Common Problems in The Design Of Unitized Curtain Wall Joints

The unitized curtain wall system is not designed with a drainage system

The unitized curtain wall uses the principle of isobaria, through the interpolation of the main and beam of the curtain wall, forming two cavities inside and outside, and the inner and outer cavities reach isobaric through the drain holes of the curtain wall beams, and the rainwater will not enter the inner cavity without the action of pressure difference, but there is a pressure difference between the inner and outer cavities when the outdoor wind pressure changes instantaneously.

In the traditional unit curtain wall system, the inner and outer cavities of the upper beam of the unit are directly communicated through the drain hole and are basically at the same elevation, and the rainwater enters the inner cavity along the drain hole from the outer cavity under the action of pressure difference, and when more rainwater enters the inner cavity, it is possible to infiltrate into the room from the inner sealing strip; In the curtain wall system of the organized drainage unit, the inner and outer cavities are not directly connected, but a transverse drainage pipe is arranged at the beam of the upper unit, and the leakage water entering the inner cavity is discharged to the transverse drainage pipe through the drainage hole, and then discharged outward through the drainage hole and along the outer vertical cavity of the main beam to the outer cavity of the upper beam of the lower unit, and the waterproof performance of the curtain wall system can be improved through organized drainage.

The design of the unit columns does not take into account the overall drainage function of the system

Organized drainage curtain wall system, after the seepage water enters the transverse drainage pipe, it is discharged through the drainage hole to the outer cavity of the unit column. At present, more designers design the inner and outer cavities of the unit column at will, and do not consider the drainage function of the leakage water, and the leakage water may still be discharged to the inner cavity of the unit column, so that the rainwater has been discharged from the highest layer to the lowest layer, until the water in the inner cavity of the unit beam is full, and then seeps into the room through the gap in the innermost layer.

Therefore, the above factors must be taken into account when designing the unit columns. As shown in Figure 4, the water entering the inner cavity is discharged to the outer cavity of the unit column after passing through the transverse drainage pipe and the corresponding drainage hole, and the water is discharged outward.

There is no drainage slope set on the upper beam of the element

Because the upper beam of each unit plate is in the lower part of the upper unit plate, the water that enters the inner cavity passes through and is discharged outward through the beam, if the beam does not set the drainage slope, it is not easy to discharge outward after the water enters the inner cavity of the beam, and the water stays in the inner cavity of the beam for a long time, not only has an impact on the anti-corrosion performance of the aluminum alloy profile, but also under the condition that the wind load and rainwater are very large, the water entering the inner cavity is easy to pour into the interior (especially the traditional unitized curtain wall system, the drainage slope should be set more).

The bottommost unit plate is not provided with a drainage system

In the unitized curtain wall system, the water entering the inner cavity is discharged outward through the unit beam at the bottom after being discharged through the unit plate, and the lower part of the bottom unit plate should be added with a long unit upper beam to meet the drainage function. If the lower drainage structure is not set, the unit column will extend all the way to the lower part, which does not meet the drainage function of the system, and the rainwater leaks directly from the unit column down to the inside of the structure.