Bridge Crane - Structural Mechanics and Metal Structures

Contents

Calculation of crane bridge

Source Data

Selecting Basic Geometric Design Parameters

Selecting Geometric Parameters of Subassemblies

Main beam

End beam

Determining Design Loads on Nodes

steel structures and forces in them

Process Part

Appointment

Operating condition

Construction Description

Justification of technical requirements

Constructability Analysis

Development of process diagram of assembly

Manufacturing Process Development

beam elements

Select Welding Method and Mode

Literature

Specification

Process Part

1. Appointment

Bridge crane is designed for lifting and movement of load in vertical and horizontal plane.

The steel structure of the crane end beam takes loads from the weight of the load, the main beam, lifting and moving mechanisms, the cockpit, as well as from its own weight. The load through the end beam is transmitted from the main beam to the axle boxes, then to the wheels, then to the rails.

Metal structures largely determine the mass, cost, and operational reliability of lifting and transportation machines. They operate under different loads, environments and must meet the requirements of rigidity, strength, stability and economy.

2. Operating conditions

The end beam operates under medium conditions, which are characterized by work with loads of different weights, with average speeds (vk = 1.25 m/s, vt = 0.63 m/s, vp = 0.28 m/s), the average number of inclusions per hour (up to 120 per hour), the average value of relative duration of inclusion (up to IR = 50%).

3.Structure Description

End beam is support and connecting element of main beam. To install crane undercarriage, mounting plates with treated surfaces are welded to end beams to which axle boxes with running wheels are bolted. On the end beam there are elastic safety devices - buffers, which operate at the crane position in the endpoints of the path, interacting with stops at the end of the crane path and softening the crane impact on these stops.

The end beam is a rigid welded metal structure, the overall dimensions of which are 5750x570x450.The metal structure of the end beam consists of two belts, two vertical walls and diaphragms located inside the beam. Since the length of the beam is small, it is made single-connector in order to disconnect the bridge after its manufacture into two halves for better transportation by rail. Split parts of the beam are connected by means of mounting strips at the manufacturer with installation of 20% of clean bolts of the total number of black bolts. When installing the crane at the site of operation, the joints of the beams with the mounting strips are connected with rivets or clean bolts. The main parameters and elements of the end beams are unified by load capacity groups, which made it possible to create typical technological processes for their manufacture.

The material for the elements of the steel structures of the end beams is steel sheet St3.sp. Thickness of used sheets for beam belts 10 mm, vertical walls and diaphragms 6 mm.

Welding of belts with walls is performed externally. The walls and belts in the beam are very thin elements, therefore, under the influence of internal forces, normal and tangent stresses (especially when reaching critical values), the walls and belts can lose their flat shape and exit the plane, which will lead to fatigue damage.

The diaphragms are welded to the beam section on three sides. Diaphragms are not welded to the stretched belt. Between them there is a technological gap of 10 mm. Along the length, the beam has a variable section (variable height of the beam) so that it meets the conditions of static and dynamic stiffness and the time of attenuation of oscillations. Bevels 75 mm long are made from local stability conditions.

Important from the design point of view is the connection of the main beams with the end beams. This connection must be rigid enough to perceive bending moments at the joints of the beams under horizontal loads. The horizontal rigidity of the bridge largely depends on the amount of skew of the crane during movement and the degree of wear of the running wheels. Since beams work on a bend in the horizontal plane, they must have sufficient rigidity in this direction, so the moment of inertia of their sections relative to the vertical axis is taken no less than the moment of inertia of the section of the main beam at the point of their connection. The connection of the main beams with the end beams is carried out by overlapping welding, which sharply reduces the labor input for the manufacture of metal structures. To improve the quality of the weld, linings are used, which leads to an increase in the weld, therefore, to the separation of structural and technological concentrators, and this increases the endurance limit and fatigue strength. In order to avoid stress concentrations and therefore fatigue fractures, sharp corners of welds must be rounded. This seam design is typical. It is the most technological, does not require a lot of money and is easy to manufacture.

At the point of connection of the main beam to the end, it is necessary to mate: opposite the inner diaphragm of the end beam there should be walls of the main beam. Straps welded from below increase stiffness. For connection of running wheels on end beam there made are plates for axle boxes.