Structural appendix document - Cornwall Council

Information Classification: CONTROLLED

Appendix F – Structural Appendix Document

Saints Trails – Perranporth to Newquay 1

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Saints Trail – Perranporth to Newquay Structural Scoping Document

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Cormac Consultancy | Structures Design Group


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Issue & Revision Record

Revision Date Originator Checked Authorised Purpose of Issue

Nature of Change

1 05.12.2019 PM DS RC First Issue -

If you would like this report in another format, please contact

CORMAC Solutions Ltd Head Office Higher Trenant Road Wadebridge CornwallPL27 6TW

Tel: 01872 323 313 Email: [email protected] www.cormacltd.co.uk/

This document has been prepared for the titled project or named part thereof and should not be relied upon or used for any other project without an

independent check being carried out as to its suitability and prior written authority of Cormac Solutions Ltd being obtained. Cormac Solutions Ltd accepts no responsibility or liability for the consequences of this document being used

for a purpose other than the purposes for which it was commissioned. Any person using or relying on the document for such other purposes agrees, and will by such use or reliance be taken to confirm his agreement to indemnify Cormac Solutions Ltd for all loss or damage resulting therefrom. Cormac Solutions Ltd accepts no responsibility or liability for this document to any party other than

the person by whom it was commissioned.

Prepared by Structures Design Group Western Group Centre

Radnor Road Scorrier Redruth

TR16 5EH


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Preamble Perranporth to Newquay Structures This report focuses on the structures along the proposed Saints Trail from Perranporth to Newquay. The document has been written to encapsulate the possible structures and describe a brief optioning approach. There are still many unknowns with the project i.e. ground conditions, landownership transfer, ecological constraints etc. Therefore the report is based on engineering judgement and shall be followed by further studies and testing. As the route is densely vegetated and some areas are restricted by access agreements there may be locations where additional structures may be required. The structural approach for these falls outside of this report and will be covered within the detailed design phase of the works.


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Contents 1 Introduction 6

History: 7 Construction: 7 Report Aims: 7

2. Structures along the route 5

3. Existing Structures 9

4. Modification of Existing Structures 9

5. New Structures 9

6. Perranporth Bridge 10 6.1 Description: 10 6.2 Features: 11 6.3 Pros: 12 6.4 Cons: 12 6.5 Potential modifications: 12

7. Design parameters 13 7.1 Width: 13 7.2 Height: 14 7.3 Gradient: 14 7.4 Materials: 14 7.5 Summary of Design Parameters: 15

Appendices 17


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1 Introduction

1.1 Purpose

1.1.1 The Cormac Solutions Ltd., Structures Design Group department have been appointed to carry out the assessment and design of new and existing structures along the proposed Saints Trail – Perranporth to Newquay route.


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History: The Perranporth to Newquay railway line was started in the Victorian era, with construction commencing in 1897 and finishing in 1905. The line was used up until its decommissioning in 1963.

Construction: The majority of the structures on the railway line are of arched masonry construction. The materials commonly used in all bridges are Brick, Granite Stone and Cast Iron Steel.

The size of the structures range from small culverts, crossing underneath the railway, to a large multi-span viaduct crossing a valley.

Report Aims: This report aims to establish suitable criteria for assessing, constructing and maintaining all the structures along the route.


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2. Structures along the route

Structures Coding:

M: Mining Feature B: Bridge C: Culvert R: Retaining Wall H: Halt

Structures List – Perranporth to Newquay Structure Number

Name Type New or Existing Structure

Proposed Works

PN03-B1 New Structure River Bridge New New retaining structure over existing bridge

PN05-C1 New Structure Culvert New Extension of culvert with earthworks and new headwall

PN05-B1 New Structure River Bridge New New structure 10 to 15m span with approach ramps

PN06-B1 Cox Hill Bridge Road Bridge Existing Parapet upgrade for cyclist and horses

PN07-B1 Cocks Viaduct Rail Bridge Existing Refurbish viaduct and remove ballast to gain extra parapet height. Address Highways England defects

PN07-B2 New Chiverton Railway underbridge Rail Bridge Existing Parapet upgrade for cyclist and horses


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PN07-C1 Railway bridge Culvert Existing Timber safety fence for maintenance

PN07-B3 Railway bridge abutments Rail Bridge New New single span deck with approach ramps

PN07-C2 Railway Culvert Culvert Existing Timber safety fence at headwalls for maintenance

PN07-M1 Railway Culvert Culvert Existing Steel handrail with mesh infill for safety at headwalls

PN07-C3 Railway Culvert Culvert Existing Timber safety fence at headwalls for maintenance

PN11-H1 Goohaven Halt Railway Station Halt to be refurbished (by others)

PN11-C1 Railway Culvert Culvert Existing Refurbish and install timber post and rail

PN11-C2 Railway crossing Culvert Existing Refurbish and install timber post and rail

PN11-C3 Lanteague Bridge Unknown Existing Unknown – currently unable to access

PN11-C4 Railway Culvert Unknown Existing Unknown – currently unable to access

PN11-C5 Railway Culvert Unknown Existing Unknown – currently unable to access

PN11-B1 Lanteague Bridge Road Bridge Existing Refurbish structure. Address Highways England identified defects. Extend the parapets to required height

PN12-B1 Fiddler’s Green Bridge Road bridge Existing No maintenance required


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PN12-C1 Railway bridge Rail Bridge Existing Clear culvert and address any defects. New edge protection

PN13-C1 Railway underbridge Unknown Existing Unknown – currently unable to access

PN13-H1 Mitchell and Newlyn Halt

Railway Station Existing Halt to be refurbished (by others)

PN13-B1 Illgram Bridge Rail bridge New New single span deck with approach ramp. Abutment stability checks/works. Address Highways England identified defects

PN13-B2 Lappa Valley access bridge/Culvert Rail bridge New New single span deck with approach ramp.

Abutment stability checks/works

PN13-B3 St Newlyn link bridge/ramp Rail bridge New New single span deck with approach ramp

PN14-C1 East wheal rose rail culvert Rail culvert Existing Timber safety fence at headwalls for

maintenance

PN15-B1 New Structure River Bridge New New single span structure

PN16-B1 Metha Bridge Rail Bridge New New bridge with off ramp and small bridge crossing the culvert at base.

PN18-B1 Benny Bridge Road Bridge Existing Refurbish structure. Address HE identified defects and crack stitch.

PN18-B2 Railway Culvert Culvert Existing New parapet and extend existing

PN18-B3 Trewerry Unknown Existing Unknown – currently unable to access


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PN20-C1 Railway underbridge Unknown Existing Unknown – currently unable to access

PN20-B1 Legonna Railway Bridge Unknown Existing Unknown – currently unable to access

PN20-C2 Legonna accommodation Bridge Unknown Existing Unknown – currently unable to access

PN20-B2 Gwills Railway Bridge Road bridge Existing Unknown – currently unable to access


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3. Existing Structures

3.1 The majority of existing structures along the route are of a masonry arch construction type. In order to appraise their condition for adoption, an assessment needs to take place to determine their capacity.

3.2 As well as carrying out the assessments we also need to look at the usage of the structures. As the trail is to be designed as multi-use, i.e. horses, cyclists and pedestrians we must evaluate the structures based on the most onerous criteria.

3.3 If the assessment finds the structure does not have sufficient capacity, further more detailed assessment or strengthening work will need to be undertaken.

4. Modification of Existing Structures

4.1 The British Horse Society guidance states that bridge parapets are required to be 1.8m in height for equestrian usage. All current bridge parapets are below 1.8m in height and therefore the parapets must be extended.

4.2 Due to the historic character of the bridges, each will need to be evaluated and a risk assessment carried out to ascertain the implication of increasing the parapet height or maintaining the current height.

4.3 Where the parapet is required to be extended to the full height an appropriate consideration method shall be taken to mitigate the visual impact. Either by use of an infill panel or by changing the form of the parapet.

5. New Structures

5.1 At present there is one new structure along the route, located on New Road in Perranporth. As this is the start of the route it provides a template for the new bridges we are looking to construct. Using this design as a basis we can then look to incorporate new ideas that will give the structure some prominence whilst maintaining the railway characteristics.

5.2 There needs to be a link to the local historic features whilst maintaining health and safety, reducing environmental impact, using sustainable products and ensuring the project can be built on cost and time.


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6. Perranporth Bridge 6.1 Description: 6.1.1 Designed by CTS and Bam Nuttall in 2015, this 19m span bridge is located at

the start of the trail in Perranporth, linking the sports field to New Road.

6.1.2 The bridge is a 19m single span, simply supported steel and timber composite structure, founded on a geotextile wrapped bank with a mass concrete bearing shelf.

6.1.3 The parapets are 1.4m high and 2m apart. There is a sign at the start of the bridge stating that the bridge can be used for horses.


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6.2 Features:

Geotextile foundations The geotextile foundations are lightly vegetated which means the material is showing, which makes the approach look untidy. Concrete bearing shelf The concrete shelf appears to be in good condition and the concrete wrap around wall hides the end of the beam well. I-beam with cross bracing design The design looks rigid, however the beams supporting the deck panels are made from timber and looks to be saturated which could cause longevity issues and increase maintenance. 600mm high steel beams The beams look robust and as the bridge is recessed into the flood channel by the surrounding walk ways they look to be suitable. However from a side elevation they look dense and stark with in the surrounding environment.


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1.4m high parapet The timber handrail is sub-standard for horses. From afar it looks good and breaks up the construction elements. However up close the design looks drab and out dated.

Timber deck with anti-slip The decking looks suitable and provides appropriate grip for users of the bridge. The gaps between panels is minimal so the view through is not apparent.

6.3 Pros: • Robust design. • Easy to lift into place and construct. • Deck panels can be maintained easily and replacement is relatively straight

forward.

6.4 Cons: • The solid steel beams makes for an overbearing, dense aesthetic. • The bridge has graffiti on one side due to easy access. • There is evidence of drinking and rubbish under the bridge, potentially

promoting antisocial behaviour.

6.5 Potential modifications: • Cladding steel beams with timber. • Increased fencing leading to bridge to prevent access to soffit. • Painted beams to make them more visually appealing, stop graffiti and

increase the life span of the structure. • Creation of voids in the main beams to allow light to pass through. • Use a facing to the meshed abutments and incorporate additional

planting.


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7. Design parameters

7.1 Width: 7.1.1 The route is being designed in accordance with the Design Manual for Roads

and Bridges (DMRB) CD 195, which is to accommodate the (predicted) less than 150 users per hour, giving a desirable minimum width of 3m with an absolute minimum width of 2.5m.

7.1.2 Due to the parapets being greater than 600mm high at the edge of the surfaced width a constraint is introduced. For cyclists this means there must be an additional 500mm either side of the track. Therefore the width of the bridge shall have a desirable minimum width of 4m and an absolute minimum of 3.5m

7.1.3 Where this cannot be reduced the cycle track can be turned into a one-way system across the structure. This would have a desirable minimum width of 3.5m and an absolute minimum width of 2.5m.

7.1.4 The absolute minimum will only be used for track sections of up to 100m in length.

Track widths across structures Cycle route type Desirable

minimum width Absolute minimum width

One-way 3.5m 2.5m

Two-way 4.0m 3.5m

7.1.5 In accordance with DMRB TA 90/05 a width of 2m is required for a horse and 3m where horses are expected to pass one another.

7.1.6 BD 29/17 states that the minimum footbridge width for combined pedestrian and equestrian usage shall be 3.5m.

7.1.7 The British Horse Society recommends a minimum width of 3m for a bridge over a railway or road.


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7.2 Height: 7.2.1 TD 27/05 requires footbridges (not designed to take impact loading) to have

a minimum headroom above the carriageway of 5.7m + sag of carriageway.

7.2.2 CD143 states that the desirable headroom for ridden horses is 3.4m with an absolute minimum of 2.8m. The British Horse Society recommend a height of 3.7m with a minimum of 3m.

7.2.3 The British Horse Society recommend a parapet height of 1.8m for equestrians. Where horses are not present this can be reduced to 1.4m.

7.3 Gradient: 7.3.1 CD143 states the following:

5% acceptable maximum gradient and 10% for short distances where significant constraints exist.

Following any significant gradient a 5m passing zone is required at a level grade.

For equestrian only routes the maximum gradient should be 20%.

7.3.2 For ramps >5% we should also start to consider BD29/17 Design Criteria for Footbridges, which states:

A ramp should be a maximum of 1 in 20 (5%) unless there are compliance difficulties where it can be changed to 1 in 12 (8.33%). A drop in gradient needs to be clearly justified and agreed by the overseeing organisation.

Landings must be provided at any rise greater than 3.5m.

7.3.3 A departure from standard would be required for anything where the 1 in 12 slope is not located on a bridge.

7.3.4 Cross-falls shall be less than 3% to reduce the risk of slipping in icy conditions. Where this is not possible the allowable maximum cross-fall gradient is 5%.

7.4 Materials: 7.4.1 Materials should be selected that do not cause alarm to horses. This may

require additional noise attenuation measures i.e. special surfacing. Alternatively signage can be used to alert the riders.

The British Horse Society’s guidance recommends a non-slip surface to dampen the noise. The use of metal deck panels should be avoided as it can scare horses. Wood is suitable but will need additional anti-slip to prevent horses slipping in the wet.

See Appendix A for more material information.


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7.5 Summary of Design Parameters:

Bridge details Element Dimensions Details

Width 3.5m To be adjusted to suite areas for constructability.

Height above obstacle

5.7m + S

Gradient on bridge 1:20 to 1:12

(5% to 8.33%)

Approach ramps 1:20 to 1:12

(5% to 8.33%)

Subject to costing of additional construction elements required and consultation with overseeing organisation.

Walking surface of deck

3.5m wide To incorporate anti-slip material.

Parapet height 1.8m Infill panels to be determined based on obstacle crossed. 600mm waterways and full height for roads. Further consultation with the British Horse Society (BHS) will be held to provide site specific criteria.

Structural deck components

Confirmed during design.

Powder coated galvanised steel, colour to be advised by the Cornwall Railway Society and determined by Cornwall Council.


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Appendices


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Appendix A


Material Durability Maintenance Strength Buildability Sustainability Cost m²

FRP

Rust free. Waterproof. Hard wearing.

Painting eliminated or reduced Medium Highly adaptable. End of life

concern. High

Steel

Very strong. Painting. Waterproofing required. High Standard parts or

custom. Heavy Highly recyclable. High

Stainless Steel

High tensile/compressive strength.

Low maintenance High Standard parts or custom. Heavy

Long life. Erosion resistant. 100% recyclable.

High

Timber

Treated can have long life.

Checks required. Painting/waterproofing possibly required.

Medium Easy to shape. Standard tools. Can be recycled. Medium

Concrete

Strong in compression. Low maintenance High Easy to shape/ lay. Not very. Low

Gabion Baskets

Very durable PVC coated wire can last 60 years. High Moderately easy

Can be modified to better fit with environment.

Medium

Plastic Bridges

Very durable Low maintenance Medium Easy to build. Material can come from waste streams.

Medium

Recycled Bridges

High. Initially high. Inspection and maintenance required. High Selected to be

dropped in place. 100% recycled Low

Galvanised Steel

Very durable Regular maintenance. Can rust particularly on welds. High Highly adaptable. Highly recyclable. High

Structural l


Material Durability Maintenance Strength Buildability Sustainability Cost m²

Accoya Cladding

Very stable. Highly durable.

60 years service life Medium Easy to erect. Standard tools.

Fast growing. Certificated.

Medium

Larch Cladding

Class 3. Moderate Checks required. Waterproofing possibly required.

Medium Easy to erect. Standard tools.

Fast growing Medium

Oak Cladding


Very low maintenance Medium Easy to erect. Standard tools.

Slow growing. Must be sourced with care.

Medium

Beech Cladding

Stable and durable. Very low maintenance Medium Easy to erect. Standard tools.

Slow growing. Must be sourced with care.

Medium

Rockpanel

Quality coating will last years.

Very dimensionally stable. Medium Standard tools. Edges do not need sealing. Quick to install.

Longevity of stone. Nearly fully recyclable.

Medium

Stainless Steel Mesh

Abrasion and corrosion resistant

Low maintenance High Easy to erect. Standard tools.

100% recyclable. High

Laser Cut Steel


Checks required. Painting/waterproofing possibly required.

High Easy to erect. Standard tools.


Stone Cladding


Very low maintenance High Fairly easy to erect. Standard tools. Slower than wood cladding.

Highly recyclable. Medium

Design


Perforated Al. Panel

Moderate Low maintenance Lightweight

Easy to erect. Standard tools.


Documents

Structural appendix document - Cornwall Council