What are the key points in building frame structure design?

Building frame structure design is a very important part of the entire design process. In addition to ensuring that the structure has sufficient safety reserves, structural design should also ensure that other disciplines can be effectively integrated into the building and that various disciplines can be effectively combined with each other. Structural design Personnel should combine architectural characteristics and design requirements, constantly improve their professional knowledge and practical capabilities, meet people's needs for architecture, ensure the smooth implementation of the project, and ultimately achieve the expected results.

1 Reasonably control the beam hinge mechanism and column hinge mechanism

The beam hinge mechanism refers to the plastic hinge appearing at the beam end. Except for the column foot, there is no plastic hinge at the column end. The column hinge mechanism refers to the plastic hinge formed at the upper and lower ends of the columns on the same layer. Beam hinges generally appear in each layer and are relatively dispersed, that is, the plastic deformation is dispersed in each layer and will not form a collapse mechanism, while column hinges are very concentrated, that is, the plastic deformation is concentrated on one layer, forming a collapse mechanism. Beams are bending members, which are easy to achieve greater ductility and energy dissipation capabilities. Columns are compression bending members, especially columns with a large axial compression ratio, which are difficult to achieve greater ductility and energy dissipation capabilities. In actual engineering, it is generally a mixed hinge mechanism in which both beam hinges and column hinges occur. During design, the cross-sectional bearing capacity of the fixed end of the column foot can be increased to delay the occurrence of plastic hinges at the column foot; strong columns, weak beams, and strong shear can be used to The design of weak bends realizes that plastic hinges appear first at the beam end, delaying or avoiding the formation of plastic hinges at the column end; the occurrence of weak and weak layers is avoided by controlling the lateral stiffness and floor bearing capacity.

2 Design of frame beams and columns

As the main horizontal and vertical components of the space frame structure, frame beams and columns must not only bear vertical loads, but also have the ability to resist horizontal loads to ensure the normal use of the house. Therefore, in actual design work, strong columns and weak beams should be considered The concepts of strong shear and weak bending, strong nodes, and strong column roots are put into practice to ensure that the structure has better ductility, greater energy dissipation capacity, and more safety reserves. In actual work, the computer program has helped us automatically consider these concepts from a calculation perspective in accordance with the requirements of Chapter 6.2 of the "Resistance Regulations", which has alleviated our work in this area, so we can start from other aspects to control the design of the overall structure. Quality, for example: (1) Reasonably select the calculated height of the column, especially the calculated height of the first-floor column to the top of the foundation. If special geology, local basements, etc. cause the foundation burial depth to be inconsistent and the height difference is large, you can Set up column piers to control the calculated height of the column in order to achieve a more reasonable and economical purpose; (2) Encrypt the full height of the stirrups on the stair frame columns to improve their ductility and improve the safety of the "safety island"; (3) ) When the live load on the floor is large, the adverse effects caused by the unfavorable arrangement of the live load should be considered; etc. Pay attention to these aspects that are easily missed or ignored.

3 Design of core area

As rigidly connected nodes, the beam-column nodes of the frame structure are subjected to very complex forces under the action of vertical loads and earthquake effects, but mainly axial pressure and shear force. In order to ensure that shear does not occur prematurely in the core area under the action of external forces. Cut the ring to ensure that node failure occurs after the rod failure. Sufficient stirrups need to be configured in the core area. When the concrete grades of beams and columns are inconsistent, the concrete in the core area should be consistent with the columns. In actual work, we often encounter the problem of over-limit shear resistance in the core area. We can first consider it from an overall perspective to see whether the structural layout is regular and uniform, whether there are areas that can be optimized, and to avoid excessive stiffness of certain areas and components. This causes the area and components to bear some unnecessary external forces, causing the shear resistance in the core area to exceed the limit; secondly, we can start with the components related to the over-limit nodes to see if there is a large eccentricity at the beam and column nodes. Does the cross-section width need to be adjusted, etc. From the above aspects, we can simply deal with the problem of over-limit shear resistance in some core areas.

4. Centerline design must comply with regulations

The so-called centerline design means that in the frame structure, the eccentricity between the column centerline and the earthquake-resistant wall centerline and beam centerline is not greater than 1/4 of the column width, otherwise the eccentricity effect should be taken into account. Control the eccentricity to better meet the stress balance of the nodes. In the process of designing the frame centerline of a multi-story building, if a serious deviation of the centerline occurs, it will lead to large changes in the column section of the structure. To address this issue, we should first communicate with other professionals , Reduce the eccentricity of structural components by optimizing the plane layout. Otherwise, these eccentric columns need to be strengthened to a certain extent, such as setting up beams with horizontal haunches to reduce the adverse effects of eccentricity.