同济大学：《木结构 Timber Engineering》课程教学资源（电子教案）04 Design of Timber Structures

CIVL439/WOOD476 Wood as a Environmental friendly Building Material Design of Wood is the only renewable building Timber nateria Structures Frank Lam,Ph-DP.Eng beo onump Sustainable Forest Management Forest coverage in major forested countries Forest coverage by region 围 Statistics on Global Wood Statistics on Global Wood Use Use aeaaaobroehocgRseandusA 强目 三目 三 China is the 5th largest wood producing

CIVL439/WOOD476 1 Design of Timber Structures Frank Lam, Ph.D., P.Eng. University of British Columbia Wood as a Environmental friendly Building Material • Wood is the only renewable building material • Replant a harvested tree with new seedlings in 50 to 100 years another seedlings, in 50 to 100 years another tree will be available for consumption • Sustainable Forest Management through proper forestry practices is the key Forest coverage in major forested countries Country/area Forest Area Annual change rate 1990 2000 2005 1990-2000 2000-2005 1000 ha 1000 ha 1000 ha 1000 ha/ yr % 1000 ha/ yr % Russian Federation 808,950 809,268 808,790 32 n.s. -96 n.s. Brazil 520,027 493,213 477,698 -2,681 -0.5 -3,103 -0.6 Canada 310,134 310,134 310,134 0 0 0 0 United States of America 298,648 302,294 303,089 365 0.1 159 0.1 China 157,141 177,001 197,290 1,986 1.2 4,058 2.2 Australia 167,904 164,645 163,678 -326 -0.2 -193 -0.1 Democratic Republic of the Congo 140,531 135,207 133,610 -532 -0.4 -319 -0.2 Indonesia 116,567 97,852 88,495 -1,872 -1.7 -1,871 -2 Data source: FAO, Global Forest Resources Assessment 2005 Forest coverage by region Country/area Forest Area Annual change rate 1990 2000 2005 1990-2000 2000-2005 1000 ha 1000 ha 1000 ha 1000 ha/yr % 1000 ha/yr % Europe 989,320 998,091 1,001,394 877 0.09 661 0.07 N th A i North America 677,801 677,971 677,464 17 n.s. -101 -0.01 South America 890,818 852,796 831,540 -3,802 -0.44 -4,251 -0.5 Africa 699,361 655,613 635,412 -4,375 -0.64 -4,040 -0.62 Asia 574,487 566,562 571,577 -792 -0.14 1,003 0.18 Central America 27,639 23,837 22,411 -380 -1.47 -285 -1.23 Total World 4,077,291 3,988,610 3,952,025 -8,868 -0.22 -7,317 -0.18 Data source: FAO, Global Forest Resources Assessment 2005 Statistics on Global Wood Use Country/area 1990 2000 2005 Total Total Total Industrial roundwood Wood fuel % of growin g stock 1000 m³ o.b. 1000 m³ o.b. 1000 m³ o.b. 1000 m³ o.b. 1000 m³ o.b. U.S. 596,920 596,920 548,065 548,065 540,838 540,838 489,586 489,586 51,252 1.5 Canada 195,869 214,788 223,500 219,500 4,000 0.7 Brazil 368,706 293,219 290,476 168,091 122,385 0.4 Russia 336,527 152,316 180,000 129,400 50,600 0.2 China 159,081 144,775 135,435 88,808 46,628 1 Sweden 58,140 70,570 76,780 68,740 8,040 2.4 Finland 47,203 60,603 64,295 59,095 5,200 3 Statistics on Global Wood Use • Sawn wood (2000) produced in USA, Canada, Russia, Brazil, Sweden, Finland, and China was 112.2, 69.6, 20.0, 18.1, 15.8, 12.8, and 6.3 million m3, respectively • Canada ranks third behind Russia and USA in terms of global softwood harvesting • China is the 5th largest wood producing country – 2/3 of its production (190.9 million m3) is burned as fuel! – Brazil and Russia commonly use wood as fuel (133.4 & 44.3 million m3)!

CIVL439/WO0D476 Increased Demands on Wood Products .In the wood and pilion m of round-wood production Current worldwide demand for wood (ast 30 lion m3)has By2050,t Why is the structural use of wood rising？ Evolution 2

CIVL439/WOOD476 2 Increased Demands on Wood Products • In 1998, the consumed wood and fiber products in the US required ~0.5 billion m3 of round-wood production • Current worldwide demand for wood (approximately 3.5 billion m3) has doubled in the last 30 years • By 2050, the consumption of wood will increase to 5.2 billion m3 •Why is the structural use of wood rising? Evolution Source: Guido Wimmers

CIVL439/W00D476 Carbon and Global Carbon Sequestration Temperature of Trees o: U.S.Energy Consumption by Sector Life Cycle Analysis ·&oufeafU8nabcateaesgstute, t all life of the budng 3

CIVL439/WOOD476 3 Carbon and Global Temperature Carbon Sequestration Sequestration of Trees On average a typical tree absorbs tree absorbs 1 tonne 1 tonne of CO2 and produce 0.7 tonne of O2 per m3 of growth Industries 22.7% Transportation 28.2% U.S. Energy Consumption by Sector Data Source: U.S. Energy Source Information Administration (2009) Buildings 49% • How do we compare the environmental impact of various construction material? Life Cycle Analysis • ATHENA™, Sustainable Materials Institute, conducted a LCA study comparing the environmental impact of building a 240 m2 single family house using wood framing, sheet metal framing and concrete sheet metal framing, and concrete • Assessed environmental effects at all stages of the product's life including resource procurement, manufacturing, on￾site construction, building service life and de-commissioning at the end of the useful life of the building Extraction Processing Design Manufacturing Distribution Use Land Water Air Cradle Repair Disposal Raw Material Energy Water Gate Grave

CIVL439/WO0D476 Global Warming Potential Embodied Energy (EE) (GWP)】 of C( a the producti n5em0 whousthan sheet er than sheet metal and Toxicity Index Toxity Index cont'd en9an8830 y,the w g ithin the ac 画 g Weighted Resource use Weighted Resource use cont'd The weighted resource use is a The weighted resource use for wood is 14%less than sheet metal and raction an 03% ess than concrete ecological carrying capacity

CIVL439/WOOD476 4 Embodied Energy (EE) • EE is a measure of the total direct and indirect energy used during the extraction, processing, manufacturing, transportation and installation of the materials from raw material to the final product in the house • EE for the wood house is 53% less than sheet metal and 120% less than concrete Global Warming Potential (GWP) • GWP is referenced by greenhouse gas emissions measured in the form of CO2 or equivalent amount of CO2 for other greenhouse gases. This measurement includes the emission of CO2 during the production process, such as steel making or cement production • GWP of wood is 23% lower than sheet metal and 50% lower than concrete Toxicity Index • The toxicity indices are represented by an estimation of the volume of air or water needed to dilute the contaminated air or water emitted during the various life cycle of the material to within the acceptable l ld f db h level defined by the most stringent standard (such as meeting the drinking level standards) Toxity Index cont’d • The air toxicity index for the wood house is 74% less than sheet metal and 115% less than concrete • Similarly, the water toxicity index for the wood house is 247% less than sheet metal and 114% less than concrete Weighted Resource use • The weighted resource use is a subjective measure based on survey of resource extraction and environmental specialists to develop subjective scores of the relative effects or ecological carrying capacity of different resource extraction activities Weighted Resource use cont’d • The weighted resource use for wood is 14% less than sheet metal and 93% less than concrete

CIVL439/W00D476 Solid Waste Generation ·8g8 onon waste .It was lowest for sheet metal.The 《1 wh m'e-3.6Mme Timber as a structural material d with inherent flaws and recognize its strengths and uire行ents: :nutrition (wood) modest temperature(-0C moisture (the only one that can berei

CIVL439/WOOD476 5 Solid Waste Generation • Solid Waste generation is the weight in kilograms of construction waste • It was lowest for sheet metal. The wood house is 21% higher and for concrete, 58% higher Zero Energy House Standard DIN /SIA… Low Energy House Room Energy Electrical Energy for Appliances Heating Energy for Water Electrical Energy for Heat Recovery Timber as a structural material • The oldest construction material and still one of the most versatile • A natural material with inherent flaws and variability • W d t i it t th d We need to recognize its strengths and weaknesses • Timber design therefore as much an art as a science One of nature’s most efficient structures: an Arbutus tree facing the onslaught of West Coast storms Decay of wood Requirements: • nutrition (wood) • modest temperature (~ 20 C) • moisture (the only one that can be readily controlled)

CIVL439/WO0D476 Decay in a poorly constructod bullding Reliability and Safety Safety Factors Strength distnbution p Load.Resistance Load.Resistance Safety factors Safety Index B=Safoty Inde Load,Resistance e-Lead 6

CIVL439/WOOD476 6 Preservative treatment of wood in marine environment Decay in a poorly constructed building envelope Reliability and Safety o Load ccurrence distribution Load, Resistance Probability of o Probability of failure (overlap area) Resistance distribution Safety Factors Load distribution Strength distribution occurrence Load, Resistance Probability of Probability of failure (overlap area) Lavg Ravg Global safety factor = Ravg/Lavg Safety factors Load distribution occurrence Load, Resistance Probability of Measure of safety Resistance distribution 95th percentile 5th percentile Nominal safety factor = R95/L05 L95 R05 Safety Index Load distribution Strength distribution Probability of occurrence currence Resistance - Load Probability of failure (overlap area) Probability of occ (Resistance – Load) distribution β (SDEV) Probability of β = Safety Index failure

CIVL439/W00D476 Reliability Based Design Design equation Factored ActionsFactored Resistance .RELAN software-Dr.R.Foschi(UBC) Resistance (Rs Load (La)Calibration factor Where does the strength of wood come from? Softwood and Hardwood Wood Anatomy Hardwoods Gymnosperms Angiosperms 7

CIVL439/WOOD476 7 Reliability Based Design • R.O. Foschi, B. Folz, and F. Yao (1993) Reliability-based design of wood structures: background to CSA-086.1-M89. Canadian Journal of Civil Engineering 30(3):349-357. • Reliability-Based Design of Wood Structures – Structural Research Series, report No. 34. Department of Civil Engineering. UBC Vancouver BC. ISBN 0-88865-356-5 • RELAN software – Dr. R. Foschi (UBC) Design equation Factored Action ≤ Factored Resistance F N ti l B ildi C d F t i l ifi αL ≤ φ R Load factor Load (L95) Calibration factor Resistance (R05) From National Building Code (same for all materials) From material specific design code, e.g. O86.1 Where does the strength of wood come from? Softwood and Hardwood Softwood Gymnosperms Hardwoods Angiosperms Growth rings Late wood Heartwood Wood Anatomy Early wood Sapwood Bark

CIVL439/WO0D476 Wood Anatomy Cell Wall Cell Wall Structure Drink Straw Analogy -Grain direction. Species and Temperature -Load Duration Directional Elastic Properties of Wood E:E:E,s20:16:1 GuR:Gur:Gar=10:9.4:1 E:G=14:1 8

CIVL439/WOOD476 8 Wood Anatomy Cell Wall Cell Wall Layer Thickness Percentage Orientation angle to the longitudinal axis P 5% Random S 9% 50° t 70° Cell Wall Structure S1 9% 50° to 70° S2 85% 10° to 30° S3 1% 60° to 90° Drink Straw Analogy • Wood is an anisotropic material with its mechanical properties dependent – Grain direction. –Species – Moisture and Temperature – Size – Load Duration Directional Elastic Properties of Wood EL : ER : ET ≈ 20 : 1.6 : 1 GLR : GLT : GRT ≈ 10 : 9.4 : 1 EL : GLR ≈ 14 : 1 Moisture Effects on Clear Wood Strengths 30 40 50 60 70 ve Strength (MPa) ×100% − = Oven dried Weight of Wood Weight of Waterin Wood MC 0 10 20 0 20 40 60 80 100 120 MC (%) Compressiv

CIVL439/W00D476 Moisture Variation Induced Stresses Moisture conditions-moist climate Moisture conditions-dry climate 18.9 9

CIVL439/WOOD476 9 Moisture Variation Induced Distortion Moisture Variation Induced Stresses Moisture conditions Moisture conditions – moist climate moist climate Courtesy of Dipl.-Ing. Philipp Dietsch Univ.-Prof. Dr.-Ing. Stefan Winter Technische Universität München Ice-rink arena (Ingolstadt, MPA BAU) Indoor riding arena (Kirchanschöring, MPA BAU) 20 mm = 25,1 % 55 mm = 18,9 % 95 mm = 19,1 % 20 mm = 21,5 % 85 mm = 19,5 % Moisture conditions Moisture conditions – dry climate dry climate Courtesy of Dipl.-Ing. Philipp Dietsch Univ.-Prof. Dr.-Ing. Stefan Winter Technische Universität München Gymnasium with skylights (Benediktbeuern, MPA BAU) Production hall (Weihenstephan, MPA BAU) 10 mm = 7,5 % 70 mm = 10,5 % 120 mm = 11,7 % 10 mm = 7,4 % 40 mm = 7,6 %

CIVL439/WO0D476 Cracks caused by shrinking Cracks caused by shrinking Temperature effects on Clear Moisture and Temperature Wood Interactions 1。★★★南女女古十 马，,-ag- Effect of SG on ear Wood .Douglas fir 0.51 ·western hemlock 0.4 western larch 0.61 .Engelmann spruce 0.425 pole pine 0.455 0.367 1 10

CIVL439/WOOD476 10 Cracks caused by shrinking • In glulam beams – possible crack distribution Courtesy of Dipl.-Ing. Philipp Dietsch Univ.-Prof. Dr.-Ing. Stefan Winter Technische Universität München ©Stefan Kühn f t,90 σc,90 σt,90 Benediktbeuern, MPA BAU) Cracks caused by shrinking • In combination with fasteners – crack distribution Courtesy of Dipl.-Ing. Philipp Dietsch Univ.-Prof. Dr.-Ing. Stefan Winter Technische Universität München (Feldkirchen, Prof. Winter) (Freiligrathstr., Munich, MPA BAU) Temperature effects on Clear Wood [1 ( )] ET2 = ET1 −α T2 −T1 Moisture and Temperature Interactions Specific Gravity of Common Softwood • Douglas fir 0.51 • western hemlock 0.47 • western larch 0.61 • Engelmann spruce 0.425 • lodgepole pine 0.455 • balsam fir 0.367 Oven dried Volume of Wood Density of water Oven dried Weight of Wood SG 1 × − − = Effect of SG on Clear Wood Strengths R2 = 0.88 (air dried) R2 = 0.81 (green)