Dapeng Town Industrial Park, Tongshan District, Xuzhou City, Jiangsu Province, China
“Strong columns and weak beams” is an important principle in structural seismic design. It aims to enhance the bearing capacity of columns so that beams yield before columns under loads such as earthquakes, thereby improving the overall seismic performance and safety of the structure.
Concept definition
“Strong columns and weak beams” refers to the design of building structures in which columns in frame structures have stronger bearing capacity and deformation capacity than beams. Specifically, it means that columns enter the yield state later than beams under external forces such as earthquakes, and when plastic hinges and large deformations occur in beams, the columns can still maintain sufficient bearing capacity and stability, thereby ensuring that the entire structure will not collapse due to column damage.
(1) Improving structural seismic performance: When an earthquake occurs, the structure will produce horizontal shaking, and beams and columns will be subjected to large bending moments and shear forces. The “strong columns and weak beams” design can make beams undergo plastic deformation before columns, consume earthquake energy, avoid premature column damage, and ensure that the structure has good integrity and stability during earthquakes.
(2) Realize ductile failure mechanism: Ductile failure of a structure is a gradual and predictable form of failure, which gives people more time to take emergency measures. “Strong columns and weak beams” make the structure fail according to the beam hinge mechanism during an earthquake. After the plastic hinge appears at the end of the beam, the structure can still bear the load to a certain extent and will not collapse suddenly.
(1) Adjust the cross-sectional size of the component: Appropriately increase the cross-sectional size of the column to make the column have greater bending and shear resistance. For example, in high-rise buildings, the bottom columns usually adopt larger cross-sectional sizes because they bear greater loads. For example, the side length of a rectangular column may be larger than that of the column on the upper floor.
(2) Reasonable configuration of steel bars: Configure a sufficient number and strength of longitudinal steel bars and stirrups in the column. Longitudinal steel bars can improve the compression and bending resistance of the column, and stirrups can enhance the shear resistance of the column and constrain the deformation of concrete. For example, in structures with higher earthquake resistance levels, the stirrups of the column will be denser to improve the ductility of the column.
(3) Selection of appropriate materials: High-strength concrete and steel bars are preferred for columns. High-strength concrete can improve the compressive strength of columns, and high-strength steel bars can improve the bearing capacity of columns without increasing the number of steel bars.
(1) Practical application: The concept of “strong column and weak beam” has been widely used in the seismic design of building structures. Through reasonable structural design, the structure can have good deformation capacity and energy dissipation capacity under earthquake action, thereby improving the seismic performance of the structure.
(2) Challenges and limitations: Although the concept of “strong column and weak beam” has significant advantages in theory, it still faces some challenges in practical application. For example, the influence of reinforcement in the floor flange, rigid domain and infill wall connection, etc. may affect the overall performance of the structure. In addition, software and calculation tools may not accurately simulate complex structural behavior, and designers may lack sufficient knowledge and experience to deal with these problems. Therefore, in actual design, it is necessary to comprehensively consider multiple factors to ensure the seismic performance of the structure.
