1 A PAPER ON CARE TO BE TAKEN FOR BETTER MAINTENANCE OF STEEL FOOT OVER BRIDGES AT DESIGN, CONSTRUCTION, INSPECTION AND MAINTENANCE STAGES BY V.B. SOOD DyCE/Br/Valsad & A.K. AWASTHI AEN/Br/HQ/Valsad. 1. BACK GROUND: Foot over bridges are important passenger amenity and passenger safety items in station yards provided to facilitate easy movement of passengers and goods from one platform to other or from platform to outside of Railway Station or for crossing station yards. Foot over bridges ensure safety by preventing the trespassing of railway track. Proper functioning and better layout of the foot over bridges shall be planned to ensure more and more people use foot over bridges. Steel foot over bridges are still popular on Indian Railways due to easy fabrication and easy launching due to light weight & ease in modification in service for the train information arrangement, advertising boards etc. even though PSC foot over bridges are also being adopted. The population of foot over bridges is steadily increasing and there are 196 foot over bridges on Western Railway as on 01-04- 2004 out of which majority are steel foot over bridges. This paper has been written with the purpose of defining some methods to be adopted in design, construction, inspection and maintenance stages of steel foot over bridges, so as to ensure proper functioning of foot over bridges. 2. INTRODUCTION: Maintenance of foot over bridges on Western Railway is the responsibility of Section Engineers (Works) under open line Assistant Engineers. The maintenance of foot over bridges is governed by para 417 of Indian Railway Works Manual & paras 117 and 104 of Indian Railway Bridge Manual. At present guidelines for maintenance of foot over bridges are not uniform and proper systems are not in place for inspection and maintenance of foot over 2 bridges. There are some instances where foot over bridges are not even entered in bridge registers. The problems of foot over bridges maintenance have been neglected in the past, resulting in accumulation of maintenance backlog over a period of time and the foot over bridges in the past have been abandoned prematurely as unrepairable, or repaired at considerable cost. Such instances are a cause of deep concern in passenger safety as well as train safety. 3. COMMON PROBLEMS IN MAINTENANCE OF STEEL FOOT OVER BRIDGES: Foot over bridges handle large volumes of commuters/passengers and the traffic peaks at the time of arrival/departure of trains. The problems in maintenance arise due to : i) Wearing course/tiles/flooring getting worn out requiring periodical renewal. ii) Corrosion of bottom boom/flooring members of truss/ railing due to contact with water/debris from foot over bridges iii) Corrosion in columns due to contact with water/debris from the platform. iv) Corrosion due to non-maintenance of members in O.H.E. area. v) Corrosion in the members due to being embedded in the walls of the rooms constructed underneath the staircase. vi) Sagging of girders due to weakness in design coupled with problems mentioned above. 3 4. CARE TO BE TAKEN DURING DESIGN: During the design stage the following care shall be taken: i) The design of the truss shall be done as to have simple, uncluttered layout of members. ii) The maintainability of the foot over bridge by providing easy access to all members for maintenance operations such as cleaning and painting shall be taken care of during design. iii) Extra care shall be taken to provide proper drainage at the flooring level of the foot over bridge so that the accumulation of water/ debris does not take place. Preferably, flooring shall be provided by keeping clear gap from the truss on either side to have better drainage and to avoid connection of truss with dust, debris and water falling on the flooring of the foot over bridge. iv) The design shall take care of corrosion at the most vulnerable locations which can not be totally eliminated by keeping some degree of redundancy in the design to ensure safe service life of the structure even after some corrosion has taken place. v) Staircase shall be designed with proper slope, length of flight, no of steps in each flight and the rise and tread of each step in accordance with the provisions of National Building Code for the convenience of the passengers. This is the single most important factor that promotes or inhibits the use of the foot over bridges by the passengers. vi) Wind load shall be taken considering the possibility of the entire height of the foot over bridge being covered in advertisement boards during use. 5. CARE TO BE TAKEN DURING CONSTRUCTION: Care taken during construction is most important and it avoids many problems arising in maintenance. i) The foot over bridges footings having holding down bolts are vulnerable to corrosion and this results in shearing off of the holding down bolts. Wherever holding down bolts are to be used, galvanized bolts shall be provided. The new 4 drawings of footings having embedded column is performance wise better in field and shall be used. ii) For gravity type foundations, the life of embedded column shall be ensured by : a) The welds and connection bolts shall be designed of adequate size to take care of corrosion in service. b) The footing shall be embedded in good quality properly compacted concrete. c) The steel embedded in concrete shall be protected against corrosion by providing one thick coat of bituminous paint. iii) The bottom boom/flooring of the foot over bridges and stairs is vulnerable to corrosion due to contact between different material, accumulation of water/debris. Such vulnerable members shall be metallised/epoxy painted outside track after complete erection, or in situ after launching. iv) Columns of foot over bridges shall be embedded in good quality concrete for a height of 1 m above floor of platform/general ground level to prevent contact with water/debris from platform surface. v) Wearing coat shall be provided in flooring with different colour pigments in concrete to give indication of the extent of wear, so that main slab does not wear off and safety is ensured by timely renewal of wearing coat. vi) Proper drainage shall be ensured to prevent any accumulation of water, especially near panel points. vii) The steel columns and bracing in rooms constructed under staircase shall not be encased in walls. However, if the same is unavoidable, the members shall be protected against corrosion by applying a coat of bituminous paint. viii) Properly anchored steel angles shall be provided at nosing of steps to prevent damage to the flooring on steps. This helps in preventing falling of the passengers by tripping over loose nosing angles or over damaged flooring of the steps. 5 6. CARE TO BE TAKEN DURING INSPECTIONS AND MAINTENANCE: The foot over bridges are to be inspected once a year before monsoons by Section Engineer (Works) and once a year after monsoons by the Assistant Engineer (Open Line) as per para 117 and 102 of Indian Railway Bridge Manual with detailed inspection being done once in five years. The record of inspections shall be kept in a properly bound register having chronological records of inspections of successive years. The drawings of foot over bridges and design details form an important part of maintenance regime for foot over bridges and shall be available with the maintenance engineers. Maintenance practice shall aim at preventing premature failure of individual components. During inspections, the following items shall be carefully inspected and the remedial action shall be taken for maintenance to ensure proper service life of the foot over bridge: Item Defects to be observed Action to be taken for maintenance during inspections Foundation i. Spalling/cracking of i. Epoxy repairs in the cracks/ concrete in foundations spalled concrete OR increasing section area of concrete in foundation ii. Loose or corroded ii. Regrouting of holding down holding down bolts bolts and/or replacement of holding down bolts iii. Looseness of nuts of iii. Provision of missing nuts and holding down bolts. providing packing in loose nuts. iv. Accumulation of water iv. Improving drainage and and lack of cleanliness near cleanliness near holding down bolts bed plates/ holding down bolts and/ or encasing the bed plates in good quality concrete upto 1m height from the ground. 6 Item Defects to be observed Action to be taken for maintenance during inspections Columns i.Verticality of columns. i. Strengthening of columns by providing stays and extra footing area. ii. Cracks in welding. ii. Repairs by welding and splicing. iii. Bends or damage in iii. Repairs by welding or secondary members such as replacement of the members bracing, gussets etc. affected. iv. Condition of painting and iv. Repainting as required and extent of corrosion, especially splicing at the places where corrosion near the junction of the truss already occurred after proper design. and column Support i. Missing/ loose bolts in i. Provide missing bolts, tighten points of connection. bolts, if required. trusses on ii. Deformation/ corrosion ii. Check from design point of columns of cleat angle supporting truss view, reasons for such deformation. over the columns. Replacing corroded cleat angles. iii. Jammed rotation/ iii. Cleaning and oiling of the movement of bearings. bearings to ensure free movement/ rotation of bearings. Dust covers to be provided where required. Steel i. Corrosion of structural i. Repainting, if required, and Truss members repairs and splicing of corroded members after proper design. ii. Distortion of the ii. Complete design check of the members due to overstressing girder and strengthening of trusses. of members. iii. Cracks in the members. iii. Splicing of the members after design check. iv. Condition of painting iv. Repainting with a. General corrosion a. Normal painting. b. Corrosion in OHE area. b. Epoxy painting/ Metallising of members in OHE area. v. Condition of the cross- v. Welding of cracks and providing girder - bracing connection. additional members in connections where only bolts are used for the connections to prevent the cross girders from falling of if the bolt loosens/falls off. 7 Item Defects to be observed Action to be taken for maintenance during inspections vi. Pinned Connections and vi. Replacement of broken pins/ cotters. cotters and proper splitting of the ends of cotter pins. vii. General condition of vii. Design check for any sagging of truss the truss or excessive vibrations under load/ train passing. PSC i. Cracks in members i. Epoxy grouting of cracks. Girders Design review. ii. Crack at junction of I- ii. Strengthening of connection of girders and deck slab. I-girders and deck slab and design review. iii. Spalling of concrete. iii. Complete stripping of spalled concrete and providing concrete cover afresh. iv. Honey combing in iv. Epoxy grouting and corrosion concrete. protection by epoxy painting on surface. v. General corrosion v. Epoxy painting on surface. vi. Loss of camber in PSC I vi. Design review and retrofitting girders of girders. Stairs vii. Spalling of concrete vii. Repairs of the slab by guniting/ from bottom side of stairs. epoxy mortar. viii. Nosing angle and viii. Repair of loose/hanging nosing flooring. angles and worn out flooring. Flooring i.Excess wear in wearing coat/ i. Renewal of wearing coat and tiles. tiles. General i. OHE induction i. Repairs by welding/ splicing in protection sheet, covering the connections. Renewal, if required. sheeting, covering sheet truss, hand railing etc. ii. Pockets having drainage ii. Improving drainage through problems. renewal of the wearing coat and/ or surface coating. iii. Damage due to wear in iii. Replacement of floor slab and/ floor slab. or re-plastering the spalled concrete. 8 7. RECOMMENDATIONS FOR IMPROVEMENTS IN EXISTING SYSTEM OF RECORDING INSPECTIONS AND ROUTINE MAINTENENACE: The following improvements are required in the present system of recording inspections and routine maintenance: i. Detailed inspection of structures once in five years as per provisions of Indian Railway Bridge Manual are not being done in field at present, the same shall be done. ii. Bottom boom of foot over bridges to be inspected after opening out the flooring once in every 10 years. iii. Metallizing after sand blasting shall be done in the bottom boom of the foot over bridges and OHE areas which are subjected to sever corrosion and which cannot be readily repainted. iv. The space under the foot over bridges shall not be permitted as far as possible to be converted into rooms since this prevents the proper inspections of the foot over bridges and also creates problems in maintenance. v. Advertising boards/ information boards/ sheeting shall be provided on the foot over bridges after consultation with the Section Engineer (Works) in charge and the same shall be so provided that the design assumptions of the foot over bridge for wind loading are not violated. 8. CONCLUSION: Foot over bridges are very important passenger amenity items, especially at busy railway stations. Proper care taken at various stages of design, construction and maintenance of a foot over bridges will go a long way in ensuring proper service and life of foot over bridges and ensuring safety of foot over bridges. This will also help the railway in serving the passengers better, ensuring passenger convenience and safety in the process. 9. BIBLIOGRAPHY: i) Indian Railway Bridge Manual, 1998. ii) Indian Railway Works Manual, 2000.