Structural Engineering Properties Research Articles

Elevated light-frame wood residential building physical and numerical modeling of damage due to hurricane overland surge and waves

An experimental program of a 1:6 scale elevated wood frame shear-wall residential building was developed to model the damage progression of buildings subjected to increasing hurricane surge depth and wave conditions until collapse. This paper presents testing and system identification methods used to characterize structural engineering properties of the physical model that accumulated damage during hydrodynamic testing under increasing surge depth and wave heights. Methods used include (a) quasi-static lateral load-deformation testing, (b) out-of-water dynamic structural characterization testing under free vibration, ambient vibration, and forced vibration, conducted on the test specimen prior to hydrodynamic testing, (c) in-water dynamic structural characterization during hydrodynamic testing, (d) quantification of accumulated damage in hydrodynamic testing through observed changes in the laser scan point cloud data of the specimen, and (e) finite element model updating. The accumulated damage in the test specimen is correlated to changes in modal features (frequency, damping, and mode shapes) assessed using two output-only system identification (SID) methods. In addition, finite volume numerical models are used to determine detailed pressure distributions on the test specimen which are coupled with finite element (FE) models that are updated, in a phased manner, to understand the contribution of structural and nonstructural components on the modeled stiffness and strength of the physical model. Lastly, the impact of the damage on the modal features of the physical model of the building and their sensitivity to FE model assumptions are presented.

Construction of carbon nanotube mediated Fe doped graphitic carbon nitride and Ag3VO4 based Z-scheme heterojunction for H2O2 assisted 2,4 dimethyl phenol photodegradation

Rational design strategy with a facile synthetic approach of environmental-friendly photocatalysts is a unique challenge in photocatalytic technology. The precedent work reports the successful synthesis of a Z-scheme Fe doped graphitic carbon nitride coupled Ag3VO4 compounded with carbon nanotubes (FeCN/AV/CNT) photocatalyst through facile precipitation-deposition technique. Characterization analysis including FESEM, XRD, FTIR, XPS and EDS was conducted to clarify the morphology and structure engineering properties of as-synthesized heterostructures (FeCN/AV/CNT). The efficient photocatalytic removal of 2,4 dimethyl phenol was attributed to multi electron transference route comprising of incorporation of Fe dopant in graphitic carbon nitride (g-C3N4), proceeded by coupling with Ag3VO4 (AV) simultaneously under solar light illumination. FeCN/AV/CNT photocatalyst was converted into a heterogeneous system with the addition of H2O2. The augmentation in catalytic activity was corroborated by photo-Fenton Fe3+ ions and H2O2 to generate more hydroxyl radicals. The positive synergistic effect between Fe-CN/AV/CNT Z-scheme approaches promoted enhancement in photodegradation performance by achieving maximum separation and rapid migration of photogenerated charge carriers, prolonged absorption in visible spectrum with augmented light absorption ability. The rate constant for FeCN/AV/CNT activated H2O2 is about 1.37 and 1.63 times high compared to FeCN/AV/CNT and FeCN/AV and exhibited outstanding catalytic efficiency and stability for five consecutive catalytic cycles. The plausible mechanism of FeCN/AV/CNT H2O2 based Z scheme system was also explored.

Experimental error analysis of dynamic properties for a reduced-scale high-rise building model and implications on full-scale behaviour

This paper presents a method to predict the uncertainty associated with dynamic identification of a reduced-scale model of a building structure from laboratory experiments. Systematic repetitions of dynamic identification experiments and their results were expanded through Hermite Polynomial chaos. The study describes the degree of uncertainty related to structural engineering properties of the model due to laboratory errors. Uncertainties in the physical experimental system should be adequately modelled to obtain an accurate estimate of structural safety. This is crucial to reduce prediction errors of full-scale structural performance. The method works using reliability-based optimization. Applicability of the framework is illustrated using a reduced-scale model of a high-rise building, constructed for multi-hazard dynamic experiments on a shaking table and in a wind tunnel. The still-air dynamic identification of model parameters closely affects the wind tunnel results. The method accounts for system variability and experimental error propagation, enabling evaluation of structural reliability for the corresponding full-scale structure. Results reveal that the variability introduced by laboratory errors propagates onto the estimation of structural frequencies and damping, leading to non-negligible variation of full-scale structural parameters. The corresponding probability density function of some relevant-mode full-scale vibration magnitudes is discussed as a compelling example for structural safety. The study demonstrates that experimental variability must be taken into account, particularly in the case of aeroelastic wind tunnel models, because structural response measurements are affected by this uncertainty.

Study of alkaline hydrothermal activation of belite cements by thermal analysis

The effect of alkaline hydrothermal activation of class-C fly ash belite cement was studied using thermal analysis (TG/DTG) by determining the increase in the combined water during a period of hydration of 180 days. The results were compared with those obtained for a belite cement hydrothermally activated in water. The two belite cements were fabricated via the hydrothermal-calcination route of class-C fly ash in 1 M NaOH solution (FABC-2-N) or demineralised water (FABC-2-W). From the results, the effect of the alkaline hydrothermal activation of belite cement (FABC-2-N) was clearly differentiated, mainly at early ages of hydration, for which the increase in the combined water was markedly higher than that of the belite cement that was hydrothermally activated in water. Important direct quantitative correlations were obtained among physicochemical parameters, such as the combined water, the BET surface area, the volume of nano-pores, and macro structural engineering properties such as the compressive mechanical strength.

FEMORAL NECK FAILURE PREDICTION: EXPERIMENTAL AND NUMERICAL STUDY

Osteoporosis is a worldwide health problem with about 1700 fractures per day only in Europe (World Health Organisation). Hip fractures are the more recurrent consequences of this disease. The fracture risk screening is usually undertaken with DualEnergy X-ray Absorptiometry (DEXA), with the fact that only the integral bone mass and the area bone density can be measured, without taking into account the bone structure. In order to improve the assessment of fracture risk, many non–invasive methods were developed. These techniques, based on densitometric properties of human bone [Lockmuller, 2002], geometric and structural engineering properties of the proximal femur [Beck, 1990; Keyak, 2000], have little precisions for estimating fracture load and identifying subjects with high fracture. Our aim was to investigate the use of anisotropic yield criteria to predict the femoral neck failure. For this, the strength of human femurs was measured by experimental test and finite element analysis.

Triaxial test results of high-strength concrete subjected to cyclic loading

High-strength concrete (HSC) has highly desirable structural engineering properties, which can lead to significant cost savings in heavily loaded concrete structures. However, its use is limited by a concern regarding an increased brittleness compared to normal strength concrete (NSC), especially under complex multi-axial loading conditions. The issue of ductility is extremely important in structures subjected to earthquake loading conditions. In order to determine the lateral confinement required for a given level of ductility, the relationship between axial stress and lateral strain of confined HSC needs to be established. This paper describes a testing programme carried out to obtain the relationships between axial stress, axial strain and lateral strain for HSC under cyclic loading and subjected to constant lateral confining pressures. Compressive strengths of concrete tested were 40, 60, 80 and 100 MPa. Uniform confining pressures applied were 4, 8 and 12 MPa. The experimental results are presented and the effects of cyclic loading and confinement on the constitutive behaviour of HSC are described.

Triaxial test results of high-strength concrete subjected to cyclic loading

High-strength concrete (HSC) has highly desirable structural engineering properties, which can lead to significant cost savings in heavily loaded concrete structures. However, its use is limited by a concern regarding an increased brittleness compared to normal strength concrete (NSC), especially under complex multi-axial loading conditions. The issue of ductility is extremely important in structures subjected to earthquake loading conditions. In order to determine the lateral confinement required for a given level of ductility, the relationship between axial stress and lateral strain of confined HSC needs to be established. This paper describes a testing programme carried out to obtain the relationships between axial stress, axial strain and lateral strain for HSC under cyclic loading and subjected to constant lateral confining pressures. Compressive strengths of concrete tested were 40, 60, 80 and 100 MPa. Uniform confining pressures applied were 4, 8 and 12 MPa. The experimental results are presented and the effects of cyclic loading and confinement on the constitutive behaviour of HSC are described.

Design of high‐strength concrete members: state‐of‐the‐art

AbstractThe advancement of material technology and production has led to higher grades of concrete strengths. In recent years a marked increase in the use of high‐strength concrete (compressive strength, f′c>50 MPa) has been evident in construction projects around the world. High‐strength concrete (HSC) offers significantly better structural engineering properties, such as higher compressive and tensile strengths, higher stiffness, better durability, compared with conventional normal‐strength concrete (NSC). Many structures built now have at least some components constructed with HSC. However, to a large extent, practice has preceded theory with constitutive equations simply being extrapolated to higher strengths. The main concern regarding the use of HS Concrete is the reduction in ductility with the increase in compressive strength observed under uniaxial compression. Past research has shown that members made of HSC exhibit, in some instances, different failure mechanisms, and simply extrapolating models and equations meant for NSC to HSC may lead to unsafe designs. Major codes of practice around the world are still based on experimental and theoretical results derived from investigations on NSC. Individual design rules codified in any of the national and international design codes need to be experimentally verified and categorized with a view to taking further action. In some instances structural designers are unable to take full advantage of the material because of insufficient information.Recent developments in design and performance of HSC members, especially the papers published within the last two or three years are presented in this paper. The paper covers the topics of engineering properties, fire design, flexural members, shear and torsion, bond and anchorage, HSC columns, transmission of HSC column loads through weaker slabs, walls, impact resistance and seismic design of HSC structures. Copyright © 2003 John Wiley & Sons, Ltd.

Slag Portland cement for hydraulic structures operating under severe climatic conditions

Industrial slag portland cements produced from granular magnesia slags were studied concurrently with laboratory slag portland cements. All passed the autoclave tests for uniformity of volume change under a pressure of 20 kb/sq cm. There were virtually no deformations in 180-day specimens. Study results show that the strength of slag portland cement (SPC) increases steadily, and after 2 years exceeds the classical 28-day strength by a factor of 1.5-2.0. As compared with the conventional SPCs, the magnesia SPCs follow a high strength gain indicator from 28 to 360 days; this has a positive effect on massive concrete placed in hydraulic structures. As compared with th conventional SPCs the magnesia SPCs exhibit an even lower heat liberation, amounting to 34 and 45 cal/g after 3 and 7 days of hardening respectively. The quality of magnesia SPC was assessed from comparative corrosion-resistance tests, and the structural-engineering properties of the magnesia SPC were tested directly in concrete. The investigations confirm that magnesia-slag-based slag portland cements satisfy the technical specifications and that they are suitable for massive concrete in hydraulic structures.