Abstract
This study pioneers the exploration of creep and shrinkage behavior in ambient-cured geopolymer concrete (GPC), a
vital yet under-researched area in concrete technology. Focusing on the influence of sodium hydroxide (NaOH) solution concentration, the research utilizes low calcium fly ash (Class-F) and alkaline solutions to prepare two sets of GPC. The results show distinct patterns in compressive strength development and dry shrinkage reduction, with a 14 M NaOH solution demonstrating a 26.5% lower dry shrinkage than the 16 M solution. The creep behavior indicated a high initial strain within the first 7 days, significantly influenced by curing conditions and NaOH concentration. This study contributes to the existing knowledge by providing a deeper understanding of the time-dependent properties of GPC, which is crucial for optimizing its performance in structural applications.
Address
Asad Ullah Qazi: Civil Engineering Department, University of Engineering and Technology Lahore, Pakistan
Ali Murtaza Rasool: Diamer Bahsa Dam Consultant Group (DBCG)-National Engineering Services Pakistan (NESPAK), Lahore, Pakistan
Iftikhar Ahmad: Civil Engineering Department, University of Engineering and Technology Lahore, Pakistan
Muhammad Ali: Diamer Bahsa Dam Consultant Group (DBCG)-National Engineering Services Pakistan (NESPAK), Lahore, Pakistan
Fawad S. Niazi: Department of Civil and Mechanical Engineering, Purdue University, Fort Wayne, USA
Abstract
High-performance fiber-reinforced cement composites (HPFRCC) are new materials created and used to repair, strengthen, and improve the performance of different structural parts. When exposed to tensile tension, these materials show
acceptable strain-hardening. All of the countries of the globe currently seem to have a need for these building materials. This study aims to create a low-carbon HPFRCC (high ductility) that is made from materials that are readily available locally which has the right mechanical qualities, especially an increase in tensile strain capacity and environmental compatibility. In order to do this, the effects of fiber volume percent (0%, 0.5%, 1%, and 2%), and determining the appropriate level, filler type (limestone
powder and silica sand), cement type (ordinary Portland cement, and limestone calcined clay cement or LC3), matrix hardness, and fiber type (ordinary and oxygen plasma treated polypropylene fiber) were explored. Fibers were subjected to oxygen plasma treatment at several powers and periods (50 W and 200 W, 30, 120, and 300 seconds). The influence of the above listed factors on the samples' three-point bending and direct tensile strength test results has been examined. The results showed that replacing ordinary Portland cement (OPC) with limestone calcined clay cement (LC3) in mixtures reduces the compressive strength, and increases the tensile strain capacity of the samples. Furthermore, using oxygen plasma treatment method (power 200 W and time 300 seconds) enhances the bonding of fibers with the matrix surface; thus, the tensile strain capacity of samples increased on
average up to 70%.
Key Words
green fiber-reinforced cementitious composites; limestone calcined clay cement; oxygen plasma treatment; polypropylene fiber
Address
Sajjad Mirzamohammadi and Masoud Soltani: Faculty of Civil and Environmental Engineering, Tarbiat Modares University, Tehran, Iran
Abstract
Significant changes have been made to estimate the punching shear capacity for edge column-slab joints in the latest
editions of most current codes. The revised equations account for axial forces as well as moments conveyed to columns from slabs, which have a substantial impact on the punching resistance of such joints. Many key design parameters, such as reinforcement-ratio, concrete strength, size-effect, and critical-section perimeter, were treated differently or even ignored in various code provisions. Consequently, wide ranges of predicted punching shear strength were detected by applying different code formulas. Therefore, it is essential to assess the various current Codes' design-equations. Because of the similarity in
estimated outcomes, only the ACI, EC, and SNiP are used in this study to cover a wide range of estimation ranges from highly conservative to unconservative. This paper is devoted to analyzing the techniques in these code provisions, comparing the estimated punching resistance with available experimental data, and finally developing efficient models predicting the punching capacity of edge column-slab connections. 63 samples from past investigations were chosen for validation. To appropriately predict the punching shear, newly updated equations for ACI and SNiP are provided based on nonlinear regression analysis. The proposed equations' results match the experimental data quite well.
Address
Hamdy A. Elgohary and Mohamed A. El Zareef: Civil Engineering Department, College of Engineering and Architecture, Umm Al-Qura University, Makkah, Saudi Arabia; Structural Engineering Department, Faculty of Engineering, Mansoura University, Mansoura, Dakahlia 35516, Egypt
Abstract
In this paper, Eringen's nonlocal thermoelasticity is constructed to study wave propagation in a rotating twotemperature thermoelastic half-space. The problem is applied in the context of the dual-phase-lag (Dual) model, coupled theory (CD), and Lord-Shulman (L-S) theory. Using suitable non-dimensional fields, the harmonic wave analysis is used to solve the problem. Comparisons are carried with the numerical values predicted in the absence and presence of the gravity field, a nonlocal parameter as well as rotation. The present study is valuable for the analysis of nonlocal thermoelastic problems under the influence of the gravity field, mechanical force, and rotation.
Key Words
dual-phase-lag model; memory-dependent derivative; nonlocal parameter; thermal conducitivity
Address
Samia M. Said: Department of Mathematics, Faculty of Science, Zagazig University, P.O. Box 44519, Zagazig, Egypt
Abstract
To improve the vibration control performance and applicability of traditional particle tuned mass damper (PTMD) and realize the significant characteristic of lightweight design, this study proposes a novel particle tuned mass inerter system (PTMIS) by introducing inerter system (IS) to the PTMD. In the study, the motion equation of single degree of freedom (SDOF) structure attached with PTMIS is established first, then the variation law of the system's vibration reduction performance (VRP) is discussed through parameter analysis, and it is compared with the PTMD to analyze its VRP advantages. Finally, its vibration reduction (VR) mechanism from the perspective of core control force and energy analysis is explored, and its cavity relative displacement from the application perspective is analyzed. The results show that the PTMIS can remarkably improve the vibration control effectiveness of the PTMD. The reason is that the inerter can store energy and transfer the energy to the cavity and particles, which further stimulates the interaction between the two parts, thereby improving the nonlinear energy consumption effectiveness. Also, the IS can amplify the damping element's energy dissipation efficiency. In addition, the PTMIS can effectively reduce the working stroke of the PTMD, and through the analysis of the lightweight characteristics of the PTMIS, it is found that its lightweight advantage can reach nearly 100%.
Key Words
energy dissipation efficiency; inerter system; lightweight; particle tuned mass damper; particle tuned mass inerter system
Address
Zheng Lu: Department of Disaster Mitigation for Structures, Tongji University, Shanghai, 200092, China; State Key Laboratory of Disaster Reduction in Civil Engineering, Tongji University, Shanghai, 200092, China
Deyu Yan: Department of Disaster Mitigation for Structures, Tongji University, Shanghai, 200092, China
Chaojie Zhou: Department of Disaster Mitigation for Structures, Tongji University, Shanghai, 200092, China
Ruifu Zhang: Department of Disaster Mitigation for Structures, Tongji University, Shanghai, 200092, China; State Key Laboratory of Disaster Reduction in Civil Engineering, Tongji University, Shanghai, 200092, China
Abstract
Assessment of existing concrete bridges is a challenge for owners. It has greater economic impact when compared to
designing new bridges. When using conventional linear analyses, judgment of the engineer is required to understand the behavior of redundant structures after the first element in the structural system reaches its ultimate capacity. The alternative is to use a predictive tool such as advanced nonlinear finite element analyses (ANFEA) to assess the overall structural behavior. This paper proposes a new reliability framework for the assessment of existing bridge structures using ANFEA. A general framework defined in previous works, accounting for material uncertainties and concrete model performance, is adapted to the context of
the assessment of existing bridges. A "shifted" reliability problem is defined under the assumption of quasi-deterministic dead load effects. The overall exercise is viewed as a progressive pushover analysis up to structural failure, where the actual safety index is compared at each event to a target reliability index.
Key Words
advanced nonlinear finite element; assessment; bridges; concrete structures; model error; structural reliability
Address
Mahdi Ben Ftima, Bruno Massicotte: Department of Civil, Geological, and Mining Engineering, Polytechnique Montréal, Montreal, QC, Canada
David Conciatori: Department of Civil and Water Engineering, Faculty of Sciences and Engineering, Laval University, Quebec City, QC, Canada
Abstract
The purpose of this research was to investigate the cyclic behavior of the D-shaped dampers (DSD). Similarly, at first, the numerical model was calibrated using the experimental sample. Then, parametric studies were conducted in order to investigate the effect of the radius and thickness of the damper on energy dissipation, effective and elastic stiffness, ultimate strength, and equivalent viscous damping ratio (EVDR). An analytical equation for the elastic stiffness of the DSD was also proposed, which showed good agreement with experimental results. Additionally, approximate equations were introduced to calculate the elastic and effective stiffness, ultimate strength, and energy dissipation. These equations were presented according to the curve fitting technique and based on numerical results. The results indicated that reducing the radius and increasing the thickness led to increased energy dissipation, effective stiffness, and ultimate strength of the damper. On the other hand, increasing the radius and thickness resulted in an increase in EVDR. Moreover, the ratio of effective stiffness to elastic stiffness also played a crucial role in increasing the EVDR. The thickness and radius of the damper were evaluated as the most effective dimensions for reducing energy dissipation and EVDR.
Key Words
cyclic behavior; D-shape damper (DSD); energy dissipation; yielding damper
Address
Kambiz Cheraghi: Department of Civil Engineering, Faculty of Engineering, Razi University, Kermanshah, Iran
Mehrzad TahamouliRoudsari: Department of Civil Engineering, Kermanshah Branch, Islamic Azad University, Kermanshah, Iran
Sasan Kiasat: Department of Civil and Environmental Engineering, AmirKabir University, Tehran, Iran
Kaveh Cheraghi: Department of Mechanical Engineering, Engineering Faculty, Razi University, Kermanshah, Iran
Abstract
This research addresses experimentally the relationship between the excitation frequency and both hoop and axial wall stresses in a water storage tank. A low-density polyethylene tank with six different aspect ratios (water level to tank radius) was tested using a shake table. A laminar box with sand represents a soil site to simulate Soil-Structure Interaction (SSI). Sine excitations with eight frequencies that cover the first free vibration frequency of the tank-water system were applied. Additionally, Ricker wavelet excitations of two different dominant frequencies were considered. The maximum stresses are compared with those using a nonlinear elastic spring-mass model. The results reveal that the coincidence between the excitation frequency and the free-vibration frequency of the soil-tank-water system increases the sloshing intensity and the rigid-like body motion of the system, amplifying the stress development considerably. The relationship between the excitation frequency and wall stresses is nonlinear and depends simultaneously on both sloshing and uplift. In most cases, the maximum stresses using the nonlinear elastic spring-mass model agree with those from the experiments.
Key Words
laminar box; seismic analysis; soil-structure interaction; tank wall stresses; water storage tanks
Address
Diego Hernandez-Hernandez, Tam Larkin and Nawawi Chouw: Department of Civil and Environmental Engineering, The University of Auckland, Auckland Mail Centre Private Bag 92019, Auckland 1142, New Zealand
