Tikrit Journal of Engineering Sciences

This paper is concerned with the bending behavior of reinforced concrete sections subjected to cyclic loads, such as wind loads or earthquake loads. Previous studies have indicated that the cyclic loading of such kind can cause failure in the joints of a structure which subsequently put the structure into the state of instability or collapse. The paper also pays attention to the behavior of reinforced concrete beams and frames. Modeling of the cyclic relationship between moment and curvature is presented for the reinforced concrete sections under effect of axial load and moment on the assumption of full bond between steel and concrete. The shear deformation however is sidestepped. The stiffness method with the effective secant stiffness is used in the analysis of the structures for calculating displacement in each section and then getting the load-displacement curves, moreover, the recurrence method is used in the analysis of simple members in structures like reinforced concrete beams subjected to cyclic loads. The current study presents a numerical model which is capable of predicting the behavior of a reinforced concrete beam, frame and joint subjected to cyclic loading. The effect of axial force on the structure is also considered. The study concludes that the effect of axial force in the structural members is to decrease the energy absorption by these members and increases their failure loads. It also shows that the model used in the analysis of reinforced concrete sections has a good accuracy, it has ability to decrease the time of computer running compared with other methods, this makes it possible to depend on the analysis .The stiffness and recurrence method show good activity in the analysis from the obtained results.

This paper present the variation between brink and critical depths for free overfall, of water over two models of broad crested weirs with different edge, straight vertical and skewed with an angle (30)o. The discharge was measured for the two models and compared with calculated one observed from theoretical equation. The results showed that the calculated discharge is greater than the measured one by (3.5&14.5)% for straight vertical and skew models respectively, and the skew model discharge is greater than that for the straight vertical by (13%). Also, the results indicated that the coefficient of discharge for skew model is less than that for the straight vertical one by (8%). Meanwhile for the same discharges the brink depth for straight vertical model is greater than that for skew model by (11%). The study also showed that the distance upstream the weir (x), at which the critical depth intersected with water surface profile, for skew model is greater than the straight vertical model by (63%).

The work has been an experimental and numerical investigation of radioactivity risk assessments using tracer test technique in open channel flow. Two types of tracer have been used and then examined, pure KCl which has dual indicator at the same time electrical conductivity and radioactivity, and Carmosine (E-122) a florescence dye which used for environmental safety requirements. Thirty three runs were performed to measure solute transport in open channels flows and calculate doses that response from these concentrations. ADE models for one and two dimensional of cases instantaneous and continuous injections in steady states were applications and shown good agreement between predict and observed concentration of the mixing in the flume. The analyses and comparisons show the average MRE equal to 7.2%, and discrepancy ratio between observed and predict of φ = 45 equal to 2.66% & r2 equal to 0.984.

In Trickle Bed Reactor Basrah crude oil was hydrotreated using a common hydrotreating catalyst (Co-Mo/γ-Al2O3) . The operating conditions of this treating was, temperature (600 – 675 K) , Liquid hourly space velocity (LHSV) (0.6 – 1.9 hr-1) , constant pressure (3 Mpa) and H2/Oil ratio 300 L/L were performed. Experiments results show that aromatic content was reduced as temperature increases and LHSV decreases, as well as the aromatic saturation were greatly enhanced at the same condition .

This study is an application of one of the non-linear programming methods ; Hooke & Jeeves method to the structural design of the trapezoidal combined footings , considering the total cost of the footing as an objective function . The cost function was formulated in terms of the following design variables : Smaller and larger footing width, footing width, thickness, depth of embedment and left and right projections A computer program was developed to solve this design problem using the conventional structural design approach in conjunction with Hooke & Jeeves method. A simple study was performed to detect the sensitivity of the objective function to its design variables.A further parametric study was performed regarding the distance between columns and loading conditions. It has been proved that the minimum cost of the trapezoidal combined footing increases with the increase of the distance between columns and loading ratio.

This study revealed the efficiency of using lime as a coagulant and coagulant aid with alum in turbidity removal when it used with medium and high initial turbidity levels (100, 500) ntu with dosage of (10, 40) mg/l respectively with alum dosage of 20 mg/l, It not recommended to use lime with low turbidity limits of (25) ntu and lower. Also the used of lime with alum improved the settling time especially in high limits of turbidity. A mathematical relationship was developed variables including in the study to determine the residual turbidity by using stepwise regression analysis.

The present work involves developing an analytical model to study the behavior of ferro-cement slabs and shell roofs, and to adopt the most realable constitutive relationships for the mortar material to predict the nonlinear response of ferro-cement roofs by using the finite element method. To represent the mortar and wire mesh, a layered approach is used. Mortar is considered as a strain-hardening material and exhibiting strain-hardening behavior till it reaches the peak stress, beyond which, mortar enters the descending portion (strain softening) until it reaches the crushing strain. Tension stiffening is used to model the post- cracking tensile strength of the mortar. Under further loading in post-cracking stage shear retention is used to model the shear transfer throughout the cracks. The behavior of steel reinforcement and wire mesh is considered as elastic perfectly plastic with linear strain hardening. The predicted results of ferro-cement slab and cylindrical shell roofs had shown a good agreement with the published experimental results.

A theoretical and experimental study on the transient natural convection heat transfer across an eccentric horizontal annulus under the condition of constant surface temperature was carried out. The numerical study was carried out using the computational fluid dynamics code, Fluent, based on the method of control volume to study the natural convection phenomena in this enclosure. The experimental work included manufacturing an experimental setup to clarifying the effect of eccentricity ratio, angular position, and time on the natural convection inside the enclosure. Results were presented in graphic forms of streamline and temperature distribution inside fluid. The study showed that the ability of the inner cylinder on transient convection heat transfer decreased as the transient Raleigh number increased which is increase as time required to reach the steady state increase, perhaps this ability increase in the case that include eccentricity ratio (ε=0.726) in the angular position (δ=180o) where this ability will be higher than concentric state (ε=0).

An experimental investigation was carried out for combined effect for unsteady natural convection and radiation heat transfer between inclined eccentric cylinders under constant surfaces temperature condition. The study included the effect of transient Raleigh number, which includes the effect time required to reach the steady state, the angular position of the inner cylinder and the eccentricity ratio for the inner cylinder on the convection and radiation heat transfer for unsteady state through enclosure between inclined cylinders. The study showed that the ability of the inner cylinder on transient convection heat transfer decreased as the transient Raleigh number increased which is increase as time required to reach the steady state increase, perhaps this ability increase as the angular position for the inner cylinder increase and decrease as eccentricityratio increase except at the ratio (ε=0.351) in the angular position (δ=180o) where this ability will be higher than concentric state (ε=0). While the radiation heat transfer depended only on thetemperature, difference, which is a function of time, required to reach the study state.