Michelangelo Laterza

Modified Steel Bar Model Incorporating Bond-Slip for Seismic Assessment of Concrete Structures

This paper presents a simplified model for describing the response of a longitudinal bar embedded in concrete, taking into account the bond-slip phenomenon. The model is developed by assuming a linear bond-slip field along the bar anchorage length and provides a simplified stress-strain relationship to assign to the longitudinal reinforcement. The analytical approach adopted makes the proposed model very convenient from a computational standpoint because, unlike many other refined models, it does not require a multilevel iterative process. Moreover, the assumptions made are particularly appropriate for modeling bond-slip of smooth bars generally used in older reinforced concrete buildings. The implementation strategy of the proposed bond-slip model in general-purpose nonlinear structural analysis software and comparisons with experimental results are discussed in a companion paper.

R/C Existing Structures with Smooth Reinforcing Bars: Experimental Behaviour of Beam-Column Joints Subject to Cyclic Lateral Loads

The paper illustrates the results of experimental tests performed on sub-assemblages of R/C (Reinforced Concrete) existing structures, designed only for gravity loads In order to estimate failure mechanisms and ductility properties, four internal and external R/C beam-column joints were built and tested. The specimens were built by using concrete with low strength and smooth reinforcing bars, without hoops into the panel zone. The tests were performed by increasing cyclic horizontal displacements up to the collapse. The experimental results show that seismic response of these kind of structures is mainly influenced by bond slips of longitudinal bars, and that the shear collapse regards external joints rather the internal ones. Failure mechanisms observed (column plastic hingings for internal joints, shear failure for external joints) point out the vulnerability of these structures due to the soft storey mechanism. The study is significant for better understanding of the inelastic seismic behavior of the R/C existing buildings with smooth bars, and for evaluating the effectiveness of the model classical assumptions.

Validation of a Modified Steel Bar Model Incorporating Bond-Slip for Seismic Assessment of Concrete Structures

In this paper the implementation and validation of a modified steel bar model including bond-slip of longitudinal bars that was proposed in a companion paper is discussed. The model is developed on the key assumption of linear slip field along the steel bar with different configurations at the ends of the bar. The simplified model is capable of predicting the axial slip displacement with suitable accuracy compared with a refined model but with considerably fewer computational steps. The proposed model avoids nested iterations in the context of fiber model discretization of a section that requires the representation of all actions in terms of stress and strain. The model is applied to two component tests—one with poor and another with improved reinforcing detailing. Findings from the simulations indicate that the proposed model is more suitable for use in connections with poor detailing and pronounced slip in the plastic hinge zones.

An Analytical Formulation of Stress-Block Parameters for Confined Con- crete

In order to evaluate the capacity of RC members, the main codes allow the use of stress-strain laws that can re- produce closely the real behaviour of concrete, as opposed to parabola-rectangular or equivalent rectangular diagrams. Both sectional strength and ductility depend on the law of concrete, therefore they are influenced by the confinement of members, as evidenced in the literature. In this paper a possible design approach is presented, based on classic section analysis methods. The method uses parameters that represent the stress-strain law of confined concrete. The studies car- ried out show that such parameters can be chosen through simple relationships depending on the strength of non-confined concrete, on the amount and geometry of longitudinal and transverse reinforcement, and on the geometry of the section. At this aim some numerical analyses have been performed using an analytical model of confined concrete, capable of tak- ing into account all the mentioned effects, even in the case of various sources of confinement, when different types of hoops and external elements (FRP wrappings, steel plates, etc.) are used. More in detail, the section interaction diagrams for the different limit states requires the definition of an appropriate upper bound for the strain of concrete. Therefore the study focuses on the possibility of using stress-blocks depending on the maximum stain assumed, or on the level of resid- ual stress accepted in concrete according to a specified limit state. Further studies will extend the parametric analysis in order to obtain design equations to be implemented in codes.

Comparisons of Codal Detailing Rules for Curvature Ductility and Numerical Investigations

In moment resisting frame structures special detailing rules are applied to critical regions of primary columns and beams to ensure adequate curvature ductility. This is necessary for dissipating earthquake energy through hysteretical behavior of critical regions where inelastic flexural excursions occur. In this paper codal detailing rules for designing lon- gitudinal and transverse reinforcement of primary elements as function of curvature ductility are assessed. Four seismic codes are considered: Italian code, New Zealand code, Eurocode 8 and American code. Non-linear monotonic moment- curvature analyses are performed on some sections of columns and beams detailed in according to the considered codal provisions. In the analyses the confinement effects within the concrete core have been taken into account as well. The pa- per concludes comparing the measured curvature ductility of the studied sections with the expected one by the codal pro- visions within the critical regions.

Estimation of Churches Frequencies Based on Simplified Geometry Parameters

Nowadays, the modal properties of structures can be obtained by experimental methods that are still expensive for professionals who have to deal with the seismic assessment. Additionally, for heritage buildings, due to their complexity, the identification of the modal properties can be challenging and requires of experience on the field. This paper aims to develop a methodology to predict the frequency response of churches based on simplified geometrical parameters. In this context, an extensive literature review was carried out to collect data, aiming to define the principal typologies of churches. Afterwards, a parametric analysis with numerical simulations of the eigenvalue problem was performed to identify which are the main geometrical parameters that influence the dynamic behavior of the churches. The correlations between the natural frequencies and relevant geometrical parameters are illustrated and discussed in order to develop a proposal for the estimation of the natural frequencies of the churches. Churches with single nave and three naves were defined as the two principal types of churches, and six equations were proposed, aiming to estimate the first three natural frequencies for each type of church. Finally, the methodology was validated on real case studies found in literature, in which experimental identification of frequencies was performed. This comparison allowed to evaluate the accuracy of the method to estimate the natural frequencies.

Seismic Vulnerability and Risk Assessment of Historic Constructions: The Case of Masonry and Adobe Churches in Italy and Chile

Nowadays, disasters in seismic-prone areas such as Italy and Chile, continue to cause dramatic human and economic consequences and affecting, among others, very ancient and historical churches, due to their high seismic vulnerability and probably due to the lack of risk management plans for the conservation of cultural property. This paper focuses on rapid seismic risk assessment by applying two simplified methods, based on expert judgement and observed damage, in old masonry churches, which aim to identify the most vulnerable elements and correlated threats that would act as site effects under the seismic action, for establishing intervention priority lists and for planning preventive conservation projects. The case studies are: the church of Sant’Agostino, built in stone masonry and located in Matera, an area with moderate seismicity in southern Italy; the church of San Francisco de Chiu Chiu, built in adobe and located in Calama, an area with average seismicity in the Andean northern Chile; and the church of San Francisco Baron, built in adobe and brick masonry, and located in Valparaiso, an area with high seismicity on the central coast of Chile.

Simplified Seismic Analyses of Ancient Churches in Matera’s Landscape

ABSTRACT Nowadays, safety assessment under seismic loading of historical masonry buildings, such as ancient churches, is an actual and important topic due to the potential human and economic losses involved even for a partial collapse. Therefore, the prevention and mitigation of their seismic risk would result the best intervention for preserving in the future these monuments of inestimable value. To date, in literature many methods are available for evaluating the seismic vulnerability and the related risk. In particular, this study focuses on the first two simplified evaluation methods proposed by the current Italian directive containing the guide lines for assessment and reduction of cultural heritage seismic risk. The methods, having an increasing precision level, may be applied in sequence at a different scale for screening and identifying the present priorities, and for designing the required interventions. In this article, these methods are applied to five ancient masonry churches located within the UNESCO site of the “Sassi” of Matera (Italy), a seismic-prone area with moderate seismicity. Afterward, also a new simplified method is applied, in the form of fast appraisal method useful for preliminary ranking the seismic performances of the case studies at a territorial scale.

Basic Seismic Response Capability of Hospitals in Lima, Peru

OBJECTIVE The objective of the study was to research the basic seismic response capability (BSRC) of hospitals in Lima Metropolitana. A large number of wounded could be registered in case of an earthquake; therefore, operational hospitals are necessary to cure the injured. The study focused on the operational performance of the hospitals, autonomies of essential resources such as power, water, medical gases, and medicine, in addition to the availability of emergency communication system and ambulances. METHODS Data by a probabilistic seismic risk analysis have been used to assess the operational level of the hospitals. Subsequently, availability of an essential resource has been combined with the immediately operational hospitals to evaluate the BSRC of the health facilities. RESULTS Forty-one of Limas hospitals have been analyzed for a seismic event with 72-100 years of a return period. Three hospitals (7.3%) were capable to work in a self-sufficient manner for 72 hours, another three (7.3%) for 24 hours, and one (2.4%) for 12 hours. CONCLUSION Results showed a low performance of the hospitals in case of an earthquake. The issue is due to the high seismic vulnerability of the existing structures. Given the importance of Lima city in Peru, structural and nonstructural retrofitting plans should be implemented to improve the preparedness of the health system in case of an emergency. (Disaster Med Public Health Preparedness. 2019;13:138-143).

Spatial Analysis and Ranking for Retrofitting of the School Network in Lima, Peru

Retrofitting and management strategies of existing buildings are actually a crucial topic. In this work, an approach based on GIS and MCDM method has been used in order to define a retrofitting ranking for seismic risk management. The main goal is to define a framework based on a multidisciplinary approach. The proposed procedure can be used in different ways and applications. It can be the basis of seismic risk mitigation strategies which are a typical problem of public administrations. Due to both the amount of essential buildings that require seismic retrofitting and the restricted economic availability, it is necessary to prioritize interventions on large territorial scale in order to optimize the allocation of available economic resources and ensure an efficient seismic risk mitigation. The paper provides a simple and rational seismic risk mitigation policy in order to consider the possible variables or disciplines that are not generally integrated in studies of risk (not only seismic) on a large territorial scale.