Issue 8

All articles published in the August 2012 issue.

The Awa Shirasagi Ohashi Bridge, which includes novel structural systems, was recently constructed in Tokushima, Japan (Figure 1). There were a number of severe design constraints for the project. The bridge is located in a very environmentally sensitive area. The site is also in a seismic region and is frequently struck by typhoons. Furthermore, the bridge was to be founded on soft alluvium, and to be constructed to a tight budget. These exceptionally challenging constraints led engineers to adopt a novel combination of structural forms, including the ‘cable egret’ cable truss system, an improved form of the permanent tubular steel pile cofferdam foundation and a steel- concrete composite sandwich slab deck.

This article reminds engineers of the hazard of Legionnaires' disease and its associated risks following an outbreak in 2012.

"Once is happenstance" Alastair Soane highlights the importance of identifying failure trends in order to help prevent future disasters.

In many cases, reinforced concrete drawings are more diagrammatic than their general arrangement counterparts and carry with them their own unique set of rules and nomenclature. This note does not cover the rules governing detailing of reinforced concrete. 

This note is split into two sections; the first contains information a designer of steel elements provides, while the second contains information a fabricator creates in order to manufacture and construct the steel structure. 

This paper looks at the possibility of using cross-laminated timber (CLT) construction to support commercial buildings to 30 levels. A prototype building structure is proposed and analysed using an elastic analysis program. The main structural elements, including a central tube core, columns and beams, are made of cross-laminated timber. The CLT panels are arranged to ensure structural efficiency with minimal material wastage. The CLT central core is assisted by steel stays (like those of a yacht), and reiforced concrete beams which act like wine barrel hoops. Consideration is given to the design of simple but stiff joints. The structural elements are examined for strength and the building deflections are noted. The paper concludes that the proposed structural system with CLT elements is likely to be suitable for buildings to 30 levels.

There are still hundreds of high-rise large panel system (LPS) dwelling blocks in the UK. These generally contain flats, but in some cases the accommodation is in the form of maisonettes or another multi-level arrangement. Block owners have a continual responsibility for their safety, which requires periodic inspection and structural assessment. The UK requirements for this particular class of building stem from the 1968 collapse of the southeast corner of Ronan Point, a 22 storey LPS dwelling block. LPS dwelling blocks are basically gravity structures, as are traditional masonry constructed buildings. Typically they comprise precast reinforced concrete floor and roof components spanning onto storey high structural precast (generally plain) concrete wall panels. Vertical loads are carried to the ground through the structural wall panels, which also provide stability against lateral loads. Historically the guidance used for the structural assessment of LPS dwelling blocks for accidental loads has been the Ministry of Housing and Local Government (MHLG) Circulars 62/68 and 71/68, which were produced shortly after the Ronan Point incident. MHLG Circulars 62/68 and 71/68 together with various other related guidance from that era, were never withdrawn and notionally remain in force today. However, the guidance has been rendered out-dated by subsequent developments. This paper provides an overview of updated technical evaluation criteria and the associated guidance for undertaking a structural assessment of an LPS dwelling block for accidental loads.

The oldest of the Institution’s international Regional Groups highlights its involvement with the National Building Regulations amongst its other activities The South Africa Branch (now Regional Group) of the Institution of Structural Engineers became the first to be established outside the UK, in 1937. Subsequently it was merged into a joint initiative between the Institution and the South African Institution of Civil Engineers, becoming the Joint Structural Division (JSD). This Division currently represents some 1345 members in South Africa and is becoming the natural home to members in the Southern African Region. At present there are members of all Institution grades located within the region and the JSD provides a vital linkage between international and local organisations. Having reinvigorated the committee we are gaining traction in many areas and now looking forward to supporting a significant number of candidates seeking to participate in the Institution’s examinations. The focus with the restructuring of the committees is to increase the benefit that this grouping can deliver to its members and to generally uplift the standard of engineering within the region. This approach is aimed initially at universities and student membership but, via the codes of practice and continuous professional development, also assisting the profession and Chartered members alike.