Building occupant movement in wide descending stairs

Abstract

Several incidents in the past confirm that crowd movement in stairs represents a risk that has potential of causing serious injuries. Extensively research has been conducted for descending stairs. However, less is known about particularly wide staircases, which is taken to be stairs with tread width of 1.2m or above. This thesis provides estimations for engineering characteristics like velocity, flow and density. This is an experimental study where three different stair widths are considered. The applied method for the experiments is video recording of approximately 1200 young adults going down the stairs. Individual location, use of handrail, social connection and time spent in the stairs was some of the input data. The density is considered as a function of the interperson distance, which is the distance from one person in the stairs to the next in front of him/her. The results are compared to previous research. The aim is to identify factors on how building occupants choose their path in stairs and suggest factors that could affect occupant movement speed. The results showed that velocity seems to be independent for low densities (0.05-1 pers/m2) and interperson distances above 0.6m. Other factors like distractions and gender indicated to cause slight variations in movement speed. The results also indicate that dividing wider stairs into several lanes, for example by middle handrails, would probably be a safer solution.

Popular Abstract

New architectural design involving high-rise buildings and larger amount of people per floor makes it important to consider the occupant flow in stairs. Extensively research has been done for descending stairs. Nevertheless, less is known regarding occupants descending in wide stairs. This thesis provides estimations for engineering characteristics like velocity, flow and density. In these analysis, the staircase is considered wide when the tread width (from wall to wall) is 1.2m or above. In this report, a wide staircase is defined as a stair in which more than two people can comfortably descend the staircase side by side. By comfortably means a continuous gait without hesitation and when it is not necessary to adjust their movement velocity according to other adjacent ascending or descending occupants. The purpose of this thesis is to identify factors on how building occupants choose their descending path in stairs, and to locate factors that may influence the descending movement speed. This is an experimental study that presents results from three different stairs with stair widths between 2.12-4.6m. The applied method for the experiments is video recording of 1263 young adults going down the stairs. Individual location, use of handrail, social connection and time spent in the stairs was some of the input data. The density is considered as a function of the interperson distance, which is the distance from one person in the stairs to the next in front of him/her.
The most valuable results are that velocity seems to be independent for low densities (0.05-1 pers/m2) and interperson distances above 0.6m. Other factors like distractions and gender indicated to cause slight variations in movement speed. Furthermore, it was also discovered that the flow increase when the density increase. The differences in flow was seen it be independent of the stair width. The variation between the stairs seems to be related to the tread/riser configuration and indicates that the shallowest treads gives the highest occupant flows.
It was observed during the experiments that occupants that were walking alone (Individuals) seemed to choose the location that offered more space, while occupants belonging to a social group would rather remain in the group and adjust their speed to the other group members. The experiments indicated that when the stair width was increased from 2.12m to a range of 2.3-4.6m, this could affect the occupants to go from queue to zigzag pattern. Nevertheless, the transition from queue towards zigzag could also be caused by other variables, for instance when the stair become more crowded. It was observed that when the density increased in a queue, the pattern resembled a zigzag, as people also started to use all locations within the staircase. Furthermore, it was clear that most occupants did not use handrail during the experiments in this report, 75-87% respectively. The percentage when occupants exposed to the middle handrail only where seen to be a slightly lower, 56% did not use the handrail. Overall, occupant velocity was seen within 0.4-0.9m/s independently of using handrail or not. Occupants using the middle handrail was seen to have a slightly lower movement speed, maximum 0.7m/s. Furthermore, walking in the middle of the stairs was the preferred location among the participants. Since this is the location furthest away from the handrails, it could be suggested to divide wide stairs into different lanes by middle handrail, to offer something to reach for in case of misstep or downward falls.

• author: Ålgård, Martha
• supervisor: Håkan Frantzich
• organization: Division of Fire Safety Engineering
• course: VBRM05 20172
• year: 2017
• type: H2 - Master's Degree (Two Years)
• subject: Technology and Engineering
• keywords: Descending stairs, occupant movement, wide stairs, handrails
• report number: 5549
• other publication id: LUTVDG/TVBB—5549—SE
• language: English
• id: 8924810
• date added to LUP: 2017-09-05 16:41:56
• date last changed: 2017-09-05 16:41:56