Composite beam string structure and prestress applying method thereof

Abstract

The present application relates to a kind of composite string beam structure and its prestress exerting method, two sides of the composite string beam structure are connected with a pair of support respectively, one side of the support is connected with a pair of composite string beam structure at both ends respectively, the composite string beam structure and support jointly resist the retaining beam of foundation pit retaining structure;The composite string beam structure includes arch structure and string structure, the arch structure includes upper chord arch beam and prestressed force transmission rod, the upper chord arch beam is connected with support, one side of the prestressed force transmission rod is connected with upper chord arch beam, the other side is connected with retaining beam, the string structure includes lower chord pull rod and prestressed support rod, the lower chord pull rod is connected with support, one side of the prestressed support rod is connected with lower chord pull rod, the other side is connected with upper chord arch beam.Compared with prior art, the present application greatly improves bearing capacity and rigidity.

Description

Technical Field

[0001] This invention belongs to the field of building construction technology and relates to a composite tensioned beam structure and its prestressing application method. Background Technology

[0002] To ensure the safety of underground structure construction and the surrounding environment of the foundation pit, it is necessary to adopt retaining, reinforcement, and protection measures for the sidewalls and surrounding environment of the foundation pit. Whether it is a deep foundation pit project for high-rise buildings or subway construction, since most of them are excavated in urban areas, there are usually various structures such as traffic arteries, existing buildings, or pipelines around the foundation pit. In order to ensure the safety of the surrounding environment of the foundation pit, as well as to save construction time and costs, the tensioned beam structure system is widely used.

[0003] When the soil layer of the foundation pit is very poor or very deep, the load borne by the tensioned beam is large, and the stiffness and bearing capacity of the existing large-span tensioned beam cannot meet the requirements of this application scenario.

[0004] Patent CN112160326A discloses a tensioned concrete truss composite support system, including a concrete retaining beam, a tensioned concrete truss, steel braces, and steel corner braces. The tensioned concrete truss comprises a concrete truss and steel tensioned members. The concrete truss is located inside the concrete retaining beam and forms an integral structure with it. The steel braces are perpendicular to the concrete retaining beam and act directly on the concrete truss. The steel corner braces are located at the corners of the concrete retaining beam. However, this patent uses a tensioned concrete truss between the steel braces, which is equivalent to increasing the width of the concrete retaining beam. Even with the tensioned beams on the concrete truss, the increased load-bearing capacity is limited, the stiffness is still insufficient, and the concrete portion cannot be reused. Summary of the Invention

[0005] The purpose of this invention is to overcome at least one of the defects of the prior art and provide a composite tensioned beam structure and its prestressing application method. This invention greatly improves the load-bearing capacity and stiffness.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] One of the technical solutions of the present invention is to provide a composite tensioned beam structure, wherein the composite tensioned beam structure and the support are arranged horizontally, and the two sides of the composite tensioned beam structure are respectively connected to a pair of supports, and the two ends of one side of the support are respectively connected to a pair of composite tensioned beam structures. The composite tensioned beam structure and the support together support the retaining beam of the foundation pit retaining structure to bear the load transmitted from the foundation pit retaining structure.

[0008] The composite tensioned beam structure includes an arch structure and a tensioned structure. The arch structure and the tensioned structure are approximately enclosed to form a bow and a string, which have high load-bearing capacity and stiffness.

[0009] The arch structure includes an upper chord arch beam and a prestressed force transmission rod. The upper chord arch beam is connected to the support, and one side of the prestressed force transmission rod is connected to the upper chord arch beam and the other side is connected to the retaining beam. The two upper chord arch beams and the main supports on both sides approximately enclose to form a circular structure, which has strong load-bearing capacity and overall performance.

[0010] The tensioned structure includes a lower chord tie rod and a prestressed strut. The lower chord tie rod is connected to a support, and one side of the prestressed strut is connected to the lower chord tie rod, while the other side is connected to the upper chord arch beam.

[0011] Furthermore, the upper chord arch beam includes side nodes, middle nodes, and several arc beam segments, wherein the two middle arc beam segments are connected by the middle node, and the two outer arc beam segments are connected by the side nodes.

[0012] The cross-sectional shape of the central node is quadrilateral, with the upper and lower sides both set as planes parallel to the retaining beam, and the left and right sides respectively fitting into the sides of the two side arc beams.

[0013] The cross-sectional shape of the edge node is hexagonal, with the top and bottom sides both set as planes parallel to the retaining beam, and the two opposite sides on the left and right respectively fitting into the sides of the two side arc beams.

[0014] The upper and lower sides of the nodes parallel to the retaining beam can ensure that when the prestressing device applies prestress, the force transmission rods and struts are only subjected to axial force, making the force transmission more direct.

[0015] Furthermore, the prestressed force transmission bar includes a force transmission bar and a force transmission bar prestressing device. The fixed end of the force transmission bar prestressing device is connected to the retaining beam, and the lifting end is connected to the force transmission bar to apply prestress between the retaining beam and the upper chord arch beam. The other end of the force transmission bar is connected to the node of the upper chord arch beam. When prestress is applied, the force transmission bar is only subjected to axial force, the force is simple and clear, and the member has high bearing capacity.

[0016] As a preferred technical solution, the other end of the force transmission rod is connected to the middle node or side node of the upper chord arch beam.

[0017] Furthermore, the lower chord tie rod comprises several tie rod segments, which are hinged together by nodes.

[0018] Furthermore, the prestressed strut includes a strut and a strut prestressing device. The fixed end of the strut prestressing device is connected to the node of the upper chord arch beam, and the lifting end is connected to the strut to apply prestress between the upper chord arch beam and the lower chord tie rod. The other end of the strut is hinged to the node of the lower chord tie rod. When prestress is applied, the strut is only subjected to axial force, the force is simple and clear, and the member has high bearing capacity.

[0019] As a preferred technical solution, the fixed end of the strut prestressing device is connected to the middle node or side node of the upper chord arch beam.

[0020] Furthermore, the tensioned structure also includes connecting rods, wherein the two sides of the middle connecting rod are respectively connected to two prestressed struts, and the two outermost connecting rods are respectively connected to the prestressed struts and supports. The connecting rods can enhance the lateral stability of the prestressed struts and also withstand the thrust transmitted from the upper chord arch beam and the lower chord tie rod. When a force is applied, the struts can deform along the axis without generating additional shear force and bending moment on the connecting rods, so that the struts and connecting rods are only subjected to axial force, the force is simple and clear, and the bearing capacity of the members is high.

[0021] As a preferred technical solution, the side of the support rod is provided with a support rod side end plate, and an elongated hole is opened on the support rod side end plate to connect with the connecting rod.

[0022] Furthermore, the support includes several main supports and composite nodes. Two main supports are connected along the axial direction through composite nodes. The main supports are connected to the lower chord tie rod, connecting rod, upper chord arch beam, diagonal web member and transverse web member respectively through composite nodes.

[0023] Furthermore, the support also includes horizontal web members and diagonal web members. Several main supports are arranged, and two main supports are connected by horizontal web members and diagonal web members. The horizontal web members are arranged in a direction perpendicular to the axis of the main support, and the diagonal web members are arranged in a direction inclined to the axis of the main support.

[0024] As a preferred technical solution, the composite node connected to the composite tensioned beam structure is equipped with tie rod connecting lugs, connecting rod end plates, arch beam end plates, main support end plates, diagonal web member connecting lugs, and transverse web member end plates. The composite node is connected to the lower chord tie rod, connecting rod, upper chord arch beam, main support, diagonal web member, and transverse web member respectively through the tie rod connecting lugs, connecting rod end plates, arch beam end plates, main support end plates, diagonal web member connecting lugs, and transverse web member end plates.

[0025] The composite node, which is not connected to the composite tensioned beam structure, is provided with a main support end plate, a diagonal web member connecting lug plate, and a transverse web member end plate. The composite node is connected to the main support, diagonal web member, and transverse web member respectively through the main support end plate, the diagonal web member connecting lug plate, and the transverse web member end plate.

[0026] Furthermore, the support also includes a main support prestressing device, the fixed end of which is connected to the retaining beam, and the lifting end is connected to the main support, for applying prestress between the two retaining beams.

[0027] One of the technical solutions of the present invention is to provide a method for applying prestress to the composite tensioned beam structure, the method comprising the following steps:

[0028] S1. First, apply prestress to the support and push the pit retaining structure outward.

[0029] S2. Apply prestress to the prestressed struts to tension the tensioned structure, and the tensioned structure part forms the prestress of the composite tensioned beam structure as a whole.

[0030] S3. Apply prestress to the prestressed force transmission rod, push the composite tensioned beam structure inward on one side and push the foundation pit retaining structure outward on the other side, enhance the equivalent stiffness of the foundation pit and the composite tensioned beam structure, and greatly reduce the deformation of the foundation pit retaining structure caused by subsequent foundation pit excavation.

[0031] S4. Finally, apply prestress to the supports, prestressed struts, and prestressed force transmission rods in the last cycle to achieve the predetermined prestress requirement.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] (1) In this invention, the arch structure and the tensioned cable structure are combined to form a composite tensioned cable beam structure, which greatly improves the load-bearing capacity and stiffness.

[0034] (2) In this invention, the upper chord arch beam and the main support form a near-circular structure, which has better stress distribution, strong overall structural stability, and high load-bearing capacity;

[0035] (3) In this invention, the connecting rod can serve as a lateral stabilizing rod for the prestressed strut to improve the stability of the strut, and can also bear the thrust transmitted from the upper chord arch beam and the lower chord tie rod, thereby improving the overall bearing capacity of the composite tensioned beam structure.

[0036] (4) In this invention, the arch structure and the tensioned structure are respectively prestressed by the prestressing device, which doubles the overall stiffness and has a good effect on reducing the deformation caused by the excavation of the foundation pit. In addition, the prestressing is applied by lifting the support rod and the force transmission rod through the prestressing device, which is efficient and convenient. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the installation of the composite tensioned beam structure in an embodiment of the present invention;

[0038] Figure 2 This is a schematic diagram illustrating the formation of a near-circular structure by the composite tensioned beam structure in an embodiment of the present invention.

[0039] Figure 3 This is a schematic diagram of the supporting structure in an embodiment of the present invention;

[0040] Figure 4 This is a schematic diagram of the composite tensioned beam structure in an embodiment of the present invention;

[0041] Figure 5 This is a schematic diagram of the arched structure in an embodiment of the present invention;

[0042] Figure 6 This is an exploded structural diagram of the prestressed force transmission rod in an embodiment of the present invention;

[0043] Figure 7 This is an exploded structural diagram of the upper chord arch beam in an embodiment of the present invention;

[0044] Figure 8 This is a schematic diagram of the tensioned structure in an embodiment of the present invention;

[0045] Figure 9 This is an exploded structural diagram of the prestressed strut in an embodiment of the present invention;

[0046] Figure 10 This is a schematic diagram of the composite node in an embodiment of the present invention.

[0047] Explanation of markings in the diagram:

[0048] 1—Enclosure beam, 2—Composite tensioned beam structure, 3—Support;

[0049] 21—Prestressed force transmission rod, 22—Upper chord arch beam, 23—Connecting rod, 24—Prestressed strut, 25—Lower chord tie rod;

[0050] 211—Prestressed device for force transmission rods; 212—Force transmission rods;

[0051] 221—Middle node, 222—Edge node, 223—Arched beam;

[0052] 241—Prestressed strut device, 242—Strut, 243—Side end plate of strut;

[0053] 31—Main support prestressing device; 32—Main support; 33—Composite node; 34—Horizontal web member; 35—Diagonal web member;

[0054] 331—Arch beam connecting end plate, 332—Connecting rod connecting end plate, 333—Tie rod connecting lug plate, 334—Main support connecting end plate, 335—Horizontal web member connecting end plate, 336—Diagonal web member connecting lug plate. Detailed Implementation

[0055] The present invention will now be described in detail with reference to specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0056] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention. Furthermore, the terms "first," "second," and "third," etc., are used to describe a common object, only indicating different instances of the same object, and do not imply that the objects described in this way must be in a given order, whether temporally, spatially, sequentially, or in any other way.

[0057] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0058] Example:

[0059] A composite tensioned beam structure, such as Figure 1 As shown, the composite tensioned beam structure 2 and the support 3 are both arranged horizontally. The two sides of the composite tensioned beam structure 2 are connected to a pair of supports 3 respectively, and the two ends of one side of the support 3 are connected to a pair of composite tensioned beam structures 2 respectively. The composite tensioned beam structure 2 and the support 3 together support the retaining beam 1 of the foundation pit retaining structure to bear the load transmitted from the foundation pit retaining structure.

[0060] like Figure 4 As shown, the composite tensioned beam structure 2 includes an arch structure and a tensioned structure. The arch structure and the tensioned structure are approximately enclosed to form a bow and a string, which have strong load-bearing capacity and stiffness.

[0061] like Figure 5 As shown, the arch structure includes an upper chord arch beam 22 and a prestressed force transmission rod 21. The upper chord arch beam 22 is connected to the support 3, and one side of the prestressed force transmission rod 21 is connected to the upper chord arch beam 22, while the other side is connected to the retaining beam 1.

[0062] like Figure 2 As shown, the two upper chord arch beams 22 and the main supports 32 on both sides of the support 3 form an approximately circular structure, which has strong load-bearing capacity and overall performance.

[0063] like Figure 7As shown, the upper chord arch beam 22 includes side nodes 222, middle nodes 221, and several arched beam segments 223. The two middle arched beam segments 223 are connected by the middle node 221, and the two outer arched beam segments 223 are connected by the side nodes 222.

[0064] The cross-sectional shape of the middle node 221 is quadrilateral, with the upper and lower sides both set as planes parallel to the retaining beam 1, and the left and right sides respectively fitting into the sides of the two side arc beams 223.

[0065] The cross-sectional shape of edge node 222 is hexagonal, with the upper and lower sides both set as planes parallel to the retaining beam 1, and the two opposite sides on the left and right respectively fitting into the sides of the two side arc beams 223.

[0066] The upper and lower sides of the node parallel to the retaining beam 1 can ensure that when the prestressing device applies prestress, the force transmission rod 212 and the strut 242 are only subjected to axial force, making the force transmission more direct;

[0067] like Figure 6 As shown, the prestressed force transmission rod 21 includes a force transmission rod 212 and a force transmission rod prestressing device 211. The fixed end of the force transmission rod prestressing device 211 is connected to the retaining beam 1, and the lifting end is connected to the force transmission rod 212 to apply prestress between the retaining beam 1 and the upper chord arch beam 22. The other end of the force transmission rod 212 is connected to the middle node 221 or the side node 222 of the upper chord arch beam 22. When prestress is applied, the force transmission rod 212 is only subjected to axial force, the force is simple and clear, and the member has high bearing capacity.

[0068] like Figure 8 As shown, the tensioned structure includes a lower chord tie rod 25 and a prestressed strut 24. The lower chord tie rod 25 is connected to the support 3, and one side of the prestressed strut 24 is connected to the lower chord tie rod 25, while the other side is connected to the upper chord arch beam 22.

[0069] The lower chord tie rod 25 includes several tie rod segments, which are hinged together by nodes;

[0070] like Figure 9 As shown, the prestressed strut 24 includes a strut 242 and a strut prestressing device 241. The fixed end of the strut prestressing device 241 is connected to the middle node 221 or the side node 222 of the upper chord arch beam 22, and the lifting end is connected to the strut 242 to apply prestress between the upper chord arch beam 22 and the lower chord tie rod 25. The other end of the strut 242 is hinged to the node of the lower chord tie rod 25. When prestress is applied, the strut 242 is only subjected to axial force, the force is simple and clear, and the member has high bearing capacity.

[0071] The tensioned structure also includes connecting rods 23, with the two sides of the middle connecting rod 23 connected to two prestressed struts 24 respectively, and the two sides of the outermost connecting rods 23 connected to the prestressed struts 24 and the support 3 respectively. The connecting rods 23 can enhance the lateral stability of the prestressed struts 24 and also bear the thrust transmitted from the upper chord arch beam 22 and the lower chord tie rod 25. When a force is applied, the strut 242 can deform along the axis without generating additional shear force and bending moment on the connecting rod 23, so that the strut 242 and the connecting rod 23 are only subjected to axial force, the force is simple and clear, and the member bearing capacity is high.

[0072] The side of the strut is provided with a strut side end plate 243, and an elongated hole is provided on the strut side end plate 243 to connect with the connecting rod 23;

[0073] like Figure 3 As shown, the support 3 includes several main supports 32 and composite nodes 33. Two main supports 32 are connected along the axial direction through composite nodes 33. The main supports 32 are connected to the lower chord tie rod 25, connecting rod 23, upper chord arch beam 22, diagonal web member 35 and horizontal web member 34 through composite nodes 33 respectively.

[0074] The support 3 also includes horizontal web members 34 and diagonal web members 35. Several main supports 32 are arranged, and two main supports 32 are connected by horizontal web members 34 and diagonal web members 35. The horizontal web members 34 are arranged in a direction perpendicular to the axis of the main support 32, and the diagonal web members 35 are arranged in a direction inclined to the axis of the main support 32.

[0075] like Figure 10 As shown, the composite node 33, which is connected to the composite tensioned beam structure 2, is equipped with tie rod connecting lugs 333, connecting rod end plates 332, arch beam end plates 331, main support end plates 334, diagonal web member connecting lugs 336, and transverse web member end plates 335. The composite node 33 is connected to the lower chord tie rod 25, connecting rod 23, upper chord arch beam 22, main support 32, diagonal web member 35, and transverse web member 34 respectively through the tie rod connecting lugs 333, connecting rod end plates 332, arch beam end plates 331, main support end plates 334, diagonal web member connecting lugs 336, and transverse web member end plates 335.

[0076] The composite node 33, which is not connected to the composite tensioned beam structure 2, is provided with a main support end plate 334, a diagonal web member connecting ear plate 336, and a transverse web member end plate 335. The composite node 33 is connected to the main support 32, the diagonal web member 35, and the transverse web member 34 through the main support end plate 334, the diagonal web member connecting ear plate 336, and the transverse web member end plate 335, respectively.

[0077] The support 3 also includes a main support prestressing device 31. The fixed end of the main support prestressing device 31 is connected to the retaining beam 1, and the lifting end is connected to the main support 32, so as to apply prestress between the two retaining beams 1.

[0078] The retaining beam 1 is made of concrete, while the composite tensioned beam structure 2 and the support 3 are both made of steel and can be reused. The prestressed device 211 of the force transmission rod, the prestressed device 241 of the strut, and the prestressed device 31 of the main support are all lifted by jacks to apply prestress.

[0079] The specific steps of the prestressing application method for the above-mentioned composite tensioned beam structure are as follows:

[0080] S1. First, apply prestress to support 3 and push the foundation pit retaining structure outward.

[0081] S2. Apply prestress to the prestressed strut 24 to tension the tensioned structure, and the tensioned structure part forms the prestress of the composite tensioned beam structure 2 as a whole.

[0082] S3. Apply prestress to the prestressed force transmission rod 21. On one side, push the composite tensioned beam structure 2 inward, and on the other side, push the foundation pit retaining structure outward. This enhances the equivalent stiffness of the foundation pit and the composite tensioned beam structure 2, which can greatly reduce the deformation of the foundation pit retaining structure caused by subsequent foundation pit excavation.

[0083] S4. Finally, apply prestress to support 3, prestressed strut 24 and prestressed force transmission rod 21 in the last cycle to achieve the predetermined prestress requirement.

[0084] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A composite tensioned beam structure, characterized in that, The two sides of the composite tensioned beam structure (2) are connected to a pair of supports (3), and the two ends of one side of the support (3) are connected to a pair of composite tensioned beam structures (2). The composite tensioned beam structure (2) and the support (3) together support the retaining beam (1) of the foundation pit retaining structure. The composite tensioned beam structure (2) includes an arch structure and a tensioned structure. The arch structure includes an upper chord arch beam (22) and a prestressed force transmission rod (21). The upper chord arch beam (22) is connected to the support (3). One side of the prestressed force transmission rod (21) is connected to the upper chord arch beam (22), and the other side is connected to the retaining beam (1). The tensioned structure includes a lower chord tie rod (25) and a prestressed strut (24). The lower chord tie rod (25) is connected to the support (3). One side of the prestressed strut (24) is connected to the lower chord tie rod (25), and the other side is connected to the upper chord arch beam (22).

2. The composite tensioned beam structure according to claim 1, characterized in that, The upper chord arch beam (22) includes side nodes (222), middle nodes (221), and several arc beams (223). The two middle arc beams (223) are connected by the middle node (221), and the two arc beams (223) on both sides are connected by the side nodes (222). The cross-sectional shape of the central node (221) is quadrilateral, with the upper and lower sides both set as planes parallel to the retaining beam (1), and the left and right sides respectively fitting into the sides of the two side arc beams (223). The cross-sectional shape of the edge node (222) is hexagonal, and the upper and lower sides are both set as planes parallel to the enclosure beam (1), and the two opposite sides on the left and right are respectively attached to the sides of the two side arc beams (223).

3. A composite tensioned beam structure according to claim 2, characterized in that, The prestressed force transmission rod (21) includes a force transmission rod (212) and a force transmission rod prestressing device (211). The fixed end of the force transmission rod prestressing device (211) is connected to the retaining beam (1), and the lifting end is connected to the force transmission rod (212). The other end of the force transmission rod (212) is connected to the node of the upper chord arch beam (22).

4. A composite tensioned beam structure according to claim 1, characterized in that, The lower chord tie rod (25) includes several tie rod segments, which are hinged together by nodes.

5. A composite tensioned beam structure according to claim 2, characterized in that, The prestressed strut (24) includes a strut (242) and a strut prestressing device (241). The fixed end of the strut prestressing device (241) is connected to the node of the upper chord arch beam (22), and the lifting end is connected to the strut (242). The other end of the strut (242) is hinged to the node of the lower chord tie rod (25).

6. A composite tensioned beam structure according to claim 1, characterized in that, The tensioned structure also includes connecting rods (23), wherein the two sides of the middle connecting rod (23) are connected to two prestressed struts (24) respectively, and the two sides of the outermost connecting rods (23) are connected to the prestressed struts (24) and the support (3) respectively.

7. A composite tensioned beam structure according to claim 1, characterized in that, The support (3) includes several main supports (32) and composite nodes (33). Two main supports (32) are connected along the axial direction through composite nodes (33). The main supports (32) are connected to the lower chord tie rod (25), connecting rod (23), upper chord arch beam (22), diagonal web member (35) and horizontal web member (34) through composite nodes (33).

8. A composite tensioned beam structure according to claim 7, characterized in that, The support (3) also includes a horizontal web member (34) and a diagonal web member (35). Several main supports (32) are arranged. Two main supports (32) are connected by a horizontal web member (34) and a diagonal web member (35). The horizontal web member (34) is arranged in a direction perpendicular to the axis of the main support (32), and the diagonal web member (35) is arranged in a direction inclined to the axis of the main support (32).

9. A composite tensioned beam structure according to claim 7, characterized in that, The support (3) also includes a main support prestressing device (31), the fixed end of which is connected to the retaining beam (1), and the lifting end is connected to the main support (32).

10. A method for applying prestress to a composite tensioned beam structure as described in any one of claims 1 to 9, characterized in that, The method includes the following steps: S1. First, apply prestress to the support (3) and push the pit retaining structure outward; S2. Apply prestress to the prestressed strut (24) to tension the tensioned structure, and the tensioned structure part forms the prestress of the composite tensioned beam structure (2) as a whole. S3. Then apply prestress to the prestressed force transmission rod (21), push the composite tensioned beam structure (2) inward on one side and push the foundation pit retaining structure outward on the other side, enhance the equivalent stiffness of the foundation pit and the composite tensioned beam structure (2), and reduce the deformation of the foundation pit retaining structure caused by subsequent foundation pit excavation. S4. Finally, apply the prestress to the support (3), prestressed strut (24) and prestressed force transmission rod (21) in the last cycle to achieve the predetermined prestress requirement.

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