1. What are the basic principles for optimal design of building structures?
1, functional principle
As the basic material living environment of human beings, the ultimate goal of building structure optimization is to meet the greatest demand of human beings for material living environment, and its structural design effect will largely determine the comprehensive efficiency of engineering construction. To optimize the design of building structure, in addition to meeting the basic functions, it needs to be improved from the perspectives of aesthetics, coordination and comfort, so as to meet the comprehensive requirements of users for the project from a larger aspect.
2. Safety principle
As the basic living environment for human survival, architecture is closely related to people. Therefore, people have always had higher requirements for its construction. With the rapid development of social economy, it is necessary to optimize the traditional architectural structure design concepts and methods. It should be noted that the structural design of building engineering should not only meet the basic use requirements, but also meet the safety use requirements, that is, to provide a safe living environment for normal production and life and improve the comprehensive requirements of engineering structure construction. Blind pursuit of optimal design of building structure, ignoring the safety of decision-making, design and construction stages. As a building, it not only has no practical significance, but will bring fatal harm to human normal production and life.
3, the principle of environmental protection
Building construction needs a lot of resources. Under the principle of sustainable development, it is necessary to ensure functional requirements and optimize resource utilization in structural design. That is, choose environmentally friendly building materials to improve the environmental protection of the overall layout of the structure, so as to carry out sustainable development to the end. For the selection of building resources and materials, it is necessary to ensure that the comprehensive requirements of structural safety, functionality and environmental protection are met. On the basis of realizing the environmental protection of the main internal structure, all kinds of waste materials should be treated and applied well to improve the comprehensive design effect of the engineering structure and reduce the impact on the environment [3].
4, the principle of economy
Economy refers to saving all kinds of material resources to the maximum extent through the optimal design of building structure, so as to achieve the purpose of reducing building costs. When optimizing the design of building structure, we should also analyze and control the design cost, and improve the rational allocation of various resources on the basis of meeting the conditions of market economy. It is necessary to comprehensively analyze the principles of economy and environmental protection, select materials with low energy consumption, minimize the utilization of various materials and reduce the input cost of materials. In addition, through the reasonable design of the structure, the efficiency of space utilization can be improved and a more effective design scheme can be obtained within a limited cost range.
5, improve the building comfort principle
A good building should be an optimized design combination from architecture, structure and decoration to water supply and drainage, HVAC, air conditioning, gas and electrical installation, and it is an overall optimized design. If only one major is well designed, it can't be called a good building, and structural design is no exception. The design of building structure should meet the requirements of building layout, internal space height, building facade and other functions and appearance perception to the maximum extent. After put into use, users will feel very comfortable in their work and life, and the building will truly become a good building praised by everyone. This is the starting point and destination of the optimal design of building structure. Therefore, the optimal design of building structure should include the optimization of structural system, the science of force transmission mode, the rationality of component arrangement, the correctness of component and material selection, etc. It should be an important basic principle to improve the comfort of buildings after they are put into use as much as possible.
6. Different components adopt different safety factors.
The restraint of cast-in-place reinforced concrete floor can greatly improve the bearing capacity of floor beam, which can be increased by about 1.5 times at the highest. However, the current domestic structural calculation software can not accurately reflect this constraint effect of cast-in-place floor slab. Therefore, if the structural design is carried out according to the mechanical calculation results, the safety factor of cast-in-place floor beam will be much higher.
On the other hand, from the investigation and analysis of the causes of collapse accidents, we can know that there are very few engineering examples of structural damage caused by floor slab or floor beam problems, unless the structural calculation itself is wrong; From many engineering examples of earthquake damage investigation, we can also know that the main reason for the collapse of buildings under the action of earthquake force is mostly due to the first destruction of vertical components such as walls and columns.
In the actual structural design work, if the actual bearing capacity of components is not considered and the same safety factor is adopted for all components, it will lead to the irrationality of the safety and economy of the building structure. Therefore, in structural design, a larger safety factor should be adopted for independent members, statically determinate structures and vertical members, while the safety factor of floor slab and floor beam can be appropriately reduced, which can not only reduce the project cost, but also improve the comprehensive safety of the structure.
Second, what is the function of optimal design of building structure?
1, reducing the total cost
In structural optimization design, compared with high-rise residential buildings, the more floors, the larger the total construction area, and the smaller the land area occupied by the unit construction area, which saves the land cost. However, with the increase of building floors, the total height of the building will also increase, and the spacing between buildings will also increase, so the amount of land saved will not be the same as the increase of building floors. For the foundation part, although it is also used on each floor, the load transferred to the foundation will increase with the increase of floors, so we need to increase the foundation, which will reduce the cost per unit area, but the effect is not obvious as the roof.
2. Improve the economy of the building structure.
The construction cost of high-rise buildings has become an important factor that has to be considered, and the corresponding structural cost has also been strictly controlled. On the basis of ensuring building quality, it is an important way for designers to realize economic and reasonable steel consumption by adopting reasonable calculation model, calculation parameters, design load, structural measures and reasonable calculation indicators. He should carefully choose according to the specifications and specific engineering conditions, reasonably use the calculation results to design according to the specifications and structural concepts, and use manual calculation to check if necessary. At present, the author compares the structural calculation results of a high-rise building project in two States.
3. What problems should be paid attention to in the optimal design of building structure?
Structural design optimization design is applied to all parts of new project design, construction drawing design and old house reconstruction, and various benefits are very considerable. In the process of model practice and structural design optimization method, we should pay attention to the following aspects:
(1) Pre-design participation. The total investment of the building is directly affected by the preliminary scheme, so the existing problem is that the structural design in the preliminary scheme stage is not involved, most architects do not consider the feasibility and rationality of the structure when designing the scheme, and the final result of the architectural design directly affects the structural design. Some schemes may increase the difficulty of structural design and increase the total investment of the building. If the structural optimization design can participate in the initial stage of the scheme, then we can choose reasonable structural forms and reasonable design schemes for different building categories and get a good start.
(2) Infrastructure design. The optimization of infrastructure design is to choose the most suitable scheme first. If it is a pile foundation, the type of pile foundation must be selected according to the specific conditions of the construction site to save costs and reduce unnecessary waste. The bearing stratum at the pile tip has a great influence on the selection of cast-in-place piles, so more comparisons should be made to determine the most suitable scheme.
(3) Optimization of detail structure design. Conceptual design is applied without specific numerical quantification, and designers need to flexibly use structural design optimization methods in the design process to achieve the best results. Corresponding to the macro grasp, the design process should also pay attention to the optimization of detailed structural design. For example, cracks are easy to appear at the corner of the special-shaped plate in the cast-in-place slab, and radial ribs should be added or divided into rectangular plates. In the design of the facade, the cantilever slab and reinforcement on the facade meet the structural requirements of the specification, so as to achieve the purpose of safety and economy.
4. What are the optimal design methods of building structures?
1, parallel algorithm
The main factor of high-rise building structure is the performance of resisting horizontal force. Therefore, the anti-lateral strength has become a key factor in the structural design of high-rise buildings, and it is also a standard to measure the safety and stability of building structures.
In building structures, among the structural materials per unit building structural area, the amount of structural materials used to bear gravity load is roughly proportional to the number of floors in the building. In addition, the amount of structural materials used in the roof of the building structure is almost constant and does not change with the number of layers of the structure; However, the amount of materials used for structural members such as walls and columns increases linearly with the number of floors of a building; However, for the amount of structural material resisting lateral movement, the relationship between the amount of structural material and the square of the number of floors of the building increases.
2. Reliability optimization method
In the scheme selection of high-rise buildings in non-earthquake disaster areas, priority should be given to structural systems with good wind resistance, that is, structural systems with small wind pressure shape coefficient. For example, the building structure with curved and streamlined shapes is circular or elliptical, or the truncated pyramidal system with decreasing structure from bottom to top, and the wind pressure shape coefficient is small, which is beneficial to wind resistance. In addition, in the plane layout of the structure, it is advisable to choose a structural system with uniform and symmetrical plane shape and structural stiffness distribution, which can greatly reduce the influence of torsional effect on structural deformation and internal force under wind load.
3. Advanced system optimization method
Due to the different performance of buildings, the requirements for internal space are also different. At the same time, the use function of high-rise building structure is different, and its plane layout also changes. Usually, rooms in houses and hotels should adopt small space layout scheme; Office buildings are suitable for large and small spaces; Shopping malls, restaurants, exhibition halls and factories are suitable for large space layout; Ballrooms and dance halls require large space, and there are no columns inside the structure. Because different structural systems can provide different internal space, in the design stage of building structure, we should first choose the appropriate structural type according to the use function of building structure.
5. What are the measures to optimize the design of building structure?
1, strengthening the design of shear wall
The experimental study of shear wall limb 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 post-yield deformation capacity of flexural members are: section size, concrete strength grade, longitudinal reinforcement, axial compression ratio, stirrup number and so on. The main factors are axial compression ratio and stirrup characteristic value. The coupled wall is composed of all the coupled walls connected by beams, which increases the constraint conditions of the coupled walls. The increase of coupling beam stiffness will inevitably increase the seismic action of the structure, so the internal force distributed between coupling beam and wall limb will also increase accordingly. At this time, it is necessary to increase the reinforcement amount of the component, which obviously leads to the waste of materials.
2. Pay attention to detail optimization
(1) While paying attention to the overall design, we should also strengthen the fine design of local components of the structure. For example, in the design of cast-in-place slab, the special-shaped slab is divided into rectangular slabs as far as possible, which not only achieves the purpose of reasonable stress, but also avoids the occurrence of corner cracks.
(2) The number of stirrups of the bottom frame beam of the bottom frame seismic wall is generally large. At this time, if cold-rolled ribbed steel bars are selected as stirrups, the number or diameter of stirrups can be reduced to reduce the cost and facilitate construction. In addition, in order to reduce the bottom section, it is a good choice to use high-strength concrete for column members, but the grade of concrete for horizontal members can be appropriately reduced, which not only meets the stress requirements, but also saves costs.
(3) Combining computer technology with the theory of structural optimization design, using computer analysis software to establish the analysis model of optimization design, using efficient computer optimization calculation method to set the target requirements of structural design, and finally achieving the optimization purpose of structural design. In the specific optimization design process, the optimization design has actually changed from an engineering problem to a mathematical problem.
3. Application of structural design optimization method
The application of structural design optimization methods and techniques is embodied in the overall optimization design of residential engineering structure and the optimization design of residential engineering substructure. Among them, the optimization design of substructure of residential engineering includes the optimization design of foundation structure scheme, roof system scheme, envelope structure scheme and structural detail design. The optimization design of the above aspects also includes type selection, layout, stress analysis and cost analysis. And on the premise of meeting the design specifications and use requirements, combined with the actual situation of specific projects, the structural optimization design should be carried out around the goal of comprehensive economic benefits.
4. Practical value of structural design optimization method.
On the premise of satisfying the long-term benefits of the building structure, the short-term investment of the building structure should be reduced as much as possible to improve the reliability and rationality of the building structure. Compared with traditional design, using design optimization technology can reduce the construction cost by 5%-30%. The realization of optimization technology can make the best use of the properties of materials, make the internal units of building structures get the best coordination, and have the safety degree stipulated in building codes. At the same time, it can also make a reasonable decision on the overall scheme design of the building, and optimizing technology is an effective way to achieve the goal of "applicability, safety and economy" in architectural design.
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