Periodica Polytechnica Civil Engineering

Strength Improvement Using Polypropylene Fiber as Reinforcement in Natural Pozzolana-lime-stabilized Expansive Clayey Soil Artificially Contaminated by Sulfates

Hamid Gadouri — 2023-09-07

This paper aims to assess the behavior of the unconfined compressive strength (UCS) of polypropylene fiber (PF) reinforced natural pozzolana-lime-stabilized expansive grey clayey soil (GS) contaminated by sulfates. Lime (0–8%), natural pozzolana (NP) (0–20%), and PF (0–3%) by dry weight of soil were used. GS was contaminated by different sulfate contents (0-6%) and UCS was assessed at various curing periods (7–120 days). Results showed that adding 8% lime alone or with 20% NP considerably improved UCS. Including 1% or 2% PF as reinforcement without sulfates in lime-stabilized GS transferred stress from GS to PF due to bonding. However, increasing PF beyond 2% formed lumps, reducing contact and friction coefficient, thus decreasing UCS. This means that the optimum PF dosage was found to be 2%. The UCS of GS increased with PF content up to 2% and then decreased. The UCS significantly increased with higher calcium sulfate content and curing period due to observed cementing agents in X-ray diffraction (XRD) and scanning electron microscopy (SEM). Adverse effect of ettringite mineral on UCS caused by sodium sulfate addition was suppressed with the combination of 20% NP and 2% PF in lime-stabilized GS. Binding forces from lime and NP resisted to ettringite expansion. Sensitivity of UCS to sulfate effect was more pronounced with sodium sulfate than calcium sulfate. In addition, NP–PF mixture in lime-stabilized GS was more effective, improving the strength of expansive soil, especially with sodium sulfate. In conclusion, reinforcement of NP-lime-stabilized expansive soils with PF is an effective method.

Monitoring Strategy of Geological Hazards Using Integrated Three-dimensional InSAR and GNSS Technologies with Case Study

László Bányai — 2023-09-07

Geodetic/geodynamic benchmarks, equipped with both ascending and descending radar corner reflectors, and a method for integrated InSAR and GNSS/GPS network observation were developed and applied as the continuation of the former geodetic monitoring at the Dunaszekcső landslide, Hungary. The attempts to apply InSAR technologies using archive and Sentinel-1 data practically failed on the most intensive landside areas (“Vár” and “Szent János” hills), where proper persistent or distributed scatterers were not found.
Our concept solved this problem, where the Simple Look Complex (SLC) images are used to interpolate the movements between two GNSS network observations using the integrated benchmarks and the method of Kalman-filtering.
Since the InSAR line-of-sight (LOS) changes are barely sensitive to the north movements, this information is essentially provided by GNSS measurement alone, moreover, the GNSS measurements are used to: a) identify the benchmarks, b) detect the unwrapping errors and missing cycles and c) provide the boundary values of Kalman-filtering.
After the installation of benchmarks three GPS observations were carried out and 69 ascending and 61 descending Sentinel-1 A and B images were processed.
The data processing properly indicated the general movement history, which fit the curves of former geodetic observations, as well. The dense data points of the East and Up (vertical) components made possible more detailed geomorphologic interpretations of the ongoing process between two GPS observations.
During the investigated periods the deceleration of movements was experienced, however, the deceleration of the dormant state needs the continuation of the monitoring.

Optimization of the Engineering Properties of Cement Concrete Containing Gravel and Waste Rock Using Dense Packing and Response Surface Methodology

Van Minh Nguyen — 2023-09-07

This study introduces a novel methodology for optimizing the distribution of aggregate particles in concrete. Utilizing locally available materials like gravel and waste rock is explored as a sustainable alternative to conventional materials like mountain rock and river sand, which are depleting. Determining the maximum bulk density involves an efficient process of gradually adding different particle sizes of gravel and waste rock to the mixture. The vibrational compaction of the container aids in identifying the optimally combined percentages of these aggregates. Besides, the study also addresses the issue of porosity in concrete. The response surface methodology is employed to optimize the mixture proportions for concrete, considering important factors such as workability, compressive strength, flexural strength, and elastic modulus. This response surface methodology allows for the development of mathematical models that aid in determining the optimal mix ratios. By exploiting the potential of gravel and waste rock, this study aims to procedure cement concrete containing gravels and waste rock (WR) with required compressive strength from 30 MPa to 35 MPa based on reasonable aggregate particle distribution in combination with response surface methodology (RSM) and minimize the disposal of non-biodegradable waste, thereby reducing the environmental pollution. Additionally, utilizing locally available materials helps to effectively use the region's resources for concrete production, promoting sustainability and reducing dependency on scarce resources. The proposed method presents a promising approach to optimizing aggregate distribution in concrete while considering the environmental and resource constraints specific to the Northwest region of Vietnam.

Evaluation of Static Nonlinear Behavior of Coupled Reinforced Concrete Shear Walls with Steel Beams

Peyman Beiranvand — 2023-09-07

The shear walls are divided into two types of reinforced concrete and steel, which behave differently. In the present study, the linear and nonlinear static behavior of coupled reinforced concrete shear walls is investigated. Therefore, to validate the results, Yuan Cheng and coworkers’ laboratory model is investigated. The results of this study show that the stresses caused by external loading in the coupled shear walls are lower compared to the separate shear walls. In addition, the behavior of this system depends on the rigidity of the coupling beams. The excessive rigidity of the coupling beams does not significantly affect the behavior of these structures. Therefore, by using the continuous analytical method and ABAQUS software, a formula is proposed to calculate the dimensions of the ideal coupling beams cross-section. Based on the reviews, the proposed formula accurately predicts the nonlinear performance of the systems under investigation.

Investigation of the Load-settlement Behavior of Box-shaped Deep Foundations

Serdar Günay — 2023-09-07

The load-settlement and monolithic behaviors of a new type of deep foundation in sand named Box-Shaped Deep Foundation (BSDF) were studied, and a comparison to Conventional Piled Raft Foundations (CPRF) was made by carrying out extensive numerical analysis. Physical model tests were also conducted to validate the numerical approach presented in this study, and it turned out to be a reasonable agreement. In the scope of this paper, the results of the parametric study are presented, and design strategies for an optimized design of BSDFs are discussed.

Mechanical Response of Thin Composite Beams Made of Functionally Graded Material Using Finite Element Method

Khaled Boumezbeur — 2023-09-07

Functionally Graded Material (FGM) is a new generation of composite materials, it can be used for different engineering fields according to the loading environment, but the study of its mechanical behavior requires sophisticated numerical and analytical models. Several investigations in these models are available in the literature, however, most of those investigations are based on simplifying assumptions. In this paper, we present a three-dimensional finite element modeling of functionally graded material (FGM) beams subjected to static loading. Material properties are assumed to vary continuously along the beam thickness according to the power-law distribution with linear elastic behavior. The FGM beams are discretized by hexahedral finite elements type C3D20R (continuum stress/displacement, three-dimensional 20-node, reduced integration). We studied several numerical examples of FGM beams and compare the obtained numerical results with those of analytical models in the literature.

Numerical Modeling of Early-age Effects on the Mechanical Behavior of Concrete Gravity Dams

Abdelsemi Taibi — 2023-09-07

The control of thermal cracks induced by the effect of early age are the main concerns in concrete dam during the construction stage. Despite its importance, detailed thermal analysis of concrete gravity dams during the construction period is relatively rarely in the literature, eventually because prediction the behavior of concrete gravity dam on early stage requires taking into account the several phenomena and interaction, demands a considerable computational effort. To overcome this drawback, the present paper proposes a numerical modeling strategy to predict the thermo-mechanical behavior of concrete gravity dams during construction periods considering the effect of early age and the construction schedule. The proposed strategy is also used to study the effect of pre-cooling methods on the thermal-mechanical fields on concrete gravity dam during construction process. For this purpose, a Chemo-Thermo-Mechanical model is developed for predicting the behavior of a gravity dam at early stages. Firstly, temperature field model was established and verified with the results reported in the literature. Furthermore, the thermo-mechanical behavior of a concrete gravity dam is performed for two configurations: Early age state with pre-cooling and early age without pre-cooling. Thermal stress analysis was also conducted and results showed that the greatest tensile stresses after construction are developed at the heel of dams and resumption of concreting interface due to the internal restraint imposed by the concrete. The numerical results showed that the pre-cooling methods is an effective way to reduce both the hydration temperature and tensile stress induced by the effect of early age.

Effects of Different Wall Openings on the Cyclic Behavior of Aerated Concrete Block Infilled RC Frames

Batuhan Aykanat — 2023-09-07

In the current study, the effects of infilled reinforced concrete (RC) frames with different window and door openings under cyclic loads were investigated. For this purpose, five in-filled RC frames with different infill wall openings were produced. The main parameters to evaluate overall performance of the RC frames with infill walls, the load carrying capacities, displacement ductility, stiffness degradation and energy dissipation capacities were determined using obtained results. At the end of the study, even if the opening ratios are the equal, it has been observed that the location and number of openings have a significant effect on the behavior and failure pattern of the RC frames. Also, increase in the openings ratio decreases the load carrying capacity, and energy consumption capacity. Based on these results, it is suggested that infill walls affect the structural behavior and failure pattern. Therefore, infill wall openings should be considered in the design of RC structures.

The Effects of Heat on the Cyclic Behavior of Retrofitted Concrete Columns (by Steel Plates and CFRP)

Seyed Amir Hashemi Amiri — 2023-09-07

In this research, in addition to ensuring the accuracy of the numerical simulations, a 3D reinforced concrete column is numerically modeled in three conditions, including a non-retrofitted state, as well as two states retrofitted with steel plates and CFRP. The coupled temperature-displacement analysis of these columns is conducted under cyclic lateral loading in various heat levels, and the effects of both the retrofits and heat on the cyclic lateral behavior of the columns are studied and compared. According to the results of the study, with temperature rise, both lateral forces and energies increase in the non-retrofitted column, the column retrofitted with steel plates, and the column retrofitted with FRP. This is even more significant at 500°C, particularly in retrofitted columns with steel plates. Besides, retrofitting the columns with steel plates (compared to FRP plates) causes a more substantial increase in the heat sensitivity of the column during cyclic lateral loading.

Widening Gap of Land Evaporation to Reference Evapotranspiration Implies Increasing Vulnerability to Droughts in Hungary

László Báder — 2023-09-07

Severe droughts of 2022 in Europe raise the question if one has sufficient knowledge and tools to predict and prevent such events. Analysis of 40 years of meteorological data for Hungary between 1981 and 2020 confirms significant upward trends with p = 0.05 in temperature, relative humidity, and net radiation. Shortwave net radiation has increased by 89.6 mm in water equivalent. Estimates of land evaporation and reference evapotranspiration also show a significantly increasing trend. The gap between them is widening with a significant trend in northeast Hungary. The demand (reference evapotranspiration) is increasing by 2.23 ± 0.3 mm yr^–1, while supply (land evaporation) by 1.64 ± 0.2 mm yr^–1. The opening gap can be interpreted as a decreasing stability of the energy distribution system, where water is the dominant energy transfer medium for climatic energy. This change could lead to an increased risk of droughts, a symptom of system underperformance. The climatic energy distribution process – a key environmental service - is shifting to a new operating point where more water would be needed to transport energy. These trends call for a process capability approach. Desertification cannot be stopped by chasing water use efficiency and using less water, but vice versa: water scarcity can only be eliminated by ensuring that there is sufficient water available for evapotranspiration. This will raise the priority for initiatives to design and implement a wide range of preventing actions, such as nature-based solutions and water retention measures.

Effect of Maximum Aggregate Size and Powder Content on the Properties of Self-compacting Recycled Aggregate Concrete

Namho Kim — 2023-09-07

The utilization of recycled aggregates and various industrial by-products is considered a sustainable strategy in the concrete industry. In this study, the effect of the maximum size of recycled coarse aggregate and the cementitious binder content on fresh and hardened properties of self-compacting concrete was investigated. Self-compacting concretes with maximum aggregate sizes of 9.5 mm, 12.5 mm, and 19 mm were prepared at water-to-binder ratios of 0.39, 0.42, and 0.45, respectively. For all mixtures, 100% recycled aggregate was used as coarse aggregate and 60% of cement was replaced by industrial by-products, i.e., fly ash and ground granulated blast furnace slag. The tests included slump flow, air content, hardened density, compressive strength, elastic modulus, and splitting tensile strength. The results showed that the increase in maximum aggregate size and binder content tended to improve both fresh and hardened properties of self-compacting concrete.

The Effect of Voids on Flexural Capacity of Reinforced Concrete Slabs

Fırat Kıpçak — 2023-09-07

The voided reinforced concrete slab system is mainly produced with polyester foam placed mostly at the bottom of the slab. The aim of the voids is to reduce the weight of the slab. In this paper behavior of the voided reinforced concrete slabs in which voids placed at the mid-height of the slab cross-section, is examined analytically. A series of models were created to come up with a lightweight slab. Two distinct slab models were analyzed using the ABAQUS software. In the first group, slabs had three layers, in which bottom and top layers were of solid reinforced concrete, but the mid layer was of voided unreinforced concrete. In the second layer, in order to increase the contact between top and bottom layers of the slab, crossties were utilized, and the mid layer was reinforced accordingly. Since all the layers were 5 cm thick, the total thickness of the slabs were 15 cm. Slabs were 100 cm wide and 200 cm long. They were simulated the three-point bending test. Concrete damaged plasticity material model (CDPM) for concrete and elastoplastic material model for steel was selected. From the results it was found that moment capacity decreased with the increase in the volume of the voids. There was a sudden decrease in strength after reaching the yield strength in voided slab without a crosstie. In addition, crossties enabled the reduction of the weight of the slabs without significant decrease in moment capacity.

Durability Evaluation of Cactus-infused M25 Grade Concrete as a Bio-admixture

Velumani M. — 2023-09-07

The durability of concrete incorporating cactus extract as a bio-admixture is the focus of this study, which is the first of its kind in the literature. Cactus-infused concrete is a novel type of concrete with exceptional fluidity, strength, and durability. In this project, cactus was employed as an addition to M₂₅(3626 psi) concrete, which was designed to Indian standards. Cactus extract (1% to 9% of the total weight) was used to replace the water in the mix. In order to look into the durability properties of cactus concrete, durability experiments such as drying shrinkage test, water absorption, porosity, sorptivity, accelerated carbonation, acid, and alkalinity tests were carried out on the material. ETC concrete enhances the fluidity of the mixture, making it more workable. To determine the particle distribution in concrete, scanning electron microscopy (SEM) was used to investigate the material. According to experimental research, polysaccharides and fats in concrete have increased their durability properties by 30% when used at their optimal level. However, a high level of durability is attained, which encourages concrete voids to be effectively filled.

Effect of Material Non-linearities on the Transient Dynamic Behavior of the Beni-Bahdel Dam in the Presence of the Dam-foundation Interaction

Mohammed Habib Daoudi — 2023-09-07

The current paper's goal is to investigate how dynamic interaction phenomena and material nonlinearities affect the dynamic behavior of a concrete gravity multi-arch dam in terms of maximum displacements, natural stresses, principal stresses, and Von Mises stresses when subjected to seismic excitation. Utilizing ANSYS APDL software, linear and nonlinear transient analysis using the finite element method was employed to analyze the interaction between the dam and its rock foundation. As a case study for this work, the multi-arch Beni-Bahdel dam was selected, and the seismic excitation used data from a simulated earthquake. The direct method is employed to model the interaction between the multi arch dam and the rock foundation using two approaches; the fixed base approach and the mass foundation approach. Six finite element models were performed using ANSYS code, “linear dam-fixed support”, “nonlinear dam-fixed support”, “linear dam-linear rock foundation” “nonlinear dam-linear rock foundation”, “nonlinear dam-nonlinear rock foundation” and “linear dam-nonlinear rock foundation”. The bilinear kinematic hardening model is employed to represent the nonlinearity of both dam body and rock foundation. The results obtained are compared to understand the effect of both material nonlinearities and interaction phenomenon on the dynamic behavior of the studied dam. In contrast to the nonlinearity of the rock foundation material, it is concluded that the nonlinearity of the concrete dam material has a significant impact on the behavior of the system.

Evaluating the Modified Uncertainty MCMC Approach to Obtain Safety-Quality Index in PC Construction with Current Models

Hamidreza Vosoughifar — 2023-09-07

Precast Concrete Construction (PCC) is a famous method in construction industry due to its different advantages. Nevertheless, this method has several discontinuous processes and they can enhance various uncertainty safety-quality issues. In this system, Building Information Modeling (BIM) technique plays a key role in managing of discontinuous processes to improve multidimensional safety and quality. Dimensionless parameters were used to evaluate the modified type of multidimensional BIM index (I_MBIM) as the target index using the Modified Fuzzy Analytic Network Process (MFANP) method. In fact, the importance weight of input indices on the target was determined by the MFANP approach. The results of statistical analysis in verification step indicate that MFANP is well compatible with other approaches, so this developed method was considered as a reference point. The modified uncertainty Markov Chain Monte Carlo (MCMC) analysis was used for the validated method to determine the optimal high occurrence rate of I_MBIM. The results demonstrate that a high percentage of occurrence frequency for I_MBIM is in the range between 0.9 and 0.925. In this range, the mean optimal value of I_MBIM as a management measure for multidimensional problems is 0.912. Stakeholders in PCC projects can use the proposed high occurrence range to assess the quality-safety of construction and make appropriate decisions.

Mechanistic-empirical Design of Perpetual Road Pavement Using Strain-based Design Approach

Manoj Kumar Sahis — 2023-09-07

Present paper deals with the development of a Mechanistic-Empirical model of the strain-based design of perpetual road pavement using Odemark's principle. The bituminous pavement which can withstand minimum design traffic of 300 msa has been classified as perpetual pavement in this paper. The pavement has been considered as a three-layered system with a top layer of bituminous mix followed by unbound granular materials which rest on soil subgrade. The constituent bituminous layer thickness in the pavement has been determined by limiting the radial tensile strain at the bottom of the bituminous layer against fatigue and the vertical compressive strain at the top of the subgrade against rutting. The allowable strain against rutting and fatigue has been used in the present analysis from mechanistic-empirical correlations recommended in IRC:37-2018. The pavement section has been transformed into a homogeneous system by Odemark's method for application of Boussinesq's theory. To validate the thickness of the perpetual pavement, the strain at different layer interfaces in the pavement was compared using IITPAVE software, which shows the pavement section using present method is safe against rutting but marginally fails under fatigue. Moreover, conventional pavement thickness obtained using IRC:37-2018 were compared with the present method, which shows reasonably good convergence. It has been found that the bituminous layer thickness in a layered system of pavement seems to be more sensitive to fatigue than rutting. In this backdrop, modified fatigue and rutting strain values have been recommended for the design of perpetual road pavement.

The Effect of Irregular Seismic Loading and Soil Density on the Liquefaction Behavior of Saturated Sand

Bahareh Katebi — 2023-09-07

Structures located on sandy soils can be significantly damaged by earthquake-induced liquefaction. A series of stress-controlled cyclic triaxial tests under harmonic and irregular loading under various soil densities 30%, and 50%, was conducted to evaluate the effects of irregularities and relative densities on the liquefaction characteristics of saturated sand. The irregular actual ground motions time histories obtained from six stations of the 1999 Chi-Chi Earthquake and harmonic sinusoidal cyclic loading time histories were applied to Firoozkooh #161 sand specimens, and the results were compared in terms of the type waveforms loading and relative densities. Based on the stress and energy method, the Correction coefficient is calculated for a variety of densities and types of irregular loading. The present results reveal that it is not precise to assume a single correction coefficient for all records, regardless of the complicated time-domain characteristics of ground motions. Furthermore, the results indicate that the relative soil density and the type of irregular loading influenced sand's pore pressure generation and liquefaction potential.

Comparison of Three Chaotic Meta-heuristic Algorithms for the Optimal Design of Truss Structures with Frequency Constraints

Ali Kaveh — 2023-09-07

The main reasons for the success of using chaos maps in meta-heuristic algorithms are fast optimization of non-linear and non-convex problems. One of these cases is the control of the natural frequencies of structures to prevent the destructive and dangerous phenomenon of resonance. Natural frequencies have useful information about the dynamic behavior of structures, and by applying dynamic constraints, a significant improvement is achieved in the optimal design of structural weight. Applying frequency limits with traditional and gradient-based methods is very difficult and time-consuming, and in most cases, the calculation process stops at local optima. Recent research shows that chaos maps play a major role in escaping from local optima and reaching global optima. By combining these maps with meta- heuristic algorithms, while avoiding premature convergence, the access to global optima is accelerated and improved, and the ideal state of balance between the exploration and exploitation stages is realized. Today, chaotic algorithms are widely accepted by researchers and are considered as a challenging topic. In a recent research, six chaotic meta- heuristic algorithms have been investigated for the formation and improvement of results with the optimal design of truss structures. In this part the chaotic algorithms include Chaotic Water Evaporation Optimization (CWEO), Chaotic Tug-of-War Optimization (CTWO) and Chaotic Thermal Exchange Optimization (CTEO) are examined.

Hybrid ECBO–ANN Algorithm for Shear Strength of Partially Grouted Masonry Walls

Ali Kaveh — 2023-09-07

In recent years, artificial neural network (ANN) has become one of the popular and effective machine learning models, having a unique ability to handle very complex problems and the potential to predict accurate results without a defined algorithmic solution. However, the ANN structure and parameters are usually chosen by experience.
The behavior of Partially Grouted (PG) masonry shear walls is complex due to the inherent anisotropic properties of the masonry materials and the nonlinear interactions between mortar, blocks, grouted cells, non-grouted cells, and reinforcing steel.
In this study, the aim is to develop an artificial neural network model by combining the ECBO meta-heuristic algorithm with the artificial neural network structure to optimize the feed forward propagation network parameters for analyzing the shear strength of PG walls.
A total of 255 test data on PG collected from the available literature were used to generate training and test data sets. Various validation criteria such as mean square error, root mean square error and correlation coefficient (R) are used to validate the models.
In this study, the optimal number of neurons used in the hidden layer and also the optimal number of CBs required in the ECBO algorithm were obtained. The mathematical formulation of the optimized neural network model with the combination of meta-heuristic algorithm is also presented.

Automating Scan to BIM Operations Using Grasshopper

Ifra Aftab — 2023-09-07

Remote sensing technologies such as laser scanning and photogrammetry have advanced significantly in the field-to-BIM workflow in recent years, becoming key instruments for modeling as-built frameworks. They can be utilized to collect dense 3D measured data on the condition of a building, and the derived point cloud can be processed to generate the as-built BIM. It provides building information to report as-built conditions and serves as a skill set for data on problem-solving issues in civil engineering. This research presents an efficient and automated workflow for modifying and evaluating point cloud data, focusing on supporting scan-to-BIM operations. The workflow utilizes cubic voxel mesh creation and voxel subsampling techniques to ensure precise representation of scanned data. The validation of this reconstruction methodology using Grasshopper and Volvox demonstrates its potential to reduce manual labor and analysis typically required in conventional scan-to-BIM methodologies. The presented workflow simplifies the critical task of acquiring building profiles, an essential BIM result, and streamlines the overall process. The integration of the Volvox plugin has further augmented the capabilities of Grasshopper and Rhino, providing users with intuitive tools for manipulating point clouds. Automating certain operations through the presented workflow has significant potential to enhance the efficiency and accuracy of the scan-to-BIM methodologies. These findings have implications in architecture and design, demonstrating how technology can be leveraged to unlock new possibilities and streamline critical processes.

Imperfections for Local and Global Interaction Buckling of Welded Square High-strength Steel Box-section Columns

Mohammad Radwan — 2023-09-07

The interaction behavior between local and global buckling modes in high-strength steel box-section columns has received limited research attention. Currently, there is a lack of a validated equivalent geometric imperfection that can be effectively employed in nonlinear plastic analysis to estimate the interaction buckling resistance. This research aims to find equivalent geometric imperfections that can be used in geometrical and materially nonlinear analysis using imperfections (GMNIA) to estimate the interaction buckling resistance of square welded box-section columns made of high-strength steel. It extends prior investigations by the authors on equivalent imperfections for normal-strength steel welded box-sections. A developed and validated numerical model is used to perform parametric studies to estimate the accurate buckling capacity using previously developed and verified combinations of imperfections and residual stresses. The accurate buckling capacities are used to calibrate equivalent local and global imperfection combinations that can be used in FEM-based design. A reliability assessment study is also performed to check the safety level of the proposed imperfection combinations.

Effect of Static Loading States on the Compressional Behavior of Foam Glass Aggregate

Waleed Sulaiman Mustafa — 2023-09-07

In this study, two groups of foam glass aggregate (FGA) samples were prepared with four different compaction ratios (10%, 20%, 30%, and 40%) and subjected to a series of static compressional loads from 50kPa to 300kPa with 50kPa interval. In first group of the test (changed load samples, ChLS), for each static load value, a new sample was prepared and tested. In the other group of the test (continuously loaded samples, CLS), all prescribed static compressional loads were sequentially applied over the same sample after satisfying the required strain rate at each load. The results revealed that the overall vertical strain values of CLS were lower than ChLS except for 10%, which shows reverse behavior. For both sample types, the required time to reach the desired vertical strain rate was much higher when the compaction ratio was low, and the compressional load was above 250 kPa. The compaction methodology used in the present study led to more reliable vertical strain values for both short- and long-term loading periods compared to other reported results executed on FGA under the same static compressional load circumstances. The evolution in the particle distribution curve of FGA particles after maximum compaction ratio (40%) was nonsignificant compared to the study works that depended on traditional standard test methods of compaction and led to severe change in particles structural component. The current findings beneficially affect civil engineering applications using FGA by defining the material's final strain values when subjected to static compressional loads at different compaction ratios.

Experimental and Numerical Study on RC Beams Strengthened by NSM Using CFRP Reinforcements

Abderrahmane Abdesselam — 2023-09-07

Near Surface Mounted (NSM) Carbon Fiber-Reinforced Polymer (CFRP) reinforcement technique to improve the flexural strength of reinforced concrete members has become increasingly attractive in recent years. In this study, the practical problem of concrete cover depth cutting limitation was investigated. Twelve specimens were tested by four-point bending until failure. Experimental parameters include concrete cover depth, CFRP reinforcement type, CFRP positioning, and stirrups status. Furthermore, a nonlinear FEA model was developed to simulate the tested beams and was able to predict the experimental behavior satisfactorily. A series of parametric studies were then performed using this model to understand the effect of various reinforcement parameters on the flexural performance of the beam. The results showed that Strengthening with CFRP resulted in a significant increase in yield and ultimate strengths, but a significant ductility loss was recorded due to CFRP strip debonding in the strengthened beams, this problem was addressed by using more efficient strengthening techniques utilizing the effective bond length and a proper groove depth and positioning for the NSM bars.

Sustainable Stabilization of Poorly Graded Desert Sand by Cement Kiln Dust and Salt Water for Using in Backfilling and Subbase Layers

Mohamed Youssef Abd El-Latif — 2023-09-07

Effective use of natural materials and industrial by products has a direct impact on economy, sustainable environment, and waste management. Poorly graded desert sand (SP) is widely observed in sand dunes and sand seas. Studies were performed to get beneficial use of cement kiln dust (CKD) in soil improvement. But there is a lack of information concerning using of CKD as an improving material for poorly graded sand with the aid of salt water. Salt water is widely available in Egypt from seas and some deep wells, using it will help in saving drink water which suffers from shortage in many countries. The aim of this research is to study the possibility of improving SP using CKD and salt water to be used in backfilling work and subbase layers of roads and pavements. Mixtures of poorly graded sand and various CKD ratios (10%, 20% and 30%) were classified and tested using grain size distribution, compaction, shear strength and California bearing tests. The results were compared with potable water. The results show that adding CKD improves the characteristic properties of SP even with salt water. The study enhances the using of 20% CKD with optimum water content of 9.12% of salt water to have noticeable improvement for SP and to be used efficiently in backfilling and subbase layers.

Discussion on Blasting Vibration Velocity of Deep Rock Mass Considering Thickness of Overlying Soil Layer

Jia Bin Ruan — 2023-09-07

The thickness of the overlying soil layer has a certain influence on the blasting vibration response of deep rock mass. The vibration wave velocity of the overlying soil layer during the construction of deep blasting is measured in this paper. Based on the measured data, parameters k and α of the Sadowski equation are used to characterize the influence of the comprehensive geological conditions of the site on the vibration wave propagation. The model of blasting vibration velocity of deep rock mass is established according to the existing blasting theory, and the calculation accuracy of the model is verified according to the field blasting parameters. The new model is used to simulate different overlying soil thicknesses, and the safe allowable distance under different soil thicknesses is calculated. The calculated results show that with the increase of the thickness of the overlying soil layer, the blasting vibration velocity decreases and the attenuation velocity decreases gradually. The research results reveal the reduction effect of overlying soil thickness on blasting vibration to some extent. In the area with overlying soil layer, the safe allowable distance of blasting vibration safety can be appropriately reduced to increase the land utilization rate, which has important reference value for the blasting design and safety prediction of deep rock mass.

Overconsolidated Stress and Strain Condition of Pavement Layers as a Result of Preloading during Construction

Máté János Vámos — 2023-09-07

The stiffness and resilient behavior of soils are essential input properties when designing pavements. There are many material models that take into account the stress dependency of stiffness. In pavements, horizontal stresses generally differ from conventional soils because of the preloading of the pavement during construction. In this research, standardized pavement cross sections were analyzed using finite element software with advanced soil constitutive models, and equations describing their behavior were calibrated with the back-analysis of in-situ and laboratory measurements. The pavement was modelled as comprising 4 layers: asphalt pavement, well graded crushed stone base course, granular subbase course and fine-medium sandy subgrade. The ratio of horizontal and vertical stresses σ₃/σ₁ and strains ε₃/ε₁ were investigated and assessed in the function of depth and loading, and recommendations are given for the description of these functions. The recommendations give useful input data for future practical applications such as simplified calculation methods that are capable of determining the permanent settlement beneath flexible pavements without the use of finite element methods.

Thermomechanical Analysis of Glass Powder Based Eco-concrete Panels: Limitations and Performance Evaluation

Abdelmoutalib Benfrid — 2023-09-07

This article presents a comprehensive investigation into the thermomechanical analysis of glass powder as an additive in concrete. The efficient Eshelby's model is utilized to determine the relevant composite properties, considering the spherical shape of the glass powder. A higher-order shear deformation plate theory is employed to theoretically simulate the reinforced concrete panel, ensuring accuracy and simplicity. Equilibrium equations are derived using the virtual work concept, and energy equations are derived using Hamilton's principle. Navier's analytical techniques are applied to obtain closed-form solutions for simply supported plates. A comprehensive parametric study is conducted, analyzing the impact of factors such as glass powder volume, geometric parameters, and thermal loading on the thermomechanical behavior of the panel. The findings highlight the challenges associated with using glass powder in concrete for thermomechanical applications and suggest the need for alternative approaches to optimize its effectiveness in such scenarios, also the study provides first-time numerical results that serve as guidelines for further research on reinforced concrete.