Static Load Test of the Bridge to Fulfill the Functional Suitability Criteria of Way Sekampung Bridge

extrapolated to 100% UDL becomes 17.888 mm, still below the allowable deflection ( L /1000 = 35.7 mm). Similarly, the strain extrapolated from the 64% UDL strain, which is 0.00013, is also below the allowable tensile strain that could potentially cause concrete cracking (= 0.00015). Throughout the structural testing stages, the structure exhibited linear elastic behavior, with a residual deflection of 1.3 mm below the allowable residual deflection (17.4 mm). Based on the assessment of static test parameters, the bridge is deemed suitable for operation.


Introduction
The Way Sekampung Bridge to be tested is a newly constructed bridge intended to replace the old bridge, as shown in Figure 1.It is a 3-span PCI Girder bridge with spans of 35.7 m + 41.2 m + 35.7 m, a traffic width of 7.2 m, and 0.5 m sidewalks on both sides of the bridge.The layout and longitudinal section of the bridge are depicted in Figure 2. Before opening to general traffic, testing is necessary to ensure the safety of the bridge users.One common assessment method for existing bridges is load testing [1].
The tested span is the first span in the Tanjung Karang direction, consisting of 5 PCI girders with a span of 35.7 m, as illustrated in the cross-section in Figure 3.   Testing bridges with dynamic load tests is an effective and efficient way to estimate bridge performance under operational conditions.With operational modal analysis (OMA), testing can be conducted without having to close bridge traffic [2].Alternatively, with experimental modal analysis (EMA), which only requires a relatively short time to close traffic to obtain dynamic response triggers from vehicle impacts, compared to static load tests that require time for load placement, staging, and response measurements [3].The test results conducted by PT.Hesa Laras Cemerlang indicate that the bridge is structurally suitable based on dynamic parameters [4].However, static load testing remains more accurate compared to dynamic load testing because the applied load can be incrementally increased up to the maximum load [5].And this is feasible because the traffic has not been opened yet.
Static load testing is a common and effective method for assessing the performance of bridges, understanding the actual operational conditions of the bridge, and identifying existing issues promptly to improve and optimize bridge quality [6], [7].Load testing also serves as a crucial starting point for monitoring operations.There is a strong correlation between the behavior of the bridge during load testing and its long-term behavior [8].To complement the results of the dynamic load test conducted in the previous study, a static load test was performed to assess the bridge's structural integrity based on parameters such as deflection, strain, and linearity of bridge response.

Research Method
The criteria for static load testing used are by the Bridge Testing Implementation Manual, 2012 [8].

Description and Technical
The test load used is a truck, and the calculation for the test truck configuration is as follows [8]:   = 0,9 × (0, ) ton/m 2   ′ ⁄ = 5,5 + 50%( − 5,5); Note: If the traffic width, b, is less than 5.5m, then UDL is multiplied by 5.5; if it exceeds, then the remaining traffic width is multiplied by 50% UDL.   =  ′ ⁄ ×   Following the concept of linearity and assuming the structure is still elastic, 50% of the UDL load will be applied. The total   is divided by the unit weight of the test truck to determine the number of trucks required for static bridge testing.Following the above provisions, the minismum load to be applied during the bridge test is:  Stages and truck loading configurations are as shown in Figure 5 below and Table 1 below:   5 illustrates the loading stage configuration, where the maximum load used in this study is 64%.Considering the span length and truck dimensions to be used as the load, it is divided into 5 stages of load increments: 0%, 16%, 32%, 48%, and 64%.Similarly, in the unloading stage, it is divided into 5 stages: 64%, 48%, 32%, 16%, and 0%.For each increment stage, 2 trucks with a weight of 15 tons each, or 30 tons per load increment, are added.The same incremental approach is applied for unloading stages, as presented in Table 1.0 0 0% Source: The calculation results refer to the provisions of Manual 004/BM/2012 [8].
LVDT, Dial Gauge, Strain Gauge, and reflector sheet are placed at ¼, ½, and ¾ spans and positioned at the bottom of the bridge, as shown in Figure 6.The LVDT data, dial gauge data, and TS (strain gauge) data are all used to measure deflection, and their characteristics crosscheck each other.The LVDT has precision up to 10 -6 m, Dial gauge 10 -5 m, and TS 10 -3 m.Since the loading stages are linear, and the measurement points are theoretically positioned, anomalies in the data will be approximated with measurement values close to theoretical values.However, if the LVDT data, dial gauge data, and TS data are close in value, the LVDT data will be used due to its precision up to μm.
The displacement of the structure due to static loading can be measured in both horizontal and vertical directions.However, vertical displacement, commonly expressed as structural deformation, is typically measured in each case using dial gauges (strain gauges), fabricated LVDTs, flatness measurements, or other measurement techniques [8] The measured values of displacement, mostly deformation, are compared with calculated values corresponding to standard loads, design loads, and loads applied during testing.Measured values are usually smaller than calculated values because even highly complex calculation models (even when using computers) are always simpler than real structures.When the opposite situation occurs, it indicates that the structural damage process has reached an advanced stage.However, when the transverse interaction of structural elements is tested under non-uniform loading, calculated values may be less than measured values in some parts of the structure.This indicates that the real transverse interaction is better than the one produced by the calculation model [ [8], [9], [10], [11], and others].The maximum allowable deflection refers to Table 3  One fundamental measure of structural quality is the elastic behavior of the bridge under loading and unloading cycles.The maximum allowable permanent deflection (∆_p) after the removal of the load is generally specified in relevant regulations or standards as a fraction of the maximum deflection (∆_max) under loading [8].In this test, the limit for permanent deflection is set at [14]: The stress-strain curve for concrete is roughly linearly elastic until the maximum tensile strength is reached.Beyond this point, concrete cracks, and the strength gradually decreas to zero [ [15], [16], [17], [18]].Figure 7 illustrates the typical stress-strain relationship in concrete.
Figure 7.Typical stress-strain relationship in concrete [18] Referring to the Wika Beton brochure [19], girders for a span of 35.7m use concrete with fc' = 50 MPa.Therefore, the stress-strain relationship for concrete from Mander for fc' = 50 MPa is as shown in Figure 8. (2)

Results and Discussions
All initial values at the stage before loading are considered as benchmarks (if not valued at 0, the measured values will be subtracted from the values of the subsequent stage).The maximum deflection that occurred is less than the allowable deflection projection; thus, the test proceeds to a 32% loading, with loading documentation as shown in Figure 11.The maximum deflection that occurred is less than the allowable deflection projection; thus, the test proceeds to a 48% loading, with loading documentation as shown in Figure 13.The maximum deflection that occurred is less than the allowable deflection projection; thus, the test proceeds to a 64% loading, with loading documentation as shown in Figure 15.4, Table 5, Table 6, and Table 7, it is evident that the deflection observed remains below the allowed maximum deflection projection.
Considering that the deflection patterns between LVDT, Dial gauge, and TS are almost identical, further discussion will use LVDT data, as it has the highest level of precision (μm).Based on the graph illustrating the linear relationship between the addition and reduction of loads against deflection (Figure 17), indicates that the structure remains elastic during loading.The residual (permanent) deflection is only 0.13 mm, which is significantly less than the allowed permanent deflection (=1.391 mm).Considering that the observed deflection is only 38.1% of the theoretical deflection and the linear relationship between the increase in load and the increase in deflection, the deflection at 100% UDL can be projected, as shown in Figure 19.

Figure 19. Projection of deflection at 100% UDL
In line with the deflection, the strain measurement results also show the same outcome.
The measured strain at each stage of load addition and reduction indicates that the bridge structure is in a linear elastic condition.The strain that occurs during the loading process does not lead to tensile strain causing cracking.This result is demonstrated by plotting the strain values from Table 9 into the graph in Figure 8, with the results shown in Figure 18.If projected to 100% UDL, the strain that occurs,  = 0,0001 ×  − 10 −6 = 0,000116068 × 100% − 1,43 × 10 −6 = 0,00011465, and the tensile stress that occurs,  = 32502 ×  − 0.1668 = 32502 × 0,000115 − 0.1668 = 3,56 MPa < 4,4 MPa.Under these conditions, it is estimated that during 100% UDL loading, the concrete in a linear elastic condition will not result in cracking.

Conclusion and Suggestion 5.1 Conclusion
The results of the static test indicate that during the loading stages (0%, 16%, 32%, 48%, 64% UDL) and unloading stages (48%, 32%, 16%, 0%), the bridge structure remains linearly elastic.The observed deflections are still below the allowed limits, with an indication that at 64% load, the deflection is 8.696 mm, much less than 64% allowable deflection (64% L/1000 = 22.848 mm).From the linearity of the test results, the deflection at 100% UDL can be estimated at 17.882 mm, which is 50.11% of the allowable deflection.Thus, it is concluded that the Way Sekampung Bridge meets the criteria for functional suitability based on static load testing.

Suggestion
For further research, a comparison can be made between the bridge capacity based on the results of static load testing and the results of dynamic load testing, which can serve as input for accurately assessing the bridge's performance using dynamic testing approaches , either with EMA or OMA.

Figure 1 .
Figure 1.Location and span of the Way Sekampung Bridge to be tested

Figure 2 .
Figure 2. Plan and long section of the Way Sekampung Bridge

Figure 3 .
Figure 3. Cross-section of the bridge at the abutment (left) and the mid span (right).
Truck specifications are as shown in Figure4.

Figure 4 .
Figure 4.The truck used as a load, with a total weight of 15 tons including the cargo.

Figure 5 .
Figure 5. Stages and truck loading configurations

Figure
Figure5illustrates the loading stage configuration, where the maximum load used in this study is 64%.Considering the span length and truck dimensions to be used as the load, it is divided into 5 stages of load increments: 0%, 16%, 32%, 48%, and 64%.Similarly, in the unloading stage, it is divided into 5 stages: 64%, 48%, 32%, 16%, and 0%.For each increment stage, 2 trucks with a weight of 15 tons each, or 30 tons per load increment, are added.The same incremental approach is applied for unloading stages, as presented in Table1.

Figure 6 .
Figure 6.Placement of LVDT, Dial Gauge, Strain Gauge, and reflector sheet

Table 1 .
The stages of loading

Table 7 .
Data on static deflection at 64% UDL

Table 8 .
Data of static deflection during the unloading stage from 64% to 0% UDL

Table 9 .
Data of static strain at the mid-span