Pretension Force Research Articles

Mechanical performance of geopolymer pre-stressed railway sleepers

This study is confined to polymerization and the base chemical used is sodium hydroxide 14 molarity and sodium silicate. High Performance Geopolymer Concrete (HPGC) was developed from Alkaline Activator Solutions (AAS) under combination 60% Ground Granulated Blast Furnace Slag (GGBS) and 40% Fly ash (FA) as binder materials produced high compressive strength of 76 N/mm2. Another mixing was made with the same proportion of binder material and filler materials M sand was replaced by Copper Slag (CS). According to the test results the substitution of 50% copper slag with M sand produced at high compressive strength of 80 N/mm2. Geopolymer Concrete was used for the casting of Wide Gauge Prestressed Concrete (PSC) sleepers as per Indian Railway standard specifications. And Pre-tensioning wires of standard High Tensile Strength wire (HTS) were used with a pre-tensioning force of 50kN. Needed Compaction was carried out using table vibrators and steam curing was adopted based on the standard production process of Indian Railways. Under power testing process the hardened concrete sleepers were tested in the laboratory by stimulating the real load transfer condensing the field called Rail Seat Centre Bottom (RSCB), Moment of Resistance (MR) and Moment of Failure (MF). As per the standard static flexural test procedure, the number of sleeper on each side of the sleeper for a load up to 230 kN (MR) and 370 kN (MF) was determined. The result of the tests reveals that the Geopolymer concrete sleeper has a high efficiency load and a high ultimate load.

Cable optimization of a cable-stayed bridge based on genetic algorithms and the influence matrix method

Structural optimization is an important tool for structural designers that helps them to find innovative design solutions and structural forms with a better exploitation of materials as well as decreased self-weight and minimum material costs. In this article, a design procedure coupling the influence matrix method and genetic algorithms to optimize stay cables in cable-stayed bridges is presented. Following that, the design procedure is utilized in the preliminary design of a twin towers double-cable planes cable-stayed bridge to be located in Ferrara, Italy. The cable cross-sectional areas and corresponding pre-tension forces are optimized simultaneously. The results demonstrate that the proposed procedure is a powerful tool for designing stay cables and predicting the optimum cross-sectional areas of stay cables under certain stress and displacement constraints.

Some aspects of custom-made 3d-printed hip joint implant structural simulation

Current article is devoted to the application of computer-aided engineering technologies to the virtual testing of customized endoprostheses of large joints. The research is performed for a representative case, where the personalized prosthesis of the hip joint is used as a part of the process of treatment of osteosarcoma, as conventional systems are not applicable. The study is highly relevant due to the intensive development of personalized medicine allowing for the patients’ successful recovery and mobilization. However, since each of the customized implants is a unique part, a rapid, accurate and financially efficient methodology of performing the structural analysis of such components is required to avoid the real testing of each implant. The article describes the all steps of the structural simulation of the series of loading scenarios for the biomechanical system consisting of the pelvis and endoprosthesis. The process of preparing the finite element models of pelvic bones and components of the implant is also explained in detail. The stress-strain state of the pelvis and implant is investigated for a number of values of the pretension force of the screws. Based on the comparative analysis, a set of practical recommendations is formulated to reduce the stress in the bone tissue. The discussed steps are the elements of the methodology of the rapid finite element virtual testing of the customized implants that is currently developed by the research group.

A Public Blockchain-Enabled Wireless LoRa Sensor Node for Easy Continuous Unattended Health Monitoring of Bolted Joints: Implementation and Evaluation

With the advent of Internet of Things (IoT) a slow shift is happening from manual checks of capital intensive assets such as bridges, wind turbines, etc., where bolted joint is used as a main fastening method, towards unattended Structural Health Monitoring (SHM). Numerous approaches are proposed for monitoring the looseness of bolted joint assemblies, however, the majority of them can only be used for looseness detection purposes and not viable for monitoring since these approaches contain design impracticalities, not scalable or hard to implement outside of the laboratory environment. Furthermore, remote unattended monitoring is still very much in its infancy. Thus, to solve this issue, we propose a TenSense M20, a custom designed smart sensor node for continuous remote SHM of bolted joints. Complete node design is presented. Each aspect of the design is evaluated both by simulation and practical tests. Long Range (LoRa) is used as a means of wireless communication and the network can cover 3.8 km. The results show that TenSense M20 is able to precisely track the pre-tension force of a bolted joint with the approach being robust and scalable. Several transmission scenarios are analyzed and in the worst case scenario the node is estimated to last more than 5 years powered by several LiSOCl <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> primary batteries. Received data is securely stored in a blockchain and is easily accessible for services targeting integration with a Smart City.

Mechanical properties of bolted connections for aluminum alloy structures at elevated temperatures

This study investigates the tensile properties of bolted connections for aluminum alloy plates from room temperature to 400 °C through elevated-temperature tensile tests of 30 single- and 24 multiple-bolted connections. Accordingly, the failure modes and tensile bearing capacity are defined at different temperatures. Then, ABAQUS is used to establish the finite element models of bolted connections for aluminum alloy plates at elevated temperatures, and the tests verified the rationality of finite element models. Considering the parameters such as thickness and width of plates, diameter and end distance of bolt holes, pretension force, and arrangements of bolts, the study performs a parametric analysis of connections and further examines the contribution of these parameters on tensile properties of bolted connection for aluminum alloy plates at elevated temperatures. This study employs a statistical regression method to derive the theoretical formula. Finally, it proposes a set of elevated-temperature reduction factors of ultimate bearing capacity suitable for aluminum alloy joints, which can serve as a guide in the analysis and design of fire resistance for aluminum alloy structures.

Studies on T-shaped one-side bolted connection to hollow section column under bending

A novel T-shaped One-side Bolted endplate Connection (TOBC) for steel beam to Hollow Square Steel Tube (HSST) was proposed and the behavior of TOBC under static bending moment was investigated through Finite Element Model (FEM). The FEM was verified by test results on Standard High-strength Bolted Connection (SHBC) in terms of the failure mode, the bending moment-rotation curve and the yield bending moment. Parametric analysis of TOBC was carried out. Studied parameters included both the general parameters of an endplate connection, such as the endplate width, the endplate thickness, the endplate strength, the bolt diameter, the bolt pretension force, the axial compression ratio of the column and the beam length, and the unique parameters of the TOBC, such as the direction of slotted bolt hole, the gap between infill block and bolt hole, the angular deviation of the T-head and the two-bolt hole of T-shaped One-side Bolt (TOB). A total of six failure modes were found namely: the beam yielding failure, the bolt failure, the endplate yielding failure, the column wall yielding failure, the column wall yielding accompanied with endplate yielding failure and the column wall yielding accompanied with bolt failure. The TOBC with slotted bolt hole in vertical direction had better performance than that in horizontal direction in terms of the initial stiffness, the yield bending moment and the ultimate bending moment. The gap between infill block and bolt hole had no effect on the bending performance of TOBC in moment connection. The angular deviation of the T-head had little influence on the bending performance of TOBC, if it was less than 30 degrees. The initial stiffness and yield bending moment of TOBC could be greatly increased by using two-bolt holes in the connection tension region.

Structural Dynamic Improvement for Petal-Type Deployable Solid-Surface Reflector Based on Numerical Parameter Study

Petal-type Deployable Solid-surface Reflector (PDSR) is a kind of important structure widely applied in deployable reflector antennas in aerospace engineering. The dynamic properties of this reflector structure in deployed state are significant to the reflector accuracy for antennas. However, the study of the dynamic evaluation of deployable structure with revolute joints is difficult and seldom concerned by researchers. In order to study dynamic properties of the PDSR, the Cable Replacement Method (CRM) was utilized to equivalently simulate the nonlinear structural stiffness of the revolute joint for numerical analyses. The Finite Element Model (FEM) of this reflector structure was established by commercial software ANSYS (ANSYS Inc., Canonsburg, PA, USA) and verified by the theoretical analysis and dynamic test of actual prototype model. The natural frequencies and mode shapes of deployed reflector were computed to study the influence of drag spring design parameters as stiffness, pre-tensioned force, and distance of two adjacent linkage butts. Finally, the analysis results were concluded that the drag springs between two adjacent petals can essentially improve the dynamic performance of reflector structure in deployed state. It can be a useful technical system for future engineering applications of PDSR antennas.

Nonlinear free vibrations analysis of geometrically imperfect FG nano-beams based on stress-driven nonlocal elasticity with initial pretension force

Size-dependent flexural nonlinear free vibrations of geometrically imperfect straight Bernoulli-Euler functionally graded nano-beams are investigated by the stress-driven nonlocal integral model (SDM). By using the Galerkin method, the governing equations is reduced to a nonlinear ordinary differential equation. The closed form analytical solution of the nonlinear natural flexural frequency for Simply-Supported, Clamped-Simply Supported and Clamped-Clamped nano-beams is then established using the Hamiltonian approach to nonlinear oscillators. Effects of nonlocal scale parameter and an initial axial tension force on fundamental frequencies are examined and compared with those obtained by Eringen’s nonlocal model. It is shown that the nonlinear approach based on nonlocal stress model, with the appropriate constitutive boundary conditions, is capable of capturing the dynamical responses of the nano-beams and provides an advantageous method for the design and the optimization of a wide range of nano-scaled beam-like components of Nano-Electro-Mechanical-Systems (NEMS).

Hanger pre-tensioning force optimization of steel tied-arch bridges considering operational loads

Full design analysis of a bridge usually has lots of load cases and leads to the analysis process, which is extremely time-consuming. To reduce the computational cost, the existing hanger pre-tensioning force optimization approaches for cable-supported bridges always consider only a few critical load cases. This study presents an efficient approach for hanger pre-tensioning force optimization of steel tied-arch bridges, which can include all the operational loads and their combinations based on the code requirements. The proposed method develops a load decoupling approach (LDA) to enhance the computational efficiency of structural analysis in optimization and utilize the particle swarm optimization algorithm to search the global optimal design. The LDA divides the structural analysis procedure into two systems: (1) iteration-varying and (2) iteration-invariant. The former evaluates the structural responses induced by different hanger forces using unit load method (ULM) and the latter solely needs a single finite element (FE) analysis before iteration to calculate the structural responses caused by the other loads. The superposition principle combines the results from the two systems to identify the minimum safety margin of the bridge under the ultimate limit state. A practical bridge is examined to compare the proposed method with three traditional hanger force determination approaches. The obtained results illustrate that the proposed method not only owns high efficiency but also leads to a safer design and has a broader application range.

Mechanism and experimental validation of innovative self‐centering conical friction damper

Past earthquakes have shown that traditional structural design relies on the component ductility to dissipate the earthquake energy. This has led to significant damage for the structure. Innovative energy dissipation devices have been developed in the past to dissipate the earthquake energy. However, the big disadvantage of traditional energy dissipation devices is the lack of self-centering capabilities. This results to significant residual deformation, which can significantly affect the building resilience. Failing to eliminate the residual deformation can lead to prolong downtime and significant financial losses. In this paper, a novel damper named self-centering conical friction damper (SCFD) is proposed. SCFD utilizes conical surfaces and posttensioning tendons to resist the earthquake loads in all directions. The conical surfaces force the SCFD to self-center, making the SCFD highly desired for earthquake applications. In this paper, detailed mechanical behavior for the SCFD is presented. The hysteresis behavior was verified through the experimental tests. The result shows that the proposed theoretical equations can predict the hysteresis response of the SCFD well. Using the derived equations, detailed parameter study including the influences of pretension forces, effective stiffness of posttension tendons, slope angle, and friction coefficients have been investigated. Results show that the hysteresis behavior can be achieved using different combinations of the slope angle, Pretension (PT) tendons, and friction coefficients. Overall, high slope and friction coefficients will lead to highly efficient SCFD with lower demands on the PT tendons. Detailed design approaches have been presented, which allows the engineers to design SCDF for different applications.

Kajian dan Evaluasi Struktur Slab Prestressed Precast Modular Concrete

Prestressed precast modular concrete slabs function rigid pavement, supporting vehicle loads above it on subgrade with relatively low bearing capacity. This slab measures 2000 x 850 x 150 mm3 of regular reinforced concrete (old production) or prestressed concrete (new production) quality K-500. After several times of use, damage occurs mainly at the end of the slab in the form of spalling. The objectives of the study and evaluation were: (1) observing damage; (2) material quality data; (3) numerical modeling by taking into account material properties, loading and soil conditions; and (4) providing slab design recommendations including materials and geometrics. The method of study and evaluation of slab damage was done by observing the damage, taking concrete core-case and testing it in the laboratory, and modeling the slab structure with various parameters (soil data, concrete quality and slab geometry). Field observations and analysis results show that concrete slab spalling occurs initially at the edge (850 mm wide) which in turn causes the effectiveness of the pre-tension force to be suboptimal and finally the concrete spalling volume increases. Apart from the frequency of collisions during installation and slab deformation when supporting vehicle loads. Concrete spalling problems also due to inappropriate concrete quality.

Fast and Optimized Calculation of the Cable Pretension Forces in Arch Bridges With Suspended Deck

This paper deals with an effective and fast approach to the optimization of the pretension forces in arched bridges with suspended deck, which makes use of the influence matrix method. The given cable-tensioning procedure leads to a linear system of equations with a reduced number of unknowns and can be effectively implemented within active control procedures that handle time-varying loading conditions. It achieves of a target bending moment distribution over the structure, which significantly mitigates the state of stress of the deck. Numerical results dealing with a Nielsen arch bridge illustrate the versatility of the proposed approach when dealing with different loading conditions

Experimental Study on the Performance of GFRP–GFRP Slip-Critical Connections with and without Stainless-Steel Cover Plates

Composite structures have become increasingly popular in civil engineering due to many advantages, such as light weight, excellent corrosion resistance and high productivity. However, they still lack the strength, stiffness, and convenience of constructions of fastener connections in steel structures. The most popular fastener connections in steel structures are slip-critical connections, and the major factors that influence their strength are the slip factors between faying surfaces and the clamping force due to the prevailing torque. This paper therefore examined the effect that changing the following parameters had on the slip factor: (1) replacing glass fiber reinforced plastic (GFRP) cover plates with stainless-steel cover plates; (2) adopting different surface treatments for GFRP-connecting plates and stainless-steel cover plates, respectively; and (3) applying different prevailing torques to the high-strength bolts. The impact on the long-term effects of the creep property in composite elements under the pressure of high-strength bolts was also studied with pre-tension force relaxation tests. It is shown that a high-efficiency fastener connection can be obtained by using stainless-steel cover plates with a grit-blasting surface treatment, with the maximum slip factor reaching 0.45, while the effects of the creep property are negligible.

The seismic reliability analysis of moment resisting frames with bolted end-plate connection

This paper presents an algorithm to determine the reliability index of moment-resisting steel frames with bolted end-plate connections, by considering the effect of the uncertainties of capacity and seismic demand. To reflect the probabilistic response of structures, the horizontal and vertical distance of the bolt from edge of end-plate, the pretension force and the ultimate strength of the bolts, yield strength and the elastic modulus of plates for beam and column, which are the main parameters of construction errors in bolted end-plate connection, considered as a random variables for the moment-rotation behavior of connections. All the components of the connections have been regarded as random parameters. Then, the probabilistic moment-rotation curve of connections was determined by means of the Latin Hypercube sampling method. Afterward, by conducting a nonlinear dynamic analysis in the 2-dimensional 5, 10, and 15 stories frames and considering the idealized random behavior of the connections as well as the random effect of different records of the earthquake, the results obtained with the aid of Monte Carlo sampling technique. Finally, the appropriate probability density function (PDF) fitted to the results, which this figure for reliability index and probability of failure for the limit state function is 1.62 and 0.052 respectively and also the mean value state is 1.85 and 0.033. This procedure has been named as the Simplified Response Surface Method (SRSM). Results show the structural reliability index is acceptable at the performance level of Life Safety, yet it exceeded this level only by a small amount.

Analytical study on pretensioned bolt-cable combined support of large cross-section tunnel

To study the mechanical responses of large cross-section tunnel reinforced by pretensioned rock bolts and anchor cables, an analytical model is proposed. Considering the interaction between rock mass and bolt-cable support, the strain softening characteristic of rock mass, the elastic-plastic characteristic of bolt-cable support, and the delay effect of installation are considered in the model. To solve the different mechanical cases of tunneling reinforced by bolt-cable support, an analytical approach has been put forward to get the solutions of stress and displacement associated with tunneling. The proposed analytical model is verified by numerical simulation. Moreover, parametric analysis is performed to study the effects of pretension force, cross-section area, length, and supporting density of bolt-cable support on tunnel reinforcement, which can provide references for determining these parameters in tunnel design. Based on the analytical model, a new Ground Response Curve (GRC) considering the reinforcement of bolt-cable support is obtained, which shows the pretension forces and the timely installation are important in bolt-cable support. In addition, the proposed model is applied to the analysis of the Great Wall Station Tunnel, a high-speed railway tunnel with a super large cross-section, which shows that the analytical model of bolt-cable support was a useful tool for preliminary design of large cross-section tunnel.

Control Effects of Pretensioned Partially Encapsulated Resin Bolting with Mesh Systems on Extremely Soft Coal Gateways: a Large-Scale Experimental Study

Pretensioned partially encapsulated resin bolting with mesh systems (PPERBMSs) are commonly employed in underground mines, particularly for soft coal gateways requiring immediate support. However, the behavior of bolts and reinforced coals has not been explained, and supporting schemes are determined by engineering analogy and experience. Herein, two large-scale physical models of extremely soft coal gateway sidewalls, reinforced with traditional and improved PPERBMSs, were constructed to probe the performance of pretensioned bolts and the deformation evolution of reinforced coal during roadway driving and panel extraction. Results reveal the bolting effect distribution characteristics of traditional PPERBMS. The mechanism and mode of bolts-mesh-surrounding coal system (BMSCS) instability were analyzed. The control effects of the two supporting schemes were compared, and stability-controlling principles for extremely soft coal roadways were proposed. High bolt pretension force and mesh stiffness are found to be important for improving the bearing capability of BMSCS, especially for reducing the extent of squeezing deformation and severe failure zones in shallow coals. The control method of “high-pretension-force bolts + fine mesh steel–plastic or rhombic screen + high-stiffness welded wire mesh + long bolt/cable for compensating reinforcement at key parts” is proposed to promote the formation of a supporting force interaction zone within surface and shallow coals, reduce the weakly reinforced region causing BMSCS structural instability, and improve the stability and bearing capability of the interaction zone in the bolt anchorage section. These findings are helpful for understanding the bolting effect of PPERBMSs and could provide guidelines for bolting design in soft coal roadways.

Fatigue failure analysis and multi-objective optimisation for the hybrid (bolted/bonded) connection of magnesium–aluminium alloy assembled wheel

This study conducted fatigue failure analysis and multi-objective optimisation for bolted/bonded magnesium–aluminium alloy assembled wheel. Firstly, the dynamic bending fatigue experiment of the bolted assembled wheel was conducted, and then the validity of the simulation model was verified. Secondly, the parameters of the constitutive model and the failure criterion of the structural adhesive were respectively obtained through tensile and shear tests. Finally, the multi-objective optimisation based on grey relational analysis coupled with the hybrid weighting method for bolted/bonded assembled wheel was conducted with optimisation objectives (the fatigue life of spoke and connecting bolts and tensile and shear failure indices of structural adhesive) and design variables (the type of adhesive, thickness of the adhesive layer, pretension force of bolts and the diameter of bolt holes). Optimisation results show that the fatigue life of spoke and the connecting bolts reached 529,000 and 208,000 cycles, respectively. Meanwhile, the adhesive had high reliability.

An initial velocity model study of electromagnetic railgun based on back propagation neural network

The velocity of launch has been the key factor restricting the application of electromagnetic rail. For electromagnetic launch system, the structural parameters change directly or indirectly affect the Launching velocity of the electromagnetic launch system. In order to improve the initial velocity of the electromagnetic railgun. The mathematical model of electromagnetic rail gun launch was set up, the structure parameters of armature and the size of the pretension force between armature and orbital were variables, based on the target function, The equivalent model of rail gun BP neural network is established by using the calculation results of mathematical model, and the model of rail gun BP neural network was optimized by electromagnetic emission test data. The error of rail gun BP neural network model optimized by experimental data is 18.5% lower than that before optimization and 6.5% lower than that of experimental data. The results show that the launch speed of the optimized rail gun BP neural network model is closer to the actual speed.

EFFECT OF MOORING LINE AZIMUTH ANGLE ON THE HYDRODYNAMIC PERFORMANCE OF A MOORED FPSO IN ULTRA-SHALLOW WATER

As the development of floating structure is rapidly growing in demand, the attention has turned towards finding alternative to move in ultra-shallow water locations. One of the most important factors affecting the performance of floating structure is the station keeping system. The station keeping system includes configuration of azimuth angle and pretension forces due to mooring line arrangement. In this study, the hydrodynamic responses of spread moored FPSO systems have been conducted by using numerical simulations. Time domain analysis of the FPSO mooring system was carried out to simulate a fully coupled integrated model using AQWA software to obtain the system responses subjected with different orientation for the azimuth angle of mooring line. The investigations were carried out to determine the impact of angle and pretension forces of each mooring line condition on the dynamic performance of FPSO, as well as to identify the critical mooring lines.

Hysteretic behavior of a new assemble joint under out-of-plane bending: Experimental and numerical studies

ABSTRACT The energy dissipation capacity of joints plays an important role in the seismic behavior of steel structures. In this study, the hysteretic curves, skeleton curves, elastic plastic deformation, and failure modes of bolt-column (BC) joints with different parameters were obtained and studied experimentally and numerically. The results indicated that the BC joints can dissipate energy stably after forming a plastic hinge. Two simplified models of the hysteretic curve of a BC joint were obtained based on whether the hysteretic curve had a slip stage. The finite element model (FEM) of the joint was verified by experimental results. Then, the hysteretic curves, carrying capacity, stiffness, damage features, hysteretic behavior, and energy dissipation behavior of the joints with different bolt pretension forces that were subject to different load combinations were investigated and discussed to provide a theoretical foundation for a secure and reliable seismic design method for BC joints.