Practice Periodical on Structural Design and Construction

The moment magnitude scale (M_w) 6.0 South Napa earthquake caused damage to stainless steel cylindrical tanks used for wine storage and fermentation. The damage observed to the tanks included local buckling of the tank walls, anchorage failure, and damage at the top of the tanks as a result of the catwalk system. Inspections of these tanks after the South Napa earthquake provided the motivation and the basis for investigating the seismic behavior of stainless steel cylindrical tanks used for liquid storage. This investigation focused on (1) the behavior of stainless steel cylindrical tanks in previous earthquakes around the world, and (2) research performed to mitigate this damage. The damage to cylindrical steel tanks after the South Napa earthquake was found to be identical to damage documented by postearthquake reconnaissance reports from around the world. Large-scale experimental research (by other researchers) has already demonstrated the inadequacy of cylindrical tank anchorage details for the seismic risk at winery locations. Simplified elastic models developed by engineers are generally inadequate for predicting the level of stresses and seismic damage (such as local buckling) in cylindrical tanks. This paper summarizes the damage observed after earthquakes to cylindrical steel tanks used in the wine industry, and previous research performed to help mitigate the damage. The authors suggest avenues for future research and code regulation of these tanks to improve seismic performance and reduce the level of risk to wine owners.

A comprehensive method was derived for the analysis of stand-off anchor bolt connections with various stand-off distances that are subjected to lateral loading. The procedure applied the load-distribution method that is commonly used for shear wall analysis in buildings, and the base plate was treated as a rigid diaphragm. The lateral load resistance provided by each anchor bolt within the anchor bolt group was calculated on the basis of its lateral stiffness, which was defined as a function of the stand-off distance. Close agreement with finite-element analysis solutions for various stand-off distance conditions was found. An irregular distribution of lateral resistive forces within the anchor bolt group was found for connections with uneven stand-off distances compared to the uniform distribution found for connections with even stand-off distances. The intensity of lateral resistive forces provided by the anchor bolts was found to be impacted by the proximity of the individual anchor bolt to the center of rigidity of the connection and the eccentricity of the center of rigidity to the centroid of the anchor bolt group.

Cylindrical water tanks that rest on the ground are commonly employed in water-supply schemes. It is preferred to rest the tank on uniform strata; however, sometimes water tanks need to be rested on strata with varying stiffness. Design professionals generally use coefficients provided by authorities to arrive at hoop forces and bending moments in the wall by considering the base as either hinged or fixed. This paper presents the results of a study of the behavior of cylindrical water tanks resting on nonuniform strata. Marked difference in forces and wall behavior from those noted by authorities were observed. The paper highlights special considerations for the effective performance of such structures in actual field conditions.

With the continuing development of displacement-based and performance-based seismic design principles in the bridge engineering community comes the need to address issues that have historically been omitted from, or else treated in a vague manner within, bridge design specifications. It is likely that future design provisions will lead engineers to conduct more refined analyses compared to those currently adopted in some cases. This paper discusses four areas in the prediction of inelastic behavior in bridges, two on the capacity side and two on the demand side. On the capacity side, (1) choice of element type, force based or displacement based, and (2) effects from geometric nonlinearities are discussed. On the demand side, (1) differences between building design spectra and bridge design spectra are discussed, and (2) issues related to viscous damping levels adopted for nonlinear analysis are brought to the attention of practicing engineers.

Concrete gravity dams are more likely to experience severe cracking during large earthquakes because concrete is quasi-brittle in nature. Thus, the prevention of concrete cracking in the dam and its successful rehabilitation are among the important issues for the engineering community. This paper investigates the suitability of a retrofitting technique, which can be used for the rehabilitation of severely damaged concrete gravity dams. The retrofitting technique adopted in this study is composed of epoxy grouting and uses anchorage bolts and external buttress wall application. A comparison is made between cyclic behavior of small-scale concrete gravity dam models before and after retrofitting to quantify the effectiveness of the retrofitting technique. Cyclic behavior of concrete gravity dam models is obtained through experimental testing, which is also verified through the finite-element model simulation. The study shows that the strength and postyield behavior of the retrofitted concrete gravity dam model is significantly improved.

Criteria for designing foundations for vibrating equipment come from published standards, recommended practices, internal company standards, and manufacturer requirements. The criteria from one source to another can vary significantly by including or omitting specific design recommendations or by providing different values for prescribed limitations. A comparison of amplitude criteria and several discussions of different practices and approaches can be found in ACI 351.3R, Foundations for Dynamic Equipment. With an update of the American Concrete Institute (ACI) report in progress, this paper provides updated comparative data between selected currently published and company specifications. Criterion topics include when a dynamic analysis is required, machine vibration limits, human vibration limits, resonant frequency range, geotechnical impedance calculation methods, and foundation sizing criteria. In addition, the background and merits of specific criteria are discussed in the paper to provide some insights on the development of criteria. The information herein provides a frame of reference for what design criteria are considered industry standard. Permissible amplitude figures are provided for users to compare with their proposed project specifications. Several recommendations for the development of project specifications are included.

This paper describes the challenges and solutions for the design and implementation of a timber structure to replace a collapsed steel structure. Wood was chosen as the structure material because it is suited for environments with high salinity and, in this context, for reducing maintenance costs. One of the most important challenges of this project was that the beam should have a long span and the wood should be able to attain the ultimate limit state and serviceability given the dimensions in the project. The entire roof was supported only by four columns, which forced the side and frontal beams to exceed span lengths of 18 m without intermediate supports. A mathematical computational model was constructed using the FEM to obtain the loads on the structural elements. During the implementation process, many parts were implemented differently from the original design, which needed to be reinforced. It is important to emphasize that the design of a wooden structure requires not only knowledge but also creativity to overcome the challenges posed by the distinctive needs of detailing and difficulty that carpenters have in reading the specific plans.