Amend 4_Slab Tests QA Final.pdf

Questions & Answers Solicitation No. NIST-RFQ-22-7301949

Structural Tests of Slab-Column and Slab-Beam-Column Connections for the Champlain Towers South

1. When will the award proceed?

The anticipated period of performance start date is 15 February 2023.

2. For slab-beam-column tests, is it acceptable to temporarily remove the 750 kip axial load on the column prior to testing in order to allow for setting up the testing equipment?

No. It is not acceptable to temporarily remove the 750 kip axial load on the column prior to testing.

3. For the slab-column connections tests, the solicitation states “the Contractor should anticipate two tests with both shear V and moment Msc transferred between the slab and column slab-column connection”. What is the expected value of the column moment?

As stated in the solicitation Performance Work Statement: “the Contractor should estimate that the moment to column force ratio is Msc/V = 12 in. NIST reserves the right to modify this ratio at a later date.”

4. Can details be provided on the corrosion protocol?

As stated in the Performance Work Statement: “Accelerated corrosion shall be achieved through a salt pond created over the damaged slab or impressed electrical current, or a combination of the two. NIST expects to engage a corrosion expert under a separate contract to develop and demonstrate the accelerated corrosion protocol. That corrosion contractor, retained by NIST, will then work with the Contractor for this project, through the NIST Contracting Officer’s Representative (COR), to advise on the corrosion protocol and view its implementation.” No further details are available.

5. How are the aggregates and cement stored in Miami?

The aggregates and cement will be stored in a warehouse in Miami. In the warehouse, they are stored as stated in the Performance Work Statement, “Coarse and fine aggregates will be provided in 3,000 lb super sacks on pallets, while cement will be provided in 2,000 lb super sacks on pallets. The pallet dimensions are 4 ft by 4 ft.”

6. Given the unique nature of the tests, will there be any restrictions for the research team to publish the data in relevant structural engineering journals?

Yes, there are restrictions. Because the work under this contract is part of a National Construction Safety Team investigation, it is subject to the disclosure restrictions contained in 15 CFR Part 270.340. In particular, the contractor may not release, reproduce, distribute, or publish any information developed as part of this work, without the permission of the NIST Director or their designee.

NIST intends to publish the data, results of the work, and reports received under this contract, without including personally identifiable information or other sensitive information that is restricted from disclosure.

At the conclusion of the contract resulting from this solicitation, and following the issuance of the final NIST report, the NIST Contracting Officer, as the designee of the NIST Director and in accordance with 15 CFR Part 270.340, intends to grant a general waiver of the restriction against disclosure of the published data, results of the work, and reports received under this Contract, and make such data and results available for use by any interested party, consistent with and subject to 15 CFR Part 270.310. Such waiver may be granted in NIST’s sole discretion and in no instance prior to the publication of the final NIST report.

After the waiver is granted, the Contractor shall be released to publish the data in relevant structural engineering journals.

7. Can you please provide additional information on the requirement for the data acquisition system to be calibrated by an external ISO-17025 accredited laboratory?

Since the requirements of the ISO-17025 are very onerous for most structural laboratories, NIST has revised the following paragraph in Tasks 1 and 2 of the Performance Work Statement using tracked changes as follows:

“The Contractor shall use equipment that is maintained and calibrated in accordance with accepted good practices, including those following in this paragraph. Unless otherwise approved by NIST, the data acquisition system shall be calibrated by an external ISO-17025 accredited lab approximately once every two years; force-measuring instruments and systems shall be calibrated at intervals not exceeding two years in accordance with ASTM E74-18e1; and position transducers shall be calibrated using the procedures and at intervals as specified in ASTM F2537-06(2017). by using high-precision calibration blocks that are certified by an ISO-17025 accredited lab of the manufacturer. Equivalent or better calibration practices shall be considered. For all measurements, the Contractor shall furnish to NIST for NIST’s approval the calibration records or methods of the instrumentation used and shall report the precision in the measurement.”

References:

• ASTM E74-18e1 (2018). “Standard Practices for Calibration and Verification for Force-Measuring Instruments,” ASTM International.

• ASTM F2537-06 (2017). “Standard Practice for Calibration of Linear Displacement Sensor Systems Used to Measure Micromotion,” ASTM International.

8. General Question: In Figure 1.4, is the 0” measurement meant to indicate a horizontal contact lap splice of the No. 4 bottom bars?

Yes, the 0” measurement is meant to indicate a horizontal contact lap slice of the No. 4 bottom bars.

9. General Question: Can 4x8 concrete cylinders be used for the companion specimens instead of 6x12s?

No. 4 in x 8 in concrete cylinders are not acceptable.

10. Geometry Question: Task 1 – Is there any flexibility on the value of the “r” in Task 1 (e.g. 4.75 vs 5 ft and 3.35 ft vs 3 ft in Figure 1)?

NIST will consider proposals to modify the value of r by +/-4 in where that modification will result in appreciable cost savings for the test apparatus. If a quoter proposes modifying the value of r by +/- 4, the quoter shall demonstrate in its technical volume what the benefits to NIST will be as a result of this modification.

11. Geometry Question: Task 1 – Do the loading/support points need to be 45 deg from one another or is it permissible to have alternative points to accommodate existing support locations (holes) in the strong floor?

Alternative test apparatus can be proposed by the prospective Contractor, but alternative apparatus should approximately reproduce the nearly axi-symmetric shear and moment distributions, as well as shear to moment ratios in the slab near the column as are produced by the apparatus shown in the PWS.

12. Geometry Question: Task 2 – Is there flexibility in the width of the slab (e.g., 72

in. vs 96 inc. in Figure 2.1)?

As stated in the Performance Work Statement (Task 2): “Modifications of any of these overall dimensions of the test specimen configuration requires review and approval by NIST.”

Prospective Contractors may propose alternative dimensions, as long as they do not result in major changes in the dimensions and they produce similar balance and stiffness. The quoter’s technical volume shall explain how similar balance and stiffness will be achieved.

13. Geometry Question: Task 2 – Is there flexibility in the length of the specimens (e.g., 144 in. vs 184 in. in Figure 2.1)?

The Performance Work Statement states: “The floor elements to the north and south (left and right, respectively, in Figure 2.1(a)) sides of the column are sized to result in approximately equal static moments about the column centerline under self-weight.”

Prospective Contractors may propose alternative dimensions, as long as they do and stiffness.

14. Geometry Question: Task 2 – Is there flexibility in the height of the column (e.g.

total column height of 14 ft. vs 16 ft. in Figure 2.1)?

As stated in the Performance Work Statement (Task 2): “Modifications of any of these overall dimensions of the test specimen configuration requires review and approval by NIST.”

Prospective Contractors may propose alternative dimensions, as long as they do and stiffness.

15. Geometry Question: Task 2 – Can the specimens be tested at a reduced scale (e.g. 75%) to accommodate existing test fixtures?

No, the specimens may not be tested at a reduced scale. Specimens must be tested at full scale as shown in the PWS; scaled specimens are not permitted.

16. Construction Question: Task 1 – Can the amount of shear reinforcement in the column stub be increased, as needed, to prevent spurious shear failure?

While the ties in the column stub are closely spaced at 3 inches as shown in Figure 1.3, yes, it is permissible to increase the shear reinforcement if needed by the Contractor.

17. Construction Question: Task 1 – Can heads rather than hooks be used to terminate the slab reinforcement?

Yes, heads rather than hooks are permitted as long as the heads satisfy ASTM A 970 or better. The Performance Work Statement has been revised accordingly.

18. Construction Question: Task 2 – Can the column concrete (lower and upper) be cast simultaneously with a voided region that will be filled with the 4000-psi slab and beam concrete?

No, the column concrete (lower and upper) may not be cast simultaneously with a voided region that will be filled with the 4000-psi slab and beam concrete. The construction sequence must match the actual building construction sequence specified in the Performance Work Statement.

19. Construction Question: Task 2 –

a) What is the maximum diameter of the holes used to accommodate the post-tensioning rods used to apply the axial force?

The required diameter of the holes shall be determined as part of the test apparatus design developed by the Contractor and approved by NIST, but should not significantly exceed the diameter of the post-tensioned (PT) rods (or other items) used to pass through the holes. NIST wishes to minimize disruption to the slab while still permitting small items to pass through the slab to facilitate the sustained loading. The quoter’s technical volume shall describe the quoter’s proposed approach.

b) What is the minimum distance from the column?

The required position of the holes shall be determined as part of the test apparatus design developed by the Contractor and approved by NIST. However, the holes shall not be located closer than about 2 inches from the column face.

c) Can the holes be placed in the beams that run E-W in Figure 2.1?

No, the holes shall not be placed in the E-W beams.

20. Construction Question Task 2 – Can penetrations be placed at the end of the beam and slab at the support/ loading areas to connect to the specimen to supports or loading devices (i.e., 96 in. and 72 in. from the face of the column, respectively)?

Yes. Penetrations may be placed at the end of the beam and slab at the support/loading areas to connect the specimen to support or loading devices.

21. Instrumentation Question Task 1 – To confirm, is it correct that electrical resistance strain gages will not be applied to the reinforcement of SC-A2, SC-A4, SC-B1, and SC-B4 (those specimens undergoing the accelerated corrosion procedure)?

Correct, NIST does not require the application of electrical resistance strain gauges for these corroded test specimens within regions where corrosion occurs.

If portions of a test specimen are not within a region of accelerated corrosion, then strain gauges similar to those used in other specimens without corrosion should be considered in those non-corroded portions. NIST welcomes, however, innovative thinking that would enable the measurement of reinforcement strains within corrosion regions in specimens undergoing the corrosion protocols. As noted elsewhere, corrosion protocols are still under development and will be conveyed to the successful Contractor after award of the contract.

22. Instrumentation Question Task 1 – Is there a preferred method (other than manual) for monitoring crack geometry?

No, there is not a preferred method. It is the responsibility of the Contractor to quote the method for monitoring crack geometry it believes is best suited for the requirement.

23. Instrumentation Question Task 2 – What deformations need to be monitored during the sustained loading period?

As stated in the Performance Work Statement: “Local axial deformations of the column, with emphasis on the axial shortening of the section of the column through the height of the floor system” shall be monitored during the sustained loading period.

24. Instrumentation Question Task 2 – What deformations and loads/reactions need to be measured during the application of the shear load, V, on the E-W beam and slab to failure?

The required measurements are all specified in the Section “Instrumentation, Testing, and Data Recording” under Task 2 of the PWS.

25. Loading Question Task 1 - For SC-B2, SC-B3, SC-B4, do the specimens need to be loaded through the column? Can the column base be restrained against rotation with the slab loaded with unbalanced forces at the loading/reaction plates shown in Fig. 1.1?

For the first question, the specimens do not necessarily need to be loaded through the column. For the second question, yes; the column base may be restrained against rotation with the slab loaded with unbalanced forces at the loading plates/reaction. Subject to NIST’s approval, the Contractor may propose a suitable way of loading and supporting the specimens to achieve the test requirements outlined in the PWS. NIST’s acceptance will depend on how well the transfer of unbalanced forces matches the transfer that occurs in a real building slab. NIST prefers to restrain the outer edge of the slab while applying an eccentric axial force to the column, but NIST will consider other proposed approaches. It is the quoter’s responsibility to demonstrate in its quotation that the proposed approach will achieve the requirements outlined in the PWS.

26. Loading Question Task 1 - Can SC-B3 be loaded with a prescribed P/M ratio, or does the moment need to occur through unbalanced reactions at the perimeter of the specimen?

As stated in the PWS: “the Contractor should estimate that the moment to shear ratio is Msc/V = 12 in. NIST reserves the right to modify this ratio at a later date.”

NIST prefers to restrain the outer edge of the slab while applying an eccentric axial force to the column, but NIST will consider other proposed approaches.

NIST’s acceptance will depend on how well the transfer of unbalanced forces matches the transfer that occurs in a real building slab. It is the quoter’s responsibility to demonstrate in its quotation that the proposed approach will achieve the requirements outlined in the PWS.

27. Loading Question Task 2 - Can the sustained load be applied with post-tensioning rods, unloaded, and then the specimen tested with the vertical load applied using a universal testing machine under displacement control?

No, this method is not acceptable. The sustained load must be maintained throughout.

28. Loading Question Task 2 - Could the sustained loading be terminated prior to 3 months, if a specific level of axial deformation was reached?

No, the column shall be loaded for the full 3-month period. Loading shall be terminated only in the case that column failure makes the column unable to support the specified loads.

29. Loading Question Task 2 - How are the slab and the N-S beam supported during the sustained loading period?

With the exception of lateral bracing, the slab and the N-S beam will remain unsupported during the sustained loading period.

30. Loading Question Task 2 - Can the two specimens be placed under sustained loads at different times, i.e., sequential testing?

No. As the Performance Work Statement states: “The sustained load tests shall be conducted on Specimens SBC-L9.1a and SBC-L9.1b simultaneously.” A short delay of no more than a few days between the starts of the sustained loading for the two test specimens is permitted to allow for time required to apply the loading. This is required for project scheduling reasons. No further delays, or sequential testing, is allowable. The Performance Work Statement has been revised to reflect this.

31. Loading Question Task 2 - Does the shear force, V, need to be applied in displacement control, load control, or is either acceptable?

At the early stages of loading, the shear force, V, may be applied in either displacement or load control. At later stages (prior to failure), the Contractor shall apply the shear force V in a manner that enables controlled displacement of the beam until complete failure of the beam is achieved.

32. Loading Question Task 2 - Is it acceptable to remove the beam through saw cutting once the post-peak strength has reached a specified percentage of the peak value? Or at a specific chord rotation?

No, it is not acceptable to remove the beam through saw cutting. The loading shall continue until the failure of the slab and/or beam is complete and the beam breaks away from the column.

33. Corrosion Question Task 1 - Is there a required plan area for the corrosion condition, or is the mass loss levels in the Performance Work Statement meant to be measured over the entire slab?

This information will be specified by the protocol that will be provided by NIST and its corrosion contractor following award.

34. Corrosion Question Task 1 - Does the bottom reinforcement need to be corroded?

and its corrosion contractor following award.

35. What is the anticipated start date of the contract?

36. Will the contractor conducting the structural tests be allowed to discuss and publish the results of the tests, or will a nondisclosure agreement be required?

There are restrictions. Because the work under this contract is part of a National Construction Safety Team investigation, it is subject to the disclosure restrictions contained in 15 CFR Part 270.340. In particular, the contractor may not release, reproduce, distribute, or publish any information developed as part of this work, without the permission of the NIST Director or their designee.

NIST intends to publish the data, results of the work, and reports received under this contract, without including personally identifiable information or other sensitive information that is restricted from disclosure.

At the conclusion of the contractor resulting from this solicitation, and following the issuance of the final NIST report, the NIST Contracting Officer, as the designee of the NIST Director and in accordance with 15 CFR Part 270.340, intends to grant a general waiver of the restriction against disclosure of the published data, results of the work, and reports received under this Contract, and make such data and results available for use by any interested party, consistent with and subject to 15 CFR Part 270.310. Such waiver may be granted in NIST’s sole discretion and in no instance prior to the publication of the final NIST report.

After the waiver is granted, the Contractor shall be released to publish the data in relevant structural engineering journals.

37. When is the expected start date (notice to proceed)?

38. Does equipment requiring ISO certification/calibration need to be certified/calibrated when the quote is submitted or by the time testing gets underway?

See answer to Question 7. Certification/calibration conformation shall be submitted and approved by NIST before testing begins.

39. Do stresses in specimens need to be monitored when specimens are transported from the casting location to the testing apparatus?

No, stresses in specimens do not need to be monitored in transport. It is expected, however, that transport of specimens will be done with an appropriate degree of care so as not to damage the specimens during transport.

40. What is the degree of detail needed in drawings included in the quote? Are schematic drawings acceptable?

Schematic drawings are acceptable.

41. What batch size (yd3) is acceptable for trial batches of concrete?

The batch size shall allow enough concrete for slump test(s) and companion cylinders.

42. Is a certification required for the person(s) tasked with bending reinforcement?

No; certification is not required for bending reinforcement. As stated in the “Key Personnel” section of the PWS: “At least one of the key personnel shall have at least ten (10) years of experience with concrete design provisions in ACI-318 and concrete construction specifications in ACI-301, along with all ASTM standards defined in the Performance Work Statement.” NIST anticipates that reinforcement will be fabricated professionally and in accordance with accepted fabrication standards.

43. Is the intent of inducing accelerated corrosion of top slab reinforcement to reduce bar cross-sectional area locally or to emulate corrosion in a uniform fashion along the bars?

The intent is to replicate natural corrosion, including loss of reinforcement cross section and damage to surrounding concrete due to increased volume of the corrosion products. Details of the corrosion protocol will be provided by NIST and its corrosion contractor to the successful contractor after award.

44. Is the intent of the accelerated corrosion of the top slab reinforcement to emulate the damage mechanics associated with chloride-induced corrosion, which would include the cracking and delamination of concrete associated with expansion of corrosion products and loss of bond along bars?

The intent is to replicate natural corrosion, including loss of reinforcement cross section and damage to surrounding concrete due to increased volume of the corrosion products. Details of the corrosion protocol will be provided by NIST and its corrosion contractor to the successful contractor after award.

45. Is the intent to have the longitudinal column bars electrically isolated from the slab bars such that there should be little or no corrosion?

The intent is to replicate natural corrosion, including loss of reinforcement cross section and damage to surrounding concrete due to increased volume of the corrosion products. Details of the corrosion protocol will be provided by NIST and its corrosion contractor to the successful contractor after award. Some corrosion of column reinforcement may be included in the protocol.

46. Can a foreign consultant be included in the investigative team?

Yes, foreign consultants may be included in the quoted investigative team. Any foreign consultants quoted shall be clearly identified as such. If foreign consultants are quoted, the following clause is applicable:

CAR 1352.237-73 Foreign national visitor and guest access to departmental resources.

(a) The contractor shall comply with the provisions of Department Administrative Order 207-12, Foreign National Visitor and Guest Access Program; Bureau of Industry and Security Export Administrative Regulations Part 734, and [insert operating unit counsel specific procedures]. The contractor shall provide the Government with notice of foreign nationals requiring access to any Department of Commerce facility or through a Department of Commerce IT system.

(b) The contractor shall identify each foreign national who requires access to any Departmental resources, and shall provide all requested information in writing to the Contracting Officer's Representative.

(c) The contractor shall include the substance of this clause, including this paragraph, in all subcontracts.

(End of clause)

If foreign consultants are not quoted, this clause does not apply.

47. Is ACI Certification needed for the conduct of concrete materials testing?

No, ACI Certification is not required for the conduct of concrete materials testing.

48. Is the use of DIC for deformation measurements during Task 1 tests intended for only the slab tension side or both sides?

The solicitation evaluation Factor A – Technical Approach states: “NIST also prefers the use of 3-D digital image correlation (DIC) system to measure slab deformations in Task 1.” This preference is intended for the slab tension side.

49. Would the use of a non-contact instrumentation system such as Optotrak be acceptable in lieu of DIC?

Yes, the use of alternative non-contact instrumentation systems that provide similar or better measurement capabilities is permitted and will be considered equivalent to DIC in evaluation factor A - Technical Approach. The quoter’s response shall clearly indicate who required specifications will be met by the proposed approach.

50. For the Task 2 has NIST calculated or determined the expected capacity of the column following the beam failure?

No, has not been calculated or determined. Such calculation of the column’s expected capacity is complex due to the potential for damage to column cross section due to failure of beam and slab.

51. Will NIST be performing high-fidelity finite element modeling (Abaqus, Atena, or similar) as part of this study that could inform the contractors test setup design?

NIST plans to conduct preliminary high-fidelity finite element pre-test analyses of uncorroded specimen SC-A1 of Task 1 using LS-DYNA and/or ATENA to provide an approximate estimate of the failure load and to inform the Contractor’s test setup. NIST might also conduct similar analyses for other specimens, but such pre-test predictions might not be as accurate.

52. Is it intended that the test cylinders in Subtasks 1.2/2.2 be moist-cured for 7-14 days as in Subtasks 1.3/1.6/2.3, or should they be cured for a standard 28 days?

The cylinders from the test batches in Subtasks 1.2 and 2.2 shall be sealed at 60 F – 80 F and stripped after 24 hours. The cylinders shall then remain immersed in a 73 F limewater bath until testing at ages 7 days, 14 days, and 28 days.

53. For Task 1, is NIST open to alternative methods to salt ponding or impressed current to accelerate corrosion or mimic corrosion damage?

As stated in the PWS: “NIST expects to engage a corrosion expert under a separate contract to develop and demonstrate the accelerated corrosion protocol. That corrosion contractor, retained by NIST, will then work with the Contractor for this project, through the NIST Contracting Officer’s Representative (COR), to advise on the corrosion protocol and view its implementation.”

and its separate corrosion contractor after award.

54. To allow for transportation of the slab-beam-column tests (i.e., Task 2) can the vertical dimensions of the columns be shortened or include cold joints?

As stated in the Performance Work Statement (Task 2): “Modifications of any of these overall dimensions of the test specimen configuration requires review and approval by NIST.”

Prospective Contractors may propose alternative dimensions, as long as they do not result in major changes in the dimensions and produce similar balance and stiffness. However, as noted in the Performance Work Statement, some regions of the columns, beams, and slabs near the connection need to be constructed as specified, but some deviations outside this region can be considered if required, for example, to connect the specimen to the test apparatus.

55. For Task 1 specimens, can changes in thickness of the slab be measured from the top and bottom rather than through the slab?

Yes, it is permissible to measure the change in slab thickness from the top and bottom of the slab.

56. For Task 1 specimens, can moment be introduced by widening the bottom of the column and loading eccentrically relative to the centerline of the slab?

Yes, that is an acceptable way of achieving the required moment, Msc.

-- No additional questions were received in relation to this solicitation --