Column Base Connections Research Articles

Pushover behaviour of bamboo portal frame structure

An experimental study of the pushover behaviour of a bamboo portal frame structure is reported. The objective of the study is to begin to establish an engineering basis for non- or marginally engineered bamboo construction appropriate for vernacular construction. The prototype frame used grouted bar column base connections and multiple single bolt culm to culm connections to affect the lateral resistance of the portal frame. The results of the pushover test revealed unanticipated column base behaviour. Therefore, a tangent study of the behaviour of single- and four-culm grouted bar column bases was performed. Through these experimental studies, the physical behaviour of the prototype structure was established. Finally, an analytical model, suitable for simple engineering environments is demonstrated and validated using the experimental results.

Comparison of Damage, Design Concept and Design Practices of Column Base Connections in Japan and the United States

Comparison of Damage, Design Concept and Design Practices of Column Base Connections in Japan and the United States

Finite element analysis of bolted column base connection without and with stiffeners

Column base plates are analyzed and designed on the assumption that the plate is rigid and its thickness is determined from the cantilever action of the plate projection beyond the column face. In the case of column base plates with stiffeners, the plate thickness is determined by considering its bending and some parameters, which define the boundaries. In the present research two aspects are investigated, the adequacy of the present provisions on the design procedure of base plates with stiffeners and degree of rigidity of the connection with foundation. The three dimensional models are analyzed and compared with the known laboratory test results under axial load and axial load with moment. The results show good agreement between finite element analysis and experimental test. Key words: Finite element analysis, steel connection, column base plate, rotational stiffness, rigidity.

Seismic performance of a 3D full‐scale high‐ductile steel–concrete composite moment‐resisting frame—Part II: Test results and analytical validation

AbstractThis paper presents the results of a multi‐level pseudo‐dynamic seismic test program that was performed to assess the performance of a full‐scale three‐bay, two‐storey steel–concrete composite moment‐resisting frame built with partially encased composite columns and partial‐strength beam‐to‐column joints. The system was designed to develop a ductile response in the joint components of beam‐to‐column joints including flexural yielding of beam end plates and shear yielding of the column web panel zone. The ground motion producing the damageability limit state interstorey drift caused minor damage while the ultimate limit state ground motion level entailed column web panel yielding, connection yielding and plastic hinging at the column base connections. The earthquake level chosen to approach the collapse limit state induced more damage and was accompanied by further column web panel yielding, connection yielding and inelastic phenomena at column base connections without local buckling. During the final quasi‐static cyclic test with stepwise increasing displacement–amplitudes up to an interstorey drift angle of 4.6%, the behaviour was ductile although cracking of beam‐to‐end‐plate welds was observed. Correlations with numerical simulations taking into account the inelastic cyclic response of beam‐to‐column and column base joints are also presented in the paper together. Inelastic static pushover and time history analysis procedures are used to estimate the structural behaviour and overstrength factors of the structural system under study. Copyright © 2008 John Wiley & Sons, Ltd.

SEISMIC RESPONSE OF CABLE-STAYED BRIDGE TOWER WITH SEMI-RIGID BASE CONNECTION MODELLING

The column base connections exhibit unpredictable semi-rigid behavior due to the fact that their basic components including base plate, anchor bolts and concrete foundation, are made from different material types and transmitting acting forces through unilateral multi-body contact. To address this need, this study seeks to develop a quite general base connection modelling capable of accurately representing material and geometrical nonlinear behavior of base connection, and its implementation in a time domain finite element seismic analysis through an incremental-iterative procedure is presented. A representative problem of cable-stayed bridges tower subjected to strong ground motion is analyzed. The maximum bearing stress on the concrete foundation as well as the tension force per anchor bolt that necessary to design the anchorage system is computed. The seismic responses of the tower structure with physical model of the base connection are compared to those of rigid base model. The semi-rigid connection model yields more economical solutions than rigid base model.

Analytical Evaluation of Plastic Resistance of Column Base Connection Using Convex Set Theory

It is important to estimate the structural safety of column base connection by calculating exact collapse loads. Column bases connection transfer reactions from the structure the foundation. In this paper, a simple mechanical model to predict their plastic resistance is proposed. An efficient linear-programming technique, which is called as Compact Procedure, is applied to column base connection model including multi-spring elements, where a column base is replaced by a set of plastic axial and bending springs. In Compact Procedure, it is not necessary to know the whole interaction surface of resistances at a plastic portion. A simple analytical model of column base connection to calculate its load-carrying capacity considering bi-axial loading effect is presented. In addition, efficiency of the proposed model is examined by comparing it with the past test results.

Characterization equations for steel column base connections

This paper presents partial results of a research program under way at Laval University for which the main goal is to introduce the behaviour of steel connections into commercial structural analysis software. The objective of this paper is to derive analytical characterization equations for three commonly used steel column base connections. The procedure to derive these equations is based on a curve standardization theory that requires a number of experimental results in the form of moment–rotation curves that characterize the behaviour of column base connections. Because of a lack of available experimental results, data were obtained from finite element models. The design of a simple steel structure introducing the semi-rigid behaviour of column bases is presented as an example. It shows that consideration of the semi-rigidity of column base connections increases the accuracy of the analysis results and leads to a decrease in structure weight and deformation.Key words: analysis, base, behaviour, column, connection, frame, partial, rigidity, steel, structure.

Experiments of Cold-Formed Steel Connections and Portal Frames

A series of connection tests which were composed of closed cold-formed steel sections were conducted to investigate the performance of the connections constituting a pitched roof portal frame. The flexural strength of the section was investigated first and the structural behavior of the connections including the moment-rotation relation, the yield, and ultimate moment capacity of the connections were studied experimentally. The connection test specimens consisted of column base, eave, and apex connections of the portal frame. The main factors of the connection test were the thickness and the shape of the mild steel connection element. Finally, the portal frame was tested under both constant vertical and increasing horizontal loads to failure. The experimental results were compared with the numerical analysis results. The semirigid connection concept was considered for the analysis of the portal frame using the secant stiffness of the connections, which were estimated from the moment-rotation curves of the connections tested.

Structural performance of cold-formed steel column bases with bolted moment connections

This paper presents a thorough investigation into the structural performance of cold-formed steel column bases using double lipped C sections with bolted moment connections. A total of four column base tests with different connection configurations were carried out, and it was found that section failure under combined bending and shear was always critical. Moreover, the proposed column bases were demonstrated to be structurally efficient attaining moment resistances close to those of the connected sections. In order to examine the structural behaviour of the column base connections, a finite element model was established using shell and spring elements to model the sections and the bolted fastenings respectively. Both material and geometrical non-linearities were incorporated, and comparison between the test and the numerical results was presented in details. The design rules originally developed for bolted moment connections between lapped Z sections were adopted and re-formulated for the design of column base connections after careful calibration against the test data. Comparison on co-existing moments and shear forces at the critical cross-sections of the column bases was fully presented. It was shown that the proposed design and analysis method was structurally adequate to predict the failure loads under combined bending and shear for column bases with similar connection configurations.

P-V-M Interaction Curves for Seismic Design of Steel Column Base Connections

Recent studies on connections have shown that the beam bending theory cannot predict the flow of forces near the connection regions. In this paper, a new truss analogy model has been proposed to better represent the flow of forces near the column base connections. Also, shear moment strength envelopes, generated for different levels of axial load using the hysteretic stress-strain curves for steel, are presented. The moment and shear demand for the design of column base connection elements are calculated using the normalized P-V-M interaction curves. Appropriate strength factors applied to the moment capacity of the column section to account for the uncertainty in the estimation of yield stress, strain hardening, compactness of the section, and slenderness of the member are discussed. Finally, a generalized procedure for the capacity design of column base connections is proposed.

Structural behaviour of bolted moment connections in cold-formed steel beam-column sub-frames

This paper presents an experimental investigation on bolted moment connections between cold-formed steel sections. A total of 20 column base connection tests and beam-column sub-frame tests with different connection configurations were carried out to assess the strength and stiffness of bolted moment connections between cold-formed steel sections. Among the tests, four different modes of failure were identified: • Mode BFcsw: Bearing failure in section web around bolt hole • Mode LTBgp: Lateral torsional buckling of gusset plate • Mode FFgp: Flexural failure of gusset plate • Mode FFcs: Flexural failure of connected cold-formed steel section For those connections failed in Mode BFcsw, the moment resistances of the connections were typically found to be below 50 % of the moment capacities of the connected sections. For those connections failed in Modes LTBgp and FFgp, the moment resistances of the connections were found to be about 60% and 75% of the moment capacities of the connected sections. Among all, the moment resistances of those connections failed in Mode FFcs were the highest with a minimum of 85% of the moment capacities of the connected sections. Consequently, it is demonstrated that through rational design and construction, effective moment connections between cold-formed steel sections may be readily achieved. Engineers are encouraged to build light-weight low to medium rise moment frames with cold-formed steel sections.

Dynamic response of column bases

In this paper, the dynamic behaviour of a column base connection simulated by a cantilever on elastic supports is studied. The model considered consists of the column with length ℓ, moment of inertia I and mass m per meter, with a concentrated mass M and rotational inertia J in its tip. In the bottom of the column the connection with the concrete foundation is obtained using two springs, one rotational and one translational. Through these two springs the behaviour of this connection is realised taking into account the influence of various parameters (i.e. base-plate, anchor bolts, material properties etc.). The equation of motion of the system is established and the shape functions of the model considered are obtained. The external excitation is a dynamic ground motion having a general equation form (with the possibility to change the parameters that affect this function), also taking into account the damping of the system. On the basis of the equations derived, the influence of the various parameters that are inserted in the problem is examined, and some of the results are presented in tabular and graphical form, giving useful deductions for further research.

Semi-rigid column–base connections in pultruded GRP frame structures

A review of moment–rotation tests on bolted connections between pultruded Glass Reinforced Plastic (GRP) Wide Flange (WF) sections highlights the lack of test data on column–base connections. Details of five bolted web and web and flange cleat connections and the test rig used to determine their moment–rotation characteristics are given. Moment–rotation responses are then presented for each connection. Simple models are described for predicting their initial rotational stiffness, ultimate moment and moment–rotation response. The models predict the response of bolted web and flange cleat column–base connections reasonably well and may be useful for design.

Utilisation of Test Data for Column Bases When Assessing Overall Frame Response: A Review

Previous studies of the behaviour of steel column base connections are reviewed; attention is concentrated on the results from programmes of laboratory testing. Nominally pinned bases are shown to provide significant rotational restraint and to be capable of transferring quite large moments into the foundations. Ways of representing these effects in frame analysis are investigated and, based on sample studies, a recommendation is provided.

Testing of semi-rigid unbraced frames for calibration of second-order inelastic analysis

This paper examines the behaviour of semi-rigid unbraced frames through a series of tests on a variety of rectangular frames as well as their joints so that the analysis and design methodology can be developed and verified against the test results. The frame and joint tests employed similar beam and column sizes and had the same connection details. The two types of connections studied were top-seat-double-web angle and extended end-plate. Column-base connections were also included in the studies. Load-displacement plots are presented for all the test frames subjected to gravity loads applied to the beam and columns, and a horizontal load applied at the beam level. The principal objective of the joint tests is to provide a comprehensive set of moment-rotation data, in terms of stiffness and moment capacity, so that a comparative assessment of the frame performance due to the different connection types could be undertaken. Detailed descriptions of test arrangement, load sequences, test methods and data acquisition techniques are given. The general observed behaviour is discussed. Results from the frame tests are compared with the corresponding theoretical results obtained from a second-order inelastic analysis.

Mathematical modelling of column base plate connections

Based on classical methods a design procedure is proposed for the derivation of M-ϕ curves of column base connections. Besides, a new simple formula is also proposed, which describes with adequate accuracy the relation between moment and rotation, and all the necessary coefficients of this formula are given for each particular case. Introducing this formula into equilibrium equations of any frame and using the appropriate M-ϕ curves, a more accurate analysis of the frames can be carried out, with a better approximation for the support conditions, regarding the assumption of fully pinned or fixed supports.

Ultimate limit strength of column-base connections

For steel structures, the new design concepts are based on plastic frame analysis and ultimate strength of beams, columns and connection fasteners. This paper deals with the calculation of the ultimate strength of the column-base connections. Several failure modes for concrete block, anchor-bolts, plate and column itself are taken into account. Otherwise, it is well recognized now that the ultimate strength of a connection is one of the main parameters that must be used in semi-rigid modelling. To investigate all loading conditions, an experimental device with two electro-hydraulic actuators is used. The experiment is controlled by a real-time synchro-system. The main features of the behaviour are reported, pointing out the representative parameters for further modelling. The calculation of the ultimate strength of the connecyion, using limit analysis methods, is detailed. Comparison with experimental results is made for ‘fixed’ and ‘pinned’ column-base connections.

曲げモーメントとせん断力をうける角形鋼管柱の埋込み形式隅柱柱脚部における力学性状

Embedded type column base connections using square steel tubes have recently come into wide use in steel construction ; however, the mechanical characteristics for exterior columns (corner columns) have not been sufficiently clarified. A total of 42 steel column bases were tested. The following variables were studied : (1) embedment length, (2) end distance, (3) U type reinforcing bars, (4) tie spacing, (5) presence or absence of anchor bolts, stud dowels or anchor reinforcing bars and (7) loading system. The results of this study may be summarized as follows : (1) When the end distance is 2D (D : Column Depth) or greater in case of the 2.5D embedment length, mechanical characteristics similar to those of interior columns can be assumed. (2) In the corner columns, the mechanical characteristics differ under the loading directions when the end distance is 1D or less than 1D. The concrete outside the column requires reinforcement at the top of the footing and near the location of the base plate. (3) When the embedment length is less than 2D in case of the 1D end distance, the load-displacement curves show slip shapes with small energy dissipation.

Experimental behaviour of steel column bases

Abstract A common feature of many steel building frames is the use of two bolts to anchor a baseplate welded to the column end to the concrete foundation. Such a connection is typically assumed to represent a ‘pinned’ connection, meaning that it is assumed for design purposes that the connection is incapable of transferring bending moment. However, virtually no experimental observations to support such a design assumption have been reported. The present paper presents experimental findings for column-base connection behaviour under axial load and bending moment. The influence of the soil is not considered in the present work.

Rotational restraint of a simple column base connection

This paper presents the results of an experimental investigation on the behaviour of steel column base connections. The purpose of the study was to determine the value of the rigidity ratio at the column base (GL). The connection is made of a steel base plate welded to the lower end of the column and attached to the footing by means of two or four anchor bolts. It is generally admitted that this type of connection behaves like a hinge and it is recommended to use GL = 10.0 to evaluate the effective length factor of the column.The test results indicate that for weak-axis buckling a conservative value of the rigidity ratio is GLY = 0.50 and for strong-axis buckling GLX = 1.50, if there is no relative displacement of column ends. The effective length of the column is therefore reduced. A design example shows that the column strength is increased by approximately 30% for slenderness ratios currently met in practice. Key words: steel column, column base connection, moment–rotation curve, buckling.