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Presents a discussion of the objectives, scope, and progress of a 4-year research project on the mechanical properties of high-performance concretes with particular reference to highway applications. High-performance concrete is defined by certain requirements of strength and durability.

Soldier Field, located on Chicago's lakefront, is one of the most historically significant buildings in the city. Opened to the public in 1924, the stadium features classic Roman colonnades above the main stands on each side of the playing field. Sixty years of exposure to harsh northern climate took its toll on the reinforced concrete structure. The tread-and-riser system was deteriorating due to reinforcement corrosion and freeze-thaw exposure. Also, ground water fluctuations accelerated the deterioration of the highly permeable concrete at the base of the columns. A major rehabilitation effort was started in the early 1980s. The concrete frames were strengthened and the stands were reinforced with an overlay of latex-modified concrete. The overlay system was designed to support its own weight, the weight of the original stands, and the expected live load. The underside of the structure was repaired with shotcrete. Circularly reinforced collars were installed at the deteriorated column bases, and the existing wood pile foundations were tested to verify their capacity to support the additional dead load. The repairs are holding up very well after 10 years of service.

As the results of CEN/PC directives in 1986 and subsequent decisions, the work of CEN/TC 104 "Concrete Performance, Protection, Placing and Compliance Criteria," was extended to cover standardization work on admixtures for concrete (TC 104/WG 3) fly ash for concrete (TC 104/WG 4), mixing water for concrete (TC 104/WG 5), grouts for prestressing tendons (TC 104/WG 6), and sheaths for prestressing tendons (TC-104WC 7). In June 1989, TC 104/WG 8, protection and repair of concrete structures, was formed.

The quality of in situ concrete construction in developing countries is affected by a number of factors. These factors may include absence of national standards and codes of practice, use of approximate methods of analysis and design, substandard materials, poor construction practices, and inadequate quality control and inspection procedures. Defects and failures may occur due to these factors that may affect the useful life of a structure. This paper evaluates the seismic behavior of reinforced concrete buildings designed and constructed by following the usual procedures in Saudi Arabia. Behavior of typical reinforced concrete frames is investigated by using nonlinear time-history analysis and Takeda hysteresis model. The factors considered in the study include compressive strength of concrete, detailing of reinforcement, and size and orientation of columns in the frame. The results show that while the frames remained elastic when subjected to an earthquake of low intensity (0.09), they developed inelastic behavior exceeding the ductility capacity at some point when subjected to an earthquake of moderate intensity (0.24). It has been also found that the orientation of columns, particularly the interior ones, has a substantial effect on the building resistance to earthquakes. The compressive strength of concrete, through it has a crucial effect on the overall behavior and durability of a building, did not significantly affect the primary moment-curvature relationships of under-reinforced member sections considered in the study when its specified value was lowered by 20 percent. A critical study of reinforcement detailing shows clearly an urgent need for implementing a national code of practice for concrete buildings in Saudi Arabia.

The ultimate goal in structural design is to insure that the structure performs a set of predefined functions satisfactorily over its design life and, if possible, at a minimum life cycle cost that includes the initial construction cost. Because of the inherent random nature of most manmade and environmental loadings and strength of materials, as well as the imperfect structural analysis, the reliability-based structural design has been recognized as a rational approach to the design problem. Based on the recent developments of the reliability-based structural analysis and design the probability-based design criteria have been successfully developed for many standards. The primary objective of the study is to establish a methodology for reliability-based structural analysis and design, which is consequently utilized to develop the probability-based design criteria for reinforced concrete structures in Korea. The procedure includes studies on the probabilistic characteristics of loadings (such as dead, live, and wind loads) as well as resistances of reinforced concrete members. The safety level implied in the current practice is to be evaluated using the probabilistic models of random phenomena. Based on the results, the rational factors of loads and resistances are derived in limit state design concept.