Splice Connection Research Articles

Behavior of steel-plate concrete wall-reinforced concrete slab joint with UHPC-strengthened lap-splice connection

The comprehensive integration of modular technology is the crucial pathway for advancing the upgraded Hua-long Pressurized Reactor (HPR1000). However, previous studies are limited and numerous challenges remain concerning the modular curved steel-plate concrete (SC) wall-reinforced concrete (RC) slab joint. This paper focuses on the behavior and design of the SC wall-RC slab joint through large-scale tests and numerical simulation. Two UHPC-strengthened non-contact lap splice (NS) connections, including versions with normal and headed rebars, were proposed to ensure effective load transfer and modular construction performance. The test results indicated that the four joint specimens subjected to cyclic loading did not experience lap splice failure but instead suffered interface shear failure and shear failure of the RC slab under shear-span ratios of 1.5 and 3.0, respectively. The excellent load transfer performance demonstrated by these two NS connections validates them as effective methods for this joint, with lap lengths of 21d for normal rebar and 13d for headed rebar deemed adequate. Besides, the developed three-dimensional FE model with non-linear spring element accurately simulated the test failure modes and F-Δ curves. The parametric study results recommended that the volumetric steel ratio of tie-bar should not be lower than 1.03 %. The tension of longitudinal rebars for normal and headed rebars can be fully transferred within 80 % of the designed lap length. Furthermore, a complete design method was established based on the load-transfer model, encompassing interfacial shear, lap length calculation and tie-bar configuration, and is applicable to SC-to-RC connections or joints.

Finite element analysis on non-contact lap splice connections in ultra-high-performance concrete

This study investigates the stress characteristics and failure modes of the lap splice region for non-contact lap-spliced rebar embedded in Ultra-High-Performance Concrete (UHPC), as well as the influence of lap parameters on these aspects. A series of refined finite element models of non-contact lap-spliced rebars embedded in UHPC were established and validated. The influences of UHPC mechanical properties, splice length, and clear spacing on lap region and the failure modes of specimens were studied. As the lap clear spacing increases from 0.5d to 4d, the ratio of principal compressive stress to principal tensile stress in the lap region of the elastic model decreases from 2.36 to 0.36. This trend indicates that with increasing clear spacing, the force transfer between rebars shifts from being dominated by compressive stress to tensile stress within the UHPC lap region. Consequently, the maximum load of the specimen transitions from being governed by compressive strength to being governed by tensile properties. With a clear spacing of 2d, the maximum load of the specimen increases with the splice length. The maximum load of 8d splice length specimen was increased by at least 27 % compared to the specimen with 0d splice length.

Experimental study on seismic behavior of RCS joints with asymmetric friction connections and slabs

This paper introduces a new reinforced concrete column-steel beam (RCS) joint that employs asymmetric frictional connections (AFC) to improve energy dissipation and moment transfer, reducing stress concentrations within the joint’s core. Two RCS joint specimens with AFC and floor slabs were designed and tested under quasi-static loading to analyze the impact of bolt preload on seismic performance. The experimental results demonstrate that RCS joints with AFC and slabs exhibit favorable seismic behavior in terms of bearing capacity, energy dissipation, and stiffness degradation. Increasing bolt preload enhances the bearing capacity, stiffness, and energy dissipation capacity of the joints. The failure occurred at the steel beam splice connections, while only minor micro-cracks appeared in the reinforced concrete column when the joint's bearing capacity dropped below 80% of the peak load. Displacement at the column top was primarily influenced by steel beam and column deformation, with minimal contribution from joint core deformation. The use of AFC effectively reduced deformation in the joint core area, meeting seismic design code requirements for “strong columns-weak beams.”

Flexural behaviour of bolted flange-plate with bonded sleeve splice connections for pultruded GFRP circular tubular hollow beams

The paper presents an experimental and finite element investigation of bolted flange-plate with bonded sleeve splice connections for joining pultruded glass fibre-reinforced polymer (GFRP) circular tubular beams. The moment-rotation behaviour was investigated in terms of initial rotational stiffness, moment capacity and rotation capacity for all the tested splice connections. The effect of the number of flange-plate bolts, flange-plate thickness and the length of the bonded sleeve were examined. Failure modes for the thinner flange-plates included opening, bending and yielding of the flange-plates in the tension zone. Thicker flange-plates and a higher number of bolts exhibited improved initial rotational stiffness with lower rotational capacity, which can be enhanced by higher bonded sleeve lengths. Available design codes for steel joints were used to classify the splice connections with regards to rigidity and strength. The failure modes from the finite element models were consistent with the experimental observations, which includes the plastic deformation of the flange-plate and the cohesive failure of the adhesive.

Optimization of non-bearing splice connection in GFRP short columns by manual testing and finite element analysis

Connection designs are established to ensure the stability of joined cut sections, the joints so designed should be based on the optimal performance as per the requirements. The connection joints so established should not be based on just strength but reliability and durability as well. This study focuses on tackling one of the major issues faced when using Glass Fibre Reinforced Polymers (GFRPs) as construction materials, which is based on the abrupt failure of the material under critical or maximum loading. Connection designs are established in GFRP short column H-sections based on Bolted Splicing connections by Eurocode 3 for steel splicing connections. A total of seven Connection designs are established using bearing and non-bearing splicing connections. A total of five models for each connection is established for manual testing and Finite Element Analysis (FEA) is used to simulate and analyze these connection designs. Parameters such as ultimate load, displacement at ultimate load, stiffness, compressive strength, failure mode, load versus displacement behavior graph, and percentage compressive strength compared to the un-cut section are provided in this study. The strongest specimen in this study displaced 128% and 127.7% compressive strength compared to an un-cut GFRP H-section when tested using manual testing and FEA accordingly.

Cyclic Behavior of the Column-Tree Moment Connection with Weakened Plates: A Numerical Approach

The use of column-tree connections is common in controlled shop environments due to their cost-effectiveness in achieving ductile welds. Field bolts are also easy to install and inspect. However, there is currently no prequalification available for these connections, their performance is not fully understood, and the cost of aftermath repairs is still a major concern for owners. In this research, analytical and numerical studies were performed to assess the cyclic behavior considering the effects of the bolted splice location, bolt slippage, and splice plate thickness. Fourteen numerical models using the finite element method in ANSYS software were analyzed to evaluate the nonlinear behavior of moment connection configurations in terms of the strength, stiffness, ductility, energy dissipation, and overall cyclic response. The results showed that appropriately proportioned bolted splice connections can meet the requirements for prequalified moment connections. The models complied with the criteria established in AISC 358 and achieved flexural resistance that was higher than 80% of the beam plastic moment at 4% of the interstory drift ratio. The weakened plates concentrated the inelastic action, which allowed us to prevent the brittle behavior and damage to the column, welding, and other components of the moment connection. Complex geometries or specially fabricated parts were not required, providing a cost-effective way to control seismic-related damage. Also, required repairs are based on the replacement of standard parts, reducing operational detentions in facilities. Finally, the moment connection studied is classified as partially restrained (PR) according to the requirements established in AISC 360.

DS-Former: A dual-stream encoding-based transformer for 3D medical image segmentation

Models that utilize self-attention mechanisms, including but not limited to Vision Transformers (ViTs), have shown promising performance in visual tasks like semantic segmentation. This is attributed to their capacity to capture global features of images, enabling them to learn more comprehensive representations. However, transformer-based models typically demand a considerable amount of training data to achieve satisfactory performance, while being deficient in the ability to efficiently extract local image features. As a result, these models may not be as effective in some computer vision tasks that involve small-scale datasets, like medical image segmentation. To address these issues, this paper proposes a dual-stream encoding-based transformer dubbed as Dual-stream Transformer (DS-Former). The dual-stream module in DS-Former can simultaneously acquire local and global features in the image and construct relation between the two kinds of features via self-attention. Compared with the simple splicing or serial connection, the dual-stream module can extract more comprehensive and hierarchical feature information from the fusion interaction of the two features. Our method is evaluated on the UK Biobank (UKBB) cardiac magnetic resonance imaging (CMR) dataset and The Beyond the Cranial Vault (BTCV) abdominal challenge dataset. The experimental results indicate that our DS-Former outperforms other state-of-the-art approaches on both datasets, indicating its potential for medical images semantic segmentation.

Numerical investigation of a novel concrete-to-steel column splice in mixed structures in height

Buildings in which the type of structural material changes between their stories are referred to as mixed-in-height structures. Typically, these buildings have concrete structures in lower stories and steel structures in upper stories. Valuable investigations have been conducted on mixed-in-height structures to explore their seismic response and changes in structural natural period due to the sudden change in the lateral stiffness at transition level and mass irregularity, but scant attention has been given to the connection between steel and concrete structures at varying heights. Given the geometrical limitations of existing concrete structures, the dimensions of steel columns in supplementary stories must align with those of reinforced concrete columns. Consequently, building codes have not yet provided guidelines for proper connection details and effective load transfer from upper steel to lower concrete structures which is crucial due to the abrupt changes in stiffness and force transfer mechanisms in such splice connections. Thus, this study considers Numerical investigation on two full-scale laboratory tested specimens, with similar details but different axial loads, and numerical analysis of a new connection between a concrete and a steel column at the transition level. This research examines the aforementioned connection under two boundary conditions. Furthermore, after validating the numerical models with experimental specimens, axial load parameters, relative percentage of reinforcement to concrete area, and the force–displacement diagrams are presented. Finally, a numerical model of a three-story column in a frame is analyzed using finite element analysis under lateral load, and the sequence of plastic hinge formation is studied. The practicality and effectiveness of the proposed splice was verified herein. Furthermore, the average value of ductility (µ) was calculated to be 5.5, while exhibiting negligible overstrength factor (Ω). Similar response parameters were calculated for F-AL-R2 (43.2 kN/mm, 21.1 kN/mm) and F-AL-R3 (43.8 kN/mm, 22 kN/mm), indicating that the influence of increased rebar percentage diminishes at higher values. The analysis demonstrates that column connection failure did not occur, and the sequence of hinge formation was from top to bottom, validating the suitable performance of the proposed connection.

Ultimate capacity and stability of topologically optimised shear plates in compliance with structural Eurocodes

Topology optimisation (TO) is increasingly used to assist metallic parts manufacturing in automotive, aerospace, and biomedical sectors. A similar trend is observed in civil engineering structures, particularly in steel construction joints representing crucial steelwork components. Yet, the widespread adoption of TO to steel members in structural engineering has been hampered by difficulties complying with code requirements and challenges in utilising cutting-edge software in real, heterogeneous, and complex cases. To fill this research gap, a methodology is developed in the current study to implement the requirements of Eurocode 3 in the TO process. Nonlinear Finite Element Analyses (NLFEA) are performed on the web cover-plates of a well-known bolted splice connection between segments of a steel beam to validate the code-compliant methodology. Results show that it is possible to reduce up to 87.5% of the plate initial volume while keeping the connection original capacity. Also, it has been found that the initial volume can be reduced up 20% without affecting the original plate capacity, and up to 60% while ensuring that the ultimate plastic displacement is larger than that of the original plate. Based on extensive buckling analyses, critical loads exceed ultimate loads from 9.3 to 12.4 folds, thus ensuring excellent stability performance. The results of this study demonstrate that validation with NLFEA is a crucial step for achieving actual code-compliant optimised steel joints, and that the linear elastic TO could not satisfy the safety requirements. Moreover, encouraging findings regarding stability and ductility of (extremely) optimised parts suggest the adequacy of TO for designing steel connections. The volume of topologically optimised solutions significantly decreased, contributing to the decarbonisation targets for steel construction.

Behavior of grouted splice sleeve connection using FRP sheet

Most existing studies on grouted splice connections have focused on the bond behavior between connected steel rebars and conventional steel or iron sleeves. These research findings cannot properly predict the bond behavior and performance of the grouted splice connections, particularly when a new splice device, such as fiber reinforced polymer (FRP) materials, are adopted. The main purpose of this study is to investigate the feasibility of the proposed grouted splice sleeve connection (GSSC) using sheet materials of carbon fiber reinforced polymer (CFRP) and glass fiber reinforced polymer (GFRP). A total of 45 GSSC specimens with various rebar embedded lengths and different polymer sleeve materials were tested to failure under incremental axial pull-out load to evaluate the bond performance of the connected steel rebars in confined grout provided by the FRP sleeves. To evaluate the confinement effect of FRP sleeves on the tensile strength of the grouted connection, an analytical model was developed. The pull-out test results showed that the rebar embedded length was the major parameter affecting the average tensile strength of the GSSC. Also, the effects of mechanical properties of FRP sheets, such as the number of FRP layers and type of FRP sheets, contributed to the tensile strength of the GSSC sleeves that allow the transmission of tensile load between rebars through the medium of grout, aluminum tube, and FRP sheets. The analytical model that incorporates the confinement effects predicted well the experimental ultimate tensile strength of GSSC connections.

Experimental and numerical studies of circular precast concrete slender columns with intermediate connection filled with high-performance concrete

Precast concrete (PC) slender columns with intermediate connections are often used in building construction. However, no studies have been performed on the behavior of PC slender columns with intermediate connections filled with high-performance concrete namely engineering cementitious composites (ECC) and strain hardening cementitious composites (SHCC). This paper presents the testing and computer modeling of axially loaded PC slender columns with splices filled with ECC and SHCC. Experimental program and results are presented on nineteen PC slender columns under concentric compressive load up to collapse. The test parameters include the longitudinal reinforcement (µ) ratio, and embedded length of steel bars/infilled concrete connection (Le). Three different reinforcement ratios of 0.027, 0.031, and 0.036 are considered. The embedded length of steel bars/intermediate concrete connection varies from 15D, 22.5D, and 30D where D is the bar diameter. Experimental results indicate that the use of longer steel bars/intermediate concrete connection and a higher reinforcement ratio can significantly enhance both the cracking and ultimate loads of PC slender columns with an intermediate concrete connection. The elastic stiffness of the PC slender columns with ECC and SHCC connection is found to increase by 150% and 93%, respectively when compared to the control specimen. Similarly, filling the splice of the PC columns with ECC and SHCC improves the energy absorption capacity by 107% and 138%, respectively. Nonlinear three-dimensional finite element models (FEMs) are developed accounting for the initial imperfection of the slender columns and their accuracy is validated by experimental results. It is shown that the FEM can provide an accurate simulation of the performance of PC columns with splice connection.

Research on Square and Circular Steel Tubular Columns with Deconstructable Splice Joint Under Cyclic and Axial Testing

Abstract: A steel tubular column is a vertical structural member used in construction to provide essential support. Splice joint is a method of joining two members end to end. When the material being joined cannot be obtained in the desired length, the splice joint is used. For high rise buildings the continuity of columns may break, hence splice connections are provided and columns are installed. Splice joints are deconstructable type joints as the failed parts can be repaired, reassembled or can be even removed when failure occurs. These papers focuses on developing models of square and circular cross sections of steel tubular columns with deconstructable splice joint using a finite element software ANSYS and study their structural behavior. This paper includes a parametric study on the effect of axial loading by varying splice length and thickness, bolt diameter and pattern of square and circular cross sections of steel tubular columns with deconstructable splice joints. Bending moment rotation curves were obtained from cyclic load testing for square and circular cross sections

Frictional mid‐spliced shear links for eccentrically braced frames

AbstractAccording to the AISC Seismic Provisions for Structural Steel Buildings (AISC341‐16) and EC8, the inelastic rotation demand at the design story drift is limited to 0.08 rad for I‐shape shear links in eccentrically braced frames (EBFs). Numerical studies on EBF archetypes show that the single‐sided inelastic rotation demands can be much higher than the limiting value. In addition, these links can fail due to low‐cycle fatigue (LCF) which depends on the loading history. A mid‐spliced end‐plated detachable replaceable link has recently been developed to promote easy replacement of end‐plated links. In this paper, a frictional mid‐spliced shear link is developed to increase the inelastic link rotation capacity and LCF life of shear links. The proposed link utilizes a splice connection at the mid‐length, where frictional faying surfaces are introduced to dissipate energy. Slip at the mid‐splice connection causes a relative vertical displacement between the link ends which eventually reduces the rotation demands on the I‐shape members. Experimental and numerical studies were conducted to study the proposed link concept. Three conventional and eight frictional mid‐spliced links were tested using a nearly full‐scale test setup. The results showed that the proposed links have a pinched link shear versus link rotation response. The links were able to sustain a link rotation demand of 0.23 rad together with a significant increase in their LCF life. Numerical studies were conducted to investigate the link rotation, interstory drift, and residual interstory drift of EBF archetypes equipped with the proposed frictional link.

Tensile behaviors and configurations of double-headed bar overlap connections for precast concrete members

The superiorities in construction time, cost, and quality of precast RC structures are accompanied by the challenges in connection, particularly in steel bars connections between RC components. The extensively used steel bar connections for either grouted sleeve splice connection or grouted spiral-confined lap connection requires on-site grouting, which is a concealed construction process with increased the risk of grouting defects, thereby impairing connection reliability. The confined headed bar connection (CHBC) with visible on-site construction has been proposed to address the unseen grouting defects concerns. However, modern structures that use large-diameter or high-strength rebars present higher demands for steel bar connection capacity. For CHBC, it is suggested to use either a long connection length or a large-size head to satisfy the capacity demand. However, the long connection length can increase field wet operation, which is disadvantage in precast concrete construction. The large-size head can help reduce the connection length, but it can cause inconvenience including construction congestion and the increased eccentric bending moment under tension. This paper presents the CHBC with double-head configuration, which can reduce the single head size. The proposed CHBC consists of confinement stirrups and two overlapped headed bars and the stirrup confining the core concrete can also improve the CHBC capacity. Experimental investigation on 21 CHBC specimens has been carried out. The failure modes, bearing capacity, and stirrup strain development have been studied. Effects of the double-head configuration and confinement stirrup ratio have been analyzed through experimental and numerical investigation. Results show that the double-head configuration has a minor impact on the tensile capacity of CHBC while the increase of confined stirrup ratio can improve the tensile capacity of CHBC. Configuration details of size and spacing for stirrup reinforcement in CHBC are proposed. Based on the test results, CHBC tensile capacity prediction method is suggested, which can take the head configuration into account.

Cyclic Behavior of Precast Double-Column Bridge Bents with Lap Splice Connections by UHPC

Cyclic Behavior of Precast Double-Column Bridge Bents with Lap Splice Connections by UHPC

Experimental and numerical study on seismic performance of precast concrete hollow shear walls

Precast hollow shear wall structure is a new type of prefabricated shear wall structure. The wall of the structure is composed of precast hollow panels, cast-in-place boundary elements and cast-in-place vertical splice joints. The precast hollow panel is provided with vertical and horizontal holes, and concrete is poured at the construction site to form solid wall. Horizontally inserted reinforcement bars are arranged in the horizontal holes of the hollow panels, which are indirectly overlapped with the horizontally distributed reinforcement bars in the hollow panels to realize the connection of horizontal reinforced bars of adjacent hollow panels in the same story. In order to study the seismic performance of precast hollow shear wall, quasi-static tests were conducted on five hollow shear wall specimens with aspect ratio of 1.61 to 2.07. The experimental results showed that the specimens failed due to flexure-compression, which achieved the expected design target of “strong shear and weak bending”, and horizontal reinforcement indirectly connected by horizontal inserts could effectively resist horizontal shear force. The ultimate drift ratios of specimens ranged from 1.4% to 2.6%. The load-carrying capacity of the hollow shear wall could be calculated according to the formula for cast-in-place shear wall provided by the GB 50010–2010. Two kinds of connection between the hollow panels (direct splicing connection and cast-in-place vertical splicing connection) could make the hollow panels become a whole. The seismic performance of the hollow shear wall with precast boundary elements also met the requirements of the GB 50011–2010. Finally, the finite element model of shear wall specimen was established and verified using MSC.MARC software. On this basis, the impact of key parameters on the seismic performance of the precast hollow shear wall was studied. The results show that the axial load ratio and boundary longitudinal reinforcement ratio had great influence on the seismic performance, while the diameter of the steel bar inserted horizontally had little effect on the seismic performance of the precast hollow shear wall with higher aspect ratio.

Non-Destructive Damage Detection of Structural Joint by Coaxial Correlation Method in 6D Space

Failure of joints can lead to structural collapse. It is vital to monitor joint stiffness during operation to prevent such failures. This paper proposes a novel method for the quality assessment of structural joints using coaxial correlation in 6D space. Coaxially placed 6D sensors on either side of the joint implemented by 3D accelerometers and 3D gyroscopes with wide frequency range, automatic synchronisation between the input signal and receivers and response signal averaging are presented. The root mean square (RMS) value from the obtained signals convolution is proposed as a measure of the similarity between two signals for monitoring joint degradation. The method’s effectiveness was tested on steel beam splice connection, where it was found that the RMS of convolution signals in 6D space showed a direct correlation between the calculated RMS value in X, Y, GX, and GY axes directions and the stiffness grades of the joint. The paper concludes that the nature of the RMS during the degradation of the joint may change in different axes, and wrongly chosen axes may lead to wrong conclusions regarding the state of the investigated joint, especially in the case of complex joints, so that the measurements in 6D provide higher reliability of the result interpretation.

Pack Rust Mitigation Strategies for Flange Splice Connections in Steel Bridges

One of the main causes of infrastructure deterioration is corrosion. Different types of corrosion such as surface and pitting corrosion have been researched and addressed by industry. However, pack rust is another type of corrosion that requires attention because of its complexity and lack of research. Pack rust occurs between overlapping plates, which makes it difficult to remove and treat. A previous survey in the State of Indiana highlighted that a significant number of steel bridges exhibit some level of pack rust in the bottom flange of splice connections. Consequently, this study focuses on evaluating mitigation strategies that can delay further development of pack rust at the interface between the connected elements in a typical tension splice. Additionally, this study also examines the effects of pack rust on the tensile strength of a flange splice connection. The ultimate goal is to develop a series of guidelines that can be implemented in the field to address pack rust. To accomplish this, specimens were created to model the bottom splice connection. These specimens were exposed to a corrosive environment for different periods, and later tested under tension to evaluate any strength reduction. The level of pack rust developed in this study, which correlates to an exposure in the field of 20 to 40 years, increased the slip resistance of the specimens tested and did not decrease the ultimate strength. Finally, out of the three mitigation products tested, two had satisfactory results that merit further research and field testing.

Simulation of bolted connections under fire: optimization and model validation

PurposeBeginners and even experienced ones have difficulties in completing the structural fire analysis due to numerical difficulties such as convergence errors and singularity and have to spend a lot of time making many repetitive changes on the model. The aim of this article is to highlight the advantages of explicit solver which can eliminate the mentioned difficulties in finite element analysis containing highly nonlinear contacts, clearance between modeled parts at the beginning and large deflections because of high temperature. This article provides important information, especially for researchers and engineers who are new to structural fire analysis.Design/methodology/approachThe finite element method is utilized to achieve mentioned purposes. First, a comparative study is conducted between implicit and explicit solvers by using Abaqus. Then, a validation process is carried out to illustrate the explicit process by using sequentially coupled heat transfer and structural analysis.FindingsExplicit analysis offers an easier solution than implicit analysis for modeling multi-bolted connections under high temperatures. An optimum mesh density for bolted connections is presented to reflect the realistic structural behavior. Presented explicit process with the offered mesh density is used in the validation of an experimental study on multi-bolted splice connection under ISO 834 standard fire curve. A good agreement is achieved.Originality/valueWhat makes the study valuable is that the points to be considered in the structural fire analysis are examined and it is a guide that future researchers can benefit from. This is especially true for modeling and analysis of multi-bolted connections in finite element software under high temperatures. The article can help to shorten and even eliminate the iterative debugging phases, which is a problematic and very time-consuming process for many researchers.

Experimental and numerical study of structural damping in a beam with bolted splice connection

The objective of this research is to develop a numerical model of one widely used bolted beam splice connection that dissipates energy through structural damping. The reference experimental setup is carefully designed to obtain the highly nonlinear dynamic response due to the suddenly released load. The fact that the monolithic beam with welded connection has a linear response is utilized for the initial calibration of the numerical and experimental models. Then, the numerical model of bolted beam splice connection is verified and adopted through an iterative process. The influences of time and spatial integration, bolt load application, element type, contact formulation, bulk viscosity, and mass scaling are discussed. A special attention is given to the load application and load release functions. After the verification, the Abaqus/Explicit numerical model is validated through the comparison with experimental data, where an appropriate friction coefficient is adopted. It is demonstrated that the nonlinear structural damping occurs due to the complex micro slip behavior at the contact interface.