Open Access

Articles

Article ID: 618

Study on compaction characteristics and discrete element simulation for rubber particle-loess mixed soil

by Wen-qi Kou, Jian-guang Bai, Hai-jun Li, Qing-hong Liu

Insight - Civil Engineering, Vol.7, No.1, 2024; 183 Views, 154 PDF Downloads

The rapid surge in traffic volume in China has resulted in a substantial accumulation of waste tires. By harnessing the lightweight and deformable characteristics of tire rubber particles, they are combined with soil to form rubber particle-loess mixed soil, which is progressively being embraced in civil engineering as a pivotal approach towards attaining green and sustainable development. In this study, waste tire rubber particles were integrated into loess to generate rubber particle-loess mixed soil, and compaction tests were conducted to investigate its compaction characteristics. Furthermore, PFC 3D (Particle Flow Code 3D) was utilized for simulating the bearing ratio test of rubber particle-loess mixed soil, thereby validating the feasibility of numerical simulation for calculating CBR (California bearing ratio) values and exploring the relationship between micromechanical characteristics and macroscopic characteristics of such mixtures. The findings indicate that the maximum dry density of rubber particle-loess mixed soil significantly decreases with an increasing content of rubber particles. The utilization of PFC 3D discrete element software proves efficacious in examining the bearing capacity of this mixture. Notably, when 20 mesh rubber particles constitute 20% by volume, the CBR value reaches its pinnacle and exhibits optimal bearing capacity. From a micromechanical perspective, the variation in internal porosity of rubber particle-loess mixed soil is positively associated with changes in macroscopic optimal water content, and negatively associated with changes in macroscopic CBR value. incorporating rubber particles enhances resistance against external forces while diminishing deformation within loess. This study provides a guidance for the efficient utilization of waste tires and the improvement of loess’s characteristics.

Open Access

Articles

Article ID: 616

Engineering geological and geotechnical evaluation of Sathya Sai Prasanthi Nilayam railway tunnel, Andhra Pradesh, India

by A. K. Naithani, Prasnna Jain

Insight - Civil Engineering, Vol.7, No.1, 2024; 109 Views, 78 PDF Downloads

Detailed engineering geological investigations were carried out for a railway tunnel which was constructed more than two decades ago. 3D engineering geological mapping was carried out using Brunton Compass and Total Station Surveying instruments in 1:100 scale. Coarse-grained pink and grey granite, hornblende-biotite gneiss and dolerite dyke of Archaean age and Lower Proterozoic age were mapped. Rock mass was intersected by sub-horizontal, inclined, and vertical joint sets, which were continuous and persistent, smooth, and planar with thick filling of decomposed and crushed sheared material or with thin coating of clay material. Based on the Q-system, rock mass was classified into different classes. On the basis of large-scale engineering geological mapping and Norwegian Method of Tunnelling, a support system was recommended which includes rock bolt, fibre reinforced shotcrete, grouting and reinforced ribs of sprayed concrete and the same is implemented by the agency. As per the best knowledge of the authors, reinforced ribs of sprayed concrete are first time used for transportation tunnels in India and it will be more effective if it will be compared with ISMB or Lattice Girder.

Open Access

Articles

Article ID: 609

A comparative study of the pliability of 2D auxetic architectonic structures by means of CAD

by Ma Dolores Álvarez Elipe

Insight - Civil Engineering, Vol.7, No.1, 2024; 109 Views, 53 PDF Downloads

Auxetic materials are a special type of materials that have a negative Poisson’s ratio (NPR): they get wider when they are stretched and they get narrower when they are compressed. In this paper a comparative study of 2D patterns of auxetic geometries, carried out by means of computer-aided design, is presented. The study consists of the development of a CAD library of auxetic geometries to apply them to architecture. The geometric behavior of the eighteen auxetic 2D patterns is tested from the developed library in order to develop a systematic comparison, analyzing relevant properties of these geometries, such as maximum achievable area reductions in relation with the total length of the bars of the structure, in order to obtain a growth factor.

Open Access

Articles

Article ID: 613

Discovering the optimal distance between spatial orthogonal tunnels: A dynamic analysis using Tehran metro as a case study

by Mehrdad Mohammadifar, Tohid Asheghi Mehmandari , Seyed Ali Mirjafari

Insight - Civil Engineering, Vol.7, No.1, 2024; 152 Views, 46 PDF Downloads

This study investigates the dynamic behavior of spatially orthogonal tunnels by employing three-dimensional numerical modeling and analyzing four different placement scenarios to determine the optimal tunnel spacing for minimizing mutual interaction while ensuring operational efficiency. This comprehensive research fills a vital gap in dynamic tunnel interaction studies and provides valuable insights for tunnel engineering in urban environments. Furthermore, in this research, the influence and response of adjacent shield tunnels under seismic conditions was evaluated based on the Tabas earthquake spectrum. Moreover, to enhance the accuracy of assumptions and achieve more logical results, the study utilizes the assumptions of the intersection tunnels of lines 6 and 7 of the Tehran metro. Dynamic analyses reveal that closer tunnel proximity (<0.5r) leads to increased bending moments, axial forces and displacements due to stress field interference, underscoring the critical importance of proper tunnel placement. Furthermore, results of the internal forces and displacements in both adjacent tunnels under dynamic loading show that positioning scenario case 2 (distance of tunnels is equal to their radius) is the most suitable option. In this scenario (compared to scenario case 1), the tunnels are less affected by each other’s stress field, and also in this positioning scenario (compared to scenarios 3 and 4), access from the ground surface to the lower tunnel will be easier and with lower construction costs.

Open Access

Articles

Article ID: 617

Structural response of reinforced LECA aggregate concrete slabs subjected to high temperatures

by Fadya S. Klak, Muyasser M. Jomaa'h

Insight - Civil Engineering, Vol.7, No.1, 2024; 64 Views, 22 PDF Downloads

This work reports tests conducted on nine one-way reinforced concrete slabs using lightweight expanded clay aggregate (LECA) as a slab weight reduction technique. Every slab had the same dimensions, steel reinforcement, and the same composition of concrete. The slabs were heated from their bottom faces through a fire chamber and subjected to a sustained line load. The specimens’ fire resistance performance and mechanical characteristics were evaluated after they had undergone the same testing conditions. The study parameters were the replacement of coarse aggregate with different percentages of LECA (20%, 40%), and different temperatures (400 ℃ and 700 ℃). Compared to the reinforced normal-weight concrete slab, the reinforced LECA aggregate concrete slabs’ fire resistance and flexural strength decreased by LECA. The slabs’ deflection rose as the LECA increased. The largest increase in slab deflection was 37.2%, while the most notable decrease in ultimate load capacity was roughly 35.1%. The stiffness depreciation was substantial, though, at roughly 50%. The results for LECA-reinforced aggregate slabs not exposed to high temperatures support this conclusion. Reinforced LECA aggregate slabs maintained structural integrity after fire testing.

Open Access

Articles

Article ID: 611

Fracture mechanism and ductility performances of fiber reinforced shotcrete under flexural loading insights from digital image correlation (DIC)

by Tohid Asheghi Mehmandari, Davood Mohammadi, Mohammadreza Ahmadi, Mehrdad Mohammadifar

Insight - Civil Engineering, Vol.7, No.1, 2024; 48 Views, 29 PDF Downloads

This paper investigates the fracture mechanism and ductility performance of fiber-reinforced shotcrete (FRS) under flexural loading through digital image correlation (DIC) analysis. The focus is on determining the optimal mix design, utilizing recycled and manufactured fibers in shotcrete through four-point bending tests. These tests reveal significant improvements in flexural strength and ductility, as well as crack resistance, attributed to the synergistic effect of both types of fiber in hybrid fiber reinforcement. Notably, the inclusion of recycled fibers from automobile tires enhances mechanical characteristics and impact resistance, contributing to environmental sustainability and cost reduction. DIC analysis offers crucial insights into crack initiation and propagation in shotcrete, highlighting the impact of fiber reinforcement on crack patterns. Manufactured fibers delay crack onset effectively, while hybridization enhances fracture characteristics, offering improved crack control and flexural strength. The study underscores the potential of hybrid fiber mixes for enhancing structural performance in tunnel support applications, emphasizing the synergistic effect of hybrid of different fiber types. Overall, the research contributes to advancing understanding of fracture behavior in fiber-reinforced shotcrete and provides practical insights for optimizing mix designs to achieve superior mechanical properties and durability.

Open Access

Articles

Article ID: 610

Nonlinear pushover analysis of the mechanical influences under the varied stories and column orientations in RC structures

by Mo Shi, Yeol Choi

Insight - Civil Engineering, Vol.7, No.1, 2024; 26 Views, 20 PDF Downloads

The natural disaster of earthquakes continues to be a catastrophic issue for urban environments, especially considering the widespread existence of RC (reinforced concrete) buildings in cities around the world. The continuous demand for expanded living spaces has led to the construction of taller structures, which brings an increased vulnerability to seismic events. The dilemma lies in the profound challenges that earthquakes pose to the structural integrity of these tall RC buildings, causing significant human and economic losses. Over the past decades, numerous analytical methods have been developed to evaluate and improve structural performance under seismic conditions. Notably, nonlinear pushover analysis has become prominent for its practicality and efficient stress calculations. This research aims to disclose the complex dynamics of seismic performance in the context of RC structures. Specifically, 10 distinct RC frame structures have been classified into two groups based on different column orientations. The overall goal is to examine and understand the mechanical influences of different stories and column orientations on the seismic resistance of RC buildings. By applying nonlinear pushover analysis, this research intends to offer valuable insights into the structural behavior of these various RC frame structures, contributing to a deeper understanding of seismic vulnerabilities and effective mitigation strategies.

Open Access

Articles

Article ID: 623

Reliability analysis and uncertainty evaluation for assessing low velocity car impacted cosmetic damage of prototyped RC bridge pier

by Suman Roy

Insight - Civil Engineering, Vol.7, No.1, 2024; 32 Views, 32 PDF Downloads

Crashworthiness of low velocity vehicles with reinforced concrete (RC) bridge pier has become widespread scenario that warrants a continuous threat on the structural viability. Even, low velocity small car collisions creates a short duration quasi-static to dynamic effect in different damage levels from low and cosmetic to collapse, depending on energy dissipation, not generally considered in design practices, making the piers susceptible to various level of damage. Bridge piers do not always collapse upon impact, and some are kept in service without pertinent health examinations that warrant serviceability. Unfortunately, little attention has been provided to keep the post impact low to medium distressed piers in service. Medium to higher damage need a complete replacement, whereas the low to cosmetic damage needs an additional meticulous investigation. This study is an attempt to assess cosmetic damage and residual capacities of RC pier via pendulum impacts to replicate low velocity car crash scenarios. To investigate post impact performance, experimental results are captured and transformed into realistic crash scenarios. Deterministic analysis via dynamic increase factor (DIF) approach to evaluate damage index ( λ ) and probabilistic method via resistance reduction method (RRM) to capture the uncertainties are performed in determining residual and reduced capacity of the representative pier. To identify damage incurred from collision and identify the probability of failure ( P f ), a limit state (LS) equation has been developed comprising impact load and resistance and utilized as a model to estimate reliability index ( β ). Both the models used are able to precisely capture reduced capacities providing a good agreement between the shear and the axial capacity which control primary resistance of the impact loads and principal serviceability respectively. This study will provide an aid to forensic structural engineers.

Open Access

Review

Article ID: 608

Vulnerabilities of water-energy and food nexus in cities of digital era

by G. Fivos Sargentis, Matina Kougkia

Insight - Civil Engineering, Vol.7, No.1, 2024; 1254 Views, 140 PDF Downloads

The edifice of civilization stands on water-energy-food nexus, speech, trading management and complexity. This paper, presents a mini review of these issues which are the foundations of civilization, and discusses their role in social prosperity. Recent year public discussion emerges that an electromagnetic pulse (EMP) could strike cities due to natural or artificial reasons therefore, we attempt to describe the impact of an EMP from the viewpoint of civil engineering. To do so, we analyze the fundamental parts of civilization in present, their roles, and their functions. Analysis estimates that an EMP will not regress cities of developed world to the 1970s or even in the Middle Ages, but rather before the agrarian era. It is noted that while the developed world will be more vulnerable, the least developed countries, could exhibit more resilience. Additionally, this paper considers the way societies and cities could demonstrate more resilience, framing the need for further research such as: technological adaptation; study and simulations of related scenarios; design of water-energy-food nexus for survival clusters; resilience measures for money, economy, communications, and trading. As we have a very small timeframe of data (less than 200 years) of the appearance and the effects of EMP, we have to study it, even if the wish is that we will never confront it. It seems unreasonable for our narcissistic and wonderful civilization to behave like ostrich hiding its’ head in the sand in order to be hidden by this threat.