In one of our Projects, Audi Centre Myaree for the Client PARKD Ltd, the typical structural drawing detail represents the precast wall panel which connects to the Delta core slab with RBA20TI inserts.
Two variations of Precast panel thickness have been used in this project: 150thk, and 200thk.
What is the Problem?
The Insert component RBA20TI or PTI20 are difficult to place on the precast panel face with a wall thickness of 150mm.
Cause for the Problem: Lack of minimum concrete cover is due to component length close to the Panel thickness.
The length of PSA Thread bar Inserts PTI20 is 148mm as per the PSA Schedule.
The minimum concrete cover required for this project is 30mm. However, placing the component with a height of 148mm on a Panel with a thickness of 150mm results in no space for concrete cover, as shown below in Image 1
Image 1: Plan View of 150thk Precast Panel with PTI20 Inserts on the panel face.
Image 2: 3D view of a 150thk precast panel with PTI20 Insert. The highlighted portion in blue indicates a lack of concrete cover.
3D Model Viewer Link for 150thk Precast Panel with PTI20 Insert:
To retain the 30mm concrete cover in the Precast panel, the PTI20 insert component needs to be replaced with PTI16, which has a length of 118mm. This will result in a 32mm concrete cover, satisfying the minimum cover criteria.
Image 3: Plan View of 150thk Precast Panel with PTI16 Inserts on the panel face.
Image 4: Elevation View of 150 thk panel with PTI16 Insert.
Critical Condition To be Remeber:
Although changing the insert size from PTI120 to PTI16. It is highly required to consider the structural strength of the connection.
The structural strength of PTI16 with starter bars of 16 Ø is lower than that of PTI20 with starter bars of 20 Ø.
To overcome this, it is advisable to increase the count of PTI16 insets by reducing their spacing compared to the spacing provided for the PTI20 insert.
Image 5: PTI20 insert with a spacing of 400 centers
Image 6: PTI16 insert with a spacing of 200 centers (The ferrule count increased to tally the structural strength)
But in our case, since we are using inserts over the Delta Core slab, two rows of PTI16 inserts with a spacing of 150mm are to be placed vertically on the Precast Panel, as shown below
Image 7: Detla Cover connects with the 16Ø Starter bars
Image 8: 3D View of Precast Panel with delta Core
3D Model Viewer Link for Precast Panel with Delta core Connection:
Length of Castin components such as Inserts and Ferrule, needs to be considered about the concrete cover and Panel thickness
If the type of insert or ferrule changes, say from PTI20 to PTI16, to reduce its height, it is mandatory to increase the component count to maintain the structural strength.
Thanks to Robin Hur, Structural Engineer and Project Coordinator from PARKD Ltd, for the support and critical suggestions.
