Optimal design of building structures?

Structural optimization design refers to the given constraints, according to a certain goal, such as the lightest weight, the lowest cost, the maximum stiffness, etc., to find the best design scheme, once known as the best structural design or structural optimal design, relative to the "structural analysis", also known as the "structural synthesis"; if the minimum weight of the structure as the goal, it is called the minimum weight design. It is also called "structural synthesis" in relation to "structural analysis"; if the weight of the structure is minimized as the goal, it is called minimum weight design. At present, many construction projects due to large investment, long construction period, so effective structural optimization design, can reduce the amount of investment accordingly, the optimal design of the building structure, is to achieve the function of the building body and the cost of the building investment of the key means.

At this stage, with the continuous improvement of the market economy, the economic performance of the building is more and more important. Therefore, it is our unremitting pursuit to use the least material or the least cost to construct a building that meets the specification and use requirements. But at the same time, how do we guarantee the safety performance of the building? Therefore, the role of structural optimization design is reflected! Structural optimization design is not simply reduce the amount of concrete and steel, but by adjusting the proportionality between the stiffness of each component, make full use of the force characteristics of each component, give full play to their respective strengths, so that the overall structure to achieve the optimum.

I. What are the basic principles of optimal design of building structure?

1. Functionality principle

As the basic material living environment of human beings, the ultimate goal of building structure optimization is to meet the maximum demand of human beings for the material living environment, and the effect of its structural design will largely determine the comprehensive efficiency of engineering construction. Optimization of building structure design, in addition to meet the basic function, but also need to improve from the perspective of aesthetics, coordination, comfort, etc., to meet the user's comprehensive requirements for the project from a larger perspective.

2, the principle of security

Building as the basic living environment for human survival, and people have close contact. Therefore, people have always been on its construction requirements are relatively high. In the context of rapid social and economic development, it is necessary to optimize the traditional building structure design concepts and methods. Among them, it should be noted that the structural design of building engineering should not only meet the basic use requirements, but also need to meet the requirements of safe use, that is, to provide a safe living environment for normal production and life, and to improve the comprehensive requirements of engineering structure construction. The pursuit of building structure optimization design, ignoring the decision-making stage, design stage, construction stage of safety, its as a building not only does not have any practical significance, but will bring fatal hazards to the normal production and life of human beings.

3, the principle of environmental protection

Construction of building projects require many resources, and in the sustainable development of the rationale, in addition to ensuring the functional requirements of the structural design, it should also do a good job of optimizing the use of resources. That is, select environmentally friendly construction materials, and improve the overall layout of the structure of the environmental protection, sustainable development will be carried out to the end. For the selection of construction resource materials, to ensure that they can meet the comprehensive requirements of structural safety, functionality and environmental protection, and in the realization of the main body of the internal structure on the basis of environmental protection, to do a good job in the treatment and application of waste materials, to improve the comprehensive design effect of the engineering structure, reduce the impact on the environment [3].

4, the principle of economy

Economy refers to the optimization of building structure design, maximize the savings of various material resources, to achieve the goal of reducing construction costs. Optimization of building structure design, should also be analyzed from the design cost, control the cost of structural design, in order to meet the market economic conditions based on improving the rational allocation of resources. It is necessary to comprehensively analyze the principle of economy and the principle of environmental protection, choose materials with low energy consumption, and minimize the use of materials to reduce material input costs. In addition, through the rational design of the internal structure, improve the efficiency of space utilization, in the limited cost range, to obtain more effective design solutions.

5, improve the principle of building comfort

A good building should be from the construction, structure, decoration to the optimization of water supply and drainage, heating and ventilation, air conditioning, gas, electrical installation and other professional design combinations, is the overall optimization of the design, if only a professional design is good, it is not possible to be called a good building, the structural design can not be an exception; the architectural design should be able to maximize the satisfaction of the structural design, the structural design should be able to maximize the satisfaction of the structural design, the structural design should be able to maximize the satisfaction of the structural design. Structural design should be able to maximize the building layout, internal space height and building elevation, such as the use of functionality and appearance requirements, put into use, so that the user feels comfortable in work and life, so that the building really becomes a good building praised by everyone, which is the starting point and landing point of the optimal design of the building structure. Therefore, the optimal design of the building structure should include the selection of the structural system, the scientific nature of the force transmission path, the reasonableness of the arrangement of the components, the correctness of the selection of components and materials, etc.; it should be taken to improve the comfort of the building as much as possible after it is put into use as one of the important basic principles of the optimal design of the building structure.

6, the principle of different safety coefficients for different components

The restraining effect of cast-in-situ reinforced concrete floor slabs can largely improve the load-bearing capacity of the floor beams, which can be increased by about 1.5 times at the highest level. While the current domestic structural calculation software can not accurately reflect this restraining effect of cast-in-place floor slabs. Therefore, according to the mechanical calculation results of structural design, for cast-in-place floor beams, its safety factor is much higher.

On the other hand, it can be learned from the investigation and analysis of the cause of the collapse accident of the project that the structural damage caused by the problems of the floor cover or the floor beam is very rare, unless the structural calculation itself is wrong; it can also be learned from the many examples of the earthquake investigation of the project that the main cause of the collapse of the building under the action of the seismic force is mostly due to the walls, columns and other vertical components were damaged in the first place. destruction of the vertical components such as walls and columns.

In the actual structural design work, if the actual bearing capacity of the components is not taken into account, the same safety factor for all components, will cause the building structure in the safety and economy of the unreasonable. Therefore, in the structural design, the independent components, static structure and vertical components should be used for a larger safety factor, while the safety factor of the floor and floor beams can be appropriately lowered, so that not only can reduce the cost of the project, but also to improve the overall safety of the structure.

Second, what is the role of optimization of building structure design?

1, reduce the total cost

Structural optimization design, multi-story residential and high-rise residential comparison, the more floors, the total floor area increases, the smaller the land area occupied per unit of floor area, saving the cost of land, but the increase in the number of floors of the building, the total height of the building will be increased, the building and the building between the distance to be increased, which occupies the amount of land to save is not the same with the increase in the proportion of the number of floors of the building. However, the total height of the building will also increase as the number of floors increases, and the spacing between buildings will also be increased. For the foundation part, although it is also used by each layer ***, but the number of layers increases, the load transmitted to the foundation will increase, we need to increase the foundation, so the cost per unit area has been reduced, but it is not as obvious as the effect of the roof.

2, improve the structural economy of the building

The construction cost of high-rise buildings has become an important factor that has to be taken into account, the corresponding structural costs are strictly controlled. A designer to ensure the quality of the building on the basis of the use of reasonable calculation models, calculation parameters, design loads, structural measures and reasonable calculation index is an important way to achieve a reasonable economic steel content, should be carefully combined with the specification and the specific project selection, and based on the specification and the structural concept of reasonable use of the calculation results of the design, the use of hand-calculated review when necessary. Now the author of a high-rise building project in two states of structural calculations to compare the results.

Three, building structure optimization design should pay attention to what problems?

Structural design optimization is applied to various parts of the design of the new project's pre-design, construction drawings design and old house renovation, a variety of benefits are very considerable. In the model for practice as well as in accordance with the structural design optimization methodology process, pay attention to the following aspects:

(1) the design of the preliminary stage of participation. The total investment of the building by the direct impact of the preliminary program, so now there are most of the problems are not involved in the structural design of the preliminary program stage, the architects design program most of the structural feasibility and reasonableness is not taken into account, while the final results of the architectural design is directly on the structural design, certain programs may increase the difficulty of the structural design and make the total investment of the building to improve. If the structural optimization design can be involved in the early stage of the program, then we can choose a reasonable structural form for different building categories, a reasonable design scheme, and get a good start.

(2) Foundation foundation structural design. Optimization of structural design of foundation foundation is first of all to choose the most appropriate program, if the pile foundation, must be based on the specific conditions of the construction site to choose the type of pile foundation, save costs and reduce unnecessary waste. The more influence on the selection of the pile is the pile end of the force layer, should be compared to determine the most appropriate program.

(3) Detailed structural design optimization. Conceptual design is applied to the situation where there is no specific numerical quantification, and the design process requires the designers to flexibly use the structural design optimization method to achieve the best results. Corresponding to the macro grasp, the design process at the same time to pay attention to the optimization of the detailed structural design, such as cast-in-place panels in the corners of the shaped plate is prone to cracks, should be added radial tendons or divided into rectangular panels. When doing fa?ade design, the fa?ade of the cantilevered plate and reinforcement, to meet the construction requirements of the code can be, to achieve both safety and economic purposes.

Four, what are the methods of optimization of building structure design?

1, parallel algorithms

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

In the building structure, the amount of structural materials used to bear gravity loads per unit of structural area of the building structure is approximately proportional to the number of floors of the house. In addition, the amount of structural material used for the roof of the building structure is almost constant and does not change with the number of storeys of the structure; however, the amount of material used for structural elements such as walls and columns increases linearly and proportionately with the number of storeys of the building; and the amount of structural material used for resisting lateral movement grows in a quadratic relationship with the number of storeys of the building structure.

2, reliability optimization method

In the non-seismic disaster area of high-rise building structure program selection, priority should be given to the selection of wind performance is better structural system, that is, the selection of wind pressure coefficient of the body type smaller building structure system. For example, the shape of the structure is curved streamlined changes in the building structure of circular, elliptical, or structure from the bottom to the top of the gradually decreasing truncated cone system of wind pressure body shape coefficient is small, is conducive to a good wind resistance. In addition, in the structural layout, suitable for the selection of structural plane shape and structural rigidity distribution of uniform symmetry of the structural system type, so that the wind load can be largely reduced under the action of torsion effect caused by the structural deformation and the impact of the internal force.

3, high-rise system optimization method

The different performance of the building, so its requirements for the internal space are different. At the same time, the use of high-rise building structure function is different, then its layout also changed. Usually, residential and hotel rooms are suitable for small space layout program; office buildings are suitable for large and small space are available; shopping malls, restaurants, exhibition halls and factories are suitable for large space layout; banquet halls, ballroom is required to structure the interior of the structure without columns of large space. Because different structural systems can provide the size of the internal space is different, therefore, in the building structure design stage, should first be based on the use of building structure function, choose the right type of structure.

V. What are the measures for optimal design of building structure?

1, strengthen the design of shear wall

The experimental study of shear wall limb also shows that the axial compression ratio exceeds a certain value, it is difficult to become a ductile shear wall. Factors affecting the ductility or deformability after yielding of compression bending members are: cross-section size, concrete strength class, longitudinal reinforcement, axial compression ratio, the amount of hoop reinforcement, etc., and the main factors are the axial compression ratio and the characteristic value of the hoop. The joint limb wall is linked by the wall limbs connected by the connecting beam, which increases the constraint conditions of the wall limbs. The increase in stiffness of the connecting beam will make the structure of the seismic effect also increased, so that the connecting beam and wall limb distribution of internal force also increased, this time must increase the amount of reinforcement components, obviously this design result will inevitably lead to a waste of materials.

2, pay attention to detail optimization

(1) in the focus on the overall design at the same time, should also strengthen the structure of local components of the fine design. For example, the cast-in-place plate design as far as possible to the shaped plate is divided into rectangular plate, so as to achieve the purpose of reasonable force, but also to avoid the emergence of corner cracks.

(2) the bottom of the frame seismic wall of the bottom frame beam hoop reinforcement is generally larger, at this time, if the selection of cold-rolled ribbed steel as a hoop, you can reduce the number of hoop limbs or hoop diameter, to achieve the reduction of the cost and the construction of the convenience of the construction. Also, in order to reduce the bottom cross-section, the use of high-strength concrete is a good choice for column members, but the horizontal members of the concrete can be appropriately reduced concrete grade, to meet the requirements of the force, but also save costs

(3) With the combination of computer technology and the theory of optimal structural design, the optimal design of the analytical model through the use of computer analysis software to establish the optimization of the design, and the use of efficient computer optimization calculation methods to set up the structural design to achieve the optimal design of the structure, and to achieve the optimal design of the structure. Calculation method, set up the structural design to achieve the target requirements, and finally realize the optimization of structural design. In the specific optimization design process, the optimization design has actually been changed from an engineering problem to a mathematical problem.

3. Application of structural design optimization method

The application of structural design optimization method and technology is specifically reflected in the optimization design of the overall housing engineering structure and the optimization design of the housing engineering branch structure. The optimization design of the housing engineering division structure includes: the optimization design of the foundation structure scheme, the optimization design of the roof system scheme, the optimization design of the enclosure structure scheme and the optimization design of the structural detail design. Optimization design of the above aspects also includes selection, arrangement, force analysis, cost analysis, etc., and should be based on the premise of meeting the design specifications and use requirements, combined with the actual situation of the specific project, structural optimization design around the goal of its comprehensive economic efficiency.

4. Practical value of structural design optimization

Under the premise of meeting the long-term benefits of the building structure, the recent investment in 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 cost of building construction by 5%-30%. The implementation of optimization techniques allows for the most rational use of material properties, the best coordination of the units within the building structure, and the degree of safety specified in the building code. At the same time, it can also be for the overall design of the building program for rational decision-making, optimization technology is to achieve the building design of "applicable, safe and economic" goal of an effective way.

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