Tikrit Journal of Engineering Sciences

This paper aims at presenting and discussing the numerical studies performed to estimate the mechanical and thermal behavior of RC flat slabs at elevated temperature and fire. The numerical analysis is carried out using finite element programs by developing models to simulate the performance of the buildings subjected to fire. The mechanical and thermal properties of the materials obtained from the experimental work are involved in the modeling that the outcomes will be more realistic. Many parameters related to fire resistance of the flat slabs have been studied and the finite element analysis results reveal that the width and thickness of the slab, the temperature gradient, the fire direction, the exposure duration and the thermal restraint are important factors that influence the vertical deflection, bending moment and force membrane of the flat slabs exposed to fire. However, the validation of the models is verified by comparing their results to the available experimental date. The finite element modeling contributes in saving cost and time consumed by experiments.

The conceptual cost estimation is a critical indicator of the future of the project's success at the initial process before submitting the project design. Pre-Design cost measuring is recognized as the very important procedure which affects the future of constructing proposed projects of roads. Pre-design cost is a preliminary cost measuring and is considered the prediction of the cost of a project during the planning and design phase. This evaluating and measure provides a great foundation for the process of financial support decisions and cost control. The aim of this study is to create pre-design cost measuring model for constructing road projects by utilizing linear regression technique. The research methodology consists of the data collected from public sectors which are the actual cost of the constructed road projects in Erbil governorate, then models have been developed by applying SPSS software, then the models summarized and selected. The mean absolute percentage error (MAPE) has been calculated using Excel program to calculate degree of the accuracy for the produced models. The accuracy was between -29% and +51%. As a result of the study regression models are useful and has a big advantage in predicting project cost in pre-design process and the planning stage of the project, by using either simplex computer scheme or any measuring tools.

This paper investigates the effects of thermal radiation and variable viscosity flow down along an inclined plane with boundary conditions at free surface. The major problem includes internal heat generation, increase or decrease in temperature, and other thermo physical properties. The thermo physical properties include Grashf number, Nusselt number, Viscosity and Solar radiation parameter. The problems created have not been examined. Thus, this work examined the effect of temperature and velocity profiles on the various values of coefficient of viscosity, also the effects of solar radiation parameter on the major property of the fluid flow down along an inclined plane.
The partial differential equations for the problem are continuity, momentum and energy equations. These are non- linear dimensionless equations governing the fluid flow down the inclined plane using integration method. The equations for the fluid flow, temperature and velocity of the problem are reduced to their final forms using perturbation method. Analytical expressions are employed to obtain the value of the velocity and temperature profiles in terms of parameters under the considerations in the flow field. The parameters are the major factors influencing the properties of the fluid flow down along an inclined plane.
Hence, the viscosity of the fluid increases as the velocity of the fluid decreases while increase in the solar radiation parameter increases velocity of the fluid. Also the quantities of radiant energy absorbed by the fluid flow bring changes in the temperature of the fluid. Increase in Nusselt decreases the velocity of the fluid. Grashof number increases while the temperature of the fluid also decreases.
In conclusion, viscosity of the fluid decreases with an increase in temperature due to cohesion and molecular momentum exchange between fluid layer and the parameters are found to have a significant effect over the velocity and temperature profiles of the fluid flow down an inclined plane at free surface. It will also useful for the industries in the production of the various fluids (liquid or gas) such as vegetable oil, palm oil and steam generation along an inclined plane and so on.

The extensional viscosity and cracking prospectus of polypropylene modified asphalt cement (PPMAC) was explored. Forty/fifty penetration class asphalt cement with five-contents of polypropylene polymer were chosen. Conventional traits such as: Standard penetration, standard softening point, ductility, utter viscosity, elasticity moduli, penetration prospectus, ageing, cracking prospectus, homogeneity, and extensional viscosity were performed on PPMAC. The PPMAC shows better viscosity, elasticity, enduringness and lower cracking properties at cold regions.

This study included (40) tests of loading a square footing (100*100 mm) resting on two layered soils (sand over gypseous soils) using a steel box with the dimensions of (900*900*500 mm). Gypseous soil was brought from Tikrit-University with gypsum content 61%. The tests were divided into two groups. The first groups included (4) tests for gypseous soil only by using the field and maximum densities (14.5, 18.75 kN/m3) respectively, without soaking and with soaking where gypseous soil lost a great value of its resistance. The second group included (36) tests of loading two layers of soil by replacing a layer of gypseous soil by sandy soil with relative density (30%, 60%, and 80%) and depths (B/2, B and 3/2 B). The results showed that the replacement process gave an improvement in the bearing capacity when the gypseous soil was compacted to field density and soaked with a relative density of sand (80%) while the other cases did not have any improvement. The results of loading the two layers of soil also show that the soaking of gypseous soil under the sandy layer affects on the resistance of sand through reducing it especially when the depth of sand was (B/2) this effect decreased gradually with increase in the depth of the sandy layer.

Combined hydraulic structure play an important role in controlling flow in open channels. This study was based on experimental and numerical modeling investigations for combined hydraulic structure. For this purpose three physical models of combined sharp crested trapezoidal weir with bottom opening and one physical model of sharp crested trapezoidal weir separately were used and tested by running eight different flow rates over each model. In which three configurations of bottom opening were tested; the first configuration is a rectangular gate while other two configuration were trapezoidal with two different side slopes of (1V:4H) and (1V:2H). The water surface profiles passing through weir-gate system were measured for all thirty two runs of all models which show uniform flow at 2.11h from the upstream of weir. The commercial computational fluid dynamic software ANSYS CFX was used to simulate flow numerically. The verification of the numerical model was based on water surface profiles and discharge which showed acceptable agreement. Also, the results showed that discharge coefficient Cd varies from (0.52-0.58). Furthermore, it was shown that both models with trapezoidal gate pass a higher discharge of flow than the model with rectangular gate with average percentage increase of discharge (40.78% and 19.40%) for trapezoidal side slopes (1H:2V and 1H:4V) respectively. In addition, the combined system with milder trapezoidal side slopes of bottom opening had a better performance for discharging weir flow which is about 40% as compared with traditional one. Finally, the empirical equations for stage-discharge relationship were estimated for all models and discharge coefficients were estimated for all runs.

The surface water in study area supports a range of uses such as water supply, irrigation and hydropower generation. Therefore, the assessment and analysis of the hydrological drought are important in the planning and management of the water resources. In this paper, hydrological drought was assessed using stream-flow drought index (SDI) based on observed mean monthly stream-flow data collected from three selected gauging stations at Greater Zab River, Lesser Zab River and Khazir River located in the North-Eastern region of Iraq. Trend analysis of the hydrological drought was investigated using Mann-Kendall non-parametric method to evaluate the significance of trends and Sen's slope method to determine the magnitude of the slope of trends for 47 years during the period 1965-2011. According to the SDI 3, 6 and 12-month time scales, the recorded drought was severe, and M-K method showed that the decreasing trends in the SDI values were statistically significant at α=0.05 mostly in the Greater Zab River and Lesser Zab River basins, increasing trend in SDI values is insignificant. This indicates that the hydrological drought is increasing over time at the study area.

California Bearing Ratio (CBR) value represents the main soil characteristic factor for paving design of flexible pavements & paving of airport sites. It should be used to determine subgrade modulus of crust soil layer, by using certain correlations. It is a very important engineering parameter for soil condition for design of subgrade of flexible roads. CBR values of soil may be affected by other parameters, like maximum dry density (MDD) & optimum moisture content (OMC), soil types, (coarse material of gravel and sand content), etc. for un-soaked condition of samples. Evaluation of CBR in direct test is a time waste process. This case study was conducted to find out the relationship between CBR values with MDD, OMC, standard penetration test (SPT) and coarse material content of some soil samples collected from the investigated project during 2011 with approximate area about (30) Km2, with Latitude (32.319810o -32.412226o) and Longitude (44.144141o - 44.243775o). A statistical method was used for estimating the relationship between the CBR and MDD, OMC, standard penetration test (SPT) and coarse material content of the soil desiring to obtain a relationship and a formula combining the previous two variables. A reasonable relationship represented by first degree formula was obtained. On the other hand, the time and efforts will be minimized in estimation of CBR instead of the used processing to determine the soil parameter.

Gypseous soil is one of the soils that suffer from problems and suffers from a reduction of shear strength and collapse when exposed to water immersion or water filtration in it. Many researchers have tried to solve these problems in different ways and by using many materials as additives to improve the performance and efficiency of this soil. In this research, the behavior of soil with a high content of gypsum (61.49%) is examined, using iron slag which is a by-product of the iron making process in melting furnaces, used as an additive in proportions (2, 4, 6, 8, 10., 12) %, by dry mixing method with soil. Tests are carried out to determine the effect of this substance on the shear strength parameters. The effect of water immersion on soil cohesion (c) is reduced until it reaches (c) in the case of immersion a value very close to the value in the dry state at slag ratio (10) %. This is the optimum ratio of slag to improve the value of (c). Whereas for the value of (ø), with the increase of the slag rate for both wet and dry cases, the value of (ø) increases, where (ø) reaches the highest value at; the slag rate (10) % for the dry state, and the slag rate (8) % for the soaked case. Whereas for the collapse potential (Cp), adding the slag reduces the value of the soil collapse potential (Cp), from (10.6) to the soil without additives until (0.95) for the slag rate (12) %. Then the soil becomes problematic soil.

Soils with highly gypsum content signify known as soils that exhibit collapsibility and sudden failure when being submerged to wetting. Many of the constructions built on this soil showed cracked and/or collapsed at some parts as these soils immersed or leached with water. The utilization of extremely fine materials, for example, Microscale or Nanoscale, is generally utilized these days. This research compared the use of Silica fume (SF) (micro material) and Nano Silica fume (NSF) (Nanomaterial) to explore the capability of these very fine materials to mend the shear strength and collapsibility properties of highly gypseous soils. The soil as Poorly Graded Sand (SP) was used, with a gypsum amount equal to 62%. A succession of direct shear tests and double odometer tests were carried on dry and submarined specimens of soil at various percentages of SF and NSF. The obtained results indicate that mixing the highly gypseous soils with SF or NSF improved the engineering properties of these soils, especially for the wet condition. The average increment in apparent cohesion when adding SF (5-20) percentage varies between (140-310) % in dry soil and (20-40) % in soaked soil. Same results obtained when mixing the gypseous soils with (1-5) % of NSF. Also, the Nanomaterial provided an improvement of the friction angle in dry and submerged cases respectively. Considering that, the SF gives adverse results upon the friction angle of the soil. The SF and the NSF both condensed the dangers of gypseous soil collapsibility. Consequently, the use of NSF can be assertively suggested to improve the engineering characteristics of highly gypseous soils when compared with SF, where only mixing of 3% of NSF gives the best results.