Code Compliance & Reference
This detail complies with HKRC2004 Clause 8.7.3.1 regarding the minimum lap lengths of 250mm; references from consultant’s drawings regarding the “minimum lap = mesh spacing +25mm” is also included.
Comments
- In reality, the steel fabric reinforcement is almost only used in on-grade slabs. At least this is what the HK consultants specified in their drawings; I seldom see consultants specifying fabric reinforcement for other elements such as slabs and walls.
- According the typical details from ArchSD and HyD, the minimum lap for ‘normal’ on-grade slabs and external driveway on-grade slabs are 300mm and 450mm respectively. (These requirements will be specified in the details of on-grade slabs.) These more stringent requirements will override this 250mm minimum lap. Hence, I highly doubt that this 250mm minimum lap will ever be considered.
- I once doubted the feasibility of the lapping of fabrics. Unlike bars (which is 1-D), a 2-D mesh will have to lap with at least 2 other fabrics at the corners, which would mean SIX layers of congested steel reinforcement! On second thoughts, since the mesh are mostly used in on-grade slabs, and (as you will see later) the mesh are discontinued at construction joints every 6m, the laps actually occur in one direction, i.e. at most 4 layers of steel.
I guess, the cross weld between cross bars would be functioned similar to hook in beam.
ReplyDeleteSo, 250 would be enough. HK use 450 lap length would be on the premise that they don't count the
interlocking force between cross bar.
May be, they consider that the welding between reinforcement would be rush the steel?
I am a technical officer~ thanks for what you share.
This blog post is a thorough dive into the technical aspects of steel reinforcement and lap lengths, which are essential in construction to ensure structural stability. The detailed explanation of lap splices for different grades and applications, as well as the importance of overlap to maintain load-bearing capacity, is incredibly valuable. For those of us involved in building and remodeling, it highlights a critical consideration when incorporating reinforcements into concrete structures.
ReplyDeleteSince I’m more focused on exterior work, particularly gutter installation, I’m curious if there are specific considerations or modifications when planning reinforcement details around exterior walls. For instance, do the placements of reinforcement bars or laps need any adjustments in areas where gutter installations or other exterior attachments are involved to prevent potential weakening over time? Would love to hear your insights on this.