conrad martin
Civil/Environmental
- May 6, 2018
- 2
thread726-197249
i have a 2 storey reinforced concrete moment frame project that I am working on which has under-reinforced columns. As a result,the idea to install retrofitted shear walls has come up as the best solution. When modelled it works and the theory is that the shear wall system will "absorb 100%" of the lateral loads, thereby leaving the under-reinforced columns to take only the gravity loads. My feeling is that this does not actually obtain in reality. I think that there must be some residual carriage of the lateral loads by the columns however small that is, so I'd like some comments on that firstly. But my major concern is the detailing of the retrofitted shear wall. It is supposed to work by allowing the first floor slab to act as a diaphram and transfer the lateral load to the shear wall, but since this is not a monolithic construction, we are relying on dowels and epoxies to create the bond required for load transfer. Is this reliable? Also, our design requires the rebars for the shear wall to be continuous between the two floors. This seems rather impractical since we would have to bore through 2 feet of concrete due to the presence of the beam and also avoid the rebars at the bottom of the beam. Assuming the drill was practical, how does one guarantee the anchorage of the rebars through such a 'mutilated' beam. I would like to know whether or not the shear wall absolutely needs to be continuous for it to function or can it be discontinuous across the floor slab-beam interface.
As an alternative, I researched a paper on External Shear Walls where the shear wall is attached to the outside face of the columns and beams at the building facade instead of between the columns themselves in the same plane. The research paper used a 1/3 building model and the results where satisfactory and they even used the ACI code in designing the dowel depths and quantities. They claim that they were able to achieve satisfactory load transfer as the system worked as one. Could this work at full scale under real earthquake dynamic loading. Thoughts please?
i have a 2 storey reinforced concrete moment frame project that I am working on which has under-reinforced columns. As a result,the idea to install retrofitted shear walls has come up as the best solution. When modelled it works and the theory is that the shear wall system will "absorb 100%" of the lateral loads, thereby leaving the under-reinforced columns to take only the gravity loads. My feeling is that this does not actually obtain in reality. I think that there must be some residual carriage of the lateral loads by the columns however small that is, so I'd like some comments on that firstly. But my major concern is the detailing of the retrofitted shear wall. It is supposed to work by allowing the first floor slab to act as a diaphram and transfer the lateral load to the shear wall, but since this is not a monolithic construction, we are relying on dowels and epoxies to create the bond required for load transfer. Is this reliable? Also, our design requires the rebars for the shear wall to be continuous between the two floors. This seems rather impractical since we would have to bore through 2 feet of concrete due to the presence of the beam and also avoid the rebars at the bottom of the beam. Assuming the drill was practical, how does one guarantee the anchorage of the rebars through such a 'mutilated' beam. I would like to know whether or not the shear wall absolutely needs to be continuous for it to function or can it be discontinuous across the floor slab-beam interface.
As an alternative, I researched a paper on External Shear Walls where the shear wall is attached to the outside face of the columns and beams at the building facade instead of between the columns themselves in the same plane. The research paper used a 1/3 building model and the results where satisfactory and they even used the ACI code in designing the dowel depths and quantities. They claim that they were able to achieve satisfactory load transfer as the system worked as one. Could this work at full scale under real earthquake dynamic loading. Thoughts please?
