A practice-oriented approach for the assessment of brittle failures in existing reinforced concrete elements

A practice-oriented approach was used to assess shear failures in existing reinforced concrete (RC) elements. A simple tool, in form of non-dimensional domains, is obtained considering the capacity models suggested by European and Italian codes. The reliability of failure domains depend strictly on the reliability of the shear capacity model employed; thus, a critical review of code and literature analytical formulations was also carried out. Sezen and Moehle’s experimental database was, then, used to compare the different shear capacity models considered. The code and literature review of shear capacity models emphasizes differences and affinities of the analytical approaches followed in different countries. The domains carried out can be used as a practical instrument aimed at checking shear–flexure hierarchy in existing RC elements and contextualized in the framework of preliminary assessment given the character of input information required. Preliminary applications of the domains are also provided, and emphasize the effectiveness of the new tool for detailed and large scale assessment of existing RC structures

Eurocode-based seismic assessment of modern heritage RC structures:The case of the <i>Tower of the Nations</i> in Naples (Italy)

Given the interest earned recently by modern heritage structures, seismic assessment criteria of Eurocode 8 for ordinary reinforced concrete structures are applied to a modern heritage RC building. This case study, the Tower of the Nations in Naples, was designed at the end of 1930s. Modal dynamic identification, in situ inspections and testing provided the necessary knowledge of the structure in terms of geometry, structural details, and material properties. Two nonlinear models of the structure are built up in both the hypotheses of accounting and not accounting for tuff infills’ stiffness and strength contribution. Lumped plasticity model for reinforced concrete elements and equivalent strut macro-models for tuff and concrete infills are employed. Seismic assessment through nonlinear dynamic analyses is carried out for both limit states of Significant Damage and Damage Limitation. Assessment of bare and infilled models emphasizes a lower demand in terms of maximum interstorey drift of the infilled model with respect to the bare model, for both limit states considered. Record-to-record variability for the sets of seven records becomes larger if infills strength and stiffness contribution is taken into account. Outcome of the assessment is not affected by infills, i.e. the structure can be considered safe (according to EC8 provisions) for both limit states, and in both modeling hypotheses. On the other hand, the ratio demand over capacity, for both the limit states considered, is strictly influenced by infills’ contribution. Assessment tools provided for ordinary RC structures can be addressed to modern heritage buildings as shown in this case study, even if specific care is necessary for nonlinear structural modeling in case of non-conventional structural elements and non-conventional structural materials (e.g., tuff infills in lieu of clay hollow brick infills)

Influence of infill panels on the seismic behaviour of a r/c frame designed according to modern buildings codes

It has been broadly shown that presence of infill panels as closing elements of R/C frame buildings has a significant influence on global structural behaviour. Nevertheless, infill elements are not usually considered in the modelling process during the design phase. The present work investigates the effect of infill masonry walls on the dynamic characteristics of a R/C MRF building, designed according to a modern seismic building code, and on its seismic performance at different levels of seismic intensity. An analytical investigation is carried out through eigenvalue analysis on both bare and infilled structure, in order to calibrate the elastic properties of the concrete and infills according to in situ tests; nonlinear static analyses are also performed to characterize the inelastic behaviour. The infill system considerably affects the behaviour of the examined structure, in agreement with earlier studies related to very simple and usually ¿unrealistic¿ structures. This result becomes more reliable due to the consistency between the results of the eigenvalue analysis and the experimental dynamic data

A component-level methodology to evaluate the seismic repair costs of infills and services for Italian RC buildings

AbstractThe reliable estimation of seismic losses due to damage to buildings is paramount for the post-emergency management and the planning of recovery activities. For residential reinforced concrete (RC) infilled buildings, a significant role in the computation of seismic loss is played by non-structural components, above all infills, partitions and services, as shown in past earthquakes. In this work, a component-based methodology is proposed to assess seismic losses for residential RC buildings in Mediterranean region. The attention is focused on the repairing activities for masonry infills (typical enclosure or partitions elements in Italian and Mediterranean RC buildings), and for services (plumbing systems, electric equipment, floor/wall tiles…), commonly enclosed within the infill panels for the considered building typology. The described methodology can be used starting from the expected damage level to infills and partitions. It adopts given repair unit costs at different damage states of infills. The loss estimation methodology has been, first, validated by comparing predicted and actual repair costs for specific case-study buildings damaged by L'Aquila (Italy) 2009 earthquake. Then, the methodology has been applied to a wide dataset of RC buildings (about 2500 residential buildings) damaged by L'Aquila earthquake available from the literature, to show its possible application at a large-scale level. A good agreement between observed and predicted costs is obtained both for specific case-study buildings and for the wider building stock, especially when damage to structural components is very limited

Evolution of the seismic vulnerability of masonry buildings based on the damage data from L'Aquila 2009 event

AbstractThe purpose of this study is the analysis of vulnerability trends, with particular emphasis to the evolution of the seismic behaviour of masonry buildings over the years due to the improvements in construction practices and to the enhancement of building materials over the years, also related to the subsequent enactment of seismic prescriptions. To this aim, residential masonry buildings damaged after the 2009 L'Aquila earthquake are considered, coming from the online platform Da.D.O. (Database di Danno Osservato, Database of Observed Damage) recently released from the Italian Department of Civil Protection. General features of all the parameters available from the original database are thoroughly analysed, a selection of which is used for vulnerability analysis, namely the period of construction and the design type, the presence of structural interventions, the type of horizontal structure. Vulnerability curves are obtained through an optimization technique, minimizing the deviation between observed and predicted damage. PGA from ShakeMap is used for ground motion characterization. Damage levels defined according to the European Macroseismic Scale are considered, obtained from the observed damage for vertical structures collected during the inspections. Vulnerability curves are firstly obtained as a function of period of construction and horizontal structural types, limited to the irregular layout and bad quality vertical type only, highlighting their clear influence on seismic behaviour. Lastly, the effectiveness of retrofit intervention is evaluated comparing the vulnerability curves for strengthened masonry buildings compared to those not subjected to any retrofit interventions

EMPIRICAL UNREINFORCED MASONRY INFILL MACRO-MODEL ACCOUNTING FOR IN-PLANE/OUT-OF-PLANE INTERACTION

Unreinforced Masonry (URM) infills are widely used in Reinforced Concrete (RC) structures in Mediterranean countries. URM infills are subjected to the seismic action in their plane, i.e. in the In Plane (IP) direction, and in the Out Of Plane (OOP) direction. The IP displacement demand reduce the OOP capacity and vice-versa: this phenomenon is called IP-OOP interaction. A large number of studies has been carried out on the IP behaviour of infills, while their OOP response and the IP-OOP interaction have been less investigated. In this paper, a review of code and literature provisions concerning URM infills OOP behaviour is presented together with a review of the experimental tests carried out to investigate the infills OOP response and the effects of the IP-OOP interaction. An experimental database is collected to assess the effectiveness of literature and code provisions and to propose new empirical formulations both for predicting infills OOP strength, stiffness and displacement capacity and for modelling the effects of IP displacement demand on the OOP behavior and vice versa. A state of art on infills OOP behaviour and IP-OOP interaction modelling is presented. Most of these distributed-plasticity models are not based on experimental evidences and do not allow taking into account the IP and OOP stiffness degradation due to OOP and IP actions, respectively. A lumped-plasticity macro-model based on the proposed empirical formulations and conceived to represent the IP and the OOP behavior taking into account the mutual interaction effects is defined. Part of the proposed modelling strategy is a routine that removes the whole infill panel from the structural model in case of its IP or OOP collapse. The proposed model is used for an example application showing the effects of taking into account or neglecting the IP-OOP interaction phenomena during structural analyses

Seismic performances and behaviour factor of wide-beam and deep-beam RC frames

[EN] Reinforced Concrete Wide-Beam Frames (WBF) are a common architectural solution in Mediterranean countries. On this structural typology there is not yet a uniform approach among European codes: while Eurocode 8, as other relevant seismic codes in USA and New Zealand, considers WBF capable of high ductility performances, still in recent versions of Spanish and Italian seismic codes there is cap to the maximum behaviour factor (q) for this structural system. In order to verify the appropriateness of such provisions, seismic performances of WBF and conventional deep beam frames (DBF) are comparatively assessed through nonlinear static analyses. The same architectural layout of a typical European 5-storey RC housing unit is designed as WBF and DBF according to Eurocode 8, adopting different stiffness assumptions, and according to the Spanish seismic code NCSE-02. Based on detailed assessment results, a simplified parametric assessment of 72 frames designed according to Eurocode 8, Italian seismic code NTC and NCSE-02 is then considered assuming similar q for WBF and DBF. Results suggest that any reduction of behaviour factor prescribed for wide-beam frames is at least obsolete. In fact, even if wide beams show lower local ductility than deep beams, generally WBF provide at least similar global seismic capacities than DBF, especially in frames whose design is ruled by serviceability limit state (i.e., damage limitation). (C) 2016 Elsevier Ltd. All rights reserved.This work has been developed in cooperation with Rete dei Laboratori Universitari di Ingegneria Sismica – ReLUIS – for the research program founded by the Dipartimento della Protezione Civile (2014–2018).Gómez-Martínez, F.; Alonso Durá, A.; De Luca, F.; Verderame, GM. (2016). Seismic performances and behaviour factor of wide-beam and deep-beam RC frames. Engineering Structures. 125:107-123. https://doi.org/10.1016/j.engstruct.2016.06.034S10712312

Ductility of wide-beam RC frames as lateral resisting system

[EN] Some Mediterranean seismic codes consider wide-beam reinforced concrete moment resisting frames (WBF) as horizontal load carrying systems that cannot guarantee high ductility performances. Conversely, Eurocode 8 allows High Ductility Class (DCH) design for such structural systems. Code prescriptions related to WBF are systematically investigated. In particular, lesson learnt for previous earthquakes, historical reasons, and experimental and numerical studies underpinning specific prescriptions on wide beams in worldwide seismic codes are discussed. Local and global ductility of WBF are then analytically investigated through (1) a parametric study on chord rotations of wide beams with respect to that of deep beams, and (2) a spectral-based comparison of WBF with conventional reinforced concrete moment resisting frames (i.e. with deep beams). Results show that the set of prescriptions given by modern seismic codes provides sufficient ductility to WBF designed in DCH. In fact, global capacity of WBF relies more on the lateral stiffness of the frames and on the overstrength of columns rather than on the local ductility of wide beams, which is systematically lower with respect to that of deep beams.Gómez-Martínez, F.; Alonso Durá, A.; De Luca, F.; Verderame, GM. (2016). Ductility of wide-beam RC frames as lateral resisting system. Bulletin of Earthquake Engineering. 14(6):1545-1569. doi:10.1007/s10518-016-9891-xS15451569146ACI (1989) Building code requirements for reinforced concrete (ACI 318-89). ACI Committee 318, American Concrete Institute, Farmington Hills, Michigan, USAACI (2008) Building code requirements for structural concrete (ACI 318-08) and commentary (318-08). ACI Committee 318, American Concrete Institute, Farmington Hills, Michigan, USAACI-ASCE (1991) Recommendations for design of beam-column connections in monolithic reinforced concrete structures (ACI 352R-91). Joint ACI-ASCE Committee 352, American Concrete Institute, Farmington Hills, Michigan, USAACI-ASCE (2002) Recommendations for design of beam-column connections in monolithic reinforced concrete structures (ACI 352R-02). Joint ACI-ASCE Committee 352, American Concrete Institute, Farmington Hills, Michigan, USAArslan MH, Korkmaz HH (2007) What is to be learned from damage and failure of reinforced concrete structures during recent earthquakes in Turkey? Eng Fail Anal 14(1):1–22ASCE (2007) Seismic Rehabilitation of Existing Buildings, ASCE/SEI 41-06. American Society of Civil Engineers, RestonASCE (2010) Minimum Design Loads for Building and Other Structures, ASCE/SEI 7-10. American Society of Civil Engineers, RestonBenavent-Climent A (2007) Seismic behavior of RC side beam-column connections under dynamic loading. J Earthquake Eng 11:493–511Benavent-Climent A, Zahran R (2010) An energy-based procedure for the assessment of seismic capacity of existing frames: application to RC wide beam systems in Spain. Soil Dyn Earthq Eng 30:354–367Benavent-Climent A, Cahís X, Zahran R (2009) Exterior wide beam-column connections in existing RC frames subjected to lateral earthquake loads. Eng Struct 31:1414–1424Benavent-Climent A, Cahís X, Vico JM (2010) Interior wide beam-column connections in existing RC frames subjected to lateral earthquake loading. Bull Earthq Eng 8:401–420BHRC (2004) Iranian Code of Practice for Seismic Resistant Design of Buildings. Standard Nº 2800, 3rd edn. Building and Housing Research Center, TehranBorzi B, Elnashai AS (2000) Refined force reduction factors for seismic design. Eng Struct 22:1244–1260Borzi B, Pinho R, Crowley H (2008) Simplified pushover-based vulnerability analysis for large-scale assessment of RC buildings. Eng Struct 30:804–820BSI (2004) Eurocode 2: Design of concrete structures: Part 1-1: General rules and rules for buildings. British Standards Institutions, LondonCalvi GM (1999) A displacement-based approach for vulnerability evaluation of classes of buildings. J Earthquake Eng 3(3):411–438CDSC (1994) Seismic construction code, NCSR-94. Committee for the Development of Seismic Codes, Spanish Ministry of Construction, Madrid, Spain (in Spanish)CDSC (2002) Seismic construction code, NCSE-02. Committee for the Development of Seismic Codes, Spanish Ministry of Construction, Madrid, Spain (in Spanish)CEN (2004) Eurocode 8: design of structures for earthquake resistance—part 1: general rules, seismic actions and rules for buildings. European Standard EN 1998-1:2003—Comité Européen de Normalisation, Brussels, BelgiumCEN (2005) Eurocode 8: design of structures for earthquake resistance—part 3: assessment and retrofitting of buildings. European Standard EN 1998-1:2005—Comité Européen de Normalisation, Brussels, BelgiumCheung PC, Paulay T, Park R (1991) Mechanisms of slab contributions in beam-column subassemblages. ACI Spec Publ 123Cosenza E, Manfredi G, Polese M, Verderame GM (2005) A multilevel approach to the capacity assessment of existing RC buildings. J Earthquake Eng 9(1):1–22Crowley H, Pinho R (2010) Revisiting Eurocode 8 formulae for periods of vibration and their employment in linear seismic analysis. Earthquake Eng Struct Dynam 39:223–235CS.LL.PP (2009) Instructions for the application of the technique code for the Constructions. Official Gazette of the Italian Republic, 47, Regular Supplement no. 27 (in Italian)De Luca F, Vamvatsikos D, Iervolino I (2013) Near-optimal piecewise linear fits of static pushover capacity curves for equivalent SDOF analysis. Earthquake Eng Struct Dynam 42(4):523–543De Luca F, Verderame GM, Gómez-Martínez F, Pérez-García A (2014) The structural role played by masonry infills on RC building performances after the 2011 Lorca, Spain, earthquake. Bull Earthq Eng 12(5):1999–2026Decanini LD, Mollaioli F (2000) Analisi di vulnerabilità sismica di edifici in cemento armato pre-normativa. In: Cosenza E (ed) Comportamento sismico di edifici in cemento armato progettati per carichi verticali. CNR—Gruppo Nazionale per la Difesa dei Terremoti, Rome (in Italian)Dolšek M, Fajfar P (2004) IN2—a simple alternative for IDA. In: Proceedings of the 13th World conference on Earthquake Engineering. August 1–6, Vancouver, Canada. Paper 3353Domínguez D, López-Almansa F, Benavent-Climent A (2014) Comportamiento para el terremoto de Lorca de 11-05-2011, de edificios de vigas planas proyectados sin tener en cuenta la acción sísmica. Informes de la Construcción 66(533):e008 (in Spanish)Domínguez D, López-Almansa F, Benavent-Climent A (2016) Would RC wide-beam buildings in Spain have survived Lorca earthquake (11-05-2011)? Eng Struct 108:134–154Dönmez C (2013) Seismic Performance of Wide-Beam Infill-Joist Block RC Frames in Turkey. J Perform Constr Facil 29(1):04014026Fadwa I, Ali TA, Nazih E, Sara M (2014) Reinforced concrete wide and conventional beam-column connections subjected to lateral load. Eng Struct 76:34–48Fardis MN (2009) Seismic design, assessment and retrofitting of concrete, Buildings edn. Springer, LondonGentry TR, Wight JK (1992) Reinforced concrete wide beam-column connections under earthquake-type loading. Report no. UMCEE 92-12. Department of Civil and Environmental Engineering, University of Michigan, Ann Arbor, Michigan, USAGómez-Martínez F (2015) FAST simplified vulnerability approach for seismic assessment of infilled RC MRF buildings and its application to the 2011 Lorca (Spain) earthquake. Ph.D. Thesis, Polytechnic University of Valencia, SpainGómez-Martínez F, Pérez García A, De Luca F, Verderame GM (2015a) Comportamiento de los edificios de HA con tabiquería durante el sismo de Lorca de 2011: aplicación del método FAST. Informes de la Construcción 67(537):e065 (in Spanish)Gómez-Martínez F, Pérez-García A, Alonso Durá A, Martínez Boquera A, Verderame GM (2015b) Eficacia de la norma NCSE-02 a la luz de los daños e intervenciones tras el sismo de Lorca de 2011. In: Proceedings of Congreso Internacional sobre Intervención en Obras Arquitectónicas tras Sismo: L’Aquila (2009), Lorca (2011) y Emilia Romagna (2012), May 13–14, Murcia, Spain (in Spanish)Gómez-Martínez F, Verderame GM, De Luca F, Pérez-García A, Alonso-Durá, A (2015c). High ductility seismic performances of wide-beam RC frames. In; XVI Convegno ANIDIS. September 13–17, L'Aquila, ItalyHawkins NM, Mitchell D (1979) Progressive collapse of flat plate structures. 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Morbidity and mortality weekly report, Vol. 2, no. 47, December 4, 1953

Provisional information on selected notifiable diseases in the United States for week ended November 28, 1953 -- Provisional statistics for deaths in selected cities for week ended November 28, 1953Epidemiological reports: Botulism -- Psittacosis -- Gastro-enteritisTable 1. Comparative data for cases for specified notifiable diseases: United States -- Table 2. Cases of specified diseases with comparative data: United States, each division and state for week ended November 28, 1953 -- Table 3. Cases of specified diseases: selected cities for week ended November 28, 1953 -- Table 4. Deaths in selected cities by geographic division -- Table 5. Deaths in selected cities for week ended November 28, 195

An empirical approach for nonlinear modelling and deformation capacity assessment of RC columns with plain bars

This study proposes an empirical-based approach for the nonlinear modelling and deformation capacity assessment of flexure-controlled Reinforced Concrete (RC) columns with plain bars, providing an estimate of the expected post-elastic response backbone through formulations based on regression of experimental data. To this end, a database of tests on RC columns with plain bars is collected from literature. The specimens have different axial load, material properties, geometry, and longitudinal and transverse reinforcement ratio. Force-displacement data are collected and processed for each specimen. The backbone of the experimental base moment-chord rotation response is evaluated for each test, and characteristic points corresponding to yielding, maximum, “ultimate”, and zero resistance conditions are identified. Potential predictors are investigated and empirical predictive equations are proposed for these points, based on a statistical analysis of data. Predictions of the proposed model are compared with literature and code provisions