1 Scope
This document specifies the application of GB/T 22437.1-2018 to bridge and portal cranes as defined by ISO 4306-1 and gives specific values for the coefficients used.
2 Normative references
The contents of the following documents constitute essential provisions of this document by means of normative references in the text. Among them, note the date of the reference document, only the date of the corresponding version applicable to this document; do not note the date of the reference document, its latest version (including all the revision of the list) applicable to this document.
GB/T 6974.5-2008 Cranes, Terminology, Part 5: Bridge and portal cranes (ISO 4306-5; 2005, IDT)
GB/T 10183.1-2018 Cranes, wheels and track tolerances for large and small vehicles, Part I: General provisions (ISO 12488-1:2012, IDT)
GB/T 20863.1-2021 Cranes, classification, part 1: general provisions (ISO 4301-1:2016, IDT)
GB/T 22437.1-2018 Design principles for cranes, loads and load combinations: Part 1: General provisions (ISO 8686-1:2012, IDT)
GB/T 30024-2020 Proficiency testing of metal structures for cranes (ISO 20332:2016, IDT)
ISO 4302:2016 Cranes-Wind load assessment
3 Terms and definitions
The terms and definitions defined in GB/T 6974.5-2008 and GB/T 22437.1-2018 apply to this document.
4 Symbols
The following symbols apply to this document.
5 Loads and applicability factors
5.1 Conventional loads
5.1.1 General requirements
In the validation calculations of the resistance to yielding, elastic instability and, if required, fatigue failure, the conventional loads in normal operation shall be considered in accordance with 6.1 of GB/T 22437.1-2018 and the following amendments.
5.1.2 Lifting and gravitational effects acting on the crane mass
5.2 Incidental loads
5.2.1 Overview
According to GB/T 22437.1-2018 and the following amendments, incidental loads and effects that rarely occur should be considered in the verification of the ability to prevent elastic instability, but can normally be excluded from the fatigue assessment.
5.2.2 Loads due to skewed operation
5.2.2.1 General rules
In general, skew loads are usually treated as incidental loads and should be attributed to load combination B. However, their frequency varies with the type of crane or trolley, the form of construction. The frequency of their occurrence varies with the type of crane or trolley, the form of construction, the accuracy of the parallelism of the axles and the operating conditions. In individual cases, the frequency of occurrence will determine whether they are incidental or conventional loads.
For cases with anti-skew operating devices, the skew lateral forces calculated without taking into account the effect of the anti-skew devices shall be assigned to load combination C. If the crane can be used normally without the anti-skew devices, the skew lateral forces shall be assigned to load combination B. The skew lateral forces for supported cranes and trolleys shall be considered in accordance with 5.2.2.2 to 5.2.2.4 and the considerations given in Appendix A. The simplified method of calculating rigidity and flexibility of crane structures. The deflected lateral force of a suspended crane should be calculated according to 5.2.2.5.
Note 1:The method given in 6.2.2 of GB/T 22437.1-2018 is applicable to rigid structures. As overhead cranes and portal cranes have both rigid and flexible characteristics, a more general method needs to be given. Furthermore, this method takes into account the flexible structure, the uneven number of wheels, the uneven distribution of wheel pressure and the different types of guiding devices and anti-skew devices.
Note 2: When the direction of the rolling synthesis of the crane operation no longer corresponds to the direction of the track, and when the front guide is in contact with the track, a skewed lateral force is generated by the skewed operation. This is caused by tolerances and errors in the manufacture of the crane (wheel holes) and the running track (bending, twisting). The size and distribution of the skewed lateral force depends mainly on the clearance between the track and the rim or guide wheel and the position of the guide wheel, but also on the number of wheels. Layout. The bearing arrangement and the synchronisation of the rotational speed as well as the flexibility of the structure.
Note 3: The use of anti-deflection devices during operation reduces the guiding forces between the track and the guide, which also reduces the lateral slip of the wheels, but it is advisable to take into account the influence of the small amount of lateral slip that remains due to the horizontal deflection tolerance of the wheels and the lateral deformation of the structure.
5.2.2.2 Deflection angle
5.3 Special loads
5.3.1 Overview
According to GB/T 22437.1-2018 and the additions and amendments described below, special loads and their effects also rarely occur and can usually be equally disregarded in fatigue assessment. Special loads include those caused by tests, non-working winds, cushioning forces, tipping and unplanned stoppages, failure of drive components and external excitation of the crane's foundation supports.
5.3.2 Test loads
The test load shall be applied in the crane's operational configuration. The crane system should not be altered, for example by increasing the counterweight.
According to 6.3.2 of GB/T 22437.1-2018, the total lifting mass suspended from the crane shall be multiplied by a factor $s under test load conditions.
In the validation calculations for the test condition, the minimum level of wind speed given in GB/T 22437.1 - 2018 shall be considered only for outdoor cranes.
5.3.3 Loads due to buffering forces
For applications where buffers are used, the collision force calculated by means of rigid body analysis shall be multiplied by the buffer collision elasticity effect factor (z) to reflect the dynamic effect according to 6.3.3 of GB/T 22437.1-2018 and the following correction.
5.3.4 Loads due to unplanned stoppage
The load due to unplanned stoppage shall be calculated according to 6.3.6 of GB/T 22437.1-2018 and the following correction. s shall be set to 2 or determined by experiment or dynamic analysis.
5.3.5 - Loads due to accidental failure of a mechanism or component
For safety reasons, these loads shall be taken into account when two (duplex) mechanisms or components are used or when they are otherwise protected.
It should be assumed that failure can occur in any part of either system. In the case of protection by a back-up brake, it shall be assumed that the failure of the working brake system and the activation of the back-up brake occur under the most unfavourable conditions.
The loads resulting from these failures should be calculated in accordance with 5.1.5 and any resulting effects should be taken into account. For both cases below, calculations shall be made for both sets of (twin) components of the hoisting mechanism.
5.4 Other loads
Other loads that should be considered according to 6.4 of GB/T 22437.1-2018 include installation loads, dismantling loads and loads on platforms and access roads.
6 Applicable loads, load combinations and coefficients
The coefficients n given in table 8, which take account of dynamic effects, should be used in the load combinations.
7 Combination of acceleration effects
For bridge and portal cranes, the load is moved by the hoisting mechanism (H), the large vehicle running mechanism (Lt), the small vehicle running mechanism (Ct) or the slewing mechanism (SI) (see Figure 4).
The acceleration effect of these mechanisms acting simultaneously on the crane depends on the crane control system and the operating conditions as well as whether the load is lifted from the ground or from a suspended position.
Therefore, the calculated rigid body acceleration forces should also be multiplied by a factor $p. When considering positioning effects, only one positioning effect is used in combination with the other movements.
In load combinations C6 or C7 or C9, only the dynamic effects of "unintentional stop" or "unintentional failure of a mechanism or component" or "dynamic cut-off of the hoisting force limiter" should be taken into account, but not the other dynamic effects. Other dynamic effects are not taken into account, assuming that these occur during steady state operation.
The combinations of acceleration effects are given in Table 10.
Appendix A (Informative) Deflected operational loads: assumptions for simplified calculation methods
Bibliography
1 Scope
2 Normative references
3 Terms and definitions
4 Symbols
5 Loads and applicability factors
6 Applicable loads, load combinations and coefficients
7 Combination of acceleration effects
Appendix A (Informative) Deflected operational loads: assumptions for simplified calculation methods
Bibliography
