Dynamic properties and application of steel fiber reinforced self-consolidating concrete to segmental bridge columns in moderate-to-high seismic regions
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In this dissertation, the application of steel fiber reinforced self-consolidating concrete (SFRSCC) to precast unbonded post-tensioned segmental bridge columns in moderate-to-high seismic regions is evaluated numerically and experimentally. Drop weight impact tests are first conducted on plain concrete and steel fiber reinforced concrete (SFRC). The standard drop test recommended by the American Concrete Institute (ACI) is first conducted and a modification to this standard ACI, which involves visual inspection of first cracking and ultimate failure, is then developed. The Kolmogorov-Smirnov (K-S) test along with fitted normal and lognormal distributions are used to examine the distribution of the number of blows required to cause first cracking and ultimate failure of the concrete. The minimum sample size required to calculate the impact strength of SFRC is determined using equations available in the literature. This sample size is used in the subsequent impact study on SFRSCC specimens. The static and dynamic properties of ten groups of SFRSCC, including one group of self-consolidating concrete (SCC) without steel fibers, are studied and compared. Dramix ® ZP305, RC-65/35-BN, and RC-80/30-BP steel fiber (glued and hooked end) at a volume of 0.25%, 0.5% and 1% are considered in the study. The static properties are calculated using compression tests, split-tension tests and flexural beam tests. The dynamic properties are determined using the modified ACI impact test. A dynamic load sensor is installed underneath the base plate of the impact test machine to measure the relative reaction force history. The recorded reaction forces are used to develop an automated impact test method, which can circumvent visual inspections. Two large-scale (1:3.37), precast, unbonded and post-tensioned segmental columns, one constructed with SCC and one constructed with SFRSCC (with 0.5% of ZP305 steel fiber by volume), are tested under cyclic loading. These segmental columns incorporate shear keys at the joints. The backbone force-displacement relationships of the segmental columns are calculated from a pushover model available in the literature. The hysteretic behavior of the segmental columns under cyclic loading is also simulated by a numerical model developed on the OpenSEES platform. A single span, large-scale (1:3.37) bridge model incorporating SFRSCC segmental columns (with 0.5% of ZP305 steel fiber by volume) is tested on a shake table. Two types of cap beam-to-superstructure connections are considered for the bridge model: a connection using non-seismic rubber bearing and a fixed connection. The bridge model is tested for far field and near field ground motions along various directions and with increasing peak ground accelerations (PGAs). The evolution of the cumulative damage to the bridge model after each seismic test is evaluated through a system identification involving white noise excitation. A flag-shaped hysteretic model is proposed and validated through the cyclic test results obtained in this research and those available in the literature. The proposed flag-shaped model is used to predict the seismic response of the bridge model. Adding steel fibers to concrete significantly improves its impact strength and ductility. The SFRSCC segmental columns suffered less damage than the SCC columns for the same level of drift. The large-scale bridge model incorporating SFRSCC segmental columns sustained high intensity far field and near field ground motions with limited damage. The proposed flag-shaped hysteretic model can be used to simulate the cyclic behavior of segmental columns, and to provide reasonable estimates of their seismic response under strong ground motions.