Steel Structural Systems Research Articles

Numerical investigation into I-shape brace connections of conventional concentrically braced frames

In many low and moderate seismic regions, a low-ductility concentrically braced frame (CBF) is used as the seismic force resisting system for steel structures. The design of such CBFs is straightforward: all members and connections are designed based on the seismic force demand obtained through linear elastic structural analysis; capacity-based design and additional seismic detailing are not required. There is no designated energy-dissipating fuse in the lateral load-carrying path. Such CBFs are referred to as Conventional CBFs (CCBFs) in this study. In CCBFs, the brace-to-gusset connections are inherently weaker in tension than the adjoining gusset plates and braces. This occurs because both the gusset plates and the braces are selected on the basis of their respective compressive buckling resistances, and hence, typically have a much greater resistance in tension. Described herein is a numerical study of the popular flange plate bolted I-shape brace connection configuration. A high-fidelity finite element (FE) simulation procedure was developed and validated against laboratory test results. The resulting numerical models were created with the objective of improving our understanding of the inelastic response of these brace connections. The force transfer mechanism within the two branches of the connection was characterized. Significant nonuniform shear distribution was found to exist within the bolt group in the flange branch, which may be detrimental to the safe functioning of these bolts in the seismic design context. The loading eccentricity on the weld group was quantified. Recommendations on how to avoid brittle bolt shear rupture and premature weld fracture are proposed.

Experimental and numerical investigations on built-up cold-formed steel beams using resistance spot welding

The lightweight steel structural systems such as trusses or built-up beams, consisting of thin gage steel elements, are highly efficient and have the advantages in ease of handling and construction. The major concern relates to the joining technique between each part of the element. Commonly, the connection between thin-walled elements is performed by self-drilling screws but the quantity of time and manpower necessary for a large number of connections, demands an improved solution. Conventional welding technology is not appropriate for connecting thin sheets, such those of 0.4 mm–1.0 mm, to thicker ones of 1.0 mm–3.5 mm. The electric resistance spot or seam welding are widely used in the automotive industry to connect thin-to-thin metal materials. These technologies can be applied in case of thin-walled cold-formed construction, too. The paper presents a study on a new technical solution for lightweight cold-formed steel beams made of corrugated sheet web and built-up steel profiles for the flanges, connected by spot welding. Starting from the investigations on simple lap joint specimens tested under tensile-shear loading for various thicknesses combinations, the research concerns also metallographic aspects and investigates the response of the full-scale beams subjected to bending. Based on the obtained results, the study intends to demonstrate the feasibility and advantages of this solution compared to self-drilling screw solution. Particularly, besides the structural performance, the spot-welding solution increase significantly the work productivity and enables for automated fabrication in order to develop the mass production of these types of beams.

A comparative study of multi-objective evolutionary metaheuristics for lattice girder design optimization

The geometric nonlinearity has been successfully integrated with the design of steel structural system. Thus, the tubular lattice girder, one application of steel structural systems have already been optimized to obtain an economic design following the completion of computationally expensive design procedure. In order to decrease its computing cost, this study proposes to employ five multi-objective metaheuristics for the design optimization of geometrically nonlinear tubular lattice girder. Then, the employed multi-objective optimization algorithms (MOAs), NSGAII, PESAII, SPEAII, AbYSS and MoCell are evaluated considering their computing performances. For an unbiased evaluation of their computing performance, a tubular lattice girder with varying size-shape-topology and a benchmark truss design with 17 members are not only optimized considering the geometrically nonlinear behavior, but three benchmark mathematical functions along with the four benchmark linear design problems are also included for the comparison purpose. The proposed experimental study is carried out by use of an intelligent optimization tool named JMetal v5.10. According to the quantitative results of employed quality indicators with respect to a statistical analysis test, MoCell is resulted with an achievement of showing better computing performance compared to other four MOAs. Consequently, MoCell is suggested as an optimization tool for the design of geometrically nonlinear tubular lattice girder than the other employed MOAs.

Modular composite building in urgent emergency engineering projects: A case study of accelerated design and construction of Wuhan Thunder God Mountain/Leishenshan hospital to COVID-19 pandemic

Wuhan Leishenshan/Leishenshan (“Leishenshan” for short) hospital is a makeshift emergency hospital for treating patients diagnosed with the novel coronavirus-infected pneumonia (NCIP). Engineering construction uses modular composite building finished products to the greatest extent, which reduces the workload of field operations and saves a lot of time. The building information model (BIM) technology assists in design and construction work to meet rapid construction requirements. Besides, based on the unmanned aerial vehicles (UAVs) data analysis and application platform, digitization and intelligence in engineering construction are improved. Simultaneously, on-site construction and overall hoisting were carried out to achieve maximum efficiency. This article aims to take the construction of Leishenshan Hospital as an example to illustrate how to adopt BIM technology and other high-tech technology such as big data, artificial intelligence, drones, and 5G for the fast construction of the fabricated steel structure systems in emergency engineering projects.

Push-out test of steel–concrete–steel composite sections with various core materials: behavioural study

Steel–concrete–steel (SCS) structural systems have economic and structural advantages over traditional reinforced concrete; thus, they have been widely used. The performance of concrete made from recycled rubber aggregate from scrap tires has been evaluated since the early 1990s. The use of rubberized concrete in structural construction remains necessary because of its high impact resistance, increases ductility, and produces a lightweight concrete; therefore, it adds such important properties to SCS members. In this research, the use of different concrete core materials in SCS was examined. Twelve SCS specimens were subjected to push-out monotonic loading for inspecting their mechanical performance. One specimen was constructed from conventional normal weight concrete core, while the other specimens were constructed with modified core materials by either partial replacement of the coarse aggregate with crumb rubber (CR), the addition of oil palm fibre (OPF) to the concrete as a volume fraction of concrete, or both in the concrete cores. The investigated push-out specimens have a height of 450 mm and constructed from two hollow steel tubes with a square cross section of 100 mm and 5 mm in thickness which fixed to concrete prism using bolt end shear connectors. The detection of the mode of failure, load–slip as well as ductility behaviour, and the energy absorption capacity was investigated. The results revealed an improvement in the energy absorption (EA) capacity averagely by 55% for the specimen with 15% CR and 1.1% addition of OPF as a volume fraction of concrete in comparison with the reference specimens due to the high shear resistance.

Design and bearing capacity analysis of cold-formed thin-walled steel-timber composite members

Cold-formed thin-walled steel has light weight, large width thickness ratio, good economy and seismic performance. It is easy to realize standardization of design, and is very suitable for the development of prefabricated buildings. Due to the large width thickness ratio of cold-formed thin-walled steel , the steel plate is prone to local buckling when it is compressed, which will reduce the ductility and bearing capacity of the structure, which also leads to the limitation of the use of cold-formed thin-walled steel structure system in medium and high-rise buildings. In this paper, a kind of cold-formed thin-walled steel-timber composite members is designed. The section steel and the board are closely linked by bolts to work together. The thickness of the board and the spacing of the bolts are designed respectively, so as to provide reference for engineering design.

A comparative life cycle assessment of structural flooring systems in Western Australia

The construction industry has the potential to address negative impact on the environment by considered use of scarce natural resources, through a more informed choice of fit-for-purpose building materials. This paper presents a holistic life-cycle assessment (LCA) to facilitate the selection of environmentally friendly designs. Building on previous studies suggesting that engineers can reduce their environmental impact through conscious material selections and a substitution of traditional specifications, this work presents a case-study related to structural flooring systems in which a LCA approach for selecting the environmentally benign option, complements structural integrity design decisions.This study examined the life cycle environmental impacts associated with timber, steel and concrete structural flooring systems' options, for WA. ISO14040-44 guidelines were followed to carry out this ‘cradle to cradle’ LCA approach for calculating respective impacts. The comparisons of options using local benchmarks concluded that timber has the lowest environmental impacts followed by steel, and then ‘GreenStar’ concrete, with eco-classifications assessing the environmental impact of each flooring system for Perth WA across key environmental impacts categories and individual life cycle stages. This showed local hotspots in environmental categories of fossil fuel depletion and climate change and life cycle stages of mining to manufacture, construction and building operation. This research provides the reflection on what makes a sustainable design and, by targeting feasible solutions for WA, and by presenting the findings of a somewhat complex LCA analyses as a singular easy-to-use value, which addresses the need for enhanced materials awareness.

Thermal Performance and Energy Efficiency of Lightweight Steel Buildings: a Case-Study

Steel façade systems follow the actual tendencies in construction offering robust and sustainable solutions, able to answer to actual conditions and to offer adequate interior thermal comfort. The modern sandwich panels provided by the current façade system producers combine the required thermal resistance by varying the thermal insulation material and its thickness with the required structural demands. In addition, the façade layer could be over-coated with different materials, thus offering the required architectural aspect. Other advantages of the systems rely on industrialized prefabrication, fast installation and adaptability. They could also be disassembled and reused. The study presents an analysis of some envelope solutions existing on the market for buildings made of thin-walled cold-formed steel structural systems. The study consists in an annual energetic analysis of Mineral Wool (MW)-based system and a more sustainable recycled-PET thermal wadding-system. The analysis includes for input the own-produced energy by power grids and additional national grid energy while for output heating / cooling and electric appliances are considered. The study is completed by a life-cycle environmental analysis. The study revealed that when the thermal insulations have nearly the same U-value, the environmental impact of the recycled-PET thermal wadding-based system is smaller than that of MW-based system. Although the environmental impact of the recycled-PET thermal wadding is higher in the production stage, the insulation quantity of the material needed for PET-recycled thermal wadding to accomplish the required thermal resistance is much smaller than that of MW. Moreover, the original material for the recycled-PET thermal wadding is 100% recycled which implies a certain benefit of circularity to the material. The study also proves that the glazing ratio has also an impact on the thermal performances of studied systems: by reducing the overall glazing ratio of the envelope, the solar gain drops significantly, which leads to an increased heating energy demand, in order to meet indoor thermal comfort.

Size optimization of single edge folds for cold-formed structural members

Parametric optimization problem for single edge fold size in cold-formed structural members subjected to central compression has been considered by the paper. Determination the load-bearing capacity of the cold-formed structural members has been performed using the geometrical properties calculated based on the constructed “effective” (reduced) cross-sections taking into account local buckling effects in the section as well as distortional buckling effects.
 Single edge fold size in cold-formed C-profile has been considered as design variable. Linear convolution of criteria, namely minimization criterion of design area of stiffener cross-section and maximization criterion effective area of stiffener cross-section which defines it reduced load-bearing capacity due to flexural buckling has been used as optimization criterion. The parametric optimization problem has been solved using the method of objective function gradient projection onto the active constraints surface with simultaneous correction of the constraints violations. In order to realize the formulated optimization problem, software OptCAD intended to solve parametric optimization problems for steel structural systems has been used.
 Optimization results of the single edge folds for the cold-formed С-profiles manufactured by «Blachy Pruszyński» company, «BF FACTORY» company as well as «STEELCO» company have been presented by the paper. The results of the performed investigation can be used as recommendations for companies-manufacturers of the cold-formed profiles, as well as a guide for creation the national assortment base of the effective cold-formed profiles promoting wider implementation of cold-formed steel structures in building practice.

Effect of reinforced concrete slab on the flexural behavior of composite beam to column joints: Parameter study and evaluation formulae

This paper presents a comprehensive numerical and theoretical investigation into the flexural capacities of composite joints with reinforced concrete (RC) slab. The improved 3D (three-dimensional) numerical models were established by MSC. Marc (2012) and calibrated by the experimental observations presented in the companion paper (Mou et al., 2019a [1]). Supplementary parametric studies were then undertaken to examine the effect of concrete slab, size effect (H), axial-force ratio (n), slab thickness (hs), concrete compressive strength (fc’), and the width-to-thickness ratio of column (D/t) on the flexural capacities of the composite joints. Employing the yield line mechanism theory, a calculation method incorporating the effect of the RC slab for the composite joint was proposed. The proposed formulae were featured with a favorable accuracy and suggested to be applied for the design of composite joints in the steel structural systems.

Self-centering energy-absorbing rocking core system with friction spring damper: Experiments, modeling and design

The Self-Centering Energy-Absorbing Rocking Core with friction spring damper (denoted as the SCENARIO system) is a novel steel structural system that can achieve excellent self-centering performance in low-rise buildings. This research presents the physical tests and design procedure of the SCENARIO system, which consists of a rocking core (RC) and two friction spring dampers (FSDs). The basic mechanical response of the friction ring spring group included in the FSD is first described through a preliminary experimental study. Three repeated rounds of reverse cyclic load tests of the SCENARIO system are conducted. The test results show reliable and stable self-centering hysteretic behavior. After removing the applied force at the maximum loading roof drift ratio of 5%, the SCENARIO specimen achieved near-zero residual drift. During the entire loading process, the RC can remain elastic. The two FSDs included in the SCENARIO specimen show yield force reduction and stiffness increase under three repeated rounds of cyclic loading. However, there was no damage to any components in the FSD after the tests. Following the experimental study, the finite element model of the SCENARIO system is introduced and verified. Then, nonlinear dynamic analyses (NDA) are performed to determine the influences of the yield force reduction and stiffness increase of the FSD on the seismic performance of the proposed system. Finally, a performance-based design procedure is proposed using the direct displacement design method for the SCENARIO system. The results from the NDA indicate that the SCENARIO system designed via the proposed design procedure can achieve the desired performance objective and excellent self-centering behavior under the maximum considered earthquakes.

Global potential for material substitution in building construction: The case of cross laminated timber

The building and construction sector is a large contributor to anthropogenic greenhouse gas emissions and consumes the vastest amount of natural resources. Widely considered a hard-to-decarbonise sector, improvements in buildings and construction are of fundamental importance for national and global targets to combat climate change. At material level, mitigation opportunities exist in terms of efficiency (using less of the same material) and substitution (using a different material). This article investigates the latter, with a global focus on the use of cross laminated timber to replace concrete floors in steel structural systems. This approach, whilst innovative, does not require any technological development nor upskilling of current professional practice, thus making it an immediately viable solution to accelerate decarbonisation. We combine Material Flow Analysis with Life Cycle Assessment across both spatial and temporal dimensions, accounting for different levels of uptake of the proposed hybrid construction in the next 30 years. Results show that greenhouse gas emissions saving potentials range between 20 and 80 Mt CO2e (95% confidence interval) with an average around 50 Mt CO2e in the case of full uptake of the hybrid construction system by 2050. Our analysis does not account for carbon sequestration potential in timber, which would make the savings much greater. Still, the overall savings represent a 1.5% reduction of the annual greenhouse gas emissions generally attributed to construction, thus making it a non-trivial contribution to progress towards global targets of net-zero carbon buildings.

Applications of Light Steel and Light Concrete Structure System in Island Building

Zhang, J. and Zhao, F.-G., 2020. Applications of light steel and light concrete structure system in island building. In: Qiu, Y.; Zhu, H., and Fang, X. (eds.), Current Advancements in Marine and Coastal Research for Technological and Sociological Applications. Journal of Coastal Research, Special Issue No. 107, pp. 73-76. Coconut Creek (Florida), ISSN 0749-0208.Because the island is surrounded by a high salinity and humidity marine environment, the buildings on the island will also be corroded and damaged by the marine environment. As a new type of building structure system, light steel light concrete system integrates the advantages of reinforced concrete and light steel structure, and has stronger corrosion resistance, so it is more widely used. Based on this, this paper first analyzes the technical characteristics of the light steel light concrete system, then studies the applicability of the light steel light concrete structure system in the island building, and finally gives the application analysis of the light steel light concrete structure system in the island building.

Experimental and analytical fragility assessment of a combined heavy timber–steel‐braced frame through hybrid simulation

SummaryA combined heavy timber–steel structural system has recently been developed for the adaptation of advanced structural braces into tall timber structures. This study investigates the system‐level performance of a seven‐story combined timber–steel friction‐braced frame using hybrid simulation and incremental dynamic analysis (IDA). The IDA results from the hybrid simulations are compared with a numerical model to assess its ability to capture the nonlinear seismic performance of the timber–steel friction‐braced frame. Experimental and numerical IDA results are used to derive fragility curves for interstory and residual drift and assess its collapse probability under different earthquake hazard levels. The hybrid test results show that the timber–steel friction‐braced frame demonstrates excellent seismic performance under a range of ground motion intensities. The experimental results from the hybrid simulations and the experimental fragility curves correlate well with the numerical modeling results.

Life Cycle Assessment of Tall Onshore Hybrid Steel Wind Turbine Towers

Increasing needs for taller wind turbines with bigger capacities, intended for places with high wind velocities or at higher altitudes, have led to new technologies in the wind energy industry. A recently introduced structural system for onshore wind turbine towers is the hybrid steel tower. Comprehension of the environmental response of this hybrid steel structural system is warranted. Even though life cycle assessments (LCAs) for conventional wind turbine tubular towers exist, the environmental performance of this new hybrid structure has not been reported. The present paper examines the LCA of 185 m tall hybrid towers. Considerations made for the LCA procedure are meticulously described, including particular attention at the erection and transportation stage. The highest environmental impacts arise during the manufacturing stage followed by the erection stage. The tower is the component with the largest carbon emissions and energy requirements. The obtained LCA footprints of hybrid towers are also compared to the literature data on conventional towers, resulting in similar environmental impacts.

Seismic Performance of a Single-Story Articulated Steel Structure System

AbstractAn innovative articulated steel frame system consisting of continuous beams, columns, and end plates with gap bolts is proposed in this study. The gap bolts are untightened with initial gap...

Vibration analysis of damaged and undamaged steel structure systems: cantilever column and frame

This paper presents the experimental and numerical studies conducted on a steel column and a steel frame structure using free vibration analysis. The effects of damages on structures were investigated, which were simulated by introducing multiple cracks at different locations in the experimental and numerical models. The acceleration responses of the test models, were recorded through an accelerometer, and were used to calibrate the numerical models developed in finite element based software. Modal frequencies of damaged and undamaged structures were compared and analyzed, to derive relationships for damaged and undamaged structures’ frequencies in terms of crack depth. It was found that, due to the presence of cracks, the mechanical properties of a structure changes, whereby, the modal frequencies decrease. An approximately linear trend was observed for the frequency decrease with the increase in crack depth, which was also confirmed by the numerical models. The derived relationships were extended to further develop a mechanics-based damage scale for steel structures, to help facilitate structural health monitoring and screening of vulnerable structures.

A thermo-mechanical analysis of stainless steel structures in fire

A novel multi-dimensional combined isotropic-kinematic plasticity material model was recently developed by the authors for thermo-mechanical analysis of steels at elevated temperatures. In this paper, the capability of the new material model was further validated for transient loading conditions during heating and cooling using recent experimental data. The multi-dimensional material model was adapted to a 1D J2 plasticity model and implemented in the open source software OpenSEES for studying the structural performance of stainless steel beam and frame structures in fire using finite element analysis (FEA). This paper presents the findings of the studies, with a focus on the behavioural comparisons between the carbon steel and the stainless steel structures. Using the FEA method, the studies provided results that filled the research gap in understanding the global structural fire performance of stainless steel structural systems. The significant impact of stainless steels’ high material non-linearity and high thermal expansion on their structural fire performance is highlighted.

Structural behavior and design of high-strength steel welded tubular connections under extreme loading

The present work is motivated by the increasing need for cost-efficient solutions in offshore structural systems for wind energy production and for improvement of their structural performance. The structural behavior and design of high-strength steel welded tubular connections (yield strength higher than 700 MPa) subjected to monotonic and strong cyclic loading is investigated. In the first part of the paper, an experimental investigation is presented on high-strength steel tubular X-joints subjected to monotonic and cyclic loading far beyond the elastic limit of the material, leading to weld fracture. Two grades of weld metal material are employed in the welding process of the specimens. The experimental results indicate that the weld material grade has a significant influence on the deformation capacity of the welded connection under monotonic loading conditions, and its low-cycle fatigue life. The experimental procedure is simulated using advanced finite element models, elucidating several features of joint behavior and complementing the experimental results. Overall, a good agreement is found between numerical simulations and experimental results, in terms of both global response and local strains at the vicinity of the welds. Furthermore, the structural performance of the welded tubular joints under consideration is assessed using available design methodologies in terms of both ultimate strength and low-cycle fatigue resistance, in an attempt to validate an efficient design methodology for low-cycle fatigue. The results from this research effort are aimed at developing the necessary background for the possible use of high-strength steel in tubular steel lattice structures, particularly in offshore platforms for renewable energy production. They can also be used as a basis for the possible amendment of relevant design specifications and recommendations for including special provisions for high-strength steel structural systems.

Stability investigations in composite steel-concrete walls for restoration purposes to enhance structural and sustainability design

In the present paper a methodology is proposed to evaluate the sustainability of intervention in existing multi-storey concrete buildings using structural steel systems. Taking into account that an intervention in an existing building can be characterized as sustainable if the design considerations include critical sustainability assessments, a method is proposed and then applied to a case study for the restoration of an eight-floor building located at the center of the city ofThessaloniki.This case study is also compared to other relevant assessments with the option of reuse of the existing building only with elementary restoration works and the design of a new composite steel-concrete building constructed at the same location. The analysis includes a description of the building characteristics and pathologies, with an estimation of the structural performance after the application of an optimization process when using structural steel systems for its enhancement.