Modares Mechanical Engineering

Modares Mechanical Engineering

Experimental Investigation of the Effect of Tensile Pre Damage and Cyclic Loading on the Flexural Capacity of GFRP Strengthened Steel Pipes under Dry and Wet Environmental Conditions

Document Type : Original Article

Authors
Ramin Beyranvand
mahdi ansari
Mechanical Engineering Department, Arak University of Technology, Arak, Iran
10.48311/mme.2026.119730.82991
Abstract
In real operating conditions, strengthened tubes rarely experience simple loading states and may be simultaneously affected by initial deformation, cyclic loading, and environmental exposure. The interaction of these factors can introduce pre damage and alter the mechanical behavior and load bearing capacity of the structure during subsequent loading.This study experimentally examines the flexural behavior of steel tubes strengthened with glass fiber–epoxy composite after tensile pre damage, cyclic loading, and exposure to dry and marine environments. Two levels of initial tensile displacement equal to 10 millimeters and 30 millimeters and two levels of cyclic loading equal to 50 and 100 cycles were applied. The influence of environmental conditions was assessed by conditioning specimens in dry air and in simulated seawater for periods of14, 25, and 40 days.The results indicate that an initial displacement of30 millimeters significantly reduces flexural capacity, lowering the maximum flexural load from 18657.4 newtons to10294.4 newtons. Under dry conditions, increasing the number of cycles decreases both cyclic load and flexural capacity, and increasing the initial displacement from 10 millimeters to 30 millimeters leads to a reduction of about 45 percent in flexural capacity. In contrast, for specimens with an initial displacement of 30 millimeters and100 cycles, longer exposure to the marine environment increases flexural capacity from5475.3 newtons to20723.7 newtons, attributed to controlled softening of the epoxy matrix and completion of post curing. The findings show that in realistic service conditions, the flexural performance of strengthened tubes is strongly influenced by pre damage, loading history, and environmental exposure.
Keywords
Reinforced Steel Pipe
Bending
Tensile Pre-Damage
Cyclic Loading
Environmental Conditions
Subjects
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Modares Mechanical Engineering
Volume 26, Issue 12
December 2026
Pages 977-988