Low-disturbance sustainable urban construction Critical issues for the assembly process...

Low-disturbance sustainable urban constructionLow-disturbance sustainable urban construction

Critical issues for the assembly process

Identification and on-site procedures

CRITICAL ISSUES DURING ASSEMBLY

Low-disturbance sustainable urban construction

Contents

1 Introduction: main goals and critical issues

2 Pre-assembly issueso Design and manufactureo Transporto Preparation of the construction siteo Storage of prefabricated elementso Supports and bearings

3 Assembly issueso Prefabricated element placemento Joints

4 Post-assembly issueso Verification o Equipment removal and facility

dismantling

5 Addressing critical issues the Pantura wayo Preassembly issueso Assembly issues

o Post assembly issues







dismantling





Introduction: main goals

Social and natural

environment

safety

cost and

time

o Optimization of costs

o Building time reduction

o Worker and bystander safety enhancement

o Minimization of disturbance

THE ASSEMBLY PROCESS IS CRUCIAL TO ACHIEVE OUR GOALS



Introduction: critical issues in the assembly process

Pre-assembly Assembly Post-

assembly







dismantling





Preassembly issues: design (1)

Dimensions

Gauge limitations condition dimensions

Similar pessimal dimensions allow for transport standardization

Excessive size conditions on-site storage and maneuverability during assembly

Shape

A compact geometry allows minimal volume occupation during transport and storage

Open sections should “fit” into each other

Elements should present at least one stable position for transport and storage, and be reasonably stable in all positions required for assembly.

Slenderness of element parts should be limited to avoid noise, vibrations and possible damage

Design should be transport, storage and assembly-oriented



Preassembly issues: design (2)

Manoeuvrability and manipulation

Support points and handles for easy and safe manipulation should be considered during design

Said points should be clearly marked, easily accessible and designed for dynamic loads

When elements are to be manipulated by hand, support points should be devoid of dangerous edges and corners

Mass and center of gravity

Prefabricated elements should have similar mass to optimize auxiliary means (e.g. cranes)

Center of gravity should be close to geometrical center to avoid misjudgment risks and facilitate element manipulation



Element identification

In order to reduce errors and facilitate storage registry, prefabricated elements should bear the following information:

o Individual ID numbero Destination and precise mounting locationo Place and time of manufactureo Weight and most relevant dimensions (pessimal gauges)o Safety relevant data

Tolerances

Fabrication tolerances must meet design requirements. These, in turn, should have taken fabrication tolerances into consideration

Whenever prefabricated and in-situ elements must be assembled, joint mechanisms shall have consideration for tolerance difference, guaranteeing functionality for a sufficiently wide range of geometrical imperfection

Preassembly issues: manufacture



Element protection during transport

Weather protection should be provided during transport to avoid following damage risks:

o Rust in steelo Paint damageo Bloating and deformation of elements through excess humidityo Accumulation of water in crevices not designed for water contacto Damage through icing-deicing cycles

Impact protection should be considered in case of low global or local tenacity of prefabricated elements

Fragile elements should be conveniently tagged for careful handling and protected against fortuitous impacts

Restraint systems should not allow for load movements under reasonable circumstances

Vibration damping should be considered when element slenderness creates vibration-related issues, such as:

o Excessive noiseo Resonance problemso Damage through hammering

Preassembly issues: transport (1)



Transporting oversize and overweight elements

Special measures should be taken to reduce discomfort to residents surrounding the building site, such as:

o Transport of oversize/overweight elements during low traffic hourso Selection of routes that avoid traffic-sensible streets o Consideration of noise emission limits during night-time

Clearance problems should be avoided through careful route planning whenever possible.

If affection to preexisting infrastructure is inevitable, temporary measures should bear minimum impact

Overweight element transport routes should be thoroughly studied to avoid structures, roads and city areas susceptible of suffering damages due to excessive weight

Delays due to transport

Due to variable building speed, risk of delays due to transport of prefabricated elements may only be mitigated through precise planning of fabrication, transport and on-site storage (when available)

When on-site storage is unavailable due to oversize elements, said elements should be delivered on-site the day they are to be positioned or in the closest non-disturbance time window available

Preassembly issues: transport (2)



Prefabricated element storage location

Storage area should be easily accessible for transport, close to the final position of elements and protected from flood and fire risks. Once storage location is decided, it should be paved, leveled an suitably marked.

Construction equipment storage and parking

Machinery storage area should be placed attending to safety and operability, striving to separate on-site traffic from building areas.Said area should be equipped with oil and waste recovery systems, designated areas for repairs, and fuel supplies

Geodesic reference service placement

Geodesic equipment should be placed considering the whole building process.Weather protection should be provided to ensure equipment integrity and comfortable work conditions.All temporary benchmarks should be duly marked and secured against movement.

Lighting

Lighting systems should be provided whenever night-time work is expected, or when natural light is prone to be insufficient.

Preassembly issues: building site preparations



Work safety and preventive analysis

The manufacturer should provide contractors with relevant safety information, and contractors should actively request said information.Workers should be informed of all special storage-related safety measures, and said measures should be included in the general safety plan.All incoming prefabricated elements should have their relevant safety information available upon reception.

Storage order and organization

Element storage should consider the order in which elements are to be assembled.A storage filing system should be established, so that element inventory is always available and specific elements may be easily located.

Element integrity during storage

Storage area should provide protection against weather exposure.Damage through machinery impact should be prevented by means of padding and protection, and in-site traffic should be limited in the vicinity of the storage areaRisks of accidental overturning of elements should be mitigated, both by stacking height limitations and stack bracing.Vibration related risks should be mitigated as proposed for transport.

Preassembly issues: on-site element storage



In-situ reinforced concrete abutments

Preassembly issues: bridge supports

Reinforced earth abutments GRS-IBS “5-day wonder” abutments



Preassembly issues: bridge bearings

Elastomeric bearings

o Cheapero Less bearing capacityo Must be replaced with timeo Direct assembly without specific

treatmento Low self-weight girders may call for

adhesive treatment

Pot bearings

o More expensiveo Designed for great loadso No maintenance neededo Requires anchoring to

abutments







dismantling





Assembly issues: equipment - cranes

CRANES ARE THE MOST COST-GENERATING MACHINES IN A BUILDING SITE

Fixed tower cranes

o Designed for great loadso One crane fits allo Range is limited, but considerableo Great initial costso Suited for long building times

Movable telescopic cranes

o Specific load limitation for each modelo Range is low, but may be optimally

positionedo High daily costso Adequate for fast building

under 30 tons

30-45 50-65 70-85 90-125 130-200 210-350 over 350 tons

0

1000

2000

3000

4000

5000

6000

7000

Rental cost per day (in thousands of euro) depending on the crane capacity



Assembly issues: prefabricated element placement

Prefabricated bridge assembly phases

1. Girder placement

2. Girder joint execution

3. Tolerance check

4. Prefabricated deck placement

5. Deck-to-deck and deck-to-girder joint execution

6. Tolerance check

7. Bridge equipment assembly

8. Final verificationsCritical issues

o Cost issues are mainly related to time, since crane rental is the most relevant cost during bridge assembly.

o Environmental issues are mainly related to noise, since heavy machinery is necesarily noisy

o Safety issues are mainly related to wind and weather, especially for low self-weight elements such as FRP decks and timber/FRP girders



Assembly issues: incorrect element placement

ELEMENT PLACEMENT ERRORS MUST BE AVOIDED: THEY GENERATE COSTS AND INFLUENCE SAFETY

Placement errors may appear when different elements are similar to each other, but not interchangeable

The easiest and most effective way to address this issue is building error avoidance-oriented design, either making sure similar elements are in fact interchangeable, or guaranteeing elements are unmistakingly different.

When design in these terms is difficult or unavailable, prefabricated elements should be clearly identifiable by means of ID number, barcode, tags or similar means.



Assembly issues: safety during assembly

Safety issues during prefabricated element assembly are mainly related to the following processes:

o Lifting of heavy loads by mechanical means: risk of falling elements

This risk should be mitigated by reducing possibility of failure during crane lifting and limiting the presence of workers in the lifting zone.

Personal protection equipment may also be used to mitigate risk of falling objects.

o Fine positioning of elements in their designated locations: risk of workers falling from great heights

This risk should be mitigated by displaying safety nets and assigning lifelines and harnesses to workers



Assembly issues: joints between elements

Mechanical fasteners

o Discrete joining facilitates inspection

o May be used with all kind of materials

o Risk of confusion between similar fasteners should be avoided through design or colored anodization

Adhesive bonding

o Continuous bonding reduces stress concentration

o Specifications of use must be strictly obeyed

o Sensitive to weather conditions during application and hardening

o Element pre-treatment required

Welding

o Bond is continuous yet easily inspected

o Soldered elements may be considered as a whole

o Use is restricted to some materialso May be used in extreme

conditions, even under water.o Strict safety measures required

during welding







dismantling





Post-assembly issues: verification

Verification of prefabricated elements

All elements should be verified after assembly to guarantee correct installation and integrity.

Visible damage to paint and protective coatings should be promptly repaired.

Visual inspection element by element can be tedious, costly and time-consuming

Joint verification

Special attention should be paid to joint integrity verification:

o They are often weak spotso Joints are assembled on-site and thus subject to

human erroro Stresses are prone to accumulate in discontinuitieso Joint failure compromises structural safety



Post-assembly issues: building site dismantling

Once the assembly is finished, the building site should be dismantled with utmost alacrity and minimum disturbance:

o In machinery parking areas, special attention should be paid to oil and waste disposal system removal, in order to prevent environmental impacts related to waste leaks during dismantling.

o Heavy machinery should be removed during low traffic hours, yet observing low-noise time windows for reduced annoyance to neighbors

o The building site should be devoid of debris, dirt and rests of building materials before it can be considered dismantled

o All infrastructure affected by the building site (pavement, public lighting, etc) should be replaced before the end of the site dismantling process

o Building site fence and access limitations to the building site should remain in place until the area has been thoroughly secured, dismantled and cleaned






4 Post-assembly issueso Verification o Equipment removal and facility dismantling

5 Addressing critical issues the Pantura wayo Preassembly issueso Assembly issueso Post assembly issues



The PANTURA way: Design and manufactureAssembly-oriented design addresses critical

issues:

o Elements size, shape and mass are optimized for easy transport and maneuverability

o Regular mass distribution provides element

stability and places center of gravity where expected

o Support points and safe handles are provided for element assembly

Prefabricated elements respect due tolerances and bear all relevant information

o Robotic manufacturing, laser measuring and automatized production provide precise fabrication within tolerance limits

o Through the use of RFID tags, barcode identification and tracking systems, elements are always locatable and their relevant info is available

o Construction manager has real-time inventory of on-

site, in-itinere and in remote storage elements.



The PANTURA way: element transport

Elements are duly protected for assured integrity

o All elements are padded, properly restrained and protected against weather conditions

o Collision Avoidance Systems implanted on transport conveyors minimize risks during loading and unloading of elements

Special sized elements are transported causing minimum disturbance

o Routes are thoroughly studied and minimum impact time windows selected to avoid disturbance

o When infrastructure must be unavoidably removed, contingency plans are made to replace or substitute all affected services as soon as possible

o Special sized element transports are equipped with

a complete ICT system to minimize collision risks: CAS shall be complemented with RFID tags on elements, GPS system and RBSS active radar surveillance

Remote and on-site storage of elements, flexible transport scheduling and building progress control reduce delays due to element delivery

o An on-site storage buffer is implemented, while primal storage is remote

o RFID tags, GPS systems and BIM models provide real-time information of element location and building progress, allowing tailoring the transport schedule to the real site needs

o RFID tags on transport conveyors suppresses the need for tedious identification for

authorization of access



The PANTURA way: preparing the construction site

The PANTURA construction site plans ahead to minimize conflicts between different aspects

o The storage area provides protection for elements, easy access for transport and assembly, is marked for improved site readability and is located so that compromises between closeness to assembly points and non-disturbance of in-site traffic

o The machinery parking lot is properly paved , leveled and equipped with oil and waste recovery systems, fuel stations and repair and maintenance area. Its location strives to separate in-site traffic from working areas for improved security

o The geodesic reference equipment is placed considering the whole building process, so that no need to move its position arises during construction. Weather protection is provided, as much for equipment integrity as for worker comfort.

o Artificial lighting systems are designed for optimal illumination during night-time work or insufficient natural lighting, taking into account possible disturbance to neighboring sleepers. Back-up power systems guarantee lighting services in the event of a power shortage

o All scaffolds and temporary structures are foreseen and included in the site planning. Current status and usability of said scaffolds is controlled by easily readable marking systems and RFID worker tagging.



The PANTURA way: the storage area

The PANTURA storage area is a safe and organized place where elements are easily accessed

o All safety-related information is available from the manufacturer in the storage filing system, and may be retrieved for each element by means of barcodes and QR-codes impressed on the element surface

o RFID tags and barcodes/QR codes allow for unerring recognition of individual elements. Crane operators are equipped with LCD monitors with information provided by the RFID management system

o RFID readers installed in machinery automatically recognize whether the transported element is being carried to the correct location.

o The storage filing system provides with an exact map locating each individual element for retrieval and assigning a specific location for every new incoming element, based in assembly order

o Stored elements are protected from weather conditions, mechanical impact, flood, fire, etc.

o Elements are stored in stable positions and stacked to a maximum height which does not compromise worker safety



The PANTURA way: fast and flexible assembling

The PANTURA assembly processes strive to reduce time, cost and impact through prefabrication, ICT tool use and assembly-oriented design

o Selected bridge abutments are either fast to build or prefabricated and easy to install

o Bridge bearings are pre-installed on prefabricated abutments

o Girders are designed for easy installation and maneuverability

o Crane size and use is optimized for minimum cost

o Cranes are equipped with distance sensors, surveying systems, anti-sway modules and rotary grippers

o Deck panels are lightweight and easily assembled

o Joints and connections are reliable, agile and easily inspected

o Tolerances are automatically checked by Visual Surveying Systems and 3D scanning

o Element placement errors are prevented by the RFID tag monitoring system interconnected with the BIM model



THANKS FOR YOUR ATTENTION

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