The optimal functioning of elevators is ubiquitous for a habitable and comfortable
indoor environment in multi-story buildings. Presently, numerous issues are encountered,
such as frequent and prolonged breakdowns, passenger entrapment, injuries, accidents,
extended waiting times, unlevelled stopping, and high energy consumption. Thus, strategies
to enhance their performance are imperative. Generally, elevators are subjected to preventive
maintenance in which only visual inspection determines their overall performance. This
methodology ignores the underlying conditions and is marred with the subjective opinions of
inspectors. Another issue affecting their performance is that many elevators around the globe
have surpassed their useful life. These elevators consume a significant amount of energy
since they incorporate conventional motor drives instead of the energy-efficient AC drives
with variable voltage variable frequency (ACVVVF). However, for the replacement of non-ACVVVF drives, the building owners need estimated quantitative potential savings. The
reliability of elevators beyond their useful life is also a big concern. For the improvement of
reliability, full-modernization is a promising option. Nevertheless, complete replacement is
not feasible in many cases due to economic and environmental constraints, thus requiring
alternate strategies. Moreover, the procurement of elevator maintenance services lacks any
guidelines, e.g., a set of rules to select an appropriate maintenance contractor does not exist.
Ineffective procurement is also a threat to the performance of elevators. Besides, there is no
evidence that the contractors accurately perceive the relative significance of building owners’
expectations/duties during procurement. This ambiguity is alarming since a lack of a clear
understanding of contractors leads to dissatisfaction of building owners, which may take a
toll on their real-time performance. Therefore, to address the issues, this thesis aims to:
1. Improvement of performance assessment during preventive maintenance.
2. Improvement of reliability and energy consumption of elevators which have surpassed their useful life.
3. Identification of the gaps in procurement and suggesting relevant enhancements.
To propose a performance measurement model, firstly, a conceptual hybrid
performance measurement model of elevators (HPMME) was proposed. The model consisted
of three latent constructs involving three key performance indicators (KPIs) (condition of
equipment, level of service, and risks) and 34 observed variables based on a comprehensive
literature review and three rounds of brainstorming sessions with elevator experts. A
questionnaire survey was carried out to evaluate the relative importance of the three KPIs and
their observed variables. The survey data’s exploratory factor analysis was then conducted to
identify the latent constructs representing the KPIs and their associated observed variables.
For the validation, modification, and improvement of the conceptual HPMME, structural
equation modelling was performed. Finally, the HPMME was further validated by experts.
Secondly, to promote the replacement of non-ACVVVF drives, an explicit data-driven multiple linear regression model for predicting the annual energy consumption of
elevators based on the type of their motor drive was proposed. The motor drives considered
in the model included: ACVVVF, AC 2 speed motor drive, DC motor drive with the solid-state
controller, and AC motor drive with a variable speed controller. This model consists of
the elevator and building parameters of average rated capacity, motor rating, number of
elevators, domestic units in the building, and motor drive type. The model was formulated
after analyzing the historical elevator energy consumption data of 196 residential buildings in
Hong Kong and validated using statistical measures and through its application to 25
additional residential buildings.
Third, for improving elevators’ reliability beyond their useful life, 25,548 breakdowns attributed to 5400 elevators in public rental housing (PRH) buildings in Hong Kong were analyzed. The Pareto analysis revealed four main risks causing elevator breakdowns: faults in
the controller, car door mechanism, landing door mechanism, and other equipment in the car
cage. A comparison of the monthly breakdown rate of these four components in elevators
belonging to different age groups (especially those within and beyond their useful life) by
employing ANOVA indicated that the faults in the controller are the trigger of the onset of a
wear-out phase and its risk-based maintenance would improve the reliability and useful life
of elevators in PRH buildings.
Fourth, for improving the selection process, the prevailing best value (BV) criteria
were determined. The content analysis of “Request for Proposals (RFPs)” of 57 projects
indicated 9 BV criteria: experience, past performance, responsiveness to RFP, maintenance
strategies, financial capability, diversity, contractor resources, and legal status. Appropriate
modifications to criteria and associated indicators were suggested in the light of literature and
KPIs, such as, assign greater significance to past performance and the qualifications.
Furthermore, utilize references and previous records to predict safety performance,
compliance with regulations, and service availability. Also, analyze the maintenance
methodology to substantiate safety performance and compliance with regulations. Moreover,
ask the contractor to validate their arrangements of adequate spare parts availability.
Fifth, this research identified the expectations of building owners. The content
analysis of RFPs revealed 40 duties, which expressed four main expectations of building
owners: prompt response to call-backs, optimal equipment performance, proper execution of
assigned duties and responsibilities, and attaining the performance requirements with
specified thresholds. A questionnaire survey was conducted to evaluate the perceptions of
contractors. Exploratory factor analysis and Structural Equation Modelling of survey data
revealed that except for the callbacks, the building owners’ remaining three expectations
were perceived significant by the contractors. Furthermore, the contractors do not consider the condition of controller and guide shoes, provision of adequate resources, quality of
replacement parts, rigorous testing of equipment as an essential indicator of their
performance, which was emphasized strongly by the building owners in the RFPs.
Each of the five parts mentioned above has its associated benefits. The hybrid
performance measurement model can act as a tool to quantitatively measure elevators’
performance, which would enable the relevant authorities in important decisions that include
but are not limited to the prioritization of elevators for the modernization and the allocation
of the workforce and other resources. Also, maintenance contractors can identify the critical
areas of performance improvement, leading to end-user satisfaction. Using the explicit energy
prediction model, the building owners could carry a cost-benefit analysis associated with
replacing non-ACVVVF drives with ACVVVF. In lines with this research’s findings, an
increase in maintenance of controller would optimize the reliability of elevators beyond their
useful life and bring it at par with those within their useful life. Hence, the building owners
facing financial or environmental constraints in replacing elevators beyond their useful life
could sustain their use for an extended duration. In the future, building owners could
formulate their future selection criteria in the light of this research leading to informed and
intelligent decision making. Moreover, the duties assigned by building owners not perceived
significant by the contractors could be given a higher preference in RFPs by associating a
reward/penalty with them.
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