The experiment resulted in diagonal crushing of the concrete at a drift ratio of 0.85% the analytical model computed the crushing of the diagonal concrete at 0.7% drift in Diagonal E1. The figure marks the points where the diagonal strain first exceeds 0.2% and 0.41% compression strain, corresponding to the instance of peak uniaxial compression strength and 0 compression strength, respectively. (a) Comparison of experimentally measured and computed response for Wall WP1105-8 (b) Stress-strain of the diagonal E1 (shown in Figure 1) including the points of first concrete diagonal softening and crushing.įigure 3(a) shows the comparison of experimentally measured and numerically computed global lateral force-displacement response. The lateral displacement is done by displacement control with a displacement increment of 1e-4 inches per step, which is equivalent to 540 steps for each 0.1% drift.įigure 3. Following that, the gravity loads are kept constant while the lateral displacements are applied at the top node of the truss model, as show in Figure 1. This is analyzed separately using 10 steps of load control.
The wall is loaded with the gravity load of 75 kips before the cyclic analysis. The method of fracture energy for determining the softening slope is explained in Lu and Panagiotou (2013) and the same values, with a reference length of 600 mm = 23.6”, is used. The input parameters for the diagonal concrete material are:įor the concrete used in the vertical, horizontal, and diagonal directions, mesh objectivity is used to define the softening in compression and tension as well as for the normal strains associated with specific values of beta.
Uniaxial cyclic hysteretic shapes for (a) concrete used in vertical trusses, (b) concrete used in diagonal trusses, and (c) reinforcing steel used in both vertical and horizontal directions. Details on the implementation and behavior of these materials can be found in their respective pages.įigure 2. The biaxial effect of normal tension is considered for the diagonal elements only. Lu and Panagiotou (2013) presents a 3D nonlinear cyclic beam-truss model for non-planar walls that also uses the Truss2 element used here.įigure 2 shows the uniaxial cyclic behavior of the vertical and diagonal concrete material models ( ConcretewBeta material) and the steel material model ( Steel02 material). The general application of the truss modeling approach can be found in Panagiotou et al (2012), including the truss model for this wall implemented in Ruaumoko and more examples of truss models for both squat and slender walls. The diagonal elements ( Truss2 Elements) span between each node in the model and have an effective width equal to 11.2”. The areas of concrete and steel used in these elements are listed in Figure 1. The location of the outer vertical truss coincides with the position of the outer longitudinal reinforcements with the location of the inner trusses distributed to allow for equidistant spacing. The lateral force was applied to the top of the wall through the top loading beam the loading beam was constrained from rotation.įor the corresponding truss model, shown in Figure 1(c), the vertical and horizontal trusses ( Truss Elements) represent the respective reinforcing bars and their surrounding concrete in the respective direction.
The compressive axial load N = 75 kips and remained constant during the test. The wall had an almost square aspect ratio (54” wide and 48” tall) with longitudinal and transverse reinforcement ratios ρw = 0.43% and ρt = 0.27%, respectively. Dimensions and reinforcing details of Wall WP1105-8 and the layout and element areas of the corresponding Truss model.įigure 1(a) shows the dimension and reinforcing details of Wall WP1105-8, see Massone Sanchez (2005).