A seismic design method for weakly connected structures

Abstract

This invention relates to a seismic design method for a weakly connected structure, mainly comprising the following steps: A cantilever member extends outward from the main tower to provide a support sliding surface for the weakly connected structure; a horizontal steel plate is embedded in the top surface of the cantilever member, and a low-friction coefficient sliding material is laid on the embedded horizontal steel plate; the weakly connected structure is made of steel, with the steel beams of the weakly connected structure having reduced beam height near the support nodes to form a variable cross-section, and the ends of the steel beams resting on the low-friction coefficient sliding material; the floor slabs of the weakly connected structure are connected to the steel beams by studs, and the reinforcing bars of the floor slabs are anchored into the adjacent main towers on both sides. Using this invention for structural design ensures that the connected structure does not experience component failure under minor earthquakes and wind loads; and under major earthquakes, it does not suffer severe seismic damage such as the collapse of the connected structure, effectively protecting the safety of the overall structure.

Description

Technical Field

[0001] This invention belongs to the field of building structure technology, and specifically relates to a seismic design method for weakly connected structures. Background Technology

[0002] With the development of society and the economy, people have increasingly higher requirements for architecture, and various new structural forms are constantly emerging. Connected structures, due to their unique facade and strong visual impact, are favored by architects and are increasingly used in modern architecture.

[0003] Connected structures link different building units together through connecting elements; compared to conventional detached towers, connected structures have a more complex shape, making it difficult to control the dynamic response of the structure under strong earthquakes. The connecting elements and the areas where they connect to the main tower are key parts of the entire structure, and their stress conditions are particularly complex, posing a great challenge to the design of connected structures.

[0004] Based on the connection method between the connecting structure and the main tower, connected structures can be broadly classified into two categories: strong connection and weak connection. Strong connection requires minimal stiffness differences between the towers in the connected structure, and the connecting structure itself must possess sufficient stiffness to coordinate the shared stress and displacement of the main towers on both sides under rare earthquakes. Therefore, the application of strong connection places strict requirements on the structural characteristics of both the connecting structure itself and the connected towers.

[0005] For most structural systems with relatively small mass and stiffness of the connecting elements, weak connections are often suitable. This means the connecting element and the main tower are connected by a sliding connection, allowing for relative sliding relative to the main structure. Weak connections can reduce the mutual influence between the main tower and the connecting element under seismic loads, decrease the mass eccentricity and torsional effects of the connecting element on the main tower, and facilitate the construction of the connection nodes. This approach has a good effect on simplifying the design process and reducing structural costs.

[0006] However, there are many earthquake cases where elevated walkways with weak connections have failed, been damaged, or even collapsed entirely.

[0007] In view of this, the present invention, through a series of reasonable designs and reliable constructions, ensures that the weakly connected monolithic structure is "undamaged by minor earthquakes and does not fall during major earthquakes," effectively protecting structural safety. Summary of the Invention

[0008] The purpose of this invention is to provide a seismic design method for weakly connected structures. Using this design method, structural design can ensure that the connected structure does not experience component failure under minor earthquakes and wind loads, and does not suffer severe seismic damage such as the collapse of connected parts under major earthquakes, effectively protecting the safety of the overall structure.

[0009] To achieve the above objectives, the present invention provides a seismic design method for a weakly connected structure, characterized in that the weakly connected structure includes main towers and weakly connected structures connecting the main towers, and the seismic design method includes the following steps:

[0010] 1) An overhanging cantilever component extends from the main tower to provide a support sliding surface for the weakly connected body;

[0011] 2) Install horizontal steel plate embedded parts on the top surface of the cantilever component, and lay low friction coefficient sliding material on the horizontal steel plate embedded parts;

[0012] 3) The weak connection body adopts a steel structure. The steel beam of the weak connection body reduces the beam height near the support node to form a variable cross section. The ends of the steel beam rest on a low friction coefficient sliding material.

[0013] 4) The floor slabs of the weakly connected structure are connected to the steel beams with studs, and the steel bars of the floor slabs are anchored into the main towers on both sides.

[0014] According to the above technical solution, in step 1), the cantilevered member extending from the main tower is a key component providing vertical support for the weakly connected structure. When designing the cantilevered member, the shear force F it experiences... v Take: The maximum shear force at the end of the steel beam of the connecting body, calculated from the overall structural model of "main tower + connecting body" under a major earthquake. This shear force is the result of dead load D, live load L, and vertical seismic action F. Evk The most unfavorable combination value; the bending moment M = F at the root of the cantilever member. v ×l, where l is the cantilever length of the cantilever member; the cantilever member is also subjected to a horizontal tensile force N along the long span of the weak connection, the magnitude of which is equal to the sliding friction force f = μ·F. v μ is the friction coefficient between the steel beam and the sliding surface material of the support. The shear bearing capacity of the cantilever member should satisfy formula (1), which satisfies the elastic requirement of a major earthquake; the bending bearing capacity of the cantilever member should satisfy formula (2), which satisfies the non-yielding requirement of a major earthquake; this ensures that the weak connection will not fall as a whole due to support failure under rare earthquake action. At the same time, in order to further enhance the reliability and safety reserve of the support at this connection, the relevant vertical members of the main tower that provide support for the weak connection are designed according to the elastic design of a moderate earthquake.

[0015]

[0016]

[0017] In the formula: S GE The effect of the representative value of gravity load; The internal forces are the standard values ​​of horizontal seismic action. The value of is not subject to the amplification factor related to the seismic resistance level; The internal forces are the standard values ​​of vertical seismic forces. The value of R does not consider the amplification factor related to the seismic resistance level; d R represents the design value of the combined tension and shear capacity of the cantilever member. k Calculate R to obtain the standard value of the combined tensile and bending bearing capacity at the root section of the cantilever member. k The material strength value is taken as the standard value.

[0018] According to the above technical solution, in step 1), the cantilevered member extending from the main tower should provide a sufficiently long support surface for the sliding support of the weak connection, so that the slippage of the support meets the displacement requirements under rare earthquake action, and ensures that the weak connection does not slip under a major earthquake. The cantilever length l of the cantilevered member should satisfy formula (3):

[0019]

[0020] In the formula: Δ1 and Δ2 are the large seismic elastic-plastic horizontal displacement values ​​of the two main towers along the long span of their structures at the height of the weak connection; b is the minimum support width of the weak connection in the long span of its structure; w is the minimum seismic joint width between the weak connection and the main tower.

[0021] According to the above technical solution, in step 3), the steel beam of the weak connection body has a reduced beam height near the support node, forming a variable cross section. The end of the steel beam rests on the cantilevered member extending from the main tower. The vertical load of the weak connection body is entirely borne by the cantilevered member that meets the elastic requirements for shear resistance in major earthquakes. This structure can ensure that the main towers on both sides of the weak connection body will not suffer serious damage under rare earthquakes, and the weak connection body itself will not fall. For the steel beam in the section with reduced beam height in the support area, its bearing capacity should meet the requirements of formula (4) under minor earthquakes and wind loads to ensure the normal use of the weak connection body structure; under major earthquakes, its cross-sectional shear bearing capacity should meet the requirements of formula (5) to ensure that the support area of ​​the steel beam does not suffer shear failure. At the same time, the bearing capacity of the mid-span section of the steel beam should be higher than that of its support area, and the "bending stress ratio" of the mid-span section should be less than that of the support area, that is, meet the requirements of formula (6) to ensure that the mid-span section of the steel beam does not enter damage before the support area under major earthquakes.

[0022] S d ≤R d / γ Rd (4)

[0023] V≤f vy ·h w ·t w (5)

[0024]

[0025] In equation (4): S d R is the design value of the effect of a combination of minor earthquakes or wind loads. d γ represents the design value of the load-bearing capacity of a weakly connected steel beam in the section where the beam height is reduced. Rd γ is the uncertainty coefficient of the resistance model of the component, under small earthquake action. Rd Take 0.75, γ under wind load Rd Take 1.0; In equation (5): V is the maximum shear force at the support node of the steel beam under a major earthquake, f vy h represents the shear yield strength of the steel. w The net height of the web of the steel beam in the lower section is t. w σ is the web thickness of the steel beam; in equation (6): m τ represents the bending normal stress at the mid-span section of the steel beam under a major earthquake. b f represents the shear stress at the support section of the steel beam under a major earthquake. y f is the bending yield strength of steel. vy This represents the shear yield strength of the steel.

[0026] According to the above technical solution, in step 4), the floor slab of the weak connection body is connected to the steel beam by studs, and the reinforcing bars of the floor slab are anchored into the adjacent main towers on both sides. This structure can ensure that the weak connection body structure remains stable under minor earthquakes and wind loads, and does not frequently vibrate or displace, meeting normal use requirements. Under a major earthquake, the connection body slides relative to the main towers. At this time, shear failure is allowed at the junction of the main tower and the connection body, which is the weakest part of the connection. The concrete of the floor slab at this junction is repeatedly crushed, and the tensile and compressive plastic deformation of the reinforcing bars in the floor slab can dissipate seismic energy. At the same time, due to the entanglement of the reinforcing bars of the floor slab at the junction and the buffering effect of the crushed concrete in the gaps between the reinforcing bars, the impact between the connection body and the main tower can be avoided. In addition, the floor slab reinforcing bars of the connection body and the main towers on both sides are mutually connected and anchored, which can prevent the connection body from being thrown out under strong earthquakes and causing serious seismic damage.

[0027] The advantages of this invention are: through a series of reasonable designs and reliable constructions, using this method for structural design can ensure that the connected structure will not experience component failure or damage under minor earthquakes and wind loads; and under major earthquakes, there will be no serious earthquake damage such as the collapse of the connecting parts, effectively protecting the safety of the overall structure. Attached Figure Description

[0028] Figure 1 This is a schematic elevation view of a weakly connected structure.

[0029] Figure 2 for Figure 1 AA cross-section view.

[0030] Figure 3 This is a schematic diagram of a support node structure with weak connection. Detailed Implementation

[0031] The present invention will now be further described with reference to the accompanying drawings.

[0032] like Figure 1 , Figure 2 , Figure 3 As shown, the present invention mainly includes: a main tower 1, a weak connection body 2, an outward cantilever component 3, a weak connection body steel beam 4, a horizontal steel plate embedded part 5, a low friction coefficient sliding material 6, and a weak connection body floor slab 7.

[0033] An extended cantilever member 3 extends from the main tower 1, providing a support sliding surface for the weak connection body 2; a horizontal steel plate embedded part 5 is set on the top surface of the extended cantilever member 3, and a low friction coefficient sliding material 6, such as polytetrafluoroethylene plate, is laid on the horizontal steel plate embedded part 5; the weak connection body 2 adopts a steel structure, and the steel beam 4 of the weak connection body reduces the beam height near the support node to form a variable cross section, and the end of the steel beam rests on the low friction coefficient sliding material 6; the floor slab 7 of the weak connection body is connected to the steel beam 4 of the weak connection body by studs, and the steel bars of the floor slab 7 of the weak connection body are anchored into the adjacent two main towers 1.

[0034] The cantilevered member 3 extending from the main tower is a key component providing vertical support for the weakly connected structure. When designing the cantilevered member, the shear force F it experiences... v Take: The maximum shear force at the end of the steel beam of the connecting body, calculated from the overall structural model of "main tower + connecting body" under a major earthquake. This shear force is the result of dead load D, live load L, and vertical seismic action F. Evk The most unfavorable combination value; the bending moment M = F at the root of the cantilever member. v ×l, where l is the cantilever length of the cantilever member; the cantilever member is also subjected to a horizontal tensile force N along the long span of the weak connection, the magnitude of which is equal to the sliding friction force f = μ·F. v μ is the friction coefficient between the steel beam and the sliding surface material of the support. The shear bearing capacity of the cantilever member should satisfy formula (1), which satisfies the elastic requirement of a major earthquake; the bending bearing capacity of the cantilever member should satisfy formula (2), which satisfies the non-yielding requirement of a major earthquake; this ensures that the weak connection will not fall as a whole due to support failure under rare earthquake action. At the same time, in order to further enhance the reliability and safety reserve of the support at this connection, the relevant vertical members of the main tower that provide support for the weak connection are designed according to the elastic design of a moderate earthquake.

[0035]

[0036]

[0037] In the formula: S GE The effect of the representative value of gravity load; The internal forces are the standard values ​​of horizontal seismic action. The value of is not subject to the amplification factor related to the seismic resistance level; The internal forces are the standard values ​​of vertical seismic forces. The value of R does not consider the amplification factor related to the seismic resistance level; d R represents the design value of the combined tension and shear capacity of the cantilever member. k Calculate R to obtain the standard value of the combined tensile and bending bearing capacity at the root section of the cantilever member. k The material strength value is taken as the standard value.

[0038] The cantilevered member 3 extending from the main tower should provide a sufficiently long support surface for the sliding bearing of the weak connection, so that the bearing slippage meets the displacement requirements under rare earthquake action, and ensures that the weak connection does not slip under a major earthquake. The cantilever length l of the cantilevered member should satisfy formula (3):

[0039]

[0040] In the formula: Δ1 and Δ2 are the large seismic elastic-plastic horizontal displacement values ​​of the two main towers along the long span of their structures at the height of the weak connection; b is the minimum support width of the weak connection in the long span of its structure; w is the minimum seismic joint width between the weak connection and the main tower.

[0041] The steel beam 4 of the weak connection body has a reduced beam height near the support node, forming a variable cross section. The end of the steel beam rests on the cantilevered members extending from the main tower. The vertical load of the weak connection body is entirely borne by the cantilevered members that meet the elastic requirements for shear resistance in major earthquakes. This structure can ensure that the main towers on both sides of the weak connection body will not suffer serious damage and the weak connection body itself will not fall under rare earthquake action. For the steel beam in the section with reduced beam height in the support area, its bearing capacity should meet the requirements of formula (4) under minor earthquakes and wind loads to ensure the normal use of the weak connection structure; under major earthquake action, its cross-sectional shear bearing capacity should meet the requirements of formula (5) to ensure that the support area of ​​the steel beam does not suffer shear failure. At the same time, the bearing capacity of the mid-span section of the steel beam should be higher than that of its support area, and the "stress ratio" of the mid-span section should be less than that of the support area, that is, meet the requirements of formula (6) to ensure that the mid-span section of the steel beam does not enter damage before the support area under major earthquakes.

[0042] S d ≤R d / γ Rd (4)

[0043] V≤f vy ·h w ·t w(5)

[0044]

[0045] In equation (4): S d R is the design value of the effect of a combination of minor earthquakes or wind loads. d γ represents the design value of the load-bearing capacity of a weakly connected steel beam in the section where the beam height is reduced. Rd γ is the uncertainty coefficient of the resistance model of the component, under small earthquake action. Rd Take 0.75, γ under wind load Rd Take 1.0; In equation (5): V is the maximum shear force at the support node of the steel beam under a major earthquake, f vy h represents the shear yield strength of the steel. w The net height of the web of the steel beam in the lower section is t. w σ is the web thickness of the steel beam; in equation (6): m τ represents the bending normal stress at the mid-span section of the steel beam under a major earthquake. b f represents the shear stress at the support section of the steel beam under a major earthquake. y f is the bending yield strength of steel. vy This represents the shear yield strength of the steel.

[0046] The weakly connected floor slab 7, i.e., the floor slab of the weakly connected structure, is connected to the steel beams by studs, and the reinforcing bars of the floor slab are anchored into the adjacent main towers on both sides. This structure ensures that the weakly connected structure remains structurally stable under minor earthquakes and wind loads, and does not frequently vibrate or displace, meeting normal use requirements. Under a major earthquake, the connected structure may slide relative to the main towers. At this time, shear failure is allowed at the junction of the main towers and the connected structure, which is the weakest point of the connection. The concrete of the floor slab at this junction is repeatedly crushed, and the tensile and compressive plastic deformation of the reinforcing bars in the floor slab can dissipate seismic energy. At the same time, due to the entanglement of the reinforcing bars of the floor slab at the junction and the buffering effect of the crushed concrete in the gaps between the reinforcing bars, impact between the connected structure and the main towers can be avoided. In addition, the floor slab reinforcing bars of the connected structure and the main towers on both sides are interconnected and anchored, which can prevent the connected structure from being thrown out and causing serious earthquake damage under strong earthquakes.

[0047] Through a series of reasonable designs and reliable constructions, this invention ensures that weakly connected structures designed using this method will not experience component failure under minor earthquakes and wind loads, and will not suffer severe earthquake damage such as the collapse of connected components under major earthquakes, effectively protecting the safety of the overall structure.

Claims

1. A seismic design method for a weakly connected structure, characterized in that, The weakly connected structure includes the main towers and the weakly connected structures between the main towers. The seismic design method includes the following steps: An overhanging cantilever component extends from the main tower, providing a support sliding surface for the weakly connected body; A horizontal steel plate is embedded on the top surface of the cantilever component, and a low-friction coefficient sliding material is laid on the horizontal steel plate embedded part. The weak connection body adopts a steel structure. The steel beam of the weak connection body has a reduced beam height near the support node to form a variable cross section. The ends of the steel beam rest on a low friction coefficient sliding material. The floor slabs of the weakly connected structure are connected to the steel beams with studs, and the steel bars of the floor slabs are anchored into the main towers on both sides. When designing cantilever components, the shear force they experience... F v Take: The maximum shear force at the end of the steel beam of the weakly connected structure, calculated from the overall structural model of "main tower + weakly connected structure" under a major earthquake. This shear force is the dead load. D Live load L Vertical seismic action F Evk The most unfavorable combination value; the bending moment at the root of the cantilever member. M = F v × l , l The cantilever length of the outrigger cantilever member; the outrigger cantilever member is also subjected to a horizontal tensile force along the long span of the weakly connected body. N Function, tensile force value N The magnitude is equal to the sliding friction force f = μ · F v , μ The friction coefficient between the steel beam and the sliding surface material of the support is given; the shear bearing capacity of the cantilever member should meet the formula (1), which can satisfy the elastic requirements of a major earthquake; the bending bearing capacity of the cantilever member should meet the formula (2), which can satisfy the non-yielding requirements of a major earthquake; this can ensure that the weak connection body will not fall as a whole due to the failure of the support under rare earthquake action; （1） （2） In the formula: The effect of the representative value of gravity load; Internal forces that are the standard values ​​of horizontal seismic action; Internal forces representing the standard value of vertical seismic action; R d This represents the design value of the combined tensile-shear bearing capacity of the cantilever component. R k This is the standard value of the combined tensile and bending bearing capacity of the root section of the cantilever member.

2. The seismic design method for a weakly connected structure according to claim 1, characterized in that: Cantilever length of the overhanging cantilever component l Formula (3) should be satisfied: （3） In the formula: Δ1 and Δ2 are the large seismic elastic-plastic horizontal displacement values ​​of the two main towers along the long span of their structure at the height of the weak connection body; b The minimum support width of the weakly connected body in the long span direction of its structure; w This refers to the minimum width of the seismic joint between the weakly connected structure and the main tower.

3. A seismic design method for a weakly connected structure according to claim 1 or 2, characterized in that: The steel beams of the weakly connected body have their height reduced near the support nodes to form a variable cross section. The ends of the steel beams are placed on the cantilever members extending from the main tower. For the steel beams in the support area with reduced beam height, under minor earthquakes and wind loads, their bearing capacity should meet the requirements of formula (4) to ensure the normal use of the connected structure. Under major earthquakes, their cross-sectional shear bearing capacity should meet the requirements of formula (5) to ensure that the support area of ​​the steel beams does not suffer shear failure. At the same time, the bearing capacity of the mid-span section of the steel beams should be higher than that of the support area, and the "stress ratio" of the mid-span section should be lower than that of the support area, which meets the requirements of formula (6) to ensure that the mid-span section of the steel beams does not enter damage before the support area under major earthquakes. （4） （5） （6） In equation (4): S d The design values ​​represent the effects of a combination of minor earthquakes or wind loads. R d This represents the design value of the load-bearing capacity of the weakly connected steel beam in the section where the beam height is reduced. γ Rd The coefficient of uncertainty in the resistance model of the component is given under small earthquake conditions. γ Rd Take 0.75, when wind load is applied. γ Rd Take 1.0; in equation (5): V This represents the maximum shear force at the support joint of the steel beam under a major earthquake. f vy This represents the shear yield strength of the steel. h w To reduce the net height of the web of the steel beam section, t w Where is the web thickness of the steel beam; in formula (6): σ m The bending normal stress at the mid-span section of the steel beam under a major earthquake. τ b This represents the shear stress at the support section of the steel beam under a major earthquake. f y The bending yield strength of steel. f vy This represents the shear yield strength of the steel.

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