Combined Truss Research Articles

SYNTHESIS OF RATIONAL CONSTRUCTIVE SOLUTION OF STEEL ROOF TRUSSES

The article examines the issue of the occurrence and influence of bending moments on the bearing capacity of a combined steel truss made of rectangular bent-welded profiles. A comparative analysis of technical and economic indicators in terms of material intensity, labor intensity, and cost of traditional-typical and lightweight combined steel trusses was carried out. The paper examines steel trusses of long-span buildings with a span of 30 m. The force graphs (bending moments and axial forces) for various calculation schemes of the combined steel truss are shown. An analysis of the forces in the combined truss for different ways of connecting the lattice to the chords was carried out. The plot of normal stresses along the middle line of the stiffening girder of the combined truss for various calculation schemes is presented. The load-bearing capacity of compressed rods with different connection methods was calculated. According to the research results, an engineering method of taking into account the influence of bending moments is proposed.

EFFICIENCY OF RATIONAL COMBINED STEEL TRUSSES

In this article, a comparative assessment of the technical and economic efficiency of rational combined steel trusses with typical trusses according to DSTU is considered. New rational constructive combined forms of covering systems (roof trusses) have been developed for spans of 18, 24 and 30 m, with less material consumption and labor intensity compared to existing analogues. It is shown that the mass of such rational combined steel trusses with a span of 18 m is less than a typical one by 13% to 16.5% depending on the value of load, for a combined truss with a span of 24 m the mass is less by 20.5% to 25%, and for a 30 m - from 12.5% to 17%. The results of the evaluation of the technical and economic efficiency are presented. The main criterion for the economic efficiency of constructions is general costs. A comparison of the technical and economic efficiency proves that our proposed option provides a significant saving of material and labor resources.Widespread implementation can provide a significant economic effect, which is important in the conditions of post-war reconstruction of Ukraine.

New design form of steel combined roof trusses

In this article, a new method of increasing the efficiency of combined steel roof trusses is proposed and considered. A rational shape of the steel roof truss, including its topology and rational geometric parameters, was obtained, but without obtaining a rational SSS. A proposed method provides the adjustment of SSS in the truss by changing the upper belt panel length. On the basis of the obtained rational SSS of the combined truss, a new structural form is proposed. It is shown that thanks to the proposed method, it is possible to obtain a more efficient design by 18-32%, compared to typical ones. The diagram of the moments in the stiffness beam of the reference truss and the truss with SSS regulation is given. Further directions of research are determined, in particular, the development or improvement of rational structural forms and the use of calculation method of regulation of SSS in the stiffness beam of the steel combined truss.

STRUCTURAL EFFICIENCY OF STEEL COMBINED TRUSSES

In this article on increasing the efficiency of steel combined structures, the tasks of rational design, regulation and control of structural parameters of elements, the use of steels with increased mechanical properties are considered. It is shown that for a six-span stiffening girder of a combined truss with elastic supports, which operates under a distributed load, the moment is 72 times smaller than the moment of a single-span beam. It is suggested to use high-strength steel for truss braces. Rationality criteria are proposed. On the basis of rationality criteria, new steel combined trusses were developed and their models were designed for stress tests. The results of experimental studies of models of combined trusses are presented. The results of experimental studies conducted on models of steel combined trusses qualitatively and quantitatively confirmed the theoretical results obtained on the basis of the proposed theory.

Conceptual Design of Cable-Supported Bridges with Road and Railway Traffic

The design and analysis of Cable-Supported Bridges (CSBs) with Road and Railway Traffic (RRT) are very complex due to the many boundary conditions and structural options, e.g. the railway tracks and road lanes can be arranged on one level, two levels, staggered levels or mixed levels; the main girders may be truss girders, a single box girder, separated box girders or a combined truss–box girder. With the experience of several national and international competitions, this paper describes the main principles and the conceptual design of CSBs with RRT, mainly focused on the selection of the relative location of road and railway, the options for the main girders and the relative locations of pylon legs. Three CSBs with RRT are presented in more detail to demonstrate how to face the challenges and solve boundary constraints, and to meet the requirements of the client and sustainable development at the conceptual design stage.

Study on Surrounding Rock Deformation Mechanism and Control of Roadway with Large Section and Extra-Thick Top Coal

In order to solve the problem of safe and rapid excavation and support of roadway with large section and extra-thick top coal under complex geological conditions, the deformation mechanism and control of roadway are analyzed by means of field investigation, numerical simulation, theoretical analysis, and field practice, taking the 2203 transportation roadway of a mine in Shanxi Province as the engineering background. The results show the following: (1) the concentration of normal tensile stress in the middle of large-span roadway roof and end shear stress is significant, which may easily lead to the separation of roof and the extrusion deformation of surrounding rock; (2) the surface shear failure depth of the roadway side is large, and the insufficient length of the bolt, the small density of the protective side, and the insufficient support strength are easy to cause the bulge and splitting of the coal wall; (3) roof joints and fractures are developed, and the dirt band of different thickness occurs, so it is easy for the roof separation and the anchor solids to cut down along the weak surface of the dirt band; (4) the geological structure produces horizontal movement of surrounding rock, which easily leads to poor supporting effect of roadway roof and material deformation and failure. Finally, a safe and economic comprehensive support system of “high-strength, high-resistance, and high-prestressed anchor cable support system + high-strength support of the two sides roadway + U-shaped anchor cable combined truss” is proposed, and the control mechanism is explained and applied successfully in the field.

Toward holistic tension- or compression-biased structural designs using topology optimization

The efficiency of a structural design relies considerably on the knowledge and experience of its design engineer. It is critical to choose the proper structural system, cross-sections, and materials as these elements significantly influence the design’s performance. Establishing computational methods that support the engineer in the design process and facilitate more objective solutions therefore represents an important step in creating proficient structural designs.In this paper, a novel approach is introduced to generate topology optimization results with an intended bias toward tension or compression for practical application in structural engineering. The results are deduced from the example of continuum elements and extended to cover truss topology optimization – assuming a linear-elastic, isotropic material model – in addition to combined truss–continuum topology optimization with bilinear, orthotropic material behavior. The effects of creating such solutions are analyzed at a simple theoretical problem. For the purposes of practically designing reinforced concrete structures, the preferable scope of application of each of the three methods is evaluated. The benefit of creating biased solutions is demonstrated by assessing their structural performance, robustness, and overall suitability on both global (system) and local (cross-section) scales and by applying them to common problems in structural engineering.

Research on the mechanical properties of a glass fiber reinforced polymer-steel combined truss structure.

An assembled plane truss structure used for vehicle loading is designed and manufactured. In the truss, the glass fiber reinforced polymer (GFRP) tube and the steel joint are connected by a new technology featuring a pretightened tooth connection. The detailed description for the rod and node design is introduced in this paper, and a typical truss panel is fabricated. Under natural conditions, the short-term load test and long-term mechanical performance test for one year are performed to analyze its performance and conduct a comparative analysis for a reasonable FEM model. The study shows that the design and fabrication for the node of an assembled truss panel are convenient, safe, and reliable; because of the creep control design of the rods, not only does the short-term structural stiffness meet the design requirement but also the long-term creep deformation tends towards stability. In addition, no significant change is found in the elastic modules, so this structure can be applied in actual engineering. Although the safety factor for the strength of the composite rods is very large, it has a lightweight advantage over the steel truss for the low density of GFRP. In the FEM model, simplifying the node as a hinge connection relatively conforms to the actual status.

Finite Element Analysis on Static Performance on Combined Truss with Rectangular Steel Tube and Concrete-Filled Steel Tube

Finite element analysis on three trusses was carried out in order to study the performance of combined truss with steel tube and concrete filled steel tube. The first specimen was a RHS truss, the second one was a combined truss with steel tube and concrete filled steel tube, and the third one was a concrete-filled steel tube truss. The results show that the finite element model can reflect the static performance of combined truss and can carry out the affective parameters analysis, which can offer theory evidence for engineering application of combined truss. The damage of three trusses was all due to the joint failure and the failure mode was all punishing shearing failure, but the concrete filled changed by the failure place of joints. The bearing capacity of three trusses was controlled by the jionts and the strength and stiffness of jionts were increased by the concrete filled in the chord, therefore the bearing capacity of trusses was increased while the deformation of trusses was decreased. In combined truss with steel tube and concrete filled steel tube, the concrete-filled steel tube joints can improve the bearing capacity and the steel tube joint can satisfy the requirements of deformation, which have obvious advantages in the engineering application.

Static Performance Analysis on Combined Truss with Steel Tube and Concrete-Filled Steel Tube Based on Total Strain Crack Constitutive Model

Based on the total strain crack constitutive model and the available testing data, finite element model on three trusses were established by the finite element procedure MIDAS/FEA and the analysis were executed in order to verify the validity of constitutive model and study the static performance of combined truss. The results show that the finite element model based on total strain crack constitutive can reflect the static performance of combined truss and can carry the affective parameters analysis, which can offer theory evidence for engineering application of combined truss. The failure of three trusses were due to joint failure, however the failure modes were different and changed by the concrete filled in chord. The bearing capacity of three trusses was controlled by the jionts and the strength and stiffness of jionts were increased by the concrete filled in the chord, therefore the bearing capacity of trusses was increased while the deformation was decreased. In combined truss with steel tube and concrete filled steel tube, the concrete-filled steel tube joints can improve the bearing capacity and the steel tube joint can satisfy the requirements of plastic deformation, which have obvious advantages in the engineering application.

RC 보에서의 전단저항기구와 주철근의 부착 작용과의 관계

The uniform truss mechanism is widely accepted as a shear transfer mechanism in reinforced concrete members. However, the uniform truss action cannot be expected when the bond stress distribution is not constant along longitudinal bars. A test method in which only the truss action takes place is developed and conducted to investigate the truss actions under various bond contributions. Based on the experimental results and analysis, the following findings can be obtained: 1) The bond stress distribution depends on the axial compression force, the amount of shear reinforcement and loading conditions. 2) The analysis using the combined truss model consisting of uniform and fan-shape trusses can predict the experimental results