Classification System for Semi-Rigid Beam-to-Column Connections

The current study attempts to recognise an adequate classification for a semi-rigid beam-to-column connection by investigating strength, stiffness and ductility. For this purpose, an experimental test was carried out to investigate the moment-rotation (M-theta) features of flush end-plate (FEP) connections including variable parameters like size and number of bolts, thickness of end-plate, and finally, size of beams and columns. The initial elastic stiffness and ultimate moment capacity of connections were determined by an extensive analytical procedure from the proposed method prescribed by ANSI/AISC 360-10, and Eurocode 3 Part 1-8 specifications. The behaviour of beams with partially restrained or semi-rigid connections were also studied by incorporating classical analysis methods. The results confirmed that thickness of the column flange and end-plate substantially govern over the initial rotational stiffness of of flush end-plate connections. The results also clearly showed that EC3 provided a more reliable classification index for flush end-plate (FEP) connections. The findings from this study make significant contributions to the current literature as the actual response characteristics of such connections are non-linear. Therefore, such semirigid behaviour should be used to for an analysis and design method

Cyclic tensile testing of a three‐way panel connection for precast wall‐slab‐wall structures

Wall-slab-wall buildings, in precast configuration or not, are relatively widespread in many European and non-European countries, independently of the level and nature of seismic hazard to which the country is prone. Thus, this building archetype, featuring no columns or beams, but only slabs and walls, can be equally found both in areas characterized by potentially high-damaging tectonic earthquakes and regions where small-to-medium-size natural/anthropogenic seismic events would instead be expected. Notwithstanding the above, relatively little information has been offered so far on the seismic response/performance of these structures and their key components, which in case of a precast system/layout will inevitably be the connections between the structural elements. To partly fill such knowledge gap, this paper concerns the latter configuration and deals with experimental testing of panel-to-panel joints, which are not only two-way links but also three-way connections because it is very common for such structures that contiguous panels are connected to a transverse shear wall. Not surprisingly, very recent pseudostatic and shake-table tests on full-scale specimens, undertaken by the authors to characterize the performance of this structural system up to incipient/near collapse, have indicated how the latter panel joints are the weakest link of the system tested, thus prompting further component testing, in cyclic/asymmetric fashion, to single out the response of the joint. Monotonic and cyclic response curves of the five specimens and the counterpart damage patterns revealed that the observed flexural failure mechanism is very stable and aligns very well with that mobilized by the full-scale building tests

Proposal of robustness-oriented performance limit states for reinforced concrete framed buildings

This work is aimed at defining performance limit states (PLSs) that are directly related to the extreme response of reinforced concrete (RC) structures under notional removal of columns. A prototype structure was selected from a companion paper [1], considering the same column removal scenarios in terms of location in plan and elevation. Five PLSs were defined in order to evaluate the corresponding levels of load capacity and their sensitivity to model properties. Nonlinear dynamic analyses were carried out to characterize the residual capacity of the case study structure after column removal. The characterization of PLSs was based on appropriate damage measures and threshold values. Analysis results show a sequential occurrence of PLSs and allow the identification of three model properties that mostly influence the limit-state load capacity

Influence of beam-to-column connections in seismic vulnerability assessment of steel structures

It is worldwide recognized the importance of assessing the vulnerability of structures in seismic prone zones. Focusing on steel structures, it is well-known that the behavior of beam-to-column connections plays a key role in the seismic response of any moment-resisting frame system. Recently, a research project funded by European Commission investigated the seismic performance of pre-qualified connections through numerical analyses and pseudo-static cyclic testing. From a designer perspective, it is, however, necessary to understand the efficiency of such connections in terms of building performance to take a rational and conscious decision when designing a building. With this in mind, this paper investigates the influence of different beam-to-column connections on the seismic response and vulnerability of medium-rise steel frame structures. The behavior of these structures has been investigated by means of non-linear dynamic analysis for increasing seismic intensity levels using the OpenSeesPy finite element software. The record selection has been carried out through the Average Sabased method. The building performance has been assessed computing both maximum and residual interstory drifts, as well as fragility curves and absolute acceleration floor response spectra. The last mentioned enables to evaluate the likely damages experienced by acceleration sensitive non-structural elements, giving an additional point-of-view for estimating the building content performance. The outcomes of this study provide useful information for practitioners and designers interested in adopting the new set of pre-qualified connections, clarifying their effects on performance of common buildings and their content

Sensitivity analysis on progressive collapse resistance of RC structures subjected to single-column notional removal

In this study, the behaviour of a typical reinforced concrete structure subjected to the sudden removal of a single column was assessed. Eight single-column removal scenarios were studied, by varying the column position (i.e. central or corner column) as well as the column location along the height of the structure, from the ground floor to the penultimate floor. Nonlinear dynamic analyses were carried out by varying the ultimate steel strain, which was set to 4% (typical figure used for conventional limit state verifications), 10% and 20%. This allowed the sensitivity of progressive collapse capacity to ultimate steel strain to be evaluated. Further analyses were carried out by varying some structural parameters related to geometry and materials, in order to identify the most influential parameters. The results showed the significant influence of ultimate steel strain on progressive collapse capacity. The yield strength of steel reinforcement and beam span lengths were found to be additional important parameters for progressive collapse assessment

Shake table testing for seismic performance evaluation of non-structural elements

In the last years an increasing interest has been addressed to the assessment of the expected mean annual losses of single buildings as well as of building portfolio(s). Field observation of damage/failure in the aftermath of past earthquakes demonstrates that the losses related to the non-structural elements could significantly exceed the structural losses. At the same time, it is worth noting that the damage related to the non-structural elements could affect the functionality of the buildings and critical facilities. Based on these considerations, a detailed assessment of the expected annual losses requires data both on the structural and non-structural elements. In comparison to structural elements and systems, however, there is much less information and experimental data to undertake the assessment and design of non-structural elements for multiple-performance levels. Shake table testing could thus be very useful to assess the seismic performance of non-structural elements and to achieve the required information for loss estimation studies. In this paper, the results of shake table testing of acceleration-sensitive non-structural elements are presented. Equivalent single degree of freedom numerical models of the analyzed acceleration-sensitive non-structural element was developed using the results of the tests and a performance evaluation was carried out