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1 INGHOUSE Page 1 of 48

2 Lars Jensen P.E., S.E. Web: INGHOUSE Page 2 of 48

3 OBJECTIVES: DESIGN OPTIONS; WHY ENGINEERED DESIGN DEVELOP AN UNDERSTANDING OF MAGNITUDE FOR LATERAL WIND FORCES AT DIFFERENT WIND SPEEDS AND DESIGN PARAMETERS CHANGES IN WIND ANALYSIS IN 9 TH EDITION MA CODE REVIEW LATERAL LOAD PATH REVIEW TYPICAL LATERAL LOAD RESISTING ELEMENTS & HOW THEY ARE DESIGNED ENGINEERED DESIGN EXAMPLE COMMON CONSTRUCTION SITE ISSUES INGHOUSE Page 3 of 48

4 INGHOUSE Page 4 of 48

5 TYPICAL STANDARDS & DESIGN TOOLS UTILIZED FOR WIND FORCE RESISTING DESIGN: IRC / IBC MA CHECKLIST WFCM (WOOD FRAME CONSTRUCTION MANUAL) ASCE-7 ( -05 in 8 th edition, -10 in 9 th edition Bldg. Code) WOOD: NDS SDPWS (SPECIAL DESIGN PROVISIONS FOR WIND AND SEISMIC) INGHOUSE Page 5 of 48

6 METHODS OF LATERAL DESIGN: PRESCRIPTIVE METHODS: MA CHECKLIST / WFCM WFCM: PRESCRIPTIVE DESIGN IRC WALL BRACING GUIDELINES (LIMITED WIND SPEED): RATED BUILDING COMPONENTS, E.G. PORTAL FRAMES ENGINEERED METHODS: IRC2015 WITH MA AMENDMENTS (WIND SPEED BY TOWN) ASCE-7 (WIND LOAD CALCULATION) NDS (GENERAL WOOD) SDPWS (SHEAR WALLS & FLOOR DIAPHRAGMS) INGHOUSE Page 6 of 48

7 IRC2015 / R30l.l.3 Engineered design. When a building of otherwise conventional construction contains structural elements exceeding the limits of Section R301 or otherwise not conforming to this code, these elements shall be designed in accordance with accepted engineering practice. The extent of such design need only demonstrate compliance of nonconventional elements with other applicable provisions and shall be compatible with the performance of the conventional framed system. Engineered design in accordance with the International Building Code is permitted for all buildings and structures, and parts thereof, included in the scope of this code. INGHOUSE Page 7 of 48

8 Building Code References of Applicable Standards for Engineered Design: IRC2015 with MA amendments, sections: R > Engineered Design: a.) designed in accordance with accepted engineering practice b.) Engineered design in accordance with IBC (current edition) R > Design Criteria, item 3: Minimum Design Loads for Buildings and other Structures ASCE-7 (ONE OF CRITERIA OPTIONS IS FORCED WHERE WIND SPEED EQUALS OR EXCEEDS Vult.=140mph) { Per reference R , b.), see above, the IBC2015 is referenced as optional guide document } IBC2015 with MA amendments, sections: General: Buildings, structures and parts thereof shall be designed and constructed in accordance with strength design, load and resistance factor design, allowable stress design, empirical design or conventional construction methods, as permitted by applicable material chapters (WOOD): General Structures using wood shear walls and diaphragms to resist wind,., shall be designed in accordance with Af&PA SDPWS and the provisions of section 2305, 2306, and (WOOD) Allowable Stress Design: The structural analysis and construction of wood elements in structures using allowable stress design shall be in accordance with the following applicable standards: NDS (National Design Specification for Wood Construction) SDPWS (Special Design Provisions for Wind and Seismic) INGHOUSE Page 8 of 48

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10 WHY DO MANY ENGINEERS WANT TO USE ENGINEERED DESIGN METHODS? INGHOUSE Page 10 of 48

11 SOME OF THE REAL REASONS: DESIGN FREEDOM FROM LIMITATIONS & PRE- REQUISITES IS HELPFUL. STANDARDIZED DESIGN APPROACH FOR MANY DIFFERENT STRUCTURES LOAD PATH DESIGN IS LOGICAL, AND SIMILAR TO GRAVITY SYSTEM! SINCE THE DESIGN PATH IS CALCULATED, ALTERNATIVE SOLUTIONS ARE EASIER TO IMPLEMENT COMPARED TO USING PRESCRIPTIVE ELEMENTS WHERE EACH DESIGN COMPONENT MAY NOT BE KNOWN, BUT THE WHOLE SYSTEM HAS TO BE MAINTAINED, E.G. PORTALFRAME. INGHOUSE Page 11 of 48

12 WHY DESIGN FREEDOM IS USEFUL: INGHOUSE Page 12 of 48

13 INGHOUSE Page 13 of 48

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15 WIND SPEED VS. DESIGN PRESSURE: Building Code -> look up WIND SPEED by town: V [mph] ASCE-7 (CHAPTER 27): VELOCITY PRESSURE: Kz: EXPOSURE ( C =0.90; B =0.62) AND HEIGHT (EXAMPLE FOR 20FT) Kzt: TOPOGRAPHY Kd: (TYPE OF STRUCTURE: BLDG., SIGN, ETC.): RANGE: qz = (Kz) (Kzt) (Kd) V 2 HEIGHT=20FT = (0.9) (1.0) (0.85) V 2 EXPOSURE C = (0.62) (1.0) (0.85) V 2 EXPOSURE B C = (V) 2 ; B = (V) 2 EXP. C EXP. B FOR V=120 mph -> qz = 28 PSF 23 PSF FOR V=110 mph -> qz = 24 PSF 19 PSF FOR V=100 mph -> qz = 20 PSF 16 PSF FOR V= 90 mph -> qz = 16 PSF 13 PSF INGHOUSE Page 15 of 48

16 .. ASCE-7 (CHAPTER 27): MAIN WIND FORCE RESISTING SYSTEM ( DIRECTIONAL PROCEDURE ): Design Pressure: p = q G Cp qi(gcpi) G: gust effect factor = 0.85 (for rigid structures) Cp: external pressure coefficient (wind wall=0.8, roof, leeward, side) GCpi: internal pressure coefficient = / (enclosed buildings) INGHOUSE Page 16 of 48

17 INGHOUSE Page 17 of 48

18 COMPONENTS & CLADDING VS. MWFRS -1.1 / NOTE: COMPARE MWFRS: WINDWARD WALL Cp = INGHOUSE Page 18 of 48

19 8 TH VS 9 TH EDITION CHANGES DESIGN LOAD DERIVED FROM ALLOWABLE WIND SPEED DESIGN LOAD DERIVED FROM ULTIMATE WIND SPEED DESIGN PRESSURE = LOAD IN LOAD COMBINATION =..WINDSPEED V 2 SQRT(0.6) = Vult. * = Vasd {IBC2015 EQ } EXAMPLE: Vult.=140MPH Vasd = 108MPH INGHOUSE Page 19 of 48

20 ASD VS. LRFD RE-ORGANIZATION EXPOSURE CATEGORY D IS BACK: INGHOUSE Page 20 of 48

21 FORMER IMPORTANCE FACTOR IS NOW INCLUDED IN WIND SPEED MAP PER RISK CATEGORY OF BUILDING TYPE OR TABULATED IN MA AMMENDMENT TABLE. INGHOUSE Page 21 of 48

22 PROTECTION OF OPENINGS (GLAZING) IN WINDBORNE DEBRIS REGIONS: INGHOUSE Page 22 of 48

23 LATERAL LOAD PATH WE INTUITIVELY UNDERSTAND THE GRAVITY LOADS AND THEIR TRANSFER PATH FROM ROOF TO FOUNDATION MUCH EASIER! IMAGINE THE LATERAL LOAD ACTING LIKE GRAVITY LOAD WITH THE HOUSE TURNED! INGHOUSE Page 23 of 48

24 INGHOUSE Page 24 of 48

25 FLOOR DIAPHRAGM -> BEAM ANALOGY INGHOUSE Page 25 of 48

26 WHAT IS A DRAGSTRUT? INGHOUSE Page 26 of 48

27 WHAT IS A DRAGSTRUT? INGHOUSE Page 27 of 48

28 BEAM MEMBER IN FLOOR A DRAGSTRUT DELIVERS LATERAL FORCES FROM FLOOR DIAPHRAGM TO LATERAL LOAD RESISTING WALL ELEMENT (HERE: A STEEL BRACED FRAME INGHOUSE Page 28 of 48

29 INGHOUSE Page 29 of 48

30 INGHOUSE Page 30 of 48

31 SEGMENTED WOOD STRUCTURAL PANEL SHEAR WALL INGHOUSE Page 31 of 48

32 PERFORATED WOOD STRUCTURAL PANEL SHEAR WALL INGHOUSE Page 32 of 48

33 WOOD STRUCTURAL PANEL SHEAR WALL: HORIZONTAL OR VERTICAL PANEL DIRECTIONS ARE ALLOWED! REQUIRES BLOCKING AT PANEL EDGES FOR HORIZONTAL LAYUP! REVIEW HOW LOADS GET INTO AND OUT OF SHEAR WALL! DOUBLE SIDED SHEATHING DOUBLES WALL CAPACITY! ½ THICK PLYWOOD, NAILED WITH 8d COMMON 4 O.C. AT PERIMETER AND 8 O.C. IN FIELD HAS JUST UNDER 500 PLF CAPACITY! INGHOUSE Page 33 of 48

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35 PORTAL FRAME : OFTEN USED EACH SIDE OF GARAGE DOORS HAS DEFINED CAPACITY OBTAINED THROUGH TESTING REQUIRES TO BE INSTALLED AS DETAILED ( = AS TESTED). IT IS A LOAD RATED BUILDING COMPONENT. SIMILAR WITH OTHER PREMANUFACTURED SYSTEMS. NOTE: ANCHORAGE REQUIREMENTS! INGHOUSE Page 35 of 48

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37 EXAMPLE: HOLD DOWN FORCE CALCULATION EXISTING BUILDING W/ NEW SLIDER OPENINGS 500 PLF x 2 (DBL SIDED SHEAR WALL) => 1,000 PLF SHEAR CAPACITY OF WALL 3FT x 1,000PLF EACH SHEAR SEGMENT = 3,000 LB 3,000 LB x 8FT HEIGHT = 24,000 FT-LB / 2.8 FT LENGTH BTWN HOLD DOWNS = 8,600 LB INGHOUSE Page 37 of 48

38 INGHOUSE Page 38 of 48

39 LARGE GLAZED OPENINGS REQUIRING A MULTI-BAY STEEL MOMENT FRAME. DEFLECTION PERFORMANCE CONSIDERATIONS! INGHOUSE Page 39 of 48

40 ~50FT INGHOUSE Page 40 of 48

41 INGHOUSE Page 41 of 48

42 EXAMPLE: SHEAR WALL & DIAPHRAGM CALCULATION: INGHOUSE Page 42 of 48

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46 TYPICAL CONSTRUCTION SITE ISSUES & QUESTIONS: DID NOT REALIZE THAT ENGINEERED LATERAL LOAD PLAN WITH INFORMATION ON SHEAR WALLS & HOLD DOWNS WAS PART OF PLANS. SHEAR WALL NAILING: SPACING, OVERDRIVEN NAILS, SHINERS, NAIL TYPES & SIZES (GUN NAILS VS. COMMON WIRE NAILS) HOLD DOWNS: WRONG TYPE, MISSING, INSTALLED THROUGH LOOSELY NAILED BLOCKING, FORGOT EMBEDDED CONCRETE TIE STRAPS, INTERIOR SHEAR WALL TRANSFER CONNECTIONS TO FLOORS MISSING CONNECTION BETWEEN WOOD FRAME AND STEEL LATERAL LOAD RESISTING ELEMENTS NOT DETAILED ON PLANS OR NOT CONSTRUCTED. ARE PLYWOOD WALL SHEATHING PANELS ALLOWED TO BE INSTALLED IN HORIZONTAL DIRECTION (NOT FULL HEIGHT). WHY DO DOUBLE WALL TOP PLATES HAVE TO BE SPLICED PROPERLY (ESPECIALLY AT CENTER OF FLOOR DIAPHRAGM BETWEEN SHEAR WALLS)? WHY CAN LVL POSTS SOMETIMES NOT BE SUBSTITUED WITH DIMENSIONAL LUMBER POST AT SHEAR WALL PERIMETERS, EVEN IF THE LOAD BEARING CAPACITY IS ADEQUATE? INGHOUSE Page 46 of 48

47 WIND LOADS ARE REAL! THANK YOU! INGHOUSE Page 47 of 48

48 Lars Jensen P.E., S.E. Web: INGHOUSE Page 48 of 48