Corporate News

Independent Review Panel announces findings of enquiry into the partial collapse of the Married Inspectorsa£á? Quarters Building at the Central Police Station Compound

11/03/2016

The Independent Review Panel (the Panel) appointed by the Board of Stewards of The Hong Kong Jockey Club (the HKJC) to enquire into the partial collapse of the Married Inspectors’ Quarters (MIQ) Building at the Central Police Station Compound on 29 May 2016, announced today its findings. 

Having examined possible causes of the incident based on technical data, construction records and information obtained from interviews with concerned parties, the three most likely causes of the incident identified by the Independent Review Panel are: settlement of the West Corbel, excavation of holes in the North Wall, and the combined effect of localised weak masonry and the cutting of holes at the brick columns.  The Panel is also of the view that, other than these three most likely causes identified, other possible causes are not direct causes of the incident.

Details of the three most likely causes are as follows:

1) Settlement of the West Corbel.  In March 2016, the West Corbel was temporarily supported by steel support while excavation was carried out at its base for the purpose of installing permanent reinforcement as part of the strengthening works on the west bay window on the North Wall.  The temporary steel support would have deflected as a result of carrying the weight of the West Corbel, causing settlement of the latter, which in turn would have caused stress to increase in the adjacent brick columns of the North Wall (identified as C3 and C4).  Whilst the increase in the stresses in those brick columns in March 2016 was not large enough to cause failure, it might have reduced the ability of those columns to take any additional load in subsequent stages of the construction works and made the columns C3 and C4 more vulnerable to collapse in the future.

2) Excavation of holes in the North Wall.  The only construction work performed to date on the collapsed North Wall was the excavation of 18 holes which was in progress between 20th May 2016 and 28th May 2016 as part of the first floor timber floor strengthening and fire resistance works.  These holes were excavated to pocket certain steel square box sections into the North Wall.  Some of the holes were located beneath and were very close to the base of columns C1 to C4, which support the North Wall from the second floor to the roof above.  These brick columns collapsed on 29th May 2016.  The excavation of the holes in the North Wall before the collapse is most likely to have been the immediate cause of the collapse.

3) The combined effect of localised weak masonry and the cutting of holes at the brick columns. Visual inspection of the North Wall columns prior to the holes excavation might have led to a conclusion that the brick columns could have remained stable during the temporary cutting of holes.  In reality, the brick columns might have had unnoticed vertical cracks or weak bonding at the first floor near the holes that allowed cracks to propagate during or shortly after the hole excavation, and led to the eventual collapse.  It is noted that the cutting of many holes in the masonry walls only occurred in MIQ Building and not in the other buildings at the CPS Compound.

The three-member Panel was chaired by Dr. Greg CY Wong, a veteran Registered Structural Engineer and a past President of the Hong Kong Institution of Engineers (HKIE).  Other members were Mr. Benny Lai Siu Lun, an Authorized Person and Registered Structural Engineer with heritage project experience, and Mr. Simon Wiltshier, a Chartered Structural Engineer based in Australia, who has served on numerous expert assessment and expert witness projects.

The Panel was tasked with undertaking an enquiry into the facts and circumstances that led to the partial collapse of the MIQ Building, to report on the likely causes of the partial collapse and whether any additional measures should reasonably or practically have been taken to prevent the collapse.

Since its establishment in late June, the Panel has held six meetings, visited the collapsed site six times and interviewed 17 persons who worked on the project.  It has also conducted laboratory and field tests on the construction materials that were used at the MIQ Building and carried out analysis of the collapsed part of the MIQ Building.  In addition, the Panel reviewed construction drawings, calculation reports, method statements, monitoring records, inspection reports, site photographs and video footages, a structural condition survey report of the MIQ Building, and other relevant documents.  The Panel has submitted the findings to the Board of Stewards of the HKJC.

“We have examined possible causes of the incident based on technical data, construction records and information obtained from interviews with concerned parties.  The Panel’s view is that there are three most likely causes, and other possible causes are not considered to be direct causes of the incident,” said Dr. Greg Wong.

The Panel believes that the collapse was most likely initiated at the North Wall and resulted from the failure of one or more of the three brick columns at a point between the ground floor and the second floor, causing the entire section of the North Wall to collapse.  This in turn pulled down the upper triangular section of the adjoining West Wall.

Regarding additional measures that should reasonably or practically have been taken to prevent the incident, the Panel has identified that, in planning for the timber floor strengthening and fire resistance works, any holes for pocketing the square steel box sections which were located within the brick columns base width should have been avoided and an alternative reinforcement detail, which did not involve cutting into the zone immediately below the brick columns, should have been adopted.

In addition, the Panel advised that the shoring and propping of the arches and floors should have been installed prior to the cutting of any holes into critical load bearing areas, including the brick columns, in substitution of the function of the brick columns.  The Panel notices that these shoring and propping have now been carried out in the remaining parts of the MIQ Building after the incident.

HKJC Executive Director of Corporate Affairs Mr. Kim Mak said the Club had shared the findings just received with the Buildings Department and the Project Management Team would carefully review the findings as well as the result of the ongoing Buildings Department statutory investigation, and take into account the relevant views and advices to determine the necessary follow-up actions. Mr. Kim Mak added, “The Club is committed to this important heritage project for Hong Kong.  The Project Management Team will continue to develop the recovery plan for Block 4 with safety as top priority and due consideration of engineering feasibility as well as heritage value.”

Other Corporate News