HOW TO. ESTIMATE the COST CONTENTS O F S T R U C T U R A L S T E E L ROBERT R. BONENFANT, JR. - JULY RATIOS AND ANALYSIS Main CSI Division

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1 HOW TO ESTIMATE the COST O F S T R U C T U R A L S T E E L CONTENTS ROBERT R. BONENFANT, JR. - JULY INTRODUCTION 7. RATIOS AND ANALYSIS Main CSI Division 8. MISCELLANEOUS AND PERTINENT Specific Sub-Division/Specification Section INFORMATION Brief Description of Structural Steel 9. GLOSSARY 2. TYPES AND METHODS OF MEASUREMENT 10. REFERENCES Steel Beam Sections and Dimensions 3. FACTORS THAT MAY AFFECT TAKE-OFF, PRICING, ETC. Large Quantities Versus Small Economies of Scale Union Labor Versus Non-Union Labor Geographical Location Supply and Demand of Steel Height of Building Site Conditions Experience of Erection Crew Renovation Project Versus New Construction Connection Details Moment Connections Beam Penetrations 4. OVERVIEW OF LABOR, EQUIPMENT, INDIRECT COSTS AND MARK-UPS 5. SAMPLE TAKE-OFF AND PRICING SHEETS 6. SPECIAL RISK CONSIDERATIONS Material Pricing Escalation Surcharges Fuel Costs Value of the Dollar Lead Times Estimating Today January 09 15

2 1. INTRODUCTION The purpose of this technical paper is to provide a basic understanding of how to prepare an estimate for structural steel beams and columns. This paper will focus on how to do a quantity survey of steel members, bent plate (pour stops), shear studs, connections, steel floor and roof decking, and price accordingly. The paper will not address AESS, diagonally braced frames, open web steel joists, trusses, steel tube, steel stairs, grating and other miscellaneous components that may be part of a building system. In addition, ancillary trades such as cementitious spray-fireproofing and intumescent fireproofing will not be considered in this technical paper. The intent of the paper is to isolate on a few key aspects of a structural steel framed building and not all possible components. Please note that CSI s 2004 MasterFormat edition has been used. Main CSI Divisions Division 05 Metals Subdivisions Metals Maintenance of Metals Common Work Results of Metals Schedules for Metals Commissioning of Metals Structural Metal Framing Structural Steel Framing Metal Decking Steel Decking BRIEF DESCRIPTION A steel framed building is an alternative to a concrete framed building. The steel framed building is equally a good choice as a concrete framed building. They each have distinct building materials, practices and benefits that have to be carefully weighed, as timing and situation will dictate the best choice. However, steel is a material that has the highest strength-to-weight ratio and is very ductile. Steel is also shop fabricated and therefore has a higher quality control as it s produced in a controlled environment. Steel beams and steel columns are used to structurally frame a building so that it supports the exterior façade, roof, interior construction, mechanical and electrical systems of the building and of course the personnel, furnishings and equipment that will occupy the building. The structural steel framed building also includes components such as steel floor decking, steel roof decking, steel joists, bolted connections, welded connections, base plates, slab pour stops, braced framing, moment connections, and other miscellaneous cold-formed metals to complete the steel framing system. Again, for the purposes of this paper I will only focus on a few of these components. 2. TYPES AND METHODS OF MEASUREMENT In the construction of structural steel building some basic design criteria needs to be developed. One is the column spacing and another is the floor-to-floor height. This leads to the sizing of columns and beams to carry the building loads. A 30 by 30 column bay is typical and a 12 deck height is typical in an office building. A 14 deck height is normal in a laboratory building due to significant HVAC requirements that need to be placed in the plenum space above ceilings. Structural steel beams and columns are designed on the basis of their yield stress. The most common design stress is 36 KSI and referenced by ASTM designation A36. Structural steel is fabricated in many sections such as wide flange (W), American standard beam (S), miscellaneous beams (M), American standard channel (C), miscellaneous channel (MC), angle (L), and structural tees (T). A beam and column is designated in the following way; W18x35. The W references the section shape; 18 references the nominal height of the beam/column flange in inches; and 35 references the weight of the beam in pounds per linear foot of beam or column length. This description is interpreted as a wide flange beam with a nominal depth of 18 inches and a weight of 35 pounds per linear foot. The standard unit of measurement for steel beams and columns is tons. The formula for calculating tons of steel will be: Wt. (Tons) = (L x Wt.) / 2,000 L = Length of Beam of Column Wt. = Unit Weight of Beam or Column in Pounds 2,000 = Conversion Factor from Pounds to Tons The unit measurement for floor and roof deck is square feet (SF). Area (SF) = (L x W) x 1.15 L = Length of Building in Feet W = Width of Building in Feet 1.10 = Excess Factor for Seams (10%) The unit measurement for pour stop is Tons. Wt. (tons) = (P x Wt.) / 2,000 P = (L + W) x 2 if rectangular or square building and measured perimeter (P) if irregular shaped L = Length of Building in Feet W = Width of Building in Feet Wt. = Unit Weight of Beam or Column in Pounds 2,000 = Conversion Factor from Pounds to Tons The unit measure of shear studs is Each. Shear Studs (Each) = Quantity Count from Structural Steel Drawings x = Excess Factor for Defective or Broken Studs (5%) 16 January 09 Estimating Today

3 Structural steel drawings will be provided that shows plan views, column schedules, and connection details. The plan drawings will show beam lengths and sizes with shear stud counts and cambering and the column schedules will show column heights and sizes. Detail drawings will also show items such as beam penetrations, moment connections, base plates, deck opening framing, HVAC support framing, and other special framing conditions. The following charts will show some typical steel sections, specifications, dimensions and welding symbols. (Diagrams Cont. page 18) Estimating Today January 09 17

4 18 January 09 Estimating Today

5 SUPPLY AND DEMAND OF STEEL Currently the strong global demand of steel; particularly in China, India and Russia is driving up the cost of steel. Even though steel mills have become more efficient and there are additional mills coming online demand is outstripping supply leading to higher prices. Foreign mills are also not exporting to the U.S. as they once did. HEIGHT OF BUILDING The height of the building will dictate the type of crane to be used on the project. Smaller projects may be able to use a mobile wheel-mounted or track-crawler crane. Tall buildings will need a tower crane that will require concrete pad foundations and electrical power requirements. SITE CONDITIONS The site conditions and constraints will also dictate the type crane that will be utilized. Tight sites in city areas will need tower cranes versus the ability to use mobile cranes in open sites assuming heights aren t an issue. EXPERIENCE OF ERECTION CREW The experience of the erection crew can affect the number of picks they make in day. The less experienced the crew the longer the erection duration will be resulting in higher erection costs. 3. FACTORS THAT MAY EFFECT TAKE-OFF AND PRICING EFFECT OF SMALL QUANTITIES VERSUS LARGE QUANTITIES; ECONOMIES OF SCALE If the project is small and there s a minimal amount of tonnage the unit cost will be higher than a project with a significant amount of tonnage. The mobilization and crane costs that need to get absorbed into the small project with less efficiency in production will make for a higher unit cost than on a large project. UNION VERSUS NON-UNION If the project is based on union labor the project will have a higher cost than non-union labor. Unions negotiate higher wage rate and benefit packages than would be provided by open-shop contractors. GEOGRAPHICAL LOCATION The location of the project may have an influence on cost due to regional material, labor, and equipment costs based on availability of resources and manpower. R.S. Means uses a coefficient factor to adjust for regional differences. RENOVATION PROJECT VERSUS NEW CONSTRUCTION Sometimes an existing building has to be structurally reinforced. The unit cost of structural steel will be higher on a renovation project than on a new building. On a renovation project the steel has to be fabricated in smaller sections to access the existing building and scissor lifts and other small hydraulic lift equipment has to be utilized in order to position the steel in place. The production rate is much slower working in an existing building, as you will be utilizing lighter equipment and probably using some handwork. CONNECTION DETAILS A project that utilizes welded connections takes longer to erect than with bolted connections. In addition, the fieldtesting of welded connections will also add time to the schedule. Curtainwall support connections will add to the cost as well as precast panel connections. Therefore, it s important to know what the façade of the building will be so connection detail costs can be accounted for. MOMENT CONNECTIONS Moment connections carry a premium cost to be installed, as they re a special condition connection to make a rigid or semi-rigid connection between a column and a beam. They re more labor intensive to install so the result is slower production leading to increased erection costs. Estimating Today January 09 19

6 BEAM PENETRATIONS Beam penetrations are cutouts made in the steel beams so that mechanical piping and ductwork can pass through. There will be unreinforced and reinforced beam penetrations depending on the size of the opening. Sometimes the architectural, structural, and mechanical drawings are coordinated enough to allow the Engineer to show on the plans where a portion of these beam penetrations may occur. The beam penetrations shown on the plans that can be fabricated in the shop will have a much lower cost than the beam penetrations that will have to be provided for in the field. There will inevitably be beam penetrations that will need to be cutout and reinforced in the field at a higher unit cost. EQUIPMENT The equipment utilized will be mobile cranes or tower cranes. Tower cranes will be predominantly utilized on high buildings in tight city quarters. INDIRECT COSTS Tower cranes also require concrete pad foundations to be set on and also require electrical power service. Safety costs for perimeter cabling needs to be considered along with other temporary construction costs to provide a secure and safe working environment. Other indirect costs to consider are sales tax, payment and performance bonds and liability insurance. 4. OVERVIEW OF LABOR, MATERIAL, EQUIPMENT AND INDIRECT COSTS The following example is intended to demonstrate a simple take-off and pricing method for a structural steel frame system including beams, columns, decking, shear studs, bent plate (pour stop), and connections. With today s technology many companies perform takeoff using OST and digitizers. OST allows you to take-off quantities on your computer screen while color coding the element you re taking off and recording up to three (3) units of measure for that element at the same time. However, for the purposes of this paper I will complete the take-off and pricing sheets on Excel to demonstrate the method being used. MATERIAL Take-off the lengths of each different size beam and column. Next I ll multiply the length of each beam and column by its respective weight. From the sum of all these beams and columns I ll then calculate the total tonnage. The shear studs will be counted for each beam and a total tallied. The perimeter of the floor plates will be calculated in order to figure the length of pour stop. The area of the floors will be calculated to determine the decking quantity. And lastly, the connections will be figured by calculating percentages of the total steel tonnage. LABOR Since the steel is fabricated in the shop the labor portion refers to the erection crew. Generally, it s assumed that for erection a crane can pick between 35 and 60 pieces a day. Assuming the average is 45 picks per day, and using common sizes of beams and columns that would probably equate to around 30 tons erected per day. 20 January 09 Estimating Today

7 Office Building Parameters Bent Plate Take-Off L W P A Structure Floor Length (lf) Width (lf) Perimeter (lf) Area (sf) SOG 1st Floor ,100 SOMD 2nd Floor ,100 SOMD 3rd Floor ,100 SOMD 4th Floor ,100 Total Interior Building SF: 32,400 SOMD Roof ,100 Assume 6"x6"x7/16" bent plate at 18 pounds per linear foot (plf). Floor Perimeter Un Unit Wt. Un Total Wt. Un Total Wt. Un 2nd Floor SOMD 360 LF PLF 6,480 LB 3.24 TN 3rd Floor SOMD 360 LF PLF 6,480 LB 3.24 TN 4th Floor SOMD 360 LF PLF 6,480 LB 3.24 TN Roof SOMD 360 LF PLF 6,480 LB 3.24 TN Total Weight: 25,920 LB TN Structural Steel Connections Take-Off Subtotal of Steel Tonnage TN Floor-to-Floor Height is 12'0" Steel Columns Take-Off Steel Tonnage Min. % Max. % Min. Wt. Un Max. Wt. Un Total Wt. Un Base Plates 2.00% 3.00% 3.20 TN 4.80 TN 9,604 LB Column Splices 4.00% 5.00% 6.40 TN 8.00 TN 16,007 LB Miscellaneous Details 4.00% 5.00% 6.40 TN 8.00 TN 16,007 LB Total Weight: TN 41,618 LB Floor # of Col. Size Unit Wt. (plf) Height (vf) Len (lf) Total Wt. Un Total Wt. Un 2nd Floor 16 W14x ,744 LB 7.87 TN 3rd Floor 16 W14x ,712 LB 5.86 TN 4th Floor 16 W14x ,712 LB 5.86 TN Roof 16 W14x ,176 LB 5.09 TN Total Weight: 49,344 LB TN Steel Deck L W A Floor Length (lf) Width (lf) Area (sf) Waste (10%) Total SF 2nd Floor , ,910 3rd Floor , ,910 4th Floor , ,910 Total Steel Floor Deck: 26,730 SF Roof , ,910 Total Steel Roof Deck: 8,910 SF Steel Beams Take-Off Total Steel Decking: 35,640 SF Typical for 2nd floor through the roof (4 levels) 2nd floor 4- Story Office Building Estimate (32,400 GSF) Qty Size Length Unit Wt. Total Wt. (lbs.) Total Wt. (tns.) 8 W24x , W36x , W21x , W8x W16x , Subtotal Weight: 61, GSF 32,400 Item Description Qty Un Mat Un Pr Mat Total Lab Un Pr Lab Tot Equip Un Pr Equip Total Total Cost $/SF 1. Structural Steel Beams & Columns tons 2, $ 323,642 $ $ 132,399 $ $ 29, $ 485,463 $ $ Bent Plate at Pour Stops tons 2, $ 28,512 $ 1, $ 14,256 $ - $ - $ 42,768 $ $ 1.32 $ Connection Steel tons 3, $ 69,714 $ 1, $ 34,337 $ - $ - $ 104,050 $ 4. Shear Studs - 3/4"x5" 5,124 each 2.68 $ 13,732 $ 1.32 $ 6,764 $ - $ - $ 20,496 $ $ 0.63 $ Steel Floor Deck - 3"x18 Gauge 26,730 sf 2.18 $ 58,271 $ 1.07 $ 28,601 $ - $ - $ 86,873 $ 6. Steel Roof Deck - 3"x20 Gauge 8,910 sf 2.01 $ 17,909 $ 0.99 $ 8,821 $ - $ - $ 26,730 $ $ 0.83 Direct Construction Cost $ 511,780 $ 225,177 $ 29,422 $ 766,380 $ Overhead & Profit 20.00% $ 153,276 $ 4.73 Total Construction Cost $ 919,655 $ rd floor Qty Size Length Unit Wt. Total Wt. (lbs.) Total Wt. (tns.) 8 W24x , W36x , W21x , W8x W16x , th floor Roof Subtotal Weight: 61, Qty Size Length Unit Wt. Total Wt. (lbs.) Total Wt. (tns.) 8 W24x , W36x , W21x , W8x W16x , Subtotal Weight: 61, Qty Size Length Unit Wt. Total Wt. (lbs.) Total Wt. (tns.) 8 W24x , W36x , W21x , W8x W16x , Subtotal Weight: 61, Total Weight: 244, SPECIAL RISK CONSIDERATIONS When estimating the cost of structural steel there is significant risk to mitigate. These risk items include the following: MATERIAL COST The cost of structural steel is increasing, as there s a huge global appetite for steel currently underway. Contributing to this escalation is also the fact that steelmakers are paying large premiums for raw materials from mining companies and passing this cost onto the consumer. Raw material costs have recently contributed to 50% of the steel cost where a short time ago they traditionally accounted for roughly 15% of the steel material cost. Steelmakers are now trying to acquire mines to provide raw materials for their own companies in order to be more self-sufficient. Estimating Today January 09 21

8 ESCALATION Escalation is a significant cost factor when putting a steel bid together. Your project may not require the steel to be on-site for many months to a year, if not longer. Many steel contractors will not even try to guess what steel prices may be at that time because of price volatility. In order to level the playing field for the steel contractors during a bid you may have to forecast as best you can the projected future steel cost and carry an escalation allowance. This strategy should be discussed should be discussed with the Owner. SURCHARGES Surcharges are added to the steel material costs because the material cost is volatile and it gives the steel supplier more flexibility to lower and raise his price. This practice eliminates the need to constantly adjust a fixed price so that you can appear to remain competitive. FUEL/ENERGY COSTS The cost of a barrel of oil is hovering around $140/barrel and the average cost of gasoline in the U.S. right now is about $4.00/gallon. Fuel and energy costs are making steel more expensive to produce and ship steel. VALUE OF THE DOLLAR The value of U.S. dollar has been declining steadily for several years now and is playing a large part in the high cost of exported steel to the U.S. Steel is exported at a higher cost to the U.S. because of the weak dollar. And many foreign companies buying U.S. steelmakers are exporting to their own country because of strong demand instead of selling to the U.S. Therefore, we re left still paying higher prices because many U.S. steel companies are foreign owned. LEAD TIME OF MATERIAL If the steel sections required for your project are not in stock then it becomes more critical to get your shop drawings approved in a timely manner to secure a place on the mill fabrication schedule. Depending on how many rolling jobs are ahead of you this lead-time will have to be taken into consideration relative to your construction schedule. 6. R A T I O S A N D A N A L Y S I S There are a few ways to analyze whether your bid or estimate is in the ballpark and reflects whether or not you are providing a reasonable cost. One way is to look at historical data from similar projects and escalate those previous project costs to current day costs. Using past project costs can be a good benchmark to gauge your bid or estimate. Another way is to use conceptual design information that has been acquired through experience with putting together conceptual estimates and/or interaction with structural engineers. For the office building example used, I will take the total steel tonnage and divide by the total building square footage (assuming the ground is a slab-ongrade) and expect to get a unit weight of between 11 psf and 15 psf. If my tonnage is not in this range I will investigate further to determine why the structure is seemingly light or heavy. Having a structure with inadequate steel strength is one issue and having a structure with excessive weight may be inefficiency in beam usage leading to an unnecessarily higher cost. In regards to shear studs I would also divide the total building square footage by the total quantity of shear studs and expect this number to be in the range of 6-8 sf per stud (or studs per sf). If not, I ll make adjustments to make sure that I carry enough shear studs in the estimate. The following logic chart below is a sample calculation used to check the validity of the estimate. I have shown how to complete a logic check on the structural steel beams, columns, bent plate, and connections to see if the unit weight of the structural steel system is in the projected range. I have also shown how to complete a logic check on the shear studs to make sure there are enough for the composite slabon-deck system. I have performed a quick check on the structural steel erection cost to see if it is in-line with my estimate. As you will the erection estimate at $161,821 is close to what I calculated in the estimate at $176,077. This again is a logic check to make sure that the numbers in the estimate are a reasonable cost for the scope of work. Columns Beams Bent Plate Connections Total Weight Building (SF) Unit Weight (PSF) Steel Logic Check Weight 49,344 LB 244,880 LB 25,920 LB 41,619 LB 361,763 LB 32,400 SF 11.2 PSF Okay: The unit weight of steel for the structure falls in the range of psf at 11.2 psf. Since this is an office building I would expect it to be closer to 11#. Shear Studs Building (SF) Square Feet Per Stud Shear Stud Logic Check 5,124 EA 32,400 SF 6.3 SF Okay: The quantity of shear studs falls in the range of one (1) stud per 6-8 sf of floor area. We're at one (1) stud per 6.3 sf of floor area for the structure. 22 January 09 Estimating Today

9 Structural Steel Erection Cost Item Qty Un Steel Columns 48 Each Steel Beams 200 Each Total # of Beams & Columns Total Weight of Beams & Columns Average Weight of Steel Member If Pick 30 Tons Per Day Production = Duration of Steel Erection Crew Unit Cost ($/Ton) $ 1, Crew Daily Cost (30 Tons Per Day) $ 33,000 Total Steel Erection Cost $ 161,821 Check Cost From Estimate $ 176, Each Tons 0.59 Tons 51 Pieces 5 Days GLOSSARY A36 ASTM Steel Designation AESS Architecturally Exposed Structural Steel OST On-Screen Take-off SOG Slab on grade SOMD Slab on metal deck BIM Building Information Modeling Moment Connection A rigid or semi-rigid column to beam connection Shear Stud A metal stud welded to the top of a beam in a composite slab on deck Intumescent Referring to fire retardant paint on architecturally exposed steel Camber An arch fabricated in the beam so that designed loads acting on the beam limit the deflection of the beam. The intent is to have a level floor. REFERENCES Means Estimating Handbook AISC Manual of Steel Construction 7. MISCELLANEOUS PERTINENT INFORMATION Recently, in order to evaluate the construction sequencing of erecting structural steel BIM modeling has been utilized. BIM stands for Building Information Modeling and is used to create a computer model of the building from the design drawings. This computer model is capable of detecting dimensional busts as well clashes with other building elements. It also has shown weaknesses in erection sequencing that can lead to a more efficient construction schedule. Another interesting development is the use of barcodes that are placed on the fabricated steel in the shop, scanned when shipped, scanned when delivered to the site, and scanned when erected in place. This real-time scanning process allows the BIM model to show the Construction Manager and Client when the steel has been fabricated, shipped, delivered to the site and erected. The computer model then displays that actual to-date work put in place showing a time sequence. Estimating Today January 09 23