GAUTENG DEPARTMENT OF INFRUSTRUCTURE DEVELOPMENT

Transcription

1 GAUTENG DEPARTMENT OF INFRUSTRUCTURE DEVELOPMENT BUILDING ASSESSMENT REPORT STRUCTURAL FOR CUSTOMS HOUSE JULY 2014 i P a g e

2 Table of Contents 1. INTRODUCTION Design Criteria and Specifications Scope of the Services Scheme Report STRUCTURAL ASSESSMENT Building configuration and interfaces with adjacent buildings Façade Roof Waterproofing and Roof Structures General Structural Floor Slab Assessment Structural Column and Concrete Wall Assessment Foundations Basement and Basement Retaining Walls Building Internal Brickwork Building Internal Finishes and Services Staircases Structural Floor Loading Allowances Allowed For Future Use PHOTOGRAPHIC EVIDENCE AND COMMENTS. 6 ii P a g e

3 1. INTRODUCTION The project brief, as issued by Gauteng Funding Agency (GFA), was to conduct an initial assessment of the building condition, services, structural integrity of Customs House, and to provide recommendations regarding the repairs and renovations of the buildings. Customs house underwent a partial refurbishment in the past which involved complete internal strip out of finishes, walls and windows. The refurbishment process was stopped due to unknown circumstances at a stage when the building was completely stripped, window frames refurbished, new internal masonry walls built (but not finished) and no internal services installed. The rubble from the demolition works has been removed from site. The condition of the structural components is described below. Design Criteria and Specifications This project will be implemented in compliance with all the requirements of the National Building Regulations and the new SANS10400, including any town planning prescripts of the local authority. Scope of the Services Scheme Report This report deals with the proposed structural services to be implemented and preliminary design for the feasibility for the repairs and renovations of the existing buildings. 2. STRUCTURAL ASSESSMENT 2.1 Building configuration and interfaces with adjacent buildings Customs House comprises 9 floors and 2 basements. The building has a localized concrete roof at level 10 and a large portion of the 9 th floor is external (roof area). It is noted that Customs House is built with co-incident floor levels with the adjacent Rand Water building and the buildings can be used as a single entity or two stand-alone buildings. 2.2 Facade The existing façade comprises a mixture of cementious rendered exterior finish, face brick and granite wall cladding which is in good condition. It was noted that the ground floor façade has been stripped and will need to be replaced. The building has aluminium windows which are in good condition. Allowance for cleaning and resealing of the façade at joint positions and around window frames is required. No systems exist for cleaning the windows on the exterior face of the building. 3

4 2.3 Roof Waterproofing and Roof Structures The localized 10 th floor roof has had all roof waterproofing systems removed, and will need to be re-screeded and waterproofed. Existing roof waterproofing on the 9th floor comprises a torch on waterproofing system covered with a cement paving tile. The condition of the existing roof waterproofing will be in good condition under the paving; however the exposed vertical and horizontal waterproofing on the building parapets will need to be reconditioned. Due to the age of the waterproofing, albeit in good condition, allowance should be made for the renewal of all of the building waterproofing. The roof rainwater disposal system comprises fulbore outlets with cast in downpipes. The system appears to be in good working order; however the fulbore outlet itself requires maintenance and renewal of covers and the pipes will need to be checked for leaks. There are numerous structural steel structures on the 9 th floor roof, namely staircases and plant support gantry systems which are structurally sound, but require treatment of the rusted surfaces and repainting. It is noted that the mechanical and electrical equipment on the roof has been completely stripped, and hence the usefulness of the existing steel support gantries for new equipment should be questioned in the proposed new works as the new plant will vary in size to the previously installed systems. As the building has been stripped, all covers and louvres to vertical and horizontal services openings on the roof will need to be replaced once new services are installed to waterproof the building envelope. 2.4 General Structural Floor Slab Assessment In general the existing concrete slab structures are in good condition, however require local maintenance. The maintenance required includes locally treating exposed reinforcement on soffits and top of floor slabs for rust with a de-rusting compound and epoxy paint protection, and locally patching areas of honeycombing due to local construction defects from original construction. Defects can be seen on second and fourth floor. Allow 5% of total building floor areas for rebar de-rusting and concrete patching remedial activities. 2.5 Structural Column and Concrete Wall Assessment The building is supported by concrete columns which are in good condition. A portion of concrete wall on seventh floor has been in-correctly broken out locally for sanitary fitting installation. The rebar is still in place. The wall must be reinstated with a 50MPa structural non-shrink repair mortar. Allow 2m 2 of 300mm thick wall with appropriate side vertical shuttering for this repair. 2.6 Foundations The building shows no signs of settlement and hence foundations and bearing strata below are in good condition. 2.7 Basement and Basement Retaining Walls Building has 2 basement levels; both are in need of repainting and local repair works. 4

5 The repairs will involve the repainting and negative waterproofing of the basement retaining walls, as well as the replacement of basement sump pumps to pump out the water present in the lower basement. 2.8 Building Internal Brickwork The building underwent a stripping and internal wall demolition process in the past due to a refurbishment process that was stopped. Hence the internal walls are not plastered and are in a state of partial demolition and reconstruction. All of the rubble from the refurbishment has been removed from the floors and the floor plates are generally uncluttered and free of debris. On the 8 th floor some cracking is present in the internal brickwork. Such cracked internal brickwork plaster to be chipped off and re-plastered. Should crack extend into brickwork (unlikely), such panel to be broken out and re-constructed. 2.9 Building Internal Finishes and Services Due to a refurbishment process that was stopped, no internal finishes exist within the building, including electrical, mechanical and internal services. Refer to architects report in this regard Staircases The Internal staircase system is constructed from concrete and is structurally sound. Refer to the fire consultant report for compliance with latest regulations. If required, a new external structural steel staircase is recommended, at 50kg/m 2 in plan including the vastrap flooring material. Disabled access is not addressed in the current building design. Refer to Architects report for solutions in this regard Structural Floor Loading Allowances Allowed For Future Use Office and reception areas: 350kg/m 2 (Office occupancy + light weight partitions) Parking: 200kg/m 2 (Car parking (no trucks)) Roof Slabs (10 th and 9 th floor): 250kg/m 2. All heavy mechanical plant over 150kg/unit to be supported on existing steel gantries on the 9 th floor roof. Note no masonry brickwork partitions are allowed, unless verified by structural engineer. In general walls which are required to be masonry (that is bathrooms and kitchens) already exist. 5

6 3. PHOTOGRAPHIC EVIDENCE AND COMMENTS 3.1 Facades Figure 1: Street frontages of Custom s house are in good condition, but will require resealing and cleaning. The ground floor façade treatment will need to be re-instated. Figure 2: Eastern façade of the building is in good condition, however the lower portion of the building that adjoined to a previous structure should be repainted. 6

7 3.2 Roof Slabs Figure 3: 9 th floor is covered with cementious tiles. The parapets of the building will require new waterproofing and the waterproofing below the tiles must be serviced. All vertical and horizontal penetrations into the building must be replaced once new services are installed. Figure 4: Structural steel gantries are present on the roof to support new plant. The gantries require derusting and painting. The existing equipment on the roof will need to be removed as it is completely stripped. 7

8 3.3 Typical Office Floor Slabs Figure 5: Structural slabs within the building are of a ribbed construction are in very good condition. Figure 6: New aluminium window frames are installed throughout the structure, however plastering to the windows and internals of the building will need to be completed. 8

9 Figure 7: Partial demolition and construction of internal walls. Internal walls will need to be completed and plastered. All structural components are in good condition Figure 8: Example of a higher floor where the previous refurbishment project was more advanced than lower floors. All structural elements are in excellent condition. 9