‘Design specific to local conditions, foundation analysis, regular audit & maintenance must for hoarding stability’

In the dynamic landscape of urban infrastructure, the safety and stability of hoardings have become a critical concern, particularly in the wake of collapse of hoardings in different cities, some with severe consequences. Those incidents underscore the urgent need for meticulous planning, robust design, and rigorous maintenance practices. To delve deeper into this issue, Rajiv Raghunath had a conversation with Prashantkumar A Jaiswal, Director, CivilTech India, Nashik. With his extensive experience and expertise in structural engineering, Prashantkumar provided invaluable insights into the factors that are paramount for ensuring the structural stability of hoardings.  

The Foundation: Bedrock of Stability 

At the heart of any stable structure lies a well-engineered foundation. Prashantkumar emphasised that one of the primary reasons for structural failures in hoardings is the lack of adequate foundation analysis and wind pressure calculations. A robust foundation must anchor the structure firmly, counteracting the forces exerted by wind and other environmental factors. 

Key Considerations for Foundation Design:

1. Load-Bearing Capacity: The foundation must be designed to bear at least 1.5 times the weight of the structure. This margin ensures that the foundation remains stable under normal and extreme conditions.
2. Soil Analysis: Before construction, a thorough geotechnical investigation should be conducted to assess the soil's bearing capacity. Different soil types require different foundation designs, and ignoring this can lead to catastrophic failures.
3. Wind Load Calculations: Accurate wind load calculations are critical. These calculations must account for the maximum wind speeds recorded in the area, ensuring that the structure can withstand even the most severe conditions.

Customising Designs for Local Conditions

A prevalent issue in the industry is the tendency to use standardised designs across various locations without considering local environmental variations. Prashantkumar highlighted that each site presents unique challenges, such as differing wind velocities, soil conditions, and exposure to environmental elements. 

Localised Design Adjustments:

1. Wind Velocity: The design must be tailored to the local wind velocity. For instance, coastal areas with higher wind speeds require more robust designs compared to inland areas.
2. Environmental Exposure: Structures in corrosive environments, such as coastal regions or industrial areas, need additional protection against corrosion. Using galvanised materials and applying protective coatings can enhance durability.
3. Soil Type: The foundation design must be adapted to the local soil type. Sandy soils, clay soils, and rocky terrains all require different foundation strategies to ensure stability.

Regular Structural Audits and Maintenance

Ensuring the long-term stability of hoardings necessitates regular structural audits and maintenance. Prashantkumar emphasised that these audits should be comprehensive, including both non-destructive and destructive testing methods to assess the overall health of the structure. 

Essential Audit Practices:

1. Non-Destructive Testing (NDT): Techniques such as ultrasonic testing, magnetic particle inspection, and radiographic testing can detect internal flaws without damaging the structure.
2. Destructive Testing: In some cases, small sections of the structure may need to be tested destructively to gain a detailed understanding of material properties and potential weaknesses.
3. Corrosion Checks: Regular checks for corrosion, especially in joints and connections, are vital. Corrosion can significantly weaken structural components, leading to failures.
4. Joint Integrity: Ensuring that all joints and connections are secure and free from defects is crucial for maintaining structural integrity.
5. Load Testing: Periodic load testing can verify that the structure can bear the intended loads without deformation or failure.

Material Selection: Suitability and Durability

Choosing the right materials is a cornerstone of building durable hoardings. The materials must be suited to the local climate and environmental conditions to ensure longevity and stability. 

Materials to be considered:

1. Galvanised Iron: In coastal areas, galvanised iron with a minimum thickness of 5mm is recommended to prevent rapid corrosion. The galvanisation process provides a protective coating that resists rust and degradation.
2. Cold Steel Sections: Cold steel sections are preferred over traditional square or circular pipes due to their superior durability and resistance to environmental stresses.
3. Composite Materials: In some cases, composite materials may offer enhanced performance characteristics, such as increased strength-to-weight ratios and better corrosion resistance.

Regulatory Oversight and Certification 

The role of regulatory bodies in ensuring the safety of hoardings cannot be overstated. However, Prashantkumar pointed out significant gaps in the current regulatory framework. Often, these bodies lack the technical expertise required for thorough evaluations, leading to superficial safety checks.

Enhancing Regulatory Effectiveness:

1. Expert Panels: Establishing panels of expert structural engineers to oversee the certification process can ensure that all structures meet stringent safety standards.
2. Mandatory Audits: Regulations should mandate regular structural audits by qualified professionals. These audits should be comprehensive and include detailed reports on the condition of the structure.
3. Accountability: Legal accountability for structural engineers and auditors should be established to ensure that certifications are accurate and reliable.

Reinforcing Existing Structures

Many existing hoardings require reinforcement to comply with current safety standards. Prashantkumarestimated that about 2% of hoardings are found to be  structurally instable, during audits. Reinforcing these structures involves addressing both visible damages and underlying foundational issues.

Steps for Reinforcement:

1. Foundation Strengthening: Reinforce the foundation to ensure it can bear the necessary loads. This may involve adding additional concrete, steel reinforcements, or other materials to enhance stability.
2. Structural Repairs: Address any visible damages such as cracks, deformations, or corrosion. This might include replacing damaged components, applying protective coatings, and sealing joints.
3. Load Redistribution: In some cases, redistributing the load across the structure can enhance stability. This may involve adding additional support columns or beams.

Designing for Wind and Environmental Forces

There are comprehensive guidelines for designing structures to withstand local wind pressures and other environmental forces. Prashantkumar explained that adhering to these standards is crucial for preventing structural failures.

 Key Design Standards:

1. Wind Load Standards: The design must account for the maximum wind pressures expected in the area, including considerations for cyclonic conditions. The standards typically include a safety margin of 0.15% to account for unexpected conditions.
2. Seismic Considerations: In regions prone to earthquakes, designs must also consider seismic forces. This involves using flexible materials and designs that can absorb and dissipate seismic energy.
3. Environmental Durability: Structures must be designed to withstand local environmental conditions, including humidity, temperature variations, and exposure to pollutants. 

Government and Industry Collaboration

Effective government regulation is essential for ensuring the safety of hoardings. However, collaboration between government bodies and the industry is equally important. Prashantkumar suggested several ways to enhance this collaboration.

Collaborative Efforts:

1. Shared Responsibilities: Both government and industry players should share the responsibility for structural safety. This includes joint initiatives for regular audits, training programs, and research into new materials and techniques.
2. Technology and Expertise: Regulatory bodies should be equipped with the latest technology and expertise to conduct thorough evaluations. This might involve partnerships with academic institutions and research organisations.
3. Public Awareness: Increasing public awareness about the importance of structural safety can drive demand for safer hoardings. Educational campaigns and transparency in reporting can help achieve this goal.

Conclusion

The safety and stability of hoardings are critical issues that require a multi-faceted approach. From ensuring robust foundations and customising designs for local conditions to regular audits, appropriate material selection, and effective regulatory oversight, each aspect plays a vital role in maintaining structural integrity.

Prashantkumar's insights underscore the importance of rigorous planning and meticulous execution in building and maintaining safe hoardings. By adhering to best practices and fostering collaboration between government and industry, the OOH industry could create a much safer urban environment for all.