Unloading method suitable for locally dismantling prestressed structure

Abstract

The invention discloses an unloading method suitable for locally dismantling a prestressed structure. The method comprises the following steps: determining the arrangement position of a steel support system through structural simulation calculation, constructing a temporary support stress system by using a steel pipe column, a steel beam and a hydraulic jack, reasonably connecting and reinforcing, and installing a monitoring dial indicator; mounting and debugging a support system, and putting into use after ensuring no abnormity through a load test; then, pre-stress grading symmetric unloading is conducted, 20% of pre-stress is unloaded in five grades, structural deformation and supporting stress are monitored in real time, and the structure is dismantled synchronously; after dismantling is completed, permanent structure newly-built reinforcement construction is conducted; and after the strength of the newly-built reinforced structure reaches the standard, the jack hydraulic device unloads step by step, the beam bottom deformation quantity is observed through the dial indicator, finally, the temporary steel supporting system is dismantled, and conversion from a stress system to a permanent structure is achieved. The method fully utilizes and retains the bearing capacity of the structure, exerts the advantages of the steel member, realizes construction controllability and safety monitoring, reduces the manufacturing cost, and shortens the construction period.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of engineering construction, in particular to a unloading method suitable for partial demolition of prestressed structures. BACKGROUND

[0002] At present, urban renewal is becoming more and more popular. The mode of large-scale demolition and reconstruction has been difficult to adapt to the demand for sustainable development. The "surgical operation" type of structure updating method has gradually become the mainstream. In actual construction, only part of the prestressed components such as beams, slabs and columns need to be demolished, while the surrounding components are retained, which involves the transformation between structure systems and prestressed unloading system measures. Such projects cover multiple links such as demolition, reinforcement and new construction. Due to the limitation of complex working conditions, each process can only be carried out step by step, making it difficult to realize cross parallel operation, resulting in low construction efficiency and increased cost. Therefore, an efficient, safe and economical construction method is needed to solve the above problems. SUMMARY

[0003] The purpose of the present application is to provide a unloading method suitable for partial demolition of prestressed structures, to solve the problems of single construction process, low efficiency, high cost and difficult to guarantee safety in the prior art, to realize efficient release of structure stress, smooth transformation of stress system in partial demolition of prestressed structures, and to ensure safety and economy in the construction process.

[0004] To achieve the above purpose, the present application provides the following technical scheme:

[0005] A unloading method suitable for partial demolition of prestressed structures, comprising the following steps:

[0006] In the partial demolition, partial retention and partial new construction project, the reasonable arrangement position of the steel support system is determined by structure simulation calculation, and a temporary support stress system is formed by using steel pipe columns, steel beams and hydraulic jacks;

[0007] Hydraulic jacks are arranged above the steel pipe columns to realize controllable loading and unloading and real-time monitoring of the load; a dial indicator is arranged on the retained structure to observe the structure deformation in real time;

[0008] After the support stress system is established, prestressed graded symmetrical unloading is carried out, the components are demolished, and the stress system is converted to the steel support system;

[0009] Permanent structure new construction and reinforcement construction are carried out, and after the new construction and reinforcement of the permanent structure is completed and the strength is up to standard, the temporary steel support system is demolished, the load is borne by the permanent structure, and the stress system is converted again.

[0010] Further, the steel pipe column adopts Q345B material, the diameter is 400mm, the wall thickness is 12mm, 4 pieces of 20mm thick stiffening ribs are arranged at the end of the steel pipe column, a 700x700x40mm steel pad plate is arranged at the bottom of the column foot, and the gap between the steel pad plate and the foundation is filled with C45 grouting material.

[0011] Further, the steel beam adopts Q345B material, the specification is HN700x300x13x24, the steel pipe column and the steel beam are connected through 4 M20 high-strength bolts, and the steel beam and the concrete structure are connected through 6 chemical anchors M24.

[0012] Further, the installation method comprises the following steps:

[0013] Step one: determine the process, calculate the steel support point and the structure load condition through structure simulation;

[0014] Step two: install the back-up steel beam and the back-up steel pipe column in the area to be removed, connect the steel beam and the steel pipe column, pour the column foot grouting material, install the hydraulic device of the jack at the top of the column and set the fixed constraint, apply the prestress in advance, and install the deformation observation dial at the bottom of the reserved beam;

[0015] Step three: load test is carried out on the stress system composed of the steel pipe column and the steel beam, the deformation of the beam bottom and whether the steel support deforms obviously during the load are observed, and the structure is put into use after ensuring that there is no abnormality;

[0016] Step four: prestress is unloaded in stages and symmetrically, a total of 5 stages, each stage is unloaded by 20%, the structure is gradually removed, disturbance to the reserved structure and the support system is avoided during the removal process, and the deformation and the dial reading are monitored in real time;

[0017] Step five: confirm that the deformation of the reserved structure meets the design requirements, and complete the remaining removal work;

[0018] Step six: complete the construction of the newly built reinforced structure and ensure that its bearing performance meets the requirements, the hydraulic device of the jack is unloaded in stages, and the deformation of the beam bottom is observed through the dial;

[0019] Step seven: remove the temporary steel support system.

[0020] Further, the reinforced steel bracket is arranged at the hydraulic jack support to realize reverse force.

[0021] Further, the structure deformation and the support system stress are monitored in real time during the prestress grading symmetric unloading process.

[0022] Compared with the prior art, the present application has the following remarkable features and beneficial effects:

[0023] Make full use of the bearing capacity of the reserved structure: in the demolition construction, the application can maximize the bearing capacity of the reserved structure, does not affect the use function of the whole building, reduces the site occupation area, reduces the structure demolition amount, and further effectively reduces the engineering cost.

[0024] Play the advantages of steel members: the application makes full use of the characteristics of convenient erection, high standardization, light weight, high strength and recyclability of steel members, greatly shortens the construction period, improves the material turnover rate, and reduces the labor, time and material cost.

[0025] Realize controllable construction and safety monitoring: by setting monitoring instruments and adopting step-by-step segmented construction, the prestress unloading is controllable, the structure demolition is controllable, and the load deformation data is known; in the demolition process, the structure deformation can be monitored in real time, and once the abnormality is found, the construction scheme can be adjusted in time, so that the occurrence of safety accidents is effectively avoided, and the safety advantage is obvious. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 It is a planar schematic view of a kind of unloading method suitable for partial demolition prestressed structure of the application;

[0027] Figure 2 It is the schematic view of column foot node in the application (one);

[0028] Figure 3 It is the schematic view of column foot node in the application (two);

[0029] Figure 4 It is the schematic view of steel beam and steel pipe column connecting node in the application (one);

[0030] Figure 5 It is the schematic view of steel beam and steel pipe column connecting node in the application (two);

[0031] Figure 6 It is the schematic view of steel bracket for jack in the application (one);

[0032] Figure 7 It is the schematic view of steel bracket for jack in the application (two). DETAILED DESCRIPTION

[0033] To make the purpose, technical scheme and advantages of the embodiments of the application clearer, the technical scheme in the embodiments of the application will be described clearly and completely below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are part of the embodiments of the application, not all. The components of the embodiments of the application described and shown in the drawings here can be arranged and designed in various different configurations.

[0034] In the description of the embodiments of the application, "a plurality of" represents at least 2.

[0035] In the description of the embodiments of the present invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" 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 the present invention according to the specific circumstances.

[0036] Example:

[0037] This embodiment provides a method for unloading a prestressed structure that is suitable for partial demolition, including the following steps:

[0038] In partial demolition, partial preservation, and partial new construction projects, the reasonable layout of the steel support system is determined through structural simulation calculations, and a temporary support force system is constructed using steel pipe columns, steel beams, and hydraulic jacks.

[0039] Hydraulic jacks are installed above the steel pipe columns to enable controllable loading and unloading and real-time load monitoring; dial gauges are installed on the retained structure to observe structural deformation in real time.

[0040] After the supporting load-bearing system is established, the prestressed components are removed in stages and symmetrically unloaded, thus transforming the load-bearing system into a steel support system.

[0041] The construction and reinforcement of the permanent structure are carried out. After the construction of the new and reinforced permanent structure is completed and the strength meets the standards, the temporary steel support system is removed, and the load is borne by the permanent structure, thus realizing the conversion of the force system again.

[0042] As a further improvement to this embodiment, the steel pipe column is made of Q345B material, with a diameter of 400mm and a wall thickness of 12mm. Four 20mm thick stiffening ribs are provided at the end of the steel pipe column, and a 700x700x40mm steel pad is provided at the bottom of the column base. The gap between the steel pad and the foundation is filled with C45 grout.

[0043] As a further improvement to this embodiment, the steel beam is made of Q345B material with specifications of HN700x300x13x24. The steel pipe column and the steel beam are connected by 4 M20 high-strength bolts, and the steel beam is connected to the concrete structure by 6 M24 chemical anchors.

[0044] As a further improvement to this embodiment, the installation method includes the following steps:

[0045] Step 1: Determine the process flow and calculate the location of steel support points and structural load through structural simulation.

[0046] Step 2: Install the backfill steel beams and backfill steel pipe columns in the area to be demolished, connect the steel beams and steel pipe columns, pour grouting material at the column base, install hydraulic jacks on the column top and set fixed constraints, apply prestress in advance, and install deformation monitoring dial gauges at the bottom of the retained beams;

[0047] Step 3: Conduct a load test on the load-bearing system composed of steel pipe columns and steel beams. During the load test, observe the deformation of the beam bottom and whether there is any significant deformation of the steel supports. After ensuring that there are no abnormalities, put it into use.

[0048] Step 4: Perform symmetrical unloading of prestressed material in five stages, with each stage unloading 20% ​​of the material. Gradually dismantle the structure, avoiding any disturbance to the remaining structure and support system during the dismantling process, and monitor the deformation and dial gauge readings in real time.

[0049] Step 5: Confirm that the deformation of the retained structure meets the design requirements, and complete the remaining demolition work;

[0050] Step Six: Complete the construction of the new reinforced structure and ensure that its load-bearing performance meets the requirements. Use the hydraulic jacks to unload the load step by step and observe the deformation of the bottom of the beam using a dial indicator.

[0051] Step 7: Dismantle the temporary steel support system.

[0052] As a further improvement to this embodiment, a reinforced steel bracket is provided at the hydraulic jack support to achieve reverse force application.

[0053] As a further improvement to this embodiment, during the prestressed graded symmetrical unloading process, the structural deformation and the stress of the support system are monitored in real time.

[0054] Specifically:

[0055] (I) Construction of Support System

[0056] Material selection and preparation

[0057] The steel pipe column is made of Q345B material, with a diameter of 400mm and a wall thickness of 12mm. According to the design requirements, four 20mm thick stiffening ribs are processed at the end of the steel pipe column, and a 700x700x40mm steel pad is prepared at the bottom of the column base. At the same time, C45 grouting material is prepared.

[0058] The steel beams are made of Q345B material and have specifications of HN700x300x13x24. Four M20 high-strength bolts are prepared for the connection between the steel pipe column and the steel beam, and six M24 chemical anchors are prepared for the connection between the steel beam and the concrete structure.

[0059] Select appropriate hydraulic jacks and equip them with reinforced steel brackets, and prepare monitoring instruments such as dial gauges.

[0060] Structural simulation calculation

[0061] By using professional structural simulation software, relevant parameters for partial demolition, partial preservation, and partial new construction are input, including structural dimensions, material properties, and load conditions, to accurately calculate the reasonable layout of the steel support system. This ensures that the support system can withstand various loads during construction and guarantees construction safety.

[0062] Support system installation

[0063] According to the points determined by structural simulation calculations, install the backfill steel beams and backfill steel pipe columns in the area to be demolished; during the installation process, ensure that the verticality and horizontality of the steel beams and steel pipe columns meet the requirements;

[0064] Four M20 high-strength bolts are used to connect the steel pipe column and the steel beam to ensure a firm connection; six M24 chemical anchors are used to connect the steel beam to the concrete structure. The installation of the chemical anchors must be carried out in strict accordance with the operating procedures to ensure the anchoring quality.

[0065] Pour grout at the column base to fill the gap between the steel plate and the foundation, ensuring a reliable connection between the bottom of the steel pipe column and the foundation; install hydraulic jacks at the top of the column and set fixed constraints to prevent the jacks from slipping; apply prestress in advance to allow the support system to initially bear the force.

[0066] Install a deformation monitoring dial gauge at the bottom of the retained beam, ensuring that the dial gauge is securely installed and the measurement is accurate.

[0067] (II) Load Test

[0068] A load test is conducted on the installed steel pipe column and steel beam load-bearing system. The load is gradually increased according to a certain proportion of the design load. During the load period, the deformation of the bottom of the beam is closely observed using a dial gauge, and the steel supports are checked for obvious deformation. If any abnormality is found, the loading is stopped immediately, the cause is analyzed, and corresponding measures are taken to deal with it. The system can only be put into use after it is ensured that there are no abnormalities in the load-bearing system.

[0069] (III) Prestressing Unloading and Structural Demolition

[0070] Prestressed staged unloading

[0071] A graded symmetrical unloading method was adopted, dividing the prestress into 5 levels, with 20% unloaded at each level. During the unloading process, professional monitoring equipment was used to monitor the structural deformation and stress of the support system in real time to ensure a smooth and safe unloading process.

[0072] Structural demolition

[0073] As the prestress is gradually unloaded, the structure is dismantled. During the dismantling process, operators must strictly follow the construction plan to avoid disturbing the remaining structure and support system. Appropriate dismantling tools and equipment should be used to ensure the smooth progress of the dismantling work. At the same time, the stress on the steel supports and the deformation of the structure should be continuously monitored, and construction parameters should be adjusted in a timely manner based on the monitoring data.

[0074] (iv) New reinforcement and load-bearing system transformation

[0075] New construction and reinforcement

[0076] After the demolition of the original structure is completed, the construction and reinforcement of the permanent structure shall be carried out in accordance with the design requirements. During the construction process, the construction quality shall be strictly controlled to ensure that the new and reinforced structure meets the strength and stability requirements.

[0077] The force system is transformed again.

[0078] After the construction of the new and reinforced permanent structure is completed and the strength meets the standards, the hydraulic jack device will gradually unload the load. During the unloading process, the deformation of the bottom of the beam will be continuously monitored by a dial gauge to ensure that the new structure can stably bear the load. Finally, the temporary steel support system will be removed to realize the transformation of the stress system from the steel support system to the permanent structure.

[0079] It should be understood that although this specification describes the specific embodiments described above, it is not intended to limit the scope of the invention. Various modifications and improvements made to the technical solutions of this invention by those skilled in the art without departing from the spirit of the invention should fall within the protection scope defined by the claims. For example, in actual construction, the specifications and materials of steel pipe columns and steel beams can be appropriately adjusted according to different engineering structures and construction requirements; the model and parameters of hydraulic jacks can be selected and optimized; and the grading of prestressed unloading and the unloading amount at each level can be reasonably set. As long as these do not deviate from the core technology and inventive concept of this invention, they all fall within the protection scope of this invention.

Claims

1. A method for unloading prestressed structures suitable for partial demolition, characterized in that, Includes the following steps: In partial demolition, partial preservation, and partial new construction projects, the reasonable layout of the steel support system is determined through structural simulation calculations, and a temporary support force system is constructed using steel pipe columns, steel beams, and hydraulic jacks. Hydraulic jacks are installed above the steel pipe columns to enable controllable loading and unloading and real-time load monitoring; dial gauges are installed on the retained structure to observe structural deformation in real time. After the supporting load-bearing system is established, the prestressed components are removed in stages and symmetrically unloaded, thus transforming the load-bearing system into a steel support system. The construction and reinforcement of the permanent structure are carried out. After the construction of the new and reinforced permanent structure is completed and the strength meets the standards, the temporary steel support system is removed, and the load is borne by the permanent structure, thus realizing the conversion of the force system again.

2. The unloading method for partial demolition of prestressed structures according to claim 1, characterized in that: The steel pipe column is made of Q345B material, with a diameter of 400mm and a wall thickness of 12mm. Four 20mm thick stiffening ribs are set at the end of the steel pipe column, and a 700x700x40mm steel pad is set at the bottom of the column base. The gap between the steel pad and the foundation is filled with C45 grout.

3. The unloading method for partial demolition of prestressed structures according to claim 1, characterized in that: The steel beams are made of Q345B material and have specifications of HN700x300x13x24. The steel pipe columns are connected to the steel beams by 4 M20 high-strength bolts, and the steel beams are connected to the concrete structure by 6 M24 chemical anchors.

4. The unloading method for partial demolition of prestressed structures according to claim 1, characterized in that: The installation method includes the following steps: Step 1: Determine the process flow and calculate the location of steel support points and structural load through structural simulation. Step 2: Install the backfill steel beams and backfill steel pipe columns in the area to be demolished, connect the steel beams and steel pipe columns, pour grouting material at the column base, install hydraulic jacks on the column top and set fixed constraints, apply prestress in advance, and install deformation monitoring dial gauges at the bottom of the retained beams; Step 3: Conduct a load test on the load-bearing system composed of steel pipe columns and steel beams. During the load test, observe the deformation of the beam bottom and whether there is any significant deformation of the steel supports. After ensuring that there are no abnormalities, the system can be put into use. Step 4: Perform symmetrical unloading of prestressed material in five stages, with each stage unloading 20% ​​of the material. Gradually dismantle the structure, avoiding any disturbance to the remaining structure and support system during the dismantling process, and monitor the deformation and dial gauge readings in real time. Step 5: Confirm that the deformation of the retained structure meets the design requirements, and complete the remaining demolition work; Step Six: Complete the construction of the new reinforced structure and ensure that its load-bearing performance meets the requirements. Use the hydraulic jacks to unload the load step by step and observe the deformation of the bottom of the beam using a dial indicator. Step 7: Dismantle the temporary steel support system.

5. The unloading method for partial demolition of prestressed structures according to claim 1, characterized in that: The hydraulic jack is supported by a reinforced steel bracket to achieve reverse force application.

6. The unloading method for partial demolition of prestressed structures according to claim 1, characterized in that: During the prestressed graded symmetrical unloading process, the structural deformation and the stress of the support system are monitored in real time.

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