Practice Periodical on Structural Design and Construction

While many arches were built with wood in the early nineteenth century, the availability of cast and wrought iron and later steel led to a proliferation of metal arch bridges after the Civil War. Cast iron was used in 1839 with the Richard Delafield’s Dunlap’s Creek Bridge, 80 ft span, and the 1858 Rock Creek Bridge, 200 ft span, by Montgomery Meigs. By the end of the century, steel arches were built with spans of 840 ft.

Movable bridges were built for centuries with wood, iron, and steel. The earliest drawbridges of short span were followed by swing bridges. In the United States, swing bridges were originally built across canals such as the Erie and the Chesapeake and Ohio (C & O) with wood and iron. Starting around the Civil War, longer span swing bridges were built across the major rivers of the country. This paper, largely a pictorial history, traces the development of the swing bridge between 1797 and 1907. After 1907 few bascule swing bridges were built, and vertical lift bridges generally replaced them.

Modern society is demanding that the use of energy associated with construction and operation of structures be investigated during the planning and design phases. The engineering community has been striving to design more sustainable buildings in an attempt to reduce both raw material requirements and energy use during all phases of design. Structural engineers currently have very limited guidance on how to incorporate sustainability concepts in their designs. Innovative methods are needed to address the environmental impact, energy use, and other sustainability issues faced during planning and design of buildings. This paper investigates and discusses five sustainable structural design methodologies: Minimizing Material Use, Minimizing Material Production Energy, Minimizing Embodied Energy, Life-Cycle Analysis/Inventory/Assessment, and Maximizing Structural System Reuse. The goal of this paper is to describe and address issues associated with the proposed design methodologies to determine which, if any, can produce the most sustainable structural designs. It was determined that no single methodology can address all the issues surrounding sustainable structural design. Also, it was determined that combinations of two or more methodologies may increase the ability of design professionals to produce more sustainable designs.

Live-load distribution is an important step in the analysis of bridge superstructures. This paper introduces a new framework to compute live-load distribution for bridge girders. The model uses elastic spring elements to simulate the reaction of main girders to the deck system. The cross-section frame of the superstructure is supported by these elastic springs. Live-load distribution factors are derived according to the maximum reaction of each spring element under random truck loads. Results from the proposed model are compared with those from bridge-design specifications. Engineering practice shows that this model is easy to use and provides results comparable with current design standards. The significance of this framework is that it can be used to compute live-load distribution without limits to parameters such as girder space, span length, and truck-wheel space. This research will provide a convenient tool for engineers to perform bridge design or for researchers to compare research results from other methods.

Approaches are discussed for addressing concerns regarding the effects of construction-related vibrations on sensitive instrumentation and activities. The availability of related vibration criteria is noted, the limitations of available criteria are explored, and difficulties in meeting some of the vibration limits are indicated. Approaches to enabling construction to proceed with minimal interference with sensitive equipment and procedures are described.

A representative volume element (RVE)–based modeling procedure, macromechanical modeling, is presented for the homogenization of orthotropic bridge superstructures. The purpose of the models is the simplification of the complex deck structures for three-dimensional (3D) load-response analyses. A numerical example for the application of the model to a prototype bridge superstructure analysis is presented. The macromechanical model was validated by performing static patch load analysis and comparing results with 3D finite element (FE) analysis results. Continuation of this work will include the development of RVEs and associated stiffness matrices of commonly used orthotropic bridge superstructures. By using these stiffness matrices in conjunction with ordinary structural analysis programs, 3D simplified models can be developed for calculating load demands.

This paper presents a rehabilitation project concerning the settlement of a 35-year-old building. The foundation system of the northwest wing of the building consists of strip footings and slab on grade. Differential settlement results in significant cracking of the masonry partition walls located on the footing, and hence rehabilitation of the footing is required to stabilize the foundation system. Geotechnical and structural investigations are conducted, including site borings and analytical modeling on the basis of one-dimensional consolidation theory that is incorporated into a finite-element analysis. The predictive model exhibits that the differential settlement does not cause noticeable distress for the primary structural members, whereas the continued settlement affects use of the building. Site implementation is performed with the push-pile method to terminate the continuous settlement of the foundation.