Effect Of Semi-rigid Connections Research Articles

Comparative Analysis of Steel Structure with Rigid and Semi Rigid Joint using Analysis Tool ETABS

Generally, in steel structure the connection between beam and column are designed as moment connection and pinned connection, but in actual condition the structure behaves between these two conditions, resulted into semi-rigid condition which is intermediate stage between rigid and pinned joints. Effect of semi-rigid connection on multi-story multi-bay frame is accomplished in this Study. The present study introduces the effect of static and dynamic loading on high rise steel structure of G+12 story with 4m, 6m and 8m three bay span length. Structure is analyzed under two different condition of partial release of semi-rigid connections which is derived by fixity factor of values 0.5 and 0.75 in this study. The analysis is done commercially available software ETABS. From the non-linear analysis, the story displacement and story drift are obtained. The overall performance of the structure from the analysis, semirigid joints display more story displacement and story drift compared to rigid joints. To overcome the results, bracing system is introduced at different location of periphery of structure. These brace frame structure consist of X- bracing and diagonal bracing. Again, comparative analysis is to be performed in ETABS on these three-bay span lengths. It is found that braced semi-rigid frame structure perform quite well as compared to unbraced frame structure.

Exploration Study on Energy Dissipation in Beam and Column Joint with Semi Rigid Connection

Abstract: The earthquake reconnaissance reports reveal that the failure of beam column joint has contributed to partial or complete collapse of reinforced buildings. The failure of a beam causes only localized effect whereas the failure of a beamcolumn joint causes instability of the whole building under seismic loading. This results in significant economic impact and loss of life. Hence it is essential to avoid failure of beam-column joint. The serious damage to the major structures during recent earthquakes is mainly attributed to lack of ductility in beam-column joint. In the present work, experimental investigation is carried out to study the effect of semi rigid connection in RCC beam column joints of reinforced concrete multi storey buildings. The effectiveness of semi rigid connection and effective positioning (stability approach) is analytically investigated for a typical four-bay four-storey and five-bay seven-storey RC frame with different percentage of joint connections by nonlinear static (pushover) and nonlinear dynamic (time-history) analyses. Poor performance was noted in rigid frame during the prediction of structural damage, lateralstrength and storey drift. The semi rigid connection isprovided in different places and it is found that performance of the structure enhanced in the stability approach. The stability approach exhibited improved performance in terms of roof displacement, for and semi-rigid connection.

GPR-based prediction and uncertainty quantification for bearing capacity of steel tubular members considering semi-rigid connections in transmission towers

In this paper, the effect of semi-rigid connections on the bearing capacity of steel tubular members in transmission towers is investigated by the numerical analysis based on experimental validation and the metamodel-based prediction method. Especially, for the stability bearing capacity of steel tubular members considering semi-rigid connections (STM-SRC), a prediction method based on the Gaussian process regression (GPR) model is proposed to accurately predict its value and to efficiently quantify its uncertainty. Firstly, on the basis of the development of mechanical model of STM-SRC in transmission towers, the experimental and numerical studies on STM-SRC are conducted. Then, a dataset of 1125 samples generated by the validated finite element model is used to train and test the GPR model, and the accuracy of the proposed method based on the GPR model is evaluated. Finally, based on the proposed prediction method and the Monte Carlo simulation, the uncertainty for the stability bearing capacity of STM-SRC is quantified under the probabilistic framework. The results show that the proposed method has high accuracy in predicting the stability bearing capacity of STM-SRC. Meanwhile, the stability bearing capacity of steel tubular members is enhanced and their reliability exhibits the linear increase after considering semi-rigid connections.

Optimizing the Design of Tall Buildings Using the Principle of Virtual Work: The Effect of Semi Rigid Connections

The Virtual Work Optimization Method (VWOM) is used to optimize tall buildings with semi rigid connections. The VWOM is an automated method that minimizes the mass of a structure with a given geometry, deflection criteria and load cases, while adhering to building code requirements. Members are selected from a user defined database to meet strength and stiffness criteria. The rotational stiffness of connections can be specified and varied, from rigid to pinned. The method is explained using an example of a two storey one bay steel frame with six members. Four case studies are presented: (i) a six storey two bay frame, (ii) a ten storey one bay steel building, (iii) a fifteen storey three bay steel frame and (iv) a twenty four storey three bay building. The examples are compared to results found in the literature. Structures were optimized for a range of connection rotational stiffnesses. The VWOM obtained results up to 44.6% lighter than published work. Optimized results showed that in most cases the semi rigid connection produced the same results as the rigid connections. This is due to the rapid plateauing of the optimized mass as the connection stiffness increases. Thus, the typical definition of semi rigid and rigid rotational stiffnesses (for example Eurocode 3) are both found on this plateau. If some members are lightly loaded, broad semi rigid and rigid bands can be produced. The effect in these cases is that structures with rigid connections are lighter than those with semi rigid connections as no compensation in the member stiffness is required to meet deflection criteria.

Stability Analysis of Frame Having FG Tapered Beam–Column

This study focuses on the analysis of the tapered beam–column having functionally graded section. By using two different methods, the substantial effects of the coupling–extensional bending of this structure are considered. Both second-order effects and flexibility of connections are considered in the analysis. The suggested exact stiffness matrix is very general and suitable for analyzing any plane frame, which has non-prismatic members and various types of connections. By using this formulation, the frame stability analysis of the FG beam with power function will be performed. Furthermore, the effects of semi-rigid connections and supports on the buckling load of 2D frames will be studied. Finally, comparing the new responses with the available solutions shows the accuracy, efficiency and capabilities of the proposed stiffness matrix. In addition, some new problems, including 2D frame, especially gabled frame, are solved using authors’ schemes.

Effect of semi-rigid connections in improvement of seismic performance of steel moment-resisting frames

Seismic performances of dual steel moment-resisting frames with mixed use of rigid and semi-rigid connections were investigated to control of the base shear, story drifts and the ductility demand of the elements. To this end, nonlinear seismic responses of three groups of frames with three, eight and fifteen story were evaluated. These frames with rigid, semi-rigid and combined configuration of rigid and semi-rigid connections were analyzed under five earthquake records and their responses were compared in ultimate limit state of rigid frame. This study showed that in all frames, it could be found a state of semi-rigidity and connections configuration which behaved better than rigid frame, with consideration of the base shear and story drifts criterion. Finally, some criteria were suggested to locate the best place of the semi-rigid connections for improvement of the seismic performance of steel moment-resisting frames.

Pushover analysis of gabled frames with semi-rigid connections

The nonlinear static analysis of structure, which is under the effect of lateral loads and provides the capacity curve of the structure, is defined as a push-over analysis. Ordinarily, by using base shear and the lateral displacement of target point, the capacity curve is obtained. The speed and ease of results interpretation in this method is more than that of the NRHA responses. In this study, the nonlinear static analysis is applied on the semi-rigid steel gabled frames. It should be noted that the members of this structure are analyzed as a prismatic beam-column element in two states of semi-rigid connections and supports. The gabled frame is modeled in the OpenSees software and analyzed based on the displacement control at the target point. The lateral displacement results, calculated in the top level of columns, are reported. Furthermore, responses of the structure are obtained for various support conditions and the rigidity of nodal connections. Ultimately, the effect of semi-rigid connections and supports on the capacity and the performance point of the structure are presented in separated graphs.

Nonlinear dynamic analysis and natural frequencies of gabled frame having flexible restraints and connections

Nonlinear dynamic and natural frequencies of a gabled frame with elastic restraints and semi-rigid connections are investigated by using a program in OpenSees software. Natural frequencies are obtained for two states, which are flexible connections and semi-rigid supports, separately. The mode shapes of structure are also obtained for the described states. Also, the effect of connection flexibility on the dynamic responses of the frame is obtained for different values of peak ground acceleration. The members of this structure are modeled as a nonlinear beam-column element. The members of structure are assumed to be prismatic. Two equal lumped masses at the head of two columns in horizontal and vertical directions are considered as the mass pattern of structure. Note that three degrees of freedom are allocated to all nodes. Furthermore, the mode shapes of frame are obtained. Conclusively, the effects of semi-rigid connections and supports on the natural frequencies and mode shapes of structure are investigated. As results, the top level displacement and base shear responses of frame are reported.

A simple formula for estimating the column ultimate load with effect of semi-rigid connections

Calculating the ultimate load of a framed column in sway structures involves, in the currently used design method, the calculation of the column effective length and utilizing the interaction formulae or tables. Therefore no allowance is made for the presence of semi-rigid connections in the currently used design method. In this paper, a new formula to calculate the column ultimate load is proposed using simple model to simulate the behavior of practical steel columns in sway structures. This formula takes into account the effect of semi-rigid connections, the column rotational end restraints and the ratio of the applied horizontal to vertical loads. Moreover, the proposed method has the advantage of allowing for the influence of the column end moments resulted from the presence of the externally applied loads. In order to verify the accuracy of the proposed formula, several examples are presented in which the column ultimate load have been calculated using the proposed formula and the well known computer program STAAD.Pro. Comparing the obtained results of the proposed method with those obtained from STAAD.Pro has shown good correlation and therefore the accuracy of the proposed method to predict the behavior of practical columns has been verified.

Seismic behavior of suspended building structures with semi-rigid connections

A method is presented in this paper to analyze the dynamic response behavior of suspended building structures. The effect of semi-rigid connections that link suspended floors with their supporting structure on structural performance is investigated. The connections, like the restrains in non-structural suspended components, are designed as semi-rigid to avoid pounding and as energy dissipation components to reduce structural response. Parametric study is conducted to assess the dynamic characteristics of suspended building structures with varying connection stiffness and suspended mass ratios. Modal analysis is applied to identify the two distinct sets of vibration modes, pendulum and bearing, of a suspended building structure. The cumulative modal mass is discussed to ensure the accuracy in applying the method of response spectrum analysis by SRSS or CQC modal combination. Case studies indicate that a suspended building having semi-rigid connections and proper suspended mass ratios can avoid local pounding failure and reduce seismic response.

An Efficient Computational Method for Semi-rigid Steel Frame with Elements of Internal Plastic Hinge

This paper proposes an efficient computational method for semi-rigid steel frame with elements of internal plastic hinge. The yield function of I or H section is derived by using section assemblage concept, and residual stress is considered in the initial yield function. Element with springs-in-series at each end is presented to consider the effect of semi-rigid connections and material nonlinearity. Based on the proposed method, it is demonstrated that internal plastic hinge can be well predicted by only using one element for the members subjected to distributed loads. The proposed element has the same nodal degrees of freedom as conventional element by condensing the non-nodal degrees of freedom introduced in the derivation. Other factors influencing the capacity of steel frames, such as shear deformation, geometric nonlinearity and initial imperfection, are explicated. Using FORTRAN, an improved nonlinear analysis program of semi-rigid steel frame is compiled. Numerical analysis shows that the proposed method has high efficiency and accuracy.

Simplified Procedure to Calculate by Hand the Natural Periods of Semirigid Steel Frames

AbstractCurrent seismic design codes provide empirical equations for the calculation of the fundamental period of a framed structure primarily as a function of height, and do not consider the effect of beam-column joint stiffness. In the literature, far too little attention has been paid to incorporate this effect in approximate formulas to calculate by hand the natural periods of semirigid steel frames, which is the aim of this paper. The proposed formulas have been developed after modifications of existing formulas in the literature for rigid-jointed plane steel frames. Then, the accuracy of these approximate formulas was verified by a finite element analysis using ABAQUS software. Finally, a parametric study was conducted to highlight the effect of semirigid connections on the natural periods of vibration of plane steel frames.

Influence of stiffness in bolted connections in wooden plane structure of truss type

Trusses are structural systems commonly used in projects, being employed mainly in roof structures, present in most rural buildings. The design of trusses, as well as other structural systems, requires the determination of displacements, strains and stresses. However, the project is developed from an ideal model of calculation, considering free rotation between the elements of a connection. This paper presents a computer program for the analysis of bidimensional wooden trusses with connections formed with two screws per node. The formulation is based on the flexibility method, taking into account the influence of the effect of semi-rigid connections formed by two screws. An example of a structure is presented and analyzed by the program developed here, highlighting the importance of behavior analysis on semi-rigid connections.

Stability of columns with semi-rigid connections including shear effects using Engesser, Haringx and Euler approaches

A complete column classification and the corresponding stability equations that can be used to evaluate the elastic critical axial loads of prismatic columns with sidesway uninhibited, partially inhibited, and totally inhibited including the simultaneous effects of bending and shear deformations and semi-rigid connections are presented and derived using three different approaches. The first two approaches are those by Engesser and Haringx that include the shear component of the applied axial force proportional to the total slope ( d y / d x ) and to the angle of rotation of the cross-section ( ψ ) along the member, respectively. The third approach is a simplified formulation based on the classical Euler theory that includes the effects of shear deformations but neglects the shear component of the applied axial force along the member. Comparisons among the critical loads obtained using these three approaches and those using the classical Euler solutions for classical column cases are presented. Examples that demonstrate the effectiveness and accuracy of the proposed stability equations and the importance of shear deformations and shear component of the applied axial force are presented in detail. These effects must be taken into account particularly in structures made of columns with relatively low effective shear areas A s (like laced columns, columns with batten plates or with perforated cover plates, and columns with open webs) or with low shear stiffness GA s of the same order of magnitude as π 2 E I / h 2 (like short columns made of laminated composites with low shear modulus G when compared to their elastic modulus E ). These effects become even more significant when the external supports are not perfectly clamped. The effects of semi-rigid connections and those due to shear forces and deformations are condensed into the proposed characteristic equations.

Effect of Semi-Rigid Connection and Pole in Different Flat on the Overall Steady-State Load-Bearing Capacity of the Steel Tubular Scaffold with Couplers

Nonlinear analysis of the steady-state load-bearing capacity of steel tubular and the steady-state load-bearing capacity of scaffold was simulated by ANSYS considering semi-rigid connection and pole in different flat. Quantitative standard of the steady-state load-bearing capacity to the steel tubular and the steel tubular scaffold with couplers is used in ANSYS. The effect of semi-rigid connection on the overall steady-state load-bearing capacity of the steel tubular scaffold with couplers is great. The effect of pole in different flat on the overall steady-state load-bearing capacity of the steel tubular scaffold with couplers is smaller. It’s generally recognized that nodes of vertical bars and horizontal bars of steel tubular scaffold by fasteners is not rigid, but semi-rigid; is not in the same plane, but in a different surface. This structural model directly affects the steady-state load-bearing capacity of scaffold. In this paper, ANSYS software was used for nonlinear analysis of steel tubular scaffold, the same models with experimental value [4] was used to establish standards for determining the instability load [1] [2], to determine the effect of bar coplanar and semi-rigid connections on steel tubular scaffolding overall stability capacity.

Stability and non-linear second-order elastic analyses of beam and framed structures with semi-rigid connections using the cross method

The main objective of this publication is to present an extended version of the Moment Distribution Method (MDM) for the stability and non-linear second-order analysis of indeterminate beams and framed structures made of beam-columns of symmetrical cross-section including the combined effects of shear and bending deformations, axial loads, and semi-rigid connections. The proposed method along each member has the following advantages: (1) it can be utilized in the first- and second-order analyses (including buckling analysis) of indeterminate beams and framed structures made of beam-columns with rigid, semi-rigid, and simple end connections; (2) the effects of semi-rigid connections are condensed into the bending stiffness and fixed-end moments without introducing additional degrees of freedom and equations of equilibrium; and (3) it is accurate, powerful, practical, versatile, and an excellent teaching tool. Analytical studies indicate that shear deformations, semi-rigid connections, and axial loads increase the lateral deflections and affect the internal moments and reactions of continuous beams and framed structures. These effects must be taken into account particularly in slender structures and when they are made of beam or columns with relatively low effective shear areas (like laced columns, columns with batten plates or with perforated cover plates, and columns with open webs) or with low shear stiffness (like short columns made of laminated composites with low shear modulus G when compared to their elastic modulus E) making the shear stiffness GAs of the same order of magnitude as EI/L2. These effects become even more significant when the external supports are not perfectly clamped. Three comprehensive examples are included that show the effectiveness of the proposed method.

Second-order slope–deflection equations for imperfect beam–column structures with semi-rigid connections

A new set of second-order slope–deflection equations for Euler–Bernoulli beam–columns of symmetric cross-section including the effects of initial imperfections (i.e., initial curvature, out-of-plumbness and axial load eccentricities) and semi-rigid connections is developed in a classical manner. The proposed method has the following advantages: (1) it can be utilized in the stability and second-order analysis of framed structures made of Euler–Bernoulli imperfect beam–columns with rigid, semi-rigid, and simple connections subject to axial and transverse loads; (2) the effects of semi-rigid connections and member imperfections are condensed into the slope–deflection equations for tension and compression axial loads; (3) it is more accurate than any other method available in the technical literature and capable of capturing not only the first-order and second-order elastic responses of frames made of imperfect beam–columns but also the phenomenon of reversals of deflections along the members as the axial loads are increased; and (4) it is powerful, practical, versatile and easy to apply. Analytical studies indicate that the initial imperfections (a) act as if they were additional transverse loads proportional to the bending stiffness and magnitudes of the imperfections of the corresponding beam–column; and (b) are detrimental to structures, increasing the lateral deflections, moments, and shears, and also reducing the critical axial loads of beam–columns and framed structures. This is particularly critical in structures made of beam–columns with initial crookedness and low stiffness connections subjected to high compressive axial loads. In addition, the effects of initial curvature are amplified by the compressive axial loads applied at the ends of the member. Four comprehensive examples are included that show the effectiveness of the proposed method.

Effects of Semi-Rigid Connection on Structural Responses

There are several idealizations in numerical analysis of structures. In the joints and supports, which is usually assumed to be pinned or rigid, semi-rigid connection should be considered to obtain more realistic, reliable and also economical results. In this study, rotational spring stiffness-connection ratio relation is clearly explained and revealed. A finite element program SEMIFEM is developed in FORTRAN language for the numerical analysis. This program provides to define semi-rigid connections in terms of rotational spring stiffness or connection ratio simultaneously. In the numerical applications, rotational spring stiffness - connection percentage relation of the semi-rigid connected structural members is submitted. Semi-rigid connections are considered in column-to-foundation connection of a portal frame, beam-to-column connection of a prefabricated structure, steel brace connection to reinforced concrete (RC) frame of a steel X-braced RC frame and truss member connection to joint of a steel truss system. The variation of moment, shear force, axial force, displacement and stress is investigated in a selected axis of the structures. Numerical examples are performed with respect to connection percentage of the related structural members by using finite element method. According to finite element analysis results, the degree of the semi-rigid connection is important as much as its existence in the design phase. This study reveals that the effect of semi-rigid connections on structural systems shows different variations from structure to structure.

Bending and rotational behaviour of semi-continuous composite beams

Stresses and deflections were measured in various semi-continuous composite beams. The bending and rotational capacities of the composite connections were measured in terms of beam curvatures and deflections by using two full-scale semi-rigid composite frames with monotonic loadings. The effect of semi-rigid connections on the performance of composite beams with various loadings was compared with predictions and codes. The tests show that the semi-continuous composite beams are more economic and effective than the simple or continuous composite beams. The semi-rigid connections affect the bending capacities and beam deflections, so the connection behavior should be considered in the design of composite beams. Yielding analysis of the steel beam bottom flange has some influence on the deflection calculation of composite beams.

The effect of semi-rigid connections on the dynamic behavior of tapered composite GFRP poles

This paper deals with the dynamic behavior of tapered composite poles with circular hollow cross-section and flexible connections, which are designed for use in power transmission lines. These poles, made from polyester reinforced with E-glass fibers, are produced using the filament winding technique. Transmission poles are mainly subjected to cantilever bending, since loading due to the wires and wind gusts is applied laterally. In the present work, a simple, but reliable, tapered beam element is developed and the dynamic behavior of the poles is accurately captured using only a few elements. A simple model for flexible connections is established and incorporated in the analysis. The material is orthotropic and its behavior is assumed linearly elastic. Shear effects are accounted for in the analysis because of their significant role due to the low shear modulus. Modal analysis is performed for design purposes to obtain the natural frequency and period of poles with various geometrical characteristics and material lay-up, as well as the effect of connection flexibility. Experimental results on the dynamic behavior of jointed composite poles are also presented and the effect of damping is estimated. The analytical results presented in this work are based on typical composite poles produced by filament winding, and are compared to commercially available finite element codes.