Specification for Bolted joints

In my previous post “Bolted joints in steel structures” I discussed about what is Bolted joint? What are the types of Bolted joint? And which joint is better and which joint is more desirable among all the joints in steel structure?

Now I entering little bit deep on that and start discussion on specification for bolted joints. 

Specification for Bolted joints

Pitch (p):

It is the distance between the centers of two consecutive bolts measured along a row of bolts.

Gauge (g):

It is the distance between the center to center distances between two consecutive bolts measured along the width of the member or connection.

Edge Distance (e):

This is the distance at right angle to the direction of stresses from the center of the bolt hole to the adjacent edge of the member whereas the distance in the direction of stress from the center of a hole to the end of the element is called edge distance.

Bolt holes should not be placed too near the edges for the following reasons:

1. The failure of plate in tension may take place, and
2. The steel of the plate opposite the hole may bulge out and may crack.

 

Shear strength of bolt, V_sb=(A_nb*f_ub)/√3*ˠ_mb.

Bearing strength of bolt, V_pb=2.5k_bdtf_u/ˠ_mb.

Tensile strength of bolt, T_nb=0.9f_ubA_nb<f_ybA_sbˠ_mb/ˠ_m0.

Tensile strength of the plate,T_nd=0.9A_nf_u/ˠ_m1.

Where,

K_b= smaller of e/3d_0, p/3d₀-0.25,f_ub/f_u, and 1.0.

e,p=edge and pitch distances.

d₀=diameter of the hole.

f_ub=ultimate tensile stress of the bolt.

f_u=ultimate tensile stress of the plate.

d=nominal dia of bolt

ˠ_mb=the partial safety factor for material of bolt=1.25

ˠ_m0=partial safety factor for material resistance governed by yielding=1.10

ˠ_m1=partial safety factor=1.25

 Efficiency of the joint

   ᶯ = (strength of bolted joint/pitch length)/(strength of solid plate/pitch length)*100

Hope this discussion clear your concept on Specification for Bolted joints.