ENERGY BASED SEISMIC DESIGN OF A TIMBER CORE-WALL MULTI-STOREY HYBRID BUILDING

Current earthquake design philosophy in North America recommends an equivalent static force procedure (ESFP). Much research lately has been in new performance based methodologies including direct displacement based design (DDBD) and energy-based design (EBD). Research in energy-based design has not had the attention of DDBD yet now is gaining in popularity because of the methods reliance on the velocity spectrum and duration of earthquake hazard. This paper discusses an energy based methodology in designing a novel multi-storey hybrid building consisting of a timber-steel core wall system. This hybrid system combines Cross Laminated Timber (CLT) panels with steel plates and connections to provide the required strength and ductility to core walled buildings. To improve the applicability of the hybrid system an EBD methodology is proposed to design the core-walled building. The methodology is proposed as it does not rely on empirical formulas and force modification factors to determine the final design of the structure. In order to assess the feasibility of the EBD method, it is implemented in the design of a 7-storey building based off an already built concrete benchmark building. The design is first carried out following the ESFP outlined by the National Building Code of Canada for Vancouver, BC. Nonlinear time history analysis is carried out on the ESFP design and the proposed EBD methodology using 10 ground motions selected at 2% in 50 years return period, to evaluate the suitability of the method and the results of the ESFP and EBD methodologies are discussed and compared

Soil methane (CH4) fluxes in cropland with permanent pasture and riparian buffer strips with different vegetation

Background Methane (CH4) has a global warming potential (GWP) 28 times that of carbon dioxide (CO2) over a 100-year horizon. Riparian buffers strips are widely implemented for their water quality protection functions along agricultural land, but conditions prevailing within them may increase the production of radiative greenhouse gases (GHGs), including CH4. However, a few information is available regarding the dynamics of unintended emissions of soil CH4 in these commonplace features of agroecosystems and how the dynamics compare with those for agricultural land. Aims To understand the dynamics of soil CH4 fluxes from a permanent upslope pasture and contiguous riparian buffer strips with different (grass, willow, and woodland) vegetation as well controls with no buffer vegetation, an experiment was carried out using the static chamber technique on a replicated plot-scale facility. Methods Gas fluxes were measured periodically with soil and environmental variables between June 2018 and February 2019 at North Wyke, UK. Results Soils under all treatments were sinks of soil CH4 with the willow riparian buffer (–2555 ± 318.7 g CH4 ha–1) having the lowest soil CH4 flux followed by the grass riparian buffer (–2532 ± 318.7 g CH4 ha–1), woodland riparian buffer (–2318.0 ± 246.4 g CH4 ha–1), no-buffer control (–1938.0 ± 374.4 g CH4 ha–1), and last, the upslope pasture (–1328.0 ± 89.0 g CH4 ha–1), which had a higher flux. Conclusions The three vegetated riparian buffers were more substantial soil CH4 sinks, suggesting that they may help reduce soil CH4 fluxes into the atmosphere in similar agroecosystems

Soil N2O and CH4 emissions from fodder maize production with and without riparian bufer strips of difering vegetation

Purpose Nitrous oxide (N2O) and methane (CH4) are some of the most important greenhouse gases in the atmosphere of the 21st century. Vegetated riparian bufers are primarily implemented for their water quality functions in agroecosystems. Their location in agricultural landscapes allows them to intercept and process pollutants from adjacent agricultural land. They recycle organic matter, which increases soil carbon (C), intercept nitrogen (N)-rich runof from adjacent croplands, and are seasonally anoxic. Thus processes producing environmentally harmful gases including N2O and CH4 are promoted. Against this context, the study quantifed atmospheric losses between a cropland and vegetated riparian bufers that serve it.Methods Environmental variables and simultaneous N2O and CH4 emissions were measured for a 6-month period in a replicated plot-scale facility comprising maize (Zea mays L.). A static chamber was used to measure gas emissions. The cropping was served by three vegetated riparian bufers, namely: (i) grass riparian bufer; (ii) willow riparian bufer and; (iii) woodland riparian bufer, which were compared with a no-bufer control. Results The no-bufer control generated the largestcumulative N2O emissions of 18.9 kg ha−1(95% confdence interval: 0.5–63.6) whilst the maize crop upslope generated the largest cumulative CH4 emissions (5.1±0.88 kg ha−1). Soil N2O and CH4-based global warming potential (GWP) were lower in the willow (1223.5±362.0 and 134.7±74.0 kg CO2-eq. ha−1 year−1, respectively) and woodland (1771.3±800.5 and 3.4±35.9 kg CO2-eq. ha−1 year−1, respectively) riparian bufers. Conclusions Our results suggest that in maize production and where no riparian bufer vegetation is introduced for water quality purposes (no bufer control), atmospheric CH4 and N2O concerns may resul

Soil CO2 emissions in cropland with fodder maize (Zea mays L.) with and without riparian buffer strips of differing vegetation

Vegetated land areas play a significant role in determining the fate of carbon (C) in the global C cycle. Riparian buffer vegetation is primarily implemented for water quality purposes as they attenuate pollutants from immediately adjacent croplands before reaching freshwater systems. However, their prevailing conditions may sometimes promote the production and subsequent emissions of soil carbon dioxide (CO2). Despite this, the understanding of soil CO2 emissions from riparian buffer vegetation and a direct comparison with adjacent croplands they serve remain elusive. In order to quantify the extent of CO2 emissions in such an agro system, we measured CO2 emissions simultaneously with soil and environmental variables for six months in a replicated plot-scale facility comprising of maize cropping served by three vegetated riparian buffers, namely: (i) a novel grass riparian buffer; (ii) a willow riparian buffer, and; (iii) a woodland riparian buffer. These buffered treatments were compared with a no-buffer control. The woodland (322.9 ± 3.1 kg ha− 1) and grass (285 ± 2.7 kg ha− 1) riparian buffer treatments (not significant to each other) generated significantly (p = < 0.0001) the largest CO2 compared to the remainder of the treatments. Our results suggest that during maize production in general, the woodland and grass riparian buffers serving a maize crop pose a CO2 threat. The results of the current study point to the need to consider the benefits for gaseous emissions of mitigation measures conventionally implemented for improving the sustainability of water resources

Nitrogen Management in Grasslands and Forage-Based Production Systems–Role of Biological Nitrification Inhibition (BNI)

Nitrogen (N), being the most critical and essential nutrient for plant growth, largely determines the productivity in both extensive- and intensive- grassland systems. Nitrification and denitrification processes in the soil are the primary drivers generating reactive-N: NO3-, N2O, and NO, and is largely responsible for N-loss and degradation of grasslands. Suppressing nitrification can thus facilitate the retention of soil-N to sustain long-term productivity of grasslands and forage-based production systems. Certain plants can suppress soil nitrification by releasing inhibitors from roots, a phenomenon termed ‘biological nitrification inhibition’ (BNI). Recent methodological developments (e.g. bioluminescence assay to detect BNIs from plant-root systems) led to significant advances in our ability to quantify and characterize BNI function in pasture grasses. Among grass-pastures, BNI-capacity is strongest in low-N adapted grasses such as Brachiaria humidicola and weakest in high-N environment grasses such as Italian ryegrass (Lolium perenne) and B. brizantha. The chemical identity of some of the BNIs produced in plant tissues and released from roots has now been established and their mode of inhibitory action determined on nitrifying bacteria Nitrosomonas. Synthesis and release of BNIs is a highly regulated and localized process, triggered by the presence of NH4+ in the rhizosphere, which facilitates the release of BNIs close to soil-nitrifier sites. Substantial genotypic variation is found for BNI-capacity in B. humidicola, which opens the way for its geneticmanipulation. Field studies suggest that Brachiaria grasses suppress nitrification and N2O emissions from soil. The potential for exploiting BNI function (from a genetic improvement and a system perspective) to develop production systems that are low-nitrifying, low N2O-emitting, economically efficient and ecologically sustainable, will be the subject of discussion

Do NO, N2O, N2 and N2 fluxes differ in soils sourced from cropland and varying riparian buffer vegetation? An incubation study

Riparian buffers are expedient interventions for water quality functions in agricultural landscapes. However, the choice of vegetation and management affects soil microbial communities, which in turn affect nutrient cycling and the production and emission of gases such as nitric oxide (NO), nitrous oxide (N2O), nitrogen gas (N2) and carbon dioxide (CO2). To investigate the potential fluxes of the above-mentioned gases, soil samples were collected from a cropland and downslope grass, willow and woodland riparian buffers from a replicated plot scale experimental facility. The soils were re-packed into cores and to investigate their potential to produce the aforementioned gases via potential denitrification, a potassium nitrate (KNO3−) and glucose (labile carbon)-containing amendment, was added prior to incubation in a specialized laboratory DENItrification System (DENIS). The resulting NO, N2O, N2 and CO2 emissions were measured simultaneously, with the most NO (2.9 ± 0.31 mg NO m−2) and N2O (1413.4 ± 448.3 mg N2O m−2) generated by the grass riparian buffer and the most N2 (698.1 ± 270.3 mg N2 m−2) and CO2 (27,558.3 ± 128.9 mg CO2 m−2) produced by the willow riparian buffer. Thus, the results show that grass riparian buffer soils have a greater NO3− removal capacity, evidenced by their large potential denitrification rates, while the willow riparian buffers may be an effective riparian buffer as its soils potentially promote complete denitrification to N2, especially in areas with similar conditions to the current study