Semi-hinged concrete column base joint and design method

Abstract

The invention discloses a semi-hinged concrete column base joint and a design method, belongs to the technical field of building structure engineering, and solves the problems that an existing vehicle base is large in inclination rigidity and large in earthquake action. The column base joint comprises a concrete foundation, a reinforced concrete column is arranged on the concrete foundation, profile steel is arranged in the reinforced concrete column, the lower end of the profile steel is inserted into the concrete foundation, the upper end of the profile steel is flush with the bottom of an upper-layer beam, and a connecting bottom plate is arranged at the bottom of the profile steel. The connecting bottom plate is connected with a concrete foundation through anchor bolts pre-embedded in the concrete foundation, a plurality of column foot longitudinal bars and continuous composite rectangular spiral hoops are arranged in a column foot section of the reinforced concrete column, and a plurality of column top longitudinal bars and composite hoops are arranged in a column top section of the reinforced concrete column. According to the semi-hinged concrete column base joint and the design method, the earthquake effect and the large chassis effect of a subway vehicle base skirt house are effectively reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of building structure engineering, and in particular to a semi-hinge concrete column foot node and a design method thereof. Background Art

[0002] The plane area of ​​the chassis structure unit of the subway vehicle base is sometimes very large. The spacing of the expansion joints of the vehicle base cover structure can be controlled at 200m and should not exceed 250m. Generally, the first floor is used as the vehicle base track layer, and the second floor is used as the car garage and frame support transfer layer, naturally forming a large chassis structure.

[0003] The vehicle base's heavy load, large area, long column spacing, and large cross-sectional component dimensions result in greater structural lateral stiffness and seismic effects. Furthermore, the large chassis effect amplifies the seismic effects on the tower above it. For example, in one example, when the building is 50m tall and the podium extends 60m on each side, the shear force on the upper floor of the podium is approximately 50% greater than the shear force on the same floor at a height of 150m, and approximately 150% greater than the shear force on the same floor at a height of 50m without a podium. At 150m, the shear force curve for the tower floors becomes curved, reflecting a curve with an inflection point in the higher-order vibration mode.

[0004] Earthquake damage in recent years has shown that collapsed frame structures are mostly due to column end failure, failing to achieve the "strong column, weak beam" yield mechanism envisioned in the design. In addition to the "strengthen-strengthen-reinforce" approach, reducing the lateral stiffness of the vehicle base's large chassis structure to mitigate seismic effects is another approach. Strengthening the ductility of the column base's podium columns and allowing for a hybrid yield mechanism with hinges at the base will involve more components than a beam-hinge mechanism in energy dissipation. While allowing for hinges at the base releases bending moments at the base, it also limits horizontal displacement compared to seismic isolation structures. As long as the top ends of the first-floor columns are not hinged, the first-floor yield mechanism will not form. The fact that a large number of frame buildings with column hinges remained standing during earthquakes also demonstrates the feasibility of this approach. Furthermore, the axial forces in the frame columns of the vehicle base's towers are so large that the bases of the first-floor columns generally do not experience bending yield. In addition, since the podium column base is allowed to be hinged, it is also beneficial to ensure the safety of the column top node on the first floor under a huge earthquake that exceeds the design earthquake intensity. However, the existing structure usually has rigidly connected column bases, and the earthquake action and large chassis effect are all borne by the rigid system, and the effect does not meet the ideal expectations. Therefore, it is urgent to design a column base structure that can meet the usage requirements. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to address the above-mentioned shortcomings of the existing technology and provide a semi-articulated concrete column base node and design method, which effectively reduces the seismic effects and large chassis effect of the subway vehicle base podium, and has the characteristics of easy use and strong practicality.

[0006] The technical solution adopted by the present invention is: a semi-hinged concrete column base node, including a concrete foundation, a reinforced concrete column is provided on the concrete foundation, a steel section is provided in the reinforced concrete column, the lower end of the steel section is inserted into the concrete foundation, the upper end of the steel section is flush with the bottom of the upper beam, the bottom of the steel section is provided with a connecting base plate, and the connecting base plate is connected to the concrete foundation by anchor bolts pre-embedded in the concrete foundation, a plurality of column base longitudinal bars and continuous composite rectangular spiral hoops are provided in the column base section of the reinforced concrete column, and a plurality of column top longitudinal bars and composite hoops are provided in the column top section of the reinforced concrete column.

[0007] As a further improvement, a steel mesh is provided in the plastic hinge area of ​​the column foot of the reinforced concrete column, and the lower end of the steel mesh extends into the concrete foundation.

[0008] Furthermore, the steel wire mesh is woven from galvanized steel wires, the diameter of the galvanized steel wires is 4mm to 6mm, and the mesh spacing is 50mm to 100mm.

[0009] Furthermore, the continuous composite rectangular spiral hoop includes an outer spiral hoop and an inner spiral hoop, the inner spiral hoop is arranged inside the outer spiral hoop, and both the outer spiral hoop and the inner spiral hoop are arranged inside the reinforced concrete column.

[0010] Furthermore, the cross section of the steel section is a cross-shaped structure, and a plurality of bolts are provided on the four flange plates of the steel section.

[0011] Furthermore, the upper end of the steel section is provided with a stiffening rib for enhancing the mechanical strength.

[0012] Furthermore, a mortar layer is provided on the outer surface of the reinforced concrete column.

[0013] A design method for a semi-hinged concrete column base node comprises the following steps:

[0014] (1) Calculate the column foot longitudinal reinforcement according to the column foot rigid connection and the current code for seismic design. When the calculated steel concrete column foot longitudinal reinforcement is less than the longitudinal reinforcement corresponding to the minimum reinforcement ratio specified in the current code, the column foot longitudinal reinforcement shall be arranged according to the minimum reinforcement ratio;

[0015] (2) When the longitudinal reinforcement of the steel concrete column foot calculated in the above steps is greater than the longitudinal reinforcement corresponding to the minimum reinforcement ratio, the longitudinal reinforcement of the column foot shall be arranged according to the maximum value of the following a), b), and c) under the condition of rigid connection of the column foot;

[0016] a) Calculate the longitudinal reinforcement at the column base according to the provisions of the current code for non-seismic design;

[0017] b) Calculate the longitudinal reinforcement at the column base according to the standard value of the combined effect of load and seismic action and the standard value of material strength, i.e., formula (1), and do not adjust the column base bending moment value for the combined seismic action according to relevant regulations;

[0018] S GE +γ Eh S Ehk +γ Ev S Evk +ψ w γ w S wk ≤R k (1)

[0019] Where: S GE is the effect of the representative value of gravity load; S Ehk 、S Evk Divided into the effects of horizontal and vertical earthquake action standard values; S wk is the effect of the standard value of wind load; ψ w is the combined value coefficient of wind load; γ Eh , γ Ev , γ w are the partial factors of horizontal earthquake action, vertical earthquake action and wind load respectively; R k is the standard value of resistance of structural components; γ Eh , γ Ev , γ w , ψ w All values ​​are taken according to the current specifications, but when greater than 1.0, they are taken as 1.0;

[0020] c) Longitudinal reinforcement corresponding to the minimum reinforcement ratio specified in the current specifications;

[0021] (3) Calculate the first-floor column top longitudinal reinforcement according to the current code, i.e., the principle of "strong column and weak beam". The excess column top longitudinal reinforcement compared to the column foot longitudinal reinforcement determined according to (1) or (2) above shall be anchored or overlapped at the mid-span along the column height direction.

[0022] (4) Calculate the column stirrups according to the current specifications. The stirrups of the lower half of the first-floor column adopt the continuous composite rectangular spiral stirrup form with excellent load-bearing performance, and the upper half adopts the usual composite stirrup form. Since the number of longitudinal bars in the lower half of the column determined by the above steps (1) or (2) is relatively small, it creates conditions for the application of continuous composite rectangular spiral stirrups.

[0023] Furthermore, the upper beam and column nodes are designed with the top of the steel section extending to the bottom of the lower longitudinal reinforcement of the upper beam but not extending into the node, and the wire mesh on the surface of the column foot is configured according to the wire mesh structure.

[0024] Beneficial effects

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] 1. By reducing the cross-section of the podium columns, making the column base semi-hinged, and improving the ductility of the column base, the seismic effects of the podium and the influence of the podium on the seismic effects of the tower above it can be reduced.

[0027] 2. Compared with the existing general reinforced concrete column base, the ductility and energy dissipation capacity of the column base are increased, and the beam hinge yield mechanism is transformed into a mixed yield mechanism of beam hinge yield and podium column base yield, which increases the energy dissipation capacity of the structure.

[0028] 3. The column foot increases the ductility of the concrete column by setting steel sections, continuous composite rectangular spiral hoops and surface wire mesh. The small cross-section of the steel sections and the small number of longitudinal reinforcements facilitate the construction of the steel-concrete column foot. At the same time, the bending yielding and hinge formation of the column foot also help to ensure the safety of the column top node of this layer under the action of a huge earthquake exceeding the intensity of a major earthquake.

[0029] 4. The steel sections in the columns do not extend into the upper beams, which facilitates the construction of the upper concrete beam and column nodes and ensures the quality of concrete pouring at the upper beam and column nodes. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a schematic diagram of the main structure of the present invention;

[0031] Figure 2 for Figure 1 Middle AA section view;

[0032] Figure 3 for Figure 1 Middle BB cross-section;

[0033] Figure 4 Schematic diagram of the outer spiral hoop of the present invention;

[0034] Figure 5 Schematic diagram of the inner spiral hoop in the present invention;

[0035] Figure 6 It is a schematic elevation diagram of the steel wire mesh in the present invention.

[0036] Among them: 1-reinforced concrete column, 2-steel section, 3-column base longitudinal reinforcement, 4-column top longitudinal reinforcement, 5-continuous composite rectangular spiral hoop, 6-composite hoop, 7-wire mesh, 8-concrete foundation, 9-upper beam, 10-stud, 11-stiffening rib, 12-anchor bolt, 13-connecting base plate, 14-flange plate, 15-mortar layer, 51-external spiral hoop, 52-inner spiral hoop. DETAILED DESCRIPTION

[0037] The present invention will be further described below with reference to the specific embodiments in the accompanying drawings.

[0038] See Figure 1-6As shown, a semi-hinged concrete column base node of the present invention includes a concrete foundation 8, a reinforced concrete column 1 is provided on the concrete foundation 8, a steel section 2 is provided in the reinforced concrete column 1, the lower end of the steel section 2 is inserted into the concrete foundation 8, the upper end of the steel section 2 is flush with the bottom of the upper beam 9, a connecting base plate 13 is provided at the bottom of the steel section 2, and the connecting base plate 13 is connected to the concrete foundation 8 by an anchor bolt 12 pre-buried in the concrete foundation 8, a plurality of column base longitudinal bars 3 and a continuous composite rectangular spiral hoop 5 are provided in the column base section of the reinforced concrete column 1, and a plurality of column top longitudinal bars 4 and a composite hoop 6 are provided in the column top section of the reinforced concrete column 1. Since the podium area of ​​a subway vehicle base is usually large, the load is large, and the cross-section of the beams and columns is large, the lateral stiffness of the podium is large and the seismic effect is large. By reducing the cross-section of the podium columns and making the column bases "semi-hinged", a small amount of necessary longitudinal reinforcement is arranged at the reinforced concrete column bases to ensure the bending bearing capacity when there is no earthquake and under the combined effect of smaller earthquakes. Under the combined effect of larger earthquakes, the longitudinal reinforcement is allowed to yield early to form plastic hinges. At the same time, measures are taken to increase the ductility of the column base, which is called a "semi-hinged" column base. The increase in ductility is achieved by setting steel sections 2, continuous composite rectangular spiral hoops 5, and surface wire mesh 7 at the column base. The change from the beam hinge yield mechanism to the mixed yield mechanism of beam hinge yield and podium column foot yield increases the energy absorption capacity of the structure, reduces the seismic action of the podium and reduces the large chassis effect of the podium's influence on the seismic action of the tower above it. In addition, due to the small cross-section of the steel section 2 and the small number of longitudinal bars, the construction of the steel-concrete column foot is convenient, and the cross-section of the podium column can be reduced. At the same time, due to the bending yield and hinge of the column foot, it is also beneficial to ensure the safety of the column top node of this layer under the action of a huge earthquake exceeding the intensity of a major earthquake. The steel section 2 in the column does not extend into the upper beam 9, which facilitates the construction of the upper concrete beam and column node and ensures the quality of the concrete pouring of the upper beam and column node. During use, the column foot is considered as a rigid connection under non-seismic design and the combined effect of smaller earthquakes, and is considered as a hinged connection under the combined effect of larger earthquakes.

[0039] Specifically, a steel mesh 7 is provided in the plastic hinge area of ​​the column base of the reinforced concrete column 1. The lower end of the steel mesh 7 extends into the concrete foundation 8. The steel mesh 7 is woven from galvanized steel wire. The diameter of the galvanized steel wire is 4mm to 6mm, and the grid spacing is 50mm to 100mm. The steel mesh 7 can prevent the concrete from falling off prematurely during an earthquake and enhance the ductility and energy consumption capacity of the column base. In order to facilitate concrete pouring, the steel mesh is placed on the surface of the concrete component. The diameter of the steel wire has reserved a corrosion allowance, and a 20mm to 30mm thick mortar layer is applied to the surface of the steel wire for protection.

[0040] Furthermore, the continuous composite rectangular spiral hoop 5 includes an outer spiral hoop 51 and an inner spiral hoop 52. The inner spiral hoop 52 is arranged on the inner side of the outer spiral hoop 51. The outer spiral hoop 51 and the inner spiral hoop 52 are both arranged in the reinforced concrete column 1. The double spiral hoop is used to increase the stability of the structure. The continuous composite rectangular spiral hoop 5 reduces the stirrup joints and enhances the bearing capacity, ductility and energy consumption capacity of the column base.

[0041] Furthermore, the cross-section of the steel section 2 is a cross-shaped structure, and multiple bolts 10 are provided on the four flange plates 14 of the steel section 2. To facilitate construction, the steel section 2 adopts a form with smaller cross-section and flange width and thicker plate thickness, such as an 800mm×800mm column section, the width and height of the steel section are both 400mm, the flange width is 200mm, and the plate thickness is 30mm.

[0042] Furthermore, a stiffening rib 11 is provided at the upper end of the steel section 2 for enhancing mechanical strength. The stiffening rib 11 can reduce debonding or cracking between the concrete and the steel section 2 caused by stress differences, improve the collaborative working performance between the two, and help improve the overall stability and bearing capacity of the structure.

[0043] Furthermore, a mortar layer 15 is provided on the outer surface of the reinforced concrete column 1. The mortar layer 15 is a high-performance composite mortar layer, which is applied under pressure to ensure that there are no bubbles in the high-performance composite mortar and that it is in close contact with the concrete. The mortar layer 15 protects the wire mesh 7 and prevents the wire mesh 7 from oxidation and rusting.

[0044] A design method for a semi-hinged concrete column base node comprises the following steps:

[0045] (1) Calculate the column foot longitudinal reinforcement according to the column foot rigid connection and the current code for seismic design. When the calculated steel concrete column foot longitudinal reinforcement is less than the longitudinal reinforcement corresponding to the minimum reinforcement ratio specified in the current code, the column foot longitudinal reinforcement shall be arranged according to the minimum reinforcement ratio;

[0046] (2) When the longitudinal reinforcement of the steel concrete column foot calculated in the above steps is greater than the longitudinal reinforcement corresponding to the minimum reinforcement ratio, the longitudinal reinforcement of the column foot shall be arranged according to the maximum value of the following a), b), and c) under the condition of rigid connection of the column foot;

[0047] a) Calculate the longitudinal reinforcement at the column base according to the provisions of the current code for non-seismic design;

[0048] b) Calculate the longitudinal reinforcement at the column base according to the standard value of the combined effect of load and seismic action and the standard value of material strength, i.e., formula (1), and do not adjust the column base bending moment value for the combined seismic action according to relevant regulations;

[0049] S GE +γ Eh S Ehk +γ Ev S Evk +ψw γ w S wk ≤R k (1)

[0050] Where: S GE is the effect of the representative value of gravity load; S Ehk 、S Evk Divided into the effects of horizontal and vertical earthquake action standard values; S wk is the effect of the standard value of wind load; ψ w is the combined value coefficient of wind load; γ Eh , γ Ev , γ w are the partial factors of horizontal earthquake action, vertical earthquake action and wind load respectively; R k is the standard value of resistance of structural components; γ Eh , γ Ev , γ w , ψ w All values ​​are taken according to the current specifications, but when greater than 1.0, they are taken as 1.0;

[0051] c) Longitudinal reinforcement corresponding to the minimum reinforcement ratio specified in the current specifications;

[0052] (3) Calculate the first-floor column top longitudinal reinforcement according to the current code, i.e., the principle of "strong column and weak beam". The excess column top longitudinal reinforcement compared to the column foot longitudinal reinforcement determined according to (1) or (2) above shall be anchored or overlapped at the mid-span along the column height direction.

[0053] (4) Calculate the column stirrups according to the current specifications. The stirrups of the lower half of the first-floor column adopt the continuous composite rectangular spiral stirrup form with excellent load-bearing performance, and the upper half adopts the usual composite stirrup form. Since the number of longitudinal bars in the lower half of the column determined by the above steps (1) or (2) is relatively small, it creates conditions for the application of continuous composite rectangular spiral stirrups.

[0054] In this embodiment, calculations show that there are fewer longitudinal reinforcements at the column base, creating favorable conditions for the application of continuous composite rectangular spiral hoops 5, so that the lower half of the hoops adopt the form of continuous composite rectangular spiral hoops 5 with excellent stress-bearing performance, and the upper half adopts the form of common composite hoops 6. The continuous composite rectangular spiral hoops 5 reduce the number of hoops joints, thereby enhancing the bearing capacity, ductility and energy dissipation capacity of the column base, thereby ensuring the safety of the column top node of this layer under the action of a huge earthquake exceeding the intensity of a major earthquake. By reducing the longitudinal reinforcement, the longitudinal reinforcement is still rigidly connected when it does not yield, meeting the bearing requirements. Under the combined effect of a larger earthquake, the steel bar yields and immediately becomes hinged, thereby increasing the ductility and energy dissipation capacity of the column base, and converting the beam hinge yield mechanism into a mixed yield mechanism of beam hinge yield and podium column base yield, thereby increasing the energy dissipation capacity of the structure.

[0055] Furthermore, the upper beam and column nodes are designed in a way that the top of the steel section extends to the bottom of the lower longitudinal reinforcement of the upper beam but does not extend into the node. The wire mesh on the surface of the column foot is configured according to the wire mesh structure to facilitate the construction of the upper concrete beam and column nodes and ensure the quality of concrete pouring of the upper beam and column nodes.

[0056] The above is only a preferred embodiment of the present invention. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the structure of the present invention. These modifications and improvements will not affect the effect of the implementation of the present invention and the practicality of the patent.

Claims

1. A semi-hinged concrete column base node, characterized in that: The invention comprises a concrete foundation (8), wherein a reinforced concrete column (1) is provided on the concrete foundation (8), a steel section (2) is provided in the reinforced concrete column (1), the lower end of the steel section (2) is inserted into the concrete foundation (8), the upper end of the steel section (2) is flush with the bottom of the upper beam (9), a connecting base plate (13) is provided at the bottom of the steel section (2), and the connecting base plate (13) is connected to the concrete foundation (8) through an anchor bolt (12) pre-buried in the concrete foundation (8), a plurality of column base longitudinal bars (3) and a continuous composite rectangular spiral hoop (5) are provided in the column foot section of the reinforced concrete column (1), and a plurality of column top longitudinal bars (4) and a composite hoop (6) are provided in the column top section of the reinforced concrete column (1).

2. A semi-hinged concrete column base node according to claim 1, characterized in that: A steel mesh (7) is provided in the plastic hinge area of ​​the column foot of the reinforced concrete column (1), and the lower end of the steel mesh (7) extends into the concrete foundation (8).

3. A semi-hinged concrete column base node according to claim 2, characterized in that: The steel wire mesh (7) is woven from galvanized steel wires, the diameter of the galvanized steel wires is 4mm to 6mm, and the mesh spacing is 50mm to 100mm.

4. A semi-hinged concrete column base node according to claim 1, characterized in that: The continuous composite rectangular spiral hoop (5) comprises an outer spiral hoop (51) and an inner spiral hoop (52), wherein the inner spiral hoop (52) is arranged inside the outer spiral hoop (51), and both the outer spiral hoop (51) and the inner spiral hoop (52) are arranged inside the reinforced concrete column (1).

5. The semi-hinged concrete column base node according to claim 1, characterized in that: The cross section of the steel section (2) is a cross-shaped structure, and a plurality of bolts (10) are provided on each of the four flange plates (14) of the steel section (2).

6. The semi-hinged concrete column base node according to claim 1, characterized in that: The upper end of the steel section (2) is provided with a stiffening rib (11) for enhancing the mechanical strength.

7. The semi-hinged concrete column base node according to claim 1, characterized in that: The outer surface of the reinforced concrete column (1) is provided with a mortar layer (15).

8. A design method for a semi-hinged concrete column base node, characterized in that: The following steps are involved: (1) Calculate the column foot longitudinal reinforcement according to the column foot rigid connection and the current code for seismic design. When the calculated steel concrete column foot longitudinal reinforcement is less than the longitudinal reinforcement corresponding to the minimum reinforcement ratio specified in the current code, the column foot longitudinal reinforcement shall be arranged according to the minimum reinforcement ratio; (2) When the longitudinal reinforcement of the steel concrete column foot calculated in the above steps is greater than the longitudinal reinforcement corresponding to the minimum reinforcement ratio, the longitudinal reinforcement of the column foot shall be arranged according to the maximum value of the following a), b), and c) under the condition of rigid connection of the column foot; a) Calculate the longitudinal reinforcement at the column base according to the provisions of the current code for non-seismic design; b) Calculate the longitudinal reinforcement at the column base according to the standard value of the combined effect of load and seismic action and the standard value of material strength, i.e., formula (1), and do not adjust the column base bending moment value for the combined seismic action according to relevant regulations; S GE +g Eh S Ehk +g Ev S Evk +ψ w c w S wk ≤R k (1) Where: S GE is the effect of the representative value of gravity load; S Ehk 、S Evk Divided into the effects of horizontal and vertical earthquake action standard values; S wk is the effect of the standard value of wind load; ψ w is the combined value coefficient of wind load; γ Eh , γ Ev , γ w are the partial factors of horizontal earthquake action, vertical earthquake action and wind load respectively; R k is the standard value of resistance of structural components; γ Eh , γ Ev , γ w , ψ w All values ​​are taken according to the current specifications, but when greater than 1.0, they are taken as 1.0; c) Longitudinal reinforcement corresponding to the minimum reinforcement ratio specified in the current specifications; (3) Calculate the first-floor column top longitudinal reinforcement according to the current code, i.e. the principle of "strong column and weak beam". The excess of the column top longitudinal reinforcement compared to the column foot longitudinal reinforcement determined according to (1) or (2) above shall be anchored or overlapped at the mid-span along the column height direction. (4) Calculate the column stirrups according to the current specifications. The stirrups of the lower half of the first-floor column adopt the continuous composite rectangular spiral stirrup form with excellent load-bearing performance, and the upper half adopts the usual composite stirrup form. Since the number of longitudinal bars in the lower half of the column determined by the above steps (1) or (2) is relatively small, it creates conditions for the application of continuous composite rectangular spiral stirrups.

9. The design method of a semi-hinged concrete column base node according to claim 8, characterized in that: The upper beam and column nodes are designed with the top of the steel section extending to the bottom of the lower longitudinal reinforcement of the upper beam but not extending into the node, and the wire mesh on the surface of the column foot is configured according to the wire mesh structure.

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