Support Truss Research Articles

Deployable support truss for parabolic cylindrical antennas with shape reconfiguration

The increasing scarcity of orbit resources has directed the focus onto the versatility of space antennas. Through shape reconfiguration, large antennas can achieve enhanced task compliance. In this paper, a two-degree-of-freedom (DOF) deployable support truss with shape reconfiguration is designed for parabolic cylindrical antennas. A design strategy is presented for the support truss, in which the synchronous deployment is realized first through the expansion of basic deployable units. The branch chains are then supplemented to realize the controllable reconfiguration of the entire support truss. Moreover, the mobility and kinematic analyses of the basic modules on the support truss are conducted to parametrically analyze the DOF space and realize the expected reconfiguration. The unit number and structure parameters of the support truss can influence the mimicking preciseness. To fulfill the mimicking error requirement with a more concise mechanism, a parameter optimization method based on the genetic algorithm is proposed to achieve the minimum number of the required deployable units. Simulation of the deployment and reconfiguration of the support truss as well as the verification test conducted on the principle prototype demonstrate the feasibility of the mechanism design. This paper may provide candidates for support trusses of large reconfigurable antennas with enhanced task flexibility and efficiency, and serve as references for the design of deployable mechanisms with the reconfiguration function.

Modeling cable-pulley deployment systems of transformable rod structures

The aim of this article is to develop a simplified method for modeling cable-pulley deployment systems of rod structures based on the calculation of cable tensions and nodal driving forces with account for friction and other features of the system. Methods of theoretical mechanics, multibody dynamics, numerical integration of differential equations, and computer modeling were used during the research. The task of developing a simplified approach to modeling cable-pulley deployment systems for rod structures is considered. It is proposed to determine nodal driving forces by calculating cable tensions with account for friction and other features of the cable-pulley system, cables, and pulleys. To develop a model of cable-pulley deployment system, a rod system was chosen as the research object, which represents two sections of the transformable support truss of a reflector. Each section consists of diagonal and horizontal rods with tubular cross-sections. The sections are interconnected by hinge units. The structure is deployed using an upper and a lower cable, which pass through pulleys and are tensioned by an electric motor. The deploying forces are implemented by transferring the cable tension forces to the structure due to static friction and pressure between the cables and the pulleys. For further implementation of the model in an open-source software package, some simplifications were made due to the complexity of the design. A simplified method was developed for nodal driving force calculation in simulating rod structure deployment with the help of cables. The tensions, elongations, slacks, and neutral length of the cables and the forces transmitted from the cables to the pulleys were calculated as a function of time. Using them, the deployment of a rod structure was simulated for a constant cable speed. The results make it possible to control the rod system deployment time and rate depending on the characteristics and tension forces of the cables. The proposed approach is implemented using open-source software, and it provides modeling flexibility and reduces the model development and run time.

Assembly Device for Supermodules of Silicon Tracking System of the BM@N Experiment

The silicon tracking system of the BM@N experiment consists of four stations based on double-sided microstrip silicon sensors. The sensors make it possible to obtain a spatial resolution for tracks of secondary charged particles up to 17 μm. Two ASIC boards, the input channels of which are connected to the strips with ultralight (0.23% X0) aluminum flex cables, are used to readout and process signals from both sides of the sensor. Such an assembly is called a module. Silicon sensors are mounted on lightweight carbon-fiber support trusses in a way that the dead zones at the edges are overlapped due to the tiled layout. The frontend electronics are housed in metal containers with a heat sink system located at the rare ends of the carbon-fiber support truss. A set of modules attached to the carbon-fiber support truss with two containers with readout electronics at the ends is called a supermodule. The accuracy of the sensor positioning in the station plane plays a crucial role in limiting the degrees of freedom of the parameters determined by the software during the final alignment of the tracking system elements. A special device that allows mounting sensors on a carbon fiber truss with an accuracy of up to 15 µm on a 1200 mm base is developed to assemble supermodules. The results of testing the device are given.

An Integrated Structure Analysis Method of Active Surface Antenna by Using the Simplified Actuator

The main surface of a large reflector antenna is composed of thousands of panels, which are inevitably deformed under natural load, leading to a great deterioration of electrical performance of the antenna. The active surface technique is an effective method to compensate antenna deformation error and has been widely used. The actuator is a complex component, it has not been established in the antenna structure analysis model, which limits the theoretical analysis ability of the active surface technology. To solve this problem, an integrated structure analysis method of active surface antenna by using the simplified actuator is proposed. First, according to the supporting characteristics and adjusting function of the actuator, the complex actuator is simplified a simple structure of support beams, support truss and adjustment beam. Second, the finite element model of the active surface antenna including the simplified actuator is established. Then, the relationship between the adjustment value (load) of adjustment beam and the deformation of the antenna structure is deduced, and the integrated analysis method for realizing the active adjustment of panels is established. Finally, the model and adjustment analysis method of the active surface antenna in this paper is applied to an 8 m antenna, and satisfactory structural analysis results are obtained, which shows the effectiveness and universality of the method, and provides a reference for the modeling and adjustment analysis of the active surface antenna.

Vibration and Noise Analysis and Experimental Study of Rail Conveyor

The rail conveyor is a new type of energy-saving system for the long-distance transportation of bulk materials. Operating noise is an urgent problem that the current model faces. It will cause noise pollution and affect the health of workers. In this paper, the factors causing vibration and noise are analyzed by modeling the wheel-rail system and the supporting truss structure. Based on the built test platform, the system vibration of the vertical steering wheel, the track support truss, and the track connection were measured, and the vibration characteristics at different positions were analyzed. Based on the established noise and vibration model, the distribution and occurrence rules of system noise under different operating speeds and fastener stiffness conditions were obtained. The experimental results show that the vibration amplitude of the frame near the head of the conveyor is the largest. The amplitude under the condition of 2 m/s running speed at the same position is 4 times that under the condition of 1 m/s. At different welds of the track, the width and depth of the rail gap have a great influence on the vibration impact, which is mainly due to the impact of the uneven impedance at the track gap, and the greater the running speed, the more obvious the vibration impact. The simulation results show the trend of noise generation, the speed of the trolley, and the stiffness of the track fasteners have a positive effect on the generation of noise in the low-frequency region. The research results of this paper will play an important role in the noise and vibration analysis of rail conveyors and help to optimize the structure design of the track transmission system.

Novel closed-loop deployable mechanisms and integrated support trusses for planar antennas of synthetic aperture radar

Synthetic aperture radar (SAR) is indispensable electronic equipment in modern life, which has been widely used in the field of geological exploration, disaster monitoring, and environmental observation. With the increasing complexity of earth observation tasks, a higher receiving resolution of SAR is required, which needs the area of the radar antenna to be increased. However, there is a contradiction between the small launch space and the large working area. The deployable antenna mechanism is expected to meet the challenge. In this paper, a graphical type synthesis method is proposed to carry out the mechanism design of deployable mechanisms. According to the structural analysis and design requirements, the articulated form is adopted to carry sub-planes of planar antennas and provide one kinematic chain of the deployable mechanism. Then, different designed kinematic chains are synthesized to construct novel closed-loop deployable mechanisms. Mobility verification of a selected closed-loop deployable mechanism is carried out by screw theory to demonstrate the validity of type synthesis results. By sharing the provided kinematic chain and symmetrical design of two deployable mechanisms, deployable units with the driving unit are proposed as basic modules of support trusses for planar antennas. As a result, three novel deployable support trusses integrated by a series of deployable units and assembly mechanisms are proposed as the platforms for planar antennas. The deployable mechanisms and integrated support trusses proposed in this paper provide candidates for planar antennas of SAR.

Calculation researches for the formation of high-level and long-life medium-level radioactive waste of activation origin for the WWER-1200 reactor of Belarusian NPP

The study of the issue of constructing a disposal facility for high-activity radioactive waste in the Republic of Belarus is associated with an assessment of the volume of radioactive waste to be deeply disposed of, generated as a result of the activation of structural materials of the VVER-1200 reactor of the Belarusian NPP. This paper presents the results of computational studies of the formation of solid high-level radioactive waste (HLW) and long-lived intermediate level radioactive waste (ILW-LL) during neutron activation of materials adjacent to the core of the VVER-1200 reactor structures of the Belarusian NPP. The assessment of the volumes of HLW and ILW-LL of activation origin, formed over 60 years of operation of the VVER-1200 reactor, was carried out on the basis of computational studies of the induced activity of structural and shielding materials using reactor and Monte Carlo program codes (SERPENT 2, TVS-M, DYN3D, MCU- PD). As a result of the research, it was found that when neutrons activate materials of the sections of the VVER-1200 reactor structures of the Belarusian NPP adjacent to the core (in the steel structures of the baffle, shaft, surfacing, part of the reactor vessel, structures of the protective tube unit (PTU), the space under the core, in heat insulation materials, rods of absorbing elements (Dy2TiO5)) are formed by HLW and ILW-LL with a total weight of 272,5 tons and a volume of 43 m3 . Calculated studies of the activation of dry protection materials, building concrete, support truss and biological protection showed that these structural elements will not belong to either HLW or ILW-LL.

Analysis of Heat Transfer Characteristics of a Heat Exchanger Based on a Lattice Filling

In response to the heat load requirements of the high-thrust liquid rocket engine, a light-weight lattice structure is used to fill traditional a heat exchanger. A parameterized model library of the lattice structure is established, and the relative density of the lattice structure is adjusted by changing the unit cell structure parameters to obtain different filling structures. A comprehensive comparison of heat exchangers with different filling structures performed in terms of weight, heat transfer efficiency, and turbulence intensity. Using the finite difference method, the numerical calculation of the non-steady heat–fluid–solid coupling conjugate heat transfer of the eight-lattice structure is performed, and the dynamic heat transfer process between the lattice structure and liquid oxygen is simulated using the VOF model and the SST k-ω model. The results show that the pressure of the fluid in the heat exchanger increases with increasing relative density, leading to a high outlet temperature and greatly increasing the outlet velocity. The support trusses close to the wall obviously hinder the flow of liquid oxygen, resulting in a sudden change in the flow rate behind the support trusses, driving the high-temperature fluid at the bottom to move upwards. The direction of the support trusses and the unit cell porosity have a greater impact on the liquid oxygen flow rate, which in turn affects the flow and heat transfer performance of the heat exchanger. In consideration of the heat load requirements of the heat exchanger, star-type lattices are used to fill the heat exchanger. When the flow is fully developed, the volume ratio of the heated fluid is 85.60%, and the outlet temperature is 390 K, which meets the design requirements.

Force density sensitivity form-finding design method for cable-mesh reflector antennas considering interactive effects between cable network and supporting truss

Form-finding design is critical in determining whether a cable-mesh reflector antenna can meet electrical performance requirements. However, the current methods rarely consider the interactive effects between the cable network and the supporting truss in the form-finding process, which requires more iteration steps for good design results. This study presents a force density sensitivity form-finding design method for cable-mesh reflector antennas based on systematic equilibrium equations. The sensitivity matrix of the support truss vertex and the cable network free node is derived with respect to force density, and the form-finding process of the reflector antenna is transformed into a sequential quadratic programming problem that can be easily solved. The antenna meets the accuracy requirements, and has a more uniform distribution of internal cable net tension and a smaller truss deformation as a result of constraining the vertex deformation of the supporting truss and cable tension. For practical engineering problems, more accurate design results can be obtained quickly. The effectiveness of the proposed method is verified through numerical examples.

Distributed vibration control for large-scale flexible space structure improved by fuzzy logic system

To deal with the problem of vibration control for large-scale flexible space structure, an detailed distributed vibration control scheme with the switch control method and PD control method improved by fuzzy logic system is proposed in this paper. Firstly, the dynamic model, the actuator model and the multi-subsystem model of a large-scale flexible space structure are established. Then, a distributed control scheme is designed, which installs multiple groups of piezoelectric actuators on the support truss. The traditional methods and the improved method based on fuzzy logic system are discussed. Through ADAMS-MATLAB co-simulation platform, the effectiveness of the distributed control to suppress the vibration of large-scale flexible space structure in both Y and Z directions is verified. The simulation results show that the control precision by the improved method based on fuzzy logic system is better than traditional methods, and the control spillover is not easy to be caused.

Fatigue damage analysis of a riveted steel overhead crane support truss

A method is proposed to evaluate the residual life of existing steel structures in terms of fatigue damage. The proposed method is demonstrated on the assessment of selected elements in a nearly 100-year old exterior riveted crane support truss. The Monte Carlo method is used to generate a time-dependent load based on the operation of the overhead crane, and detailed numerical modelling based on rainflow counting and the Palmgren-Miner rule to assess their fatigue resistance and estimate their residual life is evaluated and discussed. This study provides a novel approach to the reliability assessment of riveted joints stressed by cyclic loading and stochastic modelling of the load history of existing structures.

Simulating the optical performance of a small-sized telescope with secondary optics for the Cherenkov Telescope Array

The Gamma-ray Cherenkov Telescope (GCT) is a small-sized telescope (SST) that represents one of three novel designs that are based on Schwarzschild–Couder optics and are proposed for use within the Cherenkov Telescope Array (CTA). The GAmma-ray Telescope Elements (GATE) program has led an effort to build a prototype of the GCT at the Paris Observatory in Meudon, France. The mechanical structure of the prototype, known as the SST-GATE prototype telescope, is now complete along with the successful installation of the camera. We present the results of extensive simulation work to determine the optical performance of the SST-GATE prototype telescope. Using the ROBAST software and assuming an ideal optical system, we find the radius of the encircled point spread function (θ80) of the SST-GATE to be ∼1.3 arcmin (∼0.02°) for an on-axis (θfield=0∘) observation and ∼3.6 arcmin (∼0.06°) for an observation at the edge of the field of view (θfield=4.4∘). In addition, this research highlights the shadowing that results from the stopping of light rays by various telescope components such as the support masts and trusses. It is shown that for on-axis observations the effective collection area decreases by approximately 1 m2 as a result of shadowing components other than the secondary mirror. This is a similar loss (∼11%) to that seen with the current generation of conventional Davies–Cotton (DC) Cherenkov telescopes. An extensive random tolerance analysis was also performed and it was found that certain parameters, especially the secondary mirror z-position and the tip and tilt rotations of the mirrors, are critical in order to contain θ80 within the pixel limit radius for all field angles. In addition, we have studied the impact upon the optical performance of introducing a hole in the center of the secondary mirror for use with pointing and alignment instruments. We find that a small circular area (radius < 150 mm) at the center of the secondary mirror can be used for instrumentation without any significant impact upon optical performance. Finally, we studied the impact of reducing the size of the primary mirror for the prototype telescope and found that this comes at the cost of poorer image quality and light collection efficiency for all field angles, but at a significant cost saving for a one-off prototype.

High-accuracy numerical model of the Southern African large telescope mirror support truss

In order to calibrate the primary mirror of the Southern African large telescope, a high-accuracy numerical model of the existing mirror support truss and its actual, current behavior is required. In this investigation, structural optimization techniques are used to tune a numerical model so that it accurately matches the measured output of a structure under a given load or combination of loads. A methodology for obtaining an accurate numerical model of such a structure by first investigating the behavior of the different strut types before attempting to model the structure as a whole is presented. This method yielded vast improvements in the numerical accuracy of a smaller, simpler laboratory structure’s numerical model.

Driving Characteristic Analysis of a Planar Deployable Support Truss Structure for Space Antenna

As the development of space structures is increasing fast, analysis on the characteristics of those deployable structures deserve to be paid enough attention to ensure a reliable deployment on orbit. For a deployable truss structure, more than one position can be chosen as the driving positions, especially when the structure has not only 1 degree of freedom (DOF), an available choice of the driving positions shows significant importance on the performance of the space deployable structure. This paper mainly deals with a planar deployable support truss structure for space antenna by means of the closed loop equations and the Kane equation to discuss the deployment characteristics by comparison of the driving torque needed over time. A full comparison of all the possible examples of deployment analysis results under different driving modes is presented. The results show the importance of the choice of driving movements and the design of parameters and also provide a useful reference to other related truss structures.

Field testing and analysis of aluminum highway sign trusses

Four representative Illinois Department of Transportation (IDOT) highway sign support trusses were evaluated analytically and in the field to assess their design load capacity and fatigue resistance when subjected to wind loading. The three overhead span bridge and one cantilever welded aluminum truss structures were instrumented for static and dynamic field testing with strain gages and accelerometers to collect structural behavior data when subjected to manual excitation, wind loading, and truck gust excitation. Companion analytical models were developed and calibrated to represent the structures in the field, after which these were then used to assess the response of the trusses at full design wind loads. Current IDOT and AASHTO highway sign support structure design loading and resistance approaches with respect to both strength and fatigue have been critically assessed in light of the analyses and field test results, with recommendations made for improving future designs.

Experimental validation of a damage detection approach on a full-scale highway sign support truss

Highway sign support structures enhance traffic safety by allowing messages to be delivered to motorists related to directions and warning of hazards ahead, and facilitating the monitoring of traffic speed and flow. These structures are exposed to adverse environmental conditions while in service. Strong wind and vibration accelerate their deterioration. Typical damage to this type of structure includes local fatigue fractures and partial loosening of bolted connections. The occurrence of these types of damage can lead to a failure in large portions of the structure, jeopardizing the safety of passing traffic. Therefore, it is important to have effective damage detection approaches to ensure the integrity of these structures. In this study, an extension of the Angle-between-String-and-Horizon (ASH) flexibility-based approach [32] is applied to locate damage in sign support truss structures at bay level. Ambient excitations (e.g. wind) can be considered as a significant source of vibration in these structures. Considering that ambient excitation is immeasurable, a pseudo ASH flexibility matrix constructed from output-only derived operational deflection shapes is proposed. A damage detection method based on the use of pseudo flexibility matrices is proposed to address several of the challenges posed in real-world applications. Tests are conducted on a 17.5-m long full-scale sign support truss structure to validate the effectiveness of the proposed method. Damage cases associated with loosened bolts and weld failures are considered. These cases are realistic for this type of structure. The results successfully demonstrate the efficacy of the proposed method to locate the two common forms of damage on sign support truss structures instrumented with a few accelerometers.

Investigation of the Dayton, Ohio, IR 75 Sign Truss Failure of September 11, 2006

On September 11, 2006, “unusual” deflections of an overhead bridge-mounted sign support truss along IR 75 in Dayton, Ohio were reported. Investigation by Ohio DOT road crews revealed the complete fracture of two truss members near one of the truss supports. While total collapse did not occur, such an event could have catastrophic consequences along a major arterial roadway like IR 75. This concern, along with the fact that a similar failure occurred near Cleveland, Ohio in 2004, prompted an investigation that is the subject of this manuscript. Results of the investigation are based upon a combination of in situ field monitoring of traffic-induced bridge vibrations at the location of the failed sign support truss, finite-element simulation of the expected dynamic response of the original truss in such an environment, the length of service of the truss at the time of its failure, the volume of truck traffic on the bridge in question during that time of service, and metallurgical examination of the failed co...

Fatigue Life Prediction and Variability of New and Existing Welded CHS Y-Joints

An experimental program was undertaken to quantify fatigue life variability of the ET fatigue detail category for welded circular hollow shape (CHS) connections commonly found in sign support structures. The program included fatigue testing of existing and fabricated Y-joint specimens composed of CHS, detailed material characterization, and comparison of experimentally determined fatigue lives with a variety of analytical methodologies. The results of the research effort serve as the foundation for quantifying the expected service life for overhead sign support structures in relation to the fatigue limit state of the welded connections. The data has been used as the basis for a procedure for predicting the service lives of full-span overhead sign support trusses.

Helix Pedestrian Bridge

Amgen Incorporated, one of the world's largest biotechnology firms, recently developed a new research center on the Elliot Bay waterfront of Seattle, Washington. As part of the research center, a pedestrian bridge was built to connect the campus with a major transportation corridor. The owner's goal for the new pedestrian bridge was to create a signature gateway to Amgen's campus. The pedestrian bridge is a three-arch structure that depicts a three-dimensional helix. The overall shape of the bridge both reflects the helical DNA that connects all life and references the vital research under way at Amgen. The arches create the outline of the basic DNA helix, and the deck support and roof trusses complete the remaining components of the helix. The abstract double helix provided many design and construction challenges. The slim profile, large enclosed areas, and suspended deck meant wind and pedestrian vibration would be critical design considerations. The unique shape made it difficult to apply the standard building or bridge design codes. The contractor was faced with erecting this twisting structure over active railroad tracks while meeting tight geometric specifications. The bridge stands today as a testimony to the owner's vision, teamwork, innovation in bridge design, and creative construction techniques. The bridge combines both form and function to show how an ordinary pedestrian bridge can become an extraordinary statement while serving its intended function. The project has won broad community support in the few months that it has been open.

Reliability Analysis of Space Exploration Truss Support Structures

Anadaptivereliability estimationtechniqueforthree-dimensional trussesused inspaceexploration applications is proposed. Both component-level and system-level reliability issues are addressed. For individual member-level performance criteria, efe cient analytical methods are implemented for reliability estimation. Multiple potential failure paths are considered for system-level performance, and a hybrid adaptive sampling technique is proposed by combining the best features of analytical and sampling methods. A signie cant failure path is enumerated using analytical reliability estimation and branch and bound search. An adaptive importance sampling method is used to identify other signie cant failure paths. The proposed methodology is illustrated for application to a simplie ed solar array support truss, using a commercial e nite element code.