How to Design Solar Carports for Typhoon and High-Wind Regions
A standard solar carport spec is not wrong. It is just designed for standard conditions. In a typhoon zone, the conditions are not standard — and starting from a generic template is how projects fail.
Designing for typhoon and high-wind regions requires a fundamentally different engineering baseline. Not just bigger numbers plugged into the same formula, but different structural logic, different load combinations, and a different approach to failure tolerance.
Typhoon Wind vs. Standard Wind Design
Most wind design standards treat wind as a static or slowly varying pressure applied from a fixed direction. Typhoons are different in three ways.
Speed. A Cat 4 typhoon produces 10-minute mean wind speeds of 58–69 m/s at its eyewall. That is roughly 2.5× the 50-year return design wind speed used in many APAC countries for non-typhoon regions. The pressure load scales with the square of velocity — so a 2.5× wind speed produces more than 6× the pressure load.
Duration. A typhoon passage can last 6–24 hours of sustained high-velocity wind. Structures in standard wind zones may experience peak gusts measured in seconds. Fatigue accumulates differently. Bolt preloads shift. Connections that are adequate for a brief gust may work loose under sustained cyclic loading.
Direction changes. A typhoon does not blow from one direction. As the eye passes, the wind direction reverses — often by 180 degrees over a few hours. A carport designed primarily for one dominant wind direction, with unidirectional lateral bracing, can experience severe uplift on the originally leeward side when the storm rotates. Both faces must be treated as the windward face.
Design Wind Speeds by Typhoon Category
The Saffir-Simpson scale defines hurricane intensity by 1-minute sustained wind speeds. For structural design purposes, the relevant figure is the peak 3-second gust speed, which is what ASCE 7-16 uses, and the 10-minute mean speed, which JIS C 8955:2017 and many Asian codes use.
Approximate design wind speed equivalents for typhoon-prone regions:
- Category 1 (33–42 m/s 1-min mean): 3-second gust approximately 46–58 m/s
- Category 2 (43–49 m/s): gust approximately 60–68 m/s
- Category 3 (50–58 m/s): gust approximately 69–80 m/s
- Category 4 (58–70 m/s): gust approximately 80–97 m/s
- Category 5 (>70 m/s): gust above 97 m/s
For the Philippines, the National Structural Code of the Philippines (NSCP 2015) sets design wind speeds through basic wind speed maps by occupancy category rather than wind zones, with the highest values along the eastern seaboard that takes the most direct typhoon landfalls. Vietnam's TCVN 2737:2023 sets wind pressure maps that require 3-second gust speeds above 60 m/s in coastal central provinces. Taiwan's building code (based on AIJ Recommendations) similarly distinguishes typhoon-exposed coastal regions from inland zones.
ASCE 7-16 and JIS C 8955:2017 in Extreme Wind Zones
ASCE 7-16 Chapter 26 defines four wind speed maps for different risk categories. Solar carports typically fall under Risk Category I or II. ASCE 7-16 wind maps cover the United States and its territories, not the Philippines: projects there take the basic wind speed from NSCP 2015 (see above), which is itself based on ASCE 7-10.
The key structural implication is in the exposure category. Typhoon-zone carports in flat coastal terrain are typically Exposure Category D — the most severe. Compared to Exposure C (open terrain), the velocity pressure coefficient (Kz) increases significantly at all heights, and the gust factor climbs to account for the turbulence characteristics of open coastal terrain.
JIS C 8955:2017 (the Japanese standard specifically for photovoltaic installation structures) is the most detailed wind standard for solar racking in typhoon-prone markets. It specifies wind pressure coefficients for both positive (inward) and negative (uplift) pressures, accounts for panel inclination angles, and includes edge-and-corner zone amplification factors that can be 1.5–2× the field-zone pressure. For typhoon-zone design in Japan, Taiwan, and parts of Vietnam, JIS C 8955:2017 is often the appropriate reference even when local codes do not mandate it.
Column and Base Plate Sizing for Typhoon Regions
In a standard wind region, H-beam column sizes are typically governed by combined bending and compression from dead load plus wind pressure. In a typhoon zone, the overturning moment at the base plate increases with the square of design wind speed. A column sized for 40 m/s gust pressure that is re-designed for 80 m/s sees its base moment increase by a factor of four.
That translates to:
- Column flange widths increasing from 200–250mm to 300–400mm to resist higher bending
- Base plate dimensions growing from 400×400mm to 600×600mm or more, with corresponding increases in anchor bolt count from 4 to 8 or 12
- Anchor bolt diameter and embedment depth increasing — M24 or M30 rather than M16 or M20, with embedment depths of 600–900mm into the concrete pier
Base plate connection is often the most critical node. Under typhoon uplift, the column-to-foundation joint experiences net tension. The anchor bolts must resist both the uplift force and the bending moment simultaneously. This is a different design check from standard gravity-dominant conditions.
Moment-Resisting Frames vs. Braced Frames
Two primary lateral load systems are used in typhoon-zone carports.
Braced frames add diagonal members (steel flats, round tubes, or tension-only rod bracing) between columns along the row. The bracing carries lateral wind loads as axial force — primarily in tension, since rod and flat bracing has limited compression capacity. Braced frames are efficient for transferring longitudinal wind loads to the foundations. Their limitation: the bracing must be positioned where it does not conflict with parking lane clearances, and they do not address the multi-directional nature of typhoon wind in transverse bays without additional bracing.
Moment-resisting frames (MRF) use fully moment-restrained connections at the column-to-beam joints. No diagonal bracing is needed. The frame resists lateral load through the bending stiffness of columns and beams. MRF carports typically require heavier sections — the columns must carry both axial load and bending — but they handle wind from any direction without dependence on a specific bracing alignment.
In practice, typhoon-zone carports often combine both approaches: MRF in the transverse direction (column to rafter connections fully moment-restrained) and rod or flat bracing in the longitudinal direction. This addresses the multi-directional wind without making every connection into a full moment joint.
Panel Clamp Uplift Resistance
Solar panels in a typhoon zone are often the weakest link. The structural frame may be overdesigned, but if the panel clamps are specified for C2 or C3 wind zone loads, the panels become projectiles at Category 3 and above.
Uplift pressure on the leading and trailing edges of panels is always higher than the field zone pressure. ASCE 7-16 and JIS C 8955:2017 both define edge-zone pressure coefficients — and for panels at the perimeter of the array, the net upward pressure can be 1.5–2× higher than on interior panels.
For typhoon-zone carports:
- Mid-clamps should be tightened to the installation-manual torque (generally 15–17 N·m for Solaracks M8 clamp bolts) and checked against the site-specific uplift load — torque sets the clamping force, not the uplift capacity
- End-clamps at edge rows require uplift capacity checks against enhanced edge-zone pressures
- Purlin screw connections at the module mounting rail must be sized for the full uplift force per panel, with pull-out values verified against the specific section profile and thickness
Loose clamps or undertorqued fasteners that allow panels to flutter under sustained typhoon wind cause progressive joint fatigue even before complete panel loss.
Redundancy and Secondary Load Paths
In typhoon-zone design, the philosophy shifts from "no failure" to "no progressive collapse." A structure should be designed so that if one connection fails, the failure does not propagate to adjacent bays.
Practical redundancy provisions include:
- Tying carport bays together longitudinally through continuous primary beams or tie beams at ridge and eave, so that a single column overload redistributes to adjacent columns rather than causing a chain collapse
- Specifying multiple smaller bolts over fewer large bolts at moment connections — a pattern that increases the number of load paths
- Using tension cable cross-bracing between columns, which provides a secondary lateral path if the primary bracing connection yields but does not fracture
- Avoiding single-point anchorage for the entire longitudinal wind force — distribute the force to at least three foundation points along each row
Philippines, Vietnam, and Taiwan: Regional Design Context
These three markets are among the highest-risk typhoon zones globally and are active solar markets.
In the Philippines, NSCP 2015 replaced the three wind zones of NSCP 2010 (Zones I, II and III at 250, 200 and 150 km/h, 3-second gust on an ASCE 7-05 basis) with basic wind speed maps by occupancy category: Figure 207A.5-1A for Categories III, IV and V (300-year mean recurrence interval), Figure 207A.5-1B for Category II (700-year) and Figure 207A.5-1C for Category I (1,700-year). The mapped values are strength-level 3-second gust speeds on an ASCE 7-10 basis, so they cannot be compared one-to-one with the old zone values. Read the speed at the project site from the map for its occupancy category; the Pacific-facing coasts of Eastern Luzon and Eastern Visayas, which formed Zone I under NSCP 2010, carry the highest values. The National Structural Code of the Philippines (NSCP 2015) governs, but JIS C 8955:2017 is used as a supplemental reference for PV-specific pressure coefficients.
In Vietnam, Decree 114 and TCVN 2737:2023 govern structural wind loads. Central Vietnam provinces (Quang Nam, Da Nang, Binh Dinh) face both typhoon wind and sustained monsoon wind — the monsoon direction is roughly opposite to the typhoon direction, reinforcing the need for bidirectional design.
In Taiwan, the Building Technology Regulations and AIJ-based wind standards require site-specific wind tunnel or map-based wind speed inputs. Carport projects in Pingtung, Kaohsiung, and coastal Taitung face the full Pacific typhoon exposure.
In all three markets, the most common engineering shortfall is using a standard template design rather than a site-specific structural calculation. Template designs are not inherently wrong, but a design calibrated for C3 conditions in Thailand will be inadequate for a site on the Pacific coast of Eastern Samar.
Post-Typhoon Inspection Requirements
Even a well-designed carport should be inspected after a typhoon event above Category 2. Key inspection points:
- Anchor bolt preload verification — torque-check at least 20% of anchor bolts at the base plates; typhoon cyclic loading causes preload relaxation
- Base plate grout condition — check for cracking or uplift displacement of the non-shrink grout
- Tension rod bracing condition — check for rod elongation, turnbuckle slip, or connection deformation
- Purlin connection integrity — inspect screw pull-through at the module rails, especially at edge rows
- Panel clamp torque — re-torque end clamps after any event where sustained gusts exceeded design wind speed
- Column plumb check — a column that has moved more than 5mm from vertical indicates foundation displacement and requires geotechnical assessment
Document the post-event condition against the as-built drawings. Even minor deformations may indicate that the structure operated in its plastic range — which changes the remaining fatigue life.
Solaracks Structural Analysis for Typhoon Zones
Carport structural design in typhoon regions cannot rely on generic load tables. The combination of site-specific wind speed, column height, panel configuration, and foundation conditions must be resolved through proper structural analysis.
Solaracks provides structural calculations for every carport project: static analysis to the applicable standard (for example ASCE 7-22 or JIS C 8955:2017) with site-specific wind load inputs, using SAP2000 where simulation is needed. Projects in typhoon-exposed zones receive enhanced column sizing, moment-resisting connection details, and base plate anchor bolt designs verified for uplift under the local design wind speed.
Request a structural quote within 24 hours at solaracks.com.
