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Author: Yu-Chen Ou Publisher: ISBN: Category : Languages : en Pages : 255
Book Description
A simplified analytical model for static pushover analysis and a three-dimensional detailed finite element model for cyclic analysis of the proposed bridge columns are developed in this research. In addition, a stiffness degrading hysteretic model is proposed for response-history analysis. With the analytical models, a parametric study is conducted to examine the seismic performance of the proposed columns with different design parameters.
Author: Yu-Chen Ou Publisher: ISBN: Category : Languages : en Pages : 255
Book Description
A simplified analytical model for static pushover analysis and a three-dimensional detailed finite element model for cyclic analysis of the proposed bridge columns are developed in this research. In addition, a stiffness degrading hysteretic model is proposed for response-history analysis. With the analytical models, a parametric study is conducted to examine the seismic performance of the proposed columns with different design parameters.
Author: Yihui Zhou Publisher: ISBN: Category : Languages : en Pages : 327
Book Description
The use of stainless steel reinforcing bars in seismic applications has recently attracted much attention in the civil engineering community due to its superior material properties, including high corrosion resistance and high specific strength. However, as with all new materials, a number of shortcomings are unavoidable, such as high initial costs, unknown low-cycle fatigue behavior, uncertain ductility properties and unidentified bond-slip behavior between the embedded bar and grouted duct in precast concrete element for use in segmental bridge members. The performance of precast segmental post-tensioned concrete bridge columns in seismic regions has been investigated by many other researchers. Mild steel energy dissipation bars (ED bars) that were continuous across the column segment joints were added into the columns to increase the hysteretic energy dissipation capacity.^In phase Iexperimental study, mechanical properties and low-cycle fatigue behavior of Talley S24100, Talley 316LN, Talley 2205 and Arminox UNS S32304 stainless reinforcing steel, A706 carbon black reinforcing steel, and MMFX II high strength, corrosion resistant reinforcing steel were investigated. Talley S24100 was found to obtain the highest ductility and the best low-cycle fatigue performance among the steels investigated. Therefore, compared to A706, Talley S24100 was considered to be the superior substitute material for ED bars. Succeeding phase II and phase III study on the bond-slip response of stainless steel reinforcing bars in grouted ducts of precast concrete element was then carried out with a focus on the influence of various duct/bar diameter ratios and different embedment lengths.^A seriesof monotonic pull-out and tension cyclic tests were conducted to investigate the constitutive bond-slip relationship between the bar and duct confined grout and their further applications under seismic loadings. Results showed that for A706 and Talley S24100 steels, both the duct/bar diameter ratio and embedment length influenced the bond-slip behavior in the monotonic pull-out tests. A one-dimensional nonlinear bond spring model exhibited a good performance in simulating the test results. In addition to the conventional bond-slip model, an "end-slip model" is also proposed in this study to describe the loaded end slip behavior of a bar anchored in grouted duct with a relatively deep embedment (12,16and 24 db). Each bond-slip and end-slip model has a five segment structure (each segment is linear). Recommended design equations were developed for development lengths for A706 and Talley S24100 reinforcing steels, respectively.^The local ED bar strains at different column top drift levels were investigated.
Author: Nasi Zhang Publisher: ISBN: Category : Languages : en Pages : 394
Book Description
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℗ʼ 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.
Author: Publisher: Transportation Research Board ISBN: 0309213436 Category : Technology & Engineering Languages : en Pages : 65
Book Description
TRB’s National Cooperative Highway Research Program (NCHRP) Report 698: Application of Accelerated Bridge Construction Connections in Moderate-to-High Seismic Regions evaluates the performance of connection details for bridge members in accelerated bridge construction in medium-to-high seismic regions and offers suggestions for further research.
Author: Gabriele Guerrini Publisher: ISBN: 9781321516630 Category : Languages : en Pages : 133
Book Description
This study presents an innovative bridge column technology for application in seismic regions. The proposed technology combines a precast post-tensioned composite steel-concrete hollow-core column with supplemental energy dissipation, in a way to reduce on-site construction burdens and minimize earthquake-induced residual deformations, damage, and associated repair costs. The column consists of two steel cylindrical shells, with high-performance concrete cast in between. Both shells act as permanent formwork; the outer shell substitutes the longitudinal and transverse reinforcement, as it works in composite action with the concrete, whereas the inner shell removes unnecessary concrete volume from the column, prevents concrete implosion, and prevents buckling of energy dissipating dowels when embedded in the concrete. Large inelastic rotations can be accommodated at the end joints with minimal structural damage, since gaps are allowed to open at these locations and to close upon load reversal. Longitudinal post-tensioned high-strength steel threaded bars, designed to respond elastically, in combination with gravity forces ensure self-centering behavior. Internal or external steel devices provide energy dissipation by axial yielding. This dissertation reviews the main principles and requirements for the design of these columns. The experimental findings from two quasi-static reversed cyclic tests are then presented, and numerical simulations of the experimental response are proposed.
Author: Jeffrey A. Schaefer Publisher: ISBN: Category : Bridges Languages : en Pages : 138
Book Description
A new pre-tensioned precast bridge system has been developed that provides seismic regions the means to construct high-performance bridges that can be built quickly. The columns are designed to rock as rigid bodies, and their ends are protected against damage by a steel shoe detail. The precast feature of the system will reduce traffic delays by moving construction off-site. The pretensioning feature leads to reduced residual displacements after an earthquake. The use of epoxy-coated strands and the quality control available in a precasting plant lead to enhanced durability. The seismic performance of the system was evaluated with pseudo-static tests of two column-footing sub-assemblies. In one column-footing sub-assembly, a ductile fiber-reinforced concrete (HyFRC developed by Ostertag) was used to fill the steel shoe and the region immediately above it. This column also contained a steel dowel bar that extended down from the body of the column into the footing. The other column did not possess any ductile concrete or dowel bar. During the tests, the columns had very low residual displacements and negligible damage to the concrete, even after being subjected to drift ratios of over 10%.
Author: Yu-Chen Ou
Author: Yu-Chen Ou
Author: Yihui Zhou
Author: Joshua T. Hewes
Author: Nasi Zhang
Author: Taher Zouaghi
Author: 
Author: 
Author: Joshua Tyler Hewes
Author: Gabriele Guerrini
Author: Jeffrey A. Schaefer