Fo rm w o rk failures can occur on a small wall or ah i g h - rise building. Fa i l u res in high-rise work usual-

ly result in the most injuries and deaths. This is tru e,l o g i c a l l y, because men are either on the deck or belowit and have neither the time to move nor a place towhich they can move.

We can assume that failures are caused either by poorplanning, poor design, inadequate inspection or the hu-man element.

Almost all failures occur at the time when concre t eplacement adds considerable weight and pre s s u re onthe form w o rk. On normal wall forming, a “bre a k o u t” is acommon failure and it can occur on any height wall atany time.

Some of the major causes of breakouts are :1. Missing hard w a re2. Im p roperly connected hard w a re3. Tie ends not secured with hard w a re or form s4. Placing at too fast a ra t e5. Damaged ties left in place6. Im p roper tying7. Insufficient tying8. Vi b ra t i o n9. Inadequate waling and stro n g b a c k i n g10. Inadequate bra c i n g

Let’s look at each of these points:1. Missing Ha rd w a re —When erecting form s, it is ve ry

easy to overlook placement of hard w a re. Most systemsre q u i re hard w a re where ver a tie is used. Howe ve r, in or-der to speed up the job as forms are erected, onlyenough hard w a re is connected to hold the forms inp l a c e. The workmen plan to come back and place thebalance of the hard w a re later on. As they follow up, theymay overlook a location or two, or prior hard w a re mayloosen and weaken the total connection at a joint.

2. Im p ro p e rly Connected Ha rd w a re —This re l a t e ssomewhat to the first problem, but is a major cause by it-self. Each tie end should be checked to be sure it is se-c u red in place by hard w a re. Although most systems arefairly similar, some use attached hard w a re while othersdo not. This can be a problem, for while it appears theh a rd w a re and tie are connected, they may not be.

3. Tie Ends Not Se c u red in Pl a c e —In some systems, thetie end or loop is between the forms and the connectingh a rd w a re can miss the loop of the tie. This leaves the tieloose and the form w o rk unsecure d .

4. Placing Too Fa s t —All ties are designed for a safew o rking load and the manufacturers of ties will re c o m-mend the rate of placing under va rious conditions. Thisi n f o rmation is usually printed on tie cart o n s, packagingm a t e rials or in bro c h u re s.

5. Damaged Ties Left in Pl a c e —Ties damaged duri n g

shipping or erection should be replaced. The commonsnaptie has a breakback point for breaking back the tieends after stripping. It’s at this point where trouble mayoccur if the tie has been damaged or bent. Steel work e r sand mechanical tradesmen should be cautioned re g a rd-ing the care taken of ties. Taking chances with damagedties can mean expensive trouble and possible injury.

6. Im p roper Ty i n g —The use of the wrong size tie or theuse of ties in a manner for which they we re not intend-ed can cause tro u b l e. Ma n u f a c t u red ties are norm a l l ym a rked for size and the type of use for which they are in-tended. A difference of a quart e r- or half-inch in tielength can cause offsetting of form s. Once placing start s,additional load is placed on the shorter length ties and ab reakout may occur.

7. Insufficient Ty i n g —Ca reful planning and contro lmeans that the correct number of ties will be used, bothve rtically and hori zo n t a l l y. Ove rtying can add up, but af a i l u re due to lack of ties can be more expensive. Thenumber of ties and their spacing should be determ i n e dby wall height, rate of placement, tempera t u re of con-c rete and safe load capacity of the ties.

8. Vi b ra t i o n —The proper vibrator should be selectedfor different types of work, to avoid ove rv i b ration or ani n c rease in tempora ry pre s s u re on the forms and ties.The careful insertion and re m oval of a vibrator from thec o n c rete is important to good vibration and the pro t e c-tion of ties. Vi b rators in direct contact with ties can causea tie to snap or break under impact.

9. Inadequate Waling and St ro n g b a c k i n g —De p e n d i n gupon the form w o rk system used, walers and stro n g-backs may be used for alignment, stru c t u ral stre n g t hand tying. They should be considered for size of lumberused and location or spacing depending upon wall di-m e n s i o n s. Their function or design can have a dire c tb e a ring on the perf o rmance of the form w o rk and its sta-b i l i t y.

10. Inadequate Bra c i n g —Bracing usually begins withthe plumbing and aligning of the form w o rk. Pro p e rspacing should be determined for both ve rtical and hor-i zontal use on different wall heights. For high walls,b races can be spliced or cables and trusses used.

On high-rise buildings, as stated earlier, the pro b l e mis increased and much harder to control. A shoring fail-u re (and this appears to be the greatest cause of formf a i l u res) can result in a job shutdown, an investigation asto cause, a financial loss, and possible injuries or loss oflife to work e r s.

T h e re are, generally speaking, three methods ofs h o ring in use today: (1) the use of contra c t o r- d e s i g n e dand built shoring, (2) the use of manufactured shore sand accessori e s, and (3) the use of a complete pre f a b ri-cated shoring system.

An Analysis of Formwork Failures

When a contractor builds and erects his own shori n gm a t e ri a l s, he alone is usually responsible for its perf o r-m a n c e. He must design his form w o rk considering pro p-er loads, ease of stripping, re s h o ring, and the safety fac-t o r. The design of such work should only be undert a k e nby an engineer or a person knowledgeable enough tok n ow the re q u i re m e n t s. A failure in do-it-yourself equip-ment can be the hardest to determine or locate.

When the contractor rents or purchases shoring anda c c e s s o ri e s, the manufacturer provides printed infor-mation on shore spacing and load specifications. Ad d i-tional help is usually available from the manufacturer indetailing and field assistance. A failure can be the con-t ra c t o r’s fault if he does not follow re c o m m e n d a t i o n s, orthe manufacture r’s responsibility if the equipmentshould fail. It can be a combination of both if there is alack of communication between them. The same holdst rue if the contractor uses a complete pre f a b ricated sys-tem. If the equipment is misused, layouts are not fol-l owed, short cuts are taken, or there is inadequate su-p e rvision, a collapse is likely to occur.

In order to have an accurate shoring layout pre p a re dby any manufacture r, complete information and allk n own job conditions should be furnished. If the layo u t sa re followed and changes in job design are incorpora t e d ,no problems should ari s e.

Another failure factor may result from stripping form sand shoring before the concrete has achieved adequates t rength. Re s h o ring, if necessary, should be properly lo-cated with relation to the forming of floors above.

Bracing cannot be emphasized enough. All latera lm ovement must be eliminated. Bracing will adds t rength to the shoring if it should be bumped acciden-t a l l y, and it protects against a chain reaction if some are ashould fail. There is no guarantee against failure, butgood cross bracing is good pre ve n t i ve pra c t i c e.

T h e re are always other factors which could contri b u t eto a failure. For example, re i n f o rcing steel stockpiled inthe wrong location could trigger trouble or a crane boomcould fall across a deck. Other dangers are column fail-u re, collapse of a lower floor due to improper pra c t i c e s,and unexpected foundation settlement, due to unsoundb e a ring capacity.

Prior to concrete placement a final check should bem a d e, for overlooking even one item could be disas-t ro u s. The following are some major points that shouldbe checked, although each system will have its own de-sign and will have different erection and inspection pro-c e d u re s :

1. Check for sound bearing or sill 2. Be sure all shoring is plumb3. Be sure all shoring is resting on plate or sill, nothanging loose from deck work4. Check out bracing locations and see that all bra c i n gis connected5. Check shoring against layouts for correct positioning6. Check for proper grade adjustment 7. Check all locking devices8. Be sure shoring is properly secured to deck workabove9. Check layouts to see that correct sizes have beenused and that nothing is missing10. Double check spans so that overloading will notoccur.Re g a rdless of the type equipment or materials used,

the same attention, careful planning, supervision andinspection should pre vail on each job. Fo rming failure ss h o u l d n’t occur, but they do. The point is to do eve ry-thing possible to eliminate them, there by reducing thep e rcentage of accidents, injuries and deaths.

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