In the context of the current rapid development of urbanization, steel mixed residential buildings occupy the largest proportion in urban and rural residential buildings, and the promotion of the construction of eco-efficient buildings nationwide has become an inevitable general trend. As an earthquake-prone country, China can combine the characteristics of ecological energy-saving with seismic conditions to achieve the purpose of optimal design.
The so-called “optimal design” refers to the study of the problem and the search for the optimal solution to the problem, and the word “optimal” should be understood as the best possible result under the given conditions. The exploration of the construction of a comprehensive evaluation index system for the optimal design of steel residential building structure in accordance with China’s national conditions is a prerequisite for the optimal design of this type of residential scheme, which has important theoretical significance and can bring considerable social, economic and environmental benefits.
The author used the system design method as a tool, conducted field research under the guidance of ecological concept, and applied the hierarchical analysis method (AHP) to construct a comprehensive evaluation index system for optimal design of steel mixed residential building structure, which intuitively reflects the guidelines of optimal design and has strong operability. The research results are expected to contribute to the theory of optimal design of steel residential building structures in urban and rural areas, and can be used as a reference and reference for the national counterparts.
2 Establishment of a comprehensive evaluation index system for the optimal design of ecological energy-saving steel hybrid residential building structures under seismic conditions
2.1 General target layer
The overall objective layer is the comprehensive evaluation of the optimized design of ecological energy-saving steel hybrid residential building structure under seismic conditions, from the perspective of optimized design of building structure, to build a steel hybrid residential building with superior seismic performance and high ecological compatibility with the environment in a way of energy saving and effective use of resources, so as to achieve symbiosis and sustainable development of people and buildings with the environment. The overall goal is to insist on the organic unity of foresight and operability, based on the current reality, so that the goal is feasible and the measures are operable, but also to fully consider the needs of development, so that the planning and design program has a certain degree of advancement.
2.2 Sub-objective layer
2.2.1 Building structure design
On the premise that the structural design can achieve the goals of seismic resistance and ecological energy conservation, evaluate whether the structural design of residential buildings follows the design guidelines of economy, applicability, safety and aesthetics; the structural design should fully consider the perfection of building functions and transformability, improve construction convenience, combine local geography, geology and climate conditions, achieve energy and land conservation as much as possible, reduce the investment cost of the whole life cycle of buildings, and as much as possible Adopt high quality materials, choose the layout and structure system that is conducive to earthquake and disaster mitigation, and ensure the safety of the building. Pay attention to the inheritance and protection of local architectural characteristics, reflecting the regional and contemporary nature of architectural design.
2.2.2 Use of building materials
Evaluate whether the building materials meet the indicators of taking into account ecology and economy: whether to fully consider the local and easy availability of materials, and encourage the use of local and convenient transportation materials as raw materials for building construction as much as possible according to local conditions; whether to use 3R building materials as building materials when conditions allow; whether to reasonably use long-life materials and new materials of environmental protection and energy conservation.
2.3 The guideline layer and the basic index layer under it
Evaluate whether the building can be designed and constructed according to local conditions and local materials, so as to save labor and construction materials and funds as much as possible; whether there is thorough planning and accounting, paying attention to economic laws and economic benefits; whether the design and use requirements and technical measures of the house are unified with the corresponding cost and construction standards.
(1) Structural selection for energy saving and land saving. Evaluate the impact of the structural form of the building on the energy and land saving of the building. Generally based on the building form and geometric form, the optimal design of structural selection will increase the usable space; reasonably control the residential body shape to realize the intensive and effective use of land resources; the structural form should be conducive to improving the thermal performance of the residential envelope and the indoor and outdoor physical environment, and increasing the use of renewable energy in the building to achieve the purpose of energy conservation.
(2) Adaptability with local geography, geology and climate. Evaluate the problem of the adaptability of the building to the local natural environment, because different regions are located at different latitudes, there are obvious differences in the amount of solar radiation, temperature, humidity, seasonal cycles and geographic and geological conditions, in order to meet the requirements of building economy and cost savings, the layout of the building and the functional organization, spatial form, construction and other aspects should be reasonable use of local geography, geology, climate and other favorable conditions.
(3) Whole life cost. Including one-time cost and maintenance costs, etc. Evaluate whether the building can reasonably use the new ecological and environmental protection technology and management methods in the whole life cycle process, and study the building cost and return from the perspective of the whole life cycle.
(4) Convenience of construction. Evaluate whether the building design has better operability in construction, and can have a larger optional space in construction methods, significantly shorten the structure construction cycle, so that the building can be put into use earlier and bring considerable economic benefits.
Evaluate the impact of the building structure on the normal operation of building functions, equipment and facilities on the basis of ensuring structural safety.
(1) Functional perfection. Evaluate whether the building meets the user’s needs, including: whether the space layout has clear functional partitions; whether the space combination and division is centered on the main space, and whether the arrangement of the secondary space is conducive to the function of the main space; whether the connection and isolation of space is reasonable.
(2) The transformability of the interior space. Evaluate the potential inherent in the change of the function of the physical space of the residence under the premise of ensuring the least possible alteration of the main structural components, equipment tube wells, etc. during the use of the building. This potential is the ability to adapt to the respective needs of different occupants or occupancy groups to a certain extent in a clear residential space pattern. The same spatial pattern should have the ability to adapt to multiple use functions and expand its use, such as the effectiveness of individual office or small business extended by the residence while adapting to the residence, without the need to adjust and change the layout structure of the residential space to adapt to its functional changes, so as to extend the reasonable service life and residential quality of the residence.
To ensure the safety performance of the whole structural system, to achieve the goal that the building structure is both safe, durable and economically reasonable. Therefore, the building should be evaluated for its ability not to be damaged under the permanent effects of structural self-weight, foundation deformation, preload pressure, concrete shrinkage deformation, variable effects such as wind load, snow load, ice load, temperature change, and accidental effects such as earthquake, explosion, impact, fire, etc., with special emphasis on the corresponding indicators of seismic resistance.
(1) Form and arrangement of flat and façade structures. Evaluate the spatial distribution of the load-bearing structure of the building, requiring the arrangement to avoid as far as possible the members in a complex state of stress, and to meet the requirements of the function under the condition of satisfying the load-bearing capacity. The plan layout of the building and its lateral force-resisting structure should be regular and symmetrical, and should have good integrity; the elevation and vertical section of the building should be regular, the lateral stiffness of the structure should be uniformly changed, and the cross-sectional size and material strength of the vertical lateral force-resisting members should be gradually reduced from bottom to top to avoid sudden changes in lateral stiffness and bearing capacity of the lateral force-resisting structure. The vertical arrangement should strive for uniformity and continuity, and make the vertical stiffness and strength change evenly as much as possible to avoid the weak layer, and should reduce the center of gravity of the house as much as possible. In addition, such as through the layout of structural walls and columns and the adjustment of the length of the wall limbs, so that the irregular building shape and plan layout produce the effect of the regular structure, the same can make the building structure to achieve the predetermined goal of economic rationality and safety and durability.
(2) Design of seismic structural system. Evaluation of the size of the seismic capacity of the building seismic system should have the necessary seismic bearing capacity, good deformation capacity and the ability to consume seismic energy, and should avoid the loss of seismic capacity or the bearing capacity of the whole structure to gravity loads due to the destruction of some structures or members and yielding of weak floors, and the reasonable setting of seismic structural measures.
In addition, the main cause of building collapse under earthquake force is also mostly due to the damage of vertical members such as walls and columns in the first place. For this reason, in the actual structural design work, such as different components using different safety coefficients of structural optimization design principles, independent members, static structure and vertical members should use a larger safety coefficient, while the safety coefficient of the floor slab and floor cover beam can be appropriately reduced, such treatment can reduce the cost of construction, but also to improve the overall safety of the structure.
(3) Multi-channel seismic protection. Multiple seismic lines of defense are necessary for seismic structures. When the first line of defense against lateral force is damaged by a strong earthquake, the second to third line of defense against lateral force immediately takes over, resisting the impact of subsequent earthquakes and ensuring the minimum safety of the building from collapse.
(4) Construction quality. Evaluation of the building in accordance with the construction process construction production conditions, the quality of the components due to the instability of the workers operation caused by the actual deviation from the design, such as the denseness and strength of the concrete, steel stubble, component size, etc. to meet the requirements.
(5) Other disaster prevention. Evaluate the design of the building structure against man-made disasters such as fire and burglary and natural disasters such as tornadoes, snowstorms, mudslides and floods.
(6) Base site selection based on seismic disaster prevention. Evaluate the location of the building for the presence of adverse geological phenomena, their causes, distribution range, seismic effects, the presence of new tectonic movements, the stratigraphic structure of the area, and the physical and mechanical properties of the geotechnical soil, the burial conditions of groundwater, the magnitude and law of water level changes and their corrosiveness. In addition, the self-oscillation period of the structure should be made to avoid the characteristic period of the site.
Based on the evaluation of social and ecological benefits, architectural beauty and environmental beauty should be listed as important elements of the design. The architecture can fully realize the ecological nature of the building only by integrating the regional characteristics and keeping pace with the times.
(1) Territoriality. Evaluate whether it can be designed according to local conditions, the overall design takes into account the affinity and adaptability of the local environment and the inheritance of local traditional architectural culture, and can fully embody the ecological view while maintaining a colorful architectural style; whether the living environment can be integrated with the natural landscape, whether the planning layout can be combined with local natural conditions, fully exploit the local cultural connotation, and highlight the regional and folkloric characteristics.
(2) Periodicity. Architecture reflects the material and cultural development level of an era, and also shows the ideology and aesthetic concept of that era, so it always has the significance of the era mark.
(3) Affinity with the surrounding environment. Evaluate whether the building is coordinated and unified with the surrounding buildings and natural scenery in terms of building location, building shape, building function, etc., and is consistent with the overall urban planning.
2.3.5 Cost-effectiveness of building materials
Evaluate the capital investment in building materials in the process of building construction and use; whether the materials have the best cost performance.
(1) Ease of access to building materials. Evaluate whether the production process of building materials has wide sources of raw materials, simple production process, low energy consumption, and is conducive to large-scale promotion and use.
(2) Local building materials. Evaluate whether the building in the construction process of local materials, according to local conditions, as far as possible to use local, collection and transportation of convenient materials as raw materials and decorative elements of the building and creating the environment.
2.3.6 Ecological properties of building materials
This indicator evaluates whether the use of building materials is reliable, durable and long-lived, as well as the production of building materials, processing, the degree of impact on the local ecological environment such as the origin of raw materials, raw material production plants.
(1) Material quality. Evaluate the material tensile, compressive, shear, torsion, bending performance, density and durability, emphasizing the prohibition of the use of high energy consumption, pollution exceeds the standard materials.
(2) Long-life building materials. Evaluate whether the building uses long-life building materials, prioritize the use of new high-performance, high-strength materials, reduce the maintenance of components, the probability of replacement, improve the efficiency of the use of building materials, and extend the life cycle of the structure.
(3) 3R building materials. Evaluate whether the building uses reduced, reused and recycled (resource-based) building materials, i.e., using renewable materials as building materials where conditions allow, or increasing the use of renewable resources in the building to reduce construction waste.
After using AHP model to construct the “comprehensive evaluation index system of eco-energy-saving steel hybrid residential building structure optimization design under seismic conditions”, the relevant control factors in the evaluation system can be clearly expressed, and the relative importance of the relevant evaluation indexes can be scored by experts or experienced professionals and users, and then the The judgment matrix of each level is calculated by the AHP program on the computer for single ranking and total ranking, so as to obtain the combined weight value of each layer of factors relative to the total target.
After finding out the weight value of each basic index, it can be combined with the “evaluation value” of each evaluation index corresponding to the design scheme to be evaluated or the completed evaluation object, and calculated by using the improved TOPSIS method or fuzzy comprehensive evaluation method, etc., so that the superiority and inferiority of each object to be evaluated can be intuitively obtained, thus realizing the preferential selection of the structural design scheme of steel mixed residential building. It can also be used to evaluate the advantages and disadvantages of existing buildings in terms of seismic resistance and ecological energy conservation, so the research results are highly operable.