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• Develops a deep Bayesian survival model that integrates deep neural network and Bayesian inference into the survival analysis for rail useful lifetime modelling. • Demonstrates survival analysis is an effective way to handle censored data problems in rail useful lifetime modelling. • Conducts extensive evaluation to verify the effectiveness of this model, using Concordance index, root mean square error, and a proposed CW-index. • The estimated lifetimes obtained by this model are the closest to real lifetimes compared to other commonly used models. • This model can provide the confidence interval of the estimated lifetime, which is more useful than point estimates in decision-making and maintenance planning of railroad systems. Reliable estimation of rail useful lifetime can provide valuable information for predictive maintenance in railway systems. However, in most cases, lifetime data is incomplete because not all pieces of rail experience failure by the end of the study horizon, a problem known as censoring. Ignoring or otherwise mistreating the censored cases might lead to false conclusions. Survival approach is particularly designed to handle censored data for analysing the expected duration of time until one event occurs, which is rail failure in this paper. This paper proposes a deep Bayesian survival approach named BNN-Surv to properly handle censored data for rail useful lifetime modelling. The proposed BNN-Surv model applies the deep neural network in the survival approach to capture the non-linear relationship between covariates and rail useful lifetime. To consider and quantify uncertainty in the model, Monte Carlo dropout, regarded as the approximate Bayesian inference, is incorporated into the deep neural network to provide the confidence interval of the estimated lifetime. The proposed approach is implemented on a four-year dataset including track geometry monitoring data, track characteristics data, various types of defect data, and maintenance and replacement (M&R) data collected from a section of railway tracks in Australia. Through extensive evaluation, including Concordance index (C-index) and root mean square error (RMSE) for evaluating model performance, as well as a proposed CW-index for evaluating uncertainty estimations, the effectiveness of the proposed approach is confirmed. The results show that, compared with other commonly used models, the proposed approach can achieve the best concordance index (C-index) of 0.80, and the estimated rail useful lifetimes are closer to real lifetimes. In addition, the proposed approach can provide the confidence interval of the estimated lifetime, with a correct coverage of 81% of the actual lifetime when the confidence interval is 1.38, which is more useful than point estimates in decision-making and maintenance planning of railroad systems. [ABSTRACT FROM AUTHOR]

This paper presents experimental and numerical investigations into the post-fire cross-section compressive behaviour and resistances of circular recycled aggregate concrete-filled stainless steel tube (RACFSST) stub columns. Twelve stub column specimens, fabricated from concretes with three recycled coarse aggregate replacement ratios (0%, 35% and 70%), were tested after exposure to the ISO-834 standard fire for 0 min (i.e. at ambient temperature), 15 min, 30 min and 45 min. The experimental investigation included heating and cooling of specimens, cylinder tests and post-fire tensile coupon tests and stub column tests. The test results, including load–end shortening curves, failure loads and failure modes, were fully reported and the initial compressive stiffnesses and confinement effect were discussed. The numerical investigation was subsequently conducted, where thermal and mechanical finite element models were developed and validated against the test results and then used to perform parametric studies to generate further numerical data. Given the absence of design codes for stainless steel–recycled aggregate concrete composite structures after exposure to fire, the relevant design rules for circular natural aggregate concrete-filled carbon steel tube stub columns at ambient temperature, as set out in the European code, Australia/New Zealand standard and American specification, were assessed, using post-fire material properties, for their applicability to circular RACFSST stub columns after exposure to fire, based on the test and numerical data. The assessment results generally revealed that the European code and the Australian/New Zealand standard led to an acceptable level of design accuracy and consistency, while the American specification resulted in rather conservative and scattered post-fire cross-section compression resistance predictions. • The compressive behaviour of circular RACFSST stub columns after exposure to fire is investigated. • Post-fire compression tests on twelve circular RACFSST stub column specimens are conducted. • The influences of heating durations and RCA replacement ratios are analysed. • Thermal and mechanical FE models are validated against test results and then used to conduct parametric studies. • The relevant design codes are assessed against the test and FE data. [ABSTRACT FROM AUTHOR]

Highlights • Reviewed recent progress and directed future research for modular buildings. • Commonly used in UK, Sweden, Japan and USA with growing interest in Australia and China. • Prefabricated components have demonstrated satisfactory structural performance. • Uptake barriers are mainly related to the lack of logistical support. • Prefabricated modular buildings is the next generation of housing. Abstract Modular construction offers faster and safer manufacturing, better predictability to completion time, superior quality, less workers on site, less resource wastage, and a more environmentally friendly solution than the conventional construction process. Despite having several advantages of modular construction, the private sector still relies heavily on the traditional on-site construction method. To understand the scientific reason behind this situation, this paper critically reviews the recent developments, performances, challenges and future opportunities of modular buildings. Modular constructions are extensively used for low-rise buildings and further attracts strong interest for multi-storey building structures. Prefabricated modules demonstrated satisfactory performance under static, dynamic impact, cyclic, seismic, blast, fire and long-term sustained loading, and offer environmental, economic and social benefits. The acceptance and application of modular construction will further spread with the development of design guidelines, more skilled workers, addressing handing and transportation difficulties, and the development of novel interlocking connections between modules. Recently, composite materials demonstrated high potential to manufacture prefabricated building modules. In Australia, it is expected that modular construction will increase from the current stage of 3% to 5–10% by year 2030. [ABSTRACT FROM AUTHOR]

The paper describes a risk analysis of the economic impact of damage to metal roofing of a typical contemporary (new) Australian house subject to extreme wind loading. The failure modes considered are roof cladding and batten-to-truss connection failures, with the effect of defective construction also considered. Monte-Carlo simulation and structural reliability methods are used to stochastically model spatially varying pressure coefficients, roof component failure, and load re-distribution across the roof. This spatial reliability analysis enables fragility curves to be developed that relate likelihood and extent of roof cover loss to gust wind speed. The annual economic risk is up to 0.3% of house replacement value. A typical house with construction defects increases economic risk more than sixfold when compared to the defect-free house. There is a 10% chance that a changing climate will increase expected losses for houses in Brisbane and Melbourne by 6–18% over the next 50 years. [ABSTRACT FROM AUTHOR]

• 3D mass timber substructures were tested under an edge column removal scenario. • The applied load was mainly transferred to the three nearest columns. • CLT floors were found to be the critical elements in redistributing the applied load. • Connectors designed with progressive collapse in mind can enhance ductility. • Current industry design method for progressive was found to be conservative. Mid-rise to tall mass timber buildings are becoming internationally popular and are required, for instance in the Eurocode or the Australian building code, to be designed against progressive collapse. Designing against progressive collapse is especially important for mass timber buildings as, when compared to reinforced concrete and steel, timber is a more brittle construction material and mass timber buildings are deemed to be more elastic and have limited rotational capacities at the beam-to-column connections. However, whilst the ability of reinforced concrete and steel buildings to resist such an extreme event has been widely researched, limited studies were carried out on mass timber buildings. Their load transfer mechanisms and structural response after the loss of a load-bearing element are currently unclear. Consequently, this paper presents the outcomes of three experimental tests performed on three scaled-down, 2 × 2-bay, post-and-beam mass timber substructures under an edge column removal scenario. The capacity of the 3D substructures to resist progressive collapse was investigated for two types of beam-to-column connectors, namely two tests performed with a connector type commonly used in Australia in mass timber buildings and one test with a proposed novel connector. In the tests, Uniformly Distributed Pressures (UDP) were applied to the floors in two stages: (i) a constant UDP of 4.8 kPa was first applied to the bays not adjacent to the removed column and (ii) an idealised UDP was then increasingly applied to the remaining two bays through a hydraulic jack connected to a six-point loading tree. The load redistribution mechanisms or alternative load paths, structural response and failure modes were recorded and are presented in this paper. Results showed that the applied load was principally transferred to the three columns closest to the removed column and that the Cross Laminated Timber (CLT) panels spanning over two bays were efficient in resisting and transferring the load. The substructure with the proposed novel connector showed an 8.5% increase in capacity and higher ductility than the substructures assembled with the commonly used connector. A simplified theoretical model consistent with the methodology currently used by industry to predict the collapse resistance capacity of post-and-beam mass timber buildings was compared to the test results. The model underpredicted the test capacity by 53%. [ABSTRACT FROM AUTHOR]

In Australia and abroad screw-fixed, thin, high strength, profiled steel roof cladding systems are widely used on low rise industrial, commercial and residential buildings. Under extreme wind conditions, such as those produced by cyclones, these systems can fail as a result of low cycle metal fatigue. Current design of such systems is based entirely on standardised cyclic testing of full scale prototype assemblies. This paper describes the mechanism underlying this fatigue behaviour by studying the initiation of cracking in corrugated high strength steel cladding. When subject to repeated loading cracks initiate within the cladding at the fasteners, nucleating in the plane of maximum shear through the cladding thickness prior to propagating into the plane of the cladding. Crack initiation was considered to be the point in which the thickness of the cladding was entirely bisected and the crack was beginning to propagate into the plane of the cladding. Based on this characterisation, a crack initiation criterion dependent on the surface principal strains in the region of crack initiation was developed for both the longitudinal and transverse directions of the cladding. In combination with detailed stress analysis such criteria could be implemented in a numerical model to predict crack initiation in cladding, providing an analytical tool which could greatly assist the fatigue design process and lead to a reduction in the total reliance on prototype testing of each individual system used. [ABSTRACT FROM AUTHOR]

• Welded H-section stainless steel members were tested under combined constant compression and uniaxial cyclic bending. • The hysteretic behavior of welded H-section stainless steel beam-columns was investigated. • The cyclic hardening and effects of loading history were fully discussed. • The applicability of current design codes was evaluated. Previous studies have shown that structural stainless steel material has significant cyclic hardening characterized by strain amplitude dependence and unsaturation under cyclic loadings, which could have a remarkable impact on the seismic performance of stainless steel structures. Whether the current stainless steel structure design codes based on their static performance can accurately predict the seismic capacities of stainless steel structural members is worth studying. This paper investigates the hysteretic behavior of welded H-section stainless steel members under combined constant compression and uniaxial cyclic bending. A total of 24 specimens were tested, which covered a variety of test variables including stainless steel grade, section slenderness, axial compression ratio and loading history. Residual stresses of the welded H-sections considered in this study were measured. Then, the failure mode, hysteretic response, ductility coefficient and energy dissipation of welded H-section stainless steel beam-columns were fully obtained from the tests. Cyclic hardening was observed at the structural member level in the tests. The effect of loading history on seismic behavior was thoroughly discussed. It was found that various loading histories can obviously influence the strengths and deformation capacities of welded H-section stainless steel beam-columns resulting in their discrete seismic behavior, mainly due to the unsaturated cyclic hardening feature of stainless steels. Moreover, the current design codes including European Code, American Specification, Australia/New Zealand Standard and Chinese Specification underestimate the seismic capacities of welded H-section stainless steel beam-columns. [ABSTRACT FROM AUTHOR]

Abstract: Atmospheric CO2 is a major cause of reinforcement corrosion in bridges, buildings, wharves, and other concrete infrastructure in Australia, United States, United Kingdom and most other countries. The increase in CO2 levels associated with global warming will increase the likelihood of carbonation-induced corrosion. Moreover, temperature rises will increase corrosion rates. Clearly, the impact of climate change on existing and new infrastructure is considerable, as corrosion damage is disruptive to society and costly to repair. The paper describes a probabilistic and reliability-based approach that predicts the probability of corrosion initiation and damage (severe cracking) for concrete infrastructure subjected to carbonation and chloride-induced corrosion resulting from elevated CO2 levels and temperatures. The atmospheric CO2 concentration and local temperature and relative humidity changes with time over the next 100 years in the Australian cities of Sydney and Darwin are projected based on nine General Circulation Models (GCMs) under (i) high CO2 emission scenario, (ii) medium CO2 emission scenario, and (iii) CO2 emission reduction scenario based on policy intervention. The probabilistic analysis included the uncertainty of CO2 concentration, deterioration processes, material properties, dimensions, and predictive models. It was found that carbonation-induced damage risks can increase by over 400% over a time period to 2100 for some regions in Australia. Damage risks for chloride-induced corrosion increase by no more than 15% over the same time period due to temperature increase, but without consideration of ocean acidity change in marine exposure. Corrosion loss of reinforcement is not significant. The results were most sensitive to increases in atmospheric CO2. [Copyright &y& Elsevier]

Abstract: A unique experimental field test study that provides insight into the push-over load–deflection and collapse behaviour of a soft storey building is reported in this paper. The five storey building had been identified as being particularly vulnerable to earthquake excitation due to the particularly weak connections at each end of the ground floor precast columns that constituted the soft storey. Consequently, four field tests were undertaken to investigate the actual lateral force–deflection behaviour of the soft storey columns. Interestingly, the tests indicated that the soft storey columns possessed significant displacement capacity despite significant strength degradation. An analytical model developed to predict the overall force–displacement relationship that was influenced by the three component mechanisms of (a) connection strength at column ends, (b) gravity rocking strength and (c) ground slab interaction, was found to be in excellent agreement with the experimental test results. The presence of the ‘non-structural’ ground slab provided additional lateral strength to the system and greatly influenced the ‘as-built’ performance. The displacement capacity of the precast soft storey system was much greater than an equivalent in situ system, due to the rigid body rocking behaviour of the columns. The precast soft storey system was found to have sufficient displacement capacity for lower seismic regions, but the performance was considered marginal for higher seismic regions. [Copyright &y& Elsevier]

• Investigated the behaviour of slender screw-fastened nested channel (NC) members. • Torsional and flexural–torsional buckling are not critical for NC members. • NC member capacity can be higher than the sum of individual capacities in some cases. • Effects of screw fastener arrangements and end group fasteners are marginal. • Proposed a simplified and reliable design method based on the current DSM equations. Built-up nested channel (NC) members, which are made of asymmetric cold-formed steel (CFS) lipped channel sections are commonly used in various building applications in Australia. The aim of this research study is to provide suitable design guidelines for NC compression members, which fail by global or local–global interaction buckling. Firstly, the design rules in the current CFS design standards and recently published research studies were reviewed, and their limitations for NC members were discussed. A test series was then conducted on single channel and NC compression members, which failed by local–global interaction buckling. Based on the test results, validated finite element (FE) models were developed, followed by a detailed parametric study of NC members failing in global or local–global interaction buckling for different sections, lengths, end support boundary conditions as well as screw sizes and arrangements. The test and FE analysis results were used to: (1) compare the compression capacities of NC members with the sum of their individual member capacities, (2) evaluate the effect of screw characteristics and arrangements, and (3) investigate the design methods in the current design standards and past research studies. Finally, based on the Direct Strength Method in the current design standards, a simple and reliable design method was proposed. This paper presents the details of this research study and the results including its findings. [ABSTRACT FROM AUTHOR]

• Flat-ended circular hollow sections were tested in tension. • Three bolt configurations were established in flattened ends. • Bearing failure and net-section fracture were observed. • The test load increased with increase in the number of bolts. • An adjusted bearing coefficient is suggested for bearing. Experiments were performed to investigate the behaviour of 28 circular hollow sections (CHSs) in tension, with flat ends and three bolt configurations (2, 3 and 4 bolts). The length of the members between the flat ends was kept constant at 1500 mm for all CHSs, and the sizes of the sections ranged from 60.3x2.0 to 101.6x4.5. Two modes of failure were observed, viz; bearing failure (BF) and net-section fracture (NSF). CHSs connected with 2 bolts failed in bearing, whilst net-section fracture was dominant in sections with 3 and 4 bolts. The notion that the change in the number of bolts can lead to different behaviours of the connections is a significant contribution to knowledge, particularly if flat-ended CHSs are used as structural truss elements. This paper demonstrates that the sections are capable of supporting large loads, however, the capacity of the tested specimen did not reach the full yield strength. It is apparent from the tensile strengths that a larger increase in strength was accomplished when the number of bolts was increased from 2 to 3 bolts than from 3 to 4 bolts. A comparison of the tensile strength with the strengths predicted by the North American standard (AISI S100-16w/S1-18), Australia/New Zealand standard (AS/NZS-4600:2018) and European standard (EN 1993–1-3) confirm that both standards provides a reasonable assessment of the strength of the 3 and 4 bolt configuration, which failed purely by net-section fracture. However, for the 2-bolted connections, which failed in bearing, it is proposed to use AS/NZS 4600:2018, with a bearing coefficient of C = 2.85, instead of C = 3.0, to increase the accuracy of the bearing strength expression for these specimens. [ABSTRACT FROM AUTHOR]