Pseudodynamic Test of a Deficient RC Frame Strengthened with Buckling Restrained Braces

Three story–three bay reinforced concrete (RC) frames with and without chevron braces were tested using the continuous pseudodynamic test method. New steel–concrete composite lateral load–carrying members called Buckling Restrained Braces (BRBs) were used as chevron brace members while retrofitting the RC frame. The BRBs were fitted to the interior span of the RC frame by using anchorage rods. The chevron braced frame was observed to be effective in controlling interstory drift. The test results indicated that retrofitting with BRBs was beneficial in resisting deformation without significant damage under simulated ground motions. Furthermore, significant yielding that occurred on the core plate of the BRBs enabled the braced frame to dissipate energy induced by dynamic loading. The test results were compared with the results of the nonlinear time-history analysis. The analysis results were capable of estimating the base shear capacity and displacement demands with reasonable accuracy.

Nonlinear Error Propagation Analysis of a New Family of Model-Based Integration Algorithm for Pseudodynamic Tests

Error propagation properties of integration algorithms are crucial in conducting pseudodynamic tests. The motivation of this study is to investigate the error propagation properties of a new family of model-based integration algorithm for pseudodynamic tests. To develop the new algorithms, two additional coefficients are introduced in the Chen-Ricles (CR) algorithm. In addition, a parameter—i.e., degree of nonlinearity—is applied to describe the change of stiffness for nonlinear structures. The error propagation equation for the new algorithms implemented in a pseudodynamic test is derived and two error amplification factors are deduced correspondingly. The error amplification factors for three structures with different degrees of nonlinearity are calculated to illustrate the error propagation effect. The numerical simulation of a pseudodynamic test for a two-story shear-type building structure is conducted to further demonstrate the error propagation characteristics of the new algorithms. It can be concluded from the theoretical analysis and numerical study that both nonlinearity and the two additional coefficients of the new algorithms have great influence on its error propagation properties.

A Standalone Vision Sensing System for Pseudodynamic Testing of Tuned Liquid Column Dampers

Experimental investigation of the tuned liquid column damper (TLCD) is a primal factory task prior to its installation at a site and is mainly undertaken by a pseudodynamic test. In this study, a noncontact standalone vision sensing system is developed to replace a series of the conventional sensors installed at the TLCD tested. The fast vision sensing system is based on binary pixel counting of the portion of images steamed in a pseudodynamic test and achieves near real-time measurements of wave height, lateral motion, and control force of the TLCD. The versatile measurements of the system are theoretically and experimentally evaluated through a wide range of lab scale dynamic tests.

Pseudodynamic Response to Impulsive Loading

The application of a pseudodynamic technique to yield a shock response from an impulse might encounter a difficulty caused by a significant load discontinuity at the end of the impulse since this load discontinuity at the end of an impulse will result in an extra impulse and then an extra amplitude distortion. This extra impulse is linearly proportional to the step size and thus it is natural to consider the use of a very small time step for a whole pseudodynamic test to overcome the difficulty. However, a series of computer simulations reveal that this approach might not be feasible. This is because that the use of a small time step will lead to a very small displacement increment and it may be contaminated by experimental errors as its magnitude is less than or close to the magnitude of the experimental errors. Thus, an inaccurate test result is obtained. A technique is proposed to overcome this difficulty. This novel technique is to perform a single small time step immediately upon the termination of the applied impulse while the other time steps are conducted by using the time step determined from general considerations. This single small time step will not lead to a significant error propagation problem since only this time step is performed by using a very small step size for a complete pseudodynamic test. The feasibility of this technique was confirmed by a series of pseudodynamic tests.