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Register a new userتأثير مركزات الإجهاد في أداء المقاطع الهندسية أو فشلها تحت تأثير الأحمال الساكنة و المتغيرة
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بسبب التكاليف الباهظة في تصنيع القوالب يجب علينا اختيار التصميم الأمثل لها من خـلال معرفـة أسباب حدوث العطب ( الفشل ) فيها . و يمكن اعتبار تركز الإجهادات في القوالب و التي تنشـأ عنـد الفتحات و الثقوب و التغيرات المفاجئة في المقطع ، و التي تعد من العوامل الأساسية في حدوث الفشل لأجزاء القالب . و نظراً لأن تلك القوالب لا تكاد تخلو من أحد المسببات السابقة الذكر أو جميعهـا و بأشكال و أوضاع مختلفة بالنسبة لاتجاه التحميل. و كذلك بسبب استخدام تلك القوالـب فـي الإنتـاج الكمي الذي يؤدي لتعرضها إلى إجهادات دورية متعاقبة و مختلفة بالمقدار أو بالاتجاه التي تزيد مـن فشل القالب بسبب التعب . خلاصة البحث : أوضحت نتائج البحث أن قيمة معامل تركز الإجهاد عند الشقوق تتأثر بزاوية جذر الشق و عمقـه و نصف قطره و لكن تأثير العمق يكون ملحوظاً بشكل أكبر لأن معامل تركز الإجهاد يزداد مـن 64.1 إلى 02.5 عند زيادة العمق من mm 5 إلى mm 15 .
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References used
Robert L. Noron , 1998 , “ Machine design “ , An Integeated Approch , 2nd Edition by prentice – Hall. Inc , Simon and Schuster /A Viscom Company , Upper Saddle Rive
E. J. Hearn , 1985 , “ Machanics of Materials “ , 2nd Edition , pergamon pre Ltd, Headington Hill , Oxford Ox3 Obw , England , 1985
New port and G. Glinka , 1990 , “ Effect of Notch-Strain Calculation Method on Fatigue crack-initiation Life prediction” , Expermental Mechanics , June , p.20
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RC moment-resisting frames (RCMRFs) have commonly been used for low-to-moderate rise buildings in
seismic prone regions. RCMRFs can perform well when they are subjected to strong earthquake ground
motions if they are properly designed and detailed
to dissipate the seismic input energy through
deformations in inelastic range. The connections between beams and columns thus become critical
components to the performance of these structures.
In conventional RCMRF connections, the width of the beam does not exceed the width of the column.
Adopting a flat beam system for the design scheme provides many advantages, such as the reducing the
amount of formwork required, the simplicity for repetition, and the decrease of the required story height.
RCMRFs with flat beams have been used extensively, despite the lack of sufficient information on how
this system behaves under earthquake loading which leads the codes to restrict the use of flat beamcolumn
connections in earthquake prone regions.
The retaining walls are one of most types of engineering constructions and it have
built from natural stones before discovering concrete, Where natural stones have
considered one of the early human materials used in building engineering constructio
ns for
thousands of years, and many facilities in ancient civilization still existing effects so far,
And after the discovery of the concrete and reinforced concrete, the retaining walls which
was built from natural stones diminished relatively
Despite the years this retaining walls has not lost its luster and brilliance, and there
is increased interest in recent years in using new building material which consists of
manufactured stones where used together with traditional construction materials in several
areas both in geotechnical engineering or building … Etc .
This retaining walls present simple technical solutions and it is desirable for aesthetic
reasons and simple implementation and resistance to external conditions,
In addition to being economical solutions limited cost compared to traditional
reinforced concrete retaining walls.
This research deals with the study of the behavior of Segmental Stone Retaining
Walls (SRW) under the static and dynamic loads and parametric study of the most
important factors which influence stability of these retaining walls.
The study has been conducted in region of Sweeda on the nursery
of Era during the two seasons of 2008 and 2009 aiming at the
morphological and physiological assessment of the seedlings of
Amygdalus orientalis under different degrees of water stres
s in
different altitudes on the Arab mountain, specifying the tolerance of
those seedlings to that stress and defining the most tolerant seed
sources to water stress in order to use them as grafting stocks.
The experiment was carried out during spring season 2016 to study the effect
of foliar spraying treatment with Tecamin Flower 2.5 ml/L in comparison with
distilled water, on growth of three hybrids of tomatoes at two different levels of
irrigation
(100 and 50 % of field capacity). Three sprays were conducted started
from flowering with two weeks’ interval. The results showed that ‘Finenss’ hybrid
had significant differences in plant height, branches per plant and leaves number per
plant. ‘Hadeer’ hybrid had superiority in dry matter ratio and content of chlorophyll
in leaves. Reducing the level of irrigation resulted in a significant decrease in
plant height, total branches number, versus an increase in the leaves number per
plant, total leaves area and the percentage of dry matter. The results showed that
the treatment with Tecamin flower led to a significant increase in all indicators
studied. The interaction treatments shoed that Hadeer hybrid irrigated in level 50
% and spraying of nutrient solution (Tecamin flower) had a significant increase in
dry matter ratio and chlorophyll content in leaves. While the hybrid Finenss which
irrigated in level 100 % with nutrient solution (Tecamin flower) had a significant
increase in leaves number per plant and total leaves area.
The study was conducted in order to know the ability of
Korschinskii Almonds and Orientalis Almonds to resistance of the
drought stress using several levels of water irrigation (100, 75, 50
and 25%) from the field capacity, with several indicators
(number
of leaves, the thickness of the leaves, root growth). The results
obtained showed not affected by the stock in the Korschinskii
Almonds drought stress (255, 242, 220, 198 leaves), while the
number of leaves that accompany the burning edges under the
influence of drought stress in Orientalis Almonds (250, 130, 60, 12 leaves) at levels of irrigation water (100, 75, 50, 25%) of field
capacity respectively.
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