Search

This paper proposes an innovative data-driven vulnerability model for the classification of the existing residential building stock, by clustering observational damage data gathered after the 2009 L’Aquila earthquake. The proposed model preserves the conceptual framework at the basis of the macroseismic approach, which allows for a thorough vulnerability classification of the built environment by resorting to vulnerability classes and by accounting for the uncertain association of building typologies to vulnerability classes. Novel aspects of this study are the adoption of peak ground acceleration for the ground motion characterisation, which allows for overcoming possible limitations related to the use of macroseismic intensity, and the use of unsupervised machine learning techniques for removing subjectivity in the definition of vulnerability classes. A probabilistic framework is then set up allowing for the attribution of a given building typology to multiple vulnerability classes, based on an ad- hoc strategy, involving the use of probability theory and using empirically-derived typological fragility functions as a target. The use of a detailed post-earthquake survey form also allows for an improved definition of building types representative of the Italian building stock

Buckling-restrained braces (BRBs) have proven to be very effective in improving the seismic performance of existing and new structures. They provide strength, stiffness and added energy dissipation to the structure. However, being BRBs characterized by a low post-elastic stiffness, their use may lead to residual deformations hindering the building’s reparability and to excessive cumulative ductility demand possibly compromising the residual capacity of BRBs. To overcome these drawbacks, BRB frames (BRBFs) can be coupled with moment-resisting frames (MRFs) to form dual systems. If properly designed, MRFs acting as back-up frames, allow the control of the residual drifts and the optimization of the performance of the BRBs. The contribution of this study is to provide insights into the performance and residual capacity of BRBFs-MRFs dual systems and to shed light on the influence of the main BRB’s design parameters. To this end, a non-dimensional formulation of the equation of motion is introduced for a single-degree-of-freedom system, and an extensive parametric study is performed for a set of natural ground motion records with different characteristics and scaled to various intensity levels. This allows the investigation of a wide range of configurations, considering different levels of the relative strength and ductility demand of BRBFs and MRFs, and to obtain useful information for their design. Finally, two case study frames, modeled as two-dimensional nonlinear multi-degrees-of-freedom systems, are analyzed and the results compared to those obtained from the non-dimensional formulation to show the capabilities and the limitations of the adopted methodology and of the SDOF approximation.

Contactless structural monitoring has in recent years seen a growing number of applications in civil engineering. Indeed, the elimination of physical installations of sensors is very attractive, especially for structures that might not be easily or safely accessible, yet requiring the experimental evaluation of their conditions, for example following extreme events such as strong earthquakes, explosions, and floods. Among contactless technologies, vision-based monitoring is possibly the solution that has attracted most of the interest of civil engineers, given that the advantages of contactless monitoring can be potentially obtained thorough simple and low-cost consumer-grade instrumentations. The objective of this review article is to provide an introductory discussion of the latest applications of vision-based vibration monitoring of structures and infrastructures through an overview of the results achieved in full-scale field tests, as documented in the published technical literature. In this way, engineers new to vision-based monitoring and stakeholders interested in the possibilities of contactless monitoring in civil engineering could have an outline of up-to-date achievements to support a first evaluation of the feasibility and convenience for future monitoring tasks.

The consensus back in 2008 - ten years after the introduction of the euro - was that the adoption of a common currency had made a limited impact of around 2% in total on the trade flows of the first wave of euro area countries (Baldwin et al., 2008). Since then, six more countries have joined the euro area, and firms have internationalised their production processes. These two phenomena are interrelated and may have changed the way the common currency affects the euro area economy. Therefore, with the common currency now into its third decade - and with more countries queuing to adopt it - this paper revisits the trade effects of the euro, focusing on the newer euro adopters (i.e. those countries that have adopted the euro since 2007) and their interaction with the first wave of euro area members via supply chains. The contribution of the paper is twofold. First, it revisits the estimated aggregate impact of the euro on euro area trade, as well as on trade within and between the two waves of adopters. Data on bilateral flows between 1990 and 2015 for an extended sample of countries to estimate a gravity equation indicate a significant trade impact, ranging between 4.3% and 6.3% in total on average, with the magnitude being the highest for exports from the second wave of adopters to the first wave of adopters. If a synthetic control approach (Abadie and Gardeazabal, 2003; Abadie et al., 2010) is used instead, the estimated gains associated with euro adoption are greater. In particular, exports of both intermediate and final products from countries belonging to the first wave of euro adopters to those belonging to the second wave are estimated to have increased by about 30% using this approach. The second contribution made by this paper relates to the channels through which trade might be affected by a currency union. This question is explored by looking separately at trade in intermediate goods and final products. While we find that trade gains were mainly driven by trade in intermediate goods among countries that adopted the currency earlier (5.3%), our results also show that the euro had a positive effect on the exports of final products from the second wave of adopters to other euro area countries. This effect is as high as 10.6% with the gravity model and 32% with the synthetic control approach. One of the reasons for the difference in the range of estimates between the two approaches might be that the gravity model can control for unobserved characteristics via fixed effects, while the synthetic control approach may fail to do so. These results suggest that the euro facilitated the establishment and expansion of international production chains in Europe. In turn, this is likely to have increased business cycle synchronisation in the euro area and to have supported market access for later adopters.

Availability of resources is one of the primary criteria for communities to attain a high resilience level during disaster events. This paper introduces a new approach to evaluate resourcefulness at the community and national scales. Resourcefulness is calculated using a proposed composite resourcefulness index, which is a combination of several resourcefulness indicators. To build the resourcefulness index, resourcefulness indicators representing the different aspects of resourcefulness are collected from renowned literary publications. Every indicator is assigned a measure to make it quantifiable. Time-history data for the measures are needed to perform the analysis. While these data could be obtained from different sources, acquiring a full set of data is quite challenging. Hence, to account for missing data, the Multiple Imputation (MI) and the Markov Chain Monte Carlo (MCMC) data imputation methods are adopted. The data are then normalized, assigned weights, and aggregated to obtain the resourcefulness index. A case study is performed to demonstrate the applicability of the approach. The resourcefulness indexes of two countries, namely the United States and Italy, are evaluated. Results show that resourceful communities/countries are more resilient during disaster events as they have more tools to come up with solutions. It is also shown that knowing the current resourcefulness level helps in better identifying what aspects should be improved.

This paper describes the multivariate statistical model of the structure-related modelling uncertainty, developed with reference to reinforced concrete, masonry, steel, and seismically isolated buildings, within the framework of the RINTC project. The model describes the variability of material properties as well as the uncertainty associated with the adopted response models. Specific aspects of each structural typology are also discussed, with a focus on the statistical dependence of the random variables in the model. Finally, the paper describes also the efficient sampling procedure adopted. Effect of model uncertainty on response for each typology are discussed in the corresponding papers within this special issue dedicated to the RINTC project.

This article describes the structural design, nonlinear modeling, and seismic analysis of prototype single-storey non-residential steel buildings made of moment-resisting portal frames in the transverse direction and concentric braces in the longitudinal direction. Various design parameters (building geometry, seismic hazard, foundation soil category) and different modeling assumptions (bare frame model, model including cladding elements, ground motions including vertical accelerations, and modeling uncertainties) were considered to investigate their effects on the simulated seismic performance.

This paper investigates through nonlinear static and dynamic analyses the behaviour of a newly introduced steel and concrete hybrid coupled wall (HCW) system made by a single reinforced concrete (RC) wall coupled to steel columns by means of steel links, a structural solution of potential interest for seismic-resistant multi-storey buildings. The considered HCW is conceived as seismic resistant system where the RC wall and the steel columns remain undamaged while the seismic energy is dissipated by yielding concentrated in the steel links only. In order to achieve such a desired seismic behaviour, a proper design procedure must be adopted and validated. Accordingly, this study reviews a recently proposed design approach and presents some modifications to further improve the seismic behaviour of the considered HCW system. Case studies are designed using the proposed modified design method as well as its former version. Afterwards, the seismic behaviour of the considered case studies is analysed to identify the optimal degree of coupling between the RC wall and steel columns, also evaluating the influence of the building height and uniform or non-uniform distribution of shear links. The obtained results confirm the improvements of the modified design method proposed in this study and provide support for the selection of the design parameter that influences the most in the seismic behaviour of the innovative HCW system, i.e. the degree of coupling between RC wall and steel columns, controlled by the adopted steel links.

Background:In this work the behaviour of continuous steel-concrete composite beams with different shear connection distributions obtained from two design methods,i.e. Eurocode 4 and a proposed alternative approach, is analysed.Objective:For this purpose a finite element model specifically developed for the nonlinear analysis of steel-concrete composite beams is adopted. This finite element model includes material nonlinearity of slab concrete, reinforcement steel, beam steel as well as slab-beam nonlinear partial interaction due to the deformable shear connection. The inclusion of the partial interaction in the composite beam model provides information on the slab-beam interface slip and shear force and enables to model the failure of the shear connectors.Results and Conclusion:In this way it is possible to analyse and quantify the effect of shear connector distributions on the global and local response of continuous steel-concrete composite beams, both under service load levels and at collapse. Particular attention is focused on the ductility requirements on the shear connectors when varying the connection design approach and distribution.

Steel frames with reinforced concrete infill walls (SRCW) are an interesting seismic-resistant structural solution. However, an effective seismic design of SRCWs is not easy due to the current lack of specific capacity design rules that allow controlling the formation of a proper energy dissipating mechanism. In order to overcome such an issue, a ductile design procedure is presented in this paper. The proposed procedure leads to innovative SRCW systems where energy dissipation is expected to take place only in the vertical elements of the steel frame, which are subjected mainly to axial forces. The non-ductile components, i.e. reinforced concrete wall and steel-to-concrete connections, are expected to suffer negligible damage. Accordingly, the system is designed to control the formation of diagonal struts in the infill walls and behaves as a lattice brace instead of a shear wall. Experimental test results and nonlinear finite element analyses are illustrated to support the developed ductile design approach and highlight the advantages of SRCWs.

This paper analyses the observational damage from post-earthquake investigations carried out on churches of the Marche Region struck by the 2016 Central Italy seismic sequence. Such seismic activit...

This paper illustrates a multidisciplinary integrated approach for analysing the seismic vulnerability of historical massive defensive structures. To this end, a fortress having massive walls, internal discontinuity surfaces, cavities and internal passages organized in a complex three-dimensional geometry, is used as testbed structure. The presented workflow should be considered as a contribution to define a general framework and foster the development of guidelines for seismic vulnerability analysis of historic massive structures. In fact, massive constructions cannot be modelled as an assembly of vertical panels, horizontal floors, towers and vaults, as is the case of other more common building typologies, such as churches and palaces, for which codified catalogues of collapse mechanisms are available.

In recent years several studies have been developed on structural collapses of buildings, leaving the bridges’ field partially investigated by few researchers. However, recent events of bridge collapses, namely in Genoa (Italy) on August 14th 2018 and in Kolkata (India) on September 4th 2018, have focused the public interest on the infrastructures’ safety for their consequences in terms of fatalities and injuries, but also of economy and social losses. The present work is focused on the disproportionate collapse of the Morandi’s Bridge in Genoa and consists in an independent study that is based on the available data from literature. The possible triggering events have been deepened starting from the corrosion and the fatigue issue of the steel tendons within the stays. Furthermore, the evolution of the loading conditions in terms of trucks’ number and individual truck weight from the bridge opening (1967) is considered. Therefore, (i) corrosion and fatigue models have been selected from literature and identified through original local weather parameters as temperature, humidity, chlorides, etc. while (ii) statistical historical data of the highway traffic in Italy have been collected. They are useful in the numerical analyses with finite element models of the Morandi’s bridge to identify possible collapse initiations. Some remarks on the role of redundancy in bridges structural scheme as the strategic characteristic to avoid the disproportionate collapse and to improve robustness are provided. Furthermore, the degree of staticindeterminacy of the structure with respect to disproportionate collapse is also discussed.

This study illustrates an approach that allows evaluating the intensity and extent of non-structural damage in steel buildings. Different levels of cladding panel damage are introduced and a specific cladding panel hysteretic model is included in the structural model and calibrated on available data from experimental tests. Numerical results from nonlinear dynamic analyses are elaborated in the form of fragility curves for the damage limit state and used to compare the consequences of different cladding behaviours on prototype single-storey industrial steel buildings used as case studies. The outcomes are also compared to a damage limit state derived from structural analysis adopting bare-frame models and conventional drift-based damage criteria.

Productivity growth has slowed in most Western countries, a reality well known in the economic literature, and the slowdown is likely to persist for some time. This paper investigates the impact of this phenomenon on export performance, with a particular focus on its heterogeneity across countries. To explain such heterogeneity, we pay particular attention to the role of productivity distribution and allocative efficiency. We rely on data from the Competitiveness Research Network (CompNet), a unique micro-aggregated database that provides a rich set of information on the variables' distribution at the granular level, together with micro-founded indicators such as the level of allocative efficiency. We argue that increases in both productivity dispersion and allocative efficiency, measured with the Olley and Pakes (1996) methodology, are associated with higher export competitiveness for the set of countries in our analysis. Furthermore, we try to evaluate four separate scenarios according to different levels of productivity growth and different degrees of allocative efficiency and conclude that, while a reduction in productivity growth is always associated with a decrease in export competitiveness, for those countries placed in the top 10 percent of the distribution of the Olley and Pakes gap, this negative effect can be offset for as long as eight years.

Structural members yielding in shear are used in earthquake resistant systems, such as eccentrically braced steel frames and systems with passive energy dissipation devices, in a conscious effort to concentrate the energy dissipation capacity of the structure in components that can be repaired or replaced after a major earthquake. This paper presents an improved approach to a newly suggested design procedure of an innovative Hybrid Coupled Shear Wall (HCW) system consisting of a RC shear wall coupled with steel side columns via dissipative steel shear links. The primary design objective is to reduce or possibly avoid the damage in the RC wall while concentrating the seismic damage to the replaceable steel links which are shear critical, i.e. intended to fail in shear rather than flexure. To this purpose, a performance based approach is followed considering several limit states such as IO (Immediate Occupancy based on a limitation of the interstorey drifts), LS (Life Safety with yielding of the link, restoration possibilities of the links and limitation of the damages in the RC wall) and CP (near collapse situation with possible significant damages in the RC wall). The proposed design procedure is applied to several case studies which are analysed through nonlinear static and incremental dynamic analyses using finite element models in order to optimize the respective contribution of the wall, side columns as well as the links in terms of strength, stiffness and energy dissipation capacities.

The objective of this work is to provide insight into the expected slip demand in the shear connection of composite steel–concrete beams through the use of a numerically efficient nonlinear beam model previously validated by comparisons with experimental tests. The results of a parametric analysis involving 1680 simply supported beams are illustrated to investigate the influence that various design parameters (i.e. span length, degree of shear connection, steel beam and concrete slab cross-section geometry, connection distribution, dead load to live load ratio, propped and unpropped construction sequences, and concrete strength) and modelling parameters (i.e. shear connection representative strength and constitutive parameters) have on the slip demand. It is observed that, for a given shear connection degree, the most important parameters are the construction sequence, the span length, and the steel section shape. In addition, the shear connection distribution can have an important effect and non-uniform shear connection distributions with more connectors near the supports might be effective in limiting the slip demand. The results illustrated in this work can be a support for more efficient designs of the shear connection in composite steel–concrete beams and a basis for possible improvements of their current design recommendations.

NSFC [51261120376, 51281220267]; Open Research Fund Program of State key Laboratory of Hydroscience and Engineering in China [sklhse-2013-C-02]

This paper presents a probabilistic study based on Monte Carlo simulation (MCS) to evaluate the influence of material uncertainties on the numerically simulated structural response of composite steel–concrete floors consisting of concrete slabs cast on steel profiled sheeting and connected to steel beams by means of shear connectors. The numerical analyses are performed using a three-dimensional finite element model developed using the commercial software Abaqus, implemented using an explicit formulation. The constitutive behaviour of all materials is nonlinear. Contact regions between the concrete and steel elements are simulated using surface-to-surface and embedment techniques. Analyses are carried out for three case studies including simply-supported and continuous beams for which experimental results are available in the literature. Different realization sizes are considered for the MCS in order to evaluate their influence on the statistical characterization of the structural response. Based on the obtained results, it is observed that the adopted realization sizes provide similar statistical representation of the structural behaviour, which highlights how even a reduced number of nonlinear analyses can lead to satisfactory approximations of the statistical description of the response uncertainties in composite steel–concrete floors.

A 142-m, three-span continuous footbridge over the Esino River (Italy) is considered as a case study to illustrate a number of challenging aspects in its static and dynamic design. The adoption of an optimized steel deck with a variable cross section together with the use of external prestressing tendons in the central span allows a substantial reduction of structural weights. The resulting footbridge requires a proper model for the assessment of its behavior up to the ultimate limit state as well as attention to vibration control under pedestrian loading at the service limit state. The former issue is addressed through the use of a specifically developed material and geometric nonlinear finite-element formulation. Regarding vibration control, an original combination of two different systems is used, i.e., high damping rubber (HDR) stripes and tuned mass dampers (TMDs). The HDR stripes, applied between the steel deck and the concrete floor, increase the overall damping of the footbridge, whereas t...

An innovative hybrid coupled wall (HCW) system made of a single reinforced concrete (RC) wall coupled to two steel side columns by means of steel links is presented, its lateral load resisting mechanism illustrated, and a simple design procedure proposed. The design objective is to reduce or possibly avoid the damage in the RC wall while concentrating the seismic damage to the replaceable steel links intended to be the only dissipative components of the presented HCW system. In this way it is possible to obtain a seismic resistant system that can be easily repaired through the substitution of the yielded steel links. The proposed design procedure is applied to a case study considering various assumptions for the design parameters. The designed solutions are analysed through a nonlinear finite element model in order to evaluate the results of the design methodology and provide useful information on the ductility capacity under horizontal loads of the proposed innovative HCW system.

Timber-concrete composite beams are an increasingly common design solution for medium-to-long span floors in new buildings. Thus, there is a significant need for accurate models and analysis tools to predict the response and performance of timber-concrete composite beams. In this paper, a nonlinear finite-element (FE) frame model with deformable shear connection is adopted to estimate the short-term structural response of timber-concrete composite beams for which experimental results are available. The FE model is used in conjunction with a probabilistic analysis methodology, which explicitly accounts for the uncertainties in the parameters that describe the constitutive models for timber, concrete, and shear connectors. The objectives of this study are (1) the evaluation of the variability of global and local structural response quantities owing to the uncertainties in the constitutive parameters of timber, concrete, and shear connectors; and (2) the analysis of the correlation between experiment...

Steel frames with buckling-restrained braces (BRBs) have low lateral post-elastic stiffness, especially in the case of non-moment resisting beam-to-column connections, due to the brace limited post-yield stiffness. Thus, a tendency to soft storey formation, fostered by nonhomogeneous distributions of brace over-strength, might be observed during seismic events. The objective of this paper is to study the effects of brace over-strength distributions on the expected maximum reduction of seismic performance, as measured by local and global engineering demand parameters (EDPs). This goal is pursued using response sensitivity analysis and solving a constrained extreme problem. The general framework of the proposed sensitivity-based approach is presented and its application to steel frames with BRBs is described in detail. Realistic case studies are considered, taking as reference solution the design based on the modal response spectrum method. Interstorey drifts are used as global EDPs related to the damage of nonstructural elements, while maximum plastic strains and cumulative plastic strains of the braces are considered as local EDPs to monitor the damage of braces. The brace over-strength patterns that are the most unfavourable for each EDP are identified and the relevant maximum increment of each EDP with respect to the reference design solution is determined, obtaining a relation between the maximum seismic performance reduction and the brace over-strength used in the design. In this way, the proposed approach can be used as a tool for safer and more effective seismic designs of steel frames with BRBs.

Modern construction makes frequent use of composite steel-concrete beams for bridge and building applications. This paper describes a three-dimensional finite element model in which all components forming the composite member are modelled by means of solid elements. The proposed approach is developed using the commercial software Abaqus and is able to model the composite response without requiring information from push-out tests commonly performed to define the constitutive relationship for the shear connectors. All materials are assumed to behave in a nonlinear fashion. Contact between the elements is simulated using surface-to-surface and embedment techniques. The adequacy and accuracy of the proposed modelling approach are validated against experimental results available in the literature on simply-supported and continuous beam tests with both solid and composite slabs.

The ultimate capacity of beams prestressed with external slipping tendons cannot be evaluated by a local analysis of the critical sections and a nonlinear analysis of the whole beam-tendon structural system is required. Since this type of analysis is complex, simplified approaches are of great assistance to engineers in the design process. In this work a new simplified method is introduced for evaluating the tendon traction increment at collapse and consequently the beam flexural strength without requiring a nonlinear analysis of the whole beam-tendon structural system. A detailed description of the proposed approach is given and some applications of practical interest to externally prestressed steel–concrete composite beams are discussed.

The flexural strength of externally prestressed beams depends on the tendon stress at failure. If the tendon is free to slip at the deviators its stress will depend on the global deformation of the whole structure. Thus the tendon stress at failure, and consequently, the flexural strength cannot be evaluated by a local analysis of the critical sections, but a nonlinear analysis of the whole beam-tendon structural system is required. In the past, simplified formulas were proposed to calculate the tendon stress increment at failure avoiding the need for a nonlinear analysis of the entire structure. Some of these formulas have been adopted as code recommendations. Some approaches however do not seem to be consistent with the actual behavior of externally prestressed beams and in some cases excessively high increments of stress are recommended. On the other hand, other approaches appear to be too conservative. In this work a new simplified and rational method of analysis based on shape functions approximating deformations is proposed to study the tendon stress increment and consequently the flexural strength of externally prestressed concrete beams. The proposed simplified method reduces the analysis of externally prestressed structures from a global structure problem to an easier section problem.

This paper presents a study on the behaviour of the walls of the Rocca Roveresca of Senigallia in Italy built in the XIV century on the ruins of a former Roman defensive struc-ture. This is a peculiar example of a small fortress that had undergone in the XV century im-portant modifications of the plant in order to enhance its defensive performances. A linear finite element model is first developed in order to understand the dynamic behaviour of a ge-neric portion of the wall and to detect the probable incipient failure mechanisms. A subse-quent static nonlinear analysis is carried out, with the same finite element model, to investigate the formation of the cracking layout and to detect the position of plastic hinges. The last analysis level is carried out with a tailored macro-element constituted by three bod-ies, namely the two external curtains and the inner fill for which a degradation of the behav-iour is considered. The results obtained demonstrates the efficiency of the wall against earthquakes characterized by return times typical for ultimate limit states. Same issues that deserve further investigation are highlighted.

The objective of this study is to provide insight into the expected slip demand in composite steel-concrete beams through numerical simulations. A wide parametric analysis is carried out evaluating the partial interaction performance of simply-supported beams designed considering a variety of floors, i.e. span length, slab thickness, shear connection strength, dead load to live load ratio and slab concrete strength. For each of these beams, the slip demand required to achieve the expected design capacity is evaluated. In this process, key parameters influencing the slip requirements are identified. These also include the construction sequence (propped or unpropped) and the shear connection distribution (uniform or non-uniform with different layouts).