Flexural Behavior of Steel-Concrete Composite Beams Strengthened by Post Tension Method

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This study has attempted to suggest a proper reinforcement method by strengthening unbonded post -tensioning through height of an anchorage hole, form of a saddle, and loading time point as parameters and evaluating the reinforcement method through a bending experiment. The result of this experiment indicated effects of reinforcement since the maximum strength ratio(the ratio of an experimental value to theoretical value) of SC composite beams before prestressed was 0.97 and after prestress were 1.00~1.21. As a result of analysis on displacement and strain, irrespective of height of an anchorage hole and loading time point, the D120-series specimen where an anchorage hole was installed on the neutral axis after reinforcement showed that its deflection continuously increased without sudden load reduction after maximum load and it stably behaved with relatively low strain of each part. In terms of reinforcement effects, the maximum strength of SCR-UD120 specimen prestressed after pre-loading was increased 1.72 times comparing to SC composite beams so SCR-UD120 specimen prestressed after pre-loading was shown to be the best.

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The CFTA (Concrete Filled Tubular Arch) Girder bridge is a new type of bridge which improves the structural efficiency and the aesthetics by combining the characteristics of the CFT (Concrete Filled Tube) structure, PS (Pre-Stressed) structure, and arch structure. Before applying the proposed type of bridge to the real bridges, the structural safety should be evaluated not only in service but also under construction. Because the CFTA Girder bridge has the relatively slim section in the middle of the span, the vibration serviceability should be evaluated additionally. In this study, the real-scaled specimen of the CFTA Girder bridge was fabricated and the vibration test was conducted to evaluate the structural safety under construction and the vibration serviceability in service. The dynamic analysis considering the moving load was conducted by using the FE (Finite Element) model verified with the results of the vibration test. The results of the dynamic analysis reveal that the CFTA Girder bridge has the structural safety under construction and the excellent vibration serviceability.
This paper analyzes the behavior of steel beams prestressed with highstrength steel tendon and compositely connected to a concrete deck. In particular, the deflection and the strains in the steel beam, concrete deck, and tendons are calculated in the positive and negative bending moment regions, over the full range of loading to failure. Three types of composite beams are considered: (1) Conventional composite beam without prestressing tendon; (2) composite beam with tendons anchored at the ends, but not prestressed; and (3) composite beam with tendons prestressed. The load-deflection and the load-strain behavior of these beams are compared. The analysis shows that the ultimate and the yield loads can be increased substantially by adding high-strength tendons to the composite beams and prestressing them.
The concept of prestressing steel structures has only recently been widely considered, despite a long and successful history of prestressing concrete members. Several analytical studies of prestressed composite beams were reported in the literature, but much of that work was not experimentally verified. In particular, no test results were found on prestressed composite beams subjected to negative bending moment. This paper examines experimentally the behavior of prestressed, composite steel-concrete beams. Two beams were tested, one subjected to positive bending moment and the other to negative bending moment. The load was plotted against the deflection, and the strains in the concrete, steel beam, and prestressing bars. The values predicted with the equations of internal force equilibrium and compatibility between the deformations of the bars and the composite beam were found to correlate well with the measured data.
Analytical Study of Prestressed Composite Beams
  • S Hamid
  • A Pedro
  • M Balal
Hamid S., Pedro A., Balal M. A. "Analytical Study of Prestressed Composite Beams", ASCE., Vol. 115, No. 9, 1989, pp. 2364-2381.