This article mainly introduces the installation technology of precast concrete wall panels in construction industrialization, including the current status of precast concrete wall panel installation, installation measurement tools, analyzes existing problems, and puts forward corresponding improvement suggestions.
1. Wall panel installation and construction
The first layer of wall panels is installed on the floor or foundation that has been poured. The other layers are connected vertically on the bottom wall panels. The working area is mainly on the superimposed floor slabs.
The construction process of wall panel installation is as follows: Measure and set out → Check and correct the vertical reserved steel bars on the wall → Measure and place horizontal elevation control pads → Hoist the wall panels in place, adjust the position and verticality → Install the fixed wall panel diagonal supports → Install additional steel bars → tie the steel bars in the cast-in-place reinforced parts → formwork in the cast-in-place parts → handle the bottom and joints of the prefabricated wall panels → check and accept → pour concrete, and install concrete composite beams, composite panels, stairs, bay windows, balconies and upper floors in sequence Wall panels, repeat the above process over and over again to complete the installation of the entire building.
The quantities used in the installation process of precast concrete wall panels include: steel ruler, level, ruler, box ruler, tape measure, angle ruler, etc.
Before installing the wall panel, use a level to determine the height of the elevation pad. Use a box ruler to measure whether the length of the reserved steel bars meets the length requirements. Use a box ruler to measure the location and size of the reserved steel bars, the length of the bins, and check the elevation after the wall panels are installed. , rulers and angle rulers are used to measure the verticality of wall panels, and some construction workers use plumb lines to measure.
*Measurement and Setting Out
As shown in Figure 1, according to the design drawings, release the length of the wall panel edge line and shear wall on the base plate (floor) based on the main control line, mark the distance of each axis and the distance of the main control line, and mark the inner wall panel according to the thickness of 200mm. Obtain the horizontal position of the wall panel installation. The wall panel pads are arranged on the inside according to the exterior wall panels, the interior wall panels are arranged on both sides, and the partitions are arranged in the middle. When arranging the pads, avoid buried holes for water and electricity and door openings. And only after the compounding is correct can the next process be carried out.
Measurement and setting-out
*Check the vertical steel bars reserved for wall panels
Before assembly, check the vertical reserved steel bars of the wall panel. The construction quality inspection personnel will check whether the position of the reserved steel bars meets the design requirements according to the wall panel drawings. The general requirement is not more than ±10mm. If there is a size deviation, it should be cooled according to the requirement of 1:6. Bend correction.
*Measure and place horizontal control elevation pads
As shown in Figure 2, after measuring with a level, place horizontal control elevation pads. During the installation process of prefabricated wall panels, there will be a gap of about 40mm below the wall panels. Certain installation problems will occur during the production of wall panels and component installation. Deviation, in order to ensure that the entire floor reaches the elevation, special pads are required for each wall panel during actual construction.
Elevation pads
*Wall panel hoisting, positioning, position adjustment and vertical adjustment
Wall panel hoisting, positioning, position adjustment and vertical adjustment. Lift the wall panel from the wall panel storage area or transport vehicle. During the lifting process, the safety of the lifting points and hooks must be confirmed. As shown in Figure 3, when the wall panel is hoisted to a height of about 1m from the floor, use manual hand support to slowly fall. During the falling process, use a mirror to place it near the reserved steel bars to observe whether the grouting sleeve and vertical steel bars are aligned. After alignment, slowly lower it into position, install the diagonal support and the 7-character code, then correct the wall positioning and verticality, and continue to hoist the next wall panel after unhooking it.
Wall panels in place and installed
*Caulking, sleeve grouting
Before installing the wall panel, make compartments under the wall panel. After the wall panel is installed, use special mortar to caulk the joints. After the caulking is completed, grout the sleeve.
Cast-in-situ reinforced steel bar tying, formwork support and concrete pouring
As shown in Figure 4, steel bars and connecting bars are tied between wall panels, corners, cast-in-place columns, etc., the formwork is supported, and concrete is poured. After the formwork is supported, the formwork needs to be reinforced with diagonal supports to complete the installation and connection of the entire wall. After the stairs, balconies, bay windows and upper beams, columns and floor slabs are completed, continue to repeat the above process to complete the assembly of the entire building.
Tying steel bars, supporting formwork and pouring concrete
2. Problems with current wall panel installation and suggestions for improvement
Grouting sleeves cannot be inserted into reserved steel bars
There are many reasons why the sleeve cannot be inserted into the reserved steel bars. The main reasons and improvement measures are as follows.
Lack of strict control during the production process
During the production process, the position and verticality of the formwork of the grouting sleeve and reserved steel bars were inaccurate and the position shifted during the pouring process, resulting in the position and verticality of the grouting sleeve and reserved steel bars failing to meet the design requirements of the drawings. Inspection It is impossible to accurately measure verticality and position at the same time using inspection methods such as box rulers.
Recommendation: Before pouring the wall panel, use inspection tools to measure the position and verticality of the grouting sleeve and reserved steel bars to ensure the positioning length and firmness of the grouting sleeve and reserved steel bar positioning device of the formwork frame. Before pouring, ensure that the formwork frame is fixed reliably. , to prevent the deformation of the formwork frame during pouring from causing the position of the sleeve and steel bars to shift. Special inspection tools are used to simultaneously measure the position, verticality and outer contour to ensure that the components are qualified before leaving the factory.
Deformation of steel bars caused by transportation and stacking processes
Hoisting and transportation bumps before transportation cause the steel bars to be squeezed or impacted, resulting in deformation of the steel bars.
Recommendation: Reserve steel bars as special protective covers. Place them on special transport racks during transportation and fix them firmly. Wall panels are stacked on special support racks when they arrive at the factory to ensure that the steel bars are not stressed during hoisting, transportation, and stacking. impact.
Inspection before entering the factory, lifting, and assembly is not strict enought
When entering the factory, it is impossible to accurately measure the verticality and position at the same time using inspection tools such as box rulers and steel plate rulers.
Recommendation: Before the wall panels enter the factory, use special inspection tools to check the wall panel sleeves, the position and verticality of the reserved steel bars, the depth of the sleeves, and the length of the reserved steel bars at the same time to ensure that the wall panels enter the installation site without any problems. Qualified product.
Deformation of reserved steel bars caused by wall panel lifting and installation process
The impact during lifting and the bump during lowering caused the reserved steel bars of the wall panel to collide and deform, and the sleeve inserted into the reserved steel bars was misaligned or dropped diagonally, causing the steel bars to deform.
Recommendation: When lifting, have a dedicated person observe the construction environment and direct the tower crane driver to reasonably plan the lifting route. During the process of inserting the sleeve into the reserved steel bar, special installation equipment should be used to adjust the front, rear, left, and right of the wall panel, lower it slowly, and move the outside of the wall panel. Check whether the outline and the measurement line coincide with each other, and accurately adjust the horizontal position of the wall panel in place at one time.
The problem of substandard verticality of wall panels
The verticality of wall panels involves the structural stability and construction safety of the entire building, so the verticality of wall panel installation is crucial. The verticality error during the installation process is mainly caused by insufficient installation fine adjustment, insufficient accuracy of measuring measuring tools, human misreading and misreading of measuring tools, etc.
Recommendation: Design special verticality measuring equipment and calibrate it regularly. Installation and construction personnel and on-site management personnel should strictly control the installation to ensure that each wall panel is installed to achieve a high verticality.
The problem that the floor elevation does not meet the standard
The elevation of the floor is a very important indicator. The substandard elevation is mainly caused by the excessive height of the wall panels during the production process and incorrect elevation pads during the installation process.
Suggestion: Take the height dimension of the wall panel as an important inspection item. Some standards for the height dimension of the wall panel are plus or minus tolerances. If the wall panels on each floor are uneven, the elevation of the entire building will exceed the standard. Therefore, the height of the wall panel should be appropriately adjusted to the design elevation through elevation pads. The elevation pads should be differentiated according to the size of each wall panel, and the location of the pads should be marked. After analysis, the construction efficiency is low when using a level to measure and then place pads in actual construction. In order to ensure fast and effective construction, a dedicated identification number should be compiled and recorded for each wall panel, and the sequence of lifting identification numbers should be prepared in advance, and the corresponding The pads should have corresponding identification numbers to prevent the pads from being installed incorrectly. It can also be used as an effective control of the elevation during the construction process. The elevation should be measured with a special elevation measuring tool, which can greatly improve construction efficiency.
The degree of mechanization of inserting reserved steel bars into wall panel sleeves is low
During the process of aligning the wall panel grouting sleeve with the vertical reserved steel bars, it is necessary to manually insert the wall panel into the reserved steel bars about 1m away from the floor. Due to the movement range of the tower crane, it is difficult to move accurately in a small range. , this work is extremely difficult to construct. If the steel bars are not aligned with the wall panel during the falling process, the steel bars will be bent. Use a crowbar to adjust the position when it is dropped to the horizontal position, which will easily damage the wall panel.
Suggestion: Special wall panel fine adjustment equipment should be designed to achieve fine adjustment of the front, rear, left and right, and elevation of the wall panels. Fine adjustment equipment should be like tools, easy to move, simple to operate, reliable and durable.
The density of the grouting sleeve is difficult to guarantee
Engineering problems such as pores and lack of grouting seriously affect the construction quality. During the grouting process, the grouting channel is not smooth, the grouting cavity is too dry, there are bubbles in the slurry, the inner cavity of the sleeve and the steel bars are not clean, etc. are all defects caused by sleeve grouting. s reason. The cleanliness of the inner cavity of the vertical grouting sleeve, reserved steel bars, and grout sub-bins affects the smooth progress of subsequent grouting operations and the connection strength after grouting.
Recommendation: Before installing the wall panels, the cleanliness around the reserved steel bars should be reviewed to ensure that the grouting channels are unobstructed, there is no oil stain and construction impurities on the steel bars, and the inside of the grouting sleeve is clean. The grouting channels should be moistened before grouting. During the grouting process, To ensure that air bubbles are discharged, a removable compensation cavity should be added above the grouting exhaust hole. When the grouting material shrinks, it will be compensated by the slurry in the compensation cavity. The slurry can be poured into the grouting equipment only after the bubbles disappear during the mixing process of the grouting material. The device cannot introduce air bubbles.
