Construction method for hoist platform post-pouring beam plate of deck type suspension formwork

Abstract

The invention relates to the technical field of hydraulic building construction, in particular to a hoist platform post-cast beam and slab construction method of a deck type suspension formwork, which comprises the following steps of: erecting an operation platform by adopting a segmented prefabrication mode, arranging a pair of steel frames shaped like a Chinese character'mu 'on each side, lowering the frame body to half of the design height, and guiding transverse penetration of I-shaped steel through vertical steel pipes; clamping and anti-sliding nodes are arranged, after I-shaped steel is in place, a frame body continues to be put down, the frame body is densely suspended according to the interval of 0.6 m or 0.9 m, the frame body is unfolded from the starting point to the two sides, meanwhile, transverse connecting and limiting braces are installed on the upper flange of a main beam according to the modulus, steel scaffold boards are fully laid on bottom transverse rods, and a dense-mesh safety net is fully hung at the bottom of a platform; the method has the beneficial effects that cross-orifice-size and cross-project parameterized migration is achieved through a quantitative closed loop of model selection-monitoring-linkage, and compared with a traditional landing full framing method, the method has the remarkable advantages in the aspects of material manpower, key line construction period, forming appearance, safety and civilization.

Description

Technical Field

[0001] This invention relates to the field of hydraulic engineering construction technology, specifically to a method for constructing post-cast beams and slabs using a gate hoist platform with an upper-bearing suspended formwork. Background Technology

[0002] The hoisting platform in hydraulic gate chambers typically adopts a structural approach of "factory prefabrication + on-site assembly + post-casting integration". Traditional post-casting construction often relies on erecting a full-span scaffold on the base slab to support the beam and slab formwork and construction load. However, this method has problems such as large scaffolding volume, high material and labor input, serious site occupation, limited construction organization, and difficulty in precise control of safety during high-altitude operations. Moreover, its implementation is particularly limited in high water level or narrow gate environments.

[0003] In contrast, while some engineers have experimented with using top-supported steel sections to support the post-cast sections and reduce reliance on ground-based scaffolding, addressing the issues of large space occupation and construction limitations associated with full-span scaffolding, a mature suspended work platform system has yet to be established. Existing solutions are mostly limited to localized lifting points or simple hanging supports, lacking platform-based, systematic, and parametric design concepts. Significant shortcomings remain in areas such as stress decoupling, operational safety, formwork reusability, and construction process controllability. ① There is a lack of unified selection logic for the force path and layout parameters. For different post-cast section sizes and spans, how to determine the type of upper-bearing I-beam, the spacing between suspension points and the grid modulus (such as 0.6 m / 0.9 m), and how to control the mechanical decoupling of the platform and the formwork suspension frame, as well as the overall stiffness and deflection limits, often rely on experience and lack standardization. ② The repeatability and recyclability of the formwork system installation and demolding need to be optimized. For example, the combination of tie rods and retaining walls, the configuration and durable reuse of rigid sleeves in contact with concrete, directly affect demolding efficiency and molding quality, but lack systematic structural refinement and parameter boundaries; ③ The impact of the pouring sequence on the safety of the suspension system lacks process control indicators. Although the engineering often uses symmetrical layering of the beam "from the middle to both ends" and "short side start - along the long side" of the slab to reduce the eccentric load, there is still a lack of quantitative control and alarm mechanism that is linked to indicators such as pouring rate, instantaneous load, and main beam deflection, resulting in insufficient "process visualization and verifiability". ④ Economic efficiency and organizational efficiency must be balanced. Compared with erecting a full-span scaffold on the base plate, the prefabricated top-bearing suspended formwork method has obvious potential and practical benefits in terms of material turnover, hoisting efficiency and construction period control. However, it lacks a general parameter selection and cost comparison basis for different orifice sizes and structural types, which is not conducive to large-scale promotion. Summary of the Invention

[0004] The purpose of this invention is to provide a method for constructing post-cast beams and slabs on a hoist platform with an upper-bearing suspended formwork, so as to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A method for constructing post-cast beams and slabs of a hoist platform with an upper-bearing suspended formwork, the method comprising the following steps: Step 1: Construction preparation, including clarifying and establishing the stress model of concentrated load, pouring sequence and data thresholds to be monitored, and conducting surveying and setting out to determine the positions of the three lifting points. Based on the stress model, perform pre-calculation of the stress to obtain the equivalent total line load and estimate the concentrated force at each lifting point. Based on this, conduct preliminary selection of I-beams, estimate the number of clamps and clamping force, verify the eccentric torque and torsion angle requirements, and obtain the initial parameter data. Step 2: Prefabrication and hoisting of the hoist beams. The platform beams are divided into two sections by the boundary between one side beam and the hoist beam. Pre-shaped steel molds are designed for each section to form a three-dimensional and stable prefabrication frame system. The steel reinforcement is fabricated and installed according to the design drawings. Concrete is poured and cured until the strength meets the hoisting and installation requirements. The prefabricated beams are transported to the hoisting position using a beam transport vehicle. Step 3: Erection of the suspended work platform. The work platform is erected in sections using a prefabrication method. A set of I-beam steel frames is set up on each side. When the frame is lowered to half the design height, the I-beams are inserted laterally through the vertical steel pipes. Clamping and anti-slip nodes are set. After the I-beams are in place, the frame is lowered further. The suspended frame is densified at intervals of 0.6m or 0.9m and spread out to both sides from the starting point. At the same time, the transverse connecting and limiting strips are installed on the upper flange of the main beam according to the module. The bottom crossbar is fully covered with scaffold boards, and the bottom of the platform is fully covered with dense safety netting. Step 4: Reinforcing steel installation. The concrete at the beam ends is roughened and cleaned according to specifications. Exposed reinforcing steel is aligned to the design position. The main reinforcing bars of the beam are welded according to the design. Stirrups and additional reinforcing bars are set and fixed according to the construction drawings. Sleeves and grout-stopping measures are pre-embedded at the perforation positions of the formwork. Step 5: Install the suspended formwork system. The formwork is suspended using the pre-installed I-beams. The vertical components are hangers / tie rods, axially tensioned. The upper end of the hanger connects to the top horizontal bar / saddle of the I-beam, and the lower end connects to the retaining wall / formwork beam. After laying and positioning the bottom beam formwork on the horizontal bars, install the side beam formwork sequentially. Pre-embed tie rods and reinforce with retaining walls. Connect the tie rods from the I-beam direction to the bottom of the slab via steel pipes. After assembling the bottom slab formwork, it forms an integral load-bearing system with the hanger system. Verify the tensile load-bearing capacity of the hangers and the local bearing capacity / anti-slip properties of the upper anchorage, as well as torque transmission. Tighten all fasteners / bolts on-site and mark them. Step 6: Concrete pouring. The beam body concrete is poured symmetrically and in layers from the middle to both ends. The three variables of the layer thickness, step distance time, and pump speed are linked together to promote evenly and avoid concentrated loading. The slab body concrete is poured starting from the short side and advancing along the long side direction, controlling the feeding speed and vibration rhythm. Step 7: Online monitoring linkage. The online monitoring includes rolling verification, online monitoring and threshold values, linkage processing, and side pressure closed-loop. Step 8: Scaffold and form removal. After the concrete reaches the form removal strength and the measured deflection, cracks, and appearance inspection are qualified, the removal is carried out in accordance with the removal sequence.

[0006] Preferably, in step 8, the removal sequence is as follows: The operator enters the enclosed operation platform from the gate lifting point hole, first removes the steel pipes and forms of the slab bottom hanger, then removes the side forms of the secondary beams, the waling, the tie rods, and the forms, as well as the cross bars at the beam bottom. The脚手板 and safety nets are removed section by section from one end to the other end in sequence, and the materials are counted. Taking the distance between the lifting point holes as a unit, each unit's suspension hanger is tied tightly with a brown rope and slowly lowered to the gate chamber floor until all the scaffolds are removed.

[0007] Preferably, the stress model defined in step 1 is as follows: The two ends of the upper bearing type I-beam main girder are placed on the precast beam slabs on both sides and calculated as a simply supported beam; the net span of the on-site main girder is small; the formwork / platform load is hung to the I-beam through several suspender bars; each main girder is usually provided with 3 lifting points: , and usually take , divided into end-middle-end, where is the beam coordinate, is the distance from the end lifting point to the support, L is the calculated span of the main girder; the suspender bars work in axial tension and do not perform the stability check of compression bars, but need to check the tensile bearing capacity, the anti-slip of the anchor / clip, and the net cross-section of the thread; there is an eccentricity between the action line of the formwork and the center of the I-beam web , introducing an equivalent torque on the main girder; the upper flange is provided with transverse connections and limiters at the grid points of the eye shape to form segmented lateral constraints, and the unrestricted length is recorded as ; Among them: Load model and combination: Discrete concentrated force and semi-span moving uniform load; ① The equivalent load calculation formula is as follows:

[0008] Among them: is the total sum of the equivalent line loads, with the unit of kN / m; is the concrete volume weight, recorded as: 24–25 kN / m³, is the current layer thickness, with the unit of m, is the equivalent loaded width, with the unit of m, is the vibration and stockpiling correction coefficient, and These are the self-weight of the component and the converted live load of the platform / operation, respectively, both in kN / m; ②The formula for calculating the main beam load is as follows:

[0009] in It is the Dirac function; The position of the i-th lifting point in the beam direction coordinate system, in meters (m). Let be the equivalent concentrated force at the i-th lifting point, in kN, and according to... calculate; The contribution width for the i-th lifting point, also known as the influence width, is used to convert the surface load of the slab / formwork into the main beam line load. The unit is m. Assign a magnification factor to the suspension point, ranging from 1.0 to 1.3; function This indicates a uniformly distributed load across half the span, representing the additional uneven wiring load within that half-span, measured in kN / m. Time to take Take 0 for the remaining segments: and set Take the most unfavorable option, among which The starting position parameter for a half-span moving uniformly distributed load, in meters, is used to determine the most unfavorable envelope.

[0010] Preferably, the calculation of the internal forces, deflection, and stability of the main beam in the stress model is as follows: ①The formulas for calculating support reactions and shear forces are as follows: Symmetrical three suspension points, and hour: ; ②The formula for calculating the maximum bending moment is as follows: Three lifting points with equal strength and location... hour: ; ③ The formulas for calculating normal stress and deflection are as follows: ; in: ; ④ The calculation formulas for eccentric torsion and segmented lateral confinement are as follows: Template action line eccentricity Introducing equivalent torque: ; Twist angle By adding lateral connections and limit bars at the modular points, the unrestricted length can be controlled. Based on this, the lateral torsional buckling is checked to ensure it meets the requirements. ; in: P 1. P 2.P 3 represents the equivalent concentrated force at the three suspension points, in kN. P Equivalent concentrated force at a single lifting point, unit: kN; The sum of concentrated loads, unit: kN; R A R B The reaction force at both supports, unit: kN; Maximum bending moment, unit: kN·m; L The main beam is used to calculate the span, in meters. a The distance from the end lifting point to the support, in meters (m). The section modulus of the main beam; The maximum normal stress of the main beam, unit: MPa; [Permissible normal stress, unit: MPa;] Yield strength of steel, unit: MPa; E Elastic modulus, unit: MPa; I Moment of inertia of the cross section, unit: m 4 ; Maximum deflection, unit: m; Permissible deflection limit; This is the deflection amplification factor; Eccentricity of the formwork load line relative to the shear center of the main beam, unit: m; Equivalent torque, unit: kN·m; This is the torque amplification factor; The angle of twist is expressed in rad. G is the torsional length, in meters; G is the shear modulus, in MPa. J Torsional constant, unit: m 4 .

[0011] Preferably, the design and anchoring / clamping calculations of the suspension rod in the stress model are as follows: ①The formula for calculating tensile bearing capacity is as follows: ; The design tensile force value for the boom is given, in kN. This is the design value of the tensile bearing capacity of the hanger rod, in kN. The tensile bearing capacity reduction factor is taken as 0.9; The net cross-sectional area of ​​the hanger rod, in mm. 2 ; ②The calculation formulas for upper anchorage and anti-slip are as follows: Construction: O-ring / saddle + anti-slip pad + limit stop; Verification: (1) Local pressure:

[0012] (2) Anti-slip:

[0013] (3) Lower limit of clamping force of a single clamp:

[0014] in: Average compressive stress on the clamping / bearing surface, unit: MPa; R Normal reaction force of the clamping surface, unit: kN; Effective contact area for clamping / bearing pressure, unit: mm 2 ; Temporary pressure tolerance, unit: MPa; The resultant force of external forces along the possible slip direction, unit: kN; μ The coefficient of friction; The clamping force of the k-th fixture, in kN; n c Number of fixtures; This is the anti-skid partial factor; The clamping force of a single clamp is expressed in kN. The equivalent torque at the upper node is expressed in kN·m. Provides anti-slip / anti-torsion lever arm for the clamp, unit: m; ③Lower connection: The lifting eye / ear plate is connected to the hoop or welded connection, and the bearing capacity of the hole edge, tearing of the ear plate, and shearing of the weld are checked; ④ The formulas for force distribution and elongation calculation are as follows: Rod force distribution ; structural elongation Much smaller than the main beam deflection; sensitive time limit value for elevation And fine-tuning is done using turnbuckles; The tensile force on the i-th boom shaft, in kN; The elastic elongation of the i-th rod is expressed in mm. Calculate the length of the i-th suspension rod, in meters. The elastic modulus of the suspension rod steel, in MPa; The effective cross-sectional area of ​​the i-th hanger rod, in mm. 2 .

[0015] Preferably, the calculation of the template side pressure and the tension-restraint in the force model is as follows: ①The formula for calculating lateral pressure is as follows: ; ; in: The lateral pressure of the formwork at a depth z from the pouring surface during the pouring process is expressed in kPa. Unit weight of concrete, in kN / m³ 3 z represents the depth from the pouring surface, in meters (m). To match the pouring speed Units: m / h and slump S, units: mm. The relevant lateral pressure correction factor is taken as 0.8. 1.2; H For calculating the pouring height, the unit is m; This represents the maximum side pressure of the template, in kPa. This is the upper limit of the lateral pressure, in kPa, used to determine the most unfavorable control limit for the lateral pressure. ②The formula for calculating the stress of the tie rod is as follows: ; in: The axial normal stress of the tie rod is expressed in MPa. The effective cross-sectional area of ​​the tie rod, in mm. 2 ; , These represent the horizontal and vertical spacing of the tie rods, in meters (m). (Sleeve) is the design value of the pull-out bearing capacity at the connection between the through-wall grout-stopping sleeve / tapered sleeve and the formwork system, in kN; The peak pull-out effect generated at the joint during the pouring process is expressed in kN; 1.3 is the uncertainty amplification factor during the construction stage. ③ Enclosure: The strength and deflection are checked using the strip / simply supported beam method to ensure balanced distribution of loads at each suspension point. Approaching version 1.0.

[0016] Preferably, the calculation of the construction rate "dual control" and monitoring linkage in the stress model is as follows: ①The calculation formula for dual-rate control is as follows: ; This represents the constant baseline response; where: , These are the allowable pouring speeds determined by strength constraints and deflection constraints, respectively, in m / h. The maximum allowable pouring speed under comprehensive control, in m / h; Allowable normal stress, unit: MPa; The baseline stress response under constant load is expressed in MPa. The deflection response is based on constant load baseline, in meters (m). , b is the baseline response coefficient; b is the equivalent load width. This is a correction factor for vibration and stockpiling. ② Alarm—Downgrade—Stop Watering—Restore: Warning: → Decrease The value is 10–20%, increasing the step time by 20–30%; Stop watering: →Stop pumping and unload the load, then re-check the main beam and joints before resuming operation; recover: and It takes 3 minutes to resume the original rhythm; For monitoring deflection, the unit is meters (m). κ represents the deflection growth rate in mm / min; v represents the deflection growth rate threshold in mm / min; v represents the pouring speed in m / h; and τ represents the layer spacing time in min. ③ Closed-loop regulation of side pressure; Pull the tension / force measuring pin With calculation In comparison, if the value is greater than 1.1 times, β should be increased to reduce the tension spacing; if it is less than 0.9 times, β should be decreased to increase the spacing. The fact that the confinement deflection and stress amplify at the same frequency indicates insufficient distributed stiffness, requiring the addition of ribs or a reduction in the spacing between suspension points. .

[0017] Preferably, the online monitoring method in step seven is as follows: N1. Rolling Verification: renew ;renew With half-spanning the moving envelope, accounting Verification Check the eccentric torque, torsion angle, and unconfined length. ; N2. Online monitoring and thresholds: Crossing the middle and Displacement gauges are installed at the location to collect data in real time. ; Key suspension rods or tie rods are equipped with force-measuring pins to collect data. Let the threshold be: ; N3, Linkage Processing: Warning: When Immediately reduce pump speed by 20-30%, reduce layer thickness by 10-20%, and increase step time by 20-30%; check the lifting point distribution coefficient. In accordance with the stiffness of the enclosure, additional suspension points / reinforced side confinement may be added if necessary; Stop watering: when Continuous 2–3 min ultra Stop the pump and pump back, then unload and recheck; N4, Side pressure closed loop: Will With calculation Comparison: If >1.1 Double, increase β or decrease the pull-out pitch And enhance the stiffness of the enclosure; if <0.9 The factor can be appropriately relaxed to improve efficiency, including: for The vertex value, i.e., the maximum value. β represents the lateral pressure of the formwork at a depth z from the pouring surface during the pouring process; β is the lateral pressure correction coefficient. For horizontal / vertical tension, unit: m.

[0018] Compared with the prior art, the beneficial effects of the present invention are: This invention and its system enable high-altitude forming of post-cast beams and slabs without grounding; by using "upper-bearing I-beam main beam + suspension rod tension + double-layer decoupling", the physical separation of walking / transportation and bearing / casting is achieved, reducing additional bending moment and torsion; efficient assembly and disassembly and repeatable positioning are achieved with a 0.6 / 0.9 m module and quick clamps; rigid sleeves reduce adhesion and improve turnover; and a quantitative closed loop of "selection-monitoring-linkage" enables parameterized transfer across orifice dimensions and across projects. Compared with the traditional ground-based full-span scaffolding method, it has significant advantages in terms of materials, labor, critical path schedule, formed appearance, and safety and civilized construction. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the three-dimensional structure of the construction model of the present invention.

[0020] In the picture: 1. I-beam; 2. Anti-slip fasteners; 3. I-shaped steel frame; 4. Scaffold boards. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Please refer to the figure; this invention provides a technical solution: The overall plan is as follows: The precast beam and slab are hoisted and positioned horizontally in slices; when the suspension support is lowered to about half of the designed height, guide the horizontal erection and positioning of the I-beam 1, and then expand it in a dense pattern according to the modulus of 0.6 m or 0.9 m to form a "mesh" - shaped grid; fully lay steel scaffolding boards 4 on the top surface and hang dense mesh safety nets at the bottom to form a closed operation platform, and personnel and materials complete passage and transfer on the platform layer; Independent formwork suspension brackets are arranged below it. The upper ends of the vertical suspension rods / tension rods (axially tensioned) are connected to the top horizontal rods / saddles of the I-beam 1, and the lower ends are connected to the waling / formwork beam. Another cross bar and anti-slip fasteners 2 are provided at the bottom of the beam to form a stable support; The formwork system is installed in the order of "beam first and then slab". The beam sides are reinforced with waling + tie rods. The bottom formwork of the slab is assembled from the connection with the I-beam 1 to the bottom of the slab. All penetrations in contact with concrete are sleeved with rigid sleeves for easy formwork removal and recycling; After the reinforcement and formwork are inspected and accepted, concrete is poured. The beam body is symmetrically stratified from the middle to both ends, and the slab body is advanced along the long side direction starting from the short side to control the eccentric load and peak displacement; after reaching the formwork removal strength, it is removed in the order of slab first and then beam and by unit: the bottom formwork hanger and formwork → the side formwork, waling and tie rods of the secondary beam → the cross bar at the bottom of the beam. The scaffolding boards 4 and safety nets are removed section by section from one end to the other end. Each unit of the suspension support is tied tightly with a brown rope and slowly lowered to the bottom slab of the lock chamber.

[0023] In terms of structure and mechanism, the upper I-beam 1 main beam bears the combined effects of its own weight, the weight of the closed operation platform and the hanging basket system, the live load of the formwork and the pouring load, etc., and transfers the load to the precast beam and slab on both sides; by integrating the hanging basket and the operation platform into the main beam force system, the mechanical decoupling and coordinated support of the high-altitude operation surface and the formwork layer are achieved. The closed operation platform is responsible for personnel walking and enclosure, and the bearing function and the formwork system have clear division of labor; the formwork suspension bracket only provides support for the formwork and the newly poured concrete to avoid interference with the platform layer; the clamping / anchoring node preferably selects a reusable clamping scheme to reduce permanent drilling of the concrete, and there are no residual holes on the beam surface after removal; the waling - tie rod system provides lateral stiffness and out-of-plane stability; the guiding bracket (for the pump pipe / vibrating hose) limits the bending radius and the moving path, reducing the local impact on the side ribs of the formwork; the monitoring and alarm unit arranges displacement gauges at the mid-span and 1 / 4 span, and arranges force measuring / strain elements at key connections or tie rods to form a "monitoring - threshold - linkage" closed loop: when the deflection or growth rate exceeds the limit, automatically reduce the speed or pause the pouring.

[0024] To make this system具备可检验、可复现、可参数化迁移能力, establish an "option selection - calculation - monitoring - linkage" integrated method that matches this plan. Basic assumptions: (1) The two ends of the upper-bearing I-beam 1 main beam are placed on the precast beam and slab on both sides and calculated as a simply supported beam; the net span of the main beam on site is relatively small (typically 1.8 - 4.5 m, corrected according to the actual measurement of the project). (2) The formwork / platform load is suspended to the I-beam 1 through several suspenders (tie rods), and 3 suspension points (end - middle - end) are usually arranged on each main beam.

[0025] (3) The suspenders are in axial tension and do not need to be checked for the stability of compression members; it is necessary to check the tensile bearing capacity, anti-slip of anchoring / clamping, and the net cross-section of the thread.

[0026] (4) There is an eccentricity between the action line of the formwork and the center of the web of the I-beam 1 , introducing an equivalent torque on the main beam; transverse connections and limiters are provided at the "eye" grid points (module 0.6 / 0.9 m) on the upper flange to form segmented lateral constraints, and the unconstrained length is denoted as .

[0027] 1. Load models and combinations (discrete concentrated force + half-span moving uniform load) ① Equivalent load ; Among them is the unit weight of concrete (24–25 kN / m³), is the current layer thickness (m), is the equivalent loaded width (m), is the correction coefficient for vibration and stockpiling, and are the reduced values of the self-weight of the component and the platform / operating live load respectively.

[0028] ② Expression of the main beam load: ; Among them ( is the contribution width affected by the i-th suspension point, considering local stockpiling / vibratory compaction), at take , and the rest is 0, and let take the most unfavorable.

[0029] 2. Internal forces, deflections and stability of the main beam: ① Support reactions and shear forces For symmetric three suspension points and when: ; ② Maximum bending moment for three equal-strength suspension points and positions when: ; ③ Normal stress and deflection ; Among them ; ④ Eccentric Torsion and Segmented Lateral Confinement Template action line eccentricity Introducing equivalent torque: ; Twist angle The unrestricted length is controlled by adding lateral connections and limit bars at the modular points. Based on this, the lateral torsional buckling (LTB) is checked and found to be satisfied. .

[0030] 3. Design and anchoring / clamping of hanger (tie rod) ① Tensile bearing capacity ; Take 0.9 (or according to the relevant specifications); Effective net cross-section (for threads, use minor diameter; for wire ropes / turnbuckles, use manufacturer's effective cross-section).

[0031] ②The calculation formulas for upper anchorage and anti-slip are as follows: Construction: O-ring / saddle + anti-slip pad + limit stop; Verification: (1) Local pressure:

[0032] (2) Anti-slip:

[0033] (3) Lower limit of clamping force of a single clamp:

[0034] Where μ is the coefficient of friction (steel-steel 0.3-0.4, steel-rubber 0.6-0.8). .

[0035] ③Lower connection The lifting eye / ear plate is connected to the hoisting clamp or welded, and the bearing capacity of the hole edge, tearing of the ear plate, and shearing of the weld are checked.

[0036] ④ Stress distribution and elongation Rod force distribution Structural elongation Generally much smaller than the main beam deflection; sensitive time limit value for elevation. And fine-tuning is done using turnbuckles.

[0037] 4. Template lateral pressure and tension-enclosure ① Lateral pressure ; With pouring rate slump Related to the vibration method.

[0038] ② Pull screw ; ③ Enclosure (lateral distribution beam) The strength and deflection are checked using the strip / simply supported beam method to ensure balanced distribution of loads at each suspension point. Approaching 1.0).

[0039] 5. Dual control of construction speed and linkage with monitoring ① Dual speed control ; This is the baseline response under constant load.

[0040] ② Alarm—Downgrade—Stop Watering—Restore Warning: → Decrease Increase step time by 10–20% and increase step time by 20–30%.

[0041] Stop watering: →Stop pumping and unload, then recheck the main beam and nodes (including anti-slip, clamping force and torque) before resuming operation.

[0042] recover: and It takes 3 minutes to resume the original rhythm.

[0043] ③ Side pressure closed loop Pull the tension / force measuring pin With calculation If the ratio is greater than 1.1 times, adjust β upwards to reduce the tension spacing; if it is less than 0.9 times, adjust β downwards to widen the spacing. If the confinement deflection and stress amplify at the same frequency, it indicates insufficient distributed stiffness; ribs should be added or the spacing between suspension points should be reduced. .

[0044] 6. Overall Effects and Transferability This system achieves high-altitude forming of post-cast beams and slabs without ground contact; through "upper-bearing I-beam main beam + suspension rod tension + double-layer decoupling," it physically separates travel / transfer and load-bearing / casting, reducing additional bending moments and torsion; it achieves efficient assembly / disassembly and repeatable positioning using a 0.6 / 0.9 m module and quick clamps; it uses rigid sleeves to reduce adhesion and improve turnover; and it achieves parameterized transfer across orifice dimensions and projects through a quantitative closed loop of "selection-monitoring-linkage." Compared with the traditional ground-supported full-span scaffolding method, it has significant advantages in terms of materials, labor, critical path schedule, formed appearance, and safety and civilized construction, and the key control quantities ( Measurable and verifiable, etc., making it easy to approve and review.

[0045] 1. Construction preparation: Technical and safety briefing: Conduct detailed technical, safety, quality, and emergency briefings for all workers; clarify the stress model (concentrated loads at three points: end, middle, and end), pouring sequence (symmetrical pouring from middle to end of beam, slab starting from the short side and progressing along the long side), and monitoring thresholds (…). ).

[0046] Safety enclosure: Closed safety guardrails with a height of not less than 1.2 m are installed on the upper and lower sides of the hoist platform beam, equipped with kickboards and warning signs, and a closed working area is demarcated.

[0047] Material and equipment preparation and acceptance: ordinary steel pipes, 1 H-beam, 4 scaffold boards, dense safety net, fasteners, O-rings / saddles, anti-slip mats, limit blocks, tie rods and rigid sleeves, baskets / hanging rings, force pins / strain gauges, displacement gauges, pumping and backflow equipment, vibrators, etc.; after arrival on site, each item shall be inspected according to the specifications (steel pipes shall be free from deformation and cracks, fasteners shall rotate flexibly and bolts shall be intact, 4 hooks on scaffold boards shall be lockable, and safety net shall be undamaged).

[0048] Measurement and layout: Verify the support elevation and clear span L; determine the three lifting points: (Commonly used) Steel pads / rubber layers and reserved positions for O-rings / saddles are arranged on the top surface of the precast beams on both sides.

[0049] Stress pre-check: Calculate according to the above formula. Estimate using the above formula Based on this, the initial selection of I-beam 1, the number of fixtures, and the clamping force were determined. Estimate; verify the eccentric torque and torsion angle requirements based on the above formula. Form a "parameter card" ( ).

[0050] 2. Prefabrication and hoisting of gate hoist beams Segmentation and Standardized Steel Molds: Based on the boundary from one side beam to the hoist beam, the platform beam is divided into two horizontal sections, and standardized steel molds are designed for each section to form a three-dimensional and stable prefabricated frame system.

[0051] Reinforcing steel fabrication and installation: Complete the fabrication and installation of reinforcing steel according to the design drawings, and carry out concrete pouring and curing until the strength meets the requirements for hoisting and installation.

[0052] Transportation and hoisting: Precast beams are transported to the hoisting position using beam transport vehicles; after the crane is in place, it is tested under no-load and tested. After passing the test, the slinger will give unified command to hoist each beam into place, adjust the elevation and alignment, and complete the placement and positioning of the support pad.

[0053] 3. Erection of suspended work platform Segmented Erection Strategy: The work platform is erected using a segmented prefabrication method. A set of U-shaped steel frames is set up on each side, with a common structure of four 4-meter horizontal steel pipes and eight 2-meter vertical steel pipes connected by swivel couplers; anti-slip couplers are added to the bottom and top of the frame.

[0054] Inserting I-beam 1: When the frame is lowered to about half of the design height, guide the I-beam 1 horizontally through the vertical steel pipe; the I-beam 1 is reasonably selected and arranged according to the location of the post-cast section and the size of the beam and slab, and the end rests on the precast beam and slab, and clamping and anti-slip nodes are set according to the above formula.

[0055] Modular deployment: After the I-beam 1 is in place, continue to lower the frame, and suspend the frame at intervals of 0.6m or 0.9m, and deploy it from the starting point to both sides; at the same time, install transverse connecting and limiting strips on the upper flange of the main beam according to this module to make the length unrestricted. The working platform is formed by fully covering the bottom crossbars with four scaffold boards (locked with hooks) and hanging a dense safety net on the bottom of the platform to create a safe and enclosed working environment; and installing guide brackets for pump pipes / vibrating hoses to limit the minimum bending radius and prevent swaying impact.

[0056] 4. Reinforcement fabrication and installation (post-cast section) Interface treatment: The concrete at the beam end is roughened and cleaned according to specifications; exposed reinforcing bars are aligned to the design position.

[0057] Main reinforcement connection: Weld the main reinforcement of the beam according to the design, and the length of single / double-sided weld shall not be less than 5d or 10d (whichever is more stringent in the design or specification).

[0058] Stirrups and additional reinforcement: Set and fix stirrups and additional reinforcement according to the construction drawings to ensure the accuracy of the protective layer thickness and spacing; pre-embed sleeves and grout-stopping measures at the perforation locations of the formwork.

[0059] 5. Installation of the formwork lifting system (axis tie rods) Load-bearing components and connections: The formwork is suspended based on the already installed I-beam 1; the vertical components are hangers / tie rods, which are axially tensioned. The upper end of the hanger is connected to the top horizontal bar / saddle of the I-beam 1, and the lower end is connected to the enclosure / formwork beam.

[0060] Beam bottom and side formwork: Horizontal crossbars are set at the bottom of the beam and anti-slip fasteners are added; after laying and positioning the beam bottom formwork on the crossbars, the beam side formwork is installed in sequence, and tie rods are pre-embedded and reinforced with circumference.

[0061] Bottom formwork: The bottom formwork is connected to the bottom of the slab via steel pipes from the direction of the I-beam 1. After the bottom formwork is assembled, it forms an integral load-bearing system with the suspension system.

[0062] Rigid sleeve: All formwork components in contact with concrete are fitted with rigid sleeves to reduce adhesion and facilitate removal and turnover.

[0063] Node verification and re-tightening: Verify the tensile load-bearing capacity of the hanger and the local bearing pressure / slip resistance and torque transmission of the upper anchorage according to the above formula. Tighten all fasteners / bolts on site and mark them.

[0064] 6. Linkage between concrete pouring and online monitoring ① Beam body: The beam is poured symmetrically in layers from the middle towards both ends, with each layer having a specific thickness. Step time Pump speed Three variables work together to promote balanced progress and avoid concentrated load accumulation; Plate: Start from the short side and advance along the long side, controlling the feeding speed and vibration rhythm.

[0065] ② Rolling verification renew (follow) (and changes in construction location); updated according to formula With half-spanning the moving envelope; Accounting (If necessary, the uniform distribution is equivalent to...) enlarge); Verification ; Check eccentric torque, torsion angle and unconfined length. ; ③ Online monitoring and thresholds Crossing the middle and Displacement gauges are installed at the location to collect data in real time. ; Key suspension rods or tie rods are equipped with force-measuring pins to collect data. ; Set the threshold: ; ④ Linkage processing Warning: When Immediately reduce pump speed by 20-30%, reduce layer thickness by 10-20%, and increase step time by 20-30%; check the lifting point distribution coefficient. In accordance with the stiffness of the enclosure, additional suspension points / reinforced side confinement may be added if necessary; Stop watering: when Continuous 2–3 minutes of super Stop pumping, re-pump, unload and verify. ⑤ Side pressure closed loop Will With calculation Comparison: If >1.1 times, increase β or decrease the pull-out pitch. It also enhances the stiffness of the enclosure; if it is less than 0.9 times, it can be appropriately relaxed to improve efficiency.

[0066] 7. Scaffolding and formwork dismantling (by unit) Demolition conditions: The concrete has reached the demolding strength and the measured deflection, cracks and appearance have passed the inspection, and a demolding order has been issued.

[0067] Operating passage: Operators enter the enclosed operating platform through the gate lifting point hole.

[0068] Sequence and method (slabs first, then beams; unit by unit); First, dismantle the steel pipes and formwork of the bottom slab hanger; Next, dismantle the side formwork of the secondary beam, the surrounding wall, the tie rods and formwork, as well as the bottom crossbar of the beam; Dismantle the scaffold planks 4 and safety nets in sections from one end to the other, and take inventory of the materials; Using the spacing between the lifting points as units, each unit of the suspension frame is slowly lowered to the bottom plate of the gate chamber after being tied with hemp rope, until the entire frame is dismantled.

[0069] Material recycling: rigid sleeve → tie rod / nut → clamp → template → steel section, classified and rotated, and a ledger of wear limits and number of times is established.

[0070] The specific meanings of the above symbols are shown in the table below:

[0071] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for constructing post-cast beams and slabs on a hoist platform with an upper-bearing suspended formwork, characterized in that: The construction method includes the following steps: Step 1: Construction preparation, including clarifying and establishing the stress model of concentrated load, pouring sequence and data threshold to be monitored, and at the same time carrying out measurement and layout, setting out the positions of three lifting points, performing pre-calculation of stress according to the stress model, obtaining the equivalent total line load, estimating the concentrated force of each lifting point, and based on this, performing preliminary selection of I-beam (1), estimation of the number of clamps and clamping force, verifying the eccentric torque and torsion angle requirements, and obtaining the initial parameter data; Step 2: Prefabrication and hoisting of the hoist beams. The platform beams are divided into two sections by the boundary between one side beam and the hoist beam. Pre-shaped steel molds are designed for each section to form a three-dimensional and stable prefabrication frame system. The steel reinforcement is fabricated and installed according to the design drawings. Concrete is poured and cured until the strength meets the hoisting and installation requirements. The prefabricated beams are transported to the hoisting position using a beam transport vehicle. Step 3: Erection of the suspended work platform. The work platform is erected in a segmented prefabrication manner. A pair of I-shaped steel frames (3) are set up on each side. When the frame is lowered to half the design height, the I-beam (1) is guided to pass through horizontally through the vertical steel pipe. Clamping and anti-slip nodes are set. After the I-beam (1) is in place, the frame is lowered. The suspended frame is densified at intervals of 0.6m or 0.9m and spread out from the starting point to both sides. At the same time, horizontal connecting and limiting tie rods are installed on the upper flange of the main beam according to the module. The bottom crossbar is fully covered with scaffold boards (4). The bottom of the platform is fully covered with dense safety netting. Step 4: Reinforcing steel installation. The concrete at the beam ends is roughened and cleaned according to specifications. Exposed reinforcing steel is aligned to the design position. The main reinforcing bars of the beam are welded according to the design. Stirrups and additional reinforcing bars are set and fixed according to the construction drawings. Sleeves and grout-stopping measures are pre-embedded at the perforation positions of the formwork. Step 5: Install the formwork system. The formwork is suspended based on the existing I-beams (1). The vertical components are hangers / tie rods, which are under axial tension. The upper end of the hanger is connected to the top horizontal bar / saddle of the I-beam (1), and the lower end is connected to the retaining wall / formwork beam. After laying and positioning the bottom formwork of the beam on the horizontal bar, the side formwork of the beam is installed in sequence. Tie rods are pre-embedded and reinforced with retaining walls. The formwork is connected to the bottom of the slab through steel pipes from the direction of the I-beam (1). After the bottom formwork of the slab is assembled, it forms an integral force with the hanger system. The tensile bearing capacity of the hanger and the local bearing pressure / anti-slip of the upper anchorage and torque transmission are verified. All fasteners / bolts are tightened on site and marked. Step Six: Concrete Pouring. The beam concrete is poured symmetrically in layers from the middle to both ends. The layer thickness, step distance, time and pump speed are linked to ensure balanced progress and avoid concentrated load. The slab concrete is poured from the short side and along the long side, controlling the material feeding speed and vibration rhythm. Step 7: Online monitoring and linkage. Online monitoring includes rolling verification, online monitoring and thresholds, linkage processing, and side pressure closed loop. Step 8: Dismantle the scaffolding and formwork. After the concrete reaches the demolding strength and the measured deflection, cracks, and appearance inspection are qualified, dismantle the scaffolding and formwork in the order of dismantling.

2. The construction method for post-cast beams and slabs of a hoist platform with an upper-bearing suspended formwork according to claim 1, characterized in that: The dismantling sequence described in step eight is as follows: the workers enter the enclosed work platform through the gate lifting point hole, first dismantle the steel pipes and templates of the bottom plate hanging frame, then dismantle the secondary beam side formwork, the surrounding wall, the tie rods and templates, and the beam bottom crossbars, and dismantle the scaffold boards (4) and safety nets in sections from one end to the other, count the materials, and use the spacing between the lifting point holes as a unit. Each unit of the suspended frame is tied with a hemp rope and slowly lowered to the bottom plate of the gate chamber until all the frames are dismantled.

3. The construction method for post-cast beams and slabs of a hoist platform with an upper-bearing suspended formwork according to claim 1, characterized in that: The force model described in Step 1 is defined as follows: The main beams of the upper-bearing I-beams (1) are placed on the precast beam slabs on both sides and calculated as simply supported beams; the net span of the main beams on site is small; the formwork / platform load is suspended to the I-beams (1) through several suspenders; three suspension points are usually arranged on each main beam: , and usually take , divided into end-middle-end, where is the beam coordinate, is the distance from the end suspension point to the support, L is the calculated span of the main beam; the suspenders work in axial tension and do not perform the stability check of compression members. It is necessary to check the tensile bearing capacity, the anti-slip of anchoring / clamping and the net cross-section of the thread; there is an eccentricity between the action line of the formwork and the web center of the I-beam (1) , introducing an equivalent torque on the main beam; transverse connections and limiters are provided at the grid points of the upper flange to form segmented lateral constraints, and the unconstrained length is denoted as ; Among them: Load model and combination: Discrete concentrated force and uniformly distributed half-span movement; ①The formula for calculating the equivalent load is as follows: in: This represents the total equivalent line load, expressed in kN / m. The volumetric weight of concrete is denoted as 24–25 kN / m³. The current layer thickness, in meters (m). Equivalent load-bearing width, unit: meters. This is a correction factor for vibration and stockpiling. and These are the self-weight of the component and the converted live load of the platform / operation, respectively, both in kN / m; ②The formula for calculating the main beam load is as follows: in It is the Dirac function; The position of the i-th lifting point in the beam direction coordinate system, in meters (m). Let be the equivalent concentrated force at the i-th lifting point, in kN, and according to... calculate; The contribution width for the i-th lifting point, also known as the influence width, is used to convert the surface load of the slab / formwork into the main beam line load. The unit is m. Assign a magnification factor to the suspension point, ranging from 1.0 to 1.3; function This indicates a uniformly distributed load across half the span, representing the additional uneven wiring load within that half-span, measured in kN / m. Time to take Take 0 for the remaining segments: and set Take the most unfavorable option, among which The starting position parameter for a half-span moving uniformly distributed load, in meters, is used to determine the most unfavorable envelope.

4. The method for constructing post-cast beams and slabs of a hoist platform with an upper-bearing suspended formwork according to claim 3, characterized in that: The calculations for the internal forces, deflection, and stability of the main beam in the stress model are as follows: ①The formulas for calculating support reactions and shear forces are as follows: Symmetrical three suspension points, and hour: ； ②The formula for calculating the maximum bending moment is as follows: Three lifting points with equal strength and location... hour: ； ③ The formulas for calculating normal stress and deflection are as follows: ； in: ; ④ The calculation formulas for eccentric torsion and segmented lateral confinement are as follows: Template action line eccentricity Introducing equivalent torque: ； Twist angle By adding lateral connections and limit bars at the modular points, the unrestricted length can be controlled. Based on this, the lateral torsional buckling is checked to ensure it meets the requirements. ; in: P 1. P 2. P 3 represents the equivalent concentrated force at the three suspension points, in kN. P Equivalent concentrated force at a single lifting point, unit: kN; The sum of concentrated loads, unit: kN; R A R B The reaction force at both supports, unit: kN; Maximum bending moment, unit: kN·m; L The main beam is used to calculate the span, in meters. a The distance from the end lifting point to the support, in meters (m). The section modulus of the main beam; The maximum normal stress of the main beam, unit: MPa; [Permissible normal stress, unit: MPa;] Yield strength of steel, unit: MPa; E Elastic modulus, unit: MPa; I Moment of inertia of the cross section, unit: m 4 ; Maximum deflection, unit: m; Permissible deflection limit; This is the deflection amplification factor; Eccentricity of the formwork load line relative to the shear center of the main beam, unit: m; Equivalent torque, unit: kN·m; This is the torque amplification factor; The angle of twist is expressed in rad. G is the torsional length, in meters; G is the shear modulus, in MPa. J Torsional constant, unit: m 4 .

5. The method for constructing post-cast beams and slabs of a hoist platform with an upper-bearing suspended formwork according to claim 4, characterized in that: The design and anchoring / clamping calculations for the suspension rod in the stress model are as follows: ①The formula for calculating tensile bearing capacity is as follows: ； The design tensile force value for the boom is given, in kN. This is the design value of the tensile bearing capacity of the hanger rod, in kN. The tensile bearing capacity reduction factor is taken as 0.9; The net cross-sectional area of ​​the hanger rod, in mm. 2 ; ②The calculation formulas for upper anchorage and anti-slip are as follows: Construction: O-ring / saddle + anti-slip pad + limit stop; Verification: (1) Local pressure: (2) Anti-slip: (3) Lower limit of clamping force for a single clamp: in: Average compressive stress on the clamping / bearing surface, unit: MPa; R Normal reaction force of the clamping surface, unit: kN; Effective contact area for clamping / bearing pressure, unit: mm 2 ; Temporary pressure tolerance, unit: MPa; The resultant force of external forces along the possible slip direction, unit: kN; μ The coefficient of friction; The clamping force of the k-th fixture, in kN; n c Number of fixtures; This is the anti-skid partial factor; The clamping force of a single clamp is expressed in kN. The equivalent torque at the upper node is expressed in kN·m. Provides anti-slip / anti-torsion lever arm for the clamp, unit: m; ③Lower connection: The lifting eye / ear plate is connected to the hoop or welded connection, and the bearing capacity of the hole edge, tearing of the ear plate, and shearing of the weld are checked; ④ The formulas for force distribution and elongation calculation are as follows: Rod force distribution ; structural elongation Much smaller than the main beam deflection; sensitive time limit for elevation And fine-tuning is done using turnbuckles; The tensile force on the i-th boom shaft, in kN; The elastic elongation of the i-th rod is expressed in mm. Calculate the length of the i-th suspension rod, in meters. The elastic modulus of the suspension rod steel, in MPa; The effective cross-sectional area of ​​the i-th hanger rod, in mm. 2 .

6. The method for constructing post-cast beams and slabs of a hoist platform with an upper-bearing suspended formwork according to claim 5, characterized in that: The calculations of the template lateral pressure and the tension-restraint in the stress model are as follows: ①The formula for calculating lateral pressure is as follows: ； ； in: The lateral pressure of the formwork at a depth z from the pouring surface during the pouring process is expressed in kPa. Unit weight of concrete, in kN / m³ 3 z represents the depth from the pouring surface, in meters (m). To match the pouring speed Units: m / h and slump S, units: mm. The relevant lateral pressure correction factor is taken as 0.

8. 1.2; H For calculating the pouring height, the unit is m; This represents the maximum side pressure of the template, in kPa. This is the upper limit of the lateral pressure, in kPa, used to determine the most unfavorable control limit for the lateral pressure. ②The formula for calculating the stress of the tie rod is as follows: ； in: The axial normal stress of the tie rod is expressed in MPa. The effective cross-sectional area of ​​the tie rod, in mm. 2 ; , These represent the horizontal and vertical spacing of the tie rods, in meters (m). (Sleeve) is the design value of the pull-out bearing capacity at the connection between the through-wall grout-stopping sleeve / tapered sleeve and the formwork system, in kN; The peak pull-out effect generated at the joint during the pouring process is expressed in kN; 1.3 is the uncertainty amplification factor during the construction stage. ③ Enclosure: The strength and deflection are checked using the strip / simply supported beam method to ensure balanced distribution of loads at each suspension point. Approaching version 1.

0.

7. The method for constructing post-cast beams and slabs of a hoisting platform with an upper-bearing suspended formwork according to claim 4, characterized in that: The calculation of the construction rate "dual control" and monitoring linkage in the stress model is as follows: ①The calculation formula for dual-rate control is as follows: ； This represents the constant load baseline response; where: , These are the allowable pouring speeds determined by strength constraints and deflection constraints, respectively, in m / h. The maximum allowable pouring speed under comprehensive control, in m / h; Allowable normal stress, unit: MPa; The baseline stress response under constant load is expressed in MPa. The deflection response is based on constant load baseline, in meters (m). , b is the baseline response coefficient; b is the equivalent load width. This is a correction factor for vibration and stockpiling. ② Alarm—Downgrade—Stop Watering—Restore: Warning: → Decrease The value is 10–20%, increasing the step time by 20–30%; Stop watering: →Stop pumping and unload the load, then re-check the main beam and joints before resuming operation; recover: and It takes 3 minutes to resume the original rhythm; For monitoring deflection, the unit is meters (m). κ represents the deflection growth rate in mm / min; v represents the deflection growth rate threshold in mm / min; v represents the pouring speed in m / h; and τ represents the layer spacing time in min. ③ Closed-loop regulation of side pressure; Pull the tension / force measuring pin With calculation In comparison, if the value is greater than 1.1 times, β should be increased to reduce the tension spacing; if it is less than 0.9 times, β should be decreased to increase the spacing. The fact that the confinement deflection and stress amplify at the same frequency indicates insufficient distributed stiffness, requiring the addition of ribs or a reduction in the spacing between suspension points. .

8. The method for constructing post-cast beams and slabs of a hoist platform with an upper-bearing suspended formwork according to claim 7, characterized in that: The online monitoring method in step seven is as follows: N1. Rolling Verification: renew ;renew With half-spanning the moving envelope, accounting Verification Check the eccentric torque, torsion angle, and unconfined length. ; N2. Online monitoring and thresholds: Crossing the middle and Displacement gauges are installed at the location to collect data in real time. ; Load-measuring pins are installed on key suspension rods or tie rods to collect data. Let the threshold be: ; N3, Linkage Processing: Warning: When Immediately reduce pump speed by 20-30%, reduce layer thickness by 10-20%, and increase step time by 20-30%; check the lifting point distribution coefficient. In accordance with the stiffness of the enclosure, additional suspension points / reinforced side confinement may be added if necessary; Stop watering: when Continuous 2–3 min ultra Stop the pump and pump back, then unload and recheck; N4, Side pressure closed loop: Will With calculation Comparison: If >1.1 Double, increase β or decrease the pull-out pitch And enhance the stiffness of the enclosure; if <0.9 The factor can be appropriately relaxed to improve efficiency, including: for The vertex value, i.e., the maximum value. β represents the lateral pressure of the formwork at a depth z from the pouring surface during the pouring process; β is the lateral pressure correction coefficient. For horizontal / vertical tension, unit: m.

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