Practice Periodical on Structural Design and Construction

Tapered piles are used in place of cylindrical piles for their improved geotechnical performance. When tapered piles are subjected to axial dynamic loading, as is the case with machine foundations, an appropriate theoretical formulation must be used to obtain an accurate representation of the dynamic response. Material damping, which is the energy loss due to particle deformations, friction, and heat, is often neglected in analyses for simplicity. However, previous researchers have not quantified the implications of neglecting material damping during the dynamic design of tapered piles. The present study uses advanced symbolic computation techniques to introduce material damping within the existing theoretical formulations reported in the literature. Numerous hypothetical case studies are defined to represent a range of realistic site conditions, and the influence of material damping on the dynamic axial response is assessed. It is shown that in all cases, material damping acts to reduce the resonant amplitude and increase the resonant frequency, with the shift in resonant peak being more pronounced for piles founded in soft soils. Provided that adequate dynamic site data are available, material damping should be incorporated within the dynamic axial analyses of tapered piles to produce a more comprehensive representation.

Despite the use of traditional and novel approaches to improve construction safety management, safety performance in the construction industry is still considered poor, especially when compared with other US industries. Poor safety performance is responsible in part for an observed decrease in work quality and employee productivity and an increase in project costs and completion time. The architectural, construction, and engineering (ACE) industry should adopt and implement innovative safety practices with high total capacities throughout the project life cycle to improve safety performance in construction. Currently, technologies exist that when used appropriately, have capabilities of notably enhancing safety. However, these technologies are not applied broadly in the industry for safety management. Researchers and professionals believe the limited adoption of these technologies across the life cycle of construction projects is a potential contribution to the recorded poor safety performance in construction. To bridge this gap in practice and encourage the adoption of emerging technologies, the present paper summarizes practical applications of different types of technologies for safety risk mitigation and management in construction. Practical information regarding effectiveness, perceived and actual cost implications of the technologies, and the enablers and barriers of technology adoption are discussed. The discussion of the practical implications of these technologies will assist construction managers in making informed decisions regarding what technologies to adopt and implement, which will ultimately lead to improved safety performance.

Recent statistics indicate that the number of injuries and fatalities on highway construction projects continues to rise. This increase is attributed primarily to unsafe driver behavior, such as distracted driving, and the distinct features of highway construction projects, for example, nighttime paving. Nighttime paving helps avoid traffic congestions and benefits from the cooler temperature at night. However, poorer visibility of workers during nighttime work presents a safety risk that can lead to injuries and fatalities. Despite the work zone lighting standards and regulations developed and adopted by State departments of transportation and the Federal Highway Administration (FHWA), the number of accidents and injuries in work zones has increased in recent years. Studies in other industries indicate that wearable devices, such as wearable lighting systems (WLSs), could help improve worker safety. However, an understanding of the effectiveness of these devices and the manner by which to efficiently implement them in work zone operations is currently lacking in the construction industry. The present study proposes to fill this gap in knowledge and practice by evaluating the effectiveness of WLSs in different work zone applications. Results indicate the absence of standards or regulations for the use of WLSs. Findings from qualitative assessments of results from multiple tests and live projects show that WLSs could increase the visibility of dump operators, spotters, and density technicians. The study recommends optimum locations for WLSs accordingly.

Moment frames with gravity columns in reinforced concrete (RC) buildings have been used extensively for the last decade in the United States. Unlike traditional beam–column–slab structures, they provide some advantages in terms of construction time and architectural and economical aspects in design process. The system consists of gravity-only columns resting directly on slabs and seismic force–resisting moment frames. Reinforced concrete special moment frames in two principal directions are typically placed at the perimeter as a lateral force–resisting system. Even though the design procedure is similar to that used with steel special moment frames, there is generally no column at the corner of the plan in such buildings so as to avoid biaxial bending. This paper investigates the contribution of gravity-only columns to inelastic seismic response of low- and high-rise RC special moment frames. For this purpose, nonlinear dynamic time history analyses are carried out on 5- and 15-story RC buildings designed with current design specifications subjected to design-level earthquake ground motions. Seismic performance evaluation was also carried out through nonlinear dynamic time history analyses.

This paper reviews the design of accessible anchor galleries that allow the inspection, testing, and replacement of post-tensioned trunnion girder anchorage systems. Various means of egress were reviewed along with features to remove drainage, prevent inundation, and provide air circulation. An elastic analysis of an example gallery was performed and discussion provided regarding reinforcement detailing, safety features, and constructability.

Guardrails are an efficient way to protect construction workers against falls from height. For residential construction, job-built wooden guardrails are quite common. This article investigates the strength of temporary wooden guardrails attached to open joists or prefabricated walls. More than 350 laboratory strength tests were performed on wooden guardrail systems installed on open joists and prefabricated walls. Besides the type of fastening hardware used, the influence of the position and number of nails and screws were also taken into consideration, as well as the number of spans of the guardrail system and the location of the loading point on the top rail. Results show that larger open joists generally offer a higher strength and that wood screws and straight nails reinforced with a corner bracket are the best fixture type for the posts. The critical configuration is when the load is applied directly on the vertical post.

The concept of construction industrialization was first introduced during the 1960s. Previous studies define construction industrialization as moving onsite construction work to offsite factories, largely depending on the assistance of automated machines and equipment. In some developing countries, industrialization of construction projects is highly recommended to minimize construction waste and pollution. However, no formal method has been developed to calculate the industrialization rate of construction projects. The overall goal of this study was to develop such a method. To this end, the authors utilize energy expenditure as a basis for assessing industrialization rate. Previous research has investigated the energy expended by construction workers when performing onsite activities. To determine the differences between on-site and offsite processes in terms of energy expenditure, the present study focuses on offsite construction processes and the related energy expenditure. The findings provide input to create a quantification model of the construction process. To collect accurate and persuasive data, survey and site-observation research methods were utilized. The authors chose the overall concrete construction process as the main focus for the study, and conducted a survey of precast concrete plant personnel and observed precast concrete plant operations in the Pacific Northwest. Based on the data analysis, the physical activity level of offsite precast concrete processes was quantified as 2.51, which is within the comfort zone for human work. In addition, with newly defined levels of automation (LOAs), the authors developed correlations between the LOAs and the ratios of power to plant size, production, and expenditure, respectively. The findings from this study provide foundational knowledge needed to develop a method to quantify the industrialization rate of construction projects. With such a method available, project stakeholders can make sound decisions based on the extent of construction industrialization and associated benefits.

This case study considers a construction site with weak soil (clayey and silty sands) that has a coefficient of elastic uniform compression $C_u$ less than $3\mathrm{kN}/{\mathrm{m}}^3$ ($19.27\mathrm{lb}/{\mathrm{ft}}^3$). Instead of using a deep foundation, the weak soil under the foundation was replaced with compacted limestone in order to improve the properties of the soil and increase the coefficient of uniform compression to $7\mathrm{kN}/{\mathrm{m}}^3$ ($44.96\mathrm{lb}/{\mathrm{ft}}^3$). The replacement of the soil under the machine foundation improved the elastic soil spring constants. The coefficient of elastic uniform compression of the soil $C_u$ for the vertical vibration mode was inversely proportional to the elastic settlement of the bearing plate due to external pressure, which is a function of the bearing area for the same soil. Replacing weak soils under machine foundations with strong soils, such as limestone, reduces soil settlement and the bearing area of the machine foundations while decreasing construction costs and time by up to 50% compared with constructing deep foundations.

This study uses the finite element method to investigate the behavior of symmetrical mats subjected to concentrated loads. The analysis considers different mat geometries, soil moduli of subgrade reaction, and concrete moduli of elasticity. The effect of these parameters on the maximum soil bearing pressure, bending moment, and shear within the mat is determined. For the considered mats, the maximum soil bearing pressure is observed below the corner columns, while the minimum soil pressure occurs in the middle of the central panel. The maximum positive bending moment is found below the interior column closest to the edge, whereas the maximum negative moment was located along a column strip midway between the edge and first interior columns. The location of the maximum shear occurs at the face of the edge column nearest to the corner of the mat. The most important parameters that affect the structural response of a mat are the thickness of the mat and spacing between columns, and to a lesser extent the soil modulus of subgrade reaction, concrete modulus of elasticity, and panel aspect ratio.

One of the important and systematic methods that is used for the identification of failure of any system is the failure mode and effect analysis (FMEA). This is carried out through the identification of the most important causes of all the failure modes of a system under consideration. FMEA is based on the concepts of a probabilistic analysis. In the present study, a corresponding equivalent deterministic method has been developed in terms of a risk priority number (RPN) formulation with its application to bridge failures. The RPN will enable the practicing engineers to rank various bridge failures and take necessary steps to mitigate the associated risk.

A rehabilitation plan is presented for a two-story industrial steel structure in Iran. The building was found to have unsatisfactory performance: The first-floor two-way composite slab was prone to uncontrollable vibrations during normal operation (forklift vehicles), and the lateral load resisting system did not comply with current seismic code provisions. Notably, a recent vibration rehabilitation attempt applied to an almost identical structure had added columns and struts of nearly 120 tons of steel with little improvement. To resolve this twofold problem while respecting the minimum disruption requirement for a facility that operates nearly $24/7$ and the height/width clearance restrictions due to existing industrial machinery and vehicle traffic, a combined rehabilitation scheme was proposed that involved: (1) keeping the extra columns of the failed rehabilitation scheme, (2) stiffening the joists, (3) adopting toggle-brace dampers in the main girders, and (4) strengthening the existing lateral X-braces and their connections.

The execution of highway and bridge projects commonly subjects state transportation agencies (STAs) to challenges that cause schedule delays and cost overruns. Changes made to the project's scope are critical root causes of these delays and overruns. The main objective of this study is to develop an effective project scoping process (PSP) for highway and bridge construction projects, using the integrated definition (IDEF) modeling technique. To this end, the research team investigated and evaluated the current practices of the PSP by conducting a comprehensive literature review and various in-depth interviews. Three PSPs were developed using the IDEF; then they were analyzed by the research team to select the PSP that best represented key scoping activities and had the highest level of details for further development. The three main functions of the proposed PSP were to select the project, analyze it, and advance the preferred alternative. This process included 20 main activities. This study would assist in the adoption of the most appropriate practices and strategies that lead to mitigating costly scope changes and prevent unnecessary delays for highway and bridge projects.

In building rehabilitation and strengthening works, the need to create openings in existing walls is usual. When those walls are load-bearing walls, the loading path is locally altered; therefore, it is required to strengthen the vicinity of the new opening. In this paper, two strengthening techniques widely applied to strengthen openings in existing walls are described. Those techniques are structurally different; the first technique makes use of reinforced concrete beams, and the second uses externally bonded carbon fiber–reinforced polymer (CFRP) strips. The concrete-beam technique can also be used to underpin structural elements when existing load-bearing walls are completely eliminated. Onsite observations have allowed the conclusion that good strengthening results can be obtained. Additionally, those construction practices are carried out with minimum disruption inside the building. The main parameters defining the strengthening technique choice are the length of the opening, the material, and the width of the existing wall. The loading values acting in existing walls, in principle, have no influence on the strengthening technique choice. The knowledge described in this paper is a first step to promote numerical and laboratory research related to opening strengthening and at the same time to support the development of innovating strengthening techniques.

Heavy machinery that undergoes significant impact in its lifetime requires support and a system that can resist dynamic forces and the resulting vibrations. In this context, this technical paper reports a case study on a machine featuring hydraulic steel sheet shears and two hammers. The machine foundation of the hydraulic steel sheet shears was fixed to a concrete foundation using chemically bonded anchor bolts of a certain length and diameter. A short time after the machine had begun operating, shear failure of the anchor bolts occurred. These chemically bonded anchor bolts were then replaced with T-shaped anchor bolts of the same length and diameter, which functioned well. Two hammers were fixed in cast using J-shaped anchor bolts. The J- and T-shaped anchor bolts functioned well in the machine for over 10 years. From field studies and years of successful construction practices, traditional J- and T-shaped anchor bolts fixed with reinforcement of concrete foundations are recommended for fixing machines with impact loads and are superior to chemically bonded anchor bolts.

Having a simple and practical approach to forecast project milestones is extremely valuable to managers, especially in megaprojects in which the stakes are high. This paper, based on past records of similarly completed projects, suggests a heuristic method to forecast these completion times in a practical way. The findings of this study are of interest to practitioners, especially to project, portfolio, and high-ranking senior managers who seek a pragmatic forecasting of their ongoing projects. In this exploratory research, available forecasting methods used to predict the duration of a project based on the types of data sources were first reviewed. Next, a Heuristic Estimation Method (HEM) was suggested, in which data from similarly completed megaprojects are used to predict the completion time of an ongoing megaproject. This method was then tested on a selected number of ongoing offshore oil and gas megaprojects to forecast their delivery dates. At the end and upon completion, the predicted dates were compared with the actual completion dates of the selected megaprojects. Results show that the suggested approach was able to forecast the delivery dates within an acceptable margin of error.