PSI - Issue 81

Roman Rybak et al. / Procedia Structural Integrity 81 (2026) 255–259

256

manufacturing defects, improper backfilling, violations of transportation and installation conditions, and non-uniform soil settlement (Dovbenko et al., 2024; Drobyshynets et al., 2024). Under these conditions, there is an urgent need to implement reliable methods for the partial or complete rehabilitation of culvert pipes that would extend their service life, avoid full replacement, and reduce road construction costs (Rybak et al., 2025). One of the promising solutions is the sleeving (lining) technique, which ensures restoration of the spatial performance of the pipe and improvement of its technical characteristics. Rybak et al. (2024) note that additional reinforcement of the inter-pipe space using a reinforcing cage has the potential to increase structural resistance to deformation development and reduce stress concentrations in critical zones. The purpose of this study is a comprehensive experimental investigation of the effect of additional reinforcement on the deformability characteristics of a reinforced concrete culvert pipe strengthened by the sleeving method. The study focuses on establishing limit states, such as the onset of cracking and the moment of complete failure. The distribution of displacements along the pipe is also analyzed. Based on the results obtained, conclusions will be substantiated regarding the effectiveness of this method, which will help to improve the technology for restoring defective pipes in real-world conditions. 2. Methods of experimental research For the experimental study, a previously damaged reinforced concrete culvert pipe was used as the base specimen for performing the strengthening works. The strengthening procedure involved installing a steel liner inside the damaged pipe and placing a spatial reinforcing cage in the annular gap between the liner and the outer reinforced concrete shell. After installation of the cage, the inter pipe space was filled with a repair mortar. The structural scheme of the strengthened reinforced concrete pipe with the spatial reinforcing cage is shown in Fig. 1. The geometric parameters of the reinforced concrete pipe were as follows: outer diameter – 725 mm; inner diameter – 585 mm; wall thickness – 70 mm; length – 400 mm; weight – 130 kg; concrete class – C25/30; reinforcement – VR1 wire. The following materials and components were used to strengthen the damaged pipe: ▪ New steel pipe: welded steel pipe made of St3 steel, diameter – 500 mm, wall thickness – 2 mm, length – 450 mm. ▪ Material for filling the annular gap: repair mortar with a compressive strength of 35 MPa. ▪ Reinforcing cage: Ø6A240C reinforcement arranged in a spatial configuration

А

А - А

Layer of repair mortar

25 70

Metal pipe

25 25

70

500

725

Ø6 А240

Ø6 А240

Reinforced cage

25

Damaged reinforced concrete pipe

400

А

Fig. 1. Structural scheme of the strengthened reinforced concrete pipe with an added spatial reinforcing cage.

The load was applied to the pipe using a hydraulic press. The load was increased stepwise in increments of 5 kN at each stage. Using a preprogrammed microcontroller, deformation data were systematically recorded and stored in a computer file at a sampling rate of 4 Hz. At each loading stage, a standard holding period of 5 minutes was provided to allow for deformation stabilization and recording of stress – strain parameters (Kovalchuk et al., 2024). Throughout the entire test, continuous monitoring of vertical and horizontal displacements at characteristic points on the outer surface of the pipe was carried out. The measurement scheme, the location of strain sensors, and the laboratory equipment used are shown in Fig. 2.