Tikrit Journal of Engineering Sciences

In the design of earth dams, it must be considered that the water leakage through the earth dam generates upward and pore pressure, in addition to leakage forces that cause internal erosion, which has a direct influence on the structural stability of this system. Also, the rising and dropping in the water level has a direct effect on the stability of the dam's face slope. One way to solve these issues is the installation of a core or a horizontal water drainage system. The present study relied on the GEO-Studio computer tool to evaluate cross-sectional models of earthen dams by determining the safety factor under different situations represented by a change in filter type, and the flow state as a result of raising and lowering the water level at the dam reservoir and the full fill condition of the dam reservoir. The research found that the existence of a core substantially contributed to improving the safety coefficient for the case of rising the water level (2m) and rapidly rising by assigning it the greatest safety coefficient values. The absence of a filter had an opposite influence on the safety coefficient by decreasing it. Also, the factor of safety for the downstream slope was affected by less than 5% for different flow conditions, compared with the higher effect generated by the upstream slope. Furthermore, an artificial neural network model with an accuracy ratio of more than 97% was developed for the predicted safety factor.

Channel coding technique is a fundamental building block in any modern communication system to realize reliable, fast, and secure data transmission. At the same time, it is a challenging and crucial task, as the data transmission happens in a channel where noise, fading, and other impairments are present. The Low-Density Parity-Check (LDPC) codes give substantial results close to the Shannon limit when the complexity and processing delay time are unlimited. In this paper, the performance of the LDPC decoding with four algorithms was investigated. The investigated four algorithms were Belief Propagation (BP), Layered Belief Propagation (LBP), Normalized min-sum (NMS), and Offset min-sum (OMS). These algorithms were examined for code rates ranging from 1/3 to 9/10 and message block lengths (64, 512, 1024, and 5120) bits. The simulation results revealed the flexibility of these decoders in supporting these code rates and block lengths, which enables their usage in a wide range of applications and scenarios for fifth-generation (5G) wireless communication. In addition, the effect of the maximum number of decoding iterations on the error correction performance was investigated, and a gain of 5.6 dB can be obtained by using 32 decoding iterations at BER=2*10-3 instead of one decoding iteration. The results showed that the decoders performed better for longer message blocks than for short message blocks, and less power was required for transmitting longer messages. Finally, the comparison results of their performance in terms of bit error rate (BER) under the same conditions showed a gain of 0.8 dB using LBP at BER= 10-5 compared with the NMS decoding algorithm.

There are vertical slopes on the western banks of Tigris near Al-Alam Bridge in Tikrit, Iraq. These slopes are not supported and are located near an important road at Tikrit University. This study aims to find a safety factor (FOS) of the slope to prevent failure, besides its effect on human and financial losses. The study consists of two parts: the first part studied the layers of the slope and found the soil resistance coefficients. The second part analyzed the stability of the natural slope itself under the impact of the water level change of the Tigris River and the external loading. The analysis was done by a program called (PLAXIS 3D), which depends on the finite element method. The finite element method is a numerical approach that searches for approximate solutions and solves problems by dividing the problem into several triangular elements linked to each other by points called (nodes). The results showed that the vertical slope stability at the natural state with no influences indicated was in a semi-stable state with a factor of safety equal to (1.04865). The factor of safety decreased by (0.423%) with rising the river level until it reached (1.04074) at (93 m a.s.l.[1]). As for the applied external loads condition, the factor of safety for imposed (50,150 and 250 kN/m2) decreased by (4.738%), then the soil body failed when the factor of safety was (0.9902). In the critical state, the soil body failure at this stage and the factor of safety became equal to (0.98769) with decreasing by (5.812%).

The purpose of this study is to investigate the shear behavior of hollow ferrocement beams of self-compacting mortar reinforced with various types of metallic (steel wire mesh) and non-metallic (fiberglass mesh) reinforcement. The experimental program consists consisted of casting eight ferrocement beams with dimensions of 150×225×2000 mm, 50 mm of ferrocement thickness, and a polystyrene cork core of 50×125 mm. The studied parameters were the shear reinforcement type and the number of wire mesh layers. The results showed that the ultimate load of the beams reinforced with several layers of the fiberglass mesh (1, 2, and 3) was decreased by (3.27%, 16.52%, and 9.38%), respectively, compared to the beams reinforced with layers of steel wire mesh (1, 2, and 3). The ultimate load of these beams increased by (33.71%, 73.28%, and 122.11%) respectively, compared to beams without shear reinforcement. Also, the ultimate load of the beams reinforced with layers of welded wire mesh was increased by (38.23%, 107.56%, and 145.09%), respectively, compared to beams without shear reinforcement. The ductility and toughness of the beams reinforced with several layers of the fiberglass mesh (1, 2, and 3) were decreased by (1.68%, 2.11%, 2.68%) and (29.39%, 25.91%, 16.06%), respectively, compared to beams reinforced with several layers of steel wire mesh (1, 2, and 3). The crack propagation was reduced, and its number and width decreased using steel wire mesh and fiberglass wire mesh instead of stirrups, especially in beams with two and three layers of wire mesh. The results also showed that the use of glass fiber or welded wire mesh in the reinforcement of hollow beams instead of steel stirrups significantly affected the failure load, deflections, crack patterns, and shear stresses, despite the clear preference for beams reinforced with steel wire mesh.

This research aims to study the effect of land surface slope on the shape and size of the wetting pattern in the soil resulting from a dripping source, especially when there is a local surface runoff resulting from a water application rate higher than the soil infiltration capacity. As a result, it leads to a noticeable displacement of the center of the wetting pattern from the emitter position. The present research included finding this displacement mathematically and verifying its validity with the results of laboratory data. The studied data included 85 overlapping cases of the change in the water application rate and the slope of the soil surface for two levels of initial moisture and two soils of different textures. The results showed that the first devising equation could be used to estimate the wetting pattern center displacement from the emitter, resulting from the slope of the soil surface. The usage of the first devising equation was based on the of half the maximum horizontal surface advance (a), the maximum vertical advance under the emitter (b), and the soil surface slope, especially when the ratio (a/b) was within (0.9-1.1). The second devising equation can estimate the wetting pattern center displacement from the emitter resulting from the soil surface slope, regardless of the (a/b) ratio. That is, there was a considerable convergence between the displacement values of the center of the wetting pattern from the emitter position estimated by the first devising equation and the second devising equation when the value of (a/b) was close to one, which represents 87% of the 85 cases covered in this research.

This research aims to calculate the rate of rainfall for two consecutive years, 2018 and 2019, to study and analyze the drought periods during these years. The research was conducted in Kirkuk province north of Iraq, by dividing the study area into five regions based on five stations of rainfall records. Two types of data used in investigations; remotely sensed daily precipitations from integrated multi-satellite retrievals and monthly precipitations average rate from NASA power application. The methodology involved the calculation of rainfall rats by three methods; Mean, Thiessen’s polygons, and the Isohyetal technique. Data were analyzed, and final maps were produced using Geographic Information Systems. For the year 2018 the average annual rainfall rate produced by Mean, Thiessen’s polygons, and Isohyetal technique were; 1.376, 1.341, and 1.343 respectively. But, for the year 2019 the average annual rainfall rate produced by Mean, Thiessen’s polygons, and Isohyetal technique were; 0.966, 0.932, and 0.882 respectively. The results showed the scarcity of water and the lack of rainfall during the study years, which has a great impact on the region's exposure to drought, represented by the drying up of rivers.

Fire is one of the most severe conditions to which buildings may be exposed. However, reinforced concrete has good resistance, which makes it one of the building materials most widely used worldwide. When reinforced concrete is exposed to high temperatures, its skeletal members undergo changes that may lead to, in many cases, inclusive cracking. Beams, columns, and slabs are the most important structural elements in any concrete construction. Structural members are generally designed to satisfy the requirements of serviceability and safety limit states for various environmental conditions. Typically, structural members are created to meet a specific fire resistance grade. The characteristics of the structure and the type of occupation are just two variables that affect fire resistance. Structural fire rating's primary goals are to enable building inhabitants enough time to leave, enough time for firefighters to put out the fire, and enough time to prevent any potential structural damage. This article overviews how various reinforced concrete building structural elements behave when exposed to high temperatures. It has been found that both concrete and reinforcing bars are adversely affected by fire. Furthermore, it has been discovered that flexibility and stiffness decrease with increasing stress or the period of fire exposure. Also, the flexibility and stiffness rise with increasing structural element cross-section; however, the maximum slab deflection non-linearly decreases during the fire test. The bottom of the concrete slab begins to cool as temperatures decrease, which increases the yield strength of the bottom reinforcing and causes it to contract along with the lower half of the slab. This article also presents a review of a set of experimental and theoretical results on the thermal behavior of reinforced concrete slabs, beams, and other structural parts under different conditions and scenarios as a historical review.

One of the significant problems facing the water resource engineer is calculating the coefficient of roughness for subsequent design calculations of the discharge amount of a channel or river. In this study, experiments were conducted in a semi-circular, straight channel to investigate the factors affecting bed roughness and flow discharge using Artificial Neural Network (ANN). For this purpose, three semi-circular channel models with free overfall were constructed and installed in a 6-meter-long laboratory flume. The length of these models was 2.50 m with three different diameters (D= 150, 187, and 237mm) and three bed slopes (S=0.004, 0.008, and 0.012). Three sand particle sizes (ds) were used for each semi-circular channel to roughen the bed. The results showed that the Manning roughness coefficient obtained using a rough bed surface was higher than the channel with a smooth bed surface. Also, the results revealed that the Manning roughness coefficient and the Froude number were inversely related. (ANN) analysis showed a good agreement between the experimental and predicted results of flow and roughness. The bring depth (yb) had an 85.8% impact percentage on the free overfall discharge for semi-circular channels, while the bottom slope (S) had only 1.1%.

The presence of the openings negatively effects on the strength of the beams where they act as a weak point because of the sudden change in the cross-section of the beam, so it becomes necessary to make strengthening for the beams to resist the effect of the openings and improve the strength of the beams, especially if the beams are subjected to repeated loads because of its effect on the strength at the failure. This paper studies the effect of the openings on the beams subjected to repeated loading and determine the extent of the increase in the strength of the beams when strengthened by the NSM technique. The experimental program included casting and testing fifteen RC beams, six of them considered as a control beams (three with strengthening and three without strengthening), and nine of them having circular transverse openings in different locations and strengthened by the NSM technique. Every type of beams is tested under three different types of loads (monotonic, constant repeated load, and incremental repeated load). All of the beams have the same dimensions and same reinforcement. The results show that all the beams with transverse openings are affected by repeated loads where the ultimate torque decreases and the twist angle increases. The existence of openings has a noted effect on reducing the ultimate torque, whereas the percentage of decrease in the ultimate torsional capacity reached 43.83% at the beam where the opening location is closest to the support (at the quarter of the clear span) and subjected to constant repeated loads, and the ultimate torque is significantly improved when the opening position is moved away from the supports. Also, the existence of strengthening reduced or eliminated the influence of openings on the ultimate torque compared with related non- strengthened beams.