Please see ORBA feedback …

Please see ORBA feedback (comments, questions, and recommendations) in regards to MTO TCP Notice. No. 000-0148 on: Partial Precast Deck Panel Standard Drawings Updates - Applies to SS109-42_43 & MTOD 3960:

New Partial Depth Precast Deck Panel Drawings and Fabrication Tolerances

MTOD – 3960.100

- Which tolerances will govern, MTOD -3960.100 or the tolerances reported in SSP999S31?
- For consistency can Table 1 of MTOD – 3960.100 be incorporated into SSP999S31?
- The following fabrication tolerances are not reported but are in SSP999S31:
o Stirrup projection (SSP 999S31 = +/- 15)
o Location of inserts (SSP 999S31 = +/- 25)
o Location and size of blockouts (SSP 999S31 = +/- 25)
o Concrete cover for 90/100/110mm panels.
As a result, these tolerances would revert to +/- 5mm as per No. 6 of the Notes in MTOD – 3960.100. Can these tolerances be added to Table 1?

SS109-42

1. Can the jacking force in Table 1 be lowered to 74.5% Fpu (76 KN/Strand) to allow extra pull for additional losses? This would eliminate the need to modify jacking forces and add strands for corrections considering bed shortening and chuck slippage while maintaining the approximate original prestress design and not exceeding the 78% Fpu limit.

2. Note 5 - Projected stirrups will add additional costs to the fabrication of precast deck panels. Costs include additional materials, labour required to tie in stirrups, thicker bunking to clear the tops of the stirrups when stacking panels, and additional storage and shipping costs. Storage and shipping costs would increase since less panels could be safely placed in each stack. Although the stacks would be lighter the overall square footage of the stacks would increase resulting in a greater storage area and more trucks would be required to ship the stacks to site. Additionally, the stirrups impede the use of a vibratory screed rail, which in turn affects the production rate and the surface finish.
It should also be noted that Detail 1 shows the leg of the stirrup sitting below the bottom most 10M rebar. This will compromise the concrete cover. Can the stirrup leg be located in the same plane as the strand so that concrete cover is not compromised?

3. Note 7 – The bearing strips shall be detailed by the Contractor and not the Precaster.

4. Note 11 – Can resistance welding approvals be granted on an annual basis for precast deck panel projects? A welded rebar mat test report for each month of production, which includes a tensile test (requirements as per CSA G30.18, Table 4), an elongation test (requirements as per CSA G30.18, Table 4), a bend test (requirements as per CSA G30.18, Table 5) and a static load test (requirements as per ASTM A 184M-17), can be submitted as part of the precast report package.

5. Note 12 – Coring of panels poses several issues. SSP999S31 specifies that the length/diameter ratio must be greater than or equal to 1.5 and the minimum core diameter is 75mm. For 90mm panels, if a 75mm diameter core is taken, then the L/D ratio = 1.2. For 100mm panels, if a 75mm diameter core is taken, then the L/D ratio = 1.33. For 110mm panels, if a 75mm diameter core is taken, then the L/D ratio = 1.46. All of which do not meet the minim L/D ratio of 1.5.

SSP999S31 specifies that 1 core should be taken for AVS. A single 75mm diameter core, with a nominal max aggregate size of 13.2mm may not provide sufficient surface area (as per ASTM C457-16, Table 1) to complete AVS testing. Additionally, MTO test method LS-432 states, “when a specimen length is less than 200 mm, the laboratory staff shall notify the requestor of the test and obtain confirmation that the specimen dimensions meet applicable requirements before proceeding with specimen preparation and testing. Specimens that do not meet the requirements shall not be tested.”

As per ASTM C1202, cores or cylinders for RCP testing are required to have a nominal diameter of 100mm. If a 100mm core is extracted from a 90mm deck panel, this would result in a L/D ratio of 0.9, which does not meet the requirements of SSP999S31.

6. Detail C (Chamfer Detail) – Note that with long line casting beds it is not possible to terminate the bottom chamfer 150mm from the ends of the panels. The formwork has a 9.5mm radius along the entire length of the bed. We have not heard of any issues to date regarding leakage during the deck pour.

7. How has the strand projection over interior and exterior girders been calculated?
SS109-43 - Same notes as SS109-42 with the following additional comments:

8. Section 1 (Deck Cross – Section) does not show the distance from the outside edge of the bearing strip to the edge of the top flange. This dimension was 50mm on previous drawings.
Assuming a dimension of 50mm, a bearing strip width of 75mm, and a panel overhang of 85mm, the space between opposing deck panels equates to 815mm. With a minimum interior strand projection of 850mm the strands will collide into the opposing panel. Please provide an explanation for the 850mm minimum strand projection.

9. Section 1 (Typical Section) details an 850mm minimum strand projection for interior girders. To achieve the minimum lap length of 625mm a projection length of 800mm is adequate and has been used on previous projects. Please note that an increase in strand projection results in increased material and fabrication costs. The fabrication cost increases because less panels can be cast per day, resulting in additional casting days. Additionally, it would be helpful if the designer specifies on the drawings the length of the strand projection for interior girders in lieu of referring to the 625mm min lap detail.

10. How has the minimum lap length of 625mm been calculated for the 9.5mm diameter strand?