• International Journal of Highway Engineering
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• v.19 no.6
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• pp.47-56
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• 2017

PURPOSES : The purpose of this study is to investigate the stresses of the middle slab in a double-deck tunnel owing to the slab lift to replace the underlying elastic pads during maintenance work. METHODS : The middle slab was divided into three different sections: typical section, expansion joint section, and emergency passageway section. Finite element analysis models of these three sections of middle slab were developed, and the stress distribution and maximum stresses were obtained using the models when the middle slab was lifted to replace the underlying elastic pads. Various slab lifting methods were examined in this study such as one-, two-, and multiple-point lifts, distributed lifts, and one or both slab side edge lifts. RESULTS : When the slab side edge is lifted, the longitudinal stresses of the slab are almost the same as the principal stresses. This implies that the governing stresses are the longitudinal stresses. The maximum stresses with both-edge lifts are generally smaller than those with one-edge lifts at all three sections of middle slab. CONCLUSIONS : If the middle slab in a double-deck tunnel is lifted for maintenance, the slab should be lifted at multiple points along the longitudinal direction to reduce the tensile stresses.

• Fire Science and Engineering
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• v.30 no.2
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• pp.81-86
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• 2016

Recently, frequent traffic congestion has occurred in domestic urban roads. As a solution for downtown traffic congestion in domestic urban roads, plans for great depth underground double-deck tunnels have been made. Great depth underground double-deck tunnels that have been planned for passenger cars, has the structure of a network type; the entry of vehicles is carried out in the underground space. In these network great depth underground double-deck tunnels, the cross section and the height of the tunnel are smaller than the general road tunnel, and the smoke of a fire will propagate faster than the evacuation of tunnel passengers by the action of the traffic-ventilation and casualties are expected. Therefore, in the present study, an attempt was made to prevent the delay system for fire smoke diffusion at the time of a fire in a domestic network great depth underground double-deck tunnel according to the area of the tunnel block during the operation of the delay system for fire smoke diffusion to analyze the effects of reducing the inflow velocity. When the area of the tunnel block was not less than 50%, the effect of reducing about 21% of the wind speed acting on the tunnel was significant. If the area is more than 50%, the diffusion rate of fire smoke was reduced by approximately 21%, which will be useful for a safe evacuation.

• Journal of Korean Tunnelling and Underground Space Association
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• v.19 no.5
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• pp.717-732
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• 2017

Recently, the construction of underground structure such as a double-deck tunnel is increasing to manage rapid growth of roadway traffic volume. Double-deck tunnel includes middle slab to separate upper and lower road inside, and various sources affect the dynamic behaviour of middle slab due to dynamic loading of vehicle. Therefore, it is important to investigate the dynamic response of middle slab precisely to apply it to design and analysis of double-deck tunnel. In this study, dynamic analysis model of middle slab considering structural type, design velocity, vehicle load, and surface roughness, etc. is built. 3-dimensional dynamic analysis is performed to assess dynamic response of middle slab. Consequently, Dynamic Magnification Factor which represents dynamic response of middle slab shows maximum in case of elastomeric bearings (EB) and average roughness (Grade C). It is also expected that dynamic response can be reduced under the condition of good roughness (Grade B) and fixed bearings (FB).

• Journal of Korean Tunnelling and Underground Space Association
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• v.19 no.2
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• pp.301-317
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• 2017

In this study, as an initial study for development of stability analysis program of a double-deck tunnel during life cycle, a structural analysis solver based beam-spring model for the double-deck tunnel is constructed. Effect of parameters(slab supporting type, depth of the tunnel and ground elastic modulus) is analyzed with the beam-spring model. The model is also compared and verified by commercial structural analysis program. It is considered that the slab supporting type affects the integrated behavior with segment lining and influence of intermediate slab on the stability of the tunnel decreases as the tunnel depth increases. The relationship between the ground elastic modulus and the effect of the intermediate slab on the segment lining needs further investigation.

• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.5
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• pp.823-837
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• 2018

Congestion of the city with the rapid industrial development was accelerated to build complex social infrastructure. And numerous structures have been designed and constructed in accordance with these requirements. Recently, to solve complex urban traffic, many researches of large-diameter tunnel under construction downtown are in progress. The large-diameter tunnel has been developed with a versatile double-deck of deep depth tunnel. For the safe tunnel construction, ground reinforcement methods have been developed in the weakened pillar section like as junction of tunnel. This paper focuses on evaluation of the effects of new developed ground reinforcement methods in double-deck junction. The values of reinforcement determined from the existing and developed methods were compared to each other by numerical simulation.

• Fire Science and Engineering
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• v.30 no.2
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• pp.75-80
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• 2016

In the wake of expanding and overpopulating urban areas, traffic congestion has been worsening increasingly, causing huge economic losses. In a bid to effectively use the space of metropolitan areas, the construction and operation of a double deck tunnel has been on the rise. On the other hand, a lower height of a double deck tunnel is expected to generate more smoke and soot in a fire than other usual tunnels. Therefore, it is undesirable to apply the standard for fire intensity or smoke generation, which were designed for existing road tunnels. A part of an effort to propose a design fire curve that is useful for double deck tunnel, is intended to obtain and analyze the fire characteristics in a double deck tunnel through a real scale fire test. The test was conducted according to the fire scenario with one passenger car and two passenger cars; the monitored fire intensity was a maximum of 2.4 MW and 3.5 MW, respectively.

• Journal of the Korea Concrete Institute
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• v.29 no.1
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• pp.23-32
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• 2017

The joints between precast PSC slabs of the intermediate road slab in double deck tunnel are inevitably generated in the road traffic vehicle traveling direction. Therefore, it is important to make the behavior of parts on the joint in one piece. The imtermediate road slab system of double deck tunnel in great depth proposed in this study will be constructed with precast PSC slab in order to minimize the construction period. And the joint connection between the precast slab has been developed in two methods: the 'Transverse tendon reinforcement method' and 'High strength bolts connection method'. Also, the experiments were performed for the full scale model in order to evaluate the performance of the intermediate road deck slab with two type joints systems, the structural stability was verified through the F.E.M analsysis. The results of static loading test and F.E.M analysis investigated a very stable behavior of intermediate road deck slab in double deck tunnel applying the joint methods developed in this study, in the cracks and deflections to satisfy the design standards of Highway Roads Bridges (2011), it was determined that there is no problem even servicebility.

• Wind and Structures
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• v.24 no.4
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• pp.367-384
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• 2017

The Maanshan Bridge over Yangtze River in China is a new long-span suspension bridge with double main spans of $2{\times}1080m$ and a closed streamline cross-section of single box deck. The flutter and buffeting performances were investigated via wind tunnel tests of a full bridge aeroelastic model at a geometric scale of 1:211. The tests were conducted in both smooth wind and simulated boundary layer wind fields. Emphasis is placed on studying the interference effect of adjacent span via installing a wind deflector and a wind separating board to shelter one span of the bridge model from incoming flow. Issues related to effects of mid-tower stiffness and deck supporting conditions are also discussed. The testing results show that flutter critical wind velocities in smooth flow, with a wind deflector, are remarkably lower than those without. In turbulent wind, torsional and vertical standard deviations for the deck responses at midspan in testing cases without wind deflector are generally less than those at the midspan exposed to wind in testing cases with wind deflector, respectively. When double main spans are exposed to turbulent wind, the existence of either span is a mass damper to the other. Furthermore, both effects of mid-tower stiffness and deck supporting conditions at the middle tower on the flutter and buffeting performances of the Maanshan Bridge are unremarkable.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.37 no.4
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• pp.647-657
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• 2017

The main purpose of this study is to investigate the static & dynamic behavior of a precast bracket under precast road deck slab of double deck tunnel. In order to improve the construction speed, the field prefabricated bracket to connect the intermediate slab to the precast shield tunnel lining structure has been developed in the 'SPC (Steel Precast Concrete) bracket'. The experiments were performed for the full scale model in order to evaluate the performance of the 'SPC bracket', the structural stability was verified through the FEM analysis. The result of static loading test, no deformations or cracks of the bracket undergo the ultimate load was investigated. In addition, no pulling or deformation of the chemical anchor for fixing the bracket was measured. As a result of dynamic loading test, it was investigated that there is no problem in the chemical anchor for fixing the bracket. FEM analysis showed similar behavior to static load test and it was determined that there is no problem in serviceability and structural safety.

• Tunnel and Underground Space
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• v.27 no.3
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• pp.132-145
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• 2017

Shock loss was not applied for the tunnel ventilation of road tunnel in the past. However, pressure losses due to the shock loss can be significant in network double-deck road tunnel in which combining and separating road structures exist. For the optimum ventilation design of network double-deck road tunnel, this study conducted 3D CFD numerical analysis for the shock loss at the combining and separating flows. The CFD model was made with the real-scale model that was the standard section of double-deck road tunnel. The shock loss coefficient of various combining and separating angles and road width was obtained and compared to the existing design values. As a result of the comparison, the shock loss coefficient of the $30^{\circ}$ separating flow model was higher and that of the two-lane combining flow model was lower. Since the combining and separating angles and road width can be important for the design of shock loss estimation, it is considered that this study can provide the accurate design factors for the calculation of ventilation system capacity. In addition, this study conducted 3D CFD analysis in order to calculate the shock loss coefficient of both combining and separating flows at flared intersection, and the result was compared with the design values of ASHRAE. The model that was not widened at the intersection showed three times higher at the most, and the other model that was widened at the intersection resulted two times higher shock loss coefficients.