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The seismic behaviour of precast reinforced concrete industrial structures has been extensively investigated in recent decades, especially after the damage caused by recent earthquakes. The interaction of the roof’s horizontal diaphragm with the structural and non-structural elements can influence the seismic behaviour of these buildings. Thus, the present study aims to investigate this interaction, through nonlinear static and dynamic analyses using a simplified macro element to simulate the behaviour of cladding panels and an equivalent truss approach to simulate the roof in-plane stiffness. The analyses were performed on several structural models considering the current European single-storey precast reinforce concrete industrial building stock, with or without cladding wall panels, and with rigid or flexible diaphragm roof. Despite the uncertainties associated with the ability of common roof systems to ensure a rigid diaphragm, the analyses allowed the establishment of a correlation between the buildings generic properties and the roof horizontal stiffness required to approach a rigid diaphragm effect. In general, the results show that the consideration of a rigid diaphragm in numerical models may tend to produce a more realistic seismic behaviour of the overall structure. Furthermore, the contribution of facade cladding wall panels significantly influences the seismic behaviour of the building, especially for high-rise buildings. published

This article describes the publicly available dataset of multiple shaking table tests on a restrained rocking and sliding bridge system exhibiting negative lateral stiffness. Given the scarcity of experimental campaigns on such systems, this dataset is valuable for the development and validation of analytical and numerical models, with 184 tests. This large body of data allows the models to be validated in a statistical sense. This work describes in detail the specimen and its construction, as well as all instrumentation used during the tests. It presents the organization of the shared data, and concludes with some examples of how the available data can be postprocessed for assessing the behavior of the system. © 2022 American Society ofCivil Engineers. ISSN:0733-9445 ISSN:1943-541X

New precast frame industrial structures are seismically designed according to reliable modern criteria. However, most of the existing built stock hosting many workers and both regular and strategic industrial activities was designed and detailed neglecting the earthquake load or according to outdated seismic design criteria and regulations. Its seismic retrofit is a main challenge for the Engineering Community and a critical objective for institutional and private bodies. Among the envisaged solutions, the introduction of dissipative braces appears to be promising, although mostly inapplicable for these buildings, due to the brace lengths required by their typical large dimensions and the related proportioning against buckling. In this paper, an innovative seismic retrofitting technique based on monolateral dissipative bracing is investigated. The device proposed in this paper, yet in phase of preliminary design and testing, dissipates energy through friction in tension only while freely deforming in compression, which makes the issue related to compressive buckling irrelevant. A numerical analysis is carried out to investigate the efficiency of the proposed device in seismic retrofitting of precast industrial frame buildings with the aim to explore its feasibility and to better orient the definition of the slip threshold load range and the future development of the physical device. The simplified Capacity Spectrum Method (CSM) is employed for the global framing of the structural behaviour of the highly nonlinear retrofitted structures under seismic actions. A numerical tool is set to automatically apply the CSM based on the definition of few main parameters governing the seismic response of precast frame structures. The efficacy of the CSM is critically analysed through the comparison with the results of a set of nonlinear dynamic analyses. A smart simplified design process aimed at framing the most efficient threshold slip/yield load of the device given an existing structural configuration is presented with the application of the CSM through the identification of the most efficient performance indicator related to either displacement, shear force, equivalent dissipation of energy or a combination of them.

This is the peer reviewed version of the following article: [Čairović, Đ, de la Fuente, A, Zlámal, M, et al. Suitability of different tests for characterization of the dimpled concrete‐to‐concrete interface. Structural Concrete. 2020; 1– 18. https://doi.org/10.1002/suco.201900513], which has been published in final form at https://doi.org/10.1002/suco.201900513. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving. The main aim of this study was to assess the suitability of different existing test setups for the mechanical characterization of a dimpled interface obtained by casting concrete against dimpled high-density polyethylene (HDPE) membrane. Even though this type of interface roughening is widely used, especially for monolithic connections between precast elements, to the best of the authors' knowledge there is no research providing any data regarding its roughness parameters, tension, and shear strength, nor its failure modes. To this end, a two-fold objective was established for this research: (a) to identify and analyze, from a technical standpoint, the available test configurations for characterizing the mechanical performance of interfaces, and (b) to perform an extensive experimental program devoted to characterizing the mechanical performance of a dimpled HDPE membrane—cast concrete interface. The suitability of each test for reproducing the expected stress state and the actual resistance mechanism was analyzed. Moreover, a comparison between tension and shear tests, including its main advantages and disadvantaged are also presented. This study was conducted with the support of the Ministry of Industry and Trade of the Czech Republic, project No. FV20595 – “Steel-concrete composite for precise machine tools structures”, and the Technology Agency of the Czech Republic, project No. TH0402043 – “Extension of the application area of FRP reinforcement in concrete structures”. This support is gratefully acknowledged.

The seismic performance of precast portal frames typical of the industrial and commercial sector could be generally improved by providing additional mechanical devices at the beam-to-column joint. Such devices could provide an additional degree of fixity and energy dissipation in a joint generally characterized by a dry hinged connection, adopted to speed-up the construction phase. Another advantage of placing additional devices at the beam-to-column joint is the possibility to act as a fuse, concentrating the seismic damage on few sacrificial and replaceable elements. A procedure to design precast portal frames adopting additional devices is provided herein. The procedure moves from the Displacement-Based Design methodology proposed by M.J.N. Priestley, and it is applicable for both the design of new structures and the retrofit of existing ones. After the derivation of the required analytical formulations, the procedure is applied to select the additional devices for a new and an existing structural system. The validation through non-linear time history analyses allows to highlight the advantages and drawbacks of the considered devices and to prove the effectiveness of the proposed design procedure.

The aim of this work is to propose an efficient tool for the design of the monitoring system of precast reinforced concrete industrial buildings in seismic hazard zones, enabling the rapid post-earthquake damage assessment. The methodology, designated as spatio-temporal online monitoring (STOM) is performed by analyzing data obtained from a set of bi-directional accelerometers integrated in smart columns within the building. Acceleration records are converted into inter-story drift ratio (IDR) data, designated as engineering demand parameters, by double integration. Then, calculated IDRs are compared to three levels of alert thresholds meaning that, for the selected damage state, the structure is classified as apparently safe, restricted use or unsafe, corresponding to slight damage, moderate damage and severe damage. Finally, the STOM results trigger visual inspections, thus representing the main inputs needed by engineers in order to evaluate the structural health status and eventually decide for further actions. Measurements data are collected across time as well as space to ensure greater robustness and effectiveness. The STOM methodology allows the preliminary design, i.e., number and location of sensors and optimal demand thresholds, by exploiting the receiver operating characteristics (ROC) analysis, which classifies the different options on the basis of their performance in reporting true damage scenarios with respect to false alarms. Hence, seismic monitoring data are used in conjunction with the pre-evaluated alert states as an engineering decision-support tool for the post-earthquake diagnosis of the structure.

Economic losses associated with the structural and non-structural damage occurring after an earthquake are of particular importance in the case of industrial buildings due to the consequences of su...

Previous research projects and post-earthquake field observation showed that dry-assembled precast frame structures with hinged beams and cantilever columns restrained at their base, if correctly designed and detailed, can attain good seismic performance, mainly due to their flexibility and robustness. Their seismic design is often conditioned by the need of reducing their flexibility by increasing the cross-section of the columns, which, due to minimum reinforcement requirements, results in their over-strengthening. High flexibility may also induce displacement compatibility issues with non-structural elements. The paper concerns the proposal of an innovative enhanced structural frame system, based on the adaptation of hinged beam-column joints into rigid through the activation of special mechanical connection devices performed after the installation of the slab. While keeping all the benefits of the dry prefabrication, the resulting moment-resisting frame is provided with enhanced redundancy and stiffness. A design comparison among three precast frames with similar geometries and different static schemes shows how the joint adaptation can be exploited to optimise the structure by modifying the distribution of bending moment. The results of dynamic non-linear analyses on a three-storey precast structure with adaptable joints tested as a part of the SAFECAST research programme show the seismic performance of this system through different static schemes, and the comparison with the experimental results provides information about the validity of the models and the effectiveness of the technological solutions employed.

The Displacement Based Design (DBD) methodology for precast concrete frame structures with not-emulative connections is investigated herein. The seismic design procedure is applied to both single-storey and multi-storey structures. Industrial and office buildings, warehouses and commercial malls with a structural layout typical of the European market are considered: cantilever columns resting on isolated footings connected at the floor level to pre-stressed precast beams, supporting pre-stressed precast concrete floor or roof elements. The need to control the lateral seismic displacement is dictated by the high flexibility of these structures, which in turn is associated to the structural scheme and to the inter-storey height. Starting from the general displacement based design procedure, the paper focuses on how properly taking into account the influence of column-to-foundation and beam-to-column precast connections; expressions and procedures are developed to determine the yield curvature, the equivalent viscous damping, the effective height and the effective mass of the single degree of freedom substitute structure adopted in the DBD procedure. The proposed procedure is applied to selected case studies and validated through non-linear time history analyses, showing the ability of the design procedure in controlling lateral displacements.

A dissipative connector device, consisting of a steel plate folded at right angle along three lines to get a W-shaped profile, is proposed for the safe fastening of the horizontal cladding panels of new or existing precast structures under seismic action. Experimental tests are carried out to characterize the hysteretic behavior of the connector device. Different technological features, restraint conditions, and loading protocols are considered. Nonlinear hysteretic models are validated against the results of pseudo-dynamic tests on a full-scale prototype of precast building with cladding panels. Guidelines for the design of the dissipative connector device are provided.

The seismic performance of precast frame structures strongly depends on the mechanical devices connecting both structural and non-structural elements. Following recent post-earthquake field observations of unintended seismic interaction of the cladding panels with the frame structure, the seismic design of the cladded system is currently being critically examined by the scientific community. Design solutions involving a controlled cladding–structure interaction have been proposed to address this problem. However, the frame–panel interaction may draw high stresses into the roof diaphragm, as a consequence of the stiffening of the external frames only. This paper presents a parametric study based on linear and non-linear dynamic analyses investigating different levels of interaction among frames, panels, and diaphragm system. The results show how the deck and cladding connections influence the seismic behaviour of the structure. Innovative fastening systems aimed at enhancing the seismic performance of the structure are proposed based on the use of dissipative connection devices inserted into both cladding and deck components.

Silicone sealant is usually interposed between panels of precast facades. In ordinary cladding panel configurations, relative sliding between panels occurs under lateral actions. The shear drifts and consequent stresses arising in the silicone strips may lead to a significant increase of the load demand in the cladding panel connections and affect the seismic behaviour of the structural system. This paper presents the results of experimental tests and numerical analyses carried out to clarify the role of the silicone sealant on the seismic response of precast structures with cladding panels. An experimental campaign including monotonic and cyclic tests on both silicone strips applied to small concrete blocks and two panel sub-assembly sealed with silicone, has been developed at Politecnico di Milano. Furthermore, cyclic and seismic pseudo-dynamic tests on a full-scale prototype of precast building with cladding panels sealed with silicone, have been performed at the Joint Research Centre of the European Commission. The results of the experimental tests are presented and compared with the results of numerical simulations. Some recommendations for seismic design of precast frame structures with cladding panels, considering the effect of silicone sealant, are finally provided.

The use of precast reinforced concrete elements is rapidly increasing since this technique has several advantages over traditional cast-in-situ structural members such as lower manufacturing time and costs and a better quality control. Nevertheless, cast-in-situ solutions intrinsically allow building moment-resisting frames, a behavior that is usually hard to achieve using precast elements. In this paper a technical solution able to offer both high strength and ductility, simplicity of construction of the prefabricated elements and ease of assembly on site is presented. The solution realizes the continuity between beam and column by means of loop splices and cast-in-place concrete with steel fibers to improve the ductility of the concrete struts in the wet joint. The connection has been experimentally tested and compared to an analogous cast-in-situ one. The experimental results confirmed its good structural performances in terms of strength and ductility. Numerical investigations tuned on the basis of the experimental results allowed the improvement of the design to achieve reduced column damages for higher drift values while maintaining practically unchanged structural performances.

Multiple Slit Devices (MSDs) are plasticity-based dissipative connectors consisting of steel plates provided with slits which lead to a set of elementary beams. In this way, the shear-type behavior of the plate is turned into the flexural-type behavior of the elementary beams, which ensures better energy dissipation. The proposed MSDs are bolted to support steel profiles inserted into appropriate recesses in between precast concrete panels to improve the seismic performance of the earthquake-resisting system. The paper presents the results of monotonic and cyclic experimental tests performed on both connectors and structural sub-assemblies consisting of two full-scale precast concrete panels connected by a MSD. Steel plates with slits of various shape and size are considered. An improved version of the connector capable to dissipate energy through both plasticity and friction and to provide enhanced displacement capacity is also proposed and tested.

Current design approaches consider cladding panels (CPs) in precast RC buildings as non-structural elements not interacting with the frame. Frame/CP connections are typically designed only for wind or seismic actions perpendicular to the panel plane; unrestrained displacements in the panel plane are presumed. Past seismic events have clearly demonstrated the inadequacy of this design approach. CPs do in fact interact with the frame, modifying the response of buildings subjected to seismic action. This means that substantial and unexpected forces act on the connections and may lead to connection failure. Evidence of such out-of-plane forces in joints arising in buildings with deformable roof diaphragms is given here. This work proposes using CPs as structural elements to enhance the seismic performance of framed industrial buildings. If the friction acting between the panels is taken into account, CP walls become part of the resisting structure, leading to a dual frame/wall system. This concept can be used both in the design of new buildings and the retrofitting of existing ones. The case study reported here was conducted with CPs arranged horizontally and with pinned connections. We show that the results are highly sensitive to the assumed friction coefficient, and also that they differ substantially from analytical design values obtained disregarding friction effects. Friction between panels is known to be unpredictable, especially when structures are subjected to seismic movement with a strong vertical component. The consequence is that forces and displacements in framed buildings are random in a way which cannot be accepted in structural design. This work therefore proposes control of friction magnitude with suitable devices between panels: CPs can act as resistant and dissipative shear walls in industrial buildings, and are effective and relatively low-cost.

The seismic sequence which hit the Northern Italian territory in 2012 produced extensive damage to reinforced concrete (RC) precast buildings typically adopted as industrial facilities. The considered damaged buildings are constituted by one-storey precast structures with RC columns connected to the ground by means of isolated socket foundations. The roof structural layout is composed of pre-stressed RC beams supporting pre-stressed RC floor elements, both designed as simply supported beams. The observed damage pattern, already highlighted in previous earthquakes, is mainly related to insufficient connection strength and ductility or to the absence of mechanical devices, being the connections designed neglecting seismic loads or neglecting displacement and rotation compatibility between adjacent elements. Following the vulnerabilities emerged in past seismic events, the paper investigates the seismic performance of industrial facilities typical of the Italian territory. The European building code seismic assessment methodologies are presented and discussed, as well as the retrofit interventions required to achieve an appropriate level of seismic capacity. The assessment procedure and retrofit solutions are applied to a selected case study.

Steel angles are extensively used to connect concrete floor/roof elements to the supporting beam in typical dry-assembled precast frame structures widely diffused in Europe and other parts of the world. These connections allow for relative rotations of the floor element in its vertical plane and restrain their relative displacement, avoiding possible loss of support and consequent fall of the floor element when the structure is subjected to lateral load. The diaphragm behavior of the precast decks relies on these floor-to-beam connections. Their postaddition to unconnected floor-to-beam joints of existing buildings is a typical seismic retrofit intervention. All these applications are often made without any adequate information about the main structural parameters of the connections due to lack of experimental or theoretical knowledge. An experimental campaign has been performed at Politecnico di Milano within the framework of the Safecast and ReLUIS research projects with the scope of characterizing the mechanical behavior of postinserted floor-to-beam connections made with hot-rolled angles, cold-formed angles, and welded sockets in the direction parallel to the floor element. The results of monotonic local tests on connectors and on the bolted connection with the floor rib and of cyclic and monotonic subassembly tests allowed the determination of the main structural parameters of the joints, including elastic stiffness, strength, displacement capacity, and hysteretic shape.

Precast concrete panels are often used for the facades of modern warehouses and commercial malls. During the last two decades, they have generally been made of two concrete layers with interposed thermal insulating polystyrene boards. Traditionally, perimeter concrete ribs allow the weight of the external concrete layer to be transferred to the internal thus causing unavoidable thermal bridges which reduce the energy performance of the building. In the sandwich cladding panel, the two concrete layers can be linked by low-conductivity shear connectors crossing through the insulation layer, thus ensuring the overall thermal efficiency of the building. In this paper, the results of a wide numerical study on the behaviour of concrete sandwich panels realized with glass fibre-composite pultruded connectors are presented, focusing on the stresses and deformations caused by dead load, thermal actions and shrinkage.

The seismic vulnerability of precast reinforced concrete buildings is often governed by the performance of mechanical connections between precast elements. This aspect was highlighted by recent seismic events in Italy, where several collapses were registered among industrial buildings typical of Italian practice. The building damage was related to failure of connections between beams and columns and between beams and roof elements, which led to the loss of support of the structural elements. Starting from the results of an experimental campaign, the present work investigates the use of ductile connections between precast beams and roof elements suitable for both new structures and as a retrofit measure of existing ones. These connections are able to transfer the horizontal inertial loads and to accommodate deformations arising from seismic displacement compatibility. The relative rotation between the end of the roof elements and the beam, owing to seismic displacement demand, could lead to their contact. This leads to a load increase in rigid connections, which can cause their premature failure, or to horizontal relative displacements as in the ductile connections considered herein. Moreover, the connections investigated could be used to dissipate seismic energy.

A series of earthquakes, the highest of magnitude Mw 5.9, hit a portion of the Po Valley in Northern Italy, which was only recently classified as seismic. The paper reports the findings and the lessons learnt from a preliminary field survey which was conducted immediately after the second event. As a result of the economic attitude of the affected area, and possibly of the characteristics of the event, an unprecedented number of industrial precast buildings were affected, resulting into most of the casualties as well as in large economic losses. Whereas most of the damaged and collapsed buildings were designed for gravity loads only, evidence of poor behavior of some precast buildings designed according to seismic provisions were discovered. The paper provides a description of the performance of precast buildings, highlighting the deficiencies that led to their poor behavior as well as some preliminary recommendations., JRC.G.4-European laboratory for structural assessment