sgs114
Structural
- Oct 7, 2013
- 33
Hello,
We are doing an ASCE 41-13 Tier 3 seismic evaluation of an existing building to the Immediate Occupancy performance level. We are using the linear static procedures and per the client's request, we are using the BSE-1N and BSE-2N seismic hazard levels for our analysis. When using this methodology, the force levels returned are very large relative to what a new building would be designed to even when including the m-factors. For example our building is composed of tilt-up concrete walls. When evaluating flexural demands on the wall to the IO level the wall is effectively designed for 0.29W when including expected strength, m-factors, and comparing to nominal strength. In a new building designed to current code, the flexural demands on the concrete walls would work out to approximately 0.194W when comparing nominal strengths (Assuming Risk Category IV). I remember hearing the high force levels are due to older buildings not being designed with ductile connections throughout the building and therefore attempting to keep elements elastic when designing to the IO level. Does anyone else have any insight on this? Does anyone know of any articles that discusses this? Thanks in advance.
SGS
We are doing an ASCE 41-13 Tier 3 seismic evaluation of an existing building to the Immediate Occupancy performance level. We are using the linear static procedures and per the client's request, we are using the BSE-1N and BSE-2N seismic hazard levels for our analysis. When using this methodology, the force levels returned are very large relative to what a new building would be designed to even when including the m-factors. For example our building is composed of tilt-up concrete walls. When evaluating flexural demands on the wall to the IO level the wall is effectively designed for 0.29W when including expected strength, m-factors, and comparing to nominal strength. In a new building designed to current code, the flexural demands on the concrete walls would work out to approximately 0.194W when comparing nominal strengths (Assuming Risk Category IV). I remember hearing the high force levels are due to older buildings not being designed with ductile connections throughout the building and therefore attempting to keep elements elastic when designing to the IO level. Does anyone else have any insight on this? Does anyone know of any articles that discusses this? Thanks in advance.
SGS