What is a tie rod?

The tie rod is a kind of structure which is used to pre tighten the rotor. The structure of the tie rod, the selection of the pre tightening force and the arrangement of the shoulder will have a great impact on the overall dynamic characteristics of the rotor. There is often a kind of structure on building materials. At the same time, many building structures or materials will be built into tie rod type. Such as single-layer cylindrical reticulated shell, diffraction grating engraving machine, etc.

Here is the content list:

What are the physical and engineering principles of tie rods?

Analyze the installation clearance between different pull rods

The application program of tie rods

What are the physical and engineering principles of tie rods?

In general, because the length to cross section ratio of a typical tie rod is usually large, it will bend under the action of compressive force. The working strength of the tie rod is the product of the allowable working stress and the minimum cross-sectional area of the tie rod. If the thread is cut into a cylindrical rod, the minimum area appears at the root of the thread. In general, the tie rod will become thicker (at the end) so that the tie rod will not weaken when it cuts into the thread.

Tie bars can be connected at the ends in various ways, but the strength of the desired connection should be at least equal to that of the bar. The end can be threaded through the drill hole or hook ring and fixed by a nut screwed on the end. If both ends are right-handed threads, the length between the loading points may change.

This provides a second way to change the length by randomly pre tightening the rod by rotating the rod in the nut. One turnbuckle will do the same. The ends may also be forged to accommodate the fittings attached to the support. Another method of termination is to forge a hole or hook on the rod. On July 17, 1981, the sidewalk of the Regent Hyatt Hotel in Kansas City, Missouri, collapsed, a notorious structural failure involving tie rods. The hotel has a large atrium with three crosswalks suspended from the tie rods. Construction errors led to the collapse of several pedestrian walkways, resulting in 114 deaths and more than 200 injuries.

Analyze the installation clearance between different pull rods

The main conclusions are as follows:

(1) The static installation clearance between the pull rod shoulder and the pull rod hole does not affect the stress of the pull rod under normal working condition, but affects the maximum stress of the pull rod when the rotor speeds up;

(2) With the increase of rotational speed, there are three rotational speed regions with different variation rules of the maximum stress value of the circumferential tie rod rotor pull rod. The fundamental reason is the influence of the contact state between the pull rod shoulder and the tie rod;

(3) The results show that increasing the shoulder and reducing the shoulder span can effectively reduce the maximum stress of the tie rod. Compared with the unequal distance scheme, the improved scheme with equal distance increasing the shoulder of the tie rod has a more significant effect on reducing the stress. When the relative shoulder span coefficient is less than 0.6, the effect of reducing the shoulder span is not obvious.  

The application program of tie rods

1. In the aircraft structure, sometimes the tie rod is used in the fuselage or wing.

2. Tie rods are commonly used in steel structures such as bridges, industrial buildings, water tanks, towers and cranes.

3. Sometimes, the tie rods are converted into bendable or collapsible masonry walls (brick, block, stone, etc.) to prevent them from yielding to lateral forces.

4. The use of reinforced concrete in reinforcement is not called "tie rod", but it basically performs some of the same tension as the force counteracting the purpose of tie rod execution.

5. In the automobile, the tie rod is a part of the steering mechanism. They differ from the prototype in their push and pull (both in tension and compression). In the UK, these items are often referred to as tracking poles.

6. In the steam locomotive, the pull rod is a rod connecting multiple driving wheels to transfer the power from the connecting rod.

7. Tie bars, sometimes called drop bars, are used in combination with pur bars to withstand load components parallel to the roof.

8. The bicycle hub of the spoke is a tie rod.

9. In the ship, the tie rod is the bolt which makes the whole engine structure in compression state. They provide fatigue strength. They also provide proper travel alignment to prevent fretting. They help to reduce the bending stress transferred to the beam.