Search Results (32)

The use of both structural steel and reinforced concrete is common in civil and military infrastructure projects. Anchorage plays a crucial role in these systems, serving as the key element that connects structural components and secures attachments within complex composite structures. This research focuses on evaluating the performance of steel–concrete column connections under the combined effects of lateral loading and fire exposure. Additionally, the study investigates the use of carbon fiber-reinforced polymers (CFRP) for strengthening and repairing these connections. The research methodology combines experimental testing and finite-element modeling to achieve its objectives. First, experimental investigation was carried out to test two groups of steel-reinforced concrete column specimens, each group made of three specimens. The first group specimens were designed based on special moment frame (SMF) detailing, and the other group specimens were designed based on intermediate moment frame (IMF) detailing. These two types of design were selected based on seismic demands, with SMFs offering high ductility and resilience for severe earthquakes and IMFs providing a cost-effective solution for moderate seismic zones, both benefiting from ongoing innovations in connection detailing and design approaches. Then, finite-element analysis was conducted to model the test specimens. High-fidelity finite-element modeling was conducted using ANSYS program, which included three-dimensional coupled thermal-stress analyses for the six tested specimens and incorporated nonlinear temperature-dependent materials characteristics of each component and the interfaces. Both the experimental and numerical results of this study show that fire has a more noticeable effect on displacement compared to the peak capacities of both types of specimens. Fire exposure results in a larger reduction in the initial residual lateral stiffness of the SMF specimens when compared to IMF specimens. While the effect of CFRP wraps on initial residual lateral stiffness was consistent for all specimens, it caused more improvement for the IMF specimen in terms of post-fire ductility when compared to SMF specimens. This exploratory study confirms the need for further research on the effect of fire on the concrete–steel anchorage zones. Full article

The behaviour of horizontal floor diaphragms plays a crucial role in ensuring the overall response of a building during earthquakes, as the stiffness of these diaphragms determines whether the structure will act as an integrated system. If the diaphragms do not exhibit sufficient stiffness, differences in the redistribution of forces on wall elements arise, increasing the risk of significant deformations and even local damage, which is commonly observed in earthquake-affected areas. Additionally, flexible diaphragms heighten the risk of torsional effects. Due to these factors, more attention should be given to the response of buildings with flexible diaphragms. Eurocode standard specifies general requirements under which diaphragms should be considered rigid within their plane, depending on the maximum diaphragm moment. However, specific guidelines regarding the geometric and material properties of elements that significantly impact seismic behaviour are not included in the existing European standards. This served as a basis for conducting a numerical study analysing the in-plane behaviour of floor elements made from different materials. This study, limited to a simple box-shaped structure with masonry walls, symmetrical in both orthogonal directions, evaluated and thoroughly analysed the deformations for different types of diaphragms, including prefabricated wooden frame-panel floors, CLT panels, and reinforced concrete slabs. Special emphasis was placed on wooden structural elements due to the increased demand for timber construction, as the behaviour of these elements needs to be properly studied, especially in seismic regions. The study results were obtained through FEM analysis using the SCIA Engineer software, version 22. The modelling of elements was carried out considering the orthotropy of brick wall and wooden ceiling elements, as well as simulating the appropriate shear stiffness of the connecting means. Full article

In this work, the seismic response of a multi-story, multi-bay special truss moment frame (STMF) with Ni-Ti shape memory alloys (SMAs) incorporated in the form of X-diagonal braces in the special segment is investigated. The diameter of the SMAs per diagonal in each floor was initially determined, considering the expected ultimate strength of the special segment, developed when the frame reaches its target drift and the desirable collapse mechanism, i.e., the formation of plastic hinges, according to the performance-based plastic design procedure. To further investigate the response of the structure with the SMAs incorporated, half the calculated SMA diameters were introduced. Continuing, three more cases were investigated: the mean value of the SMA diameter was introduced at each floor (case DC1), half the SMA diameter of case DC1 (case DC2), and twice the SMA diameter of case DC1 (case CD3). Dynamic time history analyses under seven benchmark earthquakes were conducted using commercial nonlinear Finite Element software (SeismoStruct 2024). Results were presented in the form of top-displacement time histories, the SMAs force–displacement curves, and maximum inter-story drifts, calculating also maximum SMA displacements. The analysis outcomes highlight the potential of the SMAs to be considered as a novel material in the seismic retrofit of steel structures. Both design approaches presented exhibit a certain amount of effectiveness, depending on the distribution, with the placement of the SMA bars and the seismic excitation considered. Further research is suggested to fully understand the capabilities of the use of SMAs as dissipation devices in steel structures. Full article

Determining the impact of pulse-type earthquake characteristics on the vulnerability of base-isolated buildings under non-pounding conditions has yielded conflicting results in previous studies. Moreover, this issue has received less attention for pounding conditions, especially floor-to-floor pounding. Therefore, this study aims to investigate the correlation between pulse-type earthquake characteristics and the seismic response of buildings under both pounding and non-pounding conditions. In the first stage, three base-isolated buildings and one fixed-base building are analyzed separately under 40 pulse-type earthquakes using the nonlinear time history method. Three scenarios are then considered to account for pounding with adjacent buildings. In the first pounding scenario, a base-isolated building with an intermediate moment frame (IMF) is placed between two fixed-base buildings. The second scenario involves changing the base-isolated building’s superstructure system to a special moment frame (SMF). Finally, the third scenario increases the base isolation period (T_b) of the base-isolated building used in scenario two. The correlation between earthquake characteristics and the seismic response of buildings is assessed by linear regression and the Pearson correlation coefficient. The results demonstrate that peak ground acceleration (PGA) has a strong correlation with the seismic response of buildings under pounding conditions, while peak ground velocity (PGV) shows a stronger correlation under non-pounding conditions. However, predicting building vulnerability with a single pulse-type earthquake characteristic remains unreliable unless a large number of ground motions are considered. Otherwise, it is crucial to consider the correlation of all earthquake characteristics with seismic responses. Full article

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. Full article

The construction industry presents a significant environmental challenge due to its substantial environmental footprint, utilization of limited natural resources, and contribution to pollution and climate change. Additionally, optimizing the weight, cost, and duration of construction is crucial for enhancing serviceability, flexibility, efficiency, and profitability. In this research, the relationship between structure weight and other objective functions was explored using the single-objective gray wolf algorithm to investigate their impact on carbon footprint, water footprint, and construction time. Furthermore, employing a multi-objective optimization algorithm, a building structure was optimized for three systems featuring different structural frames based on the specified objective functions. The results revealed that the structure with intermediate steel moment-resisting frames exhibited the shortest construction time but incurred the highest construction cost. Conversely, the structure with intermediate steel moment-resisting frames with special steel concentric bracing demonstrated the lowest carbon footprint and water footprint among the studied structural frames. Consequently, the structure with intermediate steel moment-resisting frames with special concentric steel bracing was proposed as a green structure, emphasizing its environmentally friendly characteristics. Full article

In 2007, the American Iron and Steel Institute (AISI) established a standard for cold-formed steel–special bolted moment frames (CFS-SBMFs). This structural system is designed to resist seismic forces. The CFS-SBMF system employs double-channel beams and square hollow structural section (HSS) columns that are bolted together to create a sturdy and robust structural frame. However, the CFS-SBMF system is only suitable for constructing one-storey buildings, and ASCE 7 prohibits its use in buildings with a height of over one storey. This study was conducted to expand the use of CFS-SBMFs to the construction of multi-storey low-rise buildings. Firstly, a new moment connection detail is proposed, and a design procedure is proposed to ensure that bolted connections, instead of beams or columns, have the ductility to withstand seismic forces. Secondly, the proposed design procedure for bolted connections was verified through full-scale cyclic testing. Finally, a comprehensive evaluation was undertaken to evaluate the proposed structural system’s performance under seismic excitation. The evaluation included nonlinear dynamic analysis and incremental dynamic analysis (IDA) according to FEMA P695, which provided a detailed understanding of the seismic design factors (SDFs) in multi-storey low-rise CFS-SBMF buildings. Full article

Recognizing the vital role of a positive city image in attracting stakeholders, urban officials are increasingly implementing cultural branding strategies to establish and highlight their city’s distinct character. Culture, essential in urban development, shapes identity and local economy, encouraging social cohesion and sustainability. According to existing research, strategies for branding places—and cities in particular—through arts and culture include associating them with a famous personality (such as Barcelona’s perceived connection with Gaudi), flagship buildings (like Paris with the Eiffel Tower) and hallmark events (as exemplified by Cannes and its Film Festival). The European Capital of Culture awarded annually by the European Union, which associates a city with a good cultural reputation, was a favorable starting point for this research. Fourteen EcoC Bidbooks brought forward by candidate cities bidding for the title within the 2020–2026 time frame were analyzed in order to investigate essential components of city branding. The study delves into aspects such as perceived image of European Capital of Culture candidates, problems behind this perceived image and ideal city image, revealing recurrent themes that define cultural European cities today. In addition, the research identifies new strategies that complete Ashworth’s list (such as culture tailored to a particular natural environment, alternative spaces turned into culture hubs, artistic transportation, historical moments and movements, culture gamification, grassroots culture, culture thematization, highlighting the cultures of minorities, cultural fusions and embracing local folklore and mythical creatures). This helps bridge a gap in the specialized literature on cultural place branding. The study’s originality extends to the analysis of Ecoc Bidbooks as a sum of cultural branding strategies proposed by the candidate cities. Each Bidbook is in fact a cultural vision of the city under optimum financial circumstances, thereby carrying a significant weight in the realm of research. Full article

This study presents the performance-based seismic assessment of low-rise reinforced concrete archetype buildings, considering repair costs for ordinary moment-resistant frames (OMF) and dual systems consisting of OMF plus special shear walls (SSW). Historically, the OMF systems, conceived for residential purposes in Ecuador resulting from informal construction, have reported poor responses under seismic forces. This study analyzes damage levels through fragility curves as a function of the maximum global drift reached through incremental dynamic analysis. For this, two archetypes with OMF and two with a similar configuration, including structural walls, are modeled to define a loss function and annual collapse probabilities. As a result, it is noted that systems with structural walls significantly reduce repair costs by between 75 and 90% of the total cost of the building, and prevent collapse. Systems with ordinary moment frames report total losses, implying their use should be limited in areas of high seismicity. Full article

During the Northridge earthquake, extensive brittle failures on the weld zones of the beam bottom flanges in the rigidity connection of steel special moment frames (SMFs) were detected. One of the primary reasons is the high-tensile strain demand created at the beam bottom flange zones due to positive bending. The weak panel zone of the I-section column exhibits more shear deformation, which promotes and accelerates the brittle fracture of the beam bottom flange weld zones. A box-strengthened panel zone can minimize the shear deformation of the panel zone of the I-section column, which may also reduce the inter-story displacement of steel SMFs and enhance their seismic behavior. In order to investigate this fact, in this research we carried out a model test of a steel frame with a box-strengthened panel zone to examine SMFs’ seismic performance and inter-story displacement, as well as testing the contribution of panel zone shear deformation to inter-story drift. Numerical methods were then used to investigate the influence of the axial compression ratio and beam-to-column linear stiffness ratio on the effect of shear deformation on the box-strengthened panel zone. Design recommendations are given based on the research results. Full article

Precast concrete (PC) structures have many advantages, but their use in the construction of middle- to high-rise buildings is limited. The construction of PC structures requires skills in various operations such as transportation, assembly, lifting, and structural soundness. In particular, regarding the seismic design of PC structures, it is necessary to clearly evaluate whether they have the same structural performance and usability as integral RC (cast-in-place) structures. In this paper, an experimental study was conducted to investigate whether PC members can achieve a seismic performance equivalent to that of RC members in beam–column joints, which are representative moment-resisting frames. The main variables are the two types of structural systems (intermediate and special moment-resisting frames) and the design flexural strength ratio of the columns and beams. The experimental and analytical results showed that the seismic performance of the PC specimens was equivalent to that of the RC specimens in terms of strength, stiffness, energy dissipation, and strain distribution, except for the specimen with splice sleeve bond failure of the column reinforcement (poor filling of the internal mortar). In addition, the I series satisfied the present emulation evaluation criteria for special moment-resisting frames of PC structures, confirming the possibility of applying intermediate moment-resisting frames. Full article

The beam–column connection is a fundamental element in frame structures and requires special attention in the calculation of the forces passing through it and the corresponding modeling. For the study of the moment-resisting frame in the leading countries in seismic research, uniform procedures have been introduced. However, in their seismic codes, there is still a discrepancy in how the shear force is determined in the beam–column connection. In the present paper, a new mathematical model is proposed for the analytical determination of the forces passing through the joint in the beam–beam and column–column direction. The occurring large deformations in the beam and column, which are determined during an earthquake, are considered. The material is elastic. The obtained values are compared with results determined by mathematical procedures proposed in other literature sources. The results show that the values of the shear force determined by the new model are about 20% greater than those available in the literature. Full article

The performance-based seismic design pretends to take care of the lives of the occupants and reduce the cost of damage caused by earthquakes. Several ways of estimating damage and economic losses have been developed, but most of them lack objectivity and have great dispersion in the results. In the last decade, the advancement of technology has allowed the appearance of new methodologies, such as the one developed by the Pacific Earthquake Engineering Research Center (PEER methodology). However, the information regarding application and scope is scarce. In the present investigation, the economic seismic performance for a steel building was determined by applying the PEER methodology with different levels of seismic intensity. A multi-family residential model of special moment frames (SMF) was used, and the structure was designed by means of modal analysis. Spectral, incremental dynamic non-linear analysis was performed where the structural response was determined, with the help of the PACT software. The seismic performance, expressed as the repair costs, repair times, deaths, and injuries, was defined. The results obtained indicate that buildings designed with traditional structural standards can be demolished after the action of an earthquake because the repair costs exceed 40% of the replacement cost. Rare and very rare seismic events can cause the total suspension of the service and a considerable number of deaths and injuries. Full article

This study investigates the strain development in reinforcing bars within the plastic hinge regions of beams and columns, with the main objective of modifying the current acceptance criteria for mechanical bar splices to accommodate high-strength reinforcement. The investigation utilizes numerical analysis based on moment–curvature and deformation analysis of typical beam and column sections in a special moment frame. The results indicate that the use of higher grade reinforcement, such as Grade 550 or 690, results in lower strain demands in the plastic hinge regions compared to Grade 420 reinforcement. To validate the modified seismic loading protocol, over 100 samples of mechanical coupling systems were tested in Taiwan. The test results demonstrate that the majority of these systems can successfully complete the modified seismic loading protocol and are suitable for use in critical plastic hinge regions of special moment frames. However, caution is advised for slender mortar-grouted coupling sleeves, as they were unable to fulfill the seismic loading protocols. These sleeves may be conditionally used in plastic hinge regions of precast columns, provided they meet specific conditions and demonstrate seismic performance through structural testing. The findings of this study offer valuable insight into the design and application of mechanical splices in high-strength reinforcement scenarios. Full article

The progressive collapse of structures subjected to a truck collision with ground floor columns is numerically investigated in this paper. For this purpose, a four-story steel building with a dual system (including an intermediate steel moment frame, with a special concentric steel bracing system in the longitudinal (x) direction, and an intermediate steel moment frame in the transversal (y) direction) is considered. The structure, which was designed according to AISC, ASCE7 and 2800 Iranian seismic standard guidelines, is located in seismic-prone area and subjected to eight different truck collision scenarios. The nonlinear dynamic analyses carried out in ABAQUS on a three-dimensional finite element (FE) numerical model include variations in collision features (i.e., mass and speed of the truck, the height of collision point), and are used to support the analysis of expected damage. The presented results confirm that increasing the truck mass and speed increases damage entity for the column and structure. Several influencing parameters are involved in damage location and progressive evolution. The height of the collision point from the ground also significantly affects the magnitude of structural damage, especially in terms of stress peaks in the panel zones for the target column. Finally, the perimeter columns are more vulnerable to impact than corner columns, in structures with dual system as with the examined four-story building. The presence of a bracing system parallel to the impacting vehicle can in fact reduce the deformation—and thus the expected damage—of the adjacent target column. Most importantly, it is shown that the numerically reproduced collision scenarios (and the associated damage configurations) based on truck impact are significantly more severe than those artificially created based on the conventional column removal method (i.e., alternate path (AP) analysis approach), which confirms the importance of more sophisticated numerical calculation procedures to investigate and assess the progressive collapse of structures. Full article