Steel Detailing | Precast Detailing | Estimation

Month: September 2022

  • MDC SILVERDALE ROAD

    MDC SILVERDALE ROAD

  • TEMPORARY CONNECTION WITH DETAILS

    Precast erection procedure having the set of sequences. When the panel is installed on the slab, props are fixed to stable the panel, then panel was unhooked from crane then the temporary stich plate or stich angles are connected to the next panel through cast in ferrule, which is casted on the precast panel.

    The temporary connection is additional support for the precast panel for until grouting the grout tube & slab were connected to the particular panel. The panels are easily leveled up with respect to the connected panel. Minimize the no of brace connections. Easy to maintain the panel gap.

    Based on the position of panels & face of the connection it is classified as below,

    1. In-line stich plate connection.
    2. Internal Stich angle connection.
    3. External stich angle connection.
    4. On edge stich angle connection.

    1. In-line stich plate:

    When the panel are next to each other the temporary connections are made by the straight stich plate with ferrule as mentioned below picture.

    2.Internal Stich angle:

    When the panel is perpendicular each other and inside corner is access to perform the connection, the internal angle stich angle is being used.

    3. External stich angle:

    When the panel is perpendicular each other and outside corner alone is access to perform the connection, the external angle stich angle is being used.

    4.On edge stich angle connection.

    Some cases, same level panels one is erected on top of slab and another one is located on ceiling level is supported by on-edge ferrule mentioned as below picture.

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  • CAST-IN PLATE WITH DETAILS

    A steel plate which is casted in to concrete for connection purpose is named cast-in-plate. Connections may be required to carry shear and axial force between the precast elements for applied load conditions.

    Cast-in plates are used to tie/ fix,

    1. Concrete or precast panels to each other.
    2. Precast to insitu slab.
    3. Steel beams to the Precast panels/slabs.

    All purpose of connection except steel beam to precast connections required pair of cast in plate connected by a welded plate . But the steel beam to precast connection required only a cast-in plate with cleat plate is enough . All the plates and connections details are need to approved by Structural Engineer.

    1 Panel to Panel connection:

    Normally the lift shaft panels & stair panels have to connect withstand maximum shear and axial loads. The vertical panel joints are made by the cast-in plate connection. Minimum two no of connections per level is needed (need to get structural engineer advise).

    The cast in plate casted with pocket to cover on later stage. Both perpendicular & in line panels are also can be able to connect. We can able to connect insitu wall to precast panel also by this method. Refer blow picture for better understanding.

    2. Precast to Insitu slab Connection:

    For Particular requirement the precast should be connected with slab. One cast in plate casted in to the slab and another one is casted in to the precast and both the plates are connected through weld plate by weld on site. Refer below picture for better understanding.

    3. Steel beams to the Precast Connection:

    Now a days the construction system are versatile various types of constructions systems are used to complete the same building. Steel building with precast walls are also preferred as a one type of construction system.

    Where the steel beams are meet the precast panels the cast-in plate is used to connect it. Here instead of weld plate cleat plate is used to connect between the steel member to precast wall. The cast in plate on the precast walls not cast with the pocket it is flush with surface.

  • WATERPROOFING AND ITS ADVANTAGES

    • Waterproofing:
      Normally exterior precast walls are constructed with joints and window openings. It can be easily affecting the moisture infiltration. Waterproof materials are applied in these areas to eliminate the moisture intrusion to the precast panel.

      we are defined edges are used to avoid this, it made upon wood or Foam (Thermocol).
      Top of Step Joint.
      Bottom of Step joint.

      If we require any special type of edges, it’s formed related to the above edges.
      Below images are given to reference the edges.

    • Advantages:
      1. Increase the lifespan of the structural Elements.
      2. Prevents the rusting of reinforcement in wall.
      3. Reduced the maintenance cost of the building.
      4. Prevents wetness inside of the building.
      5. Prevents leakages from the walls and ceiling.
      6. Prevents the formation of cracks on the surface of the building.
      7. Water absorption will be reduced.

  • SHOP DRAWING AND ITS COMPONENTS

    Shop Drawing:
    Shop drawings is detailed drawing of the original design of the building. It’s a drawing or set of drawings given to our consultant or Fabricator. It is used to produce the individual precast panels in the factory. Shop drawings are typically required some prefabricated components, they are Listed below.

    Shop Drawing Components:

    1. Lifter’s [Edge lifters – (Top & side) and face lifter’s].
    2. Grout tubes & Dowel bars (Top & Bottom).
    3. Props. (Face & Edge props)
    4. Ferrules (Handrail, Temporary connection ferrule & Slab rebate ferrule,
    steel connection ferrule).
    5. Couplers.
    6. Pull-out bars and starter bars.
    7. Cast in Plate.
    8. Strong back.
    9. ID tag.
    10. Any special components required for some special cases like Conduits etc.



                   SAMPLE SHOP DRAWING ELEVATION WITH COMPONENTS

  • TYPES OF SERVICE DRAWINGS USED FOR PRECAST DETAILING

    Types of Service drawings:

    • Crane drawing
    • Lift drawing
    • PT drawing (Post tension)
    • Mechanical service drawing
    • Electrical service drawing
    • Fire service drawing
    • Steel detail drawings
    • Hydraulic service drawing
    1. Crane drawings
      1. Refer crane drawings for loading platform location, Crane tonnage & its relevant circles and other crane related data’s. (Refer Fig.01)

    Fig .01 (Ref. Crane drawing)

    2. Lift drawings

      1. Refer these drawings for lift door opening size & set-out, lift door fitment rebates, landing RL’s, penetrations and rebates for call buttons & indicators, service hatch openings, Unistrut’s locations, lifting eye locations and loading factors, switch cut-out on final floor and other lift related data. (Refer Fig.02)

    Fig .02 (Ref. Lift door & penetration details)

    3. PT drawings

      1. Must refer these drawings for PT tendons passage location. Wherever the PT tendons passing through the precast we must provide block-outs to suit accordingly. The nominal size of block-outs for PT to pass through as per engineer requirements. If not shown on any drawings, we need to raise RFI (Request for information). (Refer Fig.03)

    Fig .03 (Ref. Post tension drawing- PT)

    4. Mechanical service drawings

      1. Refer these drawings for mechanical openings in slabs & walls. Mainly for duct works, garbage chutes, kitchen exhaust chutes, stair pressurization openings, etc. (Refer Fig.04)

    Fig .04 (Ref. Mechanical service drawing)

    5. Electrical service drawings

      1. Refer these drawings for electrical penetration requirements in slabs & walls. Mainly for communication, power and other electrical related accessories to pass through. (Refer Fig.05)

    Fig .05 (Ref. Electrical service drawing)

    6. Fire service drawings

      1. Refer these drawings for Fire service penetration requirements in slabs & walls. Mainly for fire hydrants, sprinkler system and its pipe accessories to pass through. (Refer Fig.06)

    Fig .06 (Ref. Fire penetration drawing)

    7. Steel detail drawings

      1. Refer these drawings for Steel to precast connection details. Mostly if some connection like this present, we will get intimated beforehand. (Refer Fig.07)

    Fig .07 (Ref. Steel drawing)

    8. Hydraulic service drawings

      1. Refer these drawings for Hydraulic service penetration requirements in slabs & walls. (Refer Fig.08)

    Fig .08 (Ref. Hydraulic service drawing)

  • HEADER WITH DETAILS

    1. In-situ or Precast element present above the door or window opening is called header. (Ref.Fig.01&02)
    2. Usually, the height of header will be small, and it will have more load impact for the smaller load distribution area.
    3. For structural stability that header needs to have high strength. If structural engineer didn’t specify more strength means it won’t have higher load distribution impact. So, that area requires more reinforcements. (Ref.Fig.03)
    4. Structure engineer drawings specifies that detail in separate header beam detail or in core elevation drawing or even in nominal elevation or as a separate document as per the need and availability.
    5. While providing reinforcement arrangement for header, we need to consider room space on header beam. So, for header reinforcement arrangement we need to the arrangement in 1:1 scale to ensure that no complication & difficulty will arise in factory as well as site.
    6. If any penetration comes at header which is larger in size than for ties spacing, we need to add two ties at both sides of penetrations.
    7. We need to raise RFI (Request for information), if header reinforcement details not provided by structural engineers.

    Fig.01 (Ref. Precast elevation)

    Fig.02 (Ref. Header detail)

    Fig.03 (Ref. Header reinforcement detail)

  • GROUT TUBE WITH DETAILS

    GROUT TUBES:

    • Grout Tubes are hollow components and are made of plastic or thin sheet metals.
      (Refer Fig.01)
    • Grout tubes are cast into precast elements which create a void to locate and connect the elements (between two precast elements or in-situ to precast elements) together using starter bars or dowel bars.
    • Once the elements are in position, the grout tubes are filled with grouting material and locking the elements in position.

    Fig.01 (Sample bottom Grout tube with breather)

    Purpose of Grout tubes:

    • Grout tubes are used in the construction of precast concrete buildings for connecting elements like walls, tilt-up panels, beams, columns, etc.
    • It will help to increase the strength and durability of the precast or in-situ elements.

    General details for Grout tubes

    1. Hollow components with spiral designs or key ways in its walls
    2. Selection of grout tubes based on dowel size
    3. Alternatively, NMB splice sleeves or penetrations can be used or dowel bars can be directly casted if having rebar’s arrangement congestion
    4. Grouting materials must be filled for Load bearing areas and voids will be present for NLB (Non load bearing) portions.
    5. Must not clash with other components in precast (Cast in plate, Lifter, Lig-cage, lig-cage hooks, Prop, Grooves, Ferrules and etc.) – Refer Fig.02
    6. Face of breather must be inside of building and must have access, must not be placed where sequential grooves or architect patterns present.
    7. If breather has no access must provide breather extent to where the access is possible (not required when it is NLB)
    8. Must have a minimum gap of 200mm with other components especially lifters & block-outs (this value can be modified, if having difficulties to maintain that gap)
    9. Avoid the Grout tube placement near to window & major openings (wherever possible)
    10. Grout tube must be placed within 300mm from panel edge. (But can be modified if having any difficulties.)

    Fig.02 (Sample Top Grout tubes)

    Advantages:

    • Lightweight and easy to process
    • Available in a range of sizes
    • It will help to reduce the construction time on site
    • Easy to connect with precast or in-situ elements

    Disadvantages:

    • The huge amount of grout tubes needed to fill up the duct in order to secure the connection between the precast wall or in-situ.

  • DOWEL BAR WITH DETAILS

    Dowel bars:

    • Dowels are short straight steel bars and also cogged bars, used to provide mechanical or structural connection between two precast elements or in-situ to precast elements.
      (Refer Fig.01)

    (Fig.01) Dowel bars

    Purpose of Dowel bars:

    • Dowel bars used to maintain the horizontal and vertical alignments of slab and precast panel. (Ref Fig.02)
    • Dowel bar connection used to transfer the loads between two concrete elements or two precast elements or precast to in-situ elements. (Refer Fig.03&04)
    • Dowel bar is used to extend the structure easily with small drilling to insert the steel for the extension of the structure.

    General details for Dowels:

    • Dowel bar is a steel rods with spiral outer design. (Refer Fig.01)
    • Used in all the locations where Grout tubes are required.
    • Selection of Dowel based on Engineer requirement.
    • Dowel can either be black finish or galvanized finish.
    • Black finish for load bearing dowels and galvanized finish for NLB (non-load bearing) dowel. (It may be varied).
    • Alternatively, bars connected into NMB splice sleeves can be used. Also, starter bars can be casted into panel.
    • Plastic tube will be placed over upper half of dowel. And 20mm compressible cap will be placed over the top of the dowel bar for NLB (non-load bearing) portions whereas grouting material will cover the entire dowels for LB (Load bearing) conditions.
    • Dowels must be positioned within Grout Tubes with minimum amount of clearance on precast walls or slabs.

    Advantages:

    • It is reducing the corner cracking.
    • It will reduce joint faulting.
    • Dowel bar is also used to reduce the deflection and stress.

    (Fig.02) Precast wall connection

    (Fig.03) – Precast to in-situ connection

    (Fig.04) – Precast to slab connection