Fast and Slow Cyclic Tests for Reinforced Concrete Columns with an Improved Axial Force Control

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Summary It is well known that real‐time hybrid simulation (RTHS) is an effective and viable dynamic testing method. Numerous studies have been conducted for RTHS during the last 2 decades; however, the application of RTHS toward practical civil infrastructure is fairly limited. One of the major technical barriers preventing RTHS from being widely accepted in the testing community is the difficulty of accurate displacement control for axially stiff members. For such structures, a servo‐hydraulic actuator can generate a large force error due to the stiff oil column in the actuator even if there is a small axial displacement error. This difficulty significantly restricts the implementation of RTHS for structures such as columns, walls, bridge piers, and base isolators. Recently, a flexible loading frame system was developed, enabling a large‐capacity real‐time axial force application to axially stiff members. With the aid of the flexible loading frame system, this paper demonstrates an RTHS for a bridge structure with an experimental reinforced concrete pier, which is subjected to both horizontal and vertical ground motions. This type of RTHS has been a challenging task due to the lack of knowledge for satisfying the time‐varying axial force boundary condition, but the newly developed technology for real‐time force control and its incorporation into RTHS enabled a successful implementation of the RTHS for the reinforced concrete pier of this study.

“…The horizontal actuator has a 250‐kN force capacity with a 750‐mm stroke limit. A more detailed description about the test setup and FLF is provided by Chae et al…”

Section: Experimental Test Setupmentioning

confidence: 99%

Section: Implementation Of Rthsmentioning

confidence: 99%

Section: Test Bridge Structure and Its Substructuring For Rthsmentioning

confidence: 99%

Section: Test Bridge Structure and Its Substructuring For Rthsmentioning

confidence: 99%

Section: Instability Of Simulation Associated With Oil Column Resonmentioning

confidence: 99%

See 3 more Smart Citations

Real‐time hybrid simulation for an RC bridge pier subjected to both horizontal and vertical ground motions

Chae

Lee

Park

et al. 2018

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Impact of loading rate during hybrid simulation on seismic response of steel structures

Huang

Tabkhi

Sadeghian

et al. 2022

This study investigates the influence of loading rates on the seismic response of steel structures. A series of coupon tests under typical earthquake-induced loading rates are carried out. In addition to the conventional monotonic tension test, the specimens are also tested under a discontinuous loading protocol that is analogous to the ramp-and-hold scheme employed in the pseudo-dynamic hybrid simulations. The test results are used to develop a uniaxial steel material model to account for the strain rate effect and stress relaxation. The material model facilitates the reuse of existing steel hysteresis models and can be used to model different structural components, such as columns, beams, braces, etc. The material model is then used for a parametric study to evaluate the impact of various loading rates on the global seismic response of a single degree of freedom structural system with different structural periods, and types and intensities of ground motions. It is found that the impact of loading rates is more significant for structures with a period of 0.5 s or less and it thus requires a fast control of the physical specimen in pseudo-dynamic hybrid testing. In addition, the material model is applied to a five-storey buckling restrained braced frame (BRBF) building with a structural period of 1.2 s. It is found that the earthquake-induced loading rates have a minor impact on the global response of the structure.

Real‐time hybrid simulation for investigating the influence of vertical ground motions on the lateral response of RC piers

Park

Chae

et al. 2023

The vertical component of ground motions can affect the seismic performance of reinforced concrete (RC) piers as significant as its horizontal counterpart. However, real-time testing for RC piers subjected to both horizontal and vertical ground motions has been scarcely conducted due to the difficulty in multi-axial control of actuators. In this study, the seismic response of a bridge RC pier was investigated by conducting real-time hybrid simulation (RTHS), where the RC pier was physically tested in the laboratory and the bridge superstructure was numerically modeled. The test setup that can synchronously apply both horizontal and vertical ground motions was constructed by using three dynamic actuators and a flexible loading beam (FLB). The lateral response of the RC pier was investigated by varying the intensities for vertical ground motions, while the same intensity for horizontal ground motion is used. It was found that the axial force from the dead load of superstructure can significantly affect the initial stiffness, strength, and post-yield response of the RC pier. For the selected earthquake ground motions, however, the intensity of vertical ground motion did not make a substantial difference in the lateral response, although there was a notable difference in the fracture pattern.