Cyclical Events in the Life and Death of an Ephemeral Polychaete Reef on a Tropical Mudflat

The polychaete (sabellariid-spionid) reefs at Jeram shore (Malaysia) grow up on soft-bottom mudflats and appear short-lived. It is postulated that such reef building results from the succession of polychaete species in response to the changing environment modulated by the extreme hydrometeorological events. To elucidate the biological succession of the reef cycle in relation to the environment, two reef patches on the intertidal mudflat were studied, both spatially (horizontal and vertical community structure) and temporally (June 2012 to January 2014). The Jeram polychaete reef cycles through four phases within a year: pre-settlement phase (March–May), growth phase comprising primary (May–November) and secondary (October–January) successional stages, stagnation phase (December–January), and destruction phase (January–March). The reef dynamics appear to be linked to the regional monsoon climate and local hydrological conditions. At the onset of the southwest monsoon (May), strong erosive forces initiate the reef’s primary succession of the growth phase where the dominant polychaete Sabellaria jeramae colonize and rapidly grow on the exposed lag deposits of shells. During the northeast monsoon (November–March), stronger depositional forces cover the developed reef with fine sediments that are colonized by another polychaete, the spionid Polydora cavitensis during the reef’s secondary succession of the growth phase. On the muddy substrate surrounding the reef clumps, mudflat polychaetes were the most abundant macrobenthos followed by anomurans, gastropods, carideans, and brachyurans. However, these mudflat macrobenthos play no obvious or direct role in initiating the growth of the reef which is likely the result of settlement of dispersed polychaete larvae from unknown offshore reefs. On the other hand, the reef presence has a positive effect on the presence or abundance of surrounding mudflat macrobenthos such as mudflat polychaetes, shrimps, crabs, and gastropods.     

A full-scale field study for performance evaluation of axially loaded large-diameter cylinder piles with pipe piles and PSC piles

This paper presents the results from a pile load testing program for a bridge construction project in Louisiana. The testing includes two 54-in. open-ended spun cast concrete cylinder piles, one 30-in. open-ended steel pile and two (30- and 16-in.) square prestressed concrete (PSC) piles driven at two locations with very similar soil conditions. Both cone penetration tests (CPTs) and soil borings/laboratory testing were used to characterize the subsurface soil conditions. All the test piles were instrumented with vibrating wire strain gauges to measure the load distribution along the length of the test piles and measure the skin friction and end-bearing capacity, separately. Dynamic load tests were performed on all test piles at different times after pile installations to quantify the amount of setup with time. Static load tests were also performed on the PSC and open-ended steel piles. Due to expected large pile capacities, the statnamic test method was used on the two open-ended cylinder piles. The pile capacities of these piles were evaluated using various CPT methods (such as Schmertmann, De Ruiter and Beringen, LCPC, Lehane et al. methods). The result showed that all the methods can estimate the skin friction with good accuracy, but not the end-bearing capacity. The normalized cumulative blow counts during pile installation showed that the blow count was always higher for the PSC piles compared to the large-diameter open-ended cylinder pile, regardless of pile size and hammer size. Setup was observed for all the piles, which was mainly attributed to increase in skin frictions. The setup parameters “A” were back-calculated for all the test piles and the values were between 0.31 and 0.41.     

Seismic performance analysis of BRBs and gussets in a full‐scale 2‐story BRB‐RCF specimen

The implementation of buckling‐restrained braces (BRBs) for new reinforced concrete frame (RCF) constructions is limited. This study investigates the seismic forces and stability in the BRBs and gussets of a 2‐story full‐scale RCF specimen by using Abaqus models and a newly proposed stability evaluation method. The hybrid and cyclic loading test results are accurately predicted by the Abaqus analyses. Existing methods for computing the gusset interface forces for steel buildings from both the brace and the frame actions are compared with the Abaqus results. The applicability of these methods for the BRB‐RCF design is critically evaluated. It is confirmed that the Parallel‐2 method is suitable for estimating the BRB force demand imposed on the corner gusset and the generalized uniform force method is good for the corner gusset at the base. In addition, existing stability evaluation methods for BRBs and gussets are applied to investigate the out‐of‐plane (OOP) buckling of the first‐story BRB observed at the end of tests. The proposed stability model incorporates the BRB restrainer's flexural effects and 4 rotational springs in assessing the BRB's buckling. This model confirms that the BRB and the gusset's OOP buckling limit states could be coupled and must be evaluated together. By incorporating the flexural effects of the steel casing and the infilled grout, the proposed model satisfactorily predicts the OOP buckling of the first‐story BRB and gussets. These research results can be used for the implementation of BRBs in new RC frame constructions.     

Extraction of agar from Eucheuma cottonii and Gelidium amansii seaweeds with sonication pretreatment using autoclaving method

The effect of sonication pretreatment condition on Eucheuma cottonii and Gelidium amansii seaweed towards agar extraction wae studied. Four parameters were changed during sonication to investigate the effects on agar yield and quality. These parameters include the time interval, concentration ratio, frequency, and intensity. The highest amount of agar extracted from Eucheuma cottonii species could be obtained from the time interval of 30 min, seaweed weight to solvent volume ratio of 1:20, the frequency of 35 Hz, and the sonication power intensity of 30%. For Gelidium amansii species, the best agar yield also could be obtained from the time interval of 30 min, 1:20 of seaweed weight to water volume ratio, the frequency of 35 Hz, and power intensity of 30%. From the experiment, sonication pretreatment significantly influenced the yield and properties of extracted agar. The sonication with autoclaved seaweed produced agar containing less sulfate content, which is an excellent chemical property for gel electrophoresis applications.The gel strength of sonication with autoclaving for both seaweeds, Eucheuma and Gelidium species was the highest among those by sonication with direct heating, which proved that sonication pretreatment with autoclaving could enhance the physical properties of the agar.     

Spectral responses of water level in tidal river and groundwater

The water level of five river stages and seven groundwater wells in the Taipei Basin were analysed by spectral analysis in the frequency domain. The diurnal, semi‐diurnal and quarter‐diurnal tidal components of the Tanshui River appear to relate closely to astronomical tides as K₁, M₂ and M₄, respectively. It is also found that the diurnal component reveals a reversed phase angle in the middle section of the Tanshui River; the phase of the quarter‐diurnal component is also found to be reversed at stations upstream in the Tanshui River and Hsintien Stream. It is believed that these phenomena could be caused by local variation in the river channel topography. The autospectrum and cross‐spectrum between groundwater elevation and nearby river stage were observed to correlate highly with the frequency of the astronomical tides K₁, M₂ and M₄. From the study of the phase shift and time lag of water level fluctuations at river stages and groundwater wells, it was found that the tidal effects of diurnal, semi‐diurnal, and quarter‐diurnal components were significantly different. The relationships between phase and the fluctuated range of atmospheric pressure and water level imply that change in atmospheric pressure does not affect water level fluctuation in the river stage and groundwater well. Copyright © 1999 John Wiley & Sons, Ltd.     

Modeling for critical state line of granular soil with evolution of grain size distribution due to particle breakage

Determination of the critical state line(CSL)is important to characterize engineering properties of granular soils.Grain size distribution(GSD)has a significant influence on the location of CSL.The influence of particle breakage on the CSL is mainly attributed to the change in GSD due to particle breakage.However,GSD has not been properly considered in modeling the CSL with influence of particle breakage.This study aims to propose a quantitative model to determine the CSL considering the effect of GSD.We hypothesize that the change of critical state void ratio with respect to GSD is caused by the same mechanism that influences of the change of minimum void ratio with respect to GSD.Consequently,the particle packing model for minimum void ratio proposed by Chang et al.(2017)is extended to predict critical state void ratio.The developed model is validated by experimental results of CSLs for several types of granular materials.Then the evolution of GSD due to particle breakage is incorporated into the model.The model is further evaluated using the experimental results on rockfill material,which illustrates the applicability of the model in predicting CSL for granular material with particle breakage.     

Bidirectional substructure pseudo‐dynamic tests and analysis of a full‐scale two‐story buckling‐restrained braced frame

A two‐story buckling‐restrained brace (BRB) frame was tested under bidirectional in‐plane and out‐of‐plane loading to evaluate the BRB stability and gusset plate design. The test comprised pseudo‐dynamic loadings using the 1999 Chi‐Chi earthquake scaled to the 50%, 10%, and 2% probability of exceedance in 50 years and a cyclic regime of increasing amplitudes of up to 3.0% story drift ratio (SDR). The specimen had a unique configuration where the beams were connected to the columns through shear tabs welded to the column flanges and bolted to the beam webs. Stable hysteretic behavior with only minor cracking at the gusset‐to‐column welds was observed under the pseudo‐dynamic tests, with maximum in‐plane and out‐of‐plane SDRs of 2.24% and 1.47% respectively. Stable behavior continued into the cyclic test where fracture of the gusset‐to‐column welds occurred in the first cycle to simultaneous bidirectional SDR of 3.0%. The observed BRB stability is consistent with a methodology developed for BRB frames under simultaneous in‐plane and out‐of‐plane drifts. The specimen behavior was studied using a finite element model. It was shown that gusset plates are subjected to a combination of BRB force and frame action demands, with the latter increasing the gusset‐to‐beam and gusset‐to‐column interface demands by an average of 69% and 83% respectively. Consistent with the test results, failure at the gusset‐to‐column interfaces is computed when frame action demands are included, thus confirming that not considering frame action demands may results in unconservative gusset plate designs. Copyright © 2016 John Wiley & Sons, Ltd.     

Cyclic tests of four two‐story narrow steel plate shear walls. Part 2: experimental results and design implications

This paper is the second part of a two‐part paper presenting the cyclic tests of four two‐story narrow steel plate shear walls (SPSWs). The first paper introduces the analytical studies and the specimen designs. This paper describes the test results. Some design implications including the capacity design for the first story column and the width‐to‐thickness ratio check for the beam web are discussed based on key observations from the tests. Test results confirm that the simplified strip model can accurately predict the inelastic responses of the specimens. Test results also confirm that the proposed capacity design method is effective in ensuring the plastic hinge formation at the bottom end of the first story column for SPSW with or without restrainers. Test results also show that the horizontal restrainers are effective in reducing the member forces in the boundary beam and column elements. Comparing the test results of the typical SPSW with those of the restrained SPSW (R‐SPSW) specimens, it is found that the R‐SPSW possesses an improved cyclic performance and reduced material weight. Analytical results predict the compressed column moments at the onset of the column plastic hinge formation well. The analytical hysteretic energy distribution in the first story column agrees very well with the observed inelastic actions developed in the four specimens. The detailed frame response analyses and the test results confirm that the assumptions made in developing the proposed column capacity design method are reasonable. Copyright © 2009 John Wiley & Sons, Ltd.     

INTERPRETATION OF COPPER AND ZINC CONTAMINATION IN THE AQUATIC ENVIRONMENT OF PENINSULAR MALAYSIA WITH SPECIAL REFERENCE TO A POLLUTED RIVER, SEPANG RIVER

Three different aquatic ecosystems(an urban pond,Kelana Jaya Pond;a polluted river,Sepang River;and the intertidal and offshore areas of the west coast of Peninsular Malaysia)with different sets of ecological backgrounds and human activities were reviewed and assessed for the levels of Cu and Zn contamination with special reference to those found in polluted sediments collected from the Sepang River.The discussion on the contamination levels of Cu and Zn in the aquatic environment of Peninsular Malaysia was based on a comparison of the metal contamination of 4 kinds of aquatic environments.The comparison of 4 different areas was based on ① total concentrations of 2 metals;② the concentrations and percentages of the nonresistant(EFLE,acid-reducible and oxidisable-organic)and resistant geochemical fractions;and ③ correlation coefficients(R-values)based on data of 4 areas separately and a combination of 4 areas.The Sepang River recorded nonresistant fractions of 63.1% for Zn and 55.8% for Cu in addition to slightly lower metal concentrations when compared to those(60%-70%)reported before the shutting down of the piggery activities in that area.These nonresistant metal percentages(55%-63%)indicated that the metal concentrations were still dominated by anthropogenic sources since nonresistant fraction of metals were mostly contributed by anthropogenic sources.The positive results from the four different aquatic environments assessed here provided strong evidence to show that Malaysia's aquatic environment had received anthropogenic Cu and Zn.The present study also showed that the percentage of the nonresistant fraction and the R-values based on correlation analysis of Cu and Zn could be used as indicators of Cu and Zn pollution in the Malaysian aquatic ecosystem.Based on the present data,the correlation coefficients(R-values)are potential indicators of EFLE Cu and acid-reducible Cu of the sediments.The use of R-values as indicators of metal pollution is suggested and it is applicable to other heavy metal data although it should be improved in future studies.     

Uncertainty in applying the linear poroelasticity model to field situations as a result of periodic loading in heterogeneous aquifers

The solid Earth's surface frequently experience changes in total stresses as a result of periodic loading. When the fluid‐saturated porous media deform in response to changes in stress, the induced variations in pore volume affect the pore water pressure. The fluid flow therefore occurs in response to the gradient in the induced excess pore water pressure. This work aims at quantifying the spatial variability in excess pressure head produced by the periodic loading accounting for the variation of log hydraulic conductivity (lnK). It is important for the rational management of groundwater resources. A closed‐form expression is developed by the nonstationary spectral approach to analyse the influence of the statistical properties of lnK process, the hydraulic parameters, and the spatial position. The general stochastic framework outlined in this work provides a basis for assessing the impact of statistical properties of input aquifer parameters on the output variability (or uncertainty). Copyright © 2014 John Wiley & Sons, Ltd.