Steel Detailing | Precast Detailing | Estimation

Category: Precast Blogs

Tek1 has detailed over 100,000 precast panels over 19 years.
over 90,000 were detailed under a proxy name Advanced Pretty Pictures Pty Ltd

PRECAST PANEL DETIAILING
EXPERT PRECAST PANEL DETIAILING

  • CONSIDERATION OF PRECAST LID SHOP DWGS

    The purpose of LID panel:

    LID panels are most commonly used for covering up the openings on building roof areas and also some inner part of the building where the precast slab is required. It can be seen in locations like lifts, stairs, water tanks, etc.

    LID PANEL ON LIFT

    LID PANEL ON STAIR

    Manufacturing consideration of LID panels:

    • Viewing direction of the lid panel is either plan view or view from below. Depending on consideration of manufacturing difficulties and near face finish and different profile requirements, it may change as vice-versa.
    • If lifting eye/ hook is projecting outside of lid means, we have to view the face with lifting eye as near face for manufacturing purposes. (Refer lifting hook/eye elevation view)
    • In lift lid, lifting hook/ lifting eye needs to be provided if it needs to be cast in the lid. Lifting hook detail normally given in lift drawing. (Refer lifting hook/eye placement plan view)
    • We can provide face lifters and either top or side lifters used for erection, lifting off table and transportation purposes.
    • Face lifters were used for installation of the lid on site. Whether its need to be near face or Far face is decided by viewing direction.
    • Bottom connection of lid most likely by grout tube to its lower panel or In-situ.

    LIFTING HOOK/EYE ELEVATION VIEW

    LIFTING HOOK/EYE PLACEMENT PLAN VIEw

  • Difference between Normal Table and Tilt up Table

    General Details about table:

    • Tables are used for fabrication of precast panels in factories or yards with good quality, finish, curing and low time consumption.
    • Different types of materials used for tables like timber, aluminum and steel. But steel is mainly used for tables because it’s good for repetitions, gives good vibration to concrete, it’s not easily damaged and tables do not expand when it’s wet, etc.
    • The cleaning process is also easily done for steel tables with the help of air blowing or cotton waste.
    • In the yard there are different types of tables used for fabrication.
      For example normal fabrication tables and tilt up tables.

    Normal table:

    • Normal tables are mainly used to fabricate most of the precast panels.
      (Refer Fig 1)

    Fig 1

    • Advantages:
    • Normal tables will not take more manpower for cleaning and fabrication of precast panels.
    • The maintenance is easy
    • The cost is low when compared to other types of table.
    • It can easily fix where we need to fabricate the panels.
    • It will be fixed on the floor, so the visibility of the table is good for all.
    • Disadvantages:
    • It’s not suitable for doors or big opening panels. Because in case of lifting panels it may break.
    • Normal table needs additional lifting support.

    Tilt up table:

    • The tilt up tables are mainly used for Doors and big opening panels and also other types of panels. (Refer Fig 2 & 3)
    • The tilting process allows the precast concrete element to be removed safely and without damaging it.
    • The titling tables are designed in particular for mobile use and can be quickly transported from the yard.
      Fig 2


      Fig 3

    • Advantages:
    • This table is good for fabricating and lifting the door, opening type of panels.
    • Hydraulic Tilt up Tables reduce manufacturing time because it’s not require more pouring time to lift the panel from table.
    • Vibration technology based operation ensures qualitative compaction of concrete and a consistency in quality.
    • It’s very high level of concrete compacting with low noise.
    • Minimal costs when transporting the tilt up table.
    • Disadvantages:
    • Manpower is necessary and also needs knowledgeable people for handling.
    • The maintenance is difficult
    • The cost is high
    • It’s not movable, so we need to collect materials at a nearby table.

  • INSULATED PRECAST CONCRETE PANEL

    INSULATED PRECAST CONCRETE PANEL:          

    Insulated precast concrete panels consist of interior and exterior thickness of concrete with the rigid insulation inserted or ‘’sandwiched’’ between the two layers, thus their alternate name of insulated panel is “sandwich panels”.

    LAYERS IN INSULATED PRECAST CONCRETE PANEL:

    • The two layers of concrete thickness, often referred to as concrete wythes and a layer of insulating materials are connected by using one of many wythes connecting systems (connectors).
    • Each layer of concrete thickness contains reinforcement as per structural design.
    • The concrete wythes can vary in thickness depending on structural and architectural requirements of a project.

    METHOD OF MANUFACTURING:

    • The insulated precast panel is manufactured by using two pours (pour-1 and pour-2).
    • Table with reinforcement for pour 1 wythe to be arrange and start to pour concrete (Pour-1).
    • After the first wythe is poured and the pre-cut rigid insulation segments are placed on top of the wet concrete and all insulation connectors are installed.
    • The reinforcement for the interior wythe is then placed and the second wythe is poured. Finally, the interior surface can be trowelled smooth.

    APPLICATION:

    The insulated precast concrete panels are mostly used for the place where the thermal insulations are required. some of the applications are shown in below

    • Cold storage factories.
    • Residential houses.
    • Hospitals.
    • School buildings.
    • Offices.
    • Chemical laboratories.
    • Shops.

  • DEMOULDING SLOPE

    Demoulding of precast member without damage to either the components like lifter or mould is critical to successful replication process for the particular complicated design. During mould design, the designers concentrate to make minimum draft (nearly 10 ) on mould to wherever the possible  to minimize demoulding force and resultant stress on lifters and prevent on weaker part of the precast member.

    For Example,

    CONTRIBUTORS DURING DEMOULDING WITHOUT SLOPE

    The above picture shows influencing factors for demoulding force. In this case the resultant DEMOULDING forces like vacuum & friction (Area of contact, Coefficient of friction & Normal contact Pressure) along with self-weight of precast will increase demoulding force. If the demoulding force exceed the lifter capacity limit leads to fail the lifters. So, we can’t able to lift this precast member. To eliminate this type of failure. We need to provide slope where contact pressure or interface adhesion develop.

    CONTRIBUTORS DURING DEMOULDING WITH SLOPE

    The above picture shows the effect of demoulding slope. Where the 10 slope didn’t affect too much the original shape of precast, but considerably minimize the demoulding force. The slope reduces the frictional force & provide passage to air enter where vacuum force develops.

  • CONCRETE WITH SPECIFICATION DIFFERENCE (N & S)

    CONCRETE:

     (AS 1379 Specification and supply of concrete) A mixture of Cement, aggregates and water with or without the addition of chemical admixtures or other materials.      

    Cement: (AS 3972 Portland or blended cement) A hydraulic binder composed of Portland or blended cement used alone or in combination with one or more supplementary cementitious materials.

    Concrete is defined as follows,

    • Plastic concrete:

    Concrete in the state between completion of mixing and initial set as defined in AS 1012.18 Methods of determining setting time of fresh concrete, mortar and grout by penetration resistance.

    • Hardened concrete:

    Concrete after initial set, as represented by test specimens that have been subjected to a specified process and duration of curing.

    • Normal- Class Concrete:

    Concrete that is specified primarily by a standard compressive strength grade up to 50 MPa and otherwise in accordance with Clause 1.5.3.

    • Special- Class Concrete:

    Concrete that is specified to have certain properties or characteristics different from, or additional to, those of normal-class concrete and otherwise in accordance with Clause 1.5.4.

    SPECIFICATION OF CONCRETE:

    Concrete shall be specified,

    (a) as either

    (1) Normal-class(N), or

    (2) Special-class(S), or

    (b) By strength grade or other readily verifiable parameter by which compliance with the specification can be assessed.

    NOTE: Standard strength grades should be specified wherever possible.

    • NORMAL-CLASS CONCRETE:

    Normal-class concrete shall be specified only by the parameters given in Clause 1.5.3.2(Basic parameter), and shall have the following attributes:

    • A mass per unit volume in the range 2100 kg/m3 to 2800 kg/m3 when determined in accordance with (AS 1012.12.1 Determination of mass per unit volume of hardened concrete) in the saturated, surface-dry condition.
    • Acid-soluble chloride and sulfate contents within the limits given in Clause 2.7, when determined in accordance with Clause 5.5.2.
    • A shrinkage strain not exceeding 1000 × 10−6, when determined in accordance with Clause 5.6 after 56 days drying.

    NOTE: This maximum value of 1000 × 10−6 is consistent with the use for design purposes of a median basic shrinkage strain value of 850 × 10−6.

    • A mean compressive strength at 7 days, assessed in accordance with Clause 5.7, of not less than the values of Grade designation for N20-9MPa, N25-12MPa, N32-16MPa, N40-20MPa & N50-25MPa.
    • A cement complying with (AS 3972 Portland or blended cement) alone or in combination with one or more supplementary cementitious materials.
    • No lightweight aggregate as defined in AS 2758.1 Aggregates and rock for engineering purposes Concrete aggregates.

    Basic parameters of normal-class concrete:

    The following basic parameters shall be specified by the customer:

    • A standard strength grade selected from 20MPa,25MPa,32MPa,40MPa, 50MPa,65MPa,80MPa or 100MPa and designated as one of N20, N25, N32, N40 or N50.
    • The slump at the point of acceptance, selected as one of 20 mm, 30 mm, 40 mm, 50 mm, 60 mm, 70 mm, 80 mm, 90 mm, 100 mm, 110 mm or 120 mm.

    NOTES:

    1. The customer should carefully consider that the specified slump of concrete suits the placement method.
    2. For residential slabs and footings, if the slump is not specified by the customer, the specified slump should be considered to be 100 mm.
    3. The maximum nominal size of aggregate, selected as one of 10 mm, 14 mm or 20 mm. Unless otherwise specified, the default value shall be taken as 20 mm.
    4. The intended method of placement, including relevant details of equipment.
    5. If project assessment is required to be carried out by the supplier (see Note).

    NOTE: If unspecified, it will be assumed that project assessment is not required.

    • If required, a level of air entrainment up to a maximum of 5.0%.

    (2) SPECIAL- CLASS CONCRETE:

    Concrete other than normal-class concrete shall be specified by the customer as specialclass and, if applicable, by strength-grade. The parameters and attributes that should be specified for special-class concrete should be as set out listed below with reference to Appendix B and Table B1 on AS1379.

    Special-class concrete commonly has the same basic parameters as normal-class concrete with some additions and(or) exceptions. Parameters or attributes that are different from, or additional to, those of normal-class concrete should be included in specification below. If the requirements of specification for any concrete are inconsistent with those for normal-class concrete then the requirements of specification take precedence for that concrete.

    Where any parameter other than strength grade requires the specification of a special-class concrete, or the proportions of the mix are specified, the concrete should be identified by an appropriate code agreed to between the supplier and customer that identifies that particular mix.

    Basic parameter for specification of special-class concrete:

    • It is recommended to select from standard strength grades of S20, S25, S32, S40, S50, S65, S80 and S100.
    • Where concrete is specified as special-class and a strength grade is applicable, the strength grade is designated by the prefix:

    S, for compressive strength grades;

    SF, for flexural strength grades; or

    ST, for indirect-tensile strength grades.

    Where concrete is special-class and any property other than strength grade is Specified as the principal criterion, or the proportions of the mix are specified, it is designated by an appropriate alphanumeric code, agreed between the supplier and the customer, to indicate the criterion.

    • Special-class concrete should be subject to project assessment.
    • Certain concrete exposure classifications may require special provisions for aggregate durability (AS 2758.1 Aggregate & Rock for engineering Purposes.)
    • Any departures from the parameters or composition, or both, of normal-class concrete and any other criteria or limitations shall be specified by the customer in consultation with the supplier.

    NOTE: A summary list of several such parameters, some or all of which may be specified for the production of special-class concrete for a project, is given in Appendix B on AS 1379.

    • Other requirements additional to these parameters may be specified.

  • BEAM Vs COLUMN

    BEAM Vs COLUMN

    BEAM: A beam is a horizontal structural component that resists vertical loads. Its mode of deflection is primarily bending. It transfers loads imposed along its length to its endpoints to walls, column and foundations.

    The beam is structural element that stands against the bending. Mainly beam carries vertical gravitational forces, but also pull the horizontal loads on it.

    (If structural member transfers any load whichever is acting on it through bending, then that element will be refer as a beam.)

    COLUMN: A column is a vertical structural compression element that bears loads mainly in compression. It might transfer loads from a ceiling, floor slab, roof slab to a floor or foundation, it usually transfers loads from superstructure to foundation.

    Column plays an essential role in the entire load transfer system, though many columns are embedded forming part of a wall.

    Columns are commonly used to support beams or slabs or arches on which the upper parts of walls or ceilings rest. Sometimes a column is a decorative element as well as for structural purpose.

    (If structural element transfers the load through compression, it will be called as column.)

    DIFFERENCE BETWEEN BEAM AND COLUMN

    SL.NO

    DESCRIPTION

    BEAM

    COLUMN

    1

    Built

    Without a beam, a structure can be constructed.

    Without a column, a structure can’t be built.

    2

    Support

    They are supported by the column one end or both ends.

    They are directly built from the foundation.

    3

    Weight transfer

    It carries weight of slabs, ceiling. Floor, Roof of a building and transfer it to columns.

    It carries load transferred by beam and ultimately transfer it to footing and ground.

    4

    Classification

    Beams are classified based on their support end condition.

    Columns are classified based on their cross-section shape, material for construction and types of loading.

    5

    Shape

    A beam may be square, rectangular, T-shape, I-shape and H-shape.

    A column may be rectangular, circular, square, t-shape, L-shape and C-shape.

    6

    Simple Terms

    Beam is structural member carrying transverse loads.

    Column is also structural member carrying axial loads.

    IMAGES FOR BEAM AND COLUMN

    EXAMPLE:
    we have a rod of length 5 meter made out of steel and a load “P” to support

    1. We keep the rod on two supports and then place load on top of it. This time the primary mode of load transfer is by bending and thus we call it a Beam.
    2. We keep the rod vertical and apply load Horizontally to it. This time the primary mode of load transfer is also be bending and thus we call it a Beam.
    3. In this case the rod is kept vertically on the floor and the load is placed on top of it. Now the load is being transferred by compression and thus we call it a Column.
    4. We decide to hand the rod from ceiling and hook the load to the other end of the rod. The load in this case being transferred primarily by tension and thus we call it a Tie.

  • Cracking of panels at opening Corners


    Cause
    * During lifting
    * During Transportation
    * During Erection
    * After erection & slab pouring
    Problem
    * where the cracking of panel further affected the waterproofing by damaging the internal stud walls of the building.
    * Reinforcement getting Weak
    * If any interior work will damage due to the weather proof issue.
    Remedies
    * Get concentrate those location & intimate to reinforce team for additional reinforcement
    * Insist to follow the Guidelines from the engineering team
    * Insist Factory to concern the reinforcement for the specific openings
    * Insist Factory & Erection Crew to Follow the standards & guide line when the lifting from the store, during transport & installation the panel
    * During transportation take care all panels sitting on ‘A’ frame to be vertically supported on 2 points & if any additional support should only be for lateral purposes. Insist to follow the transportation guidelines
    * The Grouting must be taken care on time for the panel with openings Coordinators to advise if any special cases if needed.

  • CONSIDERATRIONS-LIFT SHOP DRAWINGS FOR PRECAST

    The important things to be considered in lift shop drawings for precast is listed below:

    1. Core Setout.
    2. Door Opening.
    3. Recess at the bottom of lift door.
    4. Landing Call Buttons penetrations.
    5. Controller Box Penetrations.
    6. Service Penetrations and internal platform box.
    7. Lifting Eye Placements & capacity.

         1. CORE SETOUT:

    1. Lift Core Panels Setout in Concrete plan and structural plan should match with lift core details.
    2. If any thickness of panels change keep inside dimensions unchanged, because inside dimensions are dictated by lift manufacturer’s drawings. Panels thickness change must affect only the outside dimensions of lift core.
    3. Propping method – Lift Cores are generally erected first. Higher level slab may not have been poured when lift core goes up. Hence propping of lift core need to have some special attention.

    2. DOOR OPENING:

    1. The door opening width and height of lift in lift drawing should match with architect and structural drawings.
    2. Make sure that the height of lift door opening in lift drawing are measured from FFL or SSL.
    3. Minimum Header height should maintained Discuss with interested parities if there any doubt.
    4. Always consider the RL’s difference between FFL and SSL while  the opening height are finalized. FFL and SSL are usually different

    3. RECESS AT THE BOTTOM OF LIFT DOOR:

    1. The recess at the bottom of lift door (as per door sill detail) is provided for door frame installation. Make sure we take this into consideration
    2. The door sill details are not same for all projects we need to confirm the depth and width of recess at the bottom of lift door before start the detailing.
    3. If the door sill height recess is wrongly provided (i.e. Measured from SSL instead of FFL) then there will be a problem in installation of lift door frame.
    4. The provided recess depth should start from the end of clear opening of lift door.
    5. Make sure that the Door sill details provided in lift drawings are measured from FFL or SSL.

    4. LANDING CALL BUTTONS PENETRATIONS:

    1. Penetrations for landing call buttons, fire switch and other electrical purpose are to be placed as per lift manufacturer’s drawings.
    2. First confirm the view direction of lift drawing (viewed from landing i.e. Outside) and precast Setout. It will clear the location of the lift call buttons and other penetrations.
    3. Ensure the height of penetrations provided in lift drawings are measured from FFL or SSL.
    4. There will be penetrations of different diameter according to its purpose i.e. call buttons, electrical, fire switch etc. so concentrate more on size and location of penetration while detailing.
    5. Penetration locations and size may vary according to the respective floor entrances so refer the details from correct floor entrance which is given in lift drawings.  

    5.CONTROLLER BOX PENETRATIONS:

    1. Controller box may need a recess or in some cases could be a penetration.
    2. Ensure the location of the control box from the panel edge, we need to maintain the sufficient gap from the edge of the panel.
    3. Ensure the sufficient cover from reinforcement with the penetrations

    6. SERVICE PENETRATIONS AND INTERNAL PLATFORM BOX:

    1. Ensure the Hatch opening / exhaust opening need to be accessible for the whole lift for installation & service.
    2. In some case there will be an internal recess requirement to allow for attaching temporary platforms inside the lift for servicing the lift. Make sure these recesses are same RL and opposite.

        7. LIFTING EYE PLACEMENTS & CAPACITY.:

                 For the whole lift is closed by 2 types of lids One by cast-insitu lid and another by precast lid. If we have the precast lid, we need to consider the following things

    1. Connection between the vertical precast & lid
    2. Slope for the water drain
    3. Finish of the face of the lid
    4. Lifting Eye & Hooks for the Lift car & accessories fixing
    5. Ensure the Capacity & size of the Hooks from the lift design.

  • How to Quote For Jobs

    The Golden Rule: Be very clear and specific about what you are quoting for. e.g. I am only going to work on the following (insert specific details), and everything else is excluded.

    Why is this important?

    • Clarity: Your client will know exactly what you are quoting for. Use diagrams, and present documentation to improve clarity. The last thing you want is your client to call you and say: “what about the stairs?”. It will not do for you to turn around and say: “oops, I meant I was only quoting for structural steel”. Clarity eliminates these types of problems.
    • Limited Liability: Do not write a blank cheque for clients. If you return a quote to: “build a house” then this quote is essentially open ended. They might get the wrong ideas in your their head: how large is the house? How much material? How long will it take? How will it be built? What if the client keeps changing the design? How much time are you willing to devote to keep making those changes? Even worse, what if you are forced to keep redesigning a house according to the caprice of a third party – whom you have no control? i.e if an engineer and architect keep changing their designs, then you may be destroying your margins and taking a steep loss, as well as massively increasing the risks something goes wrong. Always limit your costs, in some way. Make this clear to clients.

    Variations:

    • Watch out for design and build jobs: As alluded to above, the design process is fraught with difficulties. Too much back and forth with engineers. Limit this liability in some way: e.g. perhaps by hours worked on a project.
    • How we quote: we quote to a specific set of drawings. Invariable, these drawings change due to the discovery of problems as the building/structure progresses. Whenever something changes: that adds considerable risk to the project, cost, and delays. These costs need to be recorded and passed up the chain. No longer can engineers, architects and builders make changes, willy-nilly, and pass on risk, expenses to sub-contractors with equanimity.

    Specific Examples of Quoting:

    1. Limit scope to a drawing number.
    2. Limit scope to a particular drawing revision.
    3. Limit scope to the number of beams etc.
    4. Limit scope to grid lines.
    5. Limit scope to quantities.
    6. Limit scope by listing exactly what you are building.
    7. And exclude everything else.
    8. Show diagrams so that your quotes are crystal clear. This gives confidence to the quotee – they will know that your quote is well considered, and probably accurate.

    Here are some examples, of how we quote.

    Northern Retaining Wall

    Detailing structural beams, connections details, according to the following scope:

    Drawing 1: Type – T1 250UC90 HDG QTY: 299

    Drawing 2: Type – T2-L 250PFC HDG QTY: 1

    Drawing 4: Type – T2-R 250PFC HDG QTY: 1

    Drawing 5: Type – T7 250PFC HDG QTY: 26

    Drawing 6: Type – T8 250PFC HDG QTY: 1

    EPH – Station Platform Northern Retaining Wall

    Drawing 7: UC 150 x 37.2 post with base plate. QTY: 58

    Drawing 8: PFC 200 with Base Plate. QTY: 4

    Everything else is explicitly excluded. Changes might incur charges via variations. Fully documentation will be provided.

     

    Highlight Items on a Drawing

    • highlight scoped items in a drawing.
    • Add a note showing what is in scope. Why? Sometimes it is not immediately apparent what is being scoped in and out – especially if we are using a drawing with someone else’s markup. Do not simply highlight – we need the note as well. The note should say:
      • “The highlighted elements are in scope. If it is not highlighted, then it is OUT of scope”.

    Here is an example:

     

    Highlight Scopes + include a note
    Highlight Scopes + include a note