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Presentation on theme: "CONCRETE AND MASONRY CONSTRUCTION"— Presentation transcript:


2 Cooling Tower St. Mary’s West Virginia 1978
51 killed 170 feet above ground Entire form peeled away from newly placed concrete

3 looked like if it had been completed.
What the St. Mary’s West Virginia tower would have looked like if it had been completed.

4 Jump forms atop the St. Mary’s structure tore loose, pulling work platforms and concrete down inside the tower.

5 Wreckage 168 feet below the top of the St
Wreckage 168 feet below the top of the St. Mary’s tower being picked apart by investigators looking for clues. The state of West Virginia objected to the site being cleaned before it could make its own full investigation.

6 Part 1926 Subpart Q Concrete and Masonry Construction
Scope, application, and definitions applicable to this subpart. General requirements Requirements for equipment and tools. Requirements for cast-in-place Concrete. App - General Requirements for Formwork Requirements for precast concrete. Requirements for lift-slab operations. App - Lift Slab Operations Requirements for masonry construction.

7 29 CFR 1926 700 Scope, application, and definitions applicable to this subpart.
"Bull float" "Formwork" "Lift slab" "Limited access zone" "Precast concrete" "Reshoring" "Shore" "Vertical slip forms" “Jacking operation”

8 29 CFR 1926.701 General requirements
(a) Construction loads. (b) Reinforcing steel. (c) Post-tensioning operations. (d) Riding concrete buckets. (e) Working under loads. (f) Personal protective equipment.

9 (b) All protruding reinforcing steel, onto and into which employees could fall,shall be guarded to eliminate the hazard of impalement.

10 Rebar protection

11 (c) - Post-tensioning operations No employee (except those essential to the post-tensioning operations) shall be permitted to be behind the jack during tensioning operations

12 Jack

13 Cutting bars

14 1926.701(d) Riding concrete buckets No employee shall be permitted to ride concrete buckets.

15 702 Equipment and Tools. (a) Bulk cement storage. (b) Concrete mixers.
(c) Power concrete trowels. (d) Concrete buggies. (e) Concrete pumping systems. (f) Concrete buckets. (g) Tremies. (h) Bull floats. (i) Masonry saws. (j) Lockout/Tagout procedures.

16 1926.702 (b) Concrete mixers with one cubic yard or larger loading shall be equipped with:
A mechanical device to clear the skip of materials Guardrails installed on each side of the skip

17 Pumping System 1926.702(e) (1) Concrete pumping
systems shall be provided with pipe supports designed for 100 percent overload. (2) Air hoses shall be provided with positive fail-safe joint connectors.

18 (g) Tremies. Sections of tremies and similar concrete conveyances shall be secured with wire rope (or equivalent materials) in addition to the regular couplings or connections.

19 Concrete piping system
connection point

20 (f) Concrete buckets (1) Concrete buckets equipped with pneumatic gates shall have positive safety latches or similar safety devices installed to prevent premature or accidental dumping. (2) Concrete buckets shall be designed to prevent concrete from hanging up on top and the sides.

21 Power-concrete trowels Shall be equipped with a control switch that will automatically shut off the power whenever the hands of the operator are removed from the equipment handle.

22 1926.702(d) Concrete buggy handles shall not extend beyond the wheels on either side of the buggy

23 1926.702(i) (1)Masonry saws shall be guarded with a semicircular enclosure over the blade
(2)A method of retaining blade fragments shall be incorporated in the design of the semicircular enclosure.

24 1926.702(h) Bull floats - Electrocution - Handles

25 29 CFR 1926.703 Cast-in-place Concrete.
(a) General requirements for formwork. (b) Shoring and reshoring. (c) Vertical slip forms. (d) Reinforcing steel. (e) Removal of formwork.

26 Form work operations fall protection

27 Cast in-place concrete work

28 Form work

29 Form work

30 Form work

31 1926.703 Shoring & re-shoring Inspected prior to erection
Damaged equipment shall not be used Inspected immediately prior to, during, and immediately after concrete placement.

32 1926.703 (b) Shoring & re-shoring
Equipment found to be damaged or weakened, shall be immediately reinforced. Sills shall be sound, rigid, and capable of carrying maximum intended load. (b)(6) All base plates, shore heads, extension devices, and adjustment screws shall be in firm contact, and secured when necessary, with the foundation and form.

33 (b)(8) Single post shores Design prepared by qualified designer Vertically aligned Spliced to prevent movement Braced in two mutually perpendicular directions at splice level Each tier diagonally braced in the same two directions

34 Ellis shoring system

35 1926.703(c) Vertical slip forms
Jack rod Jack Thin pipe around jack rod Yoke assembly Splash board Working deck Wales Bracing for Wales Sheathing Slight batter of sheathing

36 Vertical slip-form operation

37 (d) Vertical slip form Steel rods or pipes on which jacks climb shall be designed for that purpose and adequately braced when not encased in concrete. Designed to prevent excessive distortion during jacking Provided with scaffolds or work platform where employees required to pass Jacks and lifting devices provided with mechanical dogs or other automatic holding devices Form structure maintained within all design tolerances - for plumpness during jacking operations

38 1926.703 (e) Removal of formwork
Shall not be removed until employer determines concrete has gained sufficient strength to support its weight and super imposed loads: Plans and specifications which stipulate conditions for removal of forms and shores; Concrete had been properly tested.

39 Flying forms


41 Pre-cast Concrete. (a) Adequate support of wall units, structural framing, and tilt-up panels (b) Capability of inserts (c) Imbedded inserts (d) Lifting hardware (e) No employee under pre-cast concrete members being lifted or tilted into position except those employees required for the erection of those members

42 Pre-cast concrete operation


44 Un pre-stressed slab Prestressed slab - unloaded Prestressed slab - loaded

45 29 CFR 1926.705 lift-slab operations.

46 29 CFR 1926.705 lift-slab operations.
(a) Lift-slab operations shall be designed and planned by a registered professional engineer (b) Jacks/lifting units shall be marked (c) Jacks/lifting units shall not be loaded beyond their rated capacity (d) Jacking equipment shall not be overloaded (e) Design and installation of jack lifting units

47 29 CFR 1926.705 lift-slab operations. (continued)
(f) Jacks/lifting units shall have a safety device installed (g) Jacking operations shall be synchronized (h) Automatic controlled leveling (i) Manually controlled leveling (j) Maximum number of manually controlled jacks/lifting units (k) Number of employees allowed in the building

48 29 CFR 1926.705 lift-slab operations. (continued)
(l) Temporary connections (m) Welding on temporary and permanent connections (n) Load transfer from jacks/lifting units to building columns (o) Securing Jacks/lifting units (p) Prevention of components from disengaging during lifting operations.

49 Seal block Jack rod Spearhead frame cast in floor slab Lifting angle Wedge Wedge block

50 1926.705(a) Lift-slab operations
shall be designed by a registered professional engineer who has experience in lift-slab construction.

51 Lift slab operation

52 1926.705 Jack lifting unit (b) Marked to indicate rated capacity
(c) Not loaded beyond capacity (d) Two and 1/2 times the load (e) Designed so they neither lift nor continue to lift when they are loaded in excess to rated capacity (f) Synchronized lifting to ensure uniform lifting (g) Leveling device installed ( all points 1/2 inch tolerance) (h) Stop device (exceeds 1/2 inch tolerance) (i) Manual controls located in central location - attended by competent person (must be experienced) (j) Maximum number of annually controlled units

53 Closure strip

54 (k) No employee permitted in the building structure while jacking operation taking place - unless reinforced sufficiently to ensure integrity during erection

55 (K)(2) Under no circumstance, shall any employee who is not essential to the jacking operation be permitted immediately beneath a slab being lifted

56 1926.705(i) Manual lifting controls shall be centrally located

57 29 CFR 1926.706 Masonry construction.

58 29 CFR 1926.706 Masonry construction.
a) Limited access zone prior to the start of construction of the wall equal to the height of the wall to reconstructed plus four feet, and shall run the entire length of the wall on the side of the wall which will be un-scaffolded restricted to entry by employees actively engaged in constructing the wall shall remain in place until the wall is adequately supported (b) All masonry walls over eight feet in height shall be adequately braced

59 1926.706(a) Limited access zone
Established prior to the start of construction Equal to the height of the wall plus four feet Unscaffolded side of wall Remain until adequately supported Masonry walls over 8 feet adequately braced


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