Safety requirements when building formwork is removed

Because the building formwork is a temporary support structure, how can the building formwork be removed safely? Generally speaking, there are the following requirements:

(1) Requirements for concrete strength when removing formwork. According to the "Code for Construction and Acceptance of Concrete Structural Engineering", the concrete strength of cast-in-place concrete structural formwork and support during removal should meet the design requirements; when there are no design requirements, it should be Meet the following requirements:

① Non-load-bearing side formwork, including side formwork of beams, columns and walls, can be removed as long as the concrete strength can ensure that the surface and edges and corners are not damaged due to the removal of the formwork. Generally, the large formwork of the wall can be removed when the concrete strength reaches 1N/mm2 under normal temperature conditions.

② The load-bearing formwork, including the bottom formwork of horizontal structural members such as beams and slabs, should be removed according to the strength of the test block maintained under the same conditions as the structure.

③If it is found that the actual structural concrete strength does not meet the requirements during the form removal process, and there is a quality problem affecting the structural safety, the form removal should be suspended. After proper treatment, the actual strength can reach the requirements before continuing to dismantle.

④For the concrete structure of which the formwork and its supports have been removed, the size of the building formwork should be allowed to bear all the designed use loads after the concrete strength reaches the designed concrete strength standard value. When the effect of bearing the construction load is more unfavorable than the use load, it must be After accounting, temporary support will be added.

⑤Removal of the core form or the inner form with reserved holes should be done only when the concrete can ensure that no collapse and cracks will occur.

(2) Before demolding, there must be an application for demoulding, and when the strength record of the maintenance test block under the same conditions reaches the stipulation, the demolding can be demolded only after being approved by the technical person in charge.

(3) The removal of winter construction formwork should comply with the relevant regulations of winter construction, among which the main consideration is the thermal insulation maintenance after the removal of the concrete formwork.

(4) For mass concrete, in addition to meeting the requirements of concrete strength, thermal insulation measures should also be considered. After demolition, it is necessary to ensure that the temperature difference between the inside and outside of the concrete does not exceed 20 °C to avoid temperature difference cracks.

(5) The order and method of removing various formwork should be carried out according to the provisions of formwork design. If the template design is not specified, it can be removed in the order of the first support and the latter, and the first removal of the latter support. First remove the non-load-bearing formwork, then remove the load-bearing formwork, and remove the support in the order.

(6) The dismantled formwork must be cleaned up with the dismantling, so as to avoid nails stabbing the feet and hindering the passage of the accident. 7) During the dismantling, no one can be below.

(7) When the dismantled formwork is transported downward, it must be echoed up and down, and no violent prying is allowed. When lifting the dismantled formwork with a crane, the dark red small board formwork should be stacked neatly and tied tightly before hoisting, otherwise it is very dangerous to "scatter flowers" in the air.

(8) The demolition operation must be carried out during the day, and it should be dismantled as a whole in sections and disassembled on the ground. The dismantled parts and all items on the operating platform shall not be thrown from the sky, and the site shall be cleared after completion of the work.

(9) When it encounters thunder, rain, snow or the wind reaches five poles or more, the formwork shall not be removed.

(10) When removing the formwork in the foundation pit, pay attention to the stability of the slope of the foundation pit, especially when removing the formwork support. It may cause the slope to vibrate and collapse. The demolished formwork should be transported to a place far away from the foundation pit in time for cleaning.

(11) The demoulding sequence of general cast-in-place floor and shear wall structures is as follows: demolishing shear wall diagonal bracing and tension bolts → demolishing shear wall side formwork → demolishing beam side formwork → demolishing floor bottom formwork → demolishing beam bottom mold.

(12) Before removing the floor formwork, the opening and the edge must be closed before the operation can be started. The dismantled formwork is not allowed to be thrown downward at will, but must be passed down to the ground. The active formwork must be dismantled in a row before stopping halfway, so as not to fall and hurt people.

(13) There are multiple horizontal tie rods in the formwork column. The upper one should be removed first and removed in the order from top to bottom. The removal of the last link should be carried out at the same time as the removal of the column, so as to prevent the column from falling and hurting people.

(14) For the removal of multi-storey floor formwork pillars, how many floors of floor pillars should be retained below should be determined by the technical person in charge through calculation according to the construction speed, the increase in concrete strength, and the gap between the structural design load and the formwork construction load.

When dismantling the building formwork, do not directly support the iron pry on the surface of the column beam, wall panel, etc. to pry the formwork, which is easy to cause loose edges and corners and damage. Use a wooden wedge to remove the formwork to loosen the assembled formwork first, and then pull out the assembling nails, and then the formwork can be easily removed. After the removal of the formwork is completed, the four corners of the formed concrete column, the corners of the shear wall, the openings and other external corners are protected by a 2.5-thick formwork with a thickness of 2.5 meters below, so as to avoid damage to the formed edges and corners during material handling and affect the quality of the concrete appearance.