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1.Nano-Doped Monolithic Materials for Molecular Separation

Author:Acquah, C;Obeng, EM;Agyei, D;Ongkudon, CM;Moy, CKS;Danquah, MK

Source:SEPARATIONS,2017,Vol.4

Abstract:Monoliths are continuous adsorbents that can easily be synthesised to possess tuneable meso-/macropores, convective fluid transport, and a plethora of chemistries for ligand immobilisation. They are grouped into three main classes: organic, inorganic, and hybrid, based on their chemical composition. These classes may also be differentiated by their unique morphological and physicochemical properties which are significantly relevant to their specific separation applications. The potential applications of monoliths for molecular separation have created the need to enhance their characteristic properties including mechanical strength, electrical conductivity, and chemical and thermal stability. An effective approach towards monolith enhancement has been the doping and/or hybridization with miniaturized molecular species of desirable functionalities and characteristics. Nanoparticles are usually preferred as dopants due to their high solid phase dispersion features which are associated with improved intermolecular adsorptive interactions. Examples of such nanomaterials include, but are not limited to, carbon-based, silica-based, gold-based, and alumina nanoparticles. The incorporation of these nanoparticles into monoliths via in situ polymerisation and/or post-modification enhances surface adsorption for activation and ligand immobilisation. Herein, insights into the performance enhancement of monoliths as chromatographic supports by nanoparticles doping are presented. In addition, the potential and characteristics of less common nanoparticle materials such as hydroxyapatite, ceria, hafnia, and germania are discussed. The advantages and challenges of nanoparticle doping of monoliths are also discussed.

2.Microplastics in the freshwater and terrestrial environments: Prevalence, fates, impacts and sustainable solutions

Author:Wong, JKH;Lee, KK;Tang, KHD;Yap, PS

Source:SCIENCE OF THE TOTAL ENVIRONMENT,2020,Vol.719

Abstract:The ubiquitous occurrences of microplastics in the environment have raised much concern and resulted in voluminous studies related to mia oplastics. Studies on microplastics pollution of the marine environment have received significantly higher attention compared to those of the freshwater and terrestrial environments. With the impetus to better understand microplastics in the freshwater and terrestrial environments, this review elucidates the findings of >100 articles related to the prevalence, fates and impacts of microplastics therein and the sustainable solutions, mostly in the past 10 years. This review shows the interconnection between terrestrial and freshwater microplastics with wastewater and sewage treatment plants as the most significant contributors of environmental microplastics via sludge and effluent discharges. Microplastics in both ecosystems comprise the primary and secondary forms with the latter resulted from weathering of the former. Besides retaining in soil and infiltrating with rainwater underground, terrestrial microplastics also enter the freshwater environment. The environmental microplastics interact with the biotic and abiotic components resulting in entrainment, settlement, biofouling, degradation, fragmentation and entry into the food chain, with subsequent transfer across the food chain. The abundance of environmental microplastics is attributed to population density and urbanization though tidal cycle, storms, floods and human activities can affect their distribution. The leaching of additives from microplastics poses major health concern and sustainable solutions target at reduction of plastics use and disposal, substitution with bioplastics and wastewater treatment innovations. Further studies on classification, detection, characterization and toxicity of microplastics are necessary to permit more effective formulation of solutions. (C) 2020 Elsevier B.V. All rights reserved.

3.A Method for Improving Stage Discharge Prediction in Asymmetric Compound Channels

Author:Tang, XN

Source:WATER RESOURCES AND ECOLOGICAL CARRYING CAPACITY,2018,Vol.

Abstract:In nature, asymmetric compound channels widely exist. Accurate prediction of stage-discharge in an asymmetric compound channel becomes increasingly important in flood risk management and river environmental engineering. To predict discharge precisely, momentum exchange between the main-channel and its floodplains needs to be considered. Currently, Interacting Divided Channel Method (IDCM) has considered such exchange, but has certain errors for asymmetric compound channels, particularly for roughened floodplains. In this paper, the author proposes a new parameter ofIDCM to improve flow discharge prediction. The proposed method is evaluated by a range of experimental data from the literature. 20 datasets studied include both homogeneous asymmetric compound channels (8 datasets) and heterogeneously roughened channels (12 datasets), which have different aspect ratios [the ratio of total width (B) of channel at bankfull to main-channel bottom (b) =1.5 similar to 5] and bed slopes (So = 2.65x10(-4),, 1.3x10(-2)). This study shows that the method of using the new parameter performs well (in average errors less than 6.5%%) against all the datasets except in a very steep channel with high aspect ratio (e.g. B/b >= 5 in S-o = 0.013). Close analysis shows that the proposed method can predict the zonal discharge ratio well for both homogeneous and heterogeneous compound channels. Finally, this method has also shown improved stage-discharge predictions of main channels over the conventional divided channel method (DCM).

4.Parametric investigation of polymethacrylate monolith synthesis and stability via thermogravimetric characterisation

Author:Acquah, C;Danquah, MK;Moy, CKS;Anwar, M;Ongkudon, CM

Source:ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING,2017,Vol.12

Abstract:Polymethacrylate monoliths are synthetic adsorbents with macroporous and mesoporous interconnected channels that can be engineered to target the hydrodynamic features of a wide range of molecular species. However, rigorous study into the effect of synthesis conditions on their thermal stability is limited. This work attempts to characterise the influence of key synthesis process variables on the stability of polymethacrylate monoliths using thermogravimetric analysis at a heating rate of 10 degrees C/min. Experimental results showed that the thermal stability of polymethacrylate monoliths increased with decreasing polymerisation temperature from 85 to 65 degrees C. Increasing the total porogen (P) to monomer (M) ratio increased the thermal stability of the monolith by >62%% and >50%% for P40/M60-P60/M40 and P60/M40-P80/M20, respectively. The impact of the initiator concentration, monomer variation, biporogen ratio, washing and activation of the monoliths was investigated. Nuclear magnetic resonance analyses conducted confirmed the hydrolysis of epoxy moieties on the monolith. (C) 2017 Curtin University of Technology and John Wiley & Sons, Ltd.

5.Combinations of fungal and milling pretreatments for enhancing rice straw biogas production during solid-state anaerobic digestion

Author:Mustafa, AM;Poulsen, TG;Xia, YH;Sheng, KC

Source:BIORESOURCE TECHNOLOGY,2017,Vol.224

Abstract:Rice straw was pretreated by different combinations of physical (milling) and biological (incubation with Pleurotus ostreatus fungus) treatment to improve its biodegradability and biogas production during solid-state anaerobic digestion (SS-AD). Effects of milling (62 mm) and incubation time (10, 20 and 30 d), on lignin, cellulose, and hemicellulose degradation during fungal pretreatment and methane yield during digestion were assessed by comparison with untreated rice straw. Both incubation time and milling had significant impacts on both lignin removal during fungal pre-treatment and methane yield during digestion. A combination of fungal pretreatment at 30 days followed by milling prior to anaerobic digestion resulted in 30.4%% lignin removal, the highest selectivity value (the ratio between relative lignin removal and relative cellulose removal) of 4.22, and the highest methane yield of 258 L/kg VS. This was equivalent to a 165%% increase in methane yield from SS-AD compared to untreated rice straw. (C) 2016 Elsevier Ltd. All rights reserved.

6.An improved method for predicting discharge of homogeneous compound channels based on energy concept

Author:Tang, XN

Source:FLOW MEASUREMENT AND INSTRUMENTATION,2017,Vol.57

Abstract:Accurate estimation of flow discharge in a compound river channel is increasingly important in river management and hydro-environment design. In this paper, a new model is developed to improve the prediction of flow based on Energy Concept Method (ECM) and Weighted Divided Channel Method (WDCM) along with the apparent shear stress at the interface between main channel and floodplain. The new model is compared with a wide range of our experimental data and the data available in the literature. The 27 datasets used include homogenous symmetric channels (22 datasets) and asymmetric channels (5 datasets) with various aspect ratios [channel total width (B) at bankfull / main channel bottom (b) =1.5-15.8], and bed slopes (S-0 = 4.3 x 10(-4)-1.3 x 10(-2)). It was found that the new model has significantly improved the accuracy of flow prediction compared with the traditional Divided Channel Method (DCM), and has also considerably better results than the ECM and WDCM methods against all the datasets, particularly for relatively low flow depths of floodplain where the flow discharges are most difficult to predict correctly. The new model predicts the total discharge well for both symmetric and asymmetric channels, within an averaged relative error of about 5%%.

7.Sectional analysis for design of ultra-high performance fiber reinforced concrete beams with passive reinforcement

Author:Xia, J;Chan, T;Mackie, KR;Saleem, MA;Mirmiran, A

Source:ENGINEERING STRUCTURES,2018,Vol.160

Abstract:Sectional flexural analysis, as performed in normal strength concrete design, requires uniaxial constitutive models. For ultra-high performance fiber reinforced concrete (UHPFRC), the constitutive model tensile backbone varies with section heights for different flexural members, due to the size-dependent stress-crack opening relation used to derive it. In this paper, several simplified size-independent constitutive models were investigated. For unreinforced sections with heights between 51 mm and 1067 mm, the elastic-perfectly-plastic tension model leads to conservative ultimate moment prediction (or results within 5%%) when compared to that obtained by the size-dependent model. For reinforced sections, the difference between the two models is affected by the reinforcing condition and is even smaller than the unreinforced cases. By assuming an elastic-perfectly-plastic tension model, the flexural strength of rectangular or T section UHPFRC beams was estimated analytically. The flexural strengths are greatly influenced by the reinforcement ratio and yielding strength of the longitudinal reinforcement. Including shear strength predictive equations from past research, the load capacity and failure mode for rectangular and T beams are presented in a design chart. The impact of several factors on UHPFRC beam flexural responses were investigated, such as different compressive strength, curing conditions, and anisotropic fiber orientation distributions. The load-deflection relationships generated from beam flexural analysis were compared to experimental results for both unreinforced and reinforced beams, with or without fiber alignment. Factors affecting the first crack strength in tension (i.e., fiber orientation distribution) had greater impact on the flexural strength of UHPFRC beams than the effect of using a size-dependent model.

8.Textile-reinforced mortar external strengthening of corroded reinforced concrete beams

Author:Moy, Charles K.S. ; Oluwadahunsi, Silas

Source:Sustainable Construction Materials and Technologies,2019,Vol.3

Abstract:The need for reliable material techniques for the restoration of corrosion-damaged reinforced concrete (RC) elements cannot be over-emphasised, especially when considering the sustainability aspects of reinforced concrete structures. This investigation examines the application of basalt textile-reinforced mortar for external strengthening of corroded RC beams in flexure. In that regard, a set of reinforced concrete beams subjected to accelerated corrosion to 10%% and 20%% mass loss of the main steel bars at mid-span and were strengthened using TRM. In total, 7 beams were tested under four-point bending for the following conditions 1 control, 2 corroded and 4 strengthened. Two strengthening schemes were single ply TRM of equivalent surface area. The results show that corrosion had detrimental effects on load-carrying capacity, yield strength, as well as ductility of corroded beams. Strengthening schemes restored the load capacity of the 10%% corroded beams within a range of 105%% to 112%% of control load capacity. Recovery of the load carrying capacity was not achieved for the 20%% corroded beams. All the strengthened specimens ultimately failed by fibre reinforcement rupture, thus indicating full utilisation of composite action of the TRM. © 2019 International Committee of the SCMT conferences. All rights reserved.

9.SEISMIC ANALYSIS ON SOIL-FOUNDATION-SUPERSTRUCTURE SYSTEM CONSIDERING LARGE DEFORMATION

Author:Guanlin YE;Yonglin XIONG;Yuanfeng BAO;Bin YE;Feng ZHANG

Source:The Fifteenth East Asia-Pacific Conference on Structural Engineering & Construction (2017第十五届东亚-太平洋结构工程及施工国际会议)(EASEC-15)论文集,2017,Vol.

Abstract:  In considering boundary value problems related to soil-structure interaction, both the structure and the soil are involved in the calculation.It is important to consider properly the geometric and material nonlinearities of both the structures and the soils.In this study, a rigorous numerical scheme for space beam element that can properly take the geometric and the material nonlinearities of structures into consideration was introduced and embedded into the DBLEAVES (Ye, 2011).Soil-water coupled dynamic analyses were conducted on a soil-group pile foundation-superstructure system to investigate the seismic behavior of an elevated bridge with a 12-pile foundation during a major earthquake.

10.Hysteretic performance of SPSWs with trapezoidally horizontal corrugated web-plates

Author:Kalali, H;Hajsadeghi, M;Zirakian, T;Alaee, FJ

Source:STEEL AND COMPOSITE STRUCTURES,2015,Vol.19

Abstract:Previous research has shown that steel plate shear walls (SPSWs) are efficient lateral force-resisting systems against both wind and seismic loads. A properly designed SPSW can have high initial stiffness, strength, and energy absorption capacity as well as superior ductility. SPSWs have been commonly designed with unstiffened and stiffened infill plates based on economical and performance considerations. Recent introduction and application of corrugated plates with advantageous structural features has motivated the researchers to consider the employment of such elements in stiffened SPSWs with the aim of lowering the high construction cost of such high-performing systems. On this basis, this paper presents results from a numerical investigation of the hysteretic performance of SPSWs with trapezoidally corrugated infill plates. Finite element cyclic analyses are conducted on a series of flat-and corrugated-web SPSWs to examine the effects of web-plate thickness, corrugation angle, and number of corrugation half-waves on the hysteretic performance of such structural systems. Results of the parametric studies are indicative of effectiveness of increasing of the three aforementioned web-plate geometrical and corrugation parameters in improving the cyclic response and energy absorption capacity of SPSWs with trapezoidally corrugated infill plates. Increasing of the web-plate thickness and number of corrugation half-waves are found to be the most and the least effective in adjusting the hysteretic performance of such promising lateral force-resisting systems, respectively. Findings of this study also show that optimal selection of the web-plate thickness, corrugation angle, and number of corrugation half-waves along with proper design of the boundary frame members can result in high stiffness, strength, and cyclic performances of such corrugated-web SPSWs.

11.Numerical Analysis of Multicomponent Suspension Droplets in High-Velocity Flame Spray Process

Author:Gozali, E;Mahrukh, M;Gu, S;Kamnis, S

Source:JOURNAL OF THERMAL SPRAY TECHNOLOGY,2014,Vol.23

Abstract:The liquid feedstock or suspension as a different mixture of liquid fuel ethanol and water is numerically studied in high-velocity suspension flame spray (HVSFS) process, and the results are compared for homogenous liquid feedstock of ethanol and water. The effects of mixture on droplet aerodynamic breakup, evaporation, combustion, and gas dynamics of HVSFS process are thoroughly investigated. The exact location where the particle heating is initiated (above the carrier liquid boiling point) can be controlled by increasing the water content in the mixture. In this way, the particle inflight time in the high-temperature gas regions can be adjusted avoiding adverse effects from surface chemical transformations. The mixture is modeled as a multicomponent droplet, and a convection/diffusion model, which takes into account the convective flow of evaporating material from droplet surface, is used to simulate the suspension evaporation. The model consists of several sub-models that include premixed combustion of propane-oxygen, non-premixed ethanol-oxygen combustion, modeling of multicomponent droplet breakup and evaporation, as well as heat and mass transfer between liquid droplets and gas phase.

12.Accuracy of Digital Elevation Models Derived From Terrestrial Laser Scanning Data

Author:Fan, L;Atkinson, PM

Source:IEEE GEOSCIENCE AND REMOTE SENSING LETTERS,2015,Vol.12

Abstract:Terrestrial laser scanning (TLS) has become a popular tool for acquiring source data points which can be used to construct digital elevation models (DEMs) for a wide number of applications. A TLS point cloud often has a very fine spatial resolution, which can represent well the spatial variation of a terrain surface. However, the uncertainty in DEMs created from this relatively new type of source data is not well understood, which forms the focus of this letter. TLS survey data representing four terrain surfaces of different characteristics were used to explore the effects of surface complexity and typical TLS data density (in terms of data point spacing) on DEM accuracy. The spatial variation in TLS data can be decomposed into parts corresponding to the signal of spatial variation (of terrain surfaces) and noise due to measurement error. We found a linear relation between the DEM error and the typical TLS data spacings considered (30-100 mm) which arises as a function of the interpolation error, and a constant contribution from the propagated data noise. This letter quantifies these components for each of the four surfaces considered and shows that, for the interpolation method considered here, higher density sampling would not be beneficial.

13.Quantitative Assessment of Building Constructability Using BIM and 4D Simulation

Author:Cheng Zhang;Tarek Zayed;Wissam Hijazi;Sabah Alkass

Source:Open Journal of Civil Engineering,2016,Vol.

Abstract:Despite the fact that applying constructability concepts in building designs have led to savings estimated within a range of 1%% to 14%% of the capital cost, the construction industry still lacks an advanced tool to assess and check for constructability implementations in designs. Therefore, the objective of this research is to propose a quantitative assessment of building constructability, which transforms the subjective assessment of constructability knowledge to a quantified value so that it is easy to analyze and improve building design. The proposed methodology uses the advancement of object oriented Building Information Model (BIM) and 4D simulation model to serve as a data repository models for the constructability assessment platform. Factors affecting constructability of building designs have been identified and relatively weighted using Analytical Hierarchy Process (AHP) technique based on a questionnaire survey collected throughout the Canadian provinces. Evaluation criteria are also developed to assist the designer to evaluate the design proposals. The outcome shows that the proposed method provides the designer an accurate and faster mode in evaluating project constructability by using the parametric features from BIM and taking the advantage of spatial relationship between building components.

14.Temporal Pattern Analysis of Rainstorm Events for Supporting Rainfall Design in a Tropical City

Author:Jun, CY;Qin, XS;Lu, W

Source:NEW TRENDS IN URBAN DRAINAGE MODELLING, UDM 2018,2019,Vol.

Abstract:Synthetic rainfall distributions of the design storm have been commonly used for the hydrological design of urban stormwater infrastructures in many regions of the world. However, there are still limited studies in a tropical city dealing with design storm hyetographs for flood estimation even though rainfall intensity/depth-duration-frequency (IDF/DDF) relationships have been derived to estimate rainfall depths for a specific rainfall duration and return period. This study presents a storm-event based rainfall analysis method to determine a representative quartile of the design storm in which, both inter-event time definition (IETD) and depth/duration/intensity thresholds are considered. Similar to Huff's method, 5-min rainfall data during three years at two rain gauge stations in Singapore were used to obtain the percentage frequency of the four types of quartile storms depending on the location where the heaviest rainfall occurred in each storm duration. It was found that the proposed approach could give the shape and magnitude of the design storm hyetograph from the location of peak rainfall corresponding to the largest portion of quartile storms. As a result, the second quartile design storm was suggested to be applied for flood estimation in order to better address the temporal characteristic of actual rainstorm events in the study area. It offers an alternative way of describing the temporal distribution of rainfall within a design storm period, which is helpful in improving the design of urban stormwater infrastructures in a tropical region.

15.Procurement innovation for a circular economy of construction and demolition waste: Lessons learnt from Suzhou, China

Author:Bao, ZK;Lu, WS;Chi, B;Yuan, HP;Hao, JL

Source:WASTE MANAGEMENT,2019,Vol.99

Abstract:Amidst the global trend of advocating a circular economy, various nations and regions in recent years have started to explore innovative procurement models (e.g., Public Private Partnership [PPP]) in dealing with beset issues related to construction and demolition (C&D) waste. However, PPP is suffering from problems such as 'long negotiation time', 'lack of transparency', and 'uneven risk and return allocation', which in turn lead to 'ineffective delivery' and 'poor value for money'. Using a case study, this paper reports some lessons learnt from innovative practices of procuring C&D management services in Suzhou, China. It is discovered that the public and private sectors, without prior knowledge, are operating based on a general concession framework instead of negotiating a clear-cut agreement from the outset. Several key arrangements, such as price, concession period, and strategic operations, are based on relational contract-type of agreements, which are found particularly innovative for shortening the negotiation time, fostering the trust between the relevant parties, dealing with emerging ad hoc problems, and allowing sustainable development of the circular economy. To make such PPP work, it is critical to devise institutions to prevent corruption and opportunistic behaviors. This research provides useful references to developing a circular economy. Although they focus on C&D waste management, the research findings can be applied to other public procurement settings, such as municipal solid waste management service. (C) 2019 Elsevier Ltd. All rights reserved.

16.Distributed Fiber Optic Sensing of Axially Loaded Bored Piles

Author:Pelecanos, L;Soga, K;Elshafie, MZEB;de Battista, N;Kechavarzi, C;Gue, CY;Ouyang, Y;Seo, HJ

Source:JOURNAL OF GEOTECHNICAL AND GEOENVIRONMENTAL ENGINEERING,2018,Vol.144

Abstract:Instrumented pile tests are vital to establish the performance of a pile and validate the assumptions made during initial design. Conventional instrumentation includes vibrating wire strain gauges and extensometers to measure the change in strain or displacements within a pile. Although these strain and displacement gauges are very accurate, they only provide strain/displacement readings at discrete locations at which they are installed. It is therefore common to interpolate between two consecutive points to obtain values corresponding to the data gaps between points; in practice, these discrete instrumented points could be tens of meters apart, at depths corresponding to different soil layers, and hence simple interpolation between the measurement points remains questionable. The Brillouin optical time-domain reflectometry fiber optic strain sensing system is able to provide distributed strain sensing along the entire length of the cable, enabling the full strain profile to be measured during a maintained pile load test. The strain data can also be integrated to obtain the displacement profile. This paper presents three case studies which investigate the performance of three concrete bored piles in London using both conventional vibrating wire strain gauges and distributed fiber optic strain sensing during maintained pile load tests, which enable comparisons made between the two instrumentation systems. In addition, finite-element analyses show that the ability to measure the full strain profiles for each pile is highly advantageous in understanding the performance of the pile and in detecting any abnormalities in the pile behavior. (C) 2017 American Society of Civil Engineers.

17.Electronic Document Management Systems for the Transportation Construction Industry

Author:Guo,Fangyu;Jahren,Charles T.;Turkan,Yelda

Source:International Journal of Construction Education and Research,2021,Vol.17

Abstract:The implementation of various technologies typically produces a considerable amount of digital data for transportation agencies; therefore, it is desirable to have electronic document management (EDM) systems to promote efficient data-sharing among stakeholders. Although EDM systems have been implemented in the building construction industry and their benefits are well understood, they are not as common in the transportation design and construction industry. There are only a few agencies that have broadly implemented EDM with limited research having been conducted on this topic. Accordingly, the purpose of this paper is to present and analyze the current state of the EDM system implementation within leading US transportation agencies and to develop a framework for the selection and implementation of EDM systems for other agencies. This article describes four case studies that were conducted with four transportation agencies in the US who are at the frontiers in the implementation of EDM systems. Current EDM practices at these agencies as well as the associated benefits and challenges were documented. By comparing and contrasting these case studies, the common functionalities and unique characteristics of various EDM systems were summarized and a framework was developed to guide transportation agencies with the selection and implementation of EDM systems.

18.Comparison between Analytical Equation and Numerical Methods for Determining Shear Stress in a Cantilever Beam

Author:Al-Qasem, I;Hasan, AR;Abdulwahid, MY;Galobardes, I

Source:CIVIL ENGINEERING JOURNAL-TEHRAN,2018,Vol.4

Abstract:A three meter-length cantilever beam loaded with a concentrated load at its free end is studied to determine shear stresses. In the present study, three cross sections are considered: rectangle (R); I, and T. The study presents a comparison of maximum shear stresses obtained by means of two methods: classical analytical equation derived by Collingnon, and finite element method (FEM) software. Software programs ANSYS and SAP2000 were used. The results show difference between the maximum shear stresses obtained by the analytical equation and the software, being the last is always higher. The average differences for ANSYS and SAP2000, independently of the cross section, were 12.76%% and 11.96%%, respectively. Considering these differences, correction factors were proposed to the classical analytical formula for each cross section case to obtain more realistic results. After the correction, the average differences decrease to 1.48%% and 4.86%%, regardless of the cross section shape.

19.EXPERIMENTAL AND ANALYTICAL INVESTIGATIONS ON ULTRA-HIGH PERFORMANCE FIBRE REINFORCED CONCRETE (UHPFRC)-STEEL COMPOSITE SLAB

Author:Xia, J;Li, Y;Huang, H;Zhao, L

Source:1ST INTERNATIONAL CONFERENCE ON UHPC MATERIALS AND STRUCTURES,2016,Vol.105

Abstract:Steel and concrete composite slab system makes full use of both material and is widely used in bridges and buildings. This paper presents the analytical, experimental, and numerical analysis of one innovative, ultra-high performance fibre reinforced concrete-steel composite slab. This slab system uses parallel placed rectangular steel tubes as tensile resistant members with transverse and longitudinal reinforcement mesh being used as shear keys, which is embedded in the UHPFRC layer. The load bearing capacity of experimental specimens is estimated using equations that follow classic sectional analysis, which gives conservative results when compared to experimental data. The deformation and strain readings recorded during testing exhibits expected load transfer mechanism between concrete layer and steel tubes. The provided connections by using reinforcement mesh are proved to be sufficient to transfer load from concrete portion to steel tube and cause ductile failure due to yielding of steel tubes. The finite element model of the composite slab exhibits higher stiffness and ultimate load capacity, which is due to the imperfect composite action during testing.

20.3D dynamic analysis of the soil-foundation-superstructure system considering the elastoplastic finite deformation of both the soil and the superstructure

Author:Xiong, YL;Bao, YF;Ye, B;Ye, GL;Zhang, F

Source:BULLETIN OF EARTHQUAKE ENGINEERING,2018,Vol.16

Abstract:In this study, in order to investigate the effect of the nonlinearity of superstructure supported by group-pile foundation and liquefiable ground on the piles and surrounding ground soils, three-dimensional (3D) dynamic finite element analysis is conducted, in which the strong nonlinear behavior of both soil and structure is considered during earthquake loading process. In the calculation, RC pile is modeled by AFD model proposed by Zhang and Kimura (Soils Found 42(3):77-92, 2002), which can describe the axial-force dependent nonlinear behavior of RC piles properly and a sophisticate elastoplastic constitutive model proposed by Zhang et al. (Soils Found 47(4):635-648, 2007, Front Archit Civ Eng China 5(2):121-150, 2011) is adopted, which can properly describe density (overconsolidation), structured and stress-induced anisotropy of soft soil in a unified way under drained/undrained condition subjected to monotonic/cyclic loading. For superstructure, its mechanical behavior is described by three different 3D models, (1) a beam element theory proposed by Goto et al. (J Struct Eng 41A:411-420, 1995) that can take into consideration both the material and geometric nonlinearity; (2) trilinear beam that can roughly consider the material nonlinearity; (3) linear elastic beam. The main purpose of the research is to find out, the influence of not only the material nonlinearity, but also the geometric nonlinearity of the superstructure, with a unified calculating model in which the superstructure, the foundation and the soft are included. The calculated results show that the nonlinear behavior of superstructure has less influence on soft ground, but the large deformation of the superstructure may give rise to large extra moment of pier, which, as the results, will increase the external forces acting on the piles. Therefore, both the geometric and material nonlinear behavior of superstructure should be properly taken into consideration in seismic design, especially when it is built on a liquefiable ground.
Total 153 results found
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