Copyright 2018 Multidisciplinary Optimization of Steel Structures for Cost 1 A Multidisciplinary Method to Optimize the Structural and Connection Design of Conventional Steel Structures for Cost Filippo Ranalli Research Assistant, PhD Eduardo Miranda Professor Martin Fischer Professor Ram Rajagopal Professor
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Copyright 2018
Multidisciplinary Optimization of Steel Structures for Cost
1
A Multidisciplinary Method to Optimize the Structural and Connection Design of Conventional Steel Structures for Cost
Filippo RanalliResearch Assistant, PhD
Eduardo MirandaProfessor
Martin FischerProfessor
Ram RajagopalProfessor
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Multidisciplinary Optimization of Steel Structures for Cost
Construction Planning
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Building Envelopes and
EnergyStructure and
Detailing
Optimization In the Three Phases of Design
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Structure and Detailing
When structural optimization is performed,weight is directly associated to cost
Design optimization is not the industry standard for conventional structures
Optimal solutions are hard to find manually
Constructability is often not accounted for in the design phase
Pitfalls of the Standard Practice
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Research Questions
1. How can data-driven cost estimates coupled with a detailing engine drive the member sizing and lateral system optimization towards a minimum-cost solution?
2. How can member sizing for strength and stiffness be achieved across multiple load cases to meet all AISC requirements, while minimizing for cost?
3. How can stochastic exploration of the lateral systems help find better designs?
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The Design Space The Final Structure
MDO Software• Sizing• Topology
The Original Structure
MDO: Case Study Overview
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Metrics Baseline Design MDO Design Difference
Total Weight of Steel (kg) 23411 13644 -42%
Number of Connections 813 803 -1%
Number of Unique Connection Details 17 9 -47%
MDO: Case Study Results
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Sizing Strength Stiffness
Detailing Connections Splices
Constructability
Topology Lateral System
Proposed Functionality: Overview
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Research approachMember Sizing OptimizationFormat: Journal paperExpected Submittal: February - March 2019Overview: Automated sizing for drift and strength using anenergy-based algorithm, designing across multiple load casesfor a conventional steel building.
Tasks:• Improve and extend current strength and stiffness algorithm,generalizing it to conventional building structures of largerscales.• Include inter-story drifts as constraints.• Account for composite and semi-composite floors in thegravity system.• Model more in-depth seismic analyses, such as the modalresponse spectrum approach.• Develop/refine appropriate heuristic fabrication and erectioncost model for steel, connections and slabs.• Apply to full-scale 4-storey moment frame case study (DPRConstruction, San Diego). The scale is around 5k frameelements, with composite slabs, and seismic & wind governingload combinations.
Expected Results: Automated sizing engine can find solutionsthat are compliant with strength and stiffness for all the loadcombinations, and minimal in terms of member weight, depth orweld area.
DPR Construction San Diego Case Studies
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Sizing Vertical & Lateral System of a Real Building
Floor Plan
Moment Frame
Composite Floor System
Gravity System
DecoupledCoupled
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Multidisciplinary Optimization of Steel Structures for Cost
Composite Floor System
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Sizing Vertical & Lateral System of a Real Building
Gravity System
Step 1:• Assemble accurate analytical model of the full building.• Optimize composite beams for given gravity loads prior to
running the analysis.
Step 2:• Size each individual column of the gravity system based on
loads transmitted by composite slabs, also prior to running the analysis.
Pre-AnalysisOptimization
Moment Frame
Step 3:• Optimize moment frame sizes by running the analysis on the
full scale model with gravity system and composite beams from Steps 1, 2.
Post-AnalysisOptimization
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Multidisciplinary Optimization of Steel Structures for Cost
Moment Frame
Composite Floor System
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Sizing Vertical & Lateral System of a Real Building
Gravity System
Variables: Beam size, number of studs (% of composite action), camberConstraints: Vertical deflection, beam strengthObjective: Minimum cost (structural steel + studs + labor)Approach: Exhaustive search
Variables: Column size, column splicesConstraints: Column strengthObjective: Minimum weight or member cost-driver (structural steel)Approach: Exhaustive search
Variables: Beam and column sizes, composite or non-composite beamsConstraints: Lateral building deflections, beam/column strengthObjective: Minimum weight or member cost-driver (structural steel)Approach: Energy-based envelope across load combinations
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Fabrication Cost Equipment at shop Labor at shop
Erection Cost Equipment at site Labor at site
Material Cost
Next Steps: Cost-Detailing Feedback
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Multidisciplinary Optimization of Steel Structures for Cost
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