Download Free Seismic Performance Of A Two Column Bridge Bent With Offset Plastic Hinges And Innovative Cfrp Composite On Flexible Footings Book in PDF and EPUB Free Download. You can read online Seismic Performance Of A Two Column Bridge Bent With Offset Plastic Hinges And Innovative Cfrp Composite On Flexible Footings and write the review.

The main objective of this research was to quantify the material strain limits for seismic assessment of existing sub-standard reinforced concrete bridge bents considering operational performance design criteria. Limited confidence exists in the current material strain limit state for operational performance criteria due to lack of experimental results considering the typical detailing of Oregon bridges and the cumulative damage effect resulting from an anticipated long-duration Cascadia Subduction Zone (CSZ) event. Component details for bridge bents such as geometry and reinforcing details were determined through a statistical analysis of available bridge drawings built prior to 1990 in the State of Oregon. Three full-scale bridge bent column-footing subassembly specimens were constructed and subjected to reverse cyclic lateral deformations utilizing a traditional loading protocol and a protocol representing the demands expected from a CSZ earthquake. The tests were designed so that variable axial loading could be applied in order to simulate the secondary effects experienced in a column that is part of a multi-column bent during an earthquake event. Material strains along with global and local deformation quantities were measured with a suite of external and internal sensors mounted to and embedded in the specimens. Despite having sub-standard seismic detailing, all three specimens exhibited ductile behavior under reverse cyclic lateral loading, achieving a minimum displacement ductility of 8.0. The obtained results also suggest that the material strain limits currently used for the seismic evaluation of existing bridges in Oregon considering operational performance criteria are conservative, but may still require further experimental validation. Finally, strain limits based on previous research at Portland State University (PSU) were compiled and combined with the results from this study to propose recommended strain limit values.
The main objective of this research was to evaluate the seismic performance of existing sub-standard reinforced concrete (RC) bridge column-spread footing subassemblies and to quantify the material strain limits through a full-scale experimental program. A total of six column-footing test specimens with pre-1990 construction details were subjected to reverse cyclic lateral loading, utilizing a conventional three-cycle symmetric loading protocol and a protocol representing the demands expected from a CSZ earthquake. Additionally, the tests were designed so that variable axial loading could be applied to simulate the secondary load effects experienced during an earthquake in a column that is part of a multi-column bent. A rapid repair method incorporating semi-permanent installation was also developed, anticipating the need for quick measures following the Cascadia Subduction Zone (CSZ) earthquake, which is expected to damage the existing bridges in the Pacific Northwest and spread geographically throughout the region. The proposed repair methodology uses capacity design principles to protect the remainder of the bridge from future earthquakes and eradicates the need for establishing rebar continuity, resulting in a less labor-intensive repair method. The adopted concept is to utilize U-shaped metallic plates as externally attached ductile fuses to be anchored to the non-damaged part of the column, hence bypassing the damaged zone to restore the lateral capacity.
As part of a multi-university project utilizing the NSF Network for Earthquake Engineering Simulation (NEES), a quarter-scale model of a four-span bridge incorporating plastic hinges with different advanced materials was tested to failure on the three shake table system at the University of Nevada, Reno (UNR). The bridge was the second test model in a series of three 4-span bridges, with the first model being a conventional reinforced-concrete (RC) structure. The purpose of incorporating advanced materials was to improve the seismic performance of the bridge with respect to two damage indicators: (1) column damage and (2) permanent deformations. The goals of the study presented in this document were to (1) evaluate the seismic performance of a 4-span bridge system incorporating SMA/ECC and built-in rubber pad plastic hinges as well as post-tensioned piers, (2) quantify the relative merit of these advanced materials and details compared to each other and to conventional reinforced concrete plastic hinges, (3) determine the influence of abutment-superstructure interaction on the response, (4) examine the ability of available elaborate analytical modeling techniques to model the performance of advanced materials and details, and (5) conduct an extensive parametric study of different variations of the bridge model to study several important issues in bridge earthquake engineering. The bridge model included six columns, each pair of which utilized a different advanced detail at bottom plastic hinges: shape memory alloys (SMA), special engineered cementitious composites (ECC), elastomeric pads embedded into columns, and post-tensioning tendons. The design of the columns, location of the bents, and selection of the loading protocol were based on pre-test analyses conducted using computer program OpenSees. The bridge model was subjected to two-horizontal components of simulated earthquake records of the 1994 Northridge earthquake. Over 340 channels of data were collected. The test results showed the effectiveness of the advanced materials in reducing damage and permanent displacements. The damage was minimal in plastic hinges with SMA/ECC and those with built-in elastomeric pads. Conventional RC plastic hinges were severely damaged due to spalling of concrete and rupture of the longitudinal and transverse reinforcement. Extensive post-test analytical studies were conducted and it was determined that a computational model of the bridge that included bridge-abutment interaction using OpenSees was able to provide satisfactory estimations of key structural parameters such as superstructure displacements and base shears. The analytical model was also used to conduct parametric studies on single-column and bridge-system response under near-fault ground motions. The effects of vertical excitations and transverse shear-keys at the bridge abutments on the superstructure displacement and column drifts were also explored.
Telescopic pipe-pin two-way hinges are used in concrete bridges to eliminate moments while transferring shear and axial loads from integral bridge bent caps to reinforced concrete columns. The hinges consist of a steel pipe that is anchored in column with a protruded segment that extends into the bent cap. In the absence of experimental and analytical studies, design of pipe-pin hinges has been based on pure shear capacity of the steel pipe. The primary objective of this research was two folds: (1) to investigate the seismic performance of the current detail of pipe-pin hinges and propose necessary modifications and (2) to develop a reliable design method for pipe-pin hinges that reflects their actual behavior. This research was comprised of comprehensive experimental and analytical studies of pipe-pin connections and their components including a shake table study of a two-column pier model. The experimental component of the study included three sets of test models: (1) six push-off specimens to evaluate the bearing strength of concrete against the steel pipe, (2) six pure shear specimens to determine the yielding and ultimate shear capacities, and (3) a two-column 0.2-scale bridge pier model incorporating pipe-pin hinges that were designed based on the proposed guideline. The pier model was used to evaluate the new design method under earthquake excitation. The experiments showed that the lateral failure mechanism is typically controlled by concrete diagonal tensile cracking of the column in combination with flexural yielding of the steel pipe as opposed to pure shear, although the pure shear failure mode should be considered when a large amount of lateral steel is used in the column. Another possible mode of failure is bearing failure of the concrete around the pipe in heavily reinforced columns. The shake table experiment of the pier model confirmed that the proposed design method meets the safety and performance requirements under seismic loading. The analytical studies consisted of (1) a stick model in SAP2000 that was developed for pipe shear key subassemblies, (2) detailed nonlinear FE models using ABAQUS that were used to performed an extensive parametric study in order to shed light on different aspects of the behavior and generate the required data for the design guideline, and (3) a model in OpenSees that utilized a macro model for the pipe-pin hinges. The experimental and analytical results helped identify the means to improve the performance of current pipe-pin hinge details. The pipe studs and spiral around the can proved to be unnecessary and were eliminated in the proposed standard detail. A thicker tapered hinge throat was suggested to solve the problem of local concrete damage to the throat and column edges. As a possible extension of pipe-pin application, a study was conducted on pipe-pins combined with isolation and damping systems. The analytical modeling of these details showed that modified connections can reduce the demands on the structure by dissipating a major portion of the earthquake energy.
Longitudinal bar debonding allowed spread of yielding and prevented premature failure of reinforcements in UHPC-filled duct connections and grouted coupler column pedestal. The SMA-reinforced ECC column showed superior seismic performance compared to a conventional column in which the plastic hinge damage was limited to only ECC cover spalling even under 12% drift ratio cycles. The column residual displacements were 79% lower than CIP residual displacements on average due to the superelastic NiTi SMA longitudinal reinforcement, and higher base shear capacity and higher displacement capacity were observed. The analytical modeling methods were simple and sufficiently accurate for general design and analyses of precast components proposed in the present study. The proposed symmetrical material model for reinforcing NiTi superelastic SMA was found to be a viable alternative to the more complex asymmetrical model.