Earthquake is due to the movement of the ground, so that the original buildings on the ground at rest are subjected to dynamic action and forced vibration, thus generating internal forces, deformations and displacements in the structure. After the dynamic analysis of the simplified model, i.e., the one-time seismic analysis is corrected and supplemented, some reaction mechanisms and damage forms of buildings under the action of earthquakes are obtained, and some calculation methods of building resistance and basic principles of design are proposed. These get very good results in practical application.

1. Some principles of conceptual design

1) Overall yielding mechanism. For example, strong columns and weak beams.

2) Balanced stiffness and ductility. Masonry structure in order to improve the ductility of structural columns and ring beams, forming a weaker frame.

3) Uniform strength. Structure in the plane and elevation of the bearing capacity of uniform.

4) Multiple lines of defense against earthquakes.

5) Strong node design.

6) Avoidance of site excellence cycle zones.

2. On this basis, the structural seismic response analysis is made, and its analysis methods mainly include: ① seismic load method; ② vibration mode decomposition method; ③ dynamic time course analysis method. Now also developed push-over method, ability spectrum and other methods. The goal of seismic protection has also developed from a single, life-safety based state standards to a variety of state-based design concepts that emphasize "individuality" design.

3, the shortcomings and deficiencies of the traditional seismic methods of traditional seismic structures mainly use the main structural components after yielding plastic deformation energy and hysteresis dissipation to dissipate seismic energy, which makes the energy dissipation performance of these areas become particularly important, and once due to certain factors lead to problems in these areas, the seismic performance of the structure will be seriously affected, resulting in serious damage, due to the damage site is located in the main structural components, its repair is very important, and it is very difficult to repair the structural components. structural elements, its repair is very difficult to carry out.

Since the traditional seismic structure is aimed at preventing the collapse of the structure, its seismic performance is largely dependent on the ductility of the structure (members), and many previous studies have focused on improving the ductility of the structure (members), while neglecting the control of the degree of damage to the structure.

4. Traditional seismic methods have more difficulties in improving structural performance.

The energy-consuming capacity of traditional seismic structures depends mainly on the ductility of the main structure. It is difficult to realize both the requirement of high strength and good ductility of the main structure.

1) Frame structureMany researchers recommend the strong column and weak beam system as the most suitable seismic frame system. This system can disperse the seismic input energy in many parts of the structure to dissipate, and can even control the order and location of the plastic hinges, ductility is important to save the building in rare earthquakes, but these expected plastic hinges in moderate earthquakes will also be produced, the ductility should also be regarded as a kind of "damage". ". Post-repair costs are also high.

2) shear wall structure shear wall structural system has a large lateral stiffness, in the horizontal seismic action of the lateral displacement is small, the total horizontal seismic action is also large, etc., common seismic damage in general for the diagonal cracks in the wall surface or the bottom of the floor of the horizontal construction joints in the horizontal misalignment occurs when the bottom of the yielding, the shear wall of the lateral role is very small, and the shear wall of the dissipation of the energy is also basically focused on the bottom of the plastic hinge region, the upper wall of the resistance to the plastic hinge area, the upper wall is very important for the resistance to the damage. And the energy consumption of shear wall is also basically concentrated with the bottom plastic hinge area, and the upper wall has no significant role in resisting strong earthquakes. And the shear wall to bear a certain vertical load, so the bottom of the damage is also very difficult to repair.

3) Frame-shear wall structure from the seismic conceptual design, frame-shear wall structure has multiple lines of defense against earthquakes. There are frames and walls composed of seismic structure, the frame stiffness is small, bear the seismic force is small, while the elastic limit deformation value and ductility is small. The whole structure under the action of the earthquake, the wall soon exceeds its own smaller elastic limit deformation, cracks, horizontal bearing capacity decline, at this time the frame has not yet given full play to its own horizontal resistance; after the wall cracks, the frame bears the seismic force increases, and at the same time due to the change in structural stiffness, seismic effects have also changed. But whether it is a shear wall or frame, are part of the main structure, damage to the bad repair work is more difficult, and the cost is not small.

Two, damping, vibration isolation and vibration control of the current situation in view of the above shortcomings and shortcomings of the traditional seismic methods, and in all the understanding of the whole process of earthquake-induced structural vibration.

The ground vibration generated by the source of the earthquake is transmitted to the structure through the propagation path, thus causing the vibration response of the structure. By taking vibration method control measures at different stages, it becomes different active seismic methods. Roughly, it includes the following four points:

①Source→Shock abatementShock abatement is a method to reduce structural vibration by attenuating the intensity of vibration of the earthquake source, due to the difficulty in determining the source of the earthquake, and the scale of its grand, there is no effective and feasible measures to attenuate the intensity of the source of the earthquake to the predetermined level.

②Transmission path → seismic isolation seismic isolation is through some kind of device will be separated from the structure of the earthquake, its role is to weaken and change the ground vibration when the structure of the intensity and mode of action, in order to achieve the purpose of reducing the vibration of the structure. Seismic isolation methods mainly have two kinds of base isolation and suspension isolation.

3 structure → passive damping passive damping is through the adoption of certain measures or additional substructures to absorb and consume the energy transferred to the main structure of the earthquake, to achieve the purpose of reducing structural vibration. Passive damping methods include energy dissipation damping, impact damping and shock absorption damping.

④Response→Active DampingActive damping is based on the seismic response of the structure, through the seismic system of the ground executing machine, the active control force to the structure, to achieve the purpose of reducing structural vibration.

The research and application of structural seismic isolation and damping methods began in the 1960s and has developed rapidly since the 1970s. This positive structural seismic method has the following advantages compared with the traditional negative seismic method:

1) It can greatly reduce the seismic effect received by the structure, which can reduce the cost of the structure and improve the reliability of the structure to resist. In addition, the seismic isolation method can more accurately control the maximum seismic force transmitted to the structure, thus overcoming the difficulty of accurately determining the load when designing structural components.

②It can greatly reduce the deformation of the structure under the action of the earthquake, ensure that non-structural components are not damaged by the earthquake, thus reducing the cost of post-earthquake maintenance, for a typical modern building, the cost of non-structural components (such as glass curtain walls, finishes, utilities, etc.) or even account for more than 80% of the total cost of the entire house.

3 vibration isolation and damping devices, even if a large permanent deformation or damage after the earthquake, its reset, replacement, maintenance of structural components convenient and economical.

④Structures used for high-tech precision processing equipment, nuclear industry equipment, etc., can only use seismic isolation, vibration damping methods to meet the strict seismic requirements.

(I), vibration isolation

1, base seismic isolation

1) laminated rubber cushion vibration isolation device used for vibration isolation device rubber cushion, can be used for natural rubber, can also be used for artificial synthetic rubber (neoprene). In order to improve the vertical bearing capacity and vertical stiffness of the cushion, the rubber cushion is generally made of rubber sheets and thin copper plate stacked together.

2) lead core rubber bearing so that the bearing has enough initial stiffness, in the wind load to come and braking force and other common loads to maintain a sufficient stiffness to meet the requirements of normal use, but the occurrence of strong earthquakes, the device flexible sliding, the system into the state of dissipation.

3) ball (or roller) vibration isolation has the ability to self-reset; there are plus copper tie rod wind stabilizing device; lateral hydraulic jack bit. In addition, there is the addition of energy dissipation device, energy dissipation device has a soft energy dissipation rod shear, lead extrusion energy dissipator, oil damper, light damper, etc..

4) Suspended base seismic isolation

5) Rocking bearing seismic isolation with the same principle there are step seismic isolation production, used for fine high structures, such as fontanel, piers, cabinets cylinder buildings, etc..

6) sliding bearing seismic isolation between the upper structure and the foundation to set up mutual sliding slide. Wind load, braking force or small earthquake, static friction makes the structure fixed to the foundation; large earthquake;

structure sliding horizontally, reduce seismic action, and its friction damping consumption of seismic energy.

In order to control the friction between the skids, so that it meets the requirements of seismic isolation; between the skids can be added slip layer. Currently commonly used slip layer: coating slip layer (polyvinyl chloride), powder grain slip layer (lead grain, sand grain, talc, graphite, etc.).

2, suspension isolation suspension isolation of all or most of the mass of the structure will be suspended, is the ground vibration is not transmitted to the main body of the mass, resulting in a small inertia force, thus playing a role in seismic isolation. Suspension structure in the bridge, thermal power plant boiler frame and so on have a lot of applications. The famous 43-story Hong Kong HSBC new building is used is the suspension structure.

Suspension structure of the suspension rod force is larger, must use high strength steel, and high strength steel tolerance is poor, in the vertical seismic effect is easy to pull off. In order to reduce the vertical seismic effect, can be set in the suspension point of the shock absorbing spring, and with the use of dampers.

3, the application of seismic isolation precautions:

1) seismic isolation will actually make the original structure of the intrinsic period of singing, in the following cases should not be used in seismic isolation design:

① the foundation of the soil layer is unstable;

② the substructure of the variability of the original structure of the intrinsic period of a long;

③ is located in the soft site, the extension of the cycle may cause *** vibration;

④ Negative reaction force occurs in the production;

2) The seismic isolation device must have enough initial stiffness so that it can meet the requirements of normal use. When a strong earthquake occurs, the device is flexible to dissipate the shock, and the system enters the state of energy dissipation.

3) The seismic isolation device can make the structure in the foundation surface flexible sliding, in the earthquake will inevitably produce a large displacement. In order to reduce the displacement response of the structure, the seismic isolation device should provide greater damping, with a greater ability to dissipate energy.

4, the advantages of seismic isolation system:

1) obviously and effectively reduce the seismic response of the structure. From the vibration table earthquake simulation test results and the United States, Japan built the whole structure in the earthquake isolation of the strong earthquake records that the vibration isolation system of structural acceleration response is only equivalent to the traditional structure (foundation fixed) acceleration response of 1/3 - 1/10. This effect of seismic reduction is the general traditional anti-seismic structure can not be expected. Thus, it can effectively protect the structure or internal equipment from any damage under the impact of strong earthquakes.

2) Ensure safety. When the ground shakes violently, the superstructure can still be in a normal elastic working condition. This applies both to general civil building structures, to ensure the absolute safety of residents in a strong earthquake, but also applies to some important structures and important equipment.

3) Reduce the cost of housing. From Shantou, Guangzhou, Xichang and other places to build seismic isolation houses, multi-storey seismic isolation houses than the traditional multi-storey seismic isolation houses to save the cost of housing civil construction: 7 degrees save 3 - 6%, 8 degrees save 8 - 14%, 9 degrees save 15 --20%. And the safety degree is greatly improved.

4) Seismic measures are simple and clear. The object involved in seismic resistance has been changed from the complex and unclear seismic measures considering the whole structure to the simple and clear one considering only the seismic isolation device. The structure itself is undoubtedly the same as the general practice in non-seismic areas, and the design and construction are greatly simplified.

5) Post-earthquake restoration is convenient: after the earthquake, only the necessary inspection and replacement of seismic isolation devices. And do not need to consider the repair of the building structure itself, the earthquake can be quickly restored to normal life or production, which brings very obvious social and economic benefits.

For more information about engineering/service/procurement bid writing and production, to improve the winning rate, you can click on the bottom of the official website customer service free consultation:/#/?source=bdzd