SteelPE
Structural
- Mar 9, 2006
- 2,761
I have a project that is currently under construction that is a single-story metal building. The building is somewhat large and has a base shear of Vu = 49.7 kips. We designed the foundation utilizing moment resistant foundations as we have had issues lately with clients ripping out tie rods and hairpins. We specified 4 ksi concrete on the design documents to resist this load.... things were spectacular.
Until ..... We are now running into concrete that is not hitting the 28-day compressive strength specified on the drawings. The testing agency is holding some breaks for 56 days, but the contractor is looking to start steel erection early next week. At this point, we are not exactly sure why we are having a series of breaks below the necessary compressive strength, but we were asked to go back and reevaluate the concrete strength at a lower capacity in order to help the construction schedule.
When evaluating the concrete at a lower strength we are now running into issues with the shear strength of the piers. We are calculating their capacity to be phi Vc = 88 kips. Since the capacity of the pier is not 2x the demand, we now have to provide a minimum amount of shear reinforcing in the pier. We do have stirrups that we provided in the pier, but they are not quite enough to meet the minimum shear requirements.
Just wondering what others would do in this instance. I am inclined to say it’s ok as are 1.77x vs 2x the shear requirement.
Until ..... We are now running into concrete that is not hitting the 28-day compressive strength specified on the drawings. The testing agency is holding some breaks for 56 days, but the contractor is looking to start steel erection early next week. At this point, we are not exactly sure why we are having a series of breaks below the necessary compressive strength, but we were asked to go back and reevaluate the concrete strength at a lower capacity in order to help the construction schedule.
When evaluating the concrete at a lower strength we are now running into issues with the shear strength of the piers. We are calculating their capacity to be phi Vc = 88 kips. Since the capacity of the pier is not 2x the demand, we now have to provide a minimum amount of shear reinforcing in the pier. We do have stirrups that we provided in the pier, but they are not quite enough to meet the minimum shear requirements.
Just wondering what others would do in this instance. I am inclined to say it’s ok as are 1.77x vs 2x the shear requirement.
