Post-Fire Structural Health Assessment of G+1 UCO Bank Building

The Challenge

Fire exposure can alter the condition of concrete and structural components, while existing ageing, moisture ingress and reinforcement corrosion can contribute to further deterioration.

During the site inspection, the first floor showed visible evidence of fire exposure. The report records that the entire first floor had been affected by fire, with concrete surfaces blackened due to smoke and heat exposure.

Additional deterioration was observed in different parts of the building, including cracks in beams and columns, exposed reinforcement at localized beam locations, roof-joint water leakage, dampness and seepage, deteriorated concrete and plaster, a damaged chhajja, and distress in beams and slabs.

• Fire-affected first floor with blackened concrete surfaces
• Cracks in beams and columns
• Localized exposed reinforcement
• Roof-joint leakage, dampness and seepage
• Deteriorated concrete and plaster
• Severely damaged chhajja
• Distress in beams and slabs

Investigation Methodology

Nilima Design Associates used a combination of visual inspection and non-destructive testing to investigate the observed condition of the building and identify locations requiring further attention.

• Visual inspection of cracks, concrete deterioration, exposed reinforcement, fire effects and water-related damage
• Rebound Hammer testing to obtain an indication of surface hardness and estimated concrete strength
• Ultrasonic Pulse Velocity (UPV) testing to investigate concrete uniformity and internal integrity
• Carbonation testing to assess carbonation progression and its potential effect on reinforcement protection
• Rebar scanning to identify approximate reinforcement location, spacing, diameter and concrete cover

Visual Assessment After Fire

Visual inspection was particularly important because the first floor had experienced fire exposure. The report documented that the entire first floor was fire affected, with concrete surfaces blackened following smoke and heat exposure.

Cracks were observed at multiple beam and column locations. The report identified these cracks as requiring detailed crack-width measurement and further investigation.

Localized areas of beams had exposed reinforcement, indicating loss of concrete cover and possible corrosion. Roof-joint leakage, dampness and seepage marks were also observed.

The chhajja was reported as severely damaged and requiring immediate attention.

• First-floor surfaces affected by smoke and heat
• Cracking at multiple beam and column locations
• Localized exposed reinforcement in beams
• Roof-joint leakage and moisture-related deterioration
• Severely damaged chhajja requiring urgent attention

Rebound Hammer Investigation

Rebound Hammer testing was carried out on selected columns, beams and roof slabs to obtain an indication of surface hardness and estimated concrete compressive strength.

The recorded estimated values varied considerably across the tested locations. Selected first-floor columns recorded values around 30–38 N/mm², while several beams recorded approximately 22–42 N/mm². One roof-slab location recorded an estimated value of approximately 15 N/mm².

The report references IS 516 (Part 5 / Section 4):2020 for Rebound Hammer testing. It also notes that the results primarily indicate surface characteristics and do not represent the complete internal condition of concrete.

Ultrasonic Pulse Velocity Investigation

UPV testing provided additional information about the internal condition and uniformity of the concrete. The results showed a considerable number of DOUBTFUL classifications across the tested locations.

The report applies qualitative UPV grading based on its cited standard criteria, with values below 3.5 km/s classified as doubtful for the stated M25 criterion.

The results were considered alongside the visual inspection and other NDT findings because surface appearance and surface hardness alone cannot fully describe the internal condition of fire-affected concrete.

• Column 01 — 1.956 km/s — Doubtful
• Column 02 — 2.824 km/s — Doubtful
• Column 05 — 3.597 km/s — Good
• Beam 01 — 2.977 km/s — Doubtful
• Beam 03 — 3.306 km/s — Medium
• Beam 08 — 4.048 km/s — Good
• Beam 09 — 3.902 km/s — Good
• Several roof-slab locations — Doubtful

Carbonation & Durability Assessment

Carbonation testing was undertaken to investigate the condition of the concrete surrounding the reinforcement.

The report states that carbonation had progressed to reinforcement level at several locations, with loss of alkalinity associated with reinforcement corrosion, cracking and spalling.

This was an important durability finding because adequate reinforcement cover and concrete alkalinity contribute to reinforcement protection.

Rebar Scanning & Concrete Cover Assessment

Rebar scanning was performed on selected columns, beams and slabs to investigate approximate reinforcement location, diameter, spacing, arrangement and concrete cover.

Selected column locations recorded approximate cover values of 38–49 mm, together with reinforcement diameter and spacing. Selected beam locations recorded approximately 31–39 mm of cover, while selected slab locations showed approximately 21–31 mm.

The report notes that reinforcement quantity and spacing were generally within the referenced IS 456 limits, while reduced cover and carbonation remained durability concerns.

• Columns — approximately 38–49 mm concrete cover
• Beams — approximately 31–39 mm concrete cover
• Slabs — approximately 21–31 mm concrete cover
• Reinforcement diameter and spacing recorded at selected locations
• Reinforcement arrangement assessed alongside cover and durability observations

Key Findings

The combined investigation identified fire-related deterioration alongside ageing, carbonation, water ingress, cracking and localized reinforcement exposure.

The UPV investigation produced numerous doubtful classifications at tested locations, indicating areas requiring further assessment. Carbonation was reported to have reached reinforcement level at several locations, while active roof-joint leakage and dampness presented additional deterioration concerns.

The chhajja was reported as severely damaged and requiring immediate attention.

• Fire exposure: The entire first floor was reported as fire affected, with visible smoke- and heat-related surface deterioration.
• Concrete condition: UPV testing produced numerous doubtful classifications at tested locations.
• Water ingress: Roof-joint leakage and dampness were observed.
• Reinforcement: Exposed reinforcement and localized cover concerns were recorded.
• Carbonation: Carbonation was reported to have reached reinforcement level at several locations.
• Chhajja: Severe damage was recorded, requiring immediate attention.

Recommended Rehabilitation Strategy

Based on the investigation findings, the report recommended repair and rehabilitation measures addressing the damaged chhajja, fire-affected RCC members, reinforcement protection and water ingress. Detailed structural evaluation and repair design were recommended before execution of major repairs.

• Immediate chhajja action: Repair or dismantle the damaged chhajja as appropriate following a safety assessment.
• Fire-affected RCC repair: Repair and rehabilitate fire-affected and deteriorated RCC members using appropriate repair methodologies.
• Reinforcement protection: Apply suitable anti-corrosion treatment and restore concrete cover where reinforcement is exposed or carbonation has progressed.
• Waterproofing: Treat roof slabs and joints to reduce further water ingress and deterioration.
• Detailed structural evaluation: Have a qualified structural engineer prepare a detailed evaluation and repair design before major repair works are executed.
• Post-repair NDT: Conduct fresh NDT testing after repair or strengthening to assess the resulting condition.

Engineering Approach

FIRE DAMAGE → VISUAL INSPECTION → NDT INVESTIGATION → CONDITION ASSESSMENT → REPAIR DESIGN → STRENGTHENING → POST-REPAIR NDT

This project demonstrates the importance of a multi-stage investigation following a building fire. Rather than relying on visual appearance or a single test, the assessment combined visual inspection, Rebound Hammer testing, UPV, carbonation testing and rebar scanning to develop a more complete picture of the investigated structural elements.

• Visual Inspection — Identification of visible fire effects, cracks and deterioration
• Rebound Hammer — Assessment of concrete surface hardness
• UPV — Investigation of internal concrete uniformity
• Carbonation Testing — Assessment of carbonation and reinforcement protection
• Rebar Scanning — Investigation of reinforcement arrangement and concrete cover

Project Outcome

The assessment identified fire-related deterioration together with ageing, carbonation, water ingress, cracking and localized reinforcement exposure.

The report recommended that repair and strengthening works be carried out before considering continued use under the existing loading conditions, followed by fresh NDT assessment after strengthening.

The findings demonstrate the importance of combining non-destructive testing, visual inspection and engineering assessment when evaluating an existing structure after a fire incident.

Nilima Design Associates — Post-Fire Structural Assessment

We investigate. We document. We assess. We recommend.

Nilima Design Associates provides post-fire structural assessment, structural health checkups, NDT testing and structural repair and rehabilitation consultancy for existing buildings and infrastructure.

• Post-fire structural assessment
• Structural health checkup
• Rebound Hammer testing
• UPV testing
• Carbonation testing
• Rebar scanning
• Concrete condition assessment
• Structural repair and rehabilitation consultancy
• Post-repair NDT assessment