Super-tough elastomer seamless expansion joint and construction method
By setting adjustment components on the base of the expansion joint, the problem of substrate layer offset caused by settlement of the bridge body structure is solved, the flatness and stability of the expansion joint is achieved, and the maintenance cost is reduced.
Patent Information
- Application Number
- CN202411954094.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-27
- Publication Date
- 2025-03-25
AI Technical Summary
When the existing expansion joint structure settles against the bridge structure, the substrate layer is easily affected and deviates, affecting the flatness of the elastic layer and the waterproof layer, and the post-maintenance and maintenance work is large.
A super tough elastomer seamless expansion joint is designed, and adjustment components (including support rods, support plates, balls and sockets, universal balls, etc.) are used on the base, so that it can be fine-tuned according to changes in the bridge structure, maintain the overall flatness of the expansion joints, and facilitate post-inspection joints.
By adjusting the design of the components, the substrate layer offset problem caused by the settlement of the bridge body structure is effectively avoided, the flatness and stability of the expansion joints are maintained, and the workload and cost of later maintenance are reduced.
Smart Images
Figure CN119686213A_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the field of expansion joint technology, and in particular to a super-tough elastomer seamless expansion joint and a construction method. Background Art
[0002] At present, the design and construction of expansion joints have become quite mature and are widely used in various construction projects. Traditional expansion joints mainly include two types: rigid expansion joints and flexible expansion joints. Rigid expansion joints achieve displacement through metal components. Although they have high strength and stability, they are prone to cracks and damage when facing large deformations and complex environments.
[0003] Existing expansion joint structures usually include a substrate layer, an elastic layer, a waterproof layer and other structures. The substrate layer is installed on both sides of the expansion joint of the bridge body, and the elastic layer and the waterproof layer are both installed on the substrate layer. The substrate layer is usually fixed to the bridge body structure by bolts or anchors and other structures. As the expansion joint structure is used for a longer time, the bridge body structure on both sides of the expansion joint may sink toward the middle part of the expansion joint, causing the substrate layer to shift, thereby affecting the flatness of the installation of the elastic layer and the waterproof layer. In addition, due to the fixed installation of the substrate layer, the workload of maintaining the substrate layer in the later stage is too large. Summary of the invention
[0004] In order to facilitate the inspection and maintenance of the substrate layer and thus adjust the flatness of the elastic layer and the waterproof layer, the present application provides a super-tough elastomer seamless expansion joint and a construction method.
[0005] The present application provides a super-tough elastomer seamless expansion joint adopting the following technical solution: A super-tough elastomer seamless expansion joint comprises a base, an elastomer layer and a covering layer. The base is provided with two groups, and the two bases are respectively mounted on the bridge structure on both sides of the expansion joint, the elastomer layer is mounted on the two bases, and the covering layer is laid on the elastomer layer. The covering layer is fixed to the base through the elastomer layer via an anchoring structure, and the base is mounted on the bridge structure via an adjusting component, and the adjusting component is used to adjust the flatness of the base.
[0006] By adopting the above technical solution and setting an adjustment component on the base, the base can be fine-tuned according to the changes in the bridge structure, maintaining the overall flatness of the expansion joint and avoiding damage to the expansion joint structure caused by the settlement of the bridge structure. At the same time, the adjustment component can be used to facilitate adjustments and maintenance when necessary, reducing the workload and cost of subsequent maintenance.
[0007] In a specific feasible implementation scheme, the adjustment assembly includes a support rod and a support plate, the support rod is mounted on the bridge structure, the support plate is mounted on the upper end surface of the support rod, a ball socket is mounted on the support plate, a universal ball is mounted on the lower bottom surface of the base, the universal ball is mounted in the ball socket and can rotate relative to the ball socket.
[0008] By adopting the above technical solution, the combination of support rods and support plates enables the base to be adjusted in multiple dimensions on the bridge structure, improving the flatness and accuracy of the base installation. The design of the ball socket and universal ball allows the base to rotate freely in different directions, further improving the adaptability and stability of the base when the bridge structure changes, and effectively avoiding the problem of substrate layer offset caused by bridge settlement.
[0009] In a specific feasible implementation scheme, the adjustment assembly also includes a support screw, two of which are provided and are respectively installed on both sides of the support plate along the length direction of the bridge body, and the support screw passes through the support plate and extends toward the lower bottom surface of the base.
[0010] By adopting the above technical solution, the setting of the support screw can effectively enhance the stability and adjustment ability of the base on the bridge body. Specifically, two support screws are installed on both sides of the support plate along the length direction of the bridge body, penetrate the support plate and extend to the bottom surface of the base, which can adjust the position of the base in the horizontal and vertical directions, ensure the flatness and stable installation of the base, thereby improving the reliability and service life of the entire expansion joint structure.
[0011] In a specific feasible implementation scheme, the adjustment assembly also includes a telescopic top rod, and the two connecting rods are respectively installed on both sides of the support rod along the width direction of the expansion joint. The telescopic top rod includes a first rod body and a second rod body, the first rod body is installed on the bridge body structure, a lifting groove is provided on the first rod body, one end of the second rod body is inserted in the lifting groove and can slide in the lifting groove, the first rod body and the second rod body are coaxially arranged, a plurality of elastic limiting plates are provided on the upper end of the first rod body, and the first rod body is threadedly connected to a limiting ring, the limiting ring can move to the upper end to make the elastic limiting plate deform toward the axial direction of the first rod body, and the elastic limiting plate can limit the second rod body.
[0012] By adopting the above technical solution, the setting of the telescopic top rod enables the base to be accurately adjusted in height along the vertical direction on the bridge structure on both sides of the expansion joint, ensuring that the base always remains flat and avoiding the displacement of the base due to the settlement of the bridge structure, which affects the installation flatness of the elastic layer and the covering layer. At the same time, the combined design of the elastic limit plate and the limit ring on the first rod body can effectively prevent the second rod body from detaching during the lifting process, ensuring the stability and reliability of the adjustment process. In addition, the adjustability of the telescopic top rod also facilitates later maintenance and overhaul, reducing maintenance costs and workload.
[0013] In a specific possible implementation scheme, a limiting frame is installed on the bridge structure, a slide groove is provided on the limiting frame, and the support rod is arranged through the slide groove and can move relative to the limiting frame.
[0014] By adopting the above technical solution, the setting of the limit frame can effectively limit the position of the support rod, prevent it from excessive movement in the horizontal direction, and ensure the stability and flatness of the base. At the same time, the design of the slide groove allows the support rod to move freely within a certain range, adapting to the possible slight deformation of the bridge structure, and improving the overall adaptability and durability of the expansion joint.
[0015] In a specific possible implementation manner, a plurality of prestressed springs are installed on the upper end surface of the base, the prestressed springs are arranged between the base and the elastomer layer, and the prestressed springs support the elastomer layer at one end away from the base.
[0016] By adopting the above technical solution, a number of prestressed springs are installed on the upper end surface of the base, and the prestressed springs are arranged between the base and the elastomer layer. The prestressed spring supports the elastomer layer at one end away from the base, which can effectively improve the compressive resistance and rebound performance of the elastomer layer, reduce the deformation of the elastomer layer caused by the displacement of the base, and ensure the overall stability and service life of the expansion joint.
[0017] In a specific possible implementation manner, the anchoring structure includes a pressure strip and a fastening bolt, wherein the pressure strip is installed on the covering layer along the width direction of the bridge body, and the fastening bolt passes through the pressure strip and the elastomer layer and is fixed to the base.
[0018] By adopting the above technical solution, the anchoring structure includes a pressure strip and fastening bolts. The pressure strip is installed on the covering layer along the width direction of the bridge body, and the fastening bolts pass through the pressure strip and the elastomer layer and are fixed on the base. This design can effectively enhance the fixing effect between the covering layer and the elastomer layer, prevent the covering layer from loosening or falling off due to vehicle driving or other external factors, and improve the overall stability and service life of the expansion joint.
[0019] In a specific embodiment, the elastomer layer is composed of a modified polyurethane elastomer material and has a thickness of 20 mm.
[0020] By adopting the above technical solution, the elastomer layer composed of modified polyurethane elastomer material has excellent elasticity and durability, can effectively adapt to the dynamic changes of the bridge structure, and reduce the cracking of expansion joints caused by temperature changes and vehicle loads. At the same time, the 20mm thickness design not only ensures sufficient elastic performance, but also facilitates construction operations and improves construction efficiency.
[0021] In a specific implementation manner, the cover layer is composed of a high-strength nylon fiber cloth and EPDM rubber composite material, and the thickness is set to 5 mm.
[0022] By adopting the above technical solution, the covering layer is composed of high-strength nylon fiber cloth and EPDM rubber composite material, and the thickness is set to 5mm, so that the covering layer has excellent weather resistance and anti-aging properties, which can effectively prevent external environmental factors such as ultraviolet rays and rain from eroding the internal structure of the expansion joint and extend the service life of the expansion joint. At the same time, the composite material of high-strength nylon fiber cloth and EPDM rubber also has good flexibility and wear resistance, which can adapt to the frequent expansion and contraction movement of the bridge body, reduce damage caused by wear, and improve the overall stability and safety of the expansion joint.
[0023] In summary, the present application includes at least one of the following beneficial technical effects: 1. By setting an adjustment component on the base, the base can be fine-tuned according to the changes in the bridge structure, maintaining the overall flatness of the expansion joint and avoiding damage to the expansion joint structure caused by the settlement of the bridge structure. At the same time, the adjustment component can be easily adjusted and repaired when necessary, reducing the workload and cost of later maintenance; 2. The setting of the telescopic top rod enables the base to be accurately adjusted in the vertical direction on the bridge structure on both sides of the expansion joint, ensuring that the base always remains flat and avoiding the displacement of the base due to the settlement of the bridge structure, which affects the installation flatness of the elastic layer and the covering layer. At the same time, the combination design of the elastic limit plate and the limit ring on the first rod can effectively prevent the second rod from detaching during the lifting process, ensuring the stability and reliability of the adjustment process. In addition, the adjustability of the telescopic top rod also facilitates later maintenance and overhaul, reducing maintenance costs and workload; 3. The setting of the telescopic top rod enables the base to be accurately adjusted in the vertical direction on the bridge structure on both sides of the expansion joint, ensuring that the base always remains flat and avoiding the displacement of the base due to the settlement of the bridge structure, which affects the installation flatness of the elastic layer and the covering layer. At the same time, the combination design of the elastic limit plate and the limit ring on the first rod can effectively prevent the second rod from detaching during the lifting process, ensuring the stability and reliability of the adjustment process. In addition, the adjustability of the telescopic top rod also facilitates later maintenance and overhaul, reducing maintenance costs and workload. BRIEF DESCRIPTION OF THE DRAWINGS
[0024] Figure 1 It is a cross-sectional view of an embodiment of the present application.
[0025] Figure 2 for Figure 1 Enlarged view of part A.
[0026] Figure 3 It is a schematic diagram of the structure of the connection between the adjustment component and the base in the embodiment of the present application.
[0027] Figure 4 It is a schematic diagram of the structure of the adjustment component in the embodiment of the present application.
[0028] Figure 5 Schematic diagram of the structure of the telescopic top rod in the embodiment of the present application.
[0029] Figure 6 for Figure 1 Magnified view of part B.
[0030] Explanation of the reference numerals in the accompanying drawings: 1. base; 2. elastomer layer; 3. covering layer; 4. adjusting assembly; 41. support rod; 42. support plate; 43. support screw; 44. telescopic top rod; 441. first rod body; 442. second rod body; 443. elastic limit plate; 45. limit ring; 5. limit frame; 6. prestressed spring; 7. universal ball; 8. ball socket; 9. anchoring structure; 91. pressure strip; 92. fastening bolt; 10. bridge structure. DETAILED DESCRIPTION
[0031] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "disposed" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.
[0032] The embodiment of the present application discloses a super-tough elastomer seamless expansion joint.
[0033] like Figure 1 As shown, the super-tough elastomer seamless expansion joint includes a base 1, an elastomer layer 2 and a covering layer 3, wherein two groups of bases 1 are provided, and the two bases 1 are respectively installed on the bridge structure 10 on both sides of the expansion joint, the elastomer layer 2 is installed on the two bases 1, and the covering layer 3 is laid on the elastomer layer 2. The covering layer 3 is fixed on the base 1 through the elastomer layer 2 through the anchoring structure 9, and the base 1 is installed on the bridge structure 10 through the adjustment component 4, and the adjustment component 4 is used to adjust the flatness of the base 1. This design solves the problem that the substrate layer in the existing expansion joint structure is easily affected by the uneven settlement of the bridge body, and improves the reliability and maintenance convenience of the expansion joint.
[0034] The base 1 includes two sets of metal plates, each set of metal plates is fixed to the bridge structure 10 through an adjustment device. The material of the base 1 can be selected from high-strength steel or aluminum alloy to ensure its durability and corrosion resistance in harsh environments. The surface of the base 1 can be treated with anti-corrosion, such as spraying anti-rust paint or plating, to extend its service life.
[0035] The elastomer layer 2 is a high-performance modified polyurethane elastomer material with a thickness of 20 mm. This material has excellent elasticity and wear resistance, and can effectively absorb displacement caused by temperature changes and load changes. The surface of the elastomer layer 2 can be specially treated to increase its bonding force with the base 1 and the cover layer 3 to prevent debonding. In addition, the elastomer layer 2 can also be added with flame retardants to enhance its fire resistance and improve safety.
[0036] The cover layer 3 is composed of a high-strength nylon fiber cloth and EPDM rubber composite material, and the thickness is set to 5 mm. The main function of the cover layer 3 is to protect the elastomer layer 2 from the influence of the external environment, such as ultraviolet rays, rain and chemical erosion. The surface of the cover layer 3 can be smoothed to reduce friction resistance and facilitate vehicle passage. The edge of the cover layer 3 can be fixed by hot melt welding or adhesive to ensure its close fit with the elastomer layer 2.
[0037] like Figure 2 As shown, the anchoring structure 9 includes a pressure strip 91 and a fastening bolt 92. The pressure strip 91 is installed on the covering layer 3 along the width direction of the bridge body, and the fastening bolt 92 passes through the pressure strip 91 and the elastomer layer 2 and is fixed on the base 1. The material of the pressure strip 91 can be stainless steel or galvanized steel to ensure its corrosion resistance in long-term use. The specification of the fastening bolt 92 can be selected according to actual needs, such as M12 or M16, to ensure sufficient fixing force. The head of the fastening bolt 92 can be designed as a countersunk head or a round head to reduce the wear on the covering layer 3.
[0038] like Figure 3-5As shown, the adjustment device includes a support rod 41 and a support plate 42. A limit frame 5 is installed on the bridge structure 10. A slide groove is provided on the limit frame 5. The support rod 41 passes through the slide groove and can move relative to the limit frame 5. The material of the limit frame 5 can be selected from high-strength steel, and the thickness is generally 10-15 mm. The width and depth of the slide groove can be selected according to the diameter of the support rod 41 to ensure that the support rod 41 moves smoothly in the slide groove. Stop blocks can be installed at both ends of the limit frame 5 to prevent the support rod 41 from escaping from the slide groove. The support plate 42 is installed on the upper end surface of the support rod 41. A ball socket 8 is installed on the support plate 42. A universal ball 7 is installed on the lower bottom surface of the base 1. The universal ball 7 is installed in the ball socket 8 and can rotate relative to the ball socket 8. The support rod 41 can be made of steel pipe or aluminum alloy pipe, and the diameter is selected according to actual needs. The material of the support plate 42 can be selected from high-strength steel plate, and the thickness is generally 10-15 mm. The cooperation of the ball socket 8 and the universal ball 7 can realize the free adjustment of the base 1 in three-dimensional space, ensuring that the base 1 always remains in a horizontal state and can maintain good flatness even in the case of uneven settlement of the bridge body.
[0039] In the embodiment of the present application, a support screw 43 and a telescopic top rod 44 are also included. The adjustment component 4 also includes a support screw 43. Two support screws 43 are provided. The two support screws 43 are respectively installed at the two sides of the support plate 42 along the length direction of the bridge body. The support screw 43 passes through the support plate 42 and extends to the lower bottom surface of the base 1. The material of the support screw 43 can be selected from high-strength steel, and the diameter is generally φ16 mm or φ20 mm. The thread of the support screw 43 can be designed as a fine pitch thread to improve the adjustment accuracy. An adjustment hand wheel can be installed on the top of the support screw 43 to facilitate manual adjustment of the height and flatness of the base 1.
[0040] Two telescopic top rods 44 are provided, and the two telescopic top rods 44 are respectively installed on both sides of the support rod 41 along the width direction of the expansion joint. The telescopic top rod 44 includes a first rod body 441 and a second rod body 442. The first rod body 441 is supported on the bridge structure 10, and a lifting groove is provided on the first rod body 441. One end of the second rod body 442 is inserted into the lifting groove, and the other end of the second rod body 442 is hinged on the lower bottom surface of the base 1 and can slide in the lifting groove. The first rod body 441 and the second rod body 442 are coaxially arranged, and a plurality of elastic limiting pieces 443 are provided on the upper end of the first rod body 441, and the first rod body 441 is threadedly connected to the limiting ring 45. The limiting ring 45 can move toward the upper end to make the elastic limiting piece 443 deform toward the axial direction of the first rod body 441, and the elastic limiting piece 443 can limit the second rod body 442. The material of the first rod body 441 and the second rod body 442 can be high-strength steel, and the diameter is generally φ20 mm or φ25 mm. Grease can be applied to the inside of the lifting groove to reduce friction resistance. The material of the elastic limit plate 443 can be spring steel, and the number is generally 3-5 to ensure sufficient limit force. The material of the limit ring 45 can be stainless steel to improve its corrosion resistance.
[0041] like Figure 6 As shown, a plurality of prestressed springs 6 are installed on the upper end surface of the base 1, and the prestressed springs 6 are arranged between the base 1 and the elastomer layer 2, and the prestressed springs 6 support the elastomer layer 2 at one end away from the base 1. The material of the prestressed spring 6 can be selected from high-quality carbon steel or stainless steel, and the diameter is generally φ10 mm or φ12 mm. The number of prestressed springs 6 can be selected according to actual needs, for example, 10-15 per square meter, to ensure that the elastomer layer 2 can quickly return to its original state when subjected to external force. The prestress of the prestressed spring 6 can be selected according to the thickness and hardness of the elastomer layer 2 to ensure that it will not be permanently deformed under normal working conditions.
[0042] In other embodiments, the adjustment component 4 can be installed on the bridge structure 10 by using an electric push rod, and the guide rod is installed on the push rod of the electric push rod, and the other end of the guide rod is connected to the base 1. The push rod of the electric push rod can be extended or retracted under the drive of the motor, thereby driving the guide rod to move up and down to achieve vertical adjustment of the base 1. The controller of the electric push rod can be installed in a control box near the bridge body, and the adjustment is performed by electric or manual means. The surface of the guide rod can be chrome-plated to improve its wear resistance and corrosion resistance. It also includes a lateral adjustment mechanism, which includes a cylinder and a guide rod, the cylinder is installed on the bridge structure 10, the guide rod is installed on the piston rod of the cylinder, and the other end of the guide rod is connected to the base 1. The piston rod of the cylinder can be extended or retracted under the action of compressed air, thereby driving the guide rod to move left and right to achieve lateral adjustment of the base 1. The control valve of the cylinder can be installed in a control box near the bridge body, and the adjustment is performed by electric or manual means. The surface of the guide rod can be chrome-plated to improve its wear resistance and corrosion resistance.
[0043] The implementation principle of a super-tough elastomeric seamless expansion joint in an embodiment of the present application is: through the flexible adjustment ability of the adjustment component 4, the influence of uneven settlement of the bridge body can be effectively dealt with, ensuring that the base 1 is always in a horizontal state, thereby ensuring the flatness and sealing of the elastomer layer 2 and the covering layer 3.
[0044] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in the protection scope of the present application.
Claims
1. A super-tough elastomer seamless expansion joint, characterized in that: The invention comprises a base (1), an elastomer layer (2) and a covering layer (3), wherein the base (1) is provided with two groups, the two bases (1) are respectively mounted on a bridge structure (10) on both sides of an expansion joint, the elastomer layer (2) is mounted on the two bases (1), the covering layer (3) is laid on the elastomer layer (2), the covering layer (3) is fixed to the base (1) through the elastomer layer (2) via an anchoring structure (9), the base (1) is mounted on the bridge structure (10) via an adjusting component (4), and the adjusting component (4) is used to adjust the flatness of the base (1).
2. The super-tough elastomer seamless expansion joint according to claim 1, characterized in that: The adjustment assembly (4) comprises a support rod (41) and a support plate (42), wherein the support rod (41) is mounted on the bridge structure (10), and the support plate (42) is mounted on the upper end surface of the support rod (41), and a ball socket (8) is mounted on the support plate (42), and a universal ball (7) is mounted on the lower bottom surface of the base (1), and the universal ball (7) is mounted in the ball socket (8) and can rotate relative to the ball socket (8).
3. The super-tough elastomer seamless expansion joint according to claim 2, characterized in that: The adjustment assembly (4) further comprises a support screw (43), wherein two support screws (43) are provided, and the two support screws (43) are respectively installed on both sides of the support plate (42) along the length direction of the bridge body, and the support screw (43) passes through the plate surface of the support plate (42) and extends towards the lower bottom surface of the base (1).
4. The super-tough elastomer seamless expansion joint according to claim 2, characterized in that: The adjustment assembly (4) further comprises a telescopic top rod (44), wherein two connecting rods are provided, and the two connecting rods are respectively installed on both sides of the support rod (41) along the width direction of the expansion joint, and the telescopic top rod (44) comprises a first rod body (441) and a second rod body (442), wherein the first rod body (441) is installed on the bridge structure (10), and a lifting groove is provided on the first rod body (441), and one end of the second rod body (442) is inserted into the lifting groove and can be moved in the lifting groove. The first rod body (441) and the second rod body (442) are coaxially arranged, and a plurality of elastic limiting pieces (443) are arranged on the upper end of the first rod body (441). The first rod body (441) is threadedly connected to a limiting ring (45). The limiting ring (45) can move toward the upper end to deform the elastic limiting piece (443) toward the axial direction of the first rod body (441). The elastic limiting piece (443) can limit the second rod body (442).
5. The super-tough elastomer seamless expansion joint according to claim 4, characterized in that: A limiting frame (5) is installed on the bridge structure (10), a sliding groove is provided on the limiting frame (5), and the support rod (41) is arranged through the sliding groove and can move relative to the limiting frame (5).
6. The super-tough elastomer seamless expansion joint according to claim 1, characterized in that: A plurality of prestressed springs (6) are installed on the upper end surface of the base (1); the prestressed springs (6) are arranged between the base (1) and the elastomer layer (2); and the end of the prestressed spring (6) facing away from the base (1) supports the elastomer layer (2).
7. The super-tough elastomer seamless expansion joint according to claim 1, characterized in that: The anchoring structure (9) comprises a pressure strip (91) and a fastening bolt (92); the pressure strip (91) is installed on the covering layer (3) along the width direction of the bridge body; the fastening bolt (92) passes through the pressure strip (91) and the elastomer layer (2) and is fixed on the base (1).
8. The super-tough elastomer seamless expansion joint according to claim 1, characterized in that: The elastomer layer (2) is made of modified polyurethane elastomer material and has a thickness of 20 mm.
9. The super-tough elastomer seamless expansion joint according to claim 1, characterized in that: The covering layer (3) is composed of a high-strength nylon fiber cloth and an EPDM rubber composite material, and the thickness is set to 5 mm.
10. A construction method for a super-tough elastomer seamless expansion joint, characterized in that: The following steps are involved: S10: cleaning a pre-installation area of the base (1) on the bridge structure; S20: installing the two bases (1) respectively to the bridge structure on both sides of the expansion joint, and adjusting the bases (1) to achieve the required flatness and height; S30: evenly laying the elastomer layer (2) on the base (1), and removing air bubbles in the elastomer layer (2); S40: Covering the elastomer layer (2) on the elastomer layer (2), and ensuring that the covering layer (3) completely covers the elastomer layer (2); S50: Fix the covering layer (3) and ensure that all components are installed in place.