Hiner Multiple Choice Question 6.18

[H2OEngineer]

The question wording is a bit confusing. The questions asks: " Determine the governing wall anchorage force (Fp) at the Level 1 (and Level 2) flexible floor diaphragms." The solution takes the weight to be 1/2 the wall of story 1 plus 1/2 the wall of story 2.

Is the problem really just determining the Fp for the diaphragm at level 1, or is this the sum of the Fp for Level 1 and Level 2 diaphragms combined?

I believe when evaluating a multistory structure we must use the weight of 1/2 of the wall below plus 1/2 of the weight of the wall above, however the wording of the question left me with some doubt.

 

[ptatohed]

Again, I have an older edition so excuse me if our pages or other info don't line up exactly (I assume you are studying with the latest edition). Look at (my) page 1-79, section 'Anchorage to Flexible Diaphragms'. [FYI: In my opinion, it should read 'Anchorage of Concrete or Masonry to Flexible Diaphragms' (I submitted all my suggestions to Hiner after I passed, a few years ago, but I am not sure if he took my suggested changes)]. You'll see four greater than or equal formulas from ASCE 7 12.11-1. You need to solve each one to see which governs. SDS is given and I assume you know how to calculate I. So, the only trick here is knowing how to calc Wp. At the top of page 1-79 is the section 'Anchorage of Concrete or Masonry Structural Walls' [should be called 'Anchorage of Concrete or Masonry Structural Walls to Rigid Diaphragms'!!!]. That's where Hiner defines Wp and includes two formulas to solve Wp (Wp is calc'ed the same for rigid or flexible diaphragms). Well, these two formulas both assume only a 1 story building (one w/ parapet, one without). This question is for a 3-story, right? So, how do you calculate the Wp for a multi-story building? He includes the formula in the solution but it was never in the text. So, under the formula w/out parapet, write in your own formula (for multi-story). It is Wp = Wwall(hSN/2 + hSN-1/2) Meaning, the weight of the wall tributary to the anchor (plf) equals the weight of the wall (psf) times the sum of half the wall height (ft) above and half the wall height (ft) below. Does that make sense?

The reason the question words it as "...Level 1 (and Level 2)... " is because on a three-story building the calculation of the Wp for level 1 and level 2 is exactly the same.

Did I help?

P.S. You should have bought EET's Seismic Book. Dr. Ibrahim is so kind, I bet he'd answer any questions you have via phone or e-mail. http://eet-california.com/seismic_class_textbook

 

[H2OEngineer]

Thank you, yes it clarifies it for me.