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.

After the August 17, 2000 Kocaeli, Turkey, Earthquake (Mw = 7.4) Degenkolb Engineers sent a field reconnaissance team to observe earthquake related building damage in Turkey. Observations were made in Adapazari, which is located approximately 52 km northeast of the earthquake epicenter and 3 km directly north of the North Anatolian Fault. In Adapazari, a range building performance for the typical low-rise concrete frame residential building was observed. The building performance varied from virtually no damage to complete collapse. A four-story residential building in Adapazari that was observed to have signficant structural damage was chosen for evaluation. The building was evaluated using a Tier Three evaluation in accordance with FEMA 310, Handbook for the Seismic evaluations of Buildings - A Prestandard. As expected, the evaluation indicated the building would not meet the Life Safety Performance Objective of FEMA 310 for the 10% exceedance in 50-year earthquake. Traditionally, buildings with Life Safety deficiencies would be strengthened to comply with current building code. Rather than strengthening the building with a traditional code based upgrade, a conceptual strengthening scheme for Life Safety Performanee was developed using FEMA 356, Prestandard and Commentary for the Seismic Rehabilitation of Buildings. The strengthening scheme, which includes the addition of concrete shear walls, is presented. In addition, a comparison between the FEMA 356 lateral design force level requirements for the strengthened building and current Turkish Building Code is presented.

The finite-element method is used to carry out parametric analyses on the thermal response of simulated defects in fiber-reinforced polymer (FRP) lami- nates applied to a concrete substrate. The aim is to assess the potential for qualtitative infrared thermography in not only detecting a flaw but also being able to describe its physical characteristics. Three parametric studies are presented, namely: 1) relationship between the thermal input, the maximum signal, and the maximum surface temprature; 2) effects of flaw depth and the number of FRP layers; and 3) effect of flaw width. From these simulations, procedures are established for selecting the thermal input and estimating the flaw depth and width.

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.