Digital Repository for faculty of Engineering

Different types of concrete mixtures are used as building materials. The manufacturing process of two-stage concrete (TSC) differs from that of conventional concrete. This study investigated conventional mechanical properties derive empirical relations for estimation of the mechanical parameters of TSC and conventional concrete mixtures. TSC was used to prepare 216 specimens and conventional concrete was used to prepare 108 specimens that then were aged for 28 days. Uniaxial compression, Brazilian tensile strength, and point load tests were carried out as destructive testing. Schmidt hammer and ultrasonic pulse velocity tests were carried out as nondestructive testing. The data from testing were categorized as regression or test data. Empirical relations were derived between the parameters for the two types of concrete, and these relations were validated. It was concluded that indirect, nondestructive testing of engineering materials, including concrete, considerably increases the speed and decreases the estimation cost of determining the mechanical parameters. This method can be recommended for estimation of these mechanical parameters. arabic 13 English 97
Hakim S. Abdelgader(7-2020)

Reclaimed asphalt pavement is used as an aggregate in the cold recycling of asphalt paving mixtures. The more common method involves a process in which the asphalt pavement is recycled in-place (cold in-place recycling), CIPR. Where the reclaimed asphalt pavement is combined without heat with foamed bitumen and cement and mixed at the pavement site, at full- depth to produce a new cold mix end product. There are no universally accepted structural coefficient values for cold in-place recycled mixes (CIPR). Even though, the structural capacity of CIPR mixes considered equal to that of conventional cold mix paving material, it is not the structural is equivalent to hot mix asphalt (HMA), but is superior to gravel or crushed stone base course. The structural layer coefficient is used to calculate the structure number (SN) needed for the design of layer thicknesses. In this study, the maximum vertical compressive strain on the top of the subgrade layer was used to calculate the equivalency factor and the structural coefficient. By using the KENLAYER; the elastic layered program, the subgrade compressive strains were calculated for the typical pavement system commonly used for the major highways in Libya to get the thickness of FDR layer that would give the same compressive strain as six inches (150 mm) HMA. The thickness equivalency was taken as the ratio of the thickness of the FDR layer to that of the HMA layer of six-inch (150 mm). This was done for different FDR modulus values and different mean annual air temperatures (MAATs) which imply different resilient modulus values of HMA. As a result a relationship was developed between FDR modulus and FDR structural coefficient for various MAATs which are considered as the upper bound structural coefficient values. The conservative equation: MR= 30,000(ai/0.14)3 is considered as the lower bound values of structural coefficient. A reasonable single structural coefficient value could be specified within the specified range based on the levels of experience and quality control. A case study is used to verify the developed procedure for the design of pavement structural systems with FDR layers. arabic 7 English 51
Haifa Ali Ragab Abuhaliga(9-2014)

الملخص: تعاقب على المدينة القديمة عدة حضارات وتركت بصمة تمثلت في المباني القديمة، والتي يتطلب المحافظة عليها وصيانتها وترميمها لتبقى كثروة أثرية، ولكن من الملاحظ تدهور هذه المباني نتيجة العوامل الجوية وتدخل الإنسان مع عدم الصيانة لبعضها وصيانة البعض الأخر بطرق خاطئة كاستخدام مواد الاسمنت أو الطوب بدل من الأحجار والجير والطين المستخدم قديما ، بالإضافة إلي استيراد مواد الترميم من الخارج مما دفع بالباحثين لمحاولة إيجاد مواد محلية بديلة تكون مناسبة للترميم، ومما شجع علي ذلك توفر مادتي الجير والطين بكميات كبيرة داخل ليبيا. لذلك انطلقت هذه الدراسة بحرق عينتين من الطين تمثلت في طين يفرن وسبها لتحويلها إلى مواد بوزولانية تتفاعل مع الجير من خلال تحضير عينات من المونة المحتوية على الجير والرمل مع نسب من البوزولان تراوحت من 0% إلى 50% من وزن الرمل الطبيعي لتحديد مقاومة الضغط، وأظهرت النتائج المتحصل عليها قيم مشجعة وفتحت بابا للدراسات المستقبلية بهذا المجال، وأعطت أملاً للحصول على مواد الترميم من الخامات المحلية والاستغناء عن الاستيراد arabic 100 English 0
هيفاء علي رجب ابوحليقة(11-2020)

تتضمن هذه الورقة دراسة عن الجسور وتوظيف برنامج نظم المعلومات الجغرافية GIS لأرشفة معلومات عن هذه الجسور، فمن خلال البحث عن معلومات عن الجسور لدي مؤسسات الدولة المعنية بجسور داخل مدينة طرابلس تبين عدم وجود أي بيانات، مما تطلب حصر معظم الجسور داخل مدينة طرابلس وجمع المعلومات العامة والمتمثلة في ( الاسم، الاحداثيات، الطول، العرض، ومنطقة ربط الجسر) لعدد 51 جسر، وتم عمل دراسة تفصيلية عن ثلاث جسور واجراء فحص بصري ظاهري وجمع البيانات عن حالتها ووظائف عناصرها اذا كانت تشتغل بالشكل المطلوب وما بها من عيوب ام بصحة جيدة وبعد جمع بيانات الفحص البصري وتقييم حالة الجسور تم وضع هذه البيانات في بطاقات وربط كل البيانات التي تم جمعها في برنامج نظم المعلومات الجغرافية لأرشفتها الكترونيا ليسهل الوصول اليها في أي وقت من قبل المهتمين للحصول علي معلومات عن الجسور داخل مدينة طرابلس بطريقة سهلة وميسورة وفي اسرع وقت وتكون خطوة للاستغناء عن الارشفة الورقية. arabic 135 English 3
هيفاء علي رجب ابوحليقة(3-2020)

Abstract— Horizontal-Axis Wind Turbine (HAWT) small scaled is widely employed for generating electricity for domestic uses due to higher efficiencies among other turbines. Three-Blade HAWTs power performance can be further improved by optimizing lift (CL), drag (CD) coefficients and thus power (CP) coefficient. In this study, Taguchi design of experiments (DOE) of L9 orthogonal array (OA) with three parameters and one interaction, namely airfoil, angle of attack, interaction (between the airfoil and the attack angle), and Reynolds number with three value levels are used to determine the single quality (CL, CD, CP) optimization. For multi-qualities optimization, the Grey-based Taguchi is employed which combines the Taguchi DOE orthogonal array with grey relational analysis to determine the grey relational grade, which can convert the multi-response grey relational grade into single grey relational grade, thus the optimal design parameters can be achieved. The Q-Blade software is used to determine lift and drag coefficients and empirical equation used for power coefficient. The obtained results show that the most influence design parameter on airfoil coefficients is Reynolds number with 72.6% contribution followed by attack angle with 16.8%, interaction with 9.1% and airfoil with 1.5%. The F-value indicates that Reynolds number and angle of attack give at least 97.5% and 90% confidence respectively, for this specific set of experiments. arabic 14 English 86
Abdulhamed M. Hwas, Ali M. Hatab(12-2020)

Almost all Libyan industries (both private and public) have struggled with many difficulties during the past three decades due to many problems. These problems have created a strongly negative impact on the productivity and utilization of many companies within Libya. This paper studies the current awareness and implementation levels of Just-In-Time (JIT) within the Libyan Textile private industry. A survey has been applied in this study using an intensive detailed questionnaire. Based on the analysis of the survey responses, the results show that the management body within the surveyed companies has a modest strategy towards most of the areas that are considered as being very crucial in any successful implementation of JIT. The results also show a variation within the implementation levels of the JIT elements as these varies between Low and Acceptable levels. The paper has also identified limitations within the investigated areas within this industry, and has pointed to areas where senior managers within the Libyan textile industry should take immediate actions in order to achieve effective implementation of JIT within their companies. arabic 17 English 88
ٌRajab HOKOMA(7-2010)

Supply Chain Management (SCM) is the integration between manufacturer, transporter and customer in order to form one seamless chain that allows smooth flow of raw materials, information and products throughout the entire network that help in minimizing all related efforts and costs. The main objective of this paper is to develop a model that can accept a specified number of spare-parts within the supply chain, simulating its inventory operations throughout all stages in order to minimize the inventory holding costs, base-stock, safety-stock, and to find the optimum quantity of inventory levels, thereby suggesting a way forward to adapt some factors of Just-In-Time to minimizing the inventory costs throughout the entire supply chain. The model has been developed using Micro- Soft Excel & Visual Basic in order to study inventory allocations in any network of the supply chain. The application and reproducibility of this model were tested by comparing the actual system that was implemented in the case study with the results of the developed model. The findings showed that the total inventory costs of the developed model are about 50% less than the actual costs of the inventory items within the case study. arabic 14 English 67
Rajab HOKOMA, Faraj Farhat El Dabee(9-2012)

This paper is designed to present an experimental study being recently conducted for investigating the effect of some fuel additives on the performance of spark ignition within a benzene engine. Three types of additives were added separately (Gasoline Additive, Gasoline Booster, and Octane Booster) to pure gasoline with a volumetric ratio 1:6, 1:7, and 1:8 respectively. Four separate laboratory experiments being conducted using an internal combustion engine at rotational speed ranges from 600 to 3000 rpm, where the three mixtures and the pure gasoline itself were used. The findings showed that there was a positive effect on the engine performance as the brake power increases by 8%, 13% and 23% at the use of Gasoline Additive, Gasoline Booster, and Octane Booster respectively as compared with using only the pure gasoline. The brake thermal efficiency (ɳth) was also affected positively showing its maximum value of about 8% for Octane Booster, and with a minimum value for using Gasoline Additive at about 4.7%. In addition, this study showed that the value changes in the brake specific fuel consumption for Gasoline Additive, Gasoline Booster, and Octane Booster was at the levels of 1%, 2%, and 5% respectively compared with using only the pure gasoline. Furthermore, the results also showed that the use of Octane Booster gave the highest level of air fuel ratio arabic 18 English 97
ٌRajab HOKOMA, Nabil M. Muhaisen(1-2017)