Safety Of Civil Engineering Structures Research Articles

Prediction of steel plate-based damper for improving the behavior of concentrically braced frames based on RSM and ML approaches for sustainable structures.

The stiffness (K) and slenderness factor (λ) of a steel plate-based damper has been studied on the basis of elastic-inelastic-plastic buckling (EIP) modes and flexural/shear/flexural-shear failure mechanisms (FSF-S), which has been designed for the improvement of the behavior of concentrically braced frames. Steel plate-based dampers offer significant benefits in terms of mode shapes and failure mechanisms, contributing to improved dynamic performance, enhanced structural resilience, and increased safety of civil engineering structures. Their effectiveness in mitigating dynamic loads makes them a valuable tool for engineers designing structures to withstand extreme environmental conditions and seismic events. This study was undertaken by using the learning abilities of the response surface methodology (RSM), artificial neural network (ANN) and the evolutionary polynomial regression (EPR). Steel plate dampers are special structural designs used to withstand the effect of special loading conditions especially seismic effects. Its design based on the prediction of its stiffness (K) and slenderness factor (λ) cannot be overlooked in the present-day artificial intelligence technology. In this research work, thirty-three entries based on the steel plate damper geometrical properties were recorded and deployed for the intelligent forecast of the fundamental properties (λ and K). Design ratios of the steel plate damper properties were considered and models behavior was recorded. From the outcome of the model, it can be observed that even though the EPR and ANN in that order outclassed the other techniques, the RSM produced model minimization and maximization features of the desirability levels, color factor scales and 3D surface observation, which shows the real model behaviors. Overall, the EPR with R2 of 0.999 and 1.000 for the λ and K, respectively showed to be the decisive model but the RSM has features that can be beneficial to the structural design of the studied steel plate damper for a more robust and sustainable construction. With these performances recorded in this exercise, the techniques have shown their potential to be applied in the prediction of steel damper stiffness with optimized characteristic features to withstand structural stresses.

Assessment of the Composition Effect of a Bio-Cementation Solution on the Efficiency of Microbially Induced Calcite Precipitation Processes in Loose Sandy Soil.

Soil properties are the most important factors determining the safety of civil engineering structures. One of the soil improvement methods studied, mainly under laboratory conditions, is the use of microbially induced calcite precipitation (MICP). Many factors influencing the successful application of the MICP method can be distinguished; however, one of the most important factors is the composition of the bio-cementation solution. This study aimed to propose an optimal combination of a bio-cementation solution based on carbonate precipitation, crystal types, and the comprehensive strength of fine sand after treatment. A series of laboratory tests were conducted with the urease-producing environmental strain of bacteria B. subtilis, using various combinations of cementation solutions containing precipitation precursors (H2NCONH2, C6H10CaO6, CaCl2, MgCl2). To decrease the environmental impact and increase the efficiency of MICP processed, the addition of calcium lactate (CaL) and Mg ions was evaluated. This study was conducted in Petri dishes, assuming a 14-day soil treatment period. The content of water-soluble carbonate precipitates and their mineralogical characterization, as well as their mechanical properties, were determined using a pocket penetrometer test. The studies revealed that a higher concentration of CaL and Mg in the cementation solution led to the formation of a higher amount of precipitates during the cementation process. However, the crystal forms were not limited to stable forms, such as calcite, aragonite, (Ca, Mg)-calcite, and dolomite, but also included water-soluble components such as nitrocalcite, chloro-magnesite, and nitromagnesite. The presence of bacteria allowed for the increasing of the carbonate content by values ranging from 15% to 42%. The highest comprehensive strength was achieved for the bio-cementation solution containing urea (0.25 M), CaL (0.1 M), and an Mg/Ca molar ratio of 0.4. In the end, this research helped to achieve higher amounts of precipitates with the optimum combination of bio-cementation solutions for the soil improvement process. However, the numerical analysis of the precipitation processes and the methods reducing the environmental impact of the technology should be further investigated.

Numerical investigation of characteristics and mechanism of tunnel erosion of loess with coupled CFD and DEM method

Tunnel erosion of loess can cause geological disasters such as landslide and debris flow, as well as threaten the safety of civil engineering structures. Understanding the mechanism and evolution law of tunnel erosion is not only helpful to analyze the occurrence and development of gully erosion, but also conducive to the guidance of engineering practice. Although many scholars have carried out statistical analysis on loess tunnel erosion based on field investigation, quantitative analysis and visualization at the micro level are lacking. Because the combination of computational fluid dynamics (CFD) and discrete element method (DEM) has great advantages in studying the seepage erosion process. This manuscript adopts the CFD-DEM coupling method, and the virtual cement method is used to transform the failure of cemented matrix into the reduction law of bonding strength. The micro mechanism of tunnel erosion of three areas is discussed from the aspects of particle erosion rate, cement evolution and micro mechanical field. The results show that the more the fine particle content is, the greater the cementation is, the stronger the erosion resistance is, the less developed the erosion rate of the particles is, and the dissolution failure rate of the cement is usually earlier than the erosion rate of the particles, and the variation range of the anisotropy of the contact force is also the smallest. However, under high water pressure, their erosion rates are almost synchronous and reach the slow erosion stage quickly. The anisotropic parameters of the contact force of the three samples virtually decreased gradually in the process of erosion, and finally tended to be stable.

Understanding the performance of expansive subgrade materials treated with non-traditional stabilisers: A review

Expansive soils are problematic soils which pose a risk to the safety of civil engineering structures. These soils can be treated by compaction or by adding additives to the soil. Where the strength and properties of expansive soil cannot be improved via mechanical stabilisation (Compaction), a desirable strength can be achieved through the use of chemical admixture techniques. The swelling and shrinkage of expansive soils cause movement in the soil mass resulting in a deferential settlement in engineering structures such as roads and building leading to cracks and subsequent failure leading to high cost of maintenance. Calcium based additives such as cement and lime have been used in expansive subgrade stabilisation to enhance the strength, reduce swell and subsequent differential settlement. However, the growing concerns on carbon dioxide (CO2) emission and climate change have reignited the need for a more sustainable soil stabilisation techniques using waste materials. In this study, non-traditional expansive subgrade treatment techniques using sustainable waste materials with respect to their efficiency in improving the geotechnical engineering properties of the subgrade materials have been investigated and reviewed. This study also discusses the engineering problems associated with expansive soils, proposing an effective, efficient, cheaper and sustainable application of non-traditional stabilisers in expansive soil stabilisation. The study concludes that, the addition of non-traditional stabilisers in expansive subgrade stabilisation using chemical stabilisation techniques can improve the engineering properties of expansive subgrade materials.

Long‐term displacement measurement of bridges using a LiDAR system

Long-term displacement measurements provide important information about the structural safety of civil engineering structures and the associated maintenance necessary. Most approaches developed for measuring displacement, such as direct measurements using the linear variable differential transformer and computer vision-based sensing, relate to campaign-type sensor deployment. However, these methods have critical limitations when used to accurately measure long-term displacement, because it is difficult in practice to appropriately handle unavoidable sensor movement. This study therefore proposes a long-term displacement measurement method using light detection and ranging (LiDAR) that is designed for use with short- and medium-span bridge structures. Reflectors that have higher reflectance than common construction materials (such as concrete and steel) are used to enhance measurement accuracy and reduce scanning time. Strategically deployed reflectors provide a reference point, which is independent of the LiDAR position. Thus, LiDAR can be temporarily installed in the field only when measurements are necessary. Expensive LiDAR systems can be employed to measure the long-term displacement of multiple bridges cost-effectively because permanent installation is not required. The proposed method is validated within the laboratory by focusing on LiDAR position independence and is then used during the early erection stages of a railroad bridge to measure long-term displacement.

A PVDF-Based Sensor for Internal Stress Monitoring of a Concrete-Filled Steel Tubular (CFST) Column Subject to Impact Loads.

Impact loads can have major adverse effects on the safety of civil engineering structures, such as concrete-filled steel tubular (CFST) columns. The study of mechanical behavior and stress analysis of CFST columns under impact loads is very important to ensure their safety against such loads. At present, the internal stress monitoring of the concrete cores CFST columns under impact loads is still a very challenging subject. In this paper, a PVDF (Polyvinylidene Fluoride) piezoelectric smart sensor was developed and successfully applied to the monitoring of the internal stress of the concrete core of a CFST column under impact loads. The smart sensor consists of a PVDF piezoelectric film sandwiched between two thin steel plates through epoxy. The protection not only prevents the PVDF film from impact damages but also ensures insulation and waterproofing. The smart sensors were embedded into the circular concrete-filled steel tube specimen during concrete pouring. The specimen was tested against impact loads, and testing data were collected. The time history of the stress obtained from the PVDF smart sensor revealed the evolution of core concrete internal stress under impact loads when compared with the impact force–time curve of the hammer. Nonlinear finite element simulations of the impact process were also carried out. The results of FEM simulations had good agreement with the test results. The results showed that the proposed PVDF piezoelectric smart sensors can effectively monitor the internal stress of concrete-filled steel tubular columns under impact loads.

The degree of flammability for an artificial grass surface system

The paper presents a general overview of sport and floor lining products, such as artificial grass, which are used in residential premises and public utility buildings, as well as the hazards which ensue from the use of synthetic grass [1]. An outline was made of the requirements for the fire safety of civil engineering structures arising from their designation and usage type. The results were presented from studies conducted on four samples of synthetic grass with the main ingredients being polyethylene and polypropylene. An appraisal method was determined for flammable properties and flame spread on a horizontal sample subjected to a heat radiation flux gradient in a research chamber pursuant to PN EN ISO 9239- 1 [25] applicable for all types of floors. Based on the estimated value of critical heat radiation flux (KSP) below 3 kW/m2 and in addition to the flammability of products directly subjected to a flame according to PN EN ISO 11925-2 [27], a study was made of the suitability of selected samples of artificial grass by their categorisation to class Efl - i.e. easily flammable products. The classification of artificial grass selected for the needs of the studies, which has been verified in practice, and designated for use as decoration for gazebos, balconies, terraces and public utility facilities is only admissible in residential premises of type ZL IV.

Estimation of Tsunami Force for Onshore Buildings in the Northwest Coast of Peninsular Malaysia

The northwest coast of Peninsular Malaysia had suffered various extents of structural damage and loss of 68 lives in the unprecedented 2004 Indian Ocean tsunami. Since then, the government of Malaysia concerns about the safety of civil engineering structures and human lives in coastal area. An experimental study was embarked on the formulation of tsunami force for onshore buildings in Peninsular Malaysia. Four downscaled rigid building models with various heights were subjected to probable tsunamis with three nominal wave heights and flow velocities. The wave pressures at front and back faces of building model were measured. The findings show that the front face wave pressure measured from the experiment is in good agreement with the wave pressure predicted using the equation proposed by Japanese researchers. The back face wave pressure distribution is found to be slightly higher than the hydrostatic pressure. The pressure distributions at the front and back faces were then proposed for the estimation of tsunami force on buildings in the northwest coast of Peninsular Malaysia.

Energy dissipation of steel-polymer composite beam-column connector

The connection between a column and a beam is of particular importance to ensure the safety of civil engineering structures, such as high-rise buildings and bridges. While the connector must bear sufficient force for load transmission, increase of its ductility, toughness and damping may greatly enhance the overall safety of the structures. In this work, a composite beam-column connector is proposed and analyzed with the finite element method, including effects of elasticity, linear viscoelasticity, plasticity, as well as geometric nonlinearity. The composite connector consists of three parts: (1) soft steel; (2) polymer; and (3) conventional steel to be connected to beam and column. It is found that even in the linear range, the energy dissipation capacity of the composite connector is largely enhanced by the polymer material. Since the soft steel exhibits low yield stress and high ductility, hence under large deformation the soft steel has the plastic deformation to give rise to unique energy dissipation. With suitable geometric design, the connector may be tuned to exhibit different strengths and energy dissipation capabilities for real-world applications.

Suggested continued heat-treatment method for investigating static and dynamic mechanical properties of cement-based materials

Thermo-induced damage affects the structural and material safety of civil engineering structures; the damage can induce direct or indirect extensive structural collapse.An innovative continued heat-treatment method to obtain several specimen pieces in a single cylinder of mortar was described in this paper; the intended purpose of the method was to predict the effects of heat treatment on the static and dynamic mechanical properties and characteristic width of process zones.All of the results can be regressed by a continuous equation; therefore, the regression equations obtained from the results of continued heat-damaged specimen pieces represented more accurate prediction equations. Moreover, using the Log–Log method resulted in a critical damage temperature of approximately 547.5°C. For a temperature range between room temperature and approximately 547.5°C; the variation of all of the mechanical properties decreased by approximately 10–11% per 100°C, but they decreased by approximately 29–31% per 100°C between 547.5°C and the highest temperature used in the tests. Finally, the fracture characteristics and the width of the process zones could be investigated using the acoustic emission technique; the width was wider at lower temperatures than at higher temperatures.

Diagnosis of Damage in a Steel Tank with Self-Supported Roof through Numerical Analysis

The safety of civil engineering structures is one of the most important issues of building industry. That is why the assessment of the damage-involved structural response has recently become of major concern to engineers. Among a number of different approaches to diagnosis of damage, the method of measuring the changes in natural frequencies is considered to be one of the most effective indicators of global damage. From the practical point of view, the method has been successfully applied to relatively small structures, while in-situ tests on large structures, such as bridges, tanks or dams, are very difficult. The aim of the present paper is to show the results of the numerical analysis concerning the diagnosis of damage in a cylindrical steel tank with self-supported roof which is filled with liquid. The tests have been conducted for various stages of damage, introduced in the numerical model by reducing the stiffness of tank-soil system as well as by cutting the connection between the shell and roof of the tank as well as between roof elements. The results of the numerical analysis have shown the characteristic decrease in the natural frequencies for the case of tank-soil system with reduced stiffness, which is the global type of damage. On the other hand, cutting the welds, which can be considered as the local type of damage, has not lead to the differences in the natural frequency values, although differences in local deformations of shell in the vicinity of cuts have been observed in vibration modes.

A global non-destructive damage assessment methodology for civil engineering structures

This paper describes a potential methodology to continuously assess the safety of civil engineering structures, e.g. bridges, frames and offshore platforms. The proposed damage assessment methodology not only detects and sizes damage, but also evaluates the impact of the damage on the performance of the structure. The proposed methodology deals with two broad activities: (i) periodic non-destructive damage localization and severity estimation; and (ii) the assessment of structural safety based on the results of the non-destructive damage detection. To accomplish these activities, first an established methodology which yields information on the changes in localized sectional stiffness properties (e.g. axial, bending and torsion) from changes in dynamic properties (i.e. mode shapes and frequencies) of the pre-damaged and post-damaged structures is reviewed. Next, an efficient technique to directly assess the reliability of a structural system using reliabilities of the components of the structure is developed. The efficacy of the combination of the non-destructive damage detection and the structural reliability evaluation is demonstrated using pre-damage and post-damage modal data obtained from numerical simulations of a rigid frame.

Fault identification of beams on elastic foundation

The capability of identifying both location and severity of damages of faulted elements in a structural system is greatly needed under the present demands of constantly maintaining the safety of civil engineering structures. Presented in this paper is a methodology based on vibration theory that can be used for the detection of faults in a beam of either uniform or nonuniform cross section and under a variety of boundary conditions, including simple support, cantilever support, and beam on elastic foundation. Theoretical developments of the methodology are presented first, followed by numerical experiments to demonstrate the feasibility of the method. Numerical experiments include various damage scenarios such as those faults occurring in a beam section as well as in a subgrade foundation. Furthermore, damage scenarios involving both single fault and multiple faults are also presented. The defect of the supporting subgrade foundation can be modeled either as degrading subgrade stiffness or increasing damping values. Numerical experiments demonstrate the feasibility of the developed NDT methodology which warrants the next stage of field study.