Basrah Journal for Engineering Sciences

Basrah is considered as the economic capital of Iraq. In recent years, it showed a rapid growth in population and, accordingly, an increasing investment in construction industries. This paper presents information about the geotechnical characteristics of Basrah soil. For this purpose, geotechnical data have been collected covering wide areas of the city. The study area was divided into two zones, one of them was further divided into three subzones. For each of the zones considered, geotechnical information including typical soil profiles, Standard Penetration Test (SPT-N) values, Atterberg limits, sieve analysis results, consolidation test results and other physical aspects were given. Furthermore, chemical analysis of Basrah soil was also presented. According to field and laboratory results, soils in this region can be classified into two distinct zones. The eastern zone, which mainly forms of soft and medium cohesion soils extended from the soil surface down to a depth of (16 – 26) m, and, the western zone, which can be identified by the sandy surficial and stratigraphic soil.

This work deals with the effect of using Recycled Concrete Aggregate (RCA) as a partial replacement of coarse aggregate in Self-Compacting Concrete (SCC), on the structural behavior (flexure and shear) of reinforced concrete one-way slabs. To the authors’ knowledge, this study is one of limited studies concerning the behavior of recycled aggregate concrete one-way slabs subjected to line loading with significant replacement of conventional aggregates by recycled concrete aggregate (up to 75 %). Three replacement ratios were considered 25 %, 50 % and, 75 %. The mixes (with natural stone coarse aggregate, NCA) have an averaged compressive strength of (Fcu = 42 MPa) at the age of 28 days with a tolerance of (± 1.5 MPa). While, the mixes (with RCA) have an averaged compressive strength of (38.5, 36.5 and 34 MPa) for the three replacement ratios respectively, at the age of 28 days with a tolerance of (± 2 MPa). All the slabs were cast with length of (1600 mm), width of (600 mm), while the thickness was variable. For this purpose, sixteen reinforced concrete one-way slabs were cast and divided into five groups (G1 to G5). Different parameters that affect the behavior of one-way slabs were studied and include type of failure, replacement ratios of NCA by RCA, amount of main reinforcement, thickness and locations of line loadings along the span. Hardened concrete specimens results show that the compressive strength Fcu, tensile strength Ft, modulus of rupture Fr and modulus of elasticity E were decreased as the RCA replacement increased. The experimental results of slabs show that the ultimate capacity of slabs decreased as the RCA replacement increased, the deflection and strain increase as the RCA replacement increases and the crack width increases as the RCA replacement increases. From the results of ultimate capacity, cracking load and moment, deflections, crack width and pattern and concrete surface strains, it can be concluded that the recycled concrete aggregate can be used as a partial replacement of natural coarse aggregate to produce self-compacting concrete mixes. Also, the behavior of one way slabs cast with SCC containing RCA is acceptable.

A simulation of fluid-structure interaction (FSI) and combined convective heat exchange is accomplished in an open trapezoidal cavity-channel. A non-Newtonian (power law fluid) is inspected within the laminar region. The heat source is simulated by an isothermal hot cavity bottom wall, whereas all the rest solid walls are perfectly insulated. A deformable baffle is fixed at the top wall of the channel and its free end extends towards the open cavity. The location of the deformable baffle on the top wall is varied. The baffle position is investigated together with Richardson number (Ri = 0.01-100) and power law index (n = 0.5-1.5). The problem was solved using finite element method with Arbitrary Lagrangian-Eulerian (ALE) technique. The results are compared with the non-baffled channel. The study shows that the proposed baffled channel enhances the heat transfer notably.

The present work aims to build mathematical models based on experimental data to estimate the mechanical properties of submerged arc weldment. AISI 1020 low carbon steel plates 16mm thickness were welded according to orthogonal array in order to establish the relationship between input parameters (welding current, Arc voltage and welding speed) and output parameters (ultimate tensile stress, yield stress, impact energy and hardness) by submerged arc welding (SAW) process. The relationship between input and output parameters for the welding process are conducted using two suitable mathematical models the first one based on regression analysis, while the second one based on multi input single output ANFIS model for estimation of some mechanical properties of the welded plates. It was found that ANFIS results are closer to the experimental results than regression results. The optimal parameters (which give a maximum value of ultimate tensile strength (UTS), yield stress and impact energy; 446 MPa, 318 MPa and 213 J) are welding current is (380 Amp), Arc voltage is (25 V) and welding speed is (40 cm/min), while the maximum value of hardness number is (228 HV), when current welding is (380 Amp), Arc voltage is (25 V) and welding speed is (25 cm/min).

The direct-contact evaporation method is characterized by its effectiveness in applications of heat exchangers, especially in cooling systems, due to the absence of any heat resistors that prevent the transfer of heat between the cold and hot medium. The direct contact heat transfer depends mainly on how quickly the heat is taken by the bubbles of the evaporative refrigerant from the liquid and the increase in its volume up to the top of the heat exchanger, which is usually a cylindrical liquid column so that the temperature drop therein is uniform and even. There is much research on the method of heat transfer by direct contact. In this research, we collected and summarized most of the theoretical and practical researches that examined this method with the most important findings.

This paper presents a pressure drop analysis in perforated vertical wellbores for different perforation parameters. The effect of the density of the perforations (number of perforation), the phase angle of the perforations, the diameter of the perforation and the flow rate of the crude oil from the perforations on the pressure drop and the productivity index of the perforated vertical wellbores were studied. The analysis of the vertical wellbore was performed numerically using ANSYS FLUENT 15.0 software. Three dimensional, steady-states, turbulent and incompressible fluid flow is assumed during the numerical solution of the governing equations. The results of this study show that, increased perforation density of the perforated vertical wellbore caused an increase in pressure drop, and also, decreased productivity index due to increasing the friction losses. Friction pressure drop has a significant effect on crude oil flow into the wellbore. When the main velocity is 1.5 m/s and the inlet velocity from the perforations is 2 m/s, the friction pressure drop is about 66 % and the acceleration pressure is approximately 34 % of the total pressure drop.

Welding is carried out with a very complex thermal cycle, which results in irreversible elastic-plastic deformation, and residual stresses in and around fusion zone and heat-affected zone (HAZ). A residual stress due to welding arises from the differential heating of the pipes due to the weld heat source. However, due to the presence of residual stresses in and around the weld zone the strength and life of the component is also reduced. The objective of this work is to measure the welding residual stress in ASTM (A-106 Gr. b) steel pipes with 4" diameter and 6 mm thickness welded manually (SMAW) in three-pass butt joint where shielded metal arc welding process consists of heating, melting and solidification of parent metals and a filler material in localized fusion zone by a transient heat source to form a joint between the parent metals. The welding process will have accrued without preheating and heat treatment. This measuring of residual stress occurs by using hole-drilling strain gauge method according to (ASTM E-873) then the experimental results for residual stresses obtained from welded carbon steel pipes used to provide validation for finite element simulations. The welding process and welding residual stress distribution is calculated by Ansys Finite Element techniques. Theoretical considerations can be assessed by a mechanical model. The overall, there is good agreement between the predicated and measured distributions of residual stress, but the magnitude of predicted stress tend to greater in welding region.

This paper presents a new design to implement DFT/IDFT using the two components of a sequence, which are even and odd component sequences to solve the complexity of complex multiplications and reduce the number of multipliers. The proposed two implementations reduce the number of real multipliers needed to compute the DFT. The first proposed design gives good results for N ≤ 512 as compared to conventional FFT algorithm, while the second scenario gives good results for N ≤ 1024 as compared to conventional FFT algorithm. The proposed design is performed directly from real and imaginary part equations of the DFT sequence X [k] without additional processing.