Tikrit Journal of Engineering Sciences

This investigation is to develop a numerical model suitable for nonlinear analysis of reinforced concrete shells. A nine-node Lagrangian element Figure (1) with enhanced shear interpolation will be used in this study. Table (1) describes shape functions and their derivatives of this element. An assumed transverse shear strain is used in the formulation of this element to overcome shear locking. Degenerated quadratic thick plate elements employing a layered discrelization through the thickness will be adopted. Different numbers of layers for different thickness can be used per element. A number of layers between (6 and 10) have proved to be appropriate to represent the nonlinear material behavior in structures. In this research 8 layers will be adequate. Material nonlinearities due to cracking of concrete, plastic flow or crushing of concrete in compression and yield condition of reinforcing steel are considered. The maximum tensile strength is used as a criterion for crack initiation. Attention is given to the tension stiffening phenomenon and the degrading effect of cracking on the compressive and shear strength of concrete. Perfect bond between concrete and steel is assumed. Attention is given also to geometric nonlinearities. An example have been chosen in order to demonstrate the suitability of the models by comparing the predicted behaviour with the experimental results for shell exhibiting various modes of failure.

The mathematical modeling of two heated tanks system was developed based on the heat balance and used model parameters for tuning PID and Dahlin controller parameters. The system was studied by introducing step change in the temperature of the inlet stream and heat supply and measuring the temperature change of the tanks. In this paper, a rule-based controller that incorporates fuzzy logic controller has been designed and evaluated. Through simulation study by using MATLAB, it has been shown that the estimated parameters of the model are in good agreement with the experimental values. Also the proposed fuzzy logic controller has given an excellent tracking and regulation performance compared to that of the PID control and Dahlin controller systems.

In this research, a new method for the production of the blend consists of polyester resin as a matrix-binder at fixed weigh and different weighs of epoxy resin that can be used to coat wood is developed. Several experiments are performed under different conditions to identify the most favorable operating conditions for the preparation of blend (polyester/epoxy) resins. Optimum conditions, namely, mixing speed, mixing time, heating temperature and heating time are investigated and found experimentally as 500rpm, 5min, 750C and 6hr respectively. In addition, solid palms wastes (lignin) as reinforcement fibers is employed in order to improve the mechanical properties: impact strength, bending deflection and bending distortion of coated wood. The optimum ratio of prepared blend is characterized by the mechanical (impact and bending) tests of the untreated samples occurred at a ratio of polyester/epoxy resins of 0.91w/w. It showed the best bonding force and physical interaction between two resins. The impact strength of the treated samples with one and two layers of prepared lignin fibers are higher than that of the untreated sample, while the bending distortion and bending deflection of treated samples are lower than that of the untreated sample. Experimental results showed that the treated sample with biofibers (lignin) led to enhancement in the mechanical properties of coated wood.

This paper presents a series of laboratory tests to evaluate the effects of lime and waste lime on the volume change and strength characteristics of moderately collapsible soil selected from Al-Rashidia in Mosul city. The tests are performed at different percentages of lime and waste lime of 0, 0.25, 0.5, 1.0, 2.0, 3.0, 4.0, 6.0 and 8.0% by dry weight of soil. One dimensional compression tests are conducted to clarify the influences of relative compaction, compaction water content, vertical stress level and curing time on the volume change and strength characteristics. The results of this study indicated a decrease in the plasticity, swelling potential and swelling pressure of treated soil. The soil became non-plastic at (3&6)% of lime and waste lime respectively. Swelling pressure and swelling potential reached to zero at 2% lime and 2&7 days of curing time. Unconfined compressive strength (UCS) reached to maximum value at optimum stabilizers content. The UCS of lime treated soil is more than that treated by waste lime at different curing time. The collapse index and potential of treated soil are found less than that of natural soil and decrease with increasing stabilizer content until drop to zero at 2% lime. Collapsing increased continuously with applied stresses, but with curing time reached a maximum value at 2 day. On the other hand, collapsing of treated soil with lime is less than that of waste lime treated soil at different curing time and stresses.

Compressive strength of concrete is a commonly used criterion in evaluating concrete. Although testing of the compressive strength of concrete specimens is done routinely, it is performed on the 28th day after concrete placement. Therefore, strength estimation of concrete at early time is highly desirable. This study presents the effort in applying neural network-based system identification techniques to predict the compressive strength of concrete based on concrete mix proportions, maximum aggregate size (MAS), and slump of fresh concrete. Back-propagation neural networks model is successively developed, trained, and tested using actual data sets of concrete mix proportions gathered from literature. The test of the model by un-used data within the range of input parameters shows that the maximum absolute error for model is about 20% and 88% of the output results has absolute errors less than 10%. The parametric study shows that water/cement ratio (w/c) is the most significant factor affecting the output of the model. The results showed that neural networks has strong potential as a feasible tool for predicting compressive strength of concrete.

The investigation reported in this paper is carried out to study the feasibility of using crushed bricks to substitute the coarse aggregate (gravel) in concrete. Two types of concrete mixing are prepared. The first one is a mixture of 1:2:4 without crushed bricks and is used as a reference mixture .The second one is made of different weight of crushed bricks (as a percentage from the weight of the coarse aggregate). A total of 30 numbers of concrete specimens are casted with and without crushed bricks and tested under compression and split tension as per relevant to British standard specifications. Test results indicated that using crushed bricks reduces the strength of concrete. Also, the percentage of water to cement ratio increases for constant slump when the percentage of crushed bricks increased.

The Behavior of an extended aeration activated sludge process was studied. Factors that might affect the performance of such process were also investigated. Three basins, each consisted of two parts one for aeration and the other for sedimentation were employed. Required tests and results analysis were made. It was found that removal efficiency of dissolved organic matter was limited to F/M ratio. The study revealed that such treatment was capable of treating variable characteristics wastes. The supernatant leaving secondary sedimentation was found to attain constant characteristics irrespective of variable influent. The results show that the maximum overall COD removal efficiency occur at hydraulic detention time equal to 23 h, 80% of SVI value was less than 125 ml/gm and the minimum SVI occur at F/M equal to 0.387 day-1 while the effluent SS increase with SVI decrease.

The experiments had been carried out using two stroke, single cylinder type (TD113), with compression ratio of (7.3:1) Coupled to hydraulic dynamometer type (TD115). The results showed that there is enhancement of the engine performance with increasing octane number. This appears clearly when comparing the results of performance with fuel of 75 and 95 octane number. The torque increases 10% at speed of 2750 RPM. The break power also increases 18% when the octane number changed from 75 to 95 at 3000 RPM of engine speed. The same change in octane number will increase the thermal efficiency by 9% at 2300 RPM of engine speed. The break specific fuel consumption decreases at the same ratio of thermal efficiency 9% but at 2400 RPM. The less fuel consumption happens at 2400 RPM for octane number 95.

In this work four types of wastewater namely domestic, dairy, sugar and textile are used to perform statistical analysis. These wastes are treated by extended aeration system. Inlet and outlet COD and S.S are used to make the statistical correlation for F/M range of 0.1-1. The results showed that the relation between COD and SS is linear for domestic, dairy and sugar waste having a correlation coefficient 0.9323, 0.8774 and 0.8698 respectively. The relation is of third degree for textile waste with correlation coefficient of 0.557 due to chemicals and heavy metals. The relation between F/M and COD for all wastes is linear. To predict COD value leaving treatment plant using F/M and SS values which are allowed to be thrown to the water body, Duncan test was made depending on outlet COD and SS which show that extended aeration is not suitable for textile waste.

In this work an experimental study for the vapor – compression refrigeration cycle has been performed under temperature range of 9.7-32°C. The effect of varying temperature on heat exchangers pressures, cooling capacity, net power consumption, and coefficient of performance COP are studied . The results indicated that condenser pressure, evaporator pressure, and power consumption increased with the increase of temperature. The data also indicated that cooling capacity increased as temperature increased until 15.6°C then after it decreased with further temperature increase. Also COP follow the same tread of cooling capacity.