Advances in Civil Engineering http://www.hindawi.com The latest articles from Hindawi Publishing Corporation © 2015 , Hindawi Publishing Corporation . All rights reserved. The Influence of Calcium Chloride Salt Solution on the Transport Properties of Cementitious Materials Thu, 04 Jun 2015 06:15:26 +0000 http://www.hindawi.com/journals/ace/2015/929864/ The chemical interaction between calcium chloride (CaCl2) and cementitious binder may alter the transport properties of concrete which are important in predicting the service life of infrastructure elements. This paper presents a series of fluid and gas transport measurements made on cementitious mortars before and after exposure to various solutions with concentrations ranging from 0% to 29.8% CaCl2 by mass. Fluid absorption, oxygen diffusivity, and oxygen permeability were measured on mortar samples prepared using Type I and Type V cements. Three primary factors influence the transport properties of mortar exposed to CaCl2: (1) changes in the degree of saturation, (2) calcium hydroxide leaching, and (3) formation of chemical reaction products (i.e., Friedel’s salt, Kuzel’s salt, and calcium oxychloride). It is shown that an increase in the degree of saturation decreases oxygen permeability. At lower concentrations (<~12% CaCl2 at room temperature), the addition of CaCl2 can increase calcium hydroxide leaching, thereby increasing mortar porosity (this is offset by the formation of Friedel’s salt and Kuzel’s salt that can block the pores). At higher concentrations (>~12%), the formation of chemical reaction products (mainly calcium oxychloride) is a dominant factor decreasing the fluid and gas transport in concrete. Yaghoob Farnam, Taylor Washington, and Jason Weiss Copyright © 2015 Yaghoob Farnam et al. All rights reserved. Assessing Mechanical Properties of Hot Mix Asphalt with Wire Wool Fibers Tue, 19 May 2015 13:08:10 +0000 http://www.hindawi.com/journals/ace/2015/795903/ This paper investigates the potential application of wire wool in the modification of hot asphalt mixes (HMA). Wire wool material is widely available at local markets as a by-product of wire wool industry and as waste products from homes. For the purpose of this study, wire wool was cut into small pieces so that it can be placed in the asphalt mixes. Different percentages of wire wool were incorporated with the hot asphalt mixes (0.0%, 0.25%, and 0.5%) of the total weight of the asphalt binder. Various experimental tests were used to evaluate the modification effectiveness of combining wire wool with hot asphalt mixes, namely, the Marshall Stability, indirect tensile strength (ITS), dynamic creep, fatigue, and rutting tests. Test results proved that the addition of wire wool increased the tensile strength of the asphalt concrete mixes. However, rutting increased due to increasing percentage of wire wool. Therefore, mixes containing wire wool can be used in areas where rutting is not the expected predominant distress type. Ahmed N. Bdour, Yahia Khalayleh, and Aslam A. Al-Omari Copyright © 2015 Ahmed N. Bdour et al. All rights reserved. Enhancing the Classical Closed-Loop Algorithm in terms of Power Consumption Thu, 14 May 2015 06:30:10 +0000 http://www.hindawi.com/journals/ace/2015/291076/ An approach is suggested to reduce the peak and average control forces of actively controlled structures. In this method, responses of an actively controlled building should be much smaller than the responses of the same building controlled by the similar passive control mechanism. This approach leads to a time varying gain matrix, which is not restricted by external excitation but it is related to the selection of a scalar function. Extensive numerical analyses by using various scalar functions show that the proposed strategy effectively can reduce the need of the required control force consumptions. Rahman Mirzaei and Seyed Sina Kourehli Copyright © 2015 Rahman Mirzaei and Seyed Sina Kourehli. All rights reserved. A Two-Stage Method for Structural Damage Prognosis in Shear Frames Based on Story Displacement Index and Modal Residual Force Wed, 13 May 2015 14:20:18 +0000 http://www.hindawi.com/journals/ace/2015/527537/ A two-stage method is proposed to properly identify the location and the extent of damage in shear frames. In the first stage, a story displacement index (SDI) is presented to precisely locate the damage in the shear frame which is calculated using the modal analysis information of the damaged structure. In the second stage, by defining a new objective function, the extent of the actual damage is determined via an imperialist competitive algorithm. The performance of the proposed method is demonstrated by implementing the technique to three examples containing five-, ten-, and twenty-five-story shear frames with noises and without them in modal data. Moreover, the performance of the proposed method has been verified through using a benchmark problem. Numerical results show the high efficiency of the proposed method for accurately identifying the location and the extent of structural damage in shear frames. Asghar Rasouli, Seyed Sina Kourehli, Gholamreza Ghodrati Amiri, and Ali Kheyroddin Copyright © 2015 Asghar Rasouli et al. All rights reserved. Effects of Posttensioning Slippage on 2-Way Spanning Concrete Slabs Thu, 09 Apr 2015 11:32:03 +0000 http://www.hindawi.com/journals/ace/2015/980840/ This paper investigates the effect of improper posttensioning of a 2-way spanning concrete slab subject to a central point load. Due to plate slippage alone, the support conditions only offered a 1-way spanning action which could have led to premature failure with dangerous consequences. Posttensioning can strengthen a flat slab against punching shear by controlling deflections and cracking under service loads compared with traditional punching shear reinforcing methods leading to more slender structures and economic solutions for longer spans. However, if the method is not properly applied, these thinner floor plates can fail in a brittle and sudden manner by punching at ultimate limit state and excessive deflection in serviceability. Concrete slabs containing traditional shear reinforcement performed adequately and demonstrated that the critical punching shear perimeter, defined as twice the depth of the slab, was confirmed from measured deflections and crack pattern analysis. Niall Holmes and Eoin Byrne Copyright © 2015 Niall Holmes and Eoin Byrne. All rights reserved. Evaluation of Steel Shear Walls Behavior with Sinusoidal and Trapezoidal Corrugated Plates Tue, 07 Apr 2015 07:39:00 +0000 http://www.hindawi.com/journals/ace/2015/715163/ Reinforcement of structures aims to control the input energy of unnatural and natural forces. In the past four decades, steel shear walls are utilized in huge constructions in some seismic countries such as Japan, United States, and Canada to lessen the risk of destructive forces. The steel shear walls are divided into two types: unstiffened and stiffened. In the former, a series of plates (sinusoidal and trapezoidal corrugated) with light thickness are used that have the postbuckling field property under overall buckling. In the latter, steel profile belt series are employed as stiffeners with different arrangement: horizontal, vertical, or diagonal in one side or both sides of wall. In the unstiffened walls, increasing the thickness causes an increase in the wall capacity under large forces in tall structures. In the stiffened walls, joining the stiffeners to the wall is costly and time consuming. The ANSYS software was used to analyze the different models of unstiffened one-story steel walls with sinusoidal and trapezoidal corrugated plates under lateral load. The obtained results demonstrated that, in the walls with the same dimensions, the trapezoidal corrugated plates showed higher ductility and ultimate bearing compared to the sinusoidal corrugated plates. Emad Hosseinpour, Shahrizan Baharom, and Yasser Yadollahi Copyright © 2015 Emad Hosseinpour et al. All rights reserved. Probabilistic Assessment of Degree of Bending in Tubular X-Joints of Offshore Structures Subjected to Bending Loads Thu, 05 Mar 2015 08:59:16 +0000 http://www.hindawi.com/journals/ace/2015/518450/ Fatigue life of tubular joints in offshore structures is significantly influenced by the degree of bending (DoB). The DoB exhibits considerable scatter calling for greater emphasis in accurate determination of its governing probability distribution which is a key input for the fatigue reliability analysis of a tubular joint. Although the tubular X-joints are commonly found in offshore jacket structures, as far as the authors are aware, no comprehensive research has been carried out on the probability distribution of the DoB in tubular X-joints. In the present paper, results of parametric equations available for the calculation of the DoB have been used to develop probability distribution models for the DoB in the chord member of tubular X-joints subjected to four types of bending loads. Based on a parametric study, a set of samples was prepared and density histograms were generated for these samples using Freedman-Diaconis method. Twelve different probability density functions (PDFs) were fitted to these histograms. In each case, Kolmogorov-Smirnov test was used to evaluate the goodness of fit. Finally, after substituting the values of estimated parameters for each distribution, a set of fully defined PDFs have been proposed for the DoB in tubular X-joints subjected to bending loads. Hamid Ahmadi and Amirreza Ghaffari Copyright © 2015 Hamid Ahmadi and Amirreza Ghaffari. All rights reserved. Experimental Study of Hysteretic Steel Damper for Energy Dissipation Capacity Tue, 03 Feb 2015 13:46:45 +0000 http://www.hindawi.com/journals/ace/2015/631726/ This study aims to evaluate energy absorption capacity of hysteretic steel damper for earthquake protection of structures. These types of steel dampers are fabricated from mild steel plate with different geometrical shapes on the side part, namely, straight, concave, and convex shapes. The performance of the proposed device was verified experimentally by a series of tests under increasing in-plane cyclic load. The overall test results indicated that the proposed steel dampers have similar hysteretic curves, but the specimen with convex-shaped side not only showed stable hysteretic behavior but also showed excellent energy dissipation capabilities and ductility factor. Furthermore, the load-deformation relation of these steel dampers can be decomposed into three parts, namely, skeleton curve, Bauschinger part, and elastic unloading part. The skeleton curve is commonly used to obtain the main parameters, which describe the behavior of steel damper, namely, yield strength, elastic stiffness, and postyield stiffness ratio. Moreover, the effective stiffness, effective damping ratio, cumulative plastic strain energy, and cumulative ductility factor were also derived from the results. Finally, an approximation trilinear hysteretic model was developed based on skeleton curve obtained from experimental results. Daniel R. Teruna, Taksiah A. Majid, and Bambang Budiono Copyright © 2015 Daniel R. Teruna et al. All rights reserved. Seismic Vulnerability Assessment of Deficient RC Structures with Bar Pullout and Joint Shear Degradation Wed, 28 Jan 2015 07:40:26 +0000 http://www.hindawi.com/journals/ace/2015/537405/ Pakistan is an underdeveloped country, still striving for improvement in construction practices. Most of the private construction is carried out as nonengineered which caused loss of approximately 85,000 lives in Kashmir (2005) earthquake. However, after the Kashmir (2005) earthquake, the government and engineering community emphasized on implementation of seismic codes. Although the current construction practices are considered as better than previous construction work the vulnerability of these structures is yet to be determined. It aims at the vulnerability assessment of recent RC construction in Pakistan that still needs to be assessed. Research work starts with calibration of panel zone element (PERFORM 3D) depicting joint shear degradation, while comparing the analytical results with experimental work, found in the literature. The frame work is then used for vulnerability assessment of RC structures typical of current construction practices in Pakistan while using advanced capacity spectrum method, developed by Kyriakides for which three cases have been considered, being constructed more frequently by public sector, in different seismic zones, based on design usually followed by builders in the region. Finally, the conclusion is drawn with suggestion of further improvement of seismic behavior of the structures. Arslan Mushtaq, Shaukat Ali Khan, Hamza Farooq Gabriel, and Sajjad Haider Copyright © 2015 Arslan Mushtaq et al. All rights reserved. Impact of Train Schedule on Pedestrian Movement on Stairway at Suburban Rail Transit Station in Mumbai, India Thu, 08 Jan 2015 13:01:03 +0000 http://www.hindawi.com/journals/ace/2015/297807/ Pedestrian flow takes place in confined environment on stairways under the influence of composition, direction of movement, and schedule of trains. During peak-period, alighting and boarding rate is quite high resulting in very high pedestrian movement from one platform to the other to catch the next train at interchange stations. The transfer of passengers from railway platforms through common undivided stairways becomes difficult, uncomfortable, and unsafe at times when pedestrian flow reaches the capacity level. Understanding of criteria defining quality of flow that affect the effectiveness of facilities like stairways in handling the pedestrian traffic is vital for planning and designing of such facilities to ensure the desired level of service as well as safety in case of emergency. The present paper is based on the study of pedestrian movement on stairways at busy suburban rail transit interchange station at Dadar in Mumbai, India. Pedestrian movements are captured through videography at two stairways and the effect of bidirectional movement on average walking speed is analyzed. The ascending flow in small proportion is found to be more influential in causing speed reduction on undivided stairways. The outcome of the study is useful for capacity and level of service analysis while planning and designing the transit station stairways. Shah Jiten, Joshi Gaurang, Parida Purnima, and Arkatkar Shriniwas Copyright © 2015 Shah Jiten et al. All rights reserved. Analytical Study of Common Rigid Steel Connections under the Effect of Heat Mon, 29 Dec 2014 12:37:31 +0000 http://www.hindawi.com/journals/ace/2014/692323/ One of the most important members of steel structure’s connection region is beam-to-column connection. Rigid connection in steel moment frame has special role in the behavior of these structures and the fire resistance of these connections can be important. In this paper the behaviors of three common types of rigid connections in Iran under the effect of heat were studied by the use of numerical finite element methods through ABAQUS software. The models were verified by the use of an experimental model through elastic and plastic amplitudes up to collapse and during numerical results, and the effect of large deformation in the nonlinear region has also been considered. The results show that the connection with the end plate had a better performance against heat than other connections. Also reduced stiffness and lateral buckling in this connection were less than other connections. Rohola Rahnavard, Navid Siahpolo, Mohammad Naghavi, and Akbar Hassanipour Copyright © 2014 Rohola Rahnavard et al. All rights reserved. Effects of Underground Cavities on the Frequency Spectrum of Seismic Shear Waves Wed, 10 Dec 2014 09:42:42 +0000 http://www.hindawi.com/journals/ace/2014/934284/ A numerical method is proposed to study the scattering of seismic shear waves induced by the presence of underground cavities in homogeneous soils. The method is based on the superposition of two solutions: the solution of the free-wave propagation problem in a uniform half-space, easily determined analytically, and the solution of the wave scattering problem due to the cave presence, evaluated numerically by means of an ad hoc code implemented by using the ANSYS Parametric Design Language. In the two-dimensional setting, this technique is applied to the case of a single cave, placed at a certain depth from the ground level. The frequency spectrum of the seismic shear oscillation on the ground surface is determined for different dimensions and depths of the cave and compared with the spectrum registered without caves. The influence of the cave dimensions and depth on the spectrum amplification is analyzed and discussed. G. Lancioni, R. Bernetti, E. Quagliarini, and L. Tonti Copyright © 2014 G. Lancioni et al. All rights reserved. Using Intelligent Techniques in Construction Project Cost Estimation: 10-Year Survey Tue, 02 Dec 2014 10:10:38 +0000 http://www.hindawi.com/journals/ace/2014/107926/ Cost estimation is the most important preliminary process in any construction project. Therefore, construction cost estimation has the lion’s share of the research effort in construction management. In this paper, we have analysed and studied proposals for construction cost estimation for the last 10 years. To implement this survey, we have proposed and applied a methodology that consists of two parts. The first part concerns data collection, for which we have chosen special journals as sources for the surveyed proposals. The second part concerns the analysis of the proposals. To analyse each proposal, the following four questions have been set. Which intelligent technique is used? How have data been collected? How are the results validated? And which construction cost estimation factors have been used? From the results of this survey, two main contributions have been produced. The first contribution is the defining of the research gap in this area, which has not been fully covered by previous proposals of construction cost estimation. The second contribution of this survey is the proposal and highlighting of future directions for forthcoming proposals, aimed ultimately at finding the optimal construction cost estimation. Moreover, we consider the second part of our methodology as one of our contributions in this paper. This methodology has been proposed as a standard benchmark for construction cost estimation proposals. Abdelrahman Osman Elfaki, Saleh Alatawi, and Eyad Abushandi Copyright © 2014 Abdelrahman Osman Elfaki et al. All rights reserved. Case Study of Remaining Service Life Assessment of a Cooling Water Intake Concrete Structure in Indonesia Tue, 11 Nov 2014 12:18:11 +0000 http://www.hindawi.com/journals/ace/2014/970393/ This paper deals with the assessment of remaining service life of a cooling water intake concrete structure (CWICS) subjected to corrosion due to chloride attacks. Field and laboratory tests were performed to determine the current existing condition of the structure. Both destructive and nondestructive tests were employed to obtain the parameter needed for the assessment. Based on the current condition and test results, structural analysis was carried out and the remaining safety factor of CWICS was determined. From the analysis, it was found that most concrete elements of CWICS had safety factor greater than unity and might fulfil its intended service life up to the year 2033. However, fewer elements require immediate strengthening to extend their service life. M. Sigit Darmawan, Ridho Bayuaji, N. A. Husin, and R. B. Anugraha Copyright © 2014 M. Sigit Darmawan et al. All rights reserved. Steel Fibre Reinforcing Characteristics on the Size Reduction of Fly Ash Based Concrete Tue, 04 Nov 2014 09:06:22 +0000 http://www.hindawi.com/journals/ace/2014/217473/ The behavior of glued steel fibres in high strength concrete with size reduction properties of concrete has been attempted. Glued steel fibres with both ends hooked having length to diameter ratio of 70 was added at a dosage level of 0.5% to 1.5% by volume fraction. The study was carried out to analyze the effects of fibre addition on the thickness reduction of concrete element. A high strength concrete mixture was designed and various thicknesses of concrete prisms were casted for different volume fraction of steel fibres. The hardened concrete properties were determined based on the mix constituents such as water to binder ratio 0.3 (w/b), superplasticizer dosage, fine to coarse aggregate ratio 0.6 (F/c), and fly ash replacement level at 25% and 50% by weight of binder content. The experimental test results showed that the flexural strength varies with respect to the depth of concrete specimen. It can be observed that the reduction in size up to 10% size containing 25% fly ash with 1.5% steel fibres showed better strength enhancement of 4.70 MPa and 6.69 MPa for 7 days and 28 days, respectively. Also, the addition of steel fibres at higher percentage of fly ash containing 50% showed better improvement in the flexural strength for the size reduction at 5%, when compared to plain concrete beam which exhibited higher stress carrying capacity of 6.08 MPa at 28 days and showed an increase of 7.99%. Sounthararajan Vallarasu Manoharan and Sivakumar Anandan Copyright © 2014 Sounthararajan Vallarasu Manoharan and Sivakumar Anandan. All rights reserved. On the Fresh/Hardened Properties of Cement Composites Incorporating Rubber Particles from Recycled Tires Thu, 30 Oct 2014 09:20:11 +0000 http://www.hindawi.com/journals/ace/2014/876158/ This study investigates the ameliorative effects on some properties of cement-based materials which can be obtained by incorporating rubber particles as part of the fine aggregates. The aim is to find out optimal cement composite/mortar mixtures, containing recycled-tyre rubber particles, suitable for specific engineering applications. Different percentages of rubber particles, from 0% to 75%, were used and, for each percentage, the suitable amount of sand was investigated in order to achieve the best fresh/hardened performances. In particular the following characteristics were examined: density, compressive strength, modulus of elasticity, shrinkage, weight loss, flexural behaviour, thermal conductivity, rapid freezing and thawing durability, and chloride permeability. The experimental results were compared with the ones of cement composite specimens without rubber aggregates. Test results show that the proposed rubberized mortar mixes are particularly suitable for some industrial and architectural applications, such as under-rail bearings, road constructions, paving slabs, false facades, and stone backing. Alessandra Fiore, Giuseppe Carlo Marano, Cesare Marti, and Marcello Molfetta Copyright © 2014 Alessandra Fiore et al. All rights reserved. Experimental and Empirical Time to Corrosion of Reinforced Concrete Structures under Different Curing Conditions Thu, 16 Oct 2014 00:00:00 +0000 http://www.hindawi.com/journals/ace/2014/595743/ Reinforced concrete structures, especially those in marine environments, are commonly subjected to high concentrations of chlorides, which eventually leads to corrosion of the embedded reinforcing steel. The total time to corrosion of such structures may be divided into three stages: corrosion initiation, cracking, and damage periods. This paper evaluates, both empirically and experimentally, the expected time to corrosion of reinforced concrete structures. The tested reinforced concrete samples were subjected to ten alternative curing techniques, including hot, cold, and normal temperatures, prior to testing. The corrosion initiation, cracking, and damage periods in this investigation were experimentally monitored by an accelerated corrosion test performed on reinforced concrete samples. Alternatively, the corrosion initiation time for counterpart samples was empirically predicted using Fick’s second law of diffusion for comparison. The results showed that the corrosion initiation periods obtained experimentally were comparable to those obtained empirically. The corrosion initiation was found to occur at the first jump of the current measurement in the accelerated corrosion test which matched the half-cell potential reading of around −350 mV. Ahmed A. Abouhussien and Assem A. A. Hassan Copyright © 2014 Ahmed A. Abouhussien and Assem A. A. Hassan. All rights reserved. Bridge Management Strategy Based on Extreme User Costs for Bridge Network Condition Tue, 14 Oct 2014 13:27:24 +0000 http://www.hindawi.com/journals/ace/2014/390359/ This paper presents a practical approach for prioritization of bridge maintenance within a given bridge network. The maintenance prioritization is formulated as a multiobjective optimization problem where the simultaneous satisfaction of several conflicting objectives includes minimization of maintenance costs, maximization of bridge deck condition, and minimization of traffic disruption and associated user costs. The prevalence of user cost during maintenance period is twofold; the first case refers to the period of dry season where normally the traffic flow is diverted to alternative routes usually resurfaced to regain traffic access. The second prevalence refers to the absence of alternative routes which is often the case in the least developed countries; in this case the user cost referred to results from the waiting time while the traffic flow is put on hold awaiting accomplishment of the maintenance activity. This paper deals with the second scenario of traffic closure in the absence of alternative diversion routes which in essence results in extreme user cost. The paper shows that the multiobjective optimization approach remains valid for extreme cases of user costs in the absence of detour roads as often is the scenario in countries with extreme poor road infrastructure. Ladislaus Lwambuka and Primus V. Mtenga Copyright © 2014 Ladislaus Lwambuka and Primus V. Mtenga. All rights reserved. Mobile Imaging and Computing for Intelligent Structural Damage Inspection Wed, 01 Oct 2014 06:25:09 +0000 http://www.hindawi.com/journals/ace/2014/483729/ Optical imaging is a commonly used technique in civil engineering for aiding the archival of damage scenes and more recently for image analysis-based damage quantification. However, the limitations are evident when applying optical imaging in the field. The most significant one is the lacking of computing and processing capability in the real time. The advancement of mobile imaging and computing technologies provides a promising opportunity to change this norm. This paper first provides a timely introduction of the state-of-the-art mobile imaging and computing technologies for the purpose of engineering application development. Further we propose a mobile imaging and computing (MIC) framework for conducting intelligent condition assessment for constructed objects, which features in situ imaging and real-time damage analysis. This framework synthesizes advanced mobile technologies with three innovative features: (i) context-enabled image collection, (ii) interactive image preprocessing, and (iii) real-time image analysis and analytics. Through performance evaluation and field experiments, this paper demonstrates the feasibility and efficiency of the proposed framework. ZhiQiang Chen and Jianfei Chen Copyright © 2014 ZhiQiang Chen and Jianfei Chen. All rights reserved. Structural Damage Detection Based on Modal Parameters Using Continuous Ant Colony Optimization Tue, 30 Sep 2014 07:14:56 +0000 http://www.hindawi.com/journals/ace/2014/174185/ A method is presented to detect and quantify structural damages from changes in modal parameters (such as natural frequencies and mode shapes). An inverse problem is formulated to minimize the objective function, defined in terms of discrepancy between the vibration data identified by modal testing and those computed from analytical model, which then solved to locate and assess the structural damage using continuous ant colony optimization algorithm. The damage is formulated as stiffness reduction factor. The study indicates potentiality of the developed code to solve a wide range of inverse identification problems. Aditi Majumdar, Bharadwaj Nanda, Dipak Kumar Maiti, and Damodar Maity Copyright © 2014 Aditi Majumdar et al. All rights reserved. Damage Identification for Prestressed Adjacent Box-Beam Bridges Tue, 23 Sep 2014 09:28:01 +0000 http://www.hindawi.com/journals/ace/2014/540363/ Structural health monitoring (SHM) has gained considerable attention as a tool for monitoring the health of civil infrastructure. For bridge infrastructure, previous methods have focused on the detection of localized damage through modal parameters extracted from the longitudinal direction of the structure. This paper investigates a new damage detection method based on the change in the first vertical mode extracted from the transverse direction of the bridge. The mode is determined through application of modal curve fitting to frequency response functions (FRFs) that are formed using vertical response data obtained in the direction perpendicular to the bridge’s longitudinal axis. Using this method, both local damage and global damage in the bridge reveal themselves as having a localized effect on the bridge response. Furthermore, damage is revealed in such a way that it enables differentiation of the damage types. To demonstrate the effectiveness of the method, modal parameters were extracted from acceleration data obtained from a finite element model of a full bridge. Analysis of the modal parameters showed that the proposed approach could not only detect both local and global bridge damage, but could also differentiate between damage types using only one mode shape. The proposed method was compared to a previously developed SHM method. Kenneth K. Walsh, Brendan T. Kelly, and Eric P. Steinberg Copyright © 2014 Kenneth K. Walsh et al. All rights reserved. Nonlinear Dynamic Analysis of Plates Stiffened by Parallel Beams with Deformable Connection Sun, 14 Sep 2014 00:00:00 +0000 http://www.hindawi.com/journals/ace/2014/942763/ In this paper a general solution to the geometrically nonlinear dynamic analysis of plates stiffened by arbitrarily placed parallel beams of arbitrary doubly symmetric cross-section, subjected to dynamic loading, is presented. The plate-beam structure is assumed to undergo moderate large deflections and the nonlinear analysis is carried out by retaining nonlinear terms in the kinematical relations. According to the proposed model, the arbitrarily placed parallel stiffening beams are isolated from the plate by sections in the lower outer surface of the plate, making the hypothesis that the plate and the beams can slip in all directions of the connection without separation and taking into account the arising tractions in all directions at the fictitious interfaces. These tractions are integrated with respect to each half of the interface width resulting in two interface lines, along which the loading of the beams and the additional loading of the plate are defined. Six boundary value problems are formulated and solved using the analog equation method (AEM), a BEM-based method. Both free and forced transverse vibrations are considered and numerical examples with great practical interest are presented demonstrating the effectiveness, wherever possible, the accuracy, and the range of applications of the proposed method. J. A. Dourakopoulos and E. J. Sapountzakis Copyright © 2014 J. A. Dourakopoulos and E. J. Sapountzakis. All rights reserved. Achievement of Early Compressive Strength in Concrete Using Sporosarcina pasteurii Bacteria as an Admixture Thu, 11 Sep 2014 07:50:39 +0000 http://www.hindawi.com/journals/ace/2014/435948/ Often it is observed, attainment of early compressive strength in concrete is a challenge. Researchers have tried various admixtures to achieve the objective. This work addresses the issue of achieving early compressive strength in concrete using a bacterium called Sporosarcina pasteurii. The bacterium is characterised with the ability to precipitate calcium carbonate in the presence of any carbonate source and is known for its resistive capacity in extreme temperature and pressure zones. To establish the objective of gain in early strength around 192 concrete cubes were tested at 3, 7, 14, and 28 days and the results compared with controlled concrete. The bacterium was used in combination of chemicals and the dosage proportions were altered to achieve the desired M20 compressive strength at 28 days. Rakesh Chidara, Rahul Nagulagama, and Smitha Yadav Copyright © 2014 Rakesh Chidara et al. All rights reserved. Evolutionary Modeling to Evaluate the Shear Behavior of Circular Reinforced Concrete Columns Sun, 07 Sep 2014 07:53:47 +0000 http://www.hindawi.com/journals/ace/2014/684256/ Despite their frequent occurrence in practice, only limited studies on the shear behavior of reinforced concrete (RC) circular members are available in the literature. Such studies are based on poor assumptions about the physical model, often resulting in being too conservative, as well as technical codes that essentially propose empirical conversion rules. On this topic in this paper, an evolutionary approach named EPR is used to create a structured polynomial model for predicting the shear strength of circular sections. The adopted technique is an evolutionary data mining methodology that generates a transparent and structured representation of the behavior of a system directly from experimental data. In this study experimental data of 61 RC circular columns, as reported in the technical literature, are used to develop the EPR models. As final result, physically consistent shear strength models for circular columns are obtained, to be used in different design situations. The proposed formulations are compared with models available from building codes and literature expressions, showing that EPR technique is capable of capturing and predicting the shear behavior of RC circular elements with very high accuracy. A parametric study is also carried out to evaluate the physical consistency of the proposed models. Alessandra Fiore, Giuseppe Carlo Marano, Daniele Laucelli, and Pietro Monaco Copyright © 2014 Alessandra Fiore et al. All rights reserved. Impact of Blending on Strength Distribution of Ambient Cured Metakaolin and Palm Oil Fuel Ash Based Geopolymer Mortar Sun, 31 Aug 2014 09:21:51 +0000 http://www.hindawi.com/journals/ace/2014/658067/ This paper investigates the influence of blending of metakaolin with silica rich palm oil fuel ash (POFA) on the strength distribution of geopolymer mortar. The broadness of strength distribution of quasi-brittle to brittle materials depends strongly on the existence of flaws such as voids, microcracks, and impurities in the material. Blending of materials containing alumina and silica with the objective of improving the performance of geopolymer makes comprehensive characterization necessary. The Weibull distribution is used to study the strength distribution and the reliability of geopolymer mortar specimens prepared from 100% metakaolin, 50% and 70% palm and cured under ambient condition. Mortar prisms and cubes were used to test the materials in flexure and compression, respectively, at 28 days and the results were analyzed using Weibull distribution. In flexure, Weibull modulus increased with POFA replacement, indicating reduced broadness of strength distribution from an increased homogeneity of the material. Modulus, however, decreased with increase in replacement of POFA in the specimens tested under compression. It is concluded that Weibull distribution is suitable for analyses of the blended geopolymer system. While porous microstructure is mainly responsible for flexural failure, heterogeneity of reaction relics is responsible for the compression failure. Taliat Ola Yusuf, Mohammad Ismail, Jamilu Usman, and Ainul H. Noruzman Copyright © 2014 Taliat Ola Yusuf et al. All rights reserved. Enhancement of Ultrahigh Performance Concrete Material Properties with Carbon Nanofiber Sun, 24 Aug 2014 06:31:04 +0000 http://www.hindawi.com/journals/ace/2014/854729/ Ultrahigh performance concrete (UHPC) realized distinctly high mechanical, impermeability, and durability characteristics by reducing the size and content of capillary pore, refining the microstructure of cement hydrates, and effectively using fiber reinforcement. The dense and fine microstructure of UHPC favor its potential to effectively disperse and interact with nanomaterials, which could complement the reinforcing action of fibers in UHPC. An optimization experimental program was implemented in order to identify the optimum combination of steel fiber and relatively low-cost carbon nanofiber in UHPC. The optimum volume fractions of steel fiber and carbon nanofiber identified for balanced improvement of flexural strength, ductility, energy sorption capacity, impact, and abrasion resistance of UHPC were 1.1% and 0.04%, respectively. Desired complementary/synergistic actions of nanofibers and steel fibers in UHPC were detected, which were attributed to their reinforcing effects at different scales, and the potential benefits of nanofibers to interfacial bonding and pull-out behavior of fibers in UHPC. Modification techniques which enhanced the hydrophilicity and bonding potential of nanofibers to cement hydrates benefited their reinforcement efficiency in UHPC. Libya Ahmed Sbia, Amirpasha Peyvandi, Parviz Soroushian, Jue Lu, and Anagi M. Balachandra Copyright © 2014 Libya Ahmed Sbia et al. All rights reserved. Influence of Microwave Incinerated Rice Husk Ash on Hydration of Foamed Concrete Thu, 14 Aug 2014 11:19:55 +0000 http://www.hindawi.com/journals/ace/2014/482176/ This research explains the results of an investigation carried out to understand the influence of a microwave incinerated rice husk ash (MIRHA) powder on foamed concrete (FC) hydration. The experimental work was designed using the Taguchi approach. This method was selected to have a target for the optimum working conditions of the parameter that affects some physical properties of concrete mixtures. The loss on ignition (LOI) method was used to establish the nonevaporable water () content at all selected ages of hydration. It was observed that the MIRHA powder showed lower nonevaporable water contents than the normal FC, indicating that MIRHA powder facilitated enhancement in FC hydration. The optimum FC properties were achieved at 10% MIRHA composition as proven from the highest compressive strength. This level corresponds to the highest values in change in nonevaporable water and degree of hydration. R. Bayuaji and M. F. Nuruddin Copyright © 2014 R. Bayuaji and M. F. Nuruddin. All rights reserved. Architect Critical Challenges as a Project Manager in Construction Projects: A Case Study Wed, 13 Aug 2014 00:00:00 +0000 http://www.hindawi.com/journals/ace/2014/205310/ All construction professionals such as civil, mechanical, and electrical engineers, quantity surveyors, and architects have important roles in the construction process. Among these, architects are frequently appointed as a project manager (PM). The role of a PM will drive the success of the projects implementation. Therefore, the capability of an architect as a PM (ArPM) is critical in reducing challenges encountered. Accordingly, the identification of these challenges is an important task in selecting an appropriate ArPM. The aim of this study is to identify the most critical challenges faced by an ArPM for construction projects. The data were collected through questionnaires and interviews with architects and professionals in the Malaysian construction industry. Because of the fuzziness and uncertainty of subjective responses, Fuzzy Set Ttheory is applied to identify critical challenges. A total of 65 questionnaires were distributed and 36 questionnaires were returned. The results revealed that the critical challenges faced by an ArPM are “poor planning,” “unfamiliar technology,” “unfamiliarity with green buildings and materials,” “inappropriate scheduling,” and “poor workmanship.” All critical challenges were then categorized into six main groups including technical, managerial, personal skills, contractual, psychological, and financial. Mohammadreza Yadollahi, Mohammad Mirghasemi, Rosli Mohamad Zin, and Bachan Singh Copyright © 2014 Mohammadreza Yadollahi et al. All rights reserved. Analysis, Design, and Construction of a Base-Isolated Multiple Building Structure Thu, 07 Aug 2014 07:35:48 +0000 http://www.hindawi.com/journals/ace/2014/585429/ The analysis and design of a multiple residential building, seismically protected by a base isolation system incorporating double friction pendulum sliders as protective devices, are presented in the paper. The building, situated in the suburban area of Florence, is composed of four independent reinforced concrete framed structures, mutually separated by three thermal expansion joints. The plan is L-shaped, with dimensions of about 75 m in the longitudinal direction and about 30 m along the longest side of the transversal direction. These characteristics identify the structure as the largest example of a base-isolated “artificial ground” ever built in Italy. The base isolation solution guarantees lower costs, a much greater performance, and a finer architectural look, as compared to a conventional fixed-base antiseismic design. The characteristics of the building and the isolators, the mechanical properties and the experimental characterization campaign and preliminary sizing carried out on the latter, and the nonlinear time-history design and performance assessment analyses developed on the base isolated building are reported in this paper, along with details about the installation of the isolators and the plants and highlights of the construction works. Stefano Sorace and Gloria Terenzi Copyright © 2014 Stefano Sorace and Gloria Terenzi. All rights reserved. Some Insights to the Reuse of Dredged Marine Soils by Admixing with Activated Steel Slag Tue, 05 Aug 2014 08:18:28 +0000 http://www.hindawi.com/journals/ace/2014/345134/ Regular dredging is necessary for the development of coastal regions and the maintenance of shipping channels. The dredging process dislodges sediments from the seabed, and the removed materials, termed dredged marine soils, are generally considered a geowaste for dumping. However, disposal of the dredged soils offshores can lead to severe and irreversible impact on the marine ecosystem, while disposal on land often incurs exorbitant costs with no guarantee of zero-contamination. It is therefore desirable to reuse the material, and one option is solidification with another industrial waste, that is, steel slag. This paper describes the exploratory work of admixing dredged marine soil with activated steel slag for improvement of the mechanical properties. An optimum activation concentration of NaOH was introduced to the soil-slag mixture for uniform blending. Specimens were prepared at different mix ratios then left to cure for up to 4 weeks. The unconfined compressive strength test was conducted to monitor the changes in strength at predetermined intervals. It was found that the strength does not necessarily increase with higher steel slag content, indicating an optimum slag content required for the maximum solidification effect to take place. Also, regardless of the slag content, longer curing time produces greater strength gain. In conclusion, steel slag addition to dredged sediments can effectively strengthen the originally weak soil structure by both the “cementation” and “filler” effects, though the combined effects were not distinguished in the present study. Chee-Ming Chan and Ainun Nazhirin Abdul Jalil Copyright © 2014 Chee-Ming Chan and Ainun Nazhirin Abdul Jalil. All rights reserved.