KUFA JOURNAL OF ENGINEERING

The intent of this paper is to study the structural behavior of voided normal and high strength reinforced concrete two-way slabs. Voided slab is a hollow core slab which has an advantage of reducing self-weight by reducing concrete mass within the center zone of the slab section. The experimental program included testing of twelve simply supported slab specimens with dimensions of (1100 x 1100 x 100) mm, and they were subjected to vertical four patch loads. Many parameters were included, such as shape of voids (spherical and cubic), type of concrete strength (normal of 30 MPa strength and high of 60 MPa strength), and ratio of steel reinforcement (0.002, 0.0026). In addition, they have different values of dimension of void to slab thickness (D/H) ratio (0.5, 0.6 and 0.65). The experimental results showed that the use of voided slabs tends to save in self-weight up to 21.6%. The use of spherical voids in voided slabs is more effective than cubic voids due to cracking and ultimate loads capacity and the structural behavior. The use of voided slabs led to reducing the first cracking load in a range of 15%-62% and 5%-40% for high and normal strength, respectively. Also, using voided slabs tended to reduce the ultimate load capacity in a range of 8%-26% for balls and 9%-48% for cubes. Using high strength concrete in voided slabs led to reducing the crack width in a range of 18.2%-27.8% for voided slabs (65 mm ball shapes). Decreasing the size of voids led to reducing the deflection for the same stages of load in a range of 20%-35.7% for high strength voided slab (ρ= 0.20% ball shapes) specimens. Increasing the reinforcement ratio from 0.2% to 0.26% led to reducing the deflection in a range of 1.6%-35.9% for high strength voided slab (ball shapes D=60mm) specimens.

The productivity rate is the main indicator for the development of construction projects for any developed country. The main goal of this paper is to evolve a mathematical model by using the multiple linear regression technique to predict the rate of production of concrete column molds. This is because the currently used methods in estimating productivity, such as the methods that rely on personal experience and old data, are traditional methods characterized by inaccuracy. So, there was a need to adopt new techniques to estimate the construction productivity in an accurate, fast, and easy way. In this study, eleven factors were identified which are the most affecting factors on construction productivity. They are considered independent variables that affect the productivity rate of the item column formworks. The dependent variable is the construction productivity. The work measurement form was designed for the purpose of collecting real initial data from the site. This model is based on 36 samples of data collected from various projects of Multi-story buildings for residential and commercial buildings, which are used to build the model and verify its performance. From the results of the multiple linear regression MLR results, an equation was derived to calculate the construction productivity of the column formworks. It was found that the multi-linear regression model provides a very good predictability of productivity (82.31%), and the correlation coefficient (R%) was 97.15%. The results showed that the relationship between the independent variables for "the built-in model is very good, and the values"​​calculated from the prediction model are commensurate with actual data".

In this paper, Framelet and Walsh transform are proposed for transformation, and then using arithmetic coding for compress an image. The goal is to achieve higher compression ratio by applying two levels Framelet transform (FLT), and then apply 2D Walsh-Hadamard transform (WHT) on each 8x8 block of the low frequency sub-band, while all other sub-bands are ignored. Experimental results show that the proposed algorithm gets best possible solution for tradeoff between compression ratio (size of image) and quality of compressed image, Peak Signal to Noise Ratio (PSNR). The simulation was carried using MATLAB software package version 2014. In this work, experiments were carried out on the gray scale and colored images

This study based on the laboratory experiments and numerical analysis to study the configuration of the local scour downstream of hydraulic structure result by free water jet. This jet will have a high kinetic energy making it able to transport the sediment particles downstream of the impinging area, thereby forming a scour hole. The purpose of conducting this study was to evaluate the minimum distance of scour hole from the nozzle jet. One hundred and thirty-eight runs were carried out to investigate the local scour downstream the hydraulic structure under clear-water conditions with different discharges, tail water depths, and jet angles. Two types of jets were used, normal jet and dispersion jet. Results indicated that minimum distance of scour increase with increasing densimetric Froude number and jet velocity. The increase in tail-water depth decrease the distance to the scour hole until access to a critical depth at which the scour hole is largest possible after that the distance back to become large when the depth is overstepping the critical value. The optimum jet angle depends on the jet velocity, with a value of 20° for jet discharges 60 and 80 L/min and 40° for jet discharges 100 and 120 L/min. The dispersion jet technique where used to investigate its effects on the scour processes where its observed that the scour hole resulted small than the scour hole from case of normal jet, Also, the numerical simulation was used by (FLOW3D) software program to investigated from the result of the experimental work, the results showed an acceptable agreement with the experimental results with percentage of error equal to (% 6.28).

This research is devoted to investigate the effect of Carbon Fibre Reinforced Polymer (CFRP) strips on the behavior and load carrying capacity of the strengthened concrete corbels. Numerical investigation was carried out. The experimental program variables include location, direction, amount of CFRP strips, effect of shear span to effective depth (a/d) ratio on the behavior of strengthened corbels. All corbels had the same dimensions and flexural reinforcement and they were without horizontal shear steel reinforcement. ANSYS V.11.0 software was utilized in this work. Solid65, Solid45, Link8 and shell41 elements were used to model concrete, steel bearing plates, steel flexural reinforcing bars, and CFRP strips respectively. Full bond was assumed between CFRP sheets and concrete interface. The full Newton-Raphson method is used as a nonlinear solution algorithm. The displacement criteria are used for convergence. The adopted finite element analysis showed good agreement with experimental results throughout the load-deflection history, the maximum difference in the ultimate load was less by10%. However, the finite element models show a slightly stiffer response.

This research based on experimental work included testing of thirteen specimens categorized into two groups. The first group included five beams: one is solid while the others are hollow beams with two openings of different sizes and locations. The second group included eight specimens strengthened with CFRP sheets in three systems to determine the best configuration of strengthening. The experimental results showed that the presence of openings (150*150) mm and (150*250) mm, which located flushed to the flange, led to a decrease in the load capacity by (43% and 64%) for the square and rectangular openings respectively. On the other hand, when the openings located in bottom location the reduction in capacity was found to be (48% and 70%) for the square and rectangular opening respectively. Also, the results of the test showed that the strengthening of the carbon strips led to improving in the structural capacity, where in the case of openings located flushed to the flange, there was an increased by (19% and 64%) for square and rectangular openings respectively. In contrary, in the case of opening located in the bottom location, the improvement in capacity was found to be (37% and 87%) for square and rectangular opening, respectively.

Artificial Neural Networks, ANN, technique is a computerized system that is built to simulate the neural networks in the human brain. Throughout the recent couple decades, ANNs had solved with a good degree of success many problems. In the present work, ANN model was developed by SPSS software for estimating creep strain development of self-compacting concrete mixes produced with different types of Portland cement, Type I and Type IL. The independent variables in this model were: age, compressive strength, modulus of elasticity, applied stress, initial strain, water to powder ratio, water to binder ratio, filler to cement ratio, clinker to cement ratio, aggregate size, and slump flow. The used data for model building were local, extracted from the present work. The predictions of the model have been compared to those of an international well-known model, ACI 209 Committee. The comparison revealed the good reliability of the present models in predictions (r = 0.998).

The objective of this study is to develop a model for evaluating tire/ pavement noise of the various in-service pavement sections in Baghdad city. The scope of this work includes field noise measurements for three selected conventional asphalt concrete roads which are (Senaha Street constructed in 2010), Palestine Street (resurfaced in 2012) and Street2 Locality902 (newly resurfaced in 2017) and one concrete Muhammad Al-Kassim (constructed in 1983). The tested section was selected according to AASHTO TP76 which requires the length of the section to be 440 ft. at varying constant speeds such as(20,40,60,80) km/h using two types of tire (235/45R18, 185/65R15) KUMHO tire and at a different temperature

The outdoor transmission channels condition in multiple wireless signals systems changes continuously due to signals transfer path characteristics. The path loss, multiple reflected rays Rayleigh fading and shadowing presents an important factor that effects inconsistent with signals propagation through the wireless channels of communication systems. The solutions for these effects will contribute to minimize the error probability of transferred data and maximize the data rate in high speed systems. This paper deals with the analysis of error probability using Probability density function (PDF) model of Signal to Noise ratio (SNR) for different values of transmitted signals power at outdoor receiver of multi users systems. The proposed approach use Rayleigh fading channels, 2GHz carrier frequency, (0-30) dB SNR, (0.1,0.2,0.3), (1,2,3) and (10,20,30) PW. The relationship between error probability and SNR has been studied to determine efficient transmission channels. The proposed channel model has been simulated and analyzed using MATLAB R2012b software under different users power signals values. The obtained results have showed accuracy as well as efficiency of the proposed method where the error probability is decrease when the SNR increase and the error probability decrease when decrease in the transmitted power signal.

This work seeks to statistically analyze the effect of wavelength transmission in free space over Ilorin, Kwara State, Nigeria using existing atmospheric data for wind velocity from Nigeria Meteorological Agency (NiMET). Scintillation attenuation was calculated based on Rytov approximation for wavelengths of 780nm, 850nm, 1250nm and 1550nm.The signal to noise ratio (SNR) for all the wavelengths considered were also analyzed and it was found that wavelength 1550nm is less attenuated and also has a good SNR as compared with the others. Therefore to improve the efficiency of transmission of FSO, the wavelength of 1550 nm must be used.

This work contributes two novel modified Taguchi techniques to the optimal parametric setting for minimum water absorption in epoxy composites. Taguchi method, using ASTM standards was applied with factors (initial weight, final weight, length, sample thickness and time of immersion) and four levels in the experimental design. The analysis of variance (ANOVA) evaluates the significance and individual contributions of the parameters. The optimal parametric setting was A1B4C3D4E1 (initial weight, 2.61 g; final weight, 2.69 g; length, 62.73 mm; thickness, 3.88 mm; time, 15.65 hrs). The ANOVA identifies time and length as dominant parameters (98.98 and 1.02 % contributions, respectively). Taguchi-Pareto analysis found only factor-level from the time and length parameters economical to optimality. The Taguchi-ABC analysis revealed the individual weights and contributions of the factor-level irrespective of its initial groupings. The new Taguchi techniques highlighted the importance of time and length of sample in obtaining minimum water absorption of composites.