Structure and method for reinforcing existing building foundation through section increasing method

Abstract

The invention provides a structure and method for reinforcing an existing building foundation through a section increasing method, and belongs to the technical field of building construction.The structure comprises a prefabricated foundation unit, a load conversion frame, a counter-force system and a monitoring control system; the prefabricated foundation units are arranged on the two sides of the original foundation, an elastic polymer isolation layer is arranged between the prefabricated beam type foundation and the original foundation, the load conversion frame comprises a load conversion beam and a detachable dowel bar, the counter-force system comprises a jack, a counter-force beam and a steel pull rod, and the monitoring control system comprises a vibrating wire strain gauge, a static force level gauge and a pressure control system. The newly-added strip-shaped foundation is poured at the top of the original foundation; by means of the technical means of the precast beam type foundation, the load transfer beam, the load reaction frame and the newly-added strip-shaped foundation, the newly-added load of the upper structure is accurately transferred to the newly-added foundation, and the foundation stress of the newly-added foundation is kept consistent with that of an original foundation by applying pre-applied pressure to the newly-added foundation.

Description

Technical Field

[0001] This invention relates to the field of building construction technology, specifically to a structure and method for reinforcing the foundation of an existing building by increasing its cross-section. Background Technology

[0002] With the increasing demand for existing building renovation and old house renovation, situations frequently arise where changes in functional use and spatial requirements lead to increased loads on the superstructure. As a crucial component of the building structure, the foundation plays a vital role in evenly distributing the loads from the superstructure to the ground. Insufficient foundation bearing capacity can lead to serious safety hazards such as foundation settlement, wall cracking, and even overall building tilting, directly threatening the lives and property of users. Therefore, when the additional load from the superstructure exceeds the original foundation's design bearing capacity, appropriate reinforcement measures must be taken to improve its bearing capacity to ensure the safety of the structure in subsequent use.

[0003] Traditional methods of strengthening foundations by enlarging the cross-section result in a significant difference in stress between the new foundation and the original foundation. The new foundation base is in a state of zero stress, making it difficult to ensure coordinated stress distribution between the old and new foundations. This leads to a stress lag in the new foundation structure, causing the original foundation to bear a larger share of the new load. Consequently, the enlarged cross-section foundation cannot fully function, threatening structural safety. According to measured data, approximately 30%-50% of the new load in traditional methods of enlarging the cross-section is still transferred through the original foundation, leading to safety issues such as cracking and tilting of the building structure. Summary of the Invention

[0004] Purpose of the Invention: The purpose of this invention is to address the shortcomings of existing technologies by providing a structure and method for reinforcing the foundation of existing buildings using a cross-section enlargement method. This invention employs a technical approach of "precast beam foundation + load transfer beam + load reaction frame + new strip foundation" to precisely transfer the increased load from the superstructure to the enlarged cross-section foundation, ensuring that the new and old foundations share the load collaboratively after the cross-section is enlarged, thus solving the problem of stress lag in the enlarged cross-section portion of the foundation. By applying pre-pressure to the precast beam foundation, the stress at the bottom of the precast beam foundation is made consistent with that at the bottom of the original foundation, ensuring that the new and old foundations share the load collaboratively after the existing building is loaded, thereby achieving precise transfer of the increased load from the superstructure to the new foundation.

[0005] Technical solution: The present invention describes a structure for reinforcing the foundation of an existing building by increasing the cross-section, comprising a prefabricated foundation unit, a load transfer frame, a reaction system, and a monitoring and control system;

[0006] The precast foundation unit is a precast beam foundation, located on both sides of the original foundation. An elastic polymer isolation layer is installed between the precast beam foundation and the original foundation. The precast beam foundation is a precast concrete component, prefabricated before construction and assembled on-site during construction. Its length is consistent with the spacing of adjacent load transfer beams, and its cross-section and reinforcement are confirmed through calculation. The isolation layer effectively isolates the precast beam foundation from the original foundation, preventing the diversion of new loads due to the rigid connection between the precast beam foundation and the original foundation.

[0007] The load transfer frame includes a load transfer beam and detachable dowel bars. The load transfer beam is located below the ground beam and has pre-drilled holes at both ends. The detachable dowel bars include a steel pipe and a PVC sleeve fitted over the outer wall of the steel pipe. The steel pipe is circular and has a bearing steel plate at the top. The lower end of the steel pipe abuts against the top of the precast beam foundation, and the upper end of the steel pipe passes through the pre-drilled holes in the load transfer beam. During construction, the sleeve is fitted over the outside of the steel pipe to isolate the concrete during pouring, so that the steel pipe can be removed after construction.

[0008] The reaction system includes jacks, reaction beams, and steel tie rods. The jacks are positioned between the load transfer beam and the reaction beam. The top of the steel tie rod passes through the reaction beam, and the bottom of the steel tie rod passes through the load transfer beam. The steel tie rods are made of precision-rolled threaded steel.

[0009] The monitoring and control system includes vibrating wire strain gauges and a hydrostatic level installed on the outside of the foundation beam. These gauges are connected to an external pressure control system, which in turn is connected to the jacks. The vibrating wire strain gauges are used to monitor changes in stress in the foundation beam in real time during load transitions. The pressure control system provides pressure to the jacks. During construction, the jack force is adjusted based on the upper load and the monitoring data from the hydrostatic level and vibrating wire strain gauges to ensure consistent stress levels between the old and new foundation bases.

[0010] It also includes a new strip foundation poured on top of the original foundation. The new strip foundation is a reinforced concrete strip foundation. The interior of the new strip foundation is symmetrically equipped with foundation beams along the length of the wall, and the two foundation beams are connected by a shoulder beam.

[0011] Furthermore, the elastic polymer isolation layer is a rubber pad with a thickness of 2-5 mm and an elastic modulus of less than 1 MPa.

[0012] Furthermore, the jacks are hydraulic self-locking jacks; the jacks are placed between the load transfer beam and the reaction beam, and during construction, the jacks are used to apply pre-pressure to the precast beam foundation.

[0013] Furthermore, the foundation beams are symmetrically arranged at intervals of 1-1.5m along the length of the newly added strip foundation, and their cross-sectional height is not less than 2 / 3 of the height of the newly added strip foundation.

[0014] Furthermore, the load transfer beam is an I-beam with a flange width that is more than 20mm wider than the diameter of the reserved hole.

[0015] A construction method for reinforcing the foundation of an existing building using the cross-section enlargement method as described above includes the following steps:

[0016] Step 1: Calculate the load G per unit length of the original structure and the new load F;

[0017] Step 2: Based on the new load F and the corrected characteristic value of the foundation bearing capacity f a Calculate the width b' of a single-sided precast beam foundation;

[0018] Step 3: Determine the length L and height h of the precast beam foundation;

[0019] Step 4: Excavate the working face and lay precast foundation units, with an elastic polymer isolation layer 5 between the precast foundation units and the original foundation;

[0020] Step 5: Install the load transfer frame and reaction system;

[0021] Step 6: Calculate the pre-applied pressure Q and jack force P of the precast foundation unit;

[0022] Step 7: Based on the pre-applied pressure Q and jack force P of the precast foundation unit calculated in Step 6, apply the pre-applied pressure by driving the jack through the pressure control system. Dynamically adjust the output force based on the monitoring data of the vibrating wire strain gauge and the static level to ensure that the stress at the bottom of the precast foundation unit is consistent with the stress at the bottom of the original foundation. Apply the pre-applied pressure to the precast beam foundation through the jack using the pressure control system. During loading, adjust the pre-applied pressure in real time based on the monitoring data of the vibrating wire strain gauge and the static level to ensure that the compressive stress at the bottom of the precast beam foundation is consistent with that at the bottom of the original foundation.

[0023] Step 8: Pour a new strip foundation on top of the original foundation. Inside the new strip foundation, foundation beams are set along the length of the wall in the form of clamping beams, and shoulder beams are set at intervals of 1m.

[0024] Step 9: Pour concrete to fill the gap between the precast foundation unit and the newly added strip foundation;

[0025] Step 10: After the concrete strength of the newly added strip foundation meets the design requirements, remove the jacks, nuts, steel tie rods, reaction beams, load transfer beams, steel pipes, pressure control system, vibrating wire strain gauges, and hydrostatic level. Construction is now complete.

[0026] Further, step 4 specifically involves: erecting the load transfer beam below the ground beam, inserting a steel pipe with a sleeve, installing jacks and reaction beams, and locking them with steel tie rods and nuts.

[0027] Furthermore, the formula for calculating the width b' of the single-sided precast beam foundation in step 2 is as follows:

[0028] (1)

[0029] (2)

[0030] In the formula, F represents the new load. The value is the corrected characteristic value of the foundation bearing capacity, in KN / m2. The safety factor for the width b' of the single-sided precast beam foundation is taken as 1.2.

[0031] Furthermore, the calculation formula for the pre-applied pressure Q of the precast foundation unit in step 6 is as follows:

[0032] (3)

[0033] In the formula: Q is the preload applied to the precast beam foundation, in kN / m; G is the original superstructure load value; For the width of the precast beam foundation, and B represents the original base width, in meters (m).

[0034] Furthermore, the formula for calculating the jack force P in step 6 is as follows:

[0035] (4)

[0036] In the formula, Q is the pre-stress applied to the precast beam foundation, in kN / m; L is the length of the precast beam foundation 4.

[0037] Beneficial effects: Compared with the prior art, the advantages of the present invention are as follows:

[0038] (1) Before the new load is actually applied, the present invention actively applies a precisely controlled pre-stress to the new foundation (precast beam foundation) so that the base stress is consistent with the base stress of the original foundation after the reinforcement is completed and before the new load is applied; in this way, when the new load is applied, the new and old foundations can work together immediately, and the new load is naturally and entirely borne by the new foundation.

[0039] (2) The active preloading system in this invention consists of a precast beam foundation, steel pipe, jack, reaction beam, steel tie rod, load transfer beam, and pressure control system. The jack transmits pressure to the precast beam foundation through the steel pipe. The reaction beam and steel tie rod provide the reaction force required for the jack to apply pressure. The reaction force is finally transmitted to the superstructure (ground beam) through the load transfer beam. The pressure control system precisely controls and adjusts the pressure value applied by the jack.

[0040] (3) The present invention can realize real-time stress monitoring and feedback control: the stress change of the ground beam is monitored by vibrating wire strain gauge to reflect the load transfer of the superstructure; the settlement is monitored by static level to indirectly reflect the stress change of the base; the monitoring data is fed back to the pressure control system in real time to dynamically adjust the preload applied by the jack, so as to ensure that the compressive stress at the bottom of the precast beam foundation is always consistent with the compressive stress at the bottom of the original foundation during the pressure application process. Attached Figure Description

[0041] Figure 1 This is a structural plan view of the method for reinforcing the foundation of an existing building using the enlarged cross-section method described in this invention;

[0042] Figure 2 This is the cross-section of the present invention. Figure 1 ;

[0043] Figure 3 This is the cross-section of the present invention. Figure 2 ;

[0044] Figure 4 This is the cross-section of the present invention. Figure 3 ;

[0045] In the diagram: 1. Superstructure, 2. Ring beam, 3. Original foundation, 4. Precast beam foundation, 5. Isolation layer, 6. Load transfer beam, 7. Steel pipe, 8. Sleeve, 9. Jack, 10. Reaction beam, 11. Steel tie rod, 12. Nut, 13. Vibrating wire strain gauge, 14. Pressure control system, 15. Static level, 16. New strip foundation, 17. Foundation beam, 18. Shoulder beam. Detailed Implementation

[0046] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings, but the scope of protection of the present invention is not limited to the embodiments described.

[0047] Example 1

[0048] This embodiment describes the use of the aforementioned device and method for reinforcing the foundation of an existing building using the method of increasing the cross-section. The building was constructed in 2002, is a brick-concrete structure, has four floors above ground, and the original foundation bearing capacity f... a =200kPa, the foundation is a brick masonry strip foundation, 1.2m wide, and has been used as office space since its construction. Due to the owner's upgrade of the building's function, two more floors were added to the top, resulting in the additional load on the upper part exceeding the original foundation's design bearing capacity. Therefore, the original foundation was reinforced by increasing the cross section. After research and demonstration, this invention was adopted to reinforce the original foundation, taking the transverse wall of the part with the largest additional load on the upper part of the original building as an example.

[0049] like Figures 1-4The structure shown is a method for reinforcing the foundation of an existing building by increasing the cross section, including prefabricated foundation units, load transfer frames, reaction force systems, and monitoring and control systems;

[0050] The precast foundation unit is a precast beam foundation 4, which is set on both sides of the original foundation 3. An elastic polymer isolation layer 5 is set between the precast beam foundation 4 and the original foundation 3.

[0051] The load transfer frame includes a load transfer beam 6 and a detachable force transmission rod. The load transfer beam 6 is located below the ground beam 2, and the two ends of the load transfer beam 6 are provided with reserved holes. The detachable force transmission rod includes a steel pipe 7 and a PVC sleeve 8 sleeved on the outer wall of the steel pipe 7. The lower end of the steel pipe 7 abuts against the top of the precast beam foundation 4, and the upper end of the steel pipe 7 passes through the reserved hole of the load transfer beam 6.

[0052] The reaction system includes jack 9, reaction beam 10 and steel tie rod 11. Jack 9 is set between load transfer beam 6 and reaction beam 10. The top of steel tie rod 11 passes through reaction beam 10 and the bottom of steel tie rod 11 passes through load transfer beam 6.

[0053] The monitoring and control system includes a vibrating wire strain gauge 13 and a static level 15 installed on the outside of the ground beam. The vibrating wire strain gauge 13 and the static level 15 are connected to the external pressure control system 14. The pressure control system 14 is also connected to the jack 9.

[0054] It also includes a new strip foundation 16 poured on top of the original foundation 3. The interior of the new strip foundation 16 is symmetrically provided with foundation beams 17 along the length of the wall, and the two foundation beams 17 are connected by a shoulder beam 18.

[0055] In this embodiment, the elastic polymer isolation layer 5 is a rubber pad with a thickness of 2-5 mm and an elastic modulus of less than 1 MPa. The jack 9 is a hydraulic self-locking jack. The foundation beam 17 is symmetrically arranged at intervals of 1-1.5 m along the length of the newly added strip foundation 16, and its cross-sectional height is not less than 2 / 3 of the height of the newly added strip foundation 16. The load transfer beam 6 is an I-beam with a flange width greater than the diameter of the reserved hole by at least 20 mm.

[0056] A construction method for reinforcing the foundation of an existing building using the cross-section enlargement method as described above includes the following steps:

[0057] Step 1: Calculate the load G per unit length of the original structure and the new load F; the calculated load of the upper wall of the original structure is G=200kN / m and F=100kN / m.

[0058] Step 2: Based on the new load F and the corrected characteristic value of the foundation bearing capacity f aCalculate the width b' of the single-sided precast beam foundation 4;

[0059]

[0060] Taking a safety factor of 1.2, then b is taken as 0.6m (b'=0.30m on one side).

[0061] Step 3: Calculate and confirm based on the actual condition of the original foundation and the convenience of construction, and make adjustments according to the actual situation to determine the length L and height h of the precast beam foundation 4; take L=2.0m, h=0.2m.

[0062] Calculate the bending moment M and shear force V of the precast beam foundation.

[0063]

[0064]

[0065]

[0066]

[0067]

[0068] According to calculations, the reinforcement of the precast beam foundation is 2Φ18 at the bottom, 2Φ12 at the top, and 8Φ150 stirrups.

[0069] Step 4: Excavate the working face and lay precast foundation units. An elastic polymer isolation layer 5 is set between the precast foundation units and the original foundation 3. The load transfer beam 6 is erected under the ground beam 2, and a steel pipe 7 with a sleeve 8 is inserted. Jacks 9 and reaction beams 10 are installed and locked with steel tie rods 11 and nuts 12.

[0070] Step 5: Install the vibrating wire strain gauge, hydrostatic level, load transfer beam, steel pipe, jack, reaction beam and steel tie rod, and connect the jack to the pressure control system;

[0071] Step 6: Calculate the pre-applied pressure Q and jack force P of the precast foundation unit;

[0072] Pre-stress Q of precast foundation unit:

[0073]

[0074]

[0075] Jack force value P:

[0076]

[0077] Step 7: Based on the pre-applied pressure Q and jack force P calculated in Step 6, apply pre-applied pressure to the precast beam foundation using the pressure control system via the jacks. During loading, adjust the pre-applied pressure in real time based on the monitoring data from the vibrating wire strain gauge and the hydrostatic level to ensure that the compressive stress at the bottom of the precast beam foundation is consistent with that at the bottom of the original foundation. Apply pre-applied pressure by driving the jacks 9 through the pressure control system 14, and dynamically adjust the output force based on the monitoring data from the vibrating wire strain gauge 13 and the hydrostatic level 15 to ensure that the stress at the bottom of the precast foundation unit 4 is consistent with the stress at the bottom of the original foundation 3.

[0078] Step 8: Pour a new strip foundation 16 on top of the original foundation 3. Inside the new strip foundation 16, set foundation beams 17 and shoulder beams 18 spaced 1m apart along the length of the wall.

[0079] Step 9: Pour concrete to fill the gap between the precast foundation unit and the newly added strip foundation 16;

[0080] Step 10: After the concrete strength of the newly added strip foundation meets the design requirements, remove the jacks, nuts, steel tie rods, reaction beams, load transfer beams, steel pipes, pressure control system, vibrating wire strain gauges, and hydrostatic level. Construction is now complete.

[0081] The calculated stress at the bottom of the original foundation is:

[0082]

[0083] After the additional load on the upper part is applied, the stress per unit length of the base after increasing the cross-section is:

[0084]

[0085]

[0086] Therefore, after the additional load on the superstructure of this project is completed, the load-bearing capacity of the foundation after the cross-section is increased meets the structural safety requirements.

[0087] As described above, although the invention has been shown and described with reference to specific preferred embodiments, it should not be construed as limiting the invention itself. Various changes in form and detail may be made without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. A structure for reinforcing the foundation of an existing building using the method of increasing the cross-section, characterized in that: This includes prefabricated foundation units, load transfer frames, reaction force systems, and monitoring and control systems. The prefabricated foundation unit is a prefabricated beam foundation (4), which is set on both sides of the original foundation (3). An elastic polymer isolation layer (5) is provided between the prefabricated beam foundation (4) and the original foundation (3). The load transfer frame includes a load transfer beam (6) and a detachable force transmission rod. The load transfer beam (6) is located below the ground beam (2), and the load transfer beam (6) has reserved holes at both ends. The detachable force transmission rod includes a steel pipe (7) and a PVC sleeve (8) sleeved on the outer wall of the steel pipe (7). The lower end of the steel pipe (7) abuts against the top of the precast beam foundation (4), and the upper end of the steel pipe (7) passes through the reserved hole of the load transfer beam (6). The reaction system includes a jack (9), a reaction beam (10), and a steel tie rod (11). The jack (9) is located between the load transfer beam (6) and the reaction beam (10). The top of the steel tie rod (11) passes through the reaction beam (10), and the bottom of the steel tie rod (11) passes through the load transfer beam (6). The monitoring and control system includes a vibrating wire strain gauge (13) and a static level (15) installed on the outside of the ground beam. The vibrating wire strain gauge (13) and the static level (15) are connected to an external pressure control system (14). The pressure control system (14) is also connected to the jack (9). It also includes a new strip foundation (16) poured on top of the original foundation (3), and the interior of the new strip foundation (16) is symmetrically provided with foundation beams (17) along the length of the wall, and the two foundation beams (17) are connected by shoulder beams (18).

2. The structure for reinforcing the foundation of an existing building using the cross-section enlargement method according to claim 1, characterized in that: The elastic polymer isolation layer (5) is a rubber pad with a thickness of 2-5 mm and an elastic modulus of less than 1 MPa.

3. The structure for reinforcing the foundation of an existing building using the cross-section enlargement method according to claim 1, characterized in that: The jack (9) is a hydraulic self-locking jack.

4. The structure for reinforcing the foundation of an existing building using the cross-section enlargement method according to claim 1, characterized in that: The foundation beams (17) are symmetrically arranged at intervals of 1-1.5m along the length of the newly added strip foundation (16), and their cross-sectional height is not less than 2 / 3 of the height of the newly added strip foundation (16).

5. The structure for reinforcing the foundation of an existing building using the cross-section enlargement method according to claim 1, characterized in that: The load transfer beam (6) is an I-beam with a flange width greater than the diameter of the reserved hole by more than 20 mm.

6. A construction method for reinforcing the foundation of an existing building using the cross-section enlargement method as described in any one of claims 1 to 5, characterized in that... Includes the following steps: Step 1: Calculate the load G per unit length of the original structure and the new load F; Step 2: Based on the new load F and the corrected characteristic value of the foundation bearing capacity f a Calculate the width b' of the single-sided precast beam foundation (4); Step 3: Determine the length L and height h of the precast beam foundation (4); Step 4: Excavate the working face and lay prefabricated foundation units. An elastic polymer isolation layer (5) is set between the prefabricated foundation units and the original foundation (3). Step 5: Install the load transfer frame and reaction system; Step 6: Calculate the pre-applied pressure Q and jack force P of the precast foundation unit; Step 7: Based on the pre-applied pressure Q and jack force P of the precast foundation unit calculated in Step 6, drive the jack (9) to apply the pre-applied pressure through the pressure control system (14), and dynamically adjust the output force based on the monitoring data of the vibrating wire strain gauge (13) and the static level (15) so that the stress at the bottom of the precast foundation unit (4) is consistent with the stress at the bottom of the original foundation (3). Step 8: Cast a new strip foundation (16) on top of the original foundation (3). The new strip foundation (16) is provided with the foundation beam (17) and shoulder beams (18) spaced 1m apart along the wall length direction. Step 9: Pour concrete to fill the gap between the precast foundation unit and the newly added strip foundation (16); Step 10: After the concrete strength of the newly added strip foundation meets the design requirements, remove the jack (9), nut (12), steel tie rod (11), reaction beam (10), load transfer beam (6), steel pipe (7), pressure control system (14), vibrating wire strain gauge (13), and static level (15). Construction is complete.

7. A construction method as described in claim 6, characterized in that: Step 4 specifically involves: placing the load transfer beam (6) under the ground beam (2), inserting a steel pipe (7) with a sleeve (8), installing a jack (9) and a reaction beam (10), and locking it with a steel tie rod (11) and a nut (12).

8. A construction method as described in claim 6, characterized in that: The formula for calculating the width b' of the single-sided precast beam foundation (4) in step 2 is as follows: （1） （2） In the formula, F represents the new load. The value is the corrected characteristic value of the foundation bearing capacity, in KN / m2. The safety factor for the width b' of the single-sided precast beam foundation is taken as 1.

2.

9. A construction method as described in claim 6, characterized in that: The calculation formula for the pre-applied pressure Q of the precast foundation unit in step 6 is as follows: （3） In the formula: Q is the preload applied to the precast beam foundation, in kN / m; G is the original superstructure load value; For the width of the precast beam foundation, and B represents the original base width, in meters (m).

10. A construction method as described in claim 6, characterized in that: The formula for calculating the jack force P in step 6 is as follows: （4） In the formula, Q is the pre-stress applied to the precast beam foundation, with the unit being KN / m; L is the length of the precast beam foundation (4).

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