PSI - Issue 59

Volodymyr Romaniuk et al. / Procedia Structural Integrity 59 (2024) 479–486 Volodymyr Romanіuk et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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the absence of a spacer, a significant difference between the theoretically calculated and experimentally obtained stresses was observed in the cross sections near it. This difference averaged about 60%, emphasizing the significance of accounting for the actual stiffness of such nodes in the calculation scheme. This can be explained by the flexibility of the flanged bolted connection, which opened under the action of the bending moment and longitudinal force at the node. The theoretical calculations assumed this connection to be absolutely rigid. As a result, the comb node did not behave as a rigid connection but rather as a partially hinged one. The actual calculation scheme of the operation of the two-hinged arch turned out to be partially three-hinged, leading to a lower calculated bending moment in the node due to compliance. Experimental and theoretical studies established that the stiffness of the bolted connection was compared to the stiffness of the ideal flanged connection considered as a unit. It was also established that the stiffness of the node changes with changes in the parameters of its components. For instance, a change in the bolt diameter from to resulted in a stiffness variation from to , respectively. As is known, the effectiveness of the use of perforated structures is significantly reduced due to the need to weld holes near the supports, which is necessary to absorb the transverse force. However, the presence of fastening parts in the nodes raises doubts about the expediency of such a constructive solution. Hence, for continuous beams, a significant factor influencing their load-bearing capacity, alongside size considerations, is the nature of the load (static or dynamic), load type (concentrated, evenly distributed, combined), load scheme, material strength (standard or high-strength steels), span values, and geometric parameters of the cross-section. Additionally, the structural design of the intermediate support part of the beam plays a significant role. Therefore, conducting further theoretical and experimental investigations is essential to establish a rational structural design for the intermediate support. The practical options under consideration include: 1) without a stiffening rib along the axis of the intermediate support, and with unwelded holes to the left and right of the support (type 1); 2) with a stiffening rib along the axis of the intermediate support, and with unwelded holes to the left and right of the support (type 2); 3) without a stiffening rib along the axis of the intermediate support, and with welded holes to the left and right of the support (type 3); 4) with a stiffening rib along the axis of the intermediate support, and with welded holes to the left and right of the support (type 4). Moreover, providing justification for the inclusion of unwelded holes in the beam on both sides of the axis of the intermediate support could simplify the manufacturing process and reduce the cost of the beams. The utilization of transverse stiffeners, including those positioned along the axis of the intermediate support, is not comprehensively regulated, as existing design standards only address the geometric parameters of the ribs without offering specific instructions for their placement along the length of the beams. Long-span beams subjected to insignificant loads typically require calculations based on the serviceability limit state, while short-span beams experiencing significant loads require calculations based on the ultimate limit state. In these distinct cases, the stress-strain state of the beams around the intermediate support will differ significantly. As a result of preliminary calculations of the beam model using th e finite element method in the “Lira” software complex, it was established that the stress distribution at the characteristic cross-sections with holes in the supporting part of the continuous perforated beam near the intermediate support significantly differs from the stress distribution in the span part. This disparity arises due to a change in the sign of the bending moment plot from positive in the span to negative at the support, completely changing the nature of the stress-strain state. These findings emphasize the need for further experimental and theoretical research on various types of support parts in beams to develop a comprehensive methodology for their calculation and provide recommendations for determining the rational area of application for each type. 4. Conclusions 1. Based on previously performed calculations of the load-bearing capacity for the ultimate and serviceability limit states, an experimental design of a rafter arch was developed. Notably, this design facilitates research under conditions with or without prestressing capabilities.