13 site fabricatedcolumnswallsformworkdesigns

Buildings Practice For ProfessionalsConstruction Method Statements

Chapter 13 Site Fabricated Columns & Walls Formwork DesignsSafety General

1 Refer to Chapter 3, MS 12 & 13, Chapter 4, MS1, Chapter 6 Page1 for general provisions on safety discipline in addition to those included with various method statements on this Chapter

2 Relevant point should be extracted from description in line to requirements on relevant activities

3 It is to be noted that safety standards vary from organization to organization, company to company & client to client

4 Just consideration of economy on project cannot exclusively, be a criterion to avoid or reduce safety measures

5 A minimum level of safety measures installations should be made a ‘must’ for a site supervise to ensure that workforce ‘must’ work safely

6 It is preferable to work with acceptable level of safety rather than loosening lives of workers

Site fabricated formwork designs for columns & walls

Scope/Purpose1 Purpose of this document is to define computation procedures to be adopted for site based

customized working on site designed formwork in simple terms, so that an easy & economical preparatory work production on site is affected.

2 This formula is based on experience on various activities successfully performed.3 It happens that preparatory activities are installed according to understanding on site,

without constituting any professional basis, where on otherwise, should be considered various factor respecting forces involved.

4 Results by such actions lead to either producing a bulged member, which could allow chances for opening out concrete or use of excessive materials that adds to cost

5 Site should provide optimum use of preparatory materials for required material repetition to economize cost on each member

6 This statement is not particular to any specific member, but meant only for general description of procedures involved.

Reference Documents 1 Excel sheets appended 13a & 13b documents/chapters

Design Basis1 Design concept is based on fluid mechanism involved during initial hours of concrete

pouring. 2 Concept of practical thought & varying state of concrete conduct/facts have been applied

with, for charting out this formula3 Results or effects of considerations on design should be complied with.4 This calculation should be carried out/worked out by only a qualified engineer, who

thoroughly, understands concrete pouring technology5 In case, concrete pouring method requirement is violated, this presentation shall not work

satisfactorily

of 3 2012 Int. P Eng (India) Suraj Singh


Chapter 13 Site Fabricated Columns & Walls Formwork Designs6 Concrete density to be considered 2.4 T/CUM

Material Formwork1 Wooden battens/scantlings 50 x 75mm 4 M long, 75 x 75mm 4 M long, 50 x 100 mm 4

M long2 Plywood 18/20 mm thick standard marine or waterproof3 16 T tie bolts with threaded ends, provided with washers, endplates, bolts/nuts etc4 Plastic pipe probably 20 mm dia. to be used as sleeve as lost member5 Steel clamps generally known as shikanjas6 Steel jacks to support vertical members/sides7 Clip in anchoring members for jacks or for scantlings8 Anchoring chains if so required for certain particular case

Supervision & Control presumption1 Construction manager, Site engineer, construction foreman & charge hands shall control

all concrete pouring activities on site according to meeting requirements on relevant approved procedures/methods & respective job descriptions included on project plan.

Materials ConcreteConcrete source

1 Ready mix concrete from an approved supplier shall be used with defined setting time limit.

2 Concrete shall be produced under expert controls3 Vibrator nozzle/needle should not touch formwork any time during pouring

Form fabrication1 Fabrication of plywood forms shall be carried out on site based on formwork design

working details provided by site engineer to formwork foreman.

Calculation format/ method description1 Excel worksheet utilized for calculation format 2 About 4 M pouring height considered for one time casting3 Layers have been limited to 400/450 mm thick4 Vibrator needle does not exceed this limit5 Vibrator should penetrate in to lower laid layer by 100 mm6 Each layer has to be poured, prior to previous layer sets to avoid cold joint formation7 Flash setting of concrete should be avoided8 Fluid pressure is transmitted to vertical sides from zone of transfer in catchment or

coverage of that side, which force should be calculated based on weight of concrete involved

9 Conservatively, wh2 /2 T formula is used to calculate pressure acting @ h/3 location from base, where w is unit weight of concrete & h height of layer

10 This pressure results in a bending moment equal to wh3/6 TM11 Foregoing consideration can be used for each layer, but for whole unit casting, it shall not

economically work, though there is imposed no restriction on its use



Chapter 13 Site Fabricated Columns & Walls Formwork Designs12 Concrete attains certain state of fluidity effective from time it is delivered from batching

plant, to time it sets, which states are fluid, semi fluid, plastic & set.13 Understandably, when concrete is in fluid state, it shall certainly produce full pressure on

formwork sides, while it gradually reduces its pressure within a couple of hours depending on increasing viscosity

14 It is also, agreeable that pouring of members vertically, consumers hours together even, for half a CUM, when many members are involved during one pour.

15 Since, pouring is conducted in layer followed by rotation of pouring layers pertinent to other members after say, half to 1 hour, vibrated concrete gets into a semi fluid state

16 Next pouring after rotation gets further viscosity, leading to a state of plasticity17 When final setting time is over, it starts setting in, after considerably, loosening its

plasticity.18 Therefore, it has been presumed to calculate pressures on sides of formwork, based on

such considerations19 Sequence of layers pouring have been shown on sheet20 Pressures resulting at various layers at various stages of poring have been included21 Bending moments resulting at various layers at various stages of pouring have been

included22 A reduction factor 5% has been applied between two consecutive layers, which should be

quiet reasonable from operational research viewpoint23 Once, forces are known, proposed formwork section can be checked for sustainability

using conventional resisting formula, should permissible stresses among various members, such as plywood, battens, tie bolts, jacks, supports & clamps be known

24 Such calculation shall also, guide about safety of preparatory works, where preparatory work implies/meant construction of formwork

25 Resistance of formwork could be provided by plywood, battens, tie bolts & jacking supports based on information available for new materials, while for used material, resistance should be proportionately, reduced depending on state of material.

Attachment1 Excel worksheets as chapters 13a/13b2 Sketches & formwork drawings (not included herewith)


13 site fabricatedcolumnswallsformworkdesigns

Engineering