Smartphone-based bridge frequency identification using vehicle contact-point response

Bridge frequency(BF)identification using the vehicle scanning method has attracted considerable attention during the last two decades.However,most previous studies have adopted unrealistic vehicle models,thus finding limited practical applications.This study proposes a smartphone-based BF identification method that uses the contact-point acceleration response of a four degree-of-freedom vehicle model.The said response can be inferred from the vehicle body response measured by a smartphone.For realizing practical applications,this method is incorporated into a self-developed smartphone app to obtain data smoothly and identify BFs in a timely manner.Numerical and experimental investigations are performed to verify the effectiveness of the proposed method.In particular,the robustness of this method is investigated numerically against various factors,including the vehicle speed,bridge span,road roughness,and bridge type.Furthermore,laboratory calibration tests are performed to investigate the accuracy of the smartphone gyroscope in measuring the angular velocity,where anomalous data are detected and eliminated.Laboratory experiment results for a simply supported bridge indicate that the proposed method can be used to identify the first two BFs with acceptable accuracy.

Two Novel Complexes Based on N-N Bridged Ligand:Syntheses,Crystal Structures,Fluorescence and Magnetic Property

Two novel coordination compounds,1[Zn4（L1）4（NO3）2（H2O）2]（NO3）2·2H2O and 2[Mn2（L2）2（DMF）（H2O）3]（ClO4）2·DMF（HL1 = N＇-[（1E）-pyridine-2-ylmethylidene]pyrazine-2-carbohydrazide,H2L2 = 2-hydroxy-3-methoxybenzaldehyde（pyrazin-2-ylcarbonyl）hydrazone）,based on the N-N bridged ligands were prepared and structurally characterized.Compound 1represents the[2＊2]molecular squares,in which both N atoms belonging to the N-N bridged ligands are connected to the Zn centers.The emission of compound 1 exhibits a blue shift,which can be assigned to strong electrostatic interaction between Zn^Ⅱ ions and the L1^-1.Compound 2represents a rare phenol-O bridged Mn2^Ⅱ complex.The magnetic investigation indicates weak antiferromagnetic interactions between the Mn^Ⅱ centers.

Identification of Connection Flexibility Effects Based on Load Testing of a Steel-Concrete Bridge

In the case of composite girders, an effective cooperation of both parts of the section is influenced by deformability of connectors. Limited flexural stiffness of welded studs, used commonly in bridge structures, does not provide full interaction of a steel beam and a concrete slab. This changes strain distribution in cross-sections of a composite girder and results in redistribution of internal forces in steel and concrete element. In the paper partial interaction index defined on the basis of a neutral axis position, which can be used for verification of steel-concrete interaction in real bridge structures rather than in specimens is proposed. The range of the index value changes, obtained during load testing of a typical steel-concrete composite beam bridge, is presented. The investigation was carried out on a motorway viaduct, consisting of two parallel structures. During the testing values of strains in girders under static and quasi-static loads were measured. The readings from the gauges were used to determine the index, characterizing composite action of the girders. Results of bridge testing under movable load, changing position along the bridge span is presented and obtained in-situ influence functions of strains and index values are commented in the paper.