Shaking table tests of a resilient bridge system with precast reinforced concrete columns equipped with springs

Abstract

This paper presents the shake table test results of a novel system for the design of precast reinforced concrete bridges. The specimen comprises a slab and four precast columns. The connections are dry and the columns are connected to the slab by an ungrouted tendon. One of the tendon ends is anchored above the slab, in series with a stack of washer springs, while the other end is anchored at the bottom of the column. The addition of such a flexible restraining system increases the stability of the system, while keeping it relatively flexible allowing it to experience negative post‐uplift stiffness. It is a form of seismic isolation. Anchoring the tendon within the column, caps the design moment of the foundation, and reduces its size. One hundred and eighty‐one shake table tests were performed. The first 180 caused negligible damage to the specimen, mainly abrasion at the perimeter of the column top ends. Hence, the system proved resilient. The 181st excitation caused collapse, because the tendons unexpectedly failed at a load less than 50% of their capacity (provided by the manufacturer), due to the failure of their end socket. This highlights the importance of properly designing the tendons. The tests were used to statistically validate a rigid body model. The model performed reasonably well never underestimating the median displacement response of the center of mass of the slab by more than 30%. However, the model cannot predict the torsion rotation of the slab that was observed in the tests and is due to imperfections.

Seismic response of slender MDOF structures with self‐centering base shear and moment mechanisms

“…The concept of statistical validation using the CDF plots has been applied to modelling of rocking structures that showed predictable rocking responses in the statistical sense. [30][31][32][35][36][37][38] Figure 5 presents the CDF plots used for the statistical comparison in this section. The numerical and experimental CDF plots were compared based on the Kolmogorov-Smirnov (K-S) distance 39,40 (i.e., the maximum vertical distance between the experimental and numerical CDF plots) and the relative errors (𝜀, defined as the absolute error between the experimental and numerical values divided by the experimental value) at the maximum horizontal distance, as well as at median and 90 th percentile of the experimental CDF plots, as listed in Table 1, and within each plot of Figure 5.…”

“…Following the motion‐by‐motion comparison, the numerical and experimental results of the shaking table dataset were revisited with a focus on the statistical comparison of the Cumulative Distribution Function (CDF) of key response parameters that were discussed previously. The concept of statistical validation using the CDF plots has been applied to modelling of rocking structures that showed predictable rocking responses in the statistical sense 30–32 , 35–38 . Figure 5 presents the CDF plots used for the statistical comparison in this section.…”

Development of a bidirectional rocking isolation bearing system (Bi‐RIBS) to control excessive seismic response of bridge structures

“…The systematic trend of the seismic response of rocking structures was found to emerge from the perspective of probability 28 . This conclusion was validated by numerical simulation and experimental results 30–32 . The dynamics of rocking structures experiencing complex motions and conditions were investigated from various directions, such as multiple rocking blocks, 33–36 sliding and take‐off motions, 37,38 and planar rocking frames with an eccentric top mass 39 .…”

Finite element modeling of free‐standing cylindrical columns under seismic excitation

“…The rocking oscillator is the one that can uplift from its base when subjected to sufficiently strong ground motion excitation (Figure 1). It is worth studying because it can describe a plethora of structures: First, since uplift works as a mechanical fuse, rocking can be used as a seismic design strategy for both bridges 1–24 and buildings 23,25–33 . Second, the out‐of‐plane response of masonry walls is a form of rocking motion 34–47 .…”