This paper presents numerical and theoretical studies on the performance of internal diaphragm connections to box columns. The study aims to investigate the static and cyclic performances of the ...connections including the behavior of diaphragms. This paper contains an assessment of the numerically and theoretically parametric studies on plate-to-box column connections considering several influence parameters, such as diaphragm, plate width, and column thickness. Subsequent sections discuss the prediction and validation of strength of the connections, followed by the performance of wide flange (WF) beam-to-box column connections. The results are presented and discussed as finding that diaphragms were the key elements to enhance the performance of the connections.
•Strength of the internal diaphragm connections were predicted.•Diaphragm, plate width, and column thickness affected strength of the connection.•WF beam-to-box column connections achieved the seismic requirement.•Diaphragm is the key element to improve strength and stiffness of the connection.
Reliable collapse assessment of structural systems under earthquake loading requires analytical models that are able to capture component deterioration in strength and stiffness. For calibration and ...validation of these models, a large set of experimental data is needed. This paper discusses the development of a database of experimental data of steel components and the use of this database for quantification of important parameters that affect the cyclic moment-rotation relationship at plastic hinge regions in beams. On the basis of information deduced from the steel component database, empirical relationships for modeling of precapping plastic rotation, postcapping rotation, and cyclic deterioration for beams with reduced beam section (RBS) and other-than-RBS beams are proposed. Quantitative information is also provided for modeling of the effective yield strength, postyield strength ratio, residual strength, and ductile tearing of steel components subjected to cyclic loading.
•Three new bamboo moment connections based on steel clamps are proposed.•Connections were evaluated under static monotonic and cyclic tests.•Mechanical performance of prototypes was higher than that ...of conventional connections.
Bamboo has become a promising sustainable material for structural applications. The design of normalized efficient connections is one challenge that has to be solved to increase the use of raw bamboo in construction. Current bamboo connections are considered to be unable to transmit moment, limiting the use of the material in several applications. We propose three new beam-column bamboo connections capable of transmitting moment. Each joint is comprised of five thin steel clamps tightened around the culms, which are connected with small steel angles and platens in different configurations. Steel clamps provide great versatility and avoid premature failures. Static monotonic tests showed stiffness, strength and ductility in the ranges of 73.4–230.8 kN.m/rad, 3.4–5.2 kN.m and 3.6–17.2, respectively, for the three designs. Average stiffness and strength of these connections were at least 29% and 250% higher than those reported for conventional mortar-injected bolted connections. Cyclic tests of the connections showed hysteresis loops with pinched regions without strength degradation which is characteristic of timber connections. This study shows that clamp moment connections are a feasible alternative to improve the structural performance and versatility of bamboo structures.
The research presented in this paper is part of a series of efforts to develop design recommendations for hollow structural section (HSS) connections situated at the end of a truss (or frame) under ...fatigue loading. Full-sized circular hollow section (CHS)-to-CHS regular and end connections (with open chord ends and chord-end cap plates) were tested under branch in-plane bending to measure strain concentrations at the critical locations. This experimental data was then used to verify a finite element (FE) modelling approach. An FE parametric study (totaling 1120 FE models, including 560 T-type connections and 560 X-type connections) was then carried out to investigate the effects of different chord end boundary conditions (i.e., varied chord end lengths, and open versus cap-plated chord ends). The effects of branch-to-chord width (β), chord slenderness (2γ) ratios and branch-to-chord thickness (τ) were also investigated. It was found that the stress concentration factors (SCFs) in end connections are sensitive to the boundary conditions (i.e., open chord end versus with chord-end cap plate) and all three non-dimensional parameters (β, 2γ and τ). Therefore, SCF correction factors based on e/b0, β, 2γ and τ, are derived for use with existing SCF formulae in CIDECT Design Guide 8.
•SCFs of chord-end CHS-to-CHS T- and X-type moment connections are studied.•1120 FE models are analyzed, including connections with open and cap-plated chord ends.•CIDECT DG8 SCF formulae are found to be inaccurate.•A new approach for predicting SCFs such end connections is proposed.•The approach utilizes “SCF correction coefficients” plus CIDECT DG8 formulae.
•SCFs of chord-end RHS-to-RHS T-type moment connections are studied experimentally and numerically.•448 FE models are analyzed, including connections with open and cap-plated chord ends.•CIDECT DG8 ...SCF formulae are found to be inaccurate.•A new approach for predicting SCFs such end connections is proposed.•The approach utilizes “SCF correction coefficients” plus CIDECT DG8 formulae.
The research presented in this paper is the continuation of a series of efforts to develop design formulae for rectangular hollow section (RHS)-to-RHS end connections and circular hollow section (CHS)-to-CHS end connections under fatigue loading. Normalized hot spot strains for the RHS-to-RHS T-type moment-loaded end connections (unreinforced and reinforced with a chord-end cap plate) are experimentally determined and compared to those in their regular connection counterparts (with sufficient chord continuity). Upon validation using the experimental data, a parametric finite-element study consisting of 448 models (including 336 stepped connections and 112 matched connections) is performed. The parametric study investigates the effects of chord end distance-to-width, branch-to-chord width, branch-to-chord thickness, and chord slenderness ratios, as well as the chord boundary condition (unreinforced or with a chord-end cap plate). Existing formulae in CIDECT Design Guide 8 for the calculation of the corresponding stress concentration factors (SCFs) are evaluated, and SCF correction factors are derived.
Bolted Flange Plate Moment Connections (BFP) are one of the most practical connections, used as prequalified connections in special steel moment frames. Using three full-scale BFP connections ...designed according to AISC, this paper has explored the effects of bolt pre-tension levels experimentally under SAC cyclic loading protocol. The bolt pre-tension level has been defined as α coefficient to indicate the pre-tensioning level in three specimens. The bolts of the first specimen were not pre-tensioned, called snug-tightened bolts, and considered as reference connections. The bolt pre-tension levels of the second and third specimens were established in accordance with the minimum and allowable limits of AISC design code and ultimate strength of the bolt, called pre-tensioned and fully pre-tensioned, respectively. The moment capacity, total energy absorption, and strain variation of the bolts have been investigated. Meanwhile, using the ultra-low cycle fatigue failure index obtained from experimental specimens, the capacity of modeled BFP connections in finite elements has been compared with the laboratory samples in terms of failure location and connection capacity. The experimental results revealed that final resistance in BFP connections occurs in the cycle of 7% of the drift angle of SAC protocol loading, and the location of the connection failure is around the farthest hole from the column, which is consistent with the failure results from ultra-low cycle fatigue in finite element modeling for BFP connections. The measure of moment resistance in the pre-tensioned connection (Both connections were minimum pre-tensioned according to the regulation and ultimate strength of the bolt) has increased by about 50% compared to the without pre-tensioned connection. The amount of energy absorption of the pre-tensioned connection with the ultimate strength of the bolt has increased by 176% of the energy absorption capacity of the connection without pre-tensioned and 14% of the energy absorption capacity of the connection with the minimum allowable pre-tensioning of the regulation. The extent of energy absorption in the three connections was equal to 38, 92, and 105 KJ.
Double reduced beam section connection Morshedi, Mohamad A.; Dolatshahi, Kiarash M.; Maleki, Shervin
Journal of constructional steel research,
November 2017, 2017-11-00, Volume:
138
Journal Article
Peer reviewed
In this paper, a novel beam-to-column steel moment connection, named “double reduced beam section (DRBS)” is introduced and the seismic performance of the connection is assessed using finite element ...modeling. The connection is composed of double dog bone sections close to the column face to widen the plastic hinge region; consequently, reducing the resultant equivalent plastic strain. The region between the two reduced beam sections is laterally connected to the slab to protect the plastic hinge from lateral torsional buckling. A parametric study was conducted on the influence of cut parameters on the connection's seismic behavior. The results showed that, following the limitations and guidelines stated in this research, the DRBS connection exhibits outstanding hysteresis behavior. The deformation capacity of the connection was increased up to 40% in the DRBS connection, compared to the common reduced beam section (RBS) connection. Plasticization of both reduced beam sections postponed the failure buckling modes, resulting in 50 to 75% increase in the absorbed seismic energy before buckling, compared to the traditional RBS connection. Moreover, adding a second cut to the ordinary RBS connection distributed the strains over the two reduced sections, leading to 35 to 60% reduction in the equivalent plastic strain at the reduced sections, at 6% inter-story drift.
•A novel steel moment connection (DRBS) is introduced to better distribute the plastic strain under seismic loads.•Optimum values of the cut parameters are determined using verified finite element model.•A design procedure is proposed and then verified by means of FE modeling.•Energy apsorption capacity is increased by 50-75% in DRBS connection, compared to the conventional RBS connection.•35-60% reduction in the maximum PEEQ index of DRBS is observed, compared to RBS connection.
In this paper, a method called "least-work solution" was empirically simplified to evaluate shear lag stress in the steel box moment connections with internal diaphragms in order to serve for the ...preliminary design. This approach considered the effects of column flange flexibility and depth of the beam web, and their relations on the stress distribution. The stress equations were manually obtained with a complicated form. Therefore, a simplified method was proposed to facilitate the calculation procedure. The results showed that least-work solution could be simplified to provide valid stress distribution and can thus be authenticated by FEM and existing test.
Achieving a robust connection is a challenging task for design engineers since the connection’s strength is inseparably linked to its ductility. This paper presents a novel approach that separates ...designing bolted connections for strength from designing for ductility. By inserting a steel sleeve with a designated length, thickness and wall curvature between the end plate and the washer, the load path between the end plate and the bolts can be interrupted, promoting a more ductile response. End plate connections with various sleeve geometries are numerically investigated using a validated FE model to prove the concept of the proposed method. The proposed system substantially enhances the rotational capacity up to 2.92 times that of the standard connection. An elastic response consistent with standard connections is maintained indicating that the proposed system is compatible with existing codified elastic design approaches without modification.
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