Fire events reduce the strength of the steel structure on the bridge and can cause collapse which results in losses, so it is necessary to consider the effects of fire when planning construction. Considering that the joints affect the performance of steel structures, the results of research on the performance of steel beams need to be augmented by testing the post-fire girder bridge bolt connection performance. Structural tests will be carried out on six specimens of bridge steel beam elements with high quality bolt connections in the center of the beam with sliding type bolt connections. Two control specimen beams were tested with shear loads without combustion. Two specimens with temperature of 700°C and 900°C with different torque bond variables. From the displacement control test using UTM on six specimens, it will be known the performance of each type of connection by evaluating changes in carrying capacity, stiffness, deflection capacity, ductility, and stress-strain capacity due to the influence of temperature acting during the fire process. The results can prove which type of bolt connection is better for use on bridges with fire risk.

The timber bridge design although economical, often has difficulty producing enough rigidity so that a solution is needed to solve it. The use of CFRP (Carbon Fiber Reinforced Polymer) as a reinforcement of structural elements if properly designed and implemented can produce an effective and efficient composite structure. The experimental study aims to analyse the strength, stiffness and ductility of flexural strengthening composite bridge glued laminated timber beams-concrete plates using CFRP layers. The dimensions of the composite glued laminated timber beams 100/180 mm and concrete plate 75/300 mm with a length of 2,480 mm. The number of specimens is 3 composite glued laminated timber beams-concrete plate consisting of 1 test beam without CFRP reinforcement, 1 test beam with one layer CFRP reinforcement, and 1 test beam with three layer CFRP reinforcement. Experimental testing of flexural loads is done with two load points where each load is placed at 1/3 span length. The test results show that the strength of composite laminated timber beams glued - concrete plates BN; BL-1; BL-2 in a row 81.32; 82.82; 82.69 kN/mm; stiffness in a row 7.51; 8.22; 6.32 kN/mm and successive ductility of 16.67; 28.83; 20.21.

Steel construction joints are critical parts and determine the overall strength of the structure, one of which is when subjected to high temperatures. The performance of bolt connections on steel bridges is very important to be considered in bridge design. The research results on the performance of the steel beams need to be supplemented with the performance testing of the post-fire girder bridge bolt connection. Six steel beams with shear-type high strength bolt connection in the middle of the span were tested under monotonic vertical point load located at the beam mid-span. Three specimens use proof load in their connections (Proof Load Specimens), while the others use a snug tight bolt (Snug Tight Specimens). As control specimens, two specimens (SS020 Proof Load and SS020 Snug Tight) were tested structurally without combustion. Two specimens (SS700 Proof Load and SS700 Snug Tight) were tested structurally after being burned under 700 o C. The other two specimens (SS900 Proof Load and SS900 Snug Tight) were tested structurally after being burned under 900 o C. The experimental results combined with reviewed using a scanning electron microscope (SEM) to determine changes in the microstructure due to the temperature given to charged objects. The best post-burn connection in the field is bolted connection with proof load tightening because it can increase strength up to 11%. Even after being burned, the proof load joint still proves the highest performance than the joint without being subjected to initial tensile forces.