پديد آورندگان :
مقصودي ، علي اكبر نويسنده Maghsoudi, A.A. , مقصودي، محمد نويسنده , , تركمان زاده، ميثم نويسنده ,
كليدواژه :
اُفت در تكيه گاه , بتن خودمتراكم و معمولي , دال مجوف پيش تنيده , شكل ظاهر , پوشش بتني
چكيده فارسي :
با گسترش صنعت ساختمان‌سازي، روش هاي نوين به‌منظور دسترسي به طرحي اقتصادي و ايمن مورد توجه خاص طراحان است. استفاده از بتن خودمتراكم و صنعت پيش تنيدگي به همراه سبك سازي سازه‌ها در سال هاي اخير نسبتاً رو به رشد بوده است. اما بي‌توجهي به ساخت سازه يي ايمن در صنعت، منجر به از دست‌دادن جان انسان ها مي شود. لذا براي بررسي موارد مناسب‌تر، سه دال مجوف بتن پيش تنيده‌ي ساخته‌شده با بتن خودمتراكم با ابعاد 4 متر طول، 2/1 متر عرض، و 2/0 متر ارتفاع و دو عدد دال مجوف بتن پيش‌تنيده‌‌ي ساخته‌شده با بتن معمولي با ابعاد 6 متر طول، 2/1 متر عرض، و 2/0 متر ارتفاع، مشابه روش اجرايي در صنعت ساخته شد و سپس نمونه ها تا مرحله‌ي تخريب در آزمايشگاه بارگذاري شدند. مقايسه‌‌ي هر چه بيشتر دال هاي صنعتي با عملكرد واقعي آنها، از جمله پوشش كم بتني بر فولاد پيش تنيده و استفاده از تكيه گاه هاي كارگاهي با اُفت زياد نيروي پيش‌تنيدگي و شكل ظاهر دو نوع بتن مصرفي از جمله اهداف اين نوشتار است.
چكيده لاتين :
The development of self compacting concrete, SCC, began in Japan (Tokyo University) in the mid 1980s, with the aim of reducing durability problems in complicated and heavily reinforced concrete structures, due to lack of skilled workers and poor communication between designers and construction engineers. Even though previously (and still today) conventional (vibrating) concrete in some applications was cast without any compaction, this new concrete was deliberately designed to be able to fill every corner of the form and encapsulate all reinforcements with maintained stability, only under the influence of gravitational forces.
Since that time, Japanese contractors have used SCC in different applications. In contrast with Japan, research in Europe, American and Iran started later. The advantages of SCC offer many benefits to construction practices. Elimination of compaction work results in reduced costs in placement, equipment needed for construction, shortening of construction time and improved quality control.
In recent years, there have been a number of significant developments in SCC, from either the viewpoint of concrete technology or reinforced concrete structural elements. However, very limited reports are available on prestressed concrete elements, while using high strength self compacting concrete, HSSCC. Also, more research is urgently needed in order to understand the use of HSSCC in precast prestressed lightweight slabs (hollow core slabs) to formulate design rules.
The deficiencies of industrial precast prestressed constructional members, such as the lack or unbundling of concrete covers on prestressing strands, weakness in holding prestressed jacking forces in precast prestressed end supports in industry, the loss of high amounts of prestressed jacking forces of strands before transferring the forces into the members, and etc., can cause irreparable damage. For better investigation of such cases, therefore, for the first time in Iran, three precast prestressed hollow core HSSCC slabs, with dimensions of 2.0m in length, 1.2m in width and 0.2m in height, are industrially cast and, then, experimentally load tested up to failure. Their ultimate state and experimental deflection and curvature ductility are measured, and the results are compared theoretically. The results show that producing such industrially deficient products is unsafe and uneconomic.
