RC "laboratory" structures
Publication: Out-of-plane shaking table tests on unreinforced masonry panels in RC frames (2010)
Preparation and upload by:
Filip Anic, Faculty of Civil Engineering and Architecture Osijek, Josip Juraj Strossmayer University of Osijek
List of test setups
Publication abstract (click to enlarge):
Publication abstract (click to shrink):
Shaking table tests were conducted on four full-scale single-story structures to investigate the out-of-plane behavior of unreinforced masonry (URM) panels in RC frames. Specimens included one pure frame, two frames with confined masonry panels of different thicknesses, and one with infill panels. Every specimen was subjected to single-axis ground motions with the intensity magnified each cycle
Shaking table tests were conducted on four full-scale single-story structures to investigate the out-of-plane behavior of unreinforced masonry (URM) panels in RC frames. Specimens included one pure frame, two frames with confined masonry panels of different thicknesses, and one with infill panels. Every specimen was subjected to single-axis ground motions with the intensity magnified each cycle until the structure exhibited severe damage. With strong boundary restraints, the confined masonry panels exhibited notable resistance to out-of-plane inertial forces via the arching mechanism. Infill panels also showed arching at low motion intensity, but separated from the boundary frames at higher intensity and collapsed under the inertial force caused by their self-weight. Wall thickness/slenderness was found to have a significant influence on out-of-plane strength and stiffness. An analytical model for the out-of-plane behavior of confined masonry panels in accordance with the rocking mechanism is also presented. Comparison with experimental results showed that this model affords accurate and conservative estimates for force and deformation capacities. It also suggests that the out-of-plane deformation capacity of a confined masonry panel is proportional to its thickness
A growing interest on the OOP behaviour ofURM infills is currently arising in the seismic and structural engineering community. In fact, even if less studied than the in-plane (IP) behaviour, an increasing number of numerical and experimental studies focused on the pure OOP behaviour of URM infills is proposed in recent literature. Even less studied in the past than the pure OOP behaviour of infills is the IP/OOP interaction, i.e., the effects of previous damage due to IP displacement demands on the OOP response of infills and vice-versa. This is a crucial issue, given that infills are subjected, during earthquakes, to combined IP and OOP actions and that IP damage promotes and facilitates their OOP collapse.
AIM AND SCOPE
To investigate the out-of-plane behavior of unreinforced masonry (URM) panels in RC frames. Specimens included one pure frame, two frames with confined masonry panels of different thicknesses, and one with infill panels.
DESIGN AND CONSTRUCTION OF THE TEST SPECIMENS:
Four full-scale specimens were built and tested in the laboratory of NCREE. The main variables were panel thickness and construction type (confined masonry/pre-laid panels or infill/postlaid panels).
B1 specimen detail:
Confined and unreinforced masonry wall details:
Shaking table tests on four single-story RC structures with and without URM panels were performed to investigate the out-of-plane behavior of the panels. The test results suggest that confined masonry panels can sustain considerable out-of-plane seismic loads. Strong boundary connections prevent confined masonry panels from falling out of the frame, reducing the influence of the inertial force from the panel’s self-weight. The two-hinged arching damage and deformation pattern could explain the out-of- plane resisting mechanism. The infill-type panels showed the same behavior as confined masonry panels until their boundaries were damaged. When infill panels separated from their boundary frames, they collapsed due to the out-of-plane inertial force caused by their self-weight. This indicates that the out-of-plane capacity of infill-type panels can be improved if their boundaries are properly strengthened. Panel thickness or slenderness is another main factor that affects the out-of-plane behavior. A double wythe confined masonry panel exhibited much higher strength and stiffness than a single wythe panel.
RECOMMENDATIONS FOR FUTURE RESEARCH
An analytical model based on a two-hinged arching/rocking pier mechanism was developed to estimate the out-of-plane behavior of confined masonry panels. The analytical strength predicted by this model is an accurate and conservative estimate, as determined by comparison with experimental results. The analytical results suggest that the out-of-plane deformation capacity of a confined masonry panel is proportional to its thickness. However, the effect of boundary columns and the behavior of the type of panel subjected to in-plane and out-of-plane seismic loading applied simultaneously are not yet clear and need further study.
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