Practice Periodical on Structural Design and Construction

Understanding the level of fixity and ductility provided by pile to pile-cap connections is essential for the design of piles subjected to lateral loading. In this study, a series of elastic and inelastic finite-element models were developed to replicate the behaviors of both prestressed and cast-in-shell steel piles. The goal of this study was to reproduce the elastic and inelastic load-displacement behaviors observed and recorded in prior, experimental push-over tests. Understanding appropriate modeling techniques for estimating ductility, capacity, concrete-crushing behavior, and plastic-hinge location was the focus of the research. Elastic behaviors (i.e., load, displacement, and corresponding stiffness) were captured accurately in the analytical models for both the cast-in-shell and prestressed piles. Inelastic loads and displacements were closely reproduced for the prestressed piles using a nonlinear stress-strain relationship that was based on confined concrete. The steel pile models reproduced general nonlinear shape behavior but overestimated inelastic stiffness. The research demonstrates accurate nonlinear modeling for prestressed pile connections but points to the need for further analytical research on concrete-cracking behavior at the steel-to-concrete juncture for cast-in-shell steel piles.

Nowadays, evaluation of the impact resistance of structures is receiving immense attention among engineers and researchers because of the increase in accidental and/or malicious incidents around the world. Although numerous experiments and nonlinear finite-element dynamic analysis (NLFEDA) have been carried out in the past to investigate the behavior of RC structures under impact loading, such approaches may not be applicable for routine analysis. Thus, in this study, simplified analytical models, such as energy-balance and single-degree-of-freedom (SDOF) models, were developed to predict the maximum midspan deflection of a beam, and the results were compared with the results of low-velocity impact testing conducted by the author and other researchers. Maximum midspan deflection is considered to be an important performance index to evaluate the damage levels of beams when subjected to impact loadings. Therefore, this study provides efficient yet simple tools to practicing engineers for the preliminary analysis and design of RC beams under low-velocity impact prior to the use of detailed finite-element (FE) analysis and/or laboratory testing.

Serviceability requirements are considered in any building design to maintain the occupants’ comfort and protection for nonstructural elements. Specifically, floor system deflection and vibration are two important issues that need to be considered in design for serviceability. For the most part, design codes all have provisions for deflection control. However, this is not necessarily true in regard to vibration. Although the vibration in a floor system may be related to the deflection, depending on the type of floor system, specific requirements may need to be considered for vibration control, which may not necessarily be satisfied through deflection control only. In fact, depending on the level of serviceability and occupant comfort required, a detailed study focusing on floor system vibration and dynamic response may be necessary. This is to make sure that the vibration amplitude and frequency of the floor system affected are within occupants’ tolerance levels. Although some codes offer provisions for vibration control, many others do not address the issue, even though the subject has been studied relatively well and reported in the literature. This article examines and summarizes vibration control as a serviceability requirement as suggested by various codes and standards and also as reported in published papers. Specifically, the article focuses on deflection and vibration control for floor systems based on the occupancy and usage, the structural types, and sources of vibration that may be present in a building. Methods to alter existing floor system designs to control vibration are also reviewed and summarized.

Ancient Egyptian obelisks have existed for several millennia and have withstood numerous natural disasters. This study investigated the structural dynamic characteristics and the responses of several obelisks to earthquakes using a two-staged approach. The first involved a series of tests to study the mechanical properties of the Red Aswan granite of which the obelisks were made, whereas the second incorporated the test results in modeling the obelisks using finite-element software. An eigenvalue modal analysis was performed to generate the natural periods and corresponding modes of vibration of each of the structures. These natural periods were compared to the dominant periods of earthquakes to analyze the response of each obelisk to loading and its degree of resonance. Next, a time-history analysis was performed in which each obelisk was subjected to an earthquake signal. The results show that the obelisks vary in their responses to seismic loads.

Workplace hazards, when combined with demanding task, organizational factors, work environments, personal factors, and external factors can produce unacceptable safety risks to field personnel and may lead to severe workplace injuries. Workplace accidents are undesirable; they can cause physical and psychological harm to workers, their families, and the entire community at work. Along with this potential harm, workplace accidents are associated with potential negative economic and noneconomic impacts on quality of work, worker productivity, work schedule, project cost, stakeholder relations, and corporate reputation. To effectively mitigate and control workplace safety risk, a comprehensive risk-mitigation plan should be developed and implemented before workers are exposed to risk. To develop and implement an effective risk mitigation plan, the difference between hazard and risk and the transformation process that a hazard undergoes when combined with other workplace conditions before emerging as a workplace safety risk must be fully comprehended. To facilitate this comprehension, this paper describes the differences between a hazard and safety risk and provides an explanation of the potential impact of internal, external, and project- and organizational-related, factors on the magnitude of the exposed safety risk. Hazard is not synonymous with risk, although hazard severity is a major determinant of the magnitude of exposed safety risk and the safety outcome of an operation primarily relies on the level of worker exposure to the hazard. Similarly, incentives are not tantamount to rewards even though rewards are the end result of incentives. Incentives are motivations associated with future rewards, either extrinsic or intrinsic, that are contingent upon the fulfillment of future conditions determined ahead of time before the start of work operations. The paper is expected to: (1) benefit field practitioners by helping them to increase their understanding of the transformation of a hazard into acceptable or unacceptable safety risk; and (2) provide a summary of the different types of behavioral approaches (e.g., safety incentive programs) that employers can implement to enhance workplace safety and work quality.

This article compares the current estimated debris line-load value of 6.78 kN/m (5 kips/ft) on Tainter gates within engineering manuals and technical letters to recent research findings on impact loads. The intent of this study was to investigate, modernize, and create a more defendable methodology for applying debris loads to Tainter gates. This study combined multiple references to create a range of loading values for use by designers in regions that see low, moderate, or severe concentrations of debris. Guidance and recommendations have also been provided for special debris-loading conditions sometimes encountered by design engineers. The findings of this study show that the current recommend debris load, although appropriate and conservative for certain types of debris, may lack flexibility.

Implementation of building information modeling (BIM) in all levels and types of building projects in the architectural, engineering, and construction (AEC) industry can considerably improve cost, time, quality, and sustainability outcomes. Despite the potential benefits, upfront costs required to implement BIM hinder its diffusion in small home-building businesses. These costs mainly include consultancy fees, hiring/training and retention of BIM experts, and software license fees. Based on the small business management and innovation implementation literature, this study presents a framework for effective BIM implementation in small home-building businesses. The framework posits three phases with their associated business practices: (1) initiation phase: preliminary BIM adoption setup via external and internal support, and creation of in-house BIM experts; (2) stabilization phase: retention of in-house BIM experts via business practices improving their skills and motivation; and (3) progression phase: scanning and exploiting external innovative BIM knowledge to sustain or gain a competitive advantage. The framework was qualitatively analyzed and verified via interviews. The findings can help facilitate BIM implementation in small home-building businesses as well as in other small construction firms.

Lifting lugs are most commonly designed as a flat plate with a hole to receive a shackle or as a flat plate with reinforcing plates, typically called cheek plates or doubler plates, on both sides of the main plate to reinforce the area around the pinhole. The means of design of these lugs are familiar and addressed in the literature. An alternate configuration of lifting lug uses a flat plate with a hole into which is welded a tubular bushing, the length of which may be either equal to or greater than the thickness of the plate. This article presents the derivation of a practical design method that is appropriate for use in the design of such lifting lugs.

The technical specifications of Chinese standards require cast-in-situ foamed concrete nonstructural walls to be anchored by steel ties, structural reinforced cast-in-situ concrete columns, and reinforced cast-in-situ concrete ties to ensure seismic capacity. In most cases, anchorages of this kind cannot satisfy the flexibility requirement, and such technical measures are impractical because they require increased labor, high material consumption, and long treatment time. Considering this dilemma, the authors propose a new anchorage measure. In the proposed measure, the anchorage of a cast-in-situ foamed concrete nonstructural wall is provided by three-dimensional (3D) steel trusses that act as a path to transmit loads. Given the brittleness of foamed concrete, the flexibility of a nonstructural wall made of this material must be provided with correct anchorage. Appropriate flexibility is easily achieved with the 3D steel truss. The 3D steel truss is constructed by welding hot-rolled ribbed bars and cast-in foamed concrete so that bond stress between the ribbed bar and foamed concrete is enhanced.

Footing design should satisfy the requirements as specified in the design standards of a country. The tendency of most of the conventional design approaches is to achieve design requirements first and estimate economics afterward. Also, the existing literature has recommended various approaches to reduce the cost of a foundation by reducing its base area or by achieving a minimum volume of constituents. However, discrete reduction in these quantities might not necessarily represent the least cost. As an alternative, this article describes a simplified approach for the design of eccentrically loaded RC isolated footings that explicitly considers the structural requirements and economics simultaneously and hence results in a foundation with minimum cost. The developed approach is based on Excel solver, the objective of which is to provide a simplified procedure to reduce the construction cost through the simultaneous integration of design parameters and requirements as optimization variables and constraints, respectively. This design approach is illustrated in the latter part of the article along with the comparison of results between conventional and optimized designs using design examples available in the existing literature.