Lecture 11 Steel Structures PDF

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Notes are based on Prof. Amir Lopci's lecture...

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WEEK 11 STEEL STRUCTURES ESTIMATING METAL WORK 

Topic is about:  Steel  Structural Metal Framing  Steel Framing Take Of

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General contractors typically rely on subcontractors for fabrication and erection of structural steelwork, which includes:  Columns  Beams  Lintels  Trusses  Joists  Bearing plates  Purlins  Decking  Bracing  Any other item required

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When estimating structural steel work, estimator should 1. Quantify each item separately like:  Column bases  Columns  Trusses  Lintels 2. Cost of structural steel varies depending on the type and shape of metal required

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Estimation of the field cost of transportation and erection will vary, depending on the ff:  Element size  Element weight  Weather conditions  Equipment available  Amount of riveting  Welding required  Bolting required

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Metals used for the framing of structure are primarily: 1. Wide flange Beams (w series)  Most commonly used today, designated in Figure 11.1

2. Lightweight beams 3. I-beams

4. Plates

5. Channels

6. Angles

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Special shapes and composite members require customized fabrication o it should be listed separately from the standard mill pieces. Estimator needs to be careful when quantifying each size and length It is also a good practice to check not only the structural drawings BUT ALSO THE SECTIONS AND DETAILS OPSS 906- structural steel specs

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Should include the fastening method required Drawings of the fastening details

ESTIMATING STRUCTURAL STEEL  

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Takeoff should first include a listing of all metal required for the structure Commonly used sequence is: o Columns and details o Beams and details o Bracing and flooring Floor by floor, a complete takeoff is required Among the items that may not be shown on the contract drawings but are required for a complete job are the ff: o Various field connections o Field bolts o Ties o Beam separators o Anchors o Rivets o Bearing plates o Welds o Setting plates o Templates Specs for Structural steel may require conformance with: o CISC (Canadian Institute for Steel Construction) o CSA (Canadian Standards Association) Without detailed understanding of above mentioned, the estimator can make an approximate estimate for a check on subcontractor prices o But estimator should not attempt to use those figures for compiling a bid price

Structural steel= tons or kg

When estimating structural steelwork, the estimator should quantify each item such as:      

Columns Beams Trusses/metal joists Lintels Purlins Decking

Structural steel is purchased by the ton The cost per ton varies depending on the type and shape of metal required.

Structural steel is purchased by the ton The cost per ton varies depending on the type and shape of metal required. Horizontal Framing 

Beams o Metals used for the horizontal framing of a structure o Includes:  Wide flange beams  Light beams  I beams  Plates  Channels  Angles

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Metal joists o Aka open web steel joists (OWSJ) o They are prefabricated lightweight trusses o Weight per metre is typically found in the manufacturer’ catalog o o o

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http://www http://www..canammanac.com Architects and engineers use the joist depth tables as a general guide to select the best depth and most economical joist. Engineering drawings usually identify joist mark, span, and loading and service requirements  The truss manufacturers use this information to design and supply the joists To find out the quantity of bar joists: # of Bar joists or Total weight of bar joists= Length of Joists (Weight per metre)

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Cost per kilogram is considerably greater than that for some other types of steel (i.e. reinforcing bars or wide flange shapes) because of sophisticated shaping and fabrication required. They themselves do not make an enclosed structure  THEY ARE ONE PART OF AN ASSEMBLY The other materials included in this assembly are varied, and selection may be made on the basis of the ff:  Economy  Appearance  Sound control  Fire-rating requirements  Any other criterion Mechanical and electrical requirements are typically quite compatible with steel joists  Only large ducts have to be carefully planned for job installation.

Metal Decking  used for floor and roof applications  Depending on the specific job requirements, a wide selection of shapes, sizes, thickness and accessories are available.  For floor applications, they are equally varied from the simplest type used as a form and reinforcing for concrete TO elaborate systems that combine: o Electrical and phone outlets o Electrical raceways o Air ducts o Acoustical finishes o Recessed lighting

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Metal decking is measured by the area o 1st: Estimator must determine how many square meters are required \  Decking is usually installed by direct welding via bottom of the rib (usually 300mm max OC w/ side joints mechanically fastened NOT MORE THAN 910mm OC) o 2nd: Estimator will have to find out how many of the ff:  Amount of weld washers required for installation and how long will it take to install them  Fastening is sometimes done by using clip screws and bolts

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Estimating Vertical metal framing decking  Take off should first include all metals required for the structure  COMMONLY USED SEQUENCE IS :  Columns and details  Beams and details  Bracing and flooring  Floor by Floor, a complete takeoff is required  Among the items that may not be shown on the contract drawings but are required for a complete job are the ff:  Field connections  Field bolts  Ties  Beams  Setting plates  Templates

QUANTITY TAKE OFF PROCESS: 1. 2. 3. 4. 5.

Divide building into smaller areas and bays Identify diferent shapes and section sizes Measure and recap lengths for each shape SEPARATELY Multiply lengths by the unit weight per foot or meter for each shape Add all total weight and allow 10-20% waste for the f if those members were not included in the take-of quantities: a. Base plates b. Connections c. Column splices

d. Other details 6. Convert the result to tons. STEEL DECK QUANTITY TAKE OFF PROCESS: 1. 2. 3. 4. 5.

Separate diferent types and gauges of decking Measure flat area by squared feet or squared meters Add overhang area Allow for pitch (slope) Allow for slide and end overlap...