Practice Periodical on Structural Design and Construction

There have been several new approaches and advances in sensing technologies for monitoring long-term durability of the infrastructure. With the use of new materials (such as fiber reinforced polymers, stainless steel and stainless clad rebar, etc.), identifying factors affecting and accelerating the growth of corrosion in highway bridges through monitoring has received significant attention. This paper presents a review of available systems for such purposes and case studies based on their field applications.

Restoration of cast and wrought iron bridges is not covered in civil engineering curriculum and engineers have been called upon, or volunteered, to restore these structures with little or no methodology in print to guide them in their work. The writer has restored many of these bridges as pedestrian bridges, published his work in ASCE journals and made presentations at local, regional, national, and international meetings describing methods he used. A brief history of the development of cast and wrought iron bridges in the United States from 1840 to 1890 is presented. The paper discusses properties of cast and wrought iron, methods of replacing in kind or rehabilitating bridge members using casting/riveting/bolting/welding methods, dismantling or removal intact, transportation and rebuilding the structures on new sites. It concludes with images of several bridges restored by the writer.

Wood shear wall performance is affected by the materials used for construction including the sheathing fasteners. The model building codes permit different fasteners for sheathing attachment in terms of diameter and length. In general, the nail head geometry is designated in the fastener schedule footnotes by terminology, such as “common,” “sinker,” “casing,” or “finish.” Power-driven nails are collated and the heads are formed to facilitate collation, so the heads may be flat and round with full round geometries or the flat round head may be clipped or notched. The European Yield Limit equations of the National Design Specification assume a smooth round dowel with no head, which leaves the engineering community without a rational basis for specification of head geometry requirements for shear wall construction. To address this issue, three types of nails distinguished by different head geometries were used in shear wall tests to investigate the potential effects of sheathing nail head geometry on shear wall performance. The head geometries were full-round heads (FRH), clipped heads (CLP), and casing heads (CSE), but the nails were otherwise the same. The head-area ratios for these fasteners were 0.83, 0.74, and 0.55 for the FRH, CLP, and CSE nails, respectively. These were used to fabricate shear walls sheathed one side with plywood (height/length ratio=2.0) that were tested using the sequential phase displacement method of fully-reversed cyclic testing. Shear walls with the FRH nails and the CLP nails had the same nominal strength while the CSE nails had a nominal strength that was 78% of the nominal strength of the shear walls with FRH nails. The elastic stiffness’ of shear walls were not statistically different when the source of variation was sheathing-nail head geometry. The test performance was compared to nominal strength calculated from published design values. The walls with FRH and CLP exceeded the expected nominal shear while shear walls with CSE nails underperformed the design value. Nails with FRH and CLP heads cannot be distinguished in performance and are interchangeable for design and construction. Even though CSE nails produce shear walls with the same elastic stiffness, they cause shear capacity to be less than that of walls built with FRH and CLP nails and about 8% less than allowable shear design.

A building constitutes an integrated collection of systems that together provide a controlled environment for its occupants. And as such, in addition to the frames and foundations, such components as fire protection, mechanical, electrical, and plumbing (MEP) engineered subsystems are also a vital part of any building. Considering the variety of subsystems that make up of a building, an overall design and construction process would then require a proper planning for integration of these various subsystems into the building. Furthermore, system integration has also long been recognized as the key to an effective and efficient building operation. The integration process of a fire protection subsystem, along with MEP subsystems, within a building is quite challenging indeed and can have a profound impact on client satisfaction. This process becomes especially critical when one considers the integration of technology into the building, including the possibility for future changes in technology and plan for their incorporation at a later time. The objective of this paper is to provide a discussion on the integration of safety and fire protection and several MEP systems into buildings in an effort to achieve the most efficient, economical, and environment friendly design. Specifically, the paper presents an approach that considers technical knowledge, available through codes and standards, as well as one’s experience and professional judgment.

The paper presents a simple procedure for the optimum design of a pipeline block anchor. The forces exerted by the soil on the block are computed using Rankine’s theory. The dimensioning of the block anchor is formulated as an optimization problem in which the objective function is the volume of the block to be minimized. The optimization constraints are related to block sliding, block overturning, and soil bearing capacity. The optimization problem is solved using Excel. Several examples are given to illustrate the steps of the design procedure. Simple relationships between the thrust force and the minimum required block dimensions are generated.

This article is an evaluation of bridge collapse causes in Colombia, based on the study of 63 real cases of reported failures since 1986. Through the analysis of each failure case, the main causes of total or partial collapse of the bridge structures were identified and studied. The 36% of the cases studied corresponds to steel structures that failed mainly because of structural deficiencies; and the remaining 64% corresponds to concrete bridges that collapsed mainly because of scour effect and overloads. These causes of collapse are attributed to design deficiencies. Thus to remove the deficiencies, it is recommended to conduct a rigorous program of bridge investigation along with a strengthening technique that would be specific to a given bridge type. The investigation would specifically include an evaluation of various types of deficiency in steel structures and issues related to inadequate reinforcement and scour in concrete members.

With all serious and fatal accidents occurring every year in excavation and trench work worldwide, governmental authorities recognize the dangerous nature of excavation and trench work. Regulations have been written containing a series of measures to be followed in order to protect workers in excavation and trench work. This paper sums up a review of regulations and guides in excavation and trench work of several countries. All involve a soil classification based on the description of the soils and the hydraulic conditions and the adoption of safe slopes based on the classification, while, in its current version, the Québec Safety Code for the Construction Industry (S-2.1, r.6) does not mention this important information. Thus, there is a need to update section 3.15.3 of S-2.1, r.6. Since a proposal for soil classification, taking into account the impact of the soft sensitive clay in Québec was not accepted by the review committee of S-2.1, r.6 in 1989, a research project will be submitted soon for funding to review section 3.15.3 of S-2.1, r.6.

An investigation of the stability of the roof of an 85-ft diameter cylindrical prestressed concrete wastewater treatment tank is presented. The roof of the tank is a very thick, shallow spherical dome. With a 1/16 rise to span ratio, 2 ft thickness, and an 18 ft diameter central opening at its pole, the dome falls outside the range of parameters for which the thickness design equation for domes in the ACI 350 code applies. The shallowness parameter of the dome is in the range where axisymmetric snap-through buckling can be expected. A finite-element model was used to compute the nonlinear axisymmetric deflection of the dome up to its limit point, the snap-through to its inverted configuration, and the post snap-through load deflection. Bifurcation from the symmetric deformation to a nonsymmetric buckling mode below the limit point was investigated with a different finite-element model than was used for the evaluation of the snap-through. The finite-element results are compared to a form of the design equation for dome thickness in ACI 350. The dome thickness equation in ACI 350 was used to calculate dome load capacity, given the thickness, and was found to be significantly higher than the capacity computed with the finite-element model.

This paper presents an equation to calculate the biaxial bending stresses in an unsymmetrical beam composed of elements with different modulus of elasticity values.

For the decking of dwellings a new light gauge cold-formed steel channel profile has been developed and applied. It is cold formed from steel sheet. Its design is based on AISI in 1983. Buckling and conditions at the supports are analyzed. Application to a one-family house is shown. Advantages and drawbacks are considered.

Formwork is a major contributor to profitability—or the lack of it—on most large and complex concrete jobs. Furthermore, formwork has major consequences for the project schedule, as well as all related trades, such as ironworkers and cement finishers. Consequently, selecting a formwork system and planning its field operations must consider the effects of the system on the overall project. However, due to competitive pressures and limited recourses, contractors seldom have the time to think through the construction phase specifics, and enter bids with carryover estimates adjusted for inflation. This may result in significant difficulties in meeting the project requirements. The paper illustrates the complexities involved in the selection and deployment of a formwork system through a study of the concrete formwork selection on the Bird Island Flats Tunnel project. This $290 million project was a part of the Central Artery/Tunnel project in Boston, Massachusetts. Because the conventional shoring methods could not produce the output needed to meet the project schedule and budget, the contractor solicited proposals from formwork manufacturers and chose the system from CONESCO Industries. This study has two objectives: first to identify the issues involved in the selection and sequencing of a custom-made formwork system and second to formulate a detailed analysis method to improve decision-making. The study shows that the planning of the formwork method involves two important decisions: First, the selection of a formwork system, and second the decisions regarding the sequencing and quantities of the formwork to be used on the project. The study presents the quantity/cost analysis for selecting a formwork system, and then illustrates the value of simulation in optimizing the sequencing scheme for the formwork operations. The study shows that indirect project cost plays an important role in the overall analysis, and that selection and sequencing of a formwork system can be improved using a time-cost trade-off technique.

Corrugated steel sheets are used extensively in construction. They are often bolted together in lap joints for quick and easy assemblage. These structures are built to form different shapes, such as underground curved conduits of medium and short-span bridges. Due to stress concentration around the bolt holes and reversal of loading, the bolted lap joints in such structures become susceptible to considerable reduction in the fatigue resistance of the metal. Such reduction in the fatigue resistance has not been accounted for in current codes of practice. In this technical note, the effects of bolt arrangement, steel sheet thickness and initial bolt misalignments on the fatigue resistance of bolted joints are investigated. As a result of the study, design expressions are recommended for the design of bolted lap joints under cyclic loading.