Truss Connections Research Articles

Experimental study on eccentric compressive behavior of precast concrete double-faced superposed shear walls

With the growing application of prefabricated building structural systems, precast concrete double-faced superposed shear wall (PCDSSW) structures have gained increasing popularity in multi-story and high-rise buildings. However, limited research on the eccentric compressive performance of PCDSSWs could lead to severe consequences. To address this issue, this study conducted eccentric load tests on seven full-scale PCDSSW specimens with steel truss connectors and one full-scale cast-in-place reference specimen. The influence of various design parameters, including truss web diameter, trusses layout, connection locations and methods between steel trusses and distribution reinforcement on the eccentric compressive performance of PCDSSWs was analyzed and discussed. The results revealed that both cast-in-place and PCDSSW specimens exhibited similar failure modes characterized by large eccentric compression failure. PCDSSW specimens showed no noticeable laminated interface separation and can achieve the design objective of "comparable performance to cast-in-place". Moreover, the diameter of truss web reinforcement and the layout of steel trusses had minimal impact on the eccentric compression performance of PCDSSW. While employing welded connections could boost the load-bearing capacity and cracking stiffness of PCDSSW, it also led to a marginally faster stiffness degradation rate and reduced deformation capacity. Additionally, the existing design standards yield conservative predictions for the load-bearing capacity of PCDSSWs. Furthermore, the model proposed by GB 50010–2010 is advocated due to its reliability and accuracy.

Sectional strength design of a double-skin truss-reinforced composite shear wall

The double-skin truss-reinforced composite shear wall is an innovative element which comprises two steel plates, core concrete, concrete-filled steel tubes (CFSTs), which act as boundary members, and steel truss connectors. Truss connectors decrease the out-of-plane deformation that affects the steel plates, and due to the resultant connection and constraint effects, the truss connectors enhance the bearing capacity of the wall. This paper briefly introduces the quasi-static test of five full-scale rectangular double-skin truss-reinforced composite shear wall specimens. The specimen exhibited shear compression failure with an aspect ratio of 2.0, and flexure shear failure occurred when the aspect ratio exceeded 2.0. Based on the analysis of actual stress state of the steel web and actual working performance of the infilled concrete, the shear strength and flexure strength design formulas of double-skin truss-reinforced composite shear wall were established. Comparison results with 26 specimens demonstrate that the design formulas exhibit remarkable accuracy, as most errors are within 20 % and 25 %, respectively. Which provide a preliminary sectional strength design proposal for the double-skin truss-reinforced composite shear wall.

Study of the flexural performance and a novel calculation formula for the degree of composite action for precast concrete sandwich panels

SummaryThis study investigates the flexural performance and degree of composite action (DCA) of precast concrete sandwich panels (PCSPs) with four types of connectors. Five full‐scale specimens were designed, and 4‐point bending tests were performed. The specimens included four PCSPs utilizing glass fiber reinforced polymer (GFRP) truss connectors, steel truss connectors, concrete rib connectors, and GFRP pin connectors, respectively, along with a solid panel (SP). The results indicated that the flexural performance and DCA provided by the four types of connectors followed an ascending order as follows: GFRP pin‐type connectors, GFRP truss connectors, steel truss connectors, and concrete rib‐type connectors. Moreover, the study presented a novel method for calculating DCA, namely, the neutral axis method, which was compared with the displacement and strain methods. The reasonableness and accuracy of the neutral axis method in calculating DCA during the linear elastic stage were verified. Results indicated that the neutral axis method provided more precise and reasonable DCA that closely matched the experimental results compared with the displacement and strain methods. Additionally, the neutral axis method was simpler to calculate DCA and had a broader range of applications. Finally, the study provided recommendations for the optimal application scenarios of each calculation method.

Design equations for thermal bowing and composite degree of concrete sandwich panels

Concrete sandwich panels (CSPs) are oftentimes subjected to extreme exterior temperatures, causing thermal gradients between inner and outer surfaces, and eventually bowing. In addition, the composite degree (kp) of CSPs has been conventionally estimated using methods that require costly and time-consuming experimental tests or rigorous numerical models. The lack of research and understanding on the effects of kp and bowing oftentimes result in overly conservative and uneconomic design, particularly for partially composite (PC) panels. This study develops simple design equations for thermal bowing and kp in CSPs based on a comprehensive parametric study using a transient thermal-structural coupled finite element (FE) model developed earlier by the authors. Key parameters considered are span (L); connector configuration, material, and reinforcement ratio; wythe and insulation thicknesses; concrete strength and thermal differential (ΔT) on both sides. In panels with L larger than 13 m, particularly those featuring steel and CFRP truss connectors and subjected to temperature gradients (ΔT) higher than 30 °C, bowing was larger than the deflection serviceability limit of L/360. Cracking in concrete wythes and yielding of steel connectors were also observed and were mainly dependent on ΔT and kp. Two existing theoretical models were evaluated using results of the parametric analysis and were found to overestimate thermal bow, particularly for panels with low kp. A proposed bowing model is presented which incorporates the effects of composite degree and yields much better predictions than these from literature.

Numerical analysis on fire performance of sandwich composite wall with truss connectors

Based on the previous experimental study on sandwich composite walls with truss connectors under axial loads and one-side fire, finite element analysis was conducted on the fire performance of the novel wall in this paper. Firstly, a thermal coupling analysis model was established for the sandwich composite wall by the finite element software ANSYS, and simulation of test results was performed. The comparison between the predicted results and the test results showed that this model could accurately simulate behaviors of sandwich composite walls under fire. The validated finite element analysis model was utilized to carry out parametric analysis on the fire performance of the sandwich composite walls under one-side fire and two-side fire, respectively. Results showed that wall thickness is a major parameter affecting the fire resistance of the wall under one-side fire. The axial compression ratio, the height-thickness ratio and the wall thickness are major parameters influencing the fire resistance of the wall under two-side fire. Equations for predicting the fire endurance of sandwich composite walls were obtained, by fitting with the major affecting parameters. The calculated results from the equations were in good agreement with the results from the finite element simulation, and the equations can be used as a reference for the fire-resistant design of sandwich composite walls.

Evaluation of the Ultimate Collapse Load of a High-Voltage Transmission Tower under Excessive Wind Loads

Several high-voltage transmission towers failed under excessive wind loads in a mountainous and exposed area. This study discusses the efficient and reliable modeling of lattice towers dominantly loaded by wind, a scenario which led to a collapse cascade in a high-voltage transmission line. The ultimate load-bearing capacity had to be estimated and the failure positions identified. Finite Element Analysis was employed through static analyses, Linear Buckling Analyses (LBA) and RIKS analyses (Arc-Length method) in Abaqus 2021. With the purpose of improving the accuracy in the simulation of structural instabilities of complex lattice structures, the model sensitivity to superimposed geometrical imperfections and the joint stiffness of the truss connections were investigated in brace and lattice structure sub-assemblies. Afterwards, linear analyses and non-linear analyses with imperfections were performed on the single tower model. The analysis proved that solely excessive wind can cause such failure on the lattice structures, and the critical structural elements have been correctly identified. The investigation proved that the towers had not been under-designed with respect to the standards valid at the time of erection. However, they were not designed for this exceptional storm event, and evidence was provided that wind alone could bring about the collapse. It is nevertheless not recommended to increase the safety factors in general for the design of such structures, but to base the assumed loading on actual and local wind and service load measurements.

Cyclic Behaviour of Double Skin Composite Steel Plate Shear Wall Using Shape Memory Alloy with Various Aspect Ratios

Abstract: Shear wall is commonly used in high rise buildings to resist lateral forces. Reinforced concrete shear wall and steel shear wall are the commonly used. Now a days composite shear wall is most popular. Double skin composite shear wall consisting of two steel plates, concrete core, CFST column as boundary members, steel truss connectors, double wave form steel bars connected to steel truss. In this paper steel plate is replaced by shape memory alloy plate and determine the maximum load and total deformation. Cyclic behaviour of double skin composite steel plate shear wall using shape memory alloy with various aspect ratios can be studied using the software ANSYS 2021 R2. SMA plate shear wall provides better performance than in steel plate shear wall.

Quasi-static test of the lattice-type railway bridge pier with replaceable connection component

Replaceable components are beneficial to functionality rapid restoration of structures after earthquakes, which is a good option for seismic design of resilient bridges. In this study, a lattice-type bridge pier with replaceable connection component was proposed for railway bridges. Large initial stiffness was provided by using steel truss connection system as replaceable connection component between two concrete columns. A 1/12-scaled bridge pier model was designed and fabricated to investigate its cyclic responses by quasi-static testing. It was proved that the replaceable connection component can be easily assembled between concrete columns and work well together with them. During testing, cracks occurred at the concrete columns and crack zone extended with the increase of loading displacement. At the later loading stage, some of steel rods of the connection component between the concrete columns began to yield, the hysteretic loop of the bridge pier showed obvious pinching effect. However, concrete columns were prevented to be severely damaged due to the sacrifice of replaceable connection components. There were differences in the strain distribution of the replaceable connection component and not all the replaceable components yielded during testing. Thus, steel rods with varied strength should be used in replaceable components for the lattice-type railway bridge pier. Otherwise, it should balance the stiffness and ductile in seismic design for the lattice-type railway bridge pier with replaceable connection component.

Experimental Study on Truss-Column Pinned Connections in Large-Span Steel Structures

A pin-connected joint, which was intended to accommodate a certain in-plane rotation and resist the shear forces, was introduced in this paper. Pinned-connections were applied on Truss-Column joints to support the heavy-loaded floors and roofs in a long-span steel structure. The Pinned-connection was designed in accordance with European code, and compared with other standards such as America standard and Australia standard. To better understand the behavior of materials and structure of this pin-connection structural system, four specimens, including two full-scale pin-connections and two truss connections, were tested to investigate the performance under both monotonic and cyclic loads. The load–displacement curves, hysteretic curve and ultimate loads were obtained, and the failure mode, capacity and ductility were discussed. The experimental and numerical results indicated that the pin-connection behaved good ductility, load transfer ability and capacity.

Seismic behavior of steel space truss connections to reinforced concrete supporting columns

Roof joint is a critical connection in space truss structures, which connects the upper steel space truss roofs and reinforced concrete structures. Because of its simple structural detailing and easy construction, a typical kind of roof joint is comprised of four embedded anchor rods, a mortar layer, a base plate, and stiffeners are popular in small- to medium-span space truss structures. Among them, base plates with slotted bolt holes are commonly used to release the deformation caused by temperature change or earthquake input. The roof joints were considered either as pinned or rigid connections in the design. In this paper, quasi-static tests investigating the influence of the applied axial force and the shape of bolt holes on the shear resistance and seismic behavior of roof joints were performed. The roof joints exhibited semi-rigid connection behavior and two types of initial resistance mechanisms, sliding and overturning, were observed. With the increase of applied axial force, the behavior of roof joint changes from sliding to overturning. Finally, effective methods to determine the initial resistance mechanism and calculate the ultimate shear strength of roof joints are proposed. These findings and analyses may provide guidelines for roof joint design practice for space truss structures.

Spherical harmonic shape descriptors of nodal force demands for quantifying spatial truss connection complexity

The connections of a spatial truss structure play a critical role in the safe and efficient transfer of axial forces between members. For discrete connections, they can also improve construction efficiency by acting as registration devices that lock members in precise orientations. As more geometrically complex spatial trusses are enabled by computational workflows and the demand for material-efficient spanning systems, there is a need to understand the effects of global form on the demands at the connections. For large-scale structures with irregular geometry, customizing individual nodes to meet exact member orientations and force demands may be infeasible; conversely, standardizing all connections results in oversized nodes and a compromise in registration potential. We propose a method for quantifying the complexity of spatial truss designs by the variation in nodal force demands. By representing nodal forces as a geometric object, we leverage the spherical harmonic shape descriptor, developed for applications in computational geometry, to characterize each node by a rotation and translation-invariant fixed-length vector. We define a complexity score for spatial truss design by the variance in the positions of the feature vectors in higher-dimensional space, providing an additional performance metric during early stage design exploration. We then develop a pathway towards reducing complexity by clustering nodes with respect to their feature vectors to reduce the number of unique connectors for design while minimizing the effects of mass standardization.

Study of the behavior and resistance of right-angle truss shear connector for composite steel concrete beams

The Right-Angle Truss connector is a newly developed shear connector that features efficient structural behavior and low manufacturing and installation cost. However, for the application of this connector in composite steel–concrete beams, studies that evaluate its behavior in greater detail need to be developed. Thus, this study aims to evaluate the shear resistance of the Right-Angle Truss connector with the variation of parameters inherent to the connection of composite steel–concrete beams. For this, a non-linear finite element model, capable of simulating push-out tests with a Right-Angle Truss connector was developed. The numerical model was validated with experimental results. From a parametric study, the influence of the diameter of the bar that constitutes the connector and the strength of the concrete on the shear resistance of the Right-Angle Truss connector was evaluated. The application orientation of this connector which provides the greatest shear resistance was also studied. An equation to prescribe the shear resistance of the Right-Angle Truss connector was proposed.

Isogeometric-analysis-based stiffness spreading method for truss layout optimization

A novel isogeometric analysis-based stiffness spreading method (IGA-based SSM) is proposed for the truss layout optimization design within a continuum, where the topology, geometry, and cross-sectional areas of the truss elements can be simultaneously optimized. The IGA-based SSM based on energy conservation is employed to obtain the spreading stiffness matrices of the truss elements that are embedded in weak IGA background grids. The IGA background grids are constructed using high-order continuous isogeometric elements that can overcome the limitation of discontinuous sensitivity derived by traditional C0 elements. Because the sensitivity required for the optimization can be obtained analytically, gradient-based optimization algorithms can be easily implemented. To verify the effectiveness of the IGA-based SSM for truss layout optimization design, typical illustrative examples are used, considering the compliance minimization optimization problem. The proposed method can provide a continuous and smooth sensitivity field and overcome the numerical inaccuracy caused by interpolation methods, such as the radial basis function. The different background mesh sizes, initial layouts, and orders p of nonuniform rational B-splines basis functions are investigated in truss layout optimization. The results indicate that the selection of the appropriate background mesh size can avoid the problem of discontinuous truss connections, C1-continuous isogeometric elements can provide better optimization designs with a lower computational cost, and the proposed method can provide a clear layout for different initial layouts. Moreover, the spatial truss layout optimization problem and the min–max displacement optimization problem are also studied to further verify the effectiveness of the proposed method. Finally, the proposed method is extended to solve the concentrated force diffusion problem that widely exists in the interstage adapters of launch vehicles by adding the variance constraint of reaction forces. The results indicate that the proposed method can obtain required concentrated force diffusion results with reasonable stiffness distributions.

Experimental investigation on fire resistance of sandwich composite walls with truss connectors

The sandwich composite wall with truss connectors is a new type of double-steel-plate composite wall, which consists of two external steel plates, square steel tubes at both ends, and in-fill concrete. The external steel plates are constrained by the steel trusses, thereby possessing superior mechanical performance. In order to study the fire resistance of the sandwich composite wall, 4 full-scaled walls were tested under one-side ISO-834 standard fire, aiming to investigate the effects of axial compression ratio, truss spacing to thickness ratio, and steel plate thickness on the fire resistance of the walls. The temperature, axial displacement and transverse displacement of key parts of the walls were measured. Experimental results indicate that, the walls could maintain sufficient load-bearing capacity as specified by the Class I fire resistance rating of Chinese Code. The fire endurance of the wall was controlled by its thermal insulation. The deformation pattern of the walls under the fire was overall deflection toward the unexposed surface, and the steel plate exposed to the fire experienced obvious local buckling. The axial compression ratio and the truss spacing to thickness ratio had great effects on the deformation behavior of the walls. When the axial compression ratio was reduced from 0.5 to 0.3, the axial deformation of the wall was changed from compression-predominant to expansion-predominant deformation. A larger truss spacing to thickness ratio led to more obvious buckling of the steel plate exposed to the fire. It is recommended to restrict the truss spacing to thickness ratio of the wall in engineering design.

Physical Tests of Alternative Connections of Different High Roof Purlins Regarding Upward Loading

Thin-walled cold-rolled sections are used in the construction industry, especially in the roofing of large-span halls. The load-bearing capacity of a thin-walled structure depends to a large extent on the load-bearing capacity of the details at the point of attachment to the structure and the interconnection of the individual thin-walled elements. Therefore, in the case of thin-walled structures, it is necessary to use additional structural elements such as local reinforcement, stabilising elements, supports, and other structural measures such as the doubling of profiles. This paper focused on the behaviour of tall Z300 and Z350 mm thin-walled trusses at the connection to the superstructure regarding upward loading (e.g., wind suction and so on). Two section thicknesses, 1.89 mm and 2.85 mm, were experimentally analysed. Furthermore, two types of connections were prepared, more precisely without and with a reinforced buckle. The experiments aimed to investigate the behaviour and load-carrying capacity of the detail of the roof truss connections to the supporting structure. The resulting load capacity values were compared with normative approaches. Analyses of the details of the bolt in the connection are also presented. The paper presents a practical evaluation of the physical test on real structural members.

Seismic performance assessment of a super high-rise twin-tower structure connected with rotational friction negative stiffness damper and lead rubber bearing

In this paper, a novel rotational friction negative stiffness damper (RFNSD) composed of negative stiffness device (NSD) and rotational friction dampers (RFDs) is proposed to develop flexible connection for improving the seismic performance of an asymmetrical super high-rise twin-tower connected structure. The prototype structure is rigidly connected by long-span steel truss, and shaking table test has shown that the rigid connection between the towers and the truss corridor generally cause buckling of steel truss members and structural damage on the connected floors. To mitigate seismic responses of the truss corridor and the towers, the rigid connection is replaced by flexible ones using the proposed RFNSD and lead rubber bearing (LRB). The working principle of RFNSD is introduced and the theoretical force-displacement model is derived. The numerical model for the proposed flexible connection is presented and detailed three-dimensional finite element models for the rigidly and flexibly connected structures are established. Then by nonlinear time history analysis, seismic responses of the models under three-directional excitations are analyzed, and the effect of flexible connection’s design parameters is discussed. The results show that the developed flexible connection can obviously mitigate the dynamic responses and structural damages. As the stiffness of the pre-tensioned spring in NSD increase, the dynamic response of the steel truss connection corridor would be further decreased. The RFDs can effectively control the increased deformation of the flexible connection caused by the NSD, and promotes the energy dissipation capacity. The model with the flexible connections presents good seismic performance, indicating the effectiveness of the proposed RFNSD.

Yield load estimation of plug & play N type RHS truss connections

AbstractThe article presents a new concept of II generation N type RHS plug & play truss connection, made in non‐welded technology. In II generation of such joints the tension bracing is not made with two flat bars on both sides of RHS chord and connected with a screw passing through the chord (I generation), but with single round rod going through the clamping blocks and threaded at the ends what allows to screw and fix it to the blocks. Representative connections of such truss are analyzed. Concept of resistance calculations of these joints, using the component method, is shown. Test results and the theoretical resistance follows the different modes of the connections failure are compared.

Use of Natural Fiber and Recyclable Materials for Spacers in Typical Space Truss Connections

AbstractSpace trusses are extensively used to construct large free spans in roofs. In many countries, connections in such space trusses are made with tubes linked by typical space-truss connections...

Experimental seismic behavior of T-shaped double skin composite wall with steel truss

The double skin composite wall (DSCW) with steel truss is an innovative lateral load resisting member which composed of two steel plates, core concrete, concrete-filled steel tubes (CFSTs) as boundary members, and steel truss connectors. The effects of the aspect ratio and the flange wall width on the seismic performance are investigated based on the quasi-static test of full-scale T-shaped DSCWs with steel truss. The failure mode, load-displacement response, shear strength, ductility, energy dissipation, shear deformation, and stress distribution of the specimens were analyzed. The test results showed that the failure mode of the T-shaped DSCW with steel truss specimens with aspect ratios of 2.0 and 2.5 was flexure-shear failure, which was characterized by shear buckling of the steel plate, local buckling, and fracture of the boundary members, and of crushing of core concrete. The T-shaped specimens with a small aspect ratio have a higher shear strength, ductility, energy dissipation capacity, and shear deformation proportion. The T-shaped specimen with a long flange wall also has a higher shear strength, but the ductility, energy dissipation capacity, and shear deformation proportion are small. The stress distribution indicates that the T-shaped specimen is more likely to failure due to the insufficient flexural strength of the boundary member. The theoretical formula for the flexural strength of T-shaped DSCW with steel truss is established, and the validation results show that the formula is accurate and safe.

Multiaxial fatigue assessment of complex steel connections: A case study of a vertical-lift gussetless truss bridge

Civil engineering structures grow more complex as engineers push innovation boundaries. Load complexity, costs, construction and maintenance efficiency, among other things, can lead to unique designs that are often excluded in current design codes and evaluation standards. Fatigue-induced damage is currently one of the most common damage types experienced by ordinary and complex civil engineering structures subjected to cyclic loading such as bridges. However, current fatigue evaluation and design standards provide limited guidance on how to approach complex welded connections. Uniaxial and multiaxial methods for the evaluation of fatigue life using strains histories are compared for the assessment of a welded gussetless truss connection of the Memorial Bridge, a vertical-lift bridge connecting Portsmouth, NH and Kittery, ME. As expected, using both approaches result in sufficient remaining fatigue life. However, it is demonstrated that commonly used uniaxial fatigue analysis methods can be insufficient in complex structures that experience variable amplitude, multiaxial, and non-proportional loading. Multiaxial non-proportional stresses experienced by a complex connection can cause a decrease in remaining fatigue life estimates. This paper presents assessment tools and a method for the evaluation of fatigue life of complex welded connections using strain time histories.