Steel Profiles Research Articles

A multi-stand work roll bending and shifting approach for profile contour and flatness control of electrical steel in multi-width schedule-free rolling using NSGA-II algorithm

To overcome the severe uneven work roll wear and uneven deformation of the wide-width electrical steel in the SFR (Schedule-Free Rolling) is an effective way to organize production flexibly and maximize production efficiency in hot rolling. In order to meet the increasingly stringent requirements of PCFC (Profile Contour and Flatness Control) of multi-width electrical steel in hot rolling, the collaborative control strategy of multi-stand work roll bending and shifting for profile and flatness of electrical steel in multi-width SFR was developed using NSGA-II approach. The work roll wear prediction model, thermal crown model, and strip crown model were established based on on-site measured data. Combining the work roll wear characteristics with principle, the mathematical model for work roll shifting considering multi-width was established. The main parameters of the multi-width work roll shifting strategy are obtained using the multi-objective NSGA-II algorithm. On this basis, a multi-stand collaborative control strategy, including rolling contour, short stroke roll shifting, and work roll bending, in the downstream stands during multi-width SFR was proposed. The industrial application of the developed control strategy shows that can prominently enhance the PCFC capability of electrical steel, which the uneven wear contour can be reduced.

Cost optimization of tall buildings having tube composite columns using social spider algorithm

SummaryThis study aims to develop an algorithmic approach to obtain optimum designs for tall buildings having composite columns and investigate the material cost advantages of these buildings over steel structures. The social spider optimization (SSO) algorithm, a new meta‐heuristic optimization method that has shown promising results in optimizing frame structures, was used to obtain the optimum designs. Concrete‐filled steel tube sections were chosen for composite columns. To define the optimization problem, we considered the material cost of the structure as the objective function, the size of columns (strength, deflection, drift, and geometric limitations) as the constraint functions, and ready steel sections as the design variables. We tested eight different frame structures of varying heights and irregularities to analyze how cost varied according to these parameters. Our results demonstrate that composite columns are a more cost‐effective option than steel structures, even for buildings that are not considered high rises. We found that the difference in cost between the two types of structures increases with building height and irregularity. Additionally, our optimization algorithm was unable to find feasible designs for steel structures taller than 180 m using ready steel profiles.

Finite Element Modelling and Simulation of Tunnel Gates of Dam Structures in ABAQUS Using Reduced-Integrated 8-Node Hexahedral Solid-Shell Element

Tunnel gates used for water regulation are very important and critical parts of dam safety. This is because they are exposed to the hydrostatic pressure of the total height of the water in the reservoir. In this case study, a nonlinear finite element modelling and simulation of the diversion tunnel gate of the Gokdere Bridge Dam in Adana, Turkey, are performed to investigate the performance and capacity of the structure before collapse. The maximum water level in the reservoir is 85 meters. A 3D finite element modelling of the gate structure was created, considering the details of the construction project. Both the concrete structure and the anchorages between the concrete of the first and second phases of the gate structure and the steel profiles in the gate supports are modelled to obtain composite behavior, bond stresses, and a more accurate load and stress distribution. For the nonlinear finite element modelling in ABAQUS, C3D8R reduced-integrated 8-node hexahedral solid elements with concrete damage and tension stiffening are used. For the simulation, linear and nonlinear capacity analyses of the gate structure are performed, and the stresses, strains, deformations, and crack propagation in concrete and steel are investigated. It is found that nonlinear analysis and finite element modelling of anchors for capacity and load transfer are important in the simulation of gate structures to prevent tunnel collapse. It is suggested that dam monitoring and control systems and the use of multiple gates are recommended when a problem occurs in the operation of a gate in the diversion tunnel gates of a dam structure.

A new method for rapidly capturing the strength and full nonlinear response of partially interacting steel–concrete composite beams

A semi-analytical procedure is presented for predicting the complete flexural response of partially interacting steel–concrete composite beams up to failure. The governing equation of the Euler–Bernoulli beam theory is solved wherein concrete, steel and the shear connectors joining the concrete slab to the steel beam are assumed to have nonlinear stress-deformation relationships. The adopted constitutive relationship for the connectors allows for partial or full composite action. The solution is applicable to beams and one-way slabs subjected to concentrated or uniform load and/or their combination. The governing equation is numerically solved by satisfying the equilibrium and compatibility requirements along the member. For the reinforced concrete part of the composite beam, a nonlinear moment–curvature relationship is developed that accounts for concrete nonlinearity in compression and for cracking and tension-stiffening in tension as well as for steel reinforcement nonlinearity. The steel profile is assumed to have a bilinear elasto–plastic strain-hardening moment–curvature relationship. Comparison of the proposed model results with the corresponding experimental load–deflection curves and interfacial shear–slip curves of several beams tested by others shows good agreement. The relative simplicity, efficiency and easy application of the present solution make it possible to accurately predict the failure load, interfacial slip and full nonlinear response of partially interacting composite beams.

Structural and dynamic assessment of a friction buffer stop

Under peculiar conditions railway braking system ca fail giving insufficient braking force during train ride or while standstill and buffer stops are used to avoid derailments at the end of railway tracks (dead tracks). Fixed stops are suitable only for quasi-static movements, while absorbing energy stops using hydraulic cylinders, friction shoes clamped on the rail head or a combination of both methods, are installed if crashes at higher speeds (about 25 km/h) are forecasted. Impact forces generated due to the interaction between train and buffer stops require a suitable design of the steel structure which is subjected to stress values depending on the braking performances of the buffer stop itself and a combined structural and dynamic analysis must be carried out to perform a proper design. Due to unavailability of detailed models and the uncertainties of the actual braking performances, the structure of currently available friction buffer stops is heavy and bulky, made of several steel profiles welded or bolted to each other. The paper describes an innovative and optimized design for friction buffer stops focusing on the dynamic analysis performed by Finite Element Method to assess the braking performances and structural strength of the buffer stop.

Developing a lightweight hybrid profile concept with a steel shell and polymeric lattice core for optimal mechanical performance

The building industry needs new design approaches to minimize resource consumption and negative environmental impacts. This study proposes a lightweight hybrid profile that combines a thin steel shell and a polymeric lattice core. The core density and internal structure variation possibilities control the slender steel profile’s load-bearing capacity and optimize the hybrid structure’s weight because of a synergy of the composite section components. The test campaign employs a 3D printing technology for prototyping the lattice core because the manufacturing preciseness (including the internal stiffener structure) is vital for structural optimization and developing adequate numerical models. A straightforward example illustrates the proposed concept. Lateral compression tests on 100 mm long fragments of the slender rectangular hollow section (RHS) 200/100/4 mm (height/width/thickness) profile prove the mechanical efficiency of the proposed hybrid section concept. Reducing the RHS fragment length ensures the experimental identification of the stiffening mechanism in the polymeric insert using a digital image correlation (DIC) technique and simplifies the numerical model. The 3D-printed lattice polymeric core added only 28% to the weight of the hybrid RHS fragment and increased its mechanical resistance twice compared to the reference empty shell fragments. This effect is equivalent to raising the profile thickness from 4 mm to 6 mm, resulting in a 1.5-times increase in weight. Using recycled plastics, adhesive connecting the inserts, and optimizing the internal geometry of the core stiffeners, depending on the loading conditions, may further increase the economic benefits of the proposed hybrid profile concept.

Fire design of steel-reinforced CFST stub columns with high-strength materials

Innovative composite sections are gaining popularity as they reduce the environmental impact of construction and take advantage of the collaboration of concrete and steel properties at room temperature and in fire. By introducing high-performance materials, these synergies are boosted. One typology is the steel-reinforced concrete-filled steel tubular (SR-CFST) section, in which a steel profile is embedded inside a CFST section. Despite their impressive load-bearing capacity and fire resistance, the available investigations on their thermo-mechanical capabilities are scarce. The present paper develops a numerical model to analyse the thermo-mechanical behaviour of SR-CFST stub columns subjected to fire. The model is validated against previous experiments conducted by the authors by comparing the temperature distribution and the mechanical behaviour with the experimental measurements. Afterwards, an extensive parametric study (1440 cases) is conducted to analyse the influence of several geometrical parameters – cross-sectional shape, outer tube dimensions and thickness, inner steel profile dimensions, section factor – and the use of high-strength materials for the concrete and the inner steel profile. Afterwards, a simplified temperature distribution proposal formerly designed by the authors for SR-CFST sections was tentatively tested. Based on this previous simplified temperature field and in line with the current provisions of EN1994-1-2, a new proposal is developed to evaluate the cross-sectional plastic resistance of SR-CFST stub columns under a fire scenario. This method unifies the initially developed thermal method and provides practical guidance for designers to evaluate the thermo-mechanical behaviour of SR-CFST columns, filling an existing gap in the European design code.

Numerical method for the primary torsional capacity of arbitrary steel cross sections considering nonlinear plastic behaviour

In structural design, plastic capacities of cross sections are of great importance for evaluating the capacity of steel members. Moreover, when it comes to problems of member stability, states of partial plasticisation are of interest as well. Depending on the cross section geometry and the material law to be considered, the determination can be challenging. This particularly applies to load conditions characterised by shear stress states, as for instance in the case of primary torsion (St. Venant's torsion). Simplifications are therefore often made with regard to the cross section geometry and engineering models are applied if the plastic limit moment of primary torsion Mpl,xp is to be determined. However, numerical methods allow a precise determination of properties and stress distributions of arbitrary cross section. In the present study, corresponding finite element formulations are combined with a plasticity algorithm for torsional analysis considering effects of nonlinear isotropic hardening. The approach approximates the nonlinear material law by a multilinear curve, which is stepwise evaluated based on linear hardening formulations. It allows determining states of partial cross section plasticisation for any strain or deformation state as well as the identification of the plastic limit capacity of the cross section. Results of the implemented algorithm are presented and verified for different common steel profiles showing excellent agreement to comparative studies.

Analysis of deformations of road embankments founded on displacement columns improving soft subsoil

Drilled displacement columns, constructed in the form of unreinforced or reinforced concrete elements, are currently a very commonly used method of improving soft subsoil, creating an alternative to more expensive pile foundations. A frequently used solution for improving soft soils of road or railway embankments is to design a regular pattern of columns of relatively small diameter. Columns along the perimeter of the improved area are reinforced with rigid steel profiles, while the internal ones are made as concrete elements. Column heads are usually covered with a load transfer platform (layer of compacted granular fill) which is additionally reinforced with geosynthetics. The application of soil improvement with displacement columns is not always successful. It is due to the errors and shortcomings occurring at the design stage, including simplifications in modelling, to construction faults, which may include insufficient experience of contractors and/or improper supervision. Referring to the real object that failed, the article provides the results of numerical parametric analyses taking into account the influence of the key design parameters such as: the stiffness of the load transfer layers, the amount and stiffness of the geosynthetic reinforcement as well as the column spacing. The article presents comparisons of numerical results obtained with the finite element analyses for various approaches to geometry modelling (axisymmetric, 2D and 3D). The simulations indicate that the use of the axisymmetric model of a single column in routine design may lead to the deformations exceeding the serviceability limit states.

A Detailed Numerical Model for a New Composite Slim-Floor Slab System.

The paper concerns the numerical modelling of a new slim-floor system with innovative steel-concrete composite beams called "hybrid beams". Hybrid beams consist of a high-strength TT inverted cross-section steel profile and a concrete core made of high-performance concrete and are jointed with prestressed hollow core slabs by infill concrete and tie reinforcement. Such systems are gaining popularity since they allow the integration of the main structural members within the ceiling depth, shorten the execution time, and reduce the use of concrete and steel. A three-dimensional finite element model is proposed with all parts of the system taken into account and detailed geometry reproduction. Advanced constitutive models are adopted for steel and concrete. Special attention is paid to the proper characterisation of interfaces. The new approach to calibration of damaged elastic traction-separation constitutive model for cohesive elements is applied to concrete-to-concrete contact zones. The model is validated with outcomes of experimental field tests and analytical calculations. A satisfactory agreement between different assessment methods is obtained. The model can be used in the development phase of a new construction system, for instance, to plan further experimental campaigns or to calibrate simplified design formulas.

Evaluation of Adhesive Joints Using Ultrasonic Rayleigh Waves.

Adhesive joints are non-separable connections that are used in numerous ways in vehicle construction, particularly in buses. The widespread use of adhesive joints makes it necessary to assess their quality, especially under production conditions. The main goal of this study was to develop a mathematical model to estimate the width of the adhesive path in a plywood-adhesive-closed-profile joint based on selected parameters of the ultrasonic surface wave. A digital ultrasonic flaw detector and Rayleigh wave probes were applied. The test involved evaluating different widths of hybrid adhesive and two-component epoxy adhesive. The tests were conducted on a steel profile from a bus construction. The attenuation of the ultrasonic waves on the steel profile (0.026 db/mm) and the adhesive (0.264 dB/mm) was determined. A one-size-fits-all model for estimating adhesive path width for specific conditions is proposed.

Mitigating Blast Hazards: Experimental Evaluation of Anti-Shatter Films and Catcher-Cable Systems on Conventional Windows

In light of terrorist attacks and accidents, the need for structural protection against explosive events has increased significantly in recent decades. Conventional unprotected windows pose a particularly high risk of injury to building occupants due to glass fragments and window frames being propelled into the interior and exterior of a building. This article addresses new experimental research on the protection of conventional single casement windows with insulating glass units (double-paned) and window frames made of un-plasticized polyvinyl chloride (uPVC) against blast loads. Entire window systems were tested in ten shock-tube tests using different retrofit-configurations. The retrofitted protective measures include anti-shatter films and catcher-cable systems. Furthermore, the influence of steel profiles inserted in the window frames is investigated. The applied blast loads met the requirements for ER1-certification according to EN 13541:2012 (tested at a reflected peak overpressure of 66.7 kPa and a reflected maximum impulse of 417.7 kPa∙ms). In the test series, various measurement methods were used to capture the velocity of the window fragments, the dynamic cable forces, and the hazard. The data provide valuable information for the design and implementation of catcher-cable systems for existing buildings, which can improve the occupant safety in the event of an explosion.

Optimized Building Envelope: Lightweight Concrete with Integrated Steel Framework.

This study presents a novel construction method for prefabricated wall elements by integrating a framework made of thin-walled sheet steel profiles into an optimized thermally insulating lightweight aggregate concrete (LAC) building envelope. The load-bearing function of the framework is provided by cold-formed Sigma-profiles, which are spot-welded to non-load-bearing U-profiles at the vertical ends. The LAC shapes the wall and stabilizes the thin-walled steel profiles against buckling, but has no further load-bearing function, thus allowing the reduction of its necessary compressive strength and subsequently minimizing its density. As a result, the LAC exhibits strength and density values well beyond existing standards, providing highly competitive thermal conductivity values that meet today's energy requirements without the need for additional insulation materials. Tailored composite specimens verify the stabilization of load-bearing sheet steel profiles by the LAC, which not only prevents buckling but also increases the load-bearing capacity of the overall system. The feasibility of this approach is validated by the production of two prototypes, each comprising a full-sized wall, in two different precast plants using distinct process technologies.

Bending Behavior of Hybrid Timber-Steel Beams.

Driven by climate change and the need for a more sustainable construction sector, policy is increasingly demanding and promoting timber hybrid construction methods. In the German state of Baden-Württemberg, every new public building has to be of timber or timber hybrid construction (Holzbauoffensive BW). The objective of multi-story buildings with large floor spans can only be achieved in a resource-efficient way by hybrid constructions combining timber and steel components. A research project recently completed at the Karlsruhe Institute of Technology was aimed at the development and systematic investigation of hybrid bending beams in which an advantageous combination of the materials steel and timber is used. For this purpose, steel profiles are integrated into timber cross-sections in a shear-resistant manner by adhesive bonding. As part of the experimental, numerical and analytical investigations, different cross-sections of steel and timber, as well as different construction materials, were considered (GL24h, LVL48p, LVL80p, S355 and S420). The results of large-scale four-point bending tests illustrate the potential of this new hybrid construction method. Depending on the geometry and material combinations tested, the bending stiffness could be increased by up to 250%, and the load-carrying capacity by up to 120%, compared to a glulam beam with identical dimensions.

EXPERIMENTAL STUDY OF THE LATERAL RESISTANCE OF CFS SHEAR WALLS

AbstractIn recent years, the attention grew toward sustainability issues. This led to the popularity of residential buildings made of cold formed steel profiles. In these systems the lateral bracing is provided by the shear walls. Their complex response calls for the design by testing approach. At the University of Trento an experimental study is in progress of the shear wall response under monotonic and cyclic loading. Five shear wall configurations differing in the steel skeleton and sheathings type are comprised in the programme. The paper presents the main features of the testing set‐up and the preliminary results related to two shear wall configurations. The key role of sheathing‐to‐steel framing connections is pointed out.

Finite element analysis on composite steel-concrete shear walls with centered and staggered openings

Present paper presents a comparative study made on the seismic performance of composite steel-concrete shear walls with rectangular openings, by performing numerical analyses using ATENA 3D software. Two specimens were designed at a reduced scale 1:3 having similar arrangements in the cross-section and the same geometry. First element was conceived with centered openings while the second one was designed with staggered openings. Steel connectors disposed as horizontal stiffeners were used to design and to assure the full connection between the structural steel profiles embedded in the edges and the concrete core. The openings that were considered on each story of the walls, were having the dimension of a common architectural door. A part of the results recorded from the experimental tests were used to calibrate the numerical models. This study aims to establish the seismic performance and to investigate the influence of the openings and the geometric position on the overall seismic behavior of the composite shear walls. Key parameters which describe the seismic performance of structural elements such: bearing capacity, deformation capacity, stiffness degradation, cracks and strain development are compared between the specimens and discussed. The results showed that different arrangements of the openings could significantly modify or increase the seismic performance of the composite structural walls.

BUCKLING CURVE CALIBRATION FOR STEEL I‐BEAMS WITH SEQUENTIAL WEB OPENINGS CONSIDERING RANDOM INITIAL IMPERFECTIONS

AbstractSteel beams with sequential web openings present benefits compared to plain webbed sections, especially higher bending stiffness. However, openings can affect structural behavior, requiring modifications to verification methods. In this study, a new proposal was developed to verify steel profiles with sequential web openings, based on Eurocode 3. The calculation leads to the determination of the reduction in the resistant capacity of the section due to instabilities based on an imperfection factor related to the characteristic process of manufacturing these profiles. For this, an extensive numerical study was carried out, considering random distributions of residual stresses based on experimental data.

Comparative analysis of two strengthening solutions for the structural rehabilitation of a historical masonry building

The paper presents a comparative analysis based on the Finite Element Method (FEM) for a masonry building located in Iasi, the North-Eastern side of Romania. This specific region is known to be found in a seismic area having a design peak ground acceleration of 0.25g. The building was assessed as being in the 1st seismic risk class, according to the Romanian norms, with a high probability of collapse in case of future earthquakes. Being a historical monument, the structural strengthening solutions are very limited. The study consists of modal and seismic analyses for the masonry structure. A comparison of the advantages and disadvantages of two approaches of structural rehabilitation solutions is done. The structural strengthening solution “A” consists of the addition of reinforced concrete thin wall elements, while the other - called solution “B” - consists of an interior steel profile skeleton mechanically and chemically connected to the adjacent masonry walls.

Reuse of cut concrete slabs in new buildings for circular ultra-low-carbon floor designs

The study explores an original idea that responds to the urgent need to reduce the detrimental environmental impacts of load-bearing floor construction in new buildings by reusing saw-cut reinforced concrete (RC) pieces salvaged from soon-to-be demolished structures. Cutting and reusing large RC pieces rather than crushing them to rubble is an untapped emerging circular construction method with a high potential for reducing waste generation, natural resource consumption, and upfront greenhouse gas emissions. Through an iterative design and analytical process, the study demonstrates how discarded cast-in-place RC floors can be cut and reused to build new low-carbon, little-extractive, load-bearing building floors. The study provides two new floor design solutions that valorise frequently discarded construction components (reinforced concrete slabs and steel profiles), combining construction technologies already used by the industry. The parametric design of 20′280 combinations of donor and receiver structures and their environmental analysis through Life-Cycle Assessment show that the new floor systems have shallow detrimental environmental impacts, with a reduction of upfront greenhouse gas emissions averaging 80 % compared to conventional practice. Floor-system solutions as low as 5 kgCO2e/m2 have been obtained. Structural assessments additionally show that flat slabs that are currently demolished meet the structural requirements at the preliminary design stage for reuse in new office or housing buildings. In particular, thanks to mandatory minimum reinforcement, 18-cm thick or thicker flat slabs built in Switzerland after 1956 and spanning up to 4 m are expected to be technically reusable as-is over their entire span. Overall, this study sets up a new benchmark for innovative floor systems with minimum environmental impacts and calls for considering soon-to-be demolished RC structures as mines of valuable construction components.

Metode Perbaikan Struktur pada Gedung BCA Kcp Ahmad Rivai Palembang

An investigation into the building is carried out to determine the suitability and safety of the building and the strength of the structure. The investigations to be carried out include field and laboratory investigations. This is done to determine the feasibility and safety of existing structures. Apart from that, it is also hoped that this investigation can provide recommendations regarding repair or strengthening methods if necessary, referring to the requirements for Structural Concrete for Buildings SNI 2847:2019 and Procedures for Earthquake Resistance Planning for Building and Non-Building Structures SNI 2847:2019. From the results of structural testing using UPV and Hammer Test, it was found that the structural system is an open frame consisting of plates, beams and columns using concrete material, while the joists use steel plinths. The reinforcing steel used uses plain iron U40 as flexible reinforcement with shear reinforcement with U24. The quality of concrete obtained respectively for column f'c 25 MPa, beam f'c 22 MPa and floor slab f'c 22 MPa. Based on the results of the floor leveling survey to record the potential for building subsidence or floor sagging using a water level, it was concluded that there was no slope found in the building as a whole. The deflection that occurs is local and relatively flat. To meet the requirements, strengthening was carried out by increasing the dimensions of the columns and beams, adding plates to the steel profiles on the flange and web.