Damages Inspection and Finite Element Model Analysis of Static and Dynamic Factors of Steel Girder-Concrete Composite Span Due to Vehicles Live Load and Loads Combination

A bridge consists of a set of components that are divided into two main sections, where the superstructure includes bearings, beams or girders, bridge deck, joints, paving layers, security barriers, and water disposal system, while the substructure includes foundations, columns, and column heads, while the substructure includes foundations, columns, and column heads. Bridges are built to cross barriers like rivers, roadways, and railroads. They are categorized either by the kind of materials used in their construction or by the kind of support that they utilize. Simple truss bridges and continuous bridges are included in the categorization by type of support, whereas concrete, prestressed concrete, wooden, and steel bridges are included in the classification by construction material [1-6].

A bridge is a man-made structure that crosses physical barriers, like a valley, a waterway, or a highway, without blocking traffic below. Bridge type selection is determined by site features, vendor choices, site hydraulics, profile placement, and construction expenses. The density and amount of traffic loads influence the dimensions of the bridge structure, which is essential for the region that the bridge links [7-11].

The evaluation of each bridge is crucial for gathering data regarding the structural state and sufficiency of the bridge. This data should be maintained as a permanent record of the bridge. Such documentation offers a valuable and precise historical account. It also includes information on past repairs, granting others easy access to relevant information. The aims of examining damages to the bridge elements are to assess whether the bridge structure is in a secure state, identify any essential upkeep, repairs, and fortification needed, create a foundation for funding any required maintenance and strengthening, and provide information to designers and construction engineers about aspects that need maintenance. Damage evaluation and maintenance of all bridge types are crucial for the safety of bridge users and are often tremendously significant for the local economy. Efficient bridge upkeep initiatives must be closely linked to the evaluation of the bridge parts. Hence, the maintenance department ought to comprise a permanent group of examiners referred to as the inspection team. The evaluation of the bridge encompasses all elements within the bridge to establish if it is in acceptable condition or requires repair or strengthening. The inspection strategy involves analyzing reports and conditions on-site, necessary Gears and equipment, vehicle flow management (as needed), site surveying, and constructional evaluations, which include assessing the Bridge surface, the components above the bearings, and the components under the bearing [12-20].

Superior strength and flexibility, a higher strength-to-cost ratio, and a lower strength-to-cost ratio in terms of compression as compared to concrete are just a few pros that steel frameworks have over other building materials. Steel bridges have more affordable foundations and lighter superstructures than concrete bridges. They can be made in portions in a facility with quality control measures in place. After that, these components are delivered to the location in manageable chunks and put together to create the entire bridge construction [21, 22].

Bridge designers' primary goal is to provide clients with affordable solutions that meet their objectives. By utilizing Concrete's compressive endurance in the slab and the tensile strength of steel in the primary girder, steel-concrete composite bridges offer a cost-effective solution for a range of span lengths. Shear connectors, which are welded to the upper flange of the steel girder and placed into the concrete slab, form the link between the steel and concrete elements of composite bridges. The longitudinal shear force that is conveyed through the shear connections enhances this composite action, markedly boosting bending resistance when compared to non-composite beams. Typically, composite indicates that the steel framework of a bridge is attached to the concrete structure of the deck, permitting the steel and concrete to operate together, thus lowering deflections and enhancing strength. This is achieved by using 'shear connectors,' which are secured to the steel beams and then incorporated into the concrete. Shear connectors may be welded on, potentially with the assistance of a ‘stud welder’, or, ideally in export projects, by utilizing nuts and bolts [23-26].

Constructed as concrete bridges because the superstructure constitutes a minor portion of the overall construction work for the primary contractor, who typically manages concrete foundations, piers, and abutments. The concepts of composite bridges encompass a span range of approximately 15m to 50m to connect the conventional span lengths of composite bridges-within that range, they address roughly 75% of all span requirements for road bridges. Simply supported structures are normally employed for single, short-span constructions. Multiple-span steel girder structures are engineered as continuous spans. When the total length of the continuous structure surpasses about 900', a transverse expansion joint is implemented using girder hinges and a modular watertight expansion device [27-32].

Bridge durability and strength are determined by materials used, system design, load nature, and environmental conditions. Vehicle weight has a significant impact on the structural integrity and safety of bridges. As cars drive across the bridge, dynamic parameters arise, such as vibration frequency, three-dimensional dynamic displacements, dynamic bending moments, dynamic shear pressures, and dynamic stresses and strains. These dynamic factors, which surpass static ones due to the interaction between moving cars and the bridge, can exacerbate the bridge's deterioration. The dynamic load applied by vehicles on the bridge can be affected by the dynamic characteristics of the vehicles, the dynamic properties of the bridge, the bridge's surface texture, and the speed of the vehicles. Although a gradual rise in dynamic load may not result in immediate failures of the bridge, these dynamic vehicle loads can cause damage that ultimately leads to long-term fatigue [33-37].

When bridge structures experience various forms of severe damage, stretching and repairing are necessary to restore the structural efficiency of the bridge. The enhancement of the bridge's constructional components can be pursued by changing substandard or damaged materials with superior quality materials, adding extra load-bearing components, and redistributing the loading effects through imposed deformations on the structural system. The choice of an appropriate technique for reinforcing and repairing the bridge's structural components relies on several factors. These factors include the type and age of the structure, the significance of the structure, the extent of strength that needs to be increased, the type and extent of harm, the resources available, cost, and workability, as well as aesthetics [38, 39].

This study's main goals are to: determine the structural parts of steel I-girder-concrete composite spans and identify any damage that has occurred in these components; evaluate the static responses under the influence of vehicle loads and service loads (load combination scenario) using numerical static analysis (FEM) using CSI-Bridge Ver. 25; determine the natural frequency of the bridge construction caused by its own weight using modal analysis; evaluate the dynamic responses resulting from vehicle live loads using numerical dynamic time history analysis (FEM); inspect the bridge framework's structural effectiveness and identify methods for reinforcing and repairing compromised structural elements.

The methodology of this study includes selection of bridge structure, damage inspection of structural parts of steel span of bridge structure, numerical static analysis, and numerical dynamic analysis. Figure 1 explains the flow chart of methodology of study.

In this study, Al-Thawra Bridge has been chosen to assess the structural performance because this bridge is significant due to its position in Babylon City in central Iraq. It is a composite bridge which is consists of I-steel girder span with eight precast prestressed concrete I-girders. This bridge was designed and constructed by Abdullah Owiz General Contracting Company and its construction began in 2010 as part of a strategic project aimed at alleviating traffic congestion at the entrance of Al-Hillah city and connecting Baghdad to the southern governorates. The bridge was designed with a total length of 488m and a width of 18.25 m, featuring Iraq's longest intermediate span of 56 meters. Originally planned for completion within 20 months, the bridge was successfully constructed in just 17 months due to favorable weather and dedicated engineering efforts. Originally planned for completion within 20 months, the bridge was successfully constructed in just 17 months due to favorable weather and dedicated engineering efforts. As mentioned above, it consists of nine spans. Eight of them are precast prestressed concrete I-girder section with 24 m length for each span and one of them is steel I-girder span, which has 56 m length. This study will select a steel-girder span to predict static and dynamic forces. This span has two bent supports. Each bent has three circular piers with 1.2 m diameter and 5 m height. Figure 2 shows the Al-Thawra bridge location, Figure 3 shows the Al-Thawra bridge structure, and Figure 4 shows the steel I-girder span layout and appearance.

Damage inspection findings of the steel I-girder span indicated significant harm in the structural elements of the bridge. Steel I-girders span exhibit no indications of rust or corrosion. The obstruction must be cleared, and the rainfall drainage system must be repaired. It would also be wise to apply a moisture-resistant coating to the steel I-girders. It can be noted that from damage inspection, the main problem is in the expansion joints, which need to be repaired or replaced. Figure 5 shows the damage of expansion joints.

Numerical static and dynamic analysis of steel I-girder span is done by using CSI-Bridge Ver.25, which uses finite element analysis method. The type of area object model is shell element with maximum submish size is 1.2m. Maximum segment length of concrete deck, concrete piers and concrete pier caps is 3 m, respectively. The type of steel for girders is A709Gr50 with fy is 344MPa (50ksi). For concrete deck and substructure, the compressive strength is 50MPa. The bearing type is simply supported as hinge and roller. This study adopted two load cases. Vehicle traffic load case and loads combination case. Vehicles traffic load case represents the live load which uses vehicle in AASHTO type HS20-44. Load combinations comprise Permanent load, Pre-tensioned load, Dynamic vehicle load, temperature load, wearing surface, and wind load. Figure 6 shows the steel I-girder span model.

In this research, CSI-Bridge Ver. 25 is utilized to examine static reactions caused by vehicle live load in a static condition. These reactions consist of tensile stresses, compression stresses, and vertical deflection.

The findings of tensile and compression stresses resulting from static analysis under the influence of vehicles' live load for the upper and lower sections of steel I-girders are depicted in Figures 7 and 8. In Figure 7, the highest tensile stress at the top of the steel girders is 2.27MPa, which is below the permissible tensile stress value from (AASHTO LRFD BRIDGE), set at 207MPa. Regarding compression stress, the peak value at the top of the girders is -8. 61MPa, which is also beneath the allowable compression stress (207MPa). As illustrated in Figure 8, the highest tensile stresses occur at the center bottom of the steel girders, measuring 13.56MPa, while the greater bottom compression stress is -3.15MPa, both of which are under the allowable stress limit of 207MPa.
$\sigma=0.6 \times$ fyield