Abstract This Thesis overviews the methods for calculating the stress intensity factor and employs the stress and displacement methods in the current study. The model used simulates a cracked rectangular plate which is subjected to tensile stress. The Finite element method is used to calculate inplane displacement due to applied loads. As a post processing the stress and stress intensity factor over the plate was calculated. The results show that the singularity exists at the crack tip and the components of stress and approach infinity as the crack tip approach. The comparison of the current study to theoretical and other numerical results shows a good agreement and reliability of the program. The thesis consists of five chapters, the first chapter, presents general over view and historical al review. The second chapter demonstrates the theoretical basis in fracture mechanics. The third chapter involves the numerical solution using F.E.M. The fourth chapter demonstrates a case study and the results and discussion of the obtained results. The fifth chapter concludes the work and gives recommendations.
محمد كامل الشيخ (2009)

شهدت مدينة طرابلس الكبرى قفزة نوعية في العديد من التعاقدات لتنفيذ مشاريع تنموية في البنى التحتية والاسكان وما يتطلب من مشاريع مرافقة إلا أنها في الآونة الاخيرة ومع بداية هذا العقد عانت أغلب تلك المشاريع من العديد من المشاكل، مما انعكس سلباً على كافة مراحل التنفيذ، لذلك تم القيام بهذه الدراسة هذه الدراسة للوقوف على أسباب التأخير في تلك المشاريع، وبالتالي العمل على إثراء المكتبة الليبية بالبحوث الميدانية التي تتناول موضوع أسباب التأخير في إكمال المشاريع الإنشائية، ويمكن أن تلفت الدراسة الحالية اهتمام الباحثين إلى معرفة الاسباب والتي أدت إلى التأخير في المشاريع، ودراسة كل سبب من ناحية ظروف حدوثه، وأهم النتائج المؤثرة سلبا على المشروعات، ونسق مساهمتها في التأخير، ومن خلال هذه الدراسة تم التعرف على الأسباب التي أدت للمساهمة في عرقلة تنفيذ المشاريع ببلدية طرابلس الكبرى، لأجل التركيز عليها مستقبلاً بهدف تفادي حدوثها. arabic 177 English 0
رجب عبدالله عبدالقادر حكومة, عبدالوهاب احمد دريبيكة(1-2019)

Abstract Finite element method is used to analyze the flexural vibrations of beams using Galerkin approach for both Bernoulli and Timoshenko theories.The methodology is started by integral formulation of the partial differential equations for the physical problem, and then the element stiffness, mass matrices and load vector have been obtained. Free vibrations analysis is used for the predictions of natural frequencies and mode shapes for, first flexural vibrations by classical theory, second flexural vibrations by including the effect of shear deformation and rotary inertia in the analysis. Finally, the axial and torsional vibrations, in addition to flexural vibrations, in both transverse and lateral directions together have been taken into consideration, thus the finite element equations and the element stiffness, mass, and load vector matrices have been developed for axial, torsional, and flexural vibration together.The natural frequencies are tabulated for all classical types of classical boundary conditions. The mode shapes corresponding to the natural frequencies were presented graphically. The exact solutions and results obtained by other standard methods are used for comparison with the current numerical results. The forced vibrations were introduced for the analysis of dynamic behavior of beams under several types of loading. The finite element code with Taylor series method and mode superposition for the Bernoulli and Timoshenko beams has been carried out. Numerical results are presented in the form of comparisons between the Bernoulli and Timoshenko and demonstrate how the effect of shear deformation reduced the displacement response with increasing the excitation frequency, excitation amplitude, and length of the beam. Comparisons are made with the exact and existing classical methods and checked with those obtained IVusing standard methods (ANSYS package) and are found in good agreement. It should be noted that all models of beams have always convergence to the correct solution.
أمنة احمد القلفاط (2009)