CHAPTER 16 - GANTRIES - · PDF fileAll certificates pertaining to the grade and quality of the...
Transcript of CHAPTER 16 - GANTRIES - · PDF fileAll certificates pertaining to the grade and quality of the...
Gantries 16-1
CHAPTER 16 - GANTRIES
DS Temple
16.1 SCOPE
This section covers the inspection of Sign Gantries as specified in the applicable chapter of the
Specifications. It also covers the special attention which must be given by the engineer’s monitoring
staff to the specific requirements of setting out, excavations foundations, backfill and, manufacture
and erection of the structural steel gantries.
16.2 FOUNDATIONS
16.2.1 Setting Out (Refer to Chapter 4)
The setting out of the gantries should be carried out in accordance with Chapter 3 of this document.
However the following points should be noted.
16.2.1.1 Location
The gantry location (e.g. km distance) on the structural drawings must tie in with the location given
on the road works drawings.
16.2.1.2 Horizontal Clearances
Horizontal clearances must be checked prior to the casting of the gantry foundation plinths.
16.2.1.3 Vertical Clearances
The vertical clearances as specified on the design drawings should be checked by the Monitoring Staff
on site.
Photo 16.1: Gantry foundation
16.2.2 Excavations (Refer to Chapter 4)
Note that it is preferred that the foundation concrete is cast directly against the sides of the excavation.
Gantries 16-2
16.2.3 Formwork & Falsework (Refer to Chapter 6)
16.2.4 Steel Reinforcement (Refer to Chapter 7)
16.2.5 Concrete (Refer to Chapter 8).
Note that durability concrete should be used only in extreme situations.
16.2.6 Built-in Items
• The Monitoring Staff should confirm the orientation of the Holding Down Bolt Groups.
• Confirm the position of ducts, gantry number and any other built-in items indicated on the
drawings.
Photo 16.2: Completed gantry foundation
16.3 STRUCTURAL STEEL GANTRIES
16.3.1 Materials
The Engineer’s Monitoring Staff should ensure that the contractor submits a certificate of compliance
for:
• Structural steel for manufacture of gantry
• Holding down bolts
16.3.2 Corrosion Protection
The corrosion system as specified on the drawings must be confirmed with the Contractor. The
Monitoring Staff should ensure that the manufacturer’s Quality Assurance records are made available with the delivery of the gantries. Hot dip galvanizing could be specified as a corrosion protection
measure but should be used with caution as this process is still in the experimental stages. Buckling
of thin plates occurs during the dipping process due to stress relief in the plates and therefore extreme
care should be taken before using this method of corrosion protection.
Gantries 16-3
16.3.3 Shop Drawings
The Monitoring Staff should ensure that shop drawings of the gantry and holding down bolts are
submitted for review timeously.
16.3.4 Factory Inspection
It is a requirement that monitoring staff inspect the structural steel during the manufacturing process.
The following important aspects should be checked and verified against the design drawings:
• Dimensions and thicknesses of the steel plates.
• Number and spacing of the beam and column stiffener plates.
• Type, size and quality of all the welds as specified on the drawings.
• Diameter and length of anchor bolts, as well as the dimensions of the anchor bolt cage.
The Monitoring Staff should ensure that the correct grade steel for the anchor bolts and structural steel
gantry structure is used. All certificates pertaining to the grade and quality of the steel should be
obtained from the manufacturer for construction record purposes.
Photo 16.3: Gantry manufacturing
16.3.5 Erection
• The Monitoring Staff should ensure that the Contractor submits for review a complete method
statement for the erection of the gantries.
• Accommodation of traffic measures should be submitted in accordance with Road Traffic Signs
Manual, Chapter 13.
• Monitoring Staff should ensure that the gantry is erected within the specified tolerances.
16.4 CHECKING AND TESTING
The Monitoring Staff should visit the manufacturing facility during manufacture to ensure that the
gantries are being manufactured according to the Manufacturer’s Quality Plan.
Gantries 16-4
16.4.1 Corrosion Protection
• Reference should be made to the notes on the Detailed Design drawings for the corrosion
system to be used.
• Surface preparation to SA 2.5 should be checked prior to the application of any corrosion
protection.
• Ensure that the contractor’s proposed system for the painted, galvanized or sprayed metal
coating conforms to specified requirements.
• Random testing of the thickness of the various coats of the corrosion protection system should
be carried out in the paintshop as well as on the delivered elements and especially on the site
painted areas (welded site connections on gantry beams).
• Records of the tests carried out on the dry film thicknesses (DFT) should be kept.
16.4.2 Welding
The Monitoring Staff should ensure that the process control adopted by the manufacturer complies with the Project Specification. This can be achieved by including notes on the shop drawings for
welding procedures. All QA records of process control of the welds should be provided to the
Engineer.
Proof of the welder’s qualifications should be provided.
Ultrasonic testing should be carried out on the following welded connections:
Column & base plate connection
Column & beam haunch connection At least 10% of the seam welds in the columns*
At least 10% of the seam welds in the beams*
Gusset plate connections*
Site welds**
*Where ultrasonic testing is not possible magnetic particle testing should be carried out on at least
50% of the seam welds.
**At the very least site welds should be inspected and approved by an independent qualified person. Where possible ultrasonic testing (preferable) or magnetic particle testing should be carried out. It
should be noted that these must be done before painting and after the steel has cooled.
Gantries 16-5
Photo 16.4: Gantry erection
16.5 GANTRY STRUCTURES - CONSTRUCTION MONITORING CHECK LIST
The Monitoring Staff should use the “Gantry Structures - Construction Monitoring Check List” as far
as possible to ensure the quality of the gantry structures.
Gantries 16-6
INDEX TO APPENDICES
16A - GANTRY STRUCTURES
Gantries 16-7
CONSTRUCTION MONITORING CHECKLIST
PROJECT NO. / NAME: .......................................................................................................................................
INSPECTOR’S NAME(S): ....................................................................................................................................
STRUCTURE: ........................................................... ELEMENT: ..............................................................
ACTIVITY AND DETAILS APPROVAL
SIGNED DATE Y/N N/A Comment
1. EARTHWORKS
1.1 Setting out
• Km distance
• Depth of excavation relative to edge of
road
• Distance from edge of road to
foundation centre
• Can foundation be cast directly against
side of excavation as is preferred
• If not has work space been agreed
with Engineer
1.2 Bearing pressure
• DCP Tests done
• Is soil improvement required
• If so describe
• Soil improvements tested
• Provide estimated foundation bearing
capacity in kPa
1.3 Blinding layer
• Depth to blinding layer relative to
edge of road
• Plan area of blinding layer
2. REINFORCEMENT
2.1 Footing – Bars parallel to road
• Are they Top 1 and Bottom 1
• Bar spacings - 125mm
• Bar type bottom
• Bar type top
• Alternative bar reversed (top bars)
2.2 Footing – Bars perpendicular to road
• Bar spacings - 250mm
• Bar type bottom
• Bar type top
• Alternative bar reversed (top bars)
2.3 Plinth
• Are there the correct number of "U"
bars
• Orientation
• Location
• Bar projection height
• Secondary bars, i.e. clips & stirrups
Checklist continues on next page…
GANTRY STRUCTURES
CHECK LIST(1/4)
APPENDIX 16A
Gantries 16-8
ACTIVITY AND DETAILS APPROVAL
SIGNED DATE Y/N N/A Comment
3. ANCHOR BOLTS
3.1 In workshop
• Diameter
• Steel Grade of bolt
• Bolt cage dimensions
3.2 On Site
• On site orientation
• Location within plinth
• Projection of bolts
• Top portion of bolt corrosion
protected
4. FORMWORK
4.1 Footing plan dimensions
4.2 Is footing formwork required and
approved
4.3 Footing thickness
4.4 Plinth plan dimensions (parallel and
perpendicular to road)
4.5 Height of plinth
4.6 Level difference between top of
plinth & road edge
4.7 Cover to rebar - footing 50mm
bottom, 75mm sides
4.8 Cover to rebar - plinth 50mm sides
and top
4.9 Plinth shutter - adequately propped
4.10 Plinth off shutter surface finish OK
5. SPECIAL CAST IN ITEMS
5.1 PVC ducts provided if detailed on the drawings
5.2 Location in plinth (plan)
5.3 Projection above plinth concrete
Checklist continues on next page…
GANTRY STRUCTURES
CHECK LIST(2/4)
APPENDIX 16A
Gantries 16-9
ACTIVITY AND DETAILS APPROVAL
SIGNED DATE Y/N N/A Comment
6. CONCRETE
6.1 Pre concrete inspections
• Concrete as per specification & mix
design (obtain copy of delivery note)
• Concrete Class W30MPa
• Plinth concrete: 50mm < slump <
70mm
• Proposed curing method
• Proposed curing period
6.2 Post concrete inspections
• Cracks
• Spalling
• Honeycomb
• Shutter kick
• Repair method
7. STRUCTURAL STEEL
7.1 Prior to dispatch to site
• Steel grade certificate and markings
• Column height plust the beam section
• Beam length (less the beam section
attached to column/s)
• Column cross section dimensions
• Beam cross section dimensions
• Plate thicknesses columns
• Plate thicknesses beams
• Special attachment size & plates
• Stiffener plates, thickness, spacing,
fitment
• Welds visually acceptable and
according to drawing
• Chamfering and preparation for
welding
• Holes setting out
• Ultrasonic testing of welds - certified
7.2 On site
• Method of erection approved
• Traffic accommodation approved
• Site welding method approved
• Site welding quality approved
• Anchor bolt tightening torque (provide
Nm)
• Grout under base plate - type approved
• Grout under base plate - installed
correctly
Checklist continues on next page…
GANTRY STRUCTURES
CHECK LIST(3/4)
APPENDIX 16A
Gantries 16-10
ACTIVITY AND DETAILS APPROVAL
SIGNED DATE Y/N N/A Comment
8. CORROSION PROTECTION
• Inland or coastal specification
• Paint specification approved
8.1 Prior to dispatch to site
• Abrasive blast cleaning
• Primer - paint type and DFT certified
• Approval of application of second coat
prior to dispatch
8.2 On site
• Patch repairs- paint type and DFT
certified (NB repairs at site welds)
• Second coat - paint type and DFT
certified
• Final coat - paint type and DFT
certified
• Final coat colour
• Anchor bolts corrosion protected
9. AS-BUILT DATA
• Name and address of Main Contractor
• Name and address of Steelwork
Fabricator
• Name and address of Painting
Contractor
• Paint system used
• Foundation material and safe bearing
capacity
• Date of steel structure erection
Least favourable results of test certificates:
9.1 Structural steel
• Steel grades
• Ultimate tensile strength (MPa)
• Yield strength (MPa)
• Elongation at fracture (%)
9.2 Anchor bolts
• Steel grades
• Ultimate tensile strength (MPa)
• Yield strength (MPa)
• Elongation at fracture (%)
9.3 Data included an “As-built”
drawings
GANTRY STRUCTURES
CHECK LIST(4/4)
APPENDIX 16A