A full scale static loading test on five story reinforced concrete building utilizing columns with wing walls

Abstract

This study proposes a damage control design of reinforced concrete buildings with ordinary construction approach, and demonstrate the seismic capacity by the full scale test on five story reinforced concrete buildings. In this design, the building performs base shear coefficient higher than 0.40 by utilizing wing walls as a rigid zones of soften beams and additional column section. The target damage level under extreme ground motion is less than minor for buildings, and grade II for each member. This method improves the strength and stiffness of the moment resisting frame and reduces the deformation during earthquakes. That can mitigate the damage on non-structural members or beamcolumn joint. The full scale specimen is a five-story reinforced concrete building with 1×2 bays and height of 18.7m. The wall frame has large openings in longitudinal direction. The span length is 6.0m and story height is 3.5m. Columns have 700 mm square section, and beams have 500×700 mm section. The width and length of attached wing wall section is 200 mm and 700 mm. A series of 4 actuators located on the roof level and 4th floor level in each. Those actuators pinched the center of the floor slab from upper and lower level. The relation between base shear and overturning moment given by a ratio of external force on 4th floor and roof is equalize to that given by an external force with inverted triangle load distribution. The cyclic loading peak is controlled by the total drift on roof level. The test demonstrate the frame marks calculated strength of beam side sway mechanism, and shows ductile behavior until 2.0% drift loading cycle. The story drifts on 2nd and 3rd floor are prominent, where the damage on beams is severe rather than other stories. The hysteretic loops shows slip behavior, but damping coefficient is similar to the evaluation for capacity spectrum design in Japan. Assuming from the strain of rebar or concrete cracking, the specimen reached typical beam side sway mechanism at 1.0% drift loading cycle. Cracks on beams concentrated on local hinge region due to the seismic gaps, which prevent the progressive damage on beam column joint in large drift. The large moment curvature on beam elements is observed around seismic gaps, which also indicates the location of the plastic hinge deformation can be controlled by the gaps. The moment curvature distribution of the 1st story wing wall frames are evaluated experimentally in the test. It is not obvious the inflection point is affected by the length of attached wing wall. The inflection point derived from the interpolation between moment resisting frame and wall frames approximates the test results. The residual crack width of the beam elements becomes large because of the damage concentration on the local hinge region. The damage levels based on the residual seismic capacity on the hysteretic curve is minor at 0.5% drift loading cycle, although the damage evaluated from the residual crack width is moderate at identical drift level. The scratching device on separated nonstructural panels is installed, and estimate the story drift in the test, in order to propose the simple analogical device, by which users can identify the sustainability of the building after earthquake easily and immediately. The devices roughly followed the maximum story drift at 0.25% and 0.50% drift loading cycle. Two types of windows are installed in openings on 1st floor. The concrete mortar and fibrous material are used in each for fixing the windows. The upgraded fixing method improved the capacity but both windows is not available with story drift 0.80%.