Non-linear fe modelling of seismic pounding and damped-mitigating interconnection between a r/c tower and a masonry church

The finite element analysis of pounding represents one of the most critical issues for the assessment of the seismic performance of R/C structures built at poor distance from adjacent buildings. The effects of pounding can be particularly severe in slender R/C heritage structures, including civic or bell towers. An emblematic case study falling in this class of structures, i.e. a monumental R/C bell tower constructed in the early 1960s in Florence, is analyzed in this paper. Pounding collisions are simulated with a multi-link viscoelastic contact model originally implemented in this study. The results of the non-linear dynamic enquiry carried out with this model show that pounding affects the seismic response of the bell tower and the adjacent church as early as an input seismic action scaled at the amplitude of the normative basic design earthquake level. A retrofit hypothesis to prevent pounding is then proposed, which consists in linking the two structures by means of a pair of fluid-viscous dissipaters. Thanks to the supplemental damping action produced by these devices, the impacts are totally annulled, bringing the structural members of the tower to safe levels

A viable base isolation strategy for the advanced seismic retrofit of an R/C building

A base isolation seismic retrofit solution for a reinforced concrete school building, designed with earlier Technical Standards, is presented in this paper. The structural characteristics of the building are initially discussed. The mechanical parameters and installation details of the isolation system, incorporating double friction pendulum sliding bearings as protective devices, are then illustrated. The results of the performance assessment analyses carried out in original and rehabilitated conditions show a remarkable enhancement of the seismic response capacities of the structure in base-isolated configuration. The high performance levels postulated in the retrofit design are reached with notably lower costs and architectural intrusion as compared to traditional rehabilitation strategies. \ua9 2014 Stefano Sorace and Gloria Terenzi

Retrofit hypotheses of a pre-normative steel school building by fluid viscous damper-based technologies

Two advanced seismic protection technologies, and relevant hypotheses of application to the retrofit of an Italian pre-normative steel school building, are examined in this paper. The two technologies consist in a dissipative bracing system, and a damped cable system, both incorporating pressurized fluid viscous dampers as protecting devices. The essential characteristics and performance of the dampers and the two systems, along with their analytical/computational modelling criteria, are recalled in the first part of this paper. The dimensions, layouts and locations selected for the constituting elements of the two rehabilitation solutions are then discussed. A synthesis of the nonlinear dynamic analyses and performance-based evaluations carried out on the case study building in original and protected conditions is finally proposed

Existing prefab R/C industrial buildings: Seismic assessment and supplemental damping-based retrofit

A research study on prefab reinforced concrete buildings designed with older Technical Standards is presented in this paper, where attention is focused on hall-type industrial structures. A representative case study, which includes the main sources of seismic vulnerability, is examined in detail. The possible rigid rotation of the bottom end zone of columns, which are encased in smooth socket-type foundations, and the frictional contact between the neoprene pads situated on top of the columns and the terminal zone of the roof girders are modelled in time-history assessment analyses. The latter are initially carried out by assuming an elastic behaviour of columns, highlighting unsafe response conditions under seismic action scaled at the basic design earthquake level, and near-collapse at the maximum considered earthquake level, which is caused by the loss of support of several girders from the neoprene pads. A second step of the analyses, where plastic behaviour of columns is investigated by incorporating fiber-type plastic hinges at their bottom end sections, assesses a remarkable ductility demand, as well as potential collapse induced by the complete loss of support of girders. The high lateral displacements of columns may also cause failure of the fastenings of the connected cladding panels, likely to results in their overturning-induced collapse. Based on these data, a supplemental damping-based retrofit hypothesis is proposed, consisting in the installation of dissipative braces equipped with pressurized fluid viscous spring-dampers. The protective system allows attaining a completely undamaged response of structural and non-structural members, and therefore meeting the requirements of the Immediate Occupancy limit state, up to the maximum considered earthquake level

Non-linear dynamic design procedure of FV spring-dampers for base isolation - Frame building applications

The non-linear dynamic design procedure of fluid viscous spring-dampers proposed in the accompanying paper is applied to two selected case studies, represented by a reinforced concrete and a steel five-storey frame building with identical global dimensions. The fundamental vibration periods of the two structures in fixed-base conditions, equal to 0.58 s and 1.08 s, respectively, fall within the range of technical interest for use of base isolation. The reliability of the analytical relationship by which the damping coefficient is estimated in the preliminary design phase is further verified by comparing its predictions with the loss factor values calculated from the results of numerical integration of the equations of motion. The final verification phase of the procedure is then developed with regard to a double design performance objective, for which immediate occupancy and life safety levels are targeted under the \u201cbasic design\u201d and \u201cmaximum considered\u201d earthquakes, respectively

Analysis and seismic isolation of an older reinforced concrete vaulted building

Reinforced concrete (R/C) structures designed with earlier Technical Standards often require retrofit interventions to improve their performance capacities, especially against seismic actions. A case study belonging to this class, i.e. the swimming pool building of the Naval Academy in Leghorn, Italy, rebuilt in 1948 after being destroyed by air raids during the Second World War, is examined herein. The structure of the main hall is constituted by a prefab R/C vaulted roof designed by the world-famous Italian engineer Pier Luigi Nervi, supported by a set of inclined columns with relatively small sections. The assessment analysis in current conditions shows unsafe response conditions of these members, as well as of several other columns and beams, under seismic action scaled at the basic design earthquake level. In order to minimize the impact of the retrofit intervention on the exposed structural elements, a base isolation solution is proposed for the building. The verification analyses in protected conditions highlight a substantial enhancement of the seismic response capacities of the structure, with no intervention required in the elevation structure, up to the maximum considered normative earthquake level

Non-linear finite element assessment analysis of a modern heritage structure

A synthesis of a non-linear finite element structural assessment enquiry carried out on a monumental modern heritage building is reported in this paper. The study includes a buckling analysis of the slender steel beams constituting a mushroom-type roof, and an ―integral‖ seismic pushover analysis of the supporting R/C columns. The computational solutions obtained for the steel roof beams are compared to the results derived from a calculation of the critical stress of beam panels, and the global lateral-torsional buckling resistance of members developed according to the Technical Standards adopted for structural verifications. The unconventional ―full-cracking‖ pushover application to the R/C columns offers detailed simulation of the evolution of their non-linear response, which is discussed in the paper, along with the most significant parameter and procedure choices made in the analysis