Online P-Delta Correction for Multi-Degree-Of-Freedom Hybrid Simulation Testing

Abstract eng:
Hybrid Simulation (HS) is a fast-growing computational/physical testing technique that can replace shaking table tests using an online computational substructure to update the input signal based on the feedback from the physical substructure. This paper presents the development and validation of a new Hybrid Simulation System (HSS) and communication scheme with online P-delta correction capabilities. The developed HSS utilizes readily available laboratory data acquisition (DAQ) systems along with inexpensive TCP/IP-Ethernet protocols to establish multi-degree-of-freedom communication between the physical and computational substructures. An approximate method for accounting for the P-delta effect from both of the gravity load and the vertical earthquake excitations was devised for application to bridge systems. The P-delta correction arithmetic operation is performed using a Digital Signal Processor (DSP) subroutine and relies on adjusting the lateral force feedback before it is sent back to the HS computational model to solve for the next displacement input step. The developed HSS comprises a novel hybrid computational model where part of the computations is performed using a finite element platform while another part is performed using a DSP subroutine. To verify the new system communication loop, several single and double free actuators, i.e. not attached to specimens, were used. Moreover, a repaired reinforced concrete bridge column-bent cap-box girder subassemblage was used to conduct a large-scale bidirectional HS trial tests using the developed system for further verification. Another similar bridge subassemblage specimen was used to conduct HS tests with and without including the P-delta correction to investigate and verify the correction method. The verification tests are discussed herein where the new communication scheme and the entire HSS were shown to be accurate.

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