Driven by increasing environmental demands within the construction sector, steel-timber composite structures have gained considerable attention as sustainable load-bearing alternatives. Most existing solutions rely on dowel-type fasteners, which often induce premature timber damage during early loading stages, thereby limiting mechanical performance and disassembly and reuse potential. This study introduces a novel shear connection concept aimed at increasing the yield resistance of timber, thereby promoting disassembly and reuse by reducing damage during the loading phase. The experimental programme consisted of three distinct test series: (i) isolated local timber crushing tests to examine failure mechanisms and assess the performance of existing analytical formulations; (ii) push-out tests on two configurations of the proposed steel block connection; and (iii) push-out tests on conventional bolted connections for sake of comparison. The experimental results were subsequently reproduced using analytical formulations and detailed numerical models. Subsequently, a small parametric study was conducted to identify the critical components governing the connection response. The results demonstrate that the proposed steel block connection significantly improves yield resistance and elastic stiffness compared to conventional bolted systems. By enhancing the yield resistance and thereby delaying the onset of irreversible damage to higher load levels, the connection offers improved suitability for reuse and disassembly, which is fully aligned with contemporary circular construction objectives. The study also shows that, although Eurocode-based timber crushing models yield reasonable predictions for isolated crushing behaviour, more advanced formulations are required to capture the connection response with greater accuracy.

The application of design by finite element analysis (FEA) is becoming increasingly prevalent in engineering practice; however, codified provisions remain scarce. The vision of CEN/TC250/SC3 was to develop a new comprehensive document based on the existing provisions currently distributed throughout the different Eurocode 3 parts, and with extension where necessary to cover all fields of structural steel design. Within the development process, two documents were prepared: (i) the code, EN 1993‐1‐14 and (ii) a Technical Report, TR 1993‐1‐141. The new code provides rules on the use of finite element analysis and other numerical methods for verifying ultimate limit states, serviceability limit states and fatigue. In parallel, the Technical Report provides background information and explanations on all aspects of the code, as well as benchmark cases and design examples to support the correct application of the EN 1993‐1‐14 design rules and the necessary benchmarking required for model verification and validation. The assumed stakeholders are mainly designers who can find direct guidance for design by finite element analysis in daily engineering practice. The current paper gives an overview of the new code and accompanying Technical Report, as well as the development process and harmonisation within the current Eurocode 3 framework.

Reinforced concrete dapped-end connections, which are common in existing Gerber-beam bridges, typically feature an inclined corner crack at service loads due to high stress concentrations in the re-entrant corner. These cracks exacerbate corrosion issues and increase the stresses in the dapped-end reinforcement, which in the event of further deterioration and increased loading may lead to yielding and failure of the connection. This paper proposes a kinematics-based model that predicts the opening of the corner crack based on first principles: compatibility, equilibrium, and constitutive relationships. The model stems from an earlier model for strength of dapped-end connections failing along re-entrant corner cracks and extends it to predict the crack widths under increasing load up to failure. The modelling assumptions are discussed, and the crack width predictions are extensively validated using 42 large-scale tests. The results show good agreement between measured and predicted crack widths, as well as the peak flexural resistance of dapped-end connections. The average experimental-to-predicted ratio for the flexural strength is 0.98 and the coefficient of variations is 8.8

Hybrid-coupled wall systems are a type of structural solutions that can be configured to achieve ductile seismic dissipation and enhanced post-earthquake repairability in buildings located in regions of moderate-high seismicity. In such systems, reinforced concrete or steel-concrete composite shear walls provide lateral stiffness and strength, while energy dissipation is concentrated in steel components designed to be replaceable after seismic events. This paper presents an experimental investigation on a novel hybrid-coupled wall system incorporating externally mounted, replaceable steel seismic links as dissipative components. The proposed configuration consists of a reinforced concrete or composite shear wall connected to adjacent steel columns through short steel links designed to yield in shear. The link-to-wall connection is detailed as moment-resisting to ensure force transfer and enforce the intended shear yielding mechanism in the link, while the simple link-to-column connection is configured to facilitate disassembly and replacement. A comprehensive experimental programme comprising monotonic and cyclic tests was conducted on subsystems to assess the overall response, the hysteretic behaviour, the damage localization and the connection performance. The results demonstrate stable hysteretic response with inelastic deformations effectively confined to the replaceable links, while the walls, boundary columns, and connection regions remain elastic. No degradation or unintended damage was observed outside the predefined dissipative components. The findings provide experimental evidence that hybrid-coupled walls with replaceable steel links can achieve controlled and predictable seismic response together with post-earthquake repairability, using a simplified dissipative strategy, and constitute a viable alternative for steel-concrete composite lateral load-resisting systems.

Unfired clay blocks offer a sustainable alternative to traditional masonry by reducing COQ emissions and raw material consumption. Despite these environmental benefits, detailed knowledge about their structural properties remains limited. To fill these knowledge gaps, this research focuses on the creep behaviour of unfired clay masonry by examining the creep deformation of unfired clay masonry under long-term loading. Test specimens made from various types and combinations of unfired clay blocks (Compressed Earth Blocks (CEB) and Moulded Earth Blocks (MEB)) and mortars (Earth Mortar (EM), Earth Adhesive Mortar (EAM) and Bastard Mortar with Earth adhesive (BME) were subjected to a constant compressive load for three months, during which deformations were measured. These tests are the first of their kind exploring the creep behaviour of unfired clay masonry. The results highlighted that MEB masonry has a 74-140 % higher creep deformation compared to CEB masonry (MEB-EM: 1692 & micro;s; MEB-EAM: 1441 & micro;s; CEB-EM: 705 & micro;s; CEB-EAM: 830 & micro;s), possibly due to their lower compressive strength (MEB: 4 MPa, CEB: 10 MPa). For CEB masonry, the mortar type did only influence the creep behaviour to a very limited extend, where for MEB masonry this influence was much more pronounced, with EM mortar showing 17 % higher creep deformations (1692 & micro;s for EM compared to 1441 & micro;s for EAM) and 203 % higher shrinkage (558 & micro;s for EM compared to 184 & micro;s for EAM). On the results of the tests, multiple models (Burgers, Lenczner, and Van Zijl) were fit and compared for their ability to predict the creep behaviour of unfired clay masonry. Here it was shown that the Burgers model provided the best fit if no correction for shrinkage is accounted for. If this correction is required, the Van Zijl model is the better choice.

Roman aqueduct bridges are widespread across the seismically active Mediterranean, yet their earthquake vulnerability remains insufficiently documented. This study evaluates the first-order seismic response of such structures and applies the approach to the Antioch-on-the-Orontes aqueduct at Harbiye (Antakya, Türkiye), a monument affected by multiple construction phases, repairs, and partial collapses. Linear static, modal, and time-history finite-element analyses were performed on idealized arch-and-pier configurations subjected to recorded ground motion. Variations in pier height, arch width, deck thickness, reinforcement, stiffness, Poisson’s ratio, and density were tested. The models consistently identify the arch springings and pier bases as recurrent stress-concentration zones. Vulnerability increases with pier height, arch width, deck thickness, lower stiffness, and greater structural mass, whereas buttresses, larger piers, and lower-density materials improve stability. In the Antioch models, the highest computed stresses coincide spatially with several observed damaged, collapsed, or repaired sectors. The reinforced construction stage shows reduced stress concentrations relative to the unrepaired configuration. These results support the interpretation that seismic shaking plausibly contributed to the monument’s structural evolution and demonstrate the value of simplified numerical modelling for archaeoseismological assessment of historical masonry infrastructure.

This paper presents the results of the numerical analyses conducted to reproduce the shake table tests performed in Lisboa at the LNEC laboratory (Laboratório Nacional de Engenharia Civil) on two full-scale masonry prototypes. The equivalent frame modeling strategy was chosen as an effective compromise between computational efficiency and accuracy in simulating the seismic behavior. The model was developed using a blind prediction approach, like that typically employed by practitioners in seismic assessments of existing buildings. Based on geometry and construction details, appropriate modeling strategies were implemented to capture the nonlinear behavior of structural elements. A piecewise-linear constitutive law was applied and, as a novel contribution, the flange effect was incorporated using an equivalent beam, calibrated with a practice-oriented analytical expression that accounts for geometry and material characteristics of the web and flange. Experimental data from panels with similar masonry were used to calibrate the strength parameters at the structural element scale. Another relevant contribution was the validation of EF models in predicting the seismic response of modern masonry typologies with box-like behavior under increasing levels of nonlinearity and structural irregularity in the two prototypes. To this aim, nonlinear dynamic simulations replicating the shaking table tests were performed and compared with the experimental results. Traditional techniques were combined with more innovative tools to manage the large volume of experimental data and gain insights into the prototypes’ response. The numerical analyses successfully reproduced the experimental behavior across the full set of data and for both models, without the need for further refinement.

Abstract This paper presents a newly developed shear connection for steel–timber composite (STC) floor beams. The connection's mechanical behaviour is investigated through experimental tests, including push‐out tests and hygroscopic assessments, which are used to determine the load–slip response, identify the governing failure mode, and evaluate the effects of dimensional changes in wood. Finite element method (FEM) simulations are then conducted to reproduce the connection behaviour numerically. Finally, a component‐based method is proposed to determine the shear connection properties, including stiffness and strength, and to assess its efficiency through comparison with conventional dowel‐type connections.

Due to the highly demanding energy standards in Europe, thermal break elements, such as aerated autoclaved concrete (AAC), have become increasingly popular in modern residential buildings made of masonry cavity walls. Furthermore, a damp-proof course (DPC) layer is also used on top of the thermal break element to prevent water seeping and eventual entrapment due to capillary action. The presence of a combined AAC/DPC layer can therefore have an adverse effect on the global strength of a masonry wall, and in particular its shear resistance. This study aims at filling that knowledge gap through experimental investigations on traditional masonry walls and composite masonry walls, i.e. with an AAC and a DPC layer. The in-plane shear behavior is compared between both types of wall specimens using load-displacement curves and failure modes to highlight the structural influences of AAC and DPC. Existing analytical design approaches are also assessed based on the test results.

Steel‐timber composite (STC) structures have gained increasing popularity in recent years due to their eco‐friendly character while structurally performant. To mobilize the synergy between the two materials, connections play a key role. Among the various connection methods, dowel‐type connections are the most commonly used for STC applications. Analytical models from current standards, such as the European Yield Model, are often employed to predict the strength of these connections. However, the performance of these models, particularly when applied to timber products like Cross‐Laminated Timber (CLT), which consists of layers oriented in different directions, remains uncertain and requires further validation. Accurately predicting the strength of these connections plays a critical role in ensuring the ductile response of steel‐timber connections under lateral loads. In this study, a numerical model of a steel‐to‐CLT dowel‐type connection is developed and validated against experimental data from the literature. Furthermore, analytical models proposed in the literature are critically evaluated for their ability to predict the strength of steel‐timber connections under varying configurations, including differences in timber layering and steel component properties. The limitations of these models are discussed, focusing on their inability to fully capture the load transfer mechanism in dowel‐type connections covering the diversity of timber products that are often combined with steel beams, such as CLT panels. This research provides valuable insights into the behavior of steel‐timber connections and highlights the importance of accurate strength prediction in contributing to their ductile response.

Extensive public infrastructure was built in many countries in the 1960s-1980s. As a result, in the coming decade, a large number of aging structures will require safety assessment. The structural assessment is of prime importance given the increase of loads over the last few decades, as well as outdated designs that do not satisfy the strength and detailing requirements of modern design code provisions. Particularly challenging is the shear strength assessment of prestressed concrete bridges, which nowadays is carried out according to modern shear provisions based on mechanical models. Typically, prestressed concrete structures built more than 50 years ago do not adhere to the prescribed rules because existing members possess light shear reinforcement with lacking end anchorages and tend to result in shear strength deficiency when assessed according to current codes. This paper presents the results of three full-scale tests of 1.90-m-deep posttensioned bridge girders with bonded curved tendons extracted from a 50-year-old viaduct in Belgium. The main test variable is the position of the applied point load. Global and local deformation measurements, crack diagrams, and deformed shapes at different loads were examined to establish a comprehensive picture of the behavior of the beams. It is shown that the failure of the beams is governed by concrete crushing in the top flange after yielding of the main flexural reinforcement. The girders also showed a significant reserve shear capacity not captured by shear models in current codes. Such built-in conservatism can require very disruptive and costly interventions, which are not economically and environmentally sustainable.

This article presents the experimental results obtained from the cyclic testing of an innovative hybrid coupled wall (HCW) system – a fixed-base reinforced concrete (RC) wall coupled with two steel side-columns via steel coupling links, where the wall carries almost all the horizontal shear force and the overturning moments are partially resisted by an axial tension-compression couple developed by the two steel columns rather than by the individual flexural action of the wall alone. The initial stiffness properties were primarily identified through the first cycle, estimating the yield force and displacement of the HCW system. Incremental cyclic tests were then conducted according to the ECCS 1986 provisions, targeting specific performance levels: (i) “reparability” of the HCW, i.e. the yield displacement, where the steel links yield with negligible damages in the wall and the self-centering capacity of the system is active, so that the actual replacement capacity of the elements can be validated; and (ii) a displacement level corresponding to a major earthquake with very low probability, which activates the wall as an additional dissipative element, eventually leading to a non-reparable damage state. Relevant results have been discussed through graphical and real-life illustrations. Finally, the constructional aspects are also discussed from a real-life application viewpoint.

Reinforced concrete dapped-end connections are susceptible to formation of inclined cracks at the reentrant corner under service conditions. As these connections also work with high shear stresses, they require a high amount of reinforcement to ensure sufficient load-bearing capacity. To deepen the understanding of this topic, an experimental campaign of eight large-scale dapped-end connections featuring diagonal reinforcement is presented. These specimens, which are among the largest available in the literature, are similar in size to the dapped ends typically used in bridges. The test series captures both flexural and shear failures of dapped ends. The crack displacements, crack patterns, and elongation of main reinforcement are reported, with 56 continuous measurements of deformations. The test results of this study are used in conjunction with a similar study on specimens with orthogonal reinforcement to investigate the impact of reinforcement layout. For the same amount of dapped-end reinforcement, specimens with diagonal reinforcement are considerably stronger than the corresponding connections with orthogonal reinforcement. For both reinforcement layouts, the crack widths exceeded typical code provisions under service conditions.

Steel circular hollow sections (CHS) offer a number of advantages compared to their open section counterparts such as better resistance under tension, compression, bending in all directions and an overall reduction of structural weight, required material for corrosion and fire protection. Nevertheless, the traditional methods to connect open section beams to CHS columns often demand a significant amount of fabrication work, leading to high expenditure and resource consumption – therefore limiting their use in the current industry. These issues can be solved with an automatized joint fabrication. To that purpose, this article proposes two innovative “passing-through” I-to-CHS joints, achieved via laser cutting technology (LCT). Experimental and numerical studies were conducted to assess the joint fabrication aspects as well as the structural performance of the proposed joints. The results showed that the proposed joints can offer respectively 2.5- and 10-times larger strength and stiffness properties compared to a conventional directly welded I-to-CHS joint having similar section properties for the beam and the column. However, this study focuses on the environmental sustainability and economic feasibility of the proposed joints. A cradle-to-site life cycle analysis is conducted using multi-storey frame structures. The environmental and economic impact of the proposed joints are compared with different types of existing I-to-CHS joints in order to assess their possible benefits and limitations. Thanks to the savings in the raw material, surface treatment and transportation resources, it could be stated that, the passing-through approach with LCT offers approximately 32−42% reduction in the construction and fabrication costs of the multi-storey structures while reducing the CO2 emissions by 24−28%, compared to the directly welded I-to-CHS joints.

Perforated load-bearing clay masonry walls are a very efficient construction system, with a very favorable resistance-to-weight ratio, allowing rather thin load-bearing walls (typically 12 to 14 cm, as used in Belgium or in the Netherlands). However, due their limited surface mass, additional devices must be implemented in those walls when used for instance for apartment buildings, in order to reach the requirements in terms of acoustic insulation. Those devices are rubbers layer with a thickness of 1 cm located at the base, and if needed at the top, of the walls in order to cut the vertical transmission of acoustic vibrations. Although not aiming at improving the seismic behavior of the walls, these flexible layers do however modify significantly the stiffness of the wall and hence its dynamic properties, acting as a kind of partial seismic isolation and also possibly shifting a shear failure mode to a rocking behavior. The present contribution summarizes the findings of an experimental program aiming at characterizing the cyclic behavior of such a system submitted to in-plane horizontal loads.

Hybrid testing provides an efficient and less costly way to explore the response of structural systems to realistic dynamic or seismic loading. However, the required equipment to execute hybrid tests are high-cost tools. To get insight in the hybrid testing methodology, a small-scale set-up has been developed in this project. An Arduino UNO controls the system that imposes the displacement to a linear actuator. Connecting the small-scale set-up, i.e., the Arduino UNO, to MATLAB allows imposing a time history to the physical substructure. A load cell measures the restoring force which will be communicated to MATLAB by the Arduino UNO. Numerical integration based on the Gravouil-Combescure scheme with Classic Lagrange Multipliers (CLM) determines the displacement for the next time step. This paper describes hot spots of the methodology and the results of a demonstrative experimental test. The experiment consists of a 4 degree of freedom (DOF) numerical model combined with a 1 DOF physical specimen. The installed linear actuator only has one gearing option, which leads to a possible overshooting loop. Interesting conclusions can be drawn from the analysis of the small-scale set-up in view of its future upscaling and implementation of the hybrid test method at laboratory scale. Firstly, the linear actuator requires a non-negligible amount of time to reach the imposed displacement which imposes boundary conditions in the MATLAB directives. Secondly, a velocity-controlled actuator is essential in the exploitation of hybrid testing. Thirdly, the displacement tolerance influences the stability of the system. If one increases the displacement tolerance, the risk of an overshooting loop decreases. However, the accuracy might be influenced. Good balance must therefore be found between stability and accuracy.

As recent research findings evidenced a significant potential of the steel-concrete hybrid coupled wall (HCW) systems, further research activities are still needed for addressing particular issues and for developing advancements in the analysis, design, and detailing. These aspects have been addressedwithin the European research project "HYCAD", which also represented the research framework of the current study. The first step of the studywas represented by the development of a technical solution for connecting the replaceable dissipative shear links to the steel-concrete composite wall, while the second step consisted of experimental and numerical validation. Based on experimental and numerical outcomes (i.e., component level tests and FEM/FEA), the current paper investigates the behavior and the seismic performance of a newly introduced steel-concrete HCW system. In particular, a case-study was carried out on a 3D multi-story building structure with perimeter lateral load resisting frames, each composed of: (i) a HCW, i.e. a steel-concrete compositewall coupled to steel columns through a set of replaceable steel shear links; (ii) a moment resisting frame (MRF). Alongside an introduction and a description of the case-study structural system, the current paper makes an overview of the following: (i) experimental validation of the proposed technical solution (i.e., replaceable shear link to composite wall connection); (ii) simplified numerical modeling procedure of the shear links; (iii) seismic performance of the 3D multi-story building based on nonlinear static and dynamic analyses; (iv) main conclusions.

Concrete walls or columns reinforced by one or multiple embedded steel profiles have gained popularity due to their improved strength, ductility and energy dissipation capacity. However, certain gaps in information are remaining in the available standards regarding the design of such non-conventional reinforced concrete systems. In particular, a proper characterization of the longitudinal shear transfer properties at the steel-concrete interface is required for a reliable design. Although sufficient information is available regarding mechanical connectors like shear studs, detailed information is required for any other types of mechanical connectors such as welded steel plates or for configuration without mechanical connectors. Moreover, even for cases with mechanical connectors, the orientation of the profile - and hence the distance to the face of the concrete - and the tying system can have a significant influence on the load transfer mechanisms. To this purpose, this article presents the outcomes of a set of push-out tests with the objective of comparing the force transfer mechanisms from the steel profile to the surrounding concrete wall for different types of interfaces. 13 tests specimens are investigated, with flexible (shear studs) and/or rigid (steel plates) shear connectors, considering different orientations of the profile and tying mechanisms, as well as a comparison with profiles without mechanical connectors. Based on the test results and subsequent analytical assessment, relevant conclusions are drawn regarding the longitudinal shear transfer at the steel-concrete interface. If necessary provisions are followed, welded steel plates prove to be an effective alternative to the shear stud connectors in terms of connector strength. The orientation of the embedded steel profile, consequent position of the mechanical connectors and their distance to the concrete face are observed to have a significant influence on the compression strut evolution, which therefore dictates the necessity (or not) of horizontal confinement or ties. Furthermore, combining the shear strength offered by different types of mechanical connectors and the steel-concrete bond offer a precise estimate of the longitudinal shear strength and therefore indicates towards the conservative nature of the design provisions suggested by the available standards.

The seismic behaviour of hybrid coupled walls (HCWs) made of a single reinforced concrete (RC) wall connected to two steel side columns through steel links, named as single-pier HCWs (SP-HCWs), is studied through nonlinear finite element simulations. The design concept is that the steel links are intended to work as dissipative elements while the steel side columns and the RC wall should remain elastic. Given that previous studies highlighted difficulties in avoiding damage at the base of the RC wall due to the concentration of bending moment, this study focuses on a special configuration providing very limited damage at the base of the RC wall that could be rapidly and economically repaired. The original scheme of SP-HCW with fixed base is modified introducing a hinged connection combined with vertical steel elements, called corner components. A ductile design methodology is proposed and applied for proportioning 54 case studies with different building heights, coupling ratios, height-to-length ratios of the RC wall, in addition to different base conditions (fixed base, hinged base with corner components designed as non-dissipative elements, hinged base with corner components designed as dissipative elements). Results of nonlinear finite element analyses validate the design methodology and highlight the potentialities of the proposed solutions, showing the benefits of a hinged base with corner components.

Due to the highly demanding energy standards in Europe and challenging weather conditions, thermal break elements, such as aerated autoclaved concrete (AAC), have become increasingly popular in modern day residential buildings made of masonry cavity walls. Furthermore, a dampproof course (DPC) layer is also used on top of the thermal break element to prevent water seeping and eventual entrapment due to capillary action. The presence of an AAC layer and of a DPC can have an adverse effect on the in-plane shear strength of a masonry wall, although information on this is barely available in the existing literature. This study aims at filling that knowledge gap through experimental investigations on traditional masonry walls and composite masonry walls, i.e. with an AAC and a DPC layer. The in-plane shear behaviour is compared between both types of wall specimens on the base of load-displacement curves and observation of failure modes. The capacity of analytical design approaches in predicting the test results has also been assessed. For the tested configurations, it can be concluded that the presence of AAC and DPC makes the failure mode switch from diagonal shear sliding combined with flexural toe crushing to horizontal shear sliding with crushing localized in the AAC layer, associated to a drop of the resistance by 6-9 % depending on the type of clay units and mortar. The proposed analytical method, derived from EN 1996-1-1, is providing a safe estimate of the test results with a similar level of accuracy for traditional and composite configurations (predicted values in the range of 75-86 % of the measured values). Finally, the influence of the definition of the compressed length and of the shear span ratio are shortly discussed.