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The practical application of cold-formed high strength steel is becoming increasingly popular in structural engineering due to its great efficiency and cost effectiveness. However, cold-formed steel sections are usually associated with high slenderness, hence are susceptible to buckling failure. Consequently, the buckling resistance of steel struts made of cold-formed high strength steel must be determined with carefulness, particularly for complex compound sections. To this end, the present paper aims at investigating the behaviour of back-to-back channel sections made of S700 steel with a characteristic yield strength of 700 MPa. Compressive tests on such members are conducted for the purpose of validating the finite element models. Subsequently, a numerical parametric analysis is carried out on the buckling resistance of axially loaded cold-formed steel back-to-back channel sections, using the previously validated numerical modelling approach. In particular, the effects of stiffeners and number of bolts on the buckling resistance are investigated. Furthermore, the results of the parametric analysis are also compared with the codified buckling resistance determined based on the effective width method adopted in Eurocode 3 Part 1–3, in order to evaluate the reliability of the standardised design method for buckling resistance.

This paper addresses the evaluation of the effects of corrosion on the performance of ageing steel industrial infrastructures. A novel probabilistic risk assessment method is presented with respect to a case study of a real petrochemical structure located in an atmospheric environment with high severity of corrosion. The results of damage assessment derived from refined fragility analyses revealed that long-term corrosion mass reduction can increase the probability of damage to the structure by an average of 40%. Furthermore, the risk analysis demonstrated that the annual failure rate of the corroded structure is at most 2.80 times that of the uncorroded counterpart. The vulnerability analysis showed that the difference in annual repair costs between corroded and uncorroded cases gradually increased as the severity of ground motion raised. Moreover, the results of comprehensive and refined nonlinear analyses indicated that the corroded structure after 50 and 100 years can increase the likelihood of causing corrosion repair costs in the first year by about 40 and 60 times, respectively. The evaluation of the ratio of construction to maintenance and retrofitting was also carried out; it was based on innovative retrofitting measures with the use of Carbon Fibre Reinforced Polymers for steel structures. The findings illustrated in the present numerical study can help owners and insurance companies to predict more reliably maintenance and repair costs, thus they can provide an efficient roadmap for industrial asset management.

This paper presents the fragility assessment of non-seismically designed steel moment frames with masonry infills. The assessment considered the effects of multiple earthquakes on the damage accumulation of steel frames, which is an essential part of modern performance-based earthquake engineering. Effects of aftershocks are particularly important when examining damaged buildings and making post-quake decisions, such as tagging and retrofit strategy. The procedure proposed in the present work includes two phase assessment, which is based on incremental dynamic analyses of two refined numerical models of the case-study steel frame, i.e. with and without masonry infills, and utilises mainshock-aftershock sequences of natural earthquake records. The first phase focuses on the undamaged structure subjected to single and multiple earthquakes; the effects of masonry infills on the seismic vulnerability of the steel frame were also considered. In the second phase, aftershock fragility curves were derived to investigate the seismic vulnerability of infilled steel frames with post-mainshock damage caused by mainshocks. Comparative analyses were conducted among the mainshock-damaged structures considering three post-mainshock damage levels, including no damage. The impact of aftershocks was then discussed for each mainshock-damage level in terms of the breakpoint that marks the onset of exceeding post-mainshock damage level, as well as the probability of exceeding of superior damage level due to more significant aftershocks. The evaluation of the efficiency of commonly used intensity measures of aftershocks was also carried out as part of the second phase of assessment.

Construction and demolition waste (CDW) accounts for 40% of urban municipal waste in China and around 25% in the European Union (EU). Since the EU is more developed and urbanized than China, its experience with managing CDW may be helpful to China. This study therefore compared China and the EU with respect to the flow of CDW materials and the policies, laws and regulations for CDW management. The results reveal that the CDW management practices and facilities in China are relatively underdeveloped with a large amount of low-value inert material going to landfill compared with the EU. The study also reveals the important role of government involvement in CDW management, including the use of punitive measures and preferential policies; most EU members states achieved their waste recovery rates by 2016 due to mature CDW legalization. To improve the management of CDW in China, a series of suggestions are proposed including waste prevention strategies, establishment of supervision mechanisms, and financial support.

The research on the seismic assessment of pipe racks accounting for coupling and soil-structure interaction effects is still scarce. Common industrial practice overlooks critical design aspects due to the insufficiency of current codes that might result in over-conservative or unsafe design. This work addresses the nonlinear analysis of a petrochemical plant steel pipe rack accounting for dynamic interaction with horizontal vessels and pipelines. Soil-structure interaction was evaluated both on pipe rack and pipelines in terms of interstorey-drift ratio and stress–strain response. An attempt was made for correlating the ratio with piping strain to make comparisons with common acceptance criteria for building structures, since code provisions do not address currently limit state design concept for pipe racks. Additionally, seismic fragility curves along with 95% confidence intervals were evaluated for different intensity measures and were used as a tool to demonstrate that the soil deformability could act as an isolation mechanism for pipelines. The increase of pipe rack displacements was an additional impact of soil, though, it was not as much profound as on the seismic response of the pipelines. The detailed structural assessment through extensive nonlinear dynamic analyses demonstrated that the return period of exceedance of pipe rack and pipelines limit state, considering the median spectral acceleration as a measure, occurred 1.84 and 2.64 greater than the design one, and this might be an indication that the performance-based concept should be applied for pipe rack systems to achieve a safe, risk-consistent among structural and nonstructural members and cost-effective design.

Post-earthquake reconnaissance missions are critical to understand the event characteristics, identify building and infrastructure vulnerabilities, and improve future construction practice. However, in-field missions can present logistic and safety challenges that do not make them viable in every post-disaster scenario. Remote sensing technique can be used to rapidly collect a large amount information that can be used to enrich the post-event learning process. While the possibility to deploy teams in the field remain a valuable asset for an integrated understanding of technical and socio-economic factors, a mix of remote and in-field reconnaissance activities can be a way forward in post-disaster management.This work presents the results of a hybrid mission mobilised by the Earthquake Engineering Field Investigation Team (EEFIT) after the 2021 Haiti earthquake. On 14 August 2021, a 7.2 magnitude earthquake struck the Tiburon Peninsula in the Caribbean nation of Haiti, approximately 150km east of the capital Port au Prince. The event was followed by numerous aftershocks up to magnitude 5.7, and tiggered over 1000 landslides. Over 2000 people lost their lives, with over 15,000 injured and over 137,000 houses damaged or destroyed. The estimated economic impact is of the order of US$1.6 billion. Due the complex political and security situation in Haiti, coupled with the global pandemic, a full in field mission was not considered feasible, so a hybrid mission was designed instead.First, open-source information was collected and used to characterise the seismic event, analyse the strong ground motion and compare to established national and international earthquake codes and standard. Second, remote sensing techniques including Interferometric Synthetic Aperture Radar (InSAR) and Optical/Multispectral imagery were used to understand the earthquake mechanism, the ground displacement distribution and the possibility to detect landslide on a regional scale. The general applicability of remote sensing technique in the context of post disaster assessment was also evaluated. Finally, the earthquake impact on different building typologies in Haiti was investigated through the damage assessment of over 2000 buildings comprising schools, hospitals, churches and housing. This was done in collaboration with the Structural Extreme Events Reconnaissance (StEER) team, who mobilised a team of local non-experts to rapidly record building damage.This talk summarises the mission setup and findings, and discusses the benefits of and difficulties encountered during this hybrid reconnaissance.

This study evaluates carbon emissions of construction and demolition (CD) waste generated by building refurbishment, using a life cycle assessment approach through a case study project in China. Three waste management scenarios were developed for a building refurbishment project in the city of Suzhou. Scenario 1 is under the business-as-usual CD waste management practice in China; scenario 2 is based on the open-ended 3R strategy, which focuses on the downstream impact of waste; and scenario 3 considers both the upstream and downstream impact of waste. The results reveal that the composition of the waste generated from building refurbishment projects is different from construction and demolition projects. In the life cycle of CD waste management of building refurbishment projects, the refurbishment material stage generates the highest carbon emissions compared to the dismantlement, refurbishment construction, and refurbishment material end of life stages. Scenario 1 produces higher carbon emissions than scenario 2, but the difference is not significant in the whole life cycle of the building refurbishment project, whereas carbon emissions for scenario 3 are significantly less than both scenario 1 and scenario 2. The study finds the reason for this difference is that scenario 1 and scenario 2 are based on a linear economy that relies on unsustainable demand for raw materials, whereas scenario 3 is based on a circular economy that uses upcycled materials to substitute for raw materials and considers waste management from a cradle to cradle perspective. This study fills a research gap by evaluating carbon emissions of different waste management strategies for building refurbishment projects, which are expected to be an increasing portion of overall construction activity in China for the foreseeable future.

The presence of masonry infills may significantly affect the seismic behaviour of existing steel moment-resisting frames, characterised by low lateral force resistance and inadequate energy dissipation capacity due to the lack of seismic detailing. Masonry infills may cause variation of internal force distribution along beams and columns, resulting in large local seismic demands at beam-column joints and consequently leading to soft-storey mechanisms. Several numerical models have been developed to account for the effects of masonry infills, among which the equivalent strut models were most widely used. However, it has been argued that despite its ability to capture the global response of structures, the single-strut model may not be adequate to correctly simulate the internal forces distributions in steel members. To this end, the present study investigates modelling strategies of infilled steel frames using both single- and three-strut models. The results from different modelling approaches are compared among them and with experimental tests, providing insights on the influence of the modelling strategies both at global and local levels.

The EC8 design rules and requirements for steel moment-resisting frames (MRFs) mainly address far-field seismic scenarios. However, there are specific issues to account for Near Fault (NF) strong motions that may increase inelastic demand on structural steel members and joints. The latter are usually designed or qualified for far-field earthquakes. Also, the drift displacement is often characterized by severe unidirectional concentration. Another aspect influencing the design of MRFs is the limitation of interstorey drifts, which is often rather restrictive, thus penalizing the design of steel MRFs. The use of ductile energy-efficient claddings can be beneficial to relax the drift limitations, thus allowing to optimize the structural design, reducing the constructional costs, and encouraging the use of more sustainable solutions. To investigate these aspects, an experimental testing program has been planned within the FUTURE project, funded in the framework of the H2020-INFRAIA SERA program. In this project, comprehensive shake table tests were carried out on a two-storey one-bay mock-up equipped with different types of beam-to-column joints and extra ductile non-structural components. This paper illustrates the preliminary experimental results obtained on the bare steel frame equipped with two different types of detachable joints.

Atmospheric corrosion can seriously affect the performance of steel structures over long periods of time; thus, it is essential to evaluate the rate of corrosion and subsequent modification of dynamic properties of a structure over different time periods. Standards and codes represent the general guidelines and suggest general protection techniques to prevent structures from corrosion damage. The available models in the literature propose the thickness reduction method that accounts for the exposure time of structures in corrosive environments. The purpose of this study is to review the existing corrosion models in the literature and report as well as compare their effectiveness in low (C2 level), medium (C3 level) and high (C4 level) corrosivity class in accordance with the ISO standard. Furthermore, the influence of corrosion loss during the lifetime of a structure is studied through a realistic case study model using FEM (finite element method) in both linear and nonlinear regions. The results showed that the corrosion can considerably affect the dynamic characteristics of the structure. For instance, the vibration period rose up to 15% for the C4 class and 100-year lifespan. Additionally, the corroded structure presented higher acceleration and drift demand, and the base reaction forces were reduced up to 60% for the same class and time period.

In contrast with common buildings, the limit-state assessment has not been applied to pipe-rack – piping systems yet, albeit the seismic vulnerability of critical pipes is rather high. The current engineering practice may design pipe rack – piping systems in a risk-inconsistent way due to the conservative acceptance criteria of seismic codes that keep pipes in the elastic range. Additionally, the response of pipes could become complex when considering differential displacements between internal supports, pipe edges and adjacent structures, which static methods may not describe efficiently. The design of a typical RC pipe rack – piping system in a code-consistent way resulted in two main outcomes. First, the piping required the increase of structural members cross-section, and secondly, the differential displacement was the main reason of pipe failure both in the longitudinal (unrestrained) as well as transverse direction. Finally, the performance-based assessment of this type of system demonstrated that the spectral acceleration is mildly more efficient and sufficient intensity measure than ground ones to describe the damage on piping. The observed mean annual frequency of exceedance was 57% smaller than the targeted value for the pipes, whereas the difference was considerably higher for the pipe rack. This outcome corroborated the conservativeness of codes and the risk-inconsistency between the structural and non-structural members.

The investigation of the seismic integrity of petrochemical plant steel structures should be commensurable to their importance given the high necessity for human life safety and financial robustness. To date, it is demonstrated in the existing literature that still many grey areas of knowledge exist upon the appropriate application of code provisions on non-building structures design. Indeed, the selection of seismic design parameters such as system performance factors or important classes are still vague aspects, in contrast with those for common building structures, either because of the paucity of information of seismic codes or due to the structural peculiarities that characterise the industrial structures resulting in the difficulty of defining ‘all-encompassing’ design parameters. The present paper aims at highlighting those parameters considering also a case-study that pertains to a steel pipe rack. The pipe rack is designed and analysed in the linear and nonlinear regime, both statically and dynamically, according to the Italian and European codes. American code provisions are examined as well so as possible inconsistencies might be found. It is demonstrated that the common nonlinear static analysis (pushover analysis) cannot be used to assess the response of the rack and the behaviour factor selection from current standards could be unjustifiable. Also, common engineering demand parameters, e.g. interstorey drift ratio, need further assessment vis-à-vis the response of nonstructural components of which the current design method does not comply with modern methods.

This paper presents an optimization methodology to simulate the monotonic and cyclic response of steel reinforcement smooth bars when subjected to inelastic buckling. A finite element (FE) model of steel rebars, based on non-linear fibre sections and an initial geometrical imperfection, is adopted. The multi-step optimization proposed herein to identify the main parameters of the material constitutive models is based on genetic algorithms (GA) and Bayesian model updating. The methodology consists of comparing available experimental tests from literature with the corresponding numerical results. New empirical relationships and probabilistic distributions of the optimized model parameters, such as post-yielding hardening ratio, isotropic hardening in compression and tension, plus initial curvature, are presented. Finally, utilizing both the GA-based and Bayesian-based calibration, an improvement of an existing analytical model for inelastic buckling of smooth steel rebars is proposed. Such analytical modelling can be efficient and reliable for future building codes and assessment guidelines for existing buildings.

The Sendai Framework for Disaster Risk Reduction 2015-2030 (SFDRR) highlights the importance of scientific research, supporting the ‘availability and application of science and technology to decision making’ in disaster risk reduction (DRR). Science and technology can play a crucial role in the world’s ability to reduce casualties, physical damage, and interruption to critical infrastructure due to natural hazards and their complex interactions. The SFDRR encourages better access to technological innovations combined with increased DRR investments in developing cost-effective approaches and tackling global challenges. To this aim, it is essential to link multi- and interdisciplinary research and technological innovations with policy and engineering/DRR practice. To share knowledge and promote discussion on recent advances, challenges, and future directions on ‘Innovations in Earthquake Risk Reduction for Resilience’, a group of experts from academia and industry met in London, UK, in July 2019. The workshop focused on both cutting-edge ‘soft’ (e.g., novel modelling methods/frameworks, early warning systems, disaster financing and parametric insurance) and ‘hard’ (e.g., novel structural systems/devices for new structures and retrofitting of existing structures, sensors) risk-reduction strategies for the enhancement of structural and infrastructural earthquake safety and resilience. The workshop highlighted emerging trends and lessons from recent earthquake events and pinpointed critical issues for future research and policy interventions. This paper summarises some of the key aspects identified and discussed during the workshop to inform other researchers worldwide and extend the conversation to a broader audience, with the ultimate aim of driving change in how seismic risk is quantified and mitigated.

Nowadays, there is a lack of adequate code provisions for the seismic performance and risk assessment of steel structures to be used within European countries. At the same time, in several occasions, existing steel moment resisting frames (MRFs) have demonstrated to be very fragile with respect to seismic actions due to their inadequate ductility capacity. This combination highlights the urgent need for an update of the current Eurocode 8 – Part 3 (EC8‐3), thus promoting a reliable assessment of existing steel structures. To this aim, the present study provides a comprehensive and quantitative comparison of the EC8‐3 with the three versions of the American ASCE 41 (i.e., ASCE 41‐06, ‐13 and ‐17), which are here assumed as a reference, as they reflect the evolution of ‘similar’ assessment procedures during the last two decades. The comparison of the capacity values provided by the codes for different engineering demand parameters (EDPs) highlights significant differences pointing out drawbacks of the EC8‐3. In addition, the comparison is made by assessing the seismic performance of two existing steel MRFs, by performing Incremental Dynamic Analyses and deriving fragility curves in a probabilistic approach which considers local EDPs which are compliant with the codes, and that are conventionally used in deterministic studies, e.g., chord rotations in beams and columns, shear strain in panel zones. The comparison of the codes, and the probabilistic assessment of the case studies by using code-based (i.e., local) EDPs, provide significant insights and directions for revision of the EC8‐3.

The study described and summarised in this paper was aimed at developing a framework for the definition of force-displacement relationships for single-strut models for masonry infill walls within steel moment-resisting frames. The methodology is based on a genetic algorithm optimisation and can be used for the calibration of force–displacement curves based on databases from either experiments or numerical simulation. A case study is also tested to demonstrate the framework in detail. Due to limited available experimental data on the seismic response of existing steel frames with masonry infills, a set of comprehensive finite element micro-models developed in Abaqus are used to generate a database. The optimal values of the parameters to feed a force–displacement relationship of the single-strut model of the masonry infills are obtained for each micro-model by solving optimisation problems with a genetic algorithm. The optimisation problem involves the minimisation of the discrepancies between the global responses from the database and their corresponding single-strut models through least square minimisation. With the optimal values as the input variables, a generalised quadrilinear model of the masonry strut is obtained through regression analysis and is validated against additional micro-models of infilled steel frames.

Numerous aftershocks can be triggered by a strong mainshock and may cause more severe and widespread structural damage with respect to a single seismic event. This study investigates the effect of relative differences between the incident angles of consecutive earthquakes on seismic demands of structures as bi-linear Single-Degree-Of-Freedom (SDOF) systems. To this aim, constant-strength spectra are developed based on different Normalized Engineering Demand Parameters (NEDPs) to identify this impact as a new seismic uncertainty. Several seismic sequences with one aftershock and also two aftershocks are generated considering different directions of both mainshocks and subsequent aftershocks as input excitations in nonlinear dynamic analyses of SDOF systems. The results demonstrate that taking into account the relative differences of the incident angles of sequential earthquakes can affect significantly seismic responses.

Earthquakes are not isolated events and, typically, dominated by a larger-magnitude excitation (Mainshock – MS) and many smaller-magnitude motions (Aftershock – AS). Most often, such destructive events bring more damage than a single strong motion. Nowadays, many existing non-seismic designed RC structures are classified as either functional-obsolete or sub-standards. The seismic performance of these aged structures can be even more critical if some phenomena, such as corrosion, occur. The present study aimed at evaluating the seismic vulnerability of typical existing RC structures subjected to earthquake sequences and various levels of corrosion. A probabilistic approach via the fragility analysis, and three different seismic intensity measures (IM), was carried out. A four-story RC building was used as a testbed for Incremental Dynamic Analyses (IDA) via an advanced Finite Element approach. Twenty as-recorded natural motions were selected from international databases and inserted into the three-dimensional model. A new seismic intensity measure was provided and compared to the world-wide accepted peak ground acceleration (PGA) and spectral acceleration at the first natural period of the structure (Sa(T1)); the modified spectral acceleration intensity (MASI). The limit states of limited damage (LD) and severe damage (SD) were considered as capacity thresholds. The outcomes of this numerical investigation showed that multiple excitations and corrosion significantly affect the seismic vulnerability of the investigated building; MASI appeared to be the most effective intensity measure to assess the seismic fragility of corroded RC buildings; modern seismic-based technical codes are no longer conservative for such detrimental phenomena.

Many existing steel moment-resisting frames were constructed before the provisions of modern seismic codes; therefore, they are likely to exhibit high vulnerability to earthquakes due to their inadequate ductility design, hence low energy dissipation capacity. Public concern has been raised about the development of a reliable code-based framework for assessing existing structures, however, previous research has shown that the current European code EC8–3 may not be sufficient and requires urgent improvements. Particular attention should be paid to the contribution from infill walls in steel buildings, especially those made of masonry, and beam-column connections, as they play a significant role in the structural performance under earthquakes. To this end, an updated assessment procedure, which is an extension of the current procedure in EC8–3 but with several improvements to the non-linear analysis methods, is proposed in this paper and is applied to an existing steel building as a case study. The building is a three-storey steel moment-resisting frame located at Amatrice in Central Italy, which survived the recent 2016–2017 Central Italy earthquakes. Refined 3D models of the case study building, which account for the effects of infill walls and column panel zones, were implemented in a refined finite element platform. The effects of masonry infills on structural components, such as beams and columns, were investigated through non-linear analysis methods. The results emphasise the significance of including masonry infills in the numerical model for seismic assessment especially when an optimised retrofit solution is needed.