METRO Hotel Support Works
When you see this ten storey (and five basements) hotel you don’t imagine that…
…part of it is grounded above a big city metro station!
It all started when a group of Architects
Structural Engineers
Geotechnical Engineers
and Electrical-Mechanical Engineers
envisioned a luxurious Hotel in a middle east metropolis (the location will be disclosed after the project’s realization).
When the above team of Engineers filed the plans at the city planning commission, they where surprised to be informed the Metro line would pass exactly below the proposed Hotel! The initial feelings of disappointment quickly subsided and rationalism prevailed. An elaborate plan, with innovative solutions, was devised, in order for METRO Hotel to be realized. Follow us and delve into this engineering adventure step by step.
The approximately 100,000m² Hotel has been divided with five expansion joints into a complex of five buildings. The joints take into account both thermal strains and seismic effects acting simultaneously and will be required from the top of the 1st Basement Floor and all the slabs above that. Therefore, the superstructure above the 1st Basement Floor slab will function as five different buildings, each with its own dynamic behavior and temperature fluctuation. Below the ground level, the temperature stays virtually constant causing no stresses nor strains and there is no movement caused by earthquake, so the five buildings join into one inseparable structure. In the picture below the joints are depicted with magenta:
The uniqueness of Building 1 is that it is partially seated above the tunnels of the Metro station.
Each basement will be surrounded by a retaining wall a half meter wide. The wall facing the metro station (North-East side), is going to be one meter wide, while a diaphragm wall (1000mm width and 30m height) will vertically superimpose this first basement’s wall, securing the stability of the metro tunnels. The foundation transfer slab above the metro tunnels (2000mm width) will be supported upon the basement wall and two arrays of piles (46m long — the height of a 15 storey building). The total loads from building 1 will be transferred through the piles to the ground far below the tunnels, so as not to interfere with the present stress field around the tunnels. The horizontal loads (earthquake and wind) will flow through the transfer slab, to the basements’ perimeter wall which forms a massive concrete “box.” The total horizontal load of the whole Hotel is being resisted by this rigid box and consequently transferred to the ground. In this way, the hotel’s total stiffness is greatly enhanced.
Take a look at some pics from the preliminary structural model of building 1, Hotel Support Works and the metro station (software: SCIA ENGINEER 2013):
Some examples of the modelling and construction stages:
stage5 concreting of piles and diaphragm wall, installation of tension ties
stage6 excavation to 23m depth
stage7 concreting of hotel basement slabs, application of the hotel’s operational loads
The ground stratigraphy has been extensively researched by boreholes:
Using the mohr-coulomb model, the Hotel Support Works where modelled with SOFiSTiK software by Geotechnical Engineering specialists:
Take a look:
A design verification analysis was conducted by an Independent Expert, Dr Nikos Gerolymos, Assistant Professor at the National Technical University of Athens (NTUA), representing
The analysis utilized PLAXIS code as you can see in the following output pics:
The entire Metro station has been modeled in detail with SCIA ENGINEER software as a 3D finite element structural model. The acting forces are: self-weight and earth’s bilateral pressures. On one side, the active pressure tends to push the station over the excavation (for the hotel basements), on the other side, passive pressure resists the former one. In the following picture the station’s layout with the proposed excavation for the hotel’s basements:
The purpose of this check is to ensure that the station’s Tymban Wall can withstand the shear force that will be generated by this balance of forces. In addition, the station has been checked for overturning and sliding.
Of course, monitoring devices will be installed in order to check deformations, displacements and stresses during the construction of Hotel Support Works. Optical prisms inside the tunnel sections for measuring convergence and total deformation, vibration monitors, also, strain gauges and inclinometers at the diaphragm wall and inside piles. This equipment will help us monitor the whole system’s behavior and contrast it with the predictions derived from our extensive numerical modelling.
