Crane Runway Girder Design Example (ASD)

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

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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: