BLD18-0447 - Northpoint Recovery - (Struct Rvw-2, dbeck, 7-23-2018).doc
July 23, 2018
Leif Bjorback
Building Official
City of Edmonds
121 5th Avenue North
Edmonds, WA 98020-3145
Subject: Northpoint (Structural Review – 2nd)
Permit: BLD17-1835
Per your request, Beck & Associates has completed a 2nd structural review of the drawings and calculations for conformance with the 2015 International Building Code (IBC), as adopted
and amended by the State of Washington and the City of Edmonds.
Our review of the plans and calculations indicates that corrections are necessary prior to permit issuance. The applicant should address the following comments in itemized letter format
in addition to making corrections & revisions to the drawings. Corrections and revisions to the drawing should be clouded so that they are clearly identifiable.
_______________________________________________________________________
Legend:
Faded text = initial comment adequately addressed – no further action required
Plain text = initial comment (these remain where an additional comment is made)
Blue text = additional comment in response to the resubmittal
General
General
Shannon & Wilson, Inc. is required to provide a geotechnical review of the plans and specifications to determine that they are consistent with the recommendations. Shannon & Wilson,
Inc. should summarize their review in a summary letter, providing any additional recommendations as needed. All recommendations are required to be addressed within the design drawings
resubmitted for our review (p. 14 of 16)
Analysis
Gravity
Sections 2 & 4A, as indicated in the structural calculation Table of Contents, were not included in the structural calculations. Please submit these sections in response to this review
letter.
Provide calculations or other documentation that demonstrates that the existing Level 2 structure can support the gravity loads as required for this project and as indicated on sheet
S-0-21.
Reference the Design Loads identified on sheet S-001. The Floor Live Load is indicated to be 80 psf. However, the Design Loading Table and Diagram on sheet S-021 is inconsistent with
this. We are in agreement with the Live Loads identified on sheet S-021. The Live Load on sheet S-001 should therefore be updated to reference the Design Loading Table and Diagram on
sheet S-021.
Mark C superimposed dead load is 28 psf per the calculations, not 20 psf as indicated in the Table (S-021). Provide coordination.
Mark Q superimposed dead load is 48 psf per the calculations, not 20 psf as indicated in the Table (S-021). Provide coordination.
Provide calculations to demonstrate that the existing roof framing can support imposed loads from mechanical equipment and mechanical screening.
The calculations for existing roof members are based on either HF or DF No. 1 standard roof framing. Please confirm that the existing framing is No. 1, as this is atypical for standard
roof framing.
No calculations have been provided for the support of mechanical units. Calculations were only provided for standard roof framing without mechanical loading. Provide calculations for
structural members supporting combined loads: dead, snow, mechanical.
Provide calculations and detailing for lateral anchorage of all mechanical units.
Lateral
Vertical combinations of lateral resisting elements are required to be addressed in accordance with ASCE 7-10, 12.2.3.1.The upper system (plywood shear walls) is permitted to be designed
using its own design coefficients (R, omega, Cd). The lower system (concrete shear walls) is required to be designed for its own coefficients (R, omega, Cd). Forces transferred from
the upper system to the lower system are required to be increased by multiplying by the ratio of the higher response modification coefficient to the lower response modification coefficient.
ASCE 7-10, 12.2.3.1
Provide an analysis that is consistent with these requirements.
Provide an analysis that demonstrates that the concrete shear walls are designed for their own appropriate design coefficients (R, omega, Cd).
This building meets the criteria of ASCE 7-10, 12.2.3.3 so the building with a horizontal combinations of resisting elements (plywood shear walls, concrete shear walls) may be designed
using the least value of R for the different structural systems found in each independent line of resistance. This is for your information only. No response is required. ASCE 7-10,
12.2.3.3
Diaphragms and collector elements.
The value of R used for design of the Level 2 diaphragm is required to be the least value of R for any of the systems (wood shear wall, concrete shear wall) used at that level and below.
Update the analysis, design, and detailing accordingly. ASCE 7-10, 12.2.3.3
Collector elements and collector element connections to the concrete shear walls are required to be designed considering overstrength. Provide complete design of these collector elements.
ASCE 7-10, 12.10.2.1
Reference page 17 of 117 of the submitted calculations. Seismic base shear does not appear to be based on all weight that is required to be considered for seismic load determinations.
While the loading diagrams identify interior and exterior wall loads, these loads do not appear to have been included in the weight used for determination of seismic loads. All mass
needs to be considered. ASCE 7-10, 12.7.2
Provide calculations to demonstrate that lateral boundary elements (HSS columns) are adequate to resist all imposed load combinations, including gravity (DL, LL, Snow) and seismic. 1605
Drawing Sheets
S-001 – S-004 – General Structural Notes
Update the General Structural Notes. Overall, there is a lot of information that is not applicable to this project or that is incomplete. Update the Notes to the specifics of this project.
Update the Geotechnical Information section, consistent with and referencing the geotechnical report.
Under Design Loads, Snow, a reference is made to the City of Seattle. The authority having jurisdiction for this project is the City of Edmonds. Update the plans accordingly.
Update the Seismic information, consistent with the calculations provided.
Reference the Lateral Analysis Section. Special Concrete Shearwalls are identified at the 2nd Floor Level.
Provide calculations or other documentation that demonstrates that the concrete shear walls do indeed meet the criteria to be special concrete shearwalls. Please be aware that ordinary
reinforced concrete shear walls are not permitted to be used in Seismic Design Category D. ASCE 7-10, Table 12.2-1
Provide documentation that demonstrates that existing SW-5 has the minimum reinforcement required to be considered a special reinforced concrete shear wall (rho = 0.0025 in both vertical
and horizontal directions).
Specify the seismic response coefficient, Cs, for the special concrete shear walls.
S-101 – Level 1 Framing Plan
Specify required diaphragm and diaphragm connection to supporting framing.
S-102 – Level 2 Framing Plan
Specify required diaphragm and diaphragm connection to supporting framing.
Reference Section 4B, Collector Designs, of the calculations. Values used in the calculations are based on blocked diaphragm conditions. The requirement to block all diaphragms needs
to be specified on the drawings. Alternatively, the design should be revised to not require blocked diaphragms. Additional collectors may be required.
Drag struts are called out at a couple of locations. However, information is missing. Specify the struts, connectors, and provide detailing for connection of the struts to the shearwalls.
Note 1 provides requirements for drag struts that are inconsistent with what is otherwise shown on the plans and details. Provide coordination.
S-103 – Roof Framing Plan
Specify required diaphragm and diaphragm connection to supporting framing.
Reference Section 4B, Collector Designs, of the calculations. Values used in the calculations are based on blocked diaphragm conditions. The requirement to block all diaphragms needs
to be specified on the drawings. Alternatively, the design could be revised to not require blocked diaphragms. Additional collectors may be required.
Shear wall SW-1 needs to be labeled on the plan.
SW-3 is mislabeled as SW-4. Please correct.
Drag struts are called out at a couple of locations. However, information is missing. Specify the struts, connectors, and provide detailing for connection of the struts to the shearwalls.
Note 1 provides requirements for drag struts that are inconsistent with what is otherwise shown on the plans and details. Provide coordination.
S-221 – Shearwall Elevations
Reference 1/S221 – SW-1 Elevation. Specify required straps above the openings as required by the calculations.
Reference 2/S221 – SW-2 Elevation. Specify required straps above the openings as required by the calculations.
S-581 – Typical Wood Framing Details
Reference 6/S-581.
Illustrate and specify all required connections from the shear wall to the concrete wall below.
Specify the required connection of the upper sill plate to the lower sill plate in order to transfer the full lateral loads of SW-1 to the foundation below (1134 plf factored shear per
the calculations).
½” diameter @ 12” o.c. anchor bolts in 2x wood do not have sufficient strength to resist the imposed forces (1134 plf factored shear = 794 plf ASD shear). 2x DF wood plates (shear parallel
to grain) only have an allowable capacity of 660 plf (NDS). Revise the design accordingly.
This detail needs to be called out on the plans where it applies.
Reference 7, 8, & 9/S-581.
Illustrate and specify all required connections from the shear wall to the concrete wall below.
These details need to be called out on the plans where they apply. If they are not applicable to this project, they should be removed from the drawing set.
Detail 9/S-581 specifies anchors both per the Shear Wall Schedule and ½” diameter @ 12” o.c., min 7” embed. This information conflicts. Provide coordination.
S-591 – Light Gage Steel General Notes Schedules and Framing Details
Reference details 12, 19, & 20/S-591. These details call out “sure-board.” However, sure-board is not used on this project. Update the details accordingly.
Details 19 & 20/S-591 now specify “gyp sheathing per arch.” These details are for shear walls and should specify “sheathing and connections per Light Gage Shear Wall Schedule”.
Reference 16/S-591 – Light Gage Shear Wall Schedule.
Reference the column “typ wall stud except at abutting panels.” 33 mil material is specified. However, 43 mil (18 GA) material is required per the Simpson catalog in order to achieve
the required shear wall values. Please revise.
Reference the columns “panel edge screws” and panel field screws.” Screws are identified by number (Ex: #10, not 10d). The designations need to be updated. Furthermore, the specific
screws for which this project is designed should be specified (Simpson #10 CBSDA fasteners) for connection of sheathing to the light-gage steel. Update the schedule accordingly.
Reference the column “fasten top track to framing above.”
Provide documentation (from Simpson) of the acceptability of using Simpson A35 clips to connect light-gage steel to wood. Specify required fasteners (screws to the light-gage steel and
screws/nails to the wood).
Provide calculations to demonstrate the A35s and fasteners are adequate for the imposed loads.
Reference the column “bottom track attachment” “anchorage to concrete.” ½” DIA x 4” Titen HD anchors are required at 12” o.c. in order to transfer imposed forces (per calculations).
Please revise.
The allowable value for a ½” dia x 4” Titen HD screws in 54 MIL material is 1665# (per the Simpson catalog provided in the calculations). Revise the anchorage spacing:
SW-2; load = 1274# (LFRD) / 892# (ASD) – therefore, 22” o.c. max Titen HD spacing rqd
SW-3; load = 771# (LFRD) / 540# (ASD) - therefore, 25” o.c. max Titen HD spacing rqd
SW-4; load = 1623# (LFRD) / 1136# (ASD), therefore, 17” o.c. max Titen HD spacing rqd
SW-6; load = 1270# (LFRD) / 890# (ASD), therefore, 22” o.c. max Titen HD spacing rqd
Reference the column “bottom track attachment” “bottom track.” 54 mil bottom tracks are specified. However, detail 18/S-591 requires 68 mil bottom tracks. Provide coordination.
Reference the Notes. Note #5 provides specifications for nails. However, screws are used for these shear walls. Provide specifications for the required screws.
Allowable shear panel values are based on Structural 1 sheathing (calculations). Structural 1 sheathing needs to be specified in the Shear Wall Schedule.
Light gage shear wall types are based on shear wall values that are inconsistent with the calculations. According to the calculations, the following are the shear wall values and therefore,
corresponding shear wall types.
SW Designation Shear (LRFD/ASD) Specified SW Type
SW-1 1772 plf /1240 plf (2) sides #8@3” o.c. - okay
SW-2 1274 plf/892 plf #8 @ 2”o.c. – okay
SW-3 771 plf/540 plf #8 @ 4” o.c. – okay
SW-4 1623 plf/1136 plf #8@2”o.c. – NO GOOD (Revise)
SW-6 1270 plf/890 plf #8@3”o.c. – NO GOOD (Revise)
S-592 – Light Gage Steel Framing Details
Reference detail 5/S-592. This detail needs to be called out on the plans.
Reference detail 6/S-592. This detail is not applicable and should therefore be removed from the drawing set.
Reference detail 10/S-592. Illustrate and identify all connectors for shear transfer to the concrete shear wall.
Reference detail 16/S-592 – Typical Elevation of Shearwall with Holdown Straps.
“Solid blkg to match width of post above” is specified between HSS holdowns. Provide calculations to demonstrate that this adequately transfers compression loads in all cases. Revise
the detail as necessary to illustrate actual conditions.
Double holdowns are specified on the shear wall elevations in all cases. The detail needs to be updated to reflect these conditions.
Reference 13/S-592. This detail is not applicable (never are holdown straps called out on the plans) and should therefore be removed from the drawing set.
Reference 18/S-592 – Typical Holdown at Base.
Double holdowns are specified on the shear wall elevations in all cases. The detail needs to be updated to reflect these conditions.
Specify required embedment of holdown anchors. This does not appear to be provided anywhere in the drawing set.
S-721 – Steel Canopy and Stair Details
Reference 6/S-721 – South Canopy Detail.
Provide an analysis for all elements of this canopy, including the foundation.
The required axial strength of cantilever column elements, considering only the load combinations that include seismic load effects, is required to not exceed 15% of the available axial
strength, including slenderness effects. Provide an analysis to demonstrate that this criteria is met. ASCE 7-10, 12.2.5.2
Foundations used to provide overturning resistance at the base of cantilever column elements are required to be designed to resist the seismic load effects including overstrength factor
of Section 12.4.3. Provide an analysis to demonstrate that this criteria is met. ASCE 7-10, 12.2.5.2
We assume the columns will be designed and analyzed as ordinary cantilever columns (R=1.25; overstrength = 1.25; Cd = 1.25). If they will be designed as special cantilever columns, all
the requirements for special detailing (AISC 341-10) will need to be met. AISC 341-10
Reference 16/S-721 – East Canopy Detail.
Provide an analysis for the foundation.
The required axial strength of cantilever column elements, considering only the load combinations that include seismic load effects, is required to not exceed 15% of the available axial
strength, including slenderness effects. Provide an analysis to demonstrate that this criteria is met. ASCE 7-10, 12.2.5.2
Foundations used to provide overturning resistance at the base of cantilever column elements are required to be designed to resist the seismic load effects including overstrength factor
of Section 12.4.3. Provide an analysis to demonstrate that this criteria is met. ASCE 7-10, 12.2.5.2
We assume the columns will be designed and analyzed as ordinary cantilever columns (R=1.25; overstrength = 1.25; Cd = 1.25). If they will be designed as special cantilever columns, all
the requirements for special detailing (AISC 341-10) will need to be met. AISC 341-10
S-731 – Mech Screen & Misc Roof Details
Reference 6 & 8/S-731 – Mechanical Screening. Specify the maximum spacing of vertical posts that connect to the roof structure.
The design of the horizontal screen members (HSS5x5x3/16) is based on a maximum span of 20-feet. However, the span of these horizontal screen members is approximately 26-feet for the
screens that run along grids 2.2 and 6.7. Revise the design accordingly.
Specify required metal screening (Box Rib per calculations) and connection of the metal screening to the mechanical screening structure.
Reference 9/S-731 – Mechanical Screen Post Base Plate.
Specify the weld of the post to the base plate.
Given the load on the posts (M=134 k-in, ASD, per calcs), it is clear that the connections to the wood framing and of the wood framing to resist the loads are inadequate. Provide an
analysis and complete design for these resisting elements, including addressing fall protection forces.
Reference the “Post Over (E) GLB”portion of detail 9/S-731.
Specify the required bearing plate on the underside of the GLB in order to resist bearing pressures resulting from the bolts (tension).
Reference the “Post Over 6x14” portion of detail 9/S-731.
Detailing specifies a ½-inch thick base plate. However, the base plate is required to have a thickness of 1-1/4” per the calculations (similar to the base plate specified for the “Post
Over (E) GLB” portion of the detail). Update the detail accordingly.
The required resistance of the lag bolts is 192k-in/[(10”)(2 bolts)] = 9.6k/bolt (tension). However, the withdrawal capacity of lag bolts in DF framing is only 513#/inch penetration,
resulting in a total resistance of 513#(5-in) = 2,565#/lag bolt [this excludes the tip of the lag bolt]. Revise the design accordingly.
Reference 11/S-731 – Typ Fall Protection Anchor. Provide a complete analysis and detailing/specs for the anchor and its connection to the wood framing below.
Reference 13/S-731 – Screen Wall Details. Specify all elements, including angles, bolts, etc.
New Comments (based on resubmitted drawings and calculations)
Reference Section 5B, Shear Wall Footings, of the calculations.
Reference the Footing Width noted in the calculations. The plans specify footing widths that are inconsistent with (narrower than) that required by the calculations. Provide coordination.
Reference the Footing Sliding Resistance section of the calculations. In all cases, adequate resistance is not provided. Revise the design accordingly.
Reference sheet S-102 – Level 2 Framing Plan. Provide calculations to justify framing to accommodate new floor openings. Framing specified at wide openings, in particular, does not appear
to be sufficient.
Reference sheet S-103 – Roof Framing Plan. Provide calculations to justify framing to accommodate new roof openings. Framing specified at wide openings, in particular, does not appear
to be sufficient. Additionally, numerous locations exist where framing is shown to run through the openings. Provide coordination and design.
Reference S-221 and S-222.
According to the calculations and plans all holdown/boundary elements are HSS3x3x3/16. However, the Shear Wall Elevations specify (2)-362S200-68 framing members at each of these locations.
Provide coordination. Perhaps the Elevations should simply reference the plans for required holdown/boundary elements.
Reference 4/S-221, SW-4 Elevation. Reference the drag strap at the roof level.
In order to function as a collector (drag-strut) the strap is required to extend over the top of and be connected to the shear wall. This needs to be clarified on the drawings.
Provide detailing/specifications for splicing of the drag strap. Alternatively, the drag strap should be specified to be a continuous, single piece.
Reference 1/S-222, SW-6 Elevation. Reference the drag strap at the floor level.
In order to function as a collector (drag-strut) the strap is required to extend over the top of and be connected to the shear wall. This needs to be clarified on the drawings.
Provide detailing/specifications for splicing of the drag strap. Alternatively, the drag strap should be specified to be a continuous, single piece (full-width of the building).
Reference 5/S-582, Stair Detail.
Provide calculations to demonstrate that the (E) 5-1/8x16-1/2 GLB has adequate strength to support all imposed loads including the reactions from the stair stringers.
Provide design and detailing for the connection of the prefab stair stringer to the existing GLB. While the stair stringer may be a deferred submittal, the connection of the stringer
to the GLB should be complete prior to permit issuance.
Please contact me should you have any questions.
Respectfully,
Douglas Beck, PE, SE
Beck & Associates, PLLC
BLD18-0447 (Struct Rvw)
July 23, 2018
Page 8 of 8
16425 SE 66th Street, Bellevue, WA 98006 ● beckpllc@msn.com ● PH: 206-313-3739
Beck & Associates, PLLC
Structural Engineering & Code Consulting
16425 SE 66th Street, Bellevue, WA 98006 ● beckpllc@msn.com ● PH: 206-313-3739