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Reinforced concrete (RC) buildings mostly built in Thailand were constructed under The
Engineering Institute of Thailand Under H.M. The King’s Patronage 1008-38 where the
design considerations are adopted from ACI-1995. It has been reported worldwide that
the buildings construct under that design criteria would perform in a non-ductile manner
under the earthquake events. The common failure of such buildings was known as the
beam-column joint (BCJ) failure. Therefore, this becomes the objective of this study
whether the BCJ construction in Thailand can perform under the cyclic loading. The
seismic evaluations of BCJ under this study were carried out by laboratory tests of four
reinforced concrete beam-column joints (RC-BCJ). Four specimens were categorized into
2 groups using ratios of column to beam moment capacities (Mc/Mb) with values of 0.75,
1.82. The tested specimens BC-1 and BC-3 have the steel reinforcement details as
typical using in Thailand. According to ACI-318 (มยพ.1301-54), earthquake resisting steel
reinforcement details are employed with specimen BC-2 and BC-4. All RC-BCJ were
subjected to the simulated cyclic load pattern adopted by ACI T1.1-01 using UTM.
The results shown that BC-1 and BC-2 have peak loads at 39 kN and 36 kN with
the corresponding displacements of 69 mm and 44 mm, respectively. The peak load of
BC-3 and BC-4 is identified as 56 kN and 58 kN at the same displacement of 68 mm.
According to ACI-318 (มยพ.1301-54), ACI-352, and FEMA-356, the joint shear strengths ()
are defined as 1.0, 1.0, and 0.5, respectively. However, the joint shear strengths ()
delivered from the test are varies from 0.4-0.5, which is well corresponding to FEMA-356
values. The failure mode for all test specimens can be described as the joint shear
failure. Concrete starts to diagonally crack in the joint area concentrated in the column
panel. Then the crack mostly propagates throughout the joint until the failure.
Simultaneously, small cracks occur in the beam section near the column face.
Compared with joint cracks, those beam cracks are considerably insignificant. |
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