With the continuous development of the city and the increase of population density, there are more and more high-rise buildings in China in recent years. At present, high-rise buildings mainly use reinforced concrete structure, which has high strength and load capacity and can ensure the structural stability of high-rise buildings.
Due to the easy and low cost of concrete construction, it has been widely used in China’s construction industry. The design of concrete structure for high-rise buildings is an important task in today’s construction industry, and it is necessary to improve the professional quality of designers to build high-quality and high-standard buildings, so as to promote the development of China’s urbanization process. The following article is a shallow analysis of the design of concrete structure of high-rise buildings.
Selection and conceptual design of concrete structure design of high-rise buildings
1、Structural selection.
Three aspects need to be considered when making structural selection: structural regularity problem, structural super high problem and embedded end setting problem. The new and old versions of the structural code for high-rise buildings are very different, and in the new code, the restrictions on the structure have been increased.
Moreover, the new code explicitly states that buildings should not be designed with severe irregularities. Therefore, structural engineers need to pay more attention to the differences in the implementation of the new code to avoid being in a passive state during construction design. The total height of the building structure is strictly limited in the seismic code and the height code, and the new code has new regulations for the super high problem, adding the class b height building in addition to the class a height building. Therefore, we need to pay attention to control the problem of super high height when making structural selection. High-rise buildings often have basements, so structural design engineers need to pay attention to the embedded end settings.
2、Concept design.
In order to ensure that the structure of high-rise buildings has good seismic capacity, designers need to use structural conceptual design in the design. This design method has high requirements for architects and structural designers, who must strictly comply with the specifications and regulations of structural conceptual design, and need to analyze the building structure comprehensively in the design process, not just rely on calculations to design.
In the design of structural system, it is necessary to pay more attention to the structure selection and layout rules, choose the structure type with better seismic capacity and wind resistance, and higher economy, and to design the calculation sketch of the structure to ensure the reasonable transmission of the earthquake force of the structure, and to ensure the similar dynamic characteristics in the two main directions. In addition, the conceptual design ensures that the high-rise building can be repaired after a moderate earthquake and that it will not collapse when a high earthquake occurs. In order to ensure the goal of “repairable in medium earthquakes and not collapsing in large earthquakes”, experts need to propose specific targets for the design and perfect the design of the stability and elasticity of the building.
Principles of concrete structure design for high-rise buildings
1、Integrity.
The wholeness of concrete structure design refers to the composition of each part into a whole, study the function and design law of the whole, and discover the characteristics of the whole from the whole and the parts.
2、Structural.
In the process of concrete structure design, it is very important to fully understand its structure and its various elements. The structure of the building determines the performance and quality of the building, affecting its use in the building and its development, and it is also a carrier of performance, which can also react to the structure. The stability of the movement of the elements of the concrete structure is closely related to the structure.
3. Optimality.
There is a difference integration in the design of the concrete structure, so that the various parts of the building are reasonably combined together, and the differences complement each other, support each other, and need each other to ensure the performance of the integrated. The formation of the building structure is also inseparable from the integration of differences, which fully reflects its importance, and we should pay attention to this point in the design process.
4、Dynamic.
The dynamic principle of concrete structure design is to grasp the internal and external connection of the system, as well as the development trend, the law of dynamics, the way and other aspects, so that the concrete in the building to provide better application, to meet the needs, to grasp the direction of the times, to follow the footsteps of the times.
Considerations for structural design of high-rise buildings
High-rise building design from the system selection, plan layout, vertical layout, seismic concept design all reflect the level of the designer, the following is a brief analysis of the structural design considerations of high-rise buildings.
1、Selecting structural system.
The choice of structural system should be considered from architecture, structure, construction technical conditions, building materials, economy and other professions. The problem of regularity of the structure. Code in this regard has a considerable number of restrictions, such as: planar regularity information, embedded end of the upper and lower layer stiffness ratio information, etc., and, using mandatory provisions clearly stipulate that “the building should not adopt a seriously irregular design scheme.
“Therefore, structural engineers must pay extra attention in following the code provisions to avoid the passive work in the later construction drawing design stage. The problem of super high structure. In the seismic code and high regulations, there are strict restrictions on the total height of the structure, in addition to the original limit height set to A height buildings, but also increased the B height buildings, therefore, the height of the structure must be strictly controlled, once the structure for the B height buildings or more than the B height, its design methods and handling measures will have a greater change.
2. “Setting joints”.
Temperature expansion joints, settlement joints and seismic joints are the more important structural measures in the design of high-rise structures. For temperature expansion joints, the influence of many factors, the specification with the maximum spacing of the structure expansion joints to control, but also provides the maximum spacing should be appropriately reduced and appropriate relaxation of the situation, should be based on the actual project specific implementation of the relevant provisions. Such as Beijing Chaoyang Commercial Center, Guangdong Foshan Hospital and other projects on the ground structure length are more than 100 meters, due to the adoption of reliable measures, but also not set up temperature expansion joints and good results.
Settlement joints due to the same building in the foundation of each part of the significant settlement difference, in the design, usually with “put”, “resistance”, “adjust” and other solutions, that is, set up settlement joints, the use of Rigidity of the foundation, adjust the form of each part of the foundation or construction sequence. At present, Guangzhou, Shenzhen and other places mostly use bedrock end bearing pile, main building and podium room without joints; Beijing’s high-rise buildings generally use the practice of leaving post-cast belt during construction. Designers should be flexible in practice. The seismic joints are clearly defined in the code, but should be relaxed or reduced according to the actual situation.
3、 The limit value of lateral displacement.
The horizontal displacement of high-rise building structure becomes larger rapidly with the growth of height. In order to prevent the displacement from being too large, the code has made restrictions on both the vertex displacement and inter-story displacement. The main purpose of controlling the vertex displacement u/h is to ensure the comfort of human body in the building and to prevent the collapse of the house in rare earthquakes.
However, the condition to control the collapse of the house in rare earthquakes is the ultimate deformation capacity of the structure rather than the u/h limit. In addition, in order to make the structure have better collapse prevention ability, the related effect should be considered in the structural calculation. The main purpose of controlling the inter-story displacement △u/h is to prevent the cracking and damage of non-structural components such as filling walls and decorations.
4、Twisting problem in the design of high-rise building structure.
The geometric center of the building structure, the center of rigidity and the center of gravity of the structure are the three centers of the building, and the three centers of the building are required to converge at one point as far as possible when designing the structure, that is, the three centers are united. The torsion problem of the structure means that the three centers are not united in the process of structural design, and the torsional vibration effect occurs in the structure under the horizontal load.
In order to avoid the torsional damage of the building due to horizontal load, a reasonable structural form and plan layout should be chosen during the structural design, so that the building can achieve the unity of three centers as far as possible. Under the horizontal load, the size of torsional effect of high-rise building depends on the mass distribution. In order to make the horizontal force action of the floor evenly distributed along the plane and reduce the torsional vibration of the structure, the building plane should be made to adopt simple plane forms such as square, rectangle, circle, orthogonal polygon as far as possible.
In some cases, due to the requirements of urban planning on street landscape and the restrictions of building site, it is impossible for all the high-rise buildings to adopt simple plane forms, when it is necessary to use irregular L-shaped, T-shaped, cross-shaped and other more complex plane forms, the ratio of the thickness of the projecting part to the width should be controlled within the range allowed by the code, and at the same time, the structure should be as symmetrical as possible when the structure is arranged in the plane In the meantime, the structure should be symmetrical as far as possible.
Conclusion
Improving the design of concrete structure of high-rise buildings can ensure the quality and performance of high-rise buildings, thus promoting the construction of China’s cities and the development of the construction industry. In the process of modern construction, the concrete structure of high-rise buildings needs to be designed strictly to ensure the quality of construction projects.