# An Assessment of the Impact of Protective Lifeline Safety Systems on Formwork Systems
## 3 Results  
### Test 1--A System of Two Posts and Rope  
In the first test, the arrangement of the posts with a plastic joint was uneven. As a result of the fall, both posts were deformed in the elastic joint (Figure 4), indicating that part of the fall energy was absorbed into the plastic deformation of the steel. Due to the fall factor FI = 2.0, the impact force of the weight was 6.42 kN and the free flight height was 2.2 m. As a result of the force, the textile shock absorber was torn along a length of 290 mm and both posts were bent, absorbing the energy of the falling mass. The bending took place on a flexible joint at an angle of 15\({}^{\circ}\) and 75\({}^{\circ}\). The dummy stopped above the ground.  
Figure 3: Formwork cross-beam model with dimensions used for stress calculations.  
The formwork did not move during the test, so it behaved as a rigid structure, and the total energy was transferred from the posts directly to their fastening elements and to the formwork elements. The stress distributions during the fall are shown in Figure 5. Two maxima were observed during the fall. Their presence is due to the mechanism of bending the posts and absorbing the energy of the fall. Based on the obtained measurement results, a matrix of maximum stresses and the maximum stress state in the plane stress state was determined, which result from the structure of the formwork elements. The maximum reduced stress was approximately 91 MPa, which means that there is no negative impact on the structural elements of the formwork system. In the place where the formwork was attached, no deformation of either the opening or the surface of the sections was observed. After the fall, the deformation of the joints was asymmetric, which causes a different distribution of stresses in the system and an extension of the braking time of the falling mass to approximately 0.5 s. Based on the results obtained, the force acting on a single post was determined to be only 1.3 kN at its mounting point. This indicates that more than 5 kN was absorbed by the bending of the posts and the tearing of the textile shock absorber.  
\[\begin{bmatrix}\sigma_{11}&\tau_{12}\\ \tau_{21}&\sigma_{22}\end{bmatrix}=\begin{bmatrix}56&25\\ 25&106\end{bmatrix}\text{MPa} \tag{1}\]  
\[\begin{bmatrix}\sigma_{1}&\tau_{12}\\ \tau_{21}&\sigma_{2}\end{bmatrix}=\begin{bmatrix}45&0\\ 0&116\end{bmatrix}\text{MPa} \tag{2}\]  
The FEM analysis showed that under the conditions of stresses, the degree of effort of the formwork structure in state 1 is negligible and amounts to 1-3%, in state 2 it increases to 7%, and only to 32% in state 3, reaching an effort of 32% (Figure 6). The values determined in the analysis are presented in the table in Figure 6b. Low effort values, even in the maximum impact period of the falling weight, mean that the effect of absorbing the fall energy and decelerating the mass is not transferred to the formwork system. This indicates that carrying out assembly and inspection works on the formwork and falling do not pose a threat to the structure but ensure the safety of the climber. The FEM calculation of stresses in the cross-beam indicate the stresses above the yield strength of steel (over 300 MPa) what could indicate the plastic deformation of element or the hole in the beam (Figure 7). Observations after the experiment reveal the lack of deformation of the formwork frame structure. Such differences in simulation and real measurements are explained by the effect of dynamic force expansion on element and stress distribution in the structure. Short periods of high stresses (below 0.1 s) allow the avoidance of stress concentration and steel  
Figure 4: Test 1; two posts (**a**) post-test view; (**b**) deformation in the joint area; visible chips of galvanized coating.