Critical issues for the assembly process Identification and on-site procedures

Critical issuesfortheassemblyprocessIdentificationand on-site procedures

Contents • 1 Introduction: main goals and critical issues • Pre-assembly issues • Design and manufacture • Transport • Preparation of the construction site • Storage of prefabricated elements • Supports and bearings • Assembly issues • Prefabricated element placement • Joints • Post-assembly issues • Verification • Equipment removal and facility dismantling • Addressing critical issues the Pantura way • Preassembly issues • Assembly issues • Post assembly issues

1 Introduction: main goals and critical issues • Pre-assembly issues • Design and manufacture • Transport • Preparation of the construction site • Storage of prefabricated elements • Supports and bearings • Assembly issues • Prefabricated element placement • Joints • Post-assembly issues • Verification • Equipment removal and facility dismantling • Addressing critical issues the Pantura way • Preassembly issues • Assembly issues • Post assembly issues

Introduction: main goals • Optimization of costs • Building time reduction • Worker and bystander safety enhancement • Minimization of disturbance THE ASSEMBLY PROCESS IS CRUCIAL TO ACHIEVE OUR GOALS

Introduction: critical issues in the assembly process

Preassembly issues: design (1) • Design should be transport, storage and assembly-oriented • 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

Preassembly issues: design (2) • 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 • 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

Preassembly issues: manufacture • Element identification • In order to reduce errors and facilitate storage registry, prefabricated elements should bear the following information: • Individual ID number • Destination and precise mounting location • Place and time of manufacture • Weight and most relevant dimensions (pessimal gauges) • 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: transport (1) • Element protection during transport • Weather protection should be provided during transport to avoid following damage risks: • Rust in steel • Paint damage • Bloating and deformation of elements through excess humidity • Accumulation of water in crevices not designed for water contact • 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: • Excessive noise • Resonance problems • Damage through hammering

Preassembly issues: transport (2) • Transporting oversize and overweight elements • Special measures should be taken to reduce discomfort to residents surrounding the building site, such as: • Transport of oversize/overweight elements during low traffic hours • Selection of routes that avoid traffic-sensible streets • 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: building site preparations • 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: on-site element storage • 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 area • Risks 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: bridge supports • In-situ reinforced concrete abutments • Reinforced earth abutments • GRS-IBS “5-day wonder” abutments

Preassembly issues: bridge bearings • Elastomeric bearings • Cheaper • Less bearing capacity • Must be replaced with time • Direct assembly without specific treatment • Low self-weight girders may call for adhesive treatment • Pot bearings • More expensive • Designed for great loads • No maintenance needed • Requires anchoring to abutments

Assembly issues: equipment - cranes • CRANES ARE THE MOST COST-GENERATING MACHINES IN A BUILDING SITE • Fixed tower cranes • Designed for great loads • One crane fits all • Range is limited, but considerable • Great initial costs • Suited for long building times • Movable telescopic cranes • Specific load limitation for each model • Range is low, but may be optimally positioned • High daily costs • Adequate for fast building Rental cost per day (in thousands of euro) depending on the crane capacity

Assembly issues: prefabricated element placement • Prefabricated bridge assembly phases • Girder placement • Girder joint execution • Tolerance check • Prefabricated deck placement • Deck-to-deck and deck-to-girder joint execution • Tolerance check • Bridge equipment assembly • Final verifications • Critical issues • Costissues are mainlyrelatedtotime, sincecranerentalisthemostrelevantcostduring bridge assembly. • Environmentalissues are mainlyrelatedtonoise, since heavy machineryisnecesarilynoisy • Safety issuesare mainlyrelatedtowindandweather, especiallyforlowself-weightelementssuch 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: • 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. • 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 • Discrete joining facilitates inspection • May be used with all kind of materials • Risk of confusion between similar fasteners should be avoided through design or colored anodization • Welding • Bond is continuous yet easily inspected • Soldered elements may be considered as a whole • Use is restricted to some materials • May be used in extreme conditions, even under water. • Strict safety measures required during welding • Adhesive bonding • Continuous bonding reduces stress concentration • Specifications of use must be strictly obeyed • Sensitive to weather conditions during application and hardening • Element pre-treatment required

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: • They are often weak spots • Joints are assembled on-site and thus subject to human error • Stresses are prone to accumulate in discontinuities • 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: • 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. • Heavy machinery should be removed during low traffic hours, yet observing low-noise time windows for reduced annoyance to neighbors • The building site should be devoid of debris, dirt and rests of building materials before it can be considered dismantled • All infrastructure affected by the building site (pavement, public lighting, etc) should be replaced before the end of the site dismantling process • Building site fence and access limitations to the building site should remain in place until the area has been thoroughly secured, dismantled and cleaned

The PANTURA way: Design and manufacture • Assembly-oriented design addresses critical issues: • Elements size, shape and mass are optimized for easy transport and maneuverability • Regular mass distribution provides element stability and places center of gravity where expected • Support points and safe handles are provided for element assembly • Prefabricated elements respect due tolerances and bear all relevant information • Robotic manufacturing, laser measuring and automatized production provide precise fabrication within tolerance limits • Through the use of RFID tags, barcode identification and tracking systems, elements are always locatable and their relevant info is available • Construction manager has real-time inventory of on-site, in-itinere and in remote storage elements.

The PANTURA way: element transport • Special sized elements are transported causing minimum disturbance • Routes are thoroughly studied and minimum impact time windows selected to avoid disturbance • When infrastructure must be unavoidably removed, contingency plans are made to replace or substitute all affected services as soon as possible • 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 • Elements are duly protected for assured integrity • All elements are padded, properly restrained and protected against weather conditions • Collision Avoidance Systems implanted on transport conveyors minimize risks during loading and unloading of elements • Remote and on-site storage of elements, flexible transport scheduling and building progress control reduce delays due to element delivery • An on-site storage buffer is implemented, while primal storage is remote • 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 • 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 • 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 • 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 • 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. • 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 • 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 • 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 • 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 • RFID readers installed in machinery automatically recognize whether the transported element is being carried to the correct location. • 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 • Stored elements are protected from weather conditions, mechanical impact, flood, fire, etc. • 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 • Selected bridge abutments are either fast to build or prefabricated and easy to install • Bridge bearings are pre-installed on prefabricated abutments • Girders are designed for easy installation and maneuverability • Crane size and use is optimized for minimum cost • Cranes are equipped with distance sensors, surveying systems, anti-sway modules and rotary grippers • Deck panels are lightweight and easily assembled • Joints and connections are reliable, agile and easily inspected • Tolerances are automatically checked by Visual Surveying Systems and 3D scanning • Element placement errors are prevented by the RFID tag monitoring system interconnected with the BIM model

THANKS FOR YOUR ATTENTION

Critical issues for the assembly process Identification and on-site procedures