Ferdowsi Civil Engineering
Year:2019 | Volume:32 | Issue:3 |Papers Count:8

In this research, by using mechanical and thermodynamic methods, the effect of surface coatings of aggregates with crystal calcium carbonate powder on the moisture sensitivity of asphalt mixtures has been evaluated. The results show that the indirect tensile strength of the modified specimens has been increased. as Also, the result of SFE method indicates that, with aggregate surface modification, their acidic and basic components respectively have been reduced and increased. Due to these changes, the adhesion between aggregates and bitumen (which is an acidic substance) increase. In addition, the amount of released energy in the presence of moisture has been reduced for modified specimens, which indicates a reduction in the tendency of the mixture for stripping.

In this paper, the effect of installation of a triangular vane attached to the bank on the transverse mixing and reduction of pollutant concentrations has been investigated. Triangular vanes are environment friendly structures and used for river sediment management. By generating secondary currents, these vanes can create transverse mixing in a shorter distance and help the river self-purification. The experiments were conducted in a flume 80 cm wide and 10 m long. A triangular vane with an effective length of 30 % of the channel width and an angle of 45 ° relative to the mainstream was installed at 50 cm downstream of the source of the tracer. Water and salt solution was used as a tracer. The concentration was measured by 96 sensors at each transverse section and in the four downstream sections of the tracer. In addition, around the vane, the 3D velocity pattern was also recorded. The results showed that the presence of the vane causes an increase in the amount of transverse velocity and their direction indicating the presence of secondary currents which resulted in a 30% increase in the variance of the concentration distribution. Also, the existence of this structure has led to the uniformity of concentration distribution and decrease of concentration of 80 % of the concentration at the maximum point of the concentration distribution at the center of the channel relative to the no vane condition.

Concrete-filled steel tube (CFST) columns are increasingly adopted in many modern structures due to the advantage composite action between steel tube and concrete core. The almost empirical models and design code relations can not provide the accurate predictions for the axial ultimate strength of these composite steel-concrete sections, especially high (ultra-high) strength concrete. In this paper, a novel predicted model of the ultimate axial strength was introduced based on Artificial Neural Network (ANN) using a large experimental data set more 1168 sample data on CFST. The predicted results of the developed ANN model were compared with eight empirical newest models and EC4 code relations using several error statistics. The ANN predictions are more accurate than the existing (code design) models and covers a wider range of material strengths and the ratio of diameter to thickness and height to diameter.

High performance self-compacting fiber reinforced composite concrete (HPFRSCC) are mighty and mighty materials that form a mixture of cement mortar and fiber. In this study, the mechanical and impact properties of these composite concrete have been empirically investigated. Various experiments were carried out on the samples, such as self-compacting concrete tests, compressive, splitting tensile and flexural strength tests, ultrasonic test and impact resistance test. The results of these experiments showed that steel fibers can have a negative effect on the self-compacting and cohesion properties of concrete, and have a positive effect on improving mechanical properties and impact strength of concrete, which has a significantly higher effect on impact resistance. In this study, the effect of two parameters of increasing the thickness of the slab and adding steel fibers to increase the impact strength of the slabs were surveyed and compared. The result of this study showed that steel fiber is a much more important parameter in increasing the impact strength of slabs.

An experimental work on replacing recycle pet bottles with sand in concrete in this paper. 5, 10, and 15% Pet equivalent with sand in concrete including 4 different mixes with constant water to cement ratio and totally 96 specimens was used and made; compressive strengths of cubic and cylinder specimens, tensile split strength of cylinder specimens, impact strengths plus flexural strengths of reinforced and plain concrete slabs were obtained. The results indicated that the workability of fresh concrete was decreased up to 50% by increasing the pet percentage up to 15% but the compressive and tensile strengths of hard concrete were decreased up to 18 and 21%. And also the flexural strengths and impact strength (initial and final cracks) were increased up to 13 and 19% due to increasing recycle pet percentage.

Duckbill weir is one of the water level control structures in irrigation networks. If Sediments are transferred into the irrigation networks, they trapped in the upstream of weir and effect on the upstream water level. In this study, submerged vanes are used for flushing the sediment to downstream in addition of gates. The Flow-3D software has been also used for simulation of flow and sediment pattern. The results showed that submerged vanes create secondary flow which is so effective for flushing the sediment especially in value of head over side wall to the weir height more than 0. 33. The results of image processing showed that the maximum relatived error for simulation of sediment pattern is 14. 4 percent.

Corrosion of lap spliced region causes the bond strength to change. The ratio of the bond strength in the corrotion state to the value of its corresponding in the absence of corrosion is called the relative bond strength. The results of the relative bond strength are different in Pullout test, Tension stiffening test and Beams with lap spliced bars test. The results of theTension stiffening test in the literature is more similar to those of Beams with lap spliced bars. In this study, a model has been proposed using tension stiffening tests, for determining the relative bond strength of corroded steel bars in the descending branch. Finally, this model has been optimized using genetic algorithm for determining the relative bond strength of RC Beam with corroded lap spliced steel bars. The current study shows that using the proposed model will lead to the beter result. The use of proposed model for the estimating the relative bond strength of RC beam with corroded lap spliced steel bars, leads to about 16 percent reduction in total error compared with Shihata model.

The highest cost of forecasting for a water distribution network is compared to the design and oversight section of the project. If the goal is to reduce costs, part of this can be achieved by reducing the cost of pipes used in the network and the standard pressure of water in the nodes. This study is a multiobjective optimization function that will be executed in Part of the water distribution network of the Rooydar city in Hormozgan. In optimization of water distribution network, In addition to financial problems, Should be noted to other aspects such as pressure and velocity of water in pipes which have key roles in network design. In the present study, the permitted pressure and standard speed in the network are considered as limitation constraints. For this purpose, in this study, the distribution network using the WaterGems model has been analyzed for hydraulic analysis, and then with coding software matlab2014b including target function and optimization by genetic algorithm according to the network characteristic. At the end of the optimization, Based on the dual objective function, in terms of cost reduction and improve network Pressure, a Scenario with good condition was chosen. This scenario caused a 12-15% reduction in costs.