Practice Periodical on Structural Design and Construction

The current construction industry for civil and structural engineering is considered to be one of the growing industries in the world. With the push toward a more digitized industry, emerging trends such as additive manufacturing and the use of three-dimensional (3D) printing technology, along with consumer demand, are resulting in automated development with multiple benefits. Successful applications for small-scale construction projects that have implemented 3D printing have shown improvements in cost, production time, and design freedom and complexity. However, for large-scale applications, there are various limitations and factors hindering the adoption of additive manufacturing technologies. In this paper, a systematic literature survey of recent 3D printing technologies was conducted specific to the area of construction engineering, and the various techniques, materials, software, and technical and nontechnical aspects were analyzed. The key applications and their benefits are outlined, and their potential for large-scale applications is articulated. Future research areas for these components are suggested to strengthen the technical readiness and feasibility of adopting 3D printing technology in construction engineering and industries.

Among the best methods for identifying, preventing, minimizing, and compensating for any negative effects on the environment and promoting sustainability is environmental impact assessment (EIA). However, a number of variables make it difficult for EIA practices to be effectively implemented in the construction sector. The implementation of EIA methods in the building industry is further hindered by a lack of empirical studies on the subject. With Nigeria as a model, this article seeks to understand the perceived barriers to EIA practice implementation in the construction sector. For the purpose of the study, a survey research methodology was employed. A snowball sampling strategy was adopted to determine the important stakeholders in EIA practice for the administration of the questionnaire. Participants in the survey received 187 questionnaires altogether. The data collected were analyzed using descriptive and inferential statistics. Results from data analysis show that the factors inhibiting the adoption of EIA practice can be categorized into four constructs: administrative-related factors; financial-related factors; human capacity and behavior related factors; and government regulations, legislations, and laws related factors. This study identifies the factors inhibiting EIA use in the construction sector. Understanding these elements would make it easier to build the necessary strategies to lessen the barriers to EIA use in the construction sector.

This investigation was conducted to study the response of reinforced hybrid beams exposed to flames and their capacity for carrying loads. At the age of 28 days, concrete samples and beams were exposed to fire temperatures ranging from 25°C to 600°C. Then, the beams were gradually cooled by being left in the air. The testing samples were exposed to flames for a half hour at temperatures of 600°C. All ultrahigh-performance concrete (UHPC) specimens (cubic, cylinder, and prism), upon burning at 600°C, spalled and lost some of their mechanical characteristics. Results indicate a remarkable reduction in compressive strength; the residual compressive strength was 78% and 62% for conventional and ultrahigh-performance concrete, respectively. Therefore, the remaining tensile strength was 77% and 69% for normal concrete and UHPC, respectively, and the residual flexural strength was 41% and 64% for conventional concrete and UHPC, respectively. Four beams consisting of two kinds of concrete, normal concrete (NC) and UHPC, were subjected to flame, and another four reference beams with dimensions of 12 cm width, 15 cm depth, and 170 cm length were used in this study. The results showed that the effect of firing on the UHPC part was larger than on the normal concrete part, and that led to an effect on the beams’ behavior and mode of failure. For reference beams, it can be seen the use of the UHPC layer at the compression zone played a major role by changing the mode of failure from compression (as in beam R1) to flexural failure (as in beams R2 and R3). However, after firing, the mode of failure returned to compression failure because the influence of firing on the UHPC part was greater than on the normal concrete part at 600°C. This study is considered important in buildings that must be highly durable and are likely to be exposed to fires. It is clear when using a layer of UHPC in the NC beam affected by fire that it is possible to benefit from this beam after removing the surface damaged by the fire and making repairs on the surface of the beam.

The present study proposes a novel yet straightforward method for calculating the bearing capacity of deep beams using the theory of lower-bound limit analysis. The equations of the proposed method are obtained from the evaluation of the stresses induced in concrete and reinforcements of deep beams. The modified Mohr-Coulomb yield criterion is utilized to constrain the concrete stress states. Because the proposed method and relevant equations are simple and noniterative, they can be easily employed for design purposes. Moreover, the equations can be applied to beams with and without shear reinforcement. However, the method is limited to deep beams with rectangular cross sections and without openings. In order to assess the accuracy of results, the shear strengths of deep beams obtained by the proposed method are compared with experimental results and the results obtained by the strut-and-tie model. The evaluations of 225 tested deep beams show that the mean ratio of calculated strength to the strength obtained from the test result is 0.94, and the coefficient of variation is 0.22. The variations in results of the proposed method are also investigated for various components, such as the compressive concrete strength, the shear span-to-depth ratio, and the reinforcement ratio. This study shows that the trend of changes in the strength of a deep beam with respect to these components agrees with experimental results. The simplicity of the method is illustrated by an example.

Vertical openings in beams and girders are sometimes used to facilitate the passage of essential services such as HVAC, electricity, and sewage. There is a lack of research on the effects of vertical openings on deep reinforced concrete beams. In this work, 11 RC deep beams were tested to failure, examining key parameters, namely, location of opening, opening shape, and strengthening technique around the opening. The beam ultimate load ($P_u$) and to a lesser extent stiffness were found to be affected by the presence of openings, wherein those located in the shear span reduced $P_u$ by 12%–19% and those in the constant-moment region contributed to a respective decrease of 8%–13%. The reduction in $P_u$ is also related to the opening shape with rectangular and circular shapes, resulting in the largest and smallest decrease, respectively, and square being in the middle. Two techniques were proposed to mitigate the openings effects, namely, using ultrahigh-performance concrete (UHPC) in the vicinity of the opening, and reinforcing the surrounding opening area with horizontal and vertical steel bars. Both were found effective, with the former resulting in 14% and 10% increase in $P_u$ relative to beams with openings located in the shear and moment regions, respectively, and no strengthening. Additionally, $P_u$ from tests were compared with those calculated using the strut-and-tie model (STM) and an empirical formula from current US standards. Modifications to the STM model, which resulted in better predictions than the expression from current standards, but still needed improvement, were presented, and resulted in an analytical-to-experimental $P_u$ ratio of 0.99 to 1.05.

Experimental research was carried out regarding the flexural behavior of three full-scale external beam-column concrete joints cast with plain concrete in the presence of shear reinforcements in the joint regions constituted by horizontal and/or vertical stirrups and subjected to cyclic load reversals. Three specimens were designed to fail in the joint region. One had only one stirrup in the joint; another was confined with three horizontal stirrups in the joint; and one additional specimen had three horizontal and three vertical stirrups. The experimental results show that it is also possible to increase the shear strength of the joint regions and the bond strength of longitudinal bars of beams under cyclic reversal actions. From the analytical point of view, a simple model based on the limit state due to concrete crushing with horizontal and vertical transverse stirrups in both the elastic and plastic states was proposed with good prediction of experimental results and good results in comparison with other existing analytical expressions for shear strength prediction of joint regions. The original contribution of the research is to consider the concrete confinement of a strut member and its interaction with horizontal and vertical stirrups in the prediction of shear strength of a joint region.

The installation of structural glass systems, such as skylights and curtain walls, may improve the aesthetic and functional value of a building. These attractive systems have practical benefits like increased efficiency and lower maintenance costs. The importance of structural analysis and design in developing safe and dependable structural glass systems is underscored by this study, which thoroughly evaluates various skylights installed at a height of 15 m located in Doha while subjecting them to a 1.6 kPa wind load. The temperature loading is determined by assuming an initial temperature of 10°C and an ultimate temperature of 50°C. Therefore, the temperature variation is $\pm 40°\mathrm{C}$. Several acceptance requirements have been met. It is crucial to adhere to design requirements and execute extensive performance testing and verification to guarantee the safety of structural glass buildings. The research also highlights the significance of using sound foundation design and anchoring methods on-site. The findings of this study might serve as a helpful reference for façade engineers responsible for designing structural glass structures, as it highlights the significance of careful analysis, design, and verification in ensuring the safe and dependable performance of such architectural features in a wide range of buildings. The study indicates that proper design regulations and standards, coupled with the use of specialist software tools, precise three-dimensional (3D) models and simulations, and extensive performance testing and verification, are essential in guaranteeing the safety and dependability of skylights. It has been found that the final design of the skylights is safe and structurally sound; this includes the use of fully tempered double glazed unit (DGU) glass of 6 mm (inner lite) + 16 (air gap) + 13.52 ($6+1.52+6$ outer laminated lite), 120 mm deep Mullions and transoms, and appropriate anchoring mechanisms using chemical anchors.

Bridges are among the key elements of the transportation network. Many bridges are severely damaged or destroyed when subjected to earthquakes. One of the effective methods to reduction of a bridge’s seismic damage is to upgrade the seismic codes. Equivalent static analysis (ESA) is the most conventional method for the seismic design of bridges. Bridges can be classified into two groups based on the connection system between the superstructure and substructure, namely isolated bridges and integrated bridges. In this paper, the adequacy of the ESA method is investigated to estimate the seismic base shear force (BSF) of controlled (isolated) bridges and integrated bridges according to AASHTO, Caltrans, and ATC-32 provisions. For this purpose, three bridges are modeled in three dimensions. The effects of lead rubber bearings, friction pendulum bearings, and viscous dampers on the response of bridges are evaluated using eigenvector analysis, ESA, and nonlinear dynamic analysis. The results indicate that there are significant differences between the BSF estimated by the ESA method and in different provisions. The results of nonlinear dynamic analysis indicate that energy dissipation equipments can decrease the seismic response of structures. Also, the use of the ESA method can only be employed for an initial estimate of the BSF of vibration-controlled bridges. For the detailed study and design of bridges, the ESA method does not provide an accurate estimate of the BSF. This is why the use of the ESA method is not recommended.

This paper investigates the flexural behavior of composite deck slabs using a two-point line load test. Six full-scale, one-way, single-span, simply supported composite slab specimens were tested using M20 grade concrete and two equal line loads applied symmetrically at six different shear span lengths. Additionally, two slabs containing polypropylene and steel fiber reinforcement were tested with loading at one-third span. The study analyzes various parameters such as load–deflection behavior, slip between the concrete and steel sheet, crack width, crack pattern, and ultimate load. The performance of fiber-reinforced slabs is compared with normal concrete mix slabs to assess the impact of fiber reinforcement on the flexural behavior. A standard methodology was employed to determine the slip modulus ($k$) and the slip-hardening coefficient ($m$) using the two-point test. The obtained $m$ and $k$ constants are compared with relevant data from the literature to validate the test’s accuracy. Furthermore, the ultimate load-carrying capacity of the composite slabs is calculated and analyzed. The findings confirm the relevance of the $m\text{-}k$ constants, highlighting their significance in characterizing the composite slab’s shear behavior and design considerations. Overall, the experimental investigation provides valuable insights into the flexural behavior of composite deck slabs, offering practical implications for construction practices and design guidelines. The comparison between normal and fiber-reinforced slabs sheds light on the benefits of using fiber reinforcement, while the validation of the $m$ and $k$ constants ensures their reliable application in assessing the shear performance of composite slabs.

Carbon-based nanomaterials are currently used to reinforce cement-based composite materials based on their superior properties. However, the mechanical performance of the cement-based composite materials can be improved by achieving an effective dispersion of nanomaterials in the cement matrix. Hence, this study investigates the effect of the surfactant coating method with or without the help of ultrasonication to promote the use of graphene in cement mortars. The dosages of graphene materials used were 0.01%, 0.02%, 0.03%, and 0.04% by weight of cement. A commonly used polycarboxylate superplasticizer (PCE) was used as a dispersant agent of graphene with a surfactant-to-graphene weight ratio of $9:1$. Dynamic light scattering (DLS) analysis was utilized to assess graphene aqueous suspensions and obtain the optimum surfactant-to-graphene weight ratio. In addition, compressive strength tests and scanning electron microscopic (SEM) micrographs were employed to verify the embedment and dispersion of graphene in the cement matrix. As a result, the 28-day compressive strength of the cement mortars containing graphene with 0.03% by weight of cement was enhanced by 17.5% and 13.7% for ultrasonication with surfactant coating and mechanical blending with surfactant coating employed as dispersion methods of graphene, respectively, compared to the control specimens. However, mechanical blending with surfactant coating is more convenient than ultrasonication with surfactant coating in terms of practicality and cost.

Abstract

Fatigue is an important issue for the failure of steel railway bridges. It is very challenging for a railway industry to regularly monitor the fatigue safety of millions of steel railway bridges in a cost-effective and easy way requiring the least worker effort and software expertise. This case study presents the fatigue life assessment (FLA) of an existing railway bridge in a simple and easy way. Microsoft Excel (for calculation of limit states of failure and fatigue life) and STAAD.Pro or similar structural analysis software (for modeling of the bridge truss) was used. A total station was used to ascertain the actual behavior of the bridge and to derive a correction factor. The various limit states of normal and shear stresses and strains in truss members and pot–polytetrafluoroethylene (PTFE) bearing components are addressed in a single procedure. The accuracy of the method was validated using a case study of a failed railway bridge. LVDT-based deflection measurements showed the accuracy of the adopted total station instrument–based experimental program. To check the fatigue safety of the bearing components, available equations from the literature were used to make the procedure easy and quick. In addition, the accuracy of the equations was ensured through a detailed numerical modeling of pot-PTFE bearings using finite-element modeling in Ansys. The results show that among the various limit states of normal and shear stresses and strains in truss members and bearing components, the shearing strain limit state of the elastomeric pad of the pot-PTFE bearings governs the fatigue life, which often is disregarded in usual FLA. The results indicate that the adopted method is cost- and time-effective.

Practical Applications

This case study presents a fatigue life assessment procedure executed on a real-life steel railway bridge. The procedure is quick, easy to implement, requires less funding and human effort, and can be used for many bridges. The adopted procedure requires only structural analysis software such as STAAD.Pro, MS Excel, and a total station surveying instrument. The total station surveying instrument is used to arrive at a corrected factor from the measured deflection values, which validates the analytical model of the steel bridge with the real-time behavior of the bridge at site. Skilled specialist human effort or software personnel with expertise in Ansys fatigue workbench, Abaqus, and UMAT interfaces are not required. The total station surveying–based approach quite accurately captured the failure of another real-life railway bridge, which failed in fatigue. The procedure is generic in nature and can be applied to other types of railway bridges with different types of bearings. The method can investigate the failure of stress- and strain-based fatigue failure of different bearing components and various limit states of truss or frame members in a single procedure in a computationally efficient way.

Abstract

The Tennessee Department of Transportation has charge over 31 bridges using steel girder–stringer–floor beam construction. While no distress in the stringers of these bridges has been observed during inspection, load rating calculations have indicated insufficient capacity. To reconcile this apparent contradiction, the research described herein investigated the behavior and capacity of stringers in girder–stringer–floor beam bridges by: (1) conducting a literature review of the current state-of-practice and emerging research regarding the capacity and behavior of girder–stringer–floor beam bridges; (2) experimentally measuring strain under known loading at various locations and identifying characteristic behavior in the stringers and girders of the Billy Nance Memorial Highway Bridge under live load; and (3) conducting line girder analysis of continuous stringer spans using SIMON software and identifying potential sources for the refinement of load ratings. Upon evaluation of the diagnostic load testing results, it can be inferred that the stringers in the girder–stringer–floor beam bridge, SR-114 over the Tennessee River, have a higher load rating than initially anticipated. While this is due, in part, to the fact that some of the stringers act semi-compositely with the concrete bridge deck (as demonstrated by the measured strain profile at the member cross sections), composite behavior was not relied upon in refining load ratings for stringers. The stringers do not have top flange shear studs, and not all stringers exhibited composite behavior. Live load demand on the stringers was observed to be less than that which would be predicted using the lever rule for live load distribution. Other sources of undue conservatism in typical stringer rating calculations were identified as well: lateral–torsional buckling factor computation, critical stress calculation, and the provision for web plastification in the design equations.

Practical Applications

Engineers who provide load ratings for girder–stringer–floor beam bridges with rolled-shape stringers may find the results of this study useful in refining rating factors for these bridge elements. Sources of refinement include a potential reduction in the demand on stringers through diagnostic load testing and a potential increase in resistance through the application of more accurate $C_b\text{-}\text{factors}$, critical stress calculations, and web plastification for compact, rolled-shape stringers.

An approximate method for sizing continuity tendons in cast-in-place segmental cantilever box girders is presented in this technical note. Variables investigated are the length of the main span, the length of the continuity tendons, and the geometry of the box girder. Results indicate that secondary moments due to the prestressing of the continuity tendons decrease as the span length increases and as the length of continuity tendon decreases. For girders with a curved soffit, it was found that the type of variation of the girder depth (e.g., parabolic, cubic) has a small effect on the magnitude of the secondary moments.