Static Modulus Research Articles

A new type of engineered wood product: Cross-laminated-thick veneers

The global scarcity of high-quality solid wood resources has propelled efforts towards developing high value-added products utilizing fast-growing wood. However, the inherent low quality of fast-growing wood poses a significant challenge for its use in engineered wood products. In response to this challenge, this study focuses on the transformation of larch logs into a novel engineering wood product termed cross-laminated-thick veneers (CLTV). The process involves rotary cutting larch logs into 7.5 mm thick veneers, followed by hygrothermal treatment to alleviate stress, and ultimately assembling layers of thick veneers oriented at right angles, securely bonded to form structural panels. The investigation into the mechanical properties of CLTV reveals promising results. The static bending strength and modulus of a 15-layer CLTV with a thickness of 105 mm exhibit noteworthy values of 62.29 MPa and 10986 MPa, respectively. These values stand in comparison to the performance metrics of cross-laminated-timber (CLT) with only 3 layers, indicating the viability of CLTV as a competitive alternative. Additionally, the formaldehyde emission from CLTV measures at a minimal 0.010 mg/m3, while total volatile organic compounds are limited to 47 μg/m3. The development of CLTV emerges as a sustainable solution to the shortage of high-quality solid wood resources. Its comparable performance to traditional materials such as CLT positions CLTV as an eco-friendly alternative for engineered wood products applicable in diverse global building systems. The minimal formaldehyde emission and low volatile organic compounds further emphasize the potential positive impact of CLTV on both the construction industry and broader environmental sustainability initiatives worldwide. This study sets the stage for advancing engineered wood products, addressing resource constraints, and contributing to sustainable practices in the global construction sector.

Rock Plate Impact Experiment Based on ANSYS Workbench

The study of the physical properties of laminate mainly focuses on the static strength and elastic modulus. Its impact resistance has not attracted enough attention. However, the impact resistance of the multi-layer board used in climbing walls is particularly important to protect the safety of climbers. Using the display dynamics solver ANSYS Workbench and referring to the test method in EN 12572-1-2007, a finite element model of the rock slab impact test was established. The maximum stress and strain of each part during impact were solved, and the vulnerability point of the structure was analyzed. By changing the impact height and solving the influence on the rock slab under each test condition, the results show that the maximum stress of the slab changes nonlinearly. The numerical simulation results provide reference data and new development modes for the development of test methods and testing equipment in the next step of improving national standards.

The influence of the temperature on the hydration behavior and hardening process of PCC

AbstractPCC exhibit improved durability, chemical resistance and adhesion strength compared to unmodified variants. Commonly, the modifiers consist of thermoplastics. Despite the distinct temperature‐dependent behavior of these polymers, the properties of PCC were barely investigated within different temperatures. To make statements about the effect of different temperatures on the hardening process and therewith on the load bearing and deformation behavior of PCC, the properties of the materials have to be experimentally assessed at a defined temperature range. Accordingly, the degree of hydration, the structure development, the compressive and flexural strength as well as dynamic and static modulus of elasticity of different PCC were characterized while the samples were exposed to service temperatures of ‐20 °C, 20 °C, and 60 °C. After the specimens were thermally conditioned, the samples were tested in the proposed temperature scope. The results reveal influential changes in all tested attributes for the PCC within the applied service temperature range compared to a reference. This knowledge is essential to further investigate the temperature impact on the material and develop appropriate prediction models for the application of PCC and the integration in guidelines.

Crack Resistance of Concrete Using Granulated BlastFurnace Slag Sand under Flexural Stress

AbstractGranulated blast‐furnace slag sand (BFS) has the potential to be used as an alternative to fine aggregates in concrete production. The interface between the cement paste and the aggregate in concrete is densified when BFS is used, due to the hydrates that are generated by its latent hydraulicity. This fact suggests that the crack resistance of concrete, which is closely related to the conditions at the aggregate interface, would be enhanced by the use of BFS. The fracture energy (GF) of concrete under flexural stress is here measured to evaluate the crack resistance of concrete made using BFS. BFS samples from three different steel mills in Japan are used as the fine aggregates for concrete production, and mountain sand is used as a natural sand for comparison. Compressive strength, static modulus of elasticity, and fracture energy tests are conducted at the material ages of 28 and 91 days. The GF of the BFS concretes increase with increasing compressive strength; on the other hand, the GF of the concrete made using mountain sand decrease. Thus, it is concluded that BFS concrete has superior properties to concrete made using natural sand in terms of the crack resistance under flexural stress, especially in high‐strength regions for large material ages.

Recycled materials for sublayers

The article focuses on the recycled materials used in sleeper substructure. In the introduction, it summarizes the requirements for bearing layers of railway substructure and recycling of waste construction materials. The article presents the materials on which laboratory tests have been carried out and discusses in detail the most perspective – recycled concrete. For concrete recyclate, the article describes the results of laboratory tests – sieve analysis, determination of optimum moisture, and determination of bearing capacity using California bearing ratio, Immediate bearing index and Static deformation modulus.

Prediction Unconfined Compressive Strength for Different Lithology Using Various Wireline Type and Core Data for Southern Iraqi Field

Unconfined Compressive Strength is considered the most important parameter of rock strength properties affecting the rock failure criteria. Various research have developed rock strength for specific lithology to estimate high-accuracy value without a core. Previous analyses did not account for the formation's numerous lithologies and interbedded layers. The main aim of the present study is to select the suitable correlation to predict the UCS for hole depth of formation without separating the lithology. Furthermore, the second aim is to detect an adequate input parameter among set wireline to determine the UCS by using data of three wells along ten formations (Tanuma, Khasib, Mishrif, Rumaila, Ahmady, Maudud, Nahr Umr, Shuaiba and Zubair). After calibration with core test, the results revealed that Young’s Modulus correlations are the best to predict UCS with RMSE (53.23 psi). Furthermore, the result showed that using the static Young Modulus as an input parameter in predicting UCS gives a closer result to the laboratory test than using a sonic log. This study found that many previous equations were developed for only one type of rock and tended to generalize poorly to the broader database. This study also provided more accurate rock strength estimation, leading to better prognosis in operational strategies and hydraulic fracturing location planning in oil well development when geomechanical analysis needs to be addressed where no core is available. Finally, the expected continuous rock mechanical profile indicates the formation's strength and stability around the wellbore.

Stress‐Induced Anisotropic Poroelasticity in Westerly Granite

AbstractWe measured poroelastic properties of cracked granite under triaxial conditions, at elevated confining pressure and a range of differential stresses. Skempton's coefficients and undrained Young's modulus and Poisson's ratio were determined directly by recording in situ fluid pressure during rapid cycles of axial and radial stress. Drained properties were measured both statically and dynamically at ultrasonic frequencies. At a given confining pressure, increasing differential stress leads to the development of elastically transverse isotropy, with symmetry axis aligned with the compression axis. Skempton's coefficients are also anisotropic, with larger changes in pore pressure in response to radial stress (coefficient Bx) than to axial stress steps (Bz). The anisotropy in the Skempton coefficients increases with increasing differential stress, with Bz decreasing and Bx slightly increasing. The evolution of static moduli and the Skempton coefficients is well approximated by Gassmann's equation using dry moduli obtained from ultrasonic measurements. Simplified predictions of the Skempton coefficients based on crack density tensors inverted from dynamic data also shows acceptable agreement with direct observations. Perfect quantitative agreement is not reached, due to the imprecision of our dynamic measurements, model simplifications, and inherent differences between static moduli obtained using stress steps of several MPa stress and dynamic ultrasonic stress oscillations.

Cross-laminated secondary timber: Validation of non-destructive assessment of structural properties by full-scale bending tests

The demolition of buildings creates a vast quantity of secondary timber, which is currently chipped, downcycled or incinerated. This study examines a higher value use of secondary timber as lamellae for cross-laminated timber (CLT), which will address the increasing demand for wood products that is expected in the coming decades. The longitudinal vibration test method was used to determine the dynamic modulus of elasticity (dMoE) for secondary timber. Then, four-point bending tests were conducted for the secondary timber to obtain the static modulus of elasticity (sMoE) and modulus of rupture (MoR). The test results showed a good linear relationship between dMoE and sMoE, so the dMoE results could be used to predict sMoE of secondary timber. Furthermore, the static bending stiffness of cross-laminated secondary timber (CLST), sMoECL, was predicted by the dMoE from transverse vibration tests of CLST and longitudinal vibration tests of secondary timber. Four-point bending tests of CLST showed that the latter predicted sMoECL more accurately. CLST panels were also found to meet the structural requirements in relevant standards. Finally, analytical models were used to predict the bending stiffness and strength of CLST. The closest prediction came from combining the shear analogy method and bearing model for CLT. This paper demonstrates the feasibility of using secondary timber as a feedstock for CLT/CLST production.

Mechanical Properties of PVC Fiber-Reinforced Concrete—Effects of Fiber Content and Length

This paper presents the key mechanical properties of PVC fiber-reinforced concrete. Six concrete mixtures were produced using plastic fibers obtained from clear PVC sheets. Three concrete mixtures were made using 20 mm long PVC fibers, whereas the other three were prepared with 40 mm long PVC fibers. The fiber content was varied in the range of 0–1.5 wt.% of cement for each length of fiber. The fresh concrete mixtures were tested for workability in terms of the slump. The hardened concretes were tested for their compressive and splitting tensile strengths, flexural strength and toughness, static elastic modulus, and impact resistance and toughness. The effects of the fiber content and fiber length on the workability and above-mentioned mechanical properties were observed. In addition, the correlations between various mechanical properties were sought. The test results revealed that the workability of concrete was reduced for both fiber lengths as the fiber content increased. The compressive strength, flexural strength and toughness, elastic modulus, and impact resistance and toughness increased at up to 1 wt.% fiber content, then decreased for 1.5 wt.% fibers. A similar trend was also noticed for the splitting tensile strength, particularly in the case of 20 mm long PVC fibers. Compared to the fiber length, the fiber content exhibited a more pronounced effect on the mechanical properties of concrete. The optimum fiber content was 1 wt.%, which produced the best performance in this study. Furthermore, excellent correlations were observed for the tested mechanical properties of concrete, except for splitting tensile strength, which was not well-correlated with compressive strength.

Evaluation of some physical and mechanical properties of Acacia hybrid BV10 planted in Quy Chau, Nghe An

This study aimed to evaluate some major physical and mechanical properties of 7 year old Acacia hybrid BV10 planted in Quy Chau district, Nghe An province. Small specimens with dimensions of 20 (Radial) × 20 (Tangential) × 320 (Longitudinal) mm3 were cut near the pith and near the bark at breast height from each sample tree, then placed in a standard laboratory setting until their weights reached a constant value. The resulting mean air-dry density (AD), stress wave velocity (SWV), static modulus of elasticity (MOE) and modulus of rupture (MOR) were 0.53 g/cm3, 4,241 m/s, 10.00 GPa, and 82.17 MPa, respectively. Statistical analysis showed that SWV and these wood properties examined near the bark were always higher than those values measured near the pith. Stress wave technology can be used to predict MOE and MOR; however, AD is still a more reliable indicator for predicting mechanical properties since it showed a strong correlation with MOE (r = 0.86; P < 0.001) and MOR (r = 0.80; P < 0.001).

Effect of Mud Powder on the Performance of Bridge Deck Leveling Concrete in a Seasonally Frozen Region.

Mud powders in aggregates are often found to cause deterioration of concrete properties. Based on a study of the mechanical properties of bridge deck leveling concrete (BDLC) containing different mud powders at various ages, the effects of mud powders on concrete durability were evaluated through rapid chloride permeability testing, freeze-thaw testing, and the coupling of salt solution and a freeze-thaw test. The properties of the interfacial transition zone (ITZ) were also investigated via microhardness testing. The test results showed that mud powder reduced the compressive strength, static compressive elastic modulus, and bond strength at early stages of curing. Moreover, mud powder was found to reduce the tensile properties and durability of concrete, with clay powder causing a greater reduction than mud powder in river sands and coarse aggregate. In addition, the width of the ITZ of concrete containing mud powder was found to increase by 23.1-48.3%. A significant correlation between the ITZ and the tensile properties, as well as the durability of concrete, was also observed. Therefore, in order to improve the tensile properties and durability of BDLC in seasonally frozen regions, the content of mud powder in the aggregates should be minimized according to the different compositions of mud powders. The coupling effect of salt solution and a freeze-thaw cycle should also be taken into consideration.

Feasibility study of pore-pressure prediction in carbonate rocks

In the recent past, the applicability and uncertainty of pore-pressure prediction methods that work based on seismic signals have been serious challenges in carbonate reservoirs. In this context, enormous research has been conducted on the prediction of pore pressure in these rocks, some of which have ended with failure due to the complexity of carbonates. To address the main cause of such failures, we experimentally simulate the pore fluid in carbonates under reservoir conditions to interpret and classify the factors contributing to the pore pressure. The results are then built into a novel hybrid experimental model for evaluating the feasibility of pore pressure prediction — one that could bridge the gap between laboratory and empirical approaches. For this purpose, 34 core samples are collected from different geologic formations at different wells penetrating reservoir intervals. The mechanical properties of the samples are investigated by conducting experiments in a triaxial cell where pore pressure is applied under different regimes while simultaneously acquiring the ultrasonic response of the sample. Sensitivity analyses of pore pressure are carried out under drained and undrained conditions and the results are used to evaluate our methodology. Pore pressure coefficients of P- and S-wave velocities are introduced in two different conditions, namely constant differential stress and constant pore pressure, with the same dimension as compressibility. Results are interpreted statistically and effective parameters are identified from a pool of many variables; these include the static bulk modulus, Young’s modulus, Biot’s coefficients, porosity, permeability, and sedimentary textures (e.g., micritization, neomorphism, cementation, fracture, blocky calcite, and dissolution). A feasibility study template is further introduced for investigating pore pressure detectability based on commonly available data in carbonate reservoirs by incorporating the main controlling factors. Our template and findings of this research are important for pore pressure prediction before performing further research and implementing operation programs. They also can decrease the risk of underestimating the pore pressure, thereby improving the well planning performance and mitigating the drilling hazards.

Uniform moduli characterization of asphalt mixtures under dynamic and static loading conditions

The modulus is a crucial material parameter reflecting stiffness characteristics of asphalt mixture in the elastic stage. Under specific conditions such as identical temperatures, loading velocities, and stress amplitudes, the moduli under the same stress state are theoretically identical. However, the moduli were artificially divided into dynamic moduli and static moduli based on loading methods during test, which brought uncertainties and disunity for estimating the stiffness performance of asphalt mixture. In this study, the dynamic and static moduli under distinct temperatures, loading velocities, and stress states were measured. The relationship between dynamic and static moduli was established by applying loading velocities as independent variable and moduli as the dependent variable. Through Sigmoidal function and WLF function fitting, the uniform characterization master curves of dynamic and static moduli under distinct temperatures, loading velocities, and stress states were established. The moduli of asphalt mixture under distinct test temperatures, loading velocities, and stress states can be obtained by the models, which provide material parameters for mechanical response analysis of asphalt pavements under distinct service environments. This resolves the issue of inconsistent moduli parameter selection.

Corn pomace as a substitute for wood raw material in lignocellulosiccomposite technology

Corn pomace as a substitute for wood raw material in lignocellulosic composite technology. Composites made from polymers PE, PP, PLA and modified starch with addition of corn pomace were produced and subjected quality parameters test. There were examined such parameters as: density, static bending strenght and modulus of elasticity and also water absorption and thickness swelling after 2 h and 24 h soaking in water, wettability and surface roughness. In general, the addition of corn pomace to polymers caused changes of parameters and through comparing parameters of different composites and control samples it was possible to indicate corn composite variants that occurs to have similar properties to pure polymer samples. Waste products should be seriously considered as a valuable substitute of wood raw material, but characteristics of composites should be improved through further research.

Review on the Estimation of Static Deformability Modulus of Rocks and their adoptability in Different Rock Masses

The aim of this study is to review the different mechanisms employed in the estimation of static rock mass deformability modulus (𝐸𝑚) in rock engineering applications and to investigate the adoptability of the identified mechanisms in different rock masses. The paper discusses different evaluation criteria through experimental, empirical and other means, with their merits and demerits, including influential factors. It is known that deformability modulus of intact rock depends on the imposed stress, strain rate and the confining stress on the rock sample as well as the rock texture and structure. The results generated for 𝐸𝑚 by different in-situ tests are different and an appropriate in-situ test based on the rock mass conditions should be employed to obtain reasonable results. Empirical criteria are found to produce results of reasonable precision if appropriately adopted for specific rock mass conditions, while the back analysis method is widely adopted as an insitu estimation measure for the design of rock-sockets and tunnel support. It has also been reported that substantial reduction in 𝐸𝑚 occurs due to schistosity and larger test volumes, while it is sensitive to stress and discontinuity conditions. In this work, specific recommendations are made on the estimation of 𝐸𝑚 for different types of rock masses based on the findings and reviews reported in the literature.

Estimation Criteria for Static Rock Mass Deformability Modulus for Rock-Socket Design in Metamorphic Rock Masses

This study investigates the most appropriate empirical criteria to estimate the static rock mass deformability modulus (𝐸𝑚) in the design of rock-sockets in cast-in-situ bored pile construction. The in-situ 𝐸𝑚 values are initially estimated through back analysis of static pile load test data. Secondly, the rock mass deformability estimated from back analysis (𝐸𝑚b) are tested statistically against selected established empirical equations to determine whether the latter are appropriate for use in metamorphic rock terrain of Sri Lanka. It is found that the existing empirical criterion based on the square root of intact unconfined compressive strength (𝜎𝑐) derived from back analysis of pile load test results is appropriate for weak-poor rock masses. For strong-poor rocks, it is recommended to employ the equation based on 𝜎𝑐', and in general the two equations generate lower and upper bound solutions. The equation based on intact deformability modulus (𝐸𝑖) performs well in strong-excellent quality rock masses, while the equations based on 𝐸𝑖 and rock quality designation (𝑅QD) are found to be appropriate for weak-fair to excellent rock masses. Finally, a new set of equations appropriate for different rock mass types have been proposed through regression analysis along with appropriate design measures to be adopted.

Estimation of compressive strength of cement mortars using impulse excitation technique and a genetic algorithm

Compressive strength, a crucial mechanical property of cement mortars, is typically measured destructively. However, there is a need to evaluate the strength of unique cement-based samples at various ages without causing damage. In this paper, a predictive framework using a genetic algorithm (GA) is proposed for estimating the compressive strength of ordinary cement-based mortars based on their dynamic elastic modulus, measured non-destructively using the impulse excitation technique. By combining the Popovics model (PM) and the Lydon–Balendran model (LBM), the static elastic modulus of samples was calculated using constant coefficients, representing an equivalent compressive strength. A GA was then employed to determine optimal values for these coefficients. The results showed that the LBM-based strength was dominant in the middle range of the dynamic Young's modulus while the PM-based strength was dominant for higher and lower values of the dynamic Young's modulus. The model was found to have a small root mean square error (3.1%). The findings suggest that this non-destructive model has potential for predicting the mechanical properties of cement mortars. It allows efficient evaluation of compressive strength without destructive testing, offering advantages for reliable assessments of cement-based materials.

Heterogeneity indexes of unconventional reservoir shales: Quantitatively characterizing mechanical properties and failure behaviors

Heterogeneity is an inherent feature of subsurface rocks. Unconventional reservoir shales, a group of typically fined-grained sedimentary rocks, usually exhibit strong heterogeneities due to the diversity of their constituents, including stiff silicate and carbonate minerals, ductile clay minerals, and organic matter. Understanding the influence of heterogeneities on the mechanical response as well as the failure behavior of reservoir shales plays a crucial role in numerous fields of Earth and Energy sciences, such as unconventional reservoir exploration, sealing of CO2 sequestration, nuclear waste disposal, and hydrogen storage. In this study, we propose two heterogeneity indexes, intending to quantitatively characterize the heterogeneity of mineralogical compositions in unconventional reservoir shales. The first index takes into account the heterogeneity of mineral content, and the other one comprehensively considers the mineralogical heterogeneity and its corresponding mechanical properties. We apply these heterogeneities indexes to two experimental datasets of marine and lacustrine shales. The results show that the heterogeneity index significantly influences the mechanical properties and deformation behaviors of reservoir shales. As the increment of heterogeneous indexes, the ultimate strength and static Young's modulus show a general decreasing trend. However, the effect of the heterogeneity index on the static Poisson's ratio is weak. The numerical simulation results also confirm our experimental analysis, where the ultimate strength and Young's modulus of rock have a negative correlation with the heterogeneity indexes. The proposed heterogeneity indexes provide insights into understanding the mechanical behaviors and fracability assessment of reservoir shales.

Nonlinear dynamic responses of ballasted railway tracks using concrete sleepers incorporated with reinforced fibres and pre-treated crumb rubber

Abstract Damages on railway sleepers due to heavy impact loads induced by the movement of trains can be reduced by improving their impact resistance. Fibre-reinforced/pre-treated crumb rubber concrete sleepers (RCSs) have the potential to display significant impact resistance to withstand a high-magnitude impact load. The ideal proportions of pre-treated crumb rubber, steel fibres, and polypropylene fibres (PFs) can be identified based on the minimum cost-to-impact energy ratio after conducting a drop weight impact test on prisms. The numerical model developed to assess the behaviour of ballasted tracks has been validated using both simulation results and field measurements. Numerical studies have been conducted on ballasted rail tracks with steel and PF-reinforced/pre-treated RCSs using LS-DYNA software. Dynamic strain rate-dependent material parameters are introduced in the numerical simulations. The nonlinear effect of higher train speeds on dynamic track responses has been highlighted in this article. Although the static load-carrying capacity and modulus of elasticity of rubber concrete are low, their dynamic performance controls the track displacements from exceeding permissible limits. The outcome of this study will provide new insights into the effects of railway concrete sleepers incorporated with reinforced fibres and pre-treated crumb rubber on railway track performance in order to ensure safety and reliability before it is put into services.

Correlation between sonic pulse velocity and flat-jack tests for the estimation of the elastic properties of unreinforced brick masonry: Case studies from Croatia

Historic urban cores in southern Europe are characterized by a significant number of existing unreinforced masonry structures that are known for their seismic vulnerability. The first step in the preservation of such damaged buildings is condition assessment and characterization of the mechanical properties of the masonry, which can be achieved using non-destructive, semi-destructive and destructive methods. In this paper, the emphasis is on determining the modulus of elasticity of unreinforced masonry through flat-jack and sonic pulse velocity tests. Both methods are explained in detail and results from eight different case studies are presented. The results are compared and correlations among the techniques are observed, showing that both methods can be suitable for estimating the elastic properties of existing masonry. The paper provides a wide set of experimental data that has been made available. Finally, a sensitivity analysis was performed. Differences between static and dynamic modulus of elasticity and operational and practicability issues regarding on-site testing are discussed.