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Early tied-arch bridges cannot satisfy the current traffic load demand due to their load grades and maintenance levels. Also, these tied-arch bridges have accumulated structural damage with increasingly prominent safety risks. In order to accurately evaluate the characteristics of tied-arch bridges' structural-influenced lines and identify damage of their arch ribs and suspenders, two analytical solutions are derived and established in this paper for the thrust-influenced lines of parabola and catenary two-hinged arches with a tie beam. A new method and an index for identifying damage of arch ribs and suspenders of tied-arch bridges are proposed. The results of numerical simulation in this paper verified that the proposed analytical solution has good analytical accuracy in practice on those two-hinged nonflat arches. With the use of equivalent thrust-influenced line difference curvature, the effectiveness of damage identification and the verification method were verified on the tie beam, suspender, and arch rib of plane tie arch structure as well as the suspender and arch rib of tied-arch bridges in this research. Furthermore, combining with grey relation analysis, the noise immunity of the proposed index method can be verified. Also, thrust-influenced line recognition based on VMD (variational mode decomposition) is introduced, and a practical process of bridge health assessment based on the quasistatic-influenced line loading of three-axle heavy vehicles is established. Theoretical analysis and numerical verification show that the calculated error of the analytic solution of two-hinged arches with a rise-span ratio greater than 1/8 is less than 9.57%, and the error decreases with the increase of the rise-span ratio. Therefore, it can be applied to the calculation and analysis of tied-arch bridges with a rise-span ratio range between 1/4 and 1/5. With the equivalent thrust-influenced line index proposed in this paper, the damage of suspenders and arch ribs of tied-arch bridges can be accurately located. It has been found that the proposed method is more effective to identify the damage of suspenders than the damage of arch ribs does, showing good noise immunity. In summary, this research has provided theoretical support for arch bridge design and evaluation. Combining with existing bridge-monitoring methods, the new bridge damage identification method proposed in this paper has the prospect of realizing the normal health status assessment of existing tied-arch bridges. [ABSTRACT FROM AUTHOR]

Considering that the effect of solar radiation on the super-high arch dam temperature field remains poorly studied, the calculation accuracy of dam temperature deformation is unable to be guaranteed accordingly. To address the issue, the solar radiation effect is adequately taken into consideration by proposing a practical calculation method based on the ray-tracing algorithm, the precomputation algorithm, and the ASHRAE clear sky model in this paper. With the aid of the ASHRAE clear sky model, the solar radiation received by the super-high arch dam and reservoir water is calculated. The shading effects are calculated by means of the ray-tracing algorithm, and the precomputation technology is introduced to further enhance the computational efficiency. Finally, to guarantee the authenticity of the calculation results, the dam thermodynamic parameters are inversed by employing the hybrid genetic algorithm. Based on the application in a real-life case, we concluded that around one third of the entire dam radial temperature deformation was attributable to solar radiation during continuous sunny days. The analysis results signify a critical role for taking account of the solar radiation in dam deformation calculation. Furthermore, the practicability and utilization prospect of the proposed method was verified. [ABSTRACT FROM AUTHOR]

Summary: The paper considers errors that occur during strain measurement by fiber‐optic sensors based on Bragg gratings, which are mounted on the surface of the controlled object with a connecting material. Errors due to the use of the assumption of a uniaxial stress state in the Bragg grating zone in the strains calculation based on the measured physical quantities are considered. The errors associated with the strain gradient along the Bragg grating and the strain gradient from the measurement zone to the measuring element are analyzed. To answer the question of what strain is measured, the change in the measured strain as a result of mounting the sensor on the material surface is estimated. Models and algorithms for numerical simulation of errors arising in the strain measurement are presented. Numerical results are given for estimating the considered types of errors when sensor is mounted with epoxy adhesives on the surface of isotropic and anisotropic (fiberglass, carbon fiber) materials. Variants of experiments are presented in which various options of nonuniform distribution of strains and a complex stress state are provided in the zones of strain measurement. The experimental results are compared with the results of numerical simulation based on the finite element method. The results of the analysis of the choice of the resonant wavelength from the reflected optical spectrum, which is used to calculate the strains under the assumption of a uniaxial stress state in the Bragg grating, are presented. [ABSTRACT FROM AUTHOR]

Modal parameters are used as safety assessment indicators for evaluating the structural integrity of buildings in various ways. In particular, the modal damping ratio plays a crucial role in accurately predicting the serviceability and safety of buildings, starting from the initial design stage. However, the identification results of the modal damping ratio can become unstable due to measurement time, initial configuration conditions used in the analysis, and nonstationary responses included in the structural response. To address the instability issue, this study proposes a long short-term memory-based frequency domain decomposition (FDD-LSTM) method. The FDD-LSTM method utilizes the acceleration response of the building as input data and the modal damping ratio obtained from the FDD method as output data, constructing an LSTM network model for the relationship between the acceleration response and modal damping ratio. The FDD-LSTM method exhibited a discrepancy of less than 0.02% compared to the reference value of the modal damping ratio obtained through free vibration response. Furthermore, when applied to data acquired from an actual building, the method demonstrated a variance of approximately 5%. The proposed FDD-LSTM method is validated for stability performance using a three-degree-of-freedom numerical analysis model, a 3-story steel frame structure model, and a 117-story high-rise building. The FDD-LSTM method, trained on a large dataset, enables generalized estimation and addresses instability issues related to modal damping ratio. [ABSTRACT FROM AUTHOR]

This research numerically investigates the mechanical behavior of sloped rolling-type bearings equipped with an inerter. After deriving equations of motion, the mechanical behavior, under harmonic excitation, of a sloped rolling-type bearing with its inherent rotational mass (i.e., considering the inertial and restoring forces generated by the existing roller) and one with an added rotational inerter is numerically analyzed. It is demonstrated that the latter is mechanically different from the former and, more importantly, the latter is more effective at controlling acceleration and displacement responses and practically more feasible. The acceleration control performance designed for sloped rolling-type bearings that ignore the inherent rotational mass can basically be retained when adding a rotational inerter if a suitable inertance-to-mass ratio can first be determined based on a specific acceleration target. Precisely stated, retaining the unique mechanical feature of sloped rolling-type bearings under harmonic excitation (i.e., the maximum transmitted acceleration is irrelevant to the external disturbance) is the optimum design objective in this study. Parametric and numerical analyses show that the peak acceleration responses of sloped rolling-type bearings with an added rotational inerter whose inertance-to-mass ratio is determined based on the optimum objective are less dependent on having a sufficiently large harmonic excitation period (i.e., on having the roller in motion within the sloped rolling range). In addition, the peak displacement responses under harmonic excitation can be effectively reduced compared with sloped rolling-type bearings that only consider the inherent rotational mass (i.e., without an added rotational inerter). Similar tendencies are seen when the sloped rolling-type bearings are subjected to ground motion records including far-field and pulse-like near-fault ones. Regardless of the ground motion considered in this study, the sloped rolling-type bearings with an added rotational inerter designed based on the optimum objective show steady displacement reduction. Finally, a simple, practical, and acceleration-based procedure is proposed for designing sloped rolling-type bearings equipped with added rotational inerters based on observations from the parametric and numerical analyses. [ABSTRACT FROM AUTHOR]

Summary: To support the development of low‐damage concrete structures, a system‐level shake‐table test of a two‐story concrete wall building implementing state‐of‐the‐art design concepts was conducted using the multi‐functional shake‐table array at Tongji University as part of an international collaborative project. The test building was designed with a perimeter frame and exterior post‐tensioned concrete walls in both directions. Different floor systems and wall‐to‐floor connections were incorporated in the test building to compare a number of design concepts and construction details. A range of energy dissipation devices were installed at the wall base and/or slotted‐beam joints of the test building. To simulate the test building response during the shake‐table tests, numerical models of the test building in both the longitudinal and transverse directions were established in OpenSees. Because the test building utilized flexible and isolated wall‐to‐floor connections that specifically reduced potential wall‐to‐floor interaction, planar frame numerical models were selected to represent the test building in each direction of loading. In the models, fiber hinge elements were used to simulate the unbonded post‐tensioned walls and a modified multi‐truss spring method was adopted to simulate the slotted‐beam joints with and without dampers. Inelastic time‐history analyses of the numerical models were conducted considering three earthquake intensities and comparisons of the test and simulation responses of the building are presented. The simulation results showed that the analytical model established in this study could reasonably predict both the global and local responses of the test building under different shaking intensities. [ABSTRACT FROM AUTHOR]

Summary: Past research has shown that negative stiffness may be used to good effect in mitigating the response of seismically excited structures. This has led to the emergence of several new negative stiffness devices of varying sizes, complexity, effectiveness, and practicality. In this study, a passive negative stiffness device composed of curved leaf springs using geometric nonlinearity is presented. The proposed device is designed to be simple and compact so as to be easily installed and exhibits approximately constant negative stiffness over a large range of displacements. Beyond these displacements, the negative stiffness produced by the device increases, which can help to limit the transmission of large damper forces at peak structure displacements. At displacements approaching the deformation limit of the device, the device produces positive stiffness so that stability of the structure is ensured. The objective of the research presented herein is to investigate the basic behavior of the device. Shaking table tests on specimens consisting of a vibrating part and the prototype passive negative stiffness device subjected to sinusoidal and simulated earthquake waves were conducted. The results revealed that the specimens exhibited negative restoring force characteristics, and due to the effect of the negative stiffness, an increase in the apparent period was demonstrated. Moreover, reduction of the response acceleration was shown without remarkable increase of the response displacement under the simulated earthquake inputs. Also, a numerical analysis to simulate the shake table testing and evaluate the control effect for a full‐scale building model was carried out. [ABSTRACT FROM AUTHOR]