StoyanAndreev
Structural
- Dec 14, 2012
- 32
Hi, guys!
I need to model soil-structure interaction for a large building (approx 68x68x70 meters). I am using NIST GCR 12-917-21 "Soil-structure interaction for building structures" as a reference document. I have calculated lumped spring-dashpot coefficients for vertical translations, horizontal sliding, rocking and torsion. My basemat is relatively thick and I have basement walls so I am assuming rigid basemat (for the impedance functions). I can do the design checks for all structural elements (walls, slabs, columns etc) with this approach, except for the design of the basemat. In order to calculate forces in the basemat I am distributing the spring stiffness/damping all over the nodes of the basemat. Using only the stiffness Kz/Af (Kz - total vertical spring stiffness, Af - basemat area) as distributed vertical stiffness per square meter I will underestimate the overall rocking stiffness. To account for this I need to increase the stiffness of the perimeter springs for a width Re (0.3-0.5 times half-length of the basemat). If Re=0.5L the increase is 3.8 times, if Re=0.3L the increase is 4.8 times. I am concerned that if I use 5 times stiffer springs on the perimeter it won't be conservative for the basemat. What are your opinion and advices?
I need to model soil-structure interaction for a large building (approx 68x68x70 meters). I am using NIST GCR 12-917-21 "Soil-structure interaction for building structures" as a reference document. I have calculated lumped spring-dashpot coefficients for vertical translations, horizontal sliding, rocking and torsion. My basemat is relatively thick and I have basement walls so I am assuming rigid basemat (for the impedance functions). I can do the design checks for all structural elements (walls, slabs, columns etc) with this approach, except for the design of the basemat. In order to calculate forces in the basemat I am distributing the spring stiffness/damping all over the nodes of the basemat. Using only the stiffness Kz/Af (Kz - total vertical spring stiffness, Af - basemat area) as distributed vertical stiffness per square meter I will underestimate the overall rocking stiffness. To account for this I need to increase the stiffness of the perimeter springs for a width Re (0.3-0.5 times half-length of the basemat). If Re=0.5L the increase is 3.8 times, if Re=0.3L the increase is 4.8 times. I am concerned that if I use 5 times stiffer springs on the perimeter it won't be conservative for the basemat. What are your opinion and advices?
