DAMAGE IDENTIFICATION SEGAH BRIDGE PIER DUE TO SHIP IMPACT

Identification of damage or often referred to as on-site structural forensic testing, using visual observation methods and testing of existing materials using the Non Destructive Test method, in addition to check condition the geometry of the bridge after a ship hit. Conducted to determine the extent of damage to the Segah Bridge P2 pier after it was struck by a pontoon vessel carrying coal material across the Segah Bridge. To conduct this research, in addition to collecting data from the visual survey and some field testing, the results were analyzed using LISA FEA to determine the behaviors and stresses encountered during the incident. This investigation was conducted by collecting data from the on-site visual inspection followed by an inspection using the NDT tool to determine the material condition of the elements of the struck bridge, namely the P2 pierhead of the Segah Bridge. After collecting data, it proceeds by performing a microstructural analysis using the FEA software, namely LISA FEA V.8. From the results of the research and data processing, it can be seen that the damage behavior resulting from the numerical analysis using LISA FEA is very similar to the conditions in the field, which of course is obtained from very detailed and measurable parameters and data collection, so that the behavior corresponds to the actual state.


INTRODUCTION
The Segah Bridge is a connecting bridge between the Tanjung Redeb Regency and Bulungan Province where this bridge is the only means of connecting the two regions. Identification of damage or often referred to as on-site structural forensic testing, using visual observation methods and testing of existing materials using the Non Destructive Test (NDT) method, in addition to protecting the geometry of the bridge after a ship hit. This survey was conducted to determine the extent of damage to the Segah Bridge P2 pier after it was struck by a pontoon vessel carrying coal material across the Segah Bridge.
To conduct this research, in addition to collecting data from the visual survey and some field testing, the results were analyzed using LISA FEA to determine the behaviors e-ISSN: 2620-3332 SELODANG MAYANG and stresses encountered during the incident.

RESEARCH METHODS
This investigation was conducted by collecting data from the on-site visual inspection followed by an inspection using the NDT tool to determine the material condition of the elements of the struck bridge, namely the P2 pierhead of the Segah Bridge. After collecting data, it proceeds by performing a microstructural analysis using the FEA software, namely LISA FEA V.8, by entering parameter values according to the results of the previous NDT study and identifying and validating the behavior occurring through the In-field damage results showing damage modeling results analyzed by field scale.

Types of concrete damage
Damage occurring to the structure in general can be classified into three categories, namely: 1. Cracks are cracks in concrete along a relatively long and narrow line. These cracks can be caused by a number of reasons including: Rapid evaporation of water in the concrete mix occurs due to hot, dry or windy weather. Cracks caused by this condition are called plastic cracks.
2. Cavity is a relatively deep and wide hole in the concrete. Cavities in the concrete can have various causes, among other things, compaction with a vibrator is not good because the distance between the formwork and the reinforcement or the distance between the reinforcement is too small and the mortar cannot fill. the voids between the coarse aggregates are correct.
3. Scaling/spalling/erosion is uniform surface delamination that can be caused by a variety of things including: Repeated freezing and thawing that results in surface delamination. This state is referred to as scaling.

Figure 2 Types of damage that occur in concrete materials
Another type of damage that often occurs in structural elements of civil buildings are steelconcrete connections; The bond strength is affected by the surface roughness of the steel and the quality of the concrete around the rebar. Failure of the bond leads to a reduction in the bearing capacity of structural members to service loads, an increase in deformation and even collapse of the structure [1].

Non-Destructive Testing (NDT)
Non-destructive testing or non-destructive testing is a technique for testing materials without damaging the test object. This test is performed to ensure that the material we use is still safe and has not exceeded the damage tolerance limit. The NDT method is more practical than DT, in addition NDT does not damage the test object and because NDT is more effective because it can be performed directly in the field without having to bring the test object to the laboratory. Firstly, testing the compressive strength of concrete in the laboratory.
NDT in the civilian world is growing rapidly in developed countries like America, Japan and others. One of the fundamental considerations of professionals in the development of NDT is the complexity of the damage that can occur to a structure, which is impossible or very difficult to do with the DT method (Destructive Testing) and carries a high risk of damaging the Structure. Material that can affect other structures [2]. e-ISSN: 2620-3332 SELODANG MAYANG Figure 3. NDT testing at the scene of the incident, namely Pier P2 Segah Bridge

Finite Element Method
The finite element method (FEM) is a numerical method for solving technical analysis problems. The finite element method combines several mathematical concepts to generate equations of a linear or nonlinear system. The number of equations generated is usually very large, reaching more than 20,000 equations. Therefore, this method is of little practical value unless a suitable computer is used [3].
When a structure is subjected to forces such as stress, pressure, temperature, flow rate, and heat, the result is strain (deformation), stress, temperature, pressure, and flow rate. The nature of the distribution of the resulting action (deformation) on a body depends on the properties of the force and stress system itself. In the finite element method you can find the distribution of this effect, expressed as displacement.
The finite element method uses an element discretization approach to solve the problem of finding displacements of vertices/connections/lattices and structural forces. The discrete element equations are related to the matrix method for structural analysis and the results obtained are identical to those of classical analysis for structures. The discretization can be done with onedimensional elements (line elements), twodimensional (plane elements) or threedimensional (volume/continuum elements). This approach uses a continuum element to determine a solution that is closer to the truth [4].

LISA FEA
LISA, a popular finite element analysis application, was used to estimate the temperature rise for three different models of heat exchangers. The three types of models are, in order of their simplicity and ease of construction, the line element model, the shell model, and the solid model [5]. For the other two models, it's easy to exclude the mounting surface from convection -we just don't select that surface. An internal heat generator is used in each case, and the volume of the entire floor slab is assumed to be the heat source. Care should be taken when applying boundary conditions to a line element model. LISA selects all faces of the line elements when the "face" selection is made (i.e. both "ends" of the line and all "sides" of the line) [5].

Analysis method
Static calculations to evaluate the structural feasibility based on existing sizes and conditions to determine the internal forces due to different load combinations. A computer equipped with statics software in the form of a microstructure analysis program with LISA V.8 serves as a tool. In this phase of performance, static calculations are performed in the field based on as-built drawings and the results of geometry test data. Based on the results of the static analysis and the picture check, the strength e-ISSN: 2620-3332 SELODANG MAYANG of the pile head and dolphin elements was examined.

Impact Load from Ship
The ship's impact load is determined by several factors, including the weight of the ship and the speed of the ship's collision. The magnitude of the ship's impact force depends on the ship's collision energy. Vessel impact energy is calculated in accordance with BS 6349-4 [6]. The calculation of the ship's impact energy is shown in the table below [6].

Results and discussion
Based on the results of the on-site inspection and intelligence gathering, the bridge was hit by a pontoon boat being towed by a tugboat as it was crossing the Segah Tanjung Redeb bridge. In classifying the pontoon, it is carried by the current until the tug can no longer control the position of the pontoon in the shipping lane causing it to plunge into Dolphin Safety until it collapses and the pontoon hits the downstream face of the pier head P2 and it gives a very strong friction that causes the surface of the concrete to fall off and break, thick as a concrete pavement. From the results of collecting impact load data and the material parameters of the tested elements, it appears that the behavior is the same as under the actual field conditions, as shown in Figure 1   The material is still able to withstand collisions from the ship, it is only assumed that the condition of the pile is unfavorable to friction, so that the position of the dolphin collapses, as shown in Figure 8. At the end of the pile cap, the stress due to ship friction after hitting the Dolpih is 7,29,106 N/m2, causing cracks on the surface as thick as a concrete slab exposing the rebar as shown in Figure 9 shown.

Pilecap
Dolphin Pontoon e-ISSN: 2620-3332 SELODANG MAYANG Figure 9 Damage to pile cap elements based on numerical analysis with LISA FEA and loading of the pile cap by ship friction It can be seen that the damage state of existing elements in the field agrees with the results of the numerical analysis using LISA FEA V.8. in case of concrete cover thickness chip damage/fractures on the face of the pile cap, so that the reinforcement of the element is exposed and this is very dangerous for the steel material, which cannot withstand large temperature differences.

Conclusion
From the results of the research and data processing, it can be seen that the damage behavior resulting from the numerical analysis using LISA FEA is very similar to the conditions in the field, which of course is obtained from very detailed and measurable parameters and data collection, so that the behavior corresponds to the actual state.