Search Results (10)

Many existing structures require retrofitting and reinforcement due to aging and damage. The stability of the retrofitted structure is key to the retrofitting scheme, while construction safety during the retrofitting process is another crucial consideration. This study proposed an evaluation method for assessing the stability and construction process of steel structure retrofitting projects based on an ANSYS finite element analysis. By establishing a nonlinear finite element model of a retrofitted gymnasium roof truss structure, the overall stability of the system was systematically verified. The dynamic simulation of demolition and retrofitting procedures was conducted using the birth-and-death element technique, and a comprehensive safety assessment framework covering the entire construction process was developed. The case analysis demonstrated that this method can simulate the redistribution of internal forces during component demolition and identify potential risks. The effectiveness of the retrofitting strategy was evaluated by comparing the nonlinear stability coefficients of the structure before and after retrofitting, indicating improved performance within the scope of the finite element model. The research results demonstrated the feasibility of incorporating modeling, simulation, and assessment in retrofitting projects and provided a reference for similar retrofitting projects. Full article

Cold-formed steel (CFS) unsymmetrical angles are increasingly used in structural applications such as portal frames, roof trusses, and transmission towers. However, research on built-up face-to-face unsymmetrical CFS angle columns (FFUACs) with stiffeners remains limited. This study addresses this gap by presenting the findings from six experimental investigations on intermediate FFUACs connected using intermittent screw fasteners. The results offer insights into failure deformation patterns and load-axial shortening behaviour. A nonlinear finite element (FE) model was developed to account for material and geometric nonlinearity, with experimental results used for validation. This study contributes 166 new data points, including six experimental tests under concentric compression and 160 finite element analysis (FEA) results focused on the compressive strength of FFUACs. Additionally, this study evaluates the performance of existing design guidelines based on the direct strength method (DSM). The DSM strength predictions were found to be less conservative for stub FFUAC specimens that failed due to local buckling and more conservative for short FFUAC specimens that failed due to a combination of local and flexural buckling. A revised DSM methodology is proposed to address these discrepancies. Full article

Scholars and engineers have increasingly focused on the safety of steel-structure buildings. An accurate analysis can substantially reduce the collapse probability of these buildings. This paper proposes a novel risk analysis model to assess the safety of steel-structure buildings. The vector entropy method and weight clustering were used to improve the controlled interval and memory (CIM) model. The proposed model has the advantages of a straightforward modeling approach, strong adaptability, and logical relationships. The new strategy improves the reliability and stability of the CIM model results when the maximum membership principle is not applicable. The Jiangxi Exhibition Center in China, which has a steel truss roof, is used as a case study. The results indicate a high safety risk of the project and the need for maintenance and repair. The improved CIM model has higher stability and adaptability for analyzing the safety risks of steel structure than the standard CIM model. Full article

In response to the large-scale instability failure problem of designing coal pillars and support systems for gob-side entry driving (GSED) in high-stress soft coal seams in deep mines, the main difficulties in the surrounding rock control of GSED were analyzed. The relationship between the position of the main roof breaking line, together with the width of the limit equilibrium zone and a reasonable size for the coal pillar, were quantified through theoretical calculations. The theoretical calculations showed that the maximum and minimum widths of the coal pillar are 8.40 m and 5.47 m, respectively. A numerical simulation was used to study the distribution characteristics and evolution laws of deviatoric stress and plastic failure fields in the GSED surrounding rock under different coal pillar sizes. Theoretical analysis, numerical simulation, and engineering practice were comprehensively applied to determine a reasonable size for narrow coal pillars for GSED in deep soft coal seams, which was 6.5 m. Based on the 6.5 m coal pillar size, the distribution of deviatoric stress and plastic zones in the surrounding rock of the roadway, at different positions of the advanced panel during mining, was simulated, and the range of roadway strengthening supports for the advanced panel was determined as 25 m. The plasticization degree of the roof, entity coal and coal pillar, and the boundary line position of the peak deviatoric stress zone after the stability of the excavation were obtained. Drilling crack detection was conducted on the surrounding rock of the GSED roof and rib, and the development range and degree of the crack were obtained. The key areas for GSED surrounding rock control were clarified. Joint control technology for surrounding rock is proposed, which includes a combination of a roof channel steel anchor beam mesh, a rib asymmetric channel steel truss anchor cable beam mesh, a grouting modification in local fractured areas and an advanced strengthening support with a single hydraulic support. The engineering practice showed that the selected 6.5 m size for narrow coal pillars and high-strength combined reinforcement technology can effectively control large deformations of the GSED surrounding rock. Full article

Structural fault diagnosis is an important subject for ensuring the normal use of structures. More test data will help to improve the accuracy and reliability of structural fault diagnosis. Therefore, a structural fault detection algorithm based on static–dynamic mixed sensitivity analysis is proposed. The vibration parameters used were the vibration modes of some of the nodes in the structure measured by the vibration test system. The static response parameter used was the vertical displacement of the structure under the gravity load measured by the static test system. In particular, the gravity load and the structure were connected rigidly to form a new added-mass system. The vibration mode of the additional-mass system was measured again to obtain more equations for fault evaluation. Based on the static and dynamic measurement data, the failure coefficients of all components in the structure were calculated through the mixed sensitivity of the static displacement and vibration-mode shape. According to the calculated value of the failure coefficient, the failure state of all components in the structure could be finally evaluated. The main innovation of the proposed method was the use of the static load as a part of the new added-mass system to obtain more vibration parameters for the defect diagnosis. The implementation process and effect of this method were verified using a numerical truss structure and an experimental steel beam structure. Moreover, the defect diagnosis results of the proposed hybrid method were compared with those of a pure static algorithm and a pure dynamic algorithm to illustrate the advantages of the hybrid method. The research results showed that this method has the advantages of simple implementation and high diagnosis accuracy. Especially for symmetric structures, the proposed method can successfully avoid the possible missed diagnoses of the pure static algorithm and pure dynamic method. The algorithm provides a simple and feasible method for structural defect identification. Full article

Structural stress and deformation monitoring and analysis were carried out for the 54 m long-span steel roof truss. To ensure the safety of the construction process, the stress and deformation of the steel roof trusses were monitored throughout the construction process. The numerical modeling of the structures with six different working conditions was carried out, and the points with the most critical values of stress and deformation were found. This work provides a theoretical basis for field monitoring during and after construction. The results show that the maximum vertical displacement of a steel roof truss during all modeled working conditions and the maximum measured displacement are within the Chinese building code’s requirements. The maximum value of stress found during analysis of the structure during the construction process and the maximum measured stress are much less than the yield stress. The structural stress remains in the elastic range. The reasons for the differences between the calculated and measured results were analyzed. Full article

This study investigated the failure of the roof, with steel truss construction, of a factory building in Tekirdag in the northwestern part of Turkey. The failure occurred under hefty weather conditions including lightning strikes, heavy rain, and fierce winds. In order to interpret the reason for the failure, the effects of different combinations of factors on the design and dimensioning of the roof were studied. Finite element analysis, using the commercial software Abaqus (Dassault Systèmes, Vélizy-Villacoublay, France), was performed several times under different assumptions and considering different factors with the aim of determining the dominant factors that were responsible for the failure. Each loading condition gives out a characteristic form of failure. The scenario with the most similar form of failure to the real collapse is considered as the most likely scenario of failure. In addition, the factors included in this scenario are expected to be the responsible factors for the partial collapse of the steel truss structure. Full article

Space trusses are structural systems, generally made of tubes, used worldwide because of their advantages in covering long-span roofs. In addition to having a low cost, the truss weight is relatively reduced. The load capacity of these structures depends also on the strength of their node connection. Connections made with the superposition of flattened tube ends trespassed by one bolt are, generally, known as typical nodes. They are inexpensive but present eccentricities that reduce significantly the strength of such space trusses. To increase the truss load capacity, this research presents the results of an experimental program to reduce the eccentricities of the typical nodes. This reduction is done with a new type of spacer made of encapsulated concrete with steel fiber or sisal fiber. The experimental tests showed that the trusses with typical nodes collapsed under reduced load by local failure due to high distortions at the nodes. The trusses with encapsulated concrete spacer showed good results, with an increase in collapse load of 36% and failure by buckling bars. Full article

Three-dimensional (3D) printing technologies are transforming the design and manufacture of components and products across many disciplines, but their application in the construction industry is still limited. Material deposition processes can achieve infinite geometries. They have advanced from rapid prototyping and model-scale markets to applications in the fabrication of functional products, large objects, and the construction of full-scale buildings. Many international projects have been realised in recent years, and the construction industry is beginning to make use of such dynamic technologies. Advantages of integrating 3D printing with house construction are significant. They include the capacity for mass customisation of designs and parameters to meet functional and aesthetic purposes, the reduction in construction waste from highly precise placement of materials, and the use of recycled waste products in layer deposition materials. With the ultimate goal of improving construction efficiency and decreasing building costs, the researchers applied Strand 7 Finite Element Analysis software to a numerical model designed for 3D printing a cement mix that incorporates the recycled waste product high-density polyethylene (HDPE). The result: construction of an arched, truss-like roof was found to be structurally feasible in the absence of steel reinforcements, and lab-sized prototypes were manufactured according to the numerical model with 3D printing technology. 3D printing technologies can now be customised to building construction. This paper discusses the applications, advantages, limitations, and future directions of this innovative and viable solution to affordable housing construction. Full article

To develop the cold-formed steel (CFS) building from low-rise to mid-rise, this paper proposes a new type of CFS composite shear wall building system. The continuous placed CFS concrete-filled tube (CFRST) column is used as the end stud, and the CFS-ALC wall casing concrete composite floor is used as the floor system. In order to predict the seismic behavior of this new structural system, a simplified analytical model is proposed in this paper, which includes the following. (1) A build-up section with “new material” is used to model the CFS tube and infilled concrete of CFRST columns; the section parameters are determined by the equivalent stiffness principle, and the “new material” is modeled by an elastic-perfect plastic model. (2) Two crossed nonlinear springs with hysteretic parameters are used to model a composite CFS shear wall; the Pinching04 material is used to input the hysteretic parameters for these springs, and two crossed rigid trusses are used to model the CFS beams. (3) A linear spring is used to model the uplift behavior of a hold-down connection, and the contribution of these connections for CFRST columns are considered and individually modeled. (4) The rigid diaphragm is used to model the composite floor system, and it is demonstrated by example analyses. Finally, a shaking table test is conducted on a five-story 1:2-scaled CFS composite shear wall building to valid the simplified model. The results are as follows. The errors on peak drift of the first story, the energy dissipation of the first story, the peak drift of the roof story, and the energy dissipation of the whole structure’s displacement time–history curves between the test and simplified models are about 10%, and the largest one of these errors is 20.8%. Both the time–history drift curves and cumulative energy curves obtained from the simplified model accurately track the deformation and energy dissipation processes of the test model. Such comparisons demonstrate the accuracy and applicability of the simplified model, and the proposed simplified model would provide the basis for the theoretical analysis and seismic design of CFS composite shear wall systems. Full article