• Energy Research
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Corroded transmission towers, whose load-bearing capacities are lowered, are suffering from wind-induced damage. By simulating the member corrosion through section thinning, the structural dynamic finite element model of an angle-steel transmission tower with a corrosion depth of 0 mm to 1.4 mm was established using ANSYS/LS-DYNA software. The incremental dynamic analysis method was used to study the collapse mode of the tower under different degrees of corrosion, as well as the effects of corrosion on structural self-vibration characteristics, wind-induced member stress, and tower-top displacement. The results show that with the corrosion deepening, the first three vibration frequencies decrease, and the torsional mode becomes the first mode. When the corrosion depth is smaller, the overall structure failure occurs under strong wind. The failure starts at the most unfavorable oblique rod between the upper and middle cross arm, then expands to the rods under the lower cross arm. When the corrosion depth is larger, the overall structure failure occurs restrictedly between the upper and middle cross arm. Internal axial force and bending moment redistribution happen when corrosion deepens. Under the critical failure state, the oblique rods are always at a high stress level, while the stresses of the main rods decrease. Corrosion has a stronger impact on component strength and stability than on structural stiffness.

The embedded-ring wind turbine foundations were widely applied in the early development stage of wind power industries because of its properties such as easy installation and adjustment. However, different damages occurred on some embedded-ring wind turbine foundations in recent years. Based on the common damage phenomena of embedded-ring wind turbine foundations, the structural defects and damage mechanisms of embedded-ring wind turbine foundations are analyzed in a gradual way. Cheese head studs are proposed to be welded on the lateral wall of the steel ring to strengthen the connection between the steel ring and the foundation concrete. The foundation pier is elevated 1 m to increase the embedded depth of the steel ring. The circumferential confining pressure is applied on the lateral side of the foundation pier to lead it into a state of pressure. One simplified method is proposed to calculate the contribution of welding studs in this strengthening method. Taking an embedded-ring wind turbine foundation as an example, the numerical analyses for the original foundation and the reinforced one are carried out to compare the stress and strain distribution changes. Based on the numerical results corresponding to the peak and valley value loads, the fatigue life of the concrete and studs are evaluated according to the relevant design codes. The numerical results show that this strengthening method can coordinate the deformation of the embedded steel ring and the foundation concrete by circumferential prestressing and welding studs. The maximum principal stresses of the foundation pier and the fatigue stress range of the concrete around the bottom of the steel ring have been greatly reduced after strengthening. The gaps between the embedded steel ring and the foundation pier are also obviously decreased because of these strengthening measures. The stress concentration phenomena of the concrete around the T-shaped flange have been remarkably improved. The fatigue life can meet the requirements of relevant design codes after strengthening. Therefore, it can be concluded that the safety performance and service life of the embedded-ring foundation can be guaranteed.

Abstract Improving building thermal performance is important if the UK is to meet the 80% emission reduction target by 2050. Aiming to provide insights into UK building thermal performances, relevant national policies were highlighted and a one-day workshop was run. Real-time responses of industrial stakeholders were collected using Poll Everywhere. The stakeholder perspectives on challenges, barriers, thermal performances and other concerns were reported. It showed that (i) a whole-house retrofit plan was necessary; (ii) improving thermal performances would be challenging but achievable; and (iii) industrial stakeholders were concerned about building performance, legislation, drivers, cost, professional development, technology alternatives and future vision. It was concluded that industrial consultation should be continued to assist thermal performances of buildings in the UK.

The use of lime as a binder in masonry lining mortars plays an important role in its conservation and durability. Knowledge of the mechanical characteristics of pre-existing and restoration mortars is essential in order to guarantee the compatibility between them and for avoiding the appearance of pathologies. The paper mainly focuses on the study of the mechanical performance of lime-based mortars to be applied in rehabilitation works in old buildings. Four types of mortars were tested with very similar workability, based on lime putty, aerial lime, and hydraulic lime. Sand and crushed rock powder were used as aggregates. Compressive and flexural strengths of the mortars were determined, as well as their ultrasonic pulse velocity. Furthermore, specific tests were carried out to characterize the performance of the mortar when used as a binder for plasters and coatings, such as the development of cracking, superficial water absorption under low pressure, and pull-off strength. According to the results obtained, mortars with lime putty showed better mechanical properties, while those with aerial lime had better behavior regarding water absorption under pressure. Despite that, it was generally possible to verify the adequacy of the studied mortars to be used in the rehabilitation of masonry elements.

The paper formulates a method of active reduction of structure vibrations in the selected resonance zones of the tested object. The method ensures reduction of vibrations of the selected resonance zones by determining the parameters of the active force that meets the desired dynamic properties. The paper presents a method for determining the parameters of the active force by reducing the vibrations of the structure in its resonance zones to a given vibration amplitude. For this purpose, an analytical form was formulated, which will clearly define the dynamic properties of the tested object and the force reducing the vibrations in the form of a mathematical model. The formulated mathematical model is a modified object input function, which in its form takes into account the properties of the active force reducing the vibrations. In such a case, it is possible to use the methods of mechanical synthesis to decompose the modified characteristic function into the parameters of the system and the parameters of the force being sought. In the formulated method, the desired dynamic properties of the system and the vibration reducing force were defined in such a way that the determined parameters of the active force (velocity-dependent function) had an impact on all forms of natural vibrations of the tested system. Based on the formalized method, the force reducing the vibrations of the four-story frame to the desired displacement amplitude was determined. Two cases of determining the active force reducing the vibrations to the desired vibration amplitude of the system by modifying the dynamic characteristics describing the object together with the active force were considered. For both cases, the system’s responses to the oscillation generated by harmonic force of frequencies equal to the first two forms of natural vibrations of the tested system were determined. In order to verify the determined force reducing the vibrations of the object and to create a visualization of the analyzed phenomenon, the building structure dynamics were analyzed with the use of PLM Siemens NX 12 software. The determined force parameters were implemented into the numerical model, in which the tested system was modelled, and the response time waveforms were generated with regard to the considered story. The generated waveforms were compared with the waveforms obtained in the formalized mathematical model for determining the active force reducing the vibrations. The vibrations of the tested numerical model were induced by the kinematic excitation with the maximum amplitude equal to 100 mm, which corresponds to the vibration amplitude during the earthquake with a force equal to level 5 on the Richter scale.

As a demountable structure, the structure with design for deconstruction (DfD) is considered as a key contribution on the promotion of current construction sustainability by directly reusing valuable components from old structures. As a preliminary study, this paper investigated the cyclic behavior of bolted joints consisting of three reinforced concrete blocks bolted by steel bolts under axial compressive, focusing on the damage and failure modes, resistance mechanism and stiffness development of the joints. Results showed that the number of steel bolts, the tightening process of the bolts and concrete compressive strength all had a significant effect on the overall performance and capacity of the joints. The failure mode of most of tested joints was considered as fracture of stirrups and steel bolts in the tested joints. According to the investigation of this study, several recommendations on the design of the joints were provided.

AbstractIt is quite common for researchers to use an excess dosage of superplasticizer to achieve the desired very low water to binder (w/b) ratio required for sustainable high-volume fly ash (HVFA) concrete mixes in order to obtain early strength without reporting on the effects of the excess dosage. This study investigates the effects of such excess dosages on the properties of highly sustainable HVFA concrete. Four series of concrete mixes were designed, with Series 0 being the control concrete mix containing no fly ash and no superplasticizer. Series 50, 60 and 65 contained HVFA concrete mixes that had 50, 60 and 65% fly ash content, respectively. Series 50, 60 and 65 contained three similar mixes; in each series, the three mixes were prepared with the maximum dosage of superplasticizer at 2% of the binder by mass, and excess dosages at 3% and 4%, respectively. The effect of the excess doses on slump, flowability, compressive strength, flexural strength, tensile splitting strength, and abrasion resist...

Bio-based materials help reduce the consumption of non-renewable resources, contributing to the development of sustainable construction. Industrial Hemp Concrete (IHC), which uses hemp stalk (HS) as an aggregate and a lime-based binder, is a bio-based material with various applications. This research developed a new hybrid composite in order to improve the mechanical strength and durability of hemp concrete, with the incorporation of sugarcane bagasse (SCB) as an aggregate, a resource of a renewable origin that is abundant in several countries. Different formulations were used, which were molded and pressed manually, evaluating their cohesion and compactness. The performance of the developed hybrid composite was measured considering mechanical, thermal, and durability properties. The compression test results showed an increase of 19–24% for composites with 75% hemp and 25% SCB. Thermal conductivity and thermal resistance coefficients were also improved, reaching 0.098 (W/m °C) and 0.489 (m2 °C/W), respectively. This aggregate combination also showed the lowest water absorption coefficient (reducing by 35%) and the best performance in durability tests compared to IHC. The resistance to freeze–thaw is highlighted, increasing 400%. The main reason is the influence of the SCB addition because the short and thin fiber form helps to maintain the physical integrity of the composite by filling the spaces between the hemp aggregates.