• Geomechanics and Engineering
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• v.14 no.6
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• pp.571-580
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• 2018

The failure mechanism of tunnel roof is investigated with upper bound theorem of limit analysis. The stochastic settlement and nonlinear failure criterion are considered in the present analysis. For the collapse of tunnel roof, the surface settlement is estimated by the simplified stochastic medium theory. The failure curve expressions of collapse blocks in homogeneous and in layered soils are derived, and the effects of material parameters on the potential range of failure mechanisms are discussed. The results show that the material parameters of initial cohesion, nonlinear coefficient and unit weight have significant influences on the potential range of collapse block in homogeneous media. The proportion of collapse block increases as the initial cohesion increases, while decreases as the nonlinear coefficient and the unit weight increase. The ground surface settlement increases with the tunnel radius increasing, while the possible collapse proportion decreases with increase of the tunnel radius. In layered stratum, the study is investigated to analyze the effects of material parameters of different layered media on the proportion of possible collapse block.

• Steel and Composite Structures
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• v.26 no.5
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• pp.549-556
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• 2018

Progressive building collapse occurs when failure of a structural component leads to the failure and collapse of surrounding members, possibly promoting additional failure. Global system collapse will occur if the damaged system is unable to reach a new static equilibrium configuration. The most common type of primary failure which led to the progressive collapse phenomenon, is the sudden removal of a column by various factors. In this study, a method is proposed to prevent progressive collapse phenomena in structures subjected to removal of a single column. A vierendeel peripheral frame at roof level is used to redistribute the removed column's load on other columns of the structure. For analysis, quasi-static approach is used which considers various load combinations. This method, while economically affordable is easily applicable (also for new structures as well as for existing structures and without causing damage to their architectural requirements). Special emphasis is focused on the evolution of vertical displacements of column removal point. Even though additional stresses and displacements are experienced by removal of a structural load bearing column, the proposed method considerably reduces the displacement at the mentioned point and prevents the collapse of the structural frame.

• Geomechanics and Engineering
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• v.11 no.6
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• pp.867-877
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• 2016

Collapse shape of tunnel roof in layered Hoek-Brown rock media is investigated within the framework of upper bound theorem. The traditional collapse mechanism for homogeneous stratum is no longer suitable for the present analysis of roof stability, and it would be necessary to propose a curve failure mode to describe the velocity discontinuity surface in layered media. What is discussed in the paper is that the failure mechanism of tunnel roofs, consisting of two different functions, is proposed for layered rock media. Then it is employed to investigate the impending roof failure. Based on the nonlinear Hoek-Brown failure criterion, the collapse volume of roof blocks are derived with the upper bound theorem and variational principle. Numerical calculations and parametric analysis are carried out to illustrate the effects of different parameters on the shape of failure mechanism, which is of overriding significance to the stability analysis of tunnel roof in layered rock media.

• Coupled systems mechanics
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• v.7 no.2
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• pp.111-139
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• 2018

A successful methodology for modelling controlled destruction and progressive collapse of 2D reinforced concrete frames is presented in this paper. The strategy is subdivided into several aspects including the failure mechanism creation, and dynamic motion in failure represented with multibody system (MBS) simulation that are used to jointly capture controlled demolition. First phase employs linear elasto-plastic analysis with isotropic hardening along with softening plastic hinge concept to investigate the complete failure of structure, leading to creation of final failure mechanism that behaves like MBS. Second phase deals with simulation and control of the progressive collapse of the structure up to total demolition, using the nonlinear dynamic analysis, with conserving/decaying energy scheme which is performed on MBS. The contact between structure and ground is also considered in simulation of collapse process. The efficiency of the proposed methodology is proved with several numerical examples including six story reinforced concrete frame structures.

• Earthquakes and Structures
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• v.19 no.6
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• pp.445-457
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• 2020

An ultra-high voltage (UHV) transmission system has the advantages of low circuitry loss, high bulk capacity and long-distance transmission capabilities over conventional transmission systems, but it is easier for this system to cross fault rupture zones and become damaged during earthquakes. This paper experimentally and numerically investigates the seismic responses and collapse failure of a UHV transmission tower-line system crossing a fault. A 1:25 reduced-scale model is constructed and tested by using shaking tables to evaluate the influence of the forward-directivity and fling-step effects on the responses of suspension-type towers. Furthermore, the collapse failure tests of the system under specific cross-fault scenarios are carried out. The corresponding finite element (FE) model is established in ABAQUS software and verified based on the Tian-Ma-Qu material model. The results reveal that the seismic responses of the transmission system under the cross-fault scenario are larger than those under the near-fault scenario, and the permanent ground displacements in the fling-step ground motions tend to magnify the seismic responses of the fault-crossing transmission system. The critical collapse peak ground acceleration (PGA), failure mode and weak position determined by the model experiment and numerical simulation are in relatively good agreement. The sequential failure of the members in Segments 4 and 5 leads to the collapse of the entire model, whereas other segments basically remain in the intact state.

• Journal of Korean Tunnelling and Underground Space Association
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• v.2 no.3
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• pp.13-24
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• 2000

The collapse shapes and causes of tunnel in the highway were analyzed and reinforced methods of tunnel were investigated in the paper. Collapse shapes of tunnel are divided into three types such as subsurface failure, small scale wedge failure and slickenside strata failure. These three shapes consist of 35%, 50%, and 15%, respectively. The 85% of collapse was located near the entrance and exit of tunnel. The 15% was located at the intersection of emergency laybys. When tunnel collapses are analyzed by the failure concept, sliding failure amounts to more than 83%.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.660-670
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• 2009

Neighboring construction becomes mainstream of Ground excavation in downtown area. This causes the displacement, deformation, stress condition, etc of the ground surroundings. Therefore Neighboring construction have an effect on Neighboring structure. All these years a lot of Neighboring construction carried out, and the accumulation of technology also get accomplished. But earth retaining structure collapse happens yet. Types of earth retaining structure collapse are 12. 1. Failure of anchor or strut system, 2. Insufficiency of penetration, 3. H-pile Failure on excessive bending moment, 4. Slope sliding failure, 5. Excessive settlement of the back, 6. Deflection of H-pile, 7. Joint failure of coupled H-pile, 8. Rock failure when H-pile penetration is rock mass, 9. Plane arrangement of support systems are mechanically weak, 10. Boiling, 11. Heaving, 12. Over excavation. But field collapses are difficult for classification according to the type, because collapse process are complex with various types. When we consider the 12 collapse field, insufficient recognition of ground condition is 4 case. Thorough construction management prevents from fault construction. For limitations of soil survey, It is difficult to estimate ground condition exactly. Therefore, it should estimate the safety of earth retaining system, plan for necessary reinforcement, according to measurement and observation continuously.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1997.03a
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• pp.265-272
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• 1997

In this paper the bending collapse characteristics of 60 series Al rectangular tubes were studied with a pure bending collapse test rig which could apply the pure bending moment, there occured three kinds of bending collapse modes - local buckling, delayed buckling, tensile failure - depending on the b/t(width/thickness) ratio and material properties. Experiment results are compared with the results of finite element method.

• Computers and Concrete
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• v.12 no.3
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• pp.351-375
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• 2013

Post-punching resistance of a flat slab can help redistribute the gravity loads and resist progressive collapse of a structure following initial damage. One important difficulty with accounting for the post-punching strength of a slab is the discontinuity that develops following punching shear. A numerical simulation technique is proposed here to model and evaluate post-punching resistance of flat slabs. It is demonstrated that the simulation results of punching shear and post-punching response of the model of a slab on a single column are in good agreement with corresponding experimental data. It is also shown that progressive collapse due to a column removal (explosion) can lead to punching failure over an adjacent column. Such failure can propagate throughout the structure leading to the progressive collapse of the structure. Through post-punching modeling of the slab and accounting for the associated discontinuity, it is also demonstrated that the presence of an adequate amount of integrity reinforcement can provide an alternative load path and help resist progressive collapse.

• Structural Engineering and Mechanics
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• v.37 no.1
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• pp.79-93
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• 2011

A simple mechanical model is proposed to demonstrate qualitatively the pancake progressive collapse of multi-storey structures. The impact between two collapsed storeys is simulated using a simple algorithm that builds on virtual mass-spring-damper system. To analyze various collapse modes, columns and beams are considered separately. Parametric studies show that the process of progressive collapse involves a large number of complex mechanisms. However, the proposed model provides a simple numerical tool to assess the overall behavior of collapse arising from a few initiating causes. Unique features, such as beam-to-beam connection failure criterion, and beam-to-column connection failure criterion are incorporated into the program. Besides, the criterion of local failure of structural members can also be easily incorporated into the proposed model.