Structural Design Tips for Crane Girder

September 1, 2021



Objective of This Guide

The analysis and design of the crane moving load calculate the influence of the vertical and horizontal loads (Max./Min. node displacement, Max./Min. member strength, and reaction) caused by moving the crane on the crane girder, and it means a series of analyses and design processes for designing crane girder under common structures.

This material explains the use of the crane girder analysis and design features in midas nGen, and provides the relevant technology and verification data for this analysis and design.

Two types of crane girders can be supported by nGen. As shown in Fig. 1, there is a "General (type) Crane Girder" that resists vertical and horizontal forces caused by the crane itself. There is a "Composite (Type) Crane Girder" which can be combined with horizontal truss and back girder to integrate with horizontal force.

Figure 1. Concept of General Crane GirderFigure 1. Concept of General Crane Girder





Figure 2 Concept of Composite Crane Girder

           Figure 2. Concept of Composite Crane Girder


Generally, when the crane capacity is not large, a General Crane Girder can be used. In the case of a crane having a large capacity and a large horizontal force, as shown in Fig. 2, Composite Crane Girder Resistant with the back girder and back truss can be used.

Chapters 1 and 2 provide the concept of general crane girder and tutorial data. And Chapters 3 and 4 provide the concept of composite crane girder and tutorial data.



Chapter 1. Introduction of General Crane Girder

(Moving Load Analysis and Design Technical Background)


1.1. Element Concepts (Introduction of 1D-Beam Elements and Supportable Section)

General Crane Girder is best simulated with a 1D Beam to analyze the impact of crane travel on the elements. Influence points are used to analyze the impact of moving weights (Figure 3). Here, the more Influence Points, the more accurate the moving-weight analysis results are, and the number of influence Points can be pre-specified by the user.

Figure 3. 1D Beam Element and Influence points concept

Figure 3. 1D Beam Element and Influence Points Concept


Meanwhile, General Crane Girder in the analysis and design supports 1D Beam member with certain sections, or, as shown in the Table-1, H-shape, H-shape with Flange Plate, H-C Combined Shape are used mainly.


Table 1 Crane Girder Main Section Shape

Type Combine Type Single-Sided Shape Design Substitution
H-Shape - Table1 h-shape


H-Shape with Flange Plate - Table1 h-shape with flange plate


H-Shape with Flange Plate
H-C Combined Shape Downward Table1 h-c combined shape





1.2. Influence Points of Concept

Figure 4 shows the calculation of the influence line results that were calculated by the unit weights over each point. Each of the influence points you specify has the following impact line results, where you can enter the wheel information of the crane to determine the analysis (maximum) member force, etc. for each Influence point.

Figure 4 Effect line of unit weight on influence point

Figure 4. Effect Line of Unit Weight on Influence Point


1.3. Check Position Concept

Check Position is an in-member calculation point that is recognized when performing a design after analysis, and the program assigns four sections (Figure 5) as Check Position, and you can adjust the number of Check Positions according to your intentions. The selected member is determined by NG, OK or Not Checked, which of the check positions the member has the most unfavorable Rating, and provides a one-of-a-kind view of the calculation report in the output of the detailed calculation.

Figure 5 Check Positions of Absence

Figure 5. Check Positions of Absence




Chapter 2. General Crane Girder: Introduction to Analysis and Design Procedures


This chapter uses the Crane Framing Plan in 3 spans (column 14 to column 17) of Figure 6 to follow a simple General Crane Girder model: Each column has a column spacing of 10m, and cranes with a capacity of 100Ton are located between columns D and E. Each crane girder is simply supported so that no source moment occurs.

Figure 6 Crane Framing Plan

Figure 6. Crane Framing Plan


Figure 7 shows crane wheel information and crane girder information. Crane bridge has a span of 10m, hook approach has 1m. The crane has a capacity of 1,000 KN, trolley and Hoist weighs 250 KN, and has a self-weight of 250 kN. There are eight wheels at each side of the crane bridge, the wheel load acting on each wheel is assumed to be the same.


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About Author
Young-il Seo | Principal Structural Engineer

Young-il has over 13+ years of experience in building design, especially high-rise buildings with column reduction analysis, plant structures, pushover analysis, health monitoring, and vibration control projects. Since 2016, he is planning and providing technical supports for midas building products such as midas Gen, nGen, and Design+.

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for Crane Girder

This material explains the use of the crane girder analysis and provides
the relevant technology and verification data for this analysis and design.

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