International Concrete Abstracts Portal

Current nonlinear modeling software for concrete frames typically employs line elements with plastic hinges defined at user-selected locations. While this is a simple and computationally efficient approach, a number of drawbacks limit its application. They include the challenges with defining the interacting shear and moment hinge curves, uncertainties with hinge locations and lengths, and difficulties in capturing the post-peak response. Two-dimensional continuum methods address these limitations, but their computational cost limits their applicability. This study presents an alternative modeling method, and associated computer software, with the objective of combining the simplicity of frame elements with the accuracy and result visualization capabilities of continuum methods. The method, developed in the last two decades, employs a distributed-plasticity, layered-section approach based on the Disturbed Stress Field Model (DSFM). The distributed-plasticity approach eliminates the need for defining plastic hinges while the DSFM enables capturing the shear, moment, and axial force interaction. The total-load and secant-stiffness formulation provides numerically stable solutions, even in the post-peak region. This paper presents an overview of the theoretical approach, unique aspects, and capabilities of this method. The validation studies undertaken for 148 experimental specimens, subjected to static (monotonic and cyclic) and dynamic (impact, blast, and seismic) load conditions, are also presented.

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.

Serviceability is considered a critical factor in the management of concrete bridges and structures. Typical components for evaluating the serviceability limit state include cracking, deflection, and vibration. Additionally, to ensure the adequate performance of load-bearing members, proper evaluation methodologies should be adopted. Although numerous research projects have been undertaken to examine the serviceability and performance assessment of concrete bridges and structures, significant endeavors are still required to address unexplored challenges. Of interest are the development of simplified prediction and appraisal approaches; novel techniques for quantifying stress levels; serviceability criteria under unusual distress; and the characterization of structural responses when exposed to blast, wind, and seismic loadings. This Special Publication contains 11 papers selected from technical sessions held in the ACI Fall Convention in November 2024. The Editors wish to thank all contributing authors and anonymous reviewers for their rigorous efforts. The Editors also gratefully acknowledge Ms. Barbara Coleman at ACI for her knowledgeable guidance. Yail J. Kim, University of Colorado Denver, Editor Hyeon-Jong Hwang, Konkuk University, Editor

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.

All new parking structures in California are required to be wired for photovoltaic installations, resulting in conduit requirements that are excessive for some slabs. These conditions can seriously impair the structural load path and create an unanticipated structural hazard. The California State University (CSU) system’s Seismic Review Board developed interim conduit placement requirements for CSU projects.