Thesis (M.Sc.)-Cairo University, 2023.

Bibliography: pages 73-74.

Thin-walled steel cold formed sections have been widely used in construction recently.
Cold formed sections are advantageous compared to conventional systems in various aspects
such as the profile lightweight, the material cost, efficiency to resist the applied loads (Live
and wind loads) when using them as roof purlins or side runners. However, due to the large
slenderness ratio of the elements, it is often susceptible to local and/or lateral torsional
buckling. Hence, it is necessary to understand the lateral torsional buckling behavior of cold
formed beams when subjected to uplift force while the sheeting is attached to the tension
flange. Previous research includes numerical studies on the effect of sheeting (sandwich
panel or single layer) on the lateral torsional buckling of cold formed sections using finite
element programs (Numerical modeling). However, a few researchers focused on
experimental investigation to study the above-mentioned phenomena.
The main purpose of this study is to investigate the effect of the sandwich panel
connected to the tension flange of steel cold formed beam on its lateral torsional buckling
behavior when the compression flange is unsupported along the span. Experimental
investigation is conducted to determine the ultimate capacity of steel beams affected by
lateral torsional buckling. A comparison between the test results with different design codes
was developed. Regarding the experimental investigation, twelve cold formed lipped Z- steel
sections of different cross sections and different unsupported lengths were tested to measure
the torsional restraint given to thin-walled purlins by the sandwich panels under uplift load.
The test was performed at the lab of Housing and Building National Research Center, Dokki.
Beams were tested when the tension flange is connected to sandwich panel/single layer
corrugated sheet. Beam with cantilever system is developed to make the compression flange
free and not connected to sheeting. The ultimate load capacity of the beams, vertical
deflection and horizontal displacement are observed and relationship between the ultimate
load capacity and the vertical and horizontal displacement were plotted. Additional
precautions were provided to the beams during the experimental investigation to avoid any
unwanted defect that may affect the results of the test.
The experimental test results were compared to the design provisions of North American
Specifications for the design of Cold-formed Steel Structural Members (AISI) and the
provisions of the Egyptian code of Practice for Steel Structure and Bridges. The comparison
showed a good agreement between the test results and the ultimate load calculated based on
the designed codes. It was observed that the ultimate load computed by the AISC is about
111% for beams with 2mm thickness and 84% for beams with 2.5mm thickness compared to
the experimental tests while the ultimate load computed by the Egyptian Code for beams with
2.00mm thickness and Lu 2, 3.5 and 5m is 121%, 56% and 40%. However, the ratio is 132%,
84% and 64% for beams with thickness 2.50mm.
Finally, a summary of the work carried out in this thesis along with general conclusions
obtained from the study and recommendations for future studies in the same field are
presented

يتم استخدام قطاعات الصلب المشكلة علي البارد بشكل واسع في مجالات الانشاءات سواء في مدادات السقف أو المدادات الافقية الجانبية للمباني الصلب. يفضل استخدام القطاعات المشكلة علي البارد نظرا لخفة الوزن وسهولة التشغيل. إنه من الامور ذات الاهمية فهم سلوك القطاعات المشكلة علي البارد المعرضة لعزوم اللي عند تعرضها لقوى رفع رأسية. الهدف الرئيسي من هذه الدراسة هو التحقق من تأثير الواح الصلب المتصلة بالشفة المشدودة علي الشفة الحرة المضغوة للكمرة. تم إجراء تجارب عملية علي اثنى عشر قطاع من الصلب المشكل علي البارد مع اختلاف تخانات المقاطع وكذلك اطوالها الحرة. تم ملاحظة اقصى قدرة تحميل للمقاطع وكذلك الازاحات الافقية والترخيم الرأسي وتم رسم علاقات بيانية بينها. تمت مقارنة النتائج المعملية بأحكام التصميم طبقا للكود المصري الامريكي ولوحظ أن الحمل المحسوب بواسطة الكود الامريكي يمثل حوالي 111% للكمرات بسمك 2مم و 84% للكمرات بسمك 2.5مم مقارنة بالاختبارات المعملية بينما الحمل المحسوب بواسطة الكود المصري للقطاعات ذات السماكة 2.00 مم و طول حر مقداره 2 ، 3.5 و 5 متر يمثل حوالي 121% ، 56% و 40%. بينما كانت 132% ، 84% و 64% للقطاعات ذات السماكة 2.50 مم.

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