دانلود رایگان مقاله انگلیسی بهبود مقاومت خمشی تیرآهن جوش خورده بتن پیش ساخته با استفاده از بتن پودر واکنشی - الزویر 2018

ABSTRACT

This paper presents an experimental study of improvement of flexural strength of precast concrete spliced girders using reactive powder concrete (RPC) in splice region. Experimental work has been carried out on testing of eight full scale rectangular reinforced concrete girders divided into two groups , four of them were simply supported and the other four were continuous supported. Two of these girders (one of each group) were cast as one unit without splice region as a monolithic while the other were cast of three segments for each of them and then connected in the splice region by using hooked dowels and cast-inplace splice region. All the spliced and non-spliced girders has total length of (2800 mm) and have rectangular section of (150 mm width, 230 mm height).The parameters studied in this experimental work were the concrete types of the splice region (normal concrete, RPC with 1% of steel fiber ratio, and 2% of steel fiber ratio), supports type and comparing with normal concrete non-spliced girders. Experimental tests had been carried out to investigate the behavior of each girder like first cracking load, crack width, failure load, maximum deflection and failure modes. The test results showed that the value of ultimate load capacity of the girder with normal concrete splice region is less than the value of nonspliced girder for all cases that have been tested. Furthermore, the obtained results indicated a significant increase in stiffness and ultimate load of the spliced girders due to the effect of using RPC in the spliced regions resulting in a clear improvement in the overall performance of these girders. Also, the increase of steel fiber ratio from 1% to 2% in case of RPC splice was efficient in minimizing crack width and meanwhile reducing the possibility of corrosion of steel reinforcement.

4 Conclusions

Many conclusions can be extracted depending on the experimental results that have been obtained in the present study.

1. The results of testing showed that the ultimate load capacity of the spliced girders with normal concrete splice region is less than that of non-spliced girders as a result of the fact that the splice region is weak in carrying flexural and shear stresses. The decrease in the ultimate load capacity of the spliced girders may reaches up to 6.7% as compared to the non-spliced girders.

2. The obtained results indicated that improving the characteristics of the spliced regions using reactive powder concrete (RPC) instead of normal concrete (NC) improved significantly the overall performance of the spliced girders. This improvement led to increase the ultimate load of spliced girders to reach the level for that of non-spliced girders and sometimes exceeded it. The increase due to RPC splice reached up to 15.2% as compared with NC splice region.

3. It was observed that increase of the volumetric ratio of steel fibers from 1% to 2% for the reactive powder concrete of splice region was efficient to minimize the cracks width and meanwhile it will reduce the possibility of corrosion of steel reinforcement of spliced girders.

4. It is noticed that, the increasing of steel fibers volumetric ratio led to enhance the overall behavior of spliced girders, because these fibers restrained cracks and increased the stiffness and consequently reduced the deflection of the spliced girders.