## 3 Experimentation Results
### Reinforcement Performance of Reinforced Concrete  
(1) Concrete strain at the variable cross-section  
Strain measurements were obtained using strain gauges affixed to the umbrella arch after collecting and analyzing the test data. The maximum compressive strains recorded were \(-\)1021 \(\mu\epsilon\) and \(-\)1431 \(\mu\epsilon\) in the scenarios where 1/3 and 2/3 prefabricated crack components, respectively, were reinforced by the umbrella arch under an external load of 950 KN. This suggests that the concrete experienced crushing under the external load it was designed to withstand.  
(2) Surface concrete strain near prefabricated cracks  
The strain was measured by posting strain gauges near the prefabricated cracks, and by collecting and sorting out the test data, the maximum compressive strains of concrete near the prefabricated cracks were \(-\)715 \(\mu\epsilon\) and \(-\)985 \(\mu\epsilon\) when the 1/3 prefabricated crack components and 2/3 prefabricated crack components were strengthened by the umbrella  
Figure 5: The variation of distortion and bending stiffness with load.  
arch under the external load of 550 KN. When the external load is 950 KN, the maximum compressive strain of the concrete near the prefabricated crack was \(-1669\) u\(\varepsilon\) and \(-2452\) u\(\varepsilon\), respectively, when the 1/3 prefabricated crack component and 2/3 prefabricated crack component are strengthened by the umbrella arch. Under the set load, the maximum compressive strain of the surface concrete near the prefabricated crack meets the design requirements and is not crushed. It can be concluded that the concrete is crushed under the external load of its design.  
(3) Distortion  
As depicted in Figure 6a, components 1, 2, and 3 exhibit brittle failure under load, with the rate of mid-span distortion increasing gradually as the load increases; additionally, under consistent load conditions, mid-span distortion escalates with increasing crack severity. Components 4 and 5 demonstrate relatively minor mid-span distortions prior to failure as the load increases. When the load reaches 900 KN, the rate of increase in mid-span distortion accelerates sharply, resulting in the failure of the component. Under the same load conditions, mid-span distortion of the reinforced members intensifies as crack severity increases. The mid-span distortions of components 1, 2, 3, 4, and 5 under the respective loads measure 5.01 mm, 4.78 mm, 6.31 mm, 5.16 mm, and 5.48 mm, respectively.  
As depicted in Figure 6b, as the load increases, the bending stiffness of the components generally decreases. For component 4, stiffness decreases sharply from 0 to 1500 KN, and cracking occurs along the prefabricated lines. Stiffness remains relatively stable between 1500 and 450 KN, during which the original lining and the umbrella arch are co-stressed, resulting in cracks forming within the umbrella arch. Between 450 and 900 KN, the original lining nears destruction. Concurrently, the arch, now bearing the load independently, shows a gradual decrease in stiffness and further cracking. Beyond 900 KN, component stiffness decreases sharply, leading to component failure. For component 5, stiffness decreases sharply between 0 and 100 KN, with cracking occurring along the prefabricated lines. Between 100 and 400 KN, stiffness remains relatively stable; however, as the original lining and the umbrella arch are co-stressed, the arch bears a greater load, leading to additional cracking. Between 400 and 850 KN, extensive cracking in the arch leads to a sharp decrease in its load-bearing capacity, culminating in component failure. Stiffness in components 1, 2, and 3 decreases sharply under load, exhibiting brittle failure.