Category Archives: Master Thesis

ABSTRACT

                    Reinforced concrete (RC) beams characterized by circular openings present inherent structural challenges, resulting in a compromise of their load-bearing capacity and overall structural integrity. This thesis endeavors to confront and resolve this issue through the implementation of an innovative approach involving Near Surface Mounting (NSM) steel bars. Circular openings, integral to architectural designs, frequently engender a diminution in the strength of beams. This study investigated the effectiveness of utilizing near-surface mounted (NSM) steel bars to restore the shear strength of deep beams and the presence of openings in slender beams. The experimental work involved testing fourteen simply supported reinforced concrete beams. These beams were divided into two groups, each consisting of beams with different shear span-to-depth ratios (a/h = 1.5 and 3.65). Two specimens served as control samples, while the remaining beams had openings located at various positions. The openings were categorized as large or small, with opening height ratios (h_o/h) of 0.4 and 0.2, respectively. In the second group, six specimens were strengthened using near-surface mounted (NSM) steel bars arranged in three different stirrup configurations: (square, diamond, and parallelogram). All the beams had a cross-section of 100 mm × 200 mm and a total length of 2000 mm. The variables examined in the tests included the sizes and locations of the openings, the diameter of the bars, and the arrangement of the strengthening bars around the openings. The test results revealed that the presence of openings in the beams led to a reduction in the ultimate load. For specimens with large circular openings in the deep beam's shear zone, large circular openings in the slender beam subjected to shear, large circular openings subjected to shear and flexural loads, and small openings in the slender beam subjected to shear and flexural loads, the ultimate load decreased by approximately 45%, 18.7%, 14.6%, and 19.5%, respectively. Additionally, the test results showed that specimens strengthened with diamond stirrup bars exhibited an improvement in the ultimate load of up to 33.1%. Meanwhile, specimens strengthened with square and parallelogram stirrup bars demonstrated improvements of up to 21.5% and 26.5%, respectively. Changing the bar diameter had a slight effect on increasing the ultimate load, specifically for the parallelogram and square schemes, resulting in an increase of approximately 10% and 7%, respectively.

تهدف الدراسة الى بيان أثر القياس والإفصاح المحاسبـي وفق متطلبات المعيار المحاسبـي الدولي (– )IAS8
السياسات المحاسبـية والتغيرات في التقدير ات المحاسبـية والأخطاء- في تعزيز جودة التقارير المالية، ولتحقيق أهداف
الدراسة واختبار فرضياتها تم الاعتماد على استمارة الاستبانة، إذ تم استطلاع اَراء الأكاديميين والمحاسبـين القانونيين
والمحاسبـين العاملين في الشركات في مدينة أربيل حول الموضوع، وتم اختيار ( )210فرداً منهم. وقد اعتمدت
الدراسة على أسلوب التحليل الإحصائي الوصفي وتحليل متغيرات الدراسة واختبار فرضياتها باستخدام برنامج
الحزمة الإحصائية للعلوم الاجتماعية ( .)SPSSوقد توصلت الدراسة الى مجموعة من الاستنتاجات: أهمها إن
القياس والافصاح المحاسبي في القوائم المالية وفقاً لما يتطلبه المعيار المحاسبي الدولي ( )IAS8يخدم مستخدمى هذة
التقارير لإنه يدل على العرض العادل لمحتويات هذه القوائم ويساعد على فهم الأداء المالي، وسيكون لكل ذلك تأثير
كبير في تحسين قرارت المستخدمين، لإن المعلومات المحتواه في القوائم المالية تعد المصدر الاساس لإي قرار يتخذ من
قبل المستخدم، وإن الهدف الاساس لكافة أنواع الافصاح هو اظهار المعلومات المحاسبية الملائمة في القوائم المالية
للمستخدمين وذلك لمساعدتهم في اتخاذ قرارات صحيحة. يوصى الباحث الوحدات الاقتصادية في إقليم كوردستان
بضرورة إعداد وعرض التقارير المالية وفق متطلبات المعيار المحاسبي الدولي ( )IAS 8المتعلق السياسات المحاسبية
والتغيرات في التقديرات المحاسبية والأخطاء كي تكون المعلومات الواردة في التقارير المالية بدرجة عالية من الدقة
والشفافية التي بدورها تساعد مستخدمي التقارير المالية على اتخاذ القرارات الصائبة

Re-vibration, which is the process of repeating the operation of vibration of fresh concrete after a time interval, may be useful to enhance the mechanical properties of concrete (compressive strength, tensile strength, flexural strength, and modulus of elasticity), and also to get the maximum applied load, first crack load, deflection at mid span, stiffness and strain, particularly when successive layers of fresh con[1]rete were placed and the upper layer of fresh concrete was partially hardened. After a period of time, the aggregate particles are rearranged by the re-vibration process, and any trapped water is removed, potentially enhancing the concrete's compressive and tensile strengths. The use of re-vibration can help to remove plastic shrinkage cracks for exposed concrete. The amount of time that re-vibration lasts has a big impact. Using the re-vibration technique in construction of structural members is expected to improve the structural properties of the beams, and cracking. The effect of the waiting time before re-vibration must be investigated and time duration of vibrations on the structural response of flexural reinforced concrete beams to establish and verify the best process to apply this technique. The purpose of this study is to examine the impact of waiting time before re-vibration. and variable time duration for vibration and re-vibration operation of structural response for flexural reinforced concrete beams and using Ordinary Portland Cement-type 1, with w/c ratio of 0.4, and a greater number of re-vibration time lag intervals ranging from half an hour to two hours to evaluate the impact of re-vibration on the mechanical properties of concrete with different time duration of vibrations ranging from 15 to 60 seconds. The experimental schedule includes a total of 28 twenty-eight rectangular rein[1]forced concrete beams of dimension (125 mm x 250 mm) and length of 1500 mm was prepared for this work. Which were classified into seven groups Each group includes four samples. Beams for group (A, B, C, D, E and F) reinforced with longitudinal top reinforcement of (2ø10mm) and bottom reinforcement of (2ø12mm) with transvers reinforcement (Stirrups) ø12mm all over the beams except group F which are without transverse reinforcement and group G is without longitudinal and transverse reinforcement. Additionally, 144 cylinders with dimensions of 300 mm in height and 150 mm in diameter were utilized to evaluate the concrete's compressive and tensile strengths. After 56 days, these samples were analyzed in an attempt to study the impacts of vibration, and the effect of re-vibration delay and vibration duration on the development of concrete strength. The results have shown that the mechanical properties of concrete, ultimate load, first crack load and deflection at mid-point with various time duration and re- vibration techniques was increased for the 1st one hour and re-vibrated for 45 seconds time duration. After that for waiting time 1.5 and 2 hours and re-vibrated for 60 seconds was decreased.