Background: Nowadays, with the rapid development of science and technology, the structural forms of buildings have become diversified. Frame structure is a structure composed of many beams and columns, which bears all the loads of the house. In high-rise civil buildings and multi-storey industrial workshops, brick walls can no longer meet the requirements of heavy load, and frames are often used as load-bearing structures. Concrete frame structures are widely used in residential buildings, schools and office buildings. As a common structural form, it has the advantages of flexible spatial separation, light weight, material saving, clear force transmission, flexible structural layout in line with architectural layout, good seismic resistance and integrity.

Research status at home and abroad: 1. In the aspect of design calculation theory: the reliability theory based on probability theory and mathematical statistics analysis has been adopted in the design code of engineering structures, and the calculation system of probability limit state should be continuously improved; The micro-fracture mechanism of concrete, the multi-axial strength theory of concrete and the calculation theory of nonlinear deformation also need to be broken through and applied to the design of engineering structures.

2. In terms of computer software and hardware. The popularization and multifunction of electronic computers and the development of software systems such as CAD and PKPM have shortened the time and workload of building structure design and improved economic benefits.

3. In material research. Concrete mainly develops in the direction of high strength, light weight, durability, easy forming and high performance concrete with some special properties. The research and development direction of reinforcement is high strength, corrosion resistance, good ductility and good bonding and anchoring performance.

4. In terms of structural form. Because of its good crack resistance, prestressed concrete structures can make full use of high-strength materials, and various applications are developing rapidly. Some high-performance new composite structures have the characteristics of making full use of material strength, good deformation adaptability (ductility) and simple construction, and are also widely used.

5. In terms of experimental technology. Through a lot of research on the design theory, design method and design software of concrete structure, advanced modern urban technology ensures that the experimental research is more accurate and systematic.