As the core component directly bearing heavy loads, the gantry's structural design must comprehensively consider static, dynamic, fatigue strength, stability, and environmental adaptability to ensure safe and reliable operation under complex working conditions.
From a static perspective, the gantry must possess sufficient static strength to withstand the rated load. During design, mechanical calculations must be used to determine the stress distribution of each component, ensuring that material stress does not exceed allowable stress under maximum load. For example, the main beam, as the primary load-bearing structure, requires optimization of its cross-sectional shape and dimensions based on bending moment and shear force distribution, typically employing box-type or truss structures to enhance bending resistance. Simultaneously, key components such as hooks and pulley blocks require finite element analysis to verify local stress concentration and prevent fracture accidents due to design flaws.
Dynamic conditions are another key aspect of gantry design. Gantry generates inertial loads during lifting, braking, or operation, and the impact of these additional loads must be assessed through dynamic analysis. For example, the impact load generated when the lifting mechanism starts and the load suddenly leaves the ground may reach 1.2 to 1.5 times the rated load; a sufficient safety factor must be included in the design. Furthermore, the acceleration of the trolley or crane during operation generates horizontal inertial forces, requiring a well-designed braking system or the addition of buffer devices to reduce the dynamic impact on the spreading equipment.
Fatigue strength requirements address the long-term service needs of the spreading equipment under alternating loads. Gantry spreading equipment typically endures frequent lifting-lowering cyclic loads, making it prone to metal fatigue. During design, fatigue life targets must be determined based on the working class (e.g., M3, M4), and fatigue performance can be improved by optimizing structural details (e.g., reducing welds, avoiding stress concentration). For example, the critical section of the hook should have rounded corners to prevent crack initiation caused by right-angle cuts; the matching design of the wire rope and pulleys must also consider bending fatigue, selecting appropriate rope diameter ratios and pulley diameters.
Stability requirements relate to the spreading equipment's resistance to overturning under inclined or eccentric loading conditions. When the spreading equipment is subjected to eccentric or wind loads, lateral moments may be generated, requiring structural stiffness or additional balancing devices to ensure stability. For example, lifting equipment for double-girder gantry systems requires rigid connections for synchronous lifting to prevent overloading on one side and subsequent overturning. Outdoor lifting equipment must also consider wind loads, improving wind resistance stability by adding wind-resistant wedges or anchoring devices.
Environmental adaptability requires lifting equipment to withstand specific mechanical environments under different working conditions. In high- or low-temperature environments, material properties may change, necessitating the selection of steel with appropriate temperature ranges (such as low-temperature toughness steel). In corrosive environments, galvanizing and painting are necessary to reduce the impact of rust on structural strength. Furthermore, humid environments may reduce the insulation performance of electrical systems, requiring moisture-proof design for the control system of electric lifting equipment.
Material selection and manufacturing processes directly affect the mechanical properties of the lifting equipment. The use of high-strength steel can improve structural load-bearing capacity, but it must be combined with appropriate heat treatment processes to eliminate residual welding stress and prevent brittle fracture. Welding quality is a critical control point; welds must be inspected using ultrasonic testing to ensure the absence of cracks, porosity, and other defects. Assembly precision also requires strict control to prevent operational jamming or additional vibration due to excessive component gaps.
Safety redundancy design is the last line of defense for the lifting gear structure. By adding safety devices such as lifting capacity limiters and height limiters, structural failures caused by overloading or misoperation can be prevented. For example, when the load exceeds the rated value, the limiter will automatically cut off the lifting power; the height limiter can prevent the hook from hitting the top and causing the wire rope to break. These devices, together with the lifting gear itself, form multiple layers of protection to ensure the safe operation of the gantry.
