Developed through a collaboration between SUPERLIT and Boğaziçi University under the TÜBİTAK TEYDEB 1505 University–Industry Cooperation Support Program, the seismic-resistant flexible GRP pipe joint system was evaluated through numerical analyses based on actual earthquake records, full-scale mechanical experiments and shaking-table tests. The innovative system is designed to accommodate ground movements that may occur during earthquakes while maintaining pipeline integrity and watertightness.

Earthquakes pose significant risks not only to buildings and above-ground structures but also to critical infrastructure systems used to transport drinking water, wastewater, irrigation water and industrial fluids. Ground deformation occurring during an earthquake can cause axial and angular movements in pipelines, generating high stress concentrations, particularly at joint locations. This can result in pipeline damage, leakage and service interruptions.

SUPERLIT and Boğaziçi University have undertaken a major university–industry cooperation project to enhance the seismic resilience of critical infrastructure.

The project, entitled “Design and Development of a Joint System Providing Earthquake Resistance in Composite Pipelines,” is being conducted under the TÜBİTAK TEYDEB 1505 University–Industry Cooperation Support Program.

As part of the project, an innovative GRP pipe joint system was developed to accommodate movements caused by earthquakes and different forms of ground deformation while maintaining pipeline integrity and watertightness.

A flexible joint system that accommodates seismic movements

Unlike conventional pipe joints, the developed system is designed to allow controlled angular and axial movement at the joint.

The system’s targeted movement capabilities were defined as:

• Angular deflection of up to 7.5 degrees

• Axial movement of up to 6 centimetres in either direction

• Preservation of watertightness during repeated movements

• Maintenance of system integrity under high internal pressure and mechanical loads

• Reduction of the effects of earthquake-induced ground deformation on the pipeline

These movement capabilities help prevent the forces transferred to the pipeline during an earthquake from becoming concentrated at a single point. The joint’s ability to move in a controlled manner enables the pipeline to adapt more safely to changing ground conditions.

Design, analysis and prototyping conducted together

The project was not limited to designing a new joint geometry. During the development of the system, the joint geometry, composite material structure, resin and glass-fibre properties, manufacturing parameters and sealing components were addressed through an integrated engineering approach.

Preparatory work began in 2022, and the implementation phase commenced in early 2023. Several design alternatives were developed during the project. The resulting prototypes were progressively refined based on findings obtained from numerical analyses and experimental studies.

During this process:

• The mechanical behaviour of the joint geometry was examined.

• The composite material structure was evaluated under different loading conditions.

• Resin and fibre properties were refined in line with test results.

• Manufacturing parameters were improved using data obtained from the prototypes.

• The joint system’s watertightness performance under pressure was verified.

• Different angular and axial movement scenarios were compared.

More than 50 experiments conducted throughout the project played an important role in refining and maturing the system design.

Comprehensive testing on full-scale pipes

Comprehensive mechanical tests were conducted on full-scale GRP pipes to evaluate the behaviour of the joint system under actual operating conditions.

Using empty, water-filled and pressurised pipes, the system was subjected to axial loading, cyclic movement, angular deflection and internal pressure tests. These tests examined not only the joint’s performance during a single movement but also its mechanical behaviour and continued watertightness during repeated movements.

The data obtained from these experiments were used at different stages of the design process. Consequently, the joint geometry and material properties were developed not only on the basis of theoretical calculations but also according to the results of full-scale testing.

Numerical analysis using actual earthquake records

Different earthquake scenarios and ground motions were evaluated during the numerical analysis stage of the project.

Ground-motion records obtained from the Kahramanmaraş and Kobe earthquakes were used to model the behaviour of the pipeline and joint system during an earthquake. The analyses considered the buried pipeline, surrounding soil and developed joint system together.

The numerical studies examined the axial and angular movements that could occur in the pipeline, stress distributions at the joint and the system’s response to different earthquake motions.

The findings were evaluated together with data obtained from the mechanical experiments and full-scale shaking-table tests and subsequently incorporated into the design process.

Full-scale shaking-table tests at Kandilli

Full-scale experiments were conducted at the Structural and Shaking Table Laboratory on Boğaziçi University’s Kandilli Campus to assess the performance of the developed joint system under earthquake conditions.

The pipeline was installed in the experimental setup to represent buried operating conditions. During shaking-table tests based on actual earthquake motions, the combined behaviour of the pipeline, surrounding soil and joint system was monitored.

The tests focused particularly on:

• Angular movements occurring at the joint

• Axial displacement of the pipeline

• Pipe–soil interaction

• Mechanical behaviour under repeated earthquake motions

• Watertightness performance of the joint

• Preservation of overall system integrity

The combined evaluation of the results obtained from numerical analyses, mechanical experiments and shaking-table tests provided an important basis for validating the system’s suitability for adaptation to actual field conditions.

Academic expertise and industrial experience brought together

The project brought together Boğaziçi University’s academic expertise in earthquake engineering, composite materials, numerical modelling and full-scale testing with SUPERLIT’s experience in GRP pipe systems, manufacturing technologies and field applications.

The project’s academic leadership was undertaken by Prof. Dr. Gülüm Tanırcan, a faculty member in the Department of Earthquake Engineering at Boğaziçi University’s Kandilli Observatory and Earthquake Research Institute (KOERI). Prof. Dr. Nuri Bülent Ersoy of the Department of Mechanical Engineering at Boğaziçi University’s Faculty of Engineering; Prof. Dr. Ayşe Edinçliler, Head of the Department of Earthquake Engineering at KOERI; and Dr. Hasan Emre Demirci and Dr. Kaveh Shahidi of the Department of Mechanical Engineering also made valuable contributions to the project in their respective areas of expertise.

On the SUPERLIT side, Hakan MİS led the project, while the company’s design and manufacturing teams played an active role in developing the system, preparing the prototypes, improving the manufacturing processes and carrying out the testing activities.

Conducted through the joint efforts of academics, researchers, laboratory teams, SUPERLIT’s project leadership, and its design and manufacturing teams, the project represents an important example of university–industry collaboration in transforming scientific research findings into a practical and commercially viable infrastructure solution.

Supporting service continuity for critical infrastructure

Ensuring that drinking-water, wastewater and other critical infrastructure systems remain operational after an earthquake is vital to disaster management and the continuity of everyday life.

The developed flexible GRP pipe joint system is intended particularly for use in infrastructure projects located in areas with high seismic risk or where different forms of ground deformation are anticipated.

The system’s controlled movement capability is intended to contribute to:

• Reducing stress concentrations within the pipeline

• Protecting joint locations

• Supporting continued watertightness

• Reducing the risk of damage and service interruptions

• Preserving the post-earthquake functionality of infrastructure systems

An engineering-led approach to more resilient infrastructure

Climate change, rapid urbanisation, population growth and increasing natural-disaster risks are driving the need for more resilient and adaptable infrastructure solutions.

Through its GRP pipe technologies and engineering solutions, SUPERLIT continues to develop solutions not only for existing infrastructure requirements but also for environmental and structural risks that may emerge in the future.

The project conducted with Boğaziçi University demonstrates how academic knowledge, experimental research, advanced engineering and industrial manufacturing capabilities can be combined to create safer, more resilient and sustainable infrastructure.