{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,23]],"date-time":"2026-04-23T04:38:56Z","timestamp":1776919136161,"version":"3.51.2"},"reference-count":46,"publisher":"MDPI AG","issue":"8","license":[{"start":{"date-parts":[[2024,4,13]],"date-time":"2024-04-13T00:00:00Z","timestamp":1712966400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"National Natural Science Foundation of China (NSFC)","award":["52378301"],"award-info":[{"award-number":["52378301"]}]},{"name":"National Natural Science Foundation of China (NSFC)","award":["51878305"],"award-info":[{"award-number":["51878305"]}]},{"name":"National Natural Science Foundation of China (NSFC)","award":["51608122"],"award-info":[{"award-number":["51608122"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Concrete-filled steel tube (CFST) members have been widely used in civil engineering due to their advanced mechanical properties. However, internal defects such as the concrete core voids and interface debonding in CFST structures are likely to weaken their load-carrying capacity and stiffness, which affects the safety and serviceability. Visualizing the inner defects of the concrete cores in CFST members is a critical requirement and a challenging task due to the obvious difference in the material mechanical parameters of the concrete core and steel tube in CFST members. In this study, a curved ray theory-based travel time tomography (TTT) with a least square iterative linear inversion algorithm is first introduced to quantitatively identify and visualize the sizes and positions of the concrete core voids in CFST members. Secondly, a numerical investigation of the influence of different parameters on the inversion algorithm for the defect imaging of CFST members, including the effects of the model weighting matrix, weighting factor and grid size on the void\u2019s imaging quality and accuracy, is carried out. Finally, an experimental study on six CFST specimens with mimicked concrete core void defects is performed in a laboratory and the mimicked defects are visualized. The results demonstrate that TTT can identify the sizes and positions of the concrete core void defects in CFST members efficiently with the use of optimal parameters.<\/jats:p>","DOI":"10.3390\/s24082503","type":"journal-article","created":{"date-parts":[[2024,4,15]],"date-time":"2024-04-15T08:08:12Z","timestamp":1713168492000},"page":"2503","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":4,"title":["A Concrete Core Void Imaging Approach and Parameter Analysis of Concrete-Filled Steel Tube Members Using Travel Time Tomography: Multi-Physics Simulations and Experimental Studies"],"prefix":"10.3390","volume":"24","author":[{"given":"Wenting","family":"Zheng","sequence":"first","affiliation":[{"name":"College of Civil Engineering, Huaqiao University, Xiamen 361021, China"},{"name":"College of Civil Engineering, Fujian University of Technology, Fuzhou 350118, China"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8336-3306","authenticated-orcid":false,"given":"Bin","family":"Xu","sequence":"additional","affiliation":[{"name":"College of Civil Engineering, Huaqiao University, Xiamen 361021, China"},{"name":"Key Laboratory for Intelligent Infrastructure and Monitoring of Fujian Province, Huaqiao University, Xiamen 361021, China"}]},{"given":"Zongjun","family":"Xia","sequence":"additional","affiliation":[{"name":"China Railway 15th Bureau Group City Construction Company Ltd., Luoyang 471000, China"}]},{"given":"Jiang","family":"Wang","sequence":"additional","affiliation":[{"name":"Research Institute of Urbanization and Urban Safety, School of Civil and Resource Engineering, University of Science and Technology Beijing, Beijing 100083, China"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5508-158X","authenticated-orcid":false,"given":"Jingliang","family":"Liu","sequence":"additional","affiliation":[{"name":"College of Transportation and Civil Engineering, Fujian Agriculture and Forestry University, Fuzhou 350108, China"}]},{"given":"Yudi","family":"Yao","sequence":"additional","affiliation":[{"name":"China Railway 15th Bureau Group City Construction Company Ltd., Luoyang 471000, China"}]},{"given":"Yifei","family":"Wang","sequence":"additional","affiliation":[{"name":"China Railway 15th Bureau Group City Construction Company Ltd., Luoyang 471000, China"}]}],"member":"1968","published-online":{"date-parts":[[2024,4,13]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"132566","DOI":"10.1016\/j.conbuildmat.2023.132566","article-title":"Electromechanical properties of multi-reinforced self-sensing cement-based mortar with MWCNTs, CFs, and PPs","volume":"400","author":"Thomoglou","year":"2023","journal-title":"Constr. Build. Mater."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"203","DOI":"10.1016\/j.jcsr.2018.04.014","article-title":"Research on special-shaped concrete-filled steel tubular columns under axial compression","volume":"147","author":"Liu","year":"2018","journal-title":"J. Constr. Steel Res."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"106590","DOI":"10.1016\/j.tws.2019.106590","article-title":"Stiffened concrete-filled steel tubes: A systematic review","volume":"148","author":"Alatshan","year":"2020","journal-title":"Thin-Walled Struct."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"103613","DOI":"10.1016\/j.jobe.2021.103613","article-title":"Behavior of CFST slender columns strengthened with steel tube and sandwiched concrete jackets under axial loading","volume":"45","author":"Huang","year":"2022","journal-title":"J. Build. Eng."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"849","DOI":"10.1515\/rams-2022-0274","article-title":"An experimental investigation and machine learning-based prediction for seismic performance of steel tubular column filled with recycled aggregate concrete","volume":"61","author":"Tang","year":"2022","journal-title":"Rev. Adv. Mater. Sci."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"107939","DOI":"10.1016\/j.jcsr.2023.107939","article-title":"Life-cycle based structural performance of long-span CFST hybrid arch bridge: A study on arch of Pingnan Third Bridge","volume":"207","author":"Chen","year":"2023","journal-title":"J. Constr. Steel Res."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"111142","DOI":"10.1016\/j.engstruct.2020.111142","article-title":"Behaviour and design calculations of rectangular CFST beam-columns with slender sections","volume":"222","author":"Zarringol","year":"2020","journal-title":"Eng. Struct."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"32","DOI":"10.1016\/j.istruc.2021.11.049","article-title":"Flexural behavior of concrete-filled rectangular steel tubular (CFRST) trusses","volume":"36","author":"Ma","year":"2022","journal-title":"Structures"},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"64","DOI":"10.1016\/j.jcsr.2011.08.002","article-title":"Effects of debonding on circular CFST stub columns","volume":"69","author":"Xue","year":"2012","journal-title":"J. Constr. Steel Res."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"57","DOI":"10.1016\/j.tws.2013.04.012","article-title":"Behaviour of CFST stub columns with initial concrete imperfection: Analysis and calculations","volume":"70","author":"Liao","year":"2013","journal-title":"Thin-Walled Struct."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"1441","DOI":"10.1007\/s40996-020-00434-5","article-title":"CFST Rib with circumferential gap and SWS composite defects","volume":"45","author":"Guo","year":"2021","journal-title":"Iran. J. Sci. Technol. Trans. Civ. Eng."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"106418","DOI":"10.1016\/j.jcsr.2020.106418","article-title":"Air void and ring gap effect on CFST arch bridges dynamic performance","volume":"177","author":"Lu","year":"2020","journal-title":"J. Constr. Steel Res."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"04019102","DOI":"10.1061\/(ASCE)ST.1943-541X.0002385","article-title":"Bending capacity of steel-concrete-steel composite structures considering local buckling and casting imperfection","volume":"145","author":"Guo","year":"2019","journal-title":"J. Struct. Eng."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"7","DOI":"10.1016\/j.ymssp.2011.07.029","article-title":"Active interface debonding detection of a concrete-filled steel tube with piezoelectric technologies using wavelet packet analysis","volume":"36","author":"Xu","year":"2013","journal-title":"Mech. Syst. Signal Process."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"108","DOI":"10.1016\/j.ymssp.2016.10.002","article-title":"Numerical study on the mechanism of active interfacial debonding detection for rectangular CFSTs based on wavelet packet analysis with piezoceramics","volume":"86","author":"Xu","year":"2017","journal-title":"Mech. Syst. Signal Process."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"515","DOI":"10.1016\/j.ymssp.2018.01.041","article-title":"Dominance of debonding defect of CFST on PZT sensor response considering the meso-scale structure of concrete with multi-scale simulation","volume":"107","author":"Xu","year":"2018","journal-title":"Mech. Syst. Signal Process."},{"key":"ref_17","doi-asserted-by":"crossref","unstructured":"Xu, B., Luan, L., Chen, H., Wang, J., and Zheng, W. (2019). Experimental study on active interface debonding detection for rectangular concrete-filled steel tubes with surface wave measurement. Sensors, 19.","DOI":"10.3390\/s19153248"},{"key":"ref_18","doi-asserted-by":"crossref","unstructured":"Chen, H., Xu, B., Mo, Y., and Zhou, T. (2018). Multi-scale stress wave simulation for aggregates segregation detection of concrete core in circular CFST coupled with PZT patches. Materials, 11.","DOI":"10.3390\/ma11071223"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"108135","DOI":"10.1016\/j.ymssp.2021.108135","article-title":"Mesoscale numerical analysis and test on the effect of debonding defect of rectangular CFSTs on wave propagation with a homogenization method","volume":"163","author":"Wang","year":"2022","journal-title":"Mech. Syst. Signal Process."},{"key":"ref_20","doi-asserted-by":"crossref","unstructured":"Wang, J., Xu, B., Chen, H., Ge, H., and Zhou, T. (2022). Multi-physics mesoscale substructure analysis on stress wave measurement within CFST-PZT coupling models for interface debonding detection. Sensors, 22.","DOI":"10.3390\/s22031039"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"110641","DOI":"10.1016\/j.ymssp.2023.110641","article-title":"Impact acoustic inspection of interfacial debonding defects in concrete-filled steel tubes","volume":"200","author":"Liu","year":"2023","journal-title":"Mech. Syst. Signal Process."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"110214","DOI":"10.1016\/j.ymssp.2023.110214","article-title":"Interfacial debonding detection for CFST structures using an ultrasonic phased array: Application to the Shenzhen SEG building","volume":"192","author":"Liu","year":"2023","journal-title":"Mech. Syst. Signal Process."},{"key":"ref_23","unstructured":"Mpalaskas, A.C., Matikas, T.E., and Aggelis, D.G. (2021). Acoustic Emission and Related Non-Destructive Evaluation Techniques in the Fracture Mechanics of Concrete, Woodhead Publishing. [2nd ed.]."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"105262","DOI":"10.1016\/j.autcon.2023.105262","article-title":"3D vision technologies for a self-developed structural external crack damage recognition robot","volume":"159","author":"Hu","year":"2024","journal-title":"Autom. Constr."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"112965","DOI":"10.1016\/j.measurement.2023.112965","article-title":"Lamb wave tomography for defect localization using wideband dispersion reversal method","volume":"216","author":"Ling","year":"2023","journal-title":"Measurement"},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"206","DOI":"10.1016\/j.ndteint.2010.11.003","article-title":"Tomographic reconstruction for concrete using attenuation of ultrasound","volume":"44","author":"Chai","year":"2011","journal-title":"NDT E Int."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"202","DOI":"10.1016\/j.conbuildmat.2014.05.011","article-title":"Integrated non-destructive assessment of concrete structures under flexure by acoustic emission and travel time tomography","volume":"67","author":"Behnia","year":"2014","journal-title":"Constr. Build. Mater."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"1085","DOI":"10.1007\/s10114-019-8338-0","article-title":"Travel time tomography","volume":"35","author":"Stefanov","year":"2019","journal-title":"Acta Math. Sin.-Engl. Ser."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"97","DOI":"10.1016\/S0926-9851(01)00050-7","article-title":"Improved crosshole radar tomography by using direct and reflected arrival times","volume":"47","author":"Tronicke","year":"2001","journal-title":"J. Appl. Geophys."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"171","DOI":"10.2113\/JEEG11.3.171","article-title":"Crosshole radar tomography in a fluvial aquifer near Boise, Idaho","volume":"11","author":"Clement","year":"2006","journal-title":"J. Environ. Eng. Geophys."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"171","DOI":"10.1016\/j.jhydrol.2007.01.005","article-title":"High-resolution aquifer characterization using seismic cross-hole tomography: An evaluation experiment in a gravel delta","volume":"336","author":"Becht","year":"2007","journal-title":"J. Hydrol."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"389","DOI":"10.1046\/j.1365-246X.2003.01887.x","article-title":"Discrete tomography and joint inversion for loosely connected or unconnected physical properties: Application to crosshole seismic and georadar data sets","volume":"153","author":"Musil","year":"2003","journal-title":"Geophys. J. Int."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"377","DOI":"10.1016\/j.jqsrt.2010.09.005","article-title":"Curved ray tracing method for one-dimensional radiative transfer in the linear-anisotropic scattering medium with graded index","volume":"112","author":"Zhu","year":"2011","journal-title":"J. Quant. Spectrosc. Radiat. Transf."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"229","DOI":"10.2113\/JEEG19.4.229","article-title":"Crosshole radar traveltime tomographic inversion using the fast marching method and the iteratively linearized scheme","volume":"19","author":"Wang","year":"2014","journal-title":"J. Environ. Eng. Geophys."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"29","DOI":"10.1016\/j.cageo.2017.04.002","article-title":"Seismic travel time inversion based on tomographic equation without integral terms","volume":"104","author":"Huang","year":"2017","journal-title":"Comput. Geosci."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"490","DOI":"10.1016\/j.measurement.2019.06.053","article-title":"Ultrasound computed tomography for material inspection: Principles, design and applications","volume":"146","author":"Khairi","year":"2019","journal-title":"Measurement"},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"2965","DOI":"10.12733\/jics20103808","article-title":"Improved iterative algorithm based on Snell law and disturbance ray tracing for ultrasonic computerized tomography on concrete","volume":"11","author":"Qi","year":"2014","journal-title":"J. Inf. Comput. Sci."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"103957","DOI":"10.1016\/j.jappgeo.2020.103957","article-title":"Detecting an underground tunnel by applying joint travel time and waveform inversion","volume":"174","author":"Jiang","year":"2020","journal-title":"J. Appl. Geophys."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"154","DOI":"10.1016\/j.conbuildmat.2016.10.061","article-title":"Experimental studies on void detection in concrete-filled steel tubes using ultrasound","volume":"128","author":"Dong","year":"2016","journal-title":"Constr. Build. Mater."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"210","DOI":"10.1016\/j.ymssp.2018.07.011","article-title":"Reverse time migration of acoustic waves for imaging based defects detection for concrete and CFST structures","volume":"117","author":"Liu","year":"2019","journal-title":"Mech. Syst. Signal Process."},{"key":"ref_41","doi-asserted-by":"crossref","unstructured":"Callejas, A., Palma, R., Hern\u00e1ndez-Figueirido, D., and Rus, G. (2022). Damage detection using ultrasonic techniques in concrete-filled steel tubes (CFSTs) columns. Sensors, 22.","DOI":"10.3390\/s22124400"},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"064002","DOI":"10.1088\/1361-6420\/abfb4d","article-title":"A new interpretation of (Tikhonov) regularization","volume":"37","author":"Gerth","year":"2021","journal-title":"Inverse Probl."},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"159","DOI":"10.1111\/j.1365-2478.1984.tb00726.x","article-title":"A review of least-squares inversion and its application to geophysical problems","volume":"32","author":"Lines","year":"1984","journal-title":"Geophys. Prospect."},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"28","DOI":"10.1016\/j.engstruct.2018.08.085","article-title":"Multiscale analysis of non-contact splices at drilled shaft to bridge column interface","volume":"176","author":"Chen","year":"2018","journal-title":"Eng. Struct."},{"key":"ref_45","unstructured":"Chen, H. (2018). Study on Debonding Detection Approaches for Concrete-Filled Steel Tube Using Stress Wave Measurement and Its Mechanism with Multi-Scale Simulation. [Ph.D. Dissertation, Hunan University]. (In Chinese)."},{"key":"ref_46","doi-asserted-by":"crossref","first-page":"103628","DOI":"10.1016\/j.autcon.2021.103628","article-title":"Fully automated peak-picking method for an autonomous stay-cable monitoring system in cable-stayed bridges","volume":"126","author":"Jin","year":"2021","journal-title":"Autom. Constr."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/24\/8\/2503\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T14:27:43Z","timestamp":1760106463000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/24\/8\/2503"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2024,4,13]]},"references-count":46,"journal-issue":{"issue":"8","published-online":{"date-parts":[[2024,4]]}},"alternative-id":["s24082503"],"URL":"https:\/\/doi.org\/10.3390\/s24082503","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2024,4,13]]}}}