Practice Periodical on Structural Design and Construction

Assessing large structures on the basis of multivariate static data sets is a challenging task for a number of reasons. One is that a low-frequency sample does not consistently capture longitudinal discrepancies in the data and thus cannot translate multivariate information into structural conditions and performance metrics. Another is the fluctuation in the data due to the synergy between loading and environmental factors. The precise elimination of these factors is difficult and can lead to inaccuracies in a structural condition assessment. In this study, an advanced machine learning framework employing the Continuous Hidden Markov Model (CHMM) is proposed to address this challenge using multivariate static data flows. Trained CHMMs are used to determine the probabilistic states of given degrees of freedom (e.g., a member or element within the structure) with respect to the input data. To build reliable training sets, two key factors need to be accounted for: (1) the numerical modeling errors inherent in training data, and (2) the sensitivity of the data to localized damage (e.g., the decrement of stiffness in a component). To handle Factor (1), an inversion-based regime is adopted to account for modeling errors by modifying the global (finite element) stiffness matrix. For Factor (2), the use of amplifying functions effectively increases the distinguishability of data and CHMMs to state changes. The efficacy of the CHMM-based framework is numerically demonstrated on a simple support beam and then on a cable-stayed bridge section. In both cases, the results demonstrate that the proposed method can capture the damage location and detect damage extent when the noise is below an acceptable level.

Concrete-filled double-skin steel tubular (CFDST) columns are a modern generation of composite columns optimized for a high strength-to-weight ratio with concrete sandwiched in the annulus between the inner and outer steel-tube skins. The cross-sectional shape of steel tubes can influence the confined concrete behavior and thus the axial load-bearing capacity of CFDST columns. This study proposed a unified approach using artificial neural networks (ANNs) to predict the refined axial load-bearing capacity of CFDST columns of multiple shapes based on combinations of circular and square steel tubes, i.e., circle-circle, circle-square, square-square, and square-circle forms. A total of 233 CFDST columns (82 tested specimens and 151 hypothetical columns) were used to formulate a detailed case study. The hypothetical columns were generated using calibrated nonlinear finite element modeling. Then, ANNs were trained using a subset of these hypothetical columns to map their geometric and material properties with the ultimate axial-load capacity. The 133 CFDST columns (i.e., 82 documented tests and the remaining 51 hypothetical columns) were finally used to check the trained ANN’s prediction accuracy and generalization ability. The analytical formulation based on the optimized ANN architecture showed similar axial-load capacity prediction accuracy (about 8% mean absolute error) across all cross-sectional shapes of the CFDST columns in the testing set. Lastly, for the practical utility of the ANN-based model, prediction adjustment factors were proposed in this study for making conservative axial load-bearing capacity estimations within a targeted error margin.

The postyield ductile damage of steel structures is gaining the interest of researchers and designers alike. The ability to model and quantify the damage of structural steel is the focus of this research and a novel approach that relies on micromechanical theories is presented to develop the finite element (FE) model for the ductile damage of double Tee and extended endplate connections. First, a methodology is presented to guide researchers and designers on how to model the FE fracture of steel material subjected to combined tensile and shear loadings using two built-in ductile damage models in ABAQUS [the Stress Modified Critical Strain (SMCS) and the Hooputra models]. Second, several steel base materials (A992, A572-50, and A36) and bolt materials (A325 and A490) are calibrated for use in both ductile damage models (SMCS and Hooputra). Third, FE fracture models are developed and validated against experimental results, available in the literature, of double Tee and extended endplate connections subjected to monotonic and cyclic loadings. The results show that the proposed FE fracture model predicts the failure mode and load-displacement response of double Tees and extended endplates with at most 9.5% deviation for the displacement at fracture and 7.8% deviation for the ultimate load. The FE fracture model predicts the postultimate strength and ductility required for seismic applications. Also, the FE fracture model predicts crack initiation in base or bolt material due to tensile and/or shear loadings. In a broader perspective, this research enables design engineers to accurately predict the postultimate behavior of steel connections with ease. The research also aims at including the fracture characteristics of steel material in the current design guidelines of steel connections.

This paper presents the case histories of deep excavation for the basements of two projects using 11 retaining walls supported by stabilizing berms. Most of the case studies reported in the literature are confined to the use of stabilizing berms to support retaining walls for deep excavation in firm overconsolidated clays but not soft normally consolidated clays. This paper reviews the performance of 11 retaining walls supported by stabilizing berms for deep excavation in soft normally consolidated clays. Only four of these 11 stabilizing berm-supported retaining walls performed satisfactorily while the other seven performed dismally. The larger horizontal deflection of retaining walls embedded in soft normally consolidated clays as compared to overconsolidated clays is caused by creep of soft normally consolidated clays. The effect of creep of soft normally consolidated clays in deep excavation is not well understood. Based on the case study of an excavation of 8.3 m (27.2 ft) deep, an empirical relationship between the retaining wall deflection due to creep of soft clays and the total thickness of soft clays is established. The present study highlights the need to check the slope stability of the stabilizing berms in soft normally consolidated clays during excavation. This has never been thought to be necessary for stabilizing berms supporting retaining walls in overconsolidated clays for deep basement construction.

Abstract

Basement excavation will cause installed piles to move laterally. It is very common for driven piles in developments with two-level basements to have large eccentricities from their intended positions at the cut-off level of the piles. However, this naturally occurring phenomenon is not well recognized in the construction industry. This is evident from the fact that the allowable pile eccentricity specified in many technical specifications for developments with basements is fixed at 75 mm, which normally is specified for pile foundations of developments with no basement construction. This paper used a case study to illustrate the extent of such pile lateral movements as a result of basement excavation. The effect of such lateral movements on the pile foundation design was discussed using the case study. Appropriate allowable pile eccentricity for driven piles for developments with deep basements are proposed.

Practical Applications

It generally is known that excavation for basement construction causes large lateral movement of preinstalled piles. However, the allowable pile eccentricity for single piles and pile groups specified by most practicing engineers is appropriate for developments without basements. This means that the risks for a large pile’s lateral movement as a result of the excavation are borne by piling contractors, even though to a large extent such risks are beyond the control of piling contractors. The findings of this study are useful for practicing engineers to specify the allowable pile eccentricity for single piles and pile groups in developments with basements to achieve a fairer risk allocation for piling contractors and developers. The ultimate aim is to achieve a more competitive piling cost for developments with basements, because piling contractors do not have to price for risks that have been allocated unfairly to piling contractors.

This research evaluates the geometric non-linear behavior of structures often used in transmission lines (TLs) and verifies the influence of different wire lengths, average wind speeds, and unevenness between adjacent towers, using the IEC 60826 standard. Different finite element numerical models were developed considering the isolated tower and also the complete system (tower, wires, and insulator chains). The analyses revealed that a simplified model can be employed for cases of adjacent, equal-length spans, but for cases with different lengths, the effect of geometric nonlinearities (GNLs) can become expressive and influence the type of analysis to be performed. Furthermore, it was found that increasing the average wind speed may imply an increase in the longitudinal unbalance. Finally, it was concluded that the unevenness between spans should be considered when calculating the loads to be applied to the structure, even if the simplified model is used. Based on the outcomes and considering wind speeds between 30 and $40\mathrm{m}/\mathrm{s}$ and adjacent tower unevenness between 0 and 10%, this work establishes practical design criteria to be used by designers in the design of suspension structures of TLs located in the State of Minas Gerais, Brazil. The methodology presented in this paper can be extrapolated to other regions of the country, paying attention to the fact that the recommendations proposed here are valid only for self-supporting towers.

Concrete-filled double-skin tube (CFDST) columns are considered one of most efficient forms of steel-concrete composite columns, which provide higher axial strength and better ductility compared with their counterpart concrete-filled tube (CFT) columns. This paper aims to numerically investigate and compare the performance of axially loaded circular CFDST short columns provided with stiffeners in inner tubes and outer tubes. Circular steel hollow sections have been adopted for inner as well as outer tubes, and rectangular steel stiffeners were fixed in inner and outer tubes to check the effectiveness of stiffeners in stiffened CFDST columns. These CFDST columns were investigated numerically by using a verified finite-element (FE) model from commercially available software. Behavior of 36 unstiffened, inner-tube stiffened, and outer-tube stiffened CFDST columns (12 each) was studied. The FE results were verified by comparing them with previous test results. The FE analysis study has exhibited an increase in peak load (load-carrying capacity) up to 26% and 15% in outer-tube stiffened CFDST columns compared with unstiffened and inner-tube stiffened CFDST columns, respectively. Also, enhanced ductility has been observed in case of these stiffened CFDST columns.

Point analyses of geotechnical measurement have been identified as a source of building errors. Unfortunately, more than 75% of building professionals continue to make this error. It is proposed here that beyond modifying supportive analytic tools (SAT) to interpret field measurement, there is a need to incorporate geographical information systems (GIS). At the Nya Ullevi Stadium in Gothenburg, Sweden, Eleven-point measurement of cone penetration testing (CPT) was carried out to a depth of 3 m using a 100-kN CPT machine with a 60° cone-shaped point. Aside from the soil profiling associated with CPT, spatial mapping was used to identify likely geological shifts/ground movements that may occur east to west and north to south. Localized pressure points (LPPs) were identified and traced to hard silty sandy clays. When these LPPs diverged, more LPPs occurred with relatively low cone resistance (CR) at the left side (northwest, southwest directions) and high CR at the right side (northeast, southeast directions). An undulating soil profile (based on CR magnitude) looks more like a sine wave pattern at $n=2/5$ and a cosine wave pattern at $n=4/5$. Soil movement in the construction site was nonuniform, leading to differential movement of the soil supporting the foundation. Based on the findings of this research, it is recommended that varying concrete quality for the construction of piles should be adopted due to the varying load distribution that may occur after stadium construction.

Several aftershocks can occur after a strong mainshock and lead to additional structural damage. The investigation of the seismic response of bridges is more challenging when the effects of incident angles of mainshocks and subsequent aftershocks are considered. This study investigates the effects of the ground motion incident angle on the nonlinear structural responses of skewed bridge structures against mainshock–aftershock sequences. For this objective, the seismic performance of a 60° skewed bridge located in San Fernando, California, is examined under real bidirectional mainshock–aftershock sequences. In this study, ground motion directionality effects were investigated considering the relative difference between mainshock and corresponding aftershock incident angles. The results showed that taking into account the incident angles of both mainshock and the corresponding aftershock can significantly affect the seismic performance of skew bridges. In particular, when the difference between the angles of the mainshock and corresponding aftershock was considered, the nonlinear responses of the case study increased up to 65.56%.

The structural performance of concrete structures requires swelling the bending and shear characteristics of reinforced concrete (RC) beams. The bending characteristics of RC beams consisting of waste granite aggregate (WGA), steel fibers (SF), polypropylene fibers (PF), and glass fibers (GF) are assessed in this research. Twenty-one $\mathrm{2,000}\mathrm{mm}\times 200\mathrm{mm}\times 250\mathrm{mm}$ RC beams were cast and tested. WGA was sorted and utilized instead of natural coarse aggregates (NA), with three mass replacement fractions: 0%, 50%, and 100%. Besides, SF, PF, and GF were utilized separately at three fractions of 0%, 0.5%, and 1%. Beams were loaded under a four-point bending arrangement, and the ultimate bending resistance, deformability, stiffness and crack development were recorded and assessed. Also, an evaluation of experimental results and existing design standards in terms of maximum crack width has been carried out. Moreover, a cost-sensitivity examination has been made to analyze the effectiveness of using various fibers in terms of cost. Experiments revealed that the impact of PF on enhancing the load-bearing capability of beams with WGA was greater than that of strengthened with SF and GF. However, the impact of GF on the ultimate deformability of WGA RC beam samples was superior to that of PF and SF. PF has a greater influence on enhancing the flexural capacity of RC beams than SF; nevertheless, SF has a greater influence on deformation. The ductility and deformability of RC beams were substantially enhanced when GF was introduced in specimens made with WGA.

A nearby construction with a pile foundation in an urban area can cause possible damage or an operational safety concern to the existing tunnels. The response of the tunnel will depend on the relative location of pile tip as compared to the existing tunnel depth. This paper describes an experimental investigation carried out in the laboratory to examine the effect of pile loading on the existing tunnel in Delhi silt. A small-scale testing facility was designed and built to investigate the influence of pile loading in the close vicinity of the existing tunnel. Dimensions of the model tunnel and pile were arrived at based on the physical scaling laws. The model tunnel (outer diameter of 150 mm with thickness of 0.5 mm) and piles (outer diameter of 25.4 mm with thickness of 1.0 mm) are made up of aluminum. Tests were carried out in a fabricated model steel tank (1,100 mm wide, 1,600 mm long, and 1,200 m deep). Experiments were performed at various stages of pile loading at a separation distance of 1.0, 1.5, and 2.0 times the tunnel diameter from its axis. Results indicate that the strain in tunnel lining is significantly affected by various stages of pile loading when the row of pile is placed within the distance of 12 times the pile diameter from the axis of the tunnel. Three-dimensional numerical simulations of model experiments were also carried out, which fairly predicted the phenomena measured in the experiments.

Electronic Construction (e-Construction) is being increasingly used to minimize the amount of paperwork and simplify the daily operations inherent in the construction of highway infrastructures. Electronic ticketing (e-Ticketing) is a part of e-Construction that aids in the transfer of material tickets in a digital manner, accounting for more than half of construction costs; however, the technology has been pilot tested by several states since the beginning of 2013 and has been disbanded for various reasons. The purpose of this research is to pinpoint the challenges in the deployment of an e-Ticketing platform, as well as to determine the adoption rate of state departments of transportations (DOT) and to assess the benefits. The research method includes a combination of literature review and semistructured interviews to achieve the study’s objectives. An inductive thematic analysis approach was used to analyze the interview transcripts. The study’s findings are related to the reasons for delays and misconceptions about the implementation of the e-Ticketing platform. Internet connectivity at construction sites and high investment costs were found to be the major challenges that have delayed the implementation of the e-Ticketing platform. The study’s results will aid decision makers in DOTs and engineers build a standard e-Ticketing platform, implement rules and guidelines, reduce investment costs, execute pilot testing, improve inspector safety, and complete projects in a timely and efficient manner.

Enterprise risk management (ERM) is known to be an important internal component within companies for identifying, evaluating, and managing various risks for the achievement of organizational objectives. The after-effect of the global financial crisis in 2008 as well as continued rising inflation in various countries in recent times has led to a drastic change in the management of risks by organizations. In spite of the benefits of ERM, several factors seem to influence its implementation in construction companies. This study aims to examine the factors influencing ERM implementation of construction contracting firms with the purpose of providing answers to the following research questions: what is the categorization of the factors inhibiting ERM implementation in construction contracting firms? Does the type of ownership of construction contracting firms influence the factors promoting ERM implementation within the respective firms? The study adopted survey research. A purposive sampling technique was used to administer 96 questionnaires to registered contracting organizations involved in the planning and subsequent execution of construction contracts in Lagos state, Nigeria. The data collected were analyzed using descriptive and inferential statistics. The study revealed that top management related and organizational related factors are the significant factors inhibiting ERM implementation. It was also highlighted that there is no significant difference among construction contracting companies on the factors promoting ERM implementation. The study concluded that awareness of the concept by top management aids implementation and supports as a business strategy.

Modal frequency is widely utilized to reveal the health status of bridges; however, its warning capability may be reduced due to changing environmental conditions, i.e., the variations in temperature, humidity, and wind speed. Besides, accurately tackling these problems related to the high-dimensionality of environmental data, multivariate prediction of multiorder frequencies, reasonable quantification of the environment-caused modal variability, and the nonnormal distribution limitation of data are also a prerequisite for high-quality integral performance warning of bridges. Consequently, a multiorder frequency-based performance warning method for bridges is presented in this paper. Multivariate partial least squares analysis is first employed to extract the predominant feature vectors of environmental factors, which are sensitive to measured multiorder frequencies, for dimensionality reduction. After that, the environment-induced modal variability can be quantified with the derived frequency correction formula. Based on this, a performance warning index is constructed based on the support vector data description, which aims to address the problem associated with the nonnormal distribution of model errors and further strengthen the warning capability of frequency abnormality. The test results on a cable-stayed bridge indicate that the variation of normalized frequency tends to be more relatively stable, and the slight abnormal mutations of multiorder frequencies are timely detected, whose warning rates increase as the performance degradation, significance levels and considered modal orders increase.

Testing full-scale structures in the laboratory is not always doable nor financially feasible, especially for large structures. Therefore, these structures are often modeled with Finite Element Analysis (FEA) software and packages, such as Abaqus, to understand their actual behaviors under special simulated loading and material-behavioral considerations. This study developed a material model that simulates load-induced cracking in reinforced concrete (RC) elements in the FEA of structures. The simulation of complete stress–strain concrete behavior under tension and compression (including damage characteristics) requires the application of numerical material models, potentially producing the stress–strain curves. These models include strain-softening regimes that presuppose the use of ultimate compressive concrete strength and that can be practically implemented for existing or future RC structures. The method presented in this study is valuable because it assesses existing RC structures when detailed test results are not available. However, the implemented numerical models were slightly altered in order to compare them with the damaged plasticity models available in the research literature. These are mainly the smeared crack concrete model, the brittle crack concrete model, and the concrete damaged plasticity model, which are all typically suitable for RC elements. The methodologies proposed here provide accurate and realistic modeling of the plastic damage of RC members. Although numerically extensive and very time-consuming, it is demonstrated that the material and damage modeling presented in this paper can be used to accurately represent the behavior of actual structural members tested in research laboratories. This suggests that it is applicable to structures for which experimental tests or monitoring data are not available.

To safely and effectively demolish high-rise RC buildings with heavily arranged reinforcement using an explosive technique, the use of internal blasting alone is not sufficient to reduce the strength of RC members down to the demolition level. In some cases, it is essential to employ a new explosion technique to cut reinforcing steel bars in the RC members. Thus, this paper examines the technique of using linear-shaped charges in cutting reinforcing bars in the RC members. Investigated variables include the concrete cover, the diameter of reinforcing steel bars, the compressive strength of concrete, and the amount of explosives used in the linear-shaped charge. Test results indicate that it is possible to cut the reinforcing bars embedded in concrete using a linear-shaped charge technique. The amount of explosives required for cutting reinforcing steel bars depends largely on the concrete cover and diameter of reinforcing bars rather than the compressive strength of concrete.

The seismic response of a structure is very complex owing to the behavior of soils during an earthquake. The importance of including the soil–structure interaction (SSI) effect in building frame analysis is quickly recognized, but the modeling of SSI is complicated. The present paper investigates the seismic response of a RC building incorporating soil–structure interaction. The research focuses on clayey soil conditions in situ, taking into account soft, medium, and hard soil. The SSI effect is accounted for by using a point spring element and a fixed support condition. For the study, a RC ground (G)+10-story building with a basement is considered with L-shape (L-SW) and T-shape (T-SW) shear walls resting on a raft foundation. To comprehend the different circumstances of the soil on the structure for comparison study, the responses of some parameters such as story drift, story displacement, and base shear are obtained. The findings of the study show that including SSI effects in the seismic design of multistory buildings is critical because it can result in a significant reduction in controlling design forces without compromising the structure’s safety. Moreover, assuming a fixed base can lead to a high overestimation of the structure design forces and seismic response. The aim of the present study is to obtain the behavior of the RC building under different soil conditions considering two types of shear walls.

In designing and evaluating roadway bridges in the surface transportation infrastructure, truck load is a major variable to account for. For daily operation, truck load also is a primary factor. Trucks on continuous spans were studied, with a focus on their behavior of longitudinal multiple presence in the same lane(s). Current US specifications include provisions for how to account for such multiple presence, and these provisions have evolved over the years. However, the basis for the provisions and their changes have not been well documented. An unprecedentedly large number of high-quality in-motion truck weight data were gathered in eight states across the US and used to investigate trucks’ longitudinal multiple presence behavior. A new approach to analyzing each platoon of trucks recorded in traffic was developed for this purpose. Each random platoon’s total load effect was identified, covering every truck in the platoon, to obtain reliable statistics of the maximum load effects. Results show that longitudinal multiple presence increases with truck volume and span length. Relevant current AASHTO provisions therefore were found to be conservative or overconservative. Accordingly, it was concluded that lower longitudinal multiple presence factor values for evaluation and design are more justifiable. These results may be used by bridge owners and engineers for realistic load rating and design, for more-uniform structural safety and cost effectiveness. This is consistent with the top two goals of the AASHTO Committee on Bridges and Structures’ strategic plan for extending bridge service life and assessing bridge condition.

The construction industry is a significant contributor to global greenhouse gas (GHG) emissions. A large proportion of these emissions is given off by non-road equipment used for the construction operation process. There are several models available to estimate the emissions level from the equipment, but these models do not adequately represent real-world environments and work cycles. In addition, these models do not incorporate some crucial characteristics of the equipment, such as equipment type, age, fuel type, and fuel consumption rate. This study aimed to assess the severity of air pollution caused by construction equipment by implementing a real-time simulation model. The study further analyzed the level of emissions compared to their allowable limits and statistical correlation among the pollutants. The motor vehicle emissions simulator (MOVES) was used to simulate the real-time emissions of four criteria pollutants: carbon monoxide (CO), nitrogen dioxide (${\mathrm{NO}}_2$), sulfur dioxide (${\mathrm{SO}}_2$), and particulate matter (${\mathrm{PM}}_{10}$), along with carbon dioxide (${\mathrm{CO}}_2$) from four different types of non-road construction equipment (two excavators, one forklift, and one mobile crane). The pollutants were selected for the study based on their adverse human health impacts. Data were collected for 60 days from a construction site, excluding the weekends. Analysis of the simulation suggested that the equipment released a notably high concentration of pollutants. Most of these pollutants are strongly correlated to each other. The outcomes of the study will help manufacturers and equipment operators to optimize fuel consumption rates and select environmentally friendly fuel types. Also, the study will provide insight into the severity of non-road-equipment emissions and their negative impacts on GHGs.

This case study describes an evaluation of the existing conditions of a concrete floor in an industrial hall located in Poland. The areas requiring improvement due to poor workmanship, as well as the age of the floor, were identified. The second part of the study is devoted to the procedure of making an innovative epoxy coating modified with granite powder, which is based on the authors’ previously published research. The analysis describes the effects of adding 10% to 60% (graded every 10%) of the powder. The primary aim of the tests was to obtain the highest possible pull-off strength. Compared to the reference sample, the highest increase in strength, 18%, was obtained with the addition of 20% granite powder. Moreover, resistance to thermal shock, one of the most important parameters of epoxy floors, was also analyzed and discussed. Standard coatings are typically not resistant to thermal shock, but the innovative coating proposed in this study allows for increased resistance by up to several dozen percent. The relationship between the amount of granite powder added and the limit value of thermal shock resistance is presented in the article. The novelty of the case study involves the proposal of a comprehensive procedure of renovating floors, including the assessment of their condition, the repair methods, their surface strengthening, and the presentation of the characteristics of the new coating.

This paper presents experimental and theoretical results for the pullout resistance of anchor studs embedded in concrete blocks with inclined planes that simulate punching. This type of reinforcement has been widely studied to combat punching between the slab–column connection, but little information is available about its effect on the region of the inclined shear plane. To simulate this situation, six concrete blocks were made with a single embedded stud; the inclination planes were varied (18°, 30°, and 45°). The effective heights were 50 and 75 mm, and the section widths were 300 and 500 mm. The theoretical analysis was carried out by comparing the estimated load obtained from analytical models found in the literature with the failure load of the tested specimens. The results showed that the inclination plane did not significantly influence the pullout loads of the studs for the studied effective heights, because the configurations generated by the failure surface of the concrete cone trunks tended to stabilize in tension. However, the series with the 30° angle had slightly higher failure loads. The variation in concrete compressive strength did not influence the failure loads, revealing that the concrete strength grade <40 MPa can be an economical alternative in the design of concrete blocks or slabs reinforced with inclined studs.

Twin-cell box girder bridges are among the best choices to accommodate larger carriageway width with minimal construction difficulty when compared to other multicell box girders. Simplified frame analysis (SFA) is a method used in the design of box girder bridges, using which transverse bending moments can be found either manually or with the help of a simple computer program. As SFA is an approximate method, the usual practice is to increase the transverse bending moments obtained from SFA by 20%, which may not lead to the safe design of a structure. To eliminate these errors, correction factors are established by comparing the SFA results with three-dimensional finite element analysis conducted using CSi Bridge software. So far, these correction factors are established only in the case of single-cell concrete box girder bridges. As of now no literature can provide a detailed estimate of the correction required for the results obtained from SFA in the case of twin-cell box girder bridges. In the present work, correction factors are found for a simply supported twin-cell box girder bridge. An example illustrating the use of these correction factors for a safe design is also provided in the Appendix.