Aluminum curtain walls are widely used in architecture, but their coefficient of thermal expansion differs significantly from that of commonly used structural materials like steel. This difference can easily trigger thermal stress during temperature changes, leading to curtain wall deformation or even damage. To avoid this problem, the design phase requires comprehensive consideration of structural connections, material selection, construction optimization, and construction techniques. A scientific design is needed to balance the thermal expansion effect and ensure the long-term stability and safety of the curtain wall.
The coefficient of thermal expansion of aluminum alloy is approximately twice that of steel, meaning that aluminum alloy deforms more significantly under the same temperature change. If the curtain wall panels are directly fixed to the steel frame, the inconsistent deformation during temperature changes will generate enormous thermal stress. This can lead to curtain wall deformation and sealant cracking, or even structural failure. Therefore, rigid connections should be avoided in the design phase. Instead, floating connections should be used, maintaining a certain gap between the curtain wall panels and the frame to allow the aluminum alloy to expand and contract freely. For example, by using elongated holes, elastic connectors, or adjustable supports, the curtain wall can release thermal stress through small displacements during temperature changes, preventing stress concentration.
The reinforcement design of edge and center ribs is crucial for controlling the deformation of aluminum curtain walls. Aluminum curtain wall panels typically require edge and center ribs to enhance rigidity. However, if these reinforcing ribs are too rigidly fixed to the panel, it can restrict the thermal expansion and contraction of the aluminum alloy, leading to excessive local stress. Therefore, the edge rib frame should be designed as a length- and width-adjustable structure, connected by plug-in connectors, with gaps reserved at both ends of the rods and connectors to allow the edge ribs to expand and contract synchronously with the panel. Similarly, the connection between the center ribs and the panel should not be rigidly fixed; a floating connection method can be used, such as connecting to the edge rib frame via angle brackets, with gaps reserved to allow the center ribs and panel to slide relative to each other during temperature changes, reducing thermal stress transfer.
Material selection and combination are critical for controlling thermal expansion. Aluminum curtain walls should not be directly connected to steel due to the significant difference in their coefficients of thermal expansion, which can easily lead to inconsistent deformation. If a steel frame must be used, design measures must address the temperature deformation difference issue, such as using transition connectors or installing sliding supports to allow relative movement between the aluminum alloy and the steel. Furthermore, the selection of panel materials must consider thermal expansion characteristics. Single-layer aluminum panels or honeycomb aluminum panels should be prioritized, while composite materials such as aluminum-plastic panels should be avoided, as differences in interlayer thermal expansion may lead to panel blistering or deformation.
Structural optimization is an effective means of reducing thermal stress. The panel size of the aluminum curtain wall should not be too large to reduce the impact of thermal expansion on the overall structure. Simultaneously, the design of the sealant joints must consider displacement caused by thermal expansion and contraction. This can be achieved by increasing the joint width or using highly elastic sealant to ensure the joints can accommodate the deformation of the aluminum alloy. In addition, the drainage system design of the curtain wall must be combined with thermal expansion control to avoid drainage problems caused by deformation, leading to leakage issues.
Construction techniques are equally important for controlling curtain wall deformation. During construction, the installation sequence and connection tightness of the panels must be strictly controlled to avoid panel deformation due to installation stress. For example, the screws fixing the panels should not be tightened too much; a certain amount of slack should be left to allow the aluminum alloy to expand and contract freely. Furthermore, the choice of construction environment must consider the impact of temperature, avoiding critical processes during high or low temperature periods to reduce the impact of temperature stress on construction quality.
The difference in the coefficient of thermal expansion of aluminum curtain walls needs to be comprehensively controlled through scientific design, reasonable material selection, and meticulous construction. By using measures such as floating connections, optimization of edge and center ribs, adjustment of material combinations, structural optimization, and improvement of construction techniques, thermal stress can be effectively balanced, curtain wall deformation can be avoided, and the long-term safety and aesthetics of the building curtain wall can be ensured.
