When a famous landmark building is scheduled for a facelift, everyone knows the project will be one of substance. The BT Tower (or Post Office Tower as it was originally known) in the heart of London, England is one such building. This 1960s building typified the dreams of many people, standing as it did for the ideals of the new technological age. (See the August 1964 and July 1965 issues of ELEVATOR WORLD.) It was packed with the "best of British," including two high-speed Express lifts a feature visitors could take up to the revolving viewing gallery and its spectacular views over the city. This I remember well, experiencing it as a boy with my father. (The descent speed of the elevator left my stomach in my mouth; some things you don't forget.)
The year 1999 heralded the start of an upgrading of the building services and maintenance requirements for the entire BT Tower complex to bring it up to 21st-century standards. This incidentally coincided with a total cleaning of the outside of the building which has resulted in an impressive visual improvement both inside and out. The building services and the corporate team had to impose a number of project, program and budget criteria that had to be followed, allowing the building to continue as a viable engineering centre and a corporate hospitality and conference facility.
The modernisation of the tower's two high-speed lifts was obviously a key element in the project. The lifts form the only viable access and escape route to the private revolving reception suite and viewing gallery on top of the Tower. They operate in two key modes (as freight or passenger elevators) and are the means by which all the supplies and telecommunication components are taken up to the engineering floors, as well as provide the access system for the hospitality levels, which are the highlight for the many invited visitors to the BT Centre.
The initial project brief and briefing is important to the smooth running of any job. Certainly on this project, a good understanding between client, consultant, lift company and component specialists would be required to meet the client's many needs and tight critical path program for the project. This close working relationship would be a feature right through this project, and your author was pleased to be able to sit in on many of the meetings to witness and photograph this initiative in action.
The Client's Perspective
The client, after considerable debate and evaluation, decided to use the elevator experience of Ove Arup R&D. They were selected to provide consultant advice on the basis of their strategy and evaluation of BT's problem. Fundamental to this was the view that the lift consultant should provide a detailed design solution against stipulated performance criteria.
The decision to implement refurbishment or replacement of the lifts was driven by high fault rates causing disruption to the building's operation and, more embarrassingly, the cancellation of corporate events. These factors, added to escalating costs of maintenance and repairs, meant that BT had to seek greater reliability and a more economic whole-life cost from the company's investment in its building services. A risk assessment of both equipment and services was undertaken in order to choose the best package. Ultimately, the decision to appoint any contractor had to take in to account the team's confidence in the contractor's commitment to the project and their abilities to execute and complete the work on time.
When the consultant contract was awarded to Ove Arup, it made the jobsite one of the most convenient for them to visit, as the Tower is literally over the mews from Arup's main London office and Roger Howkins' desk.
At the early stage of the project, the consultant's interpretation of the brief is important to the job, if the client's expectations are to be fulfilled. To give an overview of this, Roger Howkins explained some of the key points that needed to be addressed.
Consultant's Overview
As Howkins states, "Providing a specification and project management for a complex lift modernisation in normal circumstances is difficult, and as one might suspect, this proved doubly true for this project." The project's time scale was very tight and inflexible, requiring Arup R&D's systematic approach to lift modernisation to be finely tuned. The timetable had to be rigid yet forgiving.
Arup R&D's brief was twofold: one, to make the elevators reliable and improve the ride comfort; and, two, to provide elevator cars that were a memorable experience and added "theatre" to the tower.
After receiving a brief such as this, one of the most important exercises is to look, learn and draw upon installed examples and real working solutions. Arup R&D have a significant database of elevator modernisations and, as a result, knew that, to obtain the required level of reliability and passenger comfort, the main thrust of the initial works would have to target three areas.
1. Doors and Door Drive
2. System Controllers
3. The Riding System
It was planned that the landing door systems would need to be replaced to achieve the two-hour fire rating now required by the authorities. Also, a new system would improve the aerodynamic stability of the elevator car at high speed.
For emergency-evacuation purposes, the lift speed was critical together with special fire/evacuation controls, building-sway devices and a requirement to automatically alter the acceleration/jerk profiles in the event of an emergency.
The riding system was immediately identified as an area where significant gains to the ride quality could be made. New rails and brackets at 2.5-metre pitches were specified, along with 300-mm-diameter roller guides, and aerodynamic cowlings for the car were all components that would enhance the end ride quality.
From the outset, a five-minute building-evacuation requirement proved restrictive and would not allow any increase in population numbers. The initial computer simulations quickly showed that the car capacity and elevator speed had to be as high as possible for the tower's population to be substantially increased. The existing elevators were originally designed to operate at 1,000 feet per minute. Although this was turned up in the 1980s to 1,200 feet per minute, it was still essential to increase this to the maximum the shaft would allow. The computer indicated that the top speed that could be obtained within the limitations of the pit depths and overruns was 1,400 feet per minute; any higher speed would have required major structural alterations to the pit.
Gaining real data and a comprehensive site survey is vital to any refurbishment and replacement, and this project ably demonstrated the benefits of this exercise. Traditional survey techniques were employed, along with ultra-scans of the concrete structure. This gave a clear picture of where the reinforcing steel and hidden obstructions were that could have caused delays and problems later. (Some 1,000 post-fix drillings were anticipated.) Also, qualitative data regarding the noise and ride were recorded to give real data by which to judge the refurbished scheme on the two lifts.
Following the surveys, it was soon apparent that all the existing lift shaft and motor room equipment had to be removed, as there was not the time or budget to allow the work needed to give the old kit the additional 20/30 years of life. Also, the original "swinging sixties" wooden cars with suspended ceilings would be replaced by lift cars that had a more spatial feel and would be 3,700 millimetres in height to answer the BT engineering requirements.
The expertise of other sections of the Ove Arup partnership were needed in this project.
-- Arup structural engineers were called on to design special load-spreading structures for the new drive units and landing cill supports.
-- Arup fire developed a revised evacuation strategy.
-- Arup electrical engineers had to specify and supervise the replacement MICC cables.
The contract for the elevators was won by Thyssen Lifts. A project briefing day called by Arup allowed the different parties involved with the project to meet on site. This enabled all to feel that each individual member had a voice in the total well-being of the project. Some may feel that this was an over indulgence; however, the resultant feel-good factor enjoyed by the project members enabled the project to swing along from day one. The prevalent constructive attitude arising from this grounding resulted in any problems being sorted as effectively as possible be it by director, fitter or members of the client's staff.
Key points addressed at the briefing included:
-- Introduction by the client with an overview on the why and what the project was all about. This was particularly important, as the tower would be occupied throughout the duration of the work.
-- The consultant's brief on what and why certain designs were adopted.
-- The safety officers explained the particular hazards and stressed the working practices and expectations.
-- The project time scale and critical path were introduced to all, and if anyone saw a problem, it was aired so that all were clear when actions and decisions needed to be finalized.
The old equipment needed to be dismantled and removed, and anyone who has worked with the massive gearless machines of the 1960s knows this is a task that requires a good deal of ingenuity. Unfortunately, the old machines had to be cut down into smaller pieces, so that the remaining lift could safely handle the weight. For many engineers and liftmen, this was the saddest part of the project. To see what was once the cutting edge of lift technology being thermic lanced and chopped up is an undignified end to a faithful workhorse. However, the short project time and strict budgets allow few niceties regarding the old lift hardware.
As the shaft was cleared of all the old lift fixtures and fittings, many of the problems regarding the poor ride comfort of the old lifts became evident. Indeed, the guide rails and their fixings were particularly interesting and were probably a major factor in the ride quality. John Carroll of Arup explained that the original car guides were found to be pinned to each fixing. This restricted the vertical movement of the guide that would normally have been allowed by the guide clips to compensate for the building's movement and settlement. This, in turn, caused the guide rails to become distorted, detracting from the ride quality.
The Shaft Equipment
With the elevator operating at 7 metres/second, the shaft needs to be as aerodynamic as possible, with the air-flows and displacements being as smooth as possible. The trailing cable is sited in a channel running the whole length of the shaft, and the landing door gear is hooded again to provide cleanest air passage.
The guide rails and car rollers need to be of the highest quality and perfectly fixed, plumbed and aligned. This is not an easy task to perform in high towers, as the building is always moving and flexing, so the final setup of the guides has to be performed on a single calm day over the rail's total length.
The Lift Car
This is one of the tallest single-decker cars in the U.K. In fact, the car could not be fully assembled in Thyssen's Nottingham factory, so the streamlined cones, top and bottom, were taken directly to the site.
The Car Interior No. 1 (Sky Flight)
The interior finishes of this car certainly add a sky-like atmosphere to the journey, along with a crisp, clear, spatial sparkle. This was achieved by the use of optical white glass, which does not have that green tint to it, and 16 fibre-optic down lights. The modernist feel in the lift car is continued by the use of flat-screen indicators, special glass touch key pads and a laser-cut Tower graphic with blue LED position bars.
In the early part of November, your author, along with the professional team and a number of corporate managers from BT, had the privilege to ride in the north lift at high speed. All were impressed with the ride and experience and felt future visitors to the tower would have an experience to phone home about.
Manufacturing the elevator equipment and technical specification, the machine drive and controller, the door drives and gears will all be part of a Project of the Year submission, along with phase two of this modernisation job, which will also enjoy the lessons learnt from the close working relationships.