The vertical spacing of split bolts is the same as that of steel pipe main keel, and the horizontal spacing shall also be determined according to calculation.
Although the splicing method is correct, the formwork side is not straight or damaged due to too many turnover times or inadequate formwork corner protection during construction, and the gap is too large after assembly, resulting in slurry leakage.
After initially hanging vertically with a line drop, initially tighten the bolts in the middle part, and then check the verticality with a line drop, and then tighten the bolts in other parts symmetrically up, down, left and right.
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The slump of concrete is too large, and the lateral pressure during pouring exceeds the value in the design of formwork support, resulting in formwork expansion.
According to experience, each vibration time shall be 20s ~ 30s, and the moving distance shall not be greater than 1.5 times of the action radius and less than 1m.
4.
2.
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Why is the formwork expansion of vertical components such as walls and columns? Figure 1 Figure 2 expansion formwork of vertical components such as walls and columns.
2.
During construction, the formwork, support and joint plugging shall be observed frequently.
During pouring, the slump of each tank of concrete shall be tested, and the commercial concrete station shall be notified in time for adjustment in case of deviation.
The concrete vibration time is too long, resulting in the expansion of the formwork and slurry leakage..
Plug-in vibration shall be adopted.
5 for the effect after formwork removal.
See Fig.
For some projects, in order to reduce the times of installing and removing pump pipes, move the pump pipes after one wall is filled with concrete, resulting in too fast pouring speed and excessive local stress, resulting in the change of formwork stress, resulting in formwork expansion.
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4.
3.
6.
The distance between the primary and secondary keels of the formwork is too large, which is not set according to the calculated value; No tie rod is set for more than 600mm, as shown in Figure 1.
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3.
First install the inner formwork (with a large area for easy installation), and then install the outer formwork.
5.
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4.
Figure 3 Figure 4 figure 54.
2.
The concrete pouring method is incorrect and the pouring speed is too fast.
4.
When pouring wall columns, they shall be poured in sections and layers.
When the upper formwork is erected, press down a certain size and make full use of split bolts for reinforcement.
The distance from the first steel pipe keel shall not be greater than 200mm.
When the upper concrete is vibrated, the vibrator can only penetrate into the lower concrete for 5 ~ 10cm.
During formwork design, the splicing method of external corner formwork is incorrect, and the cross sewing method (tongue and groove method) is not adopted.
The pouring speed and sequence of concrete are also an important factor affecting the lateral pressure of concrete.
Generally, the column shall not be greater than 25cm, the wall shall not be greater than 30cm, and the inner wood edge shall cover the formwork joint; The spacing between column hoops and outer edges of wall formwork shall also be determined according to calculation.
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Although the primary and secondary keels are set according to the calculated values, the reinforcement of split bolts and fasteners is not in place.
Click here to receive 500 common specifications for free Prevention and control measures 1.
Strictly control the vibration time, which should not be long or short.
3.
The spacing between the inner edges of the wall column formwork shall be determined according to the calculation.
As shown in Figure 3 and 4.
The concrete pouring method is incorrect and the vibration is excessive, resulting in deformation or displacement of the formwork.
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In order to ensure that the formwork is vertical, diagonal bracing shall be supported at the symmetrical part, and the formwork at this part shall be connected with the adjacent formwork and inner bent through horizontal support.
As shown in Figure 1.
➤ Cause analysis 1.
The concrete formwork expansion or closing of the lower layer at the joint position is uneven, and the upper formwork is not tightly attached to the lower wall when installing the upper formwork.
Layered pouring: when the immersion vibrator is used, the layered thickness is generally controlled at 500mm.
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When pouring floor concrete, the elevation and flatness of floor concrete must be controlled in place; During formwork matching of wall column, the negative deviation of formwork matching height shall be controlled within 15mm.
Split bolts must be added for columns with section size greater than 600mm.
During the construction of the lower layer, split bolt holes shall be reserved near the upper part, and the spacing shall not be greater than 500mm.
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There is deviation in the pouring elevation of the lower concrete; The negative deviation of formwork height is greater than 15mm, resulting in the lifting of the lower foot of the formwork.
When erecting the formwork, it is necessary to repeatedly use the line to fall against the crane, and the verticality of the formwork installation must be ensured.
During construction, the reinforcement fasteners of the formwork are not tightened one by one, resulting in the sinking of the formwork or the tightness of the joints.
The concrete shall be poured in strict accordance with the concrete mix proportion, especially the slump shall be strictly controlled, which has a great impact on the lateral pressure of newly poured concrete.
3.
➤ Cause analysis 1.
4.
The vibration method is incorrect, the pouring is not carried out in sections and layers, and the formwork expansion and even formwork running are caused by excessive vibration and increased lateral pressure in some places.
The distance from the first steel pipe keel (split bolt) is too large; The root lengthening wooden ridge is not fixed, as shown in Figure 1.
During formwork erection, rubber strips shall be fixed at the contact between the lower opening and the concrete wall to prevent slurry leakage.
The vertical structure shall be poured in layers, and the pouring height of each layer shall be controlled at about 500mm.
It is strictly prohibited to extend the vibrating rod into the vibrated concrete for vibration.
5.
Figure 3 and figure 42.
The acceptance of formwork reinforcement before concrete pouring shall be strengthened.
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Segmental pouring: the height of each section of column shall not exceed 3.5m, and the height of each section of wall shall not exceed 3M.
Previous highlights 1.
Why is there slurry leakage and dislocation at the joints between the upper and lower layers of Q2 wall and column? Figure 1 Figure 2 mortar leakage and dislocation at the joints of upper and lower layers of walls and columns.
Generally, the two bottom split bolts shall be tightened with double nuts, and the gap between the same wooden ridge of the main keel of the steel pipe shall be tightened with a triangular wooden wedge.
5.
➤ Preventive measures 1.
6.
3 and 4 for the improvement of formwork at the joint part, and Fig.
Before the formwork erection of the upper layer, the formwork expansion part of the upper opening of the lower layer shall be chiseled off, and the facade shall be leveled.
The vibration time shall be controlled to prevent excessive local vibration.
When the column section is within 40cm and there are cross stirrups, a pouring hole not less than 30cm high shall be opened in the column side formwork, and the hole spacing shall not exceed 2m.
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Why is there slurry leakage at the external corners of walls, columns and beams? Figure 1 Figure 2 mortar leakage at external corners of walls, columns and beams.
Generally, the first distance from the floor shall be controlled at 15cm ~ 20cm, the spacing between the lower half shall be controlled at 45 ~ 50cm, and the spacing between the upper half can be controlled at 50 ~ 60cm.
➤ cause analysis 1.
The concrete can be poured only after the reinforcement is in place.
The inclined support caused by inconvenient formwork erection is insufficient or improper, or the integrity of connection with adjacent components or bent system is poor, resulting in the occurrence of inclination.
The steel pipe keel at the corner of the shear wall shall be tightened and fixed with double fasteners.
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3.
The specification of split bolts is generally not less than Ф 14.
2.
When erecting the formwork, the line drop is not used to hang, resulting in the non vertical installation, resulting in the displacement of the upper opening of the wall, or the verticality is not rechecked after tightening and strengthening.
2.
The wall concrete shall be poured in layers and closed enclosure; For floors with a storey height of more than 4m, the frame column should be poured first, and the beam slab should be poured after the frame column is finally set; Door and window openings shall be cut from both sides in layers.