International Concrete Abstracts Portal

The Horsetail Creek Bridge (HCB), constructed in 1912, is located along the Historic Columbia River Highway in Oregon. The cross beams of this historic structure were found to be 50 percent deficient in flexure and 94 percent deficient in shear, mainly due to the traffic loads increase. Analysis of the alternative designs indicated that glass FRP (GFRP) laminates would be most suitable for shear strengthening, while carbon FRP (CFRP) laminates would be best for flexural capacity enhancement. Concurrently, four full size beams, as similar as possible to the actual bridge beams, were constructed to simulate the retrofit of the bridge. One of the beams served as a control; one beam was strengthened for shear capacity increase only; one beam was reinforced with CFRP for flexure; and one beam was reinforced with CFRP for flexure and GFRP for shear. Results revealed that addition of either GFRP or CFRP composites strengthening provided static capacity increase of 45 percent compared to the control beam. The beam strengthened with CFRP for flexure and GFRP for shear, which simulated the HCB cross beams after the retrofit, exhibited nearly 100 percent of moment capacity increase. Post cracking stiffness of all beams was increased, primarily due to the flexural CFRP laminates. Results suggested that capacity of the experimental beam, retrofitted in the same fashion as the bridge, should exceed the bridge design load of 720 kN-m (after strengthening), sustaining up to 868 kN-m of applied moment. The addition of GFRP for shear alone was sufficient to offset the lack of steel stirrups in the actual bridge, allowing for a conventionally reinforced concrete beam with significant shear deficiency to fail by yielding of the tension steel. The ultimate deflections of the shear GFRP reinforced beam were nearly twice those of the control shear-deficient beam. The experimental beam retrofitted with only CFRP for flexure failed as a result of diagonal tension cracking at a load 45% greater than the control beam. A design method for flexure and shear was proposed before the onset of this experimental study and used on the HCB. The design procedure for flexure was refined and allowed for predicting the response of the beam at any applied moment. The flexural design procedure includes provisions for non-crushing failure modes, and was shown to be slightly conservative using the design material properties.

The 215 Fremont Street building in San Fransico, California was designed by Albert F. Roller Architect, San Fransico, and built in 1927. It was a 7-story reinforced concrete structure, "L"-shaped in plan, with a 3 story tower located over the elevator core. The structure is supported on individual spread footings at the interior columns and continuous grade beams at the building perimeter. Damaged extensively in the 1989 Loma Prieta Earthquake, the building was declared unsafe. It remained unoccupied utnil 1999, when the property was sold "as is" to a new developer (Fremont Properties LLC). The developer embarked on a seismic retrofit of the existing building and the addition of two new floors, all on a build-to-suit basis for a single tenant (Charles Schwab Inc.). This paper will dexcribe in detail the evaluation of the existing building, analysis and design of the retrofit scheme, including the foundation, which meets the 1997 Uniform Building Code.

This paper deals with the measurement of physical properties (mechanical, thermal, acoustical) of various formulations of concrete containing vegetable particles. Such material is mde up with hemp shives mixed with lime binders. Shives are very porous and so liglitweight. Thus, this concrete presents a high porosity related to the microscopic porosity of the shives and the macroscopic porosity due to the arrangement of particles. Moreover, this material presents a ductile behavior and can bears high strain without been destroyed. Depending on the binder proportion, the mechanical properties of vegetable concrete cover a wide range: maximum stress in between 0.4 and 1.2 MPa, Young madulus in between 20 and 90 MPa, strain at maximum stress in between 4 and 10%. The thermal conductivity ranges from 0.06 to 0.11 W.m-1.K-1, sound absorption between 0.5 and 1. The final aim of this study is to optimize the formulation of vegetable concrete according to its use (wall, floor, roof. . .). A theoretical model made with self-consistent method allows to calculate precisely the coefficient of conductivity l as a function of the mixture proportion and the compactness level. A comparison with experimental measurements shows a good accuracy of the results.

Recycled aggregates used in combination with high-volume fly ash is an example of sustainable construction material because it represents a judicious use of resources by recycling by-products, that results in a lower environmental impact through reduced carbon dioxide emissions and reduced natural aggregate extraction from quarries. Furthermore, the related concrete mixtuns yield satisfactory mechanical performance. The goal of the experimental work reported here was to investigate the effect of recycled aggregate andor fly ash on carbonation and chloride penetration depth, as well as the effect on corrosion behavior of either bare or galvanized steel in cracked reinforced concrete. The concrete mixture contained equal amounts of fly ash and cement. The results show that the introduction of the sustainability concept in concre&e trechnology by using recycled aggregate andor fly ash did not cause any deleterious effects on durability of reinforced concrete specimens in terms of both chloride and carbon dioxide penetration, and reinforcement corrosion in cracked concrete.

Completion of the Central A r t e r y b e l Project inchdes development of more that 20 distinct parcels along the original, elevated artery corridor. This paper presents challenges encountered during the design of Parcel 6, which is located between New Chardon and Sudbury Streets in Boston, Massachusetts. The Parcel 6 lid will cover five adjacent cast-in-place concrete boat section ramps. The final use of the lid is not yet known; however, since construction of the ramps is currently underway, the walls were re-designed to accommodate either a landscaped deck, or a five-story building. Design included both wind and seismic lateral analyses of the two types of potential lid structures, with the reinforcing in the ramp walls modified to accommodate both options in order to minimize impacts or retrofits requkd in the future. Changes to the original design included modifying wall heights and reinforcing, and inclusion of interim backwalls for temporary earth support. The landscaped option included preliminary designs of four separate deck structures, skewed portal beams, overhead impact attenuators, and a merge gore area. The building option presumed asymmetrical column loadings and locations, with a comparative analysis of column base shears used to determine maximum loading on the existing ramp walls.