Rack Structure Research Articles

Improving the Railway Stability in the Joint Zone for Modern Operating Conditions

Increasing axial loads require the best solutions for maintenance of the railway rack structure. The study is devoted to improving the railway stability in the joint zone for modern operating conditions. The relevance of the issue is substantiated according to analysis of domestic and foreign practices. The analysis shows that using under-sleeper pads reduce vibrations transferred from concrete sleepers to crashed stone, including the joint area. The possibility of solving the issue by using of under-sleeper pads for straightening the track in the joint zone is considered. The paper contains the results of studies conducted in the Experimental ring of JSC VNIIZhT in order to select durable materials for ensuring long-term track stability. In order to assess the implementation effectiveness of under-sleeper pads and to ensure the track stability in the joint zone, the accumulation of track settlements for pads with different stiffness was evaluated, as well as the accelerations in the vertical plane of the sleepers.

Accurate shading factor and mismatch loss analysis of bifacial HSAT systems through ray-tracing modeling

We have developed models using Rhino (3D modeler) and DIVA (Ray-tracing modeler), allowing system-level raytracing simulations which include nearby shade obstructions from the photovoltaic racking structures. The ray-tracing simulated irradiance profiles are coupled with cell-level IV curve modeling to provide insight into the shading factor and mismatch loss for different racking configurations. The paper focuses on reporting results for horizontal single axis tracker (HSAT) and fixed racking bifacial system, included common module portrait and landscape configurations, as well as demonstrating the distance effect of the module above the torque tube, providing important guidance for further optimizing such mounting systems and accurate parameters required in PVsyst modeling.

Finite-dimensional pointed Hopf algebras over finite simple groups of Lie type VI. Suzuki and Ree groups

We analyse the rack structure of conjugacy classes in simple Suzuki and Ree groups and determine which classes are kthulhu. Combining this results with abelian rack techniques, we show that the only finite-dimensional complex pointed Hopf algebras over the simple Suzuki and Ree groups are their group algebras.

Topology Optimization of Frame of the Rack System

Integration of the Electronics modules in the rack system has been very challenging and critical in nature. The functionality of the electronics module is of prime importance for the operation on any system or subsystem. In many cases where these electronics systems housed in a rack system which in turn mounted in aircraft fuselage make functioning of the system more severe. This paper deals with design optimization of frame of rack structure in line with increasing demand of more robust and light structure with features of high stiffness and structural integrity. Aerospace industries employ topology , size and shape optimization technique and have reported significant structural performance gains as a result ,This report deals with the topology optimization of frame of rack structure has been performed using OptiStruct software. The main objective is to find the optimal topology of frame of the rack. The rack structure has undergone the first level of optimization, in other word it is called finite element analysis with inertia loading condition which presents the stress contour with varying stress level, the stress contour highlight the maximum and minimum stress level in the structure which gives the first level of information about the material requirement within the structure. Topology optimization being the part of the structural optimization is the extended domain of the structural analysis where optimum placement of the material in the design space is the prime focus. The design space is a geometrical space where material alteration is effected to achieve the design objective. Topology optimization problems utilize the firmest mathematical basis, to account for improved weight-to-stiffness ratio and perceived aesthetic appeal of specific structural forms, enabling the Solid Isotropic Material with Penalization (SIMP) technique. Structural topology optimization is a technique for finding the optimum number, location and shape of opening with in the given design space of the rack structure to the series of loads and the boundary conditions. A range of topology of rack frame is obtained by setting varying the target volume fraction and an optimum topology of the frame is selected by satisfying stress to weight ratio requirement and manufacturing constraint.

Assessment of the Seismic Behavior of Selective Storage Racks Subjected to Chilean Earthquakes

A seismic performance evaluation of selective storage racks subjected to Chilean Earthquakes was conducted using nonlinear pushover and nonlinear dynamic time-history analyses. Nine seismic records with two horizontal components and magnitude Mw > 7.7 were applied to numerical models of prototype rack structures. The prototype racks were designed considering two types of soil and two aspect ratios. The inelastic behavior of beam connections was included in the models. The results showed a predominantly elastic behavior, mainly in the cross-aisle direction, in comparison to the down-aisle direction. The inelastic action was concentrated in pallet beams and up-rigths. Higher values of base shear were reached, due to elevated rigidity in rack configurations, and an acceptable performance was obtained. A response reduction factor was reported in both directions, reaching values larger than the limit imposed by the Chilean standard. However, values below this limit were obtained in the cross-aisle direction, in some cases. Finally, in all cases, the calculated response modification factor is highly influenced by the overstrength obtained from seismic design.

Wood retention at inclined racks: Effects on flow and local bedload processes

AbstractLarge wood (LW) transport can increase greatly during floods, leading to accumulations at river infrastructures. To mitigate the potential flood hazard, racks are a common method to retain LW upstream of endangered settlements or infrastructures. The majority of LW retention racks consist of vertical bars and, therefore, disrupt bedload transport. It can be hypothesized that inclined racks reduce backwater rise and local scour, as wood will block the upper part of the rack, thereby increasing the open flow cross‐section below the accumulation. Flume experiments were conducted under clear water conditions to analyse backwater rise and local scour as a function of (1) rack inclination, (2) hydraulic inflow condition, (3) uniform bed material, and (4) LW volume. In addition, the first experiments were performed under live bed scour conditions to study the effect of bedload transport on local scour and backwater rise. Based on the experiments, backwater rise and local scour decrease with decreasing rack angle to the horizontal. LW predominantly accumulated at the upper part of the rack, leading to an open flow cross‐section below the accumulation. The effect of rack angle was included in existing design equations for backwater rise and local scour depth. In addition, the first experiments with bedload transport resulted in smaller backwater rise and local scour depth. This study contributes to an enhanced process understanding of wood retention and bedload transport at rack structures and an improved design of LW retention racks. © 2020 John Wiley & Sons, Ltd.

Rational Hybrid Analytical Model for Steel Pipe Rack Quantification in Oil & Gas Industries

The objective of this work is to develop an analytical model to overcome the shortfalls in current engineering practices that are being used to estimate the pipe rack steel quantities during the pre-bid engineering phase in Oil & Gas industries. The research methodology consists of performing data analysis of past projects and devising a new system by developing suitable structure formulation techniques, loading system creation, structural stability analysis and LRFD design calculations, along with steel quantification procedures, which are completed in a single run. Then this rational hybrid analytical model is applied to examine a real-time project pipe rack structure module. As research findings, the results of the analytical model are compared with the outcome of both the conventional methods as well as the bench mark detailed engineering calculations. It is found that the quantity obtained using the new method is extremely close to the detailed engineering quantity with the least time consuming. Hence, this novel analytical model has proved to be a boon to structural engineers working in Oil and Gas industries since the crux of pre-bid engineering is to process voluminous data and calculate the quantities more precisely within a shorter time frame to be a successful bidder.

Analytic linear Lie rack structures on Leibniz algebras

A linear Lie rack structure on a finite dimensional vector space V is a Lie rack operation pointed at the origin and such that for any x, the left translation is linear. A linear Lie rack operation is called analytic if for any where is an n + 1-multilinear map symmetric in the n first arguments. In this case, is exactly the left Leibniz product associated to Any left Leibniz algebra has a canonical analytic linear Lie rack structure given by where In this paper, we show that a sequence of n + 1-multilinear maps on a vector space V defines an analytic linear Lie rack structure if and only if is a left Leibniz bracket, the are invariant for and satisfy a sequence of multilinear equations. Some of these equations have a cohomological interpretation and can be solved when the zero and the 1-cohomology of the left Leibniz algebra are trivial. On the other hand, given a left Leibniz algebra we show that there is a large class of (analytic) linear Lie rack structures on which can be built from the canonical one and invariant multilinear symmetric maps on A left Leibniz algebra on which all the analytic linear Lie rack structures are build in this way will be called rigid. We use our characterizations of analytic linear Lie rack structures to show that and are rigid. We conjecture that any simple Lie algebra is rigid as a left Leibniz algebra.

Urban River Water Level Increase Through Plastic Waste Accumulation at a Rack Structure

Plastic debris in water systems is a major challenge for our ecosystem, because it is extremely persistent in the environment. Apart from the importance of reducing the amount of plastic entering the ocean, clearing the rivers from debris is important for societal concerns, such as flood risks. Plastic waste accumulation at trash racks leads to a rise in upstream water level and may increase urban flood risk. Until now, most studies of riverine debris accumulation predominantly focused on organic accumulations at trash racks and bridge piers. In this study, flume experiments were used to study the behavior of plastic and mixed debris accumulations. One of the key findings from this study is that plastic debris causes a faster blockage than organic matter, as the plastic blockage contains fewer voids and therefore has a higher blockage density. In addition to the flume experiments, field measurements were performed in the Cikapundung River (Indonesia). This river is one of the tributaries of the Citarum River, which is considered one of the world’s most heavily polluted rivers. Combining the results of the flume experiments and field measurements demonstrated that a backwater rise of 1 m/h is plausible for a blocked trash rack in the Cikapundung River, illustrating the additional flood risk caused by plastic pollution. Our results emphasize the need for further quantifying riverine (plastic) debris and investigating its relation to changes in the water system behavior, including its influence on urban flood risk.

Fatigue behaviour of bolted joints for rack structures

Racking systems applied in logistics warehouses are built with thin steel sections that are joined by bolted connections. In fully automatic systems, these structures are loaded 7/7 days and 24/24 hours raising fatigue issues due to the cyclic nature of the resulting stresses. According to the current industrial practice, those bolted joints are tight with no torque control, leading to the concept of snug tight bolts, which behaves similarly to non-preloaded bolted joints. Eurocode 3 has no reference about fatigue rules of bolted connections between thin-walled cold formed steels. This paper aims at analyzing the fatigue behaviour of bolted (snug tight vs. preloaded) joints in order to provide fatigue design rules for possible update of Eurocode 3 existing rules.A significant fatigue testing program was performed to investigate the influence of different bolts arrangements, stress R-Ratios and bolt preloads, including snug tight, on fatigue life. The obtained results were analyzed under ASTM E739 procedure in order to obtain S-N curves.This work revealed an average fatigue strength of 114 MPa at 2E6 cycles for the snug tight bolted joints. Preloaded bolt joints presented an average fatigue strength of 108 MPa at 2E6 cycles. Discrepancies between S-N curves suggested by Eurocode 3 and fatigue data obtained experimentally were verified.

Lightweight Threshing Rack under Multisource Excitation Based on Modal Optimization Method

Crawler rice combine harvester threshing rack excited by different frequencies of multiple working parts would cause strong vibration response. In this paper, the rack‐type rice combine harvester threshing rack was taken as research objective, and then the static analysis of the existing threshing rack was carried out by ANSYS Finite Element software. The topology of the rack structure was optimized according to the stress and strain distribution of the threshing rack. Based on solving the 6 natural frequencies and mode shapes of the threshing rack of combine harvester, the morphological test of threshing rack was carried out and the reliability of the modal analysis was verified. Finally, the multivibration source was assembled on the rack for simulation to test and verify the optimization effectiveness. Results showed that the 1st to 6th natural frequency of threshing rack after modal optimization could avoid the excitation frequency of the working part. Compared with the original design, the optimized threshing rack had a weight reduction of 13.7%. This study can provide a theoretical reference for the structural design and optimization of combine harvester threshing rack.

Fatigue behavior of cold roll-formed rail profiles for rack structures

In large companies, warehouse logistics usually include shuttle pallet carriers that are responsible for the transportation of various goods and products. These shuttles run along steel rails, which are usually produced from thin metal sheets that are cold roll-formed into the desired section. These shuttles also work 24 hours a day, 7 days a week, so the rails are very sensitive to fatigue phenomena, caused by the cyclic loading of the moving shuttles, moreover, cracks due to material fatigue have already been observed in these types of rails. In addition, the competitiveness of the European industrial sector is pushing the design of these profiles to lower thickness requirements, which further increases concerns about their fatigue performance. Within this background, the FASTCOLD European project has been carried out, whose research plan consists in developing fatigue design rules for the mentioned applications, which are not covered by existing Eurocode 3 rules, which only addresses thick hot-rolled sections. Experimental fatigue testing has been carried out backed by numerical simulations of these tests. A new fatigue setup has been developed to generate representative fatigue cracking to the shuttle cyclic loads. Numerical simulations of the cold roll-forming fabrication process are also being carried out to determine the importance of the residual stresses in the fatigue life of the rail. With the experimental data obtained from fatigue testing backed by numerical simulations, important contributions are made to the design codes (e.g. Eurocode 3) in dealing with the fatigue design of such critical details.

랙크식 물류창고 조기 화재감지를 위한 다중센서 복합형 화재감지기의 화재감지 성능에 관한 실험연구

This paper presents combined fire detector based on the multi-sensor for early stage fire detection of rack-type warehouse. The combined fire detector suggested in this paper consist of temperature sensor of thermistor, smoke sensor of photo-electric type and CO sensor of electrochemistry type. In order to verify fire detection performance of combined fire detector suggested in this paper fire experiment is conducted in real-scale rack structure. And response characteristics combined fire detector compare with conventional heat detector and smoke detector. The results show that combined fire detector in this paper is able to detect fire very quickly.

Investigation of a Method for Strengthening Perforated Cold-Formed Steel Profiles under Compression Loads

Cold-formed steel (CFS) storage rack structures are extensively used in various industries to store products in safe and secure warehouses before distribution to the market. Thin-walled open profiles that are typically used in storage rack structures are prone to loss of stability due to different buckling modes such as local, distortional, torsional and flexural, or any interaction between these modes. In this paper, an efficient way of increasing ultimate capacity of upright frames under compression load is proposed using bolts and spacers which are added externally to the section with certain pitches along the height. Hereinto, experimental tests on 81 upright frames with different thicknesses and different heights were conducted, and the effect of employing reinforcement strategies was examined through the failure mode and ultimate load results. Non-linear finite element analyses were also performed to investigate the effect of different reinforcement spacing on the upright performance. The results showed that the reinforcement method could restrain upright flange and consequently increase the distortional strength of the upright profiles. This method can also be effective for any other light gauged steel open section with perforation. It was also observed that the reinforcement approach is much more useful for short length upright frames compared to the taller frames.

Optimization of Steel Storage Rack Column and Its Performance Analysis

The main aim of the project is to perform a finite element analysis on steel storage columns. Rack systems for pallet storage are important industrial structures by number and commercial value, yet they have been considered only recently in studies aiming at defining practical design rules for their safe use. These structures are always composed of metal elements. The fabrication of rack structures constitutes, indeed, an important application of cold-formed steel products. The need for continuously loading and unloading the shelves in service has induced designers to avoid bracing elements in the longitudinal direction of the racks. Therefore in many cases, lateral stability in this direction is ensured only by the connections between beam and column and by the constraint offered by the base of the columns. ANSYS used for the model development and analysis presented in this paper. The main requirements for a ?nite element (FE) model of storage rack frames is to have the ?exibility to represent the complex cross-section geometries of the members, and the ability to assign semi-rigid behavior to joints and to take into account the effect of local, distortion and ?exural-torsional buckling in determining the ultimate capacity of the structure and optimization.

Recent developments of the Component Method

ABSTRACTThe Component Method is well established and incorporated in Part 1.8 of Eurocode3 for the design of connections of steel frameworks. It is primarily intended to provide the elastic joint stiffness, although Part 1.8 includes provisions for also determining the inelastic moment‐rotation response from the elastic limit to the ultimate moment. The latter provisions are empirical and use an established experimentally‐based nonlinear equation to define the inelastic response.The Component Method has been further developed in recent years to determine the inelastic response using bi‐linear springs with elastic and inelastic ranges. Procedures have also been developed at the University of Sydney to extend the Method into the post‐ultimate range by defining tri‐linear springs with elastic, inelastic and softening ranges. As well, recent research at the University of Sydney has produced a simple way to predict the moment‐rotation response under fracture of components, thus enabling the Method to capture the full moment‐rotation behaviour.The ability of the Method to predict full‐range moment‐rotation behaviour is especially useful for design by advanced analysis and progressive collapse analysis, as it allows both members and connections to be checked for stiffness and strength as part of the analysis.In parallel, an ongoing joint project between Sydney University and Tongji University on the strength of beam‐to‐upright connections in rack structures has extended to Component Method to cold‐formed steel connections which include tang‐connectors and bolts. The paper provides an overview of these recent developments of the Component Method, including the opportunity to incorporate the Method in a fully nonlinear procedure for the direct design of steel frameworks including connections by advanced analysis, also referred to as the Direct Design Method.

Pengurangan Korosi di Bawah Fire Proofing dengan Metode Primer Coating

The aim of the study was to provide an overview of the specifications of primary coating materials and their application method for corrosion control under the fireproofing of pipe rack structures and supporting structures of equipment in the oil refinery industry. The target to be achieved from this research is the availability of specifications of the primary coating material and the ease of its application to the structure of the pipe rack and the supporting structure of the oil refinery industry equipment. This research is an applied research method with a case study approach, namely in order to overcome the problem of corrosion under fireproofing. Allegedly the cause of corrosion under fireproofing is because in the refinery project specifications there is no provision of primary coating applications under fireproofing. The assumptions developed in answering the research problems are the availability of specifications of materials and methods for primary coating applications under fireproofing so that corrosion under fireproofing can be controlled and reduced. Specifications of primary coating material with service temperature (-45)oC - (650)oC with hi-built epoxy coating material, epoxy phenolic, epoxy nonov, inargonic copolymer and multi polymetric matrix, fulfilling NACE SP 0198-2010 technical specifications and application methods primary coating with a variation of the thickness of the primer coating is 100-200 micron (dry film thickness) DFT, proven to be suitable and suitable to be used to control corrosion problems under fireproofing. The results of this study also recommend that the specific material and primary application method for coatings that have been compiled in the primer guidelines for coatings that are in accordance with the specifications of NACE SP 0198-2010 can be used as the standard.

Impact modelling for progressive collapse assessment of selective rack systems

Storage rack structures are pre-engineered light weight steel structures with standard details which can be quickly assembled because all building components arrive on site pre-fabricated in line with the agreed design. Since they are made using thin-walled perforated steel sections, mostly cold-formed, with mechanical joints, generally partial-strength, semi-rigid, and with a low structural redundancy, these structures are vulnerable to any action capable to induce a local damage of a member or connection. When heavily loaded, the local damage may spread progressively, generating an overall collapse or disproportional damages. Difficulties in predicting the structural behavior of storage pallet racks are amplified by the specific geometry of the structural components: members made by high slenderness thin-walled and open-section profiles (hence prone to global, local and distortional buckling problems), flexible beam-to-upright and baseplate connections with a non-linear behavior. Due to their peculiarities, additional modelling and design rules are required for these non-traditional steel structures and reference cannot be made to usual structural design recommendations and standards. In case of Selective Pallet Rack (SPR) structures, except for the earthquakes, collision of forklift trucks or other moving equipment with front upright is considered as one of the most frequent causes of local failure, with potential to develop into a progressive collapse. In the study, the robustness of SPR structures under accidental loading situations involving collision with forklift truck is assessed using both notional upright removal and explicit forklift impact approaches. Structural configurations are varied to consider different connection properties (upright base and beam-to-upright) and brace arrangements (spine bracing, top plan bracing). SPR structures are susceptible to global failure, especially if the spine bracing is in just a few spans and the rigidity of connections is low. The explicit modelling of the forklift impact provides the most accurate results, as the effects associated with the forklift impact are not properly captured when the response is evaluated using the dynamic analysis and notional upright removal approach. Non-linear static pushdown analysis can provide satisfactory results at the least computational effort, but the dynamic increase factors may require corrections.

Monotonic and Fracture Behaviours of Bolted Connections with Distinct Bolt Preloads and Surface Treatments

This paper presents a research about the monotonic and failure behaviours of bolted joints made of thin plates of S350GD and S355MC steels grades, which are used for rack structures. A full factorial test matrix was performed considering two joints configurations (1+1 and 4+4 double shear bolted joints), two material thicknesses (2 and 3mm), three coatings (“black steel”, zinc coating, zinc plus paint) and two preload levels (25%×70%Fu and 70%Fu). Tests were performed under static monotonic loading until failure. Slip tests were also performed according to the EN 1090-2 standard to evaluate joint slip factors for the three material surface conditions. In addition to the experimental tests, numerical simulation of static tests were performed using elastoplastic material behaviour, based on Mises yield theory and isotropic hardening identified with experimental tensile testing data. The models were able to reproduce conveniently the ultimate loads of the joints and failure modes, including clamping and friction effects.

Decomposition of Supercooled Austenite in Low-Carbon Pipe Steel

Controlled rolling may facilitate the transition from ferrite–pearlite structure to bainite structure and hence improve the strength of low-carbon alloy steel. A literature review shows the lack of detailed research regarding the type of bainite structure that ensures optimal properties of low-carbon alloy steel. To determine the temperature, time, and other parameters of treatment to produce such structure, it is expedient to establish the influence of the cooling rate on the structure and properties of low-carbon alloy steel. In the present work, we investigate the decomposition of supercooled austenite in low-carbon alloy pipe steel with 0.062% C, 1.80% Mn, 0.120% Mo, 0.032% Cr, 0.90% Ni, and other elements (Al, Cu, V, Nb, Ti). The treatment conditions producing bainite structure with elevated steel are determined for such steel. At low cooling rates (no more than 6°C/s), not only ferrite is formed in the microstructure but also granular (or globular) bainite consisting of bainitic α phase and an insular martensite–austenite component (1–6 μm). At a rate of 6°C/s, transition to rack bainite is observed; around the boundaries of the racks, carbides and residual austenite are seen. At cooling rates above 16°C/s, the bainite has packet–rack structure, Between 50 and 150°C/s, the mean rack width of the bainitic α phase declines from 2.24 to 1.32 μm.