Beam to beam double angles bolted  bearing type connection

Bookmark:

1. Design requirement

2. Design procedure

3. Related Code in AISC 13th ed Specifications.

   3.1. Nominal Shear Stress of bolts in bearing type of connection

   3.2. Bearing strength at bolt holes (AISC 13th ed. Section J3.10)

   3.3 Shear strength of member in connection (AISC 13th ed. section J3.2)

   3.4. Block shear strength (AISC 13th ed. Section J3.3)

   3.5 Normal tensile strength of bolts in bearing type of connection

   3.6 Available tensile strength of a bolt subject to tension and shear in bearing-type connections

4. LRFD design example

5. ASD design example

1. Design requirement:

LRFD (Load and Resistance Factor) design:

LRFD design:

1. R_u £ fR_n.

Where R_u is factored shear force calculated based on strength design provision of building code.  R_n is nominal shear strength calculated based on AISC 13th ed, f is resistance factor.

ASD (Allowable Stress ) design:

1. R £ R_n/W.

Where R is service load force calculated based on allowable stress design provision of building code, R_n is  normal shear strength calculated based on AISC 13th edition, W = is safety factor.

2. Design procedure:

1. Determine number of bolt based on bolt shear in connecting beam

2. Check number of bolt in supporting beam for shear and tension due to eccentricy.

3. Check bolt bearing on beam web.

4. Check shear strength of beam web.

5. Check block shear of beam web.

6. Check bolt bearing of connection angle.

7. Check gross shear of connection angle.

8. Check block shear of connection angle.

3. Related Code in AISC 13th ed Specifications.

3.1. Nominal Shear Strength of bolts in bearing type of connection

Resistance factor: f = 0.75 (LRFD)

Safety factor: W = 2.0 (ASD)

Nominal Shear strength

R_n = F_nv A_b

Where A_b is nominal unthreaded body area of bolt, F_nv is shown below from AISC 13th ed. TableJ3.2.

3.2. Bearing strength at bolt holes (AISC 13th ed. Section J3.10)

Resistance factor: f = 0.75 (LRFD)

Safety factor: W = 2.0 (ASD)

Nominal bearing strength of bolt holes

a. When deformation at the bolt hole at service load is a design consideration

R_n = 1.2 L_c t F_u  £   2.4 d t F_u

b. When deformation at the bolt hole at service load is not a design consideration

R_n = 1.5 L_c t F_u  £   3 d t F_u

c. The bearing resistance shall be taken as the sum of the bearing  resistance of the individual bolts.

Where d is bolt diameter, t is thickness of the member, F_u is tensile stress of connection material

L_c is clear distance, in the direction of the force, between edge of holes or edge of hole to edge of material.

3.3 Shear strength of beam web in connection (AISC 13th ed. section J3.2)

a. Shear yielding of beam web

Resistance factor: f  = 1.0 (LRFD)

Safety factor: W = 1.5 (ASD)

R_n = 0.6 F_y A_g

Where F_y is yield strength of material, Ag is gross area subject to shear.

b. Shear rupture of beam web

Resistance factor: f  = 0.75 (LRFD)

Safety factor: W = 2 (ASD)

R_n = 0.6 F_u A_nv

Where F_u is minimum tensile strength of material, A_nv is net area subject to shear.

3.4. Block shear strength (AISC 13th ed. Section J3.3)

Resistance factor: f = 0.75 (LRFD)

Safety factor: W = 2.0 (ASD)

R_n = 0.6 F_u A_nv + U_bs F_u A_nt    £     0.6 F_y A_gv + U_bs F_u A_nt

A_gv is gross area subject to shear

A_nt is net area subject to tension

A_nv is net area subject to shear

Ubs = 1 for if only one column of bolt is used., Ubs = 0.5 for more than one column of bolt is used.

3.5 Normal tensile strength of bolts in bearing type of connection    (AISC 13th ed. Table J3.2)

Resistance factor: f = 0.75 (LRFD)

Safety factor: W = 2.0 (ASD)

Nominal tensile strength

R_n = F_nt A_b

Where A_b is nominal unthreaded body area of bolt, F_nt is shown below from AISC 13th ed. TableJ3.2.

3.6 Available tensile strength of a bolt subject to tension and shear in bearing-type connections

Resistance factor: f = 0.75 (LRFD)

Safety factor: W = 2.0 (ASD)

Available tensile strength

R_n = F'_nt A_b

Where A_b is nominal unthreaded body area of bolt, F'_nt is calculated as

F'_nt = 1.3 F_nt - [F_nt/fF_nv]f_v   £  F_nt    (LRFD)

F'_nt = 1.3 F_nt - [WF_nt/F_nv]f_v   £  F_nt    (ASD)

where f_v is required shear stress, ksi.