Seismic Assessment of a Steel Braced Plan Mass Symmetric/Asymmetric Building Structure

This paper presents a seismic response investigation into a code designed concentrically braced frame structure that is subjected to but not designed for in-plan mass eccentricity. The structure has an accidental uneven distribution of mass in plan resulting in an increased torsional component of vibration. The level of inelasticity that key structural elements in plan mass asymmetric structures are subjected to is important when analysing their ability to sustain uneven seismic demands. In-plan mass asymmetry of moment resisting frame and shear wall type structures have received significant investigation, however, the plan asymmetric response of braced frame type structures is less well understood. A three-dimensional non-linear time history analysis (NLTHA) model is created to capture the torsional response of the plan mass asymmetric structure to quantify the additional ductility demand, interstorey drifts and floor rotations. Results show that the plan mass asymmetric structure performs well in terms of ductility demand, but poorly in terms of interstorey drifts and floor rotations when compared to the plan mass symmetric structure. New linear relationships are developed between the normalised ductility demand and normalised slenderness of the bracing on the sides of the plan mass symmetric/asymmetric structures that the mass is distributed towards and away from.

Energy balance of SRC willow used for managing farmyard washings - how does it compare to a conventional wastewater treatment works?

The water and wastewater industry in the UK accounts for around 3% of total energy use and just over 1% of total UK greenhouse gas emissions. Targets for greenhouse gas emissions reduction and higher renewable energy penetration, coupled with rising energy costs, growing demand for wastewater services and tightening EU water quality requirements, have led to an increased interest in alternative wastewater treatment methods. The use of short rotation coppice (SRC) willow for the treatment of wastewater effluent is one such alternative, which brings with it the dual benefits of wastewater treatment and production of biomass for energy. In order to assess the effectiveness of SRC willow, it is important to analyse the overall energy balance in terms of energy input versus energy output. This paper carries out an energy life cycle analysis of a specific SRC willow plantation in Northern Ireland to which farmyard washings (dirty water) are applied. The system boundaries include the establishment, maintenance, and harvesting of the plantation, along with the transport and drying of the wood for biomass combustion. The analysis shows that the overall energy balance is positive, and that the direct and indirect energy demands are 12% and 8% of gross energy production respectively. The energy demands of the plantation are compared with the energy required to treat an equivalent nutrient load in a conventional wastewater treatment plant. While a conventional plant consumes 2.6 MJ/m3 , the irrigation system consumes 1.6 MJ/m3 and the net energy production of the scenario is 48 MJ/m3 .

Cold-formed steel portal frames in fire: Full-scale testing and finite element analysis

A full-scale, non-uniform natural fire test on a cold-formed steel portal frame building is described. The results of the test are used to validate a non-linear, elasto-plastic, finite element shell idealisation, for the purposes of later forming the basis of a performance-based design approach for cold-formed steel portal frames at elevated temperatures.

Chloride induced corrosion of steel in alkali activated slag concretes

Alkali activated slag (AAS) is an alternative cementitious material. Sodium silicate solution is usually used to activate ground granulated blast furnace slag to produce AAS. As a consequence, the pore solution chemistry of AAS differs from that of Portland cement (PC). Although AAS offers many advantages over PC, such as higher strength, superior resistance to acid and sulphate environments and lower embodied carbon due to 100% PC replacement, there is a need to assess its performance against chloride induced corrosion duo to its different pore solution chemistry. For PC systems, resistivity measurement, as a type of nondestructive test, is usually used to evaluate its chloride diffusivity and the corrosion rate of the embedded steel. However, due to the different pore solution chemistry present in the different AAS systems, the application of this test in AAS concretes would be questionable as the resistivity of concrete is highly dependent on its conductivity of the pore solution. Therefore, a study was carried out using twelve AAS concretes mixes, the results of which are reported in this paper. The AAS mixes were designed with alkali concentration of 4%, 6% and 8% (Na₂O% of the mass of slag) and modulus (Ms) of sodium silicate solution of 0.75, 1.00, 1.50 and 2.00. A PC concrete with the same binder content as the AAS concretes was also studied as a reference. The chloride diffusion coefficient was determined using a non-steady state chloride diffusion test (NT BUILD 443). The resistivity of the concretes before the diffusion test was also measured. Macrocell corrosion current (corrosion rate) for steel rods embedded in the concretes was measured whilst subjecting the concretes to a cyclic chloride ponding regime (1 day ponded with salt solution and 6 days drying). The results showed that the AAS concretes had lower chloride diffusivity with associated higher resistivity than the PC concrete. The measured corrosion rate was also lower for the AAS concretes. However, unlike the PC, in which a higher resistivity yields a lower diffusivity and corrosion rate, there was no relationship apparent between the resistivity and either the diffusivity or the corrosion rate of steel for the AAS concretes. This is assigned to the variation of the pore solution composition of the AAS concretes. This also means that resistivity measurements cannot be depended on for assessing the chloride induced corrosion resistance of AAS concretes.

Light and electron microscopy of microstructure and fractography of an ultrahigh-strength martensitic steel

Microstructure, tensile properties and fractography have been examined in the oil-quenched samples of a low-alloy ultrahigh strength 4340 steel. Intergranular fracture was revealed to locate at the fracture origin. However, neither the quenched Charpy V-notched impact samples nor the tempered tensile samples showed such intergranular fracture behavior. The effects of loading rate and precipitation are discussed.

Hot deformation characteristics of a nitride strengthened martensitic heat resistant steel

Constitutive equations including an Arrhenius term have been applied to analyze the hot deformation behavior of a nitride-strengthened (NS) martensitic heat resistant steel in temperature range of 900–1200 °C and strain rate range of 0.001–10 /s. On the basis of analysis of the deformation data, the stress–strain curves up to the peak were divided into four regions, in sequence, representing four processes, namely hardening, dynamic recovery (DRV), dynamic strain induced transformation (DSIT), and dynamic recrystallization (DRX), according to the inflection points in ∂θ/∂σ∂θ/∂σ and ∂(∂θ/∂σ)/∂σ∂(∂θ/∂σ)/∂σ curves. Some of the inflection points have their own meanings. For examples, the minimum of ∂θ/∂σ∂θ/∂σ locates the start of DRV and the maximum of it indicates the start of DRX. The results also showed that the critical strain of DRX was sensitive to ln(Z) below 40, while the critical stress of DRX was sensitive to it above 40. The final microstructures under different deformation conditions were analyzed in terms of softening processes including DRV, DRX, metadynamic crystallization (MDRX) and DSIT.

Microstructure evolution in CLAM steel under low cycle fatigue

In the process of room-temperature low cycle fatigue, the China Low Activation Martensitic steel exhibits at the beginning cyclic hardening and then continuous cyclic softening. The grain size decreased and the martensitic lath transformed to cells/subgrains after the tests. The subgrains increase in size with increasing strain amplitude.

Constitutive modeling, microstructure evolution, and processing map for a nitride-strengthened heat-resistant steel

A constitutive equation was established to describe the deformation behavior of a nitride-strengthened (NS) steel through isothermal compression simulation test. All the parameters in the constitutive equation including the constant and the activation energy were precisely calculated for the NS steel. The result also showed that from the stress-strain curves, there existed two different linear relationships between critical stress and critical strain in the NS steel due to the augmentation of auxiliary softening effect of the dynamic strain-induced transformation. In the calculation of processing maps, with the change of Zener-Hollomon value, three domains of different levels of workability were found, namely excellent workability region with equiaxed-grain microstructure, good workability region with “stripe” microstructure, and the poor workability region with martensitic-ferritic blend microstructure. With the increase of strain, the poor workability region first expanded, then shrank to barely existing, but appeared again at the strain of 0.6.

Laves-phase in the China Low Activation Martensitic steel after long-term creep exposure

Creep test at 600 °C under 130 MPa for the China Low Activation Martensitic (CLAM) steel was performed up to 7913 h in this study. According to the stress level, the crept specimen was divided into three regions in order to investigate the influence of stress on Laves-phase formation. In addition to the expected M23C6 carbide and MX carbonitride, the amount and the size of Laves phase in these three regions on the crept specimen were characterized by transmission electron microscopy. Laves phase could be found in all the regions and the creep stress could promote the formation of Laves phase.

Low cycle fatigue properties of CLAM steel at 823 K

China Low Activation Martensitic (CLAM) steel is considered to be the main candidate material for the first wall components of future fusion reactors in China. In this paper, the low cycle fatigue (LCF) behavior of CLAM steel is studied under fully reversed tension–compression loading at 823 K in air. Total strain amplitude was controlled from 0.14% to 1.8% with a constant strain rate of 2.4×10−3 s−1. The corresponding plastic strain amplitude ranged from 0.023% to 1.613%. The CLAM steel displayed continuous softening to failure at 823 K. The relationship between strain, stress and fatigue life was obtained using the parameters obtained from fatigue tests. The LCF properties of CLAM steel at 823 K followed Coffin–Manson relationship. Furthermore, irregular serration was observed on the stress–strain hysteresis loops of CLAM steel tested with the total strain amplitude of 0.45–1.8%, which was attributed to the dynamic strain aging (DSA) effect. During continuous cyclic deformation, the microstructure and precipitate distribution of CLAM steel changed gradually. Many tempered martensitic laths were decomposed into subgrains, and the size and number of M23C6 carbide and MX carbonitride precipitates decreased with the increase of total strain amplitude. The response cyclic stress promoted the recovery of martensitic lath, while the thermal activation mainly played an important role on the growth of precipitates in CLAM steel at 823 K. In order to have a better understanding of high-temperature LCF behavior, the potential mechanisms controlling stress–strain response, DSA phenomenon and microstructure changes have also been evaluated.

Microstructure, mechanical properties and fractography of heat-treated manganese steel

A Fe-8.46%Mn-0.24%Nb-0.038%C (wt.%) manganese steel was investigated. The steel has a 100% bcc structure after heat treatment at 850°C for 1.5 h, water quenching or air cooling. Martensite interlocked microstructure consisting of fine martensite plates/needles with different spatial orientations was found. Austenite forms, in small amounts, after a 600°C reheating treatment. Scanning electron microscopy images and energy dispersive spectrometry of the fracture surfaces revealed both ductile and brittle types of failure and precipitates. Deep quenching after the heat treatments does not change the phase composition or the hardness. NbC is formed in the steel, in high number densities. It plays a role in the impact fracture process, by acting as void nucleation sites, facilitating ductile fracture with dimples appearing on the fracture surface.

Cantilever steel post damaged by wind

An analysis for the cause of fracture failure of a cantilever steel sign post damaged by wind has been carried out. An unusual cause of failure has been identified, which is the subject of this paper. Microscopy and microanalysis of the fracture surface showed that the failure was due to pre-existing cracks, from the fabrication of the post. This conclusion was reached after detecting and analysing a galvanised layer on the fracture surfaces.

The Political Economy of Swift's Satires and other Prose Works

Jonathan Swift wrote perceptively about the emerging commercial society
in Britain in the early eighteenth century. His particular focus was on the
financial revolution and its implications for economic and political stability
as well as for shifts of power between the landed and commercial
classes. Following his return to Ireland Swift’s focus shifted to the developmental
problems of his native country. In several pamphlets he advocated
consumption of domestic products, challenged existing political
structures and made trenchant criticisms of absenteeism and other dysfunctional
aspects of the land tenure system. Swift’s politico-economic
concerns are fully reflected in his best known work, Gulliver’s Travels but
his most pointed criticism of the emerging commercial system is contained
in A Modest Proposal. Written in the form of an economic pamphlet, A
Modest Proposal is ostensibly designed to address the problem of poverty
in Ireland. In addition to its implicit criticism of economic policy in Ireland,
the pamphlet challenges the separation of economics and morality as
evidenced in the writings of William Petty and Bernard Mandeville. Swift
parodies Petty’s political arithmetic but it is suggested here that he also
had in his sights the consequentialist reasoning present in the work of
both authors but explicitly so in Mandeville.
Keywords: financial revolution, public debt, paper credit, rationality, political
arithmetic, consequentialism, Petty (William), Mandeville (Bernard)

Prediction of surface roughness during hard turning of AISI 4340 steel (69 HRC)

In this study, 39 sets of hard turning (HT) experimental trials were performed on a Mori-Seiki SL-25Y (4-axis) computer numerical controlled (CNC) lathe to study the effect of cutting parameters in influencing the machined surface roughness. In all the trials, AISI 4340 steel workpiece (hardened up to 69 HRC) was machined with a commercially available CBN insert (Warren Tooling Limited, UK) under dry conditions. The surface topography of the machined samples was examined by using a white light interferometer and a reconfirmation of measurement was done using a Form Talysurf. The machining outcome was used as an input to develop various regression models to predict the average machined surface roughness on this material. Three regression models - Multiple regression, Random Forest, and Quantile regression were applied to the experimental outcomes. To the best of the authors’ knowledge, this paper is the first to apply Random Forest or Quantile regression techniques to the machining domain. The performance of these models was compared to each other to ascertain how feed, depth of cut, and spindle speed affect surface roughness and finally to obtain a mathematical equation correlating these variables. It was concluded that the random forest regression model is a superior choice over multiple regression models for prediction of surface roughness during machining of AISI 4340 steel (69 HRC).