International Concrete Abstracts Portal

Professor Dennis Mertz passed away after a prolonged battle with cancer. He spent a large portion of his professional career working on advancing of the state-of-the-art of bridge engineering. He was a great friend and colleague to many at ACI and ASCE. Joint ACI-ASCE Committee 343, joined with ACI Committees 342 and 348, sponsored four sessions to honor his contributions and achievements in concrete bridge design and evaluation. These sessions highlighted the important work and collaborative efforts that Dr. Mertz had with others at ACI and ASCE on various topics. These sessions also combined the efforts among ACI and ASCE researchers and practitioners in addressing various topics related to the design and evaluation of concrete bridges. The scope and outcome of the sessions are relevant to ACI’s mission. They raise awareness on established design methodologies applied for various limit states covering topics related flexure, shear, fatigue, torsion, etc. They address problems related to emerging design and evaluation approaches and recent development in design practices, code standards, and related applications. The Symposium Publication (SP) is expected to be an important reference in relation to design philosophies and evaluation methods of new and existing concrete bridges and structures.

Dr. Dennis Mertz was involved with the AASHTO LRFD Bridge Design Specifications [1] for 30 years. Starting with the original development of the specifications and continuing with maintenance and related course development and presentations. His last major contribution to the Specifications was to serve as Principal Investigator for the reorganization of Section 5, Concrete Structures. This presentation summarizes the changes to the structure of the Section including the increased emphasis on design of “B” and “D” regions of flexural members and introduces new and expanded material on beam ledges and inverted T-caps, shear and torsion, anchors, strut and tie modeling and durability. The product of this work was included in the 8th Edition of the Specifications as a complete replacement of Section 5.

This paper presents a numerical study of novel configurations in reinforced concrete wall systems that exhibit large structural ductility and increased post-ultimate strength, leading to potentially better performing structures under large and sustained loads. A Gravity-Based Structure (GBS) under extreme ice loading is used as use-case to investigate various scenarios to increase post-ultimate ductility. It is shown that the largest increase in the out-of-plane toughness of the exterior reinforced concrete walls is gained using post-tensioned tendons and mild “core” steel placed at the center of the exterior wall cross section. These structural features show promise in improving the global post-ultimate behavior, which would make them desirable to use in structures that are deployed in locations where extreme ice feature impacts pose a foreseeable risk and where designing the structure to remain elastic under ice impact may not be economically feasible. Lessons-learned from the GBS evaluation can also be applied to various reinforced concrete structures.

Existing road infrastructure and bridges gradually carry increasing in weight and number vehicular traffic. The objective of this study is to assess adequacy of a 100-year-old reinforced concrete framed bridge in Alabama expressed as reliability index. Geometric data about the structure was obtained using destructive and nondestructive testing methods. Material data was collected from field tests and available literature on evaluation of existing structures. Behavior of the structure was investigated during load tests performed. The most harmful load configuration for the particular bridge was established in a recent study on weigh-in-motion data for the State of Alabama. Using finite element numerical method, a three dimensional model of the bridge was developed, calibrated and used for reliability study. The statistical parameters of resistance of the bridge were obtained using Rosenblueth 2k+1 method. The reliability analysis was demonstrated on the one span structural system.

With over 80 years of history, it is only in the last 20 years that the use of fiber reinforced polymer (FRP) materials has become feasible for bridge applications in part due to the ever increasing requirement to make structures last longer, with the current American Association of State Highway Transportation Officials (AASHTO) Load and Resistance Factor Design (LRFD) Bridge Design Specifications requiring that structures be designed for a 75 year design life; but also in the development of cost effective production techniques, and the introduction of FRP materials, which bring the cost and strength of FRP materials closer to traditional steel reinforcement. Published documents provide comprehensive recommendations on design methodology, predictive equations, and recommendations for strength and service limits states. In this paper, the background of FRP-prestressed concrete bridges is discussed and trial bridges are designed. Research needs to advance the state of the art are identified and delineated.