Blast-resistance Analysis For Long Span Concrete Cable-stayed Bridges

The long-span concrete cable-stayed bridge is not only the key node of the transportation,but also the landmark,its security has important economic,social and military significance.In recent years,there have been many bridge damage events caused by terrorist attacks at home and abroad and the explosion of vehicles with dangerous goods,the key bridge structure facing the threat of explosive load can not be ignored.In contrast,the current research on the anti-blast of bridge structure is not enough,the bridge specification is not related to the anti-blast design,for long-span concrete cable-stayed bridge anti-blast research is very few.Therefore,it is necessary to establish the numerical model combined with the anti-blast theory to understand the dynamic response and damage characteristics of the concrete cable-stayed bridge under the explosive load.In this paper,a typical concrete cable-stayed bridge is used as an example.The explicit dynamic model of LS-DYNA and AUTODYN is used to establish the full-bridge model and the local model of the beam.The influence of the prestressed effect of the beam on anti-blast performance is discussed,the main results are as follows:(1)First,the model of the whole bridge of a double girder cable-stayed bridge is established.The stress response of the cable-stayed bridge under different explosive loading is analyzed and compared.The dynamic response and damage of the cable-stayed bridge are analyzed by using different load application method.The results showed that cables under blast loading are strong enough to resist breaking,but in the case of eccentrical blast loading,the cables close to the detonation point may have a high risk of break.When using of different explosive load simulation method,the bridge does not show the catastrophic continuous collapse,the concrete beam shows the characteristics of local damage;For numerical simulation for box girder relates to the reflection and flow phenomena,the fluid-solid coupling model is more accurate.(2)Then,for the concrete beam with the greatest possibility of explosion load,the numerical simulation analysis of the concrete section is carried out.The dynamic response and damage characteristics of the concrete girder under different detonation locations and different TNT equivalent weights are studied emphatically,and the influence of the different structures on the anti-blast performance of the concrete beam is discussed.The results show that the failure mode of the girder is related to the detonation locations and the TNT equivalent weights.The stiffening ribs improve the blast-resistance ability of the concrete girder under the small and medium-blast loading by enlarging its lateral rigidity and inhibiting the expansion of damage areas.More serious damage occurs in the box girder under the blast loads due to confinement effect on shock wave from inner chamber of the girder after its top slab being penetrated.(3)Finally,the influence of prestress on the anti-blast performance of concrete beams is simulated and analyzed.First,a typical concrete T-beam is selected,and models of bonded prestressed,unbonded prestressed and non-prestressed concrete beams are established.The development of local damage of concrete,the response of prestressed cables and the dynamic response of concrete beam are analyzed under different explosive conditions.Finally,the influence of prestressing on the concrete box girder of cable-stayed bridge is analyzed.The results show that the contribution of the prestressing effect to the anti-blast performance of the concrete beam depends on the position of the explosive load.Under the same TNT weights,different detonation locations may change damage mode of the prestressed concrete beams.Grout has no obvious influence on anti-blast performance of the prestressed concrete beams.