Hasil untuk "Structural engineering (General)"

K. N. Arun Kumar, G. B. Krishnappa, D. Shrinivasa et al.

Abstract The advancement of modern engineering applications demands lightweight materials with superior mechanical and tribological performance. In this context, aluminum-based hybrid metal matrix composites reinforced with ceramic and solid lubricant phases have gained significant attention. The present study investigates the influence of cryogenic treatment on the microstructure and mechanical behavior of Aluminum-Silicon Carbide-Graphite (Al-SiC-Gr) hybrid composites fabricated using the stir casting technique. Initially, Al6061 composites reinforced with varying SiC contents (11–15 wt%) were evaluated to determine the optimum reinforcement level based on tensile strength, hardness, and wear performance. An optimum SiC content of 13 wt% was identified, beyond which porosity and particle agglomeration adversely affected mechanical properties. Subsequently, hybrid composites containing 13 wt% SiC with 1–3 wt% graphite were produced and subjected to deep cryogenic treatment at -196 °C with a soaking duration of 24 h, followed by controlled warming to room temperature. The effects of cryogenic treatment on microstructure were examined using optical microscopy, scanning electron microscopy, and energy-dispersive X-ray analysis. Cryogenically treated specimens exhibited grain refinement, enhanced interfacial bonding, and increased precipitation density, leading to notable improvements in mechanical performance. Compared to untreated specimens, cryo-treated hybrid composites showed enhancements of 6–8% in ultimate tensile strength, 15–20% in yield strength, and 3–8% in hardness, accompanied by a reduction in ductility. The findings demonstrate that cryogenic treatment acts as an effective post-processing technique to further enhance the mechanical performance of Al-SiC-Gr hybrid composites, making them suitable for advanced structural and tribological applications.

Aya S.S. El-Sayed, Ahmed A. Elakhras, Hossam El-Din M. Sallam et al.

This paper studied the effects of specimen size and type on the real-mode-I fracture toughness (KIC )of steel fiber-reinforced concrete (SFRC) specimens. Mode I KIC tests were performed using semicircular bend (SCB) and center-cracked circular disk (CCCD) specimens with different sizes and crack-to-depth ratios, (a/R). SCB Specimens were tested under three-point bending, and CCCD specimens were tested under indirect tension test conditions to achieve pure Mode I crack growth. Moreover, KIC was analyzed as a function of specimen type (SCB and CCCD), specimen size (R values of 50, 75, 100, and 125 mm), and a/R ratios of 0.2, 0.3, 0.4, and 0.5. The results clearly show that the KIC of SFRC exhibits a distinct size effect: it increases with specimen radius up to a critical range of 75-100 mm, after which it levels off. The a/R ratio is an important parameter affecting the toughness; higher values of a/R result in increased KIC values, with increases of 12.9% for CCCD specimens and 22.7% for SCB specimens when a/R is raised from 0.2 to 0.5 at R=75 mm. In addition, the failure mode shifts from ductile fiber pull-out at shallow a/R to brittle fiber rupture at highera/R. The results also emphasize the importance of using geometry-adjusted models, such as Bazant's size effect law (SEL), especially when dealing with SFRC, since fiber distribution and crack-bridging efficiency depend on both size and geometry.

H. Kursat Celik, Ali Elham, Recep Cinar et al.

The integration of additive manufacturing (AM) and topology optimization (TO) is transforming mechanical design and prototyping practices across multiple engineering sectors, including agricultural and aerospace applications. This study presents the development of TODfAM, a bespoke SOLIDWORKS add-in that automates TO workflows and embeds Design for Additive Manufacturing (DfAM) principles directly within a parametric CAD environment. The tool integrates parametric modelling, finite element analysis (FEA)-based structural evaluation, and TO in a unified platform, enabling automated generation and assessment of design iterations with respect to both mechanical performance and AM-specific manufacturability constraints. A case study on a pusher-duct support bracket for an Unmanned Aerial Vehicle (UAV) was conducted to demonstrate the functionality of the developed workflow. The optimized bracket achieved a 13.77% mass reduction while maintaining structural integrity under representative loading conditions. The CAD-integrated framework reduces toolchain hand-offs and allows early manufacturability evaluation within the design environment, thereby improving workflow continuity and consistency. The principal novelty of this work lies in the establishment of a fully CAD-native, DfAM-aware optimization framework that consolidates the design-to-manufacturing process into a single automated environment. This approach not only streamlines pre- and post-processing tasks but also promotes wider industrial adoption of AM by providing a practical, designer-oriented route to lightweight and manufacturable structures.

M. Sun, Y. Duan, H. Cao et al.

Accurately and efficiently identifying rock mass structural planes and extracting their characteristic information is crucial for rock mass stability assessment. Three-dimensional (3D) laser scanning technology can significantly enhance both the efficiency and accuracy of structural plane surveying; however, current mainstream point cloud segmentation algorithms exhibit notable shortcomings, including blurred recognition of structural plane edges, insufficient segmentation accuracy, and poor integration precision among segmented blocks. To address these problems, this study proposes an improved multi-rule region growing point cloud segmentation method for rock structural planes. Specifically, plane fitting residuals are calculated from the point cloud data, and these residual values are then used to optimize seed point selection, thereby improving the segmentation accuracy of planar point sets. Next, considering the spatial relationship between the location of rock structural plane point clouds and their neighborhoods, a KD-tree data structure is employed to perform voxel downsampling for nearest-neighbor searching, and the RANSAC-based region growing algorithm is further refined. By adjusting the region growing segmentation parameters using multiple feature values and segmenting structural planes based on point cloud normal vector differences and final feature values, the proposed method facilitates the extraction of structural plane orientation, spacing, and extent, improving the overall segmentation quality. Experimental results demonstrate that the error between the segmented rock structural plane area and dimensions obtained by this method and those computed using CAD is only 1.07%, which meets the engineering error tolerance. Consequently, the proposed method provides stable and effective technical support for the identification and segmentation of rock structural planes.

Xinyuan Wang, Ping Li, Xuansheng Cheng et al.

This paper aims to solve the problems of extensive labor input and long construction periods of traditional foundation beam brick formwork. We propose using plant fiber-reinforced cementitious composites (PFRCC) panels instead of conventional foundation beam brick formwork. This study conducted tests and finite element analyses on the PFRCC panels employed as permanent formwork for foundation beams, based on a construction project in a community in Lanzhou City, Gansu Province, China. The results indicate that the maximum bending stress of the PFRCC panels utilized as permanent formwork for foundation beams is 0.4069 MPa, occurring at the junction between the side and bottom forms, which is significantly lower than the specified design strength of 13.7 MPa. Furthermore, the maximum deformation recorded was 1.528 mm at the mid-span of the side template, remaining below the permissible limit of 2.5 mm. The bending strength and stiffness deformation meet the design requirements, which shows that the PFRCC panels can be used as the permanent formwork of the foundation beam.

Lenka Hanyková, Julie Šťastná, Ivan Krakovský

Hydrogels, composed of hydrophilic homopolymer or copolymer networks, have structures similar to natural living tissues, making them ideal for applications in drug delivery, tissue engineering, and biosensors. Since Wichterle and Lim first synthesized hydrogels in 1960, extensive research has led to various types with unique features. Responsive hydrogels, which undergo reversible structural changes when exposed to stimuli like temperature, pH, or specific molecules, are particularly promising. Temperature-sensitive hydrogels, which mimic biological processes, are the most studied, with poly(<i>N</i>-isopropylacrylamide) (PNIPAm) being prominent due to its lower critical solution temperature of around 32 °C. Additionally, pH-responsive hydrogels, composed of polyelectrolytes, change their structure in response to pH variations. Despite their potential, conventional hydrogels often lack mechanical strength. The double-network (DN) hydrogel approach, introduced by Gong in 2003, significantly enhanced mechanical properties, leading to innovations like shape-deformable DN hydrogels, organic/inorganic composites, and flexible display devices. These advancements highlight the potential of hydrogels in diverse fields requiring precise and adaptable material performance. In this review, we focus on advancements in the field of responsive acrylamide-based hydrogels with IPN structures, emphasizing the recent research on DN hydrogels.

Foad Kiakojouri, Valerio De Biagi

The studies on progressive collapse have primarily focused on threat-independent methods, wherein a sudden column removal is suggested in codes. However, a real collapse scenario is necessarily threat-dependent. Focusing on blast- and impact-induced progressive collapses, the current study considers cases in which damage is concentrated in a single member, without resulting in complete column loss. It is demonstrated that the progressive collapse performance under specific threats can be better or worse compared to that of sudden column removal. Thus, dynamic column removal does not necessarily guarantee the most critical scenario, as the response in a damaged system can sometimes exceed expectations. A simple analytical model is proposed to describe in detail the observed phenomena and emphasizes the development of catenary forces in the column under lateral extreme loading scenarios. The results provide a deeper insight into the progressive collapse performance of frame systems and the involved member-level resisting mechanisms.

Hani Ali Al-Rawashdeh, Bilal Nayef Zureigat, Nahed Habis Alrawashedh et al.

The study aimed to identify the relationship between time budget pressure and the quality of external auditing in the Jordanian environment through the mediating role of professional skepticism. The moderating role of external auditors' professional commitment in this relationship was tested. The study population consisted of certified Jordanian accountants. 234 questionnaires were distributed to the respondents. The study indicated that certified Jordanian accountants are subject to a high level of pressure, in addition to having a high level of audit quality and professional skepticism, and they are professionally committed. The results of the analysis also indicated that high professional skepticism affects the quality of the external audit and that there is an impact of time budget pressure on the quality of the audit, as the pressure of deadlines for preparing audit reports reduces the level of professional skepticism practiced by external auditors in Jordan. The results also indicated that auditors' professional commitment moderates the relationship between time budget pressure, the level of professional skepticism, and audit quality. Interestingly, there is no moderating role for professional commitment in the relationship between professional skepticism and the quality of external auditing in Jordan. This study emphasizes the need for auditors to maintain professional skepticism when exposed to pressures, including time budget pressure, in order to produce high-quality audit reports.

Emmanuel Appiah-Kubi, Michael Awotwe-Mensah, Stephen Jobson Mitchual

This study assessed the properties of juvenile and matured glue-laminated bamboo for structural applications. Glue-laminated bamboo was produced from 2-year-old and 4-year-old culms of Bambusa vulgaris with a fast-curing polyurethane adhesive (Rapid Lion). The composites produced were assessed for their physical (moisture content, basic density, radial, longitudinal, tangential and volumetric shrinkage) and mechanical (modulus of rupture, modulus of elasticity and compressive strength parallel to grain) properties. The results show that the juvenile glue-laminated bamboo significantly shrinks about twice that of the matured glue-laminated bamboo with values of 6.32% for radial, 6.51% for tangential and 0.22% for longitudinal. It was further observed that the basic density of the matured glue-laminated bamboo was 810.56 kg/m³ which is 14.56% higher than that of the juvenile glue-laminated bamboo. The juvenile glue-laminated bamboo had MOE of 5876 MPa; MOR of 43.42 MPa and compressive strength of 37.58 MPa whilst that of the matured glue-laminated bamboo recorded MOE of 13379 MPa; MOR of 82.48 MPa and compressive strength of 62.78 MPa. The matured bamboo laminates had better physical and mechanical properties than that of the juvenile bamboo laminates. It is recommended that matured Bambusa vulgaris can be used as an engineered composite material for structural applications.

Shaojun Zhu, M. Ohsaki, Kazuki Hayashi et al.

Wen Zhang, Wenbo Ye, Yunfeng Yan

3D bioprinting integrating multidisciplinary advances in engineering, cell biology, and material science is able to fabricate artificial tissues and organ‐like structures with biology or clinic‐relevant size, shape, and structural integrity. Therefore, 3D bioprinting has huge potential in tissue engineering and regenerative medicine. Suitable bioink plays a key role in the modulation of the printing process, the properties, and functions of printed constructs. Herein, the advances in photocrosslinkable biomaterials are focused on, which have been proven as promising types of bioinks for 3D bioprinting. The general strategies of 3D bioprinting and the main mechanisms involved in photocrosslinking are first discussed. Then, the recent advances in photocrosslinkable bioinks including natural protein‐ and polysaccharide‐based materials, synthetic polymers, and decellularized extracellular matrix (dECM)‐based materials are highlighted. Finally, the ongoing challenges in the delicate balance between the printability and biological activities of photocrosslinkable biomaterials are discussed and the outlook for this emerging area is analyzed.

Junjie Li, Y. Anraku, Kazunori Kataoka

Synthetic polymer vesicles spur novel strategies for producing biologically intelligent nanodevices with precise and specific functions (e.g. nanoreactors). Engineering vesicular nanodevices with tunable permeability by a general platform without involving trade-offs between structural integrity, flexibility and functionality remains challenging. Here, we present a general strategy to construct responsive nanoreactors based on polyion complex vesicles by integrating stimuli-responsive linkers into crosslinking membrane network. The formulated ROS-responsive nanoreactor with self-boosting catalytic glucose oxidation could protect glucose oxidase (GOD) to maintain long-term activity to achieve cytocidal function by oxidative stress induction and glucose starvation, which is ascribed to stimuli-responsive vesicle expansion without fracture and size-selective cargo release behavior. The GOD-loaded therapeutic nanoreactor induced an immunostimulatory form of cell death by pyroptosis, which has the great potential to prime anti-tumor immune responses.

Ali Tasalloti, Gabriele Chiaro, Arjun Murali et al.

End-of-life tires (ELTs) are tires, unusable in their original form, which go into a waste management scheme (for recycling and energy recovery purposes), or otherwise are disposed. In New Zealand, the annual disposal of 3.5 million ELTs is posing critical environmental and socio-economic issues, and the reuse of ELTs through large-volume recycling engineering projects is a necessity. In this study, gravel and recycled granulated rubber were mixed to explore the possibility of obtaining synthetic granular geomaterials (with adequate geotechnical and environmental characteristics) that are suitable as structural fills for geotechnical applications including foundation systems for low-rise light-weight residential buildings. Moreover, an original framework with a set of geo-environmental criteria is proposed for the acceptance of gravel–rubber mixtures (GRMs) as structural fills. It is shown that when gravel-size like rubber particles are used, GRMs with volumetric rubber content of 40% or less have adequate strength (<i>ϕ</i>’ > 30°), low compressibility (ε_v ≤ 3%), excellent energy adsorption properties, and acceptable leachate metal concentration values (e.g., Zn < 1 mg/L), making them ideal synthetic structural fill materials for many sustainable geotechnical applications.

H. Ho, K. Chung, Xiao Liu et al.

Abstract Standard tensile tests are commonly used to determine mechanical properties of metallic materials, such as yield strength and tensile strength as well as ductility. In general, these standard tensile tests are able to provide basic mechanical properties of steel materials, commonly referred as engineering stress-strain curves. These curves are considered to be effective for linear elastic and post yielding deformations up to mobilization of tensile strengths, and they are widely adopted in structural design and analysis of steel structures. However, for detailed investigations into structural behaviour of steel structures in large deformations beyond onset of necking, cross-sectional changes in the steel materials often become very large. Hence, an improved stress-strain curve, commonly known as a true stress-strain curve, with proper adjustment according to large longitudinal deformations should be adopted in advanced finite element models. In order to develop full range true stress-strain curves of various steel materials for large deformations, a research project is conducted to perform an integrated experimental and numerical study. Standard tensile tests on two S275 steel coupons and two S690 steel coupons are carried out, and advanced optical measurements using a digital imaging correlation technique are adopted to measure deformation fields of these coupons with a high precision during the entire deformation ranges. After data analyses using three different transformation rules, namely, i) Power Law Method, ii) Linear Law Method, and iii) Instantaneous Area Method, three different true stress-strain curves for each of S275 and S690 steel materials are derived. These curves are then incorporated into advanced finite element models to simulate large deformations of these steel coupons observed in the tensile tests. Improvements to the true stress-strain curves derived from Instantaneous Area Method are made through successive corrections according to measured and predicted deformation characteristics of the steel coupons. Consequently, the proposed true stress-strain curves determined with Instantaneous Area Method are shown to be highly acceptable for numerical analyses of steel structures undergoing large plastic deformations up to fracture. Expressions of the proposed full range true stress-strain curves for S275 and S690 steel materials are also provided.

Lei Wang, Qiang Ren, Yujia Ma et al.

The performances of engineering structures are degrading in service and maintenance interventions can enhance the structural reliability and make sure that the structures are effectively functional. Engineering structures often exhibit obvious time cumulative effects due to multisource time-varying uncertainties including property degradation of materials, changeable environment conditions, and dynamic loading processes, which makes the reliability assessment and maintenance design much harder. In this paper, a new time-varying nonprobabilistic reliability-oriented optimal maintenance design method with the consideration of static and dynamic mixed uncertainties is proposed. The interval model is utilized to quantify the uncertain and time-varying characteristics and the structural reliability can be assessed combining the interval model and the first-passage theory. We try to establish a more general maintenance cost model enlightened by Frangopol's work under the nonprobabilistic system and the maintenance strategy including uncertainty assessment, reliability evaluation, and cost optimization is constructed. Three numerical examples are presented to demonstrate the effectiveness of the developed methodology.

V. Gligorijević, P. Renfrew, T. Kosciólek et al.

Recent massive increases in the number of sequences available in public databases challenges current experimental approaches to determining protein function. These methods are limited by both the large scale of these sequences databases and the diversity of protein functions. We present a deep learning Graph Convolutional Network (GCN) trained on sequence and structural data and evaluate it on ~40k proteins with known structures and functions from the Protein Data Bank (PDB). Our GCN predicts functions more accurately than Convolutional Neural Networks trained on sequence data alone and competing methods. Feature extraction via a language model removes the need for constructing multiple sequence alignments or feature engineering. Our model learns general structure-function relationships by robustly predicting functions of proteins with ≤ 30% sequence identity to the training set. Using class activation mapping, we can automatically identify structural regions at the residue-level that lead to each function prediction for every protein confidently predicted, advancing site-specific function prediction. De-noising inherent in the trained model allows an only minor drop in performance when structure predictions are used, including multiple de novo protocols. We use our method to annotate all proteins in the PDB, making several new confident function predictions spanning both fold and function trees.

Byeonguk Ahn, Thomas H.-K. Kang, Su-Min Kang et al.

The design of a post-tensioned transfer plate is typically controlled by shear force—in particular, punching shear at the slab-column connection. To verify the accuracy of the separated model only for one floor currently used in the design of a post-tensioned transfer plate, results were compared to a complete model with multi-story building system for which two representative residential building plans were used to emulate physical structural systems. Punching shear stress for the separated model was calculated using the eccentric shear stress model presented in ACI 318. Punching shear stress was found to be overestimated in the separated model, given that interaction between transfer plates and upper shear walls cannot be reflected therein. Differences at column locations were also noted as the number of stories below the transfer floor increased. Consequently, the separated model is not recommended for design of post-tensioned transfer plates. A complete model is more suitable for more realistic and potential cost-effective design, through the inclusion of the interaction between transfer plates and upper shear walls.

Mohammed Taleb Obaidat

Cellular phones cameras technological development as a hand-held electronic instrument with almost everybody nowadays will open the door to their potential usage as viable mensuration instruments. These extracted measurements would have the advantages of being inexpensive and portable ones.As a hand-held tool and wide availability, cellular phones equipped with digital cameras is anticipated to give them the potential of in-situ real-time measurements as well as the usage for documentation purposes. However, the accuracy potential of the extracted measurements affected by the small image domain, small field of view, and camera configuration. Further, the usage of high resolution cellular phones cameras is anticipated to overcome these challenges.The potential of cellular phones’ cameras in metrology using normal-based setup was investigated. In this research work, the captured images were used to extract some of traffic monitoring parameters as well as road inventory, vehicle classification and intersections. Cellular phones cameras’ resolutions that ranged from 2 to 12 Megapixels were investigated in this domain despite their fixed focus lenses and smaller sensors that would limit their performance in poor lighting.Findings of research show that the potential of using high-resolution cellular phones in traffic parameters mapping, vehicle classification and road geometric features is promising. In fact, increasing the phone’s camera resolution up to 12 Megapixels would consistently give high potential computational accuracy results for all studied parameters. Road intersection shows measurements of average errors ranging between 13% and 21% for camera resolution ranging between 8.0 Mega Pixels to 0.3 Mega Pixels. Further, speed profile could easily be generated with high accuracy potential.A CAD drawing of the mapped intersection scene was also generated. However, the computational accuracy potential degraded rapidly when changing camera resolution in case of vehicle classification study due to shutter speed problem and mapping vehicles while in motion.The promising conclusions of this technology is anticipated to open the door -for the first time usage- of cellular phones in the domain of transportation engineering computing in order to extract viable and accurate traffic and geometrical parameters. Thus, this method of gauging and computation would also be extended in order to produce surface measurements for any civil engineering application in the domains of transportation, structural, geotechnical and environmental engineering in a practical and new trend technology. It is anticipated that with the technology booming of new cellular phones production of higher resolution, mensuration accuracy would reach close values to real dimensions.