Seismic Testing of Adjacent Interacting Masonry Structures

In many historical centres in Europe, stone masonry buildings are part of building aggregates, which developed when the layout of the city or village was densified. In these aggregates, adjacent buildings share structural walls to support floors and roofs. Meanwhile, the masonry walls of the façades of adjacent buildings are often connected by dry joints since adjacent buildings were constructed at different times. Observations after for example the recent Central Italy earthquakes showed that the dry joints between the building units were often the first elements to be damaged. As a result, the joints opened up leading to pounding between the building units and a complicated interaction at floor and roof beam supports. The analysis of such building aggregates is very challenging and modelling guidelines do not exist. Advances in the development of analysis methods have been impeded by the lack of experimental data on the seismic response of such aggregates. The objective of the project AIMS (Seismic Testing of Adjacent Interacting Masonry Structures), included in the H2020 project SERA, is to provide such experimental data by testing an aggregate of two buildings under two horizontal components of dynamic excitation. The test unit is built at half-scale, with a two-storey building and a one-storey building. The buildings share one common wall while the façade walls are connected by dry joints. The floors are at different heights leading to a complex dynamic response of this smallest possible building aggregate. The shake table test is conducted at the LNEC seismic testing facility. The testing sequence comprises four levels of shaking: 25%, 50%, 75% and 100% of nominal shaking table capacity. Extensive instrumentation, including accelerometers, displacement transducers and optical measurement systems, provides detailed information on the building aggregate response. Special attention is paid to the interface opening, the global behaviour in relation to the interface separation, interstorey drifts and out-of-plane displacements

Shake-table testing of a stone masonry building aggregate: overview of blind prediction study

City centres of Europe are often composed of unreinforced masonry structural aggregates, whose seismic response is challenging to predict. To advance the state of the art on the seismic response of these aggregates, the Adjacent Interacting Masonry Structures (AIMS) subproject from Horizon 2020 project Seismology and Earthquake Engineering Research Infrastructure Alliance for Europe (SERA) provides shake-table test data of a two-unit, double-leaf stone masonry aggregate subjected to two horizontal components of dynamic excitation. A blind prediction was organized with participants from academia and industry to test modelling approaches and assumptions and to learn about the extent of uncertainty in modelling for such masonry aggregates. The participants were provided with the full set of material and geometrical data, construction details and original seismic input and asked to predict prior to the test the expected seismic response in terms of damage mechanisms, base-shear forces, and roof displacements. The modelling approaches used differ significantly in the level of detail and the modelling assumptions. This paper provides an overview of the adopted modelling approaches and their subsequent predictions. It further discusses the range of assumptions made when modelling masonry walls, floors and connections, and aims at discovering how the common solutions regarding modelling masonry in general, and masonry aggregates in particular, affect the results. The results are evaluated both in terms of damage mechanisms, base shear forces, displacements and interface openings in both directions, and then compared with the experimental results. The modelling approaches featuring Discrete Element Method (DEM) led to the best predictions in terms of displacements, while a submission using rigid block limit analysis led to the best prediction in terms of damage mechanisms. Large coefficients of variation of predicted displacements and general underestimation of displacements in comparison with experimental results, except for DEM models, highlight the need for further consensus building on suitable modelling assumptions for such masonry aggregates

SI: Natech risk assessment of hazardous facilities

Industrial plants are prone to be highly damaged when subjected to strong earthquakes. This has been clearly demonstrated in the aftermath of strong seismic events, which may trigger technological accidents usually termed natural-technological (NaTech) events. One of the most famous examples is represented by the Fukushima disaster during the 2011 Tohoku Earthquake. Nevertheless, the effort in developing new design/assessment methodologies is becoming more and more important as clearly proven by the rapid increase of the scholarly contributions on this topic. In this respect, Performance Based Earthquake engineering, which has seen rapid growth in the field of civil structures, can still be considered rather new in the world of industrial facilities because of the neuralgic role of the consequence analysis, necessary to quantify the individual or societal risk. Moreover, the recent activity on the second generation of Eurocodes—and in particular on EN1998:4 dedicated to industrial equipment like silos, storage tanks, chimneys, towers, and masts—makes urgent the identification of the most recent contributions on the topic. This Special Issue, titled Natech Risk Assessment of Hazardous Facilities, promoted by the Guest Editors, Fabrizio Paolacci, Christoph Butenweg and Dimitrios Vamvatsikos, aims to bring together the latest methodologies and techniques for a reliable assessment of NaTech risk and resilience of hazardous facilities. Contributions come from researchers and industry professionals, strongly involved in the activity of Working Group 13 that is working on seismic assessment, design and resilience of industrial facilities within the European Association of Earthquake Engineering. A total 10 papers have been accepted that cover many of the key topics related to NaTech events and consequences in industrial facilities. In particular: (1) hazard issues in NaTech risk assessment, (2) Advanced methodologies for earthquake-related NaTech risk assessment, (3) Seismic analysis of critical non-structural components, (4) Design of safety barriers to control seismic risk of hazardous plants, (5) Performance-based design/assessment of hazardous industrial facilities, (6) Resilience of industrial facilities and neighboring communities. In the first paper, devoted to topic 1 and titled “The new seismic hazard model ESHM20 of Europe: Investigating the implications to the seismic design and risk assessment of major industrial facilities across Europe”, by Pitilakis K., Butenweg C., Riga E., Apostolaki S., Renault F., a large-scale study of the impact of the potential adoption of the 2020 European Seismic Hazard model (ESHM20) on the design of new industrial facilities as well as on the potential seismic risk of existing plants at European level with respect to the national seismic codes is presented. Based on the conducted illustrative studies, the consequences of a potential adoption of the revised Eurocode 8 and ESHM20 hazard maps are discussed and summarized in view of the harmonisation process in Europe. The second paper titled “Risk‑targeted seismic design of the freeboard for steel storage tanks equipped with floating roofs” by Caprinozzi S., Žižmond J., Dolšek M., and developed within topic 2, proposes an original method for the quantification of the loss of containment due to seismically-induced liquid overtopping of tanks with floating roofs, which is addressed by introducing a risk-targeted freeboard seismic design. The proposed practice-oriented procedure can be applied to new or existing tanks for which the freeboard was designed based on the tank wall height or liquid height, respectively. It combines the conventional seismic risk equation, and the code-based equation for the maximum vertical liquid displacement at the tank wall corresponding to the seismic action. Parametric studies were conducted to obtain insights into the sensitivity of risk-targeted freeboards to the design input parameters. A design procedure was also used to develop risk-targeted freeboard maps for Slovenia. Given the attention that the scientific community is paying on topic 3, its growth is accelerating. In the industrial field the role of ancillary elements is recognized to be of vital importance because even a simple (nonstructural) failure could result in severe consequences. In this respect the third paper titled: “Acceleration‑sensitive ancillary elements in industrial facilities: alternative seismic design approaches in the new Eurocode” by Kazantzi, A. K., Karaferis N. D., Melissianos V. E., Vamvatsikos D., undertakes a comparison study to investigate the seismic performance of ancillary elements in industrial facilities that are designed according to the regulations prescribed by the three design routes offered in the 2022 revised version of Eurocode 8. With respect to ancillary elements in the civil field, the design methodologies offered in Eurocode 8 – Part 4 (prEN 1998–4:2022) are less sensitive to uncertainty in the properties of the supporting structure and the ancillary elements and hence deliver design products that possess consistently safe seismic performance even in cases where a component finds its vibration period accidentally tuned to the period of the supporting structure. Safety barriers is another critical aspect in designing new industrial facilities or mitigating the seismic vulnerability of existing ones. In this respect the fourth paper titled: “Seismic vibration mitigation of steel storage tanks by metafoundations endowed with linear and bistable columns” by Guner T. Bursi O.S., Broccardo M., a new mitigation strategy for seismic mitigation of typical storage tanks is proposed, where extreme loading conditions are considered by safe shutdown earthquakes. To protect the tank from strong earthquakes, finite locally-resonant multiple-degree-of freedom metafoundations were designed and developed; resonator parameters together with bistable columns were optimized by means of an improved time domain multiobjective optimization procedure. The performance of the optimized metafoundations was assessed by means of time history analyses and results were compared with a storage tank endowed with two rigid foundation solutions. A group of four papers are devoted to topic 5. The fifth paper is titled “The Generalized E-DVA Method: A New Approach For Multi-modal Pushover Analysis Under Multi-component Earthquakes With Local Variables Maximization” by Lherminier O., Erlicher S., Huguet M., Civera, M., Ceravolo R., Barakat M.; it deals with a new pushover analysis approach for structures in hazardous plants subjected to seismic NaTech risk. The procedure applies a linear combination of modal load patterns, defined accordingly to the well-established Direct Vectorial Addition (DVA) method. With respect to other existing multi-modal pushover analysis techniques, elliptical response envelopes are employed to calculate the corresponding combination factors. The sixth paper titled “Do soft soil layers reduce the seismic kinematic distress of onshore high-pressure gas pipelines?” by Makrakis N., Psarropoulos P.N., Sextos A., Tsompanakis Y., recognizes the importance of onshore high-pressure gas pipelines as critical infrastructure that usually cross seismic—prone regions and are vulnerable to permanent ground deformations due to active seismic faults. The study investigates the impact of soft soil layers on the seismic kinematic distress of onshore gas pipelines. An extensive parametric analysis is performed considering different faulting mechanisms and fault dip angles, as well as soil geometry and mechanical properties. The outcome of the paper is a set of design charts and tables for the preliminary seismic design of onshore high-pressure gas pipelines based on the prediction of pipeline deformations. The seventh paper titled “Field reconnaissance on seismic performance and functionality of Turkish industrial facilities affected by the 2023 Kahramanmaras earthquake sequence” by Sagbas G., Sheikhi Garjan R, Sarikaya K., Deniz D., analyzes the effects the recent catastrophic earthquakes in southeast Turkiye, affecting 15 million-residents and a significant portion of its industrial community. The inspection results show that the earthquake sequence had a significant impact on industrial facilities, resulting in enormous economic losses and business disruptions lasting three months to two years. The most affected facilities were found to be those built before 2000, as well as precast reinforced concrete structures with pin-supported roofs. As a result, these types of facilities in earthquake-prone areas are strongly advised to be re-evaluated. Furthermore, various nonstructural building components, such as infills, claddings and equipment/machinery, were substantially damaged at the majority of the assessed sites, causing lengthy interruptions. An interesting investigation on seismic performance of slender storage tanks is offered by Holtschoppen B., Knoedel P. in the eighth paper titled “Seismic response of slender storage tanks on tube feet or skirt support”. Slender storage tanks on tube feet or skirt support are essential components of industrial facilities and often contain large amounts of hazardous liquids. A procedure is suggested that lowers the overall stress resultants by calculating the hydrodynamic pressure and load components as a function of the geometrical characteristics of the tank. The general concept was developed for flat bottom tanks but can be transferred—with certain adjustments—to the considered slender storage tanks on tube feet or skirts. Its capability for design load reduction in comparison to the simplified calculation method is shown on an example case study. Papers nine and ten are devoted to quantitative NaTech risk and resilience estimation. The paper titled “A probabilistic framework for the estimation of resilience in major-hazard industrial plants under seismic loading” by Kalemi B., Caputo A.C., Corritore C., Paolacci F., presents a probabilistic process flow-based framework for assessment of industrial plant resilience and economic losses in case of seismic events. Uncertainties are considered in the ability of plant equipment to withstand the disruption, and also in the recovery process including equipment recovery durations and recovery costs. Monte Carlo Simulation is used to account for the uncertainties of the model. A black carbon plant is used as a case study to show the applicability of the model. Results and capability of the proposed model shows that it can be a useful tool for decision makers, plant owners, insurance companies, emergency managers and plant designers in their decision-making process. The last paper titled “Seismic Risk and Resilience Analysis of Industrial Facilities” by Tabandeh A., Sharma N., Gardoni P., proposes a formulation to model the functionality of interacting industrial facilities and infrastructure using a system of coupled differential equations, representing dynamic processes on interdependent networked systems. The equations are subject to uncertain initial conditions and have uncertain coefficients, capturing the effects of uncertainties in earthquake intensity measures, structural damage, and post-disaster recovery process. The paper presents a computationally tractable approach to quantify and propagate various sources of uncertainty through the formulated equations. The paper illustrates the proposed approach for the seismic resilience analysis of a hypothetical but realistic shipping company in the city of Memphis in Tennessee, United States. The example models the effects of dependent water and power infrastructure systems on the functionality disruption and recovery of networked industrial facilities subject to seismic hazards. The Guest Editors of this special issue would like to express their sincere gratitude to all authors for their valuable contributions that will certainly represent a reference point for the risk and resilience evaluation of the process industries in the future. Finally, they want to express their appreciation to the Chief Editor Prof. Atilla Ansal for embracing and helping this special issue to come to fruition. References Caprinozzi S, Žižmond J. Dolšek M, Risk-targeted freeboard for steel storage tanks equipped with single deck floating roof. https://doi.org/10.1007/s10518-022-01564-z Guner T, Bursi OS, Erlicher S, Seismic mitigation performance of periodic foundations for small modular reactors based on linear, nonlinear and bistable behavior. https://doi.org/10.1007/s10518-023-01692-0 Holtschoppen B, Knödel P, Seismic response of slender storage tanks on tube feet or skirt support. https://doi.org/10.1007/s10518-023-01704-z Kalemi B, Corritore D, Caputo A, A probabilistic framework for the estimation of resilience in major-hazard industrial plants under seismic loading Kazantzi N, Karaferis V, Melissianos, Vamvatsikos D, Acceleration-sensitive ancillary elements in industrial facilities: alternative seismic design approaches in the new Eurocode. https://doi.org/10.1007/s10518-023-01656-4 Lherminier O, Erlicher S, Huguet1 M, Civera M, Ceravolo R, Barakat M, The Generalized E-DVA Method: A New Approach For Multi-modal Pushover Analysis Under Multi-component Earthquakes With Local Variables Maximization. https://doi.org/10.1007/s10518-023-01790-z Makrakis N, Psarropoulos PN, Sextos A, Tsompanakis Y, Do soft soil layers reduce the seismic kinematic distress of onshore high-pressure gas pipelines? https://doi.org/10.1007/s10518-023-01668-0 Pitilakis K, Butenweg C, Riga E, Apostolaki S, The new seismic hazard model ESHM20 of Europe: implications to the seismic design and risk assessment of major industrial facilities across Europe. https://doi.org/10.1007/s10518-023-01661-7 Sagbas G, Garjan RS, Sarikaya K, Deniz D, Field reconnaissance on seismic performance and functionality of Turkish industrial facilities affected by the 2023 Kahramanmaras earthquake sequence. https://doi.org/10.1007/s10518-023-01741-8 Tabandeh A, Sharma N, Gardoni P, Seismic Risk and Resilience Analysis of Industrial Facilities. https://doi.org/10.1007/s10518-023-01728-

Masonry infilled reinforced concrete frames under horizontal loading

The behaviour of infilled reinforced concrete frames under horizontal load has been widely investigated, both experimentally and numerically. Since experimental tests represent large investments, numerical simulations offer an efficient approach for a more comprehensive analysis. When RC frames with masonry infill walls are subjected to horizontal loading, their behaviour is highly non-linear after a certain limit, which makes their analysis quite difficult. The non-linear behaviour results from the complex inelastic material properties of the concrete, infill wall and conditions at the wall-frame interface. In order to investigate this non-linear behaviour in detail, a finite element model using a micro modelling approach is developed, which is able to predict the complex non-linear behaviour resulting from the different materials and their interaction. Concrete and bricks are represented by a non-linear material model, while each reinforcement bar is represented as an individual part installed in the concrete part and behaving elasto-plastically. Each brick is modelled individually and connected taking into account the non-linearity of a brick mortar interface. The same approach is followed using two finite element software packages and the results are compared with the experimental results. The numerical models show a good agreement with the experiments in predicting the overall behaviour, but also very good matching for strength capacity and drift. The results emphasize the quality and the valuable contribution of the numerical models for use in parametric studies, which are needed for the derivation of design recommendations for infilled frame structures

Monte Carlo Tree Search as an intelligent search tool in structural design problems

Monte Carlo Tree Search (MCTS) is a search technique that in the last decade emerged as a major breakthrough for Artificial Intelligence applications regarding board- and video-games. In 2016, AlphaGo, an MCTS-based software agent, outperformed the human world champion of the board game Go. This game was for long considered almost infeasible for machines, due to its immense search space and the need for a long-term strategy. Since this historical success, MCTS is considered as an effective new approach for many other scientific and technical problems. Interestingly, civil structural engineering, as a discipline, offers many tasks whose solution may benefit from intelligent search and in particular from adopting MCTS as a search tool. In this work, we show how MCTS can be adapted to search for suitable solutions of a structural engineering design problem. The problem consists of choosing the load-bearing elements in a reference reinforced concrete structure, so to achieve a set of specific dynamic characteristics. In the paper, we report the results obtained by applying both a plain and a hybrid version of single-agent MCTS. The hybrid approach consists of an integration of both MCTS and classic Genetic Algorithm (GA), the latter also serving as a term of comparison for the results. The study's outcomes may open new perspectives for the adoption of MCTS as a design tool for civil engineers

Latest findings on the behaviour factor q for the seismic design of URM buildings

Recent earthquakes as the 2012 Emilia earthquake sequence showed that recently built unreinforced masonry (URM) buildings behaved much better than expected and sustained, despite the maximum PGA values ranged between 0.20-0.30 g, either minor damage or structural damage that is deemed repairable. Especially low-rise residential and commercial masonry buildings with a code-conforming seismic design and detailing behaved in general very well without substantial damages. The low damage grades of modern masonry buildings that was observed during this earthquake series highlighted again that codified design procedures based on linear analysis can be rather conservative. Although advances in simulation tools make nonlinear calculation methods more readily accessible to designers, linear analyses will still be the standard design method for years to come. The present paper aims to improve the linear seismic design method by providing a proper definition of the q-factor of URM buildings. These q-factors are derived for low-rise URM buildings with rigid diaphragms which represent recent construction practise in low to moderate seismic areas of Italy and Germany. The behaviour factor components for deformation and energy dissipation capacity and for overstrength due to the redistribution of forces are derived by means of pushover analyses. Furthermore, considerations on the behaviour factor component due to other sources of overstrength in masonry buildings are presented. As a result of the investigations, rationally based values of the behaviour factor q to be used in linear analyses in the range of 2.0-3.0 are proposed