Ultimate drift at gravity load collapse of non-ductile RC columns | |
| Author | Mehmood, Tahir |
| Call Number | AIT RSPR no.ST-10-01 |
| Subject(s) | Columns, Concrete Lateral loads |
| Note | A Research study submitted in partial fulfillment of the requirements for the Degree of Master of Engineering in Structural Engineering, School of Engineering and Technology |
| Publisher | Asian Institute of Technology |
| Series Statement | Research studies project report ; no. ST-10-01 |
| Abstract | The ultimate drift capacity of a lateral load resisting element is usually defined by the conditions at which the maximum lateral load resisting capacity is reduced to 80% of the design strength. In the regions of low to moderate seismicity such as Thailand, most columns are non-ductile and lateral strength could significantly drop below 80% soon after maximum resistance has been reached. These columns are deemed collapse although they can still safely carry their gravity load. In such case, the definition for the ultimate drift capacity could be overly conservative. Therefore, this research aims at investigating drift capacity and failure mechanism of non-ductile columns at gravity load collapse condition. The literature on behavior of gravity load collapse particularly of non-ductile columns is very limited and consequently, the gravity load collapse mechanism of such columns is still not clearly understood. Six cantilever column specimens, three specimens with lap splices and three specimens without are selected based on available literature. Tested specimens have aspect ratios varying from 3.15 to 5.85 and constant axial load ratio ( / ′ ) of 0.15 representing the mid rise buildings in Thailand. One of the important feature of lap splice specimen in the cranking of longitudinal reinforcement at just above the lap splices, which is a common practice of construction in Thailand. The cantilever columns were subjected to full gravitational loading before being displaced horizontally using a displacement-controlled actuator attached at the free end via a pin-connection. In second phase of this research non-ductile column retrofitted with FRP wrap. The results obtained from the tests revealed valuable information regarding collapse mechanism of non-ductile columns. For specimen without lap splices shear demand has significant effect of lateral strength degradation. Short specimen with highest shear demand has higher rate of lateral strength degradation. In long and medium columns longitudinal reinforcement buckled at the bottom of column, where the maximum moment occurred. It was observed that after buckling gravity load failure is warranted. For short specimen pre-mature buckling of longitudinal reinforcement was observed at an early stage after developing large shear cracks. Tests results have shown that axial deformation increases abruptly after buckling of longitudinal reinforcement in case of long and medium column specimen without lap splices. For short column without lap splices sudden increase in axial deformation has been observed due to penetration of shear plane after shear failure. Shear demand influence on bond deterioration is not significant in case of column with lap splices. Buckling of longitudinal reinforcement is concentrated in region just above the lap splices due to increase rotation of lap splices in crank portion of longitudinal reinforcement. Retrofitting of columns with FRP wrap has increase the displacement capacity and ductility of column significantly due to confinement effect of FRP. |
| Year | 2010 |
| Corresponding Series Added Entry | Asian Institute of Technology. Research studies project report ; no. ST-10-01 |
| Type | Research Study Project Report (RSPR) |
| School | School of Engineering and Technology |
| Department | Department of Civil and Infrastucture Engineering (DCIE) |
| Academic Program/FoS | Structural Engineering (STE) /Former Name = Structural Engineering and Construction (ST) |
| Chairperson(s) | Pennung Warnitchai; |
| Examination Committee(s) | Anwar, Naveed;Kittipoom Rodsin; |
| Scholarship Donor(s) | HEC, Pakistan; |
| Degree | Research report (M. BA.) - Asian Institute of Technology, 2010 |