Cypress Avenue Towers: Integrated Wind Engineering from Concept to Completion

Posted on July 31, 2025

 

Located in the wind-exposed coastal environment of Surfers Paradise, the Cypress Avenue Towers are a landmark high-rise development that demonstrates how performance-based wind engineering can unlock value across design, construction, and long-term operational performance. With Towers 1 and 2 reaching heights of 304 and 261 metres respectively, the complex presented unique engineering challenges.

Windtech Consultants provided a comprehensive suite of services. The team engaged at every stage of the design process—from initial form-finding and code compliance assessments to detailed testing for structural and cladding performance, stack effect, paver uplift, and comfort conditions. Each tower was evaluated under multiple staging scenarios using scaled wind tunnel models and high-resolution proprietary pressure instrumentation. The result was a suite of tailored wind engineering solutions that informed nearly every major design decision.

Initial Form Optimisation for Structural Efficiency

This project is a clear example of how early engagement with an experienced wind engineering team, such as Windtech, can yield significant dividends in design efficiency, cost savings, and quality outcomes. Developer Meriton, acutely aware of these benefits, sought Windtech’s input from the outset.

At approximately 303 metres (993 feet), the tallest of the Cypress Avenue Towers is set to become the second-tallest building in Australia by highest occupiable floor. With an aspect ratio of 11:1, it posed particular aerodynamic and structural challenges. Windtech initiated the project by reviewing three alternative tower massings, ultimately identifying a preferred scheme due to its superior aerodynamic performance, which resulted in structural cost savings per unit area. This recommendation, backed by preliminary desktop assessments, was adopted by the client and confirmed via wind tunnel testing.

Structural form and wind loads were assessed using Windtech’s hybrid aeroelastic model, offering higher accuracy and cost-effectiveness over the simple aeroelastic models. This method captured positive aerodynamic damping effects, which reduced the overall peak response by 6%. Motion along the tower’s weaker axis was also mitigated through a cost-neutral solution involving the shaping of two 67,000-litre rooftop fire hydrant tanks to act as tuned liquid dampers.

Refining the Structural Design and Code Comparisons

Windtech collaborated closely with the structural engineering team to refine the dynamic response of the towers under wind loading. High-Frequency Pressure Integration (HFPI) testing was conducted on a 1:400 scale model with 36 wind directions and realistic terrain features. Each tower was assessed under three scenarios—Staged, Proposed, and Future—providing comprehensive data on wind demands over time.

Compared to AS1170.2:2021 estimates, wind tunnel-derived ULS base moments for the critical cross-wind governed responses were reduced by 36% to 77%. Torsion loads were reduced by 45% to 60%.

These reductions enabled the design team to optimise structural systems, including shear wall thickness and core reinforcement. Besides the performance-based benefits, the Australian code would not permit a code-based design for the development of this height and slenderness.

Serviceability limit state (SLS) displacements remained within H/500 in all directions, confirming sufficient stiffness without overdesign. Peak accelerations remained within comfort thresholds, with sensitivity analysis provided to demonstrate the effect of variations in frequency, mass, and damping, thereby showing robust design performance.

Importantly, the staged analysis confirmed minimal adverse interactions between towers, validating the phased construction strategy without requiring significant redesign.

Motion Mitigation and Damping Considerations

Damping requirements were evaluated to ensure occupant comfort, with detailed analysis confirming that no supplemental damping was required at the design stage. However, the foundation was laid for future design decisions should damping solutions become necessary. A decision was made by Meriton, as developer, to shape the fire hydrant tanks to act as tuned liquid dampers to provide an added level of amenity over and above the stipulated criteria, understanding that human sensitivity to building motion varies substantially from one person to another.

Cladding Pressures and Façade Optimisation

Windtech’s pressure study used 1,311 sensors on a 1:400 scale model tested under both Proposed and Future conditions. Data from 36 wind directions was weighted using long-term Bureau of Meteorology data.

Key findings:

• • • Highest peak suctions occurred at re-entrant corners, parapets, and exposed podium edges.
    • Rationalisation of cladding zones enabled targeted reinforcement with substantial material savings.
    • Design envelopes for glazing, balustrades, and fixing systems were tailored to meet strength and serviceability criteria.

Windtech also used surface pressure coefficients to calculate annual mean pressures on HVAC vents and assess paver uplift. These coefficients fed into the stack effect analysis and informed waterproofing detailing.

Pedestrian Wind Comfort

Wind environment testing targeted the ground plane, podium, and balcony zones. Gust velocities were compared to thresholds for seating, standing and walking comfort.

Wind mitigations included strategic placement of screens, planting as well as positioning of pergolas and gazebos on the podium. In addition, vertical blade walls were introduced for the colonnade and porous screening on sections of the podium enclosing the car parking areas. These interventions were validated by comparative re-testing.

Stack Effect and Vertical Pressure Management

Windtech modelled the stack effects generated under the 99-percentile extreme winter and summer temperatures and with the corresponding high and low wind conditions. Stack effect study identified pressures exceeding the 50Pa capacity of the lift doors at the top floor of the shorter tower (Level 76) as well as a wind entry issue for the entry to the taller tower from podium (Level 6).

For Level 76 of the shorter tower, pressures were mitigated by eliminating lift doors and providing stair access from Level 75 to the private rooftop terraces. Wind entry issues at the entry to the taller tower from the podium were resolved using a canopy and side screens.

Roof Equipment and Paver Uplift Analysis

Windtech assessed local uplift of the proposed pedestal paver tiles, accounting for the partial pressure equalisation of the proposed paver system (referring to Windtech’s library of its own full-scale test data). The report recommended that the 600×600-20mm pavers (cavity depths ranges from 25mm to 130mm) be interconnected in groups of at least 2 x 3 to be able to resist uplift.

Wind Noise Assessment

A comprehensive wind noise review was undertaken, examining potential noise from louvres, breeze walls, and balcony screens. Recommendations were made for the internal partition walls and internal doors to avoid them generating noise during high wind event. Minor design changes were proposed to the balcony screen arrangements to prevent Helmholtz resonance.

Integrated Outcomes and Design Impact

Windtech’s holistic approach has resulted in a high-quality, integrated and efficient design:

• • • Structural efficiency through aerodynamic optimisation;
    • Façade resilience through targeted strengthening in areas where it is needed.
    • Comfort optimisation with early design interventions to avoid costly and time-wasting redesign;
    • Address all details of wind related design risks before they occur: from wind noise to paver lift-off.
    • Reliable vertical system performance year-round.

Conclusion

Windtech’s contribution to the Cypress Avenue Towers underscores the value of comprehensive, high-quality, integrated wind engineering. Across structural, façade, mechanical, and environmental comfort domains, Windtech’s unmatched depth of experience and rigorous testing enabled a high-quality design outcome.

This performance-based approach reduced conservatism, improved buildability, and enhanced the occupant experience. The Cypress Avenue Towers exemplify how tall buildings can be designed not just to resist wind, but to provide a positive all-around experience for the occupants.

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