| Bridges are an essential part of the country’s implementation of the“Outline of Building a Strong Country in Transportation",In matropoltain cities,some large bridges have become landmarks,and the safety and maintenance of bridges has become one of the important factors affecting regional security and stability.At present,various explosions due to terrorist attacks and accidents occur frequently,and the explosion load on bridges cannot be ignored.The research on explosion protection of various bridge components and building structures is of great significance.For piers,the existing anti-explosion research mainly focuses on cast-in-place monolithic piers.However,the traditional bridge and culvert structure forms and on-site construction methods have low construction efficiency,difficult management,high energy consumption,and are prone to quality and safety problems,which have been difficult to meet social needs.In recent years,the industrialization of bridge and culvert structure has become one of the hot issues in the development of bridge and culvert structure technology.Among bridge components with factory precast technology,precast segmental pier is one of the construction technologies with great potential.Therefore,it is necessary to analyze the damage and dynamic response of the precast segmental bridge piers under the blast load.The relevant results can be used as a basis for evaluating the anti-explosion performance of existing precast segment columns,and used to guide the design of precast segment columns under the blast load.Based on the LS-DYNA dynamics software,the overall model of monolithic pier columns and precast segmental pier columns is established in this paper.The dynamic response of segmental columns under blast loads is analyzed.The main results are as follows:(1)Firstly,in order to reveal the structural damage and failure mechanism of the precast segmental pier columns under the blast load,a monolithic pier column and precast segmental pier columns with different numbers of segments were established,and the explosive load was applied based on the ALE method,the explosion resistance analysis of segment columns at different explosive equivalents was carried out.The results show:Under small equivalent explosives,the overall response of the monolithic column and segment column under the impact of the explosion is within the elastic range,and the force mode is an obvious bending mode,both of which belong to local failure;Under large equivalent explosives,compared with traditional monolithic columns,the slip,opening and relative rotation between segments in a precast segmental column can effectively consume explosive energy,Therefore,the damage of the column concrete is reduced,and no penetration occurs.Increasing the number of segments in precast segmental columns can improve the explosion resistance of the column;Under the vehicle-mounted large-equivalent explosive,the fixed end of the precast segmental column consolidated at both ends suffered shear failure,and there was also shear failure between the end segments and adjacent segments.(2)Secondly,in order to study the influence of different connection structures in segmental columns on their explosion resistance,prestressed assembled segmental columns and precast segmental columns with shear key connections were established,parametric analysis of different shear key sizes(horizontal and vertical)and different initial prestress levels.The results show that:in the anti-explosive design of precast segmental columns,the addition of shear key connections between segment contacts can significantly reduce the maximum dynamic displacement of the column and effectively improve the anti-explosive performance of segmental columns.It is worth noting that increasing the vertical size of the shear key can reduce the maximum displacement of the segmental column,but the improvement of anti-explosive performance is not obvious,increasing the horizontal size of the shear key(from 14cm to 32cm),the maximum dynamic displacement in the column was reduced by 14.2%,thereby improving the explosion resistance of the precast segmental column;The application of initial prestressing force through prestressed steel strands in precast segmental columns can effectively reduce the maximum displacement of the column under the blast load,and improve the explosion resistance of segmental columns.However,it should be noted that the column of the reinforced concrete segment is an axially compressive member,so the vertical prestress should not be excessive and should not exceed the limit specified by the code.(3)Finally,based on the equivalent single-degree-of-freedom method,the maximum dynamic displacement of the monolithic reinforced concrete column under the blast load is solved by theoretical formula,then on this basis,the validity of the model is verified by the comparison between numerical simulation and empirical formulas.Finally,the maximum dynamic displacement in the segmental column under different number of segments is obtained by using finite elements,and the dynamic displacement correction coefficient is obtained by curve fitting.The results show that:under the action of blast load,only the parameters of F1/Rm and td/T need to be known,and the maximum response curve of the structure can be drawn according to the equation of motion,and the peak response of the structure can be solved;The maximum dynamic displacement of the monolithic pier under the blast load based on the equivalent single-degree-of-freedom method is 15.8mm,and the result of the numerical analysis is 13.9mm.The relative difference between the two is only 13.7%,which is in good agreement with each other;According to the numerical simulation results of extracting different numbers of segments,the functional relationship between the maximum displacement correction coefficient β of the segmental column and the number of segments n is fitted to β=2.1293e-0.265n+1,which can be used to guide the anti-explosion design of precast segmental columns in engineering... |
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