Hiner problem # 16

[danho]

Dear All,

I have a question on part A (N-S Direction), question # 1. Design Seiseimic force to diaphragm.

Why when calculating the walls on the north and the south ( there are 3 walls with widths shown as 11', 22', and 42'), Hiner assumed that there are only two walls with the full length of 70' each?

This is what I did with this problem, and I am not sure if my thinking is correct, please help. ( there is also similar problem in the same book , problem 9.13)

The total Force F = 0.19W where W = (16 psf +20%*100 psf)(40')(70') +(85 psf)(14'/2+2')(11') + (85 psf)(14'/2+2')(22') +(85 psf)(14'/2+2')(42') = 158,175 lb

Then F= 30,053 lb , then the uniform seismic load w = F/70' = 429 plf not 564plf as shown in the solution.

Sorry to bother you all, but I also have another question on chapter 5 of Hiner book. Why do we have the negative sign in front of Eh (effective of horizontal seisemic force)? To my understanding, the effect of vertical force can be positve or negative due to the additive or counteractive to gravitational load effects, but horizontal force can act in any direction why the negative sign in the calculations?

Thank you.

 

[golamycine]

Dear All,I have a question on part A (N-S Direction), question # 1. Design Seiseimic force to diaphragm.

Why when calculating the walls on the north and the south ( there are 3 walls with widths shown as 11', 22', and 42'), Hiner assumed that there are only two walls with the full length of 70' each?

This is what I did with this problem, and I am not sure if my thinking is correct, please help. ( there is also similar problem in the same book , problem 9.13)

The total Force F = 0.19W where W = (16 psf +20%*100 psf)(40')(70') +(85 psf)(14'/2+2')(11') + (85 psf)(14'/2+2')(22') +(85 psf)(14'/2+2')(42') = 158,175 lb

Then F= 30,053 lb , then the uniform seismic load w = F/70' = 429 plf not 564plf as shown in the solution.

Sorry to bother you all, but I also have another question on chapter 5 of Hiner book. Why do we have the negative sign in front of Eh (effective of horizontal seisemic force)? To my understanding, the effect of vertical force can be positve or negative due to the additive or counteractive to gravitational load effects, but horizontal force can act in any direction why the negative sign in the calculations?

Thank you.

Only the walls perpendicular to the direction of seismic force contribute to the weight. In N-S direction, there are just two walls on the E-W direction whose weight will be considered. Same applies to the Problem 9.13 Hope that helps ...Did not understand your question abt Chapter 5 can you reference the probelm number or Page Number ...Good Luck

 

[danho]

Dear All,I have a question on part A (N-S Direction), question # 1. Design Seiseimic force to diaphragm.

Why when calculating the walls on the north and the south ( there are 3 walls with widths shown as 11', 22', and 42'), Hiner assumed that there are only two walls with the full length of 70' each?

This is what I did with this problem, and I am not sure if my thinking is correct, please help. ( there is also similar problem in the same book , problem 9.13)

The total Force F = 0.19W where W = (16 psf +20%*100 psf)(40')(70') +(85 psf)(14'/2+2')(11') + (85 psf)(14'/2+2')(22') +(85 psf)(14'/2+2')(42') = 158,175 lb

Then F= 30,053 lb , then the uniform seismic load w = F/70' = 429 plf not 564plf as shown in the solution.

Sorry to bother you all, but I also have another question on chapter 5 of Hiner book. Why do we have the negative sign in front of Eh (effective of horizontal seisemic force)? To my understanding, the effect of vertical force can be positve or negative due to the additive or counteractive to gravitational load effects, but horizontal force can act in any direction why the negative sign in the calculations?

Thank you.

Only the walls perpendicular to the direction of seismic force contribute to the weight. In N-S direction, there are just two walls on the E-W direction whose weight will be considered. Same applies to the Problem 9.13 Hope that helps ...Did not understand your question abt Chapter 5 can you reference the probelm number or Page Number ...Good Luck

Thank you for your answer, but I am not sure if your explaination is correct. As you stated "Only the walls perpendicular to the direction of seismic force contribute to the weight." and I agreed with you, but in this problem the direction of seisemic force is N-S, so the weights that need to be considered are the weights of the 3 walls that I mentioned above. Walls on E-W direction are parallel to the force, so their weights will not be considered.

For problem 9.13, if you look at the drawing at line 5, the shearwall shows only 20' wide, not 40' wide as the shearwall on line 1.

For chapter 5, I mean the theory, why do we have negative for horizontal seisemic force? I don't think that the positive or negative signs mean compression or tention forces. I have checked with ASCE and IBC books and could not find any equations for horizontal forces with the negative sign in front.

Thank you.

 

[golamycine]

Dear All,I have a question on part A (N-S Direction), question # 1. Design Seiseimic force to diaphragm.

Why when calculating the walls on the north and the south ( there are 3 walls with widths shown as 11', 22', and 42'), Hiner assumed that there are only two walls with the full length of 70' each?

This is what I did with this problem, and I am not sure if my thinking is correct, please help. ( there is also similar problem in the same book , problem 9.13)

The total Force F = 0.19W where W = (16 psf +20%*100 psf)(40')(70') +(85 psf)(14'/2+2')(11') + (85 psf)(14'/2+2')(22') +(85 psf)(14'/2+2')(42') = 158,175 lb

Then F= 30,053 lb , then the uniform seismic load w = F/70' = 429 plf not 564plf as shown in the solution.

Sorry to bother you all, but I also have another question on chapter 5 of Hiner book. Why do we have the negative sign in front of Eh (effective of horizontal seisemic force)? To my understanding, the effect of vertical force can be positve or negative due to the additive or counteractive to gravitational load effects, but horizontal force can act in any direction why the negative sign in the calculations?

Thank you.

Only the walls perpendicular to the direction of seismic force contribute to the weight. In N-S direction, there are just two walls on the E-W direction whose weight will be considered. Same applies to the Problem 9.13 Hope that helps ...Did not understand your question abt Chapter 5 can you reference the probelm number or Page Number ...Good Luck

Thank you for your answer, but I am not sure if your explaination is correct. As you stated "Only the walls perpendicular to the direction of seismic force contribute to the weight." and I agreed with you, but in this problem the direction of seisemic force is N-S, so the weights that need to be considered are the weights of the 3 walls that I mentioned above. Walls on E-W direction are parallel to the force, so their weights will not be considered.

For problem 9.13, if you look at the drawing at line 5, the shearwall shows only 20' wide, not 40' wide as the shearwall on line 1.

For chapter 5, I mean the theory, why do we have negative for horizontal seisemic force? I don't think that the positive or negative signs mean compression or tention forces. I have checked with ASCE and IBC books and could not find any equations for horizontal forces with the negative sign in front.

Thank you.

You are absolutely right my friend ...Your calculations make sense. I do not know why Hiner solution considers an additional 65 feet (140-75) of wall weight for N-S Diapghram force when that wall does not exist? I guess same goes for E-W direction with 20 feet of additional weight is applied to the Diaphragm and Problem 9.13. I have checked various book and each structural engineer considers different solution some take even parallel walls others consider parallel walls in rigid diaphragm. I personally feel that ALL walls for a single story building should be considered since its an assumed earthquake direction and design should be conservation. For economical design and for Theory purpose I think your solution is accurate ...Again I am new to this subject and have no experience with Seismic.

Good Observation on the equation (-Eh) in the 5th Chapter as well. I checked Dr. Mansour notes and he does not use the negative sign neither do the codes as you pointed out. At first I thought its a Typo but there are several questions solved in the Multiple Questions section using -Eh....? Perhaps our other friends may be able to help or You may want to ask Mr. Hiner directly he is pretty good in responding back (within a day). I would have asked him myself but i have sent him several questions in past week so there is a chance my email might get ignored ....His email address is : [email protected]

These are some really good observations and I appreciate you bringing them up. Please share if you hear back from Hiner or anyone else. Best of Luck..

 

[sac_engineer]

I'm getting confused on everyone's confusion. The design seismic force is a function of the vertical load regardless of how the load is transferred to the foundation. This is why the force is in pounds per linear foot, not an absolute weight. The design forces are then applied to the walls where you'll find that the bigger the gaps, the more shear force the wall has to resist.

As for the negative horizontal force, structural designers have to consider all loading combinations. I wouldn't get too hung up about this. It's just to let you know that you're required to check all combinations when assessing the design load of a structure.