Seismic Behavior of RC Beam-Column Subassemblages with Flat Beam (original) (raw)
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Seismic Tests on RC Building Exterior Joints with Wide Beams
Advanced Materials Research, 2013
Reliable assessment procedures of existing RC buildings are currently available, and have been introduced in the Italian and European codes reporting new rules for seismic analysis. However, further studies are required in order to further improve such procedures and, specifically, obtain more accurate data on the behavior of beam-column joints, whose role on the global behavior of framed RC buildings can be crucial. Until now studies on this issue have been mainly devoted to joint specimens with stiff beams, however frame structures having wide (also called flexible or flat) beams are widely used in the European residential building stock. To this purpose, given the lack of knowledge, an experimental investigation on full scale beam-column joints with wide beam has been planned and is currently in progress. In the present paper the main results of three tests are reported and discussed. The role of different earthquake resistant design levels on joint performances is pointed out.
Influence of Axial Load on the Seismic Behavior of RC Beam-Column Joints with Wide Beam
Applied Mechanics and Materials, 2014
Beam-column joints can play a key role on the seismic behavior of reinforced concrete buildings. Until now studies and experimental investigations on this topic have been mainly focused on beam-column joints with stiff beams, i.e. beams with height larger than the thickness of the adjacent floor slab. However, especially in the European residential building stock, frame structures are often equipped with wide -therefore rather flexible -beams. However, not many studies have been devoted so far to this type of connection, therefore an experimental investigation on full scale beam-column joints with wide beam was planned at the University of Basilicata and is currently in progress. In the present paper the main results of two cyclic tests are reported and discussed specifically analyzing the role of the axial load applied to the column on the joint performances and damage mechanisms. Test results highlights that the axial load value has a significant influence of on deformation capacity and ductility behavior.
2000
The 2005-2008 DPC-Reluis Project, funded by the Italian Department of Civil Protection (DPC), is made up of ten Research Lines (RL). RL 2 specifically focuses on the seismic performance of existing RC buildings and is, in turn, organised in nine different Tasks. In the paper, the design of the research activities being carried out within the Task 7 by the four involved Research Units (RU UNIBAS, RU UNIUD, RU UNISA, and RU UNINA) and some first results are reported. Main objective of Task 7 is to investigate on the experimental behaviour of beam-column joints without or with strengthening, thus providing a contribution to a more reliable evaluation of the seismic vulnerability of Reinforced Concrete existing buildings. To this purpose the main activities carried out are devoted to design and set up of wide experimental programs on beam-column joints and base column joints relevant to typical existing RC buildings having different Earthquake Resistant Design (ERD) level, to make a literature review of the state of the art on the subject, to perform numerical simulations based on some analytical models available in literature in order to fully understand the mechanical behaviour. Further, some results of the tests already carried out are reported, analysed and compared in order to understand the failure mechanism and evaluate the seismic performance of joints with and without ERD.
Seismic Behavior of Substandard RC Beam-Column Joints Dominated by Cantilever Action
2012
Based on practical design of medium to high-rise of RC building frames, the larger size of column compared to beam is common. This approach uses to ensure that column can sustain larger loads both for gravity and lateral directions. The larger depth of column with a few percentage of reinforcement, together by permanent axial compression force is enough to produce the high column flexural capacity and consequently increases the column-to-beam flexural strength ratio which is considered for capacity design concept. In addition, the larger depth of column may lead high joint shear strength and substantially increases the anchorage length which is necessary for preventing deterioration of bond during cyclic excitation. However, if the relative stiffness of column compared to the beam is too large, the expected mode of failure from beam-sway mechanism may be alternated to unexpected cantilever action mode which is uncommon in practical design. In this paper a study of two subassemblages representing interior frame at the bottom story compared to typical cruciform beam-column joint under reversed cyclic loaded is presented experimentally. The dimensions of beam-column joint for both specimens were designed identically except the column of one specimen was extended from the joint and fixed at strong foundation. The stiffness of column is designed relatively larger than the stiffness of beams. Even though the beam hingings were detected for both specimens but the global behaviors were significantly different. Behavior of cruciform beam-column joint was controlled by beams flexural strength while behavior of beam-column joint with column was controlled mainly by column flexural strength. It can be understood that the behavior of specimen with larger column compared to beams was dominated by cantilever action 52
Frattura ed Integrità Strutturale
The Algerian seismic code assumes that the beam-column joints in monolithic reinforced concrete (RC) buildings are fully rigid. However, many experiments have proven the existence of relative rotations in these connections, and then the presence of relative transfer of bending moment. The present work aims to investigate the effect of beam-column joints modelling on the global seismic behaviour of reinforced concrete (RC) moment-resisting frames buildings, designed according to the Algerian seismic code recommendations. To consider the nonlinear deformation of the connections, an analytical model developed recently is used. This model includes two important deformation mechanisms; the first one covers the slippage of the continuous reinforcement within the column, whereas the second involves slippage caused by creating bending cracks at the extremities of the beams. Three multi-storey RC frames with different setback geometry, including a reference frame, are studied considering the...
Engineering Structures, 2013
The paper is focused on the analysis of some test results obtained in the framework of a wide experimental program on RC beam-column joints carried out at the Laboratory of Structures of the University of Basilicata in Potenza, Italy. Specifically, cyclic tests on full-scale joint specimens having different earthquake resistant design levels were performed, applying different values of axial force. Test results relevant to 4 specimens have been analyzed and compared with the results of numerical simulations based on an accurate finite element modeling using the DIANA code at the Structural Engineering Dept. of the University of Naples. Experimental results show how the value of the axial load acting on the column can change the collapse mode, spreading damage from the beam to the joint panel. Moreover, a collapse mode due to the failure of beam longitudinal rebars, sometimes neglected in structural codes, has been observed. Numerical simulations were used to evaluate the stress distribution in the joint panel as a function of the axial load and to quantify the beam rebar deformations. The reasons for the specimens' global failure and, specifically, for that of the beam longitudinal rebars were identified and highlighted through a comparison with the experimental results.
2017
Past research and empirical evidence has shown that beam-column joints play a critical role in the cyclic behaviour of reinforced concrete (RC) structures and that a good understanding of the complex mechanical interactions in beam-column connections is necessary to ensure the desired hierarchy of failure is achieved. Development of such understanding requires specifically designed numerical and experimental studies that depict realistic structures. However, reviews of published experimental literature show that most experimental studies on the seismic behaviour pre-1970’s RC beam-column connections focus on the testing of sub-assemblies without slabs or transverse beams, which are unrepresentative of reality. This paper presents the first part of a study being carried out to shed light on how (and by how much) slabs and transverse beams contribute to the seismic performance of gravity-designed interior beam-column connections, and the consequences of ignoring or wrongly representin...
Seismic Assessment of RC Exterior Beam- Column Joints
2012
The assessment of the shear strength of two dimensional (2D) reinforced concrete (RC) exterior beam-column joints is an open issue and its solution is still a point of discussion in the scientific community although significant research effort has been devoted to this topic in recent times. The uncertainty in the evaluation of joint shear strength is exacerbated if substandard detailing is present such as lack of transverse reinforcement in the core, the use of plain round bars and inadequate anchorage of the beam bars, typical of pre 1970s construction practice. The need of a reliable evaluation of the shear behaviour of substandard joints is highlighted within the framework of a performance based seismic assessment and retrofit of RC frames.
Behaviour of Beam-Column Joint on Different Shapes RC Framed Structures: A Review
2017
The behavior of reinforce concrete moment resisting frame structures in recent earthquake all over the world has highlighted the consequences of poor performance of beam-column joint. Currently practice demand is “strong column weak beam” behavior so as result for ductile failure. The present review aims at the checking of adequacy of beam-column ratio in building under cyclic loading. The beam-column ratio is gradually increase & failure of column have been noted. Analysis carried by push over analysis. Also, variation of horizontal & vertical irregularity is review.
Cracking of RC beam/column joints: Implications for the analysis of frame-type structures
Engineering Structures, 2013
The work is concerned with an analytical investigation of the behaviour of reinforced-concrete beam-column joint subassemblages under monotonic and cyclic loading in an attempt to assess the effect of cracking suffered by the joint on the overall structural response. The behaviour of the structural forms investigated was established by nonlinear threedimensional finite-element analysis, after the latter had first been validated through a comparison of analytical predictions with published experimental findings. In all case studies presented, the joints were found to suffer considerable cracking that initiated at early load stages and led to an increase of the overall displacement values by a factor larger than 2. Such behaviour indicates that the assumption of 'rigid joint', which is implicit in methods used for the practical analysis of frames, is not applicable when such methods are employed for the analysis of concrete structures, even within the elastic range of structural behaviour.