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7/29/2019 1stplace Villanova

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US Route 67 Corridor Project

Jerseyville Bypass Bridge Design

Abstract

The US Route 67 Corridor Project is a multibillion dollar roadway improvement project beingimplemented by the Illinois Department of Transportation. The Jerseyville section of the projectconsists of a new four-lane divided highway alignment with full access control to replace thecurrent two-way alignment, which consists of several traffic control devices. The new alignmentwill bypass Jerseyville, Illinois, and along with many other sections of the project, will allow fordecreased travel times and increased safety. The northern section of the Jerseyville Bypassproject consists of three highway bridges, and the design team was tasked with designing abridge over Witt Mill Road. The bridge design span was 140 feet. It was to be designed usingwelded steel plate girders acting compositely with a cast-in-place concrete deck. The number

and size of the girders, the concrete slab and reinforcement, abutments and shear studs were alldesigned according to the AASHTO LRFD Bridge Design Specifications and the Illinois DOTBridge Manual. The most efficient design was selected based on several limit state checks. Acost analysis was performed on four, five and six girder systems to determine the most efficientdesign.


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1. US 67 Corridor Project Overview

US Route 67 is a north-south running highway through Western Illinois. It runs south fromthe Rock Island Centennial Bridge to the Clark Bridge in Alton. US Route 67 extends 214 milesas it intersects with Interstate 280 in the north and Interstate 270 in the south. It is predominatelya two lane highway with a few multilane divided sections. US Route 67 is the last remainingmajor north-south roadway in Illinois not to be upgraded to the Interstate highway system.

Figure 1.1: Illinois Highway Map

The US 67 Corridor Project is a multibillion dollar roadway improvement project thatwill upgrade and in some cases reroute the current highway. Thus far $810 million dollars ofgovernment money has been invested in the project. There are five sections of the roadwaydesignated by the Illinois State Department of Transportation. The Jerseyville project area,indicated by the star in Figure 1, is the second most southern region extending from Interstate 72to Alton. Phase I engineering on this 57 mile stretch has been completed and design approvalwas received in January 1999. The Jerseyville bypass is a 6 mile section of this region thatbegins approximately 0.2 miles north of Dearcy and ends near Chrystal Lake Road in JerseyCounty. The current Route 67 alignment through Jerseyville is a two-lane roadway locatedthrough the center of Jerseyville with traffic flow impeded by intersections and traffic controldevices.

The start of land acquisition and Phase II engineering for this six mile stretch is currentlyunderway at has cost $5.4 million. The start of utilities, construction, and continued landacquisition in Jerseyville are programmed during the FY 2012-2016 portion of the FY 2011-2016 Proposed Highway Improvement Program. This northern section of the bypass has threehighway bridges and another two are located in the southern section of the bypass.


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Figure 1.2: Area of Jerseyville Bypass Project

The current alignment of US Route 67 can be seen in Figure 1.2 running diagonal fromthe upper left-hand corner to the lower right-hand corner. The bypass, the general course ofwhich is indicated by the yellow line in the figure, will create a wider four-lane dividedexpressway which will be capable of higher traffic volumes. This bypass is similar to theRoseville bypass on Route 67 which was able to increase its section speed limit to 65 mph afterits completion in 2003. Rather than intersections, highway bridges will overpass local roads andalignment will be diverted to the outskirts of Jerseyville allowing for higher rates of travel andincrease safety.

2. Information Related to Bridge Design

The simple span, plate girder bridge will pass over Witt Mill Rd and will have a span lengthof 136-6 with a design span of 140 feet. It will feature a cast-in-place concrete deck with 2structures, one northbound and one southbound, each carrying 2 lanes of traffic. Travel laneswill be 12 feet wide with a 10 foot and 6 foot shoulders on each bridge. The design will alsoinclude an allowance for a wearing surface and parapets on either side. The superstructure will

be supported by integral abutments on both ends. The area of the proposed new alignment ishighlighted in Figure 2.1.


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Figure 2.1: Proposed Area of Jerseyville Bypass Bridge to be Designed

The team was responsible for several elements of the bridge design. These included thecast-in-place concrete deck, the number, size, and spacing of the steel welded plate girders, shearstuds, as well as the integral abutments. All designs were in accordance with AmericanAssociation of State Highway and Transportation Officials (AASHTO) Bridge DesignSpecifications (2010) and the Illinois DOT using the AASHTO HS20 design truck. The mostefficient design was determined in order to ensure the most cost-effective solution. Four, fiveand six girder systems were examined, with the optimal design being the most efficient and cost-effective. The following analysis was conducted on a 5 girder system which was determined tobe the best option. The girder cross section and spacing are shown in Figure 2.3.

Figure 2.3: Girder Cross Section and Spacing

3. AASHTO Design Limit States

Design of the bridge system was based on specifications from the AASHTO BridgeDesign Specifications, which utilize the Load and Resistance Factor Design (LRFD) method tocreate limit states that the design must satisfy. A limit state represents a condition beyond whicha bridge system or bridge component ceases to fulfill the function for which it is designed.

The limit states applied to this design were Service I, Service II, Strength I, and Fatigue.Service I considers the load combination relating to the normal operational use of the bridge,


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including a 55 mph wind with all dead and live loads taken at their nominal values. The ServiceII limit state considers the load combination intended to control yielding of steel structures andslip of slip-critical connections due to vehicular live load. The Service limit states are intendedto allow the bridge to perform acceptably during its service life. The Strength I limit stateconsiders basic load combinations relating to the normal vehicular use of the bridge without

wind. Application of this limit state ensures that strength and stability are provided to resist thestatistically significant load combinations that a bridge will experience throughout its design life.The Fatigue limit state ensures the bridges resistance to fatigue and fracture due to repetitivegravitational vehicular live load and dynamic responses under a single design truck to limit crackgrowth and prevent fracture. This is accomplished by limiting the stress range induced by truckloads.

Two loading types calculated for the bridge design: dead load and live load. The deadload applied is separated into structural components (DC), and wearing surface and utilities,(DW). The DC load is further broken down into composite and non-composite loads. Non-composite loads (DC1) occur before the concrete deck is fully hardened. These loads include theweight of the concrete deck and the structural steel members of the bridge. Composite loads

(DC2) are comprised of parapets and are not applied until the deck is hardened.Load factors ()are provided by AASHTO for each limit states and can be found in Table3.1. For this design the maximum allowable load factors were used to determine the maximumshear and moments. The values provided in the LRFD specifications increase specific load casesto emphasize different loading and to determine the governing cases. Load modifiers () are alsoprovided and vary based on ductility, redundancy, and operational importance. These valueswere set equal to 1 for this bridge.

Table 3.1: Summary of Limit States and Load Factors

4. Loading Combinations and Live Load Envelopes

The first part of developing the load combinations regarded determining the dead loads.The dead loads calculated were DC1 (non composite), DC2 (composite), and DW (wearingsurface). The equations used to calculate these loads are provided in Equations 1-3.

Limit State Intended for

Load Factor i

DC DW LL+IM

Service

INormal operation of

bridge1 1 1

IISteel yield and

connection slip1 1 1.3

Strength I Ultimate strength 1.25 1.5 1.75

Fatigue Live load stress range 0 0 0.75


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(1)

(2)

(3)

Using the above equations, the dead loads were calculated and are shown in Table 4.1.

Table 4.1: Calculated Dead Loads

In order to develop the shear and moment envelopes governing the design of the bridge,influence lines were used. For the simply supported structure, three influence lines wereneeded, two for shear and one for moment. The first influence line for shear was for theminimum shear (negative shear) and the second was maximum shear (positive shear). Thispermitted the calculations to take into account the shear on either side of the point of interest.Since the structure is simply supported, it can only experience positive bending, thus onlyrequiring one influence line for moment

In accordance with AASHTO LRFD 3.6.1, five vehicular live load combinations wereused. These loads included truck loading, tandem loading, and design lane loading which wasthen coupled with both truck loading and tandem loading. The truck loading used an HS20design truck as specified by AASHTO with three axles exerting 8 kips, 32 kips, and 32 kips to

the front, middle, and rear axles, respectively. For this design, 14 foot rear axle spacing wasused to maximize the loading. The design tandem has two axles spaced 4 feet apart, eachexerting 25 kips. The design lane load is a simple uniform load of 0.64 kips/ft. This lane load isdistributed over a 10 foot width. When combined with the lane load, both the truck and tandemloads received an impact factor of 1.33.

The HS20 truck load and the tandem load each had multiple cases to account fordirection of travel as well as point of interest for shear and moment to be measured. The HS20truck has six cases, one for each axle traveling in each direction. Due to the symmetry of thetandem design, only two load cases were needed. The load cases for the HS20 truck are depictedin Figure 4.1, with the arrow indicating the point of interest.

DC1 1.288 (k/f/girder)

DC2 0.200 (k/f/girder)

DW 0.408 (k/f/girder)

Distributed Loads


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Figure 4.1: HS20 Load Cases

Figure 4.2 shows the plotted values of the maximum shear envelope for all live loads. As

shown on the plot, the governing live load combination is the lane load and HS20 truck with amaximum shear of 134.2 kips per lane occurring at the ends of the bridge.

Figure 4.2: Live Load Shear Envelope

Figure 4.3 shows the plotted values of the maximum moment envelope for all live loads.

The lane load plus HS20 truck combination produced the governing moment with a maximum of4,527 kip-feet per lane.

-150.00

-100.00

-50.00

0.00

50.00

100.00

150.00

0.00 20.00 40.00 60.00 80.00 100.00 120.00 140.00

Sh

ear(k/lane)

Location (ft)

Lane

HS20

Tandem

Lane+HS20

Lane+Tandem


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Figure 4.3: Live Load Moment Envelope

Before calculating the load combination envelopes, the distribution factors werecalculated in order to distribute the lane shear and moments to the girders. The followingequations were used to calculate the distribution factors.

(4)

(5)

Using these equations, the shear distribution factor was determined to be 0.901 and themoment distribution factor was 0.691.

5. AASHTO Limits State Checks

AASHTO LRFD Design Specifications require that several limit states be satisfied forbridge design. The following limit state checks were performed for this design: cross section

proportion limits, Service I, Service II, Strength I, Fatigue and Fracture, and Constructability.The results of these checks are dependent on girder size and spacing, construction and serviceloads, and concrete deck design. The first design provisions considered were Sections 6.10.2 and2.5.2.6.3 of the AASHTO specifications, which account for cross section proportions and overalldepth. A summary of these checks can be found in Table 5.1, in whichD is the depth of theweb, tw is the thickness of the web, bf is the width of the flange, tf is the thickness of the flange,Iyc and Iyt are the moments of inertia of the compression (top) and tension (bottom) flanges,respectively, andDtotal is the overall depth of the section, including the concrete slab.

0.00

500.00

1000.00

1500.00

2000.00

2500.00

3000.00

3500.00

4000.00

4500.00

5000.00

0.00 20.00 40.00 60.00 80.00 100.00 120.00 140.00

Moment(kft/lane)

Location (ft)

Lane

HS20

Tandem

Lane+HS20

Lane+Tandem


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Table 5.1: Cross Section Proportion Limits

Constructability requirements rely only on the strength of the steel girders, which mustsupport the wet concrete and other construction loads and are considered the noncompositesection. The Service, Strength and Fatigue and Fracture Limit States, however, rely on thecomposite behavior of the steel girders and concrete deck, which is accomplished by the transferof force through shear studs. In order to perform analysis on this section, the concrete wastransformed into an equivalent area of steel using a modular ratio of 9 for a short term section(subjected to live loads multiplied by an impact factor) and a modular ratio of 27 for the longterm section (subjected to the permanent loads of the parapets and wearing surface).

Once composite analysis was performed, the Service I Limit State was checked, which isintended to avoid undesirable structural and psychological effects due to deflections. Thedeflection due to the live load multiplied by an impact factor must be less than the span lengthdivided by 800 for bridge without sidewalks, which is 2.10 in. for this design. Two cases werechecked for deflections: Case 1, which considers the full HS20 design truck, and Case 2, whichconsiders the lane load plus 25% of the HS20 truck. In both cases the truck loads weremultiplied by the impact factor of 1.33. The Service I check is shown in Table 5.2, in whichallowable is the maximum allowable deflection, and Case1 and Case2 are the calculated deflectionsfor each case.

Table 5.2: Service I Limit State

D/tw 85.33 D/tw


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The Service II Limit State is used to prevent excessive deflections from yielding or slip inslip-critical members due to severe traffic loading in a real world situation. The stresses in boththe top and bottom flanges had to be less than 95% of the yield stress of 50 ksi. The flangestresses were calculated using the moments due to DC1, DC2, DWand LL+IMand the section

moduli upon which they act, as shown in Equation 6 below. The limit check is shown in Table5.3, in whichfallowable is the allowable service stress and ff,top andff,bottom are the calculated flangestresses for the top and bottom flanges, respectively.

(6)

Table 5.3: Service II Limit State

The Strength I Limit State is used to control the direct failure of the bridge. This failurecan occur in three different ways. The first is material failure, or yielding of the steel and plastichinge formation. The next two failure modes are stability failures: local buckling (LB) of thecompression flange and global buckling, or lateral torsional buckling (LTB), during construction.Essentially, the ultimate capacities for moment and shear, generally noted Mand V, must fall

below their respective nominal capacities with an applied load reduction factor, .

(7) (8)

As determined from plastic analysis, the compression flange is compact, thereforedictating the design criteria of this limit state as defined by AASHTO. The ultimate moment andshear were taken from the moment and shear envelopes with their respective load factors. Aplastic analysis was used to find the nominal moment of the cross section. Similarly, thenominal shear capacity was defined by the plastic shear capacity and the ratio of shear bucklingresistance, which are both dictated by the size of the web as well as strength properties of thesteel. Additionally, AASHTO requires a ductility check comparing the distance to the plastic

neutral axis,Dp, to a fraction of the total depth of the section, Dt.. A summary of all Strength Ichecks are shown in Table 5.4.

Stress Value Units

fallowable 47.50 ksi

ff,top 39.69 ksi

ff,bottom 46.80 ksi


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Table 5.4: Strength I Limit State

Constructability takes into account loading during the construction of the bridge. These

loads include the weight of the girders, formwork, wet concrete, and the live loads due toconstruction. Since the concrete has not had a chance to harden, composite action does notapply, leaving the girders to carry the entire load. Constructability shares the same load factors asStrength I, but is reduced to just construction loadings.

Once the moment is determined, the maximum flange stress, fbu, is found and comparedto the allowable flange stresses for both yielding, Fyc, and local/lateral torsional buckling, Fnc,with appropriate factors as defined by AASHTO 6.10.3.2.1 (fl is not applicable for this bridge):

(Yielding limit check) (9)

(LB and LTB check) (10)

These are compared to the nominal flexural resistance in the flange, as determined byAASHTO 6.10.8.2.2.

Table 5.5: Constructability Limit State

Additionally, lateral torsional buckling will occur in the girders induced by self weight

prior to the formwork and the concrete hardening. To prevent this, diaphragms will be placed at20 foot intervals along the span length to provide lateral bracing.

Fatigue and Fracture limits are calculated to prevent the failure of beams and connectionsdue to the repeated placement and removal of live loads. The load factors for fatigue are:

(11)

Strength Check Value Units

Moment

Ultimate, Mu 11,558 k-ft

Nominal, Mn 12,292 k-ft

Shear

Ultimate, Vu 385 kips

Nominal, Vn 870 kips

Ductility

Dp 11.78 in

0.42 Dt 31.19 in

Stress Value Units

Flange stress, fbu 16.5 ksi

Yield Limit, Fyc 50.0 ksi

Buckling Limit, Fnc 40.8 ksi


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The live load for fatigue varies from the live load for the other limit states. In fatigue,live load is calculated using 30 foot rear axle spacing on the HS20 truck as opposed to the 14foot spacing used earlier. Additionally, the impact factor is reduced from 0.33 to 0.15. Rangeconditions are used to better represent the trucks effect on fatigue. Again, the flange stress, f,is found from the factored moment and is compared to the flange stress threshold, Fn, in the

limit state as defined by AASHTO 6.6.1.2.2:

(12)The threshold is determined by all applicable detail categories of the design outlined in

AASHTO Table 6.6.1.2.5-3. The applicable detail categories are continuous fillet welds parallelto the direction of applied stress (Category B) and fillet welded connections at diaphragmconnections with welds normal to the direction of stress at (Category C). The flange stressesand detail category thresholds are shown in Table 5.6.

Table 5.6: Fatigue and Fracture Limit State

6. AASHTO Deck Design

The deck thickness and reinforcement were calculated using the traditional designmethod according to AASHTO Article 9.7.3. This method is a flexure based method which takes

into account beam action. Figure 6.1 shows the beam action assumed in the design of theconcrete deck. The loading applied has previously been estimated in Article 4.6.2.1.

Figure 6.1: Assumed Effects of Beam Action on Concrete Decks

Illinois DOT requires a minimum depth of 8 inches which will govern over the AASHTOspecification. This depth is taken without considering the sacrificial thickness on the top of thedeck which allows for future resurfacing. The bridge will require the maximum clearance on

Stress Value UnitsFlange stress, f 5.4 ksi

Stress Limit, Category B 12.0 ksi

Stress Limit, Category C 16.0 ksi


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both surfaces of the deck which is 2.5 inches on the top and 1 inch on the bottom. The transversereinforcement of the slab is to resist positive and negative moment bending. The longitudinalsteel is used for load distribution and temperature and shrinkage. The total top steelreinforcement is required to exceed 0.18 in

2/ft, while the bottom layer requires 50% more steel at

0.27 in2/ft. The bridge deck satisfies all AASHTO and Illinois DOT considerations and is shown

in Figure 6.2 below.

Figure 6.2: Reinforcement Design

In the AASHTO LRFD traditional design method, the characteristics of the deck werefirst determined in order to complete the design. In this design, the compressive strength for theconcrete was assumed to be fc = 3.5 ksi and the yield strength of the steel selected was Fy = 50

ksi. The design thickness of the deck was 8 inches, the minimum thickness as specified by theIllinois DOT. From the design thickness, the unfactored dead loads and moments werecalculated. The unfactored dead loads were calculated using the unit weight of concrete over a 1foot strip and the weight of the future wearing surface. From these factored moments, the area ofsteel required was calculated as well as checks performed for control of cracking, positive andnegative moment bending and minimum and maximum steel reinforcement.

The steel selection passed for positive and negative moments with a nominal momentcapacity of 125.1 k-in. Based on these checks, the design of transverse steel reinforcement fornegative moment at the top of the deck was selected as 10 inch center-to-center spacing. The useof 12 inch center-to-center spacing for positive moment bending on the bottom of the deck wasdetermined to be adequate.

Transverse steel was selected and checked using the previous procedure. Thelongitudinal steel was selected to ensure that it would be sufficient for temperature and shrinkagereinforcement. Number 6 bars at 12 inch center-to-center spacing were selected as an adequateamount of steel in the direction parallel to traffic.


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7. Abutment and Shear Stud Design

The abutments support the ends of the bridge superstructure and transmit loads to thesubstructure. Steel HP 12x53 piles were selected for this bridge project and offer a 50 ton perpile capacity at each girder end. Integral abutments can be used in structures with straightalignment and a maximum of 300 foot span length to accommodate for temperature expansionand shrinkage effects. The basic design of an integral abutment is shown in Figure 7.1.

Figure 7.1: Abutment Detail

Shear stud design is essential to the composite behavior of the bridge deck and girders.The shear studs allow for a more efficient structure, once the concrete has hardened andcomposite action is achieved. As shown in Figure 7.2, two rows of studs will line each girder inthe system.

Figure 7.2: Shear Stud DetailThe shear studs are 0.75 inches in diameter and have 1 inch clearance on each side of the

flange. Fatigue and strength parameters were checked to ensure proper performance of thesystem. The fatigue check takes into consideration truck traffic flow over the bridge. The 5girder system shear stud design meets all AASHTO requirements, and can be assumed to be acomposite system. The fatigue check governs, and the shear stud spacing will be 4.5 in. alongthe top flange.

Steel girder

Shear studs Deck slab

bE


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8. Cost Analysis and Efficiency

Three bridge systems were analyzed for this highway bridge project. They were 4, 5, and6 plate girder structures. In the cost analysis, values of $1.50 per pound for structural steel, $1.00per pound for reinforcement, and $750.00 per cubic yard for concrete were used. The total costsare shown in the figure below. The 5 girder system was selected based on the lowest overall costof the structures materials.

Figure 8.1: Cost Comparison

The selected structures design criteria efficiency can be seen in Table 8.1. It is mosteconomical to have girders with the least amount of structural steel, which can be accomplishedby having efficiencies as close to 1 as possible. The Service II limit state governed with a 0.985efficiency. This was as efficient a design as possible due to manufacturing restrictions on weband flange dimensions. Cross Section and Constructability local buckling and lateral torsionalbuckling were also highly efficient with the 5 girder design.

Table 8.1: Efficiency of 5 Girder Design

Cross Section Dmin/D 0.905

Service I max/all 0.763

Service II f f/.95Fy 0.985

Strength I Moment Mu/Mn 0.846

Strength I Shear Vu/Vn 0.442

Constructability Yield fbu/Fyc 0.754

Constructability LB & LTB fbu/Fnc 0.924

Fatigue f/F 0.450

Efficiency


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9. Summary

The US Route 67 Corridor Project is designed to increase safe traffic flow in Illinois andconsists of several new alignments which require safe, efficient, and cost-effective designs. Allaspects of the Witt Mill Road overpass, part of the Jerseyville Bypass portion of the project,

including plate girder size and spacing, concrete slab and reinforcement, abutment, and shearstud designs, meet the applicable AASHTO and Illinois DOT requirements. The 5 girder systemwas selected based on its efficiency and cost-effectiveness at a superstructure cost ofapproximately $476,000. This submission represents a summary of a full design reportconsisting of full calculations, tables and figures, construction drawings and 3D renderings of thebridge.

List of Variables

As = area of steel required for deck reinforcement (in2)

bf = width of flange (in)

D = depth of web (in)Dtotal = total depth of section, including girder height and slab thickness (in)

Dp = depth from top of section to plastic neutral axis

DC = structural components of dead load (composite and noncomposite elements)

DW = wearing surface and utilities components of dead load

fbu = maximum nominal flange strength (ksi)

Fnc = allowable flange stress for local/lateral torsional buckling (ksi)

Fyc = allowable flange yield stress (ksi)

FWS = weight of future wearing surface (psf)

Iyc = moment of inertia of compression (top) flange (in3)

Iyt = moment of inertia of tension (bottom) flange (in3)

Kg = moment distribution factor

L = span length (ft)

LL+IM = live loads plus impact factor

Mn, Mu = nominal moment capacity and factored Strength I moment, respectively

(kip-ft)

s = girder spacing (ft)

t = slab thickness (in)

tf, tw = thickness of flange and web, respectively (in)

Vn, Vu = nominal shear capacity and factored Strength I shear, respectively (kip)w = roadway width (ft)

wc, wf, wp, ws = linear weight of concrete, fencing, parapets, and steel, respectively (kip/ft)

f = fatigue flange stress (ksi)

F = flange stress threshold (ksi)

f = strength reduction factor

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