Andrea Belleri

Seismic Performance of Precast Industrial Facilities Following Major Earthquakes in the Italian Territory

Recent major earthquakes in the Italian territory have reaffirmed the seismic vulnerability of precast industrial buildings typical of past Italian building practices, highlighting structural deficiencies observed during previous events and primarily related to the transfer of horizontal forces between structural and nonstructural elements. An intrinsic lack of shear and ductility capacity has been observed in simply supported beam-to-joist and beam-to-column connections, primarily constituted by vertical steel dowels or solely relying on shear friction, with or without neoprene pads. These connections were designed neglecting seismic loads and their premature failure was observed during recent seismic events to cause a loss of support of beam elements, owing to the relative movements of elements, and the collapse of part of the buildings, primarily the roof. The seismic displacement demand of the industrial buildings under consideration is larger than traditional RC frame structures owing to their higher flexibility, according to both higher interstory height and to a cantilevered static scheme. Furthermore, this high flexibility may also result in displacement incompatibility between structural and nonstructural elements, such as precast cladding panels, causing their connection failure. On the basis of detailed field observations on a relevant number of buildings, collected just after the earthquakes, seven representative industrial facilities are examined to outline the primary vulnerabilities of one-story precast concrete structures not designed and detailed for seismic loads.

Dynamic behavior of rocking and hybrid cantilever walls in a precast concrete building

This paper discusses the dynamic response of precast, post- tensioned, rocking, and hybrid cantilever walls that provided lateral force resistance to a three-story precast concrete building built at half-scale. The building was subjected to extensive shake- table testing on the NEES large high-performance outdoor shake table. The tests provided a landmark opportunity to observe the dynamic response of this type of lateral force-resisting system. Excellent performance was observed overall. Comparison between the assumptions made during the design of the wall and the exper- imental results allowed the validation of the presented design procedure and of the reinforcement detailing in the critical region at the base of the walls.

Horizontal cladding panels: in-plane seismic performance in precast concrete buildings

The paper investigates the in-plane performance of horizontal precast reinforced concrete cladding panels, typically adopted in one-storey precast industrial and commercial buildings. Starting from in-field observations of cladding panels failures in recent earthquakes, the seismic performance of typical connections is evaluated by means of experimental tests on full-scale panels under quasi-static cyclic loading. The failure mechanisms highlight the vulnerability of such connections to relative displacements and, therefore, the need to accurately evaluate the connections displacement demand and capacity. An analytical model is developed to describe the force–displacement relationship of the considered connections and compared to the experimental results. In order to determine the seismic vulnerability of such connections and provide design recommendations, linear and nonlinear analyses are conducted taking as reference a precast concrete structure resembling an industrial precast building. The results of the analyses show the importance of a correct estimation of the column’s lateral stiffness in the design process and how an improper erection procedure leads to a premature failure of such connections.

The Influence of Overhead Cranes in the Seismic Performance of Industrial Buildings

The paper investigates the influence of overhead cranes with a hanging mass under earthquake type loading, considering the Emilia 2012 seismic sequence. The structural layout of precast concrete industrial buildings typical of the Italian territory is considered. The equations of motion describing the behaviour of the hoist load are derived and a sensitivity analysis is carried out on simplified three degrees of freedom systems by solving the governing differential equations. The influence of various parameters on the roof displacement and on the horizontal load transferred by the hanging mass is addressed. The considered parameters are the relative damping of the hanging mass, the length of the hoist ropes, the earthquake record, the hysteretic type of the plastic hinges at the column base, and the behaviour factor of the structural system. The results show that for a horizontal component of the considered seismic sequence the structural displacements are amplified in the case of a behaviour factor greater than 2.5. A simplified modelling strategy considering small displacements is also investigated. Such model is suitable for response spectrum analyses. Finally, a three-dimensional case study is analysed by means of non-linear time history analyses. The results show the influence of the overhead crane on the local performance of some structural and non-structural elements, such as columns and cladding panels, especially when the assumption of rigid roof diaphragm does not apply.

Combining seismic retrofit with energy refurbishment for the sustainable renovation of RC buildings: a proof of concept

In this paper, an integrated approach targeting sustainability, safety and resilience is envisioned for the renovation of the post-Second World War RC buildings clustered in urban outskirts. The so...

A Novel Framework to Include P-Δ Effects in Displacement-Based Seismic Assessment

During an earthquake, P- effects could significantly increase the horizontal displacements in a structure; hence, they should be duly accounted for in seismic assessment procedures. Considering the displacement based assessment (DBA) procedure, P- effects influence the single degree of freedom substitute structure adopted in the procedure both in terms of shear-displacement relationship and of equivalent viscous damping. The present article considers a novel framework to include P- effects in the DBA procedure. The application of the proposed procedure is illustrated considering the Takeda hysteresis model commonly adopted for reinforced concrete structures.

Displacement-Based Seismic Assessment for Precast Concrete Frames with Non-Emulative Connections

ABSTRACT The paper develops a methodology for the seismic vulnerability assessment, Displacement-Based Assessment (DBA), of one-story and multi-story precast concrete frames with non-emulative connections. The method is based on the Direct Displacement-Based Design procedure initially developed by Priestley. The DBA is particularly suitable for the evaluation of the seismic response of flexible structures, as it considers displacements as the leading parameters to estimate the seismic vulnerability. The proposed procedure specifically accounts for the influence of beam–column connections, P-∆ effects, and second mode of vibration. The validation has been performed by means of nonlinear time history analyses.

Dowel connections securing roof-diaphragms to perimeter walls in historic masonry buildings and in-field testing for capacity assessment

Abstract In the seismic retrofit of existing masonry constructions, global interventions are often needed to inhibit the onset of local mechanisms and to engage the whole building box-like structural behaviour. Such interventions are represented by perimeter ties and roof and floor diaphragms. This paper considers the roof diaphragm strengthening solution and investigates the use of stud connections securing the roof thin-folded shell to the perimeter walls. Stud connections serve the dual purpose of collecting and transferring the out-of-plane inertia forces of the masonry walls to the roof diaphragm, as well as transferring the diaphragm reaction forces to the shear walls. Specific detailing of the stud connection and the adoption of an improved lime-mortar overlay on the top of the masonry walls are proposed to improve the connection strength; without such improvements, the connection capacity would be jeopardised by the reduced shear resistance of the masonry wall due to the absence of significant vertical confining action at the roof level. The intervention entirely changes the behaviour of the connection and significantly reduces shear stresses on the masonry wall. The structural behaviour of the connection is analysed and discussed. Emphasis is made on the conceptual design of laboratory and in-field test procedures and testing frames in order to replicate the boundary conditions in real applications. In-situ tests may help during the design of the roof thin-folded shell system and allow for the efficiency assessment of the connections prior to the final intervention, thereby proving the actual feasibility of the retrofit solution.

Prefabricated responsive diagrids for holistic renovation of existing mid-rise rc buildings

The holistic renovation of existing buildings is nowadays acknowledged as an essen- tial and urgent action to reduce the environmental impact and increase the resilience of the existing building stock. Such holistic interventions envision the adoption of an exoskeleton, en- tirely built from outside. In this paper, the exoskeleton is designed as an external diagrid, con- sisting in a lattice structure. Among possible structural typologies, diagrids are particularly interesting for their remarkable architectural potential and for the possible standardization of the components, which highly increases replicability of the retrofit solution. Furthermore, pre- fabrication of components speeds up the assembly process and reduces the construction time. In the paper, focus is made on the dynamic behaviour of a retrofitted building featuring a re- sponsive diagrid. The responsive behaviour is attained by changing boundary conditions at the diagrid’ s base supports as a function of the earthquake intensity, while the diagrid lattice struc- ture remains elastic. At the Operational Limit State, the diagrid is designed as hinged at the base, whereas at Life Safety Limit State, beyond a target base shear, hinges are conceived to downgrade into non-linear supports allowing for the controlled sliding of the diagrid’s base. Non-linear restraints limit the maximum base shear force, while avoiding excessive horizontal displacements and second order effects. Non-linear time history analyses are carried out to study the responsive behaviour of a reference 3 storey building strengthened with an external responsive diagrid. Results show that responsive diagrids require preliminary interventions at the existing building ground floor to reduce the damage following the onset of the diagrid slid- ing. Such interventions are for instance the disengagement of the infills from the RC frame and the local increase of the column ends ductility.