Can increasing stiffness increase bridge load ratings

1. The bridge load grade can only be used as a data for bridge stress analysis, and cannot specifically correspond to how many tonnages. At present, the bridge load is expressed in the form of a concentrated force and uniform load, such as a first-class highway and a second-class highway. The concentration takes into account the influence of the bridge length, and the longer the bridge, the higher the probability of heavy traffic on the bridge.

So the magnitude of the concentrating force varies according to the span.

2. Bridge load refers to the general term of various possible loads that should be considered in the design of bridge structures, including dead load, live load and other loads. Including railway train live load or road vehicle load, and the impact force, centrifugal force, lateral posture sway force, braking force or traction force caused by them, crowd load, and the earth pressure generated by the train and rolling stock.

Compared with other bridge forms, suspension bridges have light self-weight and poor structural rigidity.

A suspension bridge is a bridge with cables suspended by pylons and anchored on both sides as the main load-bearing components of the superstructure. The way suspension bridges are constructed was invented in the early 19th century, and many bridges use this way of construction. Because the suspension bridge can make full use of the strength of the material, and has the characteristics of saving materials and light weight, the suspension bridge has the largest spanning capacity among the bridges of various systems.

Suspension Liming Bridge is one of the main forms of extra-large span bridges, except for the Sutong Bridge and the Hong Kong Stonecutters Island Bridge, the other spans of more than 1000m are suspension bridges. If the carbon fiber with light weight and high strength is used as the main cable, its limit span can theoretically exceed 8000m.

The history of suspension bridges is ancient. Early tropical hominids used vines, bamboos, and tree stems from the forest to make suspension bridges to cross streams, using suspension cables that were vertical, cable-pulled, or a mixture of both. Borneo, Laos, and Java primitive rattan and bamboo bridges are the prototypes of early suspension bridges.

The earliest prototype of suspension bridges with written records belonged to China, and until today, it is still influencing the development of suspension bridge forms in the world.

Construction technology of suspension bridge:

1. Construction of the main tower.

The suspension bridge is generally higher than the main tower, and most of the tower body is poured in sections by the turning formwork method, and attention should be paid to the reserved steel bars and formwork support embedded parts at the part of the main tower connecting plate. The concrete at the top of the saddle channel should be poured after the main cable is erected, so as to facilitate the construction of the saddle and the cable.

2. Saddle application and rework.

Check the elevation of the top surface of the steel plate, clean the pin holes on the surface and around after meeting the design requirements, hoist in place, align the pin holes to make the base and the steel plate pin. Oiling the surface of the base and installing the saddle body. The cable saddle is composed of a cable seat, a bottom plate, and a cable cover part, and the overall hoisting and positioning of the cable saddle is difficult; It can be hoisted and assembled in blocks by crane or winch equipment.

3. The main beam is poured.

The pouring of the main girder concrete is the same as that of the ordinary bridge, first of all, the control of the elevation of the beam body must be accurate, and the settlement deformation of the reserved support must be accurately calculated; Secondly, the pre-embedding of the embedded part of the beam body requires high precision, especially the reserved hole of the tie rod should have an accurate position and good verticality, so as to ensure that the tie rod is always located in the center of the hole limb shed in the normal tensioning process.

The bending stiffness is ei, which is the ratio of the bending moment m to the angle of turn. Its value is a constant, which can be derived from the differential equation of the deflection curve of the elastic homogeneous material beam:

ei=m/(1/r)=m/φ

Where: m—maximum bending moment in the span;

r—radius of curvature of the section;

ei—the bending stiffness of the cross-section of the beam, e is the elastic modulus of the elastic material, i is the moment of inertia of the cross-section;

Section curvature. Linear stiffness is defined as the ratio of ei to length. Linear stiffness i = ei l bending stiffness is equal to the product of the elastic modulus e and the moment of inertia i i of the beam section with respect to the axis of interest. In other words, bending stiffness is.

According to the underlying beam theory, the relationship between the applied bending moment and the resulting beam curvature is where is the deflection of the beam. In the definitions in the above text, a minus sign is sometimes used to indicate the convention on which it is based.

Stiffness refers to the ability of a material or structure to resist elastic deformation when subjected to force. It is a characterization of the ease with which a material or structure can be elastically deformed. The stiffness of a material is usually measured in terms of the modulus of elasticity e.

In the macroelastic range, stiffness is the proportionality factor of the part load proportional to the displacement, i.e., the force required to induce the unit displacement. Its reciprocal is called compliance, which is the displacement caused by a unit force. Stiffness can be divided into static stiffness and dynamic stiffness.

If you don't know the norm, don't talk nonsense.

Ultimate limit state: The total coefficient of the second order is.

Permanent load + car load + crowd).

Short-term combinations. 1 * permanent load + car (excluding impact) + crowd.

Long-term portfolio. 1 * permanent load + car (excluding impact) + crowd.

For details, please refer to the General Code for Highway Bridge and Culvert Design.

For the ultimate state of bearing capacity, how to control the short-term and long-term, the following specifications have provisions and instructions.

1. Combination of permanent load control:

2. According to the combination of variable load control:

whichever is greater:

You're Ge Er.,You don't study it well.,Run up and beg others.。。。

You Ge Er, can you not be ashamed when you come out.

The structural form of the bridge, the form of bridge deck pavement, bearings, box girders, supporting pads, bridge piers, and pile foundations. Together, this monolithic bridge structure carries the load action from above the road surface. With different bridge grades and materials, the bearing capacity and traffic capacity of high-grade pavement are higher.

In short, the bearing capacity of the bridge is the capacity of the bridge to withstand the action of the vehicle.

The structural form of the cross-section is divided into a surface layer, a base layer, a cushion layer and a subbase layer. This overall pavement structure collectively carries the load action from above the pavement. Depending on the grade and material of the road, the bearing capacity and traffic capacity of the high-grade pavement are higher.

In short, the carrying capacity of the highway is the capacity of the highway to measure the size of the vehicle.