final report - city of ryde · final report wind assessment for: 11 talavera road macquarie park,...

FINAL REPORT

Wind Assessment for:

11 TALAVERA ROAD

Macquarie Park, Australia

Prepared for:

Donald Cant Watts Corke

Level 1, 14 Martin Place

Sydney

NSW 2000

Prepared by:

Thomas Evans, Project Engineer

Adam van Duijneveldt, Project Engineer

Graeme Wood, Director

February 2017

CPP Project: 9961

February 2017 11 Talavera Road CPP Project 9961

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DOCUMENT VERIFICATION

Date Revision Prepared

by Checked

by Approved

by 09/12/16 Initial release for review TXE AVD GSW 20/01/17 Updated drawings TXE GSW GSW 01/02/17 Updated drawings AVD GSW GSW

TABLE OF CONTENTS

Introduction ................................................................................................................................................... 2 Sydney Wind Climate ................................................................................................................................... 3 Environmental Wind Speed Criteria ............................................................................................................ 4 Environmental Wind Assessment ................................................................................................................ 5 Conclusions .................................................................................................................................................... 9 References ...................................................................................................................................................... 9

TABLE OF FIGURES

Figure 1: Location of the proposed development (L), Aerial view of site (R) (Google Earth, 2016) ........ 2 Figure 2: Architectural drawing of proposed development viewed from the north ................................ 2 Figure 3: Wind rose of direction and speed for Sydney Airport ................................................................ 3 Figure 4: Flow visualisation around a tall building .................................................................................... 4 Figure 5: Lower ground (T) and upper ground (B) floor plan of proposed 11 Talavera Road

development .................................................................................................................................. 6 Figure 6: Rooftop plan of proposed 11 Talavera Road development ........................................................ 8

TABLE OF TABLES

Table 1: City of Ryde DCP (2014) wind criteria ........................................................................................... 5


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Introduction

Cermak Peterka Petersen Pty. Ltd. has been engaged by Donald Cant Watts Corke to provide an

opinion based assessment of the impact of the proposed development at 11 Talavera Road, Macquarie

Park, on the pedestrian level local wind environment in and around the proposed development.

The site is located in the Macquarie Park development area, approximately 12 km to the north

west of the Sydney CBD. The site is bounded by Lane Cove Road and Talavera Road, and sits toward

the top of a ridge overlooking the Lane Cove river to the north, Figure 1. The focus of this assessment

is a new commercial building approximately 45 m in height (10 storeys) with a rectangular planform.

An indicative drawing is shown in Figure 2.

Figure 1: Location of the proposed development (L), Aerial view of site (R) (Google Earth, 2016)

Figure 2: Architectural drawing of proposed development viewed from the north

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Sydney Wind Climate

To enable a qualitative assessment of the wind environment, the wind frequency and direction

information measured by the Bureau of Meteorology at a standard height of 10 m at Sydney Airport

from 1995 to 2015 have been used in this analysis, Figure 3. It is noted from Figure 3 that strong

prevailing winds are organised into three main groups which centre at about north-east, south, and

west. This wind assessment is focused on these prevailing strong wind directions.

Strong summer winds occur mainly from the south quadrant and the north-east. Winds from the

south are associated with large synoptic frontal systems and generally provide the strongest gusts

during summer. Moderate intensity winds from the north-east tend to bring cooling relief on hot

summer afternoons typically lasting from noon to dusk. These are small-scale temperature driven

effects; the larger the temperature differential between land and sea, the stronger the breeze. The site

location is further inland than Sydney airport, so the local strength of the winds from the north-east

would be lower than measured at the airport.

Winter and early spring winds typically occur from the south and west quadrants. West quadrant

winds provide the strongest winds affecting the area throughout the year.

Figure 3: Wind rose of direction and speed for Sydney Airport


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Wind Flow Mechanisms

When the wind hits a large isolated building, the wind is accelerated down and around the

windward corners, Figure 4; this flow mechanism is called downwash and causes the windiest

conditions at ground level on the windward and sides of the building. In Figure 4 smoke is being

released into the wind flow to allow the wind speed, turbulence, and direction to be visualised. The

image on the left shows smoke being released across the windward face, and the image on the right

shows smoke being released into the flow at about third height in the centre of the face.

Figure 4: Flow visualisation around a tall building

Techniques to mitigate the effects of downwash winds on pedestrians include the provision of

horizontal elements, the most effective being a podium to divert the flow away from pavements and

building entrances. Awnings along street frontages perform a similar function and the deeper the

horizontal element generally the more effective it will be in diverting the flow.

Channelling occurs when the wind is accelerated between two buildings or along straight streets

with buildings on either side.

Environmental Wind Speed Criteria

It is generally accepted that wind speed and the rate of change of wind velocity are the primary

parameters that should be used in the assessment of how wind affects pedestrians. Over the years, a

number of researchers have added to the knowledge of wind effects on pedestrians by suggesting

criteria for comfort and safety. Because pedestrians will tolerate higher wind speeds for a smaller

period of time than for lower wind speeds, these criteria provide a means of evaluating the overall

acceptability of a pedestrian location. A location can further be evaluated for its intended use, such as

for an outdoor café or footpath.

WindWind

High Velocity zone


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The current City of Ryde Development Control Plan (2014) specifies that new developments in

the Macquarie Park corridor are not to create uncomfortable or unsafe wind conditions, and are not to

produce an increase in wind speed from existing conditions unless the increase remains within

acceptability criteria for the intended use of the space. The criteria are given in terms of weekly gust-

equivalent mean wind speeds and annual gust wind speeds, and are outlined in Table 1.

Table 1: City of Ryde DCP (2014) wind criteria

Area Classification Maximum Weekly

Wind Speed

Maximum Annual

Gust

Outdoor dining areas, amphitheatres etc 3.5 m/s 10 m/s

Main retail centres and retail streets, parks, communal recreational areas

5.5 m/s 13 m/s

Footpaths and other pedestrian accessways 7.5 m/s 16 m/s

Infrequently used laneways, easements, private balconies

10 m/s 23 m/s

The wind speeds associated with the Maximum weekly wind speed are based on the work of

Davenport (1972) and is for a one hour mean for 5% of the time. A one hour event in a week, occurs

for about 0.6% of the time hence the description is misleading. Over 8 hours per week would be

required to occur for 5% of the time for a week, or about 4 hours if only looking at daylight hours.

The description in the DCP is therefore not clear. The serviceability criteria are based on an

integration of the wind conditions for all directions.

The maximum annual gust wind speed in the DCP are based on the work of Melbourne (1978),

with the directional 10 m/s level classified as generally acceptable for pedestrian sitting or long term

stationary activities to 23 m/s for pedestrian safety.

Environmental Wind Assessment

The building is to be located on the corner of Lane Cove and Talavera Road. The site is typically

surrounded by low rise buildings, the tallest being on the order of 5-6 storeys. The topography

immediately surrounding the site is predominantly flat, but descends steeply to Lane Cove River to

the north-east, causing the site to be relatively exposed to winds from the north-east. The proposed

development is of rectangular planform, with its broad face oriented parallel to Lane Cove Road,

Figure 5. There is a planned through-site link from the main Lane Cove entrance to the opposite side

of the building with doors on the north-west façade and the upper ground floor level, and through

sliding doors on the lower ground floor level to the open car park area, Figure 5. The existing

pedestrian walkways around the perimeter of the site would ideally achieve the rating for pedestrian

accessways in Table 1, while locations in the vicinity of retail tenancies would aim to achieve the

classification applicable to retail streets.


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Figure 5: Lower ground (T) and upper ground (B) floor plan of proposed 11 Talavera Road

development

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Winds from the north-east

The proposed development site is relatively exposed to winds from the north-east. Winds from

this direction will impinge normal to the north-east façade, generating a moderate amount of

downwash and accelerated flow around the north-west and north-east corners. The undercut design of

level 1 would be expected to slightly increase the wind speed at the building corners, which may be

undesirable for retail areas close to the north-east and north-west corners. Existing and planned

landscape planting close to the building, Figure 1(R) and Figure 5, would provide some protection for

pedestrians and could be used to discourage access close to the building corners where windy

conditions would be expected. For wind normal to the narrow face of the building, adding awnings or

other horizontal surfaces above street level would be expected to improve the wind amenity at the

base and corners of the building by redirecting a portion of the downwash away from the ground

plane. This would only be considered necessary if long-term stationary activities such as outdoor

dining are planned close to the building facades.

Winds from the south

Winds from the south will strike the development at an oblique angle, encouraging flow to pass

around the building envelope horizontally, thereby reducing downwash, and limiting the impact at

street level. Some flow will be channelled along the Lane Cove Road frontage, creating strong breezes

close to the building. Horizontal flow along the façade would be expected to expand into the entrance

passage creating slightly windy conditions inside the sliding doors. Significant existing and planned

landscaping is expected to provide additional protection to pedestrians along this frontage.

Winds from the west

The existing neighbouring building will provide some shielding from winds from the west. The

orientation of the proposed development will encourage horizontal flow along the upper portion of the

building façade. The exposed portion of the broad north-west face would be expected to produce

some downwash. Though the main western entrance is expected to be protected by the undercroft

design, conditions at the north corner of the proposed development would be expected to be windy as

the flow accelerates around this corner. Areas recessed from the building boundary are expected to

experience calmer conditions, and planned screening perpendicular to the façade will offer some local

protection to entrances.

Through-site link

Pressure-driven flow may occur inside the building when prevailing winds cause a pressure

differential between the south-east and north-west façades. In circumstances where there are

simultaneous building openings on both facades, air will move from the high to low-pressure areas via


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the through-site link and void areas, or from the south-east facade through the Lower Ground level car

park, Figure 5(T). The wind speed will be strongest at locations with small cross-sectional areas such

as doors and staircases, and extend up to 10-12 m from the narrowest section. Placing an airlock or

revolving door at the main entry, or alternatively placing porous vertical screens inside the entryway

would assist in preventing these flows from developing, particularly if sitting or dining areas are

planned in the vicinity of these entrances or along the flow paths.

Rooftop

Wind conditions on the rooftop terraces of buildings tend to be among the windiest found on or

around a building, due to their typically exposed nature to prevailing winds, and the acceleration of

flow over the building edge. The perimeter design of the rooftop terrace is good from a wind

perspective as there is likely to be a relatively calm area regardless of wind direction. Wind conditions

on the proposed rooftop terrace, Figure 6, would be considered to be classified as acceptable for

pedestrian standing. Depending on the intended use of this space, local amelioration such as vertical

screening around the perimeter may be of benefit.

Figure 6: Rooftop plan of proposed 11 Talavera Road development

Summary

Qualitatively, integrating the expected directional wind conditions around the site with the wind

climate, it is considered that wind conditions at the majority of locations around the site would be

classified as suitable for pedestrian standing under the City of Ryde serviceability criterion. Some

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locations close to the building corners would be expected to be classified as suitable for pedestrian

walking. All locations would be expected to pass the distress criterion.

Conclusions

Cermak Peterka Petersen Pty. Ltd. has provided an opinion based assessment of the impact of the

proposed development at 11 Talavera Road, Macquarie Park on the local wind environment. Our

summary assessment of the proposed development is as follows:

The proposed development is taller than the surrounding buildings, and will have an influence on

the local wind conditions, increasing the wind speed for some directions, and providing shelter for

others. On average, the wind conditions around the site would be expected to be similar to existing

conditions, with the pedestrian level wind environment for the majority of locations being classified

as suitable for pedestrian standing or walking, and all locations passing the distress criterion. If wind

conditions need to be improved for the intended use of the space, wind amelioration measures, such as

awnings, vertical temporary or permanent porous screens, or landscaping would be recommended for

areas close to the building facades and corners. Wind tunnel testing would be required to quantify the

advice provided herein.

References

City of Ryde, (2014), “Development Control Plan” Part 4.5: Macquarie Park Corridor.

Davenport, A. G., (1972), An approach to human comfort criteria for environmental wind conditions,

Colloquium on Building Climatology, Stockholm, 1972.

Melbourne, W.H., (1978), Criteria for environmental wind conditions, J. Industrial Aerodynamics, 3, 241-249.

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