JOURNAL OF SCHOOL OF ENGINEERING
Year:2004 | Volume:16 | Issue:1|Papers Count:8

Owing to new developments in structural engineering, in reduction of structural response during earthquakes, several proposals have been introduced One of the latest proposals is the use of liquid dampers inside the structure. For this, engineers and scientists have suggested two distinct liquid dampers namely Sloshing and Column dampers. In this paper tuning liquid column dampers is investigated and applied on a 20-story building to check the structural behavior. The study shows a great improvement in both acceleration and displacement of the equipped building; therefore, suggested is the use of these dampers in controlling the structural response in earthquakes.

High ability of Mont Carlo simulation techniques has been led to ever increasing application of such methods in a wide variety of different fields including structural reliability.This specific approach has been based on event simulation using random sample process and evaluation of their results. Accurate precision requires considerable amount of simulation operations. Using various strategies, one can obtain the acceptable precision with less samples.The Importance Sampling Method(ISM) and Conditional Expectation Method (CEM)are among the examples of such methods and have shown satisfactory performance in structural reliability during the past experiences. In this article a hybrid method has been used and combined with ISM and CEM approaches using a high efficient algorithm to calculate structural reliability. In this approach with the help of high ability of ISM and using the optimum sampling function configuration, the sampling operation could be done in CEM and the failure probability will be evaluated Typical samples in the article reveal the high efficiency of this approach in solving the reliability problems. In this paper the acceptable ability of the algorithm in solving the time variant reliability of structures according to a real case has been shown.

In this research, the effect of small circular opening on shear, flexural behavior and ultimate strength of reinforced concrete beams, which built from normal and high strength concrete, have been studied Diameter, location of opening, type and arrangement of reinforcement around the opening and change in strength of concrete are the main parameters in these tests. In this experimental study, the nine specimens made of normal strength concrete and five specimens made of high strength concrete have been tested. One of nine specimen made of normal concrete without any opening is used as reference. The beams are loaded under symmetrical two-point loading. The result shows that diameter and location of opening are important in ultimate load, cracking form and fracture mode of beams. Its also shown that the increasing value of strength depends on diameter and location of opening. Diagonal shear reinforcement is a good option to control the cracks and to limit their width. To increase the ultimate shear strength, diagonal reinforcement and stirrups in top and bottom of opening is clarified At the end, the results of tests are compared with some standard codes.

The fly ashes contain mainly quick lime (CaO), anhydrite (CaSo4) and larnite (βCa2SiO4). At ambient temperature and at normal consistency, their hydration leads to the formation of ettringite, slaked lime and gypsum. The crystallization of the ettringite causes quick cracking and splitting of the hydrated products. The ability of sulfo-calcic fly ashes to produce portlandite (Ca(OH)2),led for production of pozzolanic cements. The sulfo-calcic fly ashes are ground, then slaked either in ambient or hydrothermal conditions (2 or 6 hours at 1300c).The rate of hydration is investigated by study of compressive strength and analyses of the products by Differential Thermal Analysis (DTA) and X-Ray Diffraction (XRD) at various hydration times. The results of this research show that sulfo-calcic fly ashes can be used for production of cheap and anti sulfate pozzolanic cements.

Studying coefficient of permeability and parameters effecting it, is an important issue in fine-grained soil. This coefficient is needed to determine the consolidation settlement of fine-grained soil subjected to load In coarse soil, permeability can be determined by empirical equations with adequate accuracy. However, in fine grained soil, it is difficult to offer such an empirical equation due to different parameters (such as structure, mineral and chemical component) effecting permeability of the soil. So, empirical equations introducing permeability has to be based on physical and chemical characteristics of this type of soil. In this paper, with investigating the effect of different parameter on the permeability, several permeability tests were performed on fine-grained soil widely find in province of Mazandaran. Performance of existing empirical equations was evaluated using experimental results. Based on this study, the empirical equation e -log k showed a good correlation with experimental results.

The plastic shrinkage can occur in the early ages of concrete due to hot or dry air and wind blow. In the current study, the effect of different types of polypropylene (PP) fibers with low volume ratios (less than 0.2 percent) on the cracking of fresh concrete due to plastic shrinkage was evaluated. The specimens with dimensions of 300x300x50 mm were tested in a wind tunnel with the wind speed of 16 m/s. Five types of polypropylene fibers and three different volume ratios of fibers, i.e. 0.05%, 0.1% and 0.2% were used. The lengths of fibers were 6, 12 and 19 mm. Test results showed that pp fibers with sufficient length (more than 10 mm) significantly reduce concrete cracking due to plastic shrinkage. However, the fibers lowered the workability of concrete, though rather improved the concrete compression strength.

Reservoir sedimentation decreases the useful storage or the useful life of a reservoir. Knowledge of the sediment distribution in reservoirs can be used as a useful tool to discharge them at a proper time. In this study, using a hydraulic model, the concentration of density current along the reservoir and the sedimentation rate has been investigated experimentally. Two types of sediment particles, sand as non-cohesive and clay as cohesive particles were used Experiments were done for different density current flow rates on several reservoir bed slopes to consider the effect of flow rates on sediment particles size distribution and sedimentation rate along the reservoir. After sedimentation of most suspended particles, reservoir water was discharged slowly, then, samples were taken from the sediments in proper distances along the reservoir. These samples were transferred to the laboratory for particle size testing and calculation of the sedimentation rate. Results were shown that most of the coarse particles were deposited before the plunge point or a short distance down the plunge, while, the fine particles were located between the plunge point and the dam, overall, sedimentation rate decreases along the reservoir toward the dam. Equations to calculate sedimentation rate and the concentration of density current along the reservoir, were introduced.