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Structural Characteristics of RC Members Applied to Combined Loads of Bending and Torsion

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Setting of the test specimen
reinforced by a CFRP Sheet


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Overview of test specimen


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Overview of loading machine


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Test apparatus (1)

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Test apparatus (2)

ABSTRACT:
For particularly large and complicated bridges, we need a seismic design method that properly addresses torsional moments, as parts of these bridges are subjected to very large torsional moments. In this study, we have conducted combined cyclic load experiments of bending and torsion on RC members, and have experimentally proven the structural characteristics of RC members loaded by torsion.

Meanwhile, carbon fiber reinforced plastics (CFRP) offer lightness and easy construction use, and have attracted much recent attention as a seismically reinforcing material. We have examined the seismic reinforcing effect of CFRP for combined loads of bending and torsion.

DETAILED:
Recently, the advancement of bridge techniques has resulted in the construction of many large and complicated bridges. These bridges are subjected to not only axial force but also bending and torsional moments at the same time. We need a seismic design method that properly addresses torsional moments, as parts of these bridges are subjected to very large torsional moments.

In this study, we conducted combined cyclic load experiments of bending and torsion on RC members, and these had the three parameters of axial force, the pitch of hoop and the ratio of load between bending and torsion. Moreover, we have experimentally proven the structural characteristics of RC members loaded by torsion.

Meanwhile, carbon fiber reinforced plastics (CFRP) offer lightness and easy construction use, and have attracted much recent attention as a seismically reinforcing material. However, their seismic reinforcing effect has not been sufficiently clarified, especially its effect with regards to torsion. We have examined the seismic reinforcing effect of CFRP for combined loads of bending and torsion and have acquired valuable data. These experiments cover the three parameters of the method of wrapping CFRP sheets, the degree of damage and the ratio of load between bending and torsion.

  1. The reinforcing effect of the CFRP sheet for pure torsion
    Reinforcement by CFRP is not effective for initial rigidity. However, it is effective in improving torsional strength and ductility.
  2. The degree of damage before reinforcement with CFRP sheet
    The damaged members showed a decline in initial rigidity. The more seriously the members were damaged, the less the maximum torsional strength.
  3. The method of wrapping the CFRP sheet
    There was not big difference in some dynamic characteristics regarding the method of wrapping, if the CFRP was of roughly the same quantity.
  4. The reinforcing effect of the CFRP sheet for combined loads of bending and torsion
    The reinforcing effect of torsion when bending and torsion were loaded was less effective than the effect when pure torsion was loaded. However, the bending maximum strength and deformation efficiency improved because of the restraining effect.

In the future, we will establish a method of seismic design and seismic reinforced design that focuses on torsional moments based on the dynamic characteristics we clarified by experiment. oments severely based on the dynamic characteristics we clarified by experiments.

Earthquake Engineering Laboratory,
Department of Civil Engineering, Faculty of Engineering, Kyushu University
Associate Professor Yukihide Kajita
Assistant Professor Choi Joonho
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