DESIGN STRENGTH OF BOLT BETWEEN AISC AND BS STANDARD

[saruncivil]

Dear Engineers,
I need one clarification for using Design strength of Bolt in AISC and BS standards. Please look my following queries,
I. I’m using Grade 8.8 bolt in AISC connection calculation, what is the design strength of tension and shear strength….?
II. As per AISC-LRFD 2005, design strength of bolt should be multiplied by 0.75.

For eg,
Please find the attachment.

Please tell me how to find the design strength of question marked in table.

Your Budding Engineer
Arun S

 

[CoryPad]

Arun,

Your table is incorrect, the tensile strength is larger than the shear strength.

AISC 360 Specification for Structural Steel Buildings shows the following values for A325: 620 MPa for tension and 330 MPa for shear (assuming threads in the shear plane)

EN 1993-1-8 Eurocode 3 : Design of steel structures, Part 1.8 : Design of joints shows the following values for 8.8: 576 MPa for tension and 320 MPa for shear (assuming threads in the shear plane)

Cory

 

[desertfox]

Hi
Have a look at this site for 8.8 bolt strengths

http://www.roymech.co.uk/Useful_Tables/Screws/Strength.htm

 

[saruncivil]

Dear Corypad,
Sorry I had typed wrongly, thank you.
please find the attachment.

Dear Engineers,
I wanna know what the design strength of 8.8 grade (as per BS) bolt when we using in AISC connection design formula.

As per AISC-LRFD 1999,
Tension capacity of bolt, Rut = Ф X Ft X Ab where Ф = 0.75 and Ab is nominal body area of bolt.
In which Ft = 560 N/mm2 (Tension strength of grade 8.8 bolt as per BS) or it will vary.
Please describe it.

 

[wannabeSE]

I am not familiar with AISC LRFD 99. I assume it is similar to the 2005 and 2010 specification. With these, A_b is the nominal area of the unthreaded portion of the bolt. F_nt is 75% of the tensile strength, F_u. The reduction is a simple way to account for the reduced area of the threaded portion of the bolt. This explanation is in the commentary to the AISC specification. Similarly, F_nv = 0.563F_u when the threads are excluded from the shear plane and 0.450F_u when the threads are not excluded. See the AISC commentary for an explanation.

The AISI S100 specification for cold formed steel covers smaller bolts and uses a larger reduction to the tensile strength for the smaller bolts because the ratio of the threaded area to unthreaded area is smaller on smaller bolts. Since metric bolts are being used, it would be wise to check this ratio of the net tensile area to the nominal area of the unthreaded bolt before using the AISC equations. With bolt in the US, the net tensile area is commonly calculated using with 0.7854 x ( d - 0.9743 / n)². Where d is the nominal diameter and n is the threads per inch.

The current AISC specification (AISC 360-10) and commentary can be downloaded for free from AISCs website, the entire Steel Construction Manual with the design aids and tables can be purchased on the website.

 

[desertfox]

Hi

According to BS 5950 the values are 575N/mm^2 tensile and 375 N/mm^2 shear.

Desertfox

 

[saruncivil]

Thanks Mr.wannabeSE.
now i'm clear from your reply.

hi desertfox,

please refer BS 5950_1:2000, table 34 for Tension strength of bolt.
for grade 8.8 bolt tension strength was 560N/mm2.