Influence of Axial Load on the Seismic Behavior of RC Beam-Column Joints with Wide Beam (original) (raw)
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Journal of Earthquake Engineering, 2013
A wide experimental program on beam-column RC joints carried out in the framework of the DPC-Reluis Project (DPC: Department of Civil Protection, Reluis: Network of University Laboratories of Earthquake Engineering) is presented. All the experimental tests were performed at the Laboratory of Structures of the University of Basilicata, Potenza (Italy). The main objective of the experimental campaign is to study and compare the post-elastic behaviour of beam-column joints with different earthquake resistant design levels, indicating the role of some structural parameters such as the axial load value acting on the column, the beam dimensions, and the steel type, on the joint performances and failure mechanism. The analyses have mainly been devoted to improving the assessment procedures regarding existing buildings but also to verifying the prediction capability of the capacity models relevant to beam-column joints contained in literature and in the new seismic codes. Following a short description of the experimental methodologies used in other campaigns, the experimental program is presented, providing a detailed description of the specimens and of the testing set-up. This is followed by a report of the main results of the cyclic tests performed on the beam-column specimens which highlight the role played by axial load and seismic design level in determining the failure mechanism and the global response of the joints.
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.
Shear strength model for RC beam–column joints under seismic loading
Engineering Structures, 2012
This paper presents a new shear strength model for reinforced concrete (RC) beam-column joints subjected to cyclic lateral loading. In the proposed model, the reinforced concrete in the joint panel is idealized as a homogenous material in a plane stress state. The contribution of the joint shear reinforcement (including both the transverse steel reinforcement and the intermediate longitudinal steel reinforcement of the column) is taken into account through the nominal tensile strength of the idealized material. The effect of tensile straining in the transverse direction on the compressive strength of the idealized material is accounted for using the Kupfer-Gerstle biaxial tension-compression failure envelope. Comparisons with the results of 106 existing tests of both exterior and interior beam-column joints, with and without transverse steel reinforcement, demonstrate the accuracy of the proposed model. These comparisons also illustrate the superior accuracy of the proposed model over existing models. A subsequent trend analysis using the test database confirms that all key parameters influencing the shear strength of beam-column joints have been appropriately considered in the proposed model. The proposed model is believed to be suitable for design use due to its simple form, wide applicability and accuracy.
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 Reinforced Concrete Interior Wide-Beam Column Joints
In this article, experimental and finite element (FE) numerical investigations on interior wide-beam column joints are presented. The experimental research consisting of three full-scale interior widebeam column specimens was carried out at Nanyang Technological University, Singapore to study the seismic behavior. Details of the test results are discussed to understand the specimens' seismic performance in terms of general behavior, hysteresis loops response, and strain profiles of longitudinal reinforcement. In the FE numerical study, the three-dimensional (3D) model developed is validated by comparing the analysis results with the experimental test results, which has shown a good agreement. A parametric study is performed to elucidate more information and to understand the influence of critical parameters affecting the joint behavior such as column axial load, beam anchorage ratio, and wide beam participation.
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 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.
Behaviour of reinforced high-strength concrete beam—column joint. Part 1: experimental investigation
Structural Concrete, 2003
The beam-column joint is one of the important structural elements of reinforced concrete structures. It has been the subject of intensive research for the past four decades. To date, most of the design procedures of joints have been devoted to ordinary-strength concrete as implemented in the current international design codes. The use of high-strength concrete has become useful because of the advantages of member size limitation and higher structural capacity. However, its applicability is still limited because its behaviour, especially under combined stresses and shear, differs from ordinary-strength concrete in the presence of axial loading on the column. Consequently, the existing design guidelines are not completely applicable. In order to establish the salient features of the behaviour, namely modes of failure, deformational characteristics, strength parameters and strain development, an experimental programme was performed on beam-column joints under quasi-static monotonic loading. The influence of axial compression, along with other actions imposed on the joint including shear and bending moment, was taken into consideration. The practical aspects of using a composite structure-that is, ordinary-strength concrete of different grades at floor level and high-strength concrete along the rest of the column-were considered. The effects of different permutations of longitudinal as well as transverse reinforcement and various configurations of stirrups were also investigated.
FLEXURAL BEHAVIOUR OF INTERIOR R.C.BEAM COLUMN JOINT WITH AND WITHOUT SLAB UNDER CYCLIC LOADING
The behavior of reinforced concrete moment resisting frame structures in recent earthquakes all over the world has highlighted the consequences of poor performance of beam column joints. Beam column joints in a reinforced concrete moment resisting frame are crucial zones for the transfer of loads effectively between the connecting elements (i.e. beams and columns) in the structure. In 1976, the design of beam column joint is first recommended and subsequently revision is carried out in the year 1985. Design specifications only for the beam column joints are given in IS 13920:1993. There is no provision for the type of column joint whether it be Edge column, Corner column or Interior column. Effect of slab is also not considered in this code. Hence a study and investigation is required on the beam-column joint with slab to suggest improvement in reinforcement detailing based on influence of slab. Two scaled specimens, one Interior Beam-Column joint with slab (BCJS) and another Interior Beam-Column joint without slab (BCJ) were made. Tests were carried out in structural laboratory and the results are discussed here.
Seismic Behaviour of Beam-Column Joint in R/C Frames and Strengthening with FRP
2nd Croatian Conference on Earthquake Engineering ‒ 2CroCEE
Multi-story reinforced concrete structures in previous periods, in general, do not meet current seismic design code requirements, including the poor materials and execution of civil engineering works. In the scope of this, is analyzed the behavior of the structures during the Earthquake of November 2019, in Albania, specifically in different building stocks. Typical structural deficiencies observed in reinforced concrete (R/C) frame buildings affected by the 2019 earthquake reveal that many collapses occurred could be attributed to the poor quality of construction and use of non-ductile detailing and during the assessment that deficiency beam–column joints can jeopardize the integrity of structures. In general, it is accepted that beam-column joints are critical elements of reinforced concrete buildings subjected to lateral loads and that they may require specific design. Assessment reports have often indicated that beam-column joints, which are one of the most vulnerable and critic...