This study examines the structural behaviour of aged prefabricated post-tensioned concrete beams subjected to simulated anchorage failure - an essential aspect in assessing mid-20th-century industrial structures. Full-scale crane girders, in service for over 50 years, were tested to replicate emergency scenarios involving partial loss of tendon anchorages. The investigation addressed various anchorage failure configurations, grout quality levels, shear span-to-depth ratios (a/d), and the impact of low transverse reinforcement. Results showed that even in severe cases - such as loss of both bottom anchorages and insufficient tendon grouting - the beams did not exhibit brittle behaviour. Clear warning symptoms like large deflections and visible cracking preceded failure, although the capacity dropped by up to 50 %. In contrast, the failure of top tendon anchorage had a negligible impact on load-bearing capacity. Beams with low shear slenderness demonstrated higher ultimate strength, typically failing through concrete crushing, while more slender beams followed beam-type failure modes. However, anchorage failures may result in a distinct failure mode of the member. Numerical simulations using DIANA FEA, validated against the test results, extended the analysis to additional damage scenarios. Notably, simulation of the failure of all four bottom anchorages, out of five tendons in the beam, indicated that the beam could sustain load only until initial cracking, after which brittle failure occurred - identifying a critical threshold for safety evaluations. Despite limited stirrup reinforcement, all beams demonstrated sufficient shear performance. These findings contribute valuable insight into the structural assessment and sustainable long-term use or reuse of ageing post-tensioned elements, supporting more informed and sustainable infrastructure decisions.

Precast prestressed hollow core floors can often be subjected to concentrated loads. Due to the presence of adjacent units interconnected by cast-on-site joints, the load applied to a single panel can be distributed to the adjacent units. Consequently, the capacity can exceed that of an identical single element. This article presents a numerical model based on selected, well-documented experiments on a full-scale 400 mm deep hollow core floor subjected to concentrated loads. Having obtained a good fit with experimental results in terms of failure load and mechanism, a comprehensive parametric study on the floor capacity is performed. The study investigates the effects of load location, floor span, number of loaded webs, and number of elements forming the floor on the floor capacity and load distribution, expressed as element failure load to floor failure load ratio. The study shows that the floor capacity can increase by over 50 % compared to a single-element performance when the presence of adjacent elements is considered. However, the specific improvement and the effect of load distribution within a given floor depend highly on the complex nonlinear correlation between the considered parameters.

It is increasingly evident that the construction industry must undergo a thorough transformation. Globally, the construction sector is responsible for up to 50% of carbon emissions and approximately 50% of resource consumption. This high resource consumption correlates with substantial waste generation. To reduce the environmental impact of civil engineering, priority should be given to preserving existing structures, even if they require repair or significant retrofitting, or at least reusing their components.. However, practical implementation is challenging, primarily due to the lack of proper assessment of existing structures, which is crucial for making decisions regarding liability. Currently, there are no well-established rules for determining the design life and safety of structures incorporating elements derived from dismantled ones. This paper identifies, based on the report prepared for the European Commission [1], best practices in the construction industry and the most promising measures to reduce its climate impact in the future. From the structural engineer's perspective, these measures would certainly involve substituting carbon-intensive materials with low-carbon alternatives and embracing adaptive, modular, and reversible designs supported by data-driven models. Reuse and disassembly are crucial for circular systems in the construction industry, particularly in designing connections and ensuring the transfer of information about structural elements throughout their lifecycle, including the concept of creating 'smart elements' equipped with Structural Health Monitoring (SHM) systems. The possibilities for implementing the concept of reuse of building structures is also discussed in the paper.

The seismic behaviour of precast concrete modular constructions depends highly on the connections between structural elements, particularly those located in the horizontal joints in wall-based structural systems. Several dry and wet connection solutions have been developed in recent years, but most of them require complex assembly processes and additional concrete casting or were not designed to be seismic-resistant. Also, the possibility of having easy access to connection replacement in the case of seismic damage needs to be considered. The paper presents the design conception, detailing and testing of four types of a dry connection for horizontal joints between insulated bearing walls. The behaviour of the connection is investigated through a testing campaign of full-scale specimens subjected to tensile axial monotonic tests and tensile cyclic loading tests. The results are discussed in terms of force-displacement curves, tensile capacities and failure modes. The results showed a promising strength and deformation capacity when adequate detailing near the connection is ensured. 

Hollow core floors are often subjected to concentrated loads which can be further distributed from the directly loaded element to the adjacent ones. In order to study further this phenomenon, an experi-ment on full scale floor was carried out in laboratory conditions. Reaction force measurement was performed on one of the supports and based on the obtained data, distribution analysis was carried out. The analysis confirmed some inconsistencies in selected code provisions and analytical models, which generally tend to overestimate load distribution in case of loads applied in midspan regions, while the predictions obtained in support vicinity provide mainly underestimated results.

Timber-concrete composite (TCC) floor systems have gained interest as a sustainable alternative to concrete floors, particularly in applications requiring longer spans than typical timber floor systems. By connecting timber elements to concrete slabs with shear connectors, TCC systems increase the structural stiffness and improve vibrational characteristics while maintaining a reduced carbon footprint. This study investigates the dynamic performance of a 6 m span glued-laminated timber-concrete composite (GLTCC) floor by means of forced vibration testing and finite element (FE) simulations. Experimental results revealed a first natural frequency of 13.25 Hz, surpassing the 8 Hz requirement specified in Eurocode 5, and a damping ratio of 3.34% for the first mode – close to recommended values for TCC floors with a floating screed. The FE model closely predicts the experimentally measured frequencies and mode shapes, demonstrating the validity of the numerical approach. Parametric studies further highlight the importance of support conditions and connection properties. Continuous supports such as walls or sufficiently stiff beams help maintain higher frequencies, while column supports reduce the frequency in certain modes. Enhanced connection stiffness, as achieved by notches, raises the overall dynamic response, whereas less stiff alternatives, such as screws, lead to reduced composite action and lower frequencies. Overall, these findings confirm the effectiveness of GLTCC floor systems for medium-span applications and highlight the need for careful consideration of support conditions and connection details to ensure optimal vibrational performance.

Slab-column connection is one of the most critical points in reinforced concrete structures. Punching shear capacity of this connection must be properly determined in both the persistent design situation and the accidental design situation of fire. European and American codes give simplified (tabulated) requirements for minimal slab thickness and minimal column cross-section width in accordance with the required fire resistance. In many cases, a more accurate prediction of fire resistance might be needed. It can be achieved when the ultimate limit states of a structure are checked in the case of fire conditions. This paper shows the comparison between European and American code requirements for punching shear capacityas the base for further calculations of flat RC slabs subjected to fire. The second part is going to present European and American requirements for determining the effects of loads relevant to the consideration of an accidental design situation of fire and comparing these effects with the punching shear capacity of the slab-column connection, which decreases with fire duration.

The main aim of the paper is to present a computational model for assessing the transmission length of prestressing force in old post-tensioned concrete structures experiencing tendons’ anchorage failure. The model is based on a unique research program conducted on real-scale precast members dismantled after nearly 60 years of service, thus beyond their designed lifespan. An overview of the research program, including its scope and key findings, is provided. The research highlighted the robustness of these structures in emergency situations and confirmed the feasibility of prestressing force transmission from a 12Ø5 mm Freyssinet-type tendon to the member via bond stress. The developed model enables the evaluation of transmission length in anchorage or tendon failure scenarios, providing a more detailed assessment of existing post-tensioned concrete members.