دراسة مقارنة لأنواع مختلفة من الروافد الخرسانیة المسلحة الموصولة الأجزاء

Comparative Study for Different Types of Reinforced Concrete Spliced Girders

The technique of splicing girders is one of the solutions for increasing the spans of precast concrete girders. This method includes splicing two or three precast segments at joints called splice regions. The present study involves an experimental work and numerical application for the behavior of different types of spliced reinforced concrete girders. The experimental work included test of twelve reinforced concrete girders divided according to support condition into two groups; simply supported and continuous. Each group consists of six girders; one of these girders was non-spliced as a control girder, while the other girders were spliced of three precast segments using hooked dowels of 90° and cast-in-place concrete in the splice regions. Each girder has the same dimensions of (150mm width, 230mm height, and 2800mm total length). The length of splice region of a simply supported and continuous spliced girders was designed according to the requirements of development length for the main longitudinal reinforcement; therefore, the length of splice region was equal to (300mm). The simply supported girders were spliced at the first quarter from each side of girder with a distance (500mm) from each support; while the continuous girders were spliced at the inflection points. The experimental parameters were: support condition, using reactive powder concrete (RPC) instead of normal concrete (NC) in the splice regions, volumetric ratio of steel fiber by using 1% and 2%, and strengthening the splice regions by near surface mounted (NSM) CFRP bars. The load was applied for each girder by two points of loading, and the deflection has been measured at the mid-span.

    The results showed that using RPC with 2% steel fibers as an alternative to the NC led to increase of the ultimate load by 15%, and 14.55% than the ultimate load of a girder spliced by using NC for simply supported and continuous girders respectively, and the maximum deflection was increased by 28.13%, and 9.97% respectively. It was also found that strengthening the splice region by NSM CFRP bars for the simply supported and continuous spliced girders led to improve the ultimate load by 11.25% and 3.76%, the deflection was also increased by 15.56% and 8.7% for the simply supported and continuous girders respectively.

    Three dimensional finite element analysis was used to investigate the behavior of spliced reinforced concrete girders. ANSYS program (version 17.2) was used for this purpose. Fully bonding was assumed between concrete and steel reinforcement.

     Concrete was represented by SOLID65, and the reinforcement by LINK180, while the steel plates of loading and supports were represented by SOLID185. The small joints between precast segments and splice regions was utilized contact elements represented by three dimensional node-to-node (CONTACT178). The hook has been represented as the same as for the experimental work. The results of numerical application showed an acceptable degree of variation with the experimental results, where the maximum difference between numerical and experimental results in the ultimate load, and the maximum deflection for the simply supported girders reached up to (+ 8.6%) and (- 15.76%) respectively.

   It was also found that using RPC instead of NC in the splice regions was more

 ffective to increase the ultimate load, and the maximum mid-span deflection and in addition to minimize of the cracks propagation along the girder.