Retrofitting of Bridges Affected during Seismic Activity

Retrofitting of Bridges Affected during Seismic Activity

Vinay Gupta, Principal Consultant, Tandon Consultants Pvt. Ltd. New Delhi.

General

Occurrence of earthquake is no more a rare eventuality. India has witnessed several major earthquakes, involving substantial loss of lives. To name a few, a major earthquake (Richter scale 8.5) occurred in Assam in 1897 wherein the reported death toll was 1500. It was repeated at the same place in 1950 with similar number of reported deaths. Similarly, in 1934, major earthquake (Richter scale 8.4) occurred in Bihar-Nepal border area claiming 14,000 lives. It was repeated in 1988 claming about 1000 lives. The most recent major earthquake (Richter scale 8.0) in Bhuj claimed over 20,000 lives. By and far, major earthquakes have been observed to repeat in about 50 years in high earthquake prone areas. Comparatively, a larger number of bridges have been affected by seismic activities in America and Japan than those in India. Latur earthquake in 1993,did wake up the authorities to survey the bridges in Maharashtra area, retrofit and rehabilitate those bridges. Golden Gate Suspension Bridge, San Fransisco has been another example of Earthquake Retrofitting. Technique of retrofitting is not unique or predefined. It has to be decided on case to case basis, depending upon the prevailing circumstances.

Observed Damages

Retrofitting of Bridges Affected during Seismic Activity
Quite often, damage is noticed in and around the bearings due to stress concentration at these locations. Figure 1 shows an example of such damages even in a newly constructed bridge. Bearing has always been said to be a week link between massive superstructure and the substructure. Similarly Figure 2 shows that the superstructure of another bridge pounded the dirt wall, due to excessive longitudinal movement. Figure 3 shows damage of short vertical cantilever attached to the pier cap provided to negotiate difference of depths of the two adjoining superstructures. This happens due to formation of plastic hinges and lack of dissipation of earthquake energy at these locations. Similarly, Figure 4 shows damages of L-shaped superstructure at the half joints provided to house the hinge bearing.

Seismic Strengthening

Possible causes of deficiency in a bridge can be broadly the following:-
  • Inadequate Design.
  • Lack of Understanding by the Designer
  • Inadequate Construction
  • Deterioration of Material with Time
  • Upgradation of Seismic Design Requirements
  • Upgradation of Seismic Zones Therefore, main requirements of the proposed strengthening are as follows:-
  • Should be Economically Feasible
  • Should be Technically Viable
  • Should Surmount Functional Constraints
  • Should Reduce Seismic Demand - Reduce SILD and LL - Reduce Stiffness – Saw Cutting of Parapet
  • Increase Dissipation of Seismic Energy - Dampers
  • Increase the Supply Strength

Structural Strengthening

Seismic forces cause plastic hinge formation and overstressing at specified locations, such as pierfoundation junction, piersuperstructure junction in case of integral bridge, etc. For all such conditions, the pier cap can be confined to substantially enhance the performance during ultimate load conditions, see Figures 5 and 6. Figures 7 and 8 depict detailing for strength enhancement through addition of steel and concrete respectively. The additional concrete of the pier needs to be adequately anchored to the corresponding foundation.

Retrofitting of Bridges Affected during Seismic Activity
Concrete portals are commonly connected to the superstructure either through bearings or integrally. In such cases, the seismic force carrying capacity of a portal can be enhanced as depicted in Figures 9 and 10.

In the seismic conditions, foundations need to be strengthened both for downward load and uplift. Figure 11 depicts the use of additional piles to increase downward load capacity of pile foundation and the use of Passive Ground Anchors for prevention against uplift. Figure 12 depicts increase of structural strength of foundation by additional concrete and addition of prestressing after drilling hole into the foundation and grouting it after the application of prestress.

Reinforcement couplers and rebar fasteners are very useful components for enhancing the strength of an existing structures. Existing reinforcement can be suitably extended by providing reinforcement couplers, Figure 13. In case new reinforcing bars have to be added, rebar fasteners can be provided by drilling a hole of specified diameter and depth in concrete and filling high strength resin before inserting reinforcing bar, see Figure 14. This way full strength of the bar can be achieved in case a well foundation has to be strengthened, it can be done in the manner depicted in Figure 15. In case a masonry pier/abutment has to be increased in dimension, it can be done in the manner depicted in Figure 16.

Seismic forces experienced by the bridge can be substantially reduced by addition of vertical concrete upstands from the pier/ abutment cap and sandwitching flexible material, such as elastomer. Figures 19 and 20 depict the system of such an arrangement. In this arrangement, the vertical elastomeric bearings need to be detailed in a specialized way, wherein, the mating surface between the fixed side and the moveable side is made into stainless steel, in order to reduce sliding friction. For anchoring purpose a mild steel plate vulcanized on the surface of the bearing, as shown in Figure 20 is provided. Figures 21 and 22 depict an isometric view and photograph of such concrete upstands that receive the vertical elastomeric bearings. The elastomer acts as isolator by substrantially increasing time period of the structure, thereby reducing the seismic forces experienced by the structure.

The other method of strength enhancement is to provide fiber wraps. Mainly there are Carbon Fiber Wraps and Glass Fiber Wraps. These fiber wraps exhibit low creep and elongation and compared to steel, they are thinner, lighter and have up to 10 times and tensile strength capacity. Since, these wraps have unidirectional tensile capacity, they have to be carefully provided in direction, strength enhancement is desired. In case both shear and flexural strengths are required, two layers of the wrap perpendicular to each other are provided, refer Figures 23 and 24 for examples of fiber wrap application.

Conclusion

Method of seismic strengthening of bridges is a case specific matter. Depending upon the requirements of a particular location, the system of strengthening of superstructure, substructure and/or foundations has to be decided. An attempt should be made to reduce seismic demand by providing seismic isolators/dampers or increasing flexibility of the structure, provided they do not impare efficiency and functionality of the bridge. Confinement of core of piers using concrete jacket or steel jacket is an effective method of strength enhancement. When reinforcement has to be added, reinforcement couplers and rebar fasteners turn out to be useful items of structure. All the bridge components need to be investigated for strength enhancement.
NBM&CW March 2008
Performance of Thin White Topping (TWT) Overlay for NH-848

Performance of Thin White Topping (TWT) Overlay for NH-848

Vikas V. Thakar, MD, Pavetech Consultants India, presents the uses and advantages of TWT as a cost-effective treatment and a sustainable solution for rehabilitating and strengthening of flexible pavements, as seen in the NH-848 Nashik

Read more ...

REJUPAVE Technology for High RAP Recycling of Bituminous Pavement

REJUPAVE Technology for High RAP Recycling of Bituminous Pavement

Satish Pandey, Principal Scientist at CSIR-CRRI, New-Delhi, and Associate Professor, Academy of Scientific and Innovative Research, gives a brief overview of Hot Mix recycling process using bio-oil based rejuvenator REJUPAVE to facilitate

Read more ...

Safety Challenges On Indian Roads

Safety Challenges On Indian Roads

S.K. Nirmal, Secretary General, Indian Roads Congress, Director General (Road Development) & Special Secretary (Retd), MoRTH, gives an overview of India’s road network, causes of road accidents, and the safety measures and policies required

Read more ...

Dynapac Machines Deployed on Prestigious Palkhi Marg Project in Maharashtra

Dynapac Machines Deployed on Prestigious Palkhi Marg Project in Maharashtra

The Palkhi Marg holds deep significance as a pathway of faith for devotees of Lord Vitthal. Every year, thousands of ‘warkaris’ embark on a spiritual journey to the temple town of Pandharpur in Maharashtra. With the vision to create a Bhakti Marg and ensure

Read more ...

Delhi Vadodara Expressway Package-1 An overview

Delhi Vadodara Expressway Package-1 An overview

The Delhi-Vadodara Expressway is a part of the most anxiously awaited Delhi-Mumbai Expressway - the foundation stone for which was laid on March 8th 2019. Also referred to as the Delhi-Mumbai Industrial Corridor, it is planned as part of the Bharatmala

Read more ...

Bonded Rigid Pavement - A New Edge Concrete Pavement

Bonded Rigid Pavement - A New Edge Concrete Pavement

The exponential growth of the highway infrastructure in the past two decades has increased demand for long-lasting, durable pavements. Rigid pavements are suitable for heavily trafficked areas and are found to be performing satisfactorily with minimum

Read more ...

BRO Builds ‘Zero Fatality Corridors’ in Arunachal Pradesh

BRO Builds ‘Zero Fatality Corridors’ in Arunachal Pradesh

Through its unwavering commitment to road safety, eco-conscious practices, and visionary solutions, the Border Roads Organisation is elevating the standard of road infrastructure development in India. In Arunachal Pradesh, its contributions

Read more ...

Engineering Measures for Pothole Prevention

Engineering Measures for Pothole Prevention

Roads, pavements, and other paved surfaces have depressions in them called potholes which are caused by a variety of conditions. They not only present a serious risk to traffic and pedestrians, but also necessitate expensive repairs by local governments and

Read more ...

Pavement Marking Essential For Road Safety

Pavement Marking Essential For Road Safety

Vivek Singh, Founder, BuildStreet delves into the significance of pavement marking, its objective, and importance, with a focus on Hot Applied Thermoplastic paint - the predominant choice for road markings in India, its technical aspects, application methodology

Read more ...

GAEPL Achieves Record Paving of 100 lane-km in 100 hours

GAEPL Achieves Record Paving of 100 lane-km in 100 hours

Ghaziabad Aligarh Expressway Private Limited (GAEPL), under the guidance of Cube Highways, has set an example of speedy, safe, and sustainable road construction through research, integration of advanced technology, following best international practices

Read more ...

Indian Companies Delivering Projects Overseas

Indian Companies Delivering Projects Overseas

External affairs minister S. Jaishankar during his visit interacted with the workers and the senior staff, and lauded the role of Indian infra companies, saying that he was “impressed by their enthusiasm”. “Strong economics will complement shared values in taking

Read more ...

NHAI awards 6,003 km of highway projects in FY23

NHAI awards 6,003 km of highway projects in FY23

According to Motilal Oswal Financial Services, the infra project awarding activity picked up and gathered pace in Q4 of FY23, with NHAI awarding total projects of 6,003 km in FY23, much below its FY23 target of 6,500 km. The total value of projects awarded

Read more ...

Is the Indian Road Sector Navigating a Smooth Journey?

Is the Indian Road Sector Navigating a Smooth Journey?

This report covers the current state of the Indian Road Sector, performance of road projects under Hybrid Annuity Model, financial performance of major road developers, and the outlook for FY24. CareEdge Ratings analysed 235 HAM projects awarded between

Read more ...

Balanced Mix Design for Bituminous Mixes

Balanced Mix Design for Bituminous Mixes

As more than 90% of the roads in India have bituminous surfacing, a proper bituminous mix design also assumes significance for better performance of the bituminous roads. India is currently witnessing huge investments by the Indian Government towards

Read more ...

Sustainable Road Construction in Hilly Region

Sustainable Road Construction in Hilly Region

Siksha Swaroopa Kar, Principal Scientist, Amit Kumar, Technical Officer, Krishan, Technician, Flexible Pavement Division, CSIR-CRRI, New Delhi, discuss mechanized laying of cold bituminous layer, the mixer and paver that have been fabricated, and the effectiveness

Read more ...

Implementation of Road Maintenance Management System - Benefits & Technologies

Implementation of Road Maintenance Management System - Benefits & Technologies

The maintenance of road pavements is essential to ensure the safety, reliability, and sustainability of road networks. A road maintenance management system (RMMS) involves effective management of resources to optimize the life cycle of roads, reduce maintenance

Read more ...

Replacement of Steel Reinforcement with  Synthetic Fibre for Concrete Pavement & Floor

Replacement of Steel Reinforcement with Synthetic Fibre for Concrete Pavement & Floor

Manoj Didwania, Adani Total Gas Ltd, Dharamsinh Desai University (DDU-Nadiad), Cept University, presents a paper on the use of Macro Synthetic Reinforcement Fibre (MSRF) as full or partial replacement of Steel Reinforcement for Concrete Pavement

Read more ...

GTI® Reinforced Soil Slope System

GTI® Reinforced Soil Slope System

GTI® is involved in developing environmentally friendly construction products and systems, which are critical for achieving infrastructure growth in a sustainable manner. The company’s GTI® Sloping Fascia Unit and the new system GTI® Reinforced Soil Slopes

Read more ...

CRISIL: Debt to rise for road developers amid strong revenue growth

CRISIL: Debt to rise for road developers amid strong revenue growth

Sizeable equity commitments in under-construction projects and rising working capital requirement will increase the debt burden of road developers, though revenue growth will also be high in the next two fiscals driven by strong awarding and execution

Read more ...

Indian Toll Roads to witness moderation in growth to high single digits in FY2024 after a stellar 17-20% growth in FY2023: ICRA

Indian Toll Roads to witness moderation in growth to high single digits in FY2024 after a stellar 17-20% growth in FY2023: ICRA

WPI for December 2022 is significantly lower at 5.0% against WPI of 14.27% in December 2021. ICRA Ratings expects the toll road projects growth to moderate to high single digit in FY2024 after a 17-20% growth witnessed in FY2023 with moderation in the

Read more ...

To get latest updates on whatsapp, Save +91 93545 87773 and send us a 'Saved' message
Click Here to Subscribe to Our eNewsletter.