Penn Presbyterian Medical Center
On the 1st floor of a main Philadelphia hospital, a Magnetic Resonance Imaging (MRI) equipment needed to be installed. Vibration transmission from road traffic and its impact on the MRI equipment and its imaging quality was a big concern.
CDM installed a CDM-MONT solution with 2.5 Hz spring isolators in a 10” floating concrete slab. The floating floor was jacked to create an air gap of 2”.
Thanks to an in-house finite element analysis, CDM could design the special springs needed to guarantee the specified isolation performance with minimum differential deflection and tilting of the MRI equipment, while coping with the eccentric loading.
CDM-MONT prior to reinforcement
Installation of spring isolators
Jacking of floating floor
5 Everyman cinemas have been built in a new building in the centre of Harrogate which houses several other retail and leisure facilities.
The cinema directly above the ground floor retail units required a concrete floating floor whilst the 4 other cinemas required heavy dry floating floors with large floor voids.
CDM-UK supplied and installed the floating floors which consisted of CDM-LAT isolation rails supporting timber/cement board sandwich constructions or CDM-QDECK solution supporting a concrete slab.
The wall isolation and ceiling hangers completed the box-in-box construction delivering the required sound insulation between cinemas and to the retail units beneath.
The new Headquarters of Goldman Sachs in London is in a great location on Farringdon Street in the City of London. This massive office development of 1.1 million square feet includes a large auditorium which is isolated to protect it from tube train noise and to protect the rest of the building.
Sandy Brown specified that the box-in-box construction needed 10Hz bearings supporting it.
CDM-UK worked with Byrne Brothers to design supply and install the concrete floating floors and structural bearings. The complicated 3-dimensional space is supported on 5 separate floating floors with bearings beneath designed to take the column loads.
The floating floors consist of CDM-QDECK isolation rails supporting CDM-QDECK composite metal decking, reinforcement and concrete.
Some of the columns are supported on CDM-SEB bearings located outside of the floating floor areas.
The new building has been named the ‘groundscraper’ due to its mammoth size - it will become one of London’s new collection of landmark buildings.
CDM floating floor mid-installation
Part of the planning conditions included retaining the Grade II listed façade of the Wharf building which in turn is located directly above the proposed route of a tunnel. Due to concerns about structural damage to the retained façade during construction of the tunnel, it was a requirement to support the façade off pre-compressed spring boxes.
Initially the retained façade was temporarily supported. A concrete beam was then built which was supported by column stubs. The facade was then jacked by a couple of millimetres and then lowered back onto the spring boxes. When the façade was dropped onto the springs there was a differential deflection of 1mm and the pre-compression bolts were loose.
There were 30 spring boxes in total, comprising B3 and B6 boxes, with springs and nested springs chosen to take the individual loads at each point.
The springs had a cylinder device in the centre of the spring-box which restricted the differential lateral movement of the isolated structure to 2mm without compromising the natural frequency of the system
The springs also had >5% resonance damping which was created by 40mm poured elastomer layers at the top and bottom of each box.
CDM-CHR-BOX springs and hydraulic jacks
Hydraulic jack next to CDM-CHR-BOX spring
A new Premier Inn has been built in Edinburgh on Torphichen Street which lies directly above one of the two running tunnels between Edinburgh’s Haymarket and Waverley stations.
The acoustic consultant specified that the building should be isolated on 8Hz bearings to make sure that structure-borne noise levels from trains did not disturb the occupants of the hotel.
The hotel was constructed as a Metsec frame on top of a one storey concrete frame. CDM-UK worked with the design team to develop an isolation system that consisted of a fully isolated slab at first floor level that the Metsec frame was built off.
Ground floor hotel rooms were built off floating floors to create box-in-box constructions and the lift pit also had a thick concrete floating floor to complete the isolation of the main hotel structure.
The type of construction created a moment frame that made the building extremely stable, sharing all horizontal and overturning forces across all of the bearings.
Half way through installation of CDM-QDECK
One Tower Bridge is the home for a new 900-seat theatre built for the London Theatre Company on the South side of Tower Bridge called the Bridge Theatre. The theatre is one of the largest to be built in London in the past 100 years.
To protect the residential accommodation that wraps around the theatre the acoustic consultant specified that the theatre be built on a 200mm concrete floating slab supported on springs. The structural engineers specified that the floating slab must spread the loadings of the theatre structure as much as possible to the supporting structure beneath.
CDM’s in-house structural engineers used finite element analysis to optimise the load spread of the floating slab whilst retaining the acoustic requirements. The optimised design incorporated 4,300 springs with higher concentrations of springs where the imposed loads were greatest.
Reinforcement density was also increased in the higher loaded areas to optimise the load spread characteristics of the slab.
The floating slab was installed within a very tight timeframe of 3 weeks in order to comply with the project build programme
CDM springs installed in support channels
floating slab prior to concrete pour
Luka Rental apartments
BD Luka is a new residential building with 3 basement floors and 16 floors above ground. The investor has built these apartments not to be sold, but to rent them for long term.
Since the building is situated right next to Luka Station on line B of the Prague metro network, it posed a challenge for the designers to meet the noise level criteria. The vibration isolation study concluded that in order to reach this value for the apartments, the vibration isolation system needed to have a resonance frequency of maximum 13 Hz.
The height of the building and the resulting load values made it almost impossible to propose any other solutions than CDM-VHS which can take up to 12 MPa. The vibration cut was located mostly above ground level which allowed a clear approach for modelling and a solution without perimeter isolation. The investor chose the 3-layer CDM-VHS bearings (having a resonance frequency of 13 Hz).
After the installation, the measured noise levels in the apartments were very similar to the estimations based on the FEM model. The noise limits were achieved. The building was also awarded for its architectural features by the Czech real estate developers.
Hotel Damier is an historic upmarket hotel with an impressive guest list including George Bush, Margaret Thatcher, Eddy Merckx, Adamo and Sheryl Crow and is located in the “Grote Markt” in Courtray.
Because of a recent extension to the Damier, to provide space for a hotel bar, the acoustic consultant specified a CDM-BOX-IN-BOX system to prevent noise generated in the bar area from becoming a nuisance in other areas of the hotel.
The CDM-BOX-IN-BOX system comprised:
- CDM-FLOAT bespoke modular acoustic floating floor designed with an oversized void to accommodate the various building services ducts, pipes and cables – these also had to be isolated where they penetrated through the floating floor.
The benefits of this type of floor are:
- Quick and simple installation thereby minimising disruption to the building
- The floor can be designed to accommodate any working load and deflection and to accomodate any building services
- CDM-WH resilient wall ties used to isolate the secondary wall, which were supported off the CDM-FLOAT floor, from the supporting walls
- CDM-PHR resilient spring ceiling hangers were used to isolate the heavy suspended ceiling from the supporting structure.
Audiolokalen UZ Leuven
Within the university hospital campus “Gasthuisberg” in Louvain, there’s a new building next to the urgencies, where the audio rooms are located. The aim is to test patients on their hearing capabilities with the newest technologies in their field, this being the reason why the acoustic consultant Daidalos imposed high level acoustic isolation between all the spaces here. The rooms are made following the “box-in-box” principle.
The concrete floor of every audio room is floating on resilient floor battens, these being CDM-FLOOR-T. These battens result in an air void of approximately 100mm, which allows the air stiffness in the floor system to become less dominant. Located between the floor battens is an absorption layer to avoid standing wave effects.
The light gypsum walls are installed on the edge of the floating floors and acoustically decoupled from the structural ceiling by means of the CDM-WALL-FIX principle, to avoid any direct stiff contact.
The ceiling is constructed from gypsum boards which are acoustically decoupled from the ceiling by high performing spring-dampeners CDM-PHR. For reasons of fire-resistance, the maximum load per hanger is limited, in order to take up the relatively high mass of the lowered ceiling.
Additional difficulty consists in the integration of a “Faraday cage” in the box-in-box setup, being the reason why all metal connections had to be treated with the highest care, asking for very specific and complex solutions for the building nodes. One of the rooms occupies a test chair, this being “gigatorque” and is predominately used to test patients during a certain rotation. This chair has been installed on CDM-PADS via a specific anchored steel baseplate incorporated within the reinforced concrete plate.
9 Marylebone Lane
9 Marylebone Lane is a new-build high quality residential building comprising 2 basement levels, lower ground, ground and seven upper floors. The site is located in between Oxford Street and Wigmore Street.
The Jubilee Line runs directly beneath the site and the acoustic consultant, Hoare Lea, specified that the building needed to be supported on elastomer bearings with a maximum natural frequency of 15Hz.
The building is isolated at the base of columns and walls on top of the ground floor slab. Sensitive areas on the ground and lower ground floors are isolated using box-in-box constructions.
The bearing stiffnesses were used in the structural analysis to ensure that the correct bearings were used at each support location.
The 3 apartments and the gymnasium that were below the level of the main building isolation were built off CDM-MONT-100 concrete jack-up floating floors to create box-in-box constructions.