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Showing 9 results for Air

Saffar Zadeh M., Karbasi Zadeh B.,
Volume 2, Issue 1 (3-2004)

In this paper, optimal bridge management system models have been presented. These optimization models are capable of allocating limited resources to the bridge preservation schemes in order to establish the optimal time of completing the activities. Bridge-based activities are divided into two main groups: repair projects, and maintenance activities and both models are presented in this paper. Particular attention has been made to optimize the management of the two system activities. The dynamic programming approach was utilized to formulate and analyze the two models. The developed models are found to be more accurate and faster than the previous ones.
Saffar Zadeh M., Asadi M.b.,
Volume 2, Issue 2 (6-2004)

In this research, the Integrated Noise Model (INM), has been calibrated to perform the noise pollution evaluation in the vicinity of Mehrabad International Airport (MIA). First a conceptual model was developed to analyze the compatibility of airport noise with the land use based on the most widely accepted noise pollution standards. Second, the data generated from the INM package was compared with real data acquired from the test stations positioned around airport. Finally, the outputs of the calibrated model was compared with the noise pollution standards. The results show that more than 70 percent of the land use in the vicinity of airport are not compatible with the accepted noise levels. The generated noise contours was superimposed on the digital map of the city and the areas which violated the permitted levels was recognized. Moreover, the more noise sensitive facilities such as hospitals, schools, and residential units can be positioned in areas which have the permitted noise levels. The model and the procedure can be used to design new airports. Noise evaluation of existing operational airports can be performed by the model developed in this research.
M.b. Javanbarg, A.r. Zarrati, M.r. Jalili, Kh. Safavi,
Volume 5, Issue 1 (3-2007)

In the present study a quasi 2-D numerical model is developed for calculating air concentration distribution in rapid flows. The model solves air continuity equation (convection diffusion equation) in the whole flow domain. This solution is then coupled with calculations of the free surface in which air content in the flow is also considered. To verify the model, its results are compared with an analytical solution as well as a 2-D, numerical model and close agreement was achieved. The model results were also compared with experimental data. This comparison showed that the decrease in air concentration near the channel bed in an aerated flow could be well predicted by the model. The present simple numerical model could therefore be used for engineering purposes.
S. Eshghi, V. Zanjanizadeh,
Volume 5, Issue 3 (9-2007)

This paper presents an experimental study on seismic repair of damaged square reinforced concrete columns with poor lap splices, 90-degree hooks and widely spaced transverse bars in plastic hinge regions according to ACI detailing (pre.1971) and (318-02) using GFRP wraps. Three specimens were tested in “as built” condition and retested after they were repaired by glass fiberreinforced plastic sheets. They were tested under numerous reversed lateral cyclic loading with a constant axial load ratio. FRP composite wraps were used for repairing of concrete columns in critically stressed areas near the column footings. Physical and mechanical properties of composite wraps are described. Seismic performance and ductility of the repaired columns in terms of the hysteretic response are evaluated and compared with those of the original columns. The results indicated that GFRP wraps can be an effective repair measure for poorly confined R/C columns due to short splice length and widely spaced ties with 90-degree anchorage hooks. Both flexural strength and ductility of repaired columns were improved by increasing the existing confinement in critical regions of them.
Mohammad Reza Kavian Pour, H.r. Masoumi ,
Volume 6, Issue 3 (9-2008)

Hydraulics of stepped spillway is a very complicated phenomenon, as it consists of a two phase flow passing through a set of designed steps. The steps increase the rate of energy dissipation taking place on the spillway face. Turbulence, flow aeration and energy dissipation are the main tasks in the design of such structures. This study consists of the experimental investigation to determine the energy dissipation over stepped spillways. Experiments conducted at Water Research Institute on two physical models of the Siyah Bisheh stepped spillways in Iran. To develop a more generalized expression, the results of previous investigations were also considered in our study. Therefore, a wide range of variables were taken into account to estimate the energy dissipation along the non-uniform flow regime. Assuming the energy dissipation along the uniform flow regime to be equal to the vertical displacement of the jet, the total energy lost was calculated. A comparison of the results with those of measurements showed a regression of 0.92 for the total energy dissipation, which is one of the features of the present method for estimating of the energy dissipation, compared with the previous investigation.
Kwang-Suek Oh, Tae-Hyung Kim,
Volume 11, Issue 2 (11-2013)

This study was conducted to determine the effect of vibration on the curing and compressive strength of lightweight air-trapped

soil (ATS). ATS is manufactured by mixing cement with water and sand and injecting bubbles into the mixture. It is light as

compared to regular soil, can reduce the weight on the ground, and has high fluidity. If ATS is used at construction sites with

many vibration sources, such as pile driving, blasting, and construction machinery, the effect of vibration needs to be seriously

considered. If a road is expanded using ATS to reduce traffic congestion, the ATS quality may decrease because of vibration

generated by traffic moving on the road. In particular, because ATS contains many air bubbles and needs time for curing, the

effect of vibration can be greater than expected. Therefore, the effect of vibration on ATS was evaluated during the curing process

by conducting unconfined compression tests on samples prepared with different values of variables including vibration velocity,

starting vibration time, and mixing ratio. Vibration velocities of 0.25 and 0.50 cm/s did not greatly affect the strength. However,

vibration velocities of above 2.50 cm/s significantly affected the decrease in strength, and the starting vibration time also had a

clear effect on specimens cured for less than 2 hours.

A. Ahmed A, S. Naganathan, K. Nasharuddin, M.m. Fayyadh,
Volume 13, Issue 2 (6-2015)

The effect of steel plate thickness on the repair effectiveness of RC beam is presented in this paper. A total of four beams were tested, one beam repaired by CFRP with a thickness of 1.2 mm and used as a control beam, and three beams repaired by a steel plate. Steel plates with a thickness of 2 mm, 3 mm, and 4 mm were used in repairing the beams. The maximum load-carrying capacity, deflection at mid span and edge of the opening, strain in steel bars, strain in externally bonded plates, crack patterns, and failure modes were observed on each beam. The externally bonded CFRP sheet and steel plates were found to be effective in the repairing of RC beams with large rectangular web opening. The results show that increasing steel plate thickness has little effect on the maximum load capacity. The CFRP plate is more effective than steel plate in increasing the load capacity of beams.
Hassan Ziari, Parham Hayati, Jafar Sobhani,
Volume 15, Issue 1 (1-2017)

In this paper, self-consolidating concrete (SCC) mixtures are considered for airfield concrete pavements. A series of rheological, mechanical, transport and frost action durability tests were conducted on the prepared SCC mixtures with and without chemical air entraining agents (AEA). Mineral admixtures including slag, fly ash, silica fume and metakaolin were included in SCC mixtures. The results showed that application of mineral admixture led to significant improvements on the performance of airfield concrete pavement mixtures. Moreover, the performance of mixtures against frost action upgraded when AEA included in companion with the mineral admixtures.

Ziba Fazel, Masoome Fazelian, Dr. Hamed Sarkardeh,
Volume 15, Issue 2 (3-2017)

Air-water flow is a complex and challenging subject in many engineering fields as well as hydraulic engineering and discovery of its characteristics can help the engineers to predict and analyze a probable phenomenon. In the present paper, development of a device capable of measuring the flow velocity, air concentration, diameter and counts of bubbles in air-water flows is described. The heart of the present device is two resistive probes with a novel configuration. Being pressure and corrosion resistant and also having negligible resistivity in the flow are some of the unique features of the employed needles. Moreover, sampling frequency and time can be set for the intended application by the user. In the present electronic board, maximum available sampling frequency is in the order of KHz, while the time of sampling is not limited. The circuit is designed with ability for avoiding the polarization of the probe tip. Increasing the number of probes up to four which can operate together and suitable for more complex flows with no change in the electronic board is another advantage of the proposed device. Different tests for verification of the device accuracy have been performed and good results were reported for measurements.

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