Design and Construction of Lifting Beams DAVID T. RICKER Lifting beams (also known as spreader beams) are used to assist in the hoisting process. Most erectors and riggers accumulate an assortment of lifting beams during the course of time. Some common profiles are shown in Fig. The basic lifting beam is shown in Fig. Lifting calculation method 3. DYNAMIC FACTOR When the movement of the precast unit is performed by lifting gear, dynamic forces that depend on the lifting gear used, appear. The lifting classes are described in DIN 15018. Lifting factor f is the acceleration factor. When lifting and carrying precast elements, the lifting load has to be.
- Lifting Beam Design Calculations Pdf
- How To Calculate Load Of Beam
- Spreader Bar Rigging Calculations
- How To Do Beam Calculations
- Spreader Beam Calculation
How to Use The Free Beam Calculator
The ClearCalcs beam calculator allows the user to input the geometry and loading of a beam for analysis in a few simple steps. It then determines bending moment, shear and deflection diagrams, and maximum demands using a powerful finite element analysis engine.
Signing up for a ClearCalcs account will unlock further advanced features for design and analysis of beams and a variety of other structural elements. ClearCalcs enables design in steel, concrete and timber, according to Australian, US and EU Standards.
The sheet is divided into three main sections:
- ‘Key Properties’, where the user inputs the geometry of their chosen section and the beam supports.
- ‘Loads’, where the use can input distributed, point and applied moment loads,
- ‘Summary’, which displays the key outputs and diagrams.
A ‘Comments’ section is also included for the user to leave any specific design notes. Clicking on any of the input/property labels gives a descriptive reference explanation.
1. Input Key Properties
The properties of the beam and section are specified by typing directly into the input fields.
Length of Beam is the total including all spans of the beam, in mm or ft.
Young’s Modulus is set to a default value of 200,000 MPa or 29000 ksi for structural steel, but can be edited by the user.
Area of the Cross-Section is specific to the beam section selected, and is defaulted to the values for a common steel beam.
Second Moment of Area (or Moment of Inertia) is also specific to the beam section selected, and again defaulted to the properties of a common steel beam.
The properties E, A, and Ix for other beam sections can be obtained from the ClearCalcs section properties library. Alternately, you can create your own custom section using our free moment of inertia calculator.
Position of Supports from Left allow the user to input any number of supports, and specify their position along the length of the beam. The support type can either be pinned (fixed in translation, free in rotation) or fixed (fixed in both translation and rotation) and is selected from the drop-down menu. A minimum of one fixed support, or two pinned supports are required.
The beam calculator also allows cantilever spans at each end, as the position of the first support does not have to be equal to 0mm and the last support position does not have to be equal to the length of the beam.
The reactions at each of the supports are automatically updated as supports are added, changed or deleted, based on the specified loading.
2. Input Loads
The calculator supports a variety of different loading types which can be applied in combination. Each load can be named by the user.
The sign convention used for loading is (positive values shown):
Distributed Loads are specified in units of force per unit length, kN/m or plf, along the beam, and can be applied between any two points. Two different types can be applied in the calculator:
Uniform Loads have a constant magnitude along the length of application. Therefore, the start and end magnitudes specified by the user must be the same.
Linear Loads have a varying magnitude along the length of application. The different start and end magnitudes must be specified by the user, and they can be used to represent triangular or trapezoidal loads.
Point Loads are specified in units of force, kN or kip, and area applied at discrete points along the beam. For example, these can represent reactions from other members connecting to the beam. The user inputs the name, magnitude and location from the left of the beam.
The example diagram below, from the summary section, shows a two-span continuous beam with a linear distributed patch load and point load.
3. Calculation Summary Outputs
Once the loading and geometry have been specified, the calculator automatically uses the ClearCalcs finite element analysis engine to determine the moments, shear forces and deflections. The maximum values of each are output as ‘Moment Demand’, ’Shear Demand’ and ‘Deflection’, along with the diagrams along the length of the beam.
Positive values imply a downward deflection and negative values imply an upward deflection. The sign convention used in the shear force and bending moment diagrams is (positive values shown):
Using the cursor to hover over any point on the bending moment, shear force or deflection diagrams gives the specific values at that location along the beam. The example below shows the outputs for a two-span continuous beam with a linear distributed patch load and point load.
When planning to design lifting beams (or any other below-the-hook lifting devices), there are many aspects that must be considered beyond finding materials that meets a few basic engineering calculations. Along with stress, buckling is also a critical factor in lifting beams that must be addressed in detail to ensure that the structure can handling the loads imposed on it. ASME BTH-1 clearly defines rules for material selection and determining what kind of load would be permitted by the design in question. Following the procedures outlined in BTH-1, you can successfully design a below-the-hook lifting device that will handle the loads imposed on it.
What is ASME BTH-1
ASME BTH-1 “Design of Below-the-Hook Lifting Devices” is an ASME design standard and is to be used in conjunction with ASME B30.20, the ASME safety standard for Below-the-Hook Lifting Devices.
ASME B30.20 defines the safety requirements for below-the-hook lifting devices including marking, inspection, construction and operation, whereas ASME BTH-1 defines the design requirements for developing these lifting devices. BTH-1 addresses design requirements including:
- classification of the lifting device based on frequency and capacity of lifts,
- structural design requirements related to member design, connection design (pins, bolts, welds), and fatigue,
- mechanical design requirements for the mechanical components (sheaves, wire rope, gears, bearings, shafts, fasteners),
- electrical component requirements for electrical components used to operate below-the-hook lifting devices,
- lifting magnet design requirements.
While BTH-1 is broad in its coverage of design requirements for below-the-hook lifting devices, only portions of the design standard are applicable to spreader bars and lifting beams, in particular beam classification and the structural design requirements. These items are discussed in more detail below.
Classification of Spreader Bars and Lifting Beams
Spreader bars, lifting beams, and other below-the-hook lifting devices are classified based on the frequency and capacity of lifts that are required of the device. In the latest revision of BTH-1 (2017), there are three design categories, categories A, B and C, as well as five different services classes, service class 0 through 5. Together the design category and the service class define the design requirements of the beam related to material strength and fatigue.
Design Category The design category establishes the different stress factors to be used in beam design: Lifting Beam Design Calculations Pdf
- Category A lifters are designated when the magnitude and variation of load is predictable, and require a design factor of 2 on yield/buckling
- Category B lifters are designed for unpredictable lift scenarios where the magnitude of lift can vary significantly and require a design factor of 3 on yield/buckling. This is the most common design category and is what Basepoint Engineering lifting beams and spreader bars are typically designed for.
- Category C lifters are designated for special-application lifting devices where a specified design factor is required and require a design factor of 6 on yield/buckling.
Service Class
The service class designates the number of load cycles, or fatigue life for which a beam is designed. Basepoint Engineering lifting beams and spreader bars are typically designed as Service Class 0, which is for 0-20,000 load cycles, although beams with different service classes can be designed on request. Service Classes 1 through 5 cover load cycles from 20,001 through 2 million load cycles.
Structural Design
How To Calculate Load Of Beam
ASME BTH-1 specifies design calculations for different types of loading of a lifting device including tension, compression, flexure, shear and combined loading of beams. Depending on the style of lifting device, only certain structural design considerations apply to a specific device. For example, a lifting beam with a centre pick point and load suspended on the two ends of the beam are loaded in flexure, therefore compression and tension calculations aren’t specifically relevant to this device. Conversely, for a telescopic spreader bar with a centre pick point and two slings out to the ends of the spreader bar the loading on the beam would be primarily compressive, although if the ends of the spreader bar are set up such that bending is applied to the ends of the spreader bar, then a combination of load calculations must be utilized.
Spreader Bar Rigging Calculations
The structural design section of the standard also includes requirements for connection design including bolted connections (bolt quantity, allowable loading, required tightening and hole requirements), pinned connections (pin hole strength, pin clearance), and welded connections (weld size and properties).
Fatigue design is not required for bars classified as service class 0 due to the low number of total load cycles, but as the number of load cycles is increased, the potential for fatigue failure increases. BTH-1 includes a structural design section covering fatigue requirements for lifting devices classified as service classes 1 through 5.
How To Do Beam Calculations
Mechanical Design, Electrical Components and Lifting Magnets
In addition to all the information previously discussed, ASME BTH-1 also addresses design requirements for mechanical design, electrical components and lifting magnets. These sections of the standard apply to components that are loaded in below-the-hook lifting devices, and in some devices or scenarios they would be relevant. They are not discussed in this article because they do not generally apply to typical spreader bars and lifting beams.
Conclusion
Spreader Beam Calculation
This article is a brief overview of what is covered by ASME BTH-1, particularly with respect to the design of spreader bars and lifting beams. Emphasis was made to focus on the areas of BTH-1 that apply to these devices. If you are looking for more information on BTH-1, feel free to contact us, or you can wait for future articles that will discuss applying BTH-1 to design of lifting beams and spreader bars in greater detail. If you are looking to manufacture spreader bars that have been designed in accordance with requirements of ASME BTH-1, we can provide you with engineered shop drawings of designs that are ready to manufacture. They can be found at our store. If you have a unique design challenge where you could use some engineering assistance, please contact us to see how we can help you.