Steel Grid Research Articles

A global-local hybrid strategy with adaptive space reduction search method for structural health monitoring

The difficulty in computational convergence poses challenges of application for traditional heuristic optimization algorithms to solve the optimization-based structural identification problem, especially for the large-scale and complex structural systems where considerable number of unknown parameters and degrees of freedom involved. Unlike the classic identification methods, in this paper, a novel hybrid strategy, coarsely exploring the relatively large search limits with the improved Jaya algorithm and adaptive search space reduction method in the global stage, and then fine-tuning the identified best solution with local optimization methods to the optimum in the local stage, is proposed and evaluated. The improved Jaya algorithm includes three improvements compared to its original version, fuzzy clustering competitive learning, experience learning and Cauchy mutation mechanisms. Gradient based Levenberg-Marquardt method, sequential quadratic programming method and non-gradient based Nelder-Mead simplex method are inserted as local mathematical optimizers to further enhance identification accuracy and efficiency. The superiority of proposed improved Jaya algorithm is validated in optimizing classical and CEC05 benchmark functions by comparing with several state-of-the-art algorithms. Furthermore, the effectiveness of proposed global-local hybrid method is verified by a numerical example of truss structure and an experimental test of the steel grid benchmark structure with incomplete set of noise-polluted measurements. The statistical results show that the improved Jaya algorithm and adaptive search space reduction method combined with sequential quadratic programming can achieve better performance in structural damage identification than other methods.

Evaluating the applicability of seismic retrofit of an electric cabinet in a power plant

The aim of this study was to find a way to improve earthquake resistance performance more effectively through various reinforcement methods between a cabinet bottom and concrete slab, which is a vulnerable connection in the event of earthquake. In order to improve the earthquake resistance performance of an electric cabinet, methods such as installing a vibration isolation device, increasing the number of connecting bolts between the cabinet bottom panel and base channel, welding a steel grid to the cabinet bottom panel, and so on, were considered and, in order to compare the performance in each case, a three-axis shaking table test was performed. As a result of comparing the seismic performance of each case according to the acceleration response, it was found that the reduction of seismic force was best when applying the vibration isolation device. However, there is a disadvantage in that the spatial and temporal limitations are large and the unit price is high for application in the field. For this reason, it is predicted that the method of ensuring the higher rigidity of an electric cabinet by increasing the number of connecting bolts, as proved through this study, would be a more economical and realistic seismic performance method in field applications.

High-velocity projectile impact resistance of reinforced concrete slabs with ultra-high performance concrete strengthening - A numerical study

This paper adopted numerical simulations to explore the high-velocity projectile impact (HVPI) performance of 180 mm thick reinforced concrete (RC) slabs with ultra-high performance concrete (UHPC) strengthening. Finite-element modelling of the RC slab and UHPC layer subjected to HVPI was firstly performed to verify the numerical model related to the local damage and projectile residual velocity. Then, the slab configuration parameters concerning the steel rebar layer number and grid size in the UHPC layer, the spacing between the RC slab and UHPC layer, and the layout positions of the UHPC layer were investigated to determine the optimal strengthening strategy to resist projectile perforation. The numerical results demonstrated that snugly placing the UHPC layer without steel rebars upon the impact face of the RC slab was the most effective and efficient strengthening strategy. With the optimal slab configuration, the influences resulting from the unconfined compressive strength of UHPC, projectile mass and nose shape on the projectile perforation of UHPC strengthened RC slabs were explored. For each influencing factor, the relations between the projectile residual velocity and UHPC layer thickness were obtained at various projectile striking velocities. In the light of the simulated data, an empirical formula was established to estimate the ballistic limit of the 180 mm thick RC slab with UHPC strengthening..

Carbon emissions of prefabricated steel structure components: A case study in China

China has been vigorously promoting the use of prefabricated steel structure buildings (PSSBs)1 in recent years. However, owing to the deficit in carbon emission (CE) research and the lack of basic CE parameters for PSSB components (PSCs), it is not feasible to conduct reliable CE calculations or develop scientific strategies for CE reduction. Based on the actual situation in China, this study investigated the CE of upstream raw steel sheet production (CEA1-A3), measured the CEs of PSC prefabrication (CEA3+), and obtained a carbon emission factor (CEF) for PSCs in the “cradle-to-gate” stage. The CEF of PSCs was found to be 2175.7 kgCO2e/t; CEA1-A3 contributed 1959 kgCO2e/t (90.0%), while CEA3+ contributed 216.7 kgCO2e/t (10.0%). Previous studies focused almost exclusively on CEA1-A3, whereas this study systematically investigated the direct, indirect, and embodied CEs for the A3+ stage of PSCs. The sources of CEA3+ were quantified; this showed that the CEs for energy and material consumption accounted for 59.6% and 40.4%, respectively. Compared with CEA1-A3, the CE types of CEA3+ were more diverse, with indirect CE (52.4%) > embodied CE (38.4%) > direct CE (9.2%). For this reason, CE calculation methods suitable for these characteristics were discussed, mainly based on consumption–production (CP) and process analysis (PA). In the CO2 gas-shielded welding test, it was found that the CO2 shielding gas decomposed in large quantities during the welding process, and the degree of decomposition was positively correlated with the welding power; the CP method regarded the CO2 supply as the direct CE and overestimated the CEA3+. In this study, the CE parameters of the main prefabrication processes were measured and the corresponding empirical formulas were fitted, which made the PA-based CE calculations feasible. Finally, the temporal and spatial ranges of the results were clarified, and the CEF trends for PSCs were predicted according to the expected CEs for crude steel and power grids in China. The results show that the scrap proportion in the production of raw steel sheets has a major impact on the CEFs of PSCs, whereas low-carbon electricity offers considerable CE reduction potential for PSC prefabrication.

Stress-Strain State Analyses of the Composite Steel and Concrete Grid Structure

The study provides developing a method of the tress-strain state analyses of the composite steel and concrete grid structure, the main assumptions, and analysis of the geometry of the structure, the elementary states of equilibrium of the structures are considered, and the systems of determining equations are solved. The method of the stress-strain state analyses is proposed to be performed using the basic provisions of the technical theory of calculating thin shells. The method provides obtaining and solving the design models, and the equations needed for calculating the bearing capacity of the members of the composite steel and concrete grid structure. In particular, the method is for determining the essential area of the cross-section of the prestressed reinforcement, as well as to determine the forces that are acted in the composite steel and concrete structure. In general, the method provides designing the composite steel and concrete structure, determining the bearing capacity, and selecting the necessary dimensions of the structural elements of the composite steel and concrete structure.

An Experimental Study on Torsional Behavior of Reinforced Concrete Columns Retrofitted with Hybrid Concrete Jackets.

The concrete jacketing method for retrofitting old reinforced concrete (RC) columns should secure confinement and seismic performance under torsion as well as unidirectional later loads. In a previous study, a hybrid concrete jacketing method was proposed using steel wire mesh (SWM), steel grid reinforcement (SGR), which can replace reinforcement of existing concrete jacketing method, and using steel fiber non-shrinkage mortar (SFNM). These details can simplify the retrofitting process of the existing concrete jacketing method, and seismic performance was evaluated by conducting a cyclic loading test under unidirectional loading. In this paper, the torsional behavior of RC columns retrofitted with the hybrid concrete jacketing method was investigated. Four specimens were fabricated and conducted cyclic loading tests under two types of loading schemes, unidirectional and bidirectional loading, to examine the effect of the loading path. The strength and energy dissipation capacity of retrofitted columns with hybrid concrete jackets increased approximately eight times compared to the old RC columns under torsional loading. Therefore, the hybrid concrete jacketing method can improve torsional resistance.

Construction of Safety Production Standardization Information System of Ninggang

Different from other enterprises, the complexity of the production process and production environment of iron and steel enterprises has led to a very serious safety situation, which not only endangers the lives of many workers, but also has an extremely bad impact on society. It is very necessary to put forward higher requirements on safety management for iron and steel enterprises. Based on the standardization of enterprise safety production, this paper builds a safety production standardization information system with Ningbo Iron and Steel Grid Company Limited. (hereinafter referred to as Ninggang) as an example, combined with Internet intelligent tools, to assist enterprises to complete the construction of safety production standardization and improve the safety management efficiency of iron and steel enterprises.

Cyclic tests and parametric analyses of steel grid shear walls

This study proposed a novel steel grid shear wall (SGSW) composed of bidirectional diagonal steel grid members and a boundary frame, in which the steel grid members are connected to the boundary frame through fishplates. The lateral resistance performances of the steel plate shear wall (SPSW) and SGSWs were compared. Subsequently, three 1:2 scale specimens were tested under lateral cyclic loading, and the mechanical properties of the SGSWs were investigated. The failure modes of the specimens corresponded to the destruction of steel grid members. A finite element analysis (FEA) model of the SGSW was established, and the FEA model was confirmed to be able to accurately simulate the behaviors of SGSWs by comparing the numerical results with test data. Parametric analyses were then conducted through FEA to determine the influence of the T-shape steel section, vertical loads, and boundary column stiffness on the mechanical properties of SGSWs. The results demonstrated that SGSWs exhibited excellent stiffness, ductility, and bearing capacity. The changes in the T-shape steel web area and stiffness of the boundary column had a significant influence on the mechanical properties of the SGSWs.

A 3D Printed Device for In Vitro Generation of Stratified Epithelia at the Air-Liquid Interface.

Air-liquid interface (ALI) cultures are used to produce stratified epithelial tissues in vitro, notably for the production of oral mucosal equivalents. Currently, there are few purpose-built devices, which aim to enhance the ease and reproducibility of generating such tissue. Most ALI cultures utilize stainless steel grids or cell culture inserts to elevate the matrix or scaffold to the surface of the culture media. In this study, a novel buoyant epithelial culture device (BECD) was designed to both contain a fibroblast-seeded collagen hydrogel and float in culture media, thereby automatically maintaining the ALI without further user intervention. BECDs aim to mitigate several issues associated with ALI culture; reducing the chance of media flooding the epithelial layer from physical disturbance, reducing technique sensitivity for less-experienced users, and improving the reproducibility of the epithelia generated. H400 oral squamous cell carcinoma cells cultured in BECDs for 7, 14, and 21 days showed continuous increase in epithelial tissue thickness with expected localization of epithelial differentiation markers: cytokeratin 5, involucrin, and E-cadherin. Fused filament fabrication three-dimensional printing with polypropylene used in BECD production allows for rapid turnover and design iteration, presenting a versatile, adaptable, and useful tool for application in in vitro cell culture.

Experimental investigation of ultra-low cycle fatigue behaviors of laminated rubber bearings in spatial grid structures

Ultra-low-cycle fatigue failure of laminated rubber bearings in steel grid structures is likely to occur due to an earthquake, which leads to a failure or even complete collapse. The present paper investigates the effects of different variables on the hysteretic behavior, skeleton curves, and stiffness degradation of bearings and anchor bolts. The variables include the vertical force and diameter of anchor bolts. For these purposes, ultra-low-cycle fatigue tests on laminated rubber bearings were carried out under constant vertical loading and horizontal reciprocating variable loading. In addition, the morphological analysis of fatigue fractures was performed to investigate the failure mechanism of anchor bolts in the bearings. It was found that the anchor bolt is the weakest part of the bearings during strong earthquakes. Cracks originate at the root of the anchor bolt and expand as the stress concentration increases, and a typical ultra-low-cycle fatigue fracture micro-morphology appears. Also, it was also found that increasing the vertical pressure can increase the peak value of the horizontal reaction force of the specimen and increase the energy consumption. It means that increasing the diameter of the anchor bolt can increase the stiffness of the bearing, increase the peak value of the horizontal reaction force, and slow down the stiffness degradation. Furthermore, a formula for the relationship between horizontal stiffness degradation and cumulative damage of a bearing is established. This formula can provide a reference for the seismic capacity evaluation of laminated rubber bearings used in spatial grid structures.

Experimental study of a new assembled integral concrete–steel open-web sandwich plate composite bridge

This study introduces a new type of bridge structure—the assembled integral concrete–steel open-web sandwich plate composite bridge (COSPB), which is composed of a concrete slab,steel Vierendeel beams (SVBs, with top chords, bottom chords and shear keys), and studs (used for connecting SVBs and concrete slab). The bi-directional SVBs form a spatial steel grid structure, which can be used as the formwork for concrete slab casting, and divided into prefabricated units to allow on-site assembly after prefabrication in factory, leading to the reduction of on-site construction workload and the acceleration of the construction schedule. To understand the flexural behavior of this kind of structure, a static experiment was conducted on a 10-m-span full-scale test specimen with simply supported boundaries to investigate the deflection, strain distribution, and failure mode. The test results showed that there was still a large safety reserve for the flexural capacity of the section after the bottom chord of the steel–concrete composite Vierendeel beam (SCVB) began to yield. The ratio of the ultimate load to the yield load was 1.56. No concrete crushing and large area cracking were observed during loading, and the structure had good ductility. The ultimate flexural capacity of the SCVB was analyzed by the method of cross-sectional analysis, and the results were in good agreement with the test results. Finally, based on the test results, the ultimate flexural capacity and stiffness of the bridge were discussed using the Chinese Highway Bridge Design Code.

Shear behaviour of composite beams with permanent UHPC formwork and high-strength steel rebar

• The shear behaviour of UHPC-NC composite beams reinforced by high-strength rebars was discussed, where the permanent UHPC formwork and no web reinforcement were adopted. • Test parameters included the presence of UHPC and steel grids, type and thickness of formwork, strength of the NC, size of the steel grids and shear span ratio. • Based on the superposition principle, the ultimate shear capacity of the UHPC-NC composite beam was formulated. This study investigated the shear behaviour of ultrahigh-performance concrete (UHPC)-normal concrete (NC) composite beams reinforced by high-strength rebar. In the proposed UHPC-NC composite beam, the UHPC was used as a permanent formwork, and no web reinforcement was adopted. A total of twelve beams, including one reference NC beam, nine beams with pure permanent UHPC formworks and two beams with steel grid-reinforced permanent UHPC formworks, were examined via a four-point bending test. The examined parameters included the presence of UHPC and steel grids, type and thickness of the formwork, strength of the NC, size of the steel grids and shear span ratio. Three failure modes were observed depending on the shear span ratio, i.e., diagonal compression failure for a shear span ratio < 1, shear-compression failure for a shear span ratio = 1–3, and diagonal tension failure for a shear span ratio > 3. No obvious debonding was found between the UHPC formwork and NC, indicating that the interface processing method adopted in this study was effective. The test results showed that under the same shear span ratio, the shear cracking loads and ultimate shear capacities of the UHPC-NC composite beams increased by approximately 11.8–94.1 % and 16–66.6 %, respectively, compared with the reference NC beam. Among the bottom, side and U-shaped UHPC formworks, the U-shaped formwork provided the greatest improvement in the ultimate shear capacity. Based on the superposition principle, the ultimate shear capacities of the UHPC-NC composite beams were predicted.

Research on Comprehensive Technology of Steel Grid Installation and Integral Jacking

In this paper, through the construction simulation of the installation and jacking of a large steel grid project, ANSYS software is used to select the corresponding finite element module, and by analyzing the construction models of different modes and different load conditions, the analysis results and structural models are displayed. The 12 supporting hydraulic jacks can meet the overall steel structure hoisting requirements on site. At the same time, the calculation model takes into account the deformation of the overall grid during the unloading process. After testing, the maximum displacement is 7mm, which meets the requirements of national regulations. This method better supports the construction guidance, and also achieved good benefits during the on-site implementation process. The installation plan and jacking technology are worthy of reference.

Seismic Performance of Reinforced Concrete Columns Retrofitted with Hybrid Concrete Jackets Subjected to Combined Loadings.

In the existing reinforced concrete columns where they are insufficient seismic details, critical failure mode such as shear failure can be observed under seismic loads. One strategy for the retrofitting of existing concrete columns is to use concrete jacketing. Concrete jacketing consists of a new concrete layer with longitudinal and transverse reinforcements, and can improve seismic resistance capacity. In this paper, a detail of concrete jacket that can be expected for easy construction and improved adhesion performance of longitudinal and transverse reinforcement was proposed. Additionally, a combined cyclic loading test was conducted to consider the seismic load with multiaxial characteristics. The concrete jacket details utilize three components: Steel Grid Reinforcement (SGR), Steel Wire Mesh (SWM), and Steel Fiber Non-Shrinkage Mortar (SFNM). One RC column with non-seismic details and two jacketed RC columns were fabricated to demonstrate the construction efficiencies and structural capacities of the jacketed columns. Two details of jacketed section were considered as variables. It was observed that the specimens retrofitted with concrete jacket resisted torsional load more than the un-retrofitted specimen in terms of crack and failure mode. The experimental results showed that the maximum load of retrofitted specimens was increased by more than 8 times compared to the un-retrofitted specimen, regardless of the jacket details. Newly designed concrete jacket effectively increased the strength. Compared with the un-retrofitted column, the columns retrofitted with the proposed details achieved significant increase in initial stiffness and energy dissipation.

Assessment of Integrated Solutions for the Combined Energy Efficiency Improvement and Seismic Strengthening of Existing URM Buildings

The European building stock is an aging infrastructure, mainly built prior to building codes. Furthermore, 65% of these buildings are located in seismic regions, which need to be both energetic and seismically retrofitted to comply with performance targets. Given this, this manuscript presents integrated constructive solutions that combine both energy efficiency improvement and seismic strengthening. The goal and novelty is to design and to evaluate one-shot, compatible, noninvasive, and complementary solutions applied to the façades of buildings with a minimum cost. To do so, different constraints have been borne in mind: the urban environment, achievable seismic and energy performance targets, and reduced construction costs. The method was applied to an old Spanish neighbourhood constructed in the 1960s. Different retrofitting packages were proposed for an unreinforced masonry case study building. A sensitivity analysis was performed to assess the effects of each configuration. A benefit/cost ratio was proposed to comparatively assess and to rank the solutions. The results of the seismoenergetic performance assessment showed that improving the behaviour of walls leads to higher benefit ratios than improving the openings. However, this latter strategy generates much lower construction costs. Integrating seismic into energetic retrofitting solutions supposes negligible additional costs but can improve the seismic behaviour of buildings by up to 240%. The optimal solution was the addition of higher ratios of steel grids and intermediate profiles in openings while adding thermal insulation in walls and renovating the window frames with PVC and standard 4/6/4 double glazing.

Mechanical Behavior of Innovative Reinforced Aluminum Foam Panels

Metals foams are attracting great interest in aerospace, automotive and military fields. Particularly, the closed-cells aluminum foams are characterized by peculiar properties, such as low specific weight coupled with high energy absorption capacity, high specific stiffness and strength and reduced thermal and electrical conductivity. For the above reasons, aluminum foams can be effectively used as core of sandwich structures, replacing the traditional honeycomb and polymer-based foams. However, under specific loading conditions, the foam core was proved to collapse because of the bubble-cell structure, so affecting the mechanical performance of the sandwich constructions. Different solutions have been studying in literature to reinforce the foam-based core; for example, the authors in previous studies investigated the possibility to use a metal grid inside the core as a corrugated skeleton, to improve its behavior under compression. Therefore, based on these premises, the aim of this work is to improve understanding of the mechanical behavior of innovative reinforced aluminum foam panels through an experimental approach consisting of three-point bending tests. In particular sandwich structures with and without a corrugated grid structure, acting as skeleton inside the core, were manufactured. The bending properties were estimated also considering two different types of steel grid employed for the corrugated structure and for reinforcing the skins.

Information Construction Technology of Free-Form Surface Steel Grid

Taking the construction project of National Network Security Talents and Innovation Base Exhibition Center as an example, the application of building information model in the construction process of free-form surface steel structure is analyzed in this paper. The results show that the application of Building Information Modeling (BIM) technology to the construction of free-form surface structure improves the work efficiency of the construction team in multi-disciplinary collaboration, surface component manufacturing, and construction process design, and subsequently improves the construction speed and construction quality.

Hydrogel Microencapsulation Enhances Cryopreservation of Red Blood Cells with Trehalose.

Cryopreservation of red blood cells (RBCs) plays a vital role in preserving rare blood and serologic testing, which is essential for clinical transfusion medicine. The main difficulties of the current cryopreservation technique are the high glycerol concentration and the tedious deglycerolization procedure after thawing. In this study, we explored a microencapsulation method for cryopreservation. RBC-hydrogel microcapsules with a diameter of approximately 2.184 ± 0.061 mm were generated by an electrostatic spraying device. Then, 0.7 M trehalose was used as a cryoprotective agent (CPA), and microcapsules were adhered to a stainless steel grid for liquid nitrogen freezing. The results show that compared with the RBCs frozen by cryovials, the recovery of RBCs after microencapsulation is significantly improved, up to a maximum of more than 85%. Additionally, the washing process can be completed using only 0.9% NaCl. After washing, the RBCs maintained their morphology and adenosine 5'-triphosphate (ATP) levels and met clinical transfusion standards. The microencapsulation method provides a promising, referenceable, and more practical strategy for future clinical transfusion medicine.

Optimization analysis of straight-bladed vertical axis wind turbines in turbulent environments by wind tunnel testing

Although freestream turbulence is believed to improve the efficiency of vertical axis wind turbines (VAWTs), few studies have systematically assessed VAWT performance in turbulent environments. In this study, steel and aluminum grids were used to simulate the turbulence field. Three turbulence levels of Iu = 5.1%, 10.9% and 14.6% were generated, together with one low turbulence level of 0.9%. First, the parametric effects of solidity ratio σ, pitch angle β, and aspect ratio η were examined in 48 cases in various flow regimes. Then, the Taguchi method with an L16(44) orthogonal table was implemented to comprehensively and effectively investigate the parametric effects and their extent of impact on VAWT turbine performance. This reduced the number of cases from 256 to 16. Unlike smooth flow, turbulence enhanced the efficiency of the VAWTs, with improvements ranging from 7.9% to 38.0%. The factors influenced efficiency in the following order: β > σ > η > Iu. The VAWT performance peaked at β = −6.5°, and revealed that a toe-out pitch ranging from −9.5° to −6.5° is required for maximal performance. The improvements in VAWT efficiency caused by turbulence decreased as a factor approached its optimal value.

RESULTS OF EXPERIMENTAL STUDIES OF PILES ON HORIZONTAL LOADS

Statement of the problem. The results of laboratory tests of a horizontally loaded pile reinforced with a steel grid located in the ground and a free-standing pile without a grid are considered and compared.Results. A comparative assessment of the load-bearing capacity of the pile for a horizontal load is made during a laboratory experiment. To compare the results of various tests in the laboratory, experiments were performed in a tray with sand at the same diameter and length of the pile. The experiments were carried out on models at the center for collective use named after Prof. Yu. M. Borisov (Voronezh).Conclusions. The data of laboratory experiments have shown that the use of piles reinforced withsteel mesh can significantly increase the load-bearing capacity of pile foundations and reduce horizontal movements compared to free-standing piles at the same load.