Semi-arcuate concrete column base joint and design method

Abstract

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

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of building structure engineering, and particularly relates to a semi-hinged concrete column foot joint and a design method. BACKGROUND

[0002] The plane area of a base chassis structure unit of a subway vehicle base is sometimes very large, the expansion joint spacing of a vehicle base cover structure can be controlled at 200 m, and should not exceed 250 m. In general, the first layer is used as a vehicle base track layer, and the second layer is used as a garage and frame-supported conversion layer, thus naturally forming a large chassis structure.

[0003] The vehicle base has heavy load, large area, large column spacing and large component cross-sectional size, which results in large lateral stiffness and large seismic action of the structure. In addition, the large chassis effect also amplifies the seismic action on the tower above it. For example, in a certain example, when the building height is 50 m and the range of the podium on each side is 60 m, the shear force of the first layer of the podium is about 50% larger than that when the building height is 150 m, and the shear force of the first layer of the podium is about 150% larger than that when the building height is 50 m without a podium; when the building height is 150 m, the shear force curve of the tower layer becomes curved, reflecting the curve shape with a turning point of the high-order mode.

[0004] In recent years, the seismic damage shows that the collapsed frame structure is mostly column end damage, and the expected "strong column and weak beam" yielding mechanism in the design is not achieved. In addition to the "strengthening-strengthening-strengthening" method, reducing the lateral stiffness of the large chassis structure of the vehicle base to reduce the seismic action is also a thought. The components that allow the mixed yielding mechanism of the column foot hinge to participate in energy dissipation will be more than the beam hinge mechanism. Allowing the column foot hinge releases the column foot bending moment, but compared with the isolation structure, it still limits the horizontal displacement of the column foot. As long as the upper end of the first layer column does not hinge, the layer yielding mechanism of the first layer will not be formed. The fact that a large number of frame houses with column hinges still stand upright in the earthquake also shows that this thought is feasible. In addition, because the column foot hinge is allowed, it is also beneficial to ensure the safety of the column top joint of the first layer column under a huge earthquake exceeding the design earthquake intensity. However, in the existing structure, the column foot is usually rigidly connected, and the seismic action and large chassis effect are borne by the rigid system, and the effect does not reach the ideal expectation. Therefore, it is urgent to design a column foot structure that can meet the use requirements. SUMMARY

[0005] The technical problem to be solved by the present application is to provide a semi-hinged concrete column foot joint and a design method to effectively reduce the seismic action and large chassis effect of the podium of the subway vehicle base, and the method has the characteristics of convenient use and strong practicality.

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

[0007] As a further improvement, the plastic hinge zone at the base of the reinforced concrete column is provided with a wire mesh, the lower end of which extends into the concrete foundation.

[0008] Furthermore, the wire mesh is woven from galvanized steel wire, the diameter of which 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, with the inner spiral hoop arranged inside the outer spiral hoop, and both the outer spiral hoop and the inner spiral hoop are installed inside the reinforced concrete column.

[0010] Furthermore, the cross-section of the steel profile is cross-shaped, and multiple studs are provided on each of the four flanges of the steel profile.

[0011] Furthermore, the upper end of the steel section is provided with stiffening ribs to enhance mechanical strength.

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

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

[0014] (1) Calculate the longitudinal reinforcement of the column base according to the provisions of the current code for seismic design. When the calculated longitudinal reinforcement of the steel-concrete column base is less than the longitudinal reinforcement corresponding to the minimum reinforcement ratio specified in the current code, the longitudinal reinforcement of the column base shall be arranged according to the minimum reinforcement ratio.

[0015] (2) When the longitudinal reinforcement of the steel-concrete column base calculated in the above steps is greater than the longitudinal reinforcement corresponding to the minimum reinforcement ratio, the longitudinal reinforcement of the column base shall be configured according to the maximum value of a), b), and c) below in the case of rigid connection of the column base.

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

[0017] b) The column base longitudinal reinforcement is calculated according to the effect standard value of load and seismic action combination and the material strength standard value, i.e. formula (1), and the column base bending moment value of seismic action combination is not adjusted according to the relevant provisions;

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

[0019] In the formula: S GE is the effect of the representative value of gravity load; S Ehk , S Evk are the effects of the standard values of horizontal and vertical seismic action; S wk is the effect of the standard value of wind load; ψ w is the combination value coefficient of wind load; γ Eh , γ Ev , γ w are the partial coefficients of horizontal seismic action, vertical seismic action and wind load respectively; R k is the standard value of the resistance of the structural member; γ Eh , γ Ev , γ w , ψ w are all taken according to the current standard, but are all taken as 1.0 when greater than 1.0;

[0020] c) The longitudinal reinforcement corresponding to the minimum reinforcement ratio provided in the current standard;

[0021] (3) The longitudinal reinforcement at the top of the first floor column is calculated according to the principle of "strong column and weak beam" provided in the current standard, and the part of the longitudinal reinforcement at the top of the column that is more than the longitudinal reinforcement at the column base determined according to the above (1) or (2) is anchored or overlapped at the midspan in the direction of the column height;

[0022] (4) The column stirrup is calculated according to the current standard, the lower half of the column stirrup of the first floor column adopts the continuous composite rectangular spiral stirrup with excellent stress performance, and the upper half adopts the general composite stirrup. Since the number of longitudinal reinforcement in the lower half of the column determined according to the above (1) or (2) is small, it creates conditions for the application of continuous composite rectangular spiral stirrups.

[0023] Further, the upper layer beam and column joint are designed by the method that the top of the profile steel extends to the bottom of the longitudinal reinforcement of the lower part of the upper layer beam and does not extend into the joint, and the column base surface steel mesh is configured according to the steel mesh structure.

[0024] Beneficial effects

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

[0026] 1. By reducing the skirt column section, making the column foot into semi-hinged, and improving the ductility of the column foot, the earthquake action of the skirt and the large podium effect of the skirt on the tower above are reduced.

[0027] 2. Compared with the general reinforced concrete column foot, the ductility and energy dissipation capacity of the column foot are increased, the beam hinge yielding mechanism is changed to the mixed yielding mechanism of beam hinge yielding and skirt column foot yielding, and the energy dissipation capacity of the structure is increased.

[0028] 3. The ductility of the concrete column is increased by setting the steel, continuous composite rectangular spiral hoop and surface steel mesh in the column foot, and since the cross section of the steel is small and the number of longitudinal reinforcement is small, the construction of the steel reinforced concrete column foot is facilitated, and at the same time, since the column foot yields in bending and out of hinge, it is also beneficial to ensure the safety of the column top joint of this floor under the action of a huge earthquake exceeding the intensity of a major earthquake.

[0029] 4. The steel in the column does not extend into the upper layer beam, which facilitates the construction of the upper layer concrete beam and column joint and ensures the quality of the upper layer beam and column joint concrete pouring. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 It is a front view structural schematic diagram of the present application;

[0031] Figure 2 It is Figure 1 A-A sectional view;

[0032] Figure 3 It is Figure 1 B-B sectional view;

[0033] Figure 4 It is a schematic diagram of the outer spiral hoop in the present application;

[0034] Figure 5 It is a schematic diagram of the inner spiral hoop in the present application;

[0035] Figure 6 It is a schematic diagram of the steel mesh facade in the present application.

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

[0037] The present application will be further described below in combination with the specific embodiments in the drawings.

[0038] Reference Figures 1-6As shown, a semi-hinged concrete column foot joint of the present application comprises a concrete foundation 8, a reinforced concrete column 1 arranged on the concrete foundation 8, a profile steel 2 arranged in the reinforced concrete column 1, the lower end of the profile steel 2 inserted into the concrete foundation 8, the upper end of the profile steel 2 flush with the bottom of an upper beam 9, a connecting bottom plate 13 arranged at the bottom of the profile steel 2, the connecting bottom plate 13 connected with the concrete foundation 8 through anchor bolts 12 pre-buried in the concrete foundation 8, a plurality of column foot longitudinal reinforcements 3 and continuous composite rectangular spiral hoops 5 arranged in the column foot section of the reinforced concrete column 1, and a plurality of column top longitudinal reinforcements 4 and composite hoops 6 arranged 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 beam-column section is large, the lateral stiffness of the podium is large, and the seismic action is large. By reducing the podium column section and making the column foot into a "semi-hinged", a small amount of longitudinal reinforcement is arranged at the reinforced concrete column foot to ensure the flexural bearing capacity under the combination effect of no earthquake and small earthquake action, and the longitudinal reinforcement is allowed to yield early to form a plastic hinge under the combination effect of large earthquake action. At the same time, measures are taken to increase the ductility of the column foot, which is called "semi-hinged" column foot. The increase in ductility is achieved by arranging the profile steel 2, continuous composite rectangular spiral hoops 5, and surface steel wire mesh 7 in the column foot. The mechanism is changed from beam hinge yielding mechanism to a mixed yielding mechanism of beam hinge yielding and podium column foot yielding, which increases the energy dissipation capacity of the structure, reduces the seismic action of the podium, and reduces the large base effect of the podium on the seismic action of the tower above it. Since the cross section of the profile steel 2 is small and the number of longitudinal reinforcements is small, the construction of the profile steel concrete column foot is facilitated, and the column section of the podium can be reduced. Since the column foot yields in bending and out of hinge, it is also beneficial to ensure the safety of the column top joint of this layer under the action of a giant earthquake exceeding the intensity of a large earthquake. The profile steel 2 in the column does not extend into the upper beam 9, which facilitates the construction of the upper concrete beam and column joint, ensures the quality of the concrete pouring of the upper beam and column joint, and considers the column foot as rigid connection under the combination effect of non-seismic design and small earthquake action, and considers the column foot as hinged connection under the combination effect of large earthquake action.

[0039] Specifically, the column foot plastic hinge zone of the reinforced concrete column 1 is provided with a steel wire mesh 7, the lower end of the steel wire mesh 7 extends into the concrete foundation 8, the steel wire mesh 7 is woven from galvanized steel wire with a diameter of 4mm-6mm, and the grid spacing is 50mm-100mm. The steel wire mesh 7 can prevent the concrete from falling off too early during an earthquake and enhance the ductility and energy dissipation capacity of the column foot. To facilitate concrete pouring, the steel wire mesh is placed on the surface of the concrete member. The diameter of the steel wire has a corrosion allowance, and the surface of the steel wire is protected by a 20mm-30mm thick mortar layer.

[0040] Further, the continuous composite rectangular spiral hoop 5 comprises an outer spiral hoop 51 and an inner spiral hoop 52, the inner spiral hoop 52 is arranged inside the outer spiral hoop 51, both the outer spiral hoop 51 and the inner spiral hoop 52 are arranged in the reinforced concrete column 1, the double spiral hoops are adopted to increase the stability of the structure, the continuous composite rectangular spiral hoop 5 reduces the joint of the stirrup, and enhances the bearing capacity, ductility and energy dissipation capacity of the column foot.

[0041] Further, the section of the shaped steel 2 is in a cross-shaped structure, a plurality of studs 10 are arranged on each of the four flange plates 14 of the shaped steel 2, in order to facilitate construction, the shaped steel 2 adopts a form with smaller section and flange width and thicker plate thickness, for example, a column section of 800mm×800mm, the section width and height of the shaped steel are both 400mm, the flange width is 200mm, and the plate thickness is 30mm.

[0042] Further, the upper end of the shaped steel 2 is provided with a stiffening rib 11 for enhancing the mechanical strength, the stiffening rib 11 can reduce the debonding or cracking between the concrete and the shaped steel 2 caused by stress difference, improve the cooperative working performance between the two, and help to improve the overall stability and bearing capacity of the structure.

[0043] Further, the outer surface of the reinforced concrete column 1 is provided with a mortar layer 15, the mortar layer 15 is a high-performance composite mortar layer, which is applied under pressure to ensure that there are no air bubbles in the high-performance composite mortar and the mortar layer 15 is in close contact with the concrete, the mortar layer 15 plays a protective role on the steel wire mesh 7 to prevent the steel wire mesh 7 from being oxidized and rusted.

[0044] A design method of a semi-hinged concrete column foot joint, comprising the following steps:

[0045] (1) Calculate the column foot longitudinal reinforcement according to the column foot rigid connection and the provisions of the current specification for seismic design, when the calculated longitudinal reinforcement of the shaped steel reinforced concrete column foot is less than the longitudinal reinforcement corresponding to the minimum reinforcement ratio specified in the current specification, the column foot longitudinal reinforcement is configured according to the minimum reinforcement ratio;

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

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

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

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

[0050] In the formula: S GE The effect of the representative value of gravity load; S Ehk S Evk The effects are divided into the standard values ​​of horizontal and vertical seismic forces; S wk The effect of the standard value of wind load; ψ w γ is the combination coefficient for wind load; Eh γ Ev γ w These are the partial factors for horizontal seismic action, vertical seismic action, and wind load, respectively; R k γ is the standard value of the resistance of structural members; Eh γ Ev γ w ψ w All values ​​are taken according to current standards, but when the value is greater than 1.0, it is taken as 1.0;

[0051] c) The longitudinal reinforcement corresponding to the minimum reinforcement ratio specified in the current code;

[0052] (3) Calculate the top longitudinal reinforcement of the first-floor column according to the current standard, namely the principle of "strong column and weak beam". The part of the top longitudinal reinforcement of the column that is more than the column foot longitudinal reinforcement determined by (1) or (2) above shall be anchored or lapped at the mid-span along the column height direction.

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

[0054] In this embodiment, calculations show that the column base has fewer longitudinal reinforcement bars, creating favorable conditions for the application of continuous composite rectangular spiral stirrups 5. This allows the lower half of the stirrups to use the continuous composite rectangular spiral stirrups 5 with excellent stress performance, while the upper half uses the conventional composite stirrups 6. The continuous composite rectangular spiral stirrups 5 reduce stirrup joints, enhancing the column base's bearing capacity, ductility, and energy dissipation capacity. This ensures the safety of the column top node under mega-earthquakes exceeding the intensity of major earthquakes. By reducing the longitudinal reinforcement, the longitudinal reinforcement remains rigidly connected when it does not yield, meeting the bearing requirements. Under the combined effect of larger earthquake forces, the steel reinforcement immediately becomes hinged when it yields, increasing the column base's ductility and energy dissipation capacity. The yielding mechanism changes from beam hinge yielding to a mixed yielding mechanism of beam hinge yielding and podium column base yielding, increasing the structure's energy dissipation capacity.

[0055] Further, the profile steel top extends to the bottom of the upper beam lower longitudinal reinforcement, and does not extend into the joint, which designs the upper beam and column joint, and according to the steel wire mesh structure, the column foot surface steel wire mesh is configured, the upper concrete beam and column joint construction is facilitated, and the upper beam and column joint concrete pouring quality is guaranteed.

[0056] The above only describes the preferred embodiments of the present application, and it should be noted that those skilled in the art can make several modifications and improvements without departing from the structure of the present application, which will not affect the effect and practicality of the patent.

Claims

1. A design method for a semi-hinged concrete column base joint, characterized in that, Includes the following steps: (1) Calculate the longitudinal reinforcement of the column base according to the provisions of the current code for seismic design. When the calculated longitudinal reinforcement of the steel-concrete column base is less than the longitudinal reinforcement corresponding to the minimum reinforcement ratio specified in the current code, the longitudinal reinforcement of the column base shall be arranged according to the minimum reinforcement ratio. (2) When the longitudinal reinforcement of the steel-concrete column base calculated in the above steps is greater than the longitudinal reinforcement corresponding to the minimum reinforcement ratio, the longitudinal reinforcement of the column base shall be configured according to the maximum value of a), b), and c) below under the case of rigid connection of the column base; a) Calculate the longitudinal reinforcement at the column base according to the provisions of the current code for non-seismic design; b) Calculate the column base longitudinal reinforcement 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 of the combined seismic action according to relevant regulations; (1) In the formula: S GE The effect of the representative value of gravity load; S Ehk , S Evk The effects are divided into the standard values ​​of horizontal and vertical seismic forces; S wk The effect of the standard value of wind load; ψ w This is the combination value coefficient for wind load; γ Eh , γ Ev , γ w These are the partial factors for horizontal seismic action, vertical seismic action, and wind load, respectively; R k This refers to the standard value of the resistance of structural components; γ Eh , γ Ev , γ w , ψ w All values ​​are taken according to current standards, but when the value is greater than 1.0, it is taken as 1.0; c) The longitudinal reinforcement corresponding to the minimum reinforcement ratio specified in the current code; (3) Calculate the top longitudinal reinforcement of the first-floor column according to the current standard, namely the principle of "strong column and weak beam". The part of the top longitudinal reinforcement of the column that is more than the column foot longitudinal reinforcement determined by (1) or (2) above shall be anchored or lapped at the mid-span along the column height direction. (4) Calculate the column stirrups according to the current specifications. The lower half of the column stirrups of the first floor adopts the form of continuous composite rectangular spiral stirrup with excellent stress performance, while the upper half adopts the form of ordinary composite stirrup. Since the number of longitudinal bars in the lower half of the column determined by the above steps (1) or (2) is small, it creates conditions for the application of continuous composite rectangular spiral stirrups.

2. The design method for a semi-hinged concrete column base joint according to claim 1, characterized in that, The design of the upper beam and column joints is based on the method of extending the top of the steel section to the bottom of the longitudinal reinforcement of the upper beam without extending into the node, and configuring the steel wire mesh on the surface of the column base according to the steel wire mesh structure.

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