newly built doomed bridge - lack of quality control

International Journal of Innovative Research in Advanced Engineering (IJIRAE) ISSN: 2349-2163 Volume 1 Issue 9 (October 2014) www.ijirae.com

_________________________________________________________________________________________________ © 2014, IJIRAE- All Rights Reserved Page -205

NEWLY BUILT DOOMED BRIDGE - LACK OF QUALITY CONTROL

Yogita Gupta Suneet Kaur Nitin Dindorkar Ph.D scholar, Associate Professor, Professor, Civil Engineering, Civil Engineering, Civil Engineering, MANIT Bhopal MANIT Bhopal MANIT Bhopal

Abstract-- Reinforced concrete is a very versatile construction material. Properly constructed and designed concrete structures are both strong and durable. However, improper construction can cause early deterioration. Deterioration can result in loss of strength and unsafe conditions. Present case describes the distresses of bridge across river Kharun on Lakhnaghat – Jamghat Road at km 1/2-4 constructed in 2010. This bridge started showing the sign of dilapidation soon after 2-3 years of construction. Probable causes of early deterioration are also discussed. Keywords – poor construction, bridge failure, early deterioration, distress, honey combed concrete

I. INTRODUCTION

Rapid industrialization in India after independence required infrastructure for transport of goods and raw materials and that has led to construction of wide network of roads with inbuilt bridges and flyovers. Bridges represent a substantial investment of public funds, and are expected to provide satisfactory performance and remain in service for many years. For new bridges, design specifications typically require 75- or 100-year design life. Reinforced concrete Bridges deteriorate with time due to several causes such as poor quality of construction, corrosion of steel in reinforced concrete bridges, improper design and detailing for normal loads and seismic forces, improper functioning of bearings etc. A number of existing bridges are showing sign of distress within their designed service life in many cases as early as 10-12 years of construction in India and in several other countries. Bridges are designed for vehicles to pass through, they are supposed to support high traffic flow and maintain their quality and purpose. However, the poor quality of bridge construction causes the defects, deterioration, and distress of these bridges and lost its function. It caused the government to spend a lot of extra money to do the maintenance for these bridges, which is not necessary in the first place. The failure and collapse of these bridges might endanger the user and even involve in human lives lost as well. The present bridge is across Kharun river on Lakhnaghat – Jamghat Road at km 1/2-4. Yet barely five years after it opened for operation in 2008, this bridge is entering its twilight years. Bridge is in poor condition as there is loss of section, falling off concrete pieces, corrosion and crumbling of primary structural component, sagging of some spans etc.

II. The Bridge

This is a submersible bridge as the road top level is at highest flood level. The Bridge is 390m long, consisted of 26 spans, 25 piers and 2 abutments. Length of each span is 15m, simply supported on piers. Super structure is made up of RCC solid slab with cantilever at ends. It is a two lane submersible bridge of total 8.4m width. Kerbs are provided on either side of the carriageway along full length of the bridge, the width of kerb is kept 450mm and the clear carriage way is 7.5m. Piers are wall type, 3m wide flared up at top to 5.5m, resting on open type foundation. The Bridge is Designed for standard IRC class AA or Two lane of standard IRC class A loading. The salient features of the bridge are

1 Name of Bridge and Location Kharun river Bridge on Lakhnaghat – Jamghat Road at km 1/2-4 2 Date of Inspection 17/01/2013 3 Date of start of Construction 07/04/2007 4 Length of Bridge 390.0m Between Faces of Dirt Wall 5 Over all Width 8.4m 6 Span Arrangement 26 Span of 15.00m 7 Type of Piers Wall type Piers 3m wide, flaredup at top to 5.5m. 8 Type of Bearings Elastomeric Bearing 9 Deck Solid Slab with cantilever ends. 10 Foundation Pier (P1 TO P22) Open Abutment

A1, A2 Open 11 Highest Flood Level RL 102.80m 12 Road top Level RL 102.80m



III. Observations

Detailed observations of the said Bridge were carried out along with the engineer in charge. Following observations were made

A. Bridge is consisted of 15 spans, simply supported on wall type piers Fig. 1. B. The bridge is in poor condition. C. Quality of concrete in piers in first 13 spans from Raipur side appears to be alright but at flaredup

portion repairs of concrete have been carried out Fig. 2 and 3. D. Lot of honeycombing is observed in pier no. 19. It seems concrete was applied from outside.

Reinforcement of the pier is totally exposed Fig. 4, 5 and 6. E. Anchor rods are not provided through the bearing and in deck and in pier cap instead RCC wall is

constructed at the end of the pier cap going upto bottom of cantliver slab. F. The top of slab are not at one level but at different levels from span 13 to span 26. G. Span 1 to 13 appears to be alright beyond that the spans are sloping, the difference in level is about

300mm. H. Steel is exposed at the cantilever portion of pier cap and at bottom of deck Fig. 7. I. There is sag in some spans. The sag in span number 25 has occurred on completion of Bridge, the sag

is reported to be 157mm for 15m span Fig. 8. J. In span no. 16, 17, 19 & 20 the cover of concrete is exposed in the centre of span and steel is exposed

Fig. 7. K. Bottom of the span no. 15 is totally damaged and steel is exposed Fig. 7 and 9. L. Heights of pedestals is 450mm. it is rather too high for submersible bridges. M. Railing pipes over the expansion joints are continuous, need to be cut Fig. 10. N. Strip seal expansion joints are provided. O. There are several defects in formwork provided for discontinues kerbs. P. At the bottom cantilever end of the deck there is no drip because of which water marks has been

observed at the junction of solid slab and cantliver slab and poor concrete work Fig. 11. Q. On downstream side of bridge there is a stop dam. River course is straight on u/s and d/s side. R. Bridge is not aligned properly Fig. 12. S. There are so many corners in pier cap and the arrestors are not constructed properly Fig. 11 and 12.

IV. PROBABLE CAUSES OF EARLY DETERIORATION

Newly constructed RCC structures are failing in a fraction of its design life span. Therefore, the causes of premature deterioration in relatively new bridges are different as compared to those for old bridges. Generally, the main reason is poor or improper construction and/or poor or incorrect design [1]. Poor construction includes the following

A. Poor workmanship B. Inadequate cement quantity C. Excessive water cement ratio D. Inadequate concrete cover E. Honeycombed or Un-vibrated concrete F. Cold joints or bad construction joints G. Initially rust steel bars H. Congested reinforcement bars I. Porous cover blocks

Substandard workmanship in RCC can be in the form of honey combing (insufficient compaction of concrete) or inadequate cover to reinforcement (improper placement of bars) or both. These lead to early corrosion of reinforcement of structural member. Some of these deficiencies may become evident only after the full loading of structure has been put to use like 5 to 6 years. This may be the main reason of early distresses. IRC: 21-2000[2] has laid down from durability considerations, the minimum cement content in concrete, irrespective of strength depending upon the exposure conditions. The minimum quantity of cement is needed not only to coat the fine and coarse aggregate particles but also to fill the voids between the aggregate particles and to provide a thicker film of cement grout for easy workability. Thus, the aggregate particles slide over each other, during compaction of concrete. There may be the possibility of violation of this clause of IRC: 21-2000 in present case. For concrete to be durable there is a maximum w/c ratio specified for mixing concrete, as well as to give proper workability and concrete strength. Again the IRC: 21-2000[2] has laid down upper limits of water cement ratio. If water is more than the water required as per concrete mix design, extra water (not needed for Hydration) eventually evaporates and leaves minute capillary pores which permit the ingress of moisture and pollutants which lead to corrosion of steel bars and ultimate disintegration of the concrete. This may be one of the reasons of corrosion of reinforcement.



The black smiths who fix reinforcement bars are neither trained to bend the bars accurately nor to fix them effectively to ensure that the specified cover is left between bars and the formwork (shuttering). Quite often, not only the bars themselves touch form work but also the binding wire loose ends and the steel bars are seen at the surface of the concrete and they are subjected to early carbonation of concrete. Honeycombed concrete is a major source of weakness in concrete and cause of safety concern due to inadequate vibration/compaction. This can be seen at several places in present bridge. Most construction site personnel do not plan properly the sequence of pouring concrete to minimize the number of construction joints. They do not take adequate precautions to eliminate cold joints. A cold joint is a joint where fresh concrete is placed against a previous un-compacted concrete which has already hardened due to lapse of concrete setting time. Therefore, the fresh concrete will not homogeneously merge with the older concrete. This can be seen in piers of this bridge Often steel bars are stored in open areas, exposed to rain and atmospheric moisture resulting in rusting of them. The corrosion process starts rapidly in the presence of moisture. The steel bars are rarely wire-brushed and cleaned thoroughly before being placed in shuttering prior to concreting. In other cases, due to suspension of work due to reasons whatsoever, structural frame remains exposed to sun, rain and misuse for a long duration. Such prolonged exposure to weather can cause rusting of rebars. This may be one of the reasons of corrosion of reinforcement of the present bridge. If too many steel bars are provided in the narrow spaces which lead to practically no cover in concrete or even space for inserting a needle vibrator to ensure full compaction. This results in honeycombed concrete. Through honeycombing, the moisture and atmospheric pollution enters the steel bars and thus starting the corrosion process. The cover blocks are invariably made at site with no attention to the correct mix proportion or the specified water cement ratio. If the main concrete is of M30 grade, then the cover blocks too should be of the same grade and should be dense and impervious. The cover blocks are usually fixed to the steel bars at about one meter centers and if they are porous they become the starting source of decay of concrete as they permit the ingress of moisture which corrodes the steel. If dense concrete cover blocks cannot be made then it is preferable to use plastic cover blocks which are now available.

V. Conclusion In India, we come across many old bridges needing major repairs or go early in to a state of dilapidation condition. However, if a bridge has given about 25 to 30 years of service without much maintenance or major repair, then it is reasonable to expect that it would need some structural repair soon. The main cause for this is weathering and ageing effect or inadequate maintenance and care. However, generally at an age of less than 10 years; many poorly constructed and/or designed bridges are found to be in a very bad structural and general health condition needing major structural repairs. In case of present bridge this premature deterioration is largely due to poor construction. Concrete could become a treacherous construction material, if not manufactured correctly and not compacted fully. It may show low strength and high permeability. Though, it does not show signs of immediate weakness, but only after about four to ten years of construction, (depending upon the environmental conditions), signs of deterioration become visible. Therefore it is important to have an understanding of the vulnerabilities of concrete bridges in order to help minimize long-term repair and maintenan

REFERENCES [1] IRC 21:2000- Cement concrete (plain and reinforced) section III Standard specifications and code of practice for road bridges. [2] Gupta Y. P. " Causes for Accelerated Structural Deterioration of Reinforced Concrete," Advisor, Naini Bridge Information Centre;

COWI - DIPL Consortium, Allahabad, NBMCW February 2012.

Fig.1: Kharun River Bridge General view



Fig.2: Kharun River Bridge Repair on pier

Fig.3: Kharun River Bridge Repair on piers

Fig.4: Honey Combing at the flared up junction of the pier exposed steel at bottom of deck.



Fig. 5: Large size of metal is seen in the concrete of piers and steel is exposed.

Fig. 6: Exposed steel at one of the pier, size of aggregate more than 40mm.

Fig. 7: Steel is exposed at the cantilever portion of the pier cap and at bottom of slab.

Fig. 8: Sag of nearly 157mm in Span.



Fig.9: Bottom cover of Slab Exposed

Fig. 10: Kharun River Bridge top view, Steel Railing Continuous over Expansion joint.

Fig. 11: Bad Concrete work in cantilever portion.

Fig.12: Alignment of bridge is not done properly.

newly built doomed bridge - lack of quality control

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