21561

21561

مقايسه ي رفتار محوري، خمشي و شكل پذيري ستون هاي بتني تقويت شده با پوشش كامپوزيتي و ورق فولادي

كارشناسي ارشد

سازه

98-99

1398/10/10

دكتر مرتضي رئيسي دهكردي

دكتر مهدي اقبالي

عمران

چكيده به كارگيري كامپوزيت هاي FRP به طور چشم گيري در سال هاي اخير افزايش يافته است. افزايش مقاومت فشاري و ميزان جذب انرژي قبل از گسيختگي نمونه ي ستون ها در بسياري از آزمايشگاه ها گزارش شده است. در اين تحقيق تلاش بر اين بود كه بهترين روش تقويت سازه اي ستون هاي بتني بررسي شود. ستون هاي بتني در صورتي كه با مواد كامپوزيتي تقويت نشوند مشكل عمده اي تحت عنوان حجيم بودن را دارند. اين مشكل به خصوص در زماني اهميت پيدا مي كند كه بار وارده به ستون سنگين بوده و به لحاظ معماري نيز پروژه داراي محدوديت هايي باشد. حال در اين تحقيق، ستون هاي بتني به روش خارجي تقويت مي شوند. دو ماده ي FRP و فولاد به عنوان ژاكت به پيرامون ستون متصل شدند و در فضاي نرم افزار آباكوس، اين مدل ها شبيه سازي شدند تا رفتار آنها بررسي شود. پس از اتمام تحليل بر روي نمونه هاي بتني تقويت شده با FRP و نيز ژاكت هاي فولادي مشخص گرديد كه كامپوزيت هاي FRP با يك شيب نسبتا ثابت با افزايش كرنش فشاري ستون، تنش محوري قابل تحمل توسط ستون را ارتقا مي دهد. در حاليكه ژاكت هاي فولادي نقطه ي تسليم ستون را بالا مي برد. همچنين به خاطر تسليم شدن زود هنگام فولاد نسبت به نقطه گسيختگي كامپوزيت، به ضخامت بيشتري از فولاد نسبت به كامپوزيت نياز است.

1398/10/21

Comparison of Flexural, Axial Behavior and Ductility of Concrete Columns Enhanced with Composite Material and Steel Jackets

1/5/2020 12:00:00 AM

This article investigates the impression of steel and FRP jackets in concrete columns which is named steel-tube confined concrete and FRP confined concrete columns. this article did a comparison between them and considered compressive strength, ductility and bending strength of columns. All of the tests did in Abaqus software that works based on finite element method. A number of columns modeled in software, and all of the properties of columns including, the diameter of the column, the strength of the concrete core, the thichness of the Jacket and its yield strength were changed in the samples to learn the impression of them. The bending strength of concrete mainly increases by the properties of steel jacket. Concrete core had a negligible role in bending strength, because concrete is disable to bear tensile force and also, circle section is not acceptable in the case of bending moment, because the most area of the section exists in the middle of the hight that receives a small amount of linear stress. The amount of confining pressure provided by jacket, has a direct relation with thickness and strength of jacket, but it desreases by the increase of diameter and concrete strength. As the confining pressure of jacket increases, column has a more ductile behavior and can reach greater compressive strength. Steel jacket has both confining and compressive performance but FRP jacket just has confining performance because of the direction of the fibers. The strain-stress curve of models has two branches. The slope of the first branch is equal to unconfined concrete. The first branch of the curve of FRP jackets continues until the strength of unconfined concrete. Besause steel jackets have compressive behavior, their fjrst branch exceeds the strength of unconfined concrete until the jacket yields. The second slope of FRP confined columns depends on the amount of the confining pressure Steel jacket has two shapes of concrete filled steel tube (CFT) and steel tube confined concrete (STCC). The results of abaqus showed that their behavior is inentical, there is two small differences: STCC columns have better compressive strength but the initial slope of CFT columns are more than STCC columns. CFT jackets receive more compressive force while STCC jacket provides more confining pressure.

واژه‌هاي كليدي: مقاطع بتني، ژاكت‌هاي فولادي، سيستم FRP

Keywords: FRP confined concrete, steel tube confined concrete, concrete filled steel tube columns.