Naihati Railway ROH Shed Structural Health Assessment

Our Scope of Work

The investigation covered visual inspection of steel and concrete elements, selected welding-joint examinations, ultrasonic thickness measurements, ultrasonic flaw detection and concrete NDT. The findings were assessed to identify defects and provide technical recommendations.

• Visual inspection of ISMB columns, beams and truss members
• Dry penetration testing of selected steel welding joints
• Ultrasonic thickness measurement of steel members
• Ultrasonic flaw detection for possible internal discontinuities
• Visual inspection of concrete pedestals
• Rebound Hammer testing of concrete
• Ultrasonic Pulse Velocity (UPV) testing
• Assessment of observed defects and structural condition
• Technical recommendations based on NDT findings

Steel Structure Assessment

The ISMB columns, beams and truss members were visually inspected. The report recorded adequate thickness in the inspected steel members, no visible cracks in the inspected areas, satisfactory welding conditions in the examined locations, and minimal corrosion or rust on steel and truss elements.

Ultrasonic thickness measurements were performed on steel columns. Recorded east-side column thicknesses ranged approximately from 12.15 mm to 13.60 mm, while west-side measurements were also documented in the report. The report concluded that the tested steel elements had adequate measured thickness.

Dry/visible penetrant examination was carried out on selected welding joints from the east, middle and west sides of the shed. The reported observations indicated no recordable discontinuities, apart from minor spot indications below the registration level. The tested locations were reported as acceptable under the stated acceptance criteria.

Ultrasonic flaw detection was also performed on selected welding joints using a pulse-echo contact method. The report documented the equipment, probe, calibration and stated test and acceptance standards used for the examination.

Concrete Structural Assessment

A concrete-focused investigation was carried out using Rebound Hammer and Ultrasonic Pulse Velocity testing, together with visual inspection of the structural elements. These complementary methods were used to investigate surface hardness, concrete uniformity and areas potentially affected by defects.

Rebound Hammer Test

The Rebound Hammer investigation recorded estimated surface compressive-strength values at selected locations in the approximate range of 26–34 N/mm², with variations between individual structural elements. The report described a combination of poor-quality and good-quality concrete areas.

Ultrasonic Pulse Velocity Testing

UPV testing was performed to investigate concrete uniformity and identify locations potentially affected by internal cracks, voids or discontinuities. The report classified concrete quality across the tested locations from medium to excellent, while also identifying doubtful areas requiring attention.

Visual Inspection of Concrete Pedestals

The visual inspection identified cracks and voids in multiple concrete pedestals. Some areas showed compromised surface integrity, spalling or delamination.

The report recommended repair and grouting of affected pedestals before additional structural loading.

Engineering Findings

The combined investigation provided a broader understanding of the structure by examining both the steel superstructure and its concrete supporting elements using complementary inspection and testing methods.

The inspected steel members showed adequate measured thickness. No cracks were recorded during the visual inspection, and no recordable discontinuities were reported in the selected dry penetration examination.

The concrete investigation identified areas requiring rehabilitation, particularly selected pedestals and columns where cracks, voids or doubtful UPV results were observed.

The findings demonstrate why structural health assessment should not rely on a single test. Visual inspection, steel NDT and concrete NDT were used together to evaluate different aspects of the existing structure.

Recommended Rehabilitation Approach

Based on the concrete investigation, the report recommended suitable grouting for doubtful areas to address internal voids and improve the condition of affected concrete elements.

• Use non-shrink, high-strength cementitious grout for appropriate surface repairs.
• Use epoxy grout for deeper cracks and voids, where applicable.
• Clean and prepare affected pedestal surfaces.
• Drill injection holes at identified weak zones.
• Carry out pressure grouting to fill identified voids and cracks.
• Allow adequate curing according to the selected material specification.
• Repeat Rebound Hammer and UPV testing after rehabilitation to assess the treated areas.

Our Approach

Nilima Design Associates follows a systematic approach to structural health assessment, from initial inspection to technical reporting and recommendations.

01 — Visual Inspection: Detailed examination of accessible steel and concrete structural elements.

02 — NDT Investigation: Selection of appropriate non-destructive techniques for steel and concrete.

03 — Data Assessment: Review of thickness measurements, flaw indications, rebound values and UPV results.

04 — Structural Interpretation: Identification of areas requiring further investigation, repair or rehabilitation.

05 — Technical Reporting: Preparation of documented findings and recommendations for the assessed structure.

Project Outcome

The investigation provided the client with a documented assessment of the existing Railway ROH Shed PEB structure at Naihati, covering both the steel superstructure and selected concrete supporting elements.

The steel assessment found adequate measured thicknesses and no cracks or recordable discontinuities in the inspected areas. The concrete assessment identified specific areas requiring repair and grouting before additional loading.

The project demonstrates Nilima Design Associates' capability in integrated structural health assessment, combining field inspection and multiple NDT techniques to support informed structural maintenance and rehabilitation decisions.