Lifting Ring Embedded in Hollow Core Slab Ends
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Solution Overview
Problem
Hollow core slabs are difficult to handle due to issues with existing methods, including misuse of self-tightening clamps, strap placement, and on-site operations that are complex and aesthetically harmful, and require precise integration of transverse elements during manufacturing.
Innovation Solution
A lifting ring is integrated into the hollow core slab during manufacturing, which acts on the reinforcement rather than the concrete, allowing for secure anchorage without additional on-site operations, and is designed to be embedded in the concrete block without altering the slab's manufacturing process, using a process that involves creating an orifice in the upper plate and embedding the ring's branches under the prestressing wire.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If self-tightening clamps are used to move hollow core slabs, then the slabs can be handled, but accidents occur due to misuse or concrete breaking at the clamp jaws
Solution Approach 1:
The lifting ring is pre-installed during slab manufacturing, with branches embedded in concrete blocks at the slab ends. This preliminary action eliminates the need for on-site clamp installation and ensures proper anchorage before handling operations begin, preventing the safety issues associated with improper clamp usage.
Solution Approach 2:
The lifting ring acts as an intermediary gripping element between the handling equipment and the slab. Instead of clamps directly contacting and potentially damaging the concrete, the lifting ring with its reinforcement-anchored branches provides a secure intermediate connection point that distributes loads safely.
2Reliability
If straps are passed under the slab at each end for handling, then security is improved, but the slabs cannot be juxtaposed edge to edge due to strap interference
Solution Approach 1:
The lifting ring branches are extracted from the main slab body and concentrated at the ends within concrete blocks. This extraction allows the main slab surfaces to remain clear and flat, enabling edge-to-edge juxtaposition while the end-mounted branches provide the necessary gripping points for secure handling.
Solution Approach 2:
The lifting function is moved from the bottom surface of the slab (where straps would interfere with juxtaposition) to the end regions of the slab. By positioning the anchorage points at the ends rather than along the bottom surface, the slab can be securely handled while maintaining the ability to place edges against each other.
3Ease of operation
If notches are made on slab edges to receive straps for handling, then juxtaposition becomes possible, but on-site filling operations are required which are time-consuming and harm aesthetics
Solution Approach 1:
The lifting ring branches are pre-installed and embedded in concrete blocks during the manufacturing process. This preliminary action eliminates the need for on-site notching and filling operations, as the anchorage points are already properly positioned and integrated into the slab structure before delivery to the construction site.
Solution Approach 2:
The lifting ring branches are merged with the slab structure by embedding them in concrete blocks that are part of the slab's end regions. This integration means the handling elements become an inherent part of the slab rather than separate additions, eliminating the need for separate on-site installation and finishing operations.
4Reliability
If holes are made in the factory through the slab for sling placement, then secure handling is achieved, but the process is long and expensive and requires aesthetic-harmful on-site filling
Solution Approach 1:
Instead of making holes through the entire slab thickness, the lifting ring branches are embedded only in local concrete blocks at the end regions of the slab. This localized approach provides sufficient anchorage security while requiring minimal material removal and no through-hole drilling, significantly reducing manufacturing time and cost.
Solution Approach 2:
The lifting ring branches are simple steel elements embedded in concrete blocks, representing a cost-effective solution compared to through-hole drilling and sling installation. The concrete blocks themselves serve as the anchorage medium, eliminating the need for expensive drilling equipment and complex on-site assembly operations.
5Ease of operation
If transverse cables are incorporated during slab manufacture as proposed in FR 2 822 868, then handling capability is provided, but the extrusion manufacturing process is complicated and precise on-site accommodation is required
Solution Approach 1:
The lifting function is segmented from the main slab body and concentrated in discrete concrete blocks at the end regions. The lifting ring branches are positioned in these separate blocks rather than being integrated throughout the slab structure, simplifying the extrusion process while providing adequate handling points.
Solution Approach 2:
The lifting ring branches are designed to be self-accommodating within the concrete blocks, with their geometry and positioning allowing automatic alignment and secure anchorage during the extrusion process. This self-service design eliminates the need for precise manual accommodation operations on site, as the elements are already properly positioned during manufacturing.
Data Source
Figure 1~4
Figure 5~6C
Figure 7~9
AI summary
A cellular slab comprising an upper plate (2), a lower plate (3) and intermediate partitions (4) between both plates defining between them parallel and longitudinal cells (5), characterised in that it comprises at least one lifting ring (9) made of a metallic wire in the shape of a staple protruding from a concrete block (10) provided under an opening (7) formed in the lower plate (2) vertical to an intermediate partition (4), the branches of the staple (9) being folded so that their free ends (16, 17) extend under a reinforcement wire (6) of the plate provided in the base (4a) of said intermediate partition.