Retrofit components are all rated to resist a certain amount of earthquake force.  Figuring out how much force that will be is the purpose of the base shear formula. After figuring out the amount of force to resist  it is a matter of installing enough retrofit components to resist that amount of force.  Doing less than that and there is potential for failure, more than that and you are wasting your money.

 

All hardware, as well as plywood, is rated in terms of how much earthquake force it can resist if installed according to the manufacturer’s instructions.

Let’s look at this table from a manufacturer’s catalog and see that it tells us.  Reading from left to right the hardware model is a GA1, it requires (4) 10d (a nail with a certain diameter) nails that are 1 1/2 inchs long.  F1 means a lateral, as in earthquake force, direction.  Next is the interesting part. DF/SP means this only applies to Douglas Fir (DF) and Southern Pine (SP).  In the column where it says Floor (100) you see the number 235.   This means this hardware can support 235 pounds of floor weight.  In other words, if you have a floor that weighs 235 pounds you would need one of these to hold it up.

For Wind/Seismic we are told it can resist 330# which is considerably more, because it will only need to resist a lateral force for a short period of time versus for a continuous period of time when holding up a floor.

Earthquake Resistance Chart from Standard Plan A.

Even though all the capacities without exception are wrong, this table should give you an idea of how this information is helpful.  For example, according to this table a 5/8 bolt can resist 1170 lbs. of earthquake force, and H10 anchor (a type of shear transfer tie) 505 lbs. etc.

 

Table

 

Below is a listing of various types of fasteners and hardware with their earthquake resisting capacities.  DO NOT rely on these values.  I cannot guarantee their accuracy.

 

FACE NAILING/STAPLING

If both pieces are Douglas Fir

16D                                               200 POUNDS                 1” or more penetration

8D                                                 150 POUNDS                 1” or more penetration

8D toenail                                  120 POUNDS

15 ga Staples:                             80 POUNDS                 1” or more penetration

 If both or one piece of wood is redwood, multiply these values by .88 

BOLTS IN 2″ THICK CLOSE GRAIN REDWOOD

 

½ BOLT with MSP                   1340 POUNDS  

 ½ BOLT no MSP                      1119 POUNDS                

 5/8 BOLT no MSP                   1550 POUNDS                   

 5/8 BOLT with MSP               1550 POUNDS                   

URFP10                                        1530 POUNDS in redwood or Douglas Fir.

 

SHEAR TRANSFER TIES

L90        925 POUNDS  

A23       565 POUNDS

LTP4     670 POUNDS

H10AR   490 POUNDS

H10A   590 POUNDS

8D toenail  120 POUNDS

SIMPSON LAGS 

 300 POUNDS:   With minimum 1” penetration.

450 POUNDS:   Between 1 and 2 inch penetration

550 POUNDS      2 inch penetration or more

PLYWOOD

154 3 Arrows

COMMON NAILING PATTERNS

8d nails 3″ apart = 550 pounds per linear foot.

8d nails 2″ apart = 730 pounds per linear foot.

10d nails 2″ apart = 870 pounds per linear foot.

 

Stapled SW

HIGH CAPACITY PLYWOOD 

3 rows of nails with 3/4 inch plywood makes a shear wall that can resist 1800 pounds of resistance per linear foot.

138 Word

 PLYWOOD TO PLYWOOD

PLy to Ply