CN107577866B - A design method of combined isolation device under near-fault earthquake - Google Patents

Abstract

The invention provides a design method of a combined shock insulation device under the action of a near-fault earthquake, which forms the combined shock insulation device by a friction pendulum support and a buffering anti-falling beam device to uniformly and coordinately consume energy, performs combined design on technical parameters of each device in the combined shock insulation device according to the actual requirements of a bridge during earthquake resistance design, is easy to finely design and control, can ensure that an upper structure has larger deformation capacity and does not fall the beam, avoids material waste or insufficient earthquake resistance caused by design according to theoretical conditions, is favorable for saving steel bar materials, improving the energy consumption effect of the combined shock insulation device, effectively reduces the inertia force of the upper structure, thereby protecting lower structures such as piers, foundations and the like, being favorable for adjusting the distribution of earthquake force among the lower structures, improving the earthquake resistance of the bridge and ensuring that the beam does not fall under the condition of large earthquake, meanwhile, the support is protected from being seriously damaged, the safety is enhanced, and the maintenance cost of the bridge after the earthquake is reduced.

Description

A design method of combined isolation device under near-fault earthquake

technical field

The invention relates to the technical field of bridge seismic design, in particular to a design method of a combined seismic isolation device under the action of a near-fault earthquake.

Background technique

In the near-fault region, the seismic ground motion has two main characteristics: one is the forward and backward direction effects determined by the fault mechanism and the direction of the fault diffusion; the other is the permanent ground displacement along the fault slip direction. effect. Among them, the ground motion caused by the forward directional effect is a dynamic vibration process in the form of bilateral reciprocation. , which is the biggest difference between the ground motion of near-fault earthquakes and far-field seismic ground motions. Near-fault pulsed ground motions will cause greater damage to mid- and long-period structures, such as long-span bridges, shock-absorbing structures, and isolation structures. In addition, the permanent ground displacement is the irrecoverable ground displacement caused by the slip of the fault, and its velocity time history is in the form of a unilateral or unilateral pulse, and its displacement time history is a unilateral step pulse, which is close to the fault. Large-span bridges in the region can also cause damage due to the spatial variability of permanent ground displacement.

Ordinary bearings are usually difficult to play the role of vibration isolation, while friction pendulum bearings have the advantages of good durability, larger displacement and higher bearing capacity. There are usually two friction pendulums on both sides of a beam on existing bridges. Bearings, the design yield load of the four friction pendulum bearings is generally calculated according to the horizontal seismic force on a beam and the stiffness distribution between the friction pendulum bearings, but due to the small vertical ground motion of the far-field vibration, In a near-fault earthquake, it is easy to form resonance with the near-fault seismic wave, increasing its seismic response, resulting in the impact and damage of the bridge abutment, or even falling beams, and because the near-fault earthquake contains many long-period components, only the friction pendulum has a better shock absorption effect. At the same time, due to the relatively significant vertical ground motion of near-fault earthquakes, the frictional pendulum alone is used to dissipate frictional energy, which cannot meet the requirements.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to provide a combined seismic isolation device under near-fault earthquake action, aiming at the deficiencies in the prior art that the common bearing cannot reduce the earthquake isolation and the seismic isolation device has poor anti-seismic performance. In order to achieve the above-mentioned purpose of the invention, the present invention provides the following technical solutions:

A design method of a combined seismic isolation device under the action of a near-fault earthquake, the combined seismic isolation device comprises a buffering anti-drop beam device and a friction pendulum support, and the design method of the combined seismic isolation device comprises the following steps:

(1) Assuming that the natural vibration period corresponding to the initial elastic stiffness of the combined seismic isolation device is in the platform section of the response spectrum curve, obtain the initial value of the seismic force Q(1);

(2) Put the combined seismic isolation device in the elastic working stage, know the yield displacement of the buffering anti-drop beam device under the action of the initial seismic force Q(1), and obtain the elasticity of the combined seismic isolation device initial stiffness value k(1);

(3) Obtain the initial value t(1) of the natural vibration period of the structure through the mass of the upper structure and the initial elastic stiffness value k(1);

(4) Taking the initial value of the structural natural vibration period t(1) as the structural natural vibration period t(i), the seismic force Q(i) is obtained through the response spectrum curve;

(5) Make the combined seismic isolation device in the elastic working stage, know the yield displacement of the buffering anti-drop beam device under the action of the seismic force Q(i), obtain the elastic stiffness k(i), and combine the According to the mass of the superstructure, the natural vibration period t(i+1) of the structure can be obtained, and the seismic force Q(i+1) can be obtained through the response spectrum curve;

ε为预设要求；(6) Seismic force error

ε is the default requirement;

(7) Decrease the obtained seismic force Q(i+1) by 30%-40% as the design yield load, and obtain each of the combined isolation devices according to the stiffness distribution among all the combined isolation devices The yield shear force of each of the combined seismic isolation devices is subtracted from the shear force of the friction pendulum support corresponding to the yield displacement of the buffer anti-drop beam device to obtain the yield strength of the buffer anti-drop beam device The design value of the combined seismic isolation device is completed.

Compared with the existing friction pendulum bearing independently used as a buffering energy dissipation device, the method combines the friction pendulum bearing and the buffering anti-falling beam device to form a combined vibration isolation device, so that the two are unified and coordinated to dissipate energy. When designing, according to the actual needs of the bridge, a combination of the two parameters is designed, which is easy to refine the design and control, improve the seismic performance, and the design is more reasonable. Due to the waste of materials or insufficient seismic performance due to the design according to the theoretical situation, the energy dissipation effect of the combined isolation device is optimized and improved, and the inertial force of the superstructure is effectively reduced, thereby protecting the substructures such as bridge piers and foundations, and is conducive to adjusting the seismic force in each area. The distribution between the substructures improves the overall seismic performance of the bridge, ensures that the beam does not fall under the condition of a large earthquake, and at the same time protects the bearing from serious damage, enhances safety, and reduces the maintenance cost of the bridge after the earthquake.

Further, in the step (7), the design yield load can be replaced by the product of the design peak acceleration of the combined seismic isolation device and the mass of the main beam.

Further, in the step (7), the obtained seismic force Q(i+1) is reduced by 35% as the design yield load.

重复进行步骤(5)，直到地震力误差满足预设要求。Further, in the step (6), if the seismic force error

Step (5) is repeated until the seismic force error meets the preset requirement.

Further, ε=0.5%.

A bridge includes a combined seismic isolation device and a friction pendulum support, wherein the combined seismic isolation device is designed using the design method of the combined seismic isolation device under the action of a near-fault earthquake as described in any one of the above.

Because the friction pendulum bearing has a certain energy dissipation effect, compared with the combination of vibration isolation devices at both ends of each main beam, the combination of the combination vibration isolation device and the friction pendulum bearing is used to work together, which is economical and conducive to saving costs. , improve the installation rate, speed up the construction progress, ensure the safety performance of the bridge, and reduce the maintenance cost of the bridge after the earthquake.

Compared with the prior art, the beneficial effects of the present invention are: compared with the existing friction pendulum support independently used as a buffering energy dissipation device, the method combines the friction pendulum support and the buffering anti-drop beam device to form a combined vibration isolation device. In the seismic design, the technical parameters of each device in the combined seismic isolation device are combined and designed according to the actual needs of the bridge, which is easy to refine the design and control and improve the seismic performance of the overall bridge. , the design is more reasonable, which can not only ensure that the superstructure has a large deformation capacity, but also ensure that it does not fall off the beam, avoid material waste or insufficient seismic performance due to the design according to the theoretical situation, and improve the energy consumption of the combined seismic isolation device. It can effectively reduce the inertial force of the upper structure, thereby protecting the lower structures such as bridge piers and foundations, which is conducive to adjusting the distribution of seismic force among the substructures. The combination of the combined isolation device and the friction pendulum bearing is conducive to saving costs and installation. Fast, speed up the construction progress, ensure the seismic performance of the bridge, ensure that the beam will not fall in the event of a major earthquake, and at the same time protect the bearing from serious damage, enhance safety, and reduce the maintenance cost of the bridge after the earthquake.

Description of drawings

Fig. 1 is a flow chart of a design method of a combined seismic isolation device under the action of a near-fault earthquake in the present invention.

Detailed ways

The present invention will be further described in detail below with reference to the examples and specific implementation manners. However, it should not be construed that the scope of the above-mentioned subject matter of the present invention is limited to the following embodiments, and all technologies realized based on the content of the present invention belong to the scope of the present invention.

Example 1

A design method of a combined seismic isolation device under the action of a near-fault earthquake. The combined seismic isolation device includes a buffering anti-drop beam device and a friction pendulum support. As shown in Figure 1, the design method of the combined seismic isolation device includes the following steps:

(1) Assuming that the natural vibration period corresponding to the initial elastic stiffness of the combined seismic isolation device is in the platform section of the response spectrum curve, obtain the initial value of the seismic force Q(1);

(2) Put the combined seismic isolation device in the elastic working stage, know the yield displacement of the buffering anti-drop beam device under the action of the initial seismic force Q(1), and obtain the elasticity of the combined seismic isolation device initial stiffness value k(1);

(3) Obtain the initial value t(1) of the natural vibration period of the structure through the mass of the upper structure and the initial elastic stiffness value k(1);

(4) Taking the initial value of the structural natural vibration period t(1) as the structural natural vibration period t(i), the seismic force Q(i) is obtained through the response spectrum curve;

(5) Make the combined seismic isolation device in the elastic working stage, know the yield displacement of the buffering anti-drop beam device under the action of the seismic force Q(i), obtain the elastic stiffness k(i), and combine the According to the mass of the superstructure, the natural vibration period t(i+1) of the structure can be obtained, and the seismic force Q(i+1) can be obtained through the response spectrum curve;

ε为预设要求；(6) Seismic force error

ε is the default requirement;

(7) Decrease the obtained seismic force Q(i+1) by 35% as the design yield load, and obtain the yield shear of each of the combined isolation devices according to the stiffness distribution among all the combined isolation devices The shear force of the friction pendulum support corresponding to the yield displacement of the buffer anti-drop beam device is subtracted from the yield shear force value of each of the combined isolation devices to obtain the design value of the yield strength of the buffer anti-drop beam device , to complete the seismic design of the combined isolation device.

若误差不满足条件，则重复进行所述步骤(5)进行迭代计算新的Q(i+1)，然后将满足条件的Q(i+1)下调35％作为设计屈服荷载，也可以采用所述组合隔震装置的设计峰值加速度与主梁质量的乘积作为设计屈服荷载，每片主梁两端全部采用所述组合隔震装置，如共设置四个所述组合隔震装置时，根据四个所述组合隔震装置之间的刚度分配，得到每个所述组合隔震装置的屈服剪力，将每个所述组合隔震装置的屈服剪力值减去所述缓冲防落梁装置屈服位移对应的摩擦摆支座的剪力，得到所述缓冲防落梁装置屈服强度的设计值，完成组合隔震装置的抗震设计。The combined isolation device includes a buffering anti-drop beam device and a friction pendulum support. Assuming that the natural vibration period corresponding to the initial elastic stiffness of the combined isolation device is in the platform section of the response spectrum curve, the initial value of the seismic force Q(1) is obtained. , under the action of the seismic force Q(1), the combined seismic isolation device is in an elastic working stage, and the yield displacement of the buffered anti-drop beam device of the combined seismic isolation device is known, and the combined seismic isolation device is obtained. The initial elastic stiffness value k(1) of the structure is obtained, and the initial value t(1) of the natural vibration period of the structure is obtained by the mass of the upper structure and the initial elastic stiffness value k(1), and the initial value t(1) of the natural vibration period of the structure is used as the structural self-vibration period. The vibration period t(i), according to the natural vibration period t(i) of the structure, through the response spectrum curve, the seismic force Q(i) is obtained. It is known that the buffer and anti-fall under the action of the seismic force Q(i) The yield displacement of the beam device can be used to obtain the elastic stiffness k(i) of the combined isolation device. Combined with the quality of the upper structure, the natural vibration period t(i+1) of the structure can be obtained, and the seismic force can be obtained through the response spectrum curve. Q(i+1), calculate the seismic force error, when ε=0.5%, make

If the error does not meet the condition, repeat the step (5) to iteratively calculate a new Q(i+1), and then reduce the Q(i+1) that satisfies the condition by 35% as the design yield load. The product of the design peak acceleration of the combined seismic isolation device and the mass of the main beam is taken as the design yield load, and the combined seismic isolation device is used at both ends of each main beam. The stiffness distribution among the combined isolation devices, the yield shear force of each combined isolation device is obtained, and the value of the yield shear force of each combined isolation device is subtracted from the buffer drop-proof beam device The shear force of the friction pendulum support corresponding to the yield displacement is used to obtain the design value of the yield strength of the buffering anti-drop beam device, and the seismic design of the combined seismic isolation device is completed.

Example 2

A bridge includes a combined seismic isolation device and a friction pendulum support. The combined seismic isolation device is designed using the design method of the combined seismic isolation device under the action of a near-fault earthquake as in Example 1.

A bridge, one side of each main girder and the bridge pier adopts the combined seismic isolation device designed by the design method in Example 1, and only the friction pendulum bearing is used between the other side and the bridge pier, wherein the combination In the design step (7) of the seismic isolation device, the yield shear force of each of the combined seismic isolation devices is obtained according to the stiffness distribution between the two combined seismic isolation devices and the two common supports. The use of a bridge combined with a combined isolation device and a friction pendulum bearing is conducive to saving costs, improving the installation rate and speeding up the construction progress.

Claims (6)

1. the design method of the combined seismic isolation device under the action of a near-fault earthquake, is characterized in that, the combined seismic isolation device comprises a buffering anti-drop beam device and a friction pendulum support, and the design method of the combined seismic isolation device may further comprise the steps: (1) Assuming that the natural vibration period corresponding to the initial elastic stiffness of the combined seismic isolation device is in the platform section of the response spectrum curve, obtain the initial value of the seismic force Q(1); (2) Put the combined seismic isolation device in the elastic working stage, know the yield displacement of the buffering anti-drop beam device under the action of the initial seismic force Q(1), and obtain the elasticity of the combined seismic isolation device initial stiffness value k(1); (3) Obtain the initial value t(1) of the natural vibration period of the structure through the mass of the upper structure and the initial elastic stiffness value k(1); (4) Taking the initial value of the structural natural vibration period t(1) as the structural natural vibration period t(i), the seismic force Q(i) is obtained through the response spectrum curve; (5) Make the combined seismic isolation device in the elastic working stage, know the yield displacement of the buffering anti-drop beam device under the action of the seismic force Q(i), obtain the elastic stiffness k(i), and combine the According to the mass of the superstructure, the natural vibration period t(i+1) of the structure can be obtained, and the seismic force Q(i+1) can be obtained through the response spectrum curve; (6) Seismic force error

ε is the default requirement; (7) Decrease the obtained seismic force Q(i+1) by 30%-40% as the design yield load, and obtain each of the combined isolation devices according to the stiffness distribution among all the combined isolation devices The yield shear force of each of the combined seismic isolation devices is subtracted from the shear force of the friction pendulum support corresponding to the yield displacement of the buffer anti-drop beam device to obtain the yield strength of the buffer anti-drop beam device The design value of the combined seismic isolation device is completed. 2 . The method for designing a composite isolation device under a near-fault earthquake as claimed in claim 1 , wherein in the step (7), the design yield load can use the composite isolation device. 3 . The product of the design peak acceleration and the mass of the main beam is replaced. 3. The design method of a composite isolation device under a near-fault earthquake as claimed in claim 1, wherein in the step (7), the obtained seismic force Q(i+1) Decrease 35% as design yield load. 4. The design method of a composite isolation device under the action of a near-fault earthquake according to any one of claims 1-3, wherein in the step (6), if the seismic force error

Step (5) is repeated until the seismic force error meets the preset requirement. 5. The design method of a combined seismic isolation device under the action of a near-fault earthquake according to any one of claims 1-3, wherein ε=0.5%. 6. A bridge, characterized in that it comprises a combined isolation device and a friction pendulum bearing, and the combined isolation device adopts the method of the combined isolation device under the action of a near-fault earthquake as claimed in any one of claims 1-5. Design method design.

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