Section 02164 TIEBACK ANCHORS

Section 02164

_{TIEBACK ANCHORS}

PART 1 - GENERAL

1.1 THE REQUIREMENT

A. This section covers the furnishing, installation, and testing of earth anchors for the tie-back system.

B. The CONTRACTOR shall furnish all tools, equipment, materials, and supplies and shall perform all labor required to complete the Work as indicated in the Contract Documents and specified herein.

1.2 RELATED WORK SPECIFIED ELSEWHERE A. Section 02200 Earthwork

B. Section 03300 Cast-in-Place Concrete

C. Division 05 Metals

D. Division 16 Electrical

1.3 REFERENCE SPECIFICATIONS, CODES AND STANDARDS

A. Comply with the applicable reference specifications as specified in the GENERAL REQUIREMENTS.

B. Comply with the current provisions of the following Codes and Standards.

1. Commercial Standards:

ACI 318 Building Code Requirements for Reinforced

Concrete

ASTM A 123 Specifications for Zinc (Hot-Dip Galvanized) Coatings on Iron and Steel Products

ASTM A 153 Specification for Zinc Coating (Hot Dip) on Iron and Steel Hardware

ASTM A 385 Practice for Providing High-Quality Zinc

Coatings (Hot-Dip)

ASTM A 722 Specification for Uncoated High-Strength Steel

Bar for Prestressing Concrete

ASTM D 512 Test Methods for Chloride Ion in Water

ASTM D 922 Specification for Non-rigid Vinyl Chloride

Polymer Tubing

PCI Recommended Practice for Grouting of Post- Tensioned Concrete

1.4 CONTRACTOR SUBMITTALS

A. Submittals shall be made in accordance with the General Requirements.

B. The following submittals and specific information shall be submitted to the

ENGINEER.

1. Complete data, detailed drawings, and installation drawings of the earth anchors together with all components and accessories including the following items.

a. A tieback anchor schedule indicating anchor identification, design load, test load, lock-off load, type, number, and size of tendon, minimum total anchor length, minimum bond length, minimum tendon bond length, and minimum unbonded length for each earth anchor.

b. A drawing of the tieback anchor tendon and corrosion protection system including details for spacers to separate elements of the tendons and their locations, centralizers and their locations, unbonded length corrosion protection systems, bond length corrosion protection systems, anchorages and enclosure tubes (trumpets), proper identification of all welds, anchorage corrosion protection systems, drilled or formed hole sizes, level of each stage of grouting, any revisions to structure details necessary to accommodate the earth anchor system intended for use.

2. The grout mix design and procedures for placing the grout including reports of strength test results for trial mixes for the cement-rich grout.

1.5 QUALITY ASSURANCE

A. The CONTRACTOR shall provide the services of an ENGINEER, registered in the State of California, with at least 5 years of experience in the design and construction of permanently anchored walls. A foreman or superintendent experienced in the grouting of tiebacks shall be present while this Work is performed.

B. Drilling operators and foremen shall have a minimum of 3 years of experience installing permanent anchors. The CONTRACTOR shall submit satisfactory documentation that Project personnel have appropriate qualifications.

C. Mill certificates shall be submitted to the ENGINEER for the steel tendons. The certificates shall indicate ultimate load, yield stress, and percent of elongation at rupture for each heat of prestressing steel.

D. Tieback testing and lock-off shall be performed by the CONTRACTOR as detailed in the Contract Documents under the continuous observation of the ENGINEER. Test results are subject to the acceptance of the ENGINEER, and the earth anchors are subject to rejection based on the test results.

E. The CONTRACTOR shall notify “DIGALERT” 48 hours prior to beginning excavation or drilling operations.

F. The CONTRACTOR shall furnish a set of As-Built drawings showing all earth anchors remaining in place upon completion of construction operations. As-Built drawings shall show length of concrete embedment, anchor size, length, line and grade of all earth anchors remaining in place.

PART 2 - PRODUCTS

2.1 MATERIALS

A. Anchor Rods shall be: High-strength steel, uncoated; ASTM A 722, Type II (deformed).Dywidag Systems International "Threadbars," Advanced Construction Enterprises "ACE All thread," or equal.

B. Miscellaneous Metal Components, Including Enclosure Tubes, Wedge Plates, Anchor Plates, Bearing Plates, Couplers, and Nuts: Carbon steel, hot-dip galvanized after fabrication in conformity with ASTM A 123, A 153, and A 385.

C. Sheathing, Including End Cap, Grout Tube, Sealing Cap, and Similar Accessories: PVC, minimum compressive strength of 50,000 psi, minimum tensile strength of

7,000 psi; smooth and corrugated shapes as indicated on the Drawings.

D. Corrosion Inhibitors: Mastic; maximum chlorides per ASTM D 512, 10 ppm; maximum nitrates per ASTM D 922, 10 ppm; maximum sulfides per ALPHA "Sulfide in Water," 10 ppm. Visconorust 31664 as manufacutered by PelSeal Technologies, LLC, CORTEC Corporation, Or Equal.

_{E. Grout Additive shall be: Sika "Intraplast N", BASF “Tetraguard AS20” Or Equal.}

F. Centralizers and spacers shall be fabricated from plastic, steel, or material which is non-detrimental to the prestressing steel. Wood shall not be used. The centralizer shall be able to support the tendon in the drill hole and position the tendon so a minimum of 3 inches of grout cover is provided and shall permit grout to freely flow in the drill hole. A combination centralizer and spacer may be used.

2.2 GROUT

A. Grout shall be composed of portland cement, water, aggregate, and an additive as specified hereinbefore. Cement and water shall be as specified in Section 03300

Cast-In-Place Concrete.

B. The proportions of cement, water, aggregate, and additive shall, unless otherwise specified, conform to manufacturer's recommendations and the requirements of ACI

318 to produce a cement-rich grout with a compressive strength of not less than

4,000 psi at 28 days. Maximum chloride ion content of the grout shall not exceed the limits of ACI 318, Table 4.5.4.

2.3 FABRICATION

A. Anchorage and Couplers: Anchorage components shall develop at least 95 percent of the minimum ultimate strength of the bar tendon. Couplers shall develop the minimum ultimate strength of the tendon.

B. Corrosion Protected Tendons: Corrosion protection for the tendons shall be as indicated on the Drawings.

C. Corrective Retensioning: Provision for monitoring long-term prestress loss and corrective retensioning of the anchors shall be as shown on the Plans.

2.4 TENDON STORAGE AND HANDLING

A. Tendons shall be handled and stored in such a manner as to avoid damage or corrosion. Damage to the prestressing steel as a result of abrasions, cuts, nicks, welds, or weld splatter will be cause for rejection. The prestressing steel shall be protected if welding is to be performed in the vicinity. Grounding of welding leads to the prestressing steel is forbidden. Prestressing steel shall be protected from dirt, rust, or deleterious substances. If heavy corrosion or pitting is noted, the ENGINEER shall reject the affected tendons.

B. The CONTRACTOR shall use care in handling and storing the tendons at the site.

Prior to inserting a tendon in the drill hole or auger, the CONTRACTOR and the INSPECTOR shall examine the tendon for damage to the encapsulation and the sheathing. If, in the opinion of the INSPECTOR, the sheathing has been damaged, the CONTRACTOR shall repair it with ultra high molecular weight polyethylene tape. The tape shall be spiral wound around the tendon to completely seal the damaged

area. The pitch of the spiral shall ensure a double thickness at all points.

PART 3 - EXECUTION

3.1 INSTALLATION

A. Installation of the earth anchors shall be in accordance with the instructions, procedures, and details indicated in the Contract Documents.

B. Drilling:

1. The CONTRACTOR shall select the drilling method. The drilling method and procedures shall prevent loss of ground from above and around the drilled hole. Casing for anchor holes, if used, shall be removed. The location, inclination, and alignment of the drilled holes shall be as shown on the Drawings. Inclination and alignment shall be within 3 degrees of the planned angle at the bearing plate, and within 12 inches of the planned point of entry.

C. Tendon Placement:

1. Anchor tendons shall be placed in accordance with manufacturer's recommendations and secured in place by approved supports. Care shall be taken that the anchor tendon is centered in the hole for the entire bond length.

D. Grouting:

1. The anchor load shall be transferred to the ground by bond. Anchor tendons shall not be bonded to the ground in the range of the free stressing length and shall stay permanently free for load checking and any necessary load adjustments.

2. The grouting equipment shall be capable of continuous mechanical mixing to produce a grout free of lumps and undispersed cement. A manifold system with a series of valves and calibrated pressure gauge capable of measuring pressures of at least 150 pounds per inch or twice the actual grout pressures used, whichever is greater, shall permit continuous circulation and pumping of grout with accurate control of grout pressure.

3. Grouting operations shall be in accordance with the PCI "Recommended Practice for Grouting of Post-Tensioned Concrete" and the manufacturer's recommendations.

4. Grout shall be injected at the lowest point of the drilled hole. Grouting shall proceed such that the hole is filled to prevent air voids. The hole shall be filled progressively from bottom to 2 feet above the bond length (attached length).

5. The free length (unbonded length) shall be filled with a 2-sack cement-sand slurry as shown on the shop drawings.

3.2 LOAD MONITORING DEVICES

A. Permanent load cells shall be furnished and installed at the anchor locations indicated on the Drawings. The load cells shall be annular in shape and hermetically sealed, with the center hole of adequate size to accommodate the tendon. The tendon shall be concentrically located in the annular space and the axes of the tendon and load cell shall be parallel to prevent eccentric loading.

B. All necessary hardware and/or adapters required by the manufacturer for proper functioning of the load cells shall be provided. Permanent load cells shall be installed after all required tests have been successfully performed on the anchor. The capacity of each load cell shall be at least 125 percent of the design load.

C. Weatherproof and waterproof terminal boxes and conduit to group instrument leads shall be furnished and installed at the locations indicated on the drawings.

D. Load cells shall be as manufactured by: Transducers, Inc.

P.O. BOX 3344

Sedona, Arizona 86340

Phone: (800) 398-6481,

Geokon Incorporated

48 Spencer Street

Lebanon, NH 03776,

Or Equal.

3.3 STRESSING AND TESTING

A. Anchor Stressing: Stressing shall not start before the grout and the adjacent concrete lagging has reached a minimum compressive strength of 3,500 psi and

1,000 psi, respectively, and has set for at least 3 days after its placement in the drilled hole. A minimum of three grout cubes and concrete cylinders must have been tested and two must have reached the specified strength. Test reports shall be submitted to the ENGINEER for acceptance prior to stressing.

B. Testing of Anchors: The design capacities of all tiebacks shall be verified by a program of proof tests, performance tests, and creep tests.

1. The CONTRACTOR shall provide all equipment and instrumentation necessary for verification of the adequacy of the earth anchors.

a. A dial gauge with tripod support and capable of measuring displacements to

0.001 inch precision and having 6 inches of travel shall be used to measure earth anchor movement.

b. A hydraulic jack and pump shall be used to apply the test load. The jack and calibrated pressure gauge shall be used to measure the applied load. The hydraulic jack capacity shall be at least 250 percent of the earth anchor design load. The pressure gauge shall be graduated in 100 psi increments or less. The load shall be applied incrementally. The load shall be raised or lowered from one increment to another as shown on the plans.

c. The stressing equipment shall be placed over the anchor tendon in such a manner that the jack, bearing plate, and stressing anchorage are axially aligned with the tendon and the tendon is centered within the equipment.

2. Load sequencing for anchor testing and acceptance criteria for test results shall be as indicated on the plans.

3. If the load test results are acceptable to the ENGINEER, the earth anchor shall be locked-off at no less than 110 percent of the rated design load.

a. The earth anchor may be completely unloaded prior to lock-off.

b. After transferring the load and prior to removing the jack, a lift-off reading shall be made.

c. The lift-off load shall be within 10 percent of the required lock-off load (110 percent of design load); if not, the anchorage shall be reset, and the lift-off measurement repeated until an acceptable reading is obtained.

4. If the load test results are not acceptable to the ENGINEER, the earth anchor shall be replaced as directed by the ENGINEER.

5. For temporary tieback anchor installation, the number of anchors tested to the

200 percent design load shall be determined by the ENGINEER; however, a minimum of 2 percent of the anchors at each level shall be tested to the

200 percent load and held at a constant tension for a period of time not less than

24 hours. Once the loading for 200 percent of the design load is reached, the axial extension of the anchor assembly shall not exceed 1/2 inch. An axial extension exceeding 1 inch is considered as failure, while axial extensions ranging from 1/2 inch to 1 inch may be assigned partial capacity ratings subject to approval of the Structural Engineer licensed in the State of California responsible for the design of the shoring system and the ENGINEER. The total

axial anchor extension, measured form the time of initial load application to the

termination of the 200 percent load shall not exceed 4 inches. If the total axial extension of the anchor exceeds 4 inches, the ENGINEER may down rate or reject the anchor as unacceptable.

6. All remaining tieback anchors shall be proof tested to a least 150 percent of the design load. Any proof-tested anchor with axial extension exceeding 0.1 inch after 15 minutes under 150 percent of design load or a total axial extension exceeding 4 inches from initial application of load to termination of the test may be down rated or rejected by the ENGINEER.

7. The CONTRACTOR shall submit anchor-testing procedures to the ENGINEER

for acceptance prior to installation of any temporary tieback anchors.

8. Grouted anchors that depend on the maintenance of high grout pressures for their design capacity shall not be permitted.