Single Truss Research Articles

The superstructure behavior assessment of the railway bridge with truss element damage

The analysis of railway bridge accidents shows that at the present stage, the number of accidents and mechanical superstructures damage is associated with vehicle impacts. Bridge design standards recommend to check bridge structures for survivability, operational control standards do not cover such issues. To superstructure behavior assessment of a single-track railway bridge with truss element damage, a numerical study of changes in the stress-strain state of bridge superstructure was carried out within the framework of the dissertation research «Assessment of the operational reliability of metal spans with damage and methods of their monitoring». The object of the research is a typical superstructure with an estimated length of 66 m in the condition of complete or partial failure of various truss elements due to mechanical damage. As a result of the research, the nature of the redistribution of the stress-strain state of the superstructure was revealed. It is determined that the spatial redistribution of the stress-strain state occurs along the path of increasing stresses in the lattice elements of the parallel truss and longitudinal links. According to the control of allowable stresses and deflections, the survivability of the superstructure is maintained while 70 % of the single truss element elimination is reached. The elements for which mechanical damage is most dangerous have been identified.

Aerodynamic interference mechanism of vertical vortex-induced vibration of a ∏-shaped girder paralleled with a truss girder

In this study, the aerodynamic interference characteristics and mechanism of vertical vortex-induced vibration (VIV) of a ∏-shaped steel–concrete composite girder of a highway cable-stayed bridge and a steel truss girder of a railway cable-stayed bridge are investigated via experimental and numerical simulation methods, respectively. To this end, firstly, wind tunnel tests are conducted on section models with a geometry scale of 1:60, consisting of the ∏-shaped girder paralleled with truss girders to investigate their aerodynamic interference behaviors. Moreover, the fluid–structure interaction (FSI) approach based on dynamic mesh and user defined functions (UDF) is applied to study the wind-induced vibrations (WIV) of the single ∏-shaped girder and two parallel main decks for wind attack angle of 0°, respectively. Furthermore, the characteristics of vorticity, surface pressure, and vortex-induced force (VIF) distributions of the ∏-shaped girder and the truss girder are analyzed to investigate the aerodynamic interference mechanism. The results reveal that, the significant vertical vortex-induced vibrations (VIV) of the single ∏-shaped girder are observed, however, no obvious vertical VIV occurs for the single truss girder. Moreover, when the truss girder locates in the windward of the ∏-shaped girder, no obvious vertical VIV responses are observed. However, the ∏-shaped girder and the truss girder both exhibit significant vertical VIV responses for wind from the ∏-shaped girder side, and the maximum vertical VIV amplitude of the ∏-shaped girder is amplified by 32% compared with the single ∏-shaped girder. The vortices shed from the truss girder section disrupt the regular vortex shedding of the ∏-shaped girder section, thus suppressing the VIV of the ∏-shaped girder section. The WIV of the truss girder section is due to the forced vibration caused by the vortex impact of the dominant vortices shed from the ∏-shaped girder section. As the downstream flow field is blocked by the truss girder section, the scale and intensity of the dominant vortices is increased, leading to an amplification of the VIF and the VIV amplitude of the ∏-shaped girder section.

Design and Construction of High-Performance Long-Span Steel Transfer Twin Trusses Applied in One Hospital Building in Hong Kong

Long-span steel trusses are increasingly used in high-rise buildings to replace reinforced concrete thick transfer plates due to their light weight but high load-bearing capacity. To support multiple stories above the steel transfer trusses, a comprehensive method based on second-order direct analysis has been applied for design optimization of long-span steel transfer trusses in one hospital redevelopment project in Hong Kong. In the project, several 35 m long-span steel transfer trusses are adopted at the 3rd to 5th floors to support the upper 15-story reinforced concrete structure. Innovative technologies such as integrated global and local optimization and integrated design and construction have been explored and made to achieve better uniformity and compatibility in structure. In particular, twin trusses with better structural performance, less fabrication cost and ease of constructability are studied and finally adopted in primary trusses to replace the original scheme of single trusses. The optimal scheme has brought both cost and time saving in fabrication, construction, operation and maintenance stages.

Vibration Power Flow and Transfer Path Analysis of Two-Dimensional Truss Structure by Impedance Synthesis Method

The violent vibration of truss structures may cause fatigue, faults, or even an accident. Aiming to analyze the vibration power flow and transfer path of two-dimensional truss structures in the mid and high-frequency domain, this paper proposed a fast dynamic calculation method—the impedance synthesis method (ISM)—which is based on an analytical equation with litter elements. Firstly, the global coordination vibration impedance of a Timoshenko beam truss is derived; Secondly, a dynamic model of a two-dimensional truss structure is built up with a single truss beam by force balance and geometric continuity; then, real and imaginary parts of dynamic responses and force in simple and periodically truss structures are verified by compared with FEM results, respectively; finally, the transfer path analysis (TPA) method is applied to separate the contribution of different transfer paths of power flow in periodical truss structures. The results show that the TPA method can easily find the line spectrum frequency of power flow, which should be considered in vibration control. This method can also be expanded to three-dimensional, honeycomb, and other truss beam structures.

Practice-Accessible Methodology for Nonlinear Refined Analysis of Gusset Plate Connections for Steel Truss Bridges

A new approach is proposed for estimating structural capacity of gusset plate connections of steel truss bridges. The approach involves nonlinear refined analysis of a truss model, consisting of a single truss made of shell elements for two gusset plates at a subject connection and frame elements for truss members. Connectors (bolts or rivets) are excluded from the proposed model in order to simplify the model, with the knowledge that their associated failure modes can be addressed by simplified design calculations. Only yielding and buckling failure modes of gusset plates are considered. The new approach is calibrated by comparison with laboratory test data from NCHRP Project 12-84. The primary intent of this paper’s approach is to reduce the complexity of the refined analysis developed under this National Cooperation Highway Research Program project and make it more user-friendly to load rating engineers seeking accurate estimation of gusset plate capacity. Further, an imperfection sensitivity curve characterizing reduction in capacity as a function of lateral imperfection (gusset plate out-of-flatness) in gusset plate geometry is introduced as an added tool for the load rating engineer, providing more confidence in capacity estimation. Based on a limited case study, the proposed refined analysis provides an estimate of gusset plate capacity that is approximately equal to capacity calculated by the truncated Whitmore method of the AASHTO Manual for Bridge Evaluation (2018). In other words, the proposed approach validates the truncated Whitmore method as compared to the more conservative partial shear method of the AASHTO Manual.

EFFECT OF DIFFERENT WOOD DOWELS ON MECHANICAL PROPERTIES OF TRIANGULAR GIRDER TRUSSES

Static load tests were carried out on three kinds of triangular girder trusses with different diameter wood dowels, and the effects of that on the structure of girder trusses were discussed. It was found that there was a good synergy between the wood dowels and the girder trusses. Among the triangular girder trusses with different diameters, the 16 mm diameters had the best energy dissipation performance increased by 184% and deformation resistance of 0.73 mm; the 20 mm diameters had the best stability performance, the better bearing capacity of 60.42 kN and deformation resistance of 0.82 mm. The bearing capacity of the double girder trusses was 2.06-2.25 times that of two single trusses, which had the ability to ‘one plus one is greater than two’.

Progressive collapse resistance analysis of secondary shielding installation platform for A-type tank

As a key supporting equipment for the construction of LNG carriers, the installation platform undertakes the support and guarantee of LNG carrier tank internal construction. This paper takes the secondary shielding installation platform of A-type tank as the object of study, the study firstly considers the semi-rigidity of the nodes and the material nonlinearity based on finite element software, and then the residual structure is calculated using static nonlinear method after single truss, two trusses and three trusses are invalid simultaneously. The research results show that the truss with higher components importance coefficient has greater impact on the residual structure when the truss is invalid; After the 2 trusses of installation platform become invalid completely, the further progressive collapse will not occur; When A1-HJ, A2-HJ and A2-HJ are dismantled at the same time, it will lead to the local progressive damage, which can cause the collapse of large-scale structures. The research findings can support the design and use of the installation platform.

On the investigation of providing space truss roofs with ductility until failure under monotonically increasing vertical loads

The aim of this paper is to investigate the nonlinear behavior of space truss roofs subject to different load accumulation forms considering the effect of initial imperfection and slenderness ratio of the truss members. For this, a typical space truss roof using MERO-connection type with flat double-layer was selected as a sample. 3D model of the roof was developed and analyzed by using OpenSEES. Nonlinear behavior of each typical bar of the space truss roof, which, was mainly composed of particular sub-elements such as a tubular element, bolts, sleeves and spheres was represented by a single truss bar. Axial load-displacement relationship of each single truss bar was obtained from nonlinear analysis performed under reversal cyclic loading. Besides, three different types of load distribution that simulates accumulation of rainwater or drifted snow were taken into account as an external load acting on upper layer of the roof system. Analyses results showed that load carrying capacity of the space truss roofs was susceptible to the form of accumulation and reduces abnormally when the accumulation, in particular, occurred locally. Furthermore, failure mode of the system designed with optimal solution was dominated by buckled truss bars and brittle failure occurred. Also initial imperfection had a negative effect on the members in compression.

Cost optimisation of glued laminated timber roof structures using genetic algorithms

Roof structures comprising of heavy timber trusses and purlins made of glued laminated timber, as well as dowels and metal plates used as mechanical joints, are widely employed, among others, in agro-industrial settings that require large open areas. This paper presents the economic optimisation of such roof structures through the use genetic algorithm models. Two phases of optimisation were carried out: firstly, in two dimensions for a single truss and, then, an entire roof structure in three dimensions. Both models followed a discrete approach, i.e. the optimisation of the cross-section was limited by the characteristics of the commercially-available glulam timber boards, an aspect not yet included in the literature. Therefore, the models allowed the influence of the laminate thickness in the optimisation to be estimated, but also allow comparisons with the continuous cross-section variation found in the literature. Furthermore, the optimisation took into account a range of configurations of trusses, number of joints and separation between trusses and purlins. The genetic algorithms were shown as an efficient optimisation tool for roof glulam structures as a function of the laminate thickness. Among the results obtained, the most cost-effective solutions were those comprised of the fewer number of joints in the trusses and the lowest laminate thickness of those studied. Moreover, the optimal separations between trusses and purlins were also determined. Finally, a simplified method of optimum pre-dimensioning was also proposed.

Influence of Different Connection Types on Mechanical Behavior of Girder Trusses

The static test of two single light wood trusses and two girder trusses were carried out to explore the performance enhancement effect of girder trusses and the influence of different connection types on the mechanical behavior, which was studied through the comparison of the test results of four trusses. It is found that the girder trusses can show better load-carrying capacity and anti-deforming ability compared with which simply increases the cross-section size of the members. Because of the advantage of the connection materials and the non-fastening connection mechanism, the wood pin-connected truss has more ultimate bearing capacity which is 2.6 times of single truss, and better deformation resistance which is only 66.2% of the nailed one’s creep value.

WOODEN TRUSSES RECONSTRUCTION AND ANALYSIS THROUGH PARAMETRIC 3D MODELING

Abstract. This paper aims to indicate a new methodological approach, based on generative algorithms, to attempt a more in-depth and transversal understanding of the behavior of these wooden structures. The developed method accelerates modeling procedures and brings on new tools for analyzing these structural systems when surveyed through TLS devices. The main topic of this work is the most recent step of a wider research project that has analyzed a few wooden roofing structures in the area of bologna. These case studies are represented by a set of important churches in Bologna, all built between the 16th and 18th centuries, whose pitched roofs are supported by timber trusses. Among them, the most impressive is the wooden truss in the St. Peter Cathedral that has approximately 26 meters of span, 7 meters of height for nearly 9 tons of weight. It also shows a complex static conception with the coexistence of an external nondeformable triangle and an internal virtual discharging arc. The focus is on the transformation of the point cloud into 3D models using parametric modeling tools such as Grasshopper generative algorithms. These algorithms, once created for a single truss, allow to automatically generating 3D models of all trusses, changing only input parameters.

Truss optimization with buckling considerations using geometrically nonlinear beam modeling

A unified approach that accounts for various buckling phenomena in truss design optimization is presented. Euler buckling of slender members, global buckling and stability of sequences of bars are all considered by optimizing the geometric nonlinear response instead of by imposing a large number of constraints. In the proposed approach, each truss member is modeled as a sequence of co-rotational beam elements with appropriate end-releases. By applying various imperfections, buckling of single truss members, unstable configurations and global buckling can be taken into account implicitly. A detailed discussion on key aspects of the proposed approach is presented, showing how the choice of imperfections highlights certain buckling types and leads to respectively stable designs. A comparison to other approaches and to results from the literature shows that the proposed approach can ensure local and global stability without actually imposing any buckling constraints. Finally, truss optimization for various levels of global deflections is presented, exposing the potential of the formulation for optimizing highly nonlinear responses.

Metal Plate–Connected Wood Trusses Exposed to Out-of-Plane Lateral Loads

AbstractOut-of-plane loading of trusses occurs when a horizontal force is applied to the truss perpendicular to the plane of the truss. Because trusses are not specifically designed for lateral loading, the behavior of trusses during construction before adequate bracing is installed is unknown. Examples of out-of-plane loading include wind and seismic forces, as well as forces from fall-arrest anchors attached to trusses during construction. The purpose of this paper was to measure the maximum load and rotation of a single truss exposed to a horizontal out-of-plane load applied by a fall-arrest anchor. A specialized testing fixture was used to apply a horizontal load to a single unbraced truss attached to two stem walls, representing a typical construction application. A set of monoslope queen-post trusses with two different pitches were used, and load was applied at both the truss eave and peak. Maximum loads for a single truss were much less than the expected 8 kN required to act as a personal fall-arre...

Hydroponic Production of Low-Potassium Tomato Fruit for Dialysis Patients

ABSTRACTChronic kidney failure is becoming a global problem. Patients with kidney failure cannot excrete excess K, and their intake of K is often restricted. If low-potassium (K) tomato fruit can be produced, it can improve the dietary options of dialysis patients and their quality of life. A method of producing low-potassium (K) content tomato (Solanum lycopersicum L.) fruit was investigated. Several medium-sized tomato cultivars were tested, and the K supply was restricted using hydroponic production. Some plants were maintained through setting of a single fruit truss, and fruit fresh weight was not affected by K restriction. Total K uptake per plant decreased by 92% with lower K compared to conventional cultivation in which K content in fruit decreased by only 25%. Other plants were maintained until three trusses per plant were set, and fruit K content decreased 40% to 60% depending on cultivar because of K restriction. The cv. Aichan was the most sensitive and cv. Frutica was the least sensitive to K restriction. Total soluble solids content decreased slightly. Titratable acid content was affected by K restriction and decreased 20% to 40% depending on cultivar. In either case, K withdrawn in hydroponic culture following anthesis of the third truss was effective in producing low-K tomato fruit and could decrease fruit K content to at least 50% of expected tomato fruit K content.

A Convenient Method for Calculating Internal Force of Rod for Tower Crane

This paper made an assumption which considered the structure of tower crane as truss structure and equated the complex spatial structure of tower body under multi-loads to single planar truss structure. The calculation model of internal force of rods was built. The calculation formulas of four types of trellis tower mast configuration commonly used were derived. The result based on the real project given by the calculation formulas agreed with the result given by the finite element software. These explicitly expressed formulas were simple and easy to calculate by hand. An accurate and efficient method to calculate internal force of rods of tower crane was provided.

The Structural Performance of Precast Lightweight Foam Concrete Sandwich Panel with Single and Double Shear Truss Connectors Subjected to Axial Load

The progressive research upon the issue on renewal technology that can improve the construction industry has initiated the study of Precast Lightweight Foam Concrete Sandwich Panel (PLFP) as an alternative to Industrialize Building System (IBS). This paper reports the analysis of structural behavior of PLFP with double shear connectors under axial load. The PLFP panel consists of two wythes which enclosed a layer of polystyrene layer. Six (6 mm) rebar was used as the vertical and horizontal reinforcement and 9 mm steel bar bent at 450 was used as the connector. Full scaled panel was tested under axial load till failure. It was found that PLFP panel with double shear truss connector has higher ultimate strength capacity compared to PLFP with single shear connectors ehen tested under axial load.

Numerical Investigation of Corrugated Wire Mesh Laminate

The aim of this work is to develop a numerical model of Corrugated Wire Mesh Laminate (CWML) capturing all its complexities such as nonlinear material properties, nonlinear geometry and large deformation behaviour, and frictional behaviour. Development of such a model will facilitate numerical simulation of the mechanical behaviour of the wire mesh structure under various types of loading as well as the variation of the CWML configuration parameters to tailor its mechanical properties to suit the intended application. Starting with a single strand truss model consisting of four waves with a bilinear stress-strain model to represent the plastic behaviour of stainless steel, the finite element model is gradually built up to study single-layer structures with 18 strands of corrugated wire meshes consistency and double- and quadruple-layered laminates with alternating crossply orientations. The compressive behaviour of the CWML model is simulated using contact elements to model friction and is compared to the load-deflection behaviour determined experimentally in uniaxial compression tests. The numerical model of the CWML is then employed to conduct the aim of establishing the upper and lower bounds of stiffness and load capacity achievable by such structures.

Shaping and Ultimate Loading of Space Trusses, Shaped by Post-Tensioning Technique

By means of post-tensioning technique, planar space trusses, particularly the single chord space trusses can be formed into curved forms. This novel process of the shape formation results in the architecturally interesting forms with the sufficient structural stability and stiffness, and with the additional advantage of being economical due to eliminating the need to use scaffolding or heavy cranes for their construction. This paper deals with the shape formation and loading tests as well as analyses of the single chord space trusses shaped by post-tensioning technique. To validate analyses and investigate effect of curvature of the shaped models on the results, two models are included; a gently curved dome-shape and a sharply curved barrel-vault. First, shape formation analysis is carried out and next, buckling load of shaped models in loading analyses are determined and findings are compared with the experimental results. Also, effect of the residual stresses of shape formation step on the results of loading analysis is investigated.

Effects of Supplemental Lighting within the Canopy at Different Developing Stages on Tomato Yield and Quality of Single-Truss Tomato Plants Grown at High Density

The single truss tomato production system (STTPS) was used to grow tomato plants at a density of 14.3 plants·m−2 for increasing the tomato yield in Japan. We applied supplemental lighting within the canopy at different tomato development stages to identify the most sensitive stage at which supplemental lighting will most effectively increase yield and quality of tomato fruits. Fluorescent lamps were used to supply intra-canopy lighting to tomato plants (5:00–21:00) during the stages of anthesis (stage 1), rapid fruit development (stage 2), fruit ripening (stage 3), and from initial anthesis to red-ripe fruit (whole stage), respectively. Supplemental lighting applied to tomato plants during stage 2 and whole stage significantly increased the yield and sugar content of tomato fruits. Moreover, the contribution of supplemental lighting to the daily increase of tomato yield was highest at stage 2. The increase of fruit fresh weight and amount of supplemental lighting showed positive linear relationship. Supplemental lighting did not affect the ascorbic acid content of tomato fruits, fruit number per plant, and plant shoot weight among all the treatments. Thus, based on economic advantage, the use of supplemental lighting during the rapid fruit development stage of tomato plants under STTPS was most efficient.

Study on Dynamic Characteristic of 64m Railway Steel Truss Bridge on Expanding Heavy-Load Transport Condition

Through theoretical calculation, systemic analysis of dynamic performance of the 64m single and double line railway steel truss bridges on the expanding condition and conventional condition. Contrast and analysis the main dynamic performance parameters of bridges on the two kinds of operating condition. In 64m steel truss bridges of Shuozhou-Huanghuagang Railway application practice proves that on expanding heavy-load condition, the main dynamic performance parameters of bridges are slightly larger than conventional condition, but the variation law of vertical acceleration of mid-span is different.