Bouwen met Staal | Veelzijdig, flexibel, duurzaam Bouwen met Staal

Cost components

Information and literature about cost estimation of steel structures

« terug naar Parametrisch ontwerpen

When an integral analyses process is automated, the same process can be used to integrally optimize. However, a certain optimization criterion/goal is required.

An IAM produces variants, from one variant multiple quantities can be extracted. For example: the amount of welding volume and the total weight. These quantities are translated to a price/costs, which makes it possible to optimize costs. The costs assumed will determine the “ratio of relevance” between quantities extracted, and will ultimately influence the optimal solution. 

Ratio labour and material costs

The ratio between the cost of labour and the cost of material is essential when optimizing production costs. This ratio will ultimately define, what will be the optimal solution. To put in perspective, optimizing productions costs for fabrication in China, where labour is relatively cheap, will give different result compared to optimizing production costs for fabrication in the Netherlands.

Welding volume method

to be edit

Reference unit prices

On this page, reference unit prices that structural engineer in the Netherlands can use in an integral optimization are displayed. It should be noted that these reference unit prices are estimates, that will provide more insight in costs and could therefor help decision-making, but they will never be exact representation of the final projects total cost.

Material reference prices:

In the table, below reference prices can be found for different sectionstypes, steelgrades and production process. The price per kilo is defined.

    S235 S275 S355
I-Beams Hotrolled € 0,75   € 0,78
Tube Coldformed € 0,85 € 0,85 € 0,90
Tube Hotformed € 1,00   € 1,10
Pipe Welded      
Pipe Seamless      

 

Prices change through time, however price ratios are more constant. Therefore, when optimizing costs it can be more accurate the use relative ratios instead of absolute costs. In the table below the cheapest type of material, S235 hotrolled I-sections, is set to 100%. This enables to show the relative cost ratios of the different types.

    S235 S275 S355
I-Beams Hotrolled 100% tbd 104%
Tube Coldformed 113% 113% 120%
Tube Hotformed 133% tbd 147%
Pipe Welded tbd tbd tbd
Pipe Seamless tbd tbd tbd
*tbd = to be determined

Material price index:

https://brinkstaalbouw.nl/staalprijsindex.html


Labour reference prices:

The cost of labour is determined based on the welding volume. In the graph below, welding speeds can be found. This data originates from a 2566 sample data set from steel contractor, Oostingh ASK Romein. In this data set the welding volume and the amount of working hours were measured. In the graph below, vertical bars represent the frequency a certain speed has occurred. Based on this graph, an average welding speed of 50 cm^3 per hour can be assumed.

Welding:

Average welding speed 50 cm3/hour
Factor including assembly 2,0
Speed 50/2.0 = 25 cm3/hour
Salary welder €20,-
Overhead factor 3,0
Cost of welder €20,-*3.0 = €60,-
Cost per cm3 welding material €60,-/25 = €2,40 /cm3

As mentioned, an average welding speed of  50 cm3/hour is assumed. To put this in perspective, the length after one hour of welding per weld size can be estimated.

Fillet weld size   Length per hour
a5 50.000/(5^2) = 2000 mm
a7 50.000/(7^2) = 1000 mm
a10 50.000/(10^2) = 500 mm

 

Sensitivity analyses

to be edit

 

Literature:

In the list below, interesting literature can be found about cost-estimation models of steel structures.

Steel Frames:

  • L. Xu and D. E. Grierson, Computer Automated Design of Semirigid Steel Frameworks, Journal of Structural Engineering 119, 1740 (1993)
  • L.M.C. Simões, Optimization of frames with semi-rigid connections, Computers & Structures, Volume 60, Issue 4 (1996)
  • M. Steenhuis, K. Weynand, and A. M. Gresnigt, Strategies for economic design of unbraced steel frames, Journal of Constructional Steel Research 46, 88 (1998)
  • N. B. H. Ali, J. C. Mangin, and A. F. Cutting-Decelle, An overall approach to structural design of steelworks using genetic algorithms, System-based vision for strategic and creative design — Proceedings of the 2nd international conference on structural and construction engineering, Balkema, Rome , 481 (2003).
  • L. Pavlovčič, A. Krajnc, and D. Beg, Cost function analysis in the structural optimization of steel frames, Structural and Multidisciplinary Optimization 28, 286 (2004)
  • N. Bel Hadj Ali, M. Sellami, A. F. Cutting-Decelle, and J. C. Mangin, Multi-stage production cost optimization of semi-rigid steel frames using genetic algorithms, Engineering Structures 31, 2766 (2009)
  • S. O. Degertekin and M. S. Hayalioglu, Harmony search algorithm for minimum cost design of steel frames with semi-rigid connections and column bases, Structural and Multidisciplinary Optimization 42, 755 (2010)

Steel Trusses:

  • J. Jalkanen, Tubular Truss Optimization Using Heuristic Algorithms (2007)
  • K. Mela, Mixed Variable Formulations for Truss Topology Optimization (2013)
  • M. Helminen, Mika helminen, optimization of a trussed steel portal frame, (2017)
  • K. Mela, T. Tiainen, and M. Heinisuo, Economical design of high strength steel trusses using multi-criteria optimization, Eurosteel 2017 1, 9 (2017)

Welding costs:

  • K. Jármai and J. Farkas, Cost calculation and optimisation of welded steel structures, Journal of Constructional Steel Research 50, 115 (1999).
  • F. Neessen, Zin en Onzin over laskostenbeheersing, Product Informatie Bulletin , 1 (2008) (Dutch)

Rest:

  • J. Haapio, Feature-Based Costing Method for Skeletal Steel Structures based on the Process Approach, Ph.D. thesis, Tampere University of Technology (2012)

Interesting literature missing?
Please inform Rayaan Ajouz: rayaan@bouwenmetstaal.nl