Lincoln Road Footbridge South Br. No. S December 2017 Special Inspection Report

Transcription

1 Lincoln Road Footbridge South Br. No. S December 2017 Special Inspection Report

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3 Table of Contents 1. STRUCTURE DESCRIPTION 4 2. SPECIAL INSPECTION 5 3. DESCRIPTION OF DEFECTS DECK ELEMENTS LOAD-BEARING SUBSTRUCTURE DURABILITY ELEMENTS SAFETY ELEMENTS OTHER BRIDGE ELEMENTS ANCILLARY ELEMENTS PHOTOGRAPHS GENERAL BRIDGE PHOTOGRAPHS DEFECT PHOTOGRAPHS EAST ARM BCI SPAN 1 (BCI FORM 1) EAST ARM SPIRAL BCI SPAN 1 (BCI FORM 2) WEST ARM BCI SPAN 2 (BCI FORM 3) CENTRAL (NORTH) ARM BCI SPAN 3 (BCI FORM 4) CONCLUSIONS CONDITION PERFORMANCE INDICATOR SCORES OVERALL STRUCTURAL CONDITION RECOMMENDED WORKS 65 APPENDIX A GENERAL ARRANGEMENT 66 APPENDIX B CONCRETE DEFECTS DRAWING 68 APPENDIX C INSPECTION PRO FORMA 69 Page 3

4 1. Structure Description Peterborough CC Structure No. : S Highway over : Non-segregated shared-use Footway/Cycleway Highway under : A15 Bourges Boulevard and A15/A47 interchange roundabout (dual carriageway) Lincoln Road Footbridge South is a multi-span structure consisting of three arms carrying a footway/cycleway over the dual carriageway A15 and A15/A47 interchange roundabout. The three arms meet in the A15 central reserve (immediately south of the roundabout) to form a hexagonshaped hex deck segment. The structure layout is illustrated on the General Arrangement drawing and Location plans in Appendix A of this report. A Key Plan of the structure is provided below as Figure 1. Figure 1 Key Plan (Not to Scale) Radiating from the central hex, each arm of the footbridge comprises intermediate simply supported spans supported on Y-shaped raked column piers. Each pier therefore comprises two legs, with a corbel arrangement to the top of each supporting two bearings (one bearing for each adjoining span). As part of previous concrete repair schemes undertaken to the structure, the footbridge piers have been partially covered in a carbon fibre wrapping and resin coating system. The wrapping system has only been applied to some of the piers and some of these wrapped piers have also had their corbels wrapped. The existing pier/corbel wrapping situation is indicated for reference purposes on the Concrete Defects drawing in Appendix B. Two of the footbridge arms include ramped approaches; the East is spiral in plan and the West has a staircase attached. The ends of the approach ramps are of Kincrib proprietary precast concrete crib wall construction. The Central (North) arm terminates on the A15/A47 roundabout. The central hex segment is constructed from insitu reinforced concrete. The East arm spiral ramp deck is of insitu reinforced concrete box beam/girder construction with parapet cantilevers. The other spans are all of precast twin spine beam deck construction, but of varying lengths. The span Page 4

5 lengths up to 14m are reinforced concrete construction, whereas the spans greater than this are post-tensioned concrete construction. The different beam construction forms to the spans are indicated in Figure 2 below. The deck sections include a reinforced concrete slab between the beams and a parapet cantilever on each edge. The end spans land on insitu reinforced concrete abutments. There is a set of reinforced concrete stairs halfway along the West arm. Figure 2 Deck Construction Forms (Not to Scale) The footbridge was constructed in The current West arm and associated staircase were constructed circa 1978, following demolition of the originals to enable the A15 realignment. Photographs P1 to P12 show general elevations, views of the spans and over the structure. 2. Special Inspection The topside elements received a close examination, within touching distance, on 30 November The inspection was generally undertaken from ground level and an inspection ladder was used for limited access to the sides of piers. This inspection was undertaken during daylight and the weather conditions were cold, dry and light. The temperature was 5ºC. The underside elements received a close examination, within touching distance over the nights of 18 and 19 December These inspections utilised battery powered mobile work lights and a tower scaffold to achieve close touching distance access to the deck soffit and pier tops. A ladder was used to achieve access to the pier sides where tower access was not possible due to the topography. The weather conditions were cold, dry and dark. The temperature was 3ºC. A series of off-peak lane closures were implemented during the overnight inspections to provide safe access to the South central reserve and roundabout verges under the footbridge supports. Page 5

6 The public car parking area located within the retail park to the southwest of the footbridge was utilised for inspection parking. During the overnight inspections, the above mentioned lane closures were utilised for parking. The maintenance hardstanding parking area on the inside of the roundabout was also utilised. The inspection was carried out in accordance with BD 63/07 Inspection of Highway Structures, together with the guidelines given in the Inspection Manual for Highway Structures (2007). The severity, extent and type of defect for each bridge element has been recorded on the Bridge Condition Indicators (BCI) inspection pro forma in Appendix C of this report. The pro forma has been completed in accordance with the Guidance Notes on Bridge Condition Indicators produced by the Association of Directors of Environment, Economy, Planning & Transport (ADEPT); formally the County Surveyors Society (CSS). Extracts of reference information is provided in Appendix C. For the purpose of BCI inspection reporting the footbridge has been reported using 4 No. forms as shown in the table below. Note that the East Arm and East Arm spiral are considered as a single BCI span, but are recorded on individual BCI forms to cover the different construction forms. The central hex link is common to all 3 No. BCI spans, but for clarity of reporting the hex defects are recorded on BCI Form No. 1 (East Arm). BCI Form No. BCI Span No. Arm Name No. Intermediate spans 1 1 East Arm (includes hex) East Arm Spiral West Arm (includes stairs) Central (North) Arm 2 The data on the BCI inspection pro forma has been used to calculate the Condition Performance Indicator (Condition PI) score for each span and/or construction type. Note that this score was previously known as the BCI when originally developed by the CSS Bridges Group. The Condition PI score has been calculated in accordance with the HA/CSS Guidance Document for Performance Measurement of Highway Structures Part B1: Condition Performance Indicator (2007), which supersedes the Addendum to CSS Guidance Note on Bridge Condition Indicators Volume 3: Evaluation of Bridge Condition Indicators (August 2004). The Condition PI scores are calculated on a scale of 100 (best condition) to 0 (worst condition). The scale is divided into five bands (Very Good, Good, Fair, Poor and Very Poor). Generic interpretations for these bands are presented in the above HA/CSS Guidance Document Part B1 as Table 19 (Interpretation of Condition PI for individual structures), which is included as an extract in Appendix C. The calculated Condition PI scores are recorded in Appendix C (following the BCI inspection pro forma) and the following figures are provided: Condition PI Av the average Condition PI for a bridge evaluated taking into account the condition of all structural elements in a bridge except for ancillary items (Element Nos. 35 to 38). Condition PI Crit the critical Condition PI for a bridge evaluated taking into account the condition of those elements deemed to be of very high importance to the bridge; these elements have been underlined on the inspection pro forma for reference (Element Nos. 1 to 6 and 11 to 12). Current and historic Condition PI scores are given in Section 5.1 of this report to provide a quick comparison between inspection intervals. The footbridge has more than one span, therefore the range of Condition PI Crit scores calculated for the structure have been provided for information. Page 6

7 3. Description of Defects 3.1 Deck Elements Primary Deck Elements The main concern to the deck elements is areas of spalling with exposed corroding reinforcement to the soffit and beams, particularly near the leaking deck joints. The most severe defects were noted to the insitu concrete sections and particularly the central hex, staircase deck infill section and spiral ramp. These defects are likely to result from poor site control during the construction as the defects are less severe to the precast beams. East Arm BCI Span 1 (BCI Form 1) Areas of cracking and spalling noted to the insitu reinforced concrete hex. The cracking (Photo P13) is to the soffit adjacent to the joint above pier SP-1 and includes corrosion staining with minor section loss. The wet staining is indicative of the prominent ongoing joint leakage noted throughout the bridge and resultant corrosion of the deck reinforcement. Areas of spalling (P14 to 17) were noted to the hex soffit and vertical faces of the hex beams. Above pier SP-12 the hex beam spalling has exposed corroding reinforcement (P16). Adjacent pier SP-6 there is an area of hex beam soffit spalling/loss of concrete fines (P17), which is believed to be due to poor compaction at construction. Minor non-offensive graffiti to south elevation of beam spanning over the East Arm Spiral approach ramp (P5). East Arm Spiral BCI Span 1 (BCI Form 2) Large area of spalling (1000mm x 400mm) to east edge of spiral ramp soffit with exposed corroding reinforcement (P22). A further large area of spalling (760mm x 110mm) with exposed corroding reinforcement to the east edge is located above the bearing to the east leg of pier SP-4 (P23). Throughout the spiral ramp deck box beam soffit there are areas of corroding tiewire/formwork debris visible (P24). This suggests poor control of the construction process. Minor non-offensive graffiti to west edge of spiral ramp (P42). West Arm BCI Span 2 (BCI Form 3) Various areas of spalling to the soffit of staircase deck infill section with cracking, leaching, joint leakage and stalactites near pier SP-8 (P43 to 45). Small areas of spalling to posttensioned concrete section with exposed corroding debris to inside face of beam (P46) and exposed corroding reinforcement to soffit (P47) and outside face of beam (P48). Spalling with exposed corroding reinforcement (P49) and spalling with cracking (P50) to precast reinforced concrete deck soffit. Central (North) Arm BCI Span 3 (BCI Form 4) Cracking (generally hairline) with corrosion staining to precast reinforced concrete soffit at joint above pier SP-13 (P70). Failed concrete repairs with spalling exposing corroding reinforcement to deck soffit and wet staining at deck/north abutment joint (P71). Page 7

8 Regularly spaced vertical hairline cracks to east precast reinforced concrete beam (P72) Parapet Beam Cantilever Vertical cracking was noted to the parapet plinth upstands at post locations throughout the structure. P51 to the West Arm BCI Span 2 (BCI Form 3) is a typical example. The cantilever soffits were wet and stained around the joints, which is indicative of the prominent ongoing joint leakage noted throughout the bridge. P18 to the East Arm BCI Span 1 (BCI Form 1) is the worst example and shows algae growth, leaching and stalactites to the South joint by pier SP-6. P85 to the Central (North) Arm BCI Span 3 (BCI Form 4) also shows algae staining from the leaking joint and leaching to the west beam cantilever. East Arm Spiral BCI Span 1 (BCI Form 2) Prominent areas of cracking and/or spalling/section loss noted at the construction joints along the parapet plinth upstands (P28 to P32). At some joints there were loose sections of concrete (P32) and at others the section loss revealed a corroding reinforcement bar (P31). The construction joints include no provision for movement and it should be noted that the deck form in this span is spiral shape. The construction form therefore creates a hard-point at joints, which is evidenced by the cracking observed. It is also evident from the existence of previous concrete repairs at the joints that this is not a new problem to the structure. A failed concrete repair, with cracking and section loss was noted (P30). This repair included no provision for movement, which is likely to have contributed to its failure. 3.2 Load-Bearing Substructure Foundations The foundations were not visible for inspection. No signs of settlement or deterioration were observed Abutments East Arm Spiral BCI Span 1 (BCI Form 2) Sleeping materials/signs of habitation were observed in front of the East abutment (P25). It is understood that the authorities are aware of and are managing this situation. There is a substantial loss of fill material from the crib walling unit construction from behind the East abutment (P26). This material loss appears to be long-standing and is not currently causing a problem for the structure so no remedial work is recommended. West Arm BCI Span 2 (BCI Form 3) Sleeping materials were observed to the south side of the west end of the approach ramp (P53). In addition there was evidence of clothing materials being stored on the West abutment bearing shelf (P54). It is understood that the authorities are aware of and are managing this situation. Corrosion staining was noted to the West abutment ballast wall emanating from the interface with the deck soffit (P54). Page 8

9 Central (North) Arm BCI Span 3 (BCI Form 4) Leaching was noted to the North abutment emanating from the deck east cantilever/ abutment joint (P73). A construction defect was noted to the North abutment wall (P74) where a piece of timber has been cast into the concrete. This defect does not appear to be causing a problem for the structure and is not located in a conspicuous location Piers East Arm BCI Span 1 (BCI Form 1) Previous concrete repair to north face of north leg of pier SP-2 remains intact, but is hollow sounding when tapped with corrosion staining evident (P19). Cracking with spalling was noted adjacent to the repair (P19). A crack generally 4mm width with concrete loss to the mouth of the crack was noted to the northeast corner of the south leg corbel of pier SP-2 (P20). East Arm Spiral BCI Span 1 (BCI Form 2) Substantial spalling exposing corroding reinforcement with delaminated concrete and cracking to southeast corner of pier SP-3 north leg (P34). Spalling exposing corroding reinforcement to pier corbels (P33, P35 and P36). Minor non-offensive graffiti to west face of pier SP-5 (P42). West Arm BCI Span 2 (BCI Form 3) Cracking to inside face of pier SP-9 corbel (P55). Cracking with early signs of delamination and rust staining (P57 and P58) to pier SP-10 corbels. Minor non-offensive graffiti to pier SP-8 wrapping (P67). Central (North) Arm BCI Span 3 (BCI Form 4) There are several areas of cracking with corrosion staining and spalling to pier SP-13 (P75, P78 to P80). There are also areas of spalling with exposed corroding reinforcement to both of the corbels to the pier (P76 and P77) Bearings General weathering was noted to the elastomeric bearings throughout the structure, which has been exacerbated by the leaking deck joints. In addition, the following specific defects were noted: East Arm Spiral BCI Span 1 (BCI Form 2) The North bearing on the west leg of pier SP-4 has been displaced off the mortar bed (P37). Directly opposite, on the east leg, the North bearing is distorted (P23) and there is significant spalling and exposed corroding reinforcement to the deck edge. Remedial works are recommended that include concrete repairs and replacement of these bearings. West Arm BCI Span 2 (BCI Form 3) The South bearing to the West abutment is lifting up at the back due to compression of the bearing at the front face (P59). A minor tear was noted to the bearing on the North leg of pier SP-7. Significant moisture was noted to the bearings here due to the joint leakage Page 9

10 (P60). Due to partial loss of the mortar bed beneath a bearing, a steel shim has been exposed with areas of corrosion noted (P61). Central (North) Arm BCI Span 3 (BCI Form 4) Steel shims were observed left in place beside the bearing to the east leg of pier SP-13 (P81). It is not known why these shims have been left in place, however areas of corrosion were noted to them. It is recommended that the shims be removed as part of a future repair contract to prevent them from adversely affecting the function of the bearing. The south elastomeric bearing to the east leg corbel of pier SP-13 was noted to be protruding-out (P82). This misaligned bearing defect was also noted at the last Principal Inspection in January The elastomeric bearing to the west leg corbel of pier SP-13 was noted to be tilted/distorted (P83). Consider replacing defective bearings as part of the recommended concrete repairs Bearing plinth/shelf No issues noted to top of pier corbels supporting bearings, other than deck joint leakage and associated staining. West Arm BCI Span 2 (BCI Form 3) Evidence of clothing materials storage to West abutment bearing shelf (P54). 3.3 Durability Elements Superstructure Drainage East Arm Spiral BCI Span 1 (BCI Form 2) Drainage channel blocked with silt build-up and asphalt surfacing fill (P39). This defect was also noted at the last Principal Inspection in January West Arm BCI Span 2 (BCI Form 3) Deck surfacing drainage cover/grill noted to be cracked (P68). In addition a previous asphalt infill repair has been undertaken, which has blocked the drainage channel. This is all as noted at the last Principal Inspection in January Waterproofing The deck waterproofing system is not visible, because it is covered by the footbridge surfacing, however no defects evident. Wet areas of the deck soffit generally appear to result from the severe deck joint (BCI element 18) leakage issues observed to the structure see following section Movement/Expansion Joints Heavy leakage was noted through the deck movement joints, which has resulted in severe staining to the deck soffit and parapet cantilevers. East Arm BCI Span 1 (BCI Form 1) Wet staining noted to cantilever emanating from leaking joint (P18). Typical poor condition of deck joints (P21). Page 10

11 East Arm Spiral BCI Span 1 (BCI Form 2) Severe deck joint leakage noted at intersection of East Arm and Spiral ramp (P38). West Arm BCI Span 2 (BCI Form 3) Persistent severe deck joint leakage noted (P45, P60 and P67). Surfacing material noted to be infilling top of joints (P69). Central (North) Arm BCI Span 3 (BCI Form 4) Deck joint leakage noted (P71, P79, P84 and P85) Finishes: Parapets Typical weathering and algae staining noted to footbridge parapets (P30 and P32). 3.4 Safety Elements Access (Reinforced Concrete Access Stairs) West Arm BCI Span 2 (BCI Form 3) Horizontal cracks with rust staining to most of the staircase step riser faces (P62 to P64). Cracking with leachate build-up and corrosion staining to the staircase edge beams (P65 and P66). The cracking is generally <1mm width Parapets The parapets were found to be in a generally good condition. It was noted that the footbridge is designated as a non-segregated shared-use footway/cycleway and is used by several cyclists, however the parapets do not meet the 1.4m height cycle standard. It is recommended that the Client gives consideration to installing cycle standard parapets. East Arm Spiral BCI Span 1 (BCI Form 2) A single post to the Spiral ramp Northwest parapet is loose due to a failed weld at the base (P41). This defect may result from a previous impact. The loose post will affect the function of the parapet system, so it is recommended that this be repaired/replaced. Areas of impact damage were noted to the West parapet top rail of one bay and the vertical infill to the adjacent bay (P40). The damage does not significantly affect the function of the parapet system but does look unsightly, hence remedial work is recommended to be undertaken when the above post is repaired Footbridge Surfacing The footbridge surfacing was found to be in a generally good condition with moderate wear/weathering in places (P5, P10 and P68). Small potholes/loss of patches of surfacing material (P69). 3.5 Other Bridge Elements Invert No significant defects effecting the structure were noted. Page 11

12 3.5.2 Wing walls East Arm Spiral BCI Span 1 (BCI Form 2) Spalling and exposed corroding reinforcement was noted to the precast crib walling units that form the East abutment wing walls (P26). It is recommended that remedial works be scheduled however a low priority rating has been assigned. Central (North) Arm BCI Span 3 (BCI Form 4) Vegetation growth is currently obscuring and preventing views of the North abutment wing walls (P73) Embankments Dense vegetation growth was observed around all arms of the footbridge. The vegetation growth to the North embankment is currently obscuring the North abutment wing walls (P73). Substantial vegetation and ivy growth is beginning to obscure the crib walling wing walls/approach ramp to the East arm spiral (P27). No significant defects effecting the structure were noted. 3.6 Ancillary Elements Approach bollards The bollards at the foot of the East Arm Spiral and West Arm ramps are cracked. The cracking is no worse than noted at the last Principal Inspection in January 2015 and no remedial work is currently recommended. Page 12

13 4. Photographs 4.1 General Bridge Photographs East Arm (BCI Form 1) East Arm Spiral (BCI Form 2) P1 South elevation showing East Arm (BCI Forms 1 & 2) West Arm (BCI Form 3) Hex (BCI Form 1) East Arm (BCI Form 1) Pier leg Central (North) Arm (BCI Form 4) P2 South elevation showing central hex/arm arrangement Page 13

14 East Arm (BCI Form 1) West Arm (BCI Form 3) Central (North) Arm (BCI Form 4) Hex (BCI Form 1) P3 North elevation showing hex/arm arrangement and pier supports Central (North) Arm (BCI Form 4) West Arm (BCI Form 3) P4 North elevation showing West Arm (BCI Form 3) Page 14

15 East Arm Spiral (BCI Form 2) East Arm (BCI Form 1) P5 South Elevation showing East Arm (BCI Form 1) spanning over East Arm Spiral (BCI Form 2) approach ramp East Arm (BCI Form 1) East Arm Spiral (BCI Form 2) P6 East Arm Spiral (BCI Form 2) South Elevation Page 15

16 West Arm stairs (BCI Form 3) West Arm (BCI Form 3) P7 West Arm (BCI Form 3) South Elevation showing stairs West Arm (BCI Form 3) Central (North) Arm (BCI Form 4) East Arm (BCI Form 1) P8 West elevation showing hex/arm arrangement Page 16

17 Central (North) Arm (BCI Form 4) West Arm (BCI Form 3) P9 West Arm (BCI Form 3) North Elevation P10 General view along West Arm (BCI Form 3) ramp Page 17

18 P11 West Arm (BCI Form 3) approach ramp Central (North) Arm (BCI Form 4) P12 Central (North) Arm (BCI Form 4) West Elevation Page 18

19 4.2 Defect Photographs Please refer to Appendix B for drawing showing concrete defect locations. The locations shown and referred to below are referenced thus: SC#, where SC = South footbridge Concrete defect and # = the unique defect reference number. In a similar manner, the footbridge piers are referenced thus: SP-$, where SP = South footbridge Pier and $ is the unique pier reference number East Arm BCI Span 1 (BCI Form 1) Hex (BCI Form 1) soffit P13 Cracking with section loss and corrosion staining to hex soffit at joint above pier SP-1 (Concrete defect ref. SC1) Page 19

20 P14 20mm deep spall to south side of hex soffit (ref. SC14) P15 Spalling to inside face of hex beam above pier SP-6 (ref. SC15) Page 20

21 P16 Spalling with exposed corroding reinforcement to inside face of hex beam near joint, above pier SP-12 (ref. SC30) P17 Beam soffit spalling/loss of concrete fines (adjacent pier SP-6) due to poor compaction Page 21

22 Hex Stalactite/leachate build-up P18 Leaking joint with algae growth, leaching, stalactites and wet staining to South cantilever joint by pier SP-6 Page 22

23 P19 Previous concrete repair remains intact, but is hollow sounding when tapped and with corrosion staining. Cracking with spalling to north face of north leg of pier SP-2 (ref. SC2) Page 23