What is the optimal design of building structure?

Steel structure design often encounters steel structure optimization design, so let's take a look at what is steel structure optimization design!

Structural optimization design refers to finding the best design plan under certain constraints, such as the lightest weight, lowest cost, and maximum rigidity. It was once called the optimal design of the structure or the optimal design of the structure. Relative to "structural analysis", it is also called "structural synthesis"; if the weight of the structure is the minimum, it is called the minimum weight design. At present, due to the large investment and long construction period of many construction projects, the effective structural optimization design can reduce the investment amount accordingly. The optimal design of the building structure is the key means to realize the function of the building body and the investment cost of the building.

At this stage, with the continuous improvement of the market economy, the economic performance of buildings has been paid more and more attention. Therefore, it is our unremitting pursuit to build a building that meets the specifications and usage requirements with the least materials or the least cost. But at the same time, how do we guarantee the safety performance of the building? Therefore, the structure's optimization design is reflected! The structural optimization design is not simply to reduce the amount of concrete and reinforcing steel but to adjust each component. The proportional relationship between the stiffness, make full use of the stress characteristics of each member, give play to their respective strengths, and make the overall structure optimal.

A. What are the basic principles of the optimal design of building structures?

1. Security principle

As a basic living environment for human survival, architecture has a close relationship with people. Therefore, people have always had relatively high requirements for their construction. In the context of rapid social and economic development, it is necessary to optimize traditional building structure design concepts and methods. It should be noted that in addition to the basic use needs, the structural design of the building engineering also needs to meet the requirements for safe use, that is, to provide a safe living environment for normal production and life, and to improve the overall requirements for the construction of engineering structures. Blindly pursue the optimal design of building structure, ignoring the safety in the decision-making stage, design stage, and construction stage. As a building, it not only has no practical significance but will cause fatal harm to human normal production and life.

2. Economic principles

Economic efficiency refers to the maximal saving of various material resources through the optimized design of building structures, and the goal of reducing construction costs. When optimizing the design of building structures, we should also analyze the design cost, control the cost of structural design, and improve the rational allocation of various resources on the basis of meeting market economic conditions. It is necessary to conduct a comprehensive analysis of economic principles and environmental protection principles, select materials with low energy consumption, and minimize the use of various materials and reduce material input costs. In addition, through the rational design of the structure, the efficiency of space utilization is improved, and a more effective design plan is obtained within a limited cost range.

3. Functional principle

Architectural engineering is the basic material survival environment for human beings. The ultimate goal of building structure optimization is to meet the human's maximum demand for the material living environment. Its structural design effect will largely determine the overall efficiency of engineering construction. To optimize the design of the building structure, in addition to satisfying the basic functions, it also needs to be improved from the perspectives of aesthetics, coordination, comfort, etc., to meet the user's comprehensive requirements for the project from a larger aspect.

4. Environmental protection principle

There are many resources required for the construction of construction projects, and under the principle of continuous development, in addition to ensuring the functional requirements during structural design, it is also necessary to optimize the utilization of resources. That is to choose environmentally friendly construction materials and improve the environmental protection of the overall structure of the structure and will continue to develop and implement it to the end. For the selection of construction resource materials, it is necessary to ensure that they can meet the comprehensive requirements of structural safety, functionality and environmental protection, and on the basis of achieving environmental protection of the internal structure of the main body, do a good job in the treatment and application of various waste materials to improve the overall structure of the project Design effect, reduce the impact on the environment of steel structure engineering.

5. Principle of improving building comfort

A good building should be an optimized design combination from architecture, structure, decoration to water supply and drainage, HVAC, air conditioning, gas, electrical installation, and other specialties. It is overall optimized design. If only a certain professional design is good It is impossible to be called a good building, and the structural design is no exception; the structural design of the building should be able to meet the requirements of the functional layout and appearance of the building layout, internal space height, and building facade to the greatest extent. After use, it makes users feel comfortable in work and life and makes the building truly a good building that everyone praises. This is the starting point and the final point of the optimal design of the building structure. Therefore, the optimal design of the building structure should include the optimization of the structural system, the scientificity of the force transmission path, the rationality of the component layout, the correctness of the selection of components and materials, etc.; the comfort of the building after being put into use as much as possible should be taken as An important basic principle for the optimal design of steel building structures.

6. Different components adopt different safety factor principles

The restraint effect of cast-in-place reinforced concrete floor slabs can greatly increase the bearing capacity of floor beams, which can be increased by about 1.5 times at the highest. However, the current domestic structural calculation software cannot accurately reflect the restraint effect of cast-in-place floor slabs. Therefore, if the structural design is based on the mechanical calculation results, the safety factor for cast-in-place floor beams is much higher.

On the other hand, from the investigation and analysis of the causes of collapse accidents, it can be seen that there are very few engineering examples of structural damage due to problems with the floor or floor beam, unless the structural calculation itself is wrong; from many, The engineering example of earthquake damage investigation also shows that the main reason for the collapse of buildings under the action of the seismic force is also mostly due to the destruction of vertical members such as walls and columns.

In the actual structural design work, if the actual bearing capacity of the components is not taken into consideration, the same safety factor will be adopted for all components, which will cause the building structure to be unreasonable in terms of safety and economy. Therefore, in structural design, larger safety factors should be used for independent members, statically determinate structures and vertical members, and the safety factors for floor slabs and floor beams can be appropriately reduced so that the treatment can reduce the project cost and Can improve the overall safety of the structure.

B. What is the role of steel building structure optimization design?

1. Improve the economics of building structure

The construction cost of high-rise buildings has become an important factor that must be considered, and the corresponding structural cost is strictly controlled. On the basis of ensuring building quality, a designer adopting reasonable calculation models, calculation parameters, design loads, structural measures, and reasonable calculation indicators is an important way to achieve economic and reasonable steel content. It should be carefully combined with specifications and specific engineering conditions. Select and use the calculation results to design according to the specifications and structural concepts, and use a manual calculation to review if necessary. Now the author compares the structural calculation results under two conditions of a high-rise building project.

2. Reduce the total cost

In the structural optimization design, compared with multi-story houses and high-rise houses, the more floors, the larger the total construction area, the smaller the land area occupied per unit of construction area, saving land costs, but the increase in the number of buildings The total height will also increase, and the space between buildings will also increase. At this time, the amount of land occupied will not be the same as the increase in the number of building floors. For the foundation part, although it is also shared by all floors, the number of floors increases and the load transferred to the foundation will increase. We need to increase the foundation so that the cost per unit area is reduced, but there is no roof effect That's obvious.

C.  What problems should be paid attention to in the optimization design of building structure?

The structural design optimization design is applied to the various parts of the design of the new project, such as the preliminary design, construction drawing design and old house renovation. The various benefits are very impressive. During the practice of the model and the optimization method according to the structural design, attention should be paid to the following aspects:

(1) Early design participation.

The total construction investment is directly affected by the previous plan, so most of the existing problems are that the structural design of the early plan stage does not participate in the construction. Most architects do not consider the feasibility and rationality of the structure when carrying out the design plan. As a result, it directly affects the structural design. Some schemes may increase the difficulty of structural design and increase the total investment in construction. If structural optimization design can be involved in the early stage of the plan, then we can choose a reasonable structural form and a reasonable design plan for different building categories to get a good start.

(2) Design of foundation structure.

The optimization of the structural design of the foundation is to choose the most appropriate plan first. If it is a pile foundation, the type of pile foundation must be selected according to the specific conditions of the construction site, saving costs and reducing unnecessary waste. The most important influence on the choice of cast-in-place piles is the bearing layer at the pile end. More comparisons should be made to determine the most suitable solution.

(3) Optimization of the detailed structural design.

The conceptual design should be used when there is no specific numerical quantification. In the design process, designers need to flexibly use structural design optimization methods to achieve the best results. Corresponding to the macro grasp, the design process should also pay attention to the optimization of the detailed structural design. For example, the cracks in the corners of the special-shaped plate in the cast-in-place plate are prone to be added, and radial ribs should be added or divided into rectangular plates. When designing the facade, the cantilever plate and the reinforcement on the external facade can meet the structural requirements of the specification, so as to achieve the purpose of both safety and economy.

D.  What are the optimal design methods for building structures?

1. Reliability optimization method

In the selection of high-rise building structures in non-seismic disaster areas, the structural system with better wind resistance performance should be preferred, that is, the architectural structure system with a smaller wind pressure coefficient. For example, the shape of a building whose structure is curved and streamlined changes round, ellipse, etc., or the truncated cone system whose structure gradually decreases from bottom to top has a small wind pressure shape factor, which is good for wind resistance. In addition, when arranging the structure in a plane, it is suitable to select the type of structural system with uniform and symmetrical plane shape and stiffness distribution of the structure, which can greatly reduce the structural deformation and internal force caused by the torsional effect under wind load.

2. The high-level system optimization method

The performance of the building is different, so the requirements for the internal space are different. At the same time, the use of high-rise buildings differs in structure, and their layout changes. In general, the rooms of residences and hotels should adopt a small space plan; office buildings are suitable for large and small spaces; shopping malls, restaurants, exhibition halls and factory buildings are suitable for large space plans; banquet halls and dance halls It requires a large space without pillars inside the structure. Since different structural systems can provide different sizes of internal spaces, in the stage of building structure design, the appropriate structure type should be selected according to the function of the building structure.

3. Parallel algorithm

The main factor of the high-rise building structure is the structure's resistance to horizontal forces. Therefore, the strength of the lateral displacement resistance has become a key factor in the structural design of high-rise buildings, and it is a standard to measure the safety and stability of building structures.

In the building structure, among the structural materials per unit building area, the amount of structural materials used to bear the gravity load is approximately proportional to the linear relationship between the number of floors of the house. In addition, the amount of structural materials used for the roof of the building structure is almost constant, and does not change with the number of layers of the structure; but the amount of materials used for structural members such as walls and columns increases linearly in proportion to the number of layers of the building; while for the resistance side The number of structural materials moving toward the building has a relationship with the quadratic power of the number of building structural layers.

E.  What are the optimal design measures for building structure?

1. Strengthen the design of shear walls

The experimental study of the shear wall limbs also shows that it is difficult to become a ductile shear wall when the axial compression ratio exceeds a certain value. The factors that affect the ductility or deformation capacity of a member after bending are section size, concrete strength level, longitudinal reinforcement, axial compression ratio, stirrup amount, etc. The main factors are the axial compression ratio and the characteristic value of the coupling. The joint wall is formed by connecting the wall limbs connected by connecting beams, thereby increasing the constraint conditions of the wall limbs. Increasing the rigidity of the coupling beam will inevitably increase the seismic effect of the structure so that the internal force distribution of the coupling beam and the wall legs will also increase accordingly. At this time, the amount of reinforcement of the member must be increased. Obviously this design result will inevitably cause materials Waste.

2. Focus on detail optimization

(1) While paying attention to the overall design, the detailed design of local components of the structure should also be strengthened. For example, in the design of cast-in-place slabs, the special-shaped slabs are divided into rectangular slabs as much as possible, which not only achieves the purpose of reasonable stress but also avoids the appearance of corner cracks.

(2) The amount of stirrups in the bottom frame beam of the bottom frame seismic wall is generally large. If cold-rolled ribbed steel bars are used as the stirrups, the number of stirrup legs or the diameter of the stirrups can be reduced, and the cost can be reduced and Facilitate construction. In addition, in order to reduce the bottom section, the use of high-strength concrete is a good choice for column members, but the horizontal member concrete can appropriately reduce the number of concrete, which meets the requirements of stress and saves costs.

(3) With the combination of computer technology and structural optimization design theory, through the use of computer analysis software to establish an analysis model of optimal design, using efficient computer optimization calculation methods, establish the target requirements of structural design, and finally achieve the optimization purpose of the structural design. In the specific optimization design process, the optimization design has actually changed from an engineering problem to a mathematical problem. 4.

3. The practical value of structural design optimization methods

On the premise of satisfying the long-term benefits of the building structure, the near-term investment of the building structure should be reduced as much as possible and the reliability and rationality of the building structure should be improved. Compared with traditional design, the use of design optimization technology can reduce the construction cost by 5%-30%. The implementation of optimization techniques can make the most reasonable use of the properties of the materials, so that the units within the building structure are best coordinated, and have the safety level stipulated in the building codes. At the same time, it can also make reasonable decisions for the overall design of the building. Optimization technology is an effective way to achieve the "applicable, safe, and economic" goals of the building design.

For buildings, the optimal design of the architecture is an inevitable trend, and it is an important means to realize the function of the building body and control the cost of the building. In addition, neither construction investors nor developers can overemphasize the economics of structural optimization design, and cannot pursue economics simply by reducing materials, reducing technology, and lowering quality standards.

4. Application of structural design optimization methods

The application of structural design optimization methods and techniques is embodied in the overall optimization design of the housing engineering structure and the optimization design of the housing engineering sub-structure. Among them, the optimized design of the housing engineering sub-structure includes the optimized design of the basic structure scheme, the optimized design of the roof system scheme, the optimized design of the envelope structure scheme, and the optimized design of the structural detail design.

The optimization design of the above aspects also includes selection, layout, stress analysis, cost analysis, etc., and should meet the design specifications and use requirements, combined with the actual situation of the specific project, around its comprehensive economic benefits The goal is to optimize the steel structure engineering design.