2021-03-05 Final Nemah Hatchery Bridge Deck Design Report

Washington State Department of Fish and Wildlife

Nemah Hatchery Bridge Deck Replacement

Design Report

KPFF Project No. 10092100026

March 05, 2021

Submitted To:

Washington State Department of Fish and Wildlife

Olympia, Washington

Prepared By:

KPFF Consulting Engineers

2407 North 31st Street

Suite 100

Tacoma, WA 98407

(253) 396-0150

Nemah Hatchery Bridge Deck Replacement 2 KPFF Project No. 10092100026 Design Report March 05, 2021

I. T A B L E O F C O N T E N T S

DESCRIPTION PAGE NO.

I. T A B L E O F C O N T E N T S ....................................................................................................... 2

II. Introduction........................................................................................................................................... 3

III. Existing Bridge Deck and Girder Evaluations ....................................................................................... 3

IV. Deck Replacement Design ................................................................................................................... 4

V. Deck Replacement ............................................................................................................................... 6

VI. Material Specifications ......................................................................................................................... 7

VII. Summary .............................................................................................................................................. 8

VIII. Attachments: ........................................................................................................................................ 9

IX. Appendix A – Glulam Deck Strength Calculations.............................................................................. 10

X. Appendix B – KPFF Load Rating and Report Dated July 15, 2020 .................................................... 13


II. INTRODUCTION

KPFF Consulting Engineers (KPFF) has been contracted by Washington Department of Fish and Wildlife (WDFW) to provide engineering consultation and design services for the development of a Structural Design Report to support the deck replacement of the existing Nemah Hatchery Bridge in South Bend, WA. The existing structure consists of two 45-foot spans, supported on pile-supported abutments and in-stream piers. Each span consists of four built-up plate girders, with a timber deck and guardrail system.

KPFF was previously contracted to provide a load rating for the existing bridge and develop a structural alternatives analysis report for potential girder rehabilitation and deck replacement. Based on an inspection of the bridge performed by KPFF in May of 2020, a load rating for the structure was produced, which concluded that the capacity of the bridge was controlled by the existing timber deck. KPFF similarly produced a resulting capacity for the bridge if the deck structure was to be rehabilitated, at which point the capacity of the bridge would be governed by the strength of the existing built up plate girders. Based on these results and conversations with WDFW, the selected option is to replace the existing timber plank deck with a timber glulam deck system to increase the load rating of the bridge to the capacity of the existing girders. The scope of this report is to document the selection of the preferred replacement deck system, which consists of removing the existing timber deck planks and replacing with glulam timber deck panels.

The following documents are either referenced in this report, or included as appendices:

1. “Nemah Hatchery Bridge Repair”, Drawings dated November 3 and October 30, 1964 2. “Nemah Salmon Hatchery Bridge Painting”, Drawing Sheet dated June 15, 1984 3. “Nemah Salmon Hatchery Emergency Bridge Repairs R607”, Drawings dated December 3, 2008 4. “Nemah Hatchery Bridge Condition Assessment”, KPFF Load Rating and Report dated July 15,

2020

III. EXISTING BRIDGE DECK AND GIRDER EVALUATIONS

The existing bridge deck is comprised of 4x12 treated timber plank members that are 16’-0” long, spanning over the four existing girders. The existing bridge girders are built-up plate girder members spaced at 4’-9” on center, comprised of grade A36 plates per the design drawings. At each end in areas of pile caps and supports, the overall girder height is 25”, which tapers to an overall height of 31” for the central region of each span.

The existing bridge elements were evaluated based on the LRFR (Load and Resistance Factor Rating) method, as specified in the AASHTO LRFD Bridge Design Specifications (AASHTO), AASHTO Manual for Bridge Evaluation (MBE), and the WSDOT Bridge Design Manual (BDM).The members were analyzed for all tributary dead loads, as well as various vehicular live loads. The vehicles used were based on definitions for axle load magnitude and spacing as set forth in AASHTO, supplemented by requirements of the MBE and BDM. These include two HL-93 loadings (truck and tandem, with corresponding lane load), legal loads (AASHTO Type 3, 3S2, and 3-3), overload vehicles (OL 1 and OL 2), and emergency vehicles (EV 2 and EV 3). Specific axle loads and spacings can been found in the previous load rating performed for the bridge, attached.


From the load rating performed by KPFF, it was found that the strength of the bridge was controlled by the capacity of the existing deck timbers. The capacities of the existing girders were found to similarly require posting of the bridge (though at larger allowable axle loads than what would be required if the existing deck capacity was maintained). Through discussions with WDFW, and WDFW’s coordination with local agencies on specific vehicle load configurations that may be required to support the Hatchery, it was decided that rehabilitation of the deck would be sufficient and that the existing girder capacities will be the controlling bridge elements. As a result, the proposed bridge deck replacement system has been designed to achieve, at a minimum, the strength of the existing girders for each design vehicle.

IV. DECK REPLACEMENT DESIGN

A controlling rating factor for each design vehicle, based on the lower resulting factor for either shear or flexure, was produced for the existing girder and deck elements. Load factors and load combinations used to determine ultimate shear and flexural demands were as specified in the BDM. The shear and flexural capacity of the bridge element being rated is in accordance with AASHTO. A rating factor was then determined for the girder and deck elements, based on Equation 1 below:

𝑅𝐹 =𝜑 ∗ 𝜑 ∗ 𝜑 𝑅 − 𝛾 ∗ 𝐷𝐶

𝛾 ∗ 𝐿𝐿 ∗ (1 + 𝐼𝑀)

Equation 1 – LRFR Rating Factor Definition

In the equation above, φnRn represents the ultimate capacity of the element for the force being evaluated, which is modified for both the current condition of the element (φc) as well as the type of structure (φs) being evaluated. The term, γDC*DC represents the factored dead load demands, γLL*LL represents the factored live load demands, and IM is the dynamic load allowance.

To ensure that the capacity of the proposed deck system will not control the load rating of the structure once replaced, the required deck capacity in either shear or flexure was determined through Equation 1 for the Rating Factor of the proposed deck to match the rating factor of the existing girders (performed via a goal-seek analysis in Excel). This resulted in a required shear and flexural capacity for the new deck for each design vehicle, with the largest required capacities in either shear or flexure over all vehicles then being the required strength of the proposed system. The depth of the proposed glulam panels was selected to be comparable to the existing timbers, to mitigate any substantial impact on the existing bridge approach elevations. Table 1 below includes the rating factors for the existing girders for all vehicles, as well as the resulting required capacities of the deck to match the rating factor of the girders. The controlling capacities for the deck are highlighted in yellow.


VEHICLE Girder RF Deck RF Required Shear Capacity (kips)

Required Flexural Capacity (kip-ft)

INVENTORY HL-93 TRUCK 0.45 0.45 12.79 12.40 INVENTORY HL-93 TANDEM 0.46 0.46 10.26 9.93 OPERATING HL-93 TRUCK 0.59 0.58 12.72 12.54 OPERATING HL-93 TANDEM 0.60 0.60 10.32 9.99 TYPE 3 0.85 0.85 10.54 10.24 TYPE 3S2 0.92 0.92 10.40 10.10

TYPE 3-3 1.02 1.00 10.21 9.92 NRL 0.55 0.55 6.84 6.63 OL 1 0.64 0.64 8.31 8.07 OL 2 0.61 0.61 8.11 7.87 EV 2 0.81 0.81 17.70 17.21 EV 3 0.53 0.53 10.74 10.43

Table 1 – Required Deck Capacities to Match Girder Rating Factors

The selected replacement deck system is glulam deck panels, with a required shear capacity of 17.7 kips and a required flexure capacity of 17.21 kip-ft. Per AASHTO, the flexural strength for a 3 ft wide by 3-1/8” deep (net) glulam deck panel, specification 24F/V4/DF/DF-1.8E, is 20.53 kip-ft. The corresponding shear strength is 49.7 kips, both exceeding the required strengths to exceed the capacities of the existing girders. Calculations for shear and flexure for the glulam panels are provided in Appendix A. Table 2 below shows the resulting Rating Factor for each design vehicle for the capacities of the proposed deck system:

VEHICLE

Girder RF Deck RF

INVENTORY HL-93 TRUCK 0.45 0.75 INVENTORY HL-93 TANDEM 0.46 0.95 OPERATING HL-93 TRUCK 0.59 0.97

OPERATING HL-93 TANDEM 0.60 1.24 TYPE 3 0.85 1.71 TYPE 3S2 0.92 1.87 TYPE 3-3 1.02 2.07 NRL 0.55 1.71 OL 1 0.64 1.63

OL 2 0.61 1.59 EV 2 0.81 0.97 EV 3 0.53 1.04

Table 2 – Vehicle Rating Factors for Proposed Deck System


V. DECK REPLACEMENT

The existing deck system consists of 4x12 deck plank timbers, 6x12 deck nailers, and an existing timber guardrail system. Per WDFW, the existing guardrail is to be removed and reinstalled to the new glulam deck panels. It’s been assumed that the connection to the new deck system will be of a capacity at least, or greater, than what is currently installed. The existing deck plank timbers and deck nailers are to be removed and will not be reinstalled. Based on documentation provided in a previous load rating of the bridge to KPFF by WDFW, we understand that the current deck planks are installed to the nailers via lag-screws. Per the record drawings, the existing nailers are installed through holes in the top flange of the girders with 1/2" diameter bolts at 2’-0” on-center, staggered. Figure 1 shows a typical cross section of the existing bridge indicating elements to be removed. Figure 2 shows a typical cross section of the replacement deck system.

Figure 1 – Typical Bridge Section for Demolition

Figure 2 – Typical Bridge Replacement Section

The replacement nailers are 6x12 Doug-Fir No. 2, with counterbore holes to match the existing nailer installation bolts in quantity and spacing. Material specifications are provided in the following section of this


report. The glulam panels shall be installed to the timber nailers with 1/2” lag bolts at 12” on-center, each girder. There shall be a maximum gap between panels of 1/4”, and a minimum gap between panels of 3/16”. Figure 3 shows a typical connection detail at each nailer/deck panel intersection:

Figure 3 – Typical Attachment Detail

VI. MATERIAL SPECIFICATIONS

Glulam Panels

The selected glulam deck panel specification is Doug-Fir, 24F/V4-1.8E. For compatibility with the structural calculations, the deck panels must be furnished with section widths no shorter than 3’. The net thickness of the panels is 3-1/8” (4” nominal), and to match the existing width of the deck system are 16’ in length. Per discussion with WDFW, the panels will not be treated. The following minimum properties must be met or exceeded (referenced from AASHTO Table 8.4.1.1.4-1):

Extreme Fiber in Bending - Perpendicular Loading (Fbxo+): 2.4 ksi Extreme Fiber in Bending - Parallel Loading (Fbyo): 1.45 ksi Shear Parallel to Grain (Fvxo): 0.265 ksi

Deck Nailers

Replacement deck nailers are specified as Doug-Fir, Grade No. 2 or better, pressure treated in accordance with AWPA Use Category UC4B, using ACZA. Surface S4S. The following minimum properties must be met or exceeded (referenced from AASHTO Table 8.4.1.1.4-1):

Compression Perpendicular to Grain (Fco): 0.625 ksi

smikl477

Rectangle


Hardware

Hardware includes replacement of the existing 1/2” bolts connecting the timber nailers to the top flange of the built-up girders, and 1/2” lag bolts to connect the glulam deck panels to the nailers. All hardware shall be hot dipped galvanized to Grade G185 conforming to ASTM F593. Lag screws shall be embedded a minimum of 8D (8*Diameter).

1/2” Nailer Bolts: ASTM A307 1/2” Lag Bolts: ANSI/ASME Standard B18.2.1

VII. SUMMARY

KPFF has provided a glulam deck panel replacement option for the Nemah Hatchery Bridge that will increase the load rating of the bridge to the capacity of the existing girders, with supporting calculations attached. Typical connection details and material specifications have also been included, which we understand WDFW will use to generate Contract Documents for the upcoming construction. We appreciate the opportunity to provide our engineering services on the project, and look forward to any questions or comments you may have.

Regards,

Sean Story, PE Scott Kuebler, PE, SE Professional Engineer Principal


VIII. ATTACHMENTS:

Appendix A – Glulam Deck Strength Calculations

Appendix B – KPFF Load Rating and Report Dated July 15, 2020


IX. APPENDIX A – GLULAM DECK STRENGTH CALCULATIONS

Glulam Deck Strength Calculations

Description Equation Note/Reference

Design Values (Glulam Doug Fir 24F/V4-1.8E)------------------------------------

Bending: ksi1.45Fbo (T 8.4.1.1.4-1)

Tension Parallel: ksi1.1Fto (T 8.4.1.1.4-1)

Shear Parallel: ksi0.265Fvo (T 8.4.1.1.4-1)

Compression Perpenduicular: ksi0.56Fcpo (T 8.4.1.1.4-1)

Compression Parallel: ksi1.65Fco (T 8.4.1.1.4-1)

Modulus of Elasticity: ksi1800Eo (T 8.4.1.1.4-1)

Adjusted Design Values (8.4.4)-------------------------------------------------

Bending:

Resistance Factor: 0.85ϕ (8.5.2.2)

2.9412ϕ2.5CKFFormat Conversion: (8.4.4.2)

Size Factor: 1.0CV (Table 8.4.4.4-2)

Wet Service Factor: 1.0CM (8.4.4.3)

Flat-Use Factor: 1.16Cfu (Table 8.4.4.6-2)

Incising Factor: 1.0Ci (8.4.4.7)

Deck Factor: 1.0Cd (8.4.4.8)

Time Effect Factor: 1.0Cλ Associated with Strength II LC

Adjusted Strength: ksi4.9471CλCdCiCfuCVCMCKFFboFb (8.4.4.1-1)

Shear Parallel:


3.3333ϕ2.5CKFFormat Conversion: (8.4.4.2)

Wet Service Factor: 1.0CM (Table 8.4.4.3-1)

Incising Factor: 1.0Ci (Table 8.4.4.7-1)

Time Effect Factor: 1.0Cλ Associated with Strength II LC

Adjusted Strength: ksi0.8833CλCiCMCKFFvoFv (8.4.4.1-2)

4 Mar 2021 18:41:59 - Deck -GLULAM.sm

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Flexure Capacity (8.6.2)-------------------------------------------------------

Width: ft3b Per specification

Depth: in3.125d Per specification

Stability Factor: 1.0CL For width exceeding depth

3in58.59386

2dbSSection Modulus:


Nominal Resistance: inkip289.8667CLSFbMn (8.6.2-1)

Factored Resistance: ftkip20.5322MnϕMr (8.6.1-1)

Shear Capacity (8.7)----------------------------------------------------------

Width: in36b Per specification

Depth: in3.125d Per specification


kip66.251.5

dbFvVn

Nominal Resistance: (8.7-2)

Factored Resistance: kip49.6875VnϕVr (8.7-1)

4 Mar 2021 18:41:59 - Deck -GLULAM.sm

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X. APPENDIX B – KPFF LOAD RATING AND REPORT DATED JULY 15, 2020