# Code-check of bolts according to Hong Kong Code

### Bolts in tension

Bolt resistance in tension is checked according to Cl. 9.3.7.1 as:

\[ P_t = A_s \cdot p_t \]

where:

- \(A_s\) – tensile stress area
- \(p_t\) – tension strength obtained from Table 9.8

Prying forces are taken into account by finite element analysis.

### Bolts in shear

Shear capacity of bolts is taken according to Cl. 9.3.6.1.1 as:

\[ P_s = p_s \cdot A_s \]

where:

- \(p_s\) – design shear strength obtained from Table 9.5
- \(A_s\) – effective shear area; \(A_s = A_t\) if threads are intercepted by shear plane, \(A_s\) is taken as the cross sectional area of the shank otherwise
- \(A_t\) – tensile area

According to Cl. 9.3.6.1.6, when a bolt passes through packing with thickness \(t_{pa}\) greater than one-third of the nominal diameter \(d\), its shear capacity \(P_s\) should be reduced by multiplying a reduction factor \(\beta_p\) obtained from:

\[ \beta_p = \frac{9d}{8d+3t_{pa}} \le 1 \]

### Bolts in combined tension and shear

Combined tension and shear is checked according to Cl. 9.3.8.1 as:

\[ \frac{F_s}{P_s} + \frac{F_{tot}}{P_t} \le 1.4 \]

where:

- \(F_s\) – shear force in a bolt
- \(P_s\) – shear resistance of a bolt
- \(F_{tot}\) – total applied tension in the bolt including the prying force
- \(P_t\) – tensile resistance of a bolt

### Bolts in bearing

**Bearing capacity of bolts** is taken according to Cl. 9.3.6.1.2 as:

\[ P_{bb} = d \cdot t_p \cdot p_{bb} \]

where:

- \(d\) – nominal diameter of the bolt
- \(t_p\) – thickness of the connected plate
- \(p_{bb}\) – bearing strength of the bolt obtained from Table 9.6

Each plate is checked separately and the worst result is shown.

**Bearing capacity of connected parts** is taken according to Cl. 9.3.6.1.3 as the minimum of the following:

\[ P_{bs} = k_{bs} \cdot d \cdot t_p \cdot p_{bs} \]

\[ P_{bs} = 0.5 \cdot k_{bs} \cdot e \cdot t_p \cdot p_{bs} \]

\[ P_{bs} = 1.5 \cdot l_c \cdot t_p \cdot U_s \le 2.0 \cdot d \cdot t_p \cdot U_b \]

where:

- \(k_{bs}\) – hole coefficient taken as
- for standard holes \(k_{bs} = 1.0\)
- for oversized and short slotted holes \(k_{bs} = 0.7\)
- for long slotted holes \(k_{bs} = 0.5\)

- \(d\) – nominal bolt diameter
- \(t_p\) – connected plate thickness
- \(p_{bs}\) – bearing strength of connected parts
- for steel of grade S275, \(p_{bs} = 460\) MPa
- for steel of grade S355, \(p_{bs} = 550\) MPa
- for steel of grade S460, \(p_{bs} = 670\) MPa
- for steel of other grades, \(p_{bs} = 0.67 (U_s+Y_s)\)

- \(e\) – edge distance in the direction of the shear force measured from the centreline of the bolt
- \(l_c\) – net distance between the bearing edge of the holes and the near edge of adjacent hole in the same direction of load transfer
- \(U_s\) – minimum tensile strength of connected plate
- \(Y_s\) – characteristic yield strength of connected plate
- \(U_b\) – specified minimum tensile strength of bolt