International Concrete Abstracts Portal

This Symposiuml Publication includes 48 papers from the ACI Fifth International Confrence on Innovation in Design with Emphasis on Seismic, Wind, and Environmental Loading, Quality Control, and Innovation in Materials/ Hot-Weather Concreting, held in December 2002 in Cancun, Mexico. Topics include the behavior of flared-column bents under seismic loading, marine exposure of high-strength light-weight concrete, and seismic strengthening of a nonductile concrete frame building. Note: The individual papers are also available as .pdf downloads.. Please click on the following link to view the papers available, or call 248.848.3800 to order. SP209

When insulated concrete sandwich panels are used in the envelope of a building, the experior and interior are subjected to two different environments. The exterior concrete wythe is subjected to outside weather swings in the temperature and humidity causing thermal expansion and contraction, whereas the interior is exposed to a controlled steady room temperature environment. Dimensional change in the panel depends primarily on the height of the panel and the relative change in temperature. The severity increases when the outside concrete wythe of a tall panel is supported (and hence constrained) on the foundation dlowing vertical movements only at the top. If these weather cyclic movements are restricted, the panels may experience cracking and eventually may experience a premature failure. Therefore, the tie system used in the panels should be flexible enough to accommodate these differential movements. This often is the most critical issue in the service life of the building when sandwich panels are used. There is no standard test method available to evaluate the thermal non-uniform cyclic behavior of insulated panel systems. The authors have followed a sci- entific approach to evaluate these stresses by subjecting the ties to real life cycles occurring over a period of time. The system used in this study includes a low-conductivity polymer connector with extruded polystyrene rigid foam insulation. The testing was continued until the failure of the system or to more than 100 years of equivalent cycling (the expected service life of the building), whichever is less. This paper focuses on the methodology developed and parameters considered in developing the criteria for testing weather cycles. The procedure may be followed to evaluate any given insulated panel system to predict its long-term durability.

Numerical and experimental studies or Keactive rowaer doncrete (RPC), reinforced by short steel fibres, under biaxial tensile loading are reported. A semi-analytical model using the Eshelby’s method of inclusion to describe elastic fields perturbation is employed to predict crack nucleation under biaxial tensile strain. A criterion of crack nucleation is investigated theoretically by considering a locally oriented mass of fibres embedded in an homogeneous matrix. An original biaxial crucifonn specimen is designed and fabricated by a systematic testing program guided by the results of a numerical simulation. A prototype machine names ASTREE (developed by SCHENCWLMT) is used in the biaxial test of cruciform specimens. An adaptive control test method was designed, and digital image correlation is employed to obtain the displacement field and the microstructural stress concentration. These preliminary observations support our theoretical analysis based on Eshelby’s inclusion and aims at a better understanding of the mechanisms involved in the RPC damage process.

The behavior of liquid containing structures (LCS) subjected to seismic excitations is reviewed. The major parameters affecting the response of concrete circular tanks for LCS are discussed. Existing codes aud standards related to seismic design of LCS are reviewed. With the aid of a design example, results of the various design standards are compared. The effects of earthquake load on the behavior of reinforced concrete (RC) tanks are also investigated through a detailed example.

Cast-in-place deep foundations such as drilled shafts and piers are often subjected to two sources of problems. First, the integrity and uniformity of the cross-sectional area of these structural elements cannot be assured using normal concrete because of limited accessibility and visibility during construction. Cavities and soil encroachments leading to soil pockets can jeopardize their load-bearing capacity. Second, corrosion problems of steel reinforcement in deep foundations have been costly, requiring annual repair costs of more than $2 billion in the US alone. To address these two challenges, a novel technology for the construction of drilled shaft concrete piles is proposed in this study. Self-consolidating concrete, a material that compacts under its self-wight without vibration and without bleeding or segregation, is used to assure the structural integrity and uniformity of the cross-sectional area of deep foundations. The self-consolidating concrete is cast into FRP envelopes, which provide corrosion-resistant reinforcement. This paper presents results of a laboratory investigation on the mechanical performance of these novel piles including the effect of using expansive cement and shrinkage-reducing admixtures to enhance the FRP tube-concrete interfacial bond.