bridge 4930 – scoping study...bridge 4930 scoping study phase 1 – final report december 18, 2009...

BRIDGE 4930 – SCOPING STUDY Trunk Highway 99 over the Minnesota River at St. Peter, Minnesota FINAL – PHASE 1 REPORT Data Collection Project Design Criteria DECEMBER 18, 2009 Prepared by Olson & Nesvold Engineers, P.S.C. and Mead & Hunt, Inc.

Bridge 4930 Scoping Study Phase 1 – Final Report

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TABLE OF CONTENTS A. Introduction to the Feasibility Study ........................................................... 3 B. Purpose and Approach of Phase 1 .............................................................. 8 C. Rehabilitation Project Design Criteria Topic Areas ......................................... 8 D. Mn/DOT 2006 Historic Bridge Management Plan ........................................ 10 E. Bridge 4930 Records ............................................................................. 14 i. Bridge Timeline ............................................................................... 14 ii. Notable Items Found in the Bridge Records ......................................... 14 F. Findings from Meetings / Phone Calls ....................................................... 17 i. Kick-off Meeting at District 7 [8-10-09] .............................................. 17 ii. Chapter 152 Discussion at the Bridge Office [8-24-09] .......................... 17 iii. FHWA Meeting at Central Office [8-31-09] .......................................... 18 iv. Bridge Hydraulics Group Meeting [9-11-09] ......................................... 19 v. District 7 Conversations .................................................................... 20 G. Field Observations ................................................................................. 21 i. Snooper Observations and Photographs .............................................. 21 ii. Ground Observations, Measurements, and Photographs ........................ 28 H. Construction Specialist Observations ........................................................ 30 I. Rehabilitation Project – Design Criteria Findings ........................................ 32 J. Historian Commentary and Discussion: Secretary of the Interior’s Standards . 32 K. Summary ............................................................................................. 34 Appendix A - Definitions of Structurally Deficient and Functionally Obsolete ........ 36 Appendix B. 2006 Saint Peter Trail Plan ........................................................ 37 Appendix C. Secretary of the Interior’s Standards........................................... 38 Appendix D. Conceptual Redundancy Approaches and Notes ............................ 41


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A. Introduction to the Feasibility Study

The Broadway Bridge (Bridge 4930) has served the St. Peter community for over 70 years. It is a through truss bridge that carries Trunk Highway 99 over the Minnesota River. The Broadway Bridge is listed in the National Register of Historic Places and is located near the St. Peter Commercial Historic District, which also is listed in the National Register. As a result of the National Register listing and because the project is expected to receive federal funding, it will be subject to Section 106 of the National Historic Preservation Act of 1966 (as amended).

In 2006, Mn/DOT completed a Historic Bridge Management Plan (HBMP) for the Broadway Bridge. The HBMP was prepared because Bridge 4930 is one of 24 historic bridges identified by Mn/DOT for historic preservation1 by the State. Preservation of these bridges was subsequently formalized in the 2008 Programmatic Agreement (PA) between the Federal Highway Administration (FHWA), the State Historic Preservation Office (SHPO), and the Advisory Council on Historic Preservation, with Mn/DOT and the U.S. Army Corps of Engineers as invited signatories. In the PA, Mn/DOT committed to both preserving and maintaining the identified state-owned eligible bridges according to the stabilization, preservation, and maintenance items specified in the management plans. In addition, the PA mandates that the Secretary of the Interior’s Standards (SOIS) for the Treatment of Historic Properties will be used to determine whether work on any bridge would constitute an adverse effect. These provisions apply to projects receiving FHWA funding. Since the completion of the HBMP in 2006, new or updated policies and inspection information have affected or changed some of its findings and recommendations. This updated information is included in the findings in this report. A significant post-HBMP event is the action of the Minnesota Legislature regarding State Statute Chapter 152. In 2008, the Minnesota Legislature updated State Statute Chapter 152 requiring that Mn/DOT address fracture critical bridges on the trunk highway system by repairing or replacing them with a load-path redundant structure. The Broadway Bridge is a fracture critical bridge (not load-path redundant). It is in need of repair and at the onset of the Study, Mn/DOT intended to use the rehabilitation project as an opportunity to address its fracture critical nature. The objective of this report is to document the findings of Phase 1 of the Feasibility Study. It includes how the findings support or conflict with the HBMP and steps necessary to determine the feasibility for different strategies for keeping the bridge on the trunk highway system for a 75-year design life as well as a 20-year fix. The report also summarizes findings regarding waterway

1 In this report, the phrase “historic preservation” will be used to indicate the use of the term “preservation” in a historic or cultural resource context. Where the term “preservation” is used alone, it usually will indicate use of the term in an engineering context.


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opening, traffic concerns, and maintenance issues. This report includes historian commentary and discussion. In addition, decisions will be made to define the scope and cost of work necessary to meet the identified options. This study will be conducted with two or three phases.

Phase 1 – Data Gathering – Project Criteria. Phase 2 – Assessment of the feasibility of meeting project goals with

Bridge 4930 maintained at its current location Phase 3 – Assessment of the feasibility of meeting project goals with

Bridge 4930 Relocated Phase 3 may or may not be executed. A decision to move forward with Phase 3 will be made by Mn/DOT after Phase 2 findings are documented. This study will be performed in coordination and collaboration with Mn/DOT District 7, the Mn/DOT Bridge Office, Mn/DOT’s Cultural Resources Unit, SHPO, and Mn/DOT’s engineering and historical consultants. Significant Project Considerations:

Historic Preservation and Rehabilitation o Appropriately preserve Bridge 4930 in accordance with the 2006

Historic Bridge Management Plan and the Programmatic Agreement.

o Paint Superstructure (existing paint system is lead-based) o Increase load capacity of the bridge o The bridge deck will need rehabilitation within 20 years o The abutments and pier are currently in need of rehabilitation o The deck width of the existing bridge is deficient with respect to

Mn/DOT Standards Chapter 152 and Fracture Critical Bridges

o Comply with Chapter 152 updates to the Minnesota State Statutes Hydraulic Improvements

o Consider the hydraulic issues on a regional basis instead of a localized bridge basis (Potentially improve Minnesota River hydraulics at Trunk Highway 22. Potentially improve hydraulics in the vicinity of Trunk Highway 99 and thereby allow Trunk Highway 22 to stay in service for a less frequent flood event.)

o Reduce the potential for damage to Bridge 4930 from debris flowing downstream during flood events.

o Maintain appropriate sight distances for traffic on Trunk Highway 99 for any improvements that raise Bridge 4930.

Operational Issues o Limit exposure to anti-icing chemicals.

Environmental Issues o Prevent spills from going directly into river.

Geometric Characteristics: The primary geometric characteristics of Bridge 4930 are presented in two figures. Exhibit 1 contains the General Plan and General Elevation views.


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Exhibit 2 contains the transverse sections of the bridge.


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B. Purpose and Approach of Phase 1

The purpose of Phase 1 is to gather information from project stakeholders and technical specialists to define the constraints or project criteria that will guide Phase 2. Phase 2 will evaluate options to maintain the bridge at its current location. Phase 1 tasks include stakeholder meetings, field work, and the review of bridge records maintained by Mn/DOT. In addition to a kick-off meeting, Phase 1 included a meeting with the Mn/DOT Bridge Office to discuss the ramifications to the project associated with updates to State Statutes Chapter 152, a meeting with the FHWA to document FHWA’s guidance on the redundancy improvements to a truss bridge, a meeting with Mn/DOT Bridge and District Office Hydraulics Personnel, and a meeting to obtain input from District 7. In addition, the project engineers, the consultant historians, and the project’s constructability consultant conducted field work.

C. Rehabilitation Project Design Criteria Topic Areas The rehabilitation of bridges in Minnesota is typically guided by the Mn/DOT Bridge Office Document, “Bridge Preservation, Improvement and Replacement Guidelines for Fiscal Year 2006 through 2008” (PIRG). This document identifies characteristics of bridges that are suitable for preservation projects, suitable for improvement projects, and suitable for replacement. In the existing Bridge Preservation, Improvement and Replacement Guidelines, relatively minor projects such as bridge painting, expansion joint work, bridge deck overlays, railing work, partial deck replacement, and minor superstructure and substructure repairs are considered preservation activities. Larger and more extensive projects are considered improvement projects. They are expected to address deteriorated components and improve the geometrics and load-carrying capacity of the bridge. Based on the existing guidelines, the original scope for this project is considered an improvement type project. After an improvement project is completed, a bridge is expected to satisfy a set of functional criteria. The criteria for bridge improvements are:


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Criteria Category

Mn/DOT Standard

Bridge 4930 Characteristics

Comments

Load Rating Inventory Values: minimum HS18, desired HS 20

Inventory Rating is HS14.2

Controlled by interior floor beam capacity

Vertical Clearance

Minimum 14.5 ft., desired 16.0 ft.

Vertical clearance is 15.6 feet

Lateral Under clearance

N/A N/A No roadway beneath the bridge

Scour Criticality Required scour prevention methods are in place

West bank of the river stabilized after the 1997 flood event.

Deck Roadway Width

Trunk Highway with 2 lanes and ADT > 5001: Minimum 38 ft., desired 44 ft.

Deck width is 30 ft. Does not satisfy Mn/DOT criteria. Not considered functionally obsolete by the FHWA

Steel Superstructure

N/A N/A Not constructed with welded members, components, or connections

Type of Railing and End Post

Meets Mn/DOT’s Railing Policy presented in the PIRG document.

Assumed to satisfy Item 2-c in the policy

Railing is acceptable by Bridge Office. Ends of Rail and any compression members of the truss must be scrutinized under the effect of crash loads.

Superstructure Condition

No more than 10% in the 2nd lowest Pontis Condition State for the superstructure. No portion in the lowest Pontis Condition State.

Element 121–Truss Bottom- 5.5% CS 4, 0% CS 5 Element 126–Truss Top-8.2% CS 4, 0% CS 5 Element 152–Floor Beam-7.8% CS 4, 0% CS 5

Steel superstructure elements have five condition states. No more than 10% can be in Condition State 4. No portion can be in Condition State 5. Several components near 10% threshold for Bridge 4930.

Substructure No more than 10% in the 2nd lowest Pontis Condition State for the substructure. No portion in the lowest Pontis Condition State.

Element 210-Pier-28% CS 3, 0% CS 4 Element 215-Abutment- 94% CS 3, 6% CS 4

Concrete substructure elements have four condition states. No more than 10% can be in Condition State 3. No portion can be in Condition State 4. Both elements do not meet the criteria for Bridge 4930.

Culvert N/A N/A Deck Condition Deck must be in

Pontis Condition State 1, 2, or 3

Element 26-Deck in CS 3

Entire deck is placed in one condition state by Mn/DOT policy. Currently the deck for Bridge 4930 is placed in the lowest acceptable condition state


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In addition to the standard criteria for bridge improvement projects listed above, the project must satisfy Section 106 requirements and Chapter 152 requirements as discussed in this report.

D. Mn/DOT 2006 Historic Bridge Management Plan In 2006 Mn/DOT prepared a Historic Bridge Management Plan (HBMP) for Bridge 4930.2 The HBMP is part of Mn/DOT’s ongoing efforts to manage historic bridges in compliance with Section 106, including the selection of Bridge 4930 as one of 24 state-owned historic bridges identified by Mn/DOT for historic preservation. The HBMP utilized both engineering and historical data and evaluation to recommend a long-term preservation option from the five options under consideration. For Bridge 4930, option 1, rehabilitation for continued vehicular use on-site, was considered feasible and was recommended for future use. The HBMP followed the overall recommendation with additional treatment recommendations intended to guide efforts deemed necessary to achieve the overall recommendation. The treatment recommendations are categorized as Stabilization Activities, Preservation Activities, and Maintenance Activities. All recommendations, as presented in the HBMP, were determined to be in compliance with SOIS and if followed would receive a finding by Mn/DOT CRU of “no adverse effect” to the historic bridge as part of the Section 106 review process. The HBMP’s section on historical data includes a significance statement summarizing the reasons for Bridge 4930’s listing in the National Register. Following the significance statement is a list of character-defining features that make a connection between the significance statement and the bridge structure. The character-defining features provide important information to be used in the development of treatment methods for any rehabilitation, repair, and maintenance efforts. As noted above in Section A, Introduction to the Feasibility Study, information and events since the HBMP was completed in 2006 may have affected the Plan’s recommendations and the feasibility of their implementation. The statement of historical significance and the identification of character-defining features remain unaffected, as does the fundamental requirement that all work on Bridge 4390 be in compliance with SOIS. Significance Statement (excerpt) [Bridge 4930]… is 402 feet in length, consisting of two, rigid-connected, Pennsylvania, through-truss spans on a concrete substructure. The spans display conventional, built-up detailing -- two laced channel sections with cover plate in the upper chord, two laced channel sections in the lower chord, and four laced angle

2 Minnesota Department of Transportation, “Historic Bridge Management Plan, Bridge Number: 4930,” June 2006. Copy available from Mn/DOT CRU.



sections in the vertical and diagonal members. The bridge's overall design, however, is unconventional, largely because the current of the Minnesota River twists in mid-channel at the site. This hydraulic peculiarity dictated the construction of a skewed pier, so as to offer the least resistance to the flow of the water. Because of the oblique placement of the pier, the two truss spans required a skewed configuration at the end supported by the pier. This goal was achieved by designing each span with truss webs of unequal length and slightly different profile. In the west span, the north web is a ten-panel, 195-foot truss with inclined endposts at each end, while the south web is a nine-panel, 176-foot truss with an inclined endpost at the abutment and a vertical endpost at the pier. In the east span, the situation is exactly reversed. Although the east and west spans are structurally independent of each other, they are visually integrated by an ornamental linkage that joins their top chords together over the pier. Because of the linkage, the two spans appear to be part of a single, continuous truss, when they are in fact two, simply supported trusses. The Broadway Bridge has a concrete deck with a 30-foot roadway. Outside the truss web on the south side, there is a sidewalk supported on metal brackets cantilevered from the bridge's flooring system. An ornamental, metal, lattice-work railing borders the sidewalk on the river side. The bridge also has an ornamental lighting system, consisting of four metal light standards, positioned on concrete posts at the four corners of the crossing. The light standards are detailed in the Classical Revival Style, with fluting on the shaft and consoles at the base. In the mid-1960s, the state highway department raised the bridge's portals and overhead sway bracing to provide greater vertical clearance for traffic. The remodeling retained the original configuration of the features and did not significantly affect the bridge's historical integrity. The Broadway Bridge is eligible for the National Register under Criterion C in the area of engineering, within the historic context of "Iron and Steel Bridges in Minnesota." The Multiple Property Documentation Form (MPDF) associated with this context states, in Registration Criterion 12, that a bridge may eligible under Criterion C if it "exhibits exceptional engineering skill to meet unusual site conditions." With its skewed, through-truss design, the Broadway Bridge satisfies this criterion. The Broadway Bridge is also eligible under Criterion C for its high aesthetic qualities, as provided for by the MPDF in Registration Criterion 11. Character-Defining Features Character-defining features are prominent or distinctive aspects, qualities, or characteristics of a historic property that contribute significantly to its physical character. Features may include materials, engineering design, and structural and decorative details. While all historic fabric of the bridge should be treated in compliance with the SOIS, character-defining-features are the most important components of the bridge to consider when planning rehabilitation treatments. The character-defining-features of Bridge 4930 identified in the HBMP are:



Feature 1. Truss design for unusual site conditions. Because the river pier is skewed while the abutments are not, the east and west spans have unequal truss lengths and panel configurations. To avoid an irregular design situation at the skewed pier, false members were added to the trusses to create an overall configuration suggesting a continuous through-truss superstructure. This feature includes the Pennsylvania through-truss superstructure with the false members.

Figure 1 – Feature 1, south elevation of bridge, showing overall design, truss configuration, and setting.

Figure 2 – Feature 1, detail of skewed pier with single set of bearings.



During the field visit, it was observed that a single common bearing for the trusses of both spans is used at the center pier. Also observed was a lower chord member that is continuous across the trusses of both spans (See Figure 6). These elements (single bearing and continuous lower chord) should be considered part of character-defining Feature 1. Feature 2. Ornamental elements. Because Bridge 4930 was designed as a gateway to the city of St. Peter, it received an aesthetic treatment that includes ornamental metal railings and light standards (see Figure 3), and Classical Revival detailing on concrete railing posts and abutments.

Figure 3 – Feature 2, detail of ornamental light and railing



E. Bridge 4930 Records

Records, drawings, and photos pertaining to Bridge 4930 were received and reviewed from several sources. The sources include Mn/DOT District 7, the Bridge Office, and SHPO.

i. Bridge Timeline The bridge was constructed in 1931. In 1966 the portals were modified to improve the vertical clearance. In 1982 the deck was completely replaced. The last full paint job the bridge received was in 1986. Over the years there have been repairs made to the substructure components, there have been bridge hit repairs, and there have been scour repairs. In 2006, the historic bridge management plan was assembled. In 2008, a CRAVE (Cost Risk Assessment + Value Engineering) study was conducted. Also in 2008 a load rating analysis and gusset plate evaluation was conducted. In 2008, the State Legislature enacted Chapter 152, a statute that mandates all fracture critical bridges in Minnesota be addressed by 2018. On August 11, 2008, the City of St. Peter passed a resolution to take complete ownership of the entire bridge, should relocation become the most favorable option to preserve the bridge. Most recently, in 2009 a minor painting and sealing project for below deck elements was let and performed. The 2009 contract also included repairs and painting to selected gusset plates. Available data indicates that the bridge has been closed due to high water in 1993, 1997, and 2001. The District has been diligent with maintenance work on the bridge. Examples of this diligence include: the repair of concrete cracks with sealers, the repair of spalls under the bearings at both abutments, and the practice of annually flushing the bridge with water to remove debris.

ii. Notable Items Found in the Bridge Records

May 2008 Fracture Critical Inspection Report – Findings Summary The paint system is failing with areas flaking and peeling on the trusses and floor system exposing the base metal and allowing surface corrosion to form. Pack rust is active in the lower connections, particularly on the lower chord. Panel point connections to all truss members and the floor beams have pack rust ranging from minor to ¾ inches thick. Distortion of the lower chord lattice and batten plates and the floor beam connection is typical. Ultrasonic testing of the most severe areas resulted in calculated loss up to 45% with the average loss for a particular area of 20% or less. NBI condition codes for the Deck, Superstructure, Substructure, and Channel were all recommended to be a 5 (Fair Condition). Summary Statement: The presence of pack rust is a concern for any redundancy retrofit details. The Bridge Office is averse to covering up components with corrosion. Localized section loss values are significant. The NBI condition codes are on the verge of classifying the structure as



structurally deficient. An NBI condition code of 4 is required to satisfy the structurally deficient criteria.

2008 Load Rating and Gusset Plate Findings

Overall, the controlling element is an interior floor beam with an inventory rating of HS 14.2 and an operating rating of HS 23.6. The upper chord controlling member is U2U3 with an operating rating of HS 38.6 (5% assumed section loss). The upper chord gusset plates have an operating rating of HS30.0 (5% assumed section loss) The lower chord controlling member is L13L15 with an operating rating of HS 44.6 (15% assumed section loss). The lower chord gusset plates have an operating rating of HS 38.6 (25% assumed section loss). Overall, the controlling truss member is M5L5 with an inventory rating of HS21 and a operating rating of HS38.6 (5% assumed section loss) Summary Statement: The load capacity of the bridge does not satisfy the improvement criteria where a minimum value of HS18 Inventory is required. The controlling members for the load rating are the interior floor beams. The capacity of the primary truss members and gusset plates easily satisfies the load capacity criteria for improvement projects. Consequently, retrofit work required to bring the bridge in compliance with the improvement guidelines is likely limited to the floor beams.

Geology Memo of January 1998

After the 1997 flood event, several areas of the west bank of the river below the west abutment were noted to be scoured. The four mitigation strategies identified in the memo to address the scoured regions included:

Placing forms over the bedrock and injecting or pouring a concrete wall, similar to the existing wall. This wall would incorporate the outfall structure and the rock in area 4, 2) Placing rock anchors and mesh in the areas of eroded bedrock and covering with shotcrete, 3) Place concrete in the areas of the voids only (smaller scale than No. 1) and protect other areas with high quality riprap(such as granite or quartzite), 4) Do nothing, but monitor the scour carefully and be prepared to perform mitigation measures in the future.

It appears that District 7 executed Mitigation Strategy 3 to address the scoured regions.

Bridge Scour Evaluation of 1993

The analysis results indicate that Bridge 4930 should not have a serious scour problem in the channel. Trunk Highway 99 will overtop east of the



bridge between the 50 and 100 year flood (it should be noted that current hydraulic modeling indicates that Trunk Highway 99 will overtop with an event between a 10 year and 50 year flood event). Road overtopping is dependent on the condition of the overbank vegetation (heavy foliage creates higher river stage during flooding), and on maintenance of the upstream dikes during flooding. Because the majority of the flood flow passes through the bridge opening for all of the analyzed floods, it was assumed that the 500-year flood would be the critical event. Using the procedures in HEC-18, five feet of contraction scour and 12 feet of pier scour are predicted for the 500-year discharge, exposing less than half of the embedded pile length. The scour analysis did not consider the effects of pressure flow, which could increase the depth of scour. Significant abutment scour is predicted for the 500-year flood, especially at the east abutment. However, most of this scour should not occur, because the west abutment is constructed on bedrock and the east abutment is protected by a levee.

2008 CRAVE Report

The CRAVE Report identified several items that could impact a rehabilitation project including: contaminated property on the west side of the river, the potential to impact threatened or endangered species, the UP railroad line east of the bridge, utilities, staging areas, foundations, floodplains and profile grade constraints on the west end of the bridge near Front Street. The CRAVE Report estimated project costs could range anywhere between $3 and $50 million.

Miscellaneous Items from the General Files

The first bridge at the site, replaced by Bridge 4390, had a 260-foot swing span and a 100-foot approach span. The swing span pier was located 43 feet west and 10 feet south of the centerline of the existing pier and had a diameter of 30 feet. The earlier east pier was 34 feet wide and 9 feet long. Design sketches contained in the file for the 1931 bridge indicate that the rock or refusal elevations for the current substructure units are approximately 751 for the west abutment, 680-688 for the center pier, and 675-680 for the east abutment. The construction cofferdam for the current bridge’s pier called for 2 feet of free board, 22 feet of water in the channel, and a 2 foot toe. The design of Bridge 4930 assumed that the river’s low water elevation was 732.2 and that ice goes out at elevation 749.7 Summary Statement: It is likely that the foundation for the prior bridge’s center pier is still located below the current mudline. Pier retrofit activities should consider this potential obstacle in the river bed. Refusal elevations should provide approximate depths to found any temporary



piling used to support the bridge during raising or moving operations.

F. Findings from Meetings / Phone Calls

i. Kick-off Meeting at District 7 [8-10-09] Items from the meeting minutes pertinent to rehabilitation design criteria include: The elevation of the Mill Pond Park road was set at the 100 year flood elevation. Utilities located on or near the bridge include: electrical, gas, water, sanitary, storm sewer, and telecommunications. It will be necessary to continue to accommodate existing and future utilities along or on the bridge.

ii. Chapter 152 Discussion at the Bridge Office [8-24-09] Items from the meeting minutes pertinent to rehabilitation design criteria include: The Hastings bridge proposals recommended adding new members of substantial size and quantity to the bridge to provide load-path redundancy. These treatments were determined by Mn/DOT CRU and SHPO to constitute an adverse effect because they were not in compliance with SOIS in the Section 106 process. Simply plating members does not provide external load-path redundancy. Plating may provide a level of internal redundancy that would need to be confirmed with detailed structural analysis. Strategies used to develop load path redundancy need to address concerns about locked-in corrosion and distortional fatigue. The Bridge Office helped the Office of Investment Management and Performance Measures prepare the first “Trunk Highway Bridge Improvement Program – Chapter 152” Report on January 15, 2009.

The report identified Bridge 4930 as a Tier 2 bridge, that is not structurally deficient, not functionally obsolete, and with a sufficiency rating of 56.0 (the current inventory report lists the bridge with a sufficiency rating of 47.1, which classifies it as Tier 1). It was identified as having a total project cost of $43.2-$58.5 million, with construction planned for 2013-2014. The Chapter 152 work planned was identified as either rehabilitation or replacement. It was identified as a Major Bridge and a Historic Bridge. It was noted that the DOT is currently studying rehabilitation vs. replacement.

O.N.E. offered to provide follow up material to the Bridge Office



concerning load-path strategies for the St. Peter Bridge. A document was sent to the Bridge Office on September 8th. Open questions with respect to load-path redundancy requirements include: 1. Does load-path redundancy need to be provided for the floor beams or

can the connection with composite stringers and direct bearing on the lower chords provide adequate redundancy?

2. Does redundancy need to be provided for the diaphragm plates in the truss verticals at the height of the floor beams?

3. Can riveted multi-element truss members be considered redundant if they demonstrate adequate capacity with any one member severed?

4. Can truss member splices composed of multiple plates be considered redundant if their capacity is evaluated with at least one plate failed?

5. Is it preferred that supplementary members be active load carrying components or is it preferred that they only be engaged during an extreme event?

6. How much capacity should the structure have in the “extreme event” condition? What load factors and load combinations should be used to evaluate a bridge? Should the evaluation be conducted with use of the “striped” lanes on the bridge?

7. Will the Bridge Office require that compression members be load-path redundant?

8. Are there deflection limits that define what an acceptable level is for an extreme event? Such a criteria would impact the design of any “catcher” type redundancy system.

iii. FHWA Meeting at Central Office [8-31-09] Items from the meeting minutes pertinent to rehabilitation design criteria include: The bridge is currently not considered deficient according to FHWA criteria. (See Appendix A for the criteria used to classify a bridge as structurally deficient or functionally obsolete. Also presented in Appendix A are the corresponding NBI Item values for Bridge 4930). While many engineers prefer redundant bridges, the FHWA does not require bridges to be load-path redundant. Simply making a fracture-critical bridge load-path redundant is not an adequate purpose and need to utilize FHWA funding for rehabilitation work specific to adding redundancy. Federal funding for rehabilitation could be used towards items such as painting, deck repairs, etc. but only if the bridge is classified as deficient (Structurally Deficient or Functionally Obsolete, it is neither at this time) and a sufficiency rating less than or equal to 80 (which is the current case). Funding was discussed at great length. Federal dollars that would be used toward relocation of the bridge are limited to the cost of demolition and to be eligible for the monies, the bridge would need to be deficient



and have a sufficiency rating less than 50. The bridge currently is not deficient but has a sufficiency rating of 47.1.

iv. Bridge Hydraulics Group Meeting [9-11-09] Bridge Office and O.N.E. personnel met at the Bridge Office on September 11th to discuss hydraulic issues associated with rehabilitating the bridge on site. Items discussed that are pertinent to the rehabilitation design criteria include: Past project conversations have considered adding jump spans to the east end of the bridge. Adding jump spans is still an option as it provides a hydraulic benefit when utilized in conjunction with road embankment removal and/or stream widening. The bridge is currently located in the middle of a river constriction. Adding a jump span and widening the constriction downstream increases the conveyance in that stream section and lowers the water surface profile. Note that stream widening would result in the moving and reconstruction of river berms and levees. Reconstructing levees and stream widening will require extensive regulatory coordination and approval. Further modeling is needed to determine the extents of the hydraulic benefits and surrounding impacts. One of the primary hydraulic concerns is to raise the bridge to protect it from debris striking the bridge and compromising it. Another benefit of raising it is to increase the effective opening under the bridge. During a 10-year event the east approach roadway is not underwater. During a 50-year event it is underwater. The lower chord of the bridge is at elevation 755.9. The 50-year flood event elevation is 756.6. East of the bridge on Trunk Highway 99, the roadway over tops at elevation 756.1 which is at a flood interval of around 25 year frequency. This suggests the bridge would need to be raised several feet to provide the appropriate clearance for the 100-year flood event. The elevation of the lower chord should be no lower than 759.8. The 100-year event has a flow of 92,000 CFS. It should be noted that this clearance requirement is less stringent than that required by the DNR for new structures (50-year event + 3 feet for navigation (if it can reasonably be accommodated)). Should the bridge be relocated upstream it would likely need to be raised an additional 2 feet to satisfy the DNR requirement. Recent mapping of the stream bottom indicates that the bottom of the channel has an elevation of 710-712. Just downstream from the bridge on the west side of the stream the bottom of the channel drops to approximately elevation 707.



The Minnesota River is considered flashy and has a high sediment load (the flow in a flashy river significantly increases shortly after the onset of a rain event, and quickly returns to pre-rain conditions shortly after the rain event concludes). Many contractors have learned that the Minnesota River can be a difficult river in which to work. The best times to work in the river would be between September 15th and March 1st. New structures (excluding piers) would need to span the entire floodway and touchdown in the flood plain. A collection of sacrificial steel soldier piling might be considered as an alternate means to catch debris (e.g. large cottonwood trees) and potentially as a means to leave the bridge at its current elevation. It is uncertain if this approach is viable at this location due to navigational concerns.

v. District 7 Conversations District Bridge personnel expressed concern to the project team of large cottonwood trees floating downstream during a flood event and taking out the bridge. A review of recent accident data in the vicinity of the bridge does not indicate that the bridge is an unusual safety hazard to vehicular traffic. Four accidents are reported over the past 5.5 years. Driver inattention, a deer, and unsafe speeds were cited as factors associated with the accidents. The Inventory Report lists the 2004 ADT for the bridge as 7,000 and HCADT as 630. District 7 has indicated that 2% should be used as an annual traffic growth factor. The 20 year traffic forecast is completed as of October 27, 2009. This report projects an AADT of 7500 and HCADT of 440 in 2014, in 2034 an AADT of 9900 and HCADT of 590. St. Peter has incorporated Bridge 4930 into the regional bike path. In the 2008 Saint Peter Comprehensive Plan, Saint Peter anticipates a bicycle trail to circumnavigate the majority of the city as well as connect to the Sakatah Trail near Mankato. The 2006 Trail Plan is included in Appendix B.



G. Field Observations

i. Snooper Observations and Photographs Field Observations were collected September 1 and 2, 2009. District 7 provided traffic control while a Paxton Mitchell Snooper Unit was used to access below deck components of the bridge (See Figure 4). The primary purpose of the below deck observations was to identify issues associated with raising and/or relocating the bridge.

Figure 4 - Below Deck Access with a Snooper



Evidence of the 2009 painting and sealing contract work at the ends of the floor beams was apparent (See Figure 5).

Figure 5 - 2009 Paint and Sealing Work



Figure 6 shows the details of the truss over the pier. The use of a single bearing at the pier and the continuous bottom chord member over the bearing will complicate raising and/or relocating activities. Also evident in Figure 6 is localized damage to a sidewalk bracket and the lower chord from debris impact during flood events.

Figure 6 - Truss Details at the Pier



Figure 7 shows a typical splice for the lower chord. It should be noted that the splice is not integral with primary truss gusset plate connections and that each of the lower chord members spans two panel points.

Figure 7 - Lower chord splices are Adjacent to Truss Panel Points

SPLICE

TRUSS PANEL POINT



Typical details of the stringer to floor beam connections are provided in Figure 8. The use of stringers with the top flange of the stringers at the same elevation as the floor beam results in a very compact floor system.

Figure 8 - Stringer to Floor Beam Details

FLOOR BEAM

STRINGERS



Figure 9 shows the utilities carried under the sidewalk on the south or upstream side of the bridge.

Figure 9 - Utilities Carried under the Sidewalk on the South Side of the Bridge



Figure 10 shows the gas line carried on the north side of the bridge adjacent to the lower chord.

Figure 10 - Gas Line carried on the North Side of the Bridge

GAS LINE



ii. Ground Observations, Measurements, and Photographs

Several types of observations were made from the ground. General observations were made of the truss verticals, diagonals, upper chords, end posts, portals, and sway bracing. In general the upper truss components were in fair condition with paint failure common. Minor distortions associated with traffic hits were evident at the portals and a couple sway frames (See Figure 11).

Figure 11 - Bent Sway Frame from Traffic Hit Dozens of thickness measurements were taken of steel elements of the south truss to generally confirm that the sections presented in the 1931 plans were actually used to construct the bridge. The thickness measurements collected confirmed the 1931 plan sections.

DISTORTION



The storm sewer outlet on the west bank appears to have an alignment that carries it directly below the north truss bearing at the west abutment. This alignment may complicate any jacking operations for the bridge and may depend on the integrity of the rock above the storm sewer (See Figure 12). In 2009 this outlet was taken out of service as a major outlet by a Minnesota/TH 169 cooperative City/State roadway project. Only minor unknown/groundwater flows use it now.

Figure 12 - Storm Sewer Alignment

STORM SEWER OUTLET



Concrete components, railing components, and light standards at the abutments display significant deterioration (See Figure 13).

Figure 13 - Deterioration of Components NE Bridge Corner

H. Construction Specialist Observations On September 2, 2009, Jack Sehlin with A.A. Sehlin Consultants reviewed the bridge in the field with Steve Olson. A.A. Sehlin is a subconsultant to O.N.E. The lower chord continuity and the single bearing at the pier significantly complicate raising or moving the bridge. It cannot easily be moved or raised as a pair of simple spans. Only one of the truss spans would be able to use the pier joint and bearing. The other span would need to be blocked with some form of



temporary shoring. There appear to be two strategies one could use when attempting to move the bridge. The first strategy would be to reverse the original assembly process where all of the field splices and gusset connections are disassembled. The benefits of this approach are: access is provided to all of the connections for inspection and smaller, lighter pieces are handled. The downside to this approach is that it requires more extensive shoring in the river. It will take longer. It is likely to be more expensive. The second strategy to move the bridge would entail severing field connections in a limited number of locations (possibly resulting in just three assemblies) to move fewer pieces. The benefits of this approach are: reduced disassembly of connections, a shorter construction schedule, less shoring in the river, and likely a less expensive endeavor. The downside to this approach include: the use of larger more expensive equipment and the inability to examine all of the field connections as they are disassembled. With respect to raising the bridge, jacking from one substructure at a time would damage the lower chord gusset plate connections at the pier. To prevent damage to the truss at this location, simultaneous jacking would need to be executed at all three substructure locations (both abutments and the pier). The approximate rock characteristics on the west bank of the river (well-cemented sandstone over Jordan sandstone) are visible just downstream from the bridge (See Figure 14).

Figure 14 - Rock Outcropping Just Downstream of the Bridge



I. Rehabilitation Project – Design Criteria Findings Several components of Bridge 4930 are in need of improvement. Inspection findings indicate that both abutments and the pier are in need of improvement. They also indicate that the truss and floor beams are candidates for rehabilitation based on their current condition. The load capacity of the bridge is controlled by the floor beams and would need to be improved as part of any rehabilitation project. With respect to load capacity, the truss, the gusset plates, and the stringers are not in need of significant strengthening to meet minimum load capacity requirements for improvement projects. The deck width of the bridge is deficient and cannot be readily improved to satisfy minimum criteria in the Preservation, Improvement, and Replacement Guidelines. Without a significant accident history at the bridge, with the bridge not considered functionally obsolete according to FHWA criteria and with its appraisal rating of 8 for the approach alignment, pursuit of a bridge design exception for the deficient deck width appears appropriate. The issue of raising the bridge to satisfy hydraulic criteria is based on both protecting the bridge/utilities and keeping Trunk Highway 99 in service longer. The east approach roadway is overtopped prior to reaching a 50-year flood event. The primary safety concern is that large cottonwood trees would travel downstream and strike the bridge and/or create a debris dam during a large flood event. The lower chord of the east span does have member distortions that appear to be due to past flood events. Bridge 4930 is located in a constricted region of the Minnesota River. Hydraulic improvements made to the channel in the constricted region and to the bridge have the potential to improve conditions at Trunk Highway 22 and improve the conditions for Trunk Highway 99. Hydraulic issues should be considered on a regional basis and not simply a bridge basis.

J. Historian Commentary and Discussion: Secretary of the Interior’s Standards Mead & Hunt serves as the project historical consultant under separate contract with Mn/DOT. Bob Frame and Christina Slattery with Mead & Hunt, reviewed the bridge in the field on September 1, 2009. As noted in the introductory section of this report, Bridge 4930 is listed in the National Register of Historic Places and this project is expected to utilize federal funding. As a result, this project is required to comply with Section 106 regulations implementing the National Historic Preservation Act. In addition, and in compliance with the 2008 PA, work on Bridge 4930 should follow recommendations in the HBMP as feasible, considering information and events subsequent to its 2006 publication date and identified in this report. The most important and fundamental requirement common to all these documents is the stipulation that all work on the bridge should be in compliance with SOIS,



particularly the Standards for Rehabilitation, in order to receive a finding of “no adverse effect” from Mn/DOT CRU and SHPO in the Section 106 process. Lack of compliance will result in a finding of “adverse effect,” initiating additional procedures before the project can complete the Section 106 process and proceed. In addition, a finding of “adverse effect” may result in an additional process involving Section 4(f) of the U.S. Department of Transportation Act of 1966. The Secretary of the Interior’s Standards for the Treatment of Historic Properties, herein termed SOIS, are a series of concepts related to maintaining, repairing, and replacing historic materials, as well as designing new additions or altering a historic property. The SOIS are not technical or prescriptive, but are intended to promote responsible historic preservation practices by providing advice and philosophical consistency to the work. The NPS produced and promulgated the SOIS and codified them as 36 CFR Part 68 in the Federal Register (July 12, 1995, Vol. 60, No. 133). In certain cases, such as the Broadway Bridge 4930, the SOIS are regulatory, because it involves the application of Section 106 of the National Historic Preservation Act. Four treatment options are included in the SOIS: Preservation, Rehabilitation, Restoration, and Reconstruction. In the case of the Broadway Bridge, the Standards for Rehabilitation will apply: • Rehabilitation – The act or process of returning a property to a state of utility

and of making possible a compatible use for a property through repair, alterations, and additions which makes possible an efficient contemporary use while preserving those portions or features which convey its historical, cultural, or architectural values.

As noted in the Management Plan, the application of the SOIS to historic bridges may not be clear or obvious, since they were written for buildings more than engineering structures. To aid in understanding and interpreting SOIS, the Virginia Transportation Research Council (VTRC), in its Guidelines for Bridge Maintenance and Rehabilitation Based on the Secretary of the Interior’s Standards, adapted the SOIS to address the special requirements of historic bridges and to identify specific applications to bridges. For regulatory and compliance purposes, the official SOIS govern. Both the official SOIS and the VTRC adaptation are included in Appendix C. In addition to the standards for the rehabilitation work on the bridge, the SOIS for Rehabilitation recommend that historic site features and relationships between the structure and the landscape be maintained. Any proposed changes to “distinctive materials, features, spaces, and spatial relationships” should be minimal. In the Section 106 process, Mn/DOT CRU will review and approve any bridge rehabilitation and/or relocation plans for compliance with Section 106 and the SOIS. CRU will submit the plans to the SHPO for their review and concurrence that the project has complied with Section 106 and the SOIS.



The field review of the bridge for this project confirmed the findings in the 2006 HBMP and the elements identified as character-defining features. In particular, the field review resulted in additional design and construction details that supplement character-defining Feature 1, the truss design for unusual site conditions.

K. Summary

The past maintenance efforts of District 7 have been proactive and have paid dividends. Bridge 4930 is in fair condition which is excellent for a 78 year-old bridge. Preservation and Rehabilitation Preservation of Bridge 4930 must be in accordance with the 2008 Programmatic Agreement between FHWA, the SHPO, and the Advisory Council on Historic Preservation, with Mn/DOT and the U.S. Army Corps of Engineers. Additionally, the PA mandates that the Secretary of the Interior’s Standards for the Treatment of Historic Properties will be used to determine whether work on any bridge would constitute an adverse effect. The 2006 Historic Bridge Management Plan outlines the approach to stabilization, preservation, and maintenance activities necessary for Bridge 4930. Rehabilitation of the bridge, if feasible, is deemed necessary by the requirements of the Programmatic Agreement. The components of this rehabilitation include: repainting of the superstructure, replacement of the deck, rehabilitation of the substructure units, increasing the load capacity of the bridge, and replacement of deteriorated superstructure members, among other components related to hydraulic remediation. The deck width of the bridge is deficient with respect to Mn/DOT standards. Increasing the deck width, however, has not been recommended based on minimal accident history, and would constitute major geometry changes that would adversely affect the bridge’s historic integrity. Increasing the load capacity will likely be limited to increasing the capacity of the interior floor beams. Chapter 152 and Fracture Critical Bridges In order to comply with the Minnesota State Statute Chapter 152 requiring that Mn/DOT address fracture critical bridges on the trunk highway system, several options have been brought forth. Four basic concepts for load-path redundancy have been offered (See Appendix D). The Bridge Office has reached the conclusion that making the bridge carry loads in a way different than originally designed may be more risk than not adding a new load path. An exemption to the Chapter 152 load-path redundancy requirements is likely to be pursued if the bridge remains on Trunk Highway 99.



Hydraulic Remediation Improving the hydraulic characteristics in the vicinity of Bridge 4930 has become a greater concern as Phase I has progressed. The initial concern was to prevent additional damage to the bridge from debris striking the bridge during a high water event. One option considered was raising the bridge to a height that would allow debris to pass under the bridge. Other options were to increase the hydraulic opening under the bridge by adding jump spans to the East end of the bridge and widening the flow channel of the bridge. The final option considered was to add sacrificial piling to the river upstream of the bridge to catch large debris from arriving at the bridge. As Phase I progressed, the scope of the hydraulic concern has widened its area of influence to consider the effects on the Trunk Highway 22 bridge upstream and the serviceability of Trunk Highway 99. All options must maintain proper sight distances for traffic on Trunk Highway 99 in the vicinity of Bridge 4930, analyze the effects on roadway overtopping east of Bridge 4930, along with the effect on the historic integrity of Bridge 4930.



Appendix A - Definitions of Structurally Deficient and Functionally Obsolete

A bridge is defined by the Federal Highway Administration to be Structurally Deficient or Functionally Obsolete if it satisfies specific criteria. The criteria are based on the condition of the load carrying components of the bridge, the geometrics of the bridge, the load capacity of the bridge, and the amount of traffic carried by the bridge. The criteria are based on information stored in the National Bridge Inventory (NBI). Information describing individual NBI items can be found in “Recording and Coding Guide for the Structure Inventory and Appraisal of the Nation’s Bridges”. The values for Bridge 4930 (obtained from the Structure Inventory Report) are presented below in parenthesis.

Structurally Deficient

A bridge with an NBI condition rating of 4 or less for: NBI Item 58 – Deck; or (4930 = 5) NBI Item 59 – Superstructure; or (4930 = 5) NBI Item 60 – Substructure; or (4930 = 5) NBI Item 62 – Culvert (4930 = N)

Or

A bridge with an NBI appraisal rating of 2 or less for: NBI Item 67 – Structural Evaluation; or (4930 = 5) NBI Item 71 – Waterway Adequacy (4930 = 4)

Functionally Obsolete

An appraisal rating of 3 or less for NBI Item 68 – Deck Geometry; or (4930 = 4 ) NBI Item 69 – Underclearances; or (4930 = N) NBI Item 72 – Approach Roadway Alignment; (4930 = 8)

Or

An appraisal rating of 3 for: NBI Item 67 – Structural Condition; or (4930 = 5) NBI Item 71 – Waterway Adequacy (4930 = 4)



Appendix B. 2006 Saint Peter Trail Plan



Appendix C. Secretary of the Interior’s Standards Secretary of the Interior’s Standards for Rehabilitation

As provided by the National Park Service at: http://www.nps.gov/history/hps/tps/standguide/rehab/rehab_standards.htm

1. A property will be used as it was historically or be given a new use that requires minimal change to its distinctive materials, features, spaces, and spatial relationships.

2. The historic character of a property will be retained and preserved. The removal of distinctive materials or alteration of features, spaces, and spatial relationships that characterize a property will be avoided.

3. Each property will be recognized as a physical record of its time, place, and use. Changes that create a false sense of historical development, such as adding conjectural features or elements from other historic properties, will not be undertaken.

4. Changes to a property that have acquired historic significance in their own right will be retained and preserved.

5. Distinctive materials, features, finishes, and construction techniques or examples of craftsmanship that characterize a property will be preserved.

6. Deteriorated historic features will be repaired rather than replaced. Where the severity of deterioration requires replacement of a distinctive feature, the new feature will match the old in design, color, texture, and, where possible, materials. Replacement of missing features will be substantiated by documentary and physical evidence.

7. Chemical or physical treatments, if appropriate, will be undertaken using the gentlest means possible. Treatments that cause damage to historic materials will not be used.

8. Archeological resources will be protected and preserved in place. If such resources must be disturbed, mitigation measures will be undertaken.

9. New additions, exterior alterations, or related new construction will not destroy historic materials, features, and spatial relationships that characterize the property. The new work shall be differentiated from the old and will be compatible with the historic materials, features, size, scale and proportion, and massing to protect the integrity of the property and its environment.

10. New additions and adjacent or related new construction will be undertaken in a such a manner that, if removed in the future, the essential form and integrity of the historic property and its environment would be unimpaired.



Secretary of the Interior’s Standards for the Treatment of Historic Properties, as Adapted for Historic Bridges

Adapted from: Clark, Kenneth M., Grimes, Mathew C., and Ann B. Miller, Final Report, A Management Plan for Historic Bridges in Virginia, Virginia Transportation Research Council, 2001. The Secretary of the Interior's Standards for the Treatment of Historic Properties, first codified in 1979 and revised in 1992, have been interpreted and applied largely to buildings rather than engineering structures. In this document, the differences between buildings and structures are recognized and the language of the Standards has been adapted to the special requirements of historic bridges. 1. Every reasonable effort shall be made to continue an historic bridge in useful transportation service. Primary consideration shall be given to rehabilitation of the bridge on site. Only when this option has been fully exhausted shall other alternatives be explored. 2. The original character-defining qualities or elements of a bridge, its site, and its environment should be respected. The removal, concealment, or alteration of any historic material or distinctive engineering or architectural feature should be avoided. 3. All bridges shall be recognized as products of their own time. Alterations that have no historical basis and that seek to create a false historical appearance shall not be undertaken. 4. Most properties change over time; those changes that have acquired historic significance in their own right shall be retained and preserved. 5. Distinctive engineering and stylistic features, finishes, and construction techniques or examples of craftsmanship that characterize an historic property shall be preserved. 6. Deteriorated structural members and architectural features shall be retained and repaired, rather than replaced. Where the severity of deterioration requires replacement of a distinctive element, the new element should match the old in design, texture, and other visual qualities and where possible, materials. Replacement of missing features shall be substantiated by documentary, physical, or pictorial evidence. 7. Chemical and physical treatments that cause damage to historic materials shall not be used. The surface cleaning of structures, if appropriate, shall be undertaken using the most environmentally sensitive means possible. 8. Significant archaeological and cultural resources affected by a project shall



be protected and preserved. If such resources must be disturbed, mitigation measures shall be undertaken. 9. New additions, exterior alterations, structural reinforcements, or related new construction shall not destroy historic materials that characterize the property. The new work shall be differentiated from the old and shall be compatible with the massing, size, scale, and architectural features to protect the historic integrity of the property and its environment. 10. New additions and adjacent or related new construction shall be undertaken in such a manner that if removed in the future, the essential form and integrity of the historic property and its environment would be unimpaired.



Appendix D. Conceptual Redundancy Approaches and Notes

On October 7th, four general schemes were offered by O.N.E. to the Bridge Office as potential approaches to improve the redundancy of Bridge 4930. These schemes were intended to generate internal Mn/DOT conversations to identify which approaches would be acceptable for redundancy improvement. The four redundancy approaches offered were: 1) Secondary gusset plate connections – This approach tried to utilize (to the

largest extent possible) the existing internal redundancy of the members and connections. Most of the members are built up riveted sections with four or more components. If the internal redundancy of the members was sufficient, only supplemental or secondary gusset plates would need to be added to the existing primary structural steel. The secondary gusset plate connections would participate in carrying gravity loads. Consequently this system was classified as an active load carrying system.

2) Supplemental Post-Tensioning Elements – To increase the load capacity and redundancy of individual members, post-tensioning elements would be integrated into primary truss members that are tension members (bottom chords, some diagonals, some verticals). This system would also require the installation of secondary connection hardware in the vicinity of the gusset plates to anchor the post-tensioning bars. One benefit of this approach is the ability to vary the jacking force in the post-tensioning elements. One could then distribute the fraction of dead loads carried by the original members and the post-tensioning elements. Secondary gusset plate connections would be required with this approach. This system is classified as an active load carrying system.

3) Independent Longitudinal Ties – This system would require the installation of steel ties from one end of the truss to the other. It was envisioned that these ties would be detailed inside of the existing bottom chords and would penetrate each of the floor beams. At each end of the bridge the ties would be anchored in a large transfer element which could engage the truss at the bottom of each endpost. This would essentially create a new independent bottom chord. The ties would penetrate each floor beam but would have a steel detail that would allow the floor beam to bear on the tie in case a local element failed in tension. This system would only be loaded during a fracture event and is classified as a passive load carrying system.

4) Longitudinal Deck Tie- This system is a variant of Approach Three. Instead of new independent ties, the idea is to increase the longitudinal capacity of the reinforced concrete deck. The longitudinal capacity of the deck is then anchored in large transfer elements at each end of the bridge. These transfer elements would be larger than those used in Approach Three because the distance between the deck and the bottom chord is larger. The transfer elements would only engage during a fracture event, consequently this is classified as a passive load carrying system.

bridge 4930 – scoping study...bridge 4930 scoping study phase 1 – final report december 18, 2009...

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