Simulation System – Traffic Analysis for Modernisation Projects

GLOBAL INVESTMENT HQ, ZURICH

The general experience of most office buildings during the past 25 years or so has been a slow but ever increasing density of occupation.

Some buildings may even have twice as many occupants as the lift services were originally designed for 25 years ago. So called “hot desking” also can also increase the working population of the building.

If the basic lift equipment is 25 years old there may be considerable opportunity to modernise the equipment and dramatically improve lift performance to attempt to address the increase in population. Some immediate observations might be:

  1. Increase in speed of lifts without increase in pit and overhead dimensions.
  2. Solid state motor drives with direct floor approach and advance door opening.
  3. “Intelligent” door operation with high speed closed loop door operation.
  4. “Destination Hall Call Control” system in place of conventional control system.

Let’s look at what this would mean in traffic performance terms for an existing building.

“Pre-Modernisation” Existing Equipment Specification from Site Survey

The building has an eight car group of lifts which serves 14 floors above the main lobby with a typical 4.1m floor to floor distance except the main lobby to first floor which is double height i.e. 8.2m. The working population has been estimated from security turnstile system at 90 persons per floor.

Here is the existing equipment specification from a Site Survey:

– No. of Lifts:
8
– Speed:
1.6m/s
– Capacity:
1600kg
– Control System:
Conventional 2 Button Collective Control
– Clear Door Entrance Width:
1100mm with centre opening doors
– Average Door Opening Time:  
2.5s
– Average Door Closing Time:    
3.1s
– Floor to floor cycle time:          
13.0s (7.5s flight time plus 5.5s for door opening/closing times)

 

Whilst on site it was observed that there was substantial queuing at the main lobby during the morning “up peak” period.

If we put all the above variables into Adsimulo and run a single simulation using a constant 15% 5-minute handling capacity profile during up peak (which would be appropriate for a single tenant) then we see that the average waiting times are around 35s and would be rated “unacceptable”. An appropriate target would be an average waiting time of 25s or less. The simulation also indicates about 32 persons on average queuing during the up peak period which is several car loads of prospective passengers.

“Post-Modernisation” Equipment Specification

Run another simulation for “post-modernisation” and change the door systems and control system to the following specification:

– No. of Lifts:
8
– Speed:
1.6m/s
– Capacity:
1600kg
– Control System:
Destination Hall Call Control system
– Clear Door Entrance Width:
1100mm with centre opening doors
– Average Door Opening Time:  
1.4s
– Average Door Closing Time:    
1.9s
– Floor to floor cycle time:          
10.3s (7.0s flight time with 0.5s saving with pre-opening or advanced door opening feature plus 3.3s for door opening/closing times)

 

Amazingly when you observe the results of the new “post modernisation” simulation just making these changes has brought enormous benefit. The following are notable improvements:

  1. Average waiting time during “up peak” has been reduced from 35s to 18s (now well within the 25s preferred criteria for excellent quality of service).
  2. Queuing has been reduced from around 32 persons to 15 persons or not more than one car load of prospective persons.

There would therefore appear to be substantial benefits to carrying out a modernisation of these lifts which would enable today’s typical lift traffic design criteria to be met even with the increased building population and without the need to increase the speed of the lifts. The above exercise provides a part of the arguments for carrying out a modernisation of the lift equipment.

AdSimulo University