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Notional lateral loads are commonly used to capture the effects of initial out-of-plumbness in structures. Because these loads are imaginary, some assume the shear forces in the lateral force resisting system and horizontal reactions at the base can be ignored. However, for most structures, this is incorrect. This paper reviews two models for rationalizing notional loads. The first is a cantilever beam analogy that reinforces the imaginary nature of the horizontal force at the base. The second is a rigid link stabilized by a cantilever beam, which highlights that part of the notional load appears during a direct analysis. An example building is used to reinforce that, while the effect of Canadian notional loads may be artificially large, the portion of the notional load contributed by the gravity framing should not be ignored in the shear design of the lateral force resisting system, foundations, or even piers supporting gravity columns. [ABSTRACT FROM AUTHOR]

The axial compression capacity of steel reinforced concrete (SRC) stub columns with unsymmetrical steel sections (USSs) was investigated in this study. Axial compression tests were conducted on four SRC stub columns with USSs, and internal force analyses were conducted on a total of 22 finite-element models. The failure modes, load–displacement curves and internal forces were used to analyse the mechanical behaviour and bearing capacity of the columns under axial compression. Furthermore, the variables that influence the axial compression capacity comprising different width-to-thickness ratios of the steel flange, area ratio of the steel section to the confined concrete, web eccentricities and steel eccentricities were investigated in a parametric analysis. The results showed that, compared to SRC stub columns with symmetrical steel sections (SSSs), the columns with USSs showed slightly flexural failure. Steel eccentricity was the main factor that affected the axial compression capacity of SRC stub columns with USSs. An equation was proposed for calculating axial compression capacity of an SRC stub column with a USS considering steel eccentricity. Results calculated by the proposed formula showed better agreement with the experimental value than that calculated by the codes, and the formula is also applicable to SRC stub columns with SSSs. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Harbin Institute of Technology. Social Sciences Edition / Haerbin Gongye Daxue Xuebao. Shehui Kexue Ban is the property of Harbin Institute of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The computing of the fundamental period of structures during seismic design is well documented in design codes but is mainly dependent on the height of the structure, which is considered to be the most influential parameter. It is, however, important to consider a phenomenon called the soil–structure interaction (SSI), as this has been found to have a detrimental effect, especially for buildings founded on soft soils. A pilot research project foresaw the use of machine learning (ML) algorithms trained on relatively limited datasets for the development of a more accurate and objective fundamental period formula. Therefore, a dataset that consists of 98,308 fundamental period data points was created through the use of a High-Performance Computer (HPC), which is the largest dataset of its kind. The HPC results were then used to train, test, and validate different ML algorithms. It was found that XGBoost-HYT-CV with hyperparameter tuning performed the best with a correlation of 99.99% and a mean average percentage error (MAPE) of 0.5%. Furthermore, the XGBoost-HYT-CV model outperformed all under-study ML models when using an additional dataset that consisted of out-of-sample building geometries and soil properties, with a resulting MAPE of 9%. Finally, irregular buildings were also used to test the performance of the proposed predictive models. [ABSTRACT FROM AUTHOR]

As an alternative to classic repair measures of fatigue-damaged steel structures, adhesively bonded CFRP lamellas are ideal. In this way, disadvantages of the established methods can be circumvented Compared to bolted reinforcing measures, cross-sectional weakening by the bolt is avoided. Heat-induced residual stresses and distortions, as they usually occur during repair welding, can also be excluded. These disadvantages represent a weak point during cyclic loading due to the notch effect. To characterize the materials, tests are carried out on small scale specimens. With the help of tests on CT-samples a comparison with established methods such as drilling the crack tip and repair welding is realized. Based on the crack propagation, the great potential of bonded CFRP reinforcements can be deduced. By prestressing the lamellas, the remaining lifetime can generally be further increased. It should be noted, however, that with single-sided prestressing, a precamber of the specimen and, during loading, a secondary bending moment may occur. The combination of bonded CFRP with established methods can be described as particularly effective. With a reinforcement on both sides with pre-stressed plates, up to 7.9 times the remaining service life can be determined in comparison to unreinforced specimens. The effectiveness of adhesively bonded CFRP lamellas is examined in a German research project. Selected results are presented in this paper.

A new structural typology of a Steel-Reinforced Wooden (SRW) purlin made of rectangular laminated wood and C-section type cold-formed steel is presented in this article. The steel C-section profile is fitted onto the wooden purlin so that both work together as a composite unit. Although the wooden sections are weaker and have a lower elastic modulus than the steel sections, the overall dimensions of the SRW purlins are no larger than the steel C-section purlin sizes. The SRW purlins also form lighter structures than either plain steel or wooden purlins and they therefore have lower CO2 emissions. In addition, lighter purlins reduce the load on the main structure, which in turn reduces the material needed for the main structure of the building. So, reinforcement of the wooden purlin with steel sections within certain areas notably improved performance when compared with ordinary single-material purlins. The use of the SRW purlins can, therefore, improve the overall sustainability of a building. The improvements were analyzed in terms of sustainability and lower weight, as a function of span length and design load. The behaviors of the single material purlins and the SRW purlin were also compared. Both material strength and deformation design criteria and their influence were studied using an analytical approach based on loading and span length. The simple, innovative, and reliable design procedure described in this study ensured compliance with all technical requirements. Moreover, the savings relating to material weight were evaluated, neutralizing the carbon footprint in all cases under analysis. [ABSTRACT FROM AUTHOR]

Local buckling (wrinkling) is very common in metal-faced insulating sandwich panels (MFISPs) due to the small thickness of their face sheets. In some cases, wrinkling leads to sudden failures, while in others it leads to degradation of the overall stiffness and can decrease the failure load. A simplified finite-element modelling approach is presented to estimate the local buckling pressure of such panels. In the proposed approach, only the face sheet under compression is modelled, thus avoiding the need to perform a full three-dimensional (3D) structural analysis. The working assumption is that the relative deflection of the buckled face against the face under tension (unbuckled face) can be modelled using a two-parameter elastic foundation approach. The elastic foundation is simulated by closely spaced horizontal and vertical springs that model the rigidities of the foam core. Two models are used to determine the elastic foundation properties. The simplified approach was validated through comparisons with 3D analyses of full sandwich panels and available experimental results. It was found that the proposed approach can be applied to various types of MFISPs (flat or heavily profiled) with a variety of foam cores and face sheet thicknesses. [ABSTRACT FROM AUTHOR]

Web buckling of steel plate girders creates an undesirable failure mode as it can limit the ultimate load capacity of plate girders. This paper presents details of an experimental investigation aimed at strengthening slender end panels of steel plate girders using three different types of fibre-reinforced polymer (FRP) composite materials (glass-fibre-reinforced polymer (GFRP) pultruded section stiffeners and woven carbon-fibre-reinforced polymer (CFRP) and GFRP fabrics). The plate girders were fabricated using non-rigid end posts and were tested in three-point bending. The test results showed an increase of up to 54% in the ultimate strength of the FRP-strengthened end panels compared with the non-strengthened control panel, which was the result of increased out-of-plane stiffness of the web. A breakdown of the bond between the steel and the FRP fabric occurred in the end panels strengthened with CFRP and GFRP fabrics, while no bond breakdown of the pultruded sections was observed at the ultimate load. Analytical methods proposed by some of the design codes underestimated the critical buckling load and overestimated the ultimate load of the non-strengthened end panel. [ABSTRACT FROM AUTHOR]

This study focuses on assessing the seismic performance of existing single-story steel buildings used as industrial buildings. This research aims to provide a systematic procedure for evaluating the seismic response of a single-story strategic building and properly accounting for the behavior of the column–base joints. Through meticulous data collection, advanced numerical modeling, and pushover analyses, this study highlights the significant impact of column–base joint behavior on the overall seismic performance of industrial buildings. The findings reveal that while single-story steel buildings show a satisfactory seismic performance in terms of lateral resistance and stiffness in the longitudinal direction, deficiencies in the joint design can strongly impact the performance in the transversal direction. This study emphasizes the necessity of incorporating joint flexibility into numerical analyses to accurately assess structural behavior. In conclusion, a precise assessment of the base joints provides insights for informing retrofitting strategies. [ABSTRACT FROM AUTHOR]

This paper outlines the planning of a bridge in central Germany. Scheduled for construction in mid‐2024, this new bridge is a replacement for a century‐old pedestrian bridge crossing the Lahn river. The proposed bridge will be an airtight‐welded arch bridge, employing steel cross‐sections in both the arch and tension member. Designed as a single‐span, the arches extend 48.0m over the Lahn. The two arches have a flat rise of 4.65m, supporting the roadway through 9 inclined flat steel hangers. This paper delves into the structural engineering aspects, exploring challenges inherent in the design process. An examination of the parametric design process, facilitated through 3‐D modeling in Rhino® and Grasshopper®, will be presented, along with insights into their interface with the finite element modeling software, RFEM®. This process enables an engineering approach to form‐finding and structure optimisation through iterative design checks for various elements and stages of the structural analysis. [ABSTRACT FROM AUTHOR]

It is well understood that the dominant approach in the seismic design of structures is to reduce the initial cost while meeting the required safety level, as dictated by compliance codes. Nevertheless, this approach often overlooks the long-term costs that are incurred over the lifetime of the structures. A comprehensive approach is thus required for a design based on life cycle cost (LCC), where both initial and long-term costs are considered. While LCC-based design has been employed on regular structures, irregular structures have not received adequate attention. This research aims to highlight the impact of irregularity on the LCC optimization of tall structures. To do this, a bi-objective heuristic optimization framework is developed to balance the initial and long-term costs. The framework is used to analyze six steel regular and setback irregular structures with 7, 10, and 13 stories. The structures are all designed to meet the life safety performance level. The findings show that the irregular structures reveal a higher sensitivity to variations in initial costs compared to regular structures, which are mainly buildings above 13 stories. We also show that reducing the LCCs of irregular structures requires a higher increase in the initial cost compared to regular structures; for example, in the regular and irregular 13-story structures, a 17% increase in the initial cost resulted in approximately 48% and 40% reductions in the LCCs, respectively. Overall, our results confirm that the long-term costs of irregular structures are more than those of regular ones; this is an important finding that should be considered for the seismic design of tall irregular structures. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Railway Science & Engineering is the property of Journal of Railway Science & Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The current investigation delved into the seismic analysis, design intricacies, and assessment of the response of elevated steel containment tanks when supported by concentrically braced frames. The primary focus was placed on comprehending the behavior of the supporting structure, recognizing its heightened vulnerability to damage under horizontal excitation—insights gleaned from reconnaissance teams studying earthquake aftermaths worldwide. A specific case study unfolded featuring a steel concentrically braced frame as the supporting structure, aligning with prevalent industry norms. Throughout the entire process, spanning design phases, seismic vulnerability assessments, and response evaluations, special emphasis was placed on the internal fluid sloshing phenomena. This nuanced consideration plays a pivotal role in shaping the dynamic response of the system. The study introduces two distinct design methods: the first method aligns with relevant international codes, while the second method innovatively incorporates the compressive strength of the braces into its approach. To evaluate the dynamic response of the elevated tank, both linear and nonlinear advanced analyses were employed. The comparative analysis of various strategies underscores the impact of the chosen design methodology on the overall system response. This multifaceted exploration aims to contribute valuable insights to the seismic resilience and design optimization of elevated steel containment tanks, furthering the understanding of their performance under seismic forces.

Introduction. The article presents the results of a study of the calculation features of four-belt towers depending on the direction of a wind action. The purpose of the article is to identify the conditions for the redistribution of forces in the belts of a grid tower under the action of a wind load along a diagonal of a square section and loss of stability of the most compressed belt. The attention is drawn to the fact that with the development of the process of loss of stability of the compressed belt, it does not turn off completely, but continues to partially carry the load. The data obtained indicate that it is possible to calculate all the elements and the tower as a whole according to a single scheme A (a wind pressure on the face of the tower), taking into account the coefficient of the wind angle. In the calculation example, graphical dependences of the forces in the belts on the resistance are obtained.Materials and methods. A feature of the calculation of four-belt towers is the dependence of the forces in the belts on the direction of the wind load. According to the maximum compression forces under the action of wind on the rib and bending of the tower, the cross section and length of the panel of all belts are assumed. The resulting reserve of strength and rigidity of the tower of the two belts in the limiting state adopted in the design standards is not possible to implement, since the limiting state of the compressed belts is assumed by the condition of stability in the form of bifurcation. If the limiting state of the belt panels is assumed according to the condition of bearing capacity in the supercritical stage of deformation, then it is possible to calculate the redistribution of compressible forces to reserve belts. In the given example, the criterion of resistance is used to analyze the redistribution of forces between the belts when the stability of the most compressed belt is lost according to the design scheme B (wind pressure on the tower rib).Conclusions. The results of modelling the tower calculation in the LIRA PC showed that taking into account the supercritical deformation of the compressed belt in the elastic stage makes it possible to calculate all the elements and the tower as a whole according to a single scheme A (a wind pressure on the face of the tower), taking into account the coefficient of the wind angle. At the same time, even with an increase in the coefficient value to 1.4 (instead of 1.2), the calculation efficiency is greater than the traditional one. The results of the study may be the basis for reducing the estimated length of the elements of the most compressed belt according to the calculated scheme B.

Steel-coped beams are used in industrial structures to accommodate a cluster of water mains, fire hydrants, power cables and telecommunication wires. The coped regions restrict the ultimate capacity and cause unfavorable failure modes. The current study investigates the structural assessment of the coped section in offshore topsides while their use enhances operational safety for drilling and production. The structural evaluation is done through 2D digital image correlation (DIC) experiments to quantify the influence of various cope geometries. The DIC technique illustrated the strain and deformation measurements under different loading conditions for different coped geometry. The primary failure mode observed in local web buckling is characterized by noticeable lateral displacement and the development of buckling lines over the coped web. Studies showed the influence of the cope depth on the load-carrying capacity and buckling processes for different cope geometries. The results of the DIC analysis are strongly aligned with experimental data and finite element numerical results, suggesting this technique to the structural assessment of coped section. [ABSTRACT FROM AUTHOR]

Jet fires are the second most common fire scenario after spill fires. This type of fire is characteristic of gas and gas–oil fires occurring on oil platforms and gas production and processing plants. The consequences of such fires are characterized by high material damage; this is associated with extensive networks of technological communications, since there is a high density of technological facilities and installations in the territory where these fires occur. At such facilities, there is a large number of steel structures, which under the action of high temperature quickly lose their strength and deform. To protect steel structures in the oil and gas industry, fire protection is used, which consists of different types: boards in the form of flat plates, plasters, and epoxy paints. This paper compares three types of fire protection materials for steel structures under jet fire: board fireproofing, plaster composition, and epoxy coating. When comparing the efficiency in jet fire, cement boards were found to be the best. However, despite the better fire protection efficiency, their low application is expected due to their massiveness and the high cost of such protection and the difficulty of installation. Nevertheless, the development of fire depends on the place of its origin, the size of the initial fire zone, and the stability and massiveness of the metal elements of the vessel structure or the structure of the boards on which the equipment can be placed. Therefore, it is necessary to take these factors into account when selecting fire protection and to apply it depending on the required fire resistance limits of structures, which should be determined depending on the fire development scenarios. [ABSTRACT FROM AUTHOR]

This investigative study explored the potential of a novel approach called the modular insulated concrete core—advanced and optimized panelized production system (MICADO) method within the realm of modular structures, focusing on its parametric development. By combining frame-supported modular systems with premanufactured panels for exterior walls, the MICADO approach allows for simultaneous installation, and has demonstrated promising prospects. This research investigated the challenges associated with assembling and connecting MICADO structures in the face of seismic and gravity loads. Through rigorous worst-case scenarios, critical load combinations were identified and analyzed. The outcomes of this research provide valuable insights into the design of joints in MICADO structures, ensuring their overall structural integrity and stability. These findings have the potential to benefit professionals in architecture, engineering, and construction, equipping them with effective techniques and best practices for creating resilient modular structures. Ultimately, this work seeks to enhance efficiency, sustainability, and safety within the domain of built environments. [ABSTRACT FROM AUTHOR]

The present study analyzes the behavior of connections with flange-web welded plates using the finite element method in tubular columns filled with concrete, and beam, type I. An analytical study of the structural dynamic behavior of a Special Moment Frame (SMF) was carried out, in 5 levels, with HEB structural profiles, for IPE-type columns and beams, according to the requirements established by the AISC-360-16, ANSI-341 standards, and the Ecuadorian standard NEC-2015. The design process of the special frame structure was validated with the help of specialized software. Subsequently, the structural profiles were replaced following the actual construction situation in Ecuador. 3D models of the structural system and the elements of metallic connections were obtained for evaluation through the analysis of finite elements. These models were subjected to virtual tests according to the AISC 341-16 protocols and FEMA 350 standards. The evaluation of the connections showed that they did not meet the flexural strength criterion at 0.04 rad, but they exceeded 80 % of the plastic moment at 0.02 rad. Thus, flange-web welded plate connections can be valid for intermediate moment frames (IMF) in areas with moderate seismicity. In addition, it was observed that the columns filled with concrete optimize the structural elements in terms of dimensions; but do not contribute significantly to soldered connections due to the later development of plastic ball joints. [ABSTRACT FROM AUTHOR]

Lateral forces, especially seismic forces, cause significant damage to structures, especially tall ones. On the other hand, sequence earthquakes also cause irreparable damage to structures. Therefore, post-tensioned connections are one way to improve structures' seismic behavior. This study investigated 12-story tall steel structures with simple flexural connections and post-tensioned connections in two dimensions and 5- and 8-story structures with simple flexural connections and post-tensioned connections in two dimensions under sequences earthquakes. In this study, the beam and column sections of the sarees mentioned above were designed with ETABS software and simulated with OpenSees software to apply sequence records. The previous simulation was validated, and the structures were analyzed non-linearly under sequence records. The results indicated that the maximum drift angle was reduced by 50% in the 12-story structure with post-tensioned connections. As a result, post-tensioned connections improved the behavior of tall structures. [ABSTRACT FROM AUTHOR]

Structural stability tests on two‐span channel members in bending, axial compression and torsion The use of slender steel members promotes the competitiveness of steel structures in structural engineering. However, these members often necessitate stability verifications. Global research activities in this field have so far mainly focussed on single‐span members with doubly symmetric cross‐sections. For mono‐symmetric sections such as channels, only a few design models exist based on experimental evidence. Moreover, the potential of structural systems such as multi‐span members is yet not entirely exploited in the normative verification models. Therefore, this paper presents a comprehensive experimental study on the stability behaviour of two‐span members with steel channels under combined loading. Five‐point bending tests were conducted to determine the load‐bearing capacities and to experimentally analyse the influence of the constructional detail of the central support, the axial load, the slenderness ratio and other parameters on the load‐bearing behaviour. The article provides the scientific basis for extending the scope of the stability verification for members subjected to bending, axial compression and torsion in Annex C.2 of the novel EN 1993‐1‐1:2022 to two‐span channel members. [ABSTRACT FROM AUTHOR]

The desired structural performance of a novel self-centring pinned beam–column connection with friction dampers (SC-PC-FD) has been reported. An accurate mechanical model of the SC-PC-FD connection is required for easy modelling of frames with these connections using common commercial structural analysis and design software. This paper presents a simple mechanical model for a SC-PC-FD connection. The accuracy of the model was verified using results from experimental and numerical studies on two-strand and four-strand SC-PC-FD connections. Moreover, the seismic performance of frames with SC-PC-FD connections was evaluated using incremental dynamic analysis and compared with that of moment-resisting frames. For this purpose, one-, three- and five-storey building models with moment connections and SC-PC-FD connections were designed. The two-dimensional frames were subjected to far-field, pulse near-field and no-pulse near-field earthquake records and the collapse margin ratios (CMRs) and fragility curves of the models were obtained. The developed component-based mechanical model accurately predicted the monotonic and cyclic behaviour of the SC-PC-FD connection. With the novel SC-PC-FD system, the maximum residual interstorey drift ratio and the number of developed plastic hinges at the main members of the self-centring models were reduced significantly, while the CMRs were increased. [ABSTRACT FROM AUTHOR]

Headed studs are shear connectors in composite structures used at the adjoining face of a steel beam and a concrete slab. In this research, the conventional shape of a headed stud was restructured to resemble the shape of a coconut palm stem (royal palm) without a change in the overall material volume, with the aim of improving the shear strength of the composite connection. Six innovative shear connectors for composite structures, named coconut palm stem royal shaped headed stud shear connectors (CPSR studs), were examined. Abaqus/Explicit was used to model a push-out specimen and the finite-element model was successfully validated using published experimental results. The six different CPSR studs encased in three grades of concrete (C40, C50 and C60) were tested for shear strength, stiffness and load–slip performance. The results for the innovative CPSR studs were compared with those for uniform cross-section headed studs; when embedded in C40, C50 and C60 grade concrete, the results showed, respectively, 35–41%, 37–44% and 41–52% improvements in the ultimate strength of the shear connection. The improved shear strength capacity of the CPSR studs without a change in the overall volume of stud material means that fewer studs are required, leading to economic benefits. [ABSTRACT FROM AUTHOR]

This paper presents the performance-based fire safety analysis of steel structures of padel-center built in Nokia, Finland. The analyses are conducted using advanced calculation models (fire simulations using Fire Dynamics Simulator, FDS, and finite element method, FEM, based analyses of the steel frames in elevated temperatures using SAFIR software, including joint analysis) in support with less sophisticated models (critical temperatures of steel members). The following localized fire scenarios are studied: lounge area furniture fire (4 sofas), sporting equipment fire (10 sporting bags filled with flammable clothing), fire during maintenance (scissor lift fire with miscellaneous temporary fire load) and a fire on HVAC balcony near the trusses. The aim of the paper is showcase recent developments in design processes and methods that are in practical use today in performance-based fire design (PBD), to demonstrate that relatively extensive performance-based studies can be (commercially) viable also in relatively small and mundane steel buildings, and to present a fairly robust framework for PBD of similar steel structures. As a result of the performance-based design, most of the steel structures in the case building could be constructed without fire protection, but some critical structures were identified and protected to class R30. The proposed design was approved by the local municipal authorities. [ABSTRACT FROM AUTHOR]

Fire protection is a popular solution to slow down the temperature increase in steel elements subjected to fire, and simple equations, such as the mass lumped formula proposed in EN1993-1-2, may be employed to estimate the steel temperature in the cross-section. The EN1993-1-2 formula assumes that the temperature of the exposed insulation surface and the surrounding gas are equal. This simplification may provide inaccurate results for heavily insulated steel sections. Therefore, a new mass lumped formula was derived, accounting for more accurate boundary conditions considering the heat flux impinging the insulation. On these premises, this work evaluates how the new simple formula fares with respect to the EN1993-1-2 formula. In this respect, a comprehensive comparison with the results of 1-D and 2-D analyses considering several insulation materials and thicknesses of insulation and steel is thoroughly presented. The proposal results in being always safe and better estimates steel temperatures relevant in the structural fire engineering context. Its use is particularly recommended for heavily insulated sections, where the ratio between the insulation and the steel heat capacities is higher than 14, and the EN1993-1-2 formula gives unsafe predictions. [ABSTRACT FROM AUTHOR]

Ensuring the reliability of the supporting structures of existing transmission lines is a key aspect of maintaining the stability and efficiency of the energy infrastructure. Various methods and technologies are used for this purpose. This study presents a methodology for comprehensively inspecting the load-bearing structures of overhead transmission lines located in the Aksu city of Pavlodar region of Kazakhstan. The survey included 2 main stages: visual and instrumental inspection up to the moment of line de-energization and inspection of all components of transmission line supports. During the design and construction, special reliability requirements were considered, such as the consideration of engineering-geological conditions when selecting a site for the construction of each support, considering the estimated climatic conditions of the region, wind speed, and the size of ice deposits. The results obtained from the inspection of all main and fastening elements of the supports' structures allowed us to assess the current state of the infrastructure and define a strategy for its maintenance and renewal. The results showed that deviations in metal profile thickness were minimal, averaging ±0.5 mm from design specifications, indicating minor structural failure. Grounding device resistance measurements varied within a narrow range of 5 to 7.45 Ohms, which met safety and operational standards, further confirming the reliability of the infrastructure. The strength of the concrete in the foundations, evaluated without failure, averaged 25 MPa, which meets Class B30 standards and indicates environmental resistance, which allowed us to conclude that further operation of transmission lines is possible. [ABSTRACT FROM AUTHOR]

The paper deals with frame steel structures required to ensure sufficient resistance, appropriate ductility and safety against brittle failure. This special aim cannot be reached by utilizing standard procedures and standard beam elements. Therefore, the present study proposes an innovative design strategy devoted to plane steel frames constituted by I-shaped cross-section beam elements and subjected to simultaneous combinations of serviceability limit state conditions and ultimate limit state conditions. Special factory-made I-shaped uniform piecewise steel profiles are utilised to provide the optimal behaviour of the frame. The proposed design strategy consists of two subsequent steps: at first a classical sizing of the frame is performed by utilising standard steel profiles, then a specific optimal design problem is performed to define the optimal geometry of the I-shaped steel profiles that fulfils all the constraints related to the required resistance and the limited deformability as well as special introduced constraints related to the protection against the brittle failure. The reliability of the procedure and the expected optimal behaviour of the frame are checked by performing nonlinear static analyses employing a recently proposed Fibre Smart Displacement-Based (FSDB) beam element model. The proposed beam element is defined by adopting displacement shape functions capable of embedding the cross-section discontinuities by means of the use of generalised functions. Furthermore, the proposed shape functions are addressed to as "smart" since capable of update in accordance with the development of plastic deformations detected by means of fibre discretisation of the cross-section. The results related to a simple steel portal confirmed the expected optimal behaviour of the structure. [ABSTRACT FROM AUTHOR]

In this paper, the dynamic response of two 21-story buildings was studied to assess the influence of higher modes in their structural performance. While the first building was structured with ductile moment-resisting steel frames and exhibits a global shear-dominated lateral deformation, the second one uses ductile concentrically braced steel frames and has a global bending-type response. Buildings were virtually located in a soft-soil condition of the lake-bed zone in Mexico City. Nonlinear pushover and dynamic analyses were performed through OpenSees on a detailed 3D-model with plasticity spread along the elements. For this purpose, a set of accelerograms recorded during the Mexico Earthquake of September 19, 2017, were selected, and adjusted to represent the actual seismic hazard at the site. A frequency-domain system identification technique was applied to identify the dynamic characteristics of buildings through a moving-window Fourier analysis, that allows for the estimation of the contribution of higher-modes to their overall nonlinear dynamic response. A ratio of the elastic spectral pseudo-accelerations corresponding to the first two vibration modes is proposed to quantitatively anticipate cases and conditions for which the second mode adversely affects the structural performance of upper stories. The discussion includes a comparative study from the lateral global response of the analyzed models. [ABSTRACT FROM AUTHOR]

In the last decades, high priority has been given to enhancing the seismic resilience of structures by reducing the damage of structural and non-structural elements after a disaster. In this context, the European Research Fund for Coal and Steel (RFCS) project DISSIPABLE was funded to perform large demonstration tests of steel frames equipped with easily repairable seismic dissipative devices. The paper extensively describes the experimental campaign carried out at the University of Trento on a steel frame equipped with innovative Dissipative Replaceable Link Frame (DRLF) systems, composed of two rigid columns connected by weakened beams at their ends. Hybrid Simulation was employed, enabling to physically test the first floor of the building yet allowing for considering the response of the remaining five floors, which were numerically simulated. A bidimensional frame was tested under increasing seismic intensity levels: Damage Limitation, Significant Damage and Near Collapse limit states. The experimental results proved that the DRLF system was able to dissipate energy and protect the primary elements of the structure from plasticisation. Moreover, the structure's re-centring capability was verified to ensure the components' replaceability. Finally, the calibration of the nonlinear model was performed following the tests, which allowed to develop a high-fidelity model suitable for further numerical investigation. [ABSTRACT FROM AUTHOR]

The diagrid structural system has become popular in the construction of high-rise buildings in light of significant advantages over other structural systems. The present study explores the effects of the vertical near-fault earthquake component on the axial forces of diagonal elements in steel diagrid structures. Nonlinear time-history analysis was carried out using 11 near-fault earthquake records. A total of nine three-dimensional models of 12, 18, and 24 stories, each with diagonal angles of 45, 63.4, and 71.5 degrees, were designed and analyzed. Due to the three-dimensional modeling complexities of diagrid structures, a method was developed to transform three-dimensional models into two-dimensional ones. Finally, the scenarios with and without the vertical earthquake component were compared. It was found that the incorporation of the vertical earthquake component into the analysis of diagrid structures substantially influenced the axial forces of diagonal elements. This can affect the design load estimation of diagonal elements as the main components of a diagrid structure. [ABSTRACT FROM AUTHOR]