Hazendal Wine Estate – New Educational Play Center

The Educational-Play Center at the Hazendal Wine Estate in Stellenbosch is a new building forming part of the redevelopment of this heritage wine estate. The facility is named Wonderdal.

After various designs were proposed to the three heritage bodies involved in this building’s approval, the final design of the building was agreed upon. These heritage bodies did not have a unified vision and what was preferred by one was not accepted by another.

The close proximity of the new facility to the historical building had to be considered. The new building design had to respond in a sensitive manner to the scale and not dominate the existing old structure.

The nature of the building programme, that of a play center, suggested that the design of the new facility should be a simple Box Shed. This building type was approved by one heritage body but rejected by another. Therefore, to reduce the impact of this Box Shed, two new barns similar in scale to the historical buildings where introduced. This formed a rhythmic streetscape where the space between the barns formed courtyard spaces for entrance and deli spillover seating. The shed roof that floats over these barns forms the main double volume required for the play center’s apparatus and functions. Where the floating roof and barns meet, they are connected with glass. This new building also houses the main kitchen which serves as the farm’s new Deli Restaurant which is located in the attached old historical barn.

The façade and parts of the roof of the building consist of white concrete panels and large glass windows which afford little space for vertical bracing to resist high lateral wind loading the open farmland. The lateral deflection of the building had to be minimized to prevent cracking of the glass facades. This was resolved by designing all columns and bases to act as vertical cantilevers.

All roof beams were fixed to the columns with moment connections to further enhance the lateral stiffness of the building. In order to achieve neat inconspicuous connections, the top flange at the beam ends was cut away to allow a small workspace. All bolts, end plates and stiffer plates were fixed on the inside of the square hollow sections (refer to the attached details).  

The choice of materials and structural design of details resulted in a steel frame with a neat non-industrial appearance.  

STRUCTURAL STEELWORK
Completion date of steelwork May 2018
Completion date of full project March 2019
Tons of structural steel used 44.2 Tons
Structural profiles used 200x200x6 SHS, 203 x 203 x 46 H, 203x133x30 I
PROJECT TEAM COMPANY
Nominator Michael Hackner Architects
Client/ Developer Hazendal Wine Estate
Architect Michael Hackner Architects
Quantity Surveyor Prodigious
Project Manager  
Main Contractor R + N Master Builders
Steelwork Contractor TGS Concepts
Steel Erector TGS Concepts
Corrosion Protection
Galvanising
Galvatech
Nominator Michael Hackner Architects
Client/ Developer Hazendal Wine Estate
Architect Michael Hackner Architects
Structural Engineer JTL Structures cc
Quantity Surveyor Prodigious
Main Contractor R + N Master Builders
Steelwork Contractor TGS Concepts
Steel Erector TGS Concepts
Corrosion Protection
Galvanising
Galvatech
Photographer, Photo competition Michael Hackner Architects

IRPTN Pedestrian Bridges

In 2013, the City of Ekurhuleni Metropolitan Municipality embarked on an upgrade of their existing transportation route planning and infrastructure in the form of an Integrated Rapid Public Transport Network (IRPTN). The City is now set to kick off the first official run of its IRPTN service, Harambee, as part of the implementation of its Phase lA operations.  The limited service will run eight buses in mixed traffic along the 38 km service route, with 33 kerbside stops, between Tembisa and Isando.


The full roll-out of the Harambee Phase lA service includes the introduction of new elements into the system until it is ready to operate as a fully-fledged BRT (Bus Rapid Transit) scheme. Integral to the project is the construction of nine new BRT Bus Stations (see the Station layout in Figure 1 below) which run into the heart of Tembisa. These new Bus Terminals and pedestrian bridges are the projects submitted here for consideration.

The overall project scope includes the upgrade of the existing road facilities, to add new BRT lanes with sidewalk and median, as well as the construction of nine new station facilities. Due to the overall road width increase, several structures are required to be extended and upgraded – these include a road culvert water crossing and several rail culverts that cross the main road (Andrew Mapheto drive) that traverses through central Tembisa.

With the exception of the pedestrian bridges, the typical layout model that has been deployed throughout the project is similar to that which has been used in the Johannesburg CBD and Cape Town BRT systems. The Stations represent central node points that facilitate the easy access of pedestrians into the BRT system, and the brief to the Architect was to design an aesthetically pleasing solution that provided such access.

The elements generally incorporated into a typical Station are the following:

  • A median area where passengers are noused in a dedicated enclosed structure that provides direct access to the bus route and BRT lane,
  • the pedestrian bridges that cross over the road intersections, allowing pedestrians the ability to gain safe access to the median area,
  • the various interlinking walkways and stairs,
  • the lift shafts that allow users to transition from the Ground level to the First-Floor level and back

The original concept developed by the Architect and Structural Engineer is very similar to the final design that is currently under construction, which involves a curved steel truss type arrangement, made out of mostly circular hollow sections. Structural steelwork was envisaged on this project due to its ease of use for the required spans, the ability for easy erection over existing roads, as well as the overall slim look and feel that arises out of its use in the design.

The bridges incorporate a composite structural steel/reinforced concrete slab design. The top and bottom girder chords are constructed from circular hollow sections and the design has a curved top chord that is set at an angle relative to the main floor structure, making the bridge took “open” as one travels from one end to the other. Due to deflection requirements, the bridges are given a slight vertical preset to allow the deflections to normalise under dead and live load conditions. The vertical girder members are given outward curved radi, and a similarly radiused plexiglass f de is attached using aluminium mullions – the fac;ade envelops the entire truss frame, giving the bridge an aesthetically appealing look and feel, To facilitate drainage on the bridges, a longitudinal fall is provided between deck interface platforms and full-bore outlets are used on the bridge ends to facilitate the discharge.

The longest pedestrian bridge has a span of 36m and therefore it is long enough for vibration considerations to play a role. A LUSAS model was therefore developed to simulate the effects of pedestrian crowds as well i:IS single dynamic pedestrian users moving over the bridge. The analysis showed that that the maximum accelerations developed on the bridges are not in excess of the 0.5m/ s2 allowed by the relevant Codes. Acceleration results were further compared with the SETRA Pedestrian Bridge design guide as well as the TMH7 guidelines.

The Lift Tower shafts and their supporting structure represent key structural elements that directly interface with an unusual curved supporting element that takes the bridge load directly down to the foundation level after first wrapping its way around the Lift Shaft Tower. The lift shaft itself is also enclosed in an aesthetic plexiglass facade, providing cover to users of the lift as well as protection for the lift equipment. Louvered vents through the facade are also required due to the heat-build inside the Lift Shaft Tower structure.

From a design point of view, the interfacing of the plexiglass facade with the bridge structure required several Iterations to ensure that a robust and workable solution was arrived at. One of the challenges of designing with plexiglass material is that all the connections to the structure need to include a gasket sealing material and gaps are required in connections to allow for a certain degree of plexiglass movement. Interfacing with the 11ft contractor also required a thorough understanding of the details of the levels and falls on the site to ensure that the lift exit and entry points corresponded with the deck slab and ground levels.

The open frame design of the bridge girder members meant that careful attention had to be paid to the stability of the main girder structure in the transverse direction –  this meant that any member splicing along the lines of the main transverse framing action required the use of stiff moment connections.

A significant number of Shop drawings were required to be generated for the entire project. 3-D Tekla models were used by the steelwork contractor to facilitate the rapid development and approval of shop drawings. Due to aesthetic requirements, welding for the splicing of main longitudinal members was done on site under carefully controlled conditions.

For each bridge site, road closures were required for the erection of each bridge – this required a significant amount of coordination with the local traffic authorities who were fortunately very obliging. Some 32 tonnes per 36m span were lifted, and a typical station involved the erection of approximately 115 tonnes (Including the Lift Towers) per station.

For this project, the two main Contractors on the project (Stefanutti Stocks and King Civils) were required to think of solutions to the problem of how and when to  Install the concrete deck slabs whilst allowing for the concrete creep and shrinkage to occur. This produced a set of interesting and varying opinions, and ideas suggested varied from precast concrete to  in­ situ concrete with permanent formwork.

The design of the Station Bridge structures that are required to harmonize with Lift Shaft Towers presented an interesting challenge to the SMEC South Africa bridges design team. The project demonstrated that there is still a significant preference for the use of structural steel for pedestrian bridges in this country.

STRUCTURAL STEELWORK
Completion date of steelwork ± September 2018
Completion date of full project ± April 2019
Tons of structural steel used 725 Tons
Structural profiles used Chs, Ub, Uc, [, Angle
PROJECT TEAM COMPANY
Nominator Khombanani
Client Ekurhuleni Metropolitan Municipality
Structural Engineer Smec South Africa
Engineer Lte Consulting
Engineer/Project Manager Lte Consulting
Main Contractor Stefanutti Stocks / Khombanani Steel JV
Main Contractor King Civils
Steelwork Contractor Khombanani
Steel Erector Onpar Steel
Cladding Manufacturer Global Roofing Systems
Cladding Supplier Global Roofing Systems
Cladding Contractor Roofline
Corrosion Protection
Paintwork Contractor
Dram Industrial Painters
Corrosion Protection
Paintwork Contractor
RSC

Naspers Skybridge

The Naspers Skybridge is a pedestrian link between the CTICC 2 building and the Naspers building. The client tasked the architect with designing a new bridge between the new CTICC 2 building and the NASPERS building. This would aid in daily access for Media24 staff, as they did not have enough parking of their own and could then utilize some of the parking bays in the CTICC buildings. This new bridge had to link CTICC 2’s Second Floor with NASPER’s Fourth floor, roughly 13.5m above the road level.

The architects developed various concepts for the design of the bridge. Inspiration was taken from the shape of a tree, interpreted in different architectural expressions. Through workshops with the client (both CTICC and NASPERS) and the professional team, multiply small-scale physical models were built to convey the different design ideas, including an option of steel laser cut panels that form a sculptural support and leaf-pattern balustrade, and another version with steel support “branches”. Ultimately, the design was refined to form a simple yet “raw” aesthetic, with the architectural and structural logic informing the details. A composite wood decking floor in a staggered pattern was used to enhance the “raw” aesthetic, with Rheinzink roof sheeting chosen for aesthetic and practical reasons due to the slanted and curved roof. Panoramic views of the city can be experienced through the full-height glass façades.

Due to the location of the entrances to the buildings, the bridge curves for about half of its length. This creates an interesting architectural experience as one crosses the bridge, while making it possible to see the bridge’s exterior from the inside. Structurally the challenge was to support the curved section only on two columns, with the end part at the CTICC not being able to be supported by the existing building (thus creating a large cantilever that had to have minimal movement at the façade entry point).

The bridge was always envisaged as being constructed out of steelwork – to allow maximum views to the sides and to enable construction with minimal disruption to the street below. The bridge structure comprised mainly Universal Beam and Column sections, with some angles added to support the flooring and a CHS safety rail for window cleaning.

Challenges arose due to the weight of sections, which made moving these sections a challenge during both fabrication and erection. The bridge sections were assembled into just two pieces adjacent to the road, allowing these two large pieces to be erected using a 440t crane during a road closure on a Sunday. The two parts had never been spliced together before erection, with all dimensions being theoretical. The first real fit was therefore on site, and everything fitted perfectly.

Another challenge was erecting the bridge on a windy and rainy day, forcing the contractor to wait for a lull before lifting.

Since the bridge was modelled in 3D, an IFC export was provided to the contractor to aid them in the shop drawing process. In turn, they provided their fabrication model in 3D for approval by the engineer and architect, which ensured that the aesthetic intentions of the professional team could be met.

STRUCTURAL STEELWORK
Completion date of steelwork October 2018
Completion date of full project March 2019
Tons of structural steel used  
Structural profiles used UB, UC and CHS sections
CLADDING
Completion date of cladding No cladding
Cladding profile/ type used Rheinzink
Cladding area/ coverage and tonnage 165m2
PROJECT TEAM COMPANY
Nominator Anchor Steel Projects
Client/ Developer Cape Town International Convention Centre
Architect Osmond Lange Architects + Planners
Structural Engineer Sutherland
Quantity Surveyor Turner & Townsend
Project Manager Lukhozi Engineers
Main Contractor Superway Construction
Steelwork Contractor Anchor Steel Projects
Steel Erector Anchor Steel Projects
Cladding Supplier Two Oceans Metal
Cladding Contractor Naturally Slate

CTICC Skybridge

The CTICC Skybridge was intended as an above-ground link between CTICC 1 on the West of Heerengracht Street and CTICC 2 on the East. The client asked the Architects to design an enclosed pedestrian skybridge to connect the Cape Town International Convention Centre (CTICC 1) with the CTICC East Expansion (CTICC 2) across the busy Heerengracht Street. Development of the CTICC skybridge was considered critical in enabling the two buildings to function as a single integrated international events hosting venue and providing a seamless visitor’s experience.


The curved skybridge with its slender slanted steel columns has an unusually dynamic aesthetic from outside. The curved route inside provides a dynamic visual experience as one moves across the bridge in anticipation of an obscured end destination. The indirect travelling direction guides the visitor’s gaze outwards and across the historic Heerengracht Street and allows the bridge to become a unique destination in its own right. This purposefully iconic structure pays tribute to CTICC’s core purpose of ‘connecting people’.

The bridge was always envisaged as being constructed out of steelwork – to allow maximum views to the sides and to enable construction with minimal disruption to the street below. Universal Beam and Column sections were chosen to frame the concrete floor and roof, which were both cast in sections in between these steel members, with support provided by Bondek sheeting. Universal Column sections were also chosen for the Vertical members, in order to frame the glass panels.

Circular hollow sections, however, were chosen for the diagonal members to minimise the disruption of the view. The same members were also used for horizontal bracing at the roof and floor level, to keep the section sizes down. Large circular hollow sections were also used for the slanting support columns.

Challenges arose due to the weight of sections, which made moving these sections a challenge during both fabrication and erection. The bridge sections were assembled into

just two pieces adjacent to the road, allowing these two large pieces to be erected using a 440t crane during a road closure on a Sunday. The two parts had never been spliced together before erection, with all dimensions being theoretical. The first real fit was therefore on site, and everything fitted perfectly.

Another challenge was the temporary support of the bridge during erection. This was overcome by introducing the temporary towers, which made the installation much simpler and safer.

Since the bridge was modelled in 3D, an IFC export was provided to the contractor to aid them in the shop drawing process. In turn, they provided their fabrication model in 3D for approval by the engineer and architect, which ensured that the aesthetic intentions of the professional team could be met.

STRUCTURAL STEELWORK
Completion date of steelwork September 2018
Completion date of full project November 2018
Structural profiles used UB, UC and CHS sections
PROJECT TEAM ROLE COMPANY
Nominator Anchor Steel Projects
Client/ Developer Cape Town International Convention Centre
Architect Convention Architects – a JV between Makeka Design Lab cc, SVA International (Pty) Ltd and van der Merwe Miszewski Architects (Pty) Ltd
Structural Engineer Sutherland
Quantity Surveyor Turner & Townsend
Project Manager Lukhozi Engineers
Main Contractor Superway Construction
Steelwork Contractor Anchor Steel Projects
Steel Erector Anchor Steel Projects

 

No.1 Silo Bridge

The requirement for a pedestrian bridge link between two office buildings was borne out of the need of Allan Gray’s expanding workforce as they out-grow their head office capacity at No.1 Silo building in the V&A Waterfront.

Allan Gray and the V&A Waterfront together with the architect and engineers developed the idea of a linking bridge between the No.1 Silo building and the adjacent Clock Tower building to allow the internal flow of employees between the buildings.

Not far away from the site of the bridge is the defunct Collier Jetty that has a steel gantry structure along its length, historically used to convey coal and later grain. The gantry is constructed from conventional bolted angle trusses – the inspiration behind the truss form of the bridge with matching diagonal angle sections. 

The brief was thus to design and construct a bridge that would allow people movement over the 12,5m span. While it is a relatively short distance the challenge lay in designing a structure that would deal with the movement between the two buildings that are built on separate floor plates by catering for differential lateral and horizontal movements of up to 20mm.

The Allan Gray building has a fully glazed double-skin façade supported off long cantilever fins which are sensitive to additional loads. The bridge, therefore, had to be fixed on one side only, and cantilever without physically touching the glazed façade. As such columns were introduced to support the bridge at the glazed façade allowing unimpeded movement against it. The two columns, 219mm CHS, are braced by 254x146mm universal beams forming a ‘portal frame’ on which the bridge rests and on the other side, it is bolted to the reinforced concrete frame of the Clock Tower building by way of a shear key detail.

To maintain the view corridor between the two buildings, toward the working harbour, the architects motivated for a crossing at second-floor level. Limited space between the buildings, the delicate glazed façade and the limited crane load that could be applied on the podium level between the buildings meant the structure could not be erected in its entirety and craned into position – it needed to an on-site assembly, erected on a scaffold deck.

A rectangular girder comprising 200x100mm RHS sections was designed as the most efficient steel structure to span from the Clock Tower building to the ‘portal frame’ and cantilever a further 1,7m to the Allan Gray floor plate. A spliced connection along the length of the top and bottom chords created parts that could be handled on site. Rigidity is provided by expressed diagonal bracing visible externally as a structural ‘exo-skeleton’, painted red. 

The design team devised connection details between the various parts that expressed the junction of the steel members, in keeping with the industrial, maritime aesthetic. 100x100mm equal angles bolted to gusset plates brace the vertical SHS posts on  the sides of the bridge. 100x100mm SHS brace the underside and the roof level, expressed externally on the soffit and internally below the ceiling finish. Spigot connector splice details were required on the bracing diagonals to cater for the erection sequence.

Where the bridge passes through the double skin façade a flexible EPDM membrane allows for the required movement but also a weather seal. The membrane is protected by overlapping aluminium flashings.

The bridge links offices on two different floor levels – this is achieved by a sloping timber floor within the girder structure. Steel cleats on stub columns welded to beams along the length of the bridge support timber joists at varying heights.

Side wall cladding is Snap Lock profile in Armour Grey colour, selected for its broad pan and narrow flutes with wide rib spacing. Set behind the diagonal bracing, the industrial aspect of vertical sheet cladding further ties the bridge to its maritime setting. Snap Lock is also used for the roof sheeting and in conjunction with a stepped aluminium flashing detail it creates a crisp silhouette of the bridge spanning between the two buildings. 

STRUCTURAL STEELWORK
Completion date of steelwork 05 / 09 / 2018
Completion date of full project 14 / 12 / 2018
Tons of structural steel used 8.1 tons
Structural profiles used RHS, SHS, CFLC, CHS
CLADDING
Completion date of cladding 10 / 10 / 2018
Cladding profile/ type used SnapLock
Cladding area/ coverage and tonnage 48m²
PROJECT TEAM COMPANY
Nominator Loudon Perry Anderson Architects
Client/ Developer V&A Waterfront Holdings (Pty) Ltd
Architect Loudon Perry Anderson Architects
Structural Engineer Sutherland Engineers
Facade Engineer Arup Engineers
Services Engineer Solution Station
HVAC Engineer Arup Engineers
Quantity Surveyor MLC Group
Project Manager Principle Agent  Architect
Main Contractor R+N Master Builders (Pty) Ltd
Steelwork Contractor Prokon Services (Pty) Ltd
Steel Erector Prokon Services (Pty) Ltd
Cladding Manufacturer Bluescope Steel
Cladding Supplier Youngman Roofing
Cladding Contractor Metro Roofing 

 

Kusile Coal Bridge from Kusile Boiler 5 to Kusile Boiler 6

Shanahan Engineering was successful in securing an erection only contract to erect Secondary and Tertiary Structural Steelwork for Kusile Boiler 3 for Mitsubishi Hitachi Power Systems Africa in 2013.

Shanahan delights in providing well supervised and productive construction crews for all of our customers. This positive attitude during the execution of our contract at Kusile quickly led to the company securing the erection contracts for Kusile Boilers 4 and 6 as well as the Primary Coal Feed Conveyor for Kusile Boiler units 4, 5 and 6, the Steel Erection contracts for PJFF units 4 to 6 and the Coal Bridge between Boilers 5 and 6.

The execution of our contract for the latter – the Coal Bridge between Boilers 5 and 6, is the reason for our contention at the 2019 Steel Awards.

As the name suggests, the Coal Bridge feeds coal into the Boiler Mills for use in the boiler combustion process. The coal travels up to Boiler 4 via the Primary Coal Feed Conveyor and then across two bridges from Boiler 4 to 5 and then from Boiler 5 to 6 before being fed into the Boiler Mills.

The bridge is assembled at Ground Level before being lifted as a single piece construction, to its final resting place, 50 m above ground level. The total weight of the bridge is 450 tons and is therefore too heavy to be lifted by means of a Mobile or Lattice Boom Crane.

The Engineers therefore designed a system of strand jacks comprising of a series of winches, and cables that are fixed to the 4 corners of the Coal Bridge. When all necessary load and safety checks have been checked and double-checked, the winches are activated in a controlled manner to lift the Coal Bridge up before being fixed by means of bolted connections, into position.

The lift can only be performed in near perfect weather conditions. This is due to the large surface areas that are in play which would make windy and wet conditions more hazardous for the lift.

Prior to the Coal Bridge being ready to lift, the Shanahan Construction Team had to request for all the necessary components to be delivered to the erection site for the bridge to be assembled at Ground Level. The erection drawings are reviewed and a parts list was made that comprised 1556 steel sections and 11863 bolts and nuts. Some of the steel sections were quite light whilst others weighed tons. These parts lists were passed onto the Materials Handling Contractor who delivered the requested components to the erection site. On any mega – project like Kusile, there will be parts that are either incorrectly fabricated or missing, this invariably delays the process of erection due to the engineering queries that result. This process was managed closely by the Construction Team together with the Materials Handling Contractor and the Main Contractor so as to ensure the minimum possible impact to project schedule.

In this case, the Shanahan Construction team spent 10968 manhours to complete the assembly of bridge to be ready for lifting into position. The Strand Jacks were then fixed to the 4 corners of the coal bridge and the Construction Team were ready to erect by the afternoon on 7 December 2018. Weather conditions were checked and due to a favourable forecast (dry conditions and little wind), it was decided to perform the lift early the following day, 8 December 2018.

The lift started at 08h23 on 8 December 2018 following a special safety briefing which started at 06h30 earlier that morning. In the picture below you can see the 450 ton bridge section still on its trestles at Ground Level. By 15h40 on the same day, the Bridge had reached its final position. The lift took just under 7 hours and 20 minutes to complete which was just under 5 hours faster than any of the previous Coal Bridges.

Shanahan achieved a perfect Safety record during the Assembly and lifting of the Coal Bridge with no incidents having been recorded from start to finish.

STRUCTURAL STEELWORK
Completion date of steelwork 08/12/2018
Completion date of full project In progress
Tons of structural steel used 450
Structural profiles used Miscellaneous
SA content – if this is an export project  

 

PROJECT TEAM COMPANY
Nominator Shanahan Engineering
Client/ Developer MHPSA
Structural Engineer Genrec
Main Contractor MHPSA
Steelwork Contractor MHPSA
Steel Erector Shanahan
Cladding Manufacturer GRS
Cladding Supplier GRS
Cladding Contractor Southey

KZN Suspension Bridges

After heavy summer rains in KZN there are many rivers that come down in flood. This makes crossing dangerous and has resulted in sufficient incidents to have motivated KZN Transport to erect suspension bridges with a standardized design in numerous places. These hot dip galvanized bridges are user-friendly to erect in the most rural of areas.

A truly great community spirited project, this bridge is so much more than just another footbridge. For starters, we usually think of a pedestrian bridge placed in a city over some busy road or railway line……not so these bridges

If ever a bridge was placed to be of maximum benefit to the local community, to really save lives in flooded conditions, these bridges did just that. Can you imagine what this peaceful stream might look when in full spate?

Placed in rural locations, to service quite small communities, these bridges represent what service delivery by any of the 3 tier government sectors should be about.

Identify a need in many places, methodically come up with an excellent modular engineering solution that largely fits all situations, make a few small modifications to suit local conditions, and hey presto we get a cost-effective stable suspension bridge that is a win-win for both the developer, KZN transport and the community.

Now most of us think of a suspension bridge as a swing bridge……and this is where the good engineering comes into this solution, the multiple cables, the diagonal members, the standard modules and and and net result, very little by way of a swinging motion on these bridges. Hot dip galvanizing eliminates the need for future maintenance for a long time….

A truly deserving project to be recognized with a special commendation in the community development category, the KZN Rural suspension bridges.

Hanger Street Pedestrian Bridge (2012)

The Hanger Street Pedestrian Bridge caught the judges’ attention from both an engineering and architectural point of view. They said that a closer look at the bridge revealed not only excellent engineering and workmanship but also that ‘extra thought had gone into designing a beautiful bridge for daily commuters in an inner city area’.

This tapering steel-box-girder-spine bridge provides a crucial link for pedestrians between the Central Park Bus station and the newly constructed Mangaung Intermodal Public Transport Facility, which accommodates all of the city’s taxis. It also provides a safe passage for pedestrians trying to cross the busy Hanger Street, which serves as one of the arterial roads into Bloemfontein from the south. It also provides aesthetic upliftment to the downtown area and forms part of the rejuvenation of the Bloemfontein inner city area.

Aesthetic Appeal

“What is striking about the Hanger Street pedestrian bridge is its unexpected aesthetic appeal,” the judges said. “It is obvious that those involved in putting the bridge together spent much time and effort in delivering a pedestrian bridge that will not only get all who use it safely from one side of Hanger to the other but will also provide them with aesthetic appeal to enjoy while doing so.”

The bridge links up with the first floor of the existing bus station, from where the deck slopes upwards and turns toward the new taxi rank facility. This complex geometry in the deck had to be designed to accommodate the significant level difference between the adjacent building’s first-floor levels.

“While pedestrian bridges are often open, slender structures, the prerequisite for this bridge was to provide cover to pedestrians commuting between the transport facilities while still ensuring a transparent and safe enclosure. Custom-made 450x150mm rectangular hollow ribs were designed for aesthetic purposes, as well as to provide the framework for the roof and glazing panels,” said the project team.

The judges made special mention of this. “The structural solution for spanning the 62m over Hanger Street has been cleverly hidden in the boxed girder spine to which the composite walkway and rectangular hollow ribs have been fixed. The ribs, in turn, provide support to the roof and side cladding ensuring the protection of all pedestrians against the elements.”

Special LED lighting was installed on deck level, as well as into every second steel rib. These light units were recessed into the deck and frameworks in order to protect them against vandalism and theft.

The 150mm concrete deck is supported by the steel box girder via shear studs, as well as permanent shuttering.  The 51m3 of concrete deck ensures a more solid walking surface thereby adding to pedestrian comfort.

The bridge was fabricated in Omni Struct Nkosi’s workshop in Johannesburg. Its steel box girder spine, together with its steel fins and the bottom part of the frames, were welded together in their factory and the three major spans were delivered to site individually with the rest of the sections. These main components were then lifted into position and the remainder of the structure welded on site. All site welds had to undergo non-destructive testing to ensure the quality of workmanship.

The judges noted how, at every stage, the well-being of pedestrians was taken into account. “Great care has been taken to allow for easy access to the bridge with escalators provided on one end. The Hanger Street pedestrian bridge is certainly a great endeavor to avoid pedestrian deaths on a very busy thoroughfare, and doing it in steel has proven most effective,” they concluded.

PROJECT TEAM

Developer/ Owner: Mangaung Metro Municipality – Bloemfontein
Architect: Incline Architects
Structural Engineer: Vela VKE (Part of the SMEC group)
Quantity Surveyor: Rubiquant; Limco QS Arbitration & Project Management
Project Manager: Incline/Vela VKE JV
Main Contractor: RSI Intermodal Construction
Steelwork Contractor/s: Omni Struct Nkosi
Detailers/ Detailing Company: Draftline

Freespan Bridge/ Dry Mill Phase 2 & 3 Sky Walks

The Freespan bridge (“Bridge 16”) is situated on Thesen Islands in Knysna. This is on the site of the former Thesen Sawmill, which has been developed into a large residential estate with a smaller commercial core. The original island was divided into nineteen smaller islands, which necessitated the construction of various bridges. Two of these formed part of a previous Steel Awards submission in 2006 where the project won the category for “Recycling and Sustainable Projects”.

The Freespan bridge completes the pedestrian link from the residential portion of the islands to the commercial area called Harbour Town and is a continuation of the route that crosses the two Monorail bridges. Due to the width of this particular canal, the difficulty (and cost) involved with piling and the sensitive nature of the site, the only viable option was steel. A suspension bridge with pylons on both sides of the canal was considered and discarded due to cost constraints and the impact it would have had on the views from the surrounding houses. This led us to the idea of a free-span bridge.

We decided on a tubular “spaceframe” structure to keep the size of individual members down, to minimise the visual impact and because we believed it would work well aesthetically.

To work out the design in order to span the required 46 meters, calculate the sizes and install the bridge were all challenges in their own right. The entire steel structure was erected in less than a day and the bridge had to be assembled from both sides of the canal.

People in residential areas are usually skeptical of structures that consist predominantly of steel, but everyone was pleasantly surprised by this bridge. The combined efforts of everyone involved resulted in a unique and visually appealing structure that blends in well with its surroundings.

The Dry Mill Phase 2 & 3 Sky Walks

Steel girder type “skywalks” providing horizontal movement between the North and
South second floor Penthouses was the design choice in the sectional title Phase 2 and 3 of the Dry Mill in an attempt to emphasize its historic steel character.

Steel stairs on either side of the 11-meter skywalks, supplemented by a lift on the Northern blocks, provide vertical movement from the undercover parking areas on grind floor.

Three skywalks in Phase 2, & One x skywalk in Phase 3 connect the ten luxury second-floor Penthouses. By connecting the North and South Blocks, the skywalks freed-up some vital floor area in the Southern Blocks as a Lift shaft, measuring 4,77m2 x 3 floors = 14.31 m2, was only required on the Northern Blocks.

• The western façade is protected from the southwesterly wind-driven rain by aluminium shop front type window frames with small openable windows.

• On the eastern façade, only the first portion of the skywalk structure is clad while the middle section is open with a 1 200mm high slatted handrail.

• These infill elements were positioned on the inside of the skywalks so that the structural steel girders are visible from the outside.
• The floor is constructed with Balau timber decking and the roof is clad with corrugated roof sheets to match the development and to retain the historic shed like the feel of the Dry Mill.

It was decided to paint all the steel elements of the skywalks and stairs with Red Oxide so that these structures are emphasised as a design element in the development where the design philosophy is to show as much of the historic structural components as possible. The Red colour successfully compliments the red De Hoop face brick payers used on the road surface below.

The Dry Mill history

The Dry Mill is one of the oldest industrial structures of the former Thesen Sawmill, originally used for storing and processing timber. Open crawl beam structures made out of goal-post type portal frames supported a center under-slung crawl beam system.

Special permission was given by the National Monuments Commission for the adapting and re-use of the building that have since won the CNBC International Property Awards for Best Re-development in South Africa and went through as a top 5 Finalist in the World.

Project Team – Dry Mill:

Developer Owner: Thesen Islands Development Company
Architect: CMAI Architects
Structural Engineer: LSM Structures & Civils
Quantity Surveyor: Steele Consulting
Project Manager: CMAI Architects
Main Contractor: Shamwari Projects
Steelwork Contractor: Prokon Services
Other: AM Aluminium (Glazing)

Project Team – Freespan bridge:
Developer Owner: Thesen Islands Development Company
Architect: CMAI Architects
Structural Engineer: LSM Structures & Civils
Quantity Surveyor: Steele Consulting
Main Contractor: Prokon Services
Steelwork Contractor: Prokon Services
Other: Lomot (Timber work)

Repair Of Bridge No. 422 (2008)

This bridge repair project clearly portrays the art and science of civil engineering in terms of technical excellence.  It demonstrates how innovative answers were found for the challenging demands of structural stability, safety, and economy.  The repair technique implemented is unique and displays engineering ingenuity in the practical, efficient and structurally sound approach followed.  The bridge is an important link between the Free State, Transkei and Eastern Cape that is now restored to its original historic glory.  Notwithstanding the fact that the bridge had to be closed for traffic during repairs, good public relations ensured that no incidents took place.

Description Of The Project

Bridge No. 422 is located on Route P53/1 (R726) between Zastron and Sterkspruit where it crosses the Orange River near Sterkspruit on the farm Mayaputi.  It was constructed in 1934 when pre-manufactured steel was imported from the United Kingdom and erected in South Africa. These are historic bridges and concerted efforts should be made to maintain them for posterity. 

The superstructure consists of two simply supported, steel truss spans of 61 m (200 ft) each supported by a concrete substructure with a roadway width of 3 m (10 ft).  The truss members consist of laced, riveted sections.  The bridge was seriously damaged as a result of vehicular impact to certain of its structural members. 

THM Engineers Free State cc was appointed to evaluate the deficiencies, find structural solutions and compile contract documentation for the urgent repair and rehabilitation of the bridge.

Design Approach

Since this is a narrow single lane bridge, the bridge had to be closed for the whole construction period.  The contractor had no other space than the bridge deck to work from for scaffolding, rigging equipment, welding machines etc.  Closure of the bridge would have had a major impact on the local community and long-distance haulers.  Therefore, the point of departure was to complete the repair work in the shortest possible time. 

In a statically determinant truss bridge, the removal of any compression or tension member for repair will lead to an immediate and complete collapse of the bridge.  The traditional engineering solution would have been to construct very costly coffer dams and prop the complete bridge 30 m high from the river bed to make the removal of the damaged members possible.  Considering the risk of the known frequent flash runoff of the Orange River the traditional approach was not an option.

THM displayed innovation and engineering ingenuity with a unique “repair in the air” design solution satisfying the challenging demands of structural stability, safety and economy.  The challenge was to find a repair method that allows for the safe removal and replacement of damaged structural members while the damaged bridge supports the contractor’s workers and construction loads.

Repair Technique

The following “repair in the air” technique was followed to replace all damaged vertical compression members while they were carrying the full loads due to the bridge’s own dead load and applied construction loads.  Two temporary compression struts capable of supporting the full load due to dead weight and the construction loads were installed adjacent to each damaged member.  To ensure that the full load was carried by the temporary struts a simple though effective and functional support bracket was designed to pre-stress the struts in a very controlled manner before the damaged vertical laced member was removed.  Due to the complexity of the riveted connections, it was not possible to install a replacement member as a unit.  The four angle iron legs of the laced member had to be built up one by one.

The diagonal laced members are tension members and do not need composite action for stability as each angle iron leg of the member is in tension.  Tension force influence lines that were obtained from analyses were used to cleverly position heavy construction loads such to reduce the forces in the member under repair. The result was that it was possible to replace the damaged diagonals by removing and replacing the legs one by one without the use of expensive temporary tension cables while they had to resist the influence of the full dead weight and construction loads. 

An elegant steel solution

Due to the fact that the bridge is a single lane structure with limited workspace, it was, from the outset, envisaged that repair could not take place under traffic conditions.  Long distance traffic could preplan for this eventuality; however, it was problems associated with the locals that proved a thorny issue with potential political implications.

Many locals travel between the two towns on a daily basis due to work commitments as well as for the purchasing of goods.  The only practical alternative which could be considered was to accommodate pedestrian traffic over the bridge at certain stipulated times and under certain conditions as determined by prevailing construction activities.

This arrangement allowed for Taxi operators from one town could transport their passengers to the bridge; passengers could then walk across the bridge; taxi operators from the other town could then pick them up to complete the journey. Persons making use of their own transport could leave their vehicles at the bridge and arrange for transport on the opposite side.

Being fully aware of the generally aggressive attitude adopted by Taxi Associations, the Engineer and the Contractor realised that this issue had to be sorted out prior to the closing of the bridge.  A meeting was arranged with the Taxi Associations of Zastron, Sterkspruit and Aliwal North, during which all the implications and eventual advantages of the Project were discussed at length and in detail.  

By observing the daily “crossings” of the bridge one became amazed at the vital role a bridge such as this plays in the lives of a local community.  

This was indeed an out of the ordinary technical project, but also one which had close ties with the local community.   

Project team

Developer/ Owner:  Department Public Works, Roads & Transport, Directorate Land Transport Planning
Structural Engineer:  THM Engineers Free State cc
Project Manager:  THM Engineers Free State cc
Main Contractor:  Tanekk cc
Steelwork Contractor:  Tanekk cc
Other:  Rand Sandblasting Projects (Pty) Ltd