Carlos Chastre

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.

The wind energy production is a growing industry and the energy produced is renewable and environmentally cleaner than most of the energy production systems. The supports of the wind energy generators may be built with precast concrete elements. The precast solutions for these structures are competitive in comparison to other structural systems. The evolution of the technology for wind energy production shows a clear need for larger wind turbines and longer blades and, consequently, taller towers. The experience also shows that precast concrete solutions increase their competitiveness as the tower height increases. Offshore wind farms have some advantages in relation to onshore ones, which explains recent investments in this area. Also in this case, the durability of concrete in the sea when compared to steel, gives advantages to precast concrete in relation to other structural solutions. This paper shows the evolution of the supports of the wind energy generators and the advantages of the use of precast concrete towers.