Tension Members Research Articles

Experimental study on strengthening steel-truss bridge diagonal members using carbon-fibre-reinforced polymer bonding methods

This study investigated the effectiveness of carbon fibre-reinforced polymer (CFRP) materials in strengthening the diagonal tension members of steel-truss bridges. Monotonic tensile and cyclic loading tests were performed on CFRP-strengthened specimens with variations in the CFRP-bonding range on the flanges. This study focused on the strengthening methods A and B, which were proposed to address insufficient CFRP anchoring near gusset plates by bonding CFRP sheets to both sides of the flanges of the diagonal tension members. The results of the monotonic tensile loading tests indicated a significant increase in tensile stiffness and substantial improvements in yield strength (27%) and ultimate load-bearing capacity (51%) when the strengthening methods A and B were employed. Delamination of the bonded CFRP sheets was effectively delayed, occurring only after the steel yielded, owing to the use of a ductile adhesive (polyurea putty). On the other hand, the cyclic loading tests demonstrated a significant enhancement in the load-bearing capacities (33% for tensile, 32% for compressive) of the strengthened specimens. Moreover, the energy dissipation capacities of the specimens strengthened by methods A and B exhibited linear increases, with 12% and 14% higher values respectively than those of the non-strengthened specimen. Although the stiffnesses (tensile and compressive) of the strengthened specimens decreased in each loading loop, the strengthening methods A and B maintained the stiffness values at approximately 35% higher than those of the non-strengthened specimen.

The new bridge “Lahnsteg Nauheim”, Wetzlar: slender, elegant, parametrically designed

AbstractThis paper outlines the planning of a bridge in central Germany. Scheduled for construction in mid‐2024, this new bridge is a replacement for a century‐old pedestrian bridge crossing the Lahn river.The proposed bridge will be an airtight‐welded arch bridge, employing steel cross‐sections in both the arch and tension member. Designed as a single‐span, the arches extend 48.0m over the Lahn. The two arches have a flat rise of 4.65m, supporting the roadway through 9 inclined flat steel hangers.This paper delves into the structural engineering aspects, exploring challenges inherent in the design process. An examination of the parametric design process, facilitated through 3‐D modeling in Rhino® and Grasshopper®, will be presented, along with insights into their interface with the finite element modeling software, RFEM®. This process enables an engineering approach to form‐finding and structure optimisation through iterative design checks for various elements and stages of the structural analysis.

Tensegrity FlaxSeat: Exploring the Application of Unidirectional Natural Fiber Biocomposite Profiles in a Tensegrity Configuration as a Concept for Architectural Applications

Material selection is crucial for advancing sustainability in the building sector. While composites have become popular, biocomposites play a pivotal role in raising awareness of materials deriving from biomass resources. This study presents a new linear biocomposite profile, fabricated using pultrusion technology, a continuous process for producing endless fiber-reinforced composites with consistent cross-sections. The developed profiles are made from flax fibers and a plant-based resin. This paper focuses on the application of these profiles in tensegrity systems, which combine compression and tension elements to achieve equilibrium. In this study, the biocomposite profiles were used as compression elements, leveraging their properties. The methods include geometrical development using physical and digital models to optimize the geometry based on material properties and dimensions. A parametric algorithm including physics simulations was developed for this purpose. Further investigations explore material options for tension members and connections, as well as assembly processes. The results include several prototypes on different scales. Initially, the basic tensegrity principle was built and explored. The lessons learned were applied in a final prototype of 1.5 m on a furniture scale, specifically a chair, integrating a hanging membrane serving as a seat. This structure validates the developed system, proving the feasibility of employing biocomposite profiles in tensegrity configurations. Furthermore, considerations for scaling up the systems to an architectural level are discussed, highlighting the potential to enhance sustainability through the use of renewable and eco-friendly building materials, while promoting tensegrity design applications.

Feasibility and effectiveness of replacing bow truss bridge members with concrete-filled sections

A comparative study of a conventional bow truss bridge, proposed in Rishikesh, India with a composite bow truss bridge (new construction technique) was conducted. First, the bridge was designed by considering conventional steel sections. Then, adopting a modified construction technique, the top chord members of the bridge were replaced with concrete-filled steel box sections and the bottom girders, diagonals and cross-girders (tension members) were replaced with hollow steel box sections. To analyse these replacements, a finite-element model was created and validated with experimental data. A 200 × 200 × 8 mm steel section (fy = 374 MPa) filled with concrete (fck = 42.5 MPa) was found to be suitable for the top chord members. Buckling and plate yielding analyses of the box sections were also investigated and it was found that, due to the higher stress concentration, only two opposite sides of the plate yielded. A cost comparison revealed that the composite section reduced the overall cost by up to 51% when assuming pin connections and by up to 13% when assuming fixed connections. Furthermore, the effects of joints (hinge and fixed) were analysed to check the critical connection and end failure of the bridge members.

Analysis of deformation in tensegrity structures with curved compressed members

Tensegrity structures are prestressed structures consisting of compressed members connected by prestressed tensioned members. Due to their properties, such as flexibility and lightness, mobile robots based on these structures are an attractive subject of research and are suitable for space applications. In this work, a mobile robot based on a tensegrity structure with two curved members connected by eight tensioned strings is analyzed in terms of deformation in the curved members. Further, the difference in locomotion trajectory between the undeformed and deformed structure after the prestress is analyzed. For that, the theory of large deflections of rod-like structures is used. To determine the relationship between acting forces and the deformation, the structure is optimized using minimization algorithms in Python. The results are validated by parameter studies in FEM. The analysis shows that the distance between the two curved members significantly influences the structure’s locomotion. It can be said that the deformation of the components significantly influences the locomotion of tensegrity structures and should be considered when analyzing highly compliant structures.

Simulation based comparative analysis of electric field stress on insulated cross-arm

Insulated cross-arms for overhead transmission lines have become increasingly common in the past decade. The 3D finite element analysis (FEA) of the electric field distribution in insulated cross-arms is particularly intriguing due to the differences from conventional glass or ceramic insulators. The complex geometry of composite cross-arms, which feature four separate insulator strings and varying shed profiles, poses a challenge in modelling them using 3D FEA packages. The findings indicate that insulated cross-arms can operate within suitable parameters for traditional composite insulators. This paper presents and analyses the electric field distribution around an insulated cross-arm, which aims to replace existing high-voltage insulators and the steel cross-arms of transmission towers. The design of grading devices plays a crucial role in ensuring the safety of these structures. The use of grading ring devices at both ends of the insulator has proven effective in relieving stress on the insulator string under normal and abnormal conditions, enabling the insulated cross-arm to function effectively with conventional composite insulators. Significant reductions in electric field strength were observed, amounting to approximately 35.93 % inside the core, 31.14 % on the core surface, 35.64 % through the shed, and 16.67 % above the shed for compression members. For tension members, reductions from the low-voltage end to both ends were around 33.82 % inside the core, 38.55 % on the core surface, and 17.48 % through the shed. However, an 8.43 % increase was observed above the shed, indicating a deviation from the decreasing trend observed in other areas. These research findings provide valuable insights for designing and managing high-voltage systems, ensuring effective insulation and enhanced safety. It benefits electrical utilities and transmission line manufacturers by improving reliability and safety for overhead transmission lines.

Yoke-Type Elasto-Magnetic Sensor-Based Tension Force Monitoring Method for Enhancement of Field Applicability.

Tension members are key members that maintain stability and improve the strength of structures such as cable-stayed bridges, PSC structures, and slopes. Their application has recently been expanded to new fields such as mooring lines in subsea structures and aerospace fields. However, the tensile strength of the tension members can be abnormal owing to various risk factors that may lead to the collapse of the entire structure. Therefore, continuous tension monitoring is necessary to ensure structural safety. In this study, an improved elasto-magnetic (E/M) sensor was used to monitor tension force using a nondestructive method. General E/M sensors have limitations that make it difficult to apply them to operating tension members owing to their solenoid structure, which requires field winding. To overcome this problem, the magnetization part of the E/M sensor was improved to a yoke-type sensor, which was used in this study. For the development of the sensors, the numerical design and magnetization performance verification of the sensor were performed through eddy current solution-type simulations using ANSYS Maxwell. Using the manufactured yoke-type E/M sensor, the induced voltage signals according to the tension force of the specimen increasing from 0 to 10 tons at 1-ton intervals were repeatedly measured using DAQ with wireless communication. The measured signals were indexed using peak-to-peak value of induced voltages and used to analyze the signal change patterns as the tension increased. Finally, the analyzed results were compared with those of a solenoid-type E/M sensor to confirm the same pattern. Therefore, it was confirmed that the tension force of a tension member can be estimated using the proposed yoke-type E/M sensor. This is expected to become an effective tension monitoring technology through performance optimization and usability verification studies for each target tension member in the future.

Probabilistic safety assessment of truss members designed by TCVN 5575:2012

This study aims to evaluate the probabilistic safety levels of truss structures designed using the TCVN 5575:2012. A planar structure was designed according to the strength limit state (tension and compression) in the design code. Monte Carlo simulations were then executed to assess the failure probability of the design solutions designed following TCVN 5575:2012. The results help evaluate safety in terms of probability and uniformity. Accordingly, the probability safety levels are compared with those specified in international specifications. The results obtained in this study reveal that the reliability indices for compression bars are higher than those for tension members (approximately 20%). In addition, the reliability indices for the tension members were relatively close to the specified target in the American specification. In contrast, compression bars designed using the TCVN result in a higher reliability index than the target specified in the American code.

APPLICATION OF SKELETAL BIOMECHANICS TO STRUCTURAL SYSTEMS

The concept of green construction enables a revolutionary change in construction sector in terms of design, production, and management. One such method is introducing the concept of biomimicry. Biomimicry is utilized in the field of design to solve problems. This paper mainly discusses the mimicking of human skeleton for structural design. The idea is mimicking humerus bone as a tension member and femur bone as a compression member. The optimized members of compression and tension (strut and tie) were put together to form the mimicked king post truss analytically with the conventional cross-section truss. Three cases were considered analytically with average diameter, maximum diameter, and equivalent self-weight to the members of mimicked truss, and experimentally testing with non-destructive test and point-load test. The result shows that the ultimate load-carrying capacity of critical compression member and tension member was 846.16 and 1952 kN, respectively, whereas the achieved load was 780.30 and 1729 kN. Also, the ratio of analytical stiffness to self-weight is 21.83 mm<sup>-1</sup> and the ratio of experimental stiffness to self-weight was 19.15 mm<sup>-1</sup>. Therefore, from the results it was observed that the equivalent results for mimic truss can be achieved in a truss which is modeled of equivalent self-weight. Hence, the development and use of structural elements using biomimicry is feasible and will lead to economic, green, and energy-efficient structures.

Estimation of tension force in tension members using GRU algorithm based on yoke-type elasto-magnetic sensor data

Estimation of tension force in tension members using GRU algorithm based on yoke-type elasto-magnetic sensor data

Tensile behaviour of WAAM high strength steel material and members

Wire arc additive manufacturing (WAAM), a method of metal 3D printing, has the capacity to create large scale elements suitable for construction applications with a high degree of design freedom and structural efficiency. There is currently however a lack of fundamental experimental data on the material and structural performance of such elements. Towards addressing this limitation, the tensile behaviour of WAAM high strength steel produced using different printing strategies is the focus of the present study. WAAM steel plates and tubular tension members manufactured with different interpass temperatures and toolpaths using ER110S-G welding wire were examined. A total of 60 tensile coupons, consisting of 40 as-built and 20 machined specimens, and 8 as-built circular hollow section (CHS) tension members, were tested. The examined WAAM materials were found to exhibit very little anisotropy, corroborated by a nearly homogeneous crystallographic texture observed by microstructural analysis, while the inherent surface undulations were shown to result in a varying degree of reduction in the material stiffness, strength and ductility at different angles to the print layer orientation. The different printing strategies led to varying surface geometries; combined with different interpass temperatures, they also resulted in different thermal histories and thus different mechanical properties. The tension members showed good structural resistance, but a considerable reduction in ductility compared to the coupon tests, due to the greater geometric variability and manufacturing defects.

Static and Fatigue Mechanical Properties of Polymer Matrix Composite Rods

Tendons (cables or rods) are commonly employed as tension members in civil infrastructure, as well as buildings and offshore engineering structures. This study focuses on reliability evaluation of composite rods consisting of polymer matrix (carbon fiber/glass fiber hybrid thermoplastic composite rods (hybrid composite rods) and basalt fiber/polypropylene composite rod (BF/PP composite rod)). Optical and gravimetric methods were used to characterize the morphologies, including constituent volume fractions, of the composite rods. The hybrid composite rods are braided structures with varying diameters and braid angles. The BF/PP composite rod exhibits slight twisting. The volume fractions of the constituent elements (carbon fiber, glass fiber, basalt fiber, matrix, and void) were evaluated. Tensile and flexural tests were conducted under static and fatigue loadings. During the static tensile test, the stress applied to the composite rods was almost linearly proportional to the strain. The fiber-dominant behaviors of the composite rods were observed. During the static flexural test, the stress-strain relationship was initially linear, but as the stress approached its maximum, deformation became non-linear, and finally, the fibers fractured rapidly. During the fatigue tensile and flexural tests, the regression lines of the full-logarithmic curves showed good agreement with the fatigue test data. In addition, data was collected and statistical analyses were performed to assess the effects of environmental factors, such as temperature, on the static properties of the composite rods.

Crack monitoring of tension members with distributed fiber optic sensor considering substrate strain redistribution and coating/fiber interfacial slip

An analytical model is proposed to describe the strain transfer from crack opening displacement (COD) of a tension member substrate to the distributed fiber optic sensor (DFOS), considering the DFOS/fiber coating interfacial slip and strain redistribution of the cracked structural substrate. The DFOS/fiber coating interfacial bond-slip relation is simplified by using a three-phase linear model, and the analytical expression of the substrate strain distribution of a tensile plate with different depth of crack is derived. The effect of the COD and crack depth on the strain distribution of the DFOS is obtained analytically, and tensile tests were also conducted on aluminum plates with different depth of precut crack to validate the developed model. Analytical results showed that the strain distribution of the DFOS is dependent on the COD and the crack depth, and the effect of the COD on the strain distribution of the DFOS is more significant than the crack depth. The analytical results of the developed model are in good agreement with those of the tensile tests.

Preliminary Theoretical Considerations on the Stiffness Characteristics of a Tensegrity Joint for the Use in Dynamic Orthoses

Early motion therapy plays an important role for effective long-term healing of joint injuries. In many cases, conventional dynamic orthoses fail to address the intricate movement possibilities of the underlying joints, limited by their simplistic joint representations, often represented by revolute joints, enabling rotations by only one axis. In this paper, a two-dimensional compliant tensegrity joint for use in biomedical applications is investigated. It consists of two compressed members and five compliant tensioned members. Relative movement possibilities are realized by the intrinsic compliance of the structure. In the development of these systems, the first step is the determination of the static stable equilibrium. This analysis is conducted in this paper by considering the potential energy approach or by using the geometric nonlinear finite element method. The mechanical behavior of the structure is assessed with a specific emphasis on its mechanical compliance. The primary objective of this study is the investigation of the influence of structural parameters on the overall stiffness and movability of the structure. The results underscore the significant effect of member parameters on the stiffness and movability of the compliant tensegrity joint, particularly under varying load magnitudes. These findings provide insights for optimizing the joint’s performance, contributing to its potential application in advanced orthotic and exoskeleton devices.

Strain-mode-specific mechanical testing and the interpretation of bone adaptation in the deer calcaneus.

The artiodactyl (deer and sheep) calcaneus is a model that helps in understanding how many bones achieve anatomical optimization and functional adaptation. We consider how the dorsal and plantar cortices of these bones are optimized in quasi-isolation (the conventional view) versus in the context of load sharing along the calcaneal shaft by "tension members" (the plantar ligament and superficial digital flexor tendon). This load-sharing concept replaces the conventional view, as we have argued in a recent publication that employs an advanced analytical model of habitual loading and fracture risk factors of the deer calcaneus. Like deer and sheep calcanei, many mammalian limb bones also experience prevalent bending, which seems problematic because the bone is weaker and less fatigue-resistant in tension than compression. To understand how bones adapt to bending loads and counteract deleterious consequences of tension, it is important to examine both strain-mode-specific (S-M-S) testing (compression testing of bone habitually loaded in compression; tension testing of bone habitually loaded in tension) and non-S-M-S testing. Mechanical testing was performed on individually machined specimens from the dorsal "compression cortex" and plantar "tension cortex" of adult deer calcanei and were independently tested to failure in one of these two strain modes. We hypothesized that the mechanical properties of each cortex region would be optimized for its habitual strain mode when these regions are considered independently. Consistent with this hypothesis, energy absorption parameters were approximately three times greater in S-M-S compression testing in the dorsal/compression cortex when compared to non-S-M-S tension testing of the dorsal cortex. However, inconsistent with this hypothesis, S-M-S tension testing of the plantar/tension cortex did not show greater energy absorption compared to non-S-M-S compression testing of the plantar cortex. When compared to the dorsal cortex, the plantar cortex only had a higher elastic modulus (in S-M-S testing of both regions). Therefore, the greater strength and capacity for energy absorption of the dorsal cortex might "protect" the weaker plantar cortex during functional loading. However, this conventional interpretation (i.e., considering adaptation of each cortex in isolation) is rejected when critically considering the load-sharing influences of the ligament and tendon that course along the plantar cortex. This important finding/interpretation has general implications for a better understanding of how other similarly loaded bones achieve anatomical optimization and functional adaptation.

A novel winding–wedge anchorage for CFRP straps: Conceptual design and performance evaluation

Carbon fibre-reinforced polymer (CFRP) straps can be utilised as tension members in structures on account of their high-strength properties. The development of an effective anchorage device for CFRP straps that can fully utilise the strength of straps before anchorage failure is an ongoing technical challenge. To address such knowledge gap, a novel anchorage device termed winding-wedge anchorage that combines winding and wedge anchorage mechanisms is reported herein. For the winding anchorage component, different numbers of winding turns are applied. For the wedge anchorage component, three different types of wedge anchorage systems are investigated namely bonding, friction clamping, and friction non-clamping. Initially, the working mechanism, theoretical winding–wedge anchorage model (herein theoretical model), and design parameters are determined. Experimental and finite element analyses are then reported to assess the behaviour of the anchorage including failure modes and anchorage efficiencies. The accuracy of the theoretical model is also reported. It is concluded that the efficiency of the anchorage device is primarily dependent on the wedge anchorage component. Moreover, the bonding wedge anchorage component performed better than the other two wedge anchorage systems. The theoretical model and experimental results revealed that 1.5 winding turns results in an optimal interaction between the winding and wedge anchorages components.

A novel Genetic algorithm based form-finding approach towards the improved design of tensegrity utility bridge

The rapid growth of urbanization worldwide necessitates reliable infrastructure and efficient support structures like utility bridges and tunnels. However, the design of such structures has often been neglected, resulting in inconsistent standards and technical specifications. Typically, utility bridges are constructed first, and service lines like power cables and pipelines are later pulled through them, which can be a tedious process. An alternative approach involves using deployable structures with cables already placed inside, allowing for easy deployment across hindrances, such as the stream. The tensegrity concept offers a lightweight, sturdy, and deployable bridge that can be used temporarily with unique benefits like modifiable stiffness and easy dismantling.Tensegrity structures consist of strings and struts that act as dedicated tension and compression members and are characterized by their self-stressed configurations. To achieve these configurations, the cables must be pre-tensioned, requiring a form-finding approach to find the member prestresses. This study develops a Genetic Algorithm (GA)-based form finding approach that identifies a tensegrity module that complies with tensegrity properties and satisfies structural and constructional requirements. The GA combines the identified self-stressed states to create a tensegrity module capable of withstanding external operational loads while being internally stable. The resulting tensegrity bridge is compared against traditional utility bridges, highlighting its potential benefits and real-life applicability. The study concludes that a tensegrity concept is an efficient approach for utility bridge design.

Non‐Destructive Testing of Bridge Cables using MIT

AbstractThis article presents the importance of non‐destructive testing (NDT) in maintaining the safety and functionality of bridge cables, and focuses on the practical use of magnetic‐inductive testing (MIT) and ultrasonic testing (UT) for NDT of bridge cables in free length and in the area of the end connectors. MIT is a non‐invasive method that can effectively detect defects such as broken wires, corrosion symptoms, and other imperfections, making it a promising technique for inspecting and maintaining bridge cables. A research project investigated various types of magnetic induction testing on different tension members made of single wires and evaluated the advantages and limitations of the MIT method. The study also explored the impact of factors such as cable diameter and measurement speed on the effectiveness of the technique. The results suggest that the MIT method can accurately detect defects in bridge cables and provide valuable information for maintenance and repair purposes. However, the article highlights the need for further research to optimize the MIT technique, particularly in automating the detection and characterization of signals, and to expand its applicability to a wider range of cable diameters and conditions.

R.C.C Shell Structure Design of Selected Head Cap Shape

Abstract: A shell structure is a thin structure composed of curved sheets of material, so that Shell structures are inspired from natural element named “SHELL”. A thin curved member or slab usually of reinforced concrete that function as tension member and shell. The waviness plays an important role in the structural behavior realizing a spatial form. Some of natural elements like eggshell, seashell, fruit shells (walnut) etc are showing shell structure properties. The present reinforced concrete shells as a very efficient structure, spanning wide, architectonically beautiful, relevant and valuable structural solution. Shell structures are very attractive lightweight structures, which are especially suited to Architectural building, industrial application, commercial projects etc.. The actual design of shells, involves theories of shells and the use of appropriate codes of practice. Types of curved shell like Parabolic, Hyperbolic or Cylindrical members are often said to act as tension rigidity hence called tensile members. For achieving the optimized load capability and flexural strength of such an element in form of shell covering structure is checked in for M30 grade concrete. Tensile shell members are structural edifice that caries only tension and without buckling or bending. Tensile structures are the most common type of thin-shell structures used worldwide from past decades. The profile and aspect of structure used are unlike for loading conditions, geographical locations and Architecture design differs as such as horizontal, sloping or curved member (dome and shell member). In this research work the tensile shell (plate) structure is designed in the form of beam and as grid shell slab element (plate). After then load has been applied for analysis via software tool i.e. STAAD Pro. The types of load assigned dead and live loads. The Design code specifications for curved shell member in IS: 2210–1994, IS 2204-1962 “Code of practice for construction of reinforced concrete shell roof” [CED 13: Building Construction Practices including Painting, Varnishing and Allied Finishing] and the load case criteria is to be as per IS: 875(2)–2000. RCC design specifications as per IS: 456–2000

Steel–concrete bond deterioration in reinforced concrete tension members due to primary cracks

Primary cracks in reinforced concrete tension members lead to the deterioration of the steel–concrete bond. This study aims to investigate this bond deterioration by establishing a novel relationship between the bond force and slips near the cracks. The descending part of this relationship represents the bond deterioration, with its parameters determined by the structural responses. An iterative algorithm is proposed based on this relationship to analyze the bond behaviors of tension members. The effectiveness of the proposed method is validated using reinforced concrete tension members from experiments in the literature. The results demonstrate a gradual decrease in bond forces from local maximum to zero near the cracks, indicating the presence of the descending part of the bond–slip relationship. The length, slope, and characteristic points of the descending part vary with crack spacing and slips at the cracks, leading to nonlinearity in steel strains. In comparison to existing methods assuming constant length or slope, the proposed method accurately predicts these variable parameters, and provide precise estimations of bond force.