### Example 14.1.1—Crane Runway Girder Design Example (ASD)

Given:

Use ASCE/SEI 7-16 to design an ASTM A992 W-shape runway girder for a CMAA Class B crane. Assume no reduction in

allowable stress due to fatigue. The design parameters are:

Type of control: cab-operated

Crane capacity = 20 tons (40 kips)

Bridge weight = 57.2 kips

Combined trolley and hoist weight = 10.6 kips

Maximum wheel load (without impact) = 38.1 kips

ASCE 100 lb/yard rail = 34 plf

Combined clamps and electrification weight = 16 plf

Bridge span = 70 ft

Runway girder span = 30 ft

Wheel spacing = 12 ft

Solution:

From AISC Manual Table 2-4, the material properties for the girder are:

ASTM A992

Fy = 50 ksi

Fu = 65 ksi

The critical wheel location with regards to bending moment is shown in Figure 14-1. The wheel location to determine approximate

deflection is shown in Figure 14-2.

The required flexural strength of the runway girder is determined using AISC Manual Table 3-23, Case 44.

Calculate the deflection assuming the wheel locations shown in Figure 14-2. Note that this wheel location will slightly underestimate the deflection as compared to a solution based on the wheel locations shown in Figure 14-1. From AISC Manual Table 3-23, Case 9, with a = 9 ft

### Vertical Deflection

Using the vertical deflection criterion of L/600, the allowable vertical deflection and required x-axis moment of inertia are: