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Dry connections primarily consist of high-strength bolts and steel plates. They are commonly used in precast structures as they maximise time efficiency in the assembly stage compared with conventional methods. In this study, an embedded horizontal dry connection was developed using a square-shaped ring connector, high-strength hex nuts and flat washers, and grout for assembling precast concrete shear walls. Using Abaqus CAE 6.14, a numerical study was conducted on two full-scale RC shear walls including one monolithic and one precast specimen to assess the seismic performance of the bolted connection under the combined effect of axial and fully reversed cyclic loading. The average displacement ductility ratio of the precast specimen integrating the bolted connection was three times as much as the reference specimen. However, its relative energy dissipation capacity and shear strength were 21.94% and 27.92% lower, respectively. A parametric study was also carried out on the thickness and grade of the ring connector, grade of the vertical steel bars, number of ring connectors, and diameter of the vertical steel bars at the connection joints. Results showed that the seismic performance of the bolted connection was highly dependent on the bar diameter and number of ring connectors. [ABSTRACT FROM AUTHOR]

A full-scale purposely built precast concrete building, designed to comply with robustness requirements in current building codes, was subjected to two different scenarios of sudden edge-column removal under the accidental load combination established by the codes. The main aim of this study was to assess how the structural system can prevent collapse initiation after the removal of a single edge column at different locations. This building was later subjected to a larger initial failure with the aim of arresting collapse propagation as part of another piece of research and outside the scope of this specific study. The building was highly instrumented providing unique data at a building system level for the understanding of the development of alternative load paths after the column removals. This work is novel since existing tests of edge-column removal from precast systems correspond mostly to simplified beam-column-slab subassemblies where the interaction with the rest of the building is neglected. The results obtained from this work are particularly relevant towards understanding the role of tying systems used in precast concrete buildings under different accidental scenarios using typical load combinations defined in building codes. The structure was able to redistribute the loads after each column was removed due to a combination of Vierendeel and compressive arching and membrane actions, leading to very small deflections. The role of vertical, horizontal, and floor tying systems in providing continuity between prefabricated and hybrid members was analysed in view of the experimental results obtained. The response obtained differed significantly from design assumptions commonly adopted for tying systems that rely on tensile catenary action at large deflections. This research is timely considering the push to adopt prefabricated components in building construction driven by Net Zero targets while maximising robustness of buildings subjected to more extreme events exacerbated by climate change. • Two tests were carried out on a purposely built full-scale PC building structure. • Different edge columns were suddenly removed. • Alternative load paths were identified at low deformations. • The role of vertical, horizontal and floor tying systems was analysed. [ABSTRACT FROM AUTHOR]

• U-bars with a lap length of 15 times the bar diameter achieves the same load-bearing capacity as straight-through bars. • Groove-and-tongue joints have a positive impact on the bending performance of panels. • Established a Strut-and-Tie model for lapped U-bars. • Analyzed the interaction between U-bars and core concrete, and determined the calculation method for their contact height. A comprehensive experimental campaign was carried out to investigate the flexural behavior of wet joints provided with lapped U-bars connecting two precast concrete panels. Eleven assemblies were tested in 4-point bending. Nine assemblies had wet groove-and-tongue joints provided with U-bars, and different values for the overlap length, joint width, and concrete strength. As a reference, the remaining two assemblies had wet groove-and-tongue or flat joints reinforced with straight-through bars. All the assemblies but two were provided with water-stop strips. The test results show that a lap length of 15 times the bar diameter is sufficient to guarantee the same bending capacity as straight-through bars. Based on the deformations of the panels subjected to bending, a strut-and-tie model was developed to predict the flexural capacity of linear wet joints provided with lapped U-bars. The proposed model effectively predicts the flexural capacity of the assembly of two panels since the theoretical predictions and the test results differ by less than 10%. [ABSTRACT FROM AUTHOR]

Highlights • Two partially precast SRC columns with precast RPC outer-part are presented. • Effects of section shape, stirrup spacing and axial compression were examined. • A model for calculating the seismic bending moment capacity was proposed. Abstract This paper aims to develop two kinds of innovative precast steel reinforced concrete columns, which are partially precast steel reinforced concrete (PPSRC) columns and hollow precast steel reinforced concrete (HPSRC) columns. Both the two kinds of composite columns have precast reactive powder concrete (RPC) shells, and the PPSRC column has a cast-in-place column core. In this paper, a series of cyclic loading tests on 10 column specimens subjected to combined static axial loading and cyclic lateral loading were carried out to explore their seismic performances. All specimens were evaluated by the failure modes, hysteresis characteristics, strength and stiffness degradation, energy dissipation capacity and ductility. The effects of section shape, stirrup spacing, axial compression and concrete strength of cast-in-place inner-part were investigated in details. The experiment results indicated that the PPSRC columns exhibited more satisfactory seismic behavior than the HPSRC columns in terms of hysteretic behavior, strength degradation, ductility and energy dissipation, while their bearing capacities were almost identical under low axial compression. Steel fibers could effectively prevent the cracked concrete from spalling, therefore, the encased steel shape was efficiently confined by the surrounding concrete during the entire test process. Higher stirrup ratio and lower axial compression of the column leaded to more satisfactory energy dissipation capacity, stiffness degradation and higher ductility. Based on the plastic stress theory, the seismic bending moment capacity analysis was conducted, and the results obtained form the formulas agreed well with those from the experiments. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Seismic performance-based design approach is currently implemented in modern building codes. Design requirements and provisions ensure an adequate structural performance under different intensity levels of seismic action. However, the probability of attainment of a performance level is implicitly considered in the code design approach (provisions and requirements); for instance, the minimum requirements in concrete structures cannot be simply correlated to the probability of collapse of the building as well as to its overall structural response. The aim of this work is to assess the vulnerability with respect to the collapse limit state of industrial single-story RC precast buildings designed according to the current Italian seismic code. The comparison between the Italian code and the Eurocodes is provided throughout the paper. A parametric study is performed by investigating the safety against the collapse of 40 RC single-story precast structures. Multi-stripe analyses are performed by non-linear dynamic analyses at 10 intensity levels. The fragility of the structures is defined by means of the incremental N2 method, which has been demonstrated to be a suitable method for evaluating the collapse capacity of single-story precast buildings. The results demonstrate that the buildings are safe against the collapse mainly because of the structural overstrength with respect to seismic actions. The modelling assumptions are also validated in order to demonstrate the negligible influence of the cracking on the collapse as well as the importance of the geometrical nonlinearities for precast buildings. [ABSTRACT FROM AUTHOR]

The stability of precast concrete wall panels under seismic action can be ensured by means of dissipative systems of panel-to-panel connections that allow to control the level of forces and limit the displacements. This paper deals with a connection system consisting of friction-based devices inserted into appropriate recesses within the joints between vertical or horizontal panels. The results of experimental tests carried out on single connectors, as well as on structural sub-assemblies consisting of two full scale panels, are presented. The technological choices of materials and components that ensure a stable hysteretic behaviour of the devices are discussed. The effectiveness of the devices in improving the seismic performance of precast buildings under seismic action is also shown based on the results of cyclic and pseudo-dynamic tests on full-scale structural prototypes. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

• The interaction of the roof's horizontal diaphragm with the structural and non-structural elements influences the seismic behaviour of industrial buildings. • It was obtained a correlation between the stiffness required for a rigid behaviour at the roof level in terms of the shape of the building. • The consideration of a rigid diaphragm tends to produce a more realistic seismic behaviour of the overall structure. • The contribution of facade cladding wall panels significantly influences the seismic behaviour of the building, especially for high-rise buildings. 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. [ABSTRACT FROM AUTHOR]

The SAFECLADDING Project was aimed at improving the connection systems between cladding panels and precast RC buildings in seismic-prone areas. Three design criteria have been assessed: isostatic , dissipative and integrated . They can be realised using different strategies, which are represented by several test setups within the experimental campaign. The paper describes the results obtained with vertical panels arrangement and the comparison with the bare frame, which is the reference for the current design practice that considers panels like non-structural elements. The mock-up and the test sequence were designed to assess all setups with a single frame structure. The mock-up was a one-storey building, made by two parallel frames with two bays and square columns, inserted into pocket plinths. The building was designed for earthquake actions according to the Eurocode 8. Each setup was assessed using increasing levels of action, either with cyclic or pseudo-dynamic tests. The latter were performed both for serviceability and ultimate limit states. The experimental programme for vertical-panels and the bare-frame arrangement involved ten different setups, resulting in a total of twenty-eight tests. As for the isostatic criterion, the results confirm that considering panels as simple masses without stiffness is far from the real system behaviour, even using apposite devices to uncouple panels and frame displacements. In fact, despite a previous and positive experimental qualification, several devices failed in operative conditions tests. Conversely, the integrated criterion requires to bear high loads, transferred by the frame through connections, which becomes the weak point for this configuration, as demonstrated by different failures of bolts and connections. The reliability of the dissipative criterion has been confirmed by twelve tests completed without any damage. This solution in fact combines lower relative displacements with limited loads within connections, avoiding both the compatibility problems and excessive forces. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

In this paper, the finite element model calibration of precast structures was investigated by considering ambient vibration test results. Two precast structures, an overpass and a precast production facility, were selected for investigation. The initial finite element models of these structures were developed by using SAP2000 software and the initial dynamic characteristics were determined. The experimental measurements were carried out by Operational Modal Analysis method under ambient vibrations, such as wind and traffic loads, and the exact dynamic characteristics were identified experimentally. During the ambient vibration tests, structural responses were measured on different points of these precast structures. Measurement time, frequency span and effective mode number were determined by the pretest investigations. The modal parameters were extracted from the collected signals by Enhanced Frequency Domain Decomposition and Stochastic Subspace Identification techniques. At the end of the study, the analytical and experimental dynamic characteristics were compared with each other and the initial finite element models of these structures were updated by changing the stiffness coefficients of the connection joints. [ABSTRACT FROM AUTHOR]

• Excessive deformation of structural elements should be immediately identified. • The limit states conditions concern bearing and non-bearing structural elements. • Failures can occur as a result of damage to non-bearing structural elements. • The implemented concept of an effective reconstruction was presented. • The recommendation for technology of the partition walls erection was formulated. The work concerns the phenomenon of damage to internal partition walls in typical prefabricated residential buildings. As a construction system, large-panel buildings were very popular all over Europe at the end of the 20th century. Defects in structural members or layer joints in facade wall panels have been investigated many times. The neglected aspect of the operation of large-panel buildings are the consequences of excessive deformation of structural elements progressing over time, e.g., deflections of prefabricated floor slabs. The safety of building residents is determined not only by the fulfillment of the limit states conditions by basic structural elements, e.g. external walls or floor slabs. Failures can also occur as a result of damage to partition walls. Initially rigid floor slabs remain supported only at the edges of the structural walls, while in the middle zones they are deflected. Partition walls, made of various materials, are subjected to shear stress in addition to compression. This can result in cracks and even destruction of the wall structure. The problem presented for discussion was confirmed by the case of a real failure of partition walls in a building operated for more than thirty years. To find explanation and reasons of such a phenomenon, numerical calculations were carried out for partition walls and for prefabricated floor slabs that are under and above the analyzed wall. In the case of partition walls, the effort of the wall material was considered in terms of exceeding the ultimate limit state in the tensile zones. For the floor slabs the deflection values were determined. The implemented concept of an effective reconstruction of the wall structure has been also described. [ABSTRACT FROM AUTHOR]

Abstract: Structures subjected to cyclic loads show alternative tension–compression stress states; in such a case, even if certain damage (fracture) is reached during the tension cycle, the computational model of the structure should maintain its capacity to withstand subsequent compression based only on the contact effect in the damaged area (opening, closing and reopening of cracks). In order to control this behavior, a phenomenological constitutive model able to consider the contact as a structural limitation is required. From the constitutive point of view, geomaterials have different damage thresholds for tension and compression and, from the structural point of view, it must be ensured that the material damaged in tension still resist compression. In this case, it is accepted that cracks behave as a contact surface at the structural level. To meet the above mentioned phenomenology, a modification of the damage model differentiated in tension and compression proposed by Faria et al. [Faria R, Oliver J, Cervera M. A strain-based plastic viscous-damage model for massive concrete structures. Int J Solids Struct 1998; 35:1533–58] is performed in this paper, considering independent strength thresholds in each of these processes, controlled with two independent discontinuity threshold functions. Also, in this work an elasto-plastic constitutive model is used to represent the behaviour of the steel bars. [Copyright &y& Elsevier]

Abstract: There is general agreement in the fact that fully three-dimensional (3D) numerical techniques provide the most precise tools for simulating the behavior of RC buildings even when their computational costs for real structures became them unpractical. Moreover, one-dimensional formulations (1D) are rather limited for predicting the mechanical behavior of framed structures which present local weakness that can determine their global responses, such as it is the case of poor detailed joints of RC buildings in seismic zones or precast concrete structures. An alternative approach, combining both simplicity and computational efficiency, is given by coupling reduced models for prismatic elements with full 3D models for the zones corresponding to connecting joints. In this work, a two-scale approach is developed for obtaining the nonlinear dynamic response of RC buildings with local non-prismatic parts. At global scale level all the elements are rods; however, if local parts with complex geometry appear, the corresponding elements are analyzed considering fully 3D models which constitute the local scale level. The dimensional-coupling between scales is performed imposing the kinematics hypothesis of the beam model on surface-interfaces of the 3D model. An iterative Newton–Raphson scheme which considers the interaction between scales is developed to obtain the response at global level. The tangential stiffness of the local models are obtained numerically. Computationally, the problem is managed by means of a master–slave approach, where the global scale problem acts as the master and the local models are the slaves; iterative communication between scales considers internal forces and moments as well as tangential tensors. The process stops when global convergence is achieved. From the computational point of view, the developed method is implemented in a parallelized scheme, where the master and slave problems are solved independently by different programs thus minimizing the intervention on existing codes specific for beams and solids. Finally, numerical examples are included. [Copyright &y& Elsevier]

Abstract: The performance of jointed precast concrete load-bearing panel structures is evaluated using the capacity spectrum method for Australian seismic conditions which is typical of low to moderate seismicity regions. The critical element in the load path is the connection between the floor slab and the wall panel, and sub-assemblage tests are carried out in order to calibrate a finite element model for typical load displacement characteristics. The calibrated model is used to evaluate the performance of a full scale structure using the demand spectra given in the Australian code for various soil conditions. It is found that the seismic performance is inadequate under deep soil and very soft soil conditions for the structure detailed with deep embedment connections. In comparison for the structure with shallow embedment connections, local damage to the concrete topping slab would be expected for ground motions on shallow soil or very soft soil, but overall structural stability would be maintained for the ultimate limit state event. [Copyright &y& Elsevier]

Abstract: Results from an investigation aimed at developing a moment connection for a new earthquake-resistant framing system that consists of precast hybrid fiber reinforced concrete (FRC)-encased steel truss beams and reinforced concrete (RC) columns are presented. Various connection schemes between the precast hybrid beams and RC columns were experimentally evaluated for adequate moment and shear transfer during large displacement reversals. From results of four large-scale beam–column subassembly tests, a connection scheme that features external steel rods for moment transfer and a bolted connection between the embedded steel truss and the RC column for shear transfer is proposed. The steel rods are external to the beams to facilitate installation and inspection, but can pass through or outside the precast column, depending on the beam width-to-column width ratio. Force transfer between the truss chords and the external rods is achieved through steel members forming a horizontal truss. The connection components are designed to remain elastic, forcing the inelastic activity to occur in the hybrid beam. Test specimens constructed with these connection details exhibited displacement capacities exceeding 4.0% drift, with full hysteresis loops and good strength and stiffness retention capacity. Inelastic rotations concentrated in the hybrid beams and accounted for most of the applied drift, while the connection members behaved elastically, as intended in design. [Copyright &y& Elsevier]

• A beam-column joint with a replaceable artificial controllable plastic hinge (ACPH) was proposed. • Seismic behavior of joint affected by ACPH is investigated based on experimental testing. • The calculation model and formulas of yield moment bearing capacity for the ACPH are proposed. To promote and effectively control precast structures' seismic performance, a novel bending-shear decoupled prefabricated beam-column joint with a replaceable A rtificial C ontrollable P lastic H inge (ACPH) was proposed in this paper. The ACPH was composed of two energy dissipation systems with energy-dissipation plates for bearing the bending moment and a connection system for bearing the shear force. To explore the seismic behavior of joint affected by ACPH, hysteresis tests of two beam-column joints with ACPH and one cast-in-situ beam-column joint were carried out. It found that the ACPH can significantly affect the failure mode compared with cast-in-situ specimen while offering excellent hysteresis behavior, sufficient ductility, and superior energy consumption capacity. Even if half of the energy-consuming system fails, the ACPH still maintains remarkable seismic performance except for reduced bearing capacity. Although only the location of the ACPH has been changed, the crack development, skeleton curve, and energy consumption performance have all undergone significant changes. The bearing capacity of the ACPH specimen was enhanced with the distance between ACPH and column surface increasing, while other seismic performances were affected at different levels. Besides, the calculation model and formula of yield bearing moment capacity for the ACPH were proposed. [ABSTRACT FROM AUTHOR]

Single-storey precast reinforced concrete (RC) frame type buildings are mainly preferred in manufacturing plants and storehouses. The behaviour of semi-rigid beam-column connections of the buildings is one of the main sources of uncertainty. The common damages observed after credible earthquakes were falling off large-span beams and large plastic deformations at the column base. New generation Lead Extrusion Damper (LED) developed by the authors is utilized in the seismic retrofitting of these buildings in use. This paper discusses the seismic performances of pre- and post-behaviour of the retrofitted buildings and evaluates the efficiency of the applied retrofitting technique. It is exposed that seismic demands are diminished essentially. The relative storey drifts decrease by about 40-90% while the reduction in the strain at the column base section reaches to 70%. • Lead extrusion dampers can be used for the industrial buildings in use. • Structural demands are reduced drastically by the appropriate use of the damper. • The capacities of the structural members are mostly adequate after the retrofitting. • Seismic retrofitting of an industrial building is succeeded with a reasonable cost. [ABSTRACT FROM AUTHOR]