Timber structures often combine multiple lateral load-resisting systems whose interaction under serviceability loading remains insufficiently understood. This study presents a full-scale experimental investigation into the lateral response of a single-storey timber mock-up comprising lightweight timber frame wall diaphragms, a roof diaphragm, and a centrally positioned moment-resisting frame. Two loading scenarios (both in serviceability limit state to understand its initial, pre-yield behaviour) were examined, in which a horizontal load was applied at the roof diaphragm level: one without additional vertical load (Test-1) and one with a uniformly distributed roof dead load of 1 kN/m2 (Test-2). Extensive instrumentation enabled a detailed assessment of load distribution, deformation behaviour, and system interaction.The results show that the lateral response is governed mainly by the interaction between the structural components rather than the summation of their individual stiffnesses. Without additional vertical load, the timber walls carry most of the horizontal load, while the moment-resisting frame (MRF) engages only at higher load levels. When a vertical load is applied, friction between the roof and walls increases significantly, reducing overall deformation and leading to a more stable, uniform load distribution. In this case, a large part of the horizontal load is dissipated through friction, and the relative contribution of the MRF remains limited, although more consistent throughout loading.Despite identical detailing, the wall diaphragms exhibited markedly different stiffness and deformation responses, highlighting the sensitivity of full-scale timber systems to construction tolerances and boundary conditions. Overall, the findings demonstrate that vertical dead loads must be considered when assessing the lateral response of timber structures.

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 The structural assessment is of prime importance given the increase of loads over the last few decades, as well as outdated designs that do not satisfy the strength and detailing requirements of modern design code provisions.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.

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.

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.

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.

The present article is dealing with an assessment of the longitudinal shear at the steel‐concrete interface using several types of mechanical connections. Experimental and numerical tests have been performed to understand better the short and long‐term effects of the influence of the newly defined connectors.

Steel profiles are often embedded in reinforced concrete (RC) members (specially columns) to achieve higher performance in a localised manner. Although the RC and steel‐concrete composite zones of such members can be respectively designed according to the Eurocodes 2 and 4, the transition zone between the steel profile and its surrounding concrete needs to be adequately designed to ensure an effective transmission of the axial force, shear and bending moments carried by the interrupted steel component. This is currently not covered by the design standards and is only partially covered by the current literature. This article proposes a design procedure for such transition zones relying on a 2‐steps approach: (1) Definition of the transverse load to be transferred from the steel part of the composite zone to the RC part, based on a reasonable distribution of the contact pressure between the profile and the surrounding concrete; and (2) Evaluation of a suitable “strut & tie” mechanism to ensure the appropriate transfer of this load and consecutive design of the transverse reinforcement. In order to evaluate the efficiency of the design approach, the transition zone between a composite and a pure RC part of a locally composite column was investigated experimentally. Four test specimens were designed and tested in order to study the influence of certain parameters, e.g. length of the assumed transfer zone, presence of one or two lateral beams at the level of the transfer zone, compression level in the column, etc.

The European research project SmartCoCo (Smart Composite Components) aims at elaborating a design methodology to be used for all situations in which steel profiles are used to reinforce locally what for else remains a classical reinforced concrete structure. In this framework, an experimental campaign is carried out to study the transfer of compression/tension forces from a steel profile to the surrounding concrete by longitudinal shearing of the steel-concrete interface without creating local disturbances, like transverse cracking or splitting of concrete around the steel profile. The present paper presents the general context and the proposed design methodology. It describes then the test specimens, test procedure and results. It concludes with recommendations for the calibration of the design procedure, including values of the bond resistance, shear resistance associated to a load transfer using mechanical connectors (shear studs or welded plate) and detailing of the transverse reinforcement.

In the current version of EN 1992-1-1, the shear and punching capacity of beams and slabs without shear reinforcement is governed by the smallest width of the cross section in the tensile area. The semi-empirical formula in this code is appropriate for rather deep beam elements without contribution of the flanges and transfer stiffeners to the shear capacity. However, it can be presumed that for rather stocky beams or slabs with small void formers these components contribute and improve the shear capacity of the global element. To evidence the increased capacity of such slabs in comparison with the single beam theory, a limited test program was set up by Airdeck Building Concepts and Hasselt University (Belgium). Four-point bending tests were carried out on elements with a width of 600 mm, span of 2400 mm and thicknesses of 220 and 340 mm with or without void formers. Because these systems are mostly composed by a precast plank with a thickness from about 60 to 70 mm (with fixed void formers) and a topping cast on site, special attention was taken to the interface to avoid an early failure at the shear interface. Different approximations are investigated for deducing the resistance of the slab with voiding elements by application of a reduction factor on the resistance of a solid slab. It appears from this preliminary set of tests that a volumetric reduction ratio provides the best though safe estimate for this slabs.

The design of walls or columns with several encased steel profiles as reinforcement has similarities with classical reinforced concrete, but also original aspects which need specific design approaches. Until now there has been experimental research and numerical models, but simple design methods are lacking. In the proposed method, the classical truss model used to design reinforced concrete for shear is extended to bring in the encased profiles contribution to shear stiffness. This allows to distinguish the action effects in the steel profiles and in concrete and to make separate checks for shear of the steel profiles and the concrete section with transverse reinforcements. A method to evaluate longitudinal shear action effects and the compression stresses at the steel profile – concrete interface is developed. Design checks in the format of Eurocodes 2 and 4 are proposed.

The objective of the present contribution is to present the outcomes of an experimental campaign carried out in the frame of the European research program Smartcoco and aiming at validating a design approach for determining the shear performances of RC wall reinforced by multiple encased steel profiles. The experimental campaign comprises 6 walls, ranging from a classical RC wall taken as a reference to configurations with multiple profiles with studs or plate stiffeners to ensure the transfer of the longitudinal shear at the steel-concrete interface. Vertical cantilever tests were performed on the specimens specifically detailed to fail in shear. Tests are carried out on walls with a width of 240 mm, a length of 880 mm and a height of 2250 mm with a regular concrete quality (C25/30). This contribution describes the test specimens, summarizes their design, presents a summary of the most relevant observations and a short interpretation of the obtain results. It is concluded from this set of tests that the new design method is able to predict the shear capacity with a good accuracy and can therefore be considered as a suitable solution for designing practical cases.

The current state of EN 1994 and EN 1992 does not provide correlated solutions related to the design of concrete walls reinforced by multiple steel profiles. Explicitly, Eurocode 4 is setting clear boundaries in the design of composite walls by limiting the possibilities to elements reinforced by a single profile or multiple connected profiles. A number of previous studies have shown that the method proposed by Eurocode 2 regarding classical reinforced walls provides a good prediction of the bending capacity of the wall; however limited information regarding their shear capacity can be found. The current paper is having as starting point a theoretical approach for determining the shear performances of RC wall reinforced by multiple steel profiles, coupled with an experimental campaign. The experimental campaign comprises 6 walls, ranging from a classic RC wall taken as a reference to configurations with multiple profiles with studs or plate stiffeners to ensure the transfer of the longitudinal shear at the steel-concrete interface. The FE model is going to try to reproduce the behavior showed by the walls. The objective of the present paper is to present a comparative analysis between results obtained using a FE software and results from the experimental campaign carried out in the frame of the European research program SmartCoCo. The obtained results will be used to confirm once again the design method based on theoretical reasoning, proposed by the authors and presented in previous papers. This contribution contains a brief description of the test specimens, presents a selection of the most relevant experimental results in parallel with the FE results and a set of conclusions regarding the results. It can be concluded from this set of tests that the new design method is able to predict the shear capacity with a good accuracy and can therefore be considered as a suitable solution for designing practical cases.

The design of concrete walls or columns reinforced by several encased steel profiles, also called hybrid walls, is similar to the one of classical reinforced concrete, although specific features require adequate design approaches. Experimental research and numerical models demonstrated the feasibility and validity of such structural components, but simple and practical design methods are still lacking regarding their shear resistance. The evaluation of longitudinal shear action effects at the steel profile–concrete interface is a key aspect: research results have been achieved in a more or less recent past for different types of connection but without leading to design conclusions. In this paper, the classical equivalent truss model for reinforced concrete subjected to shear is extended to take into account the contribution of the encased profiles to the shear stiffness and strength. Resulting action effects in the steel profiles, in the concrete and at the steel profile–concrete interfaces are established which allows performing design checks for those three components. In particular, it is evidenced that friction is one of the main component of the resistance to longitudinal shear at the steel profile-concrete interface. It can be directly checked since the proposed method clearly identifies the compression stresses at that location. The validity of the method is assessed by referring to tests results from experimental campaigns in China and in Europe. Some of these tests were carried out without shear connectors welded to the encased steel profiles allowing however achieving the full bending resistance of the element without any apparent problem related to longitudinal shear, like slippage between concrete and steel profile. For some other tests, failure was observed as a consequence of an insufficient shear connection. A detailed assessment of these results shows that the new design proposal is perfectly consistent with all the experimental observations.