Xinqun Zhu

• PhD
• Professor (Associate) at University of Technology Sydney

The performance of prestressed concrete bridges (PCBs) is significantly affected by the prestress loss and overloading vehicles over their service life. Structural health monitoring is critical to prevent the structural collapse and life-cycle management and cost-effective maintenance for PCBs. This paper presents an innovative dynamic equilibrium-...

Damage detection of a complex spatial frame structure with semi-rigid joints is a challenging task. Most existing damage detection methods consider the joint as rigid and the nonuniform cross section of the member is not considered. This assumption results to a large error in the structural damage identification. A novel generic element is proposed...

An experimental and numerical study on the behaviour of the steel-concrete composite structure with the novel shear connectors has been conducted in this paper. The new bolted connector consists of a long tube nut and a compatible partial-thread bolt. The nut is casted in concrete and the bolt is connected to the nut through pre-drilled holes in th...

Concrete building structures are prone to cracking as they are subjected to environmental temperatures, freeze-thaw cycles, and other operational environmental factors. Failure to detect cracks in the key building structure at the early stage can result in serious accidents and associated economic losses. A new method using the SE-U-Net model based...

The drive-by bridge dynamic measurement using an instrumented vehicle during its passage over the bridge can be an indirect bridge structural health monitoring system. The identification of the contact-point (CP) responses between vehicle wheels and bridge structure from vehicle responses offers an efficient and economical way for the modal identif...

Structural damage detection is crucial for ensuring the safety of civil building structures in operational environments. Recently, deep learning-based methods have gained increasing attention from engineers and researchers. The performance of conventional deep learning methods for structural damage detection relies on a large number of labeled trai...

Full-scale dome structures intrinsically have numerous sources of irreducible aleatoric uncertainties. A large-scale numerical simulation of the dome structure is required to quantify the effects of these sources on the dynamic performance of the structure using the finite element method (FEM). To reduce the heavy computational burden, a surrogate...

With the deterioration of bridge performance and ever-increasing amounts of traffic, bridge safety is becoming a concern for the engineering community. A method that can assess a bridge’s condition in real time is urgently needed. The main factors that hinder bridge condition assessment are the uncertain operational environments. A new moving princ...

With the deterioration of the bridge performance and ever-increasing amount of traffic, the bridge safety is becoming a concern for engineering community. A method that can assess the bridge's condition in real-time is urgently needed. The main factors that hinder the bridge condition assessment are the uncertain operational environments. A new mov...

A new damaged cable identification method using the basis vector matrix (BVM) is proposed to identify multiple damaged cables in cable-stayed bridges. The relationships between the cable tension stiffness and the girder bending strain of the cable-stayed bridge are established using a force method. The difference between the maximum bending strains...

The global time-dependent performance analysis of structural systems has aroused the interest of researchers in recent years. The conventional technique using finite element analysis is very computationally intensive in evaluating the time-dependent performance of structures with multiple variables. A new hybrid method by integrating a surrogate mo...

An exact dynamic analytical method for free vibrations of continuous partial-interaction composite beams is proposed based on the Timoshenko beam theory. The main advantage of this method is that the independent shear deformations and rotary inertia of sub-beams are considered, which is more in line with the reality. Therefore, the accuracy of eige...

Investigation on the dynamic characteristics of bridges for structural condition assessment is challenging when nonlinear breathing cracks in the bridge and nonstationary vehicle-bridge interaction are considered. Variational mode decomposition (VMD) method has been widely used to analyze the nonlinear time-series, but its performance is highly dep...

Queti is an important component of Tibetan timber beam-column joint to transfer compression, shear, and bending moment from one structural component to another. The inclination of Queti is a common type of damage in Tibetan heritage buildings and it significantly reduces the load-carrying capacity and safety of the joint under vertical load. In thi...

Bridge modal identification using an instrumented test vehicle as a moving sensor is promising but challenging. A key factor is to extract bridge dynamic components from vehicle responses measured when the bridge is operating. A new method based on an advanced adaptive signal decomposition technique, the successive variational mode decomposition (S...

The drive‐by bridge health monitoring is to assess the bridge condition using the acceleration responses measured on the body or axle of instrumented vehicles. The vehicle responses are greatly affected by the road surface roughness that makes the bridge dynamic information blurred. Instead of direct using vehicle responses for the bridge monitorin...

A new two-step approach is developed for damaged cable identification in a cable-stayed bridge from deck bending strain responses using Support Vector Machine. A Damaged Cable Identification Machine (DCIM) based on support vector classification is constructed to determine the damaged cable and a Damage Severity Identification Machine (DSIM) based o...

Bridge infrastructures are always subjected to degradation because of aging, their environment, and excess loading. Now it has become a worldwide concern that a large proportion of bridge infrastructures require significant maintenance. This compels the engineering community to develop a robust method for condition assessment of the bridge structur...

For large-scale dome structures subjected to earthquake ground motions, the need for accurate and efficient approaches that account for uncertainties in design, material properties, loads, damping, and manufacturing processes has grown significantly. In uncertainty analyses, the theory of probability, uncertainty quantification, and reliability ana...

This paper presents a novel method for damage identification of steel-concrete composite beams based on modal strain energy (MSE) changes through general regression neural network (GRNN). A finite element (FE) model was developed using two Euler-Bernoulli beam elements as steel beam and concrete slab layers which are coupled by incorporating a defo...

Steel-concrete composite (SCC) beams are widely employed in bridge decks. The interfacial shear transfer between the top concrete slab and the supporting steel beams significantly affects the overall load carrying capacity and performance of a bridge deck. The inaccessibility of the connection system makes the visual inspection difficult, and the t...

Bridge infrastructures are continuously subject to degradation due to aging and excess loading, placing users at risk. It has now become a major concern worldwide, where the majority of bridge infrastructures are approaching their design life. This compels the engineering community to develop robust methods for continuous monitoring of bridge infra...

The free vibration characteristics of steel-concrete composite continuous beams (SCCCBs) are analyzed based on the Euler–Bernoulli beam theory. A modified dynamic direct stiffness method has been developed, which can be used to analyze the SCCCBs with some lumped masses and elastic boundary conditions. The results obtained by the proposed method ar...

Imprecision and uncertainty always exist in engineering structures. In recent years, an increasing emphasis is placed on quantifying structural performance by explicitly modeling uncertainties. A limited number of studies have been conducted on the uncertain analysis of complex structures. Because the time-history response analysis (THRA) is extrem...

In this study, multifunctional cementitious composites with integrated self-sensing and hydrophobicity abilities were firstly developed and investigated using conductive graphene nanoplate (GNP) and silane hydrophobic powder (SHP). The mechanical properties, permeability, water contact angle, microstructure, and piezoresistivity were studied and co...

Currently, there is no unified criterion to evaluate the failure of single-layer latticed domes, and an accurate nonlinear time-history analysis (NTHA) is generally required; however, this does not consider the uncertainties found in practice. The seismic instability of domes subjected to earthquake ground motions has not been thoroughly investigat...

For a vehicle moving over a bridge, the vehicle-bridge interaction (VBI) embraces the time-varying modal parameters of the system. The identification of non-stationary characteristics of bridge responses due to moving vehicle load is important and remains a challenging task. A new method based on the improved empirical wavelet transform (EWT) along...

Drive-by bridge parameter identification using an instrumented vehicle has drawn great attention in the field of bridge structure health monitoring. The feasibility of the drive-by inspection methods has been verified by a number of studies. However, most of the studies are conducted with numerical simulations and the successful field application f...

‘Que-Ti’ is an important component in typical Tibetan heritage timber buildings and it performs similar to corbel brackets connecting beam and column in modern structures. It transfers shear, compression and bending moment by slippage and deformation of components as well as limited joint rotation. A rigorous analytical model of ‘Que-Ti’ is needed...

Drive-by bridge inspection using acceleration responses of a passing vehicle has great potential for bridge structural health monitoring. It is, however, known that the road surface roughness is a big challenge for the practical application of this indirect approach. This paper presents a new two-step method for the bridge damage identification fro...

The composite action between the layers of steel and concrete is governed by the shear connection. Because of the complicated interconnection behavior of these composite layers, it is difficult to detect damage in the composite structures, especially, the interfacial integrity of the two layers. In this paper, anovel method has been developed for s...

A large number of studies and applications have been carried out on horizontal seismic isolation systems, and their effectiveness has been indicated. For long-span spatial structures, vertical seismic load plays an important role. However, vertical seismic isolation technology has not been extensively investigated. In this paper, a hybrid bearing w...

This paper investigates the free vibration and crack identification of functionally graded material (FGM) plates with a through-width edge crack. The material properties of the FGM plates change continuously with the power law distribution along the plate thickness direction. The crack in an FGM plate is simulated as a massless rotational spring an...

In this paper, the vibrational power flow of a cracked beam made of functionally graded materials (FGMs) is investigated. The Young's modulus and mass density change exponentially along the thickness direction of the beam. The cracked FGM beam is divided into two sub-beams at the crack section which are connected by a massless rotational spring. Ba...

The vehicle and bridge responses in a vehicle-bridge interaction (VBI) system have been widely studied with some aiming at the bridge health monitoring. The extraction of bridge modal frequencies from bridge or vehicle responses was mostly conducted with the assumption of an invariant vehicle and bridge system and/or the responses are stationary du...

The bridge infrastructures are subjected to continuous degradation due to ageing, environmental and excess loading. Monitoring of these structures is a key part of any maintenance strategy as it can give early warning if a bridge is becoming unsafe. Most of the current approaches are using direct measurements that the sensors are installed at diffe...

Currently, nonlinear dynamic analysis for large-scale single-layer domes is commonly performed using deterministic numerical methods. However, in practical engineering cases, complex large-scale single-layer domes have many uncertain parameters that cannot be considered using deterministic methods. Therefore, there is a growing awareness that class...

In this paper, we develop a radio frequency identification (RFID)-based wireless multi-sensory infrastructure health monitoring (IHM) system that can simultaneously measure dynamic acceleration and strain. The system consists of a novel multi-sensor integrated semi-passive ultra-high frequency (UHF) tag antenna that can be mounted on civil infrastr...

Drive-by bridge parameter identification has been an active research area in recent years. An instrumented vehicle passing over a bridge deck captures dynamic information of the bridge structure without bridge closure and on-site instrumentation. The vehicle dynamic response includes components associated with the bridge surface roughness and the v...

Drive-by bridge parameter identification has been an active research area in recent years. An instrumented vehicle passing over a bridge deck captures dynamic information of the bridge structure without bridge closure and on-site instrumentation. The vehicle dynamic response includes components associated with the bridge surface roughness and the v...

Guided waves are traditionally used in different non-destructive testing applications because of their cost-effectiveness and piezoelectric patches that are easy to incorporate into the structure as transducers. The non-destructive evaluation of interfacial defects such as debonding in a composite structure is critical for safety and long-term use....

A new indirect strategy is proposed to estimate the bridge modal parameters from the dynamic responses of two vehicles using stochastic subspace identification technique. The effect of ambient excitation, such as ongoing traffic, is simulated as white-noise excitation at the bridge supports. The state-space model of the vehicle-bridge interaction s...

An experimental investigation of stress concentration factor (SCF) in Steel circular hollow section brace welded to concrete-filled circular hollow section chord (CHS-to-CFCHS) T-joints has been performed under axial tension, axial compression, in-plane bending and out-of-plane bending. The distribution of SCF around the welded brace-to-chord inter...

This paper proposes a new damage index for the crack identification of beams made of functionally graded materials (FGMs) by using the wavelet analysis. The damage index is defined based on the position of the wavelet coefficient modulus maxima in the scale space. The crack is assumed to be an open edge crack and is modeled by a massless rotational...

In this article, a piezoelectric-based sensory technique is proposed for detection of the gap between surfaces of a carbon fiber reinforced polymer plate and a concrete specimen and characterization of shrinkage of early-age concrete. The proposed technique uses the propagation properties of the guided waves in the carbon fiber reinforced polymer p...

The stick–slip phenomenon is commonly found at structural connections in steel buildings. It is a major damping mechanism in a structure with bolted joints and makes a significant contribution to the total structural damping. This article reviews the stick–slip damping model of an elastic single-degree-of-freedom system with one stick–slip componen...

Railway track is one of the most important parts of the railway system, and monitoring its condition is essential to ensure the safety of trains and reduce maintenance cost. An adaptive regularization approach is adopted in this paper to identify the parameters of a railway ballasted track system (substructure) from dynamic measurements on in-servi...

A large-scale cable-stayed bridge in the state of New South Wales, Australia, has been extensively instrumented with an array of accelerometer, strain gauge, and environmental sensors. The real-time continuous response of the bridge has been collected since July 2016. This study aims at condition assessment of this bridge by investigating three asp...

This case-study article aims to share the field-test observations of a real-world cable-stayed bridge with the research community of bridge-weigh-in-motion to address the challenges of axle identification. Various structural members of the bridge, including cables, girders, and the deck, were instrumented with strain gauges at different locations t...

Concrete-filled steel tubular joints are increasingly being used for built infrastructure such as bridges and towers. In this study, the variation of the maximum Stress Concentration Factor (SCFmax) with non-dimensional geometric parameters in concrete-filled steel tubular (CFST) T-joints under axial tension has been investigated. A database of the...

An innovative approach to identify local anomalies in a structural beam bridge with an instrumented vehicle moving as a sensory system across the bridge. Accelerations at both the axle and vehicle body are measured from which vehicle-bridge interaction force on the structure is determined. Local anomalies of the structure are estimated from this in...

In the formulation of finite elements, the variation of elemental internal forces and displacements are interpolated. The force interpolation functions are known to reproduce the variations of forces better than the interpolation functions on the displacements. Layered section beam model is not as complicated as the fiber model, and yet, it is much...

‘Que-Ti’ is an important component connecting the beam and column in typical Tibetan historic timber buildings. It transfers shear, compression and bending moment by slippage and deformation of components as well as a limited joint rotation. A rigorous analytical model of ‘Que-Ti’ is needed for predicting the behaviour of a timber structure under l...

Due to changing environments and aging, the structural resistance of the heritage buildings has been reduced significantly. It has become crucial to monitor and protect the architectural heritage buildings. The objective of this research is to monitor and assess the performance of the heritage Tibetan timber building in operational environments. A...

The output of a system due to a change of its parameters is often approximated with the sensitivity matrix from the first order Taylor series. The system output can be measured in practice, but the perturbation in the system parameters is usually not available. Inverse sensitivity analysis can be adopted to estimate the unknown system parameter per...

Real world Structural Health Monitoring (SHM) systems consist of sensors in the scale of hundreds, each sensor generating extremely large amounts of data, often arousing the issue of the cost associated with data transfer and storage. Sensor energy is a major component included in this cost factor, especially in Wireless Sensor Networks (WSN). Data...

This article presents a hybrid approach for determining optimal parameters of multiple tuned mass dampers to reduce the floor vibration due to human walking. The proposed approach consists of two parts. The first one is a partial mode decomposition algorithm to efficiently calculate dynamic responses of the coupled floor–multiple tuned mass damper...

Bridge weigh-in-motion (BWIM) is an approach through which the axle and gross weight of trucks travelling at normal highway speed are identified using the response of an instrumented bridge. The vehicle speed, the number of axles, and the axle spacing are crucial parameters, and are required to be determined in the majority of BWIM algorithms. Noth...

The engineering background of this article is an ancient wooden building with extremely high historic and cultural values in Tibet. A full understanding of the dynamic behaviour of this historic building under in-service environments is the basis to assess the condition of the structure, especially its responses to earthquake, environmental and ope...

The beam-column connection, called ‘Que Ti’, is the key component of historic Tibetan timber buildings to transfer shear, compression and bending loads from one structural element to another. This kind of connections can reduce the internal forces and improve the structure’s ability to resist earthquakes. Its structure is very complicated and there...

In structural engineering, composite construction has become increasingly widespread due to the improvement of mechanical properties it provides. Retrospective application of the composite construction principle to old structures may be beneficial. Many end of life structures are decommissioned and replaced. If the structural integrity of old struc...

Recent research studies revealed that blind-bolts can be used to strengthen existing composite steel-concrete beams more efficiently and effectively than welded stud connectors. In the general retrofitting operation procedure, the holes created in the concrete slab of composite beams to fix shear connectors are finally backfilled with grout. Howeve...

Recent research studies carried out on the condition of the existing infrastructure in Australia have revealed that the percentage of structures reaching the end of their useful life has increased. These structures need alternative structural solutions to extend their useful life to reduce the costs on ‘new builds’, which are required to replace th...

This paper presents an overview on inverse problems in vehicle–bridge interaction dynamics. Dynamic interaction force exists between a vehicle and a bridge deck when the vehicle moves on top. A thorough understanding of this moving load problem is crucial for the design of bridge and its condition assessment as well as control of overweight vehicle...

This paper presents a measurement system for measuring dynamic acceleration of infrastructure remotely using semipassive radio-frequency identification (RFID) tag. This measurement is critical to the vibration-based method for infrastructure health monitoring. Design considerations of accelerometer integrated ultrahigh-frequency RFID tag and dynami...

The use of the vehicle-bridge interaction (VBI) data for structural health monitoring has received considerable interest in the last decade. Compared with the traditional bridge health monitoring, the VBI based approach allows the target bridges to be monitored or assessed under operating conditions. The VBI system has time-variant features and the...

Structural Health Monitoring (SHM) and damage detection techniques have captured much interest and attention of researchers and structural engineers owing to their promising ability to provide spatial and quantitative information regarding structural damage and the performance of a structure during its life-cycle. With the development of smart sens...

High stress concentration at the weld vicinity in welded steel tubular joints results in fatigue failure. Researchers have tried finding an effective method to reduce these stresses. Although concrete filling of the steel tubes has been used to reduce stresses at the joints in the recent two decades, the fatigue performance of concrete filled tubul...

The use of blind bolts in steel–concrete composite beams is beneficial for promoting sustainable design and for retrofitting existing steel structures. This paper presents an experimental study as well as finite element (FE) modelling analyses for the time-dependent behaviour of composite beams with blind bolts subjected to sustained loads. Four fu...

This paper addresses the issue of reliability and performance in wireless sensor networks (WSN) based structural health monitoring (SHM), particularly with decentralized damage identification techniques. Two decentralized damage identification algorithms, namely, the autoregressive (AR) model based damage index and the Wiener filter method are deve...

This paper presents a new technique based on the Ritz method for the damage detection of circular cylindrical shell structures. Sander's thin shell theory together with the Ritz method is used to analyse the dynamic behaviour of circular cylindrical shells. The crack damage on the shell surface is modelled by a rotational line spring along the circ...

Revisited herein is the response sensitivity method for structural condition assessment. The performance of a sensitivity enhancement technique for structural damage identification is discussed with reference to cases with noisy excitation or with only output. An extended study on the structural condition assessment is conducted based on a newly de...

Cables are important components of a cable-stayed bridge, and the cable tension is a crucial factor in determining the overall condition assessment of a cable-stayed bridge structure. Based on the vibration frequency method, a wireless monitoring system for bridge cable tension force monitoring has been investigated and experimentally validated thr...

Time domain substructural condition assessment method is actively researched in recent years to avoid the problem with uncertainties in the different components of the structure, boundary conditions and with an improved effort in the inverse computation. Since the interface force between substructures would vary with the existence of local damages...

Most existing time domain force identification methods are based on the state space method, which has the disadvantage of large discretization error with a low sampling frequency or a long sampling duration. This work transforms the conventional implicit Newmark-β algorithm into an explicit form for the solution of the Ax=b equations, which is an e...

Time domain structural condition assessment methods have been studied extensively in the last two decades due to their effectiveness in dealing with limited and short duration measurements from a structure under operational conditions. The sensitivity-based method is revisited in this paper with an enhancement in the sensitivity with respect to loc...

High energy consumption, excessive data storage and transfer requirements are prevailing issues associated with structural health monitoring (SHM) systems, especially with those employing wireless sensors. Data compression is one of the techniques being explored to mitigate the effects of these issues. Compressive sensing (CS) introduces a means of...

A novel damage classification method based on wavelet packet transform and statistical analysis is developed in this study for structural health monitoring. The response signal of a structure under an impact load is normalized and then decomposed into wavelet packet components. Energies of these wavelet packet components are then calculated to obta...