Intended contribution emphasizes the statics and kinematics of semi-rigid steel frames seismically acted upon. The dynamic model of analyzed structures consists of multi degree of freedom systems with lumped masses located at floor levels. The dynamic degrees of freedom are the lateral seismically induced floor displacements. A cyclic behavior of semi-rigid beam – column connections associated with the four parameters analytical bending moment M – relative rotation θ_r is considered. Time history seismic analyses are performed on multi-story steel planar frames equipped with several top and seat and web angle beam – column connections acted upon by recorded seismic actions. The computed numerical results refer to the contrary static and effects of semi-rigidity: the increase in lateral floor displacements accompanied by a decrease in the seismic base shear force. Relevant comments are drawn.

The pore structure of SCC and of all cement-based materials plays a crucial role on the mechanical and durability characteristics of the material. The pore structure is affected by mix design, water–binder ratio and the incorporation of SCM and/or nanomaterials, all of which can improve mechanical and durability characteristics by decreasing porosity. Computed tomography (CT) is a powerful, non-destructive imaging technique to investigate the internal pore structure of concrete. The main advantage compared to other investigation techniques used to assess the pore structure is in terms of sample size. More specifically, industrial CT can be used to scan large concrete samples and be able to assess the internal pore structure without damaging the specimen. CT provides accurate measurements of pore diameters, volumes and shapes and enables the assessment of the total porosity. The paper presents the results of an experimental program on the characterization of self-compacting concrete (SCC) at a very long age (7 years) in terms of static and dynamic elastic properties and compressive and splitting tensile strength, all of which are correlated with the internal pore structure assessed via the use of an industrial Nikon XTH 450 CT. The results highlight the influence of pore volume, maximum pore diameter and sphericity on the strength and elastic properties of SCC at the age of 7 years. Both the compressive strength and the static modulus of elasticity values tend to decrease with the increase in the internal total porosity, with stronger influence on the former.

Earthquake zones cover a significant part of our earth, therefore, when planning and designing residential areas, factories, or other human establishments, professionals have to take into account the seismic hazard of that area. The current earthquake standard in Romania is based on the European code. This paper presents, beside the most significant structural composition rules, the applicable methods that can be used to ensure sufficient load bearing requirements.

The accumulation of end-of-life tyres represents a growing environmental burden, motivating the incorporation of tyre rubber as a partial aggregate replacement in concrete. However, the flexural performance of reinforced rubberized concrete (RuC) beams at high rubber contents and elevated longitudinal reinforcement ratios remains insufficiently investigated. This study experimentally examined the flexural behaviour of RC beams cast with conventional concrete and RuC incorporating 40% and 60% replacement of small coarse aggregate by volume, at longitudinal reinforcement ratios of 1.5% and 2.0%, approaching the over-reinforced range. Eighteen beams were tested under four-point bending until failure by concrete crushing, with deflection, crack development, and material properties monitored throughout. Rubber incorporation reduced the modulus of elasticity and compressive strength, corresponding to a Eurocode 2 class downgrade from C45/55 to C35/40, while increasing peak axial strain. At 1.5% reinforcement, increasing rubber content progressively enhanced deflection capacity and ductility, with RuC60 beams reaching a ductility coefficient of 2.52 versus 2.43 for conventional beams. At 2.0% reinforcement, this benefit was suppressed, with ductility converging to 1.40–1.47 across all mixes as compression zone crushing increasingly governed failure. These findings indicate that the structural benefits of high-rubber-content RuC are most pronounced in moderately reinforced beams and diminish as sections approach the over-reinforced regime, informing the applicability envelope of RuC for load-bearing flexural elements.