Structural Steel (C-51) · Lesson 5 of 6

Column Anchorage, Two-Bolt Release, and Double Connections

"Column Anchorage, Two-Bolt Release, and Double Connections" is lesson 5 of 6 in the Structural Steel (C-51) Learning Hub. It opens with "Do Not Start Until the Concrete Is Ready" and works through 5 short steps, then a worked example you can check yourself against.

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Steps in this lesson

  1. Do Not Start Until the Concrete Is Ready
  2. Four Anchor Rods and the 300 Pound Test
  3. Competent Person and Rod Changes
  4. The Two-Bolt Rule Before the Load Is Released
  5. Double Connections at a Column

The worked example in the course applies this lesson to a realistic job in 6 steps, from "Concrete strength needed" through "Double connection".

What you'll be able to do

  • Explain the main idea of "Column Anchorage, Two-Bolt Release, and Double Connections" in plain language you can use on the exam.
  • Apply this step with confidence: "Competent Person and Rod Changes".
  • Apply this step with confidence: "The Two-Bolt Rule Before the Load Is Released".
  • Apply this step with confidence: "Double Connections at a Column".
  • Test yourself on the worked example and the quick-check quiz inside the classroom.
Column Base: Anchor Rods and the 300 lb TestCOLUMN BASE, ELEVATIONanchorrods300 lb18 inPLANmin. 4 rodsBEFORE THE CRANE LETS GO1. Concrete strengthf'c 4,000 psi x 75% = 3,000 psiField-cured cylinders: 3,300 psi OK2. Anchor rod test load300 lb x 18 in = 5,400 in-lb5,400 / 12 = 450 lb-ft3. Beam connectionAt least 2 bolts, wrench-tight,before the hoist line is releasedDouble connection: keep 1 bolt on first beamConcrete: 3,300 psi is at least 3,000 psi, so erection may startEach rod assembly is designed to resist 450 lb-ft at the column topSource: 8 CCR Section 1710(c), (f)(1), and (g)(1) and (g)(4) (federal counterpart 29 CFR 1926.755-.756)CC
The diagram for this lesson, exactly as it appears in the Learning Hub.

The first steps of this lesson

Step 1: Do Not Start Until the Concrete Is Ready

A steel erector may not erect steel until it has written notice that the concrete in the footings, piers, and walls (or the mortar in masonry piers and walls) has reached 75 percent of the intended minimum compressive design strength, or enough strength to carry the loads imposed during erection. Strength is shown by an approved test method on field-cured samples, such as an ASTM cylinder test. Source: 8 CCR Section 1710(c)(1) and (c)(2).

Step 2: Four Anchor Rods and the 300 Pound Test

Every column must be anchored by a minimum of four anchor rods (anchor bolts), unless it is braced or guyed to provide the stability to support the eccentric load below. Each column anchor rod assembly, including the column-to-base-plate weld and the column foundation, must be designed to resist a minimum eccentric gravity load of 300 pounds located 18 inches from the extreme outer face of the column in each direction at the top of the column shaft. The column must be set on level finished floors, pre-grouted leveling plates, leveling nuts, or shim packs adequate to transfer the construction loads. Source: 8 CCR Section 1710(f)(1)(A), (B), and (C).

The remaining 3 steps, the worked example and the quiz are in the course. This is a preview. The full lesson, with the step-by-step explanations, a worked example and a quick-check quiz, is inside the classroom.

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