Seismic Behavior and Retrofit of Older Reinforced Concrete Bridge T-joints

Seismic Behavior and Retrofit of Older Reinforced Concrete Bridge T-joints
Author: Laura N. Lowes
Publisher:
Total Pages: 180
Release: 1995
Genre: Bridges
ISBN:

A series of experimental tests investigating the seismic response of reinforced concrete beam-column T-joints was recently completed at the University of California, Berkeley. The evaluated connection was representative of an interior beam- column joint from a multi-column bridge frame built in the late 1950's. Three one-third scale models, representing the as-built connection and two retrofit connections, were tested. The results of this research project are an improved understanding of the seismic behavior of lightly reinforced bridge T-joints as well as verification of a design procedure for retrofitting this type of connection.

Experimental Characterization of Steel Jacket Retrofitted Reinforced Concrete Bridge Column Behavior in Cascadia Subduction Zone Earthquakes

Experimental Characterization of Steel Jacket Retrofitted Reinforced Concrete Bridge Column Behavior in Cascadia Subduction Zone Earthquakes
Author: Sean McGuiness
Publisher:
Total Pages: 139
Release: 2021
Genre: Bridges
ISBN:

Research on seismic retrofitting of Reinforced Concrete (RC) bridge columns in the United States (U.S.) was motivated by damage observed following the 1971 San Fernando, 1989 Loma Prieta, and 1994 Northridge earthquakes of California. The research resulted in a retrofitting procedure that consisted of installing steel jackets around RC bridge columns to enhance the lateral deformation capacity. Although the research focused on the development of this retrofit strategy for bridge columns in California, the Washington State Department of Transportation (WSDOT) implemented the program in 1991. Unlike the strike-slip faults in California, seismicity in western Washington is generally dominated by the Cascadia Subduction Zone fault. The 1964 Alaska, U.S., 2010 Maule, Chile and 2011 Tohoku, Japan are examples of mega-thrust long duration earthquakes emanating from a subduction zone fault and producing ground motions with longer durations of strong shaking than strike-slip faults. The research conducted in this study was motivated by the need to assess performance of the existing retrofit strategy when subjected to the expected demands of subduction zone earthquakes. The research conducted herein was an experimental study on the behavior of steel jacket retrofitted bridge columns subjected to demands from long duration earthquakes. Six reduced scale column specimens were designed, constructed, and tested as cantilevers. WSDOT's inventory was characterized to inform the values used for the column parameters, such that the six columns were intended to reasonably cover the range of values for critical parameters. Five of six tests utilized a modified fully reversed-cyclic lateral loading protocol to include additional cycles characteristic of long duration earthquakes. The sixth test used an earthquake protocol, obtained from the response of a single degree of freedom model to a synthetic Cascadia Subduction Zone ground motion in western Washington. Study results indicated stable drifts, including minimal pinching in the load-displacement response indicative of favorable hysteretic energy dissipation, at drifts in excess of the 4\\% expectation set forth in the steel jacket retrofit design guidelines. Total deformation was primarily a result of longitudinal reinforcement bond slip and elongation at the footing-column interface with strength degradation due to low-cycle fatigue fracture.

Experimental and Analytical Seismic Studies of a Four-span Bridge System with Composite Piers

Experimental and Analytical Seismic Studies of a Four-span Bridge System with Composite Piers
Author: Fatemeh Kavianipour
Publisher:
Total Pages: 1350
Release: 2013
Genre: Electronic books
ISBN:

Funded by the National Science Foundation through the Network for Earthquake Engineering Simulation (NEES) research program, a major multi-university research project has been in progress at the University of Nevada, Reno. This study describes the study of one of the three large-scale bridge models that were tested to failure on three shake tables system. This model was supported on fiber-reinforced polymer (FRP) composite piers implementing accelerated bridge construction (ABC) techniques. The bridge was a quarter scale model of a 4-span bridge with continuous reinforced concrete superstructure and a drop cap, two-column pier design. Each pier utilized different unconventional FRP details. The purpose of using these innovative details was to improve the seismic performance of the bridge. The first pier consisted of cast-in-place concrete-filled glass FRP tubes with ±55 degree fibers. The second pier consisted of two segmental reinforced concrete columns wrapped with layers of unidirectional carbon FRP sheets to provide confinement and shear reinforcement. Only nominal hoops were used to hold the longitudinal reinforcement, as FRP jacket and tube were sufficient in providing confinement and shear required reinforcement. The third pier had the same configuration as that of pier 1 but the columns and footing were precast. The top connections in piers 1 and 3 consisted of pipe-pin joints to facilitate ABC and provide hinge behavior. The objectives of the study presented in this document were to evaluate the biaxial seismic performance of this bridge system incorporating composite piers, investigate the performance of each detail and compared them to each other and to conventional ones, determine the influence of abutment-superstructure interaction on the response, assess the performance of a bridge model incorporating ABC techniques, evaluate sufficiency of analytical modeling of the performance of composite material and details, and to conduct parametric study of different variations of the bridge model to study the effect of several important factors such as near-fault earthquake effects and the variations in the configuration of the bridge model. large-scale 4-span bridge model was designed, constructed, and subjected to simulated earthquake loading on three shake tables. The simulated shake table motions were the modified 1994 Northridge, CA ground motion recorded in Century City and were applied to the bridge model in ten runs with increasing amplitudes. Over 380 channels of data were collected. Compared to conventional reinforced concrete bridges, experimental results showed superior performance under extreme seismic loading even under lateral drift ratios exceeding 9%. 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 response parameters such as superstructure displacements. The analytical model was also used to conduct parametric studies on response of the bridge model and its variations under near-fault excitations. The effects of changing the column section properties were also explored. It was found that concrete-filled FRP tube piers and CFRP wrapped post-tensioned segmental piers reduce residual displacements compared to their conventional reinforced concrete counter parts even under impulsive near-fault motions.

Shaking Table Evaluation of Reinforced Concrete Bridge Columns Repaired Using Fiber Reinforced Polymer Jackets

Shaking Table Evaluation of Reinforced Concrete Bridge Columns Repaired Using Fiber Reinforced Polymer Jackets
Author: Pardeep Kumar
Publisher:
Total Pages: 187
Release: 2014
Genre:
ISBN:

After an earthquake event it is the responsibility of the engineers to decide if the bridge structure is safe for the traffic flow, requires repair or needs to be replaced completely depending on the damage level. Effective, economical and timely repair of Reinforced Concrete (RC) bridges after a seismic event is crucial to avoid traffic congestion and lengthy detours. Fiber Reinforced Polymer (FRP) composite laminates are one of few options with several advantages. Use of FRP jackets in structural engineering is gaining interest in applications such as strengthening weak structural elements, improving the existing structure capacity to resist increased loads due to change in use of structure and retrofitting structural elements for seismic upgrades. The study presents shaking table experimental investigation to evaluate the use of FRP for repairing RC bridge columns with circular cross-sections. Two 1/4-scale RC columns were tested in as-built configuration. Both tests had identical geometry and reinforcement details except for the spacing of the transverse reinforcing bars. One column had closely spaced hoops satisfying code requirements and the other had larger spacing, representing a shear-critical column. The test specimens were subjected to a series of horizontal and vertical excitations on a shaking table and experienced moderate to high damage. The damaged columns were subsequently repaired with unidirectional FRP composite laminates and subjected to the same set of earthquake excitations. The obtained experimental data showed that the repaired columns achieved higher strength and ductility with lower residual displacements compared to the as-built ones contributing to the resiliency of the bridge system. A three-dimensional (3D) Finite Element (FE) model was developed and calibrated using the experimental test results. A bilinear confined concrete model was adopted to model the constitutive relationship of the FRP confined concrete without explicitly modeling the FRP composite jacket. Due to variability of the material properties, several calibration parameters were studied to develop a reliable FE model. The results of the dynamic FE analysis showed great potential for 3D modeling of the repaired test specimens. From this study, it is concluded that the used FRP composite laminates represent a viable solution for the effective and rapid repair of damaged RC bridge columns. A parametric study was conducted to evaluate the horizontal force, deformation, and confining strain response of the retrofitted RC bridge columns using the computational model. The response of the FE models with different number of FRP plies in the jacket was investigated. The analytical results suggested that increasing the number of FRP plies in the jacket significantly changed the confining strains response of the confined cross-section but the global force-deformation was not significantly affected.