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3D Concrete Printing (3DCP) is a rapidly expanding area in the field of architecture, engineering, and construction, but very limited research has quantitatively investigated its environmental impact. The existing Life Cycle Assessment (LCA) studies on 3DCP lack clearly defined functional units of comparison, especially considering load-bearing structures. This paper investigates the potential environmental benefits of 3DCP over conventional concrete construction for structural beams based on a cradle-to-grave comparative LCA. Unlike existing studies, this paper employs a recarbonation model to account for the carbon offsetting from the use-stage of 3DP concrete, which shows significant results. The assessment includes three-beam designs, each analyzed for both prefabrication and on-site construction scenarios. While currently, 3DCP has a generally higher environmental impact due to the larger quantity of cement employed in the process, the reduction of material through infill optimization for printed beams is a promising design principle to positively offset the environmental impacts in the construction sector. The paper draws recommendations for future research on material- and recarbonation-efficient 3DCP design for load-bearing structures, as well as on material development, e.g. integration of larger aggregates and low-clinker cement.

Limited investigations have evaluated the potential of using layered sections of normal-weight and lightweight concrete (NWC and LWC) mixtures in structural beams and slabs. The main objective of this paper is to assess the flexural strength properties of layered reinforced concrete (RC) beams, which help conserve natural resources and reduce construction weight. Six RC beams cast with different NWC/LWC combinations are tested to determine the damage patterns, concrete strains, ultimate load, displacements at failure, and ductility. The test results showed that the LWC cast in the tension zone (and up to the neutral axis) has a negligible effect on the beam’s stiffness and ultimate load since the overall behavior remains governed by the yielding of tensile steel reinforcement. Nevertheless, the deflection at failure and ductility seem to gradually curtail when the NWC is partially replaced by LWC at different elevations across the beam’s cross-section. A finite element analysis using ABAQUS software 6.14 is performed, and the results are compared with experimental data for model validation. Such data can be of interest to structural engineers and consultants aiming for optimized design of slabs and beams using layered concrete casting, which helps reduce the overall construction weight while maintaining the structural integrity of members.

The material constants of wood required for finite element analysis (FEA) are usually calculated using small clear specimens. However, defects, such as knots and slope of grain affect the strength reduction in the full-size specimens. Consequently, an error occurs if only the material constant calculated from the small clear specimens is used to predict modulus of rupture (MOR). Therefore, in this study, the MOR reduction coefficient according to defect was obtained through the bending test of the full-size specimens and applied to the FEA, in addition to the material constant from the small clear specimens. The maximum bending moment section was measured for a 3-section four-point load, and defects in the outermost tension layer were measured for laminated timber and glulam. The result of the bending test confirmed that MOR also decreased as the size of the defect increased. Therefore, when predicting MOR, a strength reduction ratio according to visual grade was applied. The MOR predicted FEA was twice as large as the actual MOR before defect correction, but the prediction error after defect correction was greatly reduced to 8%, thus increasing the prediction accuracy.

Defects and cracks in dried natural timber (relative permittivity 2–5) may cause structural weakness and enhanced warping in structural beams. For a pine wood beam (1200 mm × 70 mm × 70 mm), microwave reflection (S11) and transmission (S21) measurements using a cavity-backed slot antenna on the wood surface showed the variations caused by imperfections and defects in the wood. Reflection measurements at 4.4 GHz increased (>5 dB) above a major knot evident on the wood surface when the E-field was parallel to the wood grain. Similar results were observed for air cavities, independent of depth from the wood surface. The presence of a metal bolt in an air hole increased S11 by 2 dB. In comparison, transmission measurements (S21) were increased by 6 dB for a metal screw centered in the cavity. A kiln-dried pine wood sample was saturated with water to increase its moisture content from 17% to 138%. Both parallel and perpendicular E-field measurements showed a difference of more than 15 dB above an open saw-cut slot in the water-saturated beam. The insertion of a brass plate in the open slot created a 7 dB rise in the S11 measurement (p < 0.0003), while there was no significant variation for perpendicular orientation. By measuring the reflection coefficient, it was possible to detect the location of a crack through a change in its magnitude without a noticeable change (<0.01 GHz) in resonant frequency. These microwave measurements offer a simple, single-frequency non-destructive testing method of structural timber in situ, when one or more plane faces are accessible for direct antenna contact.

The construction of the Industrial Engineering Department building is an effort to support the educational infrastructure at Andalas University. However, the building construction process was stopped because the contractor had terminated the contract (breach of contract) and it took a long time to continue the construction. Before that, a structural evaluation of the building structure should be conducted due to the update of the building standards. In this study, the structural evaluation was carried out by analyzing and modelling the building using ETABS v.18 software, as well as loading analysis on the building regarding current Indonesian building standards such as SNI 1726-2019 for earthquake resistance building design, SNI 2847-2019 for requirements of the structural concrete building and SNI 1727-2020 for building minimum design loads. The results of the analysis show that several structural beams did not have a strong enough capacity to withstand the working loads, where the ultimate moment and shear values due to the influence of acting loads were more than the nominal moments and shear values. Retrofitting of the weak structural beams using the CFRP wrapping method was recommended to improve the structural capacity of the building.

One of the renewable energy sources is ocean currents which can be extracted with the Darrieus vertical axis hydrokinetic turbine (VAHT). This research aims to analyze the deformation and structural stresses that occur in the Darrieus VAHT support frame due to the loads. In the VAHT installation, it is necessary to have a support structure in the form of a solid frame, so that the turbine remains in a stable condition when operating. The VAHT frame must be able to withstand the load from a rotating turbine and have a small drag force. This study conducted a numerical simulation using the finite element analysis method. The effect of the cross-sectional shape of the structural beams on the drag due to flow was also investigated. The result is the frame designed with the ASTM A36 Grade B pipe structure has maximum stress of 63,116 MPa and it is relatively smaller and remains within the safe limits of the material. In addition, based on CFD simulation, the drag caused by the flow across the structure with this design is also smaller. Therefore, this study can be used as a consideration in making decisions to design the Darrieus VAHT frame.

The construction industry is rapidly changing to meet growing demand and reduce its environmental impact. These objectives can be met, in part, through improved selection of construction materials. However, the material properties including embodied carbon (EC) of emerging construction materials are less well documented in material property databases compared to conventional ones, providing barriers to their utilisation and correct perception of their decarbonisation potentials. This study provides material property data for emerging structural materials through a comprehensive literature review, visualises the results on material property charts, and analyses these data comparing to conventional materials. Only 18% (37 out of 204) of the emerging structural materials reviewed had EC values; less (11%) had embodied energy values. Analysis of the data demonstrates that using alternative and emerging materials for structural beams and columns can substantially reduce EC. For example, in the beam case study presented and using cradle-to-gate EC data (excluding stored carbon in wood), engineered wood products (glulam, cross-laminated timber) and reused steel achieve 3-5% of the EC of primary steel. Therefore, we highlight the benefits of collecting material property and environmental impact data for emerging materials and their potential for greater adoption to achieve lower carbon construction.

Previous studies about optimizing earthquake structural energy dissipation systems indicated that most existing techniques employ merely one or a few parameters as design variables in the optimization process, and thereby are only applicable only to simple, single, or multiple degree-of-freedom structures. The current approaches to optimization procedures take a specific damper with its properties and observe the effect of applying time history data to the building; however, there are many different dampers and isolators that can be used. Furthermore, there is a lack of studies regarding the optimum location for various viscous and wall dampers. The main aim of this study is hybridization of the particle swarm optimization (PSO) and gravitational search algorithm (GSA) to optimize the performance of earthquake energy dissipation systems (i.e., damper devices) simultaneously with optimizing the characteristics of the structure. Four types of structural dampers device are considered in this study: (i) variable stiffness bracing (VSB) system, (ii) rubber wall damper (RWD), (iii) nonlinear conical spring bracing (NCSB) device, (iv) and multi-action stiffener (MAS) device. Since many parameters may affect the design of seismic resistant structures, this study proposes a hybrid of PSO and GSA to develop a hybrid, multi-objective optimization method to resolve the aforementioned problems. The characteristics of the above-mentioned damper devices as well as the section size for structural beams and columns are considered as variables for development of the PSO-GSA optimization algorithm to minimize structural seismic response in terms of nodal displacement (in three directions) as well as plastic hinge formation in structural members simultaneously with the weight of the structure. After that, the optimization algorithm is implemented to identify the best position of the damper device in the structural frame to have the maximum effect and minimize the seismic structure response. To examine the performance of the proposed PSO-GSA optimization method, it has been applied to a three-story reinforced structure equipped with a seismic damper device. The results revealed that the method successfully optimized the earthquake energy dissipation systems and reduced the effects of earthquakes on structures, which significantly increase the building’s stability and safety during seismic excitation. The analysis results showed a reduction in the seismic response of the structure regarding the formation of plastic hinges in structural members as well as the displacement of each story to approximately 99.63%, 60.5%, 79.13% and 57.42% for the VSB device, RWD, NCSB device, and MAS device, respectively. This shows that using the PSO-GSA optimization algorithm and optimized damper devices in the structure resulted in no structural damage due to earthquake vibration.

This study utilizes ultrasonic pulse (UP) and acoustic emission (AE) techniques to assess the extent of damage in concrete under coupled thermomechanical loading conditions. It also introduces a novel normalized fire damage indicator, the shear‐to‐pressure wave velocity ratio ( V S / V P ), as a potential tool for postfire site assessments. Structural beams and columns in real fire scenarios are subjected to both thermal and load‐induced damage. To investigate the characteristics of damage and wave propagation behavior in concrete exposed to simultaneous thermal and working stress (WS), a high‐temperature furnace with top and bottom openings was developed. Concrete specimens were exposed to varying temperatures and WS, and their shear and pressure wave velocities were measured using the UP technique. AE measurement combined with the uniaxial compressive test was employed to observe macro‐ and microscale damage characteristics. The relationship between V S / V P and concrete damage temperature, stiffness, and strength was also explored. Results from AE and uniaxial compressive tests indicate that, without WS, the stiffness and strength of concrete decrease as the temperature increases, with significant reductions occurring only above 500°C, where the reduction rates approach 70% and 60%, respectively. The occurrence of microcrack clustering also shifts to earlier stages as the temperature increases. Under the influence of WS, the confining effect mitigates the reduction of stiffness and strength when the temperature is below 500°C, delaying the onset of microcrack clustering. However, when the temperature exceeds 600°C, the increased WS accelerates the reduction of stiffness and strength, while the microcrack clustering behavior becomes less pronounced. The V S / V P obtained from UP measurements is 0.67 for concrete at normal temperatures without WS. As the temperature increases, V S / V P also rises, but it decreases with increasing WS. The relationship between V S / V P and strength shows that thermal damage significantly impacts ultrasonic wave velocities when the strength reduction exceeds 60%. These findings suggest that V S / V P is a reliable and nondestructive indicator for quantifying thermal degradation in concrete, offering engineers a rapid and practical means to evaluate residual strength and peak fire temperatures on‐site after fire incidents.

To investigate the fire risk in a complex tunnel with varying cross-sections, sloped structures, and dense upper cover beams, this study considered four fire source positions: the immersed tube section, confluence section, highway auxiliary road section, and four-lane sections of the main line. It also considered four beam spacings: 1 m, 1.8 m, 3.6 m, and 7.2 m. The Fire Dynamics Simulation Software FDS was utilized to create a comprehensive tunnel model. The analysis focused on temperature and visibility changes at a 2 m height under a 20 MW fire condition for different fire source positions. These changes were then compared with critical danger values to assess the safety of evacuating personnel within the tunnel. Subsequently, this study proposed corresponding emergency rescue strategies. The findings indicated that when the beam grid spacing exceeded 3.6 m, the upper dense beam gap showed a robust smoke storage capacity, leading to a reduced distance of high-temperature smoke spread. However, this increased smoke storage disrupted the stability of the smoke layer, resulting in a heightened smoke thickness. The location of the ventilation vent at the entrance of the immersed tunnel section caused a non-uniform ventilation flow under the girder, deflecting the smoke front towards the unventilated side and decreasing visibility in the road auxiliary area. In comparison to scenarios without a beam lattice, the presence of a beam lattice in the tunnel amplified fire hazards. When the beam lattice spacing was 3.6 m or greater, the extent of the hazardous environment, which is unfavorable for personnel evacuation, expanded. With the exception of the scenario where the fire source was located in the highway auxiliary roadway, all other conditions surpassed 150 m, which is roughly one-third of the tunnel length. Consequently, more targeted strategies are necessary for effective evacuation and rescue efforts.