Bandwidth requirements for shallow, high-resolution seismic reflection

The optimum bandwidth for shallow, high-resolution seismic reflection differs from that required for conventional petroleum reflection. An understanding of this issue is essential for correct choice of acquisition instrumentation. Numerical modelling of simple Bowen Basin coal structures illustrates that, for high-resolution imaging, it is important to accurately record all frequencies up to the limit imposed by earth scattering. On the contrary, the seismic image is much less dependent on frequencies at the lower end of the spectrum. These quantitative observations support the use of specialised high-frequency geophones for high-resolution seismic imaging. Synthetic seismic inversion trials demonstrate that, irrespective of the bandwidth of the seismic data, additional low-frequency impedance control is essential for accurate inversion. Inversion provides no compelling argument for the use of conventional petroleum geophones in the high-resolution arena.

“Seismic cultural change?”: British media representations of same-sex ‘marriage’

The legal recognition of same-sex relationships is a contested terrain that has been hotly debated by feminists. This article provides a social constructionist analysis of the UK newspaper media coverage around the time of the introduction of the Civil Partnership Act (2004). In examining the 348 national newspaper coverage over a three month period (November 2005–January 2006) we highlight three prevalent, and conflicting, themes: ‘same-sex marriage becomes legal under the Civil Partnership Act’; ‘couples will not get full legal status’ and ‘marriage is a heterosexual business’. We discuss these media representations and argue that the heteronormativity of the coverage provided little space for more radical constructions of same-sex relationship recognition.

A seismic shift? An evaluation of the impact of new media on perceptions of freedom of expression and privacy

New media platforms have changed the media landscape forever, as they have altered our perceptions of the limits of communication, and reception of information. Platforms such as Facebook, Twitter and WhatsApp enable individuals to circumvent the traditional mass media, converging audience and producer to create millions of ‘citizen journalists’. This new breed of journalist uses these platforms as a way of, not only receiving news, but of instantaneously, and often spontaneously, expressing opinions and venting and sharing emotions, thoughts and feelings. They are liberated from cultural and physical restraints, such as time, space and location, and they are not constrained by factors that impact upon the traditional media, such as editorial control, owner or political bias or the pressures of generating commercial revenue. A consequence of the way in which these platforms have become ingrained within our social culture is that habits, conventions and social norms, that were once informal and transitory manifestations of social life, are now infused within their use. What were casual and ephemeral actions and/or acts of expression, such as conversing with friends or colleagues or swapping/displaying pictures, or exchanging thoughts that were once kept private, or maybe shared with a select few, have now become formalised and potentially permanent, on view for the world to see. Incidentally, ‘traditional’ journalists and media outlets are also utilising new media, as it allows them to react, and disseminate news, instantaneously, within a hyper-competitive marketplace. However, in a world where we are saturated, not only by citizen journalists, but by traditional media outlets, offering access to news and opinion twenty-four hours a day, via multiple new media platforms, there is increased pressure to ‘break’ news fast and first. This paper will argue that new media, and the culture and environment it has created, for citizen journalists, traditional journalists and the media generally, has altered our perceptions of the limits and boundaries of freedom of expression dramatically, and that the corollary to this seismic shift is the impact on the notion of privacy and private life. Consequently, this paper will examine what a reasonable expectation of privacy may now mean, in a new media world.

Seismic performance of hybrid fiber reinforced polymer-concrete pier frame systems

As an alternative to transverse spiral or hoop steel reinforcement, fiber reinforced polymers (FRPs) were introduced to the construction industry in the 1980’s. The concept of concrete-filled FRP tube (CFFT) has raised great interest amongst researchers in the last decade. FRP tube can act as a pour form, protective jacket, and shear and flexural reinforcement for concrete. However, seismic performance of CFFT bridge substructure has not yet been fully investigated. Experimental work in this study included four two-column bent tests, several component tests and coupon tests. Four 1/6-scale bridge pier frames, consisting of a control reinforced concrete frame (RCF), glass FRP-concrete frame (GFF), carbon FRP-concrete frame (CFF), and hybrid glass/carbon FRP-concrete frame (HFF) were tested under reverse cyclic lateral loading with constant axial loads. Specimen GFF did not show any sign of cracking at a drift ratio as high as 15% with considerable loading capacity, whereas Specimen CFF showed that lowest ductility with similar load capacity as in Specimen GFF. FRP-concrete columns and pier cap beams were then cut from the pier frame specimens, and were tested again in three point flexure under monotonic loading with no axial load. The tests indicated that bonding between FRP and concrete and yielding of steel both affect the flexural strength and ductility of the components. The coupon tests were carried out to establish the tensile strength and elastic modulus of each FRP tube and the FRP mold for the pier cap beam in the two principle directions of loading. A nonlinear analytical model was developed to predict the load-deflection responses of the pier frames. The model was validated against test results. Subsequently, a parametric study was conducted with variables such as frame height to span ratio, steel reinforcement ratio, FRP tube thickness, axial force, and compressive strength of concrete. A typical bridge was also simulated under three different ground acceleration records and damping ratios. Based on the analytical damage index, the RCF bridge was most severely damaged, whereas the GFF bridge only suffered minor repairable damages. Damping ratio was shown to have a pronounced effect on FRP-concrete bridges, just the same as in conventional bridges. This research was part of a multi-university project, which is founded by the National Science Foundation (NSF) - Network for Earthquake Engineering Simulation Research (NEESR) program.

Seismic performance of hybrid fiber reinforced polymer-concrete pier columns

As part of a multi-university research program funded by NSF, a comprehensive experimental and analytical study of seismic behavior of hybrid fiber reinforced polymer (FRP)-concrete column is presented in this dissertation. Experimental investigation includes cyclic tests of six large-scale concrete-filled FRP tube (CFFT) and RC columns followed by monotonic flexural tests, a nondestructive evaluation of damage using ultrasonic pulse velocity in between the two test sets and tension tests of sixty-five FRP coupons. Two analytical models using ANSYS and OpenSees were developed and favorably verified against both cyclic and monotonic flexural tests. The results of the two methods were compared. A parametric study was also carried out to investigate the effect of three main parameters on primary seismic response measures. The responses of typical CFFT columns to three representative earthquake records were also investigated. The study shows that only specimens with carbon FRP cracked, whereas specimens with glass or hybrid FRP did not show any visible cracks throughout cyclic tests. Further monotonic flexural tests showed that carbon specimens both experienced flexural cracks in tension and crumpling in compression. Glass or hybrid specimens, on the other hand, all showed local buckling of FRP tubes. Compared with conventional RC columns, CFFT column possesses higher flexural strength and energy dissipation with an extended plastic hinge region. Among all CFFT columns, the hybrid lay-up demonstrated the highest flexural strength and initial stiffness, mainly because of its high reinforcement index and FRP/concrete stiffness ratio, respectively. Moreover, at the same drift ratio, the hybrid lay-up was also considered as the best in term of energy dissipation. Specimens with glassfiber tubes, on the other hand, exhibited the highest ductility due to better flexibility of glass FRP composites. Furthermore, ductility of CFFTs showed a strong correlation with the rupture strain of FRP. Parametric study further showed that different FRP architecture and rebar types may lead to different failure modes for CFFT columns. Transient analysis of strong ground motions showed that the column with off-axis nonlinear filament-wound glass FRP tube exhibited a superior seismic performance to all other CFFTs. Moreover, higher FRP reinforcement ratios may lead to a brittle system failure, while a well-engineered FRP reinforcement configuration may significantly enhance the seismic performance of CFFT columns.