|Bid Date||August 25, 1998|
|MOWAT CONSTRUCTION CO.||(425) 398-0205||10,284,096|
|DILLINGHAM CONSTRUCTION CO.||(925) 847-7027||10,555,695|
|SHIMMICK CONSTRUCTION CO.||(510) 293-1110||11,022,500|
29) Reference Contractor's Inquiry Responses No. 1, Page 3, Question 1, and 3- Abutment 1 Temporary Bridge and Retrofit Work.
Has Caltrans performed a constructability analysis on the Abutment 1 retrofit work and temporary bridge? If so, does the analysis address the problem of the conflict of the permanent work with the temporary bridge? The section thickness of the temporary bridge will be in excess of 1', while many aspects of the permanent work is at grade. For instance, the joint armor (which will take many days and stages to construct) will be in conflict with any temporary arrangement. Most of the elements of the abutment retrofit will take many days to construct and will interfere with some portion of a temporary bridge.
Please transmit to this office, Caltrans constructability reviews pertaining to the subject work. If constructability reviews have not taken place, please confirm such in writing.
Constructability was a prime concern during the design of the seismic anchoring system behind Abutment 1. Our constructability review made on 1/29/96 was based upon the contractor taking advantage of the optional construction joints shown on plan sheets 58 and 63 of 138. It was assumed that the work could be constructed in three phases during each of the three stages shown on the plans which are required for maintaining traffic. We believe the work as shown on the plans is constructable as follows and no further addendum is needed.
Phase 1-During this phase, construction of the piles, the anchor beam, manholes and a portion of the approach slab would be constructed. If sheet piles, or other vertical shoring system, were installed flush with the concrete, the required span length for the deck bridging would be 13 feet in the direction of traffic. This would require about 10" depth for a ribbed steel deck plate system (.06 x 13ft.= say 10"). Since the depth of the approach slab is 14 inches, this will leave more than enough room for the decking needed between shifts during construction of the work below the approach slab. Construction of the approach slab to a ''ready for traffic'' condition would be done during one nighttime lane closure, as is specified.
Also constructed during Phase 1 would be the portion of the Abutment 1 expansion joint supported on the bridge. This would be the 2'6" portion shown in Section B-B on Sheet 57. A deck plate less than 1" thick would work to carry traffic between nighttime lane closures for this work.
Phase 2- During this phase, the couterfort walls and the remainder of the approach slab, except for the 3'2" portion at the abutment backwall shown in Section C-C on Sheet 63, would be constructed. The clear span across the excavation for this work would be about 10 ft. The deck bridging used for Phase 1 would also work for this phase.
Phase 3- During this phase, the portion of the expansion joint supported on the abutment backwall would be constructed. Deck plates for this work would have to span the 4'2" gap between the approach slab placed in Phase 2 and the portion of the expansion joint constructed in Phase 1. A deck plate of about 2" would work for this.
30) Abutment 1 is the major problem, but Abutment 19 has similar problems of lesser magnitude. Solving Abutment 1 as far as the parameters of a "hump" in the roadway should also solve the problems of Abutment 19.
Stage 2,3, and 4 on the traffic handling plans (Sheets 25 of 138, 28 of 138, and 31 of 138) show the work areas for Abutment 1 construction. Each stage provides 2 lanes of traffic for the public in each direction. Lane closure charts provided on Page 66 of the Special Provisions indicate a minimum working window of at least 17 hours.
31) Reference: Page 32 of the Special Provisions, Section 8-2, "Concrete", subsection "8-2.01 Portland Cement Concrete", 2nd subparagraph of paragraph 2 states, " Unless otherwise....2) a combination of Type II Modified portland cement and mineral admixture." I assume the mineral admixture is a fly ash not to exceed 20% of total cement, plus or minus. Does this requirement also apply to cast-in-place concrete piling?
The required mineral admixture content depends on the type of admixture selected for use by the Contractor and is specified in Section 90-4.08 "Required Use of Mineral Admixture" on page 34 of the Special Provisions.
32a) Ref. Plan Sheet No. 119 (Revised per Addendum No. 3): Revised Section "H-H" indicates field welding of 1" vertical side plates to top and bottom plates. Section "B-B" shows shop welding of vertical end plates to top and bottom plates. As field welds shown in section "H-H" will be inaccessible after erection, please confirm these welds should be shop welds.
b)Ref. Plan Sheet No. 119 (Revised per Addendum No. 3): Revised Section "J-J" indicates field welding of 1" vertical side plates to top and bottom plates. Please confirm these welds may be shop welds at Contractor's option.
The vertical side plates are welded to the top and bottom plates and simultaneously welded to the flanges of the existing strut member; therefore, the weld should be done in the field on the outside only.
33) Reference Stopper Block Details No. 2 Sheet 119/138 (Addendum No. 3) & Hinge Retrofit Details Sheet 72 of 89. Regarding the 1" plate assemblies shown in these details we have observed several possible conflicts in the construction/ welding of these assemblies:
a) Reference Sections A-A & B-B Sheet 119/138 for Piers 2,14 & 15-18. There is a 1/2" fillet weld called out for the new 1" stiffener plate to the existing bottom strut (W8x31, tf=7/16" & tw=5/16"). Is this correct?
Section B-B (Pier 2, 14, 15 through 18) shows 1/2" fillet welds near side only, but section H-H & J-J shows 1/4" fillet welds near & far-side. The total weld is a 1/2" fillet weld, which is correct.
b) Reference Sections B-B & J-J for Abutments 1 & 19/Sheet 119/138. The 1/4" arrow side/other side fillet weld called for the 1" stiffener plates to the 1" top & bottom plates is not accessible at the Abutments 1 & 19. We have used a 1/2" other side only weld at these locations for estimating purposes. Is this acceptable?
See Addendum #7.
c) Reference Sections A-A through H-H for Piers 2 & 5-18/Sheet 119 of 138 and Sections A-A, D-D, F-F & Detail 1 for Hinge Retrofit Sheet 121 of 138. Some of the welding called out for the closed/boxed side of the stopper block is problematic in that welds must be performed from one side (the outside) in the field in order that the bolts may be installed on that side. The symbol for plate to plate welds in Section D-D Sheet 121 of 138, while we suppose a partial penetration weld, is not clear. For estimating purposes we have used a 1/2² one sided fillet weld on all the vertical end closure plates. See attached copy of Sheets 119 & 121 annotated accordingly. Is this acceptable?
See Addendum #7.
34) Ref. Plan Sheet No. 116: Partial Plans call out "PL 3/4 (typ)" at the intersection of new W8x31 laterals to the existing laterals. Please confirm these new gusset plates are required both top and bottom.
The call out on Plan Sheets Nos. 116 and 121 designating "PL 3/4 (typ)" is hereby clarified as follows: The intent of (typ) is that these gusset plates are top and bottom and that the entire detail applies at similar locations in that view. The quantities are consistent with this interpretation.
35) Ref. Plan Sheet No. 119: Section "C-C" for Abutment 1, 19 Pier 3, 13 only shows new vertical 1" plates in the area between the existing bottom strut flanges. Section "J-J" indicates vertical 1" plates extend further toward edge of top and bottom plates opposite W8 laterals. Please confirm "hidden" lines opposite W8 laterals at Section "C-C" should be "continuous" lines indicating vertical l" plates are required between top and bottom plates.
On Plan Sheet No. 119, Section C-C, the dashed lines of outer edges of the gusset plates should be solid, as the intent is that these gusset plates extent north and south from the edge of the gusset plate to within 1" of the new W8 laterals, and vertically between the flanges of the top and bottom flanges of the existing W8 strut.
36) Ref. Plan Sheet No. 119: Section "D-D" for Abutment 1, 19 Pier 3, 13 has a continuous line at top of section (parallel to the existing bottom strut) between the vertical stiffeners. Please confirm this line is shown in error as there is no plate in this area.
See Addendum #7.
37) Ref. Plan Sheet No. 121: Same question as #1 above.
Same answer as #1.
38) Page 86, para 2. If slurry is not used to maintain the hole, does it need to be maintained within one foot of the top of the hole?
No. The special provisions say, "When slurry is used."
39) Page 86, para 7. Is a placing log required if the hole is cased the entire length?
No. The special provisions require the log, "when concrete is deposited under slurry."
40) Page 87, para 4. Is temporary steel casing required in the condition stated above? There is no temporary steel casing on the plans.
See Addendum #7.
41) Page 87, para 4. Is temporary steel casing required in a cast under slurry plan?
Temporary steel casing is required at plies at Abutment 1. See Addendum #7.
42) Page 87, last para. If the 1 90 "dummy probe" will not pass, and the state is able to perform the gamma test and/or other test of their choosing, are cored holes required?
Testing will not be performed until the inspection pipes or cored drilled holes are approved by the Engineer.