Seismic Pounding of Bridges due to Multi-Support Excitation with traveling wave

Abstract: -Among structural damages, seismic induced pounding has been commonly observed in severalearthquakes. When lateral and transverse movement of a structure occurs during earthquakes, it will hit adjacent structure and bounce back. This back and forth hitting of adjacent structures is known as pounding. The earthquake ground motion is usually assumed as uniform dynamic motion in seismic analysis. This assumption may be inadequate for structures placed at large areas like bridge, dam etc. Pounding in bridges is a result of the relative movement of the adjacent bridge superstructures at the expansion joints. This movement depends on different structural dynamic properties of the adjacent spans and characteristics of ground motions at the pier supports along the bridge. This paper includes a study of effect of pounding between bridge superstructures under the action of earthquake motion having multi-support excitation with traveling effect. The present study is a numerical investigation of pounding effect on a simply supported bridge using finite element method, using the software, OpenSees

Mutually opposing activity of PIN7 splicing isoforms is required for auxin-mediated tropic responses in Arabidopsis thaliana

Summary Advanced transcriptome sequencing has uncovered that the majority of eukaryotic genes undergo alternative splicing (AS). Nonetheless, little effort has been dedicated to investigating the functional relevance of particular splicing events, even those in the key developmental and hormonal regulators. Combining approaches of genetics, biochemistry and advanced confocal microscopy, we describe the impact of alternative splicing on the PIN7 gene in the plant model Arabidopsis thaliana. PIN7 encodes a polarly localized transporter for the phytohormone auxin and produces two evolutionary-conserved transcripts PIN7a and PIN7b. PIN7a and PIN7b, differing in a 4-amino acid motif, exhibit almost identical expression pattern and subcellular localization. We reveal that they closely associate and mutually influence their mobility within the plasma membrane. Phenotypic complementation tests indicate that the functional contribution of PIN7b per se is minor, but it markedly reduces the prominent PIN7a activity, which is required for correct seedling apical hook formation and auxin-mediated tropic responses. Our results establish alternative splicing of the PIN family as a conserved, functionally relevant mechanism, unveiling an additional regulatory level of auxin-mediated plant development.Advanced transcriptome sequencing has revealed that the majority of eukaryotic genes undergo alternative splicing (AS). Nonetheless, little effort has been dedicated to investigating the functional relevance of particular splicing events, even those in the key developmental and hormonal regulators. Combining approaches of genetics, biochemistry and advanced confocal microscopy, we describe the impact of alternative splicing on the PIN7 gene in the model plant Arabidopsis thaliana. PIN7 encodes a polarly localized transporter for the phytohormone auxin and produces two evolutionarily conserved transcripts, PIN7a and PIN7b. PIN7a and PIN7b, differing in a four amino acid stretch, exhibit almost identical expression patterns and subcellular localization. We reveal that they are closely associated and mutually influence each other's mobility within the plasma membrane. Phenotypic complementation tests indicate that the functional contribution of PIN7b per se is minor, but it markedly reduces the prominent PIN7a activity, which is required for correct seedling apical hook formation and auxin-mediated tropic responses. Our results establish alternative splicing of the PIN family as a conserved, functionally relevant mechanism, revealing an additional regulatory level of auxin-mediated plant development.Peer reviewe

Post-Consumer Carpet Fibers in Concrete: Fiber Behavior in Alkaline Environments and Concrete Durability

The widespread use of carpets in residential and commercial buildings and their relatively short life span result in large volumes of carpet being landfilled. A potential solution to this problem is the use of post-consumer carpet fibers in concrete. To this end, this paper systematically identifies the common fiber types in a typical post-consumer carpet fiber bale and evaluates their durability under exposure to varying levels of alkalinity. The tensile strengths and toughness of the fibers belonging to the nylon and polyethylene terephthalate (PET) families (the dominant fibers in most post-consumer carpets) are reduced by up to 50% following exposure to extreme alkalinity, the reasons for which are determined using spectroscopic and microscopic evaluations. The chloride ion transport resistance of concretes (~40 MPa strength) containing 2.5% carpet fibers by volume (~25 kg of fibers per cubic meter of concrete) is comparable to that of the control mixture, while mortar mixtures containing the same volume fraction of carpet fibers demonstrate negligible enhancement in expansion and loss of strength when exposed to 1 N NaOH. This study shows that moderate-strength concretes (~40 MPa) for conventional building and infrastructure applications can be proportioned using the chosen volume of carpet fibers without an appreciable loss of performance. Consideration of low volume fractions of carpet fibers in low-to-moderate-strength concretes thus provides a sustainable avenue for the use of these otherwise landfilled materials in construction applications

Carpet fiber recycling in regular-use concrete mixtures and associated life cycle analysis

This paper reports the characterization of post-consumer carpet fibers and optimization of concrete mixtures containing high volumes (2.5% and 5% as compared to ≤ 2% reported in past work) of carpet fibers, in an effort to contribute to the efficient management of such wastes. This study identifies the different fiber types in a typical post-consumer carpet bale using Fourier transform infrared (FTIR) spectroscopy and the range of tensile strengths demonstrated by the fibers. In order to quantify the sustainability of concretes containing carpet fibers, a cradle-to-gate life cycle analysis is carried out. The results demonstrate that the use of carpet fibers along with fly ash helps reduce the CO2 emission potential by ∼ 12.5% compared to conventional concrete, in addition to saving critical land area that would otherwise be needed to dispose of the ever-increasing amounts of carpet waste. Notable reductions (of up to 10%) in other environmental impact categories (e.g., acidification, eutrophication, etc.) are also observed with respect to conventional concrete. Even with the additional energy required to process the fibers, the overall energy consumption to produce carpet fiber reinforced concretes is similar to that of conventional concretes. The conditions under which carpet fibers become an environmentally sustainable approach for concretes designed to achieve a particular compressive strength are also outlined. It is expected that this work will pave the way for the management and beneficial utilization of otherwise landfilled shredded carpets in concrete applications such as slabs-on-grade