Publications

Possibility of Bridge Inspection through Drive-By Vehicles

Based on virtual simulations of vehicle–bridge interactions, the possibility of detecting stiffness reduction damages in bridges through vehicle responses was tested in two dimensional (2D) and three dimensional (3D) settings. Short-Time Fourier Transformation (STFT) was used to process vehicles’ acceleration data obtained through the 2D and 3D virtual simulations. The energy band variation of the vehicle acceleration time history was found strongly related to damage parameters. More importantly, the vehicle’s initial entering conditions are critical in obtaining correct vehicle responses through the vehicle bridge interaction models. The offset distance needed before executing the vehicle–bridge interaction (VBI) modeling was obtained through different road profile roughness levels. Through the above breakthroughs in VBI modeling, the presented study provides a new and integrated method for drive-by bridge inspection.

Dynamic interaction between vehicle and bridge deck subjected to support settlement

Many bridges inevitably experience foundation settlement during their lifetime. Structural engineers need to limit the foundation settlement so that the bridge structure does not develop intolerable stresses. One factor in the effect of foundation settlement on bridge structures that has not been considered so far is the dynamic interaction between bridge and moving vehicle. In this study, Hamilton principle is adopted to derive the governing equations for the vibration of line supported orthotropic thin plates due to moving vehicles. The effect of foundation settlement on the bridge–vehicle interaction (BVI) is investigated by modifying the interaction forces due to the deformed shape of deck. The effect of fully or partially developed membrane stresses on the BVI will be also discussed. The results show that dynamic load allowance (IM) increases depending on the support location where settlement occurs, mode of settlement, span length, and magnitude of the foundation settlement. However the effect of membrane stresses on IM is insignificant. The analysis results indicate importance of considering the effect of bridge support settlement on the dynamic BVI.

High energy absorbing materials for blast resistant design

High blast absorbing materials have been consistently sought by the US Departments of Defense and Homeland Security, especially after 9.11. These materials can be used to effectively absorb blast wave energies and impact impulses and protect human lives and properties under extreme blasting events. The chapter reviews the current research status, outlines design philosophy for blast resistant design, and points to several case studies for using advanced materials and technology for blast mitigation, such as metal and foam sandwich panels, magneto-rheological fluids, and porous shape memory alloy.

An Integrated Real-Time Health Monitoring and Impact/CollisionDetection System for Bridges in Cold Remote Regions

This report presents a research examining the feasibility of creating an integrated structural health monitoring and impact/collision detection system for bridges in remote cold regions, where in-person inspection becomes formidable. The research report includes a theoretical analysis of the impact event identification in Chapter II, laboratory experiment verification in Chapter III, and a field testing and an integrated Structural health monitoring system in Chapter IV. Based on the systematical research outcomes, the impact/collision event and the real-time bridge structural health status have been successfully identified and recorded, which could be used for bridge management and resources allocation in future.

Quasi-static Crushing Behavior of Aluminum Honeycomb Materials

The quasi-static crushing behavior of aluminum honeycomb materials is thoroughly evaluated using a combined experimental, analytical, and numerical approach. Based on experimental characterization, the constitutive properties of the honeycomb cores under flat-wise compression are approximated by an elastic perfectly plastic material with inclusion of hardening after densification. Two different cell size materials are tested and compared, and the effect of strain rate on the crushing stress is studied. The experimental results show that the crushing platen stress is directly related to the relative density of core materials, and it can be associated with the strain rate, even though the effect of strain rates is not so dominant based on the conducted quasi-static tests. A simple physical model for predicting the crushing wave length and stress is proposed and compared with the experimental data and available formulas in the literature. It is observed that the crushing wave length is close to the cell size and related to the geometric dimension and strain rate. The folding mechanism is also measured by the ARAMIS system (a photogrammetry technique), and the measured von Mises strains are compared with the numerical results from LS-DYNA, demonstrating that the folding mechanism is initiated by two plastic hinge lines formed at the cell corners. Multilayer effect is also investigated, and it indicates that including the second layer slightly decreases the maximal crushing stress, but the simple superposition is still applicable for crushing multilayer honeycomb cores with different density. Partial crushing due to small size cylindrical indenter is further studied, and the experiment shows that the partial crushing process can be described by an elastic—plastic hardening material. Side impact process of honeycomb materials is also investigated, and the collapse band and its propagation process are captured. The thorough characterization of core crushing behavior conducted in this study provides better understanding of the failure process of honeycomb materials and can be further employed to study energy absorption and impact response of sandwich structures.

Pavement repair strategies for selected distresses in FM roadways

Expansive soil is considered one of the most common causes of pavement distresses in FM roadways. Depending upon the moisture level, expansive soils will experience changes in volume due to moisture fluctuations from seasonal variations. The objective of this research was to evaluate existing repair projects on selected FM roadways. Those roadways experienced failures in the form of fatigue and rutting in the wheel path, and longitudinal (faulted) cracking including edge cracking. The causes of those failures were mainly linked to high PI expansive soil and narrow pavement.

Bridge damage localization through modified curvature method

In this paper, a systematic methodology for identifying damages in bridges is presented, which includes the baseline calibration through field testing data

Identification of delamination defects through covariance of energy change: numerical modeling

Delamination is currently a difficult detectable form of damage in composite laminate materials. This paper presents a method to more easily detect delamination damage within composite materials using finite element analysis modeling, through the covariance of energy change. Lamb waves were introduced and recorded through an actuator and sensors made of piezoelectric material. The data were then analyzed through the fast Fourier transform (FFT). Using the data from the FFT, the idea of covariance of energy change was suggested to correlate with defect characteristics. By comparing the covariance of energy change in beams with different delamination sizes, thicknesses, and depths, correlations between the covariance of energy loss and defect characteristics were able to be developed. With these correlations, the severity of these damages was able to be quantified.

Image-Based Displacement Monitoring When Considering Translational and Rotational Camera Motions

A new method to filter the effect of camera motions through background templates is proposed in this manuscript. Moreover, the effect of template sizes and

Novel machine learning approach for shape-finding design of tree-like structures

With the rapid development of machine learning (ML), it is regarded as an effective approach for the shape-finding method of tree-like structures, for optimizing their structural forms. Considering that the existing shape-finding methods are do not easily solve the shape-finding problem of tree-like structures under a non-uniform load or supporting an irregular surface roof, the combination of a shape-finding concept and ML opens a new direction for shape-finding design. This paper presents a novel ML approach by combining a new shape-finding concept with a backpropagation and particle swarm optimization neural network. The core concept is to locate the load-bearing centre of each shape-finding unit by executing a positioning program, which finds the coordinates of the optimized nodes to achieve shape-finding design. Taking a tree-like structure with bottom two-bifurcate and upper four-bifurcate types as a shape-finding example, this paper elaborates the ML shape-finding method and specific steps in detail. Moreover, different shape-finding cases are analysed and compared with the inverse-hang recursive method. Results show that the ML shape-finding method can not only solve the unsolvable problem of shape-finding design of tree-like structures under a non-uniform load or supporting an irregular surface roof but also has higher efficiency than the compared method.

Optimal Steel Section Length of the Composite Rigid-Frame Bridge

The composite rigid-frame bridge replaces a specific concrete section of the midspan girder of a concrete rigid-frame bridge with a steel section. Although the added steel section improves the bending moment distribution of the rigid-frame bridge, it increases the stress level and structural deformation in a few specific points along the bridge girder. Therefore, the determination of the steel section length needs to consider the comprehensive mechanical effects caused by the replacement of the concrete section with the steel materials. This article presents the results of a study on the influence of steel section lengths on the structural mechanical behavior of rigid-frame bridges, including bending moment, bending stress, and structural deformation. Based on the results of the sensitivity analysis, this study optimizes the steel section length by using the bending strain energy as the objective function. Taking a composite rigid-frame bridge with a span combination of 84 + 200 + 84 m as an example, the structural optimization yields an optimal steel section length ratio of 0.55 (110 m), with the least bending strain energy and with acceptable magnitudes of bending moment, bending stress, and structural deformation. The outcome of this study provides guidance regarding the steel section length for the structural design of composite rigid-frame bridges.

Innovative Joint for Cable Dome Structure Based on Topology Optimization and Additive Manufacturing

Aiming at the problems of a low material utilization rate and uneven stress distribution of cast-steel support joints in cable dome structures, topology optimization and additive manufacturing methods are used for optimization design and integrated manufacturing. First, the basic principle and calculation process of topology optimization are briefly introduced. Then, the initial model of the support joint is calculated and analyzed by using the universal software ANSYS Workbench 2020R2 and Altair OptiStruct, and the optimized joint is imported into Discovery Live to smooth the surface. The static behaviors of three types of joints (topology-optimized joints, joints after the smoothing treatment, and joints from practical engineering) are compared and analyzed. Finally, the joints are printed by using fused deposition modeling (FDM) technology and laser-based powder bed fusion (LBPBF) technology in additive manufacturing. The results show that the new support joint in the cable dome structure obtained by the topology optimization method has the advantages of a novel shape, a high material utilization rate, and a uniform stress distribution. Additive manufacturing technology can allow the manufacture of complex shape components with high precision and high speed. The combination of topology optimization and additive manufacturing effectively realizes the advanced design and integrated manufacturing of support joints for cable dome structures.

Small Hidden Object Identification Through Bridge Weigh-In-Motion Data For Security Purposes

In this paper, a framework is developed for the purpose of detecting small hidden objects through weigh-inmotion data for security purposes. The 3 statistical principle is used to separate the outlier events and noises with normal traffic flow and the collected wheel loads are further used to identify the possible locations and weights of hidden objects. Correspondingly, an in-lab experiment has been conducted to validate the algorithm and excellent results have been reached. The system can be implemented at any security port and help to increase the security screening efficiencies at these locations.

Collaborative form-finding of multiple treelike column structures based on improved numerical inverse hanging method

The mechanical properties of treelike column structures are greatly influenced by their forms, emphasizing the importance of form optimization. However, previous studies have primarily focused on optimizing the morphology of individual treelike column, neglecting the interaction of multiple column structures. This oversight leads to deviation in the optimal morphology. In order to investigate the impact of the deviation on the performances of structures, the collaborative form-finding analysis of multiple column structures has been carried out using improved Numerical Inverse Hanging Method (NIHM). This research is based on the design of a large-span roof structure supported by 8 treelike column structures at the terminal of Dalian Jinzhou Bay Airport. Firstly, the traditional NIHM was improved to achieve collaborative form-finding of multiple treelike column structures. Then the differences between collaborative form-finding analysis of multi columns and individual analysis of single column were discussed in depth. Comparative results show collaborative form-finding exhibits more reasonable over individual form-finding. In the case where all joints are located on one side of the fixed end, the results of individual form-finding are similar to those of the initial model, while collaborative form-finding shows a significant enhancement in mechanical performance. Notably, when there exists a substantial height discrepancy among branch joint, collaborative form-finding achieves a displacement reduction of 21 % compared to individual form-finding, along with a reduction of 35 % in maximum equivalent stress.

Experimental Study on Static Load of Large-Diameter Piles in Nonuniform Gravel Soil

With the development of tourism, the number of multistorey buildings in mountain areas is increasing gradually, and the requirements of the form and bearing capacity of foundation in landslide areas are getting more demanding than ever. In‐situ testing of rock and soil mass in slope area has important practical significance for improving the stability of building foundation. Taking a project in Baishi Mountain located in southwest of China as an example, firstly, the geological structure and mechanical properties of soil are analyzed. Then, two types of pile foundations, i.e., empty‐bottom pile foundations and solid‐bottom pile foundations, are designed based on the characteristics of the geological structure for carrying out the static load test on pile foundation. The test results are as follows: (a) the load settlement curve (Q‐S) of the empty‐bottom test pile shows a steep drop, while the Q‐S curve of the solid‐bottom test pile shows a gradual change, showing that the end‐bearing friction pile’s property and the ultimate bearing capacity of the solid‐bottom pile are higher than those of the empty‐bottom pile. (b) The maximum lateral friction of the four test piles is 139.158 kPa, 148.015 kPa, 150.828 kPa, and 154.956 kPa, respectively. (c) The shaft skin resistance under ultimate load is coming close to the maximum value, and the maximum values are 9.792 mm, 7.939 mm, 9.881 mm, and 14.97 mm, respectively. Research results can serve as design bases for the pile foundation of multistorey buildings located in landslide areas of Baishi Mountain in the southwest of China and also as references for the engineering application of pile foundation in similar geological fracture areas.

Innovative Beam-To-Column Joint Design Of Moment Resisting Steel Frames For Seismic Areas

No abstract is provided for this article.

Intelligent Generation and Performance Analysis of Intersect Joint of Three Rectangular Tubes Based on Generative Adversarial Networks

Re-fracture process and mechanical characteristics of cracked rock samples

Most of the rocks surrounding deep underground construction consists of cracked rock. The deformation of the surroundings is complicated, and not only involves slipping, but also involves re-fracturing. Available results in conventional uniaxial and triaxial experiments of rock samples can be used to analyze deformations of supports and surrounding rocks on underground constructions, but they cannot reflect the evolution of the re-fracture processes and the mechanical characteristics of the cracked surrounding rock mass. The purpose of this paper is to study deformations and re-fracture characteristics of surrounding rock mass in deep underground engineering. First, deformations and cracking characteristics of intact rock samples are analyzed on the basis of uniaxial and triaxial experiments. The lateral constraint testing method is then applied to study deformation and re-fracturing characteristics of cracked rock mass. The lateral constraint test provides different lateral stiffness to the cracked rock samples and causes different failure modes in the cracked rock samples. Conditions for re-fracturing have been derived and validated through the lateral constraint tests, which can be used to study load capacities and stabilities of surrounding rock in deep underground engineering under structural constraints formed by different supports.