Beam Strengthening

Overview

An office building has 10 floors above ground and 2 floors underground. The total height of the building is 62.8m, and the building area is about 36210 square meters. The structure of this office building is a cast-in-place reinforced concrete frame-shear structure, and the foundation is a reinforced concrete piled raft foundation. It has been built and put into use for 11 years. In 2011, the building underwent a large-scale functional renovation, requiring the addition of central air conditioning, with a total load of about 43t, which led to an increase in roof load. The original roof design is not a human roof, and the roof live load is small. After calculation and verification, the bearing capacity of some beams of the roof structure layer is insufficient and needs to be reinforced to ensure normal use.

Compare structural reinforcement options

Taking into account economic factors, the process requirements of several commonly used reinforcement methods are compared and based on the specific conditions of the project, the elimination method is used to determine the final reinforcement plan. The specific screening process is shown in the table.

(1) Enlarging the cross-section reinforcement method is to increase the load-bearing capacity of the component and meet the requirements of normal use by increasing the cross-sectional area of the component. The building is an office building with a relatively low original structural floor height. If the ordinary expansion surface method is adopted, the beam height and beam width will inevitably increase, and the self-weight of the structure will increase after reinforcement, and the building space will be reduced.

(2) If sticking steel is used for reinforcement, it is generally used for concrete structures. It is a reinforcement method by sticking steel plates on the surface of components. Generally, wet construction technology is used, that is, structural glue is used to paste section steel or steel plate to the surface of concrete structural members to improve its bearing and deformation capacity, often supplemented by chemical uranium bolt technology. At the same time, bonding steel reinforcement has higher requirements on the working surface of the construction site, and the cost is high and the cycle is long.

(3) Adopt more advanced pre-stressed reinforcement. Although the reinforcement effect is better, it has higher requirements for construction equipment, complicated on-site construction, and relatively high cost.

(4) Adopt the bonding carbon fiber sheet reinforcement method. Its main advantages are convenient construction, short construction period, low requirements on the construction site, and low construction noise.

Through careful screening of the 4 common reinforcement methods mentioned above, it was decided to select a more economical and convenient method of strengthening the beams to be reinforced by sticking unidirectional carbon fiber sheets.

The reinforcement construction of the carbon fiber sheet took a total of 20 days, and the construction speed was fast. The successful practice of the reconstruction and reinforcement of this project proves that for reinforced concrete members that need to increase the load during use, the method of sticking carbon fiber sheet reinforcement is an effective method of reinforcement and reconstruction to ensure the safety of the structure. At the same time, the construction period of the reinforcement method is short, and the project cost is low.