Practice Periodical on Structural Design and Construction

Forum papers are thought-provoking opinion pieces or essays founded in fact, sometimes containing speculation, on a civil engineering topic of general interest and relevance to the readership of the journal. The views expressed in this Forum article do not necessarily reflect the views of ASCE or the Editorial Board of the journal.

In the past two decades, fiber-reinforced polymer (FRP) materials have been increasingly used in civil engineering. Compared with its wide applications in the civil infrastructure system, the use of FRP in buildings is rather limited. One reason for this is that, unlike civil infrastructure, buildings have more stringent nonstructural performance requirements, including those for fire rating, smoke and toxicity, flame spread, water resistance, flood resistance, and so forth. Although numerous studies have been conducted on structural performances of FRP structures, limited studies are available on the nonstructural performance. This paper aims to identify the gap between building code requirements and the current state of research on FRP materials. The first section of this paper is devoted to a summary of the research findings on nonstructural performances. Based on codes and other specifications, the second section systematically examines the code requirements according to the FRP’s target applications, such as load bearing members, interior finishes, exterior finishes, or roofings, and their corresponding standards. The next section evaluates the research findings from the first section against the requirements from building codes in the second section. Finally, the applicability, limitations, and future work for FRP materials to be used for building applications are provided in the last section. It can be concluded that, strengthwise, FRP can be used for building applications. Fire rating can be met with different insulate schemes, which vary from 0 to 3 h based on different applications. Exposed FRP needs to meet the requirements of smoke, toxicity, and flame spread. Adding fire-retardant fillers, such as alumina trihydrate (ATH), can enhance performances and meet the code requirements. Further studies on water resistance, weathering tests, flood resistance, combustion, and so forth, are needed. Most of the insulation materials are proprietary and expensive, which restricts their wider applications. It is advantageous to develop cost-effective fire protection systems. No study is available on unified modeling and design guidelines for fire rating, smoke, toxicity, and flame spread. There is a need to provide effective design methods to design these items based on their targeted applications, similar to the methods for structural design.

The construction industry experiences a disproportionately high number of injuries and fatalities among the total U.S. employed workforce. Although correlations have been identified between physiological information, worker fatigue, and safety, minimal research efforts have collected and analyzed construction-worker physiological metrics. The objective of this case study was to quantify and analyze physiological data of two individual construction-equipment operators over a consecutive 5-day duration. Physiological metrics, including human heart rate, breathing rate, upper body posture angle, traveling speed, and acceleration, were automatically collected and assessed. Experimental trials were also conducted to validate measurement data collected by the physiological status monitoring system. The main contributions of this case study were found in the framework for assessing physiological properties of construction-equipment operators and scientifically collected and analyzed physiological data.

Concrete poles used in transmission structures usually are made using the spun-cast method. Recent surveys found that some spun-cast concrete poles have had durability problems as a result of longitudinal cracking and concrete segregation, which have resulted in corrosion of the reinforcing/prestressing steel. An innovative static-cast concrete pole system was developed to eliminate the shortfalls of spun-cast concrete poles. These poles have a nonprismatic hexagonal hollow section, made of fiber-reinforced self-consolidated concrete (SCC), and are reinforced longitudinally using glass fiber–reinforced polymer (GFRP) bars. The static-cast operation and use of nonmetallic reinforcement make these poles corrosion free and significantly reduce their lifecycle cost. The objective of this paper is to present the design, production, testing, and implementation of the proposed static-cast concrete poles. Testing results indicate that the flexural capacity, shear capacity, and deflection of the proposed static-cast concrete poles can be predicted accurately using existing approaches. The experience of implementing this approach for two poles gives an indication of the constructability of the proposed system and its ease of handling using the same equipment and procedures adopted for conventional poles.

Interface shear transfer (IST) is critical for achieving composite behavior in many concrete structures, such as between precast girders and cast-in-place decks. IST capacity has traditionally been tested using a push-off test method, in which direct shear is induced through compression loads placed at the ends of notched test specimens. In this study, a four-point bending test method as proposed by Iosipescu in 1967 was investigated for application to IST. The four-point bending test creates direct shear by strategically placing supports and loads on a beam. Its advantage is that the test specimens are easy to fabricate. In addition, it produces a more uniform stress state at the interface than the interface stress distribution of the push-off test, making the four-point bending test a better representation of the stress state at cast-in-place deck and bridge girder connections. In this study, these two test methods are compared and contrasted through an experimental program and analytical modeling. The conditions under which the proposed test method are similar and distinct from the push-off method are identified.

The construction industry continues to rank as one of the most hazardous work environments. As a result, construction safety remains a critical concern for both practitioners and researchers. Several construction industry members and government agencies have identified a lack in the number of safety personnel within the construction industry. Also, there seems to be incongruity in the formulas and strategies used for determining appropriate safety health and environment staffing needs. The objective of this study was to collect and analyze information concerning safety professionals, including the number of safety employees engaged in the construction companies, their credentials, and their experience levels. A structured survey was developed and administered to safety personnel working in different construction companies in the United States to elicit information about safety professionals in the construction industry. The findings of the study indicate that construction firms engage a higher number of safety personnel to manage construction activities than the staffing size obtained using the existing guides for determining staffing needs for safety professionals across industries. The findings also suggest that having the correct number of safety personnel with the required educational and professional qualifications can help reduce the total recordable incident rates (TRIR) of construction companies. Also, adequate staffing of safety personnel with the required educational and professional qualifications can enhance safety management in construction.

Pavement preservation is a proactive approach to maintaining existing highways. Freeway-preservation projects typically require construction workers to conduct their work in close proximity to ongoing high-speed traffic. This exposure creates a dangerous situation for both workers and passing motorists. A recent study funded by the Oregon Department of Transportation (ODOT) implemented and evaluated different types of traffic-control devices on highway-preservation projects to reduce vehicle speeds and create safer work zones. The study implemented combinations of multiple traffic-control devices [speed-limit (“Speed 50”) signs, portable changeable message signs (PCMSs), and radar speed displays] in two case study projects and evaluated their effects on vehicle speed. The researchers used fixed-location sensors and probe vehicle runs to collect data on traffic speed. The results indicate that using a combination of PCMSs and radar speed displays is the best choice. Although data from the probe vehicle runs could not be used for statistical analysis because of limitations on the number of runs conducted, the data provide a vivid and direct view of how individual motorists behave in a construction work zone. The study also provides valuable insight into the effectiveness of the traffic-control measures that contractors can use to design safety into their work operations and further improve the safety in work zones.

Simple-made-continuous (SMC) multispan concrete bridges are popular in low-to-moderate seismic regions, and sometimes horizontally curved and/or skewed configurations are needed to accommodate complex terrain. Typical SMC multispan bridges can adopt different connections between the intermediate bent cap and the continuous superstructure (bent connection). Compared to their straight counterparts, skewed and curved SMC bridges exhibit more complex seismic performance, making the design choice of using bent connections critical in low-to-moderate seismic regions. Nonlinear time-history seismic analyses using structural analysis and design software are carried out on 12 bridge models with four geometric configurations (i.e., straight, skewed, curved, and skewed and curved) and three bent connections (i.e., fixed, pinned, and roller). The skewed and curved bridge is found to exhibit a larger overall seismic response than the other bridges for most bent connections. Different bent connections affect the seismic response of a bridge by modifying the structural load path, which in turn changes the seismic load transmitted between the superstructure and the substructure. For straight, skewed-only, and curved-only bridges, pinned or roller bent connections are found to be more seismic-friendly than fixed bent connections in terms of their relatively smaller overall seismic demands, apart from abutments. For skewed and curved bridges, the situation becomes complex, and a fixed bent connection might be preferred in some instances.

In the United States, state departments of transportation (DOTs) use primarily state force (SF) or private contractors to maintain road systems. Private contractors are contracted under method-based contracting (MBC) or performance-based contracting (PBC). Limited research has been conducted to assess the quality of road-maintenance work performed by private contractors. In this study, with the help of a national survey of state DOTs, questionnaire responses from road users, and on-site visits, the quality of three road-maintenance activities—chip seal, striping, and street sweeping—was assessed. The results show that the quality of chip seal performed by the SF was significantly better than that performed by private contractors. On the basis of the survey of road users, for the activity of striping, the work performed by private contractors was significantly higher in quality than work done by the SF. For the activity of street sweeping, the road user and the nationwide DOT surveys showed that SFs significantly outperformed private contractors. The results of this study will help state DOTs identify the respective maintenance activities that should be performed using SFs and private contractors.

Worker injuries and illnesses can affect the profitability of an organization. Regardless of the regulatory requirements for safety and health, many organizations prefer to see positive returns (i.e., better safety metric performance) on their safety investments (i.e., project costs associated with injury and illness prevention programs). Understanding the relationship between costs associated with an injury and illness prevention program of a construction project and project safety performance is critical to the future success of construction organizations in the United States. In evaluating this relationship, the authors’ goal was to identify an equilibrium point of injury and illness prevention program investment at which the relationship can be beneficial to contractors. Data collected from 93 U.S. construction projects were analyzed for the presence of a relationship between project spending and safety performance. Per the analysis, an injury and illness prevention program cost of 5–6% of the total budget may be adequate to maintain injury rates at low levels. This information can be used in developing or revising a contractor’s project-specific injury and illness prevention budget.

With a growing interest in using timber as a structural material for tall buildings in response to trends in sustainable design, several timber buildings between 7 and 10 stories have been built in Europe and Australia. However, in the United States, timber buildings are still limited to 6 or fewer stories. The availability of glued laminated timber enables the fabrication of structural members with cross-section sizes and shapes capable of supporting heavy loads. Although this may be appealing for use in tall buildings, from a structural engineering point of view, there are also other timber properties that may be attractive to architectural designers as well. Among these properties, timber has favorable performance in fire (at least for solid sections). These properties may offer some advantages for wood to become a candidate for tall building construction as an alternative material. This paper presents an overview of available literature on the use of timber as a potential material for use in tall buildings. Specific properties of wood in offering a renewable material with a favorable strength-to-density ratio and fire-resistance rating are discussed. Recent and ongoing fire tests and the significance of adhesive effects in laminated timber members are reviewed. Fire safety and structural design challenges in making wood an alternative material in tall building construction are also presented.

Earthmoving equipment plays an important role in most construction projects. The earth must first be moved by dump trucks, dozers, and possibly scrapers. The material is then spread and compacted by motor graders and compactors. The activities of the different pieces of equipment must be coordinated to ensure a smooth operation. Unfortunately, accidents do occur, and workers are occasionally injured or killed when mishaps occur. An investigation was conducted on 15,000 fatalities that occurred due to equipment operations during a 20-year time period. Results show that many of the victims are workers who are on the ground, whether performing work related to the equipment or performing nonrelated work. Many of the accidents occurred when the equipment was traveling in reverse, a situation that is exacerbated by the blind spots on equipment. Half of the fatalities were the result of dump truck incidents.

Proper hazard recognition and communication are fundamental to injury prevention in construction. When construction hazards remain unrecognized, the likelihood of injuries in the workplace increases. Therefore, construction employers encourage their workers to actively participate in prejob safety meetings to facilitate the recognition, communication, and management of potential safety hazards. However, field-level hazard communication challenges, including ineffective communication channels, differences in language proficiency, and poor safety climate, are significant impediments to effective safety management. In this study, social network analysis was adopted to evaluate the relationship between safety communication patterns among workers and hazard-recognition performance. Specifically, (1) crew-level safety interaction data were compiled for 18 active crews representing six diverse projects in the United States, (2) the hazard-recognition performance of the participating crews was measured though field observatory studies, and (3) the relationship between social interactions and hazard-recognition performance was assessed using social network methods. The research findings suggest that well-connected crews with higher numbers of safety communication ties (i.e., network density) collectively recognize a larger proportion of hazards compared to those crews with fewer ties. Moreover, supervisor centrality in safety communication patterns differentiate crews with higher hazard-recognition levels from their lower-performance counterparts. The findings highlight the importance of network patterns in the communication of construction hazards.

Studies show that application of the prevention through design (PtD) concept with respect to construction worker safety, although compulsory in some countries, is inconsistent throughout the United States. This paper presents a study that explored the impacts and experiences in a construction community resulting from PtD implementation to benefit those countries where PtD is predominantly absent. Informed by a comprehensive review of PtD literature and governing regulations, the researchers conducted a structured, randomized survey of the construction sector in the United Kingdom, where PtD is prevalent. Based on analyses of 228 survey responses, it is clear that PtD is viewed as a positive enhancement to design practice, project team collaboration, and safety. Those experienced in its application hold it in high regard. Obstacles to implementing PtD may be present but can be overcome. PtD provides an opportunity to change the way safety is viewed and practiced in the United States and to make it more inclusive of the entire project team, with active participation consistent with current project team roles and responsibilities. The research reveals how the construction industry can make this change and the impacts to be expected. Doing so will create a supportive and participatory safety environment throughout the design profession.

Design plays a vital role in the building process. As the demand for design creativity and innovation continues to grow, high-performance designs have received significant attention in the built environment. In the ideal world, high-performance designs address customer demands with regard to the physical performance of the design while ensuring technical feasibility as well as economic and social viability. Among social viability goals, a design should respond in a practical and creative manner to the needs of field personnel by employing innovation in a way that minimizes safety risks in the workplace. However, in reality, high-performance design thinking does not explicitly account for worker health and safety. Therefore, such design elements can be associated with substantial safety risks to those who assemble, operate, and maintain a facility, in part because of the complexity of the design resulting from the high demand for innovation. Innovation is defined as the process of integrating new, effective systems and techniques into a process. With regard to design, this integration can be problematic because of the complexities and risks introduced to construction and maintenance operations. The purpose of the present paper is to support the premise that worker health and safety should be integrated into the design process as an integral part of innovation. This process can be facilitated by the implementation of a new design approach, referred to as prevention through design (PtD), an effective and practical method of addressing worker health and safety early in the design process. This paper provides examples of PtD-incorporated practices in the design process and discussion that highlights motivations and enablers of integrating worker health and safety in high-performance project designs. Discussion and information provided in this paper are expected to benefit design professionals and practitioners who are interested in pursuing designs that yield innovative, yet safe, outcomes.

Safety climate has been widely used as a leading indicator of safety performance across multiple high-risk industries, including construction. Despite extensive efforts to measure the safety climate on construction projects, few tools incorporate environmental factors to address construction-industry-specific or project-site-specific indicators. This research focused on identifying the context-specific construction indicators that affect safety climate on construction sites. A literature review was used to develop the framework of safety climate environmental factors of construction sites. Then two focus-group discussions with 17 safety experts were conducted to identify and validate the safety climate factors and indicators specific to the construction context. The results reveal a framework of dynamic and environmental safety climate indicators that could influence on-site safety and be captured through safety climate survey methods. Twenty-five environmental safety climate indicators, across four categories of environmental safety topics not addressed by currently used safety climate tools, were identified by the focus-group discussions. These indicators address the dynamic environment of construction sites and the unique concerns emerging from evolving trade interactions. The results serve to advance the value and application of safety climate assessments to improve proactive approaches for identifying and mitigating safety risks specific to the construction industry.

Designers (architects and engineers) in the U.S. construction industry find it difficult to consider prevention through design (PtD) in the projects they undertake, primarily due to the lack of knowledge of the solutions available to them. This lack of knowledge creates the fear that incorporating PtD is prohibitively expensive, interferes with contractor means and methods, and opens the way for additional risk and litigation. PtD solutions are available in academic literature and some trade periodicals that are not always available or accessible to designers. To assist in the expansion of the knowledge base for PtD, this paper has two objectives: (1) to identify the kinds of solutions available to designers through existing literature, and (2) to identify existing methods that can inform and educate designers on PtD solutions.

Interactions between project personnel, passing motorists, and mobile equipment in a restricted area make work zones risky for construction workers. In addition, the pressure on workers to maintain a high level of production can often lead to increased exposure to hazards. An analysis of reports on occupational fatalities in work zones in the United States indicated that the most common accident involving mobile equipment was workers being struck by backing dump trucks. This paper evaluates strategies for reducing accidents involving mobile equipment using different systems of backing cameras on dump trucks. An ordered probit model with random effects was developed to evaluate the factors that influence the identification of a worker (represented by a mannequin) in the path of a backing dump truck. Results of the analysis of this model indicate that the position of the mannequin, similarity in colors of the safety vest used and that of some construction equipment, and the presence of glare in images reduced the likelihood of identifying the mannequin at a safe distance from the truck. This paper concludes with recommendations for implementing strategies to reduce the occurrence of accidents involving backing dump trucks.

A stiffness-based approach founded on the moment-distribution method evaluated the effect of uneven standoff distances in double-nut anchor-bolt connections on the axial-resistive forces provided by the anchor bolts in response to connection loads. The uneven condition affected the intensity and distribution of resistive forces as determined when analyzed within the framework of the anchor-bolt group. The relative axial stiffness and proximity of the anchor bolts to the center of rigidity of the group were the major contributors. Comparisons with finite-element analysis showed close agreement for anchor-bolt configurations with even, uneven, and excessive standoff distances. The developed approach is comprehensive and applicable for various standoff distances, numbers, spacings, and sizes of anchor bolts. The approach is valid for fatigue-level (or greater) loads provided anchor-bolt stress does not exceed the elastic limit and the base plate supplies rigid diaphragm action.

In this paper, a simplified calculation model for the prediction of the load-carrying capacity of an RC column footing with a square cross section is presented. A detailed background of available experimental data and existing models for the prediction of the load-carrying capacity of slender and deep footings is presented. Cases of flexural failure and punching shear failures for slender footing and concrete strut crushing and tie yielding in deep members are analyzed. The aim of the paper is to propose a simple design formula for slender and deep footing verified by available experimental data and in agreement with other existing expressions. Expressions of the maximum mechanical ratio of main steel for slender and deep footing are defined to avoid brittle failure. The effects of the main parameters, such as the dimensions of the footing and column (depth, width) and the mechanical ratio of longitudinal steel and type of soil, were investigated both numerically and analytically. A comparison between analytical and numerical results shows good agreement.

For the safe design concept to take hold within the design community, the negative connotations of safety within the design world must be removed. Considering safety during the design phases of projects presents a key opportunity for innovative and creative responses that can not only enhance safety but also positively affect cost, quality, schedule, and other traditional business parameters. Safe design is an untapped source for innovation. This paper describes the creative opportunities that can occur when safe design is embedded and practiced. Examples are provided that demonstrate these innovations. Working up the hierarchy of controls, eliminating and reducing foreseeable site hazards is difficult but yields a greater opportunity for creativity. Construction and safety professionals should educate designers about these opportunities and adapt their approach to work with the design professions. Design professionals should evaluate safety as any other idea, approach safe design as an expansion of their design deliverables, and use it as a source for creative and innovative design.

Pricing of construction change orders is one of the major causes of conflict among owners, designers, and contractors on a construction project. This article analyzes the inclusion and treatment of various direct-cost items in change orders prepared by trade contractors. It also discusses various markup percentages proposed and allowed for overhead and profit. It starts by compiling various direct-cost items and markup percentages from major standard contract documents. It then analyzes direct-cost items in terms of the categories of allowed, disallowed, and maybe/depends based on a weighting system; the markup percentages are also analyzed. The weighting system and the averaging are based on four standard contract documents; legal cases; federal regulations; surveys of 148 electrical contractors and 16 construction owners represented by the National Electrical Contractors Association (NECA), the ELECTRI Council, and the Construction Owners Association of America (COAA); six case studies provided by NECA members; industry standards; and other literature. Finally, the need to consider impact factors and corresponding consequential costs in the pricing of change orders is discussed. The work presented in this paper highlights the prevailing confusion and conflicts related to change-order pricing among owners, designers, general contractors, construction managers, and subcontractors. A major contribution of the research is the development of a standard process of costing change orders by providing change-order specifications for contractors within the project manual Division 1 specification.

Construction of buildings with conventional formwork/falsework systems involves using a great deal of wood as shoring, which involves cutting more trees, extra costs, more construction time, consuming a great deal of energy, and emitting a great deal of CO₂. A new design is presented within this study that involves the use of funicular arched wooden trusses instead of the conventional stringer-shore falsework systems. A closed-form solution for the truss is formulated to calculate the straining actions and deflections. A parametric study is performed using the closed-form solution to study the variations of the straining actions and deflections within the members while changing the truss span. The weights of the proposed trusses are compared with the weights of conventional formwork to judge the economic and environmental soundness of the new system. The new system is proven to consume lower amounts of wood; to be more economic, easier, and faster to assemble and transport; to produce less carbon emissions; and to save more energy.