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Elastography is of great interest in biomechanics and medical imaging due to its nondestructive capability of mapping elasticity of tissues. The elastography framework relies on external excitations which actuate deformation inside an object. The internal response is then acquired and analyzed to map the distribution of elastic moduli. In this paper, with no need of measuring any internal responses, an integrated elastography method is developed which only requires the transmitted responses of applied sound waves. During the process, the tomography image (e.g., CT or MRI) and the applied waves are integrated into a computational model. Following a procedure of inverse analysis, the elasticity of all phases in the object is reconstructed when the computational transmission of waves matches with the measured transmission. The numerical simulation on brain tissues and a demonstration on silicon rubber phantom are conducted to validate the proposed method. Both cases demonstrate that the integrated method successfully predicts the real elasticity of samples. The verification measurements on the phantom further show that the predicted elastic moduli agree well with the experimental results of uniaxial compression testing.

A new type of UHPC‐NC (normal concrete) structure in the negative moment zone was proposed to improve the bearing capacity of the connection structure in the negative moment zone of prefabricated prestressed concrete (PC) beam bridges. First, the distribution characteristics of the crack, cracking load, ultimate moment, and ductility coefficient of the new structure were obtained by the 1:4 scale model tests. The feasibility of the connection structure is verified. Then, the value ranges of critical structural parameters affecting the bearing capacity of the connection structure based on the plane section assumption analysis, including the reasonable thickness of the UHPC layer, the reinforcement ratio of the longitudinal tensile reinforcement, and the diameter of the reinforcement, are obtained. At the same time, based on the verification of the finite element model, the influence of crucial research parameters on the bending capacity of the connection structure is obtained by using the finite element method. Finally, a theoretical method for the bending moment capacity of the connection structure of the UHPC‐NC structure is proposed, considering the high ductility characteristics of UHPC materials. The average relative error between the calculation results and the finite element method is within 7.2%, which verifies the reliability of the calculation method in this paper and provides a reference for its design and engineering application. [ABSTRACT FROM AUTHOR]

The existing anti-cracking measures in the negative bending moment zone of prestressed concrete beam bridges have many disadvantages. The application of Ultra-high-performance concrete (UHPC) provides a new option for the anti-cracking measures in the negative bending moment zone A prefabricated continuous connection structure of UHPC-NC (normal concrete) with a higher reinforcement ratio in the negative bending moment zone was proposed to improve the cracking resistance in the negative bending moment zone. The cracking load calculation method was given based on theoretical analysis under different loading modes of the UHPC-NC structure. The experimental investigations of the scaled models of 1:4 were conducted. The experimental results verified the reliability of the new structures. The thickness of the UHPC layer and the steel reinforcement ratio was considered to calculate the cracking load of the structure by the finite element method. The results show that the relative errors between the proposed method and the FEM are less than 11%. When the bending-shear combination effect is considered, the relative errors between the two methods are less than 10%. The reliability and applicability of the connection structure were verified, which provides a reference for the design and engineering application. [ABSTRACT FROM AUTHOR]

In order to analyze the influence position of prestressed reinforcement on the cracking load of composite girders, scale test and finite element analysis is used to study the cracking behavior of prestressed composite beam at the negative moment zone. The load–deflection curve and the cracking law of the scaled beam are obtained from the experimental results. The influence law of the resultant point and the spacing change through the symmetrical axis of the prestressed beam on the cracking load is obtained through the finite element parametric analysis. Furthermore, the prototype beam's mechanical performance in terms of the scaled test data is verified by both similarity theory and the prototype beam's numerical model. The results show that: Under different prestress levels, the cracking load is larger when the resultant force point of prestressed reinforcement on one side of the concrete slab's symmetric axis is within 0.15 ~ 0.50 times of slab half-width. In addition, the cracking moment of the specimen can be increased up to 11% by optimizing the prestress arrangement. [ABSTRACT FROM AUTHOR]

A new type of prefabricated abutment with a weak connection is proposed. The longitudinal load (like banking force, earth pressure) distribution of this new type of prefabricated abutment was analyzed based on the hinge-joined slab method. A simplified method for calculating the stiffness parameters of the panels was introduced. The influence lines of the longitudinal load on the prefabricated abutment of an actual bridge were calculated by using the proposed theoretical method and finite element method. The comparison between theoretical calculation and simulation results shows that the theoretical calculation method proposed in this paper is correct. In order to investigate the influence of the different thicknesses of the cap beam and dimensions of prefabricated panels on the calculation error of the theoretical calculation method. The influence lines of the prefabricated abutments with different parameters were calculated theoretically and simulated. All calculation errors of the central values of influence lines were less than 20% when the thickness of the cap beam changes from 0.8 to 2.4 m, the errors were all less than 10% when the thickness of the cap beam was 1.2–1.575 m. This calculation further verified that the theoretical calculation method proposed in this paper is suitable for longitudinal load distribution of a weakly connected Prefabricated bridge abutment. It provides a reference for the design and theoretical calculation of prefabricated abutment. [ABSTRACT FROM AUTHOR]

Due to their variable stiffness characteristics, magnetorheological elastomers (MREs) can be applied for seismic isolators in civil infrastructure systems. The lateral stiffness variation of MRE isolators is affected by the change of MRE shear stiffness. The natural frequency of the MRE-based isolation systems is related to the lateral stiffness of the MRE isolators with the range of lateral stiffness variation of MRE isolators serving as a critical objective to determine the shift ability of natural frequencies of the isolation systems. Here we develop a multiscale computational method to determine the magneto-mechanical coupling of MRE isolators. The field-dependent stiffness variation of the isolators is achieved with the consideration of combined magnetic field and deformation. Effects of MRE microstructural feature (e.g., particle concentrations in chains and between chains) and macroscopic geometry (e.g., thicknesses of MRE laminate and steel) on the magneto-mechanical responses of the isolators are specifically investigated, so as to guide the design of MRE-based isolating structures. The magnetic field and lateral stiffness of several MRE-based isolator prototypes from experiments are obtained by finite element-based shear simulation. Simulation results are quantitatively compared with experimental data, verifying and validating the accuracy and applicability of the proposed method. [Display omitted] • A multiscale magneto-mechanical coupling model is developed under large deformation. • Field-dependent responses of smart isolators are achieved with consideration of combined magnetic field and deformation. • Effects of MRE micro-/macro-structural features on the magneto-mechanical responses of isolators are investigated. [ABSTRACT FROM AUTHOR]

This study investigates the interface bond strength and anchorage performance of steel bars within prefabricated concrete. Twenty-two specimens were designed and manufactured to study the interface bond behavior of deformed and plain steel bars under a larger cover thickness. Diameter of steel bars, strength grade of concrete, and anchorage length were considered influential factors. The finite element method (ABAQUS) was used for the validation of experimental results. The interface bond's failure mechanism and the anchorage length in the prefabricated concrete under different concrete strength levels were explored and compared to national and international codes. A suitable value of the basic anchoring length for the prefabricated structure was recommended. The results show that the interface bond strength of prefabricated bridge members is directly proportional to the strength grade of the concrete, inversely proportional to the reinforcement diameter, and less related to anchorage length. The effect of the cover thickness of the surrounding concrete is negligible. Conversely, the bearing capacity of prefabricated bridge members depends on the strength of the concrete, the diameter of the steel bar, and the anchorage length. Furthermore, it is concluded that the mechanical bond strength accounts for 88% of the bond strength within prefabricated concrete. [ABSTRACT FROM AUTHOR]