Wind load is the primary external force acting on curtain wall structures. In coastal areas where typhoons are frequent, curtain wall damage during typhoons is very common. Therefore, special attention must be paid to curtain wall projects in these regions. This article takes the damage caused by Typhoon “Mokha,” which made landfall in Hainan in 2024, as a case study focused on a project in Haikou. We first analyze the typical failure modes of curtain walls under typhoon conditions. Then, through comparative data analysis, we evaluate the typhoon resistance of various curtain wall materials. The results show that curtain walls designed according to current load standards can withstand the impact of most typhoons. Finally, in the article, we summarize key factors affecting typhoon resistance and proposes measures to enhance the performance of curtain walls in typhoon-prone regions.
The damage is more common in podiums and lower floors, while higher elevations of the main building often remain intact. As shown in the image below, shattered glass from the panels has fallen to the ground, while fragments near the frame remain adhered due to the bonding effect of structural silicone sealant.
Metal panels can be dented by flying stones or broken glass, ceiling panels may be torn apart, and fastening screws sheared off. Under extreme typhoon conditions, due to insufficient stiffness, metal panels experience a shift in stress mode from out-of-plane bending to in-plane tension. The tensile forces are much greater than the local pressure-bearing capacity of the panels or the shear capacity of the screws, making it easy for the panels to tear and the screws to shear off.
As shown in the image below, curtain wall units and glass panels that were stored on the ground and not yet installed were blown over and broken. The panels were inadequately secured, and during the typhoon, the fixing measures failed, leaving the panels exposed to impact from windborne debris.
Other types of damage, such as mullion failure, detachment of embedded parts, malfunction or detachment of operable windows, and the complete fallout of glass panels, were rarely observed at the scene.
“Load Code for the Design of Building Structures” GB50009-2012” defines basic wind speed as “the wind speed determined by the 10-minute average wind speed observation data at a height of 10m on the local open and flat ground (Class B landform), and the maximum wind speed once in 50 years is obtained by probability statistics”.
Typhoons can be divided into three categories according to wind speed:
When typhoons make landfall, they blow from the sea surface, and their landform is equivalent to Class A landform in the load specification. And the wind speed time interval uses a 2-minute time interval. Therefore, the “maximum wind speed when the typhoon lands” refers to the average maximum wind speed of 2 minutes under Class A landform conditions.
It can be seen that the “basic wind speed” and “maximum wind speed when the typhoon lands” in the load code cannot be directly compared. A conversion between the two is necessary. The specific conversion steps are as follows.
The first step is to convert the average maximum wind speed in 2 minutes to 10 minutes. According to the World Meteorological Organization’s guidelines, for landfalling typhoons, the conversion can be roughly as follows:
V10min = 0.945V2min
The second step is to convert the 10m high wind speed under Class A terrain to the 10m height of Class B terrain. The load code gives the wind pressure height variation coefficient of Class A terrain at 10m height as 1.28, which corresponds to the wind speed conversion coefficient of (1.28)^0.5=1.13, so:
VB = VA / 1.13
In this way, we can convert the “maximum wind speed when the typhoon lands” into the 10-minute average maximum wind speed at a height of 10m in Class B landforms.
Take Typhoon Makar, No. 11 in 2024, as an example. When it landed in Hainan on September 6, the maximum wind speed near the center was 60m/s. Convert it to 10min average maximum wind speed:
V10min = 0.945V2min = 0.945 * 60 = 56.7m/s
Convert it to Class B landform:
VB=VA/1.13=56.7/1.13=50.2m/s
The basic wind speed is calculated using the Bernoulli equation to obtain the basic wind pressure
W0 = VB2 / 1600 = 50.2 * 50.2 / 1600 =1.58 Kpa
Take the 2024 No. 13 typhoon “Bebejia” as an example. When it landed in Shanghai on September 16, the maximum wind speed near the center was 38m/s. Convert it to 10-minute average maximum wind speed:
V10min = 0.945 V2min = 0.945 * 38 = 35.91 m/s
Convert it to Class B landform:
VB = VA / 1.13 = 35.91 / 1.13 = 31.77m/s
Use the Bernoulli equation to calculate the basic wind speed to get the basic wind pressure:
W0 = VB2 / 1600 = 31.77 * 31.77 / 1600 = 0.63 Kpa
To determine how many levels of typhoons a building can withstand, it only need to calculate the “maximum wind speed at typhoon landing” corresponding to the basic wind speed. For example, the basic wind pressure in Haikou, Hainan is 0.75Kpa. Buildings designed according to this standard can withstand the maximum wind speed of 34.6m/s (average of 10 minutes under standard landforms), that is, level 12 wind. Besides, they can also withstand the maximum wind speed of 41.4m/s (average of 2 minutes under Class A landforms) at landing, that is, level 13 typhoons.
The basic wind pressure in Wuhan, Hubei is 0.35 Kpa. Buildings designed according to this standard can withstand the maximum wind speed of 23.66m/s (average of 10 minutes under standard landforms), that is, level 9 wind. What’s more, they can also withstand the maximum wind speed of 28.29m/s (average of 2 minutes under Class A landforms) at landing, that is, level 11 typhoons.
When the wind speed exceeds the wind speed level listed in the table, the building may not be damaged. Because in the ultimate bearing capacity state design, the wind load needs to be multiplied by a partial factor of 1.5, and the material also has a certain safety reserve factor. The following is an analysis of the typhoon resistance of various materials in glass curtain walls through specific data.
According to the provisions of the curtain wall glass code and considering the national context in China, the overall safety factor K for glass panels is taken as 2.5. For the Haikou region, based on this safety factor, the basic wind pressure that glass panels designed in accordance with current codes can withstand is:
0.75 × 2.5 = 1.875 kPa.
This corresponds to a design wind speed of 54.77 m/s (based on a 10-minute average wind speed under standard terrain conditions as per the load code), equivalent to a Grade 16 wind.
Additionally, it can withstand a maximum typhoon wind speed of 65.5 m/s (2-minute average wind speed under Terrain Category A), which is equivalent to a Grade 18 typhoon.
Taking 3003-H14, a commonly used aluminum material for curtain wall panels, as an example: the design strength is 89 MPa, and the yield strength is 115 MPa.
The aluminum plate maintains an elastic working state without yielding as the basis for judgment. At this time, the total safety factor of the aluminum plate is:
115 / 89 * 1.5 =1.94.
For the Haikou region, the basic wind pressure the panel can resist is:
0.75 × 1.94 = 1.46 kPa,
corresponding to a design wind speed of 48.33 m/s, or Grade 15.
This equates to a maximum typhoon wind speed of 57.79 m/s, or Grade 17.
Taking granite as a representative material, and assuming a material partial factor of 2.15, with a wind load partial factor of 1.5, the total safety factor K is:
2.15 × 1.5 = 3.225.
For the Haikou region, the basic wind pressure the stone panel can resist is:
0.75 × 3.225 = 2.419 kPa,
corresponding to a wind speed of 62.21 m/s, or Grade 18, and a maximum typhoon wind speed of 74.39 m/s, also Grade 18.
Table 1 Wind Resistance Analysis of Different Panel Materials in Haikou Region
Material | Wind Speed（m/s） | Wind Force Scale | Typhoon Wind Speed（m/s） | Typhoon Scale |
Glass | 54.77 | 16 | 65.5 | 18 |
Aluminum | 48.33 | 15 | 57.79 | 17 |
Stone | 62.21 | 48 | 74.39 | 18 |
Table 2 Wind Resistance Analysis of Different Panel Materials in Shanghai Region
Material | Wind Speed（m/s） | Wind Force Scale | Typhoon Wind Speed（m/s） | Typhoon Scale |
Glass | 46.90 | 15 | 56.10 | 17 |
Aluminum | 41.32 | 13 | 49.41 | 15 |
Stone | 53.26 | 16 | 63.69 | 18 |
Brittle materials, due to the higher safety factors adopted in the design process, tend to have greater potential for resisting typhoon loads. As shown in the tables above, most curtain wall panels designed in accordance with the load code can withstand typhoons of Grade 17 or above in the Haikou region, and Grade 15 or above in the Shanghai region.
The commonly used steel in curtain wall projects is Q235B/Q355B, and stainless steel is 304/316. Taking the common steel Q235B (t≤16mm) as an example, the strength design value is 215Mpa and the yield strength is 235Mpa. The judgment basis is that the steel maintains elastic work without yielding. At this time, the total safety factor is
235/ 215*1.5 =1.64.
For the Haikou area, the basic wind pressure that steel can withstand is
0.75*1.64 =1.23Kpa.
And the corresponding load specification (10min average under standard terrain) wind speed is 44.36m/s, that is, level 14 wind. The corresponding maximum typhoon wind speed is 53.04m/s, that is, level 16.
Material | Wind Speed（m/s） | Wind Force Scale | Typhoon Wind Speed（m/s） | Typhoon Scale |
Q235B | 44.36 | 14 | 53.04 | 16 |
Q335B | 45.78 | 14 | 54.74 | 16 |
304/316 | 45.52 | 14 | 54.43 | 16 |
Common aluminum alloy profiles include 6061 series and 6063 series. Taking 6063-T6 as an example, the strength design value is 150Mpa and its yield strength is 180Mpa. The total safety factor of the profile is 180/ 150*1.5 = 1.8.
For Haikou area, the basic wind pressure that the profile can withstand is 0.75*1.8 = 1.35Kpa. And the corresponding load specification (10min average under standard terrain) wind speed is 46.48m/s, that is, level 15 wind. The corresponding maximum typhoon wind speed is 57.79m/s, that is, level 17.
Material | Wind Speed（m/s） | Wind Force Scale | Typhoon Wind Speed（m/s） | Typhoon Scale |
6063-T5 | 46.90 | 15 | 56.08 | 16 |
6063-T6 | 46.48 | 15 | 55.57 | 16 |
6061-T6 | 46.48 | 15 | 55.57 | 16 |
Take the stainless steel rods used in curtain walls as an example. The design value of tensile strength is the yield strength divided by 1.4. Considering the wind load partial factor of 1.5, the total safety factor of the rod is 1.4*1.5=2.1. Similarly, according to the cable structure code, the overall safety factor of the cable is 2*1.5=3.
Material | Wind Speed（m/s） | Wind Force Scale | Typhoon Wind Speed（m/s） | Typhoon Scale |
Rods | 50.2 | 15 | 60.03 | 17 |
cables | 60 | 17 | 71.7 | 18 |
The current Chinese standard stipulates that the tensile strength of silicone structural sealants shall not be less than 0.6N/mm2. The design value of the structural adhesive strength is 0.2N/mm2, and the material partial factor is 3.0. Considering the wind load partial factor of 1.5, the total safety factor of the structural adhesive is 4.5.
For the Haikou area, the basic wind pressure that the structural adhesive can resist is 0.75*4.5=3.38Kpa. And the corresponding load specification (10min average under standard terrain) wind speed is 73.54m/s, that is, 18-level wind. The corresponding maximum typhoon wind speed is 87.94m/s, that is, 18-level.
Take A2-70 stainless steel bolts as an example, the strength design value is 325Mpa, and its yield strength is 450Mpa. The bolt is judged as not yielding in normal working state. At this time, the total safety factor of the bolt is 450/325*1.5=2.08. Similarly, for 5.8-level ordinary bolts, the yield strength is 400Mpa, and the strength design value is 210Mpa. As a result, the overall safety factor of the bolt is 400/210*1.5=2.8.
For Haikou area, the basic wind pressure that A2-70 stainless steel bolts can resist is 0.75*2.08=1.56Kpa. While the corresponding load specification (10min average under standard terrain) wind speed is 49.96m/s, that is, level 15 wind. The corresponding maximum typhoon wind speed is 59.74m/s, that is, level 17.
Take Q235B fillet welds as an example, and select E43 welding rods. According to the steel structure design standard, the weld strength design value is 0.38 times the tensile strength of the weld metal. Considering the wind load partial factor of 1.5, the total weld safety factor is 1/0.38*1.5=3.95. Similarly, for Q355B steel, the weld strength design value of E43 welding rods is 0.41 times the tensile strength of the weld metal. Considering the wind load partial factor, the total weld safety factor is 1/0.41*1.5=3.66.
For Haikou area, the basic wind pressure that Q235B fillet welds can withstand is 0.75*3.95=2.96Kpa, and the corresponding load specification (10-minute average under standard terrain) wind speed is 68.82m/s, that is, level 18 wind. The corresponding maximum typhoon wind speed is 82.29m/s, which is level 18.
Table: Wind Resistance Performance of Curtain Wall Connection Systems
Material | Wind Speed（m/s） | Wind Force Scale | Typhoon Wind Speed（m/s） | Typhoon Scale |
Structural Sealant | 73.54 | 18 | 87.94 | 18 |
A2/A4-70 Stainless Bolt | 46.48 | 15 | 57.79 | 17 |
Grade 5.8 Carbon Steel Bolt | 57.97 | 17 | 69.31 | 18 |
Q235B Weld Seam | 68.82 | 18 | 82.29 | 18 |
Q355B Weld Seam | 66.27 | 48 | 79.24 | 18 |
In the calculation formula of embedded parts, HRB400 grade steel bar has a yield strength of 360MPa. And the strength design value of 300MPa is used in the calculation of anchor bar area. It can be approximately considered that the material partial factor is 1.2, and the total safety factor of embedded parts considering the wind load partial factor is 180/ 150*1.5=1.8.
For Haikou area, the basic wind pressure that bolts can resist is 0.75*1.8=1.35Kpa. And the corresponding load specification (10min average under standard terrain) wind speed is 46.48m/s, that is, 15-level wind. While the corresponding maximum typhoon wind speed is 57.79m/s, that is, level 17.
According to the concrete post-anchoring regulations, in the calculations of the post-anchoring system, the minimum partial coefficient of the tensile and shear failure bearing capacity of the anchor steel is 1.2. The total safety factor of the post-embedded parts considering the wind load partial coefficient is 180/ 150*1.5=1.8.
For the Haikou area, the basic wind pressure that the post-embedded parts can withstand is 0.75*1.8=1.35Kpa. And the corresponding load specification (10-minute average under standard terrain) wind speed is 46.48m/s, that is, level 15 wind. The corresponding maximum typhoon wind speed is 57.79m/s, that is, level 17.
Table: Wind Resistance Performance of Embedded Anchor Systems
Material | Wind Speed（m/s） | Wind Force Scale | Typhoon Wind Speed（m/s） | Typhoon Scale |
Cast-in Anchors | 46.48 | 15 | 55.57 | 16 |
Post-installed Anchors | 46.48 | 15 | 55.57 | 16 |
From the previous analysis data, it can be seen that according to the current load specification design, even if the utilization rate of panels, rods, and connection systems is close to 100%, the safety of the rods of each part of the curtain wall should not be a problem under normal conditions. However, why do building curtain walls designed according to normal specifications still suffer abnormal damage under strong typhoons? There are mainly the following reasons:
Due to the “venturi effect” (also known as wind corridor or channeled wind) caused by narrow gaps between buildings, and the abrupt changes in façade geometry, the distribution of wind loads on certain parts of a complex building can become highly irregular. In such cases, wind tunnel test results often show significantly higher local wind loads compared to those obtained from theoretical calculations.
This indirectly suggests that the typhoon load experienced by the curtain wall in these localized areas can be much higher than the official or reported typhoon intensity levels for the region.
Taking cold-formed hollow steel sections as an example, the standard allows a negative tolerance of up to 10% for wall thicknesses less than or equal to 10 mm. According to this, a steel tube labeled 120 × 60 × 4 mm that arrives on site as 120 × 60 × 3.6 mm would still be considered compliant. However, the section modulus of the thinner tube is only 91% of the original design value. In practice, many materials exceed the allowable negative tolerance, which can negatively impact wind resistance performance.
Curtain wall systems often involve components with cut-outs or perforations. In structural calculations, stress concentration effects at these discontinuities are frequently neglected. For instance, in a slotted plate under tension, the maximum stress around a circular hole can reach up to three times the average stress across the section.
For ductile materials such as steel, stress redistribution through plastic deformation can reduce the impact of stress concentration. However, for brittle materials like glass or stone, once the localized stress exceeds the material’s ultimate strength due to stress concentration, sudden failure is likely to occur.
In actual construction, the skill level of curtain wall workers varies, and deviations from standard procedures are common. For example, screw spacing on aluminum panels or actual weld height often falls short of design specifications. These deficiencies, though sometimes minor, collectively reduce the overall wind resistance capacity of the curtain wall system.
8.1 During the curtain wall design process, a certain amount of surplus should be reserved for locations with large wind loads (eaves, corridor ceilings, and locations where the outer contour of the building surface changes suddenly) to improve the overall safety reserve.
8.2 For some locations that are prone to typhoon damage, some additional structural measures should be added during the curtain wall design process, such as anti-fall ropes for opening doors and wind-resistant clips for metal roofs.
8.3 Materials entering the factory should be strictly inspected in accordance with the specifications. For materials with deviations exceeding the specifications, the on-site inspection personnel should communicate with the designers to confirm whether they can be downgraded or withdrawn.
8.4 For curtain walls located on the ground floor, some temporary protection measures such as flexible fabric covering should be taken to prevent the panels from being smashed by flying gravel.
8.5 Improve the technical level of on-site management personnel and labor workers, and strictly follow the drawings for construction.
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