Metal Space Frame Research Articles

RESULTS OF THE TECHNICAL INSPECTION OF A MULTI-STORY RESIDENTIAL BUILDING DAMAGED AS A RESULT OF A ROCKET IMPACT

The article presents the results of the examination of the technical condition of part of the construction structures of the building damaged as a result of a missile strike, the determination of the characteristics and classification of their defects and damage, the provision of conclusions and recommendations regarding the correction of the life cycle and further safe and reliable operation of the building. As part of the study, the object of the survey was a monolithic 22-story residential building with a basement (ATP) floor and a complex configuration in plan. The structural scheme of the complex is a monolithic reinforced concrete frame with stiffening cores. The stability and rigidity of the frame is ensured by diaphragms of stiffness in the form of reinforced concrete walls, elevator-stair nodes and rigid nodes connecting pylons and horizontal disks of monolithic reinforced concrete floor slabs. During the examination, visual and instrumental methods of research were performed. Before the field work, measures were taken to collect design and archival information about the research object. Instrumental studies to determine the actual concrete strength of reinforced concrete frame elements and to determine the diameter, protective layer and pitch of the working rods of the reinforcing frames of the load-bearing elements were carried out by non-destructive methods. The calculation model of the spatial scheme of the structure of the frame of the residential building, taking into account the damage, was made in the subsystem (PS) "COMPOSITION" of the software complex (PC) "MONOMAH CAD". The result of the survey is conclusions and recommendations, which indicate the specifics of damage and types of defects, destruction and debris in various structural elements that were discovered during the survey. The general technical condition of the residential building is classified as emergency. As for the recommendations, two options for carrying out repair and restoration works were provided. The first option is to restore the plan-elevation position of the building, the design marks of vertical and horizontal structures and the unloading of overloaded structures, to be performed with the help of an automatic hydraulic complex. The second option is the arrangement of temporary strengthening of emergency structures with the help of a metal space frame, without restoring the planned height position of the residential building.

An Overview of Radomes for Large Ground-Based Antennas

This tutorial provides an overview of RF-transparent protective enclosures or “radomes” for ground-based antennas. In addition to electromagnetic behavior, structural and environmental considerations are highlighted which are important in large antenna installations such as those for satellite communication and deep space radar applications. Different radome types such as metal space frame, inflatable, and sandwich are contrasted with emphasis on the tradeoffs they entail for the antenna system.

Integrated optimum design of metal space frame radomes with variable size members involving electromagnetic and structural analysis

The presence of a metal space frame (MSF) radome inevitably degrades the electromagnetic (EM) performance of the enclosed antenna, while the deformation of the radome can worsen the degradations. In this study, with the introduction of the concept of variable size member, a multidisciplinary optimisation model is proposed to implement the sizing optimisation for the members of MSF radomes to improve simultaneously the EM performance, structural performance, and self-weight simultaneously where EM analysis and structural analysis are involved. Furthermore, a method is presented to boost the efficiency of the EM performance analysis, which makes possible the optimisation of electrically large MSF radomes. A 70 m MSF radome is simulated, and the results indicate that the proposed radome design with variable size members is superior to the conventional radome design with constant size members in terms of all the optimisation objectives, especially the EM performance and self-weight. Several conclusions with guidance values are drawn based on the results.

Normative approaches to structural design calculations in a non-linear framework

This article considers the issue of taking non-linearity into account when performing design calculations for buildings and structures exposed to intense seismic impact. The existing rule codex 14.13330.2014 «SNIP II-7-81* “Construction in seismic areas” regulates the possible behavior beyond the elastic range with by introducing a damage tolerance factor. However, extensive research conducted by the authors of this article and other experts in the seismic resistance theory reveal that the values of this factor for buildings of various structural layouts must be corrected. The paper investigates the behavior of multi-element systems exposed to seismic impact, the structural layouts of them being as follows: wall-supported slab systems, reinforced concrete rigid frame buildings and buildings with a metal space frame. Calculations were made which describe the behavior of the buildings exposed to an intense earthquake modeled in the form of accelerograms standardized as 8 points on the MSK 64 scale. The calculations were performed using the LS-DYNA software package which makes use of the direct dynamic method and provides means for making all the calculations in the time domain and for taking the physical, geometric and structural non-linearity into account. The results obtained indicate that wall-supported slab buildings and rigid frame RC buildings collapse due to emerging and developing plastic deformations, while metal frame buildings lose their stability before their bearing capability is exhausted. The research carried out by the authors enabled them to pinpoint the reason for the discrepancy between the obtained values of the damage tolerance factor and the values stipulated by the regulation, as well as to draw a conclusion that these values should be refined.

A Novel Compensation Strategy for the Radiation Characteristics of Large Dielectric Radomes Based on Phase Modification

To mitigate the degradation of radiation characteristics for large ground-reflector antennas due to dielectric radomes, a simple compensation strategy based on phase modification has been proposed. A modification of the phase distribution in the original aperture of an enclosed reflector antenna via moving the feed or subreflector along axial direction opportunely could compensate the phase shift caused by dielectric radome, minimize the phase difference in transmission aperture, and reduce the distortion of the antenna’s far-field pattern. The movement of the subreflector could be calculated by a formula, which has been provided in this work based on geometrical optics (GO). Good compensated results are obtained in a 9.14-m one-piece dielectric sandwich radome. The proposed compensation strategy could also be applied to metal-space frame radome; a 20-m radome is presented to verify the results .

EM Analysis of Deformed Metal Space Frame Radome

The presence of radome inevitably degrades the electromagnetic (EM) performance of the enclosed antenna while the deformation of the radome may make the degradations even worse. This letter studies the effect of structural deformation of a metal space frame (MSF) radome on EM performance. Far field of the antenna-radome system is obtained by adding the far field transmitted through skin to the scattered field of elements, both fields varying when deformation occurs. A 20-m MSF radome is employed for simulation, whose structural deformation under wind and self-weight is analyzed using finite element method (FEM). Several significative characteristics about the effect of deformation on EM performance are pointed out.

A Fast Hybrid Method for EM Analysis of Electrically Large Metal Space Frame Radomes

This letter proposes a fast hybrid method that combines the physical optics (PO) method and aperture integration-surface integration (AI-SI) method for electromagnetic (EM) radiation analysis of electrically large metal space fame radomes. First, the magnetic or/and electric fields on the surface of the metal space frame and inner surface of the dielectric radome are calculated by the Stratton-Chu equation. Second, the scattering fields from the metal space frame are calculated by the PO method, and the transmitted fields on the outer surface of the dielectric radome are determined by the transmission coefficient calculated by the network theory. To accelerate the implementation of the procedure, an efficient parallelization scheme is adopted, and the Lagrange interpolation is used to calculate the transmission coefficients. Numerical results demonstrate that there is a good agreement between the proposed method and the numerical method, and the computation can be accelerated by 3.9 times with interpolation.

Design of a tuned sandwich chassis for competition go-kart

In this paper, the design procedure for a new chassis concept for competition go-karts is presented. Such a vehicle requires an unconventional design procedure for the frame due to the lack of suspensions and the need to sustain load transfer from the ground with the help of the tyres' radial stiffness. A sandwich panel built with a lightweight aluminium honeycomb core and carbon skins is proposed. An optimal sandwich stacking has been found imposing the same torsional stiffness and the same margin of strength typical of a traditional metal space frame. The effects on global vehicle performances have been evaluated by means of a simulation programme based on compliance data calculated by means of finite elements analysis.

A comparison of radome‐ and astrodome‐enclosed large radio telescopes at millimeter wavelengths: The Large Millimeter Telescope

We present a systematic comparison of the main figures of merit for an open‐air radio telescope and two different types of enclosed antennas: (1) an ordinary radome, with a metal space frame providing the required mechanical rigidity and a dielectric membrane, and (2) an “astrodome,” i.e., a corotating rigid dome with a large window covered by a tensile membrane structure. The analysis is limited to submillimeter and millimeter wavelengths and large (≳30 m) antenna/enclosure systems, where the window tensile structure is very unlikely to be removable and is supported by either a metal space frame or cable networks. As compared with previous studies of this type, here we concentrate on the specific effects that these large metallic support structures have on sensitive astronomical observations. In particular, we critically discuss how the wind‐induced random motions of the metal space frame can limit the sensitivity of continuum observations, as a result of fluctuating shadowing and spillover effects combined with various beam‐chopping techniques. Using the Large Millimeter Telescope as a benchmark, we provide baselines for future projects where a similar comparison is needed.

Corrections for the effects of a radome on antenna surface measurements made by microwave holography

Measurements of the surface deviations of a parabolic antenna by microwave holography have been corrected for the effects of an enclosing radome. The largest correction, which is due to diffraction from the metal space frame, is made by using a model computed from the radome structure. This model accounts for the changing diffraction as the antenna is scanned during the interferometric mapping of the complex beam pattern. Correction for reflections from the radome panels is made by simultaneously measuring the beam pattern at multiple frequencies to provide delay discrimination to reject antenna sidelobes generated by multiple reflections which arrive with delays different from that of the main beam.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Radome crosspolarisation on Intelsat standard ‘A’ communication satellite antennas

The reduction in size of Intelsat standard 'A' satellite communication antennas from 30.5 m to 15 m in diameter has necessitated the computation of depolarisation effects when the smaller antennas employ metal and dielectric space frame radomes for hardening and protection. Using the standard 15 m antennas enclosed by appropriately scaled-down metal and dielectric space frame radomes, the crosspolar discrimination (XPD) and the boresight shift (BS) have been computed close to antenna axis at 4 and 6 GHz. Comparison with the larger 30.5 m antennas enclosed by 45 m radomes have been made. It is reported that within 0.1 degrees of antenna boresight, the XPD introduced by the radomes does not exceed 33.0 dB as the worst case at 4 GHz. In particular, the Intelsat Specification of 30.7 dB for the XPD within the antenna's tracking beamwidth in clear weather conditions for frequency re-use satellite communication systems is satisfied. The BS is negligibly low. >

Depolarization properties of metal space frame radomes for use in satellite communication systems

AbstractRadomes have traditionally only been used in military satellite systems. However, higher availability civil applications are demanding their consideration in the higher frequency bands and for dualpolarization frequency re‐use systems. This paper investigates the depolarization performance of metal space frame radomes and presents results of XPD for radome covered antennas in the 4/6 and 11/14 GHz bands and for antennas of 30, 11, 5 and 3 m diameters. It is demonstrated that current polarization specifications adopted in the INTELSAT system should be able to be met by radome covered earth‐stations using conventional antennas.

Electrical design of metal space frame radomes

Formulation and results are presented of a digital computer program, which analyzes the electrical effects of a metal space frame radome, using a single scattering approximation. Under the assumption of uniform or nearly uniform distribution of space frame elements over the surface of the radome, simple approximate formulas are presented for the same effects. Computed values agree well with measured data. The effects of shaping the element cross section, varying the radome geometry, and varying the frequency have been systematically studied in certain cases. The results are presented here as applications of the theory. The effects of multiple scattering have been measured and also analyzed by an approximate theory so that they are fairly well understood. Formulas for the effects of radome tolerances on electrical performance are given.