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The current ACI Building Code (ACI 318-99) procedure for the shear design of pile caps is the same approach used for two-way slabs. The procedure involves determining a section thickness such that the concrete shear stress (@,) is greater than the applied shear stress (vu) on the critical section. For footings supported on piles, the ACI Code recognizes that these general provisions are not applicable as the depth of the footing increases and some of the pile loads fall within the critical section. In deep pile caps, the critical section may even be located outside the footing, making it impossible to investigate shear at d or dn. For these situations, the ACI Commentary states that the designer should examine shear strength at the face of the column and it refers to procedures outlined in the CRSI Handbook (1996). ACI has recently published proposed revisions for the ACI 318-02 Code, which promotes the use of strut-and-tie models as an alternative to the existing ACI and CRSI procedures. The design methodology involves limiting the concrete stresses in the compression struts and nodal zones to insure that the tension tie (longitudinal reinforcement) yields before significant diagonal cracking develops in the compression struts or crushing in the nodal zones. This paper explains the existing ACI and CRSI procedures and the proposed ACI provisions for strut-and-tie design.

Reinforced concrete structures constructed in coastal zones have constantly been threatened by environmental damaging elements. The chloride ion is known as one of the most aggressive of these elements, causing, among other damages, corrosion of the steel reinforcement and degradation of concrete. The goal of this work was to determinate the influence of the cement type and cement content, as well as the concrete cover thickness, in the resistance and durability of reinforced concrete elements exposed to aging in a 3.4% sodium chloride aqueous solution. Many concrete mixtures were made using CPII-F32 (with filler), CPII-Z 32 (pozzolanic mixture) and CPV-ARI RS (sulfur resistance) portland cements, with contents of about 290 and 350 kg/m3 (490 and 590 lb/yd3), and with the concrete cover thicknesses of 10, 15, 25 and 30 mm (0.394, 0.591, 0.984 and 1.18 in). The evaluation of the concrete behavior was taken from the results of physical and mechanical tests of cylindrical concrete samples and electrochemical tests-mainly the electrochemical impedance spectroscopy (EIS)-of small prismatic reinforcedconcrete samples. The results are presented for each combination of cement type and content, in terms of the aging time. Half cell potential measurements show that concretes made with CPV-ARI RS cement presented the best results, with longer periods necessary to produce electrical change in the samples. The concrete made with CPII-Z 32 cement and cement content of 288 kg/m3 (485 lb/yd3) was the mixture with the worst durability, with some samples showing fracture after 110 days of aging.

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.

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.