ASCE 7-16 Section 12.14.3.2 The use of the overstrength factor

[minorchord2000]

Subsection 12.14.3.2.1, equation 12.14-9 specifies that Emh = 2.5*Qe. My question is when to use the 2.5 factor and when not to. The Code is unclear. I am designing anchorage forces for a vertical rigid steel storage tank and I use equation 15.4-5 to calculate the lateral seismic force, V, when the period is less than 0.06 seconds Is this force V the same as Qe? And do I apply the 2.5 factor to this V or Qe?

Thanks for you assistance.

 

[phamENG]

Do a search. The threads on this subject are legion.

 

[HTURKAK]

Dear minorchord2000,

Pls find below my responds to your questions ;

- The code is clear but the use of overstrength factor distributed in the code .. several days ago i responded the use of overstrength factor for some cases pls look thread176-489232

- You may use 15.4-5 ( V =0.30*SDS*W*Ie where V is the total design lateral seismic base shear force applied to a
nonbuilding structure;

- In case of tanks , you should look also 15.7 TANKS AND VESSELS

- 15.7.3=
Strength and Ductility. Structural members that are part of the seismic force-resisting system shall be designed to provide the following:
a. Connections to seismic force-resisting elements, excluding anchors (bolts or rods) embedded in concrete, shall be
designed to develop Ω0 times the calculated connection design force. For anchors (bolts or rods) embedded in
concrete, the design of the anchor embedment shall meet the requirements of Section 15.7.5. ....
. The overstrength requirements of Section 12.4.3 and the Ω0 values tabulated in Table 15.4-2 do not apply to the
design of walls, including interior walls, of tanks or vessels.....


The overstrength factor is not applied to anchors bolts or rods but applied to the connection elements ( such as chairs, brackets etc)..


I will suggest you to look
- Guidelines for seismic evaluation and design of petrochemical facilities (ASCE) ,
- Anchorage Design of the Petrochemical Facilities ( ASCE ) ,

You may search the previous threads ( as suggested by MR PHAMENG ) or provide more detail ( tank dimensions, service, seismicity etc...) to get better responds..