Large-scale test as the basis of investigating the fire-resistance of underground RC substructures

Lu, Limin; Qiu, Junnan; Yuan, Yong; Jin, Tao; Yu, Haitao; Wang, Hui; Mang, Herbert A.

doi:10.1016/j.engstruct.2018.09.083

Cited by 22 publications

(25 citation statements)

References 22 publications

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“…In the real structure, the distance of neighboring columns in the axial direction of the tunnel amounts to 7500 mm. Cross-sectional view (vertical cut through the structure, normal to the axis of the tunnel) of a three-span two-floor reinforced concrete frame, providing the inspiration for fire testing in [40].…”

Section: Experimental Results From a Scaled Fire Testmentioning

confidence: 99%

“…Inspired by the structure illustrated in Figure 1, a model of the upper floor was tested at a scale of 1:4; see Figure 2 and [40] . The width of the tested structure was 5260 mm; its height was 1880 mm; and its axial length was 1200 mm; see Figure 3.…”

Section: Production Of the Tested Structurementioning

confidence: 99%

“…The design of the columns was the result of the following considerations: The scaled distance of neighboring columns in the axial direction of the tunnel amounted to 7.5 m/4 = 1.875 m. This is by a factor of 1.5652 larger than the axial length of the tested structure. Thus, the 1:4 scaled cross-sectional area of the columns, amounting to 300 mm × 200 mm, had to be divided by a factor of 1.5652; see [40] for details. In order to obtain a geometrically similar cross-section, both scaled dimensions were divided by √ 1.5652 = 1.25.…”

Section: Production Of the Tested Structurementioning

confidence: 99%

“…It represents a statically indeterminate RC structure, consisting of a top slab, a bottom slab, two lateral walls and two columns connecting the top and bottom slabs. A 1:4-scale model of this structure was tested by Lu et al [40]. Before the fire test, the structure was subjected to mechanical loads, simulating a combination of in situ ground pressure, water pressure, as well as dead and live loads that occur in the tunnel under service conditions.…”

Section: Introductionmentioning

confidence: 99%

“…Here, the first 30 min of the fire test by Lu et al [40] are analyzed, based on three-dimensional Finite Element simulations using the commercial software Abaqus FEA 2016 [42]. This period of time is chosen since it is representative of a moderate fire.…”

Section: Introductionmentioning

confidence: 99%

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Numerical Analysis of a Moderate Fire inside a Segment of a Subway Station

et al. 2018

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A 1:4 scaled fire test of a segment of a subway station is analyzed by means of three-dimensional Finite Element simulations. The first 30 min of the test are considered to be representative of a moderate fire. Numerical sensitivity analyses are performed. As regards the thermal boundary conditions, a spatially uniform surface temperature history and three different piecewise uniform surface temperature histories are used. As regards the material behavior of concrete, a temperature-independent linear-elastic model and a temperature-dependent elasto-plastic model are used. Heat transfer within the reinforced concrete structure is simulated first. The computed temperature evolutions serve as input for thermomechanical simulations of the fire test. Numerical results are compared with experimental measurements. It is concluded that three sources of uncertainties render the numerical simulation of fire tests challenging: possible damage of the structure prior to testing, the actual distribution of the surface temperature during the test and the time-dependent high-temperature behavior of concrete. In addition, the simulations underline that even a moderate fire represents a severe load case, threatening the integrity of the reinforced concrete structure. Tensile cracking is likely to happen at the inaccessible outer surface of the underground structure. Thus, careful inspection is recommended even after non-catastrophic fires.

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Section: Experimental Results From a Scaled Fire Testmentioning

confidence: 99%

Section: Production Of the Tested Structurementioning

confidence: 99%

Section: Production Of the Tested Structurementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Numerical Analysis of a Moderate Fire inside a Segment of a Subway Station

et al. 2018

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Stability analysis of a fire‐loaded shallow tunnel by means of a thermo‐hydro‐chemo‐mechanical model and discontinuity layout optimization

Sun

Zhang

Yuan

et al. 2019

Num Anal Meth Geomechanics

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When subjected to fire loading, shallow tunnels may experience loss of stability. This may result in large deformations and ultimately in local collapse of such structures. High temperature has a great negative influence on tunnels, not only because of thermal-induced mechanical degradation of the heated lining but also because of thermal spalling in consequence of the build-up of pore pressure. Thermal spalling causes quick loss of lining sections. Mechanical degradation sole can be simulated by thermo-mechanical models, while consideration of mechanical degradation and spalling requires thermo-hydro-chemo-mechanical (THCM) models and a spalling criterion. After simulation of both processes, the stability of a tunnel structure can be assessed by means of limit analysis. In this work, at first, a fully coupled THCM model is developed. Then, by using a "stress vs strength" criterion and a boundary shifting strategy, the coupled mechanical degradation and thermal spalling processes are captured, providing time-dependent and space-dependent information of the heated lining. Finally, a novel numerical approach, termed discontinuity layout optimization (DLO), is applied to quantify the stability of the tunnel structure with the help of a factor of safety. The proposed numerical procedure is used to conduct numerical studies with, as well as without, consideration of spalling. The results show that spalling has a great impact on the stability of the tunnel. It reduces the thickness of the lining section and accelerates the heating process of the inner concrete.

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Influence of end restraint strength on the structural fire behavior and deterioration mechanism of RC frame beams

Lu,

Zhao,

et al. 2024

Structural Concrete

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The end restraint strength of the reinforced concrete (RC) beams under the fire conditions may greatly influence the inner force redistribution and the structural behavior of the beams, even the stability of the whole structure. The structural fire behavior of two full‐scale frame beams with different end restraint strength under load were studied based on experiment and simulation. The temperature field, reinforcement strain, beam deflection, end axial displacement, and rotation angle of the structure during the whole heating and cooling process were measured. The influence of end restraint strength on the structural behavior was analyzed. The results show that the vertical displacement, axial force, end bending moment, and angular displacement first increase rapidly, then decrease gradually and become stable in the whole process; the lateral displacement increases first and then stabilizes; the change of axial and rotational deformations appeared to be non‐proportional with the corresponding restraining forces, reflecting that the axial and the rotational restraint strength at the ends of the beams decreased with the rise of temperature. The restraining strength of beams that submitted to fire globally decreased faster, and leading to a severe fire response and an earlier failure of the structure. The analysis results and the conclusions will supply scientific basis for the fire‐resistance design and safety evaluation on complex structures.

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Large-scale test as the basis of investigating the fire-resistance of underground RC substructures

Cited by 22 publications

References 22 publications

Numerical Analysis of a Moderate Fire inside a Segment of a Subway Station

Numerical Analysis of a Moderate Fire inside a Segment of a Subway Station

Stability analysis of a fire‐loaded shallow tunnel by means of a thermo‐hydro‐chemo‐mechanical model and discontinuity layout optimization

Influence of end restraint strength on the structural fire behavior and deterioration mechanism of RC frame beams

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