^{1}

^{1}

In this paper, ANSYS/LS-DYNA dynamic analysis software was used to establish finite element truss models with six trusses. The models with impact loads aimed to simulate the scenarios that structures were crashed by heavy truck. By changing the crashed position, the impact load intensity and structure height-span ratio, the models could give out the structural performance, including the stress, strain and other impacts in different scenarios. Besides, considering the component failure, this paper analyzed the possibility of structural progressive collapse. Results for the load cases from below indicate that it will be more destructive if impact load is arranged on 3rd side pillar and progressive collapse will occur if pillar fails after crashed.

Truss structure, which is one of the most widely used architectural structures, is generally used in gymnasiums, museums, theaters and terminals, and other public buildings [

The models were established by ANSYS/LS-DYNA dynamic analysis software. The parameter of model is shown in following

Assuming the truck density is 148 kg/m^{3} (weight is 8 t), then the impact load intensity is 8 × 104 kg∙m/s (8 t × 10 m/s). Considering the symmetry of the structure,

The results indicate that loads on the 3rd side pillar will result in maximum stress in the structure, which is most destructive.

Through assuming different density of impactors and constant size and velocity, different impact loads could be arranged on truss.

Element | Truss Structure | Truck | ||
---|---|---|---|---|

Unit | Link160 | Beam161 | Shell163 | Solid164 |

Size | diameter: 0.048 m span: 28 m truss number: 6 | Inner diameter: 0.20 m outer diameter: 0.14 m height: 9 m | thickness: 0.03 m | length: 6 m width: 3 m height: 2.5 m velocity: 10 m/s |

Density | EX | Failure strain | Yield stress | NUXY | Tangent module |
---|---|---|---|---|---|

7850 kg/m^{3} | 2.06 × 10^{11} | 5% | 3.45 × 10^{8} Pa | 0.3 | 6.1 × 10^{9} |

performance of truss under No. 7 load.

^{5} kg∙m/s (18 t × 10 m/s). With 2 × 10^{5} kg∙m/s (20 t × 10 m/s) loads, the maximum stress in structure will be yield stress (3.45 × 10^{8} Pa) and the relative deformation in some components will exceed 5%, which could result in structure failure.

8 × 10^{4} kg∙m/s (8 t × 10 m/s) impact load was arranged on 3rd side pillar in structures with different height-span ratio, and structural performances show in

No. | Load position | Max-stress | Max-prin strain | Displacement |
---|---|---|---|---|

1 | Front-1st | 4.14 × 10^{7} Pa | 3.38 × 10^{−4} | 0.3414 m |

2 | Side-1st | 4.73 × 10^{7} Pa | 3.22 × 10^{−4} | 0.3302 m |

3 | Side-2nd | 5.15 × 10^{7} Pa | 3.05 × 10^{−4} | 0.3267 m |

4 | Side-3rd | 6.68 × 10^{7} Pa | 2.50 × 10^{−4} | 0.3258 m |

No. | Load Intensity | Max Stress | Max-prin Strain | Displacement | Notes |
---|---|---|---|---|---|

1 | 8 t × 10 m/s | 4.14 × 10^{7} Pa | 3.38 × 10^{−4} | 0.3414 m | |

2 | 10 t × 10 m/s | 5.73 × 10^{7} Pa | 3.92 × 10^{−4} | 0.3302 m | |

3 | 12 t × 10 m/s | 7.14 × 10^{7} Pa | 4.45 × 10^{−4} | 0.3267 m | |

4 | 14 t × 10 m/s | 8.67 × 10^{7} Pa | 5.51 × 10^{−4} | 0.3258 m | |

5 | 16 t × 10 m/s | 1.043 × 10^{8} Pa | 6.77 × 10^{−4} | 0.5914 m | |

6 | 18 t × 10 m/s | 1.246 × 10^{8} Pa | 8.08 × 10^{−4} | 0.6511 m | |

7 | 20 t × 10 m/s | 4.349 × 10^{8} Pa | 5.94 × 10^{−4} | 1.1321 m | Fail |

No. | Height-span ratio | Max-stress | Max-prin strain | Displacement |
---|---|---|---|---|

1 | 0.3214 | 4.14 × 10^{7} Pa | 3.38 × 10^{−4} | 0.3414 m |

2 | 0.3571 | 6.02 × 10^{7} Pa | 2.07 × 10^{−4} | 0.3623 m |

3 | 0.3929 | 7.25 × 10^{7} Pa | 2.40 × 10^{−4} | 0.3645 m |

4 | 0.4286 | 8.40 × 10^{7} Pa | 2.20 × 10^{−4} | 0.3551 m |

5 | 0.4643 | 8.57 × 10^{7} Pa | 3.51 × 10^{−4} | 0.3498 m |

6 | 0.5000 | 9.08 × 10^{7} Pa | 3.30 × 10^{−4} | 0.3492 m |

7 | 0.5357 | 9.41 × 10^{7} Pa | 3.09 × 10^{−4} | 0.3497 m |

8 | 0.5714 | 9.65 × 10^{7} Pa | 2.75 × 10^{−4} | 0.3501 m |

9 | 0.6071 | 9.88 × 10^{7} Pa | 3.48 × 10^{−4} | 0.3578 m |

10 | 0.6429 | 9.51 × 10^{7} Pa | 2.62 × 10^{−4} | 0.3521 m |

11 | 0.6786 | 9.76 × 10^{7} Pa | 2.67 × 10^{−4} | 0.3499 m |

12 | 0.7143 | 1.01 × 10^{8} Pa | 2.79 × 10^{−4} | 0.3541 m |

13 | 0.7500 | 1.039 × 10^{8} Pa | 3.82 × 10^{−4} | 0.3614 m |

The axial load in the 3rd side pillar was about 20 kN. For analyzing the possibility of progressive collapse, the failure part (3rd pillar) was removed and the inverse axial load was arranged on the same position, which was demonstrated in

As it was showed in

Group | 1 | 2 | 3 |
---|---|---|---|

T | 0 s | 1 s | |

Q | −20 kN | −20 kN | |

F | 1000 kN | 1000 kN | |

T1 | 0 s | 0.033 s | 1 s |

FT | −1000 kN | −1000 kN |

In this paper, the finite element truss model with six trusses was established with ANSYS/LS-DYNA dynamic analysis software. It simulated the situations that structures were crashed by heavy truck. Through changing variables, such as the crash positions, the impact load intensity and structural height-span ratio, this paper concluded their effects to the stress and strain in truss structure. Besides, considering the component failure, this paper analyzed the possibility of structural progressive collapse. Conclusions are shown as below:

1) Impact load on the 3rd side pillar will result in maximum stress in the structure, which is most destructive. The bearable maximum impact load intensity truss is about 1.8 × 10^{5} kg∙m/s (18 t × 10 m/s).

2) The stress will be stronger in truss with greater height-span ratio. When the ratio is less than 0.6, the maximum stress in structure will increase by 1 × 10^{7} Pa with ratio increasing by 0.05. When the ratio is more than 0.6, is has not significant effect to the stress.

3) If the 3rd side pillar fails due to impact, components will progressively fail and the truss structure will collapse even though the impact load intensity is less than 1.8 × 10^{5} kg∙m/s (18 t × 10 m/s).

Zheng, Z.W. and Bai, Y. (2017) Effects of Impact Loads on Mechanical Performance for Truss Structure. World Journal of Engineering and Technology, 5, 135-140. https://doi.org/10.4236/wjet.2017.53B015