Embodied Carbon of Concrete / Steel - Building Structures using Nonlinear Optimization

Dept. of Civil and Environmental Engineering Material Science and Technology in Engineering Conference Frontiers of Sustainable Materials Embodied Carbon of Concrete / Steel - Building Structures using Nonlinear Optimization Ir Julian LEE Manager - Research, Construction Industry Council Siu-Lai CHAN, Han YU Department of Civil and Environmental Engineering, 25 June 2015

Outline 1 Background 2 Research Aim and Scope 3 Methodology 4 Results Discussion 5 Conclusions and Prospects 2

Buildings and Construction Contribution to Global GHG Emissions #1. Building and Construction (>40%) #2. Transportation (~20%) #3. Industry (~20%) Buildings in Hong Kong accounted for 60% of total local GHG emissions. Source: International Energy Agency (2012) CO 2 Emissions from Fuel Combustion 3

Building Energy Use & Actions Taken Energy Consumption by Building Sector Worldwide Actions Taken towards Energy Efficiency Worldwide Sources: Asia Business Council (ed.) (2007) Building Energy Efficiency Why Green Buildings are Key to Asia s Future. European Insulation Manufacturers Association (Eurima). (ed.). (2011). Energy Efficiency in Buildings: Tackling Climate Change. U.S. Department of Energy (ed.) (2012) Buildings Sector. Buildings Energy Data Book. Energy Efficiency & Renewable Energy. 4

Construction Material Consumption & Carbon Footprint by Construction Sector in HK Among various economic sectors, the construction industry consumes 40% of materials entering the global economy. Construction sector accounts for second largest carbon footprint 85% of carbon emission is embodied in upstream materials and services Source: WWF-Hong Kong (2011), Hong Kong Ecological Footprint Report 2010, Paths to Sustainable Future, Hong Kong California Integrated Waste Management Board (CIWMB) (2000). Designing with Vision: A Technical Manual for Materials Choices in Sustainable Construction. 5

Carbon Footprint & Actions Taken UK USA KOREA CANADA JAPAN FRANCE N. AMERICA TAIWAN 6

CIC Carbon Labelling Scheme for Construction Products Aim: Provide verifiable and accurate information on the carbon footprint of construction materials for users to make informed decision thereby to combat the climate change. Material Coverage Cement Rebar Structural Steel Ready-mixed Concrete 7

Development of the Scheme Two of the key functions of the Construction Industry Council (CIC): To promote green building practices and sustainable construction To encourage research activities and the use of innovative techniques and, to establish or promote the establishment of standards for the construction industry CIC has commissioned HKU to conduct a research on: Establishment a Hong Kong Based Carbon Labelling Framework for Construction Materials (the Research ) Prof. Thomas NG, Department of Civil Engineering, HKU Research period: 15 months; completed in late 2012 8

Development of the Scheme Implementation& Development Inspiration of Carbon Labelling for construction products 2009 HKU developed the carbon labelling framework for 6 types of construction products 2012 CIC Carbon Labelling Scheme Launched and open for applications Jan 2014 Research Phase II commences (covering 10 additional product types incl. concrete, stainless steel, asphalt, etc.) Mar 2014 Promote the application and the use of low carbon materials Low-carbon design/construct ion Carbon tendering Export service on carbon certification 9

Involved Stakeholders / Organisations 10

Embodied Carbon Footprint Ready-mixed Concrete vs. Steel Concrete is everywhere. It is the second most consumed material after water, the most widely used man-made material and it shapes our built environment. (Direct Industrial CO 2 Emission, 2006) Reinforcing bar and structural steel are extensively used in the construction industry as they are the bones of buildings. Concrete Concrete vs. Steel (Lower Carbon?) Source: Industrial Development Report, 2011 Material Type Carbon Footprint (kg CO 2 e/kg) * a general range collected from worldwide data sources Concrete 0.1 ~ 0.2 depending on strength, SCM rate, cement carbon footprint, etc. Virgin Steel 1.5 ~ 3.5 depending on the manufacturing furnace type, fuel type and use, etc. Recycled Steel 0.5 ~ 1.5 depending on recycled scrap usage, furnace type, fuel type and use, etc. 11

What is missing? What we know:- Building & Construction Consumes Much Energy and Generates GHG Emissions Building Design Structural Safety, Economic Efficiency & Environmental Sustainability Material Use Associated with Embodied Carbon (EC) & Energy What we are doing:- Energy Supply Increase Energy Efficiency Improvement (Green Building (GB) techniques, GB rating tools, etc.) Optimised Structural Design is Saving Material Consumption Carbon Labelling Scheme is Promoting Use and Manufacture of Low Carbon Materials What is missing:- Least Material Consumption Least Carbon Emissions Optimised Structure Design Lowest Carbon Footprint of Structure Selection and Use of Low Carbon Material Lowest Carbon Footprint of Building Structure Smart Integration of Structural Design and Low Carbon Materials Lowest Carbon Footprint of the Whole Building Structure? 12

Research Aim and Scope This study aims to examine the potential of embodied carbon reduction through optimising different steel and reinforced concrete structural designs (typical Hong Kong Layout with local geological condition, loading & design requirements such as wind load). The Nonlinear Optimization Method will be used to optimise the structural design of building structures which enables the safety, economic efficiency as well as environmental sustainability. The embodied carbon footprint data of ready-mixed concrete and steel (virgin / recycled) will be used to calculate the overall carbon footprint of optimised building structure Comparison will be conducted to investigate the influence of structure design and material usage on the building's overall carbon footprint. 13

Methodology Building Model Configurations Steel Steel Beam + Steel Columns Coupled with Concrete Corewall Reinforced Concrete 14

Methodology Building Model Configurations (Cont.) Both types are in 25 floors Maximum Height = 97.6m Plan Area = 27.69m x 23.26m Steel Building Steel Beams+Steel Columns Concrete Core Wall (Beams) RC Building RC Beams+RC Columns Concrete Core Wall (Beams) 15

Methodology Computer Analysis Method 3-D analysis and modeling are used in determining the capacities and forces in members and connections. Steel Building Second-order plastic (P-Δ-δ) analysis RC Building Linear elastic analysis Computer Programme Used NAF serious Nonlinear Integrated Design and Analysis (NAF-NIDA) version 9 All design shall be in accordance with the BD of the Hong Kong SAR Government. All aspects of the structural design shall comply with: 1. Hong Kong Building (Construction) Regulations 1990 2. Code of Practice for Structural Use of Concrete 2004 3. Code of Practice for the Structural Uses of Steel, 2011 4. Code of Practice on Wind effects in Hong Kong, 2004 5. Code of Practice for Fire Resisting Construction 1996 6. BS8007 Design of Concrete Structures for Retaining Aqueous Liquid 7. BS4466:1989 Schedule, dimensioning, bending and cutting of steel reinforcement for concrete 8. Practice Notes for AP/RSE/RGE No. APP-68 (PNAP 173) Design and Construction of Cantilevered Concrete Structures 9. Eurocode-3, EN 1993-1-8, Design of joints, 2005 16

Methodology Computer Analysis Method (cont.) Second-order analysis of constant load Newton-Raphson method is employed to account for both P-Δ and P-δ effects, as well as initial imperfections Load combinations for ultimate limit state (ULS) and serviceability limit state (SLS) checking are considered Only section capacity check by is adequate (1) (2) No need of traditional member design No plastic moment re-distribution is allowed in the Advanced Analysis in accordance with HKSC2011 Fc(Δx+δx) & Fc(Δy+δy) - Additional moments due to frame & member deflections including effects of initial imperfections; Member lateral-torsional buckling check is carried out by replacing Mcx in Equation (1) by the buckling resistance moment Mb. 17

Methodology Control of Variation Comparison 1: Superstructure Only (Sup) Steel Building (Core wall in C60, C80, C100; Steel Section / Bar in Virgin, 39% recycled scrap, 59% recycled scrap) RC Building in C60 (Steel Bar in Virgin, 39% recycled scrap, 59% recycled scrap) RC Building in C80 (As above) RC Building in C100 (As above) Comparison 2: Superstructure + Foundation (Sup + F) Variation the same as above in Comparison 1 Steel Building RC Building in C60 RC Building in C80 RC Building in C100 18

Methodology Embodied Carbon Database Due to the limited data collected from Hong Kong local industry and market, this study firstly applies the carbon footprint data obtained from Inventory of Embodied Carbon & Energy (ICE), a comprehensive carbon footprint database for construction materials developed by UK. Concrete (C20 C50; 100% OPC; PFA 15% / 30% replacement; GGBS 25% / 50% replacement). C 60, C80, C100 Avg value Steel (Section, Bar, pipe, plate; 100% virgin;39%, 59% recycled scrap) 19

Methodology Embodied Carbon Data The Carbon footprint data of concrete applied in this study (unit: kg CO 2 e/m 3 ) : Concrete Grade 100% OPC (Upper Limit) 50% GGBS (Lower Limit) Average Value C60 491 306 413 C80 598 381 507 C100 * 598 381 507 *The carbon footprint value of super high strength concrete will not be increased with the increasing strength but tending to be steady. It is assumed that the carbon footprint of C100 the same as the C80. The Carbon footprint data of steel applied in this study (unit: kg CO 2 e/kg) : Steel Type 100% virgin steel 39% recycled scrap 59% recycled scrap Section 3.03 2.03 1.53 Bar 2.77 1.86 1.40 20

Results Discussion 1.1 Superstructure(Sup) Total Weight Weight (kn) Steel Building RC Building in C60 RC Building in C80 RC Building in C100 Section 8654 0 0 0 Concrete 47636 98239 86560 76668 Bar 5163 10893 10001 9640 Total 61452 109132 96561 86308 TOTAL WEIGHTS COMPARISON C100 0 76668 9640 C80 0 86560 10001 C60 0 98239 10893 Steel 8654 47636 5163 0 20000 40000 60000 80000 100000 120000 WEIGHT (KN) Section Concrete Bar 21

CONCRETE VARIETY CONCRETE VARIETY CONCRETE VARIETY Results Discussion 1.2 Sup In Different Concrete Grades ICE Virgin Steel with Different Concrete C60 LL C60 Avg C60 UL RC Building, 4.35 Steel Buiilding, 4.75 RC Building, 4.80 Steel Building, 4.97 RC Building, 5.13 Steel Building, 5.13 Concrete Grade Increases--- 0.00 1.00 2.00 3.00 4.00 5.00 6.00 C80 LL RC Building, 4.23 Steel Building, 4.90 C80 Avg C80 UL RC Building, 4.69 Steel Building, 5.16 RC Building, 5.02 Steel Building, 5.34 0.00 1.00 2.00 3.00 4.00 5.00 6.00 C100 LL RC Building, 3.96 Steel Building, 4.90 C100 Avg C100 UL RC Building, 4.37 Steel Building, 5.16 RC Building, 4.67 Steel Building, 5.34 0.00 1.00 2.00 3.00 4.00 5.00 6.00 ECe value (10^6 kgco 2 e/m 3 ) Total Embodied Carbon decreases The Difference of Total EC values between RC and Steel Buildings increases Same trends apply to models using recycled steel Concrete RC Building Steel Steel Building 22

Steel Variety VIRGIN 39%R 59%R Steel Variety VIRGIN 39%R 59%R Steel Variety VIRGIN 39%R 59%R Results Discussion 1.3 Sup In Different Kinds of Steel C60 UL with Different Steel RC Building, 3.60 Steel Building, 3.08 RC Building, 4.12 Steel Building, 3.76 RC Building, 5.13 Steel Building, 5.13 C60 Avg with Different Steel 0.00 1.00 2.00 3.00 4.00 5.00 6.00 ECe Value RC Building, (10^6 kgco2e/m3) 3.28 Steel Building, 2.92 RC Building, 3.79 Steel Building, 3.61 RC Building, 4.80 Steel Building, 4.97 C60 LL with Different Steel 0.00 1.00 2.00 3.00 4.00 5.00 6.00 RC Building, 2.83 Steel Building, ECe Value 2.71 (10^6 kgco2e/m3) RC Building, 3.34 Steel Building, 3.39 RC Building, 4.35 Steel Building, 4.75 0.00 1.00 2.00 3.00 4.00 5.00 6.00 ECe Value (10^6 kgco2e/m3) Recycled Content of Scrap in Steel Products Increases-- Total Embodied Carbon decreases The advantage of steel building in terms of total EC increases Same trends apply to models in C80 & C100 23

Results Discussion CIC Carbon Labelling Applicant Data Applicant Region Product Category Carbon Footprint Value Rebar and Structural Steel Unit: tonne CO 2 e/tonne Thailand Section 0.55 Mainland China Pipe 2.95 Taiwan Section 1.37 Middle East Rebar 2.08 Middle East Section 2.36 Ready-mixed Concrete Unit: kg CO 2 e/m 3 concrete C30s 240 C40s 308 C40s 209 C40s 229 Hong Kong C40s 233 C40s 255 C40s 287 C40s 282 C60s 310 C60s 240 24

Steel Variety VIRGIN 39%R 59%R HK APPLICANT Steel Variety VIRGIN 39%R 59%R Steel Variety VIRGIN 39%R 59%R HK APPLICANT HK APPLICANT Results Discussion 1.3 Sup In Different Kinds of Steel C60 UL with Different Steel C60 Avg with Different Steel Steel Bldg, 2.57 RC Bldg, 4.36 Steel Bldg, 2.42 RC Bldg, 4.03 RC Bldg, 3.60 Steel Bldg, 3.08 RC Bldg, 3.28 Steel Bldg, 2.92 RC Bldg, 4.12 Steel Bldg, 3.76 RC Bldg, 3.79 Steel Bldg, 3.61 RC Bldg, 5.13 Steel Bldg, 5.13 RC Bldg, 4.80 Steel Bldg, 4.97 0.00 1.00 2.00 3.00 4.00 5.00 6.00 ECe Value (10^6 kgco 2 e/m 3 ) 0.00 1.00 2.00 3.00 4.00 5.00 6.00 ECe Value (10^6 kgco 2 e/m 3 ) C60 LL with Different Steel Steel Bldg, 2.20 RC Bldg, 3.59 Keep the Embodied Carbon Data for C60 from ICE unchanged RC Bldg, 2.83 Steel Bldg, 2.71 RC Bldg, 3.34 Steel Bldg, 3.39 RC Bldg, 4.35 Steel Bldg, 4.75 0.00 1.00 2.00 3.00 4.00 5.00 6.00 ECe Value (10^6 kgco 2 e/m 3 ) Data for steel section and steel rebar obtained from CIC Carbon Labelling Applicants (certain content of steel is using recycled scrap as raw material) Steel Section ECe = 0.55 kgco 2 e/kg Steel Rebar ECe = 2.08 kgco 2 e/kg 25

Steel Building Advantage Effect Results Discussion 1.4 Sup Steel Building Advantage Effect Under what condition, Steel Building s carbon footprint would be lower than RC Building? Steel Building Advantage Effect to RC Building with Concrete in Different Grades UL 15% C60 Avg C80 10% LL 59% 5% C100 0% Concrete ECe (kgco 2 e/m 3 39% ) 200 250 300 350 400 450 500 550 600-5% 0% -10% -15% As the Concrete with higher ECe in use The advantage effect of Steel Building presents especially when recycled steel is in use Recycled Content of Scrap in Steel Products Increases The advantage of steel building in terms of total EC increases RC Building still wins with high strength concrete in use. -20% -25% Virgin 0%R C60 39%R C60 59%R C60 Virgin 0%R C80 39%R C80 59%R C80 Virgin 0%R C100 39%R C100 59%R C100 26

Steel Building Advantage Effect Results Discussion 1.4 Sup Steel Building Advantage Effect 45% 35% Steel Building Advantage Effect to RC Building with Concrete in Different Grades LL Avg UL 40.51% 41.30% 39.19% Keep the Embodied Carbon Data for C60 from ICE unchanged 25% 15% 5% 59% Concrete ECe (kgco 2 e/m 39% 3-5% 200 250 300 350 400 450 500 550 600 0% Data for steel section and steel rebar obtained from Applicants in HK Steel Section s Embodied Carbon Value is as low as 0.55 kgco2e/kg -15% -25% Virgin 0%R C60 39%R C60 59%R C60 Virgin 0%R C80 39%R C80 59%R C80 HK Applicant C60 By using the steel with low ECe value, the steel building design option has absolute advantage in terms of carbon footprint over RC building. 27

Total ECe (10^6kgCO 2 /kg) Total ECe (10^6kgCO 2 /kg) Comparison 1.5 Sup Total EC Values Comparisons Total Carbon Emission Equivalent Values Comparison 6 5 4 3 2 1 0-10% 0% 10% 20% 30% 40% 50% 60% Percentage of Recycled Steel Included Whole Building Steel C60 Avg RC C60 Avg Steel C80 Avg RC C80 Avg Steel C100 Avg RC C100 Avg The more recycled steel used, the more environmental friendly the design will be. However, it is not practical to use recycled steel in the whole building structure due to size limitation of recycled steel products. Q: How much percentage of the recycled steel accounts for in the overall steel consumption could make the Steel Building be lower carbon than RC Building? Total Carbon Emission Equivalent Values Comparison for Steel and RC Buildings in C60 Avg (Superstructure Only) 6 5 4 3 < 28% of Recycled Steel RC Bldg > 28% of Recycled Steel Steel Bldg 2 1 0-10% 0% 10% 20% 30% 40% 50% 60% Percentage of Recycled Steel Included in Whole Building 28

Total ECe (10^6kgCO 2 /kg) Total ECe (10^6kgCO 2 /kg) Comparison 1.5 Sup Total EC Values Comparisons (cont.) Total Carbon Emission Equivalent Values Comparison for Steel and RC Buildings in C80 Avg (Superstructure Only) 6 5 4 3 < 54% of Recycled Steel RC Bldg > 54% of Recycled Steel Steel Bldg 2 St80 1 RC80 0-10% 0% 10% 20% 30% 40% 50% 60% Percentage of Recycled Steel Included in Whole Building Total Carbon Emission Equivalent Values Comparison for Steel and RC Buildings in C100 Avg (Superstructure Only) 6 5 4 3?% of Recycled Steel RC Bldg 2 St100 1 RC100 0-10% 0% 10% 20% 30% 40% 50% 60% Percentage of Recycled Steel Included in Whole Building 29

Total ECe (10^6kgCO 2 /kg) Total ECe (10^6kgCO 2 /kg) Results Discussion 1.6 Sup+F Total EC Values Comparisons By adding foundation, the concrete usage dramatically increases: Total Carbon Emission Equivalent Values Comparison for Steel and RC Buildings in C60 Avg (Superstructure+Foundation) 7 6 5 4 3 2 1 0-10% 0% 10% 20% 30% 40% 50% 60% Percentage of Recycled Steel Included in Whole Building From 54% (Sup) to 32% (Sup + F) < 32% of Recycled Steel RC Bldg > 32% of Recycled Steel Steel Bldg From 28% (Sup) to 5% (Sup + F) < 5% of Recycled Steel RC Bldg > 5% of Recycled Steel Steel Bldg Total Carbon Emission Equivalent Values Comparison for Steel and RC Buildings in C80 Avg (Superstructure+Foundation) 7 6 5 4 3 2 St80 RC80 1 St80+F RC80+F 0-10% 0% 10% 20% 30% 40% 50% 60% Percentage of Recycled Steel Included in Whole Building 30

Total ECe (10^6kgCO 2 /kg) Results Discussion 1.6 Sup+F Total EC Values Comparisons (cont.) Total Carbon Emission Equivalent Values Comparison for Steel and RC Buildings in C100 Avg (Superstructure+Foundation) 7 6 5 4 3 2 St100 RC100 1 St100+F RC100+F 0-10% 0% 10% 20% 30% 40% 50% 60% Percentage of Recycled Steel Included in Whole Building If Foundation is included, an interception might be found at around 62% <~62% of Recycled Steel RC Bldg >~62% of Recycled Steel Steel Bldg 31

Conclusions RC Building vs. Steel Building (Which one is lower carbon?) Material type and constitutes (recycled/virgin steel, recycled percentage, concrete with SCM such as PFA or GGBS, etc.); Combination of material (concrete, rebar, structural steel) Design (performance requirement, local factor, approach of optimisation) Material, structural and geotechnical (foundation) condition. Composite Structure Building? To be investigated More Carbon Footprint Data of Locally Used Material Needed CIC Carbon Labelling Scheme Carbon Footprint Benchmark of Different Building Types Caron Footprint Index CO 2 e / GFA 32

Future Study Comparison 3: Superstructure Only Vary the Building Heights Steel Building in 15 Floors RC Building in C60 in 15 Floors Steel Building in 35 Floors RC Building in C60 in 35 Floors Comparison 4: Superstructure + F Vary the Building Heights Steel Building in 15 Floors RC Building in C60 in 15 Floors Steel Building in 35 Floors RC Building in C60 in 35 Floors Comparison 5: Change to Composite Floor System Steel Building in 12 Floors (Sup+F) RC Building in C60 in 12 Floors (Sup+F) Apply more Hong Kong local values instead of ICE Database to examine the practicability of the study; Provide a guidance for environmental structure system optimization; Link the integrated environmental structural design optimisation with BEAM Plus to easily assess the overall carbon footprint of green building. 33

Future Development: Think Low Carbon Low Carbon / Green Materials Low Carbon / Environmental Structural Design Green Building Design and Promotion G r e e n C u l t u r e 34

Future Development: Think Low Carbon Implement the design for construction and further promotion of green building Integrate the design with BEAM Plus to assess the green performance of the building Identify the low carbon material options Low Carbon / Green Materials Propose Structural Design Options Low Carbon / Environmental Structural Design Green Building Design Low carbon design and Promotion Compute and compare alternative G r e e n C structural u l t u and r e material options Optimize the design to achieve low carbon, low cost and safety 35

Green moving towards a low-carbon city Green Building sources of photos: http://widedscreen.com/3d-architecture-wallpaper-2/ http://www.maximizingprogress.org/2008/11/singapore-green-buildings-in-garden.html http://www.globalmayorsforum.org/en/citiesdetails.aspx?tid=115&id=129 Green Construction

Thank You Ir Julian LEE Manager - Research, Construction Industry Council 25 June 2015