The American Concrete Institute (ACI) has released a paper presenting the behaviour of six tests of planar prestressed concrete frames under the loss of a middle column.
The paper, Progressive Collapse-Resisting Mechanisms of Planar Prestressed Concrete Frame, consisted of two non-prestressed reinforced concrete (RC) specimens and four prestressed concrete (PC) specimens with bonded post-tensioning tendons (BPT).
ACI says: “The structural response of the specimens with different flexural reinforcement ratio, span-depth ratio, and effective prestress level has been reported. In addition, the impact of parabolic BPT on the behavior of RC frames to resist progressive collapse is also evaluated.”
The experimental results indicated that the BPT increases the initial stiffness and yielding load of the RC counterparts as well as the ultimate load capacity in the catenary action stage. Also, it will impact the load-resisting mechanisms and the failure modes.
“Contrary to the commonly accepted sequential mobilisation of compressive arch action and catenary action to resist progressive collapse of RC frames, no effective compressive arch action is developed in PC frames to mitigate progressive collapse risk,” ACI adds.
Based on experimental observations, results show that higher effective prestress in BPT results in enhanced initial stiffness and yielding load but less deformation capacity and ultimate load capacity.
“It is also found that higher non-prestressed flexural tensile reinforcement ratio could improve the behaviour of PC specimens to resist progressive collapse,” ACI concludes.
This paper was written by Kai Qian, Xi-De Zhang, Feng Fu, and Bing Li.
ACI presents behaviour of six tests six tests of planar prestressed concrete frames
