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Practice Periodical on Structural Design and Construction

Practice Periodical on Structural Design and Construction

Archives Papers: 110
The American Society of Civil Engineers
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Transverse Bending Analysis of Twin-Cell Concrete Box Girder Bridges Using Simplified Frame Analysis
Chithra Jayasree; Praveen Nagarajan; and Sajith Arumughom Sreekumari
Abstracts: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.
Influence of Fiber Type on the Performance of Reinforced Concrete Beams Made of Waste Aggregates: Experimental, Numerical, and Cost Analyses
Arash Karimi Pour, S.M.ASCE; Amir Shirkhani, S.M.ASCE; Mehmet Serkan KIRGIZ; and Ehsan Noroozinejad Farsangi
Abstracts: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 2,000    mm × 200    mm × 250    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.
Effects of Ground Motion Incident Angle on Inelastic Seismic Demands of Skewed Bridges Subjected to Mainshock–Aftershock Sequences
Alireza Garakaninezhad; Saeed Amiri; and Ehsan Noroozinejad Farsangi
Abstracts: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%.
Simulation of Real-Time Operational Level Emissions from Nonroad Equipment: Case Study of a Construction Site
Sai Akhila Boddi Reddy; Shafayet Ahmed; and Ingrid Arocho, M.ASCE
Abstracts: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 ( NO 2 ), sulfur dioxide ( SO 2 ), and particulate matter ( PM 10 ), along with carbon dioxide ( 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.
Geometric Nonlinear Analysis of Self-Supporting Structures for Overhead Transmission Lines
Elvys Dias Reis; Hermes Carvalho; Camila Cordeiro de Oliveira; João Antônio de Vasconcelos; Ricardo Luiz da Silva Adriano; and Danilo Campos Lopes
Abstracts: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    m / 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.
Allowable Eccentricity of Pile Groups for Deep Basements
Yue Choong Kog, Ph.D.
Abstracts: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.
Deep Excavation in Soft Normally Consolidated Clay
Yue Choong Kog, Ph.D.
Abstracts: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.
Methodology and Application of Ductile Damage Modeling on Double Tee and Extended Endplate Connections
Sana N. El Kalash and Elie G. Hantouche, A.M.ASCE
Abstracts: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.
Applying the Continuous Hidden Markov Model to Structural State Estimation
Li Lai; Iman Hajirasouliha; Kypros Pilakoutas; Xu He; and Danny Smyl, A.M.ASCE
Abstracts: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.
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