The maximum pull-out force of the anchor bolt is between 22.5kN-30kN, and the total slip amount reaches 1mm-1.2mm. The first large sliding between the bolt and the concrete in each test piece releases the energy. After that, the rebalancing continues to withstand the tension. This phenomenon may or may not occur again, and eventually it will fail due to the increase in the amount of bolt slip. In the new composite shell structure, the bolt's pull-out resistance directly affects the bending resistance of its joints. Similar to the bond between steel and concrete in reinforced concrete structures, the factors affecting the bolt's pull-out resistance are various, including concrete strength, anchor length, and bolt diameter.
Computational model analysis In the composite component, the bending moment bearing capacity depends on two parts: one is steel) concrete composite section; the other is bolted section. Take the model as shown: for section BB, its bending resistance can be obtained by the following formula: fcmbx=RstAt+RsbAbM=RstAt(h0-x2-c)+RsbAb(h0-x2) where Rst,At is the steel side The average stress and area of ​​the plate; Rsb, Ab is the stress and area of ​​the bottom plate; c, x are the center distance of the side plates and the height of the section being pressed; fcm is the bending compressive strength of the concrete; h0 is the total height of the section.
For the AA section, the elements on both sides of the bolt joint are assumed to be rigid bodies in the analysis, and the other sections are not rotated except for the joint. Under the action of bending moment, if the corner of the node is H, then: fcmbx=FcosHM=F(h0-d-x2)cosH where F is the pulling force of the bolt. F consists of two parts: the pull-out force of the side panels and the anchoring force of the bolts. It can be obtained by the following expression: F=Fb+AFs where Fb is the anchoring strength of the bolt in concrete; Fs is the tensile strength of the side panel. A is the reduction factor, because Fb and Fs usually do not reach the maximum value at the same time. According to the test results, when the anchor length of the bolt is sufficient, A=0.3, otherwise A=1; obviously F
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