applied sciences Article The Behaviour of Half-Slabs and Hollow-Core Slab in Four-Edge Supported Conditions Jakub Zaj ˛ ac 1, * , Lukasz Drobiec 1 , Radoslaw Jasi ´ nski 1 , Miroslaw Wieczorek 1 , Wojciech Mazur 1 , Krzysztof Grzyb 1 and Artur Kisiolek 2   Citation: Zaj ˛ ac, J.; Drobiec, L.; Jasi ´ nski, R.; Wieczorek, M.; Mazur, W.; Grzyb, K.; Kisiolek, A. The Behaviour of Half-Slabs and Hollow-Core Slab in Four-Edge Supported Conditions. Appl. Sci. 2021, 11, 10354. https:// doi.org/10.3390/app112110354 Academic Editor: Muhammad Junaid Munir Received: 3 September 2021 Accepted: 2 November 2021 Published: 4 November 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). 1 Department of Building Structures, Silesian University of Technology, 44-100 Gliwice, Poland; lukasz.drobiec@polsl.pl (L.D.); radoslaw.jasinski@polsl.pl (R.J.); miroslaw.wieczorek@polsl.pl (M.W.); wojciech.mazur@polsl.pl (W.M.); krzysztof.grzyb@polsl.pl (K.G.) 2 Institute of Economics, Wielkopolska Higher School of Social Sciences and Economics, 63-000 ´ Sroda Wielkopolska, Poland; a.kisiolek@wwsse.pl * Correspondence: jakub.zajac@polsl.pl Abstract: In this study, qualitative tests were carried out to compare the behaviour of selected slabs exposed to short- and long-term loading. Full-scale models of the half-slab and hollow-core slab with dimensions of 6.30 m × 6.30 m, built of four different precast panels, were tested. The first two were semi-precast lattice girder slabs, the third semi-precast prestressed ribbed panels, and the last was composed of hollow-core panels. A common feature was the lack of joint reinforcement and the same modular width of 600 mm. The short-term load was applied sequentially in the first stage, and displacement was measured using an electronic method. In the second stage of long-term testing, the load was mainly applied to one part of the slab. Testing under short-term and long-term load allows determining the change in the performance of panel slabs over time. The panels maintained the ability of load redistribution based on their interaction despite the work of the longitudinal joints being only through the concrete cross-section. The behaviour of slabs with concrete topping shows more significant lateral interactions than elements connected only by shear key. Comparative calculations were made based on four computational models. Comparative analysis showed that the current design procedures lead to a safe but conservative estimation of the slab behaviour. Keywords: structural analysis and design; half-slab; hollow-core slab; precast slab; long term load 1. Introduction Composite slabs with precast panels are being increasingly used in the construction sector as an alternative to monolithic slabs or beam and block systems [1]. Half-slabs consist of (flat or ribbed) reinforced concrete or prestressed slab serving as stay-in-place formwork and monolithic concrete topping. Compared to beam and block floor systems or monolithic slabs, use of this type of structure is characterised by allowing a rapid erection time requiring lower work input in addition to having elements of relatively low cost [2–4]. Prestressed slabs are more crack-resistant and lighter at the same length, allowing consid- erably greater spans. Being able to reduce the number of erection supports to a minimum is a crucial advantage of panel slabs, as they usually tend to be self-supporting. Due to the extrusion method used during their production, the cross-section of panels can be easily shaped. Different types of filling inserts can reduce the weight of panels and improve their insulation properties [5–7]. Many tests have been performed in recent years, and new types of composite slabs have been designed. They include but are not limited to a slab bonded to vertical tongues serving as shear keys that join two layers of the slab [8], multi-span slabs of slimfloor type with prestressed steel beams bonded to hollow-core (HC) slabs [9], and one- or two-way slabs on thin prestressed boards (narrow slabs) [10]. Basalt rebars are pretensioned using various methods [11], and steel reinforcements have been used as Appl. Sci. 2021, 11, 10354. https://doi.org/10.3390/app112110354 https://www.mdpi.com/journal/applsci