Steel and Precast Detailing Services

Category: Processes

  • UPSTAND Vs CORBEL

    Upstand:
    Upstand is typically used for return legs in a precast element (Panel, Column, Spandrel). Generally, upstand preferred near face in shop drawing. If any special requirement (architectural design) only goes for Far face.
    Because far face is a table face, so we can’t provide upstand on Far face due to manufacturing difficulties.

    Corbel:
     Corbel is typically used for panel thickening increases in a precast element. Its also preferred near face in shop drawing.

    Thickness for Upstand:
    Total length of return value (sum of panel thickness) to be considered as upstand thickness.

    Thickness for Corbel:
    Thickness increase value (Apart from panel thickness) to be considered as corbel thickness.

    Advantages:
    1. The upstand and corbel profile formation used to avoid small size precast elements manufacturing.
    2.And also it will help to avoid some small part of in-situ elements on site.
    3. The construction time will be reduced.
    4. The cost of manufacturing also will be reduced.

  • THE USAGE OF NEAR FACE(NF) AND FAR FACE(FF) INDICATION ON SHOP DRAWINGS

    Near face (NF): Near face is a front view of the precast wall.

    Far Face (FF): Far face is an outside view or trowel face or table face of the precast wall.

    • Near face and Far face indication playing a major role on shop drawings to identify the component placing for factory people while manufacturing panel. (Refer Fig.02)
    • At initial stage we draw the panel footprint on marking plan and fix the panel view based on where the panel comes like inside or outside of the building.
    • In marking plan, we viewing the panels both inside and outside of the building because to achieve architect and structural aspects or requirements and to avoid some manufacturing difficulties.
    • The below mentioned details are used to fix the views for precast panels from marking plan.1. To View from inside of the building:
    • Good table finish will be on Far face.
    • Grooves, patterns, different profile design comes at outside of the building, so it will easy to assign profiles on far face of the panel and it will be on table face on factory. (Refer Fig.03 & 05)
    • For upstand or corbel to be comes at near face of the precast panels to avoid manufacturing difficulties.
    • If any bars connecting to in-situ at near face, we also view the panel from inside.2. To View from outside of the building:
    • For basement level panels no need trowel finish or good table finish on far face of the panel (Outside of the building). In this case we looking the panels from outside of the panel.
    • If panel have upstand or corbel profiles at outside of the buildings, we need to view the panel from outside to avoid manufacturing difficulties on factory. (Refer Fig.01)
    • In few cases, building inside is fully balcony and outside side is partially inside of the building. So, this kind of scenario we viewing the panel from outside of the building due to panel finish. (Refer Fig.04)

    General:

    • For multi-storied buildings, we follow the same elevation number for same set-out from lower level to above levels.
    • The starting level of panels we will fix viewing direction as per current level architectural and structural aspects.
    • Some cases the lower-level panels come at inside of the building and above level panels comes at outside of the building. In this case we viewing the panels same as per lower levels but we flipped the above level panels for manufacturing purpose.

    Advantages:

    • Drawing study is easy for factory people.
    • It will reduce the time delay of manufacturing the panels.
    • It will also avoid the manufacturing difficulties and Errors.

    Fig.01

    Fig.02

    Fig.03

    Fig.04

    Fig.05

  • RIGGING DIAGRAM AND IT’S USES

    • The rigging detailed diagrams are shown on shop drawings. (Ref Fig.01,02 & 03)
    • The rigging diagrams are designed based on the precast panel profiles.
    • It is indicating the lifting point position of precast panels for both factory and site.
    • Erection engineer will be approved the rigging diagram details.
    • The site people are preplanning to lifting the precast panels for erection.
    • It is indicating the demolding lifting points. So, the factory people will aware while lifting the panels on factory.
    • It is designed to distribute loads equally between all anchors in precast components such as walls, beams or flat slabs and etc.
    • It is also used for loading and unloading the panel while transportation.
    • The lifting accessories may be in the form of cables, hooks and etc.
    • Many accidents and failures will be avoided with the help of rigging diagram.
    • The time delay of the lifting to be reduced.

    (SAMPLE RIGGING DIAGRAMS FOR REFERENCE)

  • VIBRATING TABLE FOR PRECAST FABRICATION

    • Vibrating table using for compacting and consolidating the stiff and harsh mixes in precast structures on factory or yards.
    • While using this vibrator the concrete will be spreads equally at all corners of the precast structure in mold.
    • It will help to improve the strength and quality of precast concrete structure.
    • The void or bubble formation will be avoided.
    • So, the cracks formation also to be reduced.
    • It will reduce the man power.
    • The fabrication time is less.

    Fig.01 (Vibrating table)

  • VARIOUS SPANDREL PROFILES

    • Spandrel profiles are designed based on architectural aspects on Elevation purpose.
    • When doing this kind of profiles, it’s challenging and more interesting to achieve.
    • And also, it will help to improve our drawing knowledge and skill.
    • We handled and come across different types of precast spandrel profiles as per below,
    1. Spandrel with straight profile
    2. Spandrel with curve profile
    3. Spandrel with curve & triangle profile
    4. Spandrel with L shaped profile
    5. Spandrel with U shaped profile
    6. Spandrel with V shaped profile
    7. Beam type spandrel1. Spandrel with straight profile (Ref. Fig.01)

    Fig.01

    2. Spandrel with curve profile (Ref. Fig.02)

    Fig.02

    3. Spandrel with curve & triangle profile (Ref. Fig.03)


    Fig.03

    4. Spandrel with L shaped profile (Ref. Fig.04)

    Fig.04

    5. Spandrel with U shaped profile (Ref. Fig.05)

    Fig.05

    6. Spandrel with V shaped profile (Ref. Fig.06)

    Fig.06

    7. Beam type spandrel (Ref. Fig.07)

    Fig.07

  • Memo 13 – How to Remind clients about variation approvals

    The Building industry in Australia is tough. The insolvency rate is over: 20%. Lies, non-paying etc. strikes, cost surges etc. is all de rigger. Builders are stressed. There’s no need to stress them out even more. Variation work is common the industry.

    Simply use the forms on our quote app – they are standard template fields which will save you a lotta headaches.

    If you need to remind clients about a variation:

    1. Ask nicely.
    2. Ask the proper way.

    DO NOT DO THIS:

    • “This is a variation for both of us”.
    • “Please approve the variation. So that we will proceed with the changes”.

    No: it is not a variation for both of you: the client will decide the variation. You shouldn’t tell him that. If you do, you will simply annoy the client.

    No: do not ever say: “please approve so that we will proceed”. This is akin to threatening the client, and holding up the job. Never, ever do this! It’s the worst way. You will annoy the client and he will walk – this has actually happened (yes there were other factors contributing) but it could be avoided.

    Never do this!
    Never do this either!

    WHAT SHOULD I DO?

    • We want our clients to voice objections. That’s right, we WANT to hear the objections. Everything we do should be clear, fair, transparent, and should have the consent of all parties. The communication should reflect that. So ask like this:

    These are all “no-orientated” questions. They are decided to illicit a “no” – to make it easy and welcoming for the client to object. Use the exact wording above.

    1. Do you have any objections to this proposed variation request?
    2. Do you object?
    3. Sounds like you have an issue with this request?

    Fixed Price Contracting

    • Some clients agree to our contract, knowing full well that we do not do fixed price contracting. If any client rejects variations because they want fixed price contracting – then please feel to contact me directly about this.

    Be Honest

    • If it takes 1 hour, then write down: 1 hour.
    • Do not write down 3 hours. If you get caught, then clients will loose trust in you, in our firm, and so will I. You will get a reputation as a liar, and that reputation is hard to shake.

  • 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.