Streamlined Hazard Mitigation Cost Assessment Framework for Residential Buildings

Transcription

1 Streamlined Hazard Mitigation Cost Assessment Framework for Residential Buildings Mehdi Noori Jeremy Gregory Randolph Kirchain Reed Miller FLASH 2017

2 Costs from hazards are enormous Slide 2

3 Costs from hazards are enormous Slide 3

4 We prioritize response over mitigation FEMA Pre-Disaster Mitigation Grant Spending Compare to $7.2 billion spent on average on annual recovery assistance Slide 4

5 Resilience: a system s response to problems Hazard Resistance Slide 5

6 Which is preferred from a life cycle perspective? Lower design standard Higher design standard Same location Same appearance Lower initial cost Higher initial cost Worse energy performance Better energy performance Worse hazard resistance Better hazard resistance Quantitative information is lacking on economic and environmental benefits of sustainable and resilient construction Slide 6

7 Cost effectiveness of hazard mitigation DOE reference building for midrise apartments 32 apartments, 34k ft 2 Baseline and enhanced designs Wood Masonry Concrete % ~ Break-Even Mitigation Percent (BEMP) Enhanced Initial Baseline Investment Hazard Mitigation Investment Baseline Hazard Expected Cost $ Slide 7

8 Streamlined hazard mitigation cost analysis framework Sample buildings (Hazus- MH) Wind maps (ASCE-7-10) Calculate hazard costs for conventional & enhanced building designs (FEMA BCA) Repeat for sample of counties across all states Create metamodel from regression analysis Noori et al, 2017 (Under review) Calculate BEMP for all building types, mitigation mechanisms, and counties Slide 8

9 BEMP building scenarios for a single region Shift to Shift from Baseline Enhanced Wood Masonry Concrete Wood Masonry Concrete Baseline Wood Masonry Concrete Enhanced Wood Masonry Concrete Slide 9

10 Baseline wood to enhanced concrete West Palm Beach, FL Shift to Shift from Baseline Enhanced Wood Masonry Concrete Wood Masonry Concrete Baseline Wood 14.6% Masonry Concrete Enhanced Wood Masonry Concrete Slide 10

11 All building scenarios for Miami Dade County, FL Shift to Shift from Baseline Enhanced Wood Masonry Concrete Wood Masonry Concrete Baseline Wood % 12.6% 16.4% 13.6% 17.3% Masonry -7.1% % 8.1% 5.5% 9.0% Concrete -11.2% -4.4% % 0.9% 4.2% Enhanced Wood % 0.8% Masonry 2.4% % Concrete -0.8% -3.3% -- Slide 11

12 All building scenarios for Miami Dade County, FL Shift to Shift from Baseline Enhanced Wood Masonry Concrete Wood Masonry Concrete Baseline Wood % Shifts to 12.6% 16.4% 13.6% 17.3% Masonry -7.1% masonry & All shifts are concrete -- are 4.6% 8.1% beneficial 5.5% 9.0% beneficial Concrete -11.2% -4.4% % 0.9% 4.2% Enhanced Wood % 0.8% All enhanced Masonry 2.4% designs -- perform 3.3% well Concrete -0.8% -3.3% -- Slide 12

13 BEMP building scenarios for a single region Shift to Shift from Baseline Enhanced Wood Masonry Concrete Wood Masonry Concrete Baseline Wood Masonry Concrete Enhanced Wood Masonry Concrete Slide 13

14 All building scenarios for Miami Dade County, FL Shift to Shift from Baseline Enhanced Wood Masonry Concrete Wood Masonry Concrete Baseline Wood % Shifts to 12.6% 16.4% 13.6% 17.3% Masonry -7.1% masonry & All shifts are concrete -- are 4.6% 8.1% beneficial 5.5% 9.0% beneficial Concrete -11.2% -4.4% % 0.9% 4.2% Enhanced Wood % 0.8% Values depend on All enhanced Masonry design scenarios and 2.4% designs -- perform 3.3% well location Concrete -0.8% -3.3% -- Slide 14

15 A single building scenario for all regions Online tool enables exploration of results BEMP for baseline wood to enhanced concrete BEMPs can be as high as 20% Slide 15

16 A single building scenario for all regions BEMP for baseline concrete to enhanced masonry Slide 16

17 Break-Even Mitigation Investment (BEMI) BEMI = Actual cost of construction * BEMP Slide 17

18 BEMI per area of new construction Shift from baseline wood to enhanced concrete BEMI ($/sqft) Slide 18

19 Key takeaways LCCA Hazard repair costs can exceed initial costs Investing in hazard mitigation can pay off in the long term BEMP BEMPs can be as high as 20% Values depend on design scenarios and location Enhanced designs for all material types are beneficial Slide 19

20 More information available at:

21 Back-up slides Slide 21

22 20% Average value of wood buildings BEMP $116M Slide 22

23 BEMI per capita Slide 23

24 Results New construction cost/area Wood structure 1-7 stories, multi family, new construction, Slide 24

25 Results New construction costs Wood structure 1-7 stories, multi family, new construction, Slide 25

26 Results New construction area Wood structure 1-7 stories, multi family, new construction, Slide 26

27 Results New construction cost/area Wood structure 1-7 stories, multi family, new construction, Slide 27

28 Results Break Even Mitigation Investment Wood structure 1-7 stories, multi family, new construction, Slide 28

29 Baseline and enhanced designs Building properties Baseline Enhanced Wood Masonry-M 1 Masonry-E 2 Concrete Wood Masonry-M 1 Masonry-E 2 Concrete FEMA Designation WMHU3 MMUH3 MERBM CERBM WMHU3 MMUH3 MERBM CERBM Roof shape Flat Flat Flat Flat Hip Hip Flat Flat Roof cover type SPM SPM SPM SPM N/A N/A BUR BUR Roof cover quality Good Good N/A N/A Good Good N/A N/A Shutters No No No No Yes Yes Yes Yes Roof-Wall connection Strap Strap N/A N/A Strap Strap N/A N/A Roof deck attachment 6"/12" 6"/12" Standard N/A 6d/8d Mix 6d/8d 6"/6" Superior N/A Window area N/A N/A Medium Medium N/A N/A Low Low Wind debris N/A N/A Resi. Resi. Resi. Resi. N/A N/A /Comm. Mix /Comm. Mix /Comm. Mix /Comm. Mix Secondary water resistance No No N/A N/A Yes Yes N/A N/A Masonry reinforcing N/A No N/A N/A N/A Yes N/A N/A 1 medium engineered masonry, 2 engineered masonry DOE reference building for midrise apartments 32 apartments 33763ft 2 Slide 29

30 Baseline and enhanced designs Hip to Gable roof shape % increase in average building damage state Slide 30

31 Baseline and enhanced designs Roof cover quality Average damage state per storm Wood Damage state Masonry-M Damage state Masonry-E Damage state # of stories Slide 31

32 Mitigation improves hazard resistance Elevated structure & utilities Storm shutters Safe rooms Roof structure & connections Slide 32

33 Earthquake statistics The annualized nationwide loss from earthquakes is estimated to be $5.3 billion per year California, Oregon, and Washington accounting for $4.1 billion, or 77%. 20% chance that northern Oregon will be hit by a magnitude-8.0-or-higher quake in the next 50 years. Slide 33

34 Earthquake hazard cost assessment 50,000 sq.ft Project Summary Government Office Location: Salem, OR Structure: Reinforced concrete frame Type of mitigation: Structural Retrofit 3 stories height on large spread footings Project lifetime: 50 years Building replacement value: $12,000,000 Average occupants: 250 Before Built to low code Wood stud walls with drywall, not seismically detailed Unbraced Ceilings, lights, and utilities Unanchored service equipment After Retrofitted to high code Steel chevron braces added to the exterior Metal stud walls with drywall, seismically detailed. Braced ceilings and lights Anchored service equipment Cost of retrofit: $1,160,000 Slide 34

35 Investing in hazard mitigation is cost effective Millions Before and after mitigation annual losses Annual Damage cost (K$) Before After Mitigation investment 0 Slight Moderate Extensive Complete Damage state Slide 35

36 Fragility curves for reinforced concrete frame Probability Fragility curves - C1M Model Building Type - High code seismic design Spectral Displacement (inches) Slight Moderate Extensive Complete Probability Fragility curves - C1M Model Building Type Low code seismic design Spectral Displacement (inches) Slight Moderate Extensive Complete Slide 36

37 Two measures in severity of ground motions Slide 37

38 Assignment of design levels is dependent on vintage and location Slide 38

39 US Seismic Zone Map Slide 39

40 3 Main Damage Categories Loss of Function Casualties Direct Physical Damage Drift-Sensitive Structural Damage (STR) Damage due to inner story displacements(drift) Drift-Sensitive Non-Structural Damage (NSD) Damage to the architectural components (partitions, cladding, etc) caused by drifts Acceleration-Sensitive Non-Structural Damage (NSA) Damage to building service equipment. Slide 40

41 Non structural damage take up majority of costs The nonstructural components typically make up the largest part of the building replacement value. recommended to include nonstructural retrofit STR+NSD+NSA in Complete damage state = 100% Slide 41

42 Loss of Function Slide 42

43 Example: Government Office Slide 43

44 Example: Government Office Slide 44

45 Example: Government Office Slide 45

46 Earthquake facts Mean recurrence times are therefore revised to 340 years for the central and northern Oregon coast. Used to be 500 years Meaning, there is about a 20 percent chance that northern Oregon a region that includes Portland and Astoria will be hit by a magnitude-8.0-or-higher quake in the next 50 years ~TheAtlantic.com Slide 46

47 Earthquake facts A large inventory of existing structures lack earthquakeresistant design and have not been retrofitted to meet current design codes. Vulnerability to earthquakes in the U.S. in growing at an alarming rate. Population, growth, urbanization, and infrastructure expansion are all contributing to this trend. The United States has been fortunate in recent years in that its urban centers have largely avoided a direct hit from a major (M7.0 or greater) earthquake. Since the great Alaska earthquake of 1964, there have been 26 major earthquakes in the United States, with as many as 65 lives lost in a single earthquake. Slide 47

48 Earthquake facts The annualized nationwide loss from earthquakes is estimated to be $5.3 billion per year with California, Oregon, and Washington accounting for $4.1 billion, or 77 percent. Structural mitigation projects that attempt to bring every element of the building up to current code are rarely costeffective, even in high seismic hazard areas, because the project costs are typically too high. The ground motion data used is in the form of peak ground acceleration (PGA) for non-structural projects and Spectral Acceleration (SA) for structural projects, Slide 48

49 uncertainty in the damage state threshold of the structural system ( M(Sds) = 0.4, for all structural damage states and building types) variability in capacity (response) properties of the model building type/seismic design level of interest ( C(Au) = 0.25 for Code buildings, C(Au) = 0.30 for Pre Code buildings) a variability in response due to the spatial variability of ground motion Slide 49