Checking of Formwork and Common Defects

We will now summarise critical factors of workmanship, which  should be  checked by the site engineer/construction supervisor. 

The most critical factors to be examined in a falsework system are listed below: 

1. Adequacy of the ground below the foundation arrangements 
2. Variability of  the ground below the foundations 
3. Precautions taken to prevent deterioration of the ground froni rain snow, frost, sunshine, nearby water courses, or drips, drips of water from concrete or curing. 
4. Bedding of the foundation pads,  sleepers or bearers into the ground. 
5. Seating of sole plates onto the  bearing  pads or sleepers. 
6.  Horizontal restraint to vertical supporting members just above ground level. 
7. Evidence of misuse or deterioration of the components of the falsework. 
8. The vertical alignment of the vertical members. 
9. Vertical  tightness of the whole assembly 
10. Adequacy of bracing provisions for overall stability, local stability, and  is the bracing directly positioned. 
11. Compliance with design and drawings. 
12. Can horizontal restraint, to horizontal forces which may arise, be seen? 
13. Eccentricity of runners onto vertical  members. 
14. Restraints in foreheads and local lacing at that level. 
15. Are adequate provision made where load is applied to  girder sections to avoid web bucking  or instability? 
16. How are horizontal loads adsorbed by the falsework from the formwork and does the latter offer  stiffening to the combined  assembly'? 
17. Are all the bolts  necessary in position and are they. including scaffold fittings, correctly tightened? 
18. Are any reused sections correctly identified and satisfactory'? 
19. Will the work be connected  or loaded in the manner def:;ed on the  drawings? 
20. Are any members which arc: required to remain in position after general stripping and dismantling readily identifiable? 
21. Lacing to reduce slenderness factors on props. 
22. Effect of fatigue on reused material. 
23. Damaged flanges and webs of rolled steel sections. 
24. Has proper  wedges been used for shrinkage of falsework? 

We are giving below a list of defects of commonly found in  falsework systems: 

a)  At Foundation Level 

1. Sole plates not levelled in or eccentrically placed. 
2. Inadequate load carrying capacity of the ground and  uneven hedding. 
3. Deterioration of ground, due to weather conditions, erosion or other effects. 
4. Crushing of sole plates due to inadequate load distribution. 
5. Unsatisfactory sole plate  members or their omission. 
6. Insufficient lateral restraint to bedding where standards are founded on sloping  ground. 

b)  Horizontal Supports 

1. Folding wedges cut to too coarse a taper,  not properly  secured, too small, or of  poor material. 
2. Adequate lateral and torsional  bracing, e.g. between telescopic essences, between  centres carrying heavy  loads over  long spans, between  steel props supporting heavy  loads at, or near, maximum extension and between towers  supporting independent  spans. 
3. Horizontal members  not Central in forkheads or properly packed  in position. 
4. Inadequate supports to cantilevers, e.g. struts supporting deep beam  sides on the outer  face of the  structure. 
5. Inadequate bearing' areas to vertical supports and underside or principal members, causing crushng. 
6. Inadequate support to prevent  overturning of deep principal members. 
7. Bolted timber  connection not staggered, creating tendency to split out. 
8. A need for bracing  when forkheads are excessively extended. 
9. Omission of compression  flange restraints. 
10. Centres loo far apart. 
11. Inadequate sizes of section. 
12. Unsatisfactory quality of material, especially when materials are reused. 
13. Bracing installed in  wrong positions. 
14. Bolted connections not properly  tightened. 
15. Sections of members lapping for continuity varying in depth. 

c)  Vertical Supports 

1. Inadequate bracing  during erection or in use and need for extra lacing. 
2. Supports not plumb enough. 
3. No lacing between  standards at point of loading  (most important  where telescopic centres  are being supported). 
4. Incorrect provision of props from  floor to floor. 
5. Lack of rigidity of screw connections due to over-extension or lack bracing. 
6. Adjustable steel props with nails, mild steel bolts and reinforcing bars used in place of correct pins. 
7. Timber  standards of more than one piece with inadequate  splice plates. 
8. Heads of standards not firmly secured to underside of horizontal  support members. 
9. Omission of scaffold forkheads or supports other side eccentrically loaded .without allowance having been made for this  condition. 
10. Bearing plates (e.g. top and bottom plates of  steel props)  distorted. 
11. Inadequate or discontinuous bracing 
12. Centres too far apart. 
13. Inadequate sections. 
14. Insufficient fixings. 
15. Unsatisfactory quality of material, especially when  second hand materials are used (e.g. corroded or damaged scaffold tube). 
16. Eccentricity of solid plates. 

d) General 

1. Errors due to difficulties in identifying properties of members being used. 
2. Members being erected with their  axes at right  angles to the correct position so that the weaker axis is subjected to the  critical loading. 
3. Over tensioning of guy ropes or tension restraints. 
4. Deposition of stored materials or spoil against the  side of falsework. 
5. Excessive loading from stored materials placed on the falsework 
6. Reliance on high tensile members or bolts  without safeguards to ensure they are not replaced by mild steel. 
7. Excessive tolerances  used in construction. 
8. Failure to check tightness of bolts  and  wedges immediately prior to loading. 
9. Inadequate allowance for loads of access provisions. 
10. Insufficient stiffening to prevent web buckling poor quality welding. 
11. Inadequate provision of guard rails, height control guides to prevent traffic impacts 
12. Failure to examine threads to ensure that bolts  can be correctly tightened. 
13. Inadequate lateral stability with a need for bracing,  tying hack etc. 
14. Provision of means of access to operatives.