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CONTENTS
Volume 43, Number 4, May25 2022 (Special Issue)
 


Abstract
A variety of research methods are applied for gaining an understanding of the behavior and failure of steel and composite infrastructures. Experimental, numerical and analytical investigations are some of the conventional and powerful research methods. Field & forensic monitoring, non-destructive research and statistical or data-driven approaches are also getting more attention these days. All of such methods that focus on the steel and composite infrastructures are included in this special issue of Steel and Composite Structures: An International Journal, with more of a focus on forensic investigation and engineering. Forensic engineering of infrastructure is the application of engineering knowledge to the investigation of failure, collapse and other performance problems of construction facilities and built environments. Due to various geometric and material complexibility, it is very hard to investigate the causes, mechanism, and scenario of the failure and collapse of various infrastructures which may result in serious damage to society. For more precise investigation of the accidents and effective execution planning against the failures, advanced forensic engineering and its application based on innovative sensing, analysis, and experiment are required. The purposes of the special issue are to introduce analyses and experiments related to the (forensic) engineering of composite super-structures, sub-structures, and integrated infrastructures, and to promote the forensic practice. All the papers by renowned authors were reviewed by peer scholars and practitioners. An emphasis of the special issue was on research methods relevant to forensic investigation of hyper-converged infrastructure.

Key Words


Address


Abstract
In response to the sustainability requirements set in the EU Commission's "Green Deal" towards reduction of the greenhouse gas emissions, it is estimated that the structural design for deconstruction is going to contribute considerably to the sustainable development of the built environment. The demountability of multi-material structural systems basically depends on the shear connectors used in the structural system. This paper focuses on a type of demountable injected shear connector with an injected steel-reinforced resin (iSRR) which consists of spherical steel particles embedded in a resin. Its application to steel-toconcrete and steel-to-Fiber Reinforced Polymer (FRP) decks is presented along with its benefits. In parallel, an overview of the experimental and numerical research on the evaluation of the mechanical properties of the demountable bolted connectors with iSRR is discussed. Last, detailed finite element (FE) models and a parametric study are performed to quantify the confinement level of the SRR material influenced by the oversized hole diameter.

Key Words
demountable and reusable structures; demountable shear connectors; Fiber Reinforced Polymer (FRP) panels; injected steel-reinforced resin (iSRR) connections; multi-material floor system, confinement; sustainable structural design

Address
Florentia Kavoura, Angeliki Christoforidou, Marko Pavlovic and Milan Veljkovic: Faculty Of Civil Engineering and Geosciences, Delft University of Technology, 2628 CN Delft, Netherland

Abstract
A double-skinned composite tubular (DSCT) column, which is an internally confined concrete-filled tubular column with a hollow section, has been developed for efficient use of materials that reduce self-weight and enhance seismic performance. It exhibits excellent material behavior with ductility owing to the confinement induced by outer and inner steel tubes. This study conducted axial compression tests considering the effects of steel tube thickness and hollow diameter ratios of DSCT columns on the material behavior of confined concrete under pure axial compression on concrete cores. From the axial compression tests, various combinations of outer and inner tube thicknesses and two different hollow section ratios were considered. Additionally, confined concrete material behavior, axial strength, failure modes, and ductility of DSCT columns were evaluated. Based on this study, it was concluded that the tests show a good correlation with peak strength and shapes of nonlinear stress-strain curves presented in literature; however, the thinner outer and inner steel tubes may reduce the ductility of DSCT columns when using thinner outer and inner tubes and higher confined stress levels. Finally, the minimum thickness requirements of the steel tubes for DSCT columns were discussed in terms of strength and ductility of test specimens.

Key Words
DSCT column; confined concrete; axial compression tests; stress-strain relationship; ductility

Address
Jeonghwa Lee:Futhre and Fusion Lab of Architectural Civil and Environmental Engineering, Korea University,
145 Anam-ro, Seongbuk-gu, Seoul 02841, Republic of Korea

Namju Byun:Futhre and Fusion Lab of Architectural Civil and Environmental Engineering, Korea University,
145 Anam-ro, Seongbuk-gu, Seoul 02841, Republic of Korea

Young Jong Kang:School of Civil, Environmental and Architectural Engineering, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul 02841, Republic of Korea

Deok Hee Won:Department of Civil Engineering, Halla University, 28 Halla University-gil, Wonju-si, Gangwon-do, 26404, Republic of Korea

Seungjun Kim:School of Civil, Environmental and Architectural Engineering, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul 02841, Republic of Korea

Abstract
Recent experimental studies showed that deep steel I-shaped profiles classified as high ductility class sections in seismic design international codes exhibit low deformation capacity when subjected to cyclic loading. This paper presents an innovative retrofit solution to increase the rotation capacity of beams using bonded carbon fiber reinforced polymers (CFRP) patches validated with advanced finite element analysis. This investigation focuses on the flexural cyclic behaviour of I-shaped hot rolled steel deep section used as beams in moment-resisting frames (MRF) retrofitted with CFRP patches on the web. The main goal of this CFRP reinforcement is to increase the rotation capacity of the member without increasing the overstrength in order to avoid compromising the strong column-weak beam condition in MRF. A finite element model that simulates the cyclic plasticity behavior of the steel and the damage in the adhesive layer is developed. The damage is modelled using the cohesive zone modelling (CZM) technique that is able to capture the crack initiation and propagation. Details on the modelling techniques including the mesh sensitivity near the fracture zone are presented. The effectiveness of the retrofit solution depends strongly on the selection of the appropriate adhesive. Different adhesive types are investigated where the CZM parameters are calibrated from high fidelity fracture mechanics tests that are thoroughly validated in the literature. This includes a rigid adhesive commonly found in the construction industry and two tough adhesives used in the automotive industry. The results revealed that the CFRP patch can increase the rotation capacity of a steel member considerably when using tough adhesives.

Key Words
CFRP; cyclic; rotation capacity; seismic moment resisting frames; steel

Address
Anis I. Mohabeddine:1)Construct, Faculty of Engineering University of Porto, 4200-465 Porto, Portugal
2)Faculty of Civil Engineering and Geosciences, Delft University of Technology, Netherlands

Cyrus Eshaghi:Construct, Faculty of Engineering University of Porto, 4200-465 Porto, Portugal

José A.F.O. Correia:Construct, Faculty of Engineering University of Porto, 4200-465 Porto, Portugal

José M. Castro:Construct, Faculty of Engineering University of Porto, 4200-465 Porto, Portugal

Abstract
Optimization in distribution of stay cable forces is one of the most difficult aspects in the design of cable-stayed bridges. This article attempts to examine tension force influence on structural behavior of cable-stayed bridges. For the examination, finite element modeling using nonlinear static and nonlinear modal analyses was completed and compared to structural experimental results. Variables analyzed in this parametric study were: 1) Number of stay cables; 2) Tension of the stay cables, and 3) Stay cable pattern - harp and semi-fan patterns. Though the findings from the analysis are limited to the tested models, the study gives insight on the structural behavior of actual cable stayed bridges.

Key Words
cable-stayed bridge; harp and semi-fan stay cable patterns; static and dynamic analysis; tension force

Address
Pauline Lin Li Lam and Thomas H.-K. Kang:Department of Architecture & Architectural Engineering, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 08826, Republic of Korea

Abstract
This paper presents a comprehensive integrity assessment of welded structural components, including uniform high-and low-cycle fatigue assessment of welded plate joints and fatigue-induced fracture assessment of welded plate joints. This study reports a series of fatigue and fracture tests of welded plate joints under three-point bending. To unify the assessment protocol for high- and low-cycle fatigue of welded plate joints, this study develops a numerical damage assessment framework for both high- and low-cycle fatigue. The calibrated damage material parameters are validated through the smooth coupon specimens. The proposed damage-based fatigue assessment approach describes, with reasonable accuracy, the total fatigue life of welded plate joints under high- and low-cycle fatigue actions. Subsequently, the study performs a tearing assessment on the ductile crack extension of the fatigue-induced crack. The tearing assessment diagram derives from the load-deformation curve of a single-edge notched bend, SE(B) specimen and successfully predicts the load-crack extension relation for the reported welded plate joints during the stable tearing process.

Key Words
continuum damage mechanics; fatigue assessment; fracture failure; tearing assessment; welded plate joint

Address
Liuyang Feng, Tianyao Liu and Xudong Qian and Cheng Chen: Department of Civil and Environmental Engineering, National University of Singapore, Singapore 117576

Abstract
Cold-formed steel wall panels sheathed with gypsum plasterboard have shown superior thermal and structural performance in fire. Recent damage caused by fire events in Australia has increased the need for accurate fire resistance ratings of wall systems used in low- and mid-rise construction. Past fire research has mostly focused on light gauge steel framed (LSF) walls under uniform axial compression and LSF floors under pure bending. However, in reality, LSF wall studs may be subject to both compression and bending actions due to eccentric loading at the wall to-roof or wall-to-floor connections. In order to investigate the fire resistance of LSF walls under the effects of these loading eccentricities, four full-scale standard fire tests were conducted on 3 m x 3 m LSF wall specimens lined with two 16 mm gypsum plasterboards under different combinations of axial compression and lateral load ratios. The findings show that the loading eccentricity can adversely affect the fire resistance level of the LSF wall depending on the magnitude of the eccentricity, the resultant compressive stresses in the hot and cold flanges of the wall studs caused by combined loading and the temperatures of the hot and cold flanges of the studs. Structural fire designers should consider the effects of loading eccentricity in the design of LSF walls to eliminate their potential failures in fire.

Key Words
cold-formed steel; combined compression and bending; loading eccentricity; LSF wall panels; standard fire tests

Address
Mithum Peiris and Mahen Mahendran: Queensland University of Technology (QUT), Australia

Abstract
Cracks are common defects in concrete structures. Thus far, crack inspection has been manually performed using the contact inspection method. This manpower-dependent method inevitably increases the cost and work hours. Various noncontact studies have been conducted to overcome such difficulties. However, previous studies have focused on developing a methodology for non-contact inspection or local quantitative detection of crack width or length on concrete surfaces. However, crack depth can affect the safety of concrete structures. In particular, although macrocrack depth is structurally fatal, it is difficult to find it with the existing method. Therefore, an experimental investigation based on non-contact infrared thermography and multivariate machine learning was performed in this study to estimate the hidden macrocrack depth. To consider practical applications for inspection, an experiment was conducted that considered the simulated piloting of an unmanned aerial vehicle equipped with infrared thermography equipment. The crack depths (10–60 mm) were comparatively evaluated using linear regression, gradient boosting, and random forest (AI regression methods).

Key Words
AI; Concrete macrocrack; machine learning; infrared thermography; UAV

Address
Jaehoon Bae:Department of Architectural Design, College of Engineering Science, Chonnam National University, Jeonnam 59626, Republic of Korea

Arum Jang:School of Civil, Environmental, and Architectural Engineering, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul 02841, Republic of Korea

Min Jae Park:School of Civil, Environmental, and Architectural Engineering, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul 02841, Republic of Korea

Jonghoon Lee:School of Civil, Environmental, and Architectural Engineering, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul 02841, Republic of Korea

Young K. Ju:School of Civil, Environmental, and Architectural Engineering, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul 02841, Republic of Korea

Abstract
An experimental investigation to study the behaviour of connections between cold-formed steel (CFS) joist and plywood structural panel is presented in this paper. Material testing on CFS and plywood was carried out to assess their mechanical properties and behaviour. Push-out tests were conducted to determine the slip modulus and failure modes of three different shear connection types. The employed shear connectors in the study were; size 14 (6mm diameter) self-drilling screw, M12 coach screw, and M12 nut and bolt. The effective bending stiffness of composite cold-formed steel and plywood T-beam assembly is calculated based on the slip modulus values computed from push-out tests. The effective bending stiffness was increased by 25.5%, 18% and 30.2% for self-drilling screw, coach screw, nut and bolt, respectively, over the stiffness of coldformed steel joist alone. This finding suggests the potential to enhance the structural performance of composite cold-formed steel and timber flooring system by mobilisation of composite action present between timber sheathing and CFS joist.

Key Words
cold-formed steel joists; structural plywood; material tests; push-out tests; load-slip behaviour; slip modulus

Address
Dheeraj Karki, Harry Far and Suleiman Al-hunity:School of Civil and Environmental Engineering, Faculty of Engineering and Information Technology, University of Technology Sydney (UTS),
Building 11, Level 11, Broadway, Ultimo, NSW 2007, Australia


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