# The Behaviour of Half-Slabs and Hollow-Core Slab in Four-Edge Supported Conditions
## 3 Results
### Effect of Long-Term Loading  
The long-term tests were performed under permanent loading (the sequence L-12), and the surveying measurements were taken at time intervals of one month. During the tests, temperature and humidity were measured (Figure 17). The results in the form of a graph presented in Figure 18 were based on the readings taken on days 100, 200, and 300 and after a year of loading. A regular increase in the displacements was found for the LGR and LGF models during the testing period. When compared to short-term loading, the displacements in the LGR model increased by 263% (day 100) and 315% (day 200), and  
Figure 16: Displacements in the X- and Y-axes for sequence J-10: (**a**) LGR; (**b**) LGF; (**c**) RP; (**d**) HC. (**e**) Comparison of panels, (**f**) performance of panels in the X-axis, and (**g**) performance of panels in the Y-axis. those of the LGF model by 461% (day 100) and 536% (day 200). Contrary to the tests under short-term loading, the displacements in the RP and HC models were substantially smaller than in LGR and LGF after completing the long-term tests. Differences in readings between days 100 and 370 varied from 1 to 2 mm. The indirect measurement for the RP model on day 189 showed nearly the same deflection as on day 301. The first reading on day 113 and the second on day 197 were convergent for the HC model, except for one measuring point. The HC model exposed to long-term loading also differed in the displacement behaviour with reference to other models. The deflection line was shifted the most towards the maximum loading. Figure 17 illustrates daily temperature and humidity readings separately for the LGR, LGF, RP, and HC models. The last two models were tested after a month interval from the ending of LGR and LGF research. The average humidity throughout the tests on the LGR and LGF models was 72.0%, and the temperature was equal to 10.9 \({}^{\circ}\)C. For the LGR and LGF models, the average humidity and temperature did not significantly differ and were equal to 71.8% and 10.7 \({}^{\circ}\)C, respectively. During the period of increased humidity (>90%), a minor increase in displacements was recorded (days 150-240) compared to in other periods. There was no effect of temperature on the increase in displacements and crack patterns. The mean value of humidity during the test was used in the calculation of long-term displacements. Figure 19 presents the maximum displacements for each model during all measurements. According to [55; 57], most displacements are observed during the first 100 days, and the largest increase is found during the first 30 days after the load is exerted. Percentage increase in the maximum displacements referred to short-term displacements of the individual models was as follows: 574%--LGR, 610%--LGF, 208%--RP, and 180%--HC. Varied deflections of reinforced concrete and prestressed slabs were observed. Moreover, no cracking in the bottom area of panels was found in the RP and HC models. The comparison of displacement behaviour of the slabs after the final measurement that was taken on the day of loading and around day 365 after the loading (Figure 20) indicates a greater rotation in the LGR, LGF, and RP models at the joint of panel 5-6 (LGR and RP) or 6-7 (LGF), corresponding to an increase in loading from 1.7 to 7.7 kN/m\({}^{2}\). The displacement behaviour of these slabs became similar to the deflection curve for the HC model prior to long-term testing. The curve for the HC model has shifted to the centre of the area of maximum load. Compared with other models, this curve was the closest to the wall edge. Data for long-term displacements are compared in Table 5.  
Figure 17: Ambient temperature and humidity during the load period. Figure 19: Maximum displacement of models during the load period. Figure 18: Displacement in the Y-axis during the load period for slabs made of (**a**) lattice girder panels with rebars; (**b**) lattice girder panels with fibre reinforcement; (**c**) prestressed ribbed panels; (**d**) hollow-core panels.