Research On Strengthening Performance Of RC Beams With Large Web Openings Using Externally Bonded CFRP And Steel Plates

In retroficaiton of exist buildings,it is an efficient solution to install large-diameter pipes through web openings of reinforced concrete(RC)beams to save the space beneath the beams..However,large web openings can seriously weaken beam’s shear capacity,which require strengthening measures taken to restore the structural capacity.Thus,It is significant toconduct research on the strengthening techniques aiming at providing a reliable guildline for the field practice.Three groups of specimens were prepared with different opening size and strengthened with externally bonded CFRP or steel plate,which were tested subsequently under flexure to investigate comparatively the crack development,failure modes and structural performances.Shown by test results,both the CFRP and steel plate strengthening constrained the crack development effectively and enhance considerably the shear capacity of the weakened beams.There was no obvious difference on the load capacity improvement,whereas CFRP strengthening showed advantage on deformation capability while steel plate strengthening had greater contribution on recovery of flexural stiffness.Size of web opening plays an important role in the strengthening efficiency,which can result in different failure mode of the specimens.In addition,bond between the strengthening material and concrete is another important influencing factor.Based on the experiment results,finite element models were built and calibrated to further investigate the strengthening techniques.Parameter study were conducted on opening height and opening length.Shown by analysis results,both strengthening techniques are effective on condition of moderate large web opening,whereas the effectiveness will drop rapidly with opening becoming over large,especially the opening height.In this work,investigation was performced on shear performance restoration of RC beams weakened by large web openings and strengthened with externally bonded CFRP and steel plate,and strengthening effectiveness was deeply explored under influence of different factors.Results of the research will provide reliable theoretical basis for field application.