Prefabricated Structural Elements: Connections, Handling, Assembly and Control

EHE-08

Art. 59.1.3. Connection and Support Elements, Prefabricated:

59.1.3.1. Materials: Stable, durable, physically and chemically compatible, fire-resistant materials. Metallic connectors resistant to corrosion or protected against it. Supports resistant with properties indicated in the project.

59.1.3.2. Connection Design: Connections must resist all considered actions, following holistic efforts to design and accommodate movements and deformations. To prevent damage to the concrete of the elements at extremes, take into account: relative movements, imperfections, execution tolerances, and ease of inspection.

59.1.3.3. Compression Connections: When holistic efforts shear less than 10% of the compression force, the shear is neglected. Support materials: mortar, concrete, or polymers. They must allow relative movement of surfaces during hardening. Connections should be used only when proper quality and surface preparation are guaranteed.

59.1.3.4. Connections for Bending and Traction: Continuous truss and anchored embedment with adjacent elements through: rebar injection in mortar-filled pockets, ensuring armor continuity; welded bars or plates; pre-stressing; or mechanical devices such as threaded couplings.

Art. 76.4. Connections of Prefabricated Elements: Connections must ensure the correct transmission of holistic efforts between each piece and adjacent ones. They must be built so that the dimensional tolerances of normal prefabrication can be absorbed. Elements must not present irregularities, and it is not permitted to attempt to correct them with cement mortar, as this does not guarantee transmission. Care must be taken that heat-welded connections do not cause damage to the concrete or frames. Post-tensioning connections must use special devices without long threads. Threaded connections require attention to the calibration of tension equipment, using torque wrenches consistent with the project.

Art. 76.2. Collection of Prefabricated Elements on Site: Where appropriate, seek stockpile areas large enough to allow sufficient management, and allow the same wing to be served whenever possible by trucks, maneuvers, or cranes if necessary. Elements must be stockpiled on horizontal supports sufficiently rigid according to the soil characteristics and their dimensions and weight. In the case of joists and hollow-core slabs, they must not be stored in the same vertical alignment with cantilevers, nor stacked more than 0.50 m apart, nor stack heights exceeding 1.50 m unless a greater height is indicated by the manufacturer. Where appropriate, fixings and similar items must be stored in a dedicated warehouse area with their characteristics maintained to ensure the necessary traceability.

Art. 76.1. Transport, Unloading, and Handling of Prefabricated Elements: At a minimum, the following conditions must be taken into account:

• Supports on truck beds must not create holistic efforts in the elements not contemplated in the project.
• Loading must begin with tied movements to avoid indiscriminate movement.
• All parts must be secured with devices that avoid impacts and any necessary effects during transport.
• If transport is carried out at very early ages, its detachment during transport must be avoided.
• For unloading and handling on site, the builder or, where appropriate, the precast supplier must use suitable unloading means according to the dimensions and weight of the element, taking special care to avoid losses of verticality or alignment that could produce inadmissible stresses.

In all cases, the manufacturer's instructions for handling the elements must be followed. Any damaged element that may affect its load-bearing capacity must be handled according to its assessment.

Art. 76.3.2. Assembly of Prefabricated Elements: When assembling prefabricated beams, take timely measures to prevent overturning or landslides at supports. The project must include a study in which the assembly of prefabricated elements is planned, and provisional struts must be included to prevent instability and potential problems during the structural assembly. Assembly must conform to the project, especially to the plans and drawings indicated, and must follow the sequence of operations as well as the manufacturer's installation instructions for the specified product. Depending on the type of prefabricated element, assembly may need to be carried out by specialized personnel with appropriate training.

Art. 91. Control of Prefabricated Elements: The control will be carried out at the factory and will include inspection of the behavior of the concrete as well as the steel reinforcement and the behavior of the precast element itself. This may include checks of manufacturing processes as well as the materials used and the final geometry of the element. The supplier shall require from the manufacturer or constructor documentation on all processes related to prefabrication and, in particular, information proving the existence of production control.

Art. 99. Control of Assembly of Prefabricated Elements and Connections: Before the start of assembly, the following checks must be carried out: a) the elements conform to the project specifications and are properly collected, with no apparent damage present; b) sufficiently defined levels exist for the assembly of the prefabricated elements, as well as any additional measures required; c) a program is available for execution, clearly defining the assembly sequence of the prefabricated elements; d) sufficient human and material resources are available for the assembly. During assembly, ensure that all project indications are met, paying special attention to dimensions and execution conditions of the supports, links, and joints.