Strengthening of glass fiber sheets for multi-bolted pultruded GFRP connections: Effects of connection type and bolt-tightening force

This study investigated the effects of bolt-tightening forces on the connection strengths of non-strengthened and glass fiber sheet (GFS)-strengthened pultruded glass fiber reinforced polymer (PGFRP) connections through a series of experiments using double-lap and single-lap specimens. A total of 96 specimens (3 specimens for each parameter), half of which were non-strengthened, were tested under tensile loads and four bolt-tightening forces: 0, 5 N.m, 10 N.m, and 20 N.m. The (0 degrees/90 degrees)/chopped strand mat/(0 degrees/90 degrees) lamination was bonded to both PGFRP plates' outside surfaces and improved the connection strengths. The results indicated that maximum failure loads increased with an increase in bolt-tightening forces. However, there were different trends in the maximum failure load changes, depending on the specimen type (non-strengthened or GFS-strengthened specimens; double-lap or single-lap specimens) and bolt-tightening forces. In addition, GFSs could effectively improve PGFRP's connection strengths and ductility performances.