Modal testing

About: Modal testing is a research topic. Over the lifetime, 4047 publications have been published within this topic receiving 64772 citations.

System and method for detecting structural damage

Abstract: A system and method for detecting structural damage is provided that utilizes a general order perturbation methodology involving multiple perturbation parameters. The perturbation methodology is used iteratively in conjunction with an optimization method to identify the stiffness parameters of structures using natural frequencies and/or mode shape information. The stiffness parameters are then used to determine the location and extent of damage in a structure. A novel stochastic model is developed to model the random impact series produced manually or to generate a random impact series in a random impact device. The random impact series method or the random impact device can be used to excite a structure and generate vibration information used to obtain the stiffness parameters of the structure. The method or the device can also just be used for modal testing purposes. The random impact device is a high energy, random, and high signal-to-noise ratio system.

Seismic analysis of two‐way asymmetric building systems under bi‐directional seismic ground motions

Abstract: An approximation approach of seismic analysis of two-way asymmetric building systems under bi-directional seismic ground motions is proposed. The procedures of uncoupled modal response history analysis (UMRHA) are extended to two-way asymmetric buildings simultaneously excited by two horizontal components of ground motion. Constructing the relationships of two-way base shears versus two-way roof translations and base torque versus roof rotation in ADRS format for a two-way asymmetric building, each modal pushover curve bifurcates into three curves in an inelastic state. A three-degree-of-freedom (3DOF) modal stick is developed to simulate the modal pushover curve with the stated bifurcating characteristic. It requires the calculation of the synthetic earthquake and angle β. It is confirmed that the 3DOF modal stick is consistent with single-degree-of-freedom modal stick in an elastic state. A two-way asymmetric three-story building was analyzed by UMRHA procedure incorporating the proposed 3DOF modal sticks. The analytical results are compared with those obtained from nonlinear response history analysis. It is shown that the 3DOF modal sticks are more rational and effective in dealing with the assessment of two-way asymmetric building systems under two-directional seismic ground motions.

Vibro‐acoustical modal analysis: Reciprocity, model symmetry, and model validity

Abstract: For low‐frequency applications, a modal approach can be useful to describe vibro‐acoustical coupling. Based on combined vibrational/acoustical frequency response function measurements, either with respect to acoustical or structural excitation, modal vibro‐acoustical analysis can be carried out. This paper presents a consolidation of the theory behind the vibro‐acoustical modal model. The model formulation is shown to be a nonsymmetrical formulation. It is shown that this is not contradictory to the well‐known vibro‐acoustical reciprocity principle. The implications of the nonsymmetry for the modal model are discussed. It is pointed out which variables must be measured and what kind of scaling must be used in order to end up with a consistent modal formulation. The theory is illustrated and verified by measurements on an experimental vibro‐acoustical system, consisting of a rigid cavity with one flexible wall.