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The objective of this study is to design and validate distributed strain field monitoring using a patterned nanocomposite “sensing mesh” that is coupled with an electrical impedance tomography (EIT) measurement strategy and algorithm. Although EIT has been used in other studies and in conjunction with a piezoresistive thin film for spatial damage detection, different strain components cannot be directly extracted from reconstructed EIT conductivity maps. Therefore, this study seeks to address this issue by patterning piezoresistive graphene-based thin films to form a mesh-like pattern. The high aspect ratio of each nanocomposite grid interconnect acts as a linear distributed strain sensor, capable of resolving strains along the entire length and direction of the element. This study first began with the design, fabrication, and characterization of the strain sensing response of a graphene-based thin film of high strain sensitivity. Second, the strain-sensitive film was spray-coated onto patterned polymer substrates to form the sensing meshes, which were then subjected to load tests. Upon validating distributed strain field monitoring through EIT, its applicability for field implementation and damage characterization was also demonstrated by instrumenting sensing meshes in the column of a seven-story reinforced-concrete building subjected to shaking table earthquake excitations. The large-scale shaking table test results successfully validated distributed damage detection.

This study aims to validate a piezoelectric driven-rod scour monitoring system that can sense changes in scour depth along the entire rod at its instrumented location. The proposed sensor is a polymeric slender rod with a thin strip of polyvinylidene fluoride that runs through its midline. Extraction of the fundamental frequency allows the direct calculation of the exposed length (or scour depth) of the slender rod undergoing fluid flow excitation. First, laboratory validation in dry conditions is presented. Second, hydrodynamic testing of the sensor system in a soil-bed flume is discussed. Each rod was installed using a three-dimensional-printed footing designed for ease of installation and stabilization during testing. The sensors were installed in a layout designed to capture symmetric scour conditions around a scaled pier. In order to analyze the system out of steady-state conditions, water velocity was increased in stages during testing to induce different degrees of scour. As ambient water flow excited the portion of the exposed rods, the embedded piezoelectric element outputted a time-varying voltage signal. Different methods were then employed to extract the fundamental frequency of each rod, and the results were compared. Further testing was also performed to characterize the relationship between frequency outputs and flow velocity, which were previously thought to be independent. In general, the proposed driven-rod scour monitoring system successfully captured changing frequencies under varied flow conditions.

Data‐driven structural health monitoring (SHM) is an approach which relies on the information contained in the data and through signal analysis techniques captures the features, variations, and uncertainties that data contain. This paper presents the response of shaking table tests of a full‐scale, 3‐story building with sliding slabs connected by horizontal buckling‐restrained braces for energy dissipation. First, the global dynamic characteristics of the structure were identified from a series of the building response data under different intensity level of base excitations. The variation of the identified modal parameters, such as the mode frequencies and modal shapes, was discovered. The influence of sliding slabs on the dynamic characteristics of the frame was also investigated through the measured response and the equation of motion with six degree of freedom systems. Comparison on the achieved interstory stiffness due to the implementation of sliding slabs and the fixed (locked up) slab was examined. The mechanism and dynamic characteristics of sliding slabs, including energy dissipation of the friction force, BRB hysteresis behavior, and unintended damping force during strong base excitation were analyzed directly using the ARX/recursive model. The extracted unintended damping force performed like a friction hysteretic response, which needs to be considered for frame modeling in shaking table tests. The findings through the data analysis have clarified the important aspects of sliding slabs and demonstrated the benefits and applicability of sliding slabs on reducing the frame response. [ABSTRACT FROM AUTHOR]

In this study, a probabilistic seismic hazard analysis (PSHA) using a traditional approach with a simple logic tree that handles a single-site sigma is developed to present a site-specific ground motion hazard. The analysis relies on the accelerometer data collected from the I-Lan Plain, a deep sedimentary basin in Northeastern Taiwan where hundreds of earthquake sequences (with M w = 4.0–7.6) were recorded by the Taiwan Strong Motion Instrument Program (TSMIP) network between 1992 and 2016. The performance of PSHA on soil and hard sites is evaluated from two representative instrumented sites (ILA048 and ILA025), using residual measures available from a ground motion model (GMM) developed by Phung et al. [2023] (referred to as Ph23), from which the uncertainties in site terms ( δ S 2 S s) and single-site sigma ( σ S S , S) are estimated. We address key conceptual issues in the current PSHA approach and introduce a new region- and site-specific PSHA approach in which (1) site-to-site variability ( ϕ S 2 S) is estimated as a random variance in a mixed effects GMM regression and (2) the GMM site-specific single-site sigma ( σ S S , S) is replaced with a generic site-corrected aleatory variability ( σ 0 ). Comparison of the region- and site-specific hazard curves from our method against the traditional method estimates at two well-recorded sites in the I-Lan region shows an approximate 50% difference in prediction ground motion values considering for 2% and 10% probability of exceedance in 50 years. [ABSTRACT FROM AUTHOR]

Estimating the story drift directly from acceleration records is challenging. This paper presents a systematic integration scheme involving the empirical mode decomposition of signals to estimate the earthquake-induced displacement of buildings, including their permanent deformation after an earthquake. A three-phase algorithm is proposed. In phase-1, the displacement waveform without residual displacement is estimated, then in phase-2 the residual deformation is calculated. Combining both phase-1 and phase-2, the displacement waveform is estimated. Three types of acceleration data, namely, shaking table test data, seismic response data for a building, and near-fault ground motion data, were used to validate the proposed method. [ABSTRACT FROM AUTHOR]

Structural health monitoring is conducted to ensure the structural integrity of a building during earthquakes. This study aimed to improve our understanding of the dynamic response of buildings subjected to a series of earthquake excitations, focusing on interpreting structural dynamic characteristics and identifying potential seismic damage subjected to a series of earthquake excitations. To this end, a series of seismic response data of a 13‐story reinforced‐concrete/steel building were collected through long‐term monitoring over 2 years. A systematic approach for monitoring the health of the building was established by integrating several algorithms for vibration‐based (both output‐only and input–output parametric nonparametric feature‐discrimination algorithms) and model‐based feature extraction techniques. Furthermore, the time‐varying dynamic characteristics of the building were determined, including its modal frequency, mode shape, and stiffness, as extracted from features obtained over the monitoring period of 2 years. Safety assessment of this newly compound high‐rise building is investigated to explore the system dynamic characteristics through long‐term seismic monitoring. [ABSTRACT FROM AUTHOR]

A new methodology is proposed for developing a scenario‐based site‐specific response spectrum (RS) considering near‐fault effects in Taiwan. First, source parameters, together with reference rock site conditions, are defined according to the available geological and geophysical information at a target site close to a potential active fault in northern Taiwan. Secondly, the scenario‐based response spectrum for a reference rock site condition is developed theoretically through an empirical approach by using a ground motion prediction equation (GMPE). The effect of the pulse period and the occurrence probability of near‐fault pulse‐like ground motion on RS is evaluated by using the ground motion simulation (GMS) technique, in which the stochastic finite‐fault simulation method is validated and applied for evaluating velocity pulse. Third, site‐specific site amplification is incorporated into RS through a site transfer function calculated from the measured horizontal‐to‐vertical Fourier spectral ratio through the microtremor (MHVR) of the target site. Finally, the design spectrum of the target site is compared with the derived site‐specific RS to evaluate the impact of the neighbor fault on the structure of the target site. [ABSTRACT FROM AUTHOR]

The need to identify the physical properties of a structure given its force-response (input-output) relationship is driven primarily by the need to validate the approximate solution models, such as finite-element models. This paper proposes a method, which combines the structural system identification and model updating techniques, for the damage detection of a steel frame structure and a RC frame. The damage detection procedure consists of two steps: (1) identifying the system dynamic characteristics using the subspace identification (SI) technique from input/output measurements and (2) developing a damage assessment method for structural members (including joints) based on a progressive finite-element model updating and a large-scale optimization using a nonlinear least-square technique. The proposed method was verified through a shaking table experimental study using: (1) a 1/4-scale six-story steel frame structure by loosening the connection bolts for damage simulations and (2) a two-story RC frame subject to different levels of ground excitations back to back. As demonstrated by experimental results, the proposed damage detection method, based on the combination of SI technique and the model updating approach, is very effective for the damage assessment of frame structures. The method not only can detect the damage locations but also can quantify the damage severities. DOI: 10.106 I/(ASCE)ST. 1943-541 X.0000079 CE Database subject headings: Algorithms; Model studies; Optimization; Damage; Finite element method; Data analysis; Structural analysis.

This work presents a modified modal strain energy change (M-MSEC) method and its corresponding iteration process to detect damage to frame structures. Analytical results of a three-dimensional frame structure demonstrate that the quantity of damage can be identified correctly by using different modes in the M-MSEC method. A full-scale experimental study is also performed to evaluate the robustness of the M-MSEC method on damage detection as well as damage quantification. Satisfactory results are shown in relation to the modeling error, noise effect, and limited measurements. DOI: 10.1061/(ASCE)0733-9399(2008)134:11(1000) CE Database subject headings: Damage; Structural dynamics; Strain energy; Three-dimensional analysis; Framed structures.

This paper presents both the centralized and decentralized control strategies by using semiactive control devices (magnetorheological dampers) for building structural control under seismic excitations. The control algorithms used in this study only focus on the linear quadratic Gaussian control theory with acceleration measurements as feedback signals. In the centralized control, the control force is generated directly from the measurement in each degree of freedom, while in the decentralized control, only measurement from local subsystems is used to calculate the control force with respect to the locations of control devices and measurements. Four groups of centralized/decentralized control algorithms are studied: fully centralized control, fully decentralized control, half-centralized control, and partially decentralized control. The ASCE 20-story benchmark building is selected as an example to evaluate the control performance among different control strategies. DOI: 10.1061/(ASCE)0733-9399(2008)134:11(970) CE Database subject headings: Algorithms; Damping; Structural control.

The research results are presented of the joint project of the National Center for Research on Earthquake Engineering (Taiwan) and Stanford University on the pseudodynamic testing of a three-story full-scale reinforced concrete steel moment frame. Nonlinear stress-strain relations, corresponding to oscillations in the frame, were estimated for successive time intervals from a pseudodynamic test of strong ground motion excitation. Numerical models of the behavior of the frame under the pseudodynamic loading of four levels of input ground motion were constructed and used for estimating changes in the shear moduli in the frame during its loading and for the nonlinear identification of the frame behavior. The contents of linear and nonlinear quadratic and cubic components in the response of the frame were estimated. It was found that the frame possesses mostly odd-order nonlinearities, such as the third, fifth, seventh, etc. order nonlinearities, whereas, even-order nonlinearities, such as, quadratic, the fourth, sixth, eighth, etc. order nonlinearities, are weak. Temporal changes in the behavior of the frame were observed during the test, indicating a substantial decrease in the elastic shear moduli, increase in the absorption of seismic waves and in the contents of the nonlinear part in the response of the frame. CE Database subject headings: Pseudodynamic method; Data analysis; Numerical models; Full-scale tests; Building frames; Ground motion.