Experimental study on the movement characteristics of pedestrians in asymmetric merging structures

Nowadays, the continuous development of high-rise and mega buildings brings new challenges for evacuating people inside during emergencies such as fire outbreaks. The design of evacuation passageways in buildings is closely related to the performance of the building evacuation system, and some existing deficiencies have caused serious crowd accidents. The merging structure is one of the common components in evacuation passageways, which will greatly affect the evacuation process within from the building, as it shows more complex crowd movement characteristics and has a higher probability of becoming a potential bottleneck, extending the evacuation time, causing congestion, and even posing a risk of crowd accidents. However, research on the evacuation performance of some typical merging structures in building layouts is still limited. In this study, we carried out a series of controlled experiments to investigate the impact of merging structures on building evacuation. We studied the movement characteristics of pedestrians during the evacuation process in two typical types of merging structures namely width-asymmetrical and position-asymmetrical merging structures. In detail, lane formation, Shannon entropy, fundamental diagram, velocity, density, flow, and time headway are analyzed to compare the degree of order within channels, the movement status of pedestrians, and the traffic efficiency of merging areas. It is concluded that the width-asymmetrical merging structures would reduce the degree of order within channels, affect the overall traffic efficiency, increase the density in the merging area, and have a higher potential to cause safety accidents during the evacuation process. On the contrary, some position-asymmetrical merging structures are possible to alleviate those negative effects. However, the performance could be limited in some cases as the stable flow may not be formed in scenarios with short branch spacing. The results can provide references for the safe design and structural optimization of evacuation passageways inside the building, as well as the route planning and guidance for crowd emergency evacuation within from the building.