- Minimise the amount of building materials needed
- Increase the saleable floor space
- Reduce unnecessary costs and risks
- Get Planning Applications (i.e. DA, MCU, EIS, ERA) approved faster
- Ensure a reliable design that offers occupancy comfort and structural safety.
Watch Vipac being interviewed by Channel 9 News, highlighting the importance of Wind Engineering as buildings become taller and conditions windier.
Vipac’s state-of-the-art facilities
- Two open-circuit boundary layer wind tunnels where natural wind is simulated for environments that range from open country to city centres.
- An onsite model and fabrication centre where we make models of your development and surrounding area, typically at a scale of 1:400.
What tests do we offer?
- Wind conditions for public safety in outdoor areas
- Other analyses based on the Australian Wind Standard AS/NZS 1170.2:2011 for wind loads on buildings and structural response
- Desktop natural ventilation assessments.
Wind tunnel testing
- Wind conditions for public safety in outdoor areas on pedestrian levels around the building
- Wind-induced structural response and cladding loads imposed on the building and its dynamic response to them
- Structural vibrations
- Optimal locations of ventilation inlets and exhausts
- Dispersal and concentrations of pollutants expelled from the building
- Building internal flows and natural ventilation
- Full scale building component assemblies, e.g. perforated plate, architectural features, etc.
- Wind driven rain
- Wind noise
- Car park ventilation
Car Park Ventilation
The need for car park ventilation stems from two key concerns: controlling carbon monoxide (CO) from engine exhausts and smoke from a fire. The concentrations of both these types of contaminants can be evaluated using Vipac’s methods to help optimise the natural ventilation system.
Carbon monoxide is an issue compounded when the car is idling or moving at low speed after having been started from cold. Through Boundary Layer Wind Tunnels and Vipac’s algorithms, our Wind Engineering Group provides expert evaluations of their effect on the overall emission into the space. For wide area and background pollutant evaluations, see our Air Quality page.
Working hand-in-hand with the project’s traffic engineers and the design team, Vipac also offers professional design assistance for the performance of naturally ventilated, conventionally (mechanically) ventilated, and newer hybrid systems, including fan-only (and ‘impulse’) systems. Our analysis considers:
- Whether the car park is elevated or underground
- Whether it’s a single or multiple compartment
- What the floor plan and details of the layout are
- Whether there are ventilation or access openings
- Whether there are ducted or free supply and exhaust locations
- The nature of any recirculation devices
- Whether there’s any spill of air from adjacent spaces
- Management operation of the monitoring and control systems
Best Industry Practice
Vipac applies a range of codes and standards related to acceptable levels of CO concentrations in the air, these might be 400 parts per million (ppm) over a minute, 60 ppm over an hour, and 30 ppm over an eight hour average.
The Vipac Difference – Using Intelligent Design to Improve Performance
There are two types of design methods for National and International standards – namely ‘deemed to comply’ (bespoke) and ‘performance’. While a bespoke method may nominate permanent wall openings to provide cross flow ventilation, anticipated performance method is applied through simulation, known as fluid flow analysis. This method assists designers achieve performance over larger area car parks, at lower capital cost, and with less operational energy than for bespoke design systems.
Step 1: Desktop Study
A good initial step to evaluate candidate layouts, understand potential complications and incorporate recommended design alterations, a Desktop Study is based on experience, previous studies and a literature survey. For simple cases, a Desktop Study may be sufficient to evaluate the car park ventilation.
Step 2: Wind Tunnel Study
To grasp the fullest possible picture on pollutant dispersion, a Wind Tunnel Study is recommended. It provides the most comprehensive information on pressure distribution on the façade that, once integrated with the local wind climate, allows Vipac to predict the average air changes achievable for a particular design.
Other Considerations and Influences
- Nearby and neighbourhood buildings that interact with the local wind flows
- Exit vs entry movements
- Keeping the aircon running
- Proportion of diesel vs petrol engines
- Fleet mix (range of engine size)
- Travel distances (find a spot, distance to exit)
Design Pressure Analysis
Design Pressure Analysis refers to the wind testing of scale models that is used to determine wind-induced facade cladding pressure loads.
Who benefits from Design Pressure Analysis?
- Larger developments
- Structures with an unusual form
- Buildings with an unusual wind exposure
Why is Design Pressure Analysis important?
Without scale model wind tunnel testing, wind loads cannot be estimated accurately due to the randomness inherent in turbulent flows. Conservative load estimates can lead to higher structural costs by requiring glazing., cladding and associated structures to be of thicker gauge than necessary. Conversely, less rigorous load estimates may lead to structural failure.
Cladding pressure studies can lead to effective natural ventilation, improved air quality, reduced reliance on fan power and energy savings. Results can be used to determine optimal air inlet and exhaust locations.
Wind pressures at local points (e.g. at one sheet of cladding) can vary significantly from those experienced by the underlying structure (i.e. the sub-framing, the trusses and columns). Wind tunnel testing can assist to determine these localised and overall loads to an accuracy unobtainable from standard based analyses.
Furthermore, Vipac’s engineers have developed a technique to successfully harness facade pressures for the natural ventilation of single-sided apartments (on a double-loaded corridor).
Large buildings like airport hangars, stadium grandstands and warehouses can all experience substantial differences between the local maxima- that is, the points of maximum pressure – and the underlying structural loads. These areas are specially related to the details of the edge treatments. In one building, Vipac’s engineering consultants saved 100 tonnes of steel in the roof by carefully controlling the edge conditions.
Structural Wind Tunnel Testing
Whether you’re a structural engineer, an architect, a planner or a construction engineer, Vipac’s Wind Tunnel Testing can help you determine the following dynamic properties of the building:
- Overturning moments
- Equivalent static load on towers.
Vipac’s prediction process considers all wind directions, thereby providing all of the wind load values needed to inform the structural design and potentially save significant structural engineering costs.
Combined with the data provided by structural engineers, our Wind Tunnel Test results offer a thorough understanding of the building’s dynamic behaviour, including any acceleration experienced by occupants caused by the building moving in the wind. Preventing this perceived motion is important both for code compliance and occupant comfort.
Results from our Wind Tunnel Tests enable us to assess whether additional dynamic controls, such as a damping system, is required. If so, we can offer services for dynamic control design and for monitoring the building in operation.
Why does it move?
There are two main types of wind forces on a structure – the first is the force measured along the wind direction and the second is its cross-wind response. Problems can occur if the regular frequency of the cross-wind vortex shedding coincides with the natural frequency of the structure.
Contrary to popular belief, wind can be problematic at low speeds (5 – 20 m/s) for this very reason. Testament to this is the famous failure at the Tacoma Narrows Bridge in Washington D.C. at only 18 m/s. In non-cyclonic areas, ‘design’ wind speeds are around 40m/s and in cyclonic or typhoon areas up at about 60m/s.
The Australian wind codes are some of the most developed in the world. They set guidelines by which buildings may be judged as candidates deserving ‘dynamic analysis’ or special wind tunnel testing. For these wind sensitive structures, it is an Australian code requirement that analysis be carried out to check for excessive response or for incipient instability. We can conduct wind tunnel testing on these buildings using a High Frequency Force Balance technique.
Approved by the ASCE and the AWES, the Force Balance Method measures the forces and the moments that are experienced by the building. This data is combined with the structural properties of the building to determine the dynamic response (motion) of the structure when subjected to these incoming forces.
Calculation results are floor-by-floor predicted forces, moments and building motions under service and ultimate wind conditions. Reworking after changes to the building properties is quick since the outside envelope of the building remains constant.
Wind Impact Assessment
Most medium to large scale developments require wind analyses that address comfort within amenities and surrounding adjacent land. For some, a desktop assessment may be sufficient. However, to meet criteria set by relevant authorities and to pursue the highest level of accuracy, testing in the wind tunnel is ideal. Especially if a development has any of the following:
- A unique shape
- Unpredictable wind exposures
- Complex flow scenarios and wind loads
- Predicted flow conditions that are well in excess of the recommended criteria.
Comfortable and safe conditions
For many of us, the wind conditions around a building are only noticeable when they’re unfavourable. Combining state-of-the-art technology with some of Australia’s best engineering minds, Vipac’s wind tunnel tests can help you understand the wind environment under a wide range of conditions and directions.
Wind tunnel testing enables an optimisation of shapes, surfaces, and protrusions with two major benefits; enhancing safety and comfort, and maximising design. Other capabilities include:
- Quickly verifying the effectiveness of design modifications for wind control are
- Polar plotting results from single-point data
- Detailed information on wind speeds at all locations around the development
- Flow visualisation and omni-directional wind speed sensor measurements.
After testing is complete, our wind engineers present the final report and work closely with the design teams to explain the wind effects and interactions observed. We interpret the data and help these teams incorporate the observations back into their designs — thereby maximising value. One notable example was on Lilli Apartments in Melbourne, where Vipac’s advice led to natural ventilation of the interior spaces, reducing the reliance on air-conditioning and reducing occupants’ energy bills.
Our team of experienced wind engineers can determine what assessment is relevant to your development and deliver comprehensive reports to facilitate planning approval. We work hand-in-hand with the design team to suggest controls and treatments that maintain the intent of the architect’s objectives.
Wind-driven rain is rain affected by the wind such that it does not fall straight down. It is considered one of the main sources of moisture penetrating building façades, adversely affecting their performance and durability. Wind-driven rain assessments help companies save thousands on building-related costs and maximise the use and profitability of public areas through pedestrian comfort.
Vipac’s analysis of wind-driven rain and its effects on façades and pedestrians rely on a detailed study of meteorological data as well as an understanding of the wind flow patterns around the site. The effects of local architecture are also considered to determine the rain protection offered by the shelter.
Vipac uses two methods within its analysis; experimental and empirical:
- Full-scale on-site measurements
- Full-scale wind-tunnel testing of products
- Reduced-scale wind-tunnel measurements.
- Wind-driven rain index
- Wind-driven rain maps
- Wind-driven rain relationship.
Wind noise can be generated at screens, gaps, openings, edges and slots, or even inside buildings. They are often airborne whistles, roars and whines, which are likely to annoy occupants.
Structure Borne Response
Some structure-borne vibrations can be caused by wind’s effect on building attachments such as fins, blades, screens and masts. They sound like hums, engines or are more felt than heard. These can be the more dangerous since the forces can be large and component metal fatigue is a real possibility.
Mostly occurring under large roofs, but also where metal facades or metal components of facades (e.g. sun louvres) are attached to the structure.
Vipac’s Desktop Study determines the expected wind-induced noise, saving you re-installation and redesign costs, while the Wind Tunnel allows for full-scale measurement of building components to determine the expected decibel level for various wind directions. In one notable case, Vipac was commissioned to advise on the wind noise generated by attachments on the building facade of a public hospital, which led to a disturbance for patients trying to recover.