Search Results (50)

For many years, granular fill has been the preferred fill material in reinforced fill structures (RFSs) due to its high strength and drainage properties. However, the global scarcity of granular fill has necessitated the exploration of alternative fill materials. This study aims to evaluate the performance of three different alternative fill materials: (i) weak onsite fill (fill 1), (ii) lime-stabilized onsite fill (fill 2), and (iii) recycled construction and demolition (C & D) waste (fill 3). A finite element analysis (FEA) was conducted to assess the stability and horizontal displacement of an RFS and the long-term creep deformation of geogrid using viscoelastic (time-dependent) model in Plaxis. This RFS comprised a combination of wire mesh and geogrids, serving as primary and secondary reinforcement materials, respectively. The results indicate that fill 1, with low shear strength and stiffness, induces excessive lateral displacement and was unstable, making it unsuitable for RFS applications. In contrast, Fill 2 and Fill 3 achieve Eurocode-based safety factors of 1.12 and 1.19, respectively, while significantly reducing horizontal displacement. The long-term creep deformation analysis of geogrid in the case of fill 1 exceeds the prescribed serviceability strain limit threshold, while in the cases of fill 2 and fill 3, it conforms to the serviceability strain limit, which indicates effective mobilization of tensile resistance without excessive elongation. Finally, an analysis was conducted to optimize the geogrid length and to see its impact on cost and performance. The results revealed up to a 29% cost reduction while ensuring performance criteria. These findings validate lime-stabilized onsite fill and recycled C&D waste as viable, cost-effective alternatives to conventional granular backfill, ensuring not only stability and serviceability but also the long-term performance of geogrids in RFSs. Full article

In some occasions, outdoor steel structures like wind towers, bridges, winter sports facilities, and so on are subjected to extreme environmental conditions with the presence of ice and/or with below-zero temperatures. Sometimes in these situations, surface protection of the steel structure is usually designed using hot-dip galvanizing to improve its durability. In these special circumstances, the structure’s connections are also exposed to adverse climatic agents. International standards and codes such as Eurocode 3 or EN1090-2 do not provide indications for these cases. In this experimental research, 24 specimens of non-slip joints with hot-dip galvanized faying surfaces and HV M16 and M20 bolts have been studied. Twelve specimens were subjected to fourteen twelve-hour freeze-thaw cycles, with temperature oscillation and periodic immersion in water. Next, six of the connections were subjected to a slip test under monotonic load at a temperature of −20 ± 0.5 °C and the other six at room temperature. The results were compared with joints kept at room temperature and not subjected to freeze-thaw cycles for the same period of time. The main conclusion of this piece of research is that the short-term slip resistance behavior of joints with hot-dip galvanized surfaces is not reduced for the cases studied. Full article

The article provides information about strengthening cold-formed thin-walled steel beams made of the sigma profile. An innovative concept for sectional transverse strengthening of thin-walled beams subjected to concentrated forces was investigated. The proposed solution’s novelty lies in attaching the sectional transverse strengthening to the beam’s cross-section, employing a point crimping technique. This technique requires a specific modification of the cross-section edges, necessitating double-lipped flanges. This strengthening method is innovative, as it has not been previously applied to cold-formed structures. Typically, strengthening is achieved using other cold-formed elements or materials, such as timber, lightweight concrete, or CFRP tapes. The laboratory experimentally validated the proposed method using short- and medium-length beams. The experimental results were then compared with the results of the numerical analyses and the conventional design approach described in EC3. The results demonstrated the feasibility of implementing this type of strengthening, its reliability under load, and the confirmation of an increase in the load-bearing capacity of the experimental samples by 11–24%. Full article

Recently, steel girders with sinusoidal corrugations have become increasingly popular compared to those with traditional flat webs. This paper presents the second part of the research on the application of corrugated plates with different sinusoidal profiles as webs in girders. Parametric studies have been carried out in both linear and nonlinear domains, based on a representative numerical model developed and validated by experimental results. The research focused on the influence of the sinusoidal shape of the web on the shear capacity of the girders and the ultimate failure mode. The analyses were carried out using Abaqus software. Based on the results of the numerical analyses, it was concluded that increasing the wavelength of the sinusoidal wave decreases the ultimate shear capacity of the girders. This parameter also influences the failure mode. The results show that the wave amplitude has a small effect on the critical capacity. However, the amplitude influences the increase in the post-critical load and the size of the plastic zones located in the webs during the final phase of failure. With regard to the geometric parameters of the web, it was found that increasing the web thickness significantly improves the performance of the girders, while the web height has a negligible effect. It was also shown that the design guidelines in Eurocode 3 are very conservative in terms of estimating the shear buckling capacity of beams with sinusoidal corrugated webs and significantly underestimate the values. Full article

The paper addresses the fatigue resistance, fracture behavior, and damage tolerance of a new type of ultrahigh-strength bar for prestressing concrete made of a low-alloy lath martensitic steel. The fracture tests show that the bar steel has a medium-high fracture toughness of 75 MPa m^1/2 and a fatigue cracking resistance that fits the Paris-Erdogan Law as most of Eurocode 3 structural steels. The damage tolerance analysis combines two failure assessment diagrams (FADs), the first focused on the damage level and the second on toughness and yielding capacity as material properties of the bar steel, whose influence and interaction are determinant for failure. The location of the experimental failure data in the FADs indicates that the steel is endowed with a combination of strength, ductility, and toughness able to prevent unexpected failures. The damage micro-mechanisms revealed from the examination of broken specimens differ from fatigue to fracture cracking, but in a manner consistent with the observed mechanical behavior and microstructure of the bar steel. Full article

The verification of a column made from a lipped cold-formed channel section, subjected to pure axial compression relative to the gross cross-section, often results in a combined verification of bending and compression due to the appearance of a shift of the centroid of its effective cross-section. Following Eurocode 3 rules, this requires the determination of two distinct effective cross-sections and various interaction factors. This paper, based on an analytic approach, offers a modification to the actual buckling curve, based on Ayrton–Perry formulation, to include the second-order effects raised by the eventual shift of the effective centroid due to local buckling of the compressed web plate. This eliminates the need to use an interaction formula. The modified buckling curve is verified based on a GMNIA analysis performed on a numerical parametric model, which was previously validated by laboratory tests. In addition, the results are compared with strength results provided by appropriate Eurocode 3 formulas and AISI Direct Strength Method for global-local interaction and with classic experimental results. Full article

This study investigates five cases of municipal solid waste (MSW) landfill slope failures in the USA, China, Sri Lanka, and Greece, with the aim of assessing the safety margins and reliability of these slopes. The stability and reliability of the landfill slopes were evaluated under both static and seismic loading conditions, using pre-failure geometries and geotechnical data, with analyses conducted in accordance with Eurocode 7, employing all three design approaches. Under static loading, the factors of safety were close to unity, and reliability indexes ranged from 1.0 to 2.8, both falling below the recommended values set by Eurocode. The landfill slopes failed to meet the stability criteria in Design Approaches 2 and 3, while in Design Approach 1, four out of five landfills met the criteria. Under seismic conditions, safety factors and reliability indexes were significantly lower than the prescribed criteria in all analyses. Sensitivity analyses revealed that in two cases, unit weight and friction angle were the dominant parameters, while cohesion was the dominant parameter in one case. The findings of this study underscore the importance of establishing minimum design requirements for MSW landfill slope stability to mitigate potential risks to public health and the environment. Full article

This paper presents research concerning the numerical simulation of existing masonry buildings when subjected to pushover analysis. A nonlinear static analysis is undertaken using the commercial software ABAQUS standard, in which masonry structures are modelled using damage mechanics. To validate the chosen input parameters, this study compares two different approaches for static nonlinear modelling, the Finite Element Method (FEM) and the Equivalent Frame Method (EFM), for a simple masonry building. The two methods are compared using the guidelines from Part 3 of Eurocode 8. This study identifies the advantages and disadvantages of various modelling approaches based on the results obtained. The results are also compared in terms of capacity curves and damage distributions for the simple case study of a masonry building created to compare numerical methods. Subsequently, nonlinear pushover analyses with ABAQUS (FEM) were performed on the North Tower of Monserrate Palace, Portugal, in which the material parameters were calibrated by considering the results of dynamic characterisation tests conducted in-situ. Regarding the circular body of Monserrate Palace, the damage distribution of the structure is analysed in detail, aiming to contribute to the modelling of such structural configurations through the Equivalent Frame Method. Full article

The amplitude of a bolt load in dynamically loaded bolted flange joints depends on several factors: the resilience of the bolt and the clamping parts, the magnitude of the working load, the point of action of the working load, the way the working load is transferred from the structure to the bolt, the preload, and the geometrical imperfections of the contact surfaces of the joint. These factors are analysed in many papers, and they are covered in the VDI 2230 guideline and in standards. Fatigue curves (S-N curves) of bolts are determined by tests in which an ideal axial load is usually applied to the bolts. The effects of the bolt strength class, the thread manufacturing process, the surface protection, and the cross-section size on the fatigue strength of bolts are precisely defined. The main problem in the evaluation of bolted joints is the calculation of the actual stress, which is compared with the fatigue curves. Despite extensive research, fatigue-related bolt failures still occur in practise. This article provides a systematic overview of the influences that affect the fatigue of bolts. The conclusions are based on the research results of many authors and on our own analytical, numerical, and experimental investigations. The effects are illustrated using two practical examples of flange bolting. The assessment of fatigue according to Eurocode 3 and the VDI 2230 guideline is discussed in more detail. Full article

A parametric investigation of several unbraced steel frames with regular and irregular geometry subjected to elevated temperatures is carried out in this study to determine the most accurate procedure and buckling lengths to be considered during the structural design under a fire situation. In such conditions, the stiffness and strength of steel decrease considerably due to high temperatures, and uncertainty remains in the application of the fire design rules of Eurocode 3 Part 1-2 (EN 1993-1-2) for unbraced frames as no information is given regarding the treatment of the deformed geometry (the so-called second-order effects). More precisely, it is unclear in the norm whether the verification based on the buckling length concept could be used or if a second-order analysis to calculate the internal forces is sufficient to ensure the stability of the frame in case of fire. Based on the linear buckling analysis of the steel frames accounting for the temperature development during a fire, recommendations for the appropriate buckling lengths to be used are given. Finally, it is demonstrated that using the recommended buckling lengths together with the design rules of EN 1993-1-2 leads to results in favor of safety when compared to the results obtained with the finite element method. On the other hand, it is concluded that using second-order internal forces and the real length of the columns as the buckling length, as suggested for room temperature design, yielded results outside safety when compared with the finite element method, and this analysis and verification procedure should not be used for the case of fire. Full article

An earthquake is one of the most significant and shocking natural disasters ever documented anywhere on the planet. Throughout history, it has claimed millions of lives and wreaked devastation on infrastructure. Because earthquake forces are spontaneous and unpredictable, engineering methods must be honed to investigate buildings under the impact of these forces. The dynamic and static computations of four RC multistory structure prototypes with various elevations in a high seismic zone are compared in this paper. The project under review is modeled as a 3, 6, 12, and 18-story establishment, and it is analyzed employing ETABS vs. 2019. The Equivalent Lateral Force (ELF) Procedure is used for static experimentation, while the Response Spectrum (RS) Procedure is employed for dynamic investigation. Both calculations are performed as per the EUROCODE 8-2004 recommendation. The ELF seismic load practice utilized was for the country of Norway, which has similar parameters to the ES-EN 8-15 seismic regulation Type I target RS, with ag/g = 0.1, spectrum type = I, soil factor S = 1.3 ground type, spectrum period (Tb, Tc, and Td) 0.1 s, 0.25 s, and 1.5 s. For the RS investigation, the parameters employed are as per ESEN-2015, ag/g = 0.1, and the spectrum type = I and ground type = B parameters were involved in the same manner for the RS analysis. The soil factor was set to 1.35; the spectrum period was set to (Tb, Tc, and Td) 0.05 s, 0.25 s, and 1.2 s. The behavior factor = 3.8, the lower bound factor = 0.2, and the damping ratio = 0.05. The results are then compared by employing different components such as displacement, story drift, story stiffness, base story shear, and story moment. Ultimately, a comparison of static and dynamic investigations has been carried out. Compared to the RS approach, the ELF technique produces more additional displacement, total drift, and base shear. As per the findings of this paper, for high-rise and tall buildings, dynamic analysis such as RS should be used rather than static analysis (ELF). Full article

This paper concerns the Eurocode 3 Part 1-3 (EN 1993-1-3) methods for calculating the distortional buckling (bifurcation) load of cold-formed steel-lipped channels subjected to axial force, major and minor axis bending. More specifically, the paper presents the results of a parametric study that assesses the accuracy of the simplified method in EN 1993-1-3, which relies on direct/iterative hand calculations and an approximate mechanical model, through comparison with “exact” numerical results, obtained using semi-analytical linearized buckling analyses based on Generalized Beam Theory, which are also allowed by the code. Isoline error maps are presented for a wide range of geometric and material parameters, covering common commercial profiles and corresponding to a dataset of more than 24,000 cases. These maps make it possible to identify the parameter ranges leading to an acceptable error and, even though they strongly depend on the loading, general remarks concerning the expected error pertaining to the simplified method are drawn. Full article

Structures must provide strength, stability, and stiffness to buildings and at the same time be efficient. This study addressed the effect of design elements and parameters on the strength of bolted lateral connections in steel beams under bending using the component-based finite element method. The variables evaluated were plate thickness, horizontal and vertical spacing between bolts, and geometric arrangement of bolts. Finite element software was used to evaluate the stress state of the junction plate, its plastic deformation, and bolt shear. A sensitivity analysis was performed to determine which bolt arrangements result in safer and more efficient designs using the same components. Stress distribution within the junction plate and plastic deformation values were used to evaluate the structural performance of the joints according to EuroCode 3. The results showed that placing bolts near the edge of a plate affected the bolts’ utilization, especially with thinner plates. Additionally, introducing an offset between central and outer bolt rows is not recommended as it worsened the stress distribution and the structural performance. Full article

The use of pultruded fiber reinforced polymers (PFRPs) in strengthening and sustainable design of bridges and other structures exposed to corrosion and resistance reduction factors is growing rapidly. However, a comprehensive understanding of the structural behavior of these materials under various loading conditions is crucial to unlock their full potential and promote their wider use in diverse structural and industrial applications. Pultrusion profiles can be also used as beams in bridges. One important aspect of the structural behavior of PFRPs is their buckling behavior, particularly in thin-walled open cross sections. Lateral torsional buckling is a probable instability mode for beams with thin-walled open cross sections that are not laterally restrained along their span. Therefore, research on the buckling behavior of PFRP members is essential. In this study, the analytical responses of channel-shaped PFRP beams in bridges under pure bending are calculated using an equation in the Eurocode 3 regulation. The buckling behavior of these beams is then investigated through numerical modeling using the finite element package Abaqus. A total of 75 specimens of PFRP channel profiles with different thicknesses in various spans and lateral restraint conditions are studied for their lateral-torsional buckling behavior. This study uniquely explores the behavior of PFRP beams with lateral restraints, a novel aspect in the field of lateral-torsional buckling research of PFRP beams. The results show that the analytical equation used for these beams needs to be modified to more accurately estimate the buckling loads of FRP beams under the conditions studied in this paper. Full article

In a previous work, the fatigue behaviour of different hot riveted joints under fatigue loadings were experimentally calculated. In particular, the experimental data showed a Wöhler curve slope close to five against the slope of three proposed by Eurocode 3. However, two series of shear splice riveted joints showed, at two million cycles, a stress range very close to the value suggested by Eurocode for shear splices that use non-preloaded high-strength bolts. In order to clarify the fatigue behaviour of riveted joints at high- and medium-fatigue regimes, this paper presents a preliminary three-dimensional non-linear FE analysis of a double-riveted lap joint previously analysed experimentally. Different friction coefficients and rivet clamping stress have been taken Into account, as well as the elastoplastic behaviours of the main plate subjected to tensile loadings. The numerical analysis shows that the friction force tends to reduce the range of stresses at the net section during fatigue loadings, and the force distribution or the stress concentration on the rivets is always critical for the external rivet, which is also the case regarding the non-linear behaviour of the material. Full article