Beam Connections Research Articles

Thermomechanical Modeling of Welding and Galvanizing a Steel Beam Connection Detail to Examine Susceptibility to Cracking

Abstract Hot-dip galvanizing is the process of submerging steel elements into molten zinc to form a metallurgically bonded zinc coating that serves as corrosion protection for the steel substrate. Used with great success on an industrial scale for many decades, hot-dip galvanizing is a ubiquitous process. On occasion, cracks in steel members develop during galvanizing. While such cracking remains a poorly understood phenomenon, previous research has attributed the formation of cracks to the combined effects of residual strains introduced by welding and temperature-induced deformations caused by the hot-dip galvanizing process. This article presents thermomechanical analyses of a structural steel beam with a welded double-angle connection detail where cracking occurred during hot-dip galvanizing. Three-dimensional finite element models of the beam and connection detail were analyzed using the finite element analysis software Abaqus (Dassault Systèmes, Vélizy-Villacoublay, France). The welding process was simulated using the Abaqus Welding Interface, maintaining the welding sequence of the connection. After welding, the entire beam was subjected to a temperature field that was specified through a user subroutine in Abaqus, simulating the hot-dip galvanizing process. The temperature field had a bath temperature of 450°C and a thermal cycle that included dipping, dwell time, and removal from the bath. Material properties used in the simulation were nonlinear and temperature dependent. The parameters of the study were the welding sequences, heat input during welding, and the depth of the double-angle connection. It was observed that strain demands due to welding and hot-dip galvanizing were high magnitude at the cracked location in the beam. The relative significance of strain demands due to welding and of hot-dip galvanizing on the propensity for the beam to develop cracks are discussed.

Model Of Precast Beam-Column Connection Towards Structure Rigidity By Using Steel Plate Causes By Cyclic Load

Precast connection system in structure element must be designed in such way to result in required behaviour, such as plastic hingesmust be well-planned to be able to shed earthquake energy and to limit seismic loading that goes inside the structure. This research is experimental study that precast beam connection which is modeled using steel plate. The result of this model design use to compare the occurence of structure deformity rigidity in monolith concrete construction (BN) and precast concrete (BP1 and BP2). The testing dimension consists of column with the size 300x300 mm and height 3300mm, beam 200x300 mm and width 3300 mm, with steel plate 200x400x8 mm and 300x400x8. This study resulted in monolith testing material (BN) produces average value 47.8 % from its previous rigidity, BP1is 57.13% from its previous rigidity, and BP2 is 52.22% from its previous rigidity.

In-plane torsional stiffness in a macro-panel element for practical finite element modelling

Finite element (FE) analysis produces results, which, in most cases, gain in accuracy, as the size of the FE mesh is reduced. However, this is not necessarily the case when beam and shell element connections induce in-plane torsional effects in the shell. In such situations, shell elements either do not allow for an in-plane torsional stiffness, or, when present, the in-plane torsional stiffness is incorrectly affected by the sizes of the elements. To overcome this problem, we propose a macro- panel element that has fewer degrees of freedom, includes a new model for in-plane torsional stiffness, and produces results with sufficient accuracy to meet engineering requirements. The panel element is based on the principle of sub-structuring, i.e., the panel is meshed internally by smaller shell elements. As shown in the paper, the proposed panel element can be quite large, yet, it can give accurate analysis results. This work helps to overcome a common dilemma in practical use of finite element analysis, where finite element theory requires element sizes to be sufficiently small, but practical considerations suggest the use of large-size elements that simplify the modelling process and reduce excesses in generated results. A model built using macro-panel elements is equivalent to the model built using smaller shell elements, with the normal and shear stresses in the former being the same as the stresses in the finely meshed shell element model, We identify a number of performance benefits that become available as a consequence of modelling the shell elements at a higher level of abstraction.

Macroscopic modelling of coupled concrete shear wall

This study explores several types of macroscopic models, by modifying Multiple-Vertical-Line-Element-Model (MVLEM), to represent the coupled concrete shear wall, with different ways of connection to simulate coupling beam. For this purpose, an existing shear wall in which several openings are symmetrically embedded was studied. The wall was analyzed by the microscopic Finite-Element Method (FEM) in ABAQUS. In order to investigate the macroscopic modelling of the mentioned wall, three different macroscopic coupled shear walls, composed of several nonlinear springs, representing flexural and shear behaviors were studied. The main difference among the three walls is in the type of the coupling beam connection used. Hence, three connections were proposed with different stiffnesses. Unlike the connection, the macroscopic coupling beams for the three models were identical based on moment distribution. In order to model the coupling beam, two separate shear walls were considered which were connected to each other from the uppermost part. Responses of the walls under cyclic, monotonic, and dynamic loadings were compared with those of the verified FEM model. The results indicate that the macroscopic wall with moderate connection stiffness has acceptable consistency in terms of static and dynamic responses of the microscopic model.

Influence of Different Shank Distribution on Slip in Composite Beams

The beam model is modeled by simple beam analysis model. The finite element software ANSYS was used to analyze the model, and the two sets of models were not considered, and the shear deformation of the concrete and the steel was not taken into account. The model-one composite beam connection was adopted in the uniform arrangement of the model. The method of arrangement, comparing the results of the two groups, the value of the interface slip can be seen in the model two, due to the uniform arrangement of the way, the interface slip value is significantly reduced.

Plastic analysis and performance-based design of coupled steel plate shear walls

The coupled steel plate shear wall (C-SPSW) configuration consisting of two SPSWs linked by coupling beams at the floor levels, in addition to providing architectural flexibility, has been shown to exhibit superior seismic performance. While the shear strength of the infill panels due to tension field action is the primary source of lateral load resistance in a C-SPSW, the moment resisting actions of the boundary frames and the coupling beams connections provide substantial strength for the system. As such, in order to achieve material-efficient designs, rational procedures are needed to explicitly account for this strength, while maintaining the desirable performance for various hazard levels. Similar to planar SPSWs, the C-SPSW systems have been designed using the conventional force-based design approach, which typically requires several iterations to optimize the design for performance and efficiency. This research employs the principles of plastic analysis to quantify the contribution of the frame action to the overall strength of C-SPSWs and adopts the philosophy of the performance-based plastic design (PBPD) methodology to develop procedures for the efficient seismic design of such systems. To investigate the effectiveness of the proposed design procedure, 8- and 12-story case study C-SPSWs were designed, and their numerical models were analyzed using pushover and response history analyses. The seismic performance of the prototypes were evaluated using two suits of ground motions representing 10/50 and 2/50 hazard levels. The analysis results indicated that the C-SPSWs designed using the proposed approach successfully met the desired performance objectives for both seismic hazard levels considered.

Proposal of Strength Formula and Type Development of Composite Mega Column to Beam Connections with T-shaped Stiffener

Proposal of Strength Formula and Type Development of Composite Mega Column to Beam Connections with T-shaped Stiffener

Towards the LISA backlink: experiment design for comparing optical phase reference distribution systems

LISA is a proposed space-based laser interferometer detecting gravitational waves by measuring distances between free-floating test masses housed in three satellites in a triangular constellation with laser links in-between. Each satellite contains two optical benches that are articulated by moving optical subassemblies for compensating the breathing angle in the constellation. The phase reference distribution system, also known as backlink, forms an optical bi-directional path between the intra-satellite benches.In this work we discuss phase reference implementations with a target non-reciprocity of at most μrad , equivalent to 1 pm for a wavelength of 1064 nm in the frequency band from 0.1 mHz to 1 Hz. One phase reference uses a steered free beam connection, the other one a fiber together with additional laser frequencies. The noise characteristics of these implementations will be compared in a single interferometric set-up with a previously successfully tested direct fiber connection. We show the design of this interferometer created by optical simulations including ghost beam analysis, component alignment and noise estimation. First experimental results of a free beam laser link between two optical set-ups that are co-rotating by ±1° are presented. This experiment demonstrates sufficient thermal stability during rotation of less than 10−4 K at 1 mHz and operation of the free beam steering mirror control over more than 1 week.

The Timber-Precast UHPC Composite Connection

This paper deals with the connection of timber beams and precast concrete slabs. The connection of timber and concrete has many advantages associated with the efficient use of both materials, not only in terms of their stress. Timber is a natural renewable material. It can be achieved some savings of volume of the concrete by its application and thereby also reducing of the environmental burden. By the combining of the timber and ultra-high performance concrete (UHPC), it can be designed very subtle, bearable, aesthetic and durable structures. The conventional timber-concrete composite structures are most often realized by joining of the timber beams and the cast in-situ reinforced concrete slabs. However, the cast in-situ slab is not very suitable for UHPC application and it has some structural disadvantages, in particular the need to protect the timber beams against moisture penetration from the fresh concrete mix, the need for formwork, etc. The prefabrication eliminates some disadvantages of the cast in-situ design, increases the quality of the structure and speeds up the construction process. In the case of the timber-concrete composite structures, the prefabrication has a positive impact on the reduction of the concrete shrinkage projections as the development of deflections and the redistribution of internal forces between the connected parts of the cross-section. Some special coupling elements must be used for connection in the case of precast slabs. This paper summarizes the research findings in the field of development of special coupling elements for composite timber-precast concrete structures. The development of the new coupling elements for pedestrian and cyclist timber-UHPC composite footbridges is presented.

Seismic performance of precast RC column to steel beam connections with variable joint configurations

In the last decades, noticeable experimental and analytical investigations have been carried out on cast-in-place Reinforced Concrete column to Steel beam (RCS) connections, however rarely have been conducted on the precast RCS. In this paper, test results of four half-scale interior precast RCS connections with variable joint configurations are presented. The steel beams were connected to the precast column, using three specimens with extended face bearing plates and one with extended cover plates, embedded in the connection zone. The flanges of beams were strengthened with respect to scaled section, in order to increase the load transfer to the joint. All samples were loaded under reversed displacement controlled condition. The failure mode, joint distortion, lateral load capacity, stiffness retention, stiffness degradation and energy dissipation capacity were evaluated. Presence of shear keys in the joint enhances strength and stiffness of subassemblies and reduces joint distortion. Utilization of extended cover plates considerably reduces shear distortion and rigid body rotation and also significantly increases shear resistance of the joint.

Internally coupled metamaterial beam for simultaneous vibration suppression and low frequency energy harvesting

The paper proposes a modified metamaterial beam for simultaneous vibration suppression and energy harvesting. Local resonators in the modified metamaterial beam are alternately coupled, and each resonator is associated with a piezoelectric element for converting vibrations into electrical energy. First, the mathematical model of the modified metamaterial beam based piezoelectric energy harvester (PEH) is developed. The vibration suppression and energy harvesting performances of this system are analysed and compared with those of a conventional metamaterial beam PEH. The analytical results predict that not only the energy harvesting performance can be massively reinforced in the low frequency range, but also the vibration suppression performance can be slightly enhanced due to the appearance of an additional band gap. Subsequently, two finite element models, Models A and B, are developed. Model A is expected to be equivalent to the analytical model for validation and the local oscillators represented by lumped parameters in the analytical model are modelled by using cantilevers with tip masses. These tip masses are alternately coupled with ideal springs. The finite element analysis results in terms of both vibration suppression and energy harvesting show good agreement with the analytical results. Finally, to propose a more practical design of the internal coupling, Model B is established. Every two neighbouring tip masses are alternately coupled by using a beam connection. The finite element analysis results show that Model B is not completely equivalent to the proposed analytical model: no significant enhancement in terms of energy harvesting but a remarkably enhanced vibration suppression performance.

Low Damage Moment Resisting Connection Using Blind Bolts

Concrete Filled Steel Tubes (CFSTs) are being used as columns in moment resisting frames in many parts of the world. Because of their aesthetic appearance, favourable ductility and large load bearing capacity, they are popular with architects and engineers. The use of CFSTs is limited in some countries (like Australia) due to the problems and cost associated with the connection of steel beams to the closed column section, unlike open H-shaped columns where ordinary structural bolts can be used. In this paper, a structural system is proposed which uses moment resisting frames as the lateral load resisting system. This system eliminates the use of welds at the site, which is the most common method, although expensive, which is used to achieve a moment resisting connections. The proposed system uses double T-stub connections to connect universal beams on opposite sides of the CFST column, and headed anchored blind bolts are used to connect those T-stubs to the column. This system provides sufficient stiffness and strength to be used in low to mid-rise buildings in low to moderate seismic regions. The proposed system uses a capacity design method to limit the load and non-recoverable damage in the connection (especially in the anchorage). One of the components in the connection, the web of the bottom T-stub, is designed as a fuse to create a low damage system for very rare earthquakes.

Can ground densification improve seismic performance of the soil‐foundation‐structure system on liquefiable soils?

SummaryOver the past few decades, soil densification has been widely employed to reduce the liquefaction hazard or consequences on structures. The decision to mitigate and the design of densification specifications are typically based on procedures that assume free‐field conditions or experience. As a result, the influence of ground densification on the performance of structures and the key mechanisms of soil‐structure interaction remains poorly understood. This paper presents results of four centrifuge tests to evaluate the performance of 3‐ and 9‐story, potentially inelastic structures on liquefiable ground with and without densification. Densification was shown to generally reduce the net excess pore pressures and foundation permanent settlements (although not necessarily to acceptable levels), while amplifying the accelerations on the foundation. The influence of these demands on the performance of the foundation and superstructure depended on the structure's strength and dynamic properties, as well as ground motion characteristics. In addition, densification tended to amplify the moment demand at the beam and column connections, which increased permanent flexural deformations and P‐Δ effects (particularly on the heavier and weaker structure) that could have an adverse effect on foundation rotation. The experimental results presented aim to provide insight into the potential tradeoffs of ground densification, which may reduce foundation permanent settlement, but amplify shaking intensity that can result in larger foundation rotation, flexural drifts, and damage to the superstructure, if not considered in design. These considerations are important for developing performance‐based strategies to design mitigation techniques that improve performance of the soil‐foundation‐structure system in a holistic manner.

Numerical simulation of improved RHS column-to-I beam flange-plate bolted connections for avoiding tensile fracture

In an attempt to find possible solution for avoiding premature occurrences of brittle fracture in rectangular hollow section (RHS) column-to-I beam connections, an improved type of connection was t...

The effects of beam-column connections on behavior of buckling-restrained braced frames

Buckling Restrained Braced (BRB) frames have been widely used as an efficient seismic load resisting system in recent years mostly due to their symmetric and stable hysteretic behavior and significant energy dissipation capacity. In this study, to provide a better understanding of the behavior of BRB frames with various beam-column connections, a numerical study using non-linear finite element (FE) analysis is conducted. All models are implemented in the Abaqus software package following an explicit formulation. Initially, the results of the FE model are verified with experimental data. Then, diverse beam-column connections are modeled for the sake of comparison from the shear capacity, energy dissipation and frame hysteresis behavior points of view until appropriate performance is assessed. The considered connections are divided into three different categories: (1) simple beam-column connections including connection by web angle and connection by seat angle; (2) semi-rigid connection including connection by web and seat angles; and (3) rigid beam-column connections by upper-lower beam plates and beam connections with web and flange splices. Results of the non-linear FE analyses show that these types of beam-column connections have little effect on the maximum story drift and shear capacity of BRB frames. However, the connection type has a significant effect on the amount of energy dissipation and hysteresis behavior of BRB frames. Also, changes in length and thickness of the angles in simple and semi-rigid connections and changes in length and thickness of plates in rigid connections have slight effects (less than 4%) on the overall frame behavior.

Probability-based structural response of steel beams and frames with uncertain semi-rigid connections

Within a probabilistic framework, this paper addresses the determination of the static structural response of beams and frames with partially restrained (semi-rigid) connections. The flexibility of the nodal connections is incorporated via an idealized linear-elastic behavior of the beam constraints through the use of rotational springs, which are here considered uncertain for taking into account the largely scattered results observed in experimental findings. The analysis is conducted via the Probabilistic Transformation Method, by modelling the spring stiffness terms (or equivalently, the fixity factors of the beam) as uniformly distributed random variables. The limit values of the Eurocode 3 fixity factors for steel semi-rigid connections are assumed. The exact probability density function of a few indicators of the structural response is derived and discussed in order to identify to what extent the uncertainty of the beam constraints affects the resulting beam response. Some design considerations arise which point out the paramount importance of probability-based approaches whenever a comprehensive experimental background regarding the stiffness of the beam connection is lacking, for example in steel frames with semi-rigid connections or in precast reinforced concrete framed structures. Indeed, it is demonstrated that resorting to deterministic approaches may lead to misleading (and in some cases non-conservative) outcomes from a design viewpoint.

Numerical study on beam-column connection of cantilever precast concrete beam with asymmetric shape under static load

Cantilever beams are generally used in all infrastructures, including precast concrete structures. In that type of structure, the asymmetric-section shape usage will be optimum and effective. However, in precast concrete structures, it might be susceptible especially in beamto- connection parts due to its strength. In this research, the damage mechanism of connections between cantilever beams and columns in precast concrete will be analyzed. The asymmetric shape will be applied in cantilever beams. Three samples were made with a length of 1500 mm equipped with six 10 mm-diameter deformed rebar and stirrup with 6 mmdiameter plain rebar. The results show that each of the three speciments has its own effectiveness based on stress, strain, displacement, load, and other related parameters.

Experimental and Theoretical Study of Deformation Processes in a Flange Connection of Iron Beams

Flange connections are the critical elements of metal structures, as they determine the whole structure rigidity and strength. In this paper, we present the results of experimental and theoretical studies performed to evaluate the deformation behavior of the elements of metal beam-to-column flange connections. The experimental investigations were carried out on samples subjected to elastic and inelastic deformations up to their full failure. Displacements at the characteristic points of the samples were registered during the loading process. Relative deformations were measured at the points of greatest stress and strain concentration. The data obtained at different scales accurately characterize the interrelations between the deformed elements, especially when the deformation becomes inelastic. Our theoretical studies were concerned with the development of a mathematical model capable of providing an adequate description of elastic and inelastic stress-strain states in the elements of flange connections.

Numerical methods for calculation of compound rods

Presented calculation of the compound rod for free oscillations and test tasks of calculation of monolithic rods, which in fact began testing the above methods, which the authors considered necessary before using these methods on more complex – composite rods, the results of the applied methods are compared. The purpose of this work - the calculation of the composite rods on the dynamic effects of the method of successive approximations and finite element method, comparing the results; determining the limits of rational use of successive approximations method (SAM). The method of successive approximations (SAM) is used as a resolving method of differential equations. The application of this method to the calculation of structures has a number of advantages: the ability to consider a simplified design scheme of the beam with a distributed load (instead of a system of concentrated forces); the ability to abandon the direct simulation of the design scheme in the design and computer complex (the time of which depends on the number of connections of the composite beam); gives the result of high accuracy at low time costs.

Rehabilitation and Strengthening of Aged Steel Railway Bridges in Japan

In Japan, nearly a half or even more of the existing bridges with a span exceeding 15 meters were predicted to be over 50 years old in next 10 years. Appropriate repair, strengthening, or replacement work should be performed on aged steel bridge structures to ensure their performance in service condition. A novel strengthening method using rubber-latex mortar, glass fiber reinforced polymer plates, lightweight rapid hardening concrete, and reinforcement bars is proposed for strengthening short-span steel railway bridge superstructures and for improving the seismic performance of aged column structures. To confirm the effectiveness of the strengthening method, loading tests were performed on test specimens for short-span steel railway bridges, longitudinal-lateral beam connections as well as steel columns. Numerical models were also built to simulate the structural behavior of both original and strengthened steel structures. According to the obtained results, the present renovation method can significantly enhance both rigidity and load carrying capacity of short-span steel bridge superstructure, connections, and column structures, resulting in the extension of the residual fatigue service life of bridge tarp structures and improvement of seismic performance of column structures.