Steel Lattice Research Articles

Low-Complexity Candidate for Benchmarking Collapse Prediction of Steel Braced Structures

To aid in the evaluation of the collapse-prediction capability of competing methodologies, a case study of a water tank subjected to the Takatori near-source record from the 1995 Kobe earthquake, scaled down by a factor of 0.32, is presented. The water tank, supported by a five-segment steel lattice tower, is so configured as to have a characteristic collapse mechanism that is triggered due to catastrophic column and brace buckling at the bottommost segment of the lattice under all forms of ground motion. A FRAME3D model of the tank reveals severe buckling in the bottom megacolumns and one of the two braces on the west face of the tower when the structure is impacted by the Takatori near-source pulse, resulting a tilt in the structure. This is followed by sequential compression buckling of braces on the south and north faces leading to P−Δ instability and complete collapse of the tank. In order to verify the predictions of the FRAME3D model, a comparable PERFORM-3D model of the tank, using fiber elements and constitutive material models that are suitably calibrated against experimental data, is developed. The response of this model to the scaled Takatori ground motion compares very well against that of the FRAME3D model; the smallest scaling factor needed to collapse the PERFORM-3D model is 0.323, whereas the corresponding factor needed to collapse the FRAME3D model is 0.315. The sequence of column- and brace-buckling failures and the collapse mechanisms are quite similar in the two models.

Experimental study on mechanical performances of lattice steel reinforced concrete inner frame with irregular section columns

Based on the test on a 1/2.5-scaled model of a two-bay and three-story inner frame composed of reinforced concrete beams and lattice steel reinforced concrete (SRC) irregular section columns under low cyclic reversed loading, the failure process and the features of the frame were observed. The subsequence of plastic hinges of the structure, the load-displacement hysteresis loops and the skeleton curve, load bearing capacity, inter-story drift ratio, ductility, energy dissipation and stiffness degradation were analyzed. The results show that the lattice SRC inner frame is a typical strong column-weak beam structure. The hysteresis loops are spindle-shaped, and the stiffness degradation is insignificant. The elastic-plastic inter-story deformation capacity is high. Compared with the reinforced concrete frame with irregular section columns, the ductility and energy dissipation of the structure are better. The conclusions can be referred to for seismic design of this new kind of structure.

Experimental Investigation of the Behavior of a Lattice Steel Column Repaired with Pultruded GFRP Profiles

AbstractIn this paper, a series of joint tests and full-scale structural tests were performed to assess the effectiveness of pultruded glass fiber-reinforced polymer (GFRP) profiles for rehabilitating lattice steel columns. The data for the displacements and strains of typical members were recorded. The experimental results showed that the failure modes are generally identical for the original column, the column restored using angles, and the column that adopted the stiffer GFRP-to-steel bolted joints (using steel cover plates, bolts, and nuts) repaired with pultruded GFRP sections. In contrast, the failure pattern of the column that used the ordinary GFRP-to-steel bolted joints (only using bolts and nuts) was not the same. Additionally, the ultimate strength of the specimen that employed the stiffer GFRP-to-steel connections was slightly higher than that of the specimen retrofitted by angles, and the ultimate capacity of the sample that adopted the ordinary GFRP-to-steel connections was significantly low...

The Numerical Calculation Based on ABAQUS of Lattice Type Steel Sheet Pile Wharf Structure

This paper uses the world universal finite element software ABAQUS to establish a finite element numerical calculation model of the structure of lattice type steel sheet pile. for the same condition of different soil depth of design elements of lattice type steel sheet pile wharf structure, calculation and analysis of the calculation results and research get the relevant conclusions for reference.

PROBLEMS WITH RECTIFICATION OF HOIST SUPPORTS ON THE EXAMPLE OF A SEMI-PORTAL BRIDGE-CRANE WITH A LATTICE STRUCTURE

The long period and conditions of operation are the cause of various types of severe damage to cranes used in the steelworks industry. Among the more dangerous and difficult to eliminate crane damage types, there is excess durable deflection of its supports from vertical axis. The object of the study is the semi-portal grab bridge-crane with steel lattice structure, for which deflection of a fixed support was detected that several times exceeded permissible values. For this crane, rectification was performed aimed at bringing fixed supports to the vertical line by stabilisation of the corrected location of the bearing structure of the crane using additional angle braces. The analysis of periodical geodetic measurements of the crane structure showed insufficient effect of the rectification, whereas loss of stability of some rods in the fixed support was detected. The study involved the FEM strength analysis of the crane, which revealed that the applied rectification method caused redistribution of forces in the rods of the fixed support, resulting in the loss of stability of some rods of the support, thus questioning the effectiveness of the rectification method applied.

Theoretical and Experimental Research on Joint Slippage Effects of Lattice Angle Steel Tower

In lattice angle steel transmission tower, as the bolt diameter is small and member connection is relatively thin, lower clamping force is commonly used in bolted joint. It is common in lattice tower during full tower tests, joint slippage occur even under design load. However, traditionally trussed beam hybrid finite element model without explicitly considering slippage effects has been widely used in the analysis of the tower. In this paper, the HD-1 tower was experimentally studied under various static load cases, and several numerical models with including joint eccentricity and slippage are established. After comparing the theoretical analysis results and the experimental results, the following conclusions are presented: joint eccentricity almost has not effects on leg member axial force; Among all the studied load cases, joint slippage effects the leg member force most under torsional condition than the other load conditions; Numerical model with including joint slippage effects yield much better axial force results in leg member compared with experimental test results.

Carbon diffusion in carbon-supersaturated ferrite and austenite

Abstract Carbon diffusion was studied in three carbon-supersaturated ferrite materials: in pure α-Fe, in model α-Fe–Cr alloy, in commercial ferrite-martensite chromium steel P91 and in two carbon-supersaturated austenite materials: in Fe–Ni–Cr model alloy and in commercial steel AISI 316. The carbon surface layer, the thickness of which was about 40 nm, was physical-vapor-deposited and isothermal diffusion anneals were carried out at selected temperatures between 573 K and 1073 K. The depth profiles of carbon were measured by SIMS. It was found that carbon diffusion proceeds much more slowly in carbon-supersaturated austenite and ferrite matrices than in matrices with an equilibrium carbon concentration. The carbon diffusion coefficients obtained, D , were close to the values reported in the literature for C diffusion in the carbide phase. The measured values of D for pure α-Fe, α-Fe–Cr and P91 steel at temperatures above 773 K were identical. However, significantly higher values of D were measured in P91 at temperatures below 773 K, which was ascribed to equilibration of carbon concentration in the Cr steel lattice. The differences observed between the D in the austenite Fe–Ni–Cr alloy and in the AISI 316 were explained by different chemical composition of the two materials.

Low-velocity impact performance of lattice structure core based sandwich panels

This paper outlines the findings of a study on a range of stainless steel and titanium alloy lattice structures manufactured using the selective laser melting technique. The effect of varying key manufacturing parameters on the properties of lattice strands was studied through a series of single-filament tensile tests. The resulting failure mechanisms were investigated using a scanning electron microscope. The resulting observations have shown that the properties of these lattice strands are determined by the laser energy during the manufacturing process, which in turn is controlled by the laser power and laser exposure time. The quasi-static and low-velocity penetration behaviour of lattice core-based sandwich panels has been examined, and an aluminium foam and an aluminium honeycomb were chosen to benchmark their performance. The impact resistance of the lattice core-based sandwich structures were shown to be dependent on both the manufacturing parameters and lattice unit-cell geometry of the lattice structure. The impact resistances were improved by increasing manufacturing laser energy and lattice core density. A series of drop-weight tests at velocities up to 6 m/s have shown that the penetration behaviour of the titanium alloy lattice cores and the aluminium honeycomb cores is similar.

Eco Deck Plate의 구조적 거동 평가를 위한 실험적 연구

에코 데크 플레이트 시스템은 철선일체형 거더와 아연도금 강판을 볼트에 의해 일체화시키기 때문에 기존에 용접에 의해 제작된 철선일체형 데크 플레이트에 비해 친환경 및 우수한 공법으로 인정받고 있다. 본 연구에서는 에코 데크 플레이트의 구조적 거동을 평가하기 위해 12가지 형태의 시험체를 동일한 조건으로 2개씩 총 24개의 시험체를 실물크기로 제작하여 실험적 연구를 수행한다. 실험결과 시공하중 작용에 대한 허용 처짐은 설계값 이내의 값을 나타내 만족하는 것으로 나타났으며, 래티스 철선의 가공은 아래로 향하게 절단해 제작하는 것이 구조적으로 유리한 것으로 나타났다. 또한, 하부철선으로 D13을 사용한 시험체의 경우에는 하부철선과 래티스 철선의 용접부위에서 파괴가 발생해 공장 제작 시 용접에 대한 개선안의 마련이 필요하다. Eco deck plate system is a construction method that deconstruction of galvanized steel sheets is possible by integrating steel-wire-integrated girders and the galvanized steel sheets with bolts. Therefore, compared with previous steel-wire-integrated deck plates which were joined by welding, the system is acknowledged as the construction method possible management and repair. This study conducted an experimental research by manufacturing total 24 full size specimens in a same condition for 12-shape specimens by two parts to evaluate structural behaviors of the eco deck plates. In the results after the test, permissible deflection for the construction load action was shown to be values under design values and satisfactory. The processing of lattice steel wires was presented to be structurally advantageous in being manufactured by cutting downward. Also, in case of a specimen that D13 as a steel wire was used, destruction occurred at the welding part of the bottom steel wire and the lattice steel wire, so improvement measures for the welding in factory manufacture are necessary.

Dynamic characteristics measurements as a part of design assisted by testing in estimation of the steel latticed towers wind loading according to Eurocode

Previous authors’ publications, related to the analysis of steel lattice towers, describe some problems connected with it, especially ones referring to the calculations made according to the past Polish Standards. This paper presents the possibilities of measuring the dynamic characteristics of towers, as one of experimental methods allowed in Eurocode, practicable in verification of load capacity of existing structures.

High temperature reaction tests between high-Cr ODS ferritic steels and U–Zr metallic fuel

Out-of-pile high-temperature reaction tests are carried out on the diffusion couples between U–Zr fuel and ODS ferritic steels, in which the concentrations of Cr and Al were systematically changed for improvement of corrosion resistance. The results show that the Al addition to ODS ferritic steel considerably improves the compatibility between U–Zr fuel and the ODS steel. The threshold temperature for reaction layer formation is roughly 50K higher in the Al-containing ODS ferritic steels than in the steels without Al addition for the testing time up to 900min. The compatibility improvement mechanism by Al addition is discussed from the viewpoint of activity change. The activity calculation results obtained using general thermodynamic data indicate the possibility that stabilization of the intact α-Zr layer by Al addition is the main mechanism and occupation of steel lattice sites by Al that does not easily diffuse into γ-U–Zr also partly contributes to suppression of the inter-diffusion.

Hydrogen embrittlement of Zn-, Zn–Ni-, and Cd-coated high strength steel

Sacrificial coatings, such as Zn and Cd, are used to protect steel against corrosion. During the electrodeposition of metals, hydrogen is evolved due to electrolysis. The evolved hydrogen may diffuse outward and become trapped in the substrate/coating interface or migrate inward into the steel lattice causing delayed embrittlement when the component is subjected to stress. This study reports two principal variables for Zn, Zn–Ni, and Cd coatings: (i) the quantity of hydrogen absorbed by the coating and substrate by vacuum thermal desorption and (ii) the permeability of the coating material to hydrogen by electrochemical permeation. The findings were analyzed in correlation with the microstructural characteristics of both the coating material and the coating/substrate interface. With Zn–Ni, both coating process and coating material combined to significantly reduce the risk of internal hydrogen embrittlement by (i) introducing the least amount of hydrogen during the electrodeposition process and (ii) by the ease with which hydrogen can be extracted by baking due to the presence of cracks in the coating.

The Possibility of Using Numerical Modeling for Assessment of Welded Joint Load-Bearing Capacity / Možnost Využití Numerického Modelování Pro Posouzení Únosnosti Svařovaného Styčníku

Abstract The subject of this paper the practical example of the steel lattice structure was used. Specifically, the joint consisting of H-profile bottom chord and a RHS (Rectangular Hollow Section) brace members has been elected. This particular joint has an exceptional feature which is a deviation from the geometric conditions required by Eurocode. The aim is to create a numerical model that will adequately reflect the actual behavior of this type of joint as well as comparison of such behavior with that expected on the basis of assessment according to standardized formulas.

Study on Capacity of High-Strength Angle Struts Connected by Single Limb

Experiment on bearing capacity of 24 Q460 high strength angle steel for compression members attached by one leg shows: the ultimate bearing capacity of the experiment value are higher than the calculated of the “Design of Latticed Steel Transmission Structures” (ASCE10-1997), on the same section in different slenderness ratio of components, the larger slenderness ratio, the higher the ratio; while on the same slenderness ratio in different sections, the greater width-thickness radio, the greater the ratio. Based on this problem, analyzing the current standard, a set of formulas based on high-strength angle struts connected by single Limb was brought, which can used for the design of the Q460 high-strength angle.

Experimental Study on the Mechanical Behavior and Failure Mechanism of a Latticed Steel Transmission Tower

AbstractTransmission tower collapses caused by strong winds or severe freezing rains frequently occur in many parts around the world. To study the mechanical behavior and failure mechanism of tower structures under such environmental loads, three pairs of tower subassemblages, including one single-panel pair and two double-panel pairs, were designed and statically tested at Tongji University. The difference between the two specimens in each pair was that one had an additional diaphragm as a method of retrofitting while the other did not. One pair of double-panel specimens was tested to simulate and capture the failure pattern of transmission towers subjected to wind load. Correspondingly, two pairs were used to investigate the relevant response of structures under the combination of vertical ice and wind loads. A comparative study on strains at critical sections and local and global deformations as well as failure modes of the tower subassemblages was carried out. The favorable effects of adding the diaph...

Experimental study on multi-panel retrofitted steel transmission towers

Due to the increasing demands on power supply and telecommunication services, existing transmission towers are frequently being required to carry extra loads above their initial design limits. A range of methods have therefore been used to increase the capacity of existing towers by retrofitting them in some way. This paper addresses steel lattice transmission towers with main leg members retrofitted by steel angles through bolted double steel angle connectors, a method that is widely used in practice but to date with little experimental research to support it. Three unreinforced tower models and four groups of retrofitted tower models with and without preloading have been tested in the structural laboratories at the University of South Australia. The experimental results verify the effectiveness of the retrofitting method. Load sharing analysis shows that axial loads can be effectively transferred between original tower members and reinforcing members through the bolted-splice system. Preloading reduces the load sharing in reinforcing members in the early loading stage but does not have significant influence on the ultimate strength of the whole structure.

Modelling of steel lattice tower angle legs reinforced for increased load capacity

As a result of changes in design code requirements for wind loads, increased demand for electrical power, and the growing communication industry, retrofitting of existing steel lattice towers has become an important strategy in the transmission tower industry. At present there are two main reinforcing methods that are used in practice for lattice transmission towers. The first method involves adding a number of horizontal braces (diaphragms) to the mid-length of slender, inadequately braced members along the height of the tower; while the second method is focused on strengthening the capacity of the existing legs only by retrofitting them with additional members. In this paper, the most effective leg retrofitting method has been investigated through an experimental testing program using a one-panel angle leg retrofitting model and a nonlinear finite element (FEM) model. A 3D continuum element was developed to model the panels and bolted connections and the results are compared with those obtained from experiments, with good agreement. The model was then simplified using a simple locking system where a special technique was developed to simulate the bolt slip, which was found to be a critical issue from the experiments. The simplified model can then be extended to multi-panel modelling.

Static Behavior Study for Latticed Concrete-Filled Steel Tubular Wind Turbine Tower Joints

Six latticed concrete-filled steel tubular (CFST) wind turbine tower K-shape joints were carried on the static load test, which included the weld intersecting joint and gusset plate joint. The failure mechanism and characteristics on the two kinds of K-shape joints, the deformation development process after joints entered plastic stage and the stress state and distribution of joint intersection area were studied. The results show that the failure mode and mechanical behavior of CFST K-shape joints are greatly different from that of the hollow steel tube K-shape joints because of the existence of core concrete, the failure mode of the weld intersecting joints showed the local buckling of compression web member and that of the gusset plate joints presented as the compression buckling and tension tearing of the gusset plates, while the plastic deformation failure of tower column tube wall in joint area was not appear. It is also shown by test results that the stress distribution of tower column tube wall and gusset plate in joint intersection is extremely non-uniform, individual parts already enter plastic state but some other parts are still in elastic state. According to the failure mode and stress distribution conditions of the two kinds of K-shape joints, some design suggestions are drawn, which can provide reference for the latticed CFST wind turbine tower joints.

The Study on Force Behavior of Concrete Filled Steel Tube Lattice Wind Turbine Tower with Three Limb Columns

This paper refers to currently the 1.5MW cone tube type wind-driven generator tower, design the model of the concrete-filled steel tube wind turbine tower with three limb columns, and research on the force performance, such as the change of internal force, the process of failure, hysteretic behavior, bearing capacity, ductility and energy dissipation capacity by the pseudo-static experiment on the scale model of wind turbine tower. The study shows that the P- hysteretic curve of lattice concrete-filled steel tube wind-driven generator tower with three limb columns is asymmetric, relatively full “spindle” and the phenomenon of “knead shrink” is not obvious, which account for it has good force behavior and energy dissipation capacity. This kind of tower structure, of which the reverse bearing capacity is greater than the positive, and the reverse ductility coefficient is less than the positive, indicates that it’s reverse plastic deformation ability of the tower structure is weaker than it’s positive.

Damage assessment, repair and field test of steel lattice shell after fire

A real case of a steel lattice shell suffering a fire was studied. Based on the theory of field modeling, fire dynamic simulator (FDS) was used to identify the temperature field. The damage mechanism of the structure was determined by FEM analysis. After damage assessment, the shell was repaired with the pipe-encasement method. Finally, field test was employed to check the capacity of the structure after repair. The numerical study results indicate that the damage assessment agrees well with field inspection, verifying the accuracy of fire numerical simulation and FEM analysis. The field test results prove that the pipe-encasement method is secure and reasonable, and the repaired shell is safe.