Assessing the behaviour of RC beams subject to significant gravity loads under cyclic loads

• Published in: Engineering structures Vol. 59; pp. 512 - 521
• Main Authors: Gião, Rita, Lúcio, Válter, Chastre, Carlos
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.02.2014; Elsevier
• Subjects: Applied sciences; Beams (structural); Beams’ critical zones; Building failures (cracks, physical changes, etc.); Building structure; Buildings. Public works; Computer simulation; Construction (buildings and works); Cyclic loads; Cyclic test; Ductility; Durability. Pathology. Repairing. Maintenance; Exact sciences and technology; Fatigue (materials); Gravitation; Hysteresis; Imposition; Nonlinear analysis; Reinforced concrete; Reinforced concrete structure; Seismic response; Stresses. Safety; Structural analysis. Stresses; Testing procedure; Testing procedure; Ductility; Beams’ critical zones; Cyclic test; Nonlinear analysis; Seismic response; Reinforced concrete; Dynamic response; Earthquake effect; Stress strain relation; Experimental study; Beam(mechanics); Failure analysis; Beams' critical zones; Concrete construction; Numerical simulation; Beam column structure; Behavior; Gravity
• ISSN: 0141-0296; 1873-7323
• DOI: 10.1016/j.engstruct.2013.11.012

•Assessment of the effect of gravity load on the cyclic response of beams’ critical zones.•A procedure for cyclic tests that include gravity load effects is proposed.•Failure occurs when beam is unable to resist gravity load or a maximum admissible value of the drift is attained.•Gravity load leads to unidirectional plastic hinges and higher negative deformations.•The behaviour of tested beams was simulated using nonlinear analysis software. Gravity loads can affect a reinforced concrete structure’s response to seismic actions, however, traditional procedures for testing the beam behaviour do not take this effect into consideration. An experimental campaign was carried out in order to assess the influence of the gravity load on RC beam connection to the column subjected to cyclic loading. The experiments included the imposition of a conventional quasi-static test protocol based on the imposition of a reverse cyclic displacement history and of an alternative cyclic test procedure starting from the gravity load effects. The test results are presented, compared and analysed in this paper. The imposition of a cyclic test procedure that included the gravity loads effects on the RC beam ends reproduces the demands on the beams’ critical zones more realistically than the traditional procedure. The consideration of the vertical load effects in the test procedure led to an accumulation of negative (hogging) deformation. This phenomenon is sustained with the behaviour of a portal frame system under cyclic loads subject to a significant level of the vertical load, leading to the formation of unidirectional plastic hinges. In addition, the hysteretic behaviour of the RC beam ends tested was simulated numerically using the nonlinear structural analysis software – OpenSees. The beam–column model simulates the global element behaviour very well, as there is a reasonable approximation to the hysteretic loops obtained experimentally.