In the structural reinforcement project, the enlarged section method and the outsourcing steel method are often compared like the south Murong and the north Qiaofeng. First of all, both of them are one of the traditional reinforcement methods. The technology is mature and widely used. There are many similarities, but in practical applications, there are still some differences.

1）definition

Enlarged section reinforcement

Enlarged section reinforcement technology is also known as outsourcing concrete reinforcement technology. It mainly increases the section and reinforcement of the component, thereby improving the strength, stiffness, crack resistance and stability of the component. This method can also be applied to crack repair, but the most commonly used places are beams, columns, foundations, slabs, roof trusses and other components.

Outsourcing section steel method

Outsourcing section steel method, usually use section steel or steel plate to cover the surface, four corners or both sides of the original component, and pour high-strength cement mortar or epoxy resin slurry between the surface of the concrete component and the gap of the outer steel. At the same time, horizontal slats or ferrules are used as connectors to improve the overall mechanical performance of the reinforced member. It can be divided into two forms: dry outer steel and wet outer steel.

2） application

Enlarged section reinforcement

It is suitable for the reinforcement of common components such as concrete beams, slabs and columns, as well as bending or compression (axial and eccentric) components. This method is also more suitable for beam and plate members with poor bearing capacity and low stiffness. However, the premise of applying this method is that the strength grade of the original concrete tested on site needs to be ≥C10. If the superimposed layer is in the tension zone, it can play a similar role as the steel bar protection layer. If it is in the compression zone, the effective height of the section of the member can be increased to achieve the purpose of improving the bearing capacity of the member.

Outsourcing section steel method

It is suitable for the reinforcement of concrete structures that do not allow a significant increase in the cross-sectional size of the original member, but requires a substantial increase in its bearing capacity, and is mostly used for reinforcement of columns. Among them, the general bending and tension members that are subjected to static force require that the ambient temperature does not exceed 60 °C, the relative humidity does not exceed 70%, and there is no chemical corrosion, otherwise effective protective measures should be taken. When the concrete strength of the member is lower than C15, this method should not be used for reinforcement.

3) materials

Enlarged section reinforcement

The main materials are: steel bar, planting bar glue, concrete (or cement-based grouting material mixed with fine stone concrete)

Outsourcing section steel method

The main materials are: angle steel, trim board, epoxy structural adhesive (pouring glue)

4) process

Enlarged section reinforcement

Positioning and lay-out→Interface processing→Drilling and hole clearing→Gluing and planting→Connecting and binding reinforcing steel→Supporting formwork→Pouring concrete→Curing and curing→Quality inspection

Outsourcing section steel method

Cleaning components → repairing and leveling → positioning and laying out → steel processing → steel frame installation → plate welding → positioning drilling → pre-embedded glue injection device → edge sealing treatment → air pressure test → configuration of pouring glue → glue injection construction → static maintenance →Quality inspection →Protection treatment

5)advantages

Enlarged section reinforcement

1. The strength, stiffness and stability of the components are significantly improved. The effect is guaranteed;

2. At the same time, it can be flexibly designed as one-sided, two-sided or three-sided jackets according to the force characteristics and reinforcement purposes, which provides flexible processing methods for some components that are difficult to construct;

3. It is not limited to increase the strength by 40% like other fixing methods, which is especially suitable for the situation where the bearing capacity is quite different;

Outsourcing section steel method

1. The force is reliable, and the bearing capacity of the structure and components can be significantly improved;

2. The construction is simple and the wet work is less, especially suitable for the reinforcement of emergency reinforcement projects;

3. Compared with the concrete surface layer and the cross section of the original concrete member, the reinforcement has little influence on the appearance and clearance of the house, and the cross-sectional area of the member has no obvious change, which is aesthetically pleasing.

6)disadvantage

Enlarged section reinforcement

1. Compared with other reinforcement methods, there are more construction techniques involved, and the site wet operation is large and the cycle is long, which has a certain impact on site production and life;

2. The joint processing of new and old concrete, welding of new and old longitudinal bars and stirrups is cumbersome, and the quality of completion has a great influence on the quality of the construction team;

3. The self-weight and section size of the structure itself are increased, and the stiffness distribution of the structure itself may also be changed, resulting in the interlocking reinforcement of other adjacent components.

4. When the section of the component is increased, the dead load of the upper structure will increase, which will have a certain impact on the original structure and the bearing capacity of the foundation.

Outsourcing section steel method

1. The price of steel is high, the consumption is large, and the maintenance cost of the later protection of the steel plate is high, and the economic benefit is slightly inferior to the method of increasing the section.

2. Before construction, the surface of the original component must be smooth and free of debris and dust, and the cleanliness of its interface is required to be high, otherwise it will affect the construction quality and bonding performance.

3. The reinforcement effect mainly depends on the connection performance of the newly added section steel and the original concrete, so the external bonded section steel reinforcement method has high requirements on the horizontal hoop, glue quality and welding quality.

Summarize

Compared with the outsourcing steel method, the increased section method has a wider application range, a greater increase in strength and stiffness, and a lower price. Compared with the enlarged section method, the outsourcing steel method has a simpler process, a faster construction period, and hardly affects the cross-sectional area and headroom of the component.