近场爆炸时预应力混凝土梁体抗爆分析

为了研究预应力混凝土梁在爆炸荷载下的动力响应、破坏模式以及不同预应力条件对结构抗爆性能的影响,结合流固耦合理论,采用LS-DYNA有限元软件建立预应力混凝土梁实体模型,开展不同炸药条件,不同预应力度和不同爆心位置条件下的预应力混凝土梁体结构抗爆分析。结果表明:①混凝土梁体的破坏模式随炸药当量的增加而变化,小当量炸药条件下,混凝土梁体表现为传统的受弯构件,随着炸药当量增加,梁体迎爆面出现压溃破坏,继续增大炸药当量,梁体迎爆面压溃引起的混凝土剥离面积和深度增大,导致截面抗压能力减弱,梁体由适筋设计的塑性破坏转为脆断;②当中等炸药当量在梁上方爆炸时,按抗弯要求设置的预应力效应能提高抗爆能力10%左右,反之,当其在梁体下方爆炸时,由于预应力效应的不利叠加会导致梁体抗爆能力明显下降;③对于同等炸药当量条件下沿梁跨径方向不同位置的爆炸,跨中爆炸时梁体受力最为不利,爆点位于支座处梁体上方时,由于支座的边界约束作用,梁体动力响应和损伤较小;④同等炸药当量条件下,爆心相对梁体上下位置的改变将引起预应力混凝土梁体破坏模式的改变;⑤灌浆对预应力混凝土梁体的抗爆性能影响不明显,有黏结预应力和无黏结预应力混凝土梁体在不同爆炸荷载作用下表现出相似的动力特性和力筋应力增量变化规律。

Anti-blast Resistance Analysis of Prestressed Concrete Bridges Under Close-by Blast

To study the dynamic responses and failure modes of prestressed concrete beams under blast loads, finite element models for the concrete beams based on LS-DYNA were established using the fluid-solid coupling method to perform dynamic analyses of constructions under different TNT weights, detonation locations, and stress conditions. The results show that:① The damage mode changes with increase in TNT equivalent weights. Under the condition of low TNT weight, the concrete beam behaves as a traditional bent member. As the TNT weights increases, the beam begins to crack. When the TNT equivalent weight is large enough, owing to the continuous peeling of the concrete compression area, the damage mode changes from plastic failure to brittle fracture.② When medium-blast loading occurs above the beam, prestressed concrete beams can improve anti-blast resistance by approximately 10%;on the contrary, when exploding beneath the prestressed concrete beams, the prestressing has a great negative influence on the anti-blast resistances.③ Under the same TNT weights, the most serious damages occur when the explosions are in the mid-span region compared to explosions in other positions along the beam. When the explosions are located above the support, the dynamic response and damage of beams are small due to the boundary constraint of the support.④ Under the same TNT weights, different detonation locations may change the damage modes of the prestressed concrete beams.⑤ Grout has no obvious influence on the anti-blast resistances of the prestressed concrete beams, and they exhibited similar dynamic characteristics and change rules of stress force under different blast loads.