RESPONSE TO DILGP LETTER, REF. DEV2017/846, D17/159138 DATED 27 JUNE 2017 PREPARED BY: ARUP
DATE OF ISSUE: 31.07.2017
REVISION: 4
DOCUMENT NO: ARP-RPT-HYD-PWD-00009 REVISION DATE DESCRIPTION 1 07.07.2017 Issued for review 2 13.07.2017 Issued for review 3 21.07.2017 Issued for review 4 31.07.2017 Final
Copyright 2017 © DBC 2017 This publication is subject to copyright. Except as permitted under the Copyright Act 1968, no part of it may in any form or by any means (electronic, mechanical, photocopying, recording or otherwise) be reproduced, stored in a retrieval system or transmitted without prior written permission. Enquiries should be addressed to the publishers. DESTINATION BRISBANE CONSORTIUM www.queenswharfbrisbane.com.au
Destination Brisbane Consortium for DILGP Queens Wharf Brisbane Response to DILGP Letter (DEV2017/846, D17/159138, dated 27 June 2017)
ARP-RPT-HYD-PWD-00009
Rev 4 | 31 July 2017
This report takes into account the particular instructions and requirements of our client. It is not intended for and should not be relied upon by any third party and no responsibility is undertaken to any third party.
Job number 247660
Arup Arup Pty Ltd ABN 18 000 966 165
Arup Level 4, 108 Wickham Street Fortitude Valley QLD 4006 GPO Box 685 Brisbane QLD 4001 Australia www.arup.com
Document Verification
Job title Queens Wharf Brisbane Job number 247660 Document title Response to DILGP Letter (DEV2017/846, File reference D17/159138, dated 27 June 2017) Document ref ARP-RPT-HYD-PWD-00009 Revision Date Filename ARP -RPT-HYD-PWD-00009_DOCX_1.docx Draft 1 07 Jul Description First draft 2017
Prepared by Checked by Approved by Dr. Tomoko Cecile Peille Name Jasvinder Opkar Shimamoto (RPEQ 18578)
Signature
Rev 2 13 Jul Filename ARP -RPT-HYD-PWD-00009_DOCX_2.docx 2017 Description Second draft
Prepared by Checked by Approved by Dr. Tomoko Cecile Peille Name Jasvinder Opkar Shimamoto (RPEQ 18578)
Signature
Rev 3 21 Jul Filename ARP -RPT-HYD-PWD-00009_DOCX_3.docx 2017 Description Third draft
Prepared by Checked by Approved by Dr. Tomoko Cecile Peille Name Jasvinder Opkar Shimamoto (RPEQ 18578)
Signature
Rev 4 31 Jul Filename ARP -RPT-HYD-PWD-00009_DOCX_4.docx 2017 Description Final for Issue
Prepared by Checked by Approved by Dr. Tomoko Cecile Peille Name Jasvinder Opkar Shimamoto (RPEQ 18578)
Signature
Issue Document Verification with Document
ARP-RPT-HYD-PWD-00009 | Rev 4 | 31 July 2017 | Arup J:\247000\247660-00 QUEENS WHARF\WORK\INTERNAL\DESIGN\CIVIL\FLOODING\02 REPORTING\05 REVIEWS\20170706 DILGP_EDQ\ARP-RPT-HYD-PWD-00009_DOCX_4.DOCX
Destination Brisbane Consortium for DILGP Queens Wharf Brisbane Response to DILGP Letter (DEV2017/846, D17/159138, dated 27 June 2017)
Contents
Page
1 Context 1
2 Responses to DILPG 2
3 Further Discussion 7 3.1 Brisbane River Catchment Flood Study (BRCFS) 7 3.2 Comparison with Existing Bridges 8 3.3 Modelling precision 9
4 Conclusion 9
Attachment 1 DILGP Letter, Ref. DEV2017/846, D17/159138 dated 27 June 2017
Attachment 2 Arup Memo, Ref. ARP-RPT-MAR-PWD-00004 dated 15 June 2016
Attachment 3 Email correspondence, Arup and WSP dated May 2016
ARP-RPT-HYD-PWD-00009 | Rev 4 | 31 July 2017 | Arup J:\247000\247660-00 QUEENS WHARF\WORK\INTERNAL\DESIGN\CIVIL\FLOODING\02 REPORTING\05 REVIEWS\20170706 DILGP_EDQ\ARP-RPT-HYD-PWD- 00009_DOCX_4.DOCX
Destination Brisbane Consortium for DILGP Queens Wharf Brisbane Response to DILGP Letter (DEV2017/846, D17/159138, dated 27 June 2017)
1 Context
This technical note has been prepared in response to the Department of Infrastructure, Local Government and Planning (DILGP) letter dated 27 June 2017 (Attachment 1) with regards to the Priority Development Area (PDA) application for the Queens Wharf Brisbane Integrated Report Development (QWBIRD). The Minister for Economic Development Queensland (MEDQ) requested that a Hydraulic assessment technical note be prepared in relation to flooding considerations; the letter states:
“The purpose of the requested Hydraulic assessment technical note is for EDQ to undertake an informed consideration of the practicality and implications for the proposed development to achieve a maximum of 10mm outside the PDA for all events up to and including the 1% AEP and 2011 event.”
This Hydraulic technical note should be read in conjunction with the Plan of Development (POD), Volume 3 – Attachment K – Hydraulic Assessment Report1. As a reminder, the hydraulic modelling indicates that the maximum increase in flood levels as a result of the QWBIRD is +17mm along Montague Road in West End, observed in a modelled 2011 design storm event and in a 1% AEP (Annual Exceedance Probability) storm. Modelling indicates that this location is sensitive to small increase in the river levels, i.e. in the order of 5-10mm.
1 http://www.dilgp.qld.gov.au/planning/development-assessment/priority-development- area-development-applications.html.
ARP-RPT-HYD-PWD-00009 | Rev 4 | 31 July 2017 | Arup Page 1 J:\247000\247660-00 QUEENS WHARF\WORK\INTERNAL\DESIGN\CIVIL\FLOODING\02 REPORTING\05 REVIEWS\20170706 DILGP_EDQ\ARP-RPT-HYD-PWD- 00009_DOCX_4.DOCX
Destination Brisbane Consortium for DILGP Queens Wharf Brisbane Response to DILGP Letter (DEV2017/846, D17/159138, dated 27 June 2017)
2 Responses to DILPG
For ease of reference, Sections 3 (a) to 3 (d) of the DILPG letter (attachment 1) are provided in blue text, with the corresponding responses in black text.
The Hydraulic assessment technical note shall assess potential mitigation options, which must include: a) Redesign of the proposed bridge pier and pile cap to reduce bridge head losses and therefore afflux. Whilst more challenging from a structural engineering viewpoint, the realignment of the pier component to the direction of flow is to be investigated.
The Redesign of the proposed central bridge pier and pile cap has already been discussed between Arup (the hydraulic modeller for DBC) and WSP (the bridge design engineer for DBC), upon request from Arup at various stages of the design. Attachment 2 provides a technical note prepared by Arup on the discussions regarding bridge pier flood afflux. Further email discussion dated May 2016 is also included in Attachment 3.
Prior to the design refinement, modelling was performed by Arup to better understand the contribution to flooding of each vertical component (main supporting piles, pile cap, upper supporting cap and superstructure). It was found that for all the modelled events, the supporting piles were the main contributor to the flood impact, in generating approximately 50% of the impact, with the pile cap and upper structure generating each 25% of the impact (the exact contribution depends on the event). It is important to note here that the numerical modelling is 2D-depth averaged and the form loss is distributed across the water column. Alternate numerical modelling including CFD and 3D modelling were discussed as a method to better evaluate the impact from the bridge and overcome the simplification of the 2D scheme. These approaches were deemed not suitable for this assessment as being non-traditional for the assessment of impact and likely to be rejected by the State reviewers.
Refinements of the central pier have been performed including:
- Realignment and streamlining of the main supporting piles arrangement (16x1500mm piles) in the direction of the flow. This involved a rotation of approximately 18 degree to reach optimum alignment. - Consideration and testing of a larger pier support element with a more hydrodynamic efficient shape. It was identified that a series of circular piers was in theory less ‘efficient’ from a hydrodynamic perspective than a larger pier, oval shape of the same footprint. A steel skirt was tested as a flood mitigation option, however due to lateral freeboard requirements and other structural restrictions, the subsequent improvement with regards to flood impact was found to be negligible. A larger single circular supporting pier was also tested instead of two rows of smaller piers; the improvement on flood impact was also negligible.
The outcome of various discussions was that the central bridge pier shape, size and configuration could not be further refined or redesigned whilst maintaining the architectural vision (June 2016).
ARP-RPT-HYD-PWD-00009 | Rev 4 | 31 July 2017 | Arup Page 2 J:\247000\247660-00 QUEENS WHARF\WORK\INTERNAL\DESIGN\CIVIL\FLOODING\02 REPORTING\05 REVIEWS\20170706 DILGP_EDQ\ARP-RPT-HYD-PWD- 00009_DOCX_4.DOCX
Destination Brisbane Consortium for DILGP Queens Wharf Brisbane Response to DILGP Letter (DEV2017/846, D17/159138, dated 27 June 2017)
Further analysis has been performed to investigate whether the bridge pier could be relocated closer to the river banks in a lower flood velocity zone, as illustrated in Figure 1 to Figure 3 below.
Figure 1: Velocity Magnitude and Pier Relocation, 2011 Flood event
Figure 2: Pier relocation investigation, 2011 Flood event (plan view)
Figure 3: Pier relocation investigation, 2011 Flood event (section views)
ARP-RPT-HYD-PWD-00009 | Rev 4 | 31 July 2017 | Arup Page 3 J:\247000\247660-00 QUEENS WHARF\WORK\INTERNAL\DESIGN\CIVIL\FLOODING\02 REPORTING\05 REVIEWS\20170706 DILGP_EDQ\ARP-RPT-HYD-PWD- 00009_DOCX_4.DOCX
Destination Brisbane Consortium for DILGP Queens Wharf Brisbane Response to DILGP Letter (DEV2017/846, D17/159138, dated 27 June 2017)
As a minimum, the bridge pier would need to be relocated 45m towards south bank. As stated by WSP and Grismshaw: ‘such relocation would upset the balanced nature of the spans, and may disrupt the concept to such an extent so as to require a complete redesign. The resulting out-of-balance will require significant ballast or tension foundations to be constructed at the South Bank end to act as a counter balance for the cable stayed main span. From an engineering perspective, this is not practicable due to significant constraints at the South Bank, including the Wheel of Brisbane, significant in-ground services, and the required clearances at Clem Jones Promenade - notwithstanding the significant costs associated with a less optimal design.
Any notable increase in the main span, will necessitate an increase in the height of the mast […]. Any increase beyond the current height of mast will further impact constructability; the current mast height maxes out construction access for available craneage, hence an alternative construction methodology may be required, which will may have more onerous temporary works requirements in the river during construction. Potential issues relating to controlled airspace would need to be investigated’.
The benefits of relocating the bridge pier with regards to flooding is estimated to be in the order of 4mm reduction in afflux.
The current position of the pier is deemed to balance the minimal hydraulic impacts with the architectural and structural design of the bridge while not compromising South Bank and the QWBIRD public realm.
b) Redesign of the proposed bridge to achieve a design with no central support pier. Please document any associated undesirable impacts on matters of public interest resulting from this option and estimate of additional costs
The Arup hydraulic model with the bridge pier removed (i.e. ‘no bridge’ configuration, or redesign of the bridge with no central pier) indicates that the 10mm impact criteria is achieved overall in this scenario and for all the events modelled.
Incorporating a bridge design with no pier would require a complete redesign from concept stage, with many restrictions on bridge typology that is able to be employed. As stated by WSP and Grimshaw: ‘the only practical solution would be to adopt a traditional arch bridge. The nature of a tied arch bridge (deck acts as a tie to resist arch trust forces) is feasible within the site constraints, as it would mitigate any intrusion into the public realm at South Bank and at the REX / IRD. It should be stressed that the option to eliminate the mid-river pier places such significant constraints on the structural design, that this decision must be viewed in an Urban Planning context; the Neville Bonner Bridge seeks to give a distinctive look to the family of bridges along the Brisbane River. It seeks to contribute to the projected goals and city shaping envisioned by Brisbane City Council (BCC). Grimshaw and WSP strongly maintain that a generic arch bridge would not be appropriate for the site context, and would simply not achieve the vision outlined by BCC.
ARP-RPT-HYD-PWD-00009 | Rev 4 | 31 July 2017 | Arup Page 4 J:\247000\247660-00 QUEENS WHARF\WORK\INTERNAL\DESIGN\CIVIL\FLOODING\02 REPORTING\05 REVIEWS\20170706 DILGP_EDQ\ARP-RPT-HYD-PWD- 00009_DOCX_4.DOCX
Destination Brisbane Consortium for DILGP Queens Wharf Brisbane Response to DILGP Letter (DEV2017/846, D17/159138, dated 27 June 2017)
c) A reduction in the extent of proposed land reclamation works in proposed Sub- precinct 1e The Landing
The Landing alignment has been already been optimised by Arup in collaboration with CUSP, the landscape architects for DBC, as part of the Design. An iterative process was undertaken whereby various landforms were tested using the Arup model. A range of landform with varying height, shape and alignment were input into the model to assess the results’ sensitivity to either of these parameters, in an effort to optimize the geometry with regards to hydraulic efficiency.
The final adopted Landing configuration was selected to ensure minimal contribution to the flood impact. Figure 4 shows the modelled 2011 flood event2 without the Landing (i.e. with the bridge, North Quay and Mangrove walk only). The criteria of 10mm set by DILPG is still exceeded; this means that further reduction in the extent of proposed land reclamation works would not reduce the flood impact to below the 10mm criteria.
d) Any other mitigation measures, including offsetting compensatory works above normal tidal influence.
There are no suitable mitigation measures that DBC can implement that does not result in the complete redesign of the bridge. Dredging, which had been identified as a potential flood mitigation option in the concept phase of QWBIRD, would provide satisfactory modelling outcome; however it is not supported by Arup and DBC as it is not considered a sustainable solution. The natural variation of the river bed bathymetry is not captured by the flood model, and more importantly, dredging has the potential to cause adverse environmental impact. More specifically, dredging of the Brisbane River has the potential to result in the suspension of very fine sediments that can be transported in the water column. These have the potential be reduce water quality, release contaminated material and be transported and deposited downstream from the site.
2 2011 hydrology including flood gates
ARP-RPT-HYD-PWD-00009 | Rev 4 | 31 July 2017 | Arup Page 5 J:\247000\247660-00 QUEENS WHARF\WORK\INTERNAL\DESIGN\CIVIL\FLOODING\02 REPORTING\05 REVIEWS\20170706 DILGP_EDQ\ARP-RPT-HYD-PWD- 00009_DOCX_4.DOCX
Destination Brisbane Consortium for DILGP Queens Wharf Brisbane Response to DILGP Letter (DEV2017/846, D17/159138, dated 27 June 2017)
Figure 4: ‘No Landing’ Scenario, 2011 Flood Event
ARP-RPT-HYD-PWD-00009 | Rev 4 | 31 July 2017 | Arup Page 6 J:\247000\247660-00 QUEENS WHARF\WORK\INTERNAL\DESIGN\CIVIL\FLOODING\02 REPORTING\05 REVIEWS\20170706 DILGP_EDQ\ARP-RPT-HYD-PWD- 00009_DOCX_4.DOCX
Destination Brisbane Consortium for DILGP Queens Wharf Brisbane Response to DILGP Letter (DEV2017/846, D17/159138, dated 27 June 2017)
3 Further Discussion
3.1 Brisbane River Catchment Flood Study (BRCFS) The DILGP letter also states:
“Alternatively, DBC may choose to incorporate the details of the Arup model into the Brisbane River Catchment Flood Study (BRCFS) hydraulic model (i.e. nest the Arup model into the BRCFS model) and run the above listed mitigation options in the nested BRCFS model”.
Arup does not recommend the use of the BRCFS model in this instance. The BRCFS has been developed for planning purposes and it covers a significantly greater extent of the floodplain compared to the Arup model. For that reason, it is based on a coarser grid size resolution (30m versus Arup’s model of 6m) to maintain reasonable simulation runtimes, as illustrated in Figure 5. A coarse grid size is not recommended for the analysis of flood impact from QWBIRD, as many design components are sub-grid scale (i.e. smaller than a 30m grid cell) and therefore will not be accurately represented in the model. In addition to this, the Arup model has been specifically re-oriented so that the grid is well aligned with the flow of the Brisbane River along the proposed development, to ensure the most robust technical approach to the modelling. The Arup model is also based on the latest BRCFS hydrology and it has been re-calibrated to ensure that flood levels are as close as possible to the BRCFS.
Due to the above mentioned coarseness of the BRCFS it is expected that it would exacerbate the flood impact from QWBIRD.
Figure 5: Model grid comparison
ARP-RPT-HYD-PWD-00009 | Rev 4 | 31 July 2017 | Arup Page 7 J:\247000\247660-00 QUEENS WHARF\WORK\INTERNAL\DESIGN\CIVIL\FLOODING\02 REPORTING\05 REVIEWS\20170706 DILGP_EDQ\ARP-RPT-HYD-PWD- 00009_DOCX_4.DOCX
Destination Brisbane Consortium for DILGP Queens Wharf Brisbane Response to DILGP Letter (DEV2017/846, D17/159138, dated 27 June 2017)
3.2 Comparison with Existing Bridges A comparison of the flood afflux from the QWBIRD proposed pedestrian bridge with other existing bridges is provided below for information only, as a request by DBC (Table 1). This is not intended to be interpreted as a justification of the impact from QWBIRD, but an indicator of the relative magnitude of the afflux with respect to existing Brisbane River bridges. Bridge affluxes have been compared in the immediate vicinity of the bridge. The comparison presented below does not apply to all points in space across the floodplain. The comparison shows that the QWBIRD pedestrian bridge has impacts of a similar magnitude to the bridges built in the last decade. Table 1: Flood afflux from various Brisbane bridges for the 2011 flood event, relative to QWBIRD pedestrian bridge (Source: BRCFS 2017)
Bridge Impact (relative to Year opened QWBIRD pedestrian bridge) Sir Leo Hielscher Bridge 10 times more impact 1986 Story Bridge 7 times more impact 1940 Captain Cook Bridge 11 times more impact 1972 Goodwill Bridge 4 times more impact 2001 Victoria Bridge 8 times more impact 1969 Kulripa Bridge 2 times more impact 2009 William Jolly Bridge 3 times more impact 1932 Merivale St Bridge 27 times more impact 1978 Go between Bridge 2 times more impact 2010 Eleanor Schonell (Green) Bridge same impact 2006 Jack Pesch Bridge 6 times more impact 1998 Indooroopilly Railway Bridge 6 times more impact 1957 Walter Taylor Bridge 6 times more impact 1936
ARP-RPT-HYD-PWD-00009 | Rev 4 | 31 July 2017 | Arup Page 8 J:\247000\247660-00 QUEENS WHARF\WORK\INTERNAL\DESIGN\CIVIL\FLOODING\02 REPORTING\05 REVIEWS\20170706 DILGP_EDQ\ARP-RPT-HYD-PWD- 00009_DOCX_4.DOCX
Destination Brisbane Consortium for DILGP Queens Wharf Brisbane Response to DILGP Letter (DEV2017/846, D17/159138, dated 27 June 2017)
3.3 Modelling precision Results have been interpreted to the nearest millimetre for this project upon request from the reviewers, who provided the following reasoning: ‘Defining the impact in millimetres is a relatively long standing (15-20 years) and accepted practice, particularly within the Planning and Environment Court of Queensland.’ (Extract from Letter dated 6 April 2017, BMT WBM acting on behalf of DILPG as technical reviewer).
There is, however, no formal guideline or industry standard that defines the acceptable flood impact or flood level precision.
In general Arup does not support the interpretation of flood results to the nearest millimetre, due to a number of factors such as: o Precision limitation of numerical modelling o Building floor levels generally not surveyed to the nearest millimetre o Water surface varying by more than a few millimetres during floods
The maximum impacted area is located along a section of Montague Road in West End; this area is already inundated by approximately 0.5 to 1m in the 1% AEP storm event. The FloodWise Property Report (Brisbane City Council) indicate that these properties were also flooded in the January 2011 event; it should be noted that results are reported to the nearest 100 millimetre. For this project, given that there are no additional buildings inundated as a result of QWBIRD and that the area of interest is already inundated, Arup recommends that flood results be rounded to the nearest centimetre, making the ‘no impact’ threshold tolerance 1cm instead of 10mm.
Upon this recommendation, around forty buildings have been identified to be impacted by more than 1cm of flood levels from QWBIRD. Floor levels would be required to identify the buildings’ flood immunity and assess potential damage; preliminary assessment indicate that these would be negligible.
4 Conclusion
Sensitivity analyses have been undertaken in modelling the QWBIRD site with respect to the bridge pier design and proposed land reclamation. The bridge pier configuration has been refined in the early stages of design in collaboration with WSP. It was concluded that the design cannot be further refined to satisfy the 10mm flood impact criteria whilst maintaining the architectural vision and structural requirements of the bridge. The Landing reclamation alignment and configuration is currently deemed optimal with regards to flood impact.
There are currently no official guidelines regarding the precision of flood modelling results, which suggests that there should be more deliberation on these technical points. The reporting of flood levels to the nearest centimetre instead of nearest millimetre is recommended.
ARP-RPT-HYD-PWD-00009 | Rev 4 | 31 July 2017 | Arup Page 9 J:\247000\247660-00 QUEENS WHARF\WORK\INTERNAL\DESIGN\CIVIL\FLOODING\02 REPORTING\05 REVIEWS\20170706 DILGP_EDQ\ARP-RPT-HYD-PWD- 00009_DOCX_4.DOCX
Attachment 1
DILGP Letter, Ref. DEV2017/846, D17/159138 dated 27 June 2017
Attachment 2 Arup Memo, Ref. ARP-RPT- MAR-PWD-00004 dated 15 June 2016
File Note
Level 4, 108 Wickham Street t +61 7 3023 6000 Fortitude Valley f +61 7 3023 6023 QLD 4006 GPO Box 685 Brisbane QLD 4001 Australia www.arup.com Project title Queen Wharf Brisbane Job number 247660 cc Jeroen Devos, Katrina Face, Jeremy Skues, Kevin File reference Winward, Adam Read, Mike Straughton, Jasvinder ARP-RPT-MAR-PWD-00004 Opkar Prepared by Cecile Peille Date 15 June 2016 Subject Bridge Pier Flood Afflux si
1 Context
The Destination Brisbane Consortium (DBC) is developing the Queens Wharf project on the banks of the Brisbane River in the Brisbane CBD. The development includes a pedestrian bridge across the Brisbane River, a two span structure connecting the main tower with Southbank, and supported by one central pier in Brisbane River. Arup has carried out hydraulic modelling based on inputs provided by WSP. The modelling results indicate that the current configuration of the bridge - as for 15/06/2016 - results in a flood afflux that is beyond the acceptable criteria set by the relevant State authorities for this project (EDQ and DILPG). It should be noted that the current criteria is stricter than for previous developments following the recent 2011 flood events that occurred in Brisbane.
2 Bridge Pier Impact on Flooding
2.1 Initial Flood Afflux Estimate A desktop calculation of the bridge afflux has been performed using the theory set out in the Hydraulics of Bridge Waterways, FHWA, Bridge Division (1978) – see ‘expression for computation of backwater”. This theory is based on laboratory and field measurements and it is still to date the most comprehensive method for the estimate of bridge flood afflux. Assuming a simplified case of two supporting rows of 1.2 diameter circular piles (i.e only piles and no pier cap) aligned with the flow, the calculated far field afflux is in the order of 2cm in a 2011 flood event. In conjunction with the remainder of the pier design, the Landing, the North Quay area and the walkway, this exceeds the flood impact criteria set by the State authorities (3cm within river banks, 1cm on developed land). Note: The bridge deck and superstructure have been excluded from the analysis since the soffit level is higher than the 2011 flood event considered (zero impact in any events lower than 0.05% AEP).
\\GLOBAL.ARUP.COM\AUSTRALASIA\BNE\PROJECTS\247000\247660-00 QUEENS WHARF\WORK\INTERNAL\DESIGN\CIVIL\FLOODING\02 REPORTING\04 OTHER - TECHNICAL NOTE\ARP-RPT-MAR-PWD-00008[1].DOCX
Arup | F0.15 Page 1 of 4
File Note
247660 15 June 2016
2.2 Modelling Assumptions and Considerations The above quantification is an estimate only of the far field afflux across the entire river section (i.e. once the afflux is balanced over the entire section). Other hydrodynamic processes would in reality influence the propagation of the impact and afflux magnitude. Several tests have been performed by Arup using the ‘QWB-Stage 1’ model1 adopted by the State for this assessment; it was found that the key factors influencing the flood impact results are: 1. Bridge general arrangement and pier configuration (design inputs from WSP) 2. Pier representation in the model (Arup responsibility) 3. Model resolution grid size (Arup responsibility) 4. Remainder of the development representation in the model (Arup responsibility) Items 2, 3, and 4 have been optimized by Arup by assessing several ‘scenarios’. The most suitable configuration will be used in the next iteration of model runs. The model is considered suitable for this application, and although other modelling techniques have been considered these are not recommended in this instance due to the following timing and technical considerations: - a 3D flexible mesh model would not capture the vertical variation of the pier shape (3D terminology can be misleading); - a CFD model would require significant computational effort and as such, afflux could only be estimated in the near field over a small area centred on the pier. The results would then need to be added to the overall ‘QWB-Stage 1’ model afflux from the remainder of the development. This approach is likely to be rejected by the State reviewers as non-standard. - Any new model would need to be verified and calibrated to historical events and would need to be reviewed by the State authorities for use in his assessment; the timing of which would delay Stage 1 application and approvals.
2.3 Pier orientation and configuration Discussions were held between WSP, DBC and Arup on the bridge pier configuration on the 14/06/2016. Arup recommends that further considerations on pier configuration be given at this stage of the development, in particular to minimise the inefficiencies from a hydrodynamic perspective which causes greater drag and form loss coefficient.
Overall the afflux from a bridge pier is mainly influenced by:
1 Refer to POD Volume 3 Attachment K: Hydraulic Assessment Report
\\GLOBAL.ARUP.COM\AUSTRALASIA\BNE\PROJECTS\247000\247660-00 QUEENS WHARF\WORK\INTERNAL\DESIGN\CIVIL\FLOODING\02 REPORTING\04 OTHER - TECHNICAL NOTE\ARP-RPT-MAR-PWD-00008[1].DOCX
Arup | F0.15 Page 2 of 4
File Note
247660 15 June 2016
The arrangement and type of piers; for instance a large pier element with a hydrodynamic efficient shape may result in less drag coefficient than that of a group of piles with a smaller footprint. The total area of piers projected to the main direction of the flow; drag force is reduced on piers that are shielded. Thus the orientation of the pier at a skew is far less efficient than the pier being either perpendicular or parallel with the flow, latter being the most efficient from hydraulic perspective. The flood velocity; this parameter varies depending on the event considered. In this instance the flood velocity of 3m/s needs to be considered for the location, in a 2011 modelled flood event. The afflux being a function of the squared velocity, the location of the pier within the river has significant influence on its associated impact (higher velocities are occur in the centre of the river).
We understand that non-aligned raked piles are also being considered as a potential structural solution needed to achieve vessel load impact requirements. This will further exacerbate the afflux issues. In order to facilitate this Stage 1 objective with regards to flooding approval, we suggest that this approach be revisited and other alternatives to deal with the ship impact considered (i.e. consider plastic and elastic structural analysis).
3 Proposed Action
Arup proposes the following alternatives in order to resolve the current issue: (1) WSP: Minimize the afflux from the proposed bridge as much as possible using streamlined piers and/or hydrodynamic efficient shape. Pier orientation, pier general arrangement (eg location and number of), as well as configuration of the piles should be reviewed and revised. (2) Arup: Use ‘QWB-Stage 1’ flood model to re-assess the overall impact from the development using the revised bridge pier design. Please note that modelling simulations take up to 3 days depending on the event modelled; therefore careful consideration should be given to the dimensions and arrangement provided. (3) Arup / DBC: Arrange a meeting with EDQ and DILPG to refine the flood impact tolerance criteria, specifically discuss the criteria for extreme events when large velocities occur and propose a refined criteria based on relative increase in flood levels versus flood depth. A ‘lower and upper bounds’ approach could be considered, i.e. Arup could provide the minimum pier design requirements to achieve the flood impact criteria. However this approach is not deemed suitable considering the timing constraints for approval; it is preferred and suggested that WSP propose an alternative design that is more efficient hydraulically and that still meets all the other requirements and constraints.
\\GLOBAL.ARUP.COM\AUSTRALASIA\BNE\PROJECTS\247000\247660-00 QUEENS WHARF\WORK\INTERNAL\DESIGN\CIVIL\FLOODING\02 REPORTING\04 OTHER - TECHNICAL NOTE\ARP-RPT-MAR-PWD-00008[1].DOCX
Arup | F0.15 Page 3 of 4
File Note
247660 15 June 2016
4 Relevant Design References
The below criteria are recommended for consideration in the refinement of bridge pier configuration:
1. TMR Design Criteria for Bridges & Other Structures (August 2014), Clause 3.12.2 (b): Piles and abutments shall be aligned with the expected flood flow directions. If at bed level, pile caps shall be detailed to provide minimum disturbance to the flow. 2. TMR Bridge Scour Manual (March 2003), Clause 2.4.6: Align piers with the direction of flood flows. Assess the hydraulic advantages of circular piers, particularly where flood patterns are complex and change with flood stage. 3. AS5100.2-2004, Clause 15, Forces from Water Flow: The Drag and Lift forces on piers from water flow (calculated through Cl. 15.3.1 & 15.3.2) are greatly increased with the extent of area exposed to the flow. 4. Navigational Clearance requirements (design approval from MSQ currently pending)
DOCUMENT CHECKING Prepared by Checked by Approved by
Name Cecile Peille Aida Bartels Jasvinder Opkar
Signature
\\GLOBAL.ARUP.COM\AUSTRALASIA\BNE\PROJECTS\247000\247660-00 QUEENS WHARF\WORK\INTERNAL\DESIGN\CIVIL\FLOODING\02 REPORTING\04 OTHER - TECHNICAL NOTE\ARP-RPT-MAR-PWD-00008[1].DOCX
Arup | F0.15 Page 4 of 4
Attachment 3 Email correspondence, Arup and WSP dated May 2016
From: Cecile Peille To: Cecile Peille Subject: OveArup-CADV-000189: Fwd: Pedestrian Bridge Configuration ACNXREF
You have received a new Consultant Advice: OveArup-CADV-000189
Project: Queens Wharf BNE Type: Consultant Advice Mail Number: OveArup-CADV-000189 To: Cecile Peille, Arup Group From: C Peille, Arup Group Sent: 12/07/2017 6:33:34 AM WST (GMT +08:00) Attribute 1: Structural Attribute 2: Pedestrian Bridge Attribute 3: Z – Not Building Specific Status: N/A Subject: Fwd: Pedestrian Bridge Configuration
From: C Peille Sent: 26/05/2016 12:56:30 PM WST (GMT +08:00) To: Cecile Peille, Peter Hindmarch Cc: Jasvinder Opkar, Mike Straughton, Jeroen Devos, Katrina Face, Jeremy Skues, Cameron Ritter, Neil Stonell, Sajith Khan, Kevin Winward Mail Number: OveArup-GCOR-000058 Subject: Pedestrian Bridge Configuration
Hi Peter,
We have undertaken several testing using our model and we can now confirm that the pedestrian bridge pier is the element of design that leads to the greatest flood impact. If the pier is not aligned with the flow, or if the pier is wider than 5m, the resulting flood impact is above the tolerance criteria set by EDQ; this is because the pier is located in the middle part of the river where high velocity fields occur during a flood.
We understand that this is a work in progress and that the bridge configuration is subject to changes; therefore as part of this process we wanted to highlight the below criteria:
1. TMR Design Criteria for Bridges & Other Structures (August 2014), Clause 3.12.2 (b): Piles and abutments shall be aligned with the expected flood flow directions. If at bed level, pile caps shall be detailed to provide minimum disturbance to the flow.
1. TMR Bridge Scour Manual (March 2003), Clause 2.4.6: Align piers with the direction of flood flows. Assess the hydraulic advantages of circular piers, particularly where flood patterns are complex and change with flood stage.
1. AS5100.2-2004, Clause 15, Forces from Water Flow: The Drag and Lift forces on piers from water flow (calculated through Cl. 15.3.1 & 15.3.2) are greatly increased with the extent of area exposed to the flow.
On another note and in relevance to the above, consultation with Maritime Safety Queensland (MSQ) is recommended to review the central pier configuration as it is currently not aligned with the adjacent bridges (Victoria and Goodwill Bridge) which may impact on vessel navigation. From our experience in designing bridges in Brisbane CBD, navigation safety and flood impacts are two important criteria to be assessed.
From our ends, the modelling of the bridge requires a lot of computational effort and time. Therefore we would like to lock in its concept as early as possible. If you could keep us advised on configuration changes, whether it comes from MSQ for navigation safety or for architectural purposes, this would be great.
At this stage, we also intend to propose a new bridge configuration supported with 2 piers closer to the banks as a flood mitigation option (which results in less afflux). We understand the impact this would have on the architectural vision, so this is for consideration only, mainly to inform all parties on the Brisbane River hydrodynamics sensitivity.
In terms of levels as requested by Sajith: anything beyond 11.5m AHD does not interfere with our flood impact assessment (this is the 2000yr flood level + 300mm freeboard).
Please do not hesitate to contact me to discuss.
Regards,
Cecile Peille Civil Engineer | Transport and Resources
Arup Level 4 108 Wickham Street Fortitude Valley QLD 4006 Australia GPO Box 685 Brisbane QLD 4001 Australia t +61 7 3023 6282 m +61 434 877 807 www.arup.com
From: C Peille Sent: 03/05/2016 1:49:23 PM WST (GMT +08:00) To: Peter Hindmarch Cc: Jasvinder Opkar, Mike Straughton, Jeroen Devos, Katrina Face, Jeremy Skues, Cameron Ritter, Neil Stonell, Kevin Winward Mail Number: OveArup-CADV-000005 Subject: Re: Re: 2011 Flood Velocities at main pier
Hi Peter,
I am on annual leave this week.
I will get back to you early next week on this. I apologize for the delay.
Regards, Cecile
------
From: Mr Peter Hindmarch Sent: 02/05/2016 01:07:33 To: Cecile Peille Cc: Mr Kevin Winward, Mr Neil Stonell, Mr Cameron Ritter, Mike Straughton, Mr Jasvinder Opkar, Mr Jeremy Skues, Katrina Face, Mr Jeroen Devos Mail Number: WSPS-CADV-000043 Subject: Re: 2011 Flood Velocities at main pier
Cecile Can you please quantify the effect of the mid river pier at 18 degree to the stream flow and parallel to the stream flow. This will help the bridge team to evaluate the various options for this pier considering other parameters such as aesthetics, costs etc.
Regards, Peter Hindmarch Director WSP Structures Level 15, 28 Freshwater Place Southbank VIC 3006 Australia T. +61 3 8327 8600 D. +61 3 8327 8603 M. +61 4 3889 9446 [email protected] www.wspstructures.com.au
From: C Peille Sent: 29/04/2016 4:47:55 PM EST (GMT +10:00) To: Cecile Peille, Peter Hindmarch Cc: Jasvinder Opkar, Mike Straughton, Jeroen Devos, Katrina Face Mail Number: OveArup-CADV-000004 Subject: Re: 2011 Flood Velocities at main pier
Hi Peter,
Thank you for providing the pedestrian bridge configuration; we have noted that the supporting pier is not aligned with the main direction of flow. From a hydrodynamic perspective this is not the preferred option and we recommend a rotation of approximately 18 degree to reach optimum alignment as illustrated in the attached image.
Could you please advise if this an option from your ends, as the pier currently contributes to the overall flood impact to a non-negligible degree?
Please note I am on leave next week, returning on the 07/05. In my absence you can contact Jasvinder Opkar.
Regards, Cecile
From: C Peille Sent: 26/04/2016 12:38:48 PM WST (GMT +08:00) To: Peter Hindmarch Cc: Jasvinder Opkar Mail Number: OveArup-GCOR-000025 Subject: 2011 Flood Velocities at main pier
Hi Peter, The velocity at the pedestrian bridge pier is 3m/s in a 100yr event (adopted 2011 flood event).
Cheers, Cecile
This is an automatic notification from Aconex . To reply to this message, hit the Reply button on your email program or view this Mail on Aconex. Do not edit the subject line.
Aconex Project success. Easy as Aconex.
This email is automatically generated by Aconex. If you would like to turn off email messages, log into Aconex and edit your "Notifications" user preferences.
If you need assistance please contact our helpdesk at the following numbers : Australia: 1300 ACONEX (1300 226 639) Int: +61 3 9240 0200
Regards, The Aconex Team
This email and any attachments are confidential, subject to copyright and may be privileged. No confidentiality or privilege is lost by an erroneous transmission. If you have received this email in error, please let us know by reply email and delete or destroy this email and all copies. If you are not the intended recipient of this email you must not disseminate, copy or use the information in it.
COVER_[2].DOCX 8