Structural Concrete, Vol. 3, no. 3, December 2002

Written on 19 August 2011.

Boston's Central Artery/Tunnel project and its interchanges

Vijay Chandra, Parsons Brinckerhoff Quade and Douglas, Inc.
Anthony L. Ricci, Massachusetts Turnpike Authority
Hany Riad, Parsons Brinckerhoff Quade and Douglas, Inc.
Jonathan Hren, Parsons Brinckerhoff Quade and Douglas, Inc.

Boston's Central Artery/Tunnel project is the largest infrastructure undertaking ever attempted at a single US location. It involves reconstructing Interstate 93 (I-93) by depressing it into a tunnel and subsequently removing the original elevated highway (known as the 'Central Artery'). The new I-93 will emerge from the tunnel near the south bank of the Charles River and rise to cross the river on a cable-stayed bridge. This structure, unique in the world, will be both longitudinally and transversely asymmetrical. The second phase of the project extends the Massachusetts Turnpike (I-90) through South Boston and under Boston Harbour to Logan International Airport. This paper reports on the current status of the project and its many interchanges.

Structural Concrete, Vol. 3, no. 3, December 2002

Written on 19 August 2011.

Central Artery/Tunnel project: innovative use of precast segmental technology

Paul J. Towell, Parsons Brinckerhoff Quade and Douglas, Inc.
Vijay Chandra, Parsons Brinckerhoff Quade and Douglas, Inc.
Peter A. Mainville, Parsons Brinckerhoff Quade and Douglas, Inc.
Elie Homsi, Rizzani de Eccher

The first part of this series of articles on Boston's Central Artery/Tunnel project presented an overview of the scope of the work and the many interchanges that form the hubs of the project. This second paper describes the innovative use of precast segments, as well as other construction techniques, on two major interchanges.

Structural Concrete, Vol. 3, no. 3, September 2002

Written on 19 August 2011.

Advances in precast concrete in mixed construction

K. S. Elliott, University of Nottingham

Mixed construction is now being used in the majority of new multi-storey buildings, once the traditional domain of cast-in-situ concrete and structural steelwork. Mixed precast construction means the combined use of precast concrete with steelwork, timber, cast-in-situ concrete and masonry. The combination is made for the benefit of the building process at large and does not necessarily have to be designed and constructed compositely. Mixed construction maximises the structural and architectural advantages in combining components made of different materials, but it requires the cooperation of the architect, structural designer, services engineer, manufacturer, supplier and contractor. It is possible that some client and architectural demands can only be satisfied using mixed construction. In 2002 the fib Commission 6 on Prefabrication will publish a state-of-the-art report on the use of precast concrete in mixed construction. This paper summarises the report.

Structural Concrete, Vol. 3, no. 3, December 2002

Written on 19 August 2011.

Influence of traffic loads on permanent deflections of prestressed concrete bridges

Z. Smerda Technical University Brno, VIAPONT Ltd, Brno, Czech Republic
J. Smerda VIAPONT Ltd, Brno, Czech Republic

The rising volume of traffic on concrete road bridges has caused designers to consider the problem of permanent deflections caused by repeated traffic loading. However, it should be stated that the correct method for calculating such deflections is currently unclear and consequently gives rise to unrealistic estimations. Moreover, a lack of knowledge regarding the full spectrum of traffic loads and the effects of repeated loads upon concrete deformation exacerbate the problem. This paper attempts to determine the permanent deflection of prestressed concrete bridges without cracks.

Structural Concrete, Vol. 3, no. 3, December 2002

Written on 19 August 2011.

Minimum cost design of concrete sandwich panels made of HPC faces and PAC core: the case of in-plane loading

Catherine G. Papanicolaou, University of Patras, Greece
Thanasis C. Triantafillou, University of Patras, Greece

This paper presents a minimum cost design procedure for precast structural sandwich panels made of HPC (high-performance concrete - i.e. high-strength and fibre-reinforced) faces and a pumice aggregate concrete (PAC) core, which might also include a layer of thermal insulating material. Attention has been focused on the selection of materials' strength and members' geometrical parameters, as well as on the material cost functions for both concrete types. The strength-based design case study resides with the format of Eurocode 2 and takes into consideration failure modes associated with in-plane loading, such as flexure, shear and local buckling of the compressed faces, with respect to the presence of the insulating layer. The solution of the optimisation problem is attained through the development of a computer program using available algorithm codes provided by Matlab®. The optimisation procedure results in the derivation of design recommendations, which encompass the objective of minimum cost for the elements under investigation.

Structural Concrete, Vol. 3, no. 3, September 2002

Written on 19 August 2011.

Assessment of fire-damaged concrete using crack density measurements

Neil R. Short, Aston University, Birmingham
John A. Purkiss, Aston University, Birmingham
Sarah E. Guise, Aston University, Birmingham

Petrographic techniques have been developed to determine the nature and density of cracks that have developed after subjecting concrete to steady-state and transient heating regimes. The steady-state investigations showed that there was a good correlation between measurements of crack density and measurements of residual compressive strength. Crack density measurements taken on samples after transient heating have shown that the depth to which the compressive strength of the concrete is likely to have been significantly affected can be identified. Thus, this technique should provide very useful information for the evaluation of fire-damaged concrete.