Practice Periodical on Structural Design and Construction

Errors in structural analysis and design are inevitable, but finding them early in the design process saves time and money. Knowledge of the broad causes of errors and how experienced engineers identify the presence of errors can inform training for structural engineers, thus empowering them to find their own errors early in the design process. Therefore, this study presents 145 pieces of information about errors in structural analysis and design compiled from structured interviews with 35 structural engineers. The strategies used to find errors have been classified into eight categories: (1) comparison, (2) rule of thumb, (3) information check, (4) visualization, (5) extreme value, (6) previous experience, (7) field, and (8) other. Evaluation of the information shows that responsibility for quality control should not be held only with reviewers but should also be shared with the engineers creating the designs. Also, quality control training should be heavily influenced by the comparison strategies. Overall, the specific examples of errors and the problems they cause could be helpful in developing in-house training and updating quality control procedures.

Analysis of a structure is a crucial procedure to ensure its reliable design and performance. These analytical procedures are generally performed deterministically. However, the input parameters defining the material and geometric properties possess uncertainties. These uncertainties can arise from various sources including modeling, manufacturing, and construction. The quantification of uncertainties can be based on either probability theories (using random variables) or possibility theories (using interval and fuzzy variables). In this work, several finite-element-based probabilistic and possibilistic methods are discussed and compared. Case studies of structures analyzed using static and dynamic uncertainty using the aforementioned approaches are presented. Moreover, the analysis methods are compared for both sharpness and computational efficiency. The results of those analyses suggest that the incorporation of uncertainty in the analysis procedure provides a higher level of confidence in the analysis results. It is also observed that the choice of the analytical procedure must be based on both the problem complexity as well as the level of available information.

Although research has identified factors affecting engineering design defects, these defects remain the primary cause of construction phase rework and poor project performance. The authors consolidated similar causal factors identified from their previous study, reducing the list to 96 unique causal factors. Then, Pearson’s Chi-Square test was used to identify any associations between these causal factors and their impacts. This analysis revealed associations between 96 unique causal factors and the impact priority scores, which indicate the relative frequency and relative impact severity. This study also identified the associations between the 96 unique causal factors and defect impact types. The result of this analysis showed that causal factors related to human resources were found to be significantly associated with higher impact priority scores and increased costs or negative schedule impacts. The significance of this study is the identification of causal factors by category, the identification of the impact of each causal factor, and the defect impact types that are associated with each causal factor. The principal beneficiaries of the analysis include directors and project managers. Design discipline helps to eliminate engineering design quality defects.

Public services in Iraq have been deemed to perform unsatisfactorily. In this study, the theory of total quality management (TQM) is used to identify the quality shortcomings of public service projects in Iraq. Accordingly, data derived from 55 online completed surveys were used to assess the TQM of public service construction. The elements of TQM that were assessed are leadership, communication and cooperation, workforce management, process management, continuous improvement, and client satisfaction. The collected data were analyzed utilizing standardized scores to measure the relative shortcoming of TQM’s variables. The results show that, in general, Iraqi engineers perceived the existence of citizens’ satisfaction as being relatively higher than other elements. Furthermore, the results suggest that several key performance indicators (KPIs) scored relatively lower than others. Thus, the study highlights where improvements are needed most for TQM of public service projects in Iraq. In addition, there is a lack of quantitative research that supports TQM benefits within the construction context. Therefore, this study contributes to the body of knowledge regarding the usability of TQM within the construction industry.

In the 2017, ASCE graded the national infrastructure of the United States as D+ overall. The ASCE gave the national School Buildings category a D+ grade and the Bridges category a C+ grade. Steel corrosion is the main reason for the trend toward deterioration in US infrastructure, including buildings, bridges, pipelines, and wharves. Reinforced concrete (RC) is among the most widely used primary construction materials worldwide. Objectives of the current research were to determine the design parameters that have the greatest impact on the reduced shear capacity of RC beams in the presence of corrosion, and to create a model to estimate the reduced shear capacity by refining the ACI shear design model for RC beams in buildings. Using a database of experimental tests, an artificial neural network model was created to estimate reduced shear strength and to perform a sensitivity analysis of the parameters affecting residual shear capacity. The sensitivity analysis showed that the compressive strength of concrete is the most influential parameter affecting reduced shear strength. A multiple linear-regression analysis was also performed to aid in proposing a new model.

Cities account for more than 70% of global fossil fuel use and greenhouse gas emissions. This number is likely to increase due to urban population growth. Much of the energy used in cities is consumed in buildings (e.g., for space conditioning and lighting). Better understanding of energy use patterns therefore is paramount. This paper leveraged advances in machine learning to model energy consumption in residential buildings and gain insights into building energy consumption trends in Chicago. By merging demographic and socioeconomic data collected from the US Census Bureau with energy benchmarking data for Chicago, three models were developed using three different machine learning algorithms: back-propagation neural network (BPNN), extreme gradient boosting (XGBoost), and random forest (RF). The results showed that XGBoost better predicts the building energy use, with an accuracy of 68%. Furthermore, Shapley Additive Explanations (SHAP) was used to interpret the impact of each variable used on building energy consumption. Overall, the insights gained in this study can help policy makers and planners to address building energy use better.

Despite being introduced in Europe nearly $20\mathrm{years}$ ago, cross-laminated timber (CLT) is still not widely used in North America, and it has only recently garnered attention as a new construction material in the US. One primary reason for this is because of a lack design procedures for CLT as a lateral force resisting system for seismically active regions of the US. A CLT subassembly that has not been fully investigated is a horizontal diaphragm for floors, roofs, or bridge decks. The purpose of this study was to investigate CLT diaphragm behavior through a series of large-scale cyclic loading tests. A $5\times 4.27\mathrm{m}$ ($16\mathrm{ft}5\mathrm{in.}\times 14\mathrm{ft}$) CLT diaphragm was tested in a cantilever configuration in which the assembly was subjected to the Consortium Universities for Research in Earthquake Engineering (CUREE) (reversed cyclic) loading protocol applied under displacement control. These diaphragm tests illustrated the rigid behavior of the CLT panels and the ability of the shear connectors between CLT panels to dissipate energy. These tests highlighted possible failure mechanisms and the importance of chord strength on the CLT diaphragm load-deflection performance. The failure mechanism observed and load-deflection results from this experimental study provide information for the development of design procedures for CLT diaphragms.

Earthquake response control of base-isolated bridges using supplementary passive dampers is presented. A benchmark highway overcrossing located in California is selected to indicate the effectiveness of such hybrid response control schemes. The bridge is modeled as a lumped mass three-dimensional stick model. The coupled differential equations of motion for the system are derived and solved using Newmark’s step-by-step iteration method. Considering a bidirectional interaction of the seismic forces, the bridge responses are investigated using various combinations of base isolators and damper systems, called hybrid systems. Further, a parametric study is carried out to investigate the dynamic response of the highway bridge by changing the characteristic parameters of the control devices and the isolation period of the structure for different hybrid systems under various real earthquake ground motions. The variations in seismic responses, such as bearing displacement and base shear in the bridge pier, are computed and compared to study the effectiveness of the various damper-isolator combinations. The present study concludes better performance of the fluid viscous damper when used as supplementary dampers with the lead-core rubber bearing or friction pendulum system for the base isolation, leading to reduced bearing displacements and pier base shear.

The codes of practice do not provide a methodology for estimation of deflection in two-way reinforced concrete (RC) slabs. Hence, a methodology has been proposed for immediate estimation of central deflections in two-way RC slabs considering cracking under service load for use in everyday design. The methodology covers the derivation of a closed-form expression for deflections in two-way simply supported RC slabs. The terms of the expression are based on weights, biases, and transfer functions from the developed supervised artificial neural network (ANN). First, a sensitivity analysis has been performed to identify significant input parameters for generating the data sets. The training, validating, and testing data sets for the development of the ANN are produced through an automated process using a programmed Python script and the finite-element software ABAQUS in accordance with the selected significant input parameters. The expression predicts the inelastic deflection (considering cracking) from the elastic deflection (neglecting cracking). In order to gain general applicability, the expression has been verified for a number of slabs that differ in size and reinforcement detailing. The small differences indicate that it can be used for preliminary design purposes. The use of the closed-form expression requires a computational effort that is a fraction of that required in iterative procedures available in the literature. The proposed methodology can be applied under different types of support conditions of the two-way slabs.

Cold-formed steel (CFS) sections can be designed in many configurations and, compared to hot-rolled steel elements, can lead to more efficient and economic design solutions. While CFS moment-resisting frames can be used as an alternative to conventional CFS shear-wall systems to create more flexible space plans, their performance under strong earthquakes is questionable due to the inherited low local/distortional buckling of thin-walled CFS elements and the limited ductility and energy dissipation capacity of typical CFS bolted-moment connections. In this paper, the behavior of the connections of CFS frames with bolts has been investigated. A finite element modeling and a nonlinear analysis of the geometry and the materials under the cyclic loads are performed using ANSYS14 and compared to the experimental sample. Afterward, the modeling results are compared using the same model with some specimens in which their connections are of frictional and bearing types. Finally, the stresses created around holes in different types of specimens are compared, and the more appropriate solutions are provided. The results showed that the connections in which the prestress has been applied on the bolts and where the friction factor between the contact surfaces has been defined seem to be more rigid connections, given that the part of the force is borne by the friction before the location of the hole. This can increase the friction factor up to 0.6 without any costs and strengthen the connections of CFS frames. As a result, due to the higher bearing capacity of the bolts, the number of holes in the model can be reduced.

This paper presents analysis and vibration control of tall benchmark building under wind and earthquake excitations. The study compared the most recent advanced bracing scheme (ABS) and the most recent schemes of tuned mass dampers (TMDs) for reduction of dynamic responses of tall buildings under both wind and earthquake loads. The coupled equations of motion were formulated and solved using numerical methods. The uncontrolled building (NC) and the controlled building were subjected to a set of 100 earthquake ground motions and wind forces with uncertain velocity at the top of the building. The optimal placement of ABS and TMDs were identified. It was found that the ABS scheme is effective for wind response mitigation but not for seismic response mitigation of tall buildings. However, the TMD scheme was found to be effective for controlling both wind and earthquake induced vibrations. Furthermore, the problem of need for a large space for placing a TMD was significantly reduced by installing distributed TMDs (d-MTMDs) along the height of the building. The d-MTMDs significantly enhanced performance compared with a single TMD (STMD) when subjected to both wind and earthquake excitations.

Elastic cables have the advantages of desirable seismic mitigation effect, low cost, and convenient installation, and have been used widely in low-to-mid-span bridges. However, their utilization in long-span cable-stayed bridges has been limited. To study the effect of elastic cable on the seismic response mitigation of long-span cable-stayed bridges, an experimental model (half-bridge model) with a geometric similarity ratio of $1:40$ was established. Both the semifloating system and the elastic restraint system were considered, and the seismic responses of the two systems under earthquake excitation were tested on the shaking table. The results demonstrated the seismic mitigation effect of the elastic restraint system, which is dependent on the characteristics of the seismic wave. The mechanism of the seismic response mitigation of the long-span cable-stayed bridge with longitudinal elastic restraint was discussed.

This work examined the behavior of a RC beam on a soil foundation subject to concentrated vertical loads and bending moment in both the elastic and the plastic phases. Some of the simplified methods for hand calculations available in the literature, which are useful for preliminary design of foundation structures, were presented and compared. A simplified plastic calculation method is proposed considering limit cases of partial or full plasticization of the soil and the formation of plastic hinges in the beam with elastic or plasticized soil. The proposed method had good agreement with other methods presented in the literature. The proposed method provides a simple calculation tool useful for the calculation of the foundation’s bearing capacity and for verifying the overstrength of the soil–foundation system. The plastic resources of the soil–foundation complex depend not only on the characteristics of the soil, such as cohesion and friction angle, but also on the geometrical and mechanical characteristics of the RC beam and the vertical load characteristics (intensity and eccentricity). It also was shown that the maximum ratio of longitudinal steel bars should be determined to ensure strength hierarchy. with plasticization of RC beams before soil plasticization.

Mass timber is a promising building material that has been used in Europe for a long time. Structural rigidity, renewable characteristics, and low-carbon footprint have made this material a major structural component in the European construction market. While the concept of mass timber building has been successful in Europe, the US construction practitioners are still dubious to adopt this material on a greater scale. In the US construction industry, mass timber has received very little consideration from the stakeholders. Lack of case study projects, awareness, and work experience in mass timber materials have created an industrywide knowledge gap that is hindering the progress of this innovative building material in the US construction market. This study evaluates the feasibility of mass timber products in the US construction industry by analyzing its level of awareness, existing challenges and difficulties, and recommendations to improve the existing perceptions to help solve the knowledge gap and increase the current acceptability of mass timber products among the US construction practitioners. The research method includes three different sets of semistructured questionnaire surveys, distributed among 1,200 construction companies, 300 architectural firms, and 55 mass timber manufacturers in the US. Data analysis of the surveys suggested that the US construction practitioners have significantly low involvement level and work experience in timber building design and construction. The main perceived benefits of using mass timber material are the requirement of a small workforce during construction, aesthetic appeal, and prefabricated characteristics of timber panels. Major perceived downsides are lack of work experience, insufficient timber manufacturing plants, high cost of engineered wood products, and code limitations. Several recommendations were provided on the survey including from the study such as increasing awareness among the stakeholders by undertaking more timber building projects, establishing more manufacturing facilities, developing codes and standards, and developing a skilled workforce experienced in timber construction. The outcomes of the study will be a helpful reference source for US construction practitioners to evaluate the actual feasibility of mass timber as a building material. It will further help increase the acceptability of mass timber products in the US.

Extended shear tab connections have a long history in the steel construction industry as a practical solution to many framing problems, such as framing the supported member to the weak axis of a column without the need for coping. Extended shear tab connections were introduced to the AISC Manual in 1992 as they allow greater geometric variation to the counter conventional configuration. The use of extended tab connections, however, comes to a position of concern when the connection flexibility is not satisfied. Higher rigidity of the connection could result in unanticipated moment development in the column that may cause yield mechanism failure due to substantial distortions in the flexible column web or sudden rupture of the bolts or weld. The excess deformation also causes a shift in the connection rotation to the weld centerline, thus limiting the relative end beam rotation. To address these concerns, a parametric study was performed to evaluate the effect of plate thickness, a-distance (distance between bolt line and weld line), skewed angle, number of bolts, and number of bolt columns. These parameters were evaluated in terms of shear strength, corresponding beam end rotation, support rotation, unanticipated moment, and connection failure mechanisms. It was observed that when the tab is connected to flexible supports the connection rotation is partially accommodated by the support, which could result in excessive distortions in the support. The a-distance is the parameter that mostly affects such behavior. Further, connections with multiple bolt columns showed most of their inelastic rotational behavior at the first column of bolts.

Fire is a common occurrence in recent years. Judging from the 21 case studies reviewed in the present study, the approaches adopted in the assessment of fire-damaged concrete building structures varied considerably. A practical comprehensive guide for adopting the best approach for the assessment of fire-damaged concrete building structures is presented after a review of existing literature, including the case studies. Some issues in the assessment of fire-damaged concrete building structures are discussed, including the advantages and disadvantages of various nondestructive tests and core tests, to help practicing engineers in selecting the most appropriate in situ testing of concrete of fire-damaged concrete building structures. The various tests and image analyses to determine the depth of the fire damage to concrete structures are also discussed. The most common repair materials for structurally inadequate structural members are sprayed concrete and flowable polymer-modified cementitious materials. The advantages and disadvantage of sprayed concrete for the repair of structurally inadequate structural members of fire-damaged structures are represented.

This research project focuses on evaluating the influence of Canadian seismic design provisions on the resistance of reinforced concrete buildings against the differential settlement of their foundation. Three types of moment-resisting frame buildings located in Vancouver, Montreal, and Toronto were designed in accordance with the latest editions of the [NRCC (National Research Council Canada). 2010. National building code of Canada. Ottawa: National Research Council Canada]. The buildings in each location were designed for three span lengths, namely, 4, 6, and $8\mathrm{m}$. A total of nine finite-element models were developed using SAP2000 version 20 with structural element nonlinearity being represented through plastic hinges at the ends of beams and columns. A nonlinear analysis was performed on each model by gradually subjecting a center column to a settlement of 100 mm. The analysis reveals that buildings with a shorter span (e.g., $4\mathrm{m}$) length are more vulnerable to settlement-induced damage than buildings with longer spans (e.g., $8\mathrm{m}$). Failure of the settling column occurs at settlements that exceed the range of maximum allowable differential settlements prescribed in the Canadian Foundation Engineering Manual.

Early in the morning of March 3, 2020, a storm system producing multiple tornadoes passed through middle Tennessee. One of the tornadoes—touching down in Cookeville and Putnam County—was classified as an EF4 with winds of approximately 282 km/h (175 mph). Damage observations after the tornado in Cookeville suggest that modifications to certain common construction practices might significantly enhance resistance to extreme wind forces. This paper provides recommendations for improving strength and resiliency within residential structures, particularly in four critical areas: (1) stiffness and strength of gable trusses, (2) wall-to-floor connections, (3) sill plate anchorage, and (4) shear and tensile capacity at interior foundation piers. Though improvements to construction practices are unlikely to eliminate damage to residential structures, such measures may well mitigate damage and extend the time between onset of the extreme forces and final damage or collapse.

Calculation of stresses within a soil body due to surface loading is a required step when designing buried commodities and subgrade wall structures. The Boussinesq equation is commonly used for determining stresses in soil due to surface loading, with examples for use found industrywide. However, the available formulations have limitations, or they only cover simple cases. The purpose of this work is to review the derivation of the Boussinesq equation for vertical and lateral stresses in a soil body and to present several new, closed-form solutions for various surface load cases, including finite line and finite area loads. The formulations are presented as Cartesian coordinate functions such that the stress at any point in the subsurface plane of interest can be found, not just the peak stress or the stress contour at a specific line. This is particularly useful when considering load distribution at a lateral extent from a finite loading, which may be significantly lower than the peak loading.