 stiffness ratios. The results indicate that the stiffness ratio of 1 has a more reasonable effect, for which the response of structure is more logical and appropriate.

Various factors, including the thermal stabilization and the presence of chemicals such as bentonite for the protection of nuclear waste lead to the exposure of clay soil to the heat. Besides, the presence of large amounts of carbonate as one of the main components of clay soils, especially in the arid and semi-arid regions, and its effect on the soil engineering properties emphasize the necessity to study the combined effect of heat and carbonate on the engineering behavior of clay soils. Accordingly, the present paper studies the interaction of clay-bentonite, clay-lime, and clay-fiber at high temperatures and its effect on the properties of clay soils. In this regard, a series of macro-structural experiments are conducted. The different thermal levels considered in the present study, according to the previous research, are 0 to 900. The soil behavior is investigated using numerical and laboratory methods. The experiments conducted in this area include the weight changes and the unconfined compressive strength of the soil. The effect of using the bentonite and fiber on the strength indicates that at a given temperature, increasing the percentage of bentonite leads to increased strength. In addition, the rate of increase is different at different temperatures, so that the highest increase occurs for the addition of 30% bentonite to the soil, reaching the unconfined compressive strength to 1.88 times the control sample. However, adding 0.5% fiber and 4% lime shows the maximum strength.