STRUCTURAL EVALUATION REPORT

Transcription

1 STRUCTURAL EVALUATION REPORT Pedestrian Bridge Structural Evaluation Activity ID PREPARED FOR CITY OF DES MOINES ENGINEERING DEPARTMENT OCTOBER 2015

2 TABLE OF CONTENTS EXECUTIVE SUMMARY SECTION 1 Introduction 1 Scope of the Report 1 Field Inspection 2 Certification 4 SECTION 2 Indianola Avenue Existing Structure 1 Condition 2 Test Data 4 Repair Concepts 5 Replacement Concept 7 At-Grade Crossing Concept 8 Estimated Costs 11 Life Cycle Cost Evaluations & Summary 15 Conclusions and Recommendations 20 Photos Replacement Structure Location

3 SECTION 3 University Avenue Existing Structure 1 Condition 2 Test Data 4 Repair Concepts 5 Replacement Concept 7 At-Grade Crossing Concept 8 Estimated Costs 11 Life Cycle Cost Evaluation Evaluations & Summary 15 Conclusions and Recommendations 20 Photos Replacement Structure Location SECTION 4 SW 9 th Street Existing Structure 1 Condition 2 Test Data 4 Repair Concepts 5 Replacement Concept 7 At-Grade Crossing Concept 8 Estimated Costs 11 Life Cycle Cost Evaluation Evaluations & Summary 15 Conclusions and Recommendations 20 Photos Replacement Structure Location

4 SECTION 5 Terracon Chloride Content Test Report SECTION 6 City Traffic Department Memorandum City HAWK Signal Information

5 EXECUTIVE SUMMARY Structural and traffic evaluations have been completed for three existing pedestrian overpass bridges located in Des Moines over Indianola Avenue, University Avenue, and SW 9 th Street. Each bridge is located adjacent to Howe, Windsor and Park elementary schools. The evaluation included assessing the current condition of the bridges, evaluating repair options with associated costs, evaluating replacement options with associated costs, and evaluating removal options in conjunction with at-grade crossing enhancements with associated costs. The following executive summary is provided for overview. We recommend reading the report in its entirety for complete understanding of the items contained herein. The existing concrete bridges range in age from 32 to 43 years old. The concrete bridge decks and concrete beams are in poor condition. The existing structures do not meet current ADA requirements primarily due to approach ramp slopes. A repair option was considered for the existing bridges. Repairing existing deterioration will not extend the life of the structures significantly. A partial replacement option was considered for the existing bridges. This option would require updating the bridges to meet current ADA requirements. Partial replacement would involve replacing the concrete beams and decks on the bridges. Because the existing approach ramp slopes on the bridges exceed ADA requirements, elevators would need to be added at each end of the bridge for vertical access. A full replacement option was considered for the existing bridges. This option would require approach ramps significantly longer than the original ramps to meet current ADA requirements. The new replacement structures for University Avenue and SW 9 th Street would need to be relocated slightly to accommodate the longer approach ramps. However, between the two replacement options, the full replacement option was deemed to be the most cost effective. Removal of the existing bridges and replacement with at-grade crossing enhancements was considered. The at-grade crossing option for SW 9 th Street would involve utilizing the existing pedestrian signalized intersection south of the current bridge location with adult crossing guards. The at-grade crossing options for Indianola Avenue or University Avenue would involve the installation of new designated pedestrian crossings with HAWK pedestrian signal traffic control devices. Each location also included a provision for additional street parking inset adjacent to the school grounds to improve parent drop off/pick up access for students, and to further minimize the major street crossings by students.

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7 INTRODUCTION The three prestressed concrete pedestrian overpasses evaluated in this report currently allow pedestrians to cross major City streets. These crossings include Indianola Avenue, University Avenue, and SW 9 th Street. Schools are located near each of the pedestrian overpasses, including Howe Elementary School at the Indianola Avenue structure, Windsor Elementary School/St. Teresa Catholic School at the University Avenue structure, and Park Avenue Elementary School at the SW 9 th Street structure. SCOPE OF THE REPORT Shuck-Britson Inc. was retained by the City of Des Moines to perform engineering studies on the pedestrian overpass structures. The scope of the study is as follows: 1. Assemble and review existing data, plans and other pertinent data. 2. Physically inspect the pedestrian overpass structures. Investigation of the piers and abutments is limited to exposed surfaces above grade. 3. Determine the condition of elements of the bridge by inspection. 4. Evaluate and summarize all the data collected and prepare design concepts for rehabilitation recommendations, replacement recommendations, and removal with at-grade crossing recommendations. 5. Summarize the investigation, field inspection and recommendations in a written report which shall allow the City to critically evaluate the conclusions and recommendations. 1

8 FIELD INSPECTION Field inspections of the three overpass structures were performed to determine the existing condition of the various components of each structure. Field inspection of the bridge was conducted with two goals in mind; determination of existing conditions and determination of areas needing repair. Field inspections were performed by Joe Stanisz, P.E. and Bryan McCombs, P.E. of Shuck-Britson Inc. Terracon was retained to perform material testing of deck concrete for chloride intrusion levels. Results of these tests are shown in section 5 of the report. The field inspection was conducted in several phases. The structures were visually inspected. The existing concrete was sounded with the use of hammers to determine the extent and location of deterioration. The deck was sounded using a chain drag. Concrete samples were taken from various locations of the deck and were analyzed to assist in determining the amount of chloride intrusion in the concrete. Numerous photos were taken during the field inspection to record the conditions that were discovered. Photographs of the existing bridge were taken at various times. These photographs provide a complete photographic record of the visible conditions of the bridge in its present condition. Utilizing information obtained from the field inspection, an appraisal of the structural condition of the bridge was made, and repair/replacement concepts were developed. Estimated costs for these repairs/replacements were prepared. Presented herewith is a summary of our findings, including general information, field inspection information, results of the material testing and estimated costs. The written text has been supplemented with drawings and photographs to clarify information and concepts presented. Conclusions and recommendations are contained at the end of each bridge site section. 2

9 Glossary of common terms used to describe concrete deterioration are as follows: Leaching : Scaling : Light Scale : Medium Scale : Heavy Scale : Severe Scale : Cracks : Spalling : Small Spall : Large Spall : Disintegration: Shotcrete : Water seeping through cracks and voids in the hardened concrete leaches or dissolves the calcium hydroxide and other material compounds. The result of such action is either efflorescence or incrustation at the surface of the cracks. The gradual and continuing loss of surface mortar and aggregate over an area, further described by light, medium, heavy and severe. Loss of surface mortar up to 1/4 inch deep, with surface exposure of coarse aggregates. Loss of surface mortar from 1/4 inch to 1/2 inch deep, with some added mortar loss between the coarse aggregates. Loss of surface mortar surrounding aggregate particles of 1/2 inch to one inch deep. Aggregates are clearly exposed and stand out from the concrete. Loss of coarse aggregate particles as well as surface mortar surrounding the aggregates. Depth of the loss exceeds one inch. A linear separation in the concrete. A roughly circular or oval depression in the concrete, further described by small or large. Not more than one inch deep or approximately six inches in diameter. More than one inch deep and greater than six inches in diameter. Deterioration into small fragments or particles due to any cause. A brief descriptive term given to a mixture of Portland cement, sand and water placed pneumatically by means of a machine that discharges water and pre-mixed cement and sand, under regulated pressures, through pipe or hose and discharge nozzle, the water being combined with the sand and cement at the nozzle. 3

10 CERTIFICATION This report was prepared to evaluate the Des Moines pedestrian bridges over Indianola Avenue, University Avenue, and SW 9 th Street. Please feel free to contact us, should you have questions or wish to discuss any aspect of the report in further detail. Pedestrian Bridge Evaluation I hereby certify that this report was prepared by me or under my direct personal supervision and that I am a duly registered Professional Engineer under the laws of the State of Iowa. Date: Joseph W. Stanisz, P.E. Iowa Reg. No Registration renewal 12/31/2015 At-Grade Crossing Evaluation I hereby certify that this report was prepared by me or under my direct personal supervision and that I am a duly registered Professional Engineer under the laws of the State of Iowa. Date: Mark A. Perington, P.E. Iowa Reg. No Registration renewal 12/31/2015 4

11 INDIANOLA AVENUE EXISTING STRUCTURE This structure was built in The overpass consists of a 67' prestressed single tee main span, a 45' prestressed single tee approach span at the south and a 71' and 47' prestressed single tee approach spans at the north. There is an intermediate landing at the east approach span. There is one single tee member in the bridge cross section with no concrete topping. The approaches terminate at grade with cast-in-place ramp/abutment structures. The out to out width of the walkway is 6'-0". Chain link fence is installed at each deck edge. The fence post base plates are bolted vertically through the deck. Steel handrails are mounted to the inside face of the chain link fence. The single tee members are supported on cast-in-place concrete piers and abutments. The abutments and associated approach ramps are supported on timber piles. The three piers consist of a concrete cap, a single concrete column and a concrete pile cap. The piers are also supported on timber piles. The total length of structural walkway is approximately 244'. Existing drawings indicate the east approach ramp has a slope in the longitudinal direction of 15%, the west approach 11.25% and the main span over the roadway is level. The cross slope of the walkway is ¼" per foot. There are currently two lanes of eastbound traffic, two lanes of westbound traffic, and two sidewalks under the main span. The overpass is designed for a live load of 85 pounds per square foot. Overhead power lines terminate just to the east of the east approach landing. In 1994, repairs were completed on the overpass by Herberger Construction. Existing single tee beams were removed and replaced with new members, along with new joints. New fencing was also installed. Repair work was completed on the substructures. Information concerning the existing structure was obtained from the following plan sets: original plan set prepared by the City of Des Moines reconstruction plan set prepared by Shuck-Britson Inc. and construction documentation 1 Indianola Avenue

12 CONDITION Major deficiencies and conditions discovered during the field inspection are described as follows: Fence: The galvanized chainlink fence and steel handrails are in fair condition. Corrosion is present on fence post base plates and fasteners. Corrosion is present on the steel handrails. Main Span Prestressed Single Tee: Extensive spalling is present at the edges and underside of the single tee flange. Reinforcing steel is exposed in these areas with heavy corrosion present. Cracks on the underside of the flange have efflorescence buildup. Moisture is visible on the underside of the flange. Rust stains and minor spalling are present on the top of the flange where the lifting loops were cut off and at some of the fence post locations. Extensive spalling and exposed reinforcing steel is present at the north and south ends of the flange in the area of the joints. South Approach Ramp Single Tee: Extensive spalling and exposed reinforcing steel is present at the west edge of the single tee flange. Reinforcing steel is exposed with heavy corrosion present. Moderate spalling and rust stains are present on the east edge of the single tee flange. Moisture is visible on the underside of the flange near the rail post anchorages. Rust stains and spalling are present on top of the flange where the lifting loops were cut off. Extensive spalling and exposed reinforcing steel is present at the north end of the flange in the area of the joint. Upper and Lower North Approach Ramp Single Tees: Extensive spalling is present at the edges and underside of the single tee flanges. Reinforcing steel is exposed in these areas with heavy corrosion present. Moisture is visible on the underside of the flanges. Cracking is present on the upper single tee at the east end on the bottom of the stem. Rust stains and minor spalling are present on the top of the flange where the lifting loops were cut off and at some of the fence post locations. Extensive spalling and exposed reinforcing steel is present at the west end of the lower single tee in the area of the joint. Moderate spalling and exposed reinforcing steel is present at the ends of the single tees at the intermediate landing area. North Abutment: Minor cracks are present in the side walls of the abutment. The abutment diaphragm concrete appears to be in good condition. The top of the walkway slab appears to be in good condition. South Abutment: Minor cracks are present in the side walls of the abutment. The lower area of the abutment diaphragm concrete is spalled with exposed reinforcing steel. The top of the walkway slab appears to be in good condition. South Pier Supporting Main Span: Minor cracks and rust stains are present in the pier cap. The pier column appears to be in good condition. The pier diaphragm concrete appears to be in good condition. 2 Indianola Avenue

13 North Pier Supporting Main Span: Moderate cracking, leaching, and rust stains are present on the pier cap and pier diaphragm concrete. The pier column appears to be in good condition. North Pier Supporting Intermediate Landing at North Approach Ramp: Moderate cracking, leaching and rust stains are present on the west face of the pier cap. Vertical cracks and rust staining are present on the pier column on the west face. Minor to moderate cracking and rust stains are present on the cantilevered landing slab edges. Moderate spalling and exposed rebar are present on the pier diaphragm concrete. The top of the intermediate landing slab appears to be in good condition. 3 Indianola Avenue

14 TEST DATA Material testing for this structure included the collection of powdered concrete deck samples at varying depths using a hammer drill. The concrete powder samples were tested for chloride ion content. The locations of the samples were selected to assess the general condition of the deck concrete along the length of the bridge. The sample holes were patched with an epoxy filler after drilling. The material test reports are included in the section 5 of this report. The following will summarize the test results and their current implications. Chloride Ion Content Corrosion of reinforcing steel initiates when water, oxygen and sufficient chloride ions are present. The primary source of chloride ions is road salt used for deicing. The penetration of chloride ions into the concrete is a function of the porosity of the concrete and the frequency of wetting/drying cycles. A high frequency of wetting/drying cycles increases the penetration rate. Review of test data indicates a high concentration of chloride ions in most of the samples at the surface with exposure to salt laden water. Infiltration of chloride ions and additional corrosion may be reduced or prevented by the following actions: Repairing concrete deck deterioration. Reducing the use of de-icing salts, or utilization of de-icers without corrosive chemicals. Application of a penetrating sealer to superstructure surfaces. In addition, the deck expansion joints must be maintained to prevent leakage of salt laden water onto the substructures below. Chloride content analysis was performed at three locations on the structure. Chloride content was evaluated at a depth of 0" to ½" below the deck surface and 2" to 2½" below the deck, in order to identify the penetration of chlorides. Of the six samples, all six samples are above the total chloride content threshold of 0.15% by weight of cementitious, above which conventional reinforcing steel will begin to corrode. This level of chlorides must be at the level of steel reinforcement for the corrosion activity to occur. The chloride content percentage by weight of cementitious is determined by assuming 564 lb of cement per cubic yard of concrete, and a concrete weight of 3,645 lb per cubic yard. The weight of the chloride (per cubic yard) is determined by multiplying the measured value (total chloride content, %) by the weight of one cubic yard of concrete. The weight of chloride is then divided by weight of cement to obtain the chloride content by weight of cementitious. The maximum total chloride content, by weight of cementitious in a deck sample was 4.14%, which exceeds the threshold value by a factor of approximately 27. The minimum total chloride content in a deck sample, by weight of cementitious was 1.29%, which exceeds the threshold value by a factor of approximately 9. 4 Indianola Avenue

15 REPAIR CONCEPTS Single Tee Beam Repair Two repair options were reviewed in our evaluation. The first repair option would involve conventional concrete repair methods. For sections where the depth of the repair is 2 or less, the deteriorated concrete would be removed to sound concrete and the final surface sandblasted. Exposed reinforcing steel would be sandblasted to remove the rust and polymer mortar used for the repair. For sections where the depth of the repair is more than 2, the deteriorated concrete would be removed and the final surface sandblasted. Exposed reinforcing steel would be sandblasted to remove rust. The sections would be formed as necessary and portland cement concrete used to repair the patch. Current interpretation of the Proposed Guidelines for Pedestrian Facilities in the Public Right-of-Way (PROWAG) is the repair of the superstructure on the bridge would be considered maintenance. As such, the structure is not required to be modified to meet current ADA accessibility guidelines. It is estimated a conventional concrete repair method would not be a long term solution and may last approximately 10 years. The second repair option would involve replacing the single tee beams with new double tee beams. Several local precast suppliers no longer produce single tee members. Using a 6 wide pre-topped double tee would improve the superstructure condition while adding minimal additional dead load to the substructures. Reinforcing steel in the flange area could be epoxy coated. A penetrating concrete sealer could also be applied to the top flange, edges of the flange, and a portion of the flange overhang to prevent penetration of chloride into the concrete. Current interpretation of the Proposed Guidelines for Pedestrian Facilities in the Public Right-of-Way (PROWAG) is the replacement of the superstructure on the bridge would be considered an alteration. As such, the structure would need to be modified to meet current ADA accessibility guidelines. One way to accomplish this would involve adding an elevator at each side of the bridge. This would require modifying the existing bridge to accommodate the elevators, providing an enclosure to house each elevator, potential acquisition of additional right of way, and providing power to each elevator location. It is estimated the superstructure replacement option would last 25 to 30 years. Abutment and Pier Repairs Deteriorated concrete on the substructures can be repaired using conventional concrete repair methods as described in the singe tee beam repair section. The pier and abutment diaphragm concrete will need to be replaced if the beams are replaced. Joint Repairs New compression seals will need to be installed at the piers and abutments. 5 Indianola Avenue

16 Fence and Handrails The existing fence and handrails will need to be removed to complete repairs on the beams. With the age of the fence and the condition of the fence anchors, new fence installation is recommended. 6 Indianola Avenue

17 REPLACEMENT CONCEPT Replacement of the existing structure with a new structure will require longer approach ramps to meet current ADA accessibility guidelines. If the slope on the new ramps in the longitudinal direction is kept to 5% or less, no intermediate landings are required. The maximum slope that can be used to meet ADA requirements is 8.3%. However, intermediate landings are required for every 2.5 of rise in the ramp. This would require many intermediate landings for each ramp. See the attached sketch for the proposed location for the new structure. For the purposes of this report, it was assumed a replacement structure would use a maximum longitudinal slope on the approach ramps of 5%. The replacement structure length would be approximately 562 (existing bridge length is approximately 244 ). The structure would have a walkway width of 8 clear. The replacement structure would consist of two prestressed bridge beams in the cross section. The deck, piers and abutments would be cast in place concrete. Railing can be either chain link fence or a decorative steel rail. Alternately, the city may wish to consider a prefabricated steel truss for the main span of the replacement structure if this type of aesthetic is desired. It is estimated the replacement structure will have a design life of 75 years with intermediate maintenance periods. 7 Indianola Avenue

18 AT-GRADE CROSSING CONCEPT As a no-build replacement alternative to the grade separate structures, removal of the structure and replacement with an at-grade pedestrian crossing was evaluated. City staff performed field evaluations in the spring of 2014, and a technical memorandum was prepared for each location and is attached in Section 6 of this report. Review included review of existing roadway conditions, before/after school activity at crossings and adjacent streets, and recommendations regarding potential at grade crossing treatment. City Evaluation Indianola Avenue carries approximately 13,800 vehicles per day (vpd) Posted Speed Limit of 35MPH with a 25MPH School Zone flasher Nearest Traffic Signals & Crossing (no Adult Crossing Guards in area) o Park Avenue intersection 2,000 feet to the southeast o SE 5th/6th Street intersection 650 feet to the northwest Bridge usage 4 in AM school arrival, 17 in PM school departure, 31 total daily crossings on average Key Observations Most students that crossed on bridge continued on foot to neighborhoods to north and east of Indianola. Drop off/pick up parking is limited on adjacent street surrounding school site, parents utilized SE 7 th to drop off behind the school. Buses do not use inset on Indianola Avenue, but use an area behind the school. Additional Considerations Ten year crash history from included one crash with a major injury related to a pedestrian in 2008 on Indianola Avenue between SE 5th and SE 8th Street. SE bound traffic on Indianola has some minor visibility issues between horizontal curve and some of the trees on south side of Indianola at SE 7th. Stopping distance should be adequate, especially within reduced speed zone. Other signalized elementary school crossings on similar four lane arterial roads include: o Monroe - Rice / 30 th & Hickman 12-14,000 vpd adjacent signalized intersection o Hillis Elementary / 56 th & Hickman 14-15,000 vpd adjacent mid-block signal o Jackson Elementary / Indianola & Watrous 10,000 vpd signalized entrance/intersection 8 Indianola Avenue

19 Based on the review performed by City Traffic & Transportation staff, and the field review by the Engineer, it is recommended that an At-Grade Crossing concept would include a Hawk Pedestrian Crossing Signal installation to provide students, parents, and potential crossing guards the ability to request a priority in right of way from the traffic on Indianola Avenue for a crossing maneuver. The HAWK signal is a variation from the traditional red/yellow/green signal indications that have been used for many years. HAWK, Highintensity, Activated crosswalk signal is a pedestrian pushbutton activated signal. This provides pedestrians with a mechanism to request a stop by traffic on the street for additional safety in crossing, yet it minimizes the delay for opposing traffic. In the past four years the City of Des Moines has installed HAWK signals at four locations in the community. Two locations, Grand Avenue on the Principal Riverwalk in downtown, and Grand Avenue near the Art Center/Polk Boulevard are shown in the photos. The City of Des Moines has 36 midblock traditional pedestrian traffic signals, most located near schools. There is very limited information specifically comparing the safely performance of a pedestrian overpass to a regular traffic signal or HAWK pedestrian signal. Clearly an overpass, if used by pedestrians, provides a complete separation from vehicular traffic conflicts. Studies related to safety effectiveness of the HAWK pedestrian signal have determined a 97% driver stopping compliance rate which is comparable to traditional traffic signals. Further there is a 60-70% reduction in pedestrian crash potential with the HAWK pedestrian signal versus simple pedestrian crosswalk signing. Additional information on HAWK signals is listed on the Traffic & Transportation webpage of the City of Des Moines website. These pages are included in the appendix. 9 Indianola Avenue

20 The proposed at-grade concept improvements at Howe Elementary include: Removal of the pedestrian overpass bridge and all associated ramps. Reconstruction of sidewalk on each side of Indianola with ADA ramps and a larger pedestrian queuing area for students and a potential adult crossing guard. HAWK pedestrian signal installation. 10 Indianola Avenue

21 ESTIMATED COSTS This section provides an estimate of costs to repair the existing bridge, replace the superstructure on the existing bridge, replace the bridge, and install an at-grade crossing. These costs are approximate only and intended for preliminary budgeting purposes. All estimated costs are in August 2015 dollars. Option 1 Repair Existing Structure Item Quantity Unit Unit Cost Item Total Concrete Repair Single Tee Top 124 SF $100 $12,400 Concrete Repair - Single Tee Under 302 SF $250 $75,500 Concrete Repair Substructures 41 SF $175 $7,175 Joint Replacement 52 LF $75 $3,900 Chain Link Fence/ Handrail Replace 568 LF $25 $14,200 Traffic Control 1 LS $3,000 $3,000 Mobilization (8%) $9,300 Subtotal $125,475 Contingency (20%) $25,100 Total Estimated Construction Cost (Rounded) $151, Indianola Avenue

22 Option 2 Replace Single Tees with Double Tees Item Quantity Unit Unit Cost Item Total New 6-6 Double Tee Beams (4) 1,505 SF $45 $67,725 Remove & Dispose Existing Beams 1 LS $15,000 $15,000 Rebuild Diaphragms at Beam Ends 9 CY $1000 $9,000 Joint Replacement 52 LF $75 $3,900 Chain Link Fence/ Handrail Replace 568 LF $25 $14,200 New Elevators at Each Side of Bridge 1 2 EA $200,000 $400,000 Traffic Control 1 LS $3,000 $3,000 Additional Right-of-Way (Allowance) $25,000 Mobilization (8%) $43,000 Subtotal $580,825 Contingency (15%) $87,100 Total Estimated Construction Cost (Rounded) $668,000 Notes: 1 Includes allowance for modification of existing bridge, providing power to elevators, and elevator enclosure structure. 12 Indianola Avenue

23 Option 3 Replace Entire Bridge Item Quantity Unit Unit Cost Item Total Remove Existing Bridge 1 LS $25,000 $25,000 New 9 x580 PPCB Bridge 5,220 SF $125 1 $652,500 Additional Right-of-Way (Allowance) $100,000 Subtotal $777,500 Contingency (15%) $116,600 Total Estimated Construction Cost (Rounded) $894,000 Notes: 1 - Includes mobilization and traffic control. 13 Indianola Avenue

24 Option 4 Install At-Grade Crossing Item Quantity Unit Unit Cost Item Total Initial Costs Remove Existing Pedestrian Bridge 1 EA $25,000 $25,000 Hawk Signal or Signal Improvements 1 EA $65,000 $65,000 Sidewalk Queuing Area Adjacent/ 60 SY $60 $3,600 Leading to Signal ADA/Ramp Improvements 1 2 EA $1,750 $3,500 Pavement Curb Removal 40 LF $15 $600 Misc Marking/Signing 1 LS $2,000 $2,000 Traffic Control 1 LS $3,000 $3,000 Mobilization (8%) $16,200 Subtotal $118,900 Contingency (10%) $11,900 Total Estimated Initial Construction Cost (Rounded) $131,000 Annual Costs Crossing Guard Cost 2 1 EA $6,600 $6,600 Energy & Maintenance for Signal 1 EA $2,700 $2,700 Total Estimated Annual Costs $9,300 Notes: 1 Pavement & truncated domes. 2 Potential crossing guard (50/50 cost share with schools). 14 Indianola Avenue

25 Indianola Avenue Pedestrian Bridge Life Cycle Cost Analysis Input value Calculated value Option Repair single tee beams / substructures, replace deck joints, replace chain link fence / handrail 2025 Repair single tee beams 2035 Repair single tee beams 2045 Replace bridge with PPC beam bridge 2075 Deck and substructure repairs Existing Bridge Area: 1755 SF length 6.50 width Replacement Bridge Area: 5220 SF length 9.00 width Interval Year Year Description Present Cost 2015 Repair $151,000 Future Cost at Interval Year Cost of Required Future Work in Present-Day Dollars 2025 Repair $72,398 $117,929 $87,750 $50 /SF 2035 Repair $59,732 $158,486 $87,750 $50 /SF 2045 Replace $502,083 $2,169,973 $894, Indianola Avenue 2075 Repair $41,161 $768,854 $130,500 $25 /SF $826,374 Remaining Value -$169,186 at end of assumed useful life (negative value denotes credit) -$3,160, % of useful life remaining Net Present Cost $657,188 ASSUMPTIONS: Dollar figures in Present Cost column represent actual expenditures, or sinking fund values to cover expenditures in later years. Construction Inflation assumed (annualized) = 3% 0.03 Investment rate of return assumed (annualized) = 5% 0.05

26 Indianola Avenue Pedestrian Bridge Life Cycle Cost Analysis Input value Calculated value Option Replace single tee beams, replace deck joints, replace chain link fence/handrail, repair substructures 2045 Replace bridge with PPC beam bridge 2075 Deck and substructure repairs Existing Bridge Area: 1755 SF length 6.50 width Replacement Bridge Area: 5220 SF length 9.00 width Interval Year Year Description Present Cost 2015 Repair $668,000 Future Cost at Interval Year Cost of Required Future Work in Present-Day Dollars 2045 Replace $502,083 $2,169,973 $894, Repair $41,161 $768,854 $130,500 $25 /SF $1,211, Indianola Avenue Remaining Value -$169,186 at end of assumed useful life (negative value denotes credit) -$3,160, % of useful life remaining Net Present Cost $1,042,058 ASSUMPTIONS: Dollar figures in Present Cost column represent actual expenditures, or sinking fund values to cover expenditures in later years. Construction Inflation assumed (annualized) = 3% 0.03 Investment rate of return assumed (annualized) = 5% 0.05

27 Indianola Avenue Pedestrian Bridge Life Cycle Cost Analysis Input value Calculated value Option Replace bridge with PPC beam bridge 2045 Deck and substructure repairs 2075 Deck and substructure repairs Existing Bridge Area: 1755 SF length 6.50 width Replacement Bridge Area: 5220 SF length 9.00 width Interval Year Year Description Present Cost 2015 Replace $894,000 Future Cost at Interval Year Cost of Required Future Work in Present-Day Dollars 2045 Repair $73,291 $316,758 $130,500 $25 /SF 2075 Repair $41,161 $768,854 $130,500 $25 /SF $1,008, Indianola Avenue Remaining Value -$56,395 at end of assumed useful life (negative value denotes credit) -$1,053, % of useful life remaining Net Present Cost $952,056 ASSUMPTIONS: Dollar figures in Present Cost column represent actual expenditures, or sinking fund values to cover expenditures in later years. Construction Inflation assumed (annualized) = 3% 0.03 Investment rate of return assumed (annualized) = 5% 0.05

28 Indianola Avenue Pedestrian Bridge Life Cycle Cost Analysis Input value Calculated value Option Replace bridge with at-grade pedestrian crossing 2035 Replace at-grade crossing 2055 Replace at-grade crossing 2075 Replace at-grade crossing Interval Year Year Description Present Cost 2015 Replace $131,000 Future Cost at Interval Year Cost of Required Future Work in Present-Day Dollars 2035 Replace $44,246 $117,397 $65, Replace $30,118 $212,032 $65, Replace $20,502 $382,954 $65,000 $225, Indianola Avenue Remaining Value -$20,502 at end of assumed useful life (negative value denotes credit) -$382, % of useful life remaining Net Present Cost $205,364 ASSUMPTIONS: Dollar figures in Present Cost column represent actual expenditures, or sinking fund values to cover expenditures in later years. Construction Inflation assumed (annualized) = 3% 0.03 Investment rate of return assumed (annualized) = 5% 0.05

29 Life Cycle Cost Evaluation Summary Indianola Avenue Net Present Cost Option 1 - Repair Existing $657,200 Option 2 - Replace Superstructure $1,042,100 Option 3 - Replace Bridge $952,100 Option 4 - Remove Bridge & Install $205,400 At-Grade Crossing 19 Indianola Avenue

30 CONCLUSIONS AND RECOMMENDATIONS 1. Moisture and chloride intrusion appear to be the cause of the concrete deterioration on the bridge superstructure and substructures. Concrete deterioration is heaviest at the edges and underside of the single tee flanges. Substructure deterioration on the bridge is minor, with most of the deterioration occurring in the area of failed deck joints. 2. The original single tee beams were replaced after approximately 22 years in service. The replacement single tee beams have been in service for approximately 21 years and are again in need of repair or replacement. From the history of the structure, it appears the useful life of the precast single tee beams as previously fabricated is approximately 20 to 25 years before repairs or replacement are required. 3. Of the three repair/replacement options presented in this report, we recommend pursuing the replacement of the entire bridge. Attempting to repair the existing single tees will not be a long term solution and will require repairs at more frequent intervals. The net present cost of the entire replacement option is lower than the superstructure replacement option. Replacing the superstructure only will require the addition of exterior elevators to bring the structure into ADA compliance. It is anticipated the exterior elevators will require frequent maintenance due to the temperature and weather extremes experienced throughout the seasons. 4. The pedestrian structure can be replaced with an at-grade crossing and the installation of a mid-block HAWK pedestrian activated traffic signal approximately 100 feet east of the current bridge. Additional considerations include: Likely expansion of sidewalk areas on the south and north side of Indianola Avenue for student waiting areas at signal. Possible school site sidewalk reconstruction for ADA compatible grade needs. Evaluate potential adult crossing guard need at the signal. The life cycle cost analysis of all options considered indicates the removal of the existing bridge and replacement with an at-grade crossing has the lowest costs of all options considered. 5. The estimated costs of improvements included in this report are provided as a tool to use in comparison of alternates and determine magnitude of funding required. Estimates presented should not be relied on to provide a guarantee of prices obtained by competitive bidding. 20 Indianola Avenue

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32 (A1) Overall structure (looking west) (A2) Overall structure (looking east) Indianola Avenue

33 (A3) North approach ramp (A4) South approach ramp Indianola Avenue

34 (A5) Main span (A6) Main span and south approach ramp Indianola Avenue

35 (A7) North approach ramp (looking east) (A8) North approach ramp - deterioration at west end of lower single tee at abutment Indianola Avenue

36 (A9) North approach ramp - deterioration at west end of lower single tee at abutment (A10) North approach ramp - deterioration of single tees at intermediate landing Indianola Avenue

37 (A11) North approach ramp - intermediate landing (A12) North approach ramp - upper single tee (looking west) Indianola Avenue

38 (A13) North approach ramp - west end of upper single tee at north pier (A14) Main span (looking north) Indianola Avenue

39 (A15) Main span - spalling on top of flange (A16) Single tee flange deterioration between main span and south approach ramp Indianola Avenue

40 (A17) South approach ramp (looking north) (A18) Typical corrosion on handrails Indianola Avenue

41 (A19) North approach ramp - edge deterioration on lower single tee (A20) North approach ramp - edge deterioration on lower single tee Indianola Avenue

42 (A21) North approach ramp - deterioration on upper single tee (A22) North approach ramp - cracking on bottom of stem on upper single tee Indianola Avenue

43 (A23) Main span - edge deterioration on single tee (A24) Main span - edge deterioration on single tee Indianola Avenue

44 (A25) South approach ramp - edge deterioration on single tee (A26) South approach ramp - edge deterioration on single tee Indianola Avenue

45 (A27) South abutment (looking south) (A28) North abutment Indianola Avenue

46 (A29) North abutment (A30) South pier at main span (looking north) Indianola Avenue

47 (A31) South pier at main span (looking southeast) (A32) South pier at main span (looking southwest) Indianola Avenue

48 (A33) South pier at main span - cap (looking northeast) (A34) South pier at main span - cap (looking northwest) Indianola Avenue

49 (A35) North pier at main span (looking north) (A36) North pier at main span (looking east) Indianola Avenue

50 (A37) North pier at main span (looking west) (A38) North pier at main span (looking south) Indianola Avenue

51 (A39) North pier at main span - west face of cap (A40) North pier at main span - south face of cap Indianola Avenue

52 (A41) North pier at main span - east face of cap (A42) North pier at approach ramp - deterioration on west face of cap and column Indianola Avenue

53 (A43) North pier at north approach ramp - east face (A44) North pier at north approach ramp - deterioration on south face of cap Indianola Avenue

54 (A45) North pier at north approach ramp - deterioration on north face of cap (A46) North pier at north approach ramp - deterioration on west face of column Indianola Avenue

55

56 LEGEND SIDEWALK RAMP 205'-0 SE 7th ST. 50'-0 70'-0 9'-0 TYP. 9'-0 TYP. INDIANOLA AVE. 50'-0 PRELIMINARY PROPOSED LOCATION FOR NEW PEDESTRIAN BRIDGE INDIANOLA AVE. CITY OF DES MOINES JANUARY 2015 DESIGN SHEET NO. OF FILE NO. DESIGN NO. DESIGN TEAM 400 EAST COURT AVE. SUITE 140 DES MOINES, IOWA CITY OF DES MOINES PROJECT NUMBER SHEET NUMBER 3 1/8/ :53:05 AM V8i_IDOTRoad D:\ \ New 2015 Aerial Backgrounds.dgn TSL_CC_D003 11x17_pdf.pltcfg