International Concrete Abstracts Portal

This article describes trends observed between measures of building robustness and observations of performance collected after 15 earthquakes. It provides comparisons between countries that followed the Japanese preference for “stiff” structures and those that build less-stiff structures and discusses implications of the latest field observations in relation to the future of reinforced concrete practice.

Design of buildings to withstand wind loads necessitates meeting criteria for two limit states: serviceability under frequent loads and strength under extreme loads. Performance-based wind design (PBWD) represents the state-of-the-art approach to wind design that provides a comprehensive framework for estimating wind load, assessing structural dynamic response, and achieving safe and cost-effective design solutions. This paper presents an overview of the current design methodology and the associated challenges in addressing serviceability wind design concerns, particularly for tall buildings with reinforced concrete structural systems. Firstly, the wind actions on buildings are briefly outlined in this paper, and the limit states and criteria governing the serviceability wind design, including comfort, deformation, and strength considerations, are discussed. Additionally, the inherent connections between serviceability wind design and seismic design for tall buildings are elaborated. Subsequently, the requirements for wind hazards, structural modeling, analysis technique, damping, and stiffness modification factors are explained. Finally, a detailed examination of serviceability wind design is provided through a case study involving a reinforced concrete tall building for further insight and discussion.

During construction, the load on the slabs can be up to 2 to 3 times their self-weight, which can damage serviceability and structural safety of the slabs with early-age concrete. In the present study, an existing model to predict the load on slabs during construction was modified to account for the use of regular supports and temporary supports in the shoring system, considering construction step where temporary supports are removed. Additionally, the effective supporting area of the shore was introduced to account for the uneven distribution of shores, thereby improving the prediction of construction loads on slabs. To verify the accuracy of the modified model, loads on shores were measured at a wall-type residential building under construction in South Korea. For 2 stories, the loads on shores were measured and the measurement lasted for 45 days. The comparison between predicted and measured slab construction loads showed that the predicted construction load agreed with the measured construction load.

Modular construction has been attracting attention worldwide as a promising solution to reduce construction time and labor demand. In this study, a new inter-module composite floor system that connects the upper module floor beams and lower module ceiling beams was experimentally and analytically investigated with an emphasis on vibration performance under service loading. First, the upper module floor of 2 m [6.56 ft] wide and 6 m [19.7 ft] long was fabricated as a composite system consisting of precast concrete (PC) panels, steel beams and ultra high-performance concrete (UHPC) connectors. Structural integrity between PC panels, steel beams and UHPC connectors were secured using grouting and topping mortar. Then, the lower module ceiling beams were connected to the upper module floor beams by fully tensioned high-tension bolts (i.e., slip-critical connection) to complete the inter-module composite floor. The vibration frequencies, damping ratio, and acceleration responses of the inter-module composite floors were measured from laboratory tests such as impact hammer, heel drop and walking tests, considering the number and location of the connecting bolts as the test parameter. The vibration characteristics of the inter-module composite floors were investigated further through finite element analysis. The measured and predicted vibration performances were compared with the acceptance criteria in AISC Design Guide 11 and ISO 10137.

The containment structure of a nuclear power plant is the last barrier of defense to maintain safety in the event of a severe accident, and the integrity of the containment building is the last line of defense against the release of radioactive material. Nuclear power plant containment buildings are most commonly constructed of prestressed concrete, but there are also some constructed of steel. In the case of PS concrete containment building, in order to prepare for the increase in internal pressure in the event of a severe accident, compression force is applied using a tendon in advance to secure sufficient safety, but due to the characteristics of concrete, cracks may occur, and these cracks may become a pathway for external leakage of radioactive materials in the event of a severe accident. In addition, a number of corroded cavities and degradation of liner plates have been found in recent Korean nuclear power plants. Therefore, a study to evaluate the safety of PS concrete containment buildings began in 2022, started by the Korea Atomic Energy Research Institute, and will be conducted for eight years until 2029. The purpose of the research can be categorized into two main areas. The first is to derive the probability of failure of concrete containment buildings due to an increase in internal pressure in the event of a severe accident. The second objective is to estimate the amount of radioactive material leakage through cracks in the containment building when cracks occur. The current methods for calculating the amount of leakage are approximate and based on many assumptions, and therefore contain too much uncertainty. The results of this study will be used to determine the probability of damage to the containment building in the event of a severe accident at a nuclear power plant, and to quantitatively evaluate the amount of radioactive material leakage to the outside, thereby quantitatively evaluating the amount of external exposure. This paper describes progress to date and potential outcomes rather than highly technical results.