Abstract
This research is carried out to study the effect of the external post-tensioning technique on the flexural capacity of simply supported composite castellated beam experimentally. In this research, seven composite castellated beams having the same dimensions and material properties were cast and tested up to failure by applied two concentrated loads at 700 mm from each end. Two external strands of 12.7 mm diameter were fixed at each side of the web of strengthening beams and located at depth 180 mm from top fiber of the section (dps) at each end of the beam. The strands have been tensioned by using a hydraulic jack with a constant stress of 100 MPa. This research aims to study the effect of the strengthening by different shapes of strand profiles of external post-tensioning techniques on the flexural capacity of the composite castellated beam. These beams were divided into three groups. Each group contained two composite castellated beams while 7th composite castellated beam kept without strengthening by external post-tensioning technique As control beam. The first group included two beams with straight strand profile of external Post-tensioning. The second group included two beams with a triangular strand profile of external post-tensioning. The third group included two beams with a trapezoidal strand profile of external post-tensioning. All composite castellated beams were simply supported, and all of them were fully shear connections between the concrete slab and steel girder. All beams included the 16 castellated openings and were stiffened by six stiffener plates welded on the web of castellated beams. Three stiffener plates are welded on each side of the web. Two of these stiffener plates welded at the middle of the beam, and four of them welded at locations under the loads. The experimental results of this research were increasing 5.43% in load capacity of an average of the straight profile of composite castellated beams, increasing 18.92% in load capacity of an average of triangular profile composite castellated beams, and increasing 20.71% in load capacity of the trapezoidal profile of composite castellated beams. All the above results were compared with control beams.
Highlights
It should be recognized that rehabilitation techniques include three subgroup techniques[1]; that are: (a) repairing technique: this type of rehabilitation become the right choice if the non-structural or some structural members exposed to damage to obtain the pass their performance before the damage, there are many reasons caused the damage such as earthquake, blast, fire, corrosion, accidents by vehicles [2]. (b) retrofitting technique: if the existing sections need to change in designed performance, this process is done [3]. (c) strengthening approach: if the structures need to increase the reinforced due to different reasons such as financial or sociological problems [2]
These results showed that the ultimate load capacity was 279.80 kN, which means the load capacity increased 5.43% by external post-tensioning
These results showed that the ultimate load capacity was 327.27 kN, which means the load capacity increased 23.339% by external post-tensioning
Summary
It should be recognized that rehabilitation techniques include three subgroup techniques[1]; that are: (a) repairing technique: this type of rehabilitation become the right choice if the non-structural or some structural members exposed to damage to obtain the pass their performance before the damage, there are many reasons caused the damage such as earthquake, blast, fire, corrosion, accidents by vehicles [2]. (b) retrofitting technique: if the existing sections need to change in designed performance, this process is done [3]. (c) strengthening approach: if the structures need to increase the reinforced due to different reasons such as financial or sociological problems [2]. In other word including the feasibility of project, because of this decision is final decision, the knowledge of reasons of rehabilitation become very necessary. These reasons as briefly [4]: There are some errors in the original design of the structure. The external post-Tensioning technique is placed the prestressed tendon outside of the structural section and the prestressing force transferred to the structural section by deviators and anchorages [6]. This technique is spread widely in the many countries rapidly because of its advantages
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