Search Results (5)

Monolithic reinforced concrete floor slabs are one of the most common types of building structures, and their optimization is an urgent task. The article presents the methodology for finding the optimal position of point supports under a reinforced concrete floor slab of arbitrary configuration at arbitrary load. The slab is considered thin, elastic and isotropic, with constant over-the-area stiffness, that is, the reinforcement is not taken into account or is constant. The solution is performed using the finite element method in combination with the nonlinear optimization methods. Finite element analysis is implemented by authors in MATLAB (R2024a) environment in such a way that the location of the columns may not coincide with the nodes of the finite element mesh of the slab. This allows to significantly increase the efficiency of solving the optimization problem compared to previously used algorithms, including the Monte Carlo method. Boundary conditions are taken into account using the Lagrange multiplier method. As an optimization criterion, the maximum deflection value is used, as well as the value of the potential strain energy. The effectiveness of six nonlinear optimization methods is compared in the example of a square slab under the action of a uniformly distributed load. For solutions obtained using the pattern search, simulated annealing and internal point methods, the maximum deflections are at least 1.2 times higher than for solutions obtained using the particle swarm method and genetic algorithm. An example of real object optimization is also presented. By changing the position of seven columns, it was possible to reduce the maximum deflection of the floor slab by 1.6 times. Full article

In order to study how to improve the spatial action of precast monolithic composite floor slabs, and examine replacing the cast-in-place surface layer for reducing the weight of structure, we used pseudo-dynamic tests on one-quarter scale models of two-span and three-story frame structures. The lateral load tests compared the stresses and displacements with a cast-in-place floor frame–shear wall structure (SJ1) and a precast monolithic floor frame–shear wall structure with X horizontal braces at the bottom of the floor (SJ2). The results show the X horizontal braces can improve the spatial action. Structural integrity (SJ2) as well as the effective transmission of the horizontal force can be ensured by additional X bracing at the bottom of the rigidity of the floor without a cast-in-place concrete topping. The results show that X horizontal braces more effectively transfer horizontal stress, which provides a beneficial reference for similar research. Full article

This study introduces precast concrete beam–column connections comprised of composite beams, precast columns, and a monolithic joint core. The composite beams consist of U-shaped beams and floor slabs, leveraging the U-shaped beams for their lightweight nature, acceptable stiffness, and reduced demand for on-site support systems. To mitigate reinforcement congestion in the joint core, the precast connections incorporate large-diameter rebars (greater than 25 mm). This study conducted cyclic loading tests on four full-scale beam–column connections under 0.3 normalized compression, encompassing precast interior and exterior connections, along with two monolithic reference specimens, to investigate their behavior under seismic actions. The results revealed that all specimens exhibited bending failure at the beam ends, with minimal concrete deterioration observed in the joint core areas and columns. The hysteresis curves of the precast specimens and the monolithic connections exhibited a slight pinching effect. The strengths of the interior and exterior precast specimens were 13.3% and 7.8% lower than those of the reference monolithic connections, respectively. The ductility of interior precast connections and monolithic specimens stood at 2.36 and 2.23, respectively, indicating a negligible difference of less than 5%. Meanwhile, the positive and negative ductility of exterior precast connections were 3.06 and 2.34, which was approximately 8% lower than that of the reference connections. Furthermore, the stiffness degradation and energy dissipation capacity of the precast specimens aligned closely with the performance of the reference monolithic ones. Full article

The article presents ways of selecting effective designs and technological and organizational solutions for the bonded thermal insulation systems of complex-shaped facades based on thermal field and flow modeling using the SolidWorks Simulation Xpress 2021 software and experimental–statistical modeling using the Compex program. Determining optimal insulation parameters at the design stage will help eliminate the negative effects of thermal bridges at balcony junctions and reduce the cost of implementing bonded thermal insulation systems for facades with complex shapes. It has been established that the most effective approach is to insulate not the entire perimeter of the balcony slab, as required by normative documentation, but rather to insulate a sufficient portion of the exterior wall, which is equal to 750 mm, with a 30 mm insulation thickness on top of the slab and 50 mm beneath it. This insulation technology is economically feasible for modern multistory buildings with nonstandard volumetric and architectural solutions, constructed using frame–brick, frame–monolithic, or monolithic schemes without thermal breaks between the balcony slab and the monolithic floor slab, with open-type balconies, bays, or uncovered loggias. Full article

Static calculations of experimental models in an elastic formulation were carried out, and the regularities connecting the dependences of forces in the calculated cross-section of punching out from the main structural parameters of contacting elements (reinforced concrete slabs and pylons) and from the used concrete class were revealed. This article concerns the safety issues of reinforced concrete slabs under punching with different ratios and combinations of pylon and slab thickness parameters, as well as concrete strength. The objectives of the research are consideration of the fracture pattern of reinforced concrete monolithic slabs due to punching shear; comparative analysis of modern normative calculation methods and flat reinforced concrete slabs due to static punching shear; finite element modelling and analysis of the punching shear calculation results for reinforced concrete floor slabs; and the force distribution over the area of the contacting elements-saw and floor slab. The practical significance of the results lies in the use of the obtained forces in the contacting elements for the calculation and design of reliable structures of beamless floor slabs. Full article