## 4 Fabrication of the Damaged Prestressed Hollow Slab
### Static Load Test of the Reinforced Prestressed Hollow Slab  
To test the effects of the two reinforcement methods on the test plate, a static load test was performed on the test plate reinforced by different reinforcement methods. The test method and procedure of the static load test were the same as those prior to reinforcement. The carrying capacity of the prestressed hollow slab beam after reinforcement had changed; therefore, the load applied to the prestressed hollow slab beam after reinforcement was appropriately reduced, and the maximum load applied was 150 kN based on previous static load test results. As shown in Tables 3 and 4, D-1/2 is the mid-span deflection value of the test plate after reinforcement, D-1/4 is the 1/4 span deflection value of the prestressed hollow slab beam after reinforcement, S-1 is the compressive strain of the concrete at the top of the mid-span web of the test slab, and S-2 is the tensile strain of the concrete at the bottom of the mid-span web of the test slab.  
Tables 3 and 4 show that the deflections before and after reinforcement increased with increasing load level, and the trend of the change was stable. Under a static load, the deflections at the quarter span and half span of the prestressed hollow slabs strengthened using steel plates and carbon fiber sheets were significantly lower than those of the damaged specimens prior to strengthening. Under a load of 150 kN, the deflection at the 1/2 span of the carbon fiber sheet strengthened specimen was 0.79 mm, which was 0.94 mm  
Figure 6: Construction drawing of the test beam reinforced with carbon fiber sheets.  
Figure 7: Construction drawing of the test beam strengthened by pasting steel plates.  
relative to the deflection of the half span prior to reinforcement, and the deflection value decreased by 14.2%. The deflection at the one-half span of the prestressed hollow slab components strengthened using steel plates under a load was 0.82 mm, which was 15.4% lower than the value of 0.97 mm obtained prior to reinforcement; when subjected to a constant load, the tensile and compressive strains generated by the mid-span concrete of the test plate before and after reinforcement were compared. The compressive strain in the mid-span top concrete of the prestressed hollow slab and the tensile strain generated by the bottom concrete were both lower than those of the prestressed hollow slab prior to strengthening. When the applied load was 150 kN, the compressive and tensile strains of the carbon fiber cloth strengthened specimens were reduced by 6% and 4.9%, respectively, and the compressive and tensile strains of the bonded steel plate strengthened specimens were reduced by 5.2% and 10%, respectively. In addition, the fundamental frequencies and damping ratio of the test plate before and after strengthening were analyzed. The damping ratio of the prestressed hollow slab prior to strengthening was 5.88 and 5.52, respectively, and the damping ratio values of the prestressed hollow slab strengthened with steel plates and carbon fiber cloth were 5.49 and 5.33, respectively. The test showed that the damping ratio before reinforcement was greater than that after reinforcement, which could be attributed to the friction between the original cracks of the test plate being restrained after reinforcement by sticky steel plates and sticky carbon fiber cloths; another possibility is a change in the overall stiffness of the plate resulting from their strengthening. The input capacity of the dissipating external energy of the test plate was lower, the vibration attenuation was slower, and the damping ratio was smaller. Through a comprehensive analysis of the static load data of the two reinforcement methods, it was found that both methods improved the failure load and structural stiffness of the damaged prestressed hollow slab beams to varying degrees. Neglecting other factors, the reinforcement effect achieved by using bonded steel plates was better that than using pasted carbon fiber cloths.