ISRN Civil Engineering The latest articles from Hindawi Publishing Corporation © 2014 , Hindawi Publishing Corporation . All rights reserved. Investigation of the Potential for Evaluation of Concrete Flaws Using Nondestructive Testing Methods Sun, 11 May 2014 12:11:24 +0000 Adoption of periodic or continuous monitoring strategies to assess condition state of infrastructure elements is a vital part of service life management (SLM). NDT methods are increasingly seen as an attractive and viable strategy to support condition monitoring. Over the last 15 years, the LEME research group at UFRGS has investigated several aspects related to the use of the ultrasonic pulse velocity (UPV) method and its potential for real field applications. One of the main advances involved the development of artificial neural network (ANN) models for correlating compressive strength and UPV measurements. Another examined problem was how to deal with the large amount of raw data derived from inspection of large structures. Several studies were carried out to check different mapping techniques, as reported by Lorenzi et al. 2011. This paper relates one investigation where UPV and rebound hammer (RH) measurements were collected from a beam containing several induced defects, simulated using different materials. The results were processed using a mapping strategy, which indicated suspicious points where core extraction was undertaken. All cores taken from points derived from UPV results were found to have flaws providing evidence that this may be a suitable tool to assess concrete structures, when data is properly interpreted. Alexandre Lorenzi, Luciane Fonseca Caetano, Josue Argenta Chies, and Luiz Carlos Pinto da Silva Filho Copyright © 2014 Alexandre Lorenzi et al. All rights reserved. Evaluation of Seismic Performance of Buildings Constructed on Hillside Slope of Doronka Village-Egypt Thu, 10 Apr 2014 08:56:07 +0000 Construction on the hillside slope is more challenging to the structural engineer, especially under seismic load due to the presence of a powerful earthquake in addition to the forces of sliding slope itself. Regarding the population growth and narrowness of available lands, people take hillside slopes to build their houses. One of the main sources of seismic vulnerability in Egypt is represented by the instability of slopes; therefore, this is a subject of great significance, particularly in view of the growing attention that has been recently dedicated to the reduction of seismic hazard. This paper evaluates the seismic performance of Doronka city buildings constructed on rocky hillside slope and its foundations system by studying base shear, acceleration, and displacements. The stability of the slope was first evaluated under seismic loads and then the stability of constructed buildings was checked on the hillside slope. The results of study show that these buildings will collapse if subjected to earthquake even if its peak ground acceleration (PGA) magnitude is less than 0.25 g, but the hillside slope remains stable within a high earthquake magnitude. Ahmed Abdelraheem Farghaly Copyright © 2014 Ahmed Abdelraheem Farghaly. All rights reserved. Estimation of the Impact of the Forces from an External Explosion to Building Faces on the Responses of a 3D Frame Structure Mon, 31 Mar 2014 09:05:46 +0000 Surface explosions resulting from terrorist attacks will produce a hemispherical shock wave in the air, which, upon release, can affect five faces of the building which is in front of it. Given the fact that conventional buildings are usually exposed to such explosions, this study examined the effect of pressure to each face of a building on the responses of the structure and has compared different relevant scenarios. This study, which includes the following two steps, was conducted as a case study on earthquake resistant RC buildings, with the help of UFC guideline and using the software SAP2000. In the first step, responses of loading on each face were separately calculated so that they were compared with the responses from overall loading on all faces. The sensitivity of the responses and their ratio to the variables considered were evaluated in the second step. Accordingly, an outline was formed on the explosion hazards considered for these types of buildings. Farzad Sadeghi, Seyyed Reza Sarafrazi, and Ali Ghods Copyright © 2014 Farzad Sadeghi et al. All rights reserved. Structural Behavior of Precast Lightweight Foam Concrete Sandwich Panel with Double Shear Truss Connectors under Flexural Load Sun, 16 Mar 2014 07:21:56 +0000 This paper presents the structural behaviour of precast lightweight foam concrete sandwich panel (PFLP) under flexure, studied experimentally and theoretically. Four (4) full scale specimens with a double shear steel connector of 6 mm diameter and steel reinforcement of 9 mm diameter were cast and tested. The panel’s structural behavior was studied in the context of its ultimate flexure load, crack pattern, load-deflection profile, and efficiency of shear connectors. Results showed that the ultimate flexure load obtained from the experiment is influenced by the panel’s compressive strength and thickness. The crack pattern recorded in each panel showed the emergence of initial cracks at the midspan which later spread toward the left and right zones of the slab. The theoretical ultimate load for fully composite and noncomposite panels was obtained from the classical equations. All panel specimens were found to behave in a partially composite manner. Panels PLFP-3 and PLFP-4 with higher compressive strength and total thickness managed to obtain a higher degree of compositeness which is 30 and 32.6 percent, respectively. Noridah Mohamad, A. I. Khalil, A. A. Abdul Samad, and W. I. Goh Copyright © 2014 Noridah Mohamad et al. All rights reserved. Properties of Concrete at Elevated Temperatures Thu, 13 Mar 2014 07:06:38 +0000 Fire response of concrete structural members is dependent on the thermal, mechanical, and deformation properties of concrete. These properties vary significantly with temperature and also depend on the composition and characteristics of concrete batch mix as well as heating rate and other environmental conditions. In this chapter, the key characteristics of concrete are outlined. The various properties that influence fire resistance performance, together with the role of these properties on fire resistance, are discussed. The variation of thermal, mechanical, deformation, and spalling properties with temperature for different types of concrete are presented. Venkatesh Kodur Copyright © 2014 Venkatesh Kodur. All rights reserved. Effect of Dynamic Soil-Structure Interaction on Raft of Piled Raft Foundation of Chimneys Mon, 20 Jan 2014 12:35:19 +0000 This paper presents numerical analysis of soil-structure-interaction (SSI) of tall reinforced concrete chimneys with piled raft foundation subjected to El Centro ground motion (1940) using finite element method. Seismic analysis in time domain was performed on the basis of direct method of SSI on the three-dimensional SSI system. The chimney, foundation, and soil were assumed to be linearly elastic in the analysis. The stress resultants and settlement of raft of piled raft foundation were evaluated under different soil properties and different geometrical features of raft and chimney. Soil properties were selected based on the shear wave velocity corresponding to sand in the loose to dense range. Chimneys with different elevations of 100 m, 200 m, and 400 m were taken with a ratio of height to base diameter of chimney of 17. Raft of different thickness was considered to evaluate the effect of stiffness of foundation. Results were analysed to assess the significance of characteristic of the ground motion. It is found that the response in the raft depends on the different parameters of chimney, foundation, and soil. It is also found that the higher modes of SSI system are significant in determining the response in the raft. B. R. Jayalekshmi, S. V. Jisha, R. Shivashankar, and S. Soorya Narayana Copyright © 2014 B. R. Jayalekshmi et al. All rights reserved. Soil Water Retention Modeling Using Pedotransfer Functions Tue, 10 Dec 2013 11:24:43 +0000 The unsaturated hydraulic functions are key input data in numerical models of vadose zone processes. The direct measurement of soil moisture at different suction heads requires detailed analysis of soil samples with sophisticated instruments which can be replaced with the help of pedotransfer functions (PTFs) which are empirical relationships between the soil hydraulic properties and the more easily obtainable basic soil properties. The CalcPTF software has been used to compute the parameters of the most commonly used models of Brooks and Corey (BC) and Van Genuchten (VG) from PTFs for determination of soil water retention curves on seventeen sites in the commands of Benisagar and Rangawan reservoirs in Chhatarpur district (MP), India. The parameters of sixteen PTFs have been estimated and results have been compared with observed data using root mean square error (RMSE), coefficient of determination (R2), , and graphical representation. The PTF of BC model suggested by Rawls and Brakensiek, 1985 (BC-RB), has been found to be the best-fit PTF for sites 1, 2, 5, 6, 10, 11, 14, 15, and 17, where BC model by Saxton et al., 1986 (BC-SEL), can be used for modeling the soil moisture for sites 3, 4, 9, 12, and 16. It may be concluded that the PTF suggested by Rawls and Brakensiek, 1985 (BC-RB), or Saxton et al., 1986 (BC-SEL), can be used for computation of soil moisture retention curves in the region. R. K. Jaiswal, T. Thomas, R. V. Galkate, and Jaivir Tyagi Copyright © 2013 R. K. Jaiswal et al. All rights reserved. Fast Dynamic Control of Damaged Historical Buildings: A New Useful Approach for Structural Health Monitoring after an Earthquake Tue, 03 Dec 2013 18:45:24 +0000 The structures damage conditions assessment requires numerous precautions to ensure the safety of people during site visits and inspections. Among several methods providing useful information about the conservation status of the structures, dynamic monitoring techniques are suitable to retrieve the global behavior of the buildings. The anomalous features diagnosis of the structural dynamic response is an index of alterations of the material state and, in the worst cases, is related to the presence of damaged structural elements. This paper proposes the use of remote control systems for the structural evaluation of the damage state of buildings and describes the results achieved in an interesting application: the experimental dynamic analysis carried out on the inaccessible damaged bell tower of the Church of Santi Giacomo and Filippo in Mirandola (Italy). The study is based on observations performed using the IBIS-S ground-based radar interferometer to remotely measure the displacements of several elements of the building above 0.01 mm amplitude. This totally noninvasive and nondestructive approach has proved to be reliably implemented as a useful method to structural health monitoring procedures and especially for extensive and fast inspection analyses aiming at the first evaluation of the damage level and the soundness of slender buildings after earthquakes. Sergio Vincenzo Calcina, Luca Piroddi, and Gaetano Ranieri Copyright © 2013 Sergio Vincenzo Calcina et al. All rights reserved. Vibration Characteristics of Composite Footbridges under Various Human Running Loads Tue, 22 Oct 2013 08:35:14 +0000 Various types of human running dynamic loads are numerically studied and compared to assess vibration characteristics of the light and slender composite footbridges. Running, which is a common human activity, has been categorized with respect to its intensity into jogging, normal running, and sprinting. To explore the footbridge’s performance, the vibration responses are investigated through a series of analyses in terms of the peak accelerations and displacements. In the model verification, the acquired first natural frequency of structure has shown good agreement with the value reported in the literature. The structural performance of the slender composite footbridge is then evaluated with regard to the serviceability requirement given by the current design standards. It is generally found that the maximum acceleration of the composite footbridge due to the excitation of one person running varies under different running types because of diversities in the velocity and the step frequency. Furthermore, it is shown that the investigated structure provides sufficient human comfort against vibrations for all the examined three types of running loads. Faraz Sadeghi, Ahmad Kueh, Ali Bagheri Fard, and Nasim Aghili Copyright © 2013 Faraz Sadeghi et al. All rights reserved. A Conceptual Design Approach of Coupled Shear Walls Wed, 09 Oct 2013 15:26:42 +0000 Earthquake causes considerable damage to a large number of RCC high-rise buildings and tremendous loss of life. Therefore, designers and structural engineers should ensure to offer adequate earthquake resistant provisions with regard to planning, design, and detailing in high-rise buildings to withstand the effect of an earthquake and minimize disaster. As an earthquake resistant system, the use of coupled shear walls is one of the potential options in comparison with moment resistant frame (MRF) and shear wall frame combination systems in RCC high-rise buildings. Furthermore, it is reasonably well established that it is uneconomical to design a structure considering its linear behavior during earthquake. Hence, an alternative design philosophy needs to be evolved in the Indian context to consider the postyield behavior wherein the damage state is evaluated through deformation considerations. In the present context, therefore, performance-based seismic design (PBSD) has been considered to offer significantly improved solutions as compared to the conventional design based on linear response spectrum analysis. Dipendu Bhunia, Vipul Prakash, and Ashok D. Pandey Copyright © 2013 Dipendu Bhunia et al. All rights reserved. Liquefaction-Induced Lateral Deformations Computational Assessment during Tohoku Earthquake Mon, 05 Aug 2013 13:51:56 +0000 Liquefaction-induced lateral spreading during Tohoku earthquake resulted in significant damage, and disruption of functionality for structures and life. The paper aims at reproducing this on-site evidence presenting the state of the art about the most credited qualitative approach and comparing these methods with numerical computation. In this regard, finite element (FE) simulations are increasingly providing a versatile environment in order to assess economical and effective damage. In the study, several systematic three-dimensional FE computations have been conducted to numerically evaluate the effects in terms of liquefaction-induced lateral deformations. The analysis is performed in correspondence with Urayasu City, where the registered liquefaction consequences on residential buildings were wide if compared with the ordinary seismic shake. This study can be used both for post-earthquake evaluations and for pre-earthquake vulnerability predictions. Davide Forcellini, Fabio Della Bartola, and Angelo Marcello Tarantino Copyright © 2013 Davide Forcellini et al. All rights reserved. Poisson’s Theory for Analysis of Bending of Isotropic and Anisotropic Plates Sun, 14 Jul 2013 09:15:16 +0000 Sixteen-decade-old problem of Poisson-Kirchhoff’s boundary conditions paradox is resolved in the case of isotropic plates through a theory designated as “Poisson’s theory of plates in bending.” It is based on “assuming” zero transverse shear stresses instead of strains. Reactive (statically equivalent) transverse shear stresses are gradients of a function (in place of in-plane displacements as gradients of vertical deflection) so that reactive transverse stresses are independent of material constants in the preliminary solution. Equations governing in-plane displacements are independent of the vertical (transverse) deflection . Coupling of these equations with is the root cause for the boundary conditions paradox. Edge support condition on does not play any role in obtaining in-plane displacements. Normally, solutions to the displacements are obtained from governing equations based on the stationary property of relevant total potential and reactive transverse shear stresses are expressed in terms of these displacements. In the present study, a reverse process in obtaining preliminary solution is adapted in which reactive transverse stresses are determined first and displacements are obtained in terms of these stresses. Equations governing second-order corrections to preliminary solutions of bending of anisotropic plates are derived through application of an iterative method used earlier for the analysis of bending of isotropic plates. K. Vijayakumar Copyright © 2013 K. Vijayakumar. All rights reserved. Pulse Velocity Measurements in Fly Ash Blended Cementitious Systems Containing 43 Grade Cement Mon, 27 May 2013 15:13:51 +0000 Investigations on the different supplementary cementitious materials based on the hardening properties and the optimized dosage in cementitious systems find the right choice of pozzolanic material. It is essential to combine various additive/admixtures in concrete in proper proportions to maximize the benefits resulting in cost savings in construction. In the recent years, production technology and composition of hydraulic cements affect the setting and early age behavior of cementitious material. The addition of fly ash in cement is one viable technology to derive maximum benefits in terms of the economy and improved pozzolanic reaction. Ultrasonic pulse velocity testing is a feasible method for evaluating the hardening properties of cementitious materials. In this study, an attempt was made to derive the engineering basis for understanding the development of hardness during hydration of fly ash (FA) based cementitious systems. The tests conducted using pulse velocity technique proved to be an effective method for characterizing the early strength gain properties of different cementitious systems. V. M. Sounthararajan and A. Sivakumar Copyright © 2013 V. M. Sounthararajan and A. Sivakumar. All rights reserved. Modeling the Effect of Crude Oil Impacted Sand on the Properties of Concrete Using Artificial Neural Networks Tue, 21 May 2013 10:48:16 +0000 A network of the feedforward-type artificial neural networks (ANNs) was used to predict the compressive strength of concrete made from crude oil contaminated soil samples at 3, 7, 14, 28, 56, 84, and 168 days at different degrees of contamination of 2.5%, 5%, 10%, 15%, 20% and 25%. A total of 49 samples were used in the training, testing, and prediction phase of the modeling in the ratio 32 : 11 : 7. The TANH activation function was used and the maximum number of iterations was limited to 20,000 the model used a momentum of 0.6 and a learning rate of 0.031056. Twenty (20) different architectures were considered and the most suitable one was the 2-2-1. Statistical analysis of the output of the network was carried out and the correlation coefficient of the training and testing data is 0.9955712 and 0.980097. The result of the network has shown that the use of neural networks is effective in the prediction of the compressive strength of concrete made from crude oil impacted sand. W. O. Ajagbe, A. A. Ganiyu, M. O. Owoyele, and J. O. Labiran Copyright © 2013 W. O. Ajagbe et al. All rights reserved. A Numerical Model of the Wave-Induced Currents in the Turbulent Coastal Zone Wed, 08 May 2013 10:38:48 +0000 A numerical model is developed, validated and applied to the turbulent coastal currents. The currents are driven by the sea surface slope and the radiation stresses of water waves. They are resisted by friction due to turbulent eddies and sea bottom. The k-ε model is used to model the turbulent stresses. Five simultaneous nonlinear partial differential equations govern the depth-averaged dynamics in the surf zone. An implicit finite-difference scheme is used to obtain an accurate numerical solution of the resulting initial-boundary value problem. It is tested against the case of straight coast with uniform bottom slope and a protective jetty. To investigate the actual wave-induced currents, the model is applied to simulate the currents for three real case studies. Results show that the model could be used to compute currents caused by the constructing coastal protection measures and could predict the locations of accretion and scouring. O. Fahmy, K. M. Fassieh, and M. A. Zaki Copyright © 2013 O. Fahmy et al. All rights reserved. Bars under Torsional Loading: A Generalized Beam Theory Approach Thu, 21 Mar 2013 18:08:37 +0000 In this paper both the static and dynamic analyses of the geometrically linear or nonlinear, elastic or elastoplastic nonuniform torsion problems of bars of constant or variable arbitrary cross section are presented together with the corresponding research efforts and the conclusions drawn from examined cases with great practical interest. In the presented analyses, the bar is subjected to arbitrarily distributed or concentrated twisting and warping moments along its length, while its edges are supported by the most general torsional boundary conditions. For the dynamic problems, a distributed mass model system is employed taking into account the warping inertia. The analysis of the aforementioned problems is complete by presenting the evaluation of the torsion and warping constants of the bar, its displacement field, its stress resultants together with the torsional shear stresses and the warping normal and shear stresses at any internal point of the bar. Moreover, the construction of the stiffness matrix and the corresponding nodal load vector of a bar of arbitrary cross section taking into account warping effects are presented for the development of a beam element for static and dynamic analyses. Having in mind the disadvantages of the 3D FEM solutions, the importance of the presented beamlike analyses becomes more evident. Evangelos J. Sapountzakis Copyright © 2013 Evangelos J. Sapountzakis. All rights reserved. Flexible Pavement Performance in relation to In Situ Mechanistic and Volumetric Properties Using LTPP Data Tue, 12 Mar 2013 11:03:08 +0000 This research study focuses on the actual performance of the flexible pavements and its relationship with the in-situ mechanistic and volumetric properties. The data required for the study were obtained using the Long Term Pavement Performance database. Approximately, 116 flexible pavement sections throughout United States were analyzed and discussed. The results indicated that the temperature has a significant affect on the backcalculated modulus of the hot mix asphalt layer. However, no strong relationship was observed between the hot mix asphalt backcalculated modulus and in situ air voids. It was found that fatigue life was a function of tensile strain at the bottom of hot mix asphalt layer, peak surface deflection, hot mix asphalt air voids and maximum specific gravity, and ambient air temperature. Similar relationships between the rut life, mechanistic and volumetric properties were established for wet-freeze and wet-no-freeze climatic zones. The sensitivity analysis revealed that the rut performance in wet-no-freeze sections is mainly affected by higher base and roadbed compressive stresses and strains. On the other hand, the performances in wet-freeze sections are highly depended on roadbed compressive strain and modulus ratio of subbase to roadbed. Mohammad Jamal Khattak and Nagaraju Peddapati Copyright © 2013 Mohammad Jamal Khattak and Nagaraju Peddapati. All rights reserved. 3D FE Analysis of an Embankment Construction on GRSC and Proposal of a Design Method Thu, 07 Mar 2013 15:45:00 +0000 Stone column is often employed for strengthening of an embankment seated on deep soft clay. But in very soft clay having undrained shear strength less than or equal to 15 kPa, stone column may not derive adequate load carrying capacity and undergo large lateral deformation due to inadequate lateral confinement. In such circumstances, reinforcement to individual stone column by geosynthetics enhances load carrying capacity and reduces lateral deformation. This paper addresses parametric study on behaviour of embankment resting on Geosynthetic Reinforced Stone Column (GRSC) considering parameters such as stone column spacing to diameter ratio, deformation modulus of stone column material, geosynthetic stiffness, thickness of soft clay, and height of embankment by 3D numerical analysis. Finally, equation for Settlement Improvement Factor (SIF), defined as ratio between settlement of embankment without treatment and with geosynthetic reinforced stone column, is proposed that correlates with the major influence parameters such as stone column spacing to diameter ratio, deformation modulus of soft clay, and geosynthetic stiffness. Yogendra K. Tandel, Chandresh H. Solanki, and Atul K. Desai Copyright © 2013 Yogendra K. Tandel et al. All rights reserved. Infiltration Kinetics of Wetting in a Building Plaster and the Effect of Added Glass and Hemp Fibers Wed, 06 Mar 2013 15:00:10 +0000 Capillary rise is an important cause of deterioration for plaster in building. This phenomenon has been studied by the tensiometric experimental technique. Structural and hydric characteristics of plaster have been determined. Decane, a perfectly impregnate fluid, has been used to calculate the porous constant characteristic called and other structural parameters like pore radius and specific surface. Evaluation of the sensibility of plaster for water has been evaluated in a second time. The angle constant and the capillary moisture content have been determined. A comparison between results for plaster and composite plaster with fiber has been done. The addition of glass and hemp fiber does not have important effect on hydric properties (angle constant), but we have observed influence on structural charecteristics (pore radius, porosity, and degree of heterogeneity). Serge Gassita, Laurent Marmoret, Anne Perwuelz, and Hassen Beji Copyright © 2013 Serge Gassita et al. All rights reserved. Rutting Model for HMA Overlay Treatment of Composite Pavements Tue, 26 Feb 2013 08:23:41 +0000 Timely rehabilitation and preservation of pavement systems are imperative to maximize benefits in terms of driver’s comfort and safety. However, the effectiveness of any treatment largely depends on the time of treatment and triggers governed by treatment performance models. This paper presents the development of rutting model for overlay treatment of composite pavement in the State of Louisiana. Various factors affecting the rutting of overlay treatment were identified. Regression analysis was conducted, and rut prediction model is generated. In order to better predict the pavement service life, the existing condition of the pavement was also utilized through the model. The developed models provided a good agreement between the measured and predicted rut values. It was found that the predictions were significantly improved, when existing pavement condition was incorporated. The resulting rutting model could be used as a good pavement management tool for timely pavement maintenance and rehabilitation actions to maximize LADOTD benefits and driver’s comfort and safety. Mohammad Abdullah Nur, Mohammad Jamal Khattak, and Mohammad Reza-Ul-Karim Bhuyan Copyright © 2013 Mohammad Abdullah Nur et al. All rights reserved. Analysis of Fatigue and Fracture of Hot Mix Asphalt Mixtures Mon, 25 Feb 2013 13:21:28 +0000 An accurate assessment of the fatigue life of hot mix asphalt (HMA) mixtures depends on the criteria used in the fatigue analysis. In the past, various studies have been conducted on crack initiation and crack propagation of the HMA mixtures. Most of these studies were focused on the beam samples with or without a sawed crack at the bottom. This paper presents and discusses two different fatigue life criteria for two-dimensional problems represented by cylindrical samples. One criterion is based on the rate of accumulation of the tensile horizontal plastic deformation (HPD) as a function of the number of load repetitions. The second criterion is based on fracture mechanics, stress intensity factor, and the rate of crack growth with respect to the number of load repetitions. It was found that, because of three-dimensional nature of the crack growth in cylindrical samples, the Paris' law was violated. It is shown that the rate of crack growth criterion provides higher values of fatigue life relative to the rate of accumulation of HPD criterion. Although a trend could be established among the fatigue lives obtained by using the two criteria, it was found that the fatigue lives obtained from the rate of accumulation of HPD were consistent and based on the actual measurement of HPD for HMA mixtures. Mohammad Jamal Khattak and Gilbert Y. Baladi Copyright © 2013 Mohammad Jamal Khattak and Gilbert Y. Baladi. All rights reserved. Finite Element Models for Thin-Walled Steel Member Connections Sun, 30 Dec 2012 08:59:58 +0000 The behavior of connections associated with the thin-walled steel members is distinctly different from that of hot-rolled steel connections, primarily because of the flexibility of the plates. A typical cold-formed steel structural construction may entail such numerous connections. The incorporation of large number of such connections in an analysis and design, using sophisticated finite element models, is very tedious and time consuming and may present computational difficulties. The objective of this investigation is to create simplified, yet reasonably accurate, finite element models for the analysis of screw connections and bolted connections associated with thin-walled sheet steel construction. The primary plates were modeled using quadrilateral shell elements, and nonlinear stress-strain relationship was established based on experiments. The fasteners were modeled as an elastic medium. The plate-to-plate interactions and the plate-to-screw interactions were incorporated using contact elements. The study considered two finite element models of different complexity. The performance of these models was established through comparisons with the corresponding experimental results. The finite element analysis results exhibit reasonably good agreement with the test results in terms of connection stiffness, screw tilting, end curling, and average longitudinal strain. The recommended simplified connection model is capable of reproducing the behavior of sheet steel screw and bolt connections. Sandesh R. Acharya and K. S. Sivakumaran Copyright © 2012 Sandesh R. Acharya and K. S. Sivakumaran. All rights reserved. Some Remarks on the Seismic Demand Estimation in the Context of Vulnerability Assessment of Large Steel Storage Tank Facilities Thu, 27 Dec 2012 17:22:36 +0000 The seismic behavior of steel tanks is relevant in industrial risk assessment because collapse of these structures may trigger other catastrophic phenomena due to loss of containment. Therefore, seismic assessment should be focused on for leakage-based limit states. From a seismic structural perspective, damages suffered by tanks are generally related to large axial compressive stresses, which can induce shell buckling near the base and large displacements of unanchored structures resulting in the detachment of piping. This paper approaches the analysis of seismic response of sliding, nonuplifting, unanchored tanks subject to seismic actions. Simplified methods for dynamic analysis and seismic demand estimation in terms of base displacement and compressive shell stress are analyzed. In particular, attention is focussed on some computational issues related to the solution of the dynamic problem and on the extension of the incremental dynamic analysis (IDA) technique to storage tanks. Antonio Di Carluccio and Giovanni Fabbrocino Copyright © 2012 Antonio Di Carluccio and Giovanni Fabbrocino. All rights reserved. Effects of Hybrid Polypropylene-Steel Fiber Addition on Some Hardened Properties of Lightweight Concrete with Pumice Breccia Aggregate Sun, 16 Dec 2012 08:28:25 +0000 Lightweight concrete application in construction field is growing rapidly in these recent years due to its advantages over ordinary concrete. In this paper, pumice breccia which can be found abundantly in Indonesia is proposed to be utilized as the coarse aggregate. In spite of its benefits, lightweight concrete exhibits more brittle characteristics and lower tensile strength compared with normal concrete. On the other hand, fiber addition into concrete has become widely used to improve its tensile properties. Furthermore, the utilization of hybrid fiber in a suitable combination may potentially improve the mechanical properties of concrete. This paper experimentally examines the effects of hybrid polypropylene-steel fiber addition on some hardened properties of pumice breccia aggregate lightweight concrete. Five groups of test specimens with fixed volume fraction of polypropylene fiber combined with different amounts of steel fiber were added in concrete to investigate the density, compressive strength, modulus of elasticity, splitting tensile strength, and the modulus of rupture of the concrete mixtures. Test results indicate that hybrid fiber addition leads to significant improvement to the compressive strength, modulus of elasticity, splitting tensile strength, and the modulus of rupture of the pumice breccia lightweight aggregate concrete and meet the specification for structural purposes. Slamet Widodo, Iman Satyarno, and Sri Tudjono Copyright © 2012 Slamet Widodo et al. All rights reserved. Performance Updating of Concrete Structures Using Proactive Health Monitoring: A Systems Approach Mon, 10 Dec 2012 11:48:12 +0000 Uncertainties in predictive models for concrete structures performance can influence adversely the timing of management activities. A methodology has been developed that uses data obtained through proactive health monitoring to increase the confidence in predicted performance by reducing the associated uncertainties. Due to temporal and spatial variations associated with climatic changes, exposure conditions, workmanship, and concrete quality, the actual performance could vary at different locations of the member. In this respect, the use of multiple sensors may be beneficial, notwithstanding cost and other constraints. Two distinct cases are identified for which an updating methodology based on data from multiple sensors needs to be developed. In the first case the interest lies in improving the performance prediction for an entire member (or a structure) incorporating spatial and temporal effects. For this purpose, the member is divided into small zones with the assumption that a sensor can be located in each zone. In the second case, the objective is to minimise uncertainties in performance prediction, or to increase the redundancy of health monitoring systems, at critical locations. The development of updating methodologies for the above-mentioned scenarios is described in this paper. Its implications on the management activities, for example, establishing the timing of principal inspections, are evaluated and discussed. M. Imran Rafiq Copyright © 2012 M. Imran Rafiq. All rights reserved. Manufacturing Light Concrete with PET Aggregate Sun, 09 Dec 2012 10:01:29 +0000 The manufacture of concrete using a polymer instead of a stony coarse aggregate known as gravel is presented. Polyethylene terephthalate (PET) is the polymer used, recycling soft drink containers with sufficient tenacity. PET is a material commonly used by engineers as a structural element, not as an aggregate. The research work revealed that PET aggregate produces good quality mixtures with lower volumetric weight but mechanical behavior similar to that of natural concrete with adequate granulometry. The water/cement (W/C) ratio is lower for light concretes than for natural concrete. Regarding stress and Flexural strength, it was found that for 300 kg/cm3 and higher cement consumption, which may be due to the fact that at low W/C ratios, the coarse aggregate behavior prevails, while at high W/C ratios, the paste behavior prevails. This leads us to the fact that PET aggregate is best applied on low cement consumption up to 300 kg/m3, since expensive mixtures for higher consumption may result from use on higher consumption. Modulus of elasticity for light concretes is lower than for natural concretes. Deformations are lower for light concretes than for natural concretes. A feature of using PET to substitute coarse aggregate is volumetric weight, since it is 68.88% lighter than concrete with natural aggregates. Francisco Casanova-del-Angel and Jorge Luis Vázquez-Ruiz Copyright © 2012 Francisco Casanova-del-Angel and Jorge Luis Vázquez-Ruiz. All rights reserved. Some Studies on Prestressed Reinforced Granular Beds Overlying Weak Soil Mon, 26 Nov 2012 14:26:17 +0000 This paper mainly investigates, from a series of laboratory scale bearing capacity tests carried out on a model square footing, the improvement in bearing capacity and reduction in settlement of a geonet reinforced granular bed (RGB) overlying weak soil due to prestressing the reinforcement. The parameters are the strength of the underlying weak soil, thickness of the granular bed, and magnitude and direction of prestressing force. The settlements at the interface are also measured. The addition of prestress to geonet reinforcement results in significant improvement in the load carrying capacity and settlement response of the prestressed geonet RGB. Improvement in bearing capacity is found to be more with biaxial prestressing than with uniaxial prestressing. Experimental results are also used to validate a proposed numerical model. The BCR (bearing capacity ratio) values predicted from this model are found to be in good agreement with the experimentally obtained BCR values. Finite element analyses are also carried out using the programme PLAXIS, to study the effect of prestressing the reinforcement. Results obtained from finite element analyses are also found to be in good agreement with the experimental results. J. Jayamohan and R. Shivashankar Copyright © 2012 J. Jayamohan and R. Shivashankar. All rights reserved. Rehabilitation of Shear-Damaged Reinforced Concrete Beams Using Self-Compacting Concrete Jacketing Wed, 14 Nov 2012 10:04:18 +0000 The application of a reinforced self-compacting concrete jacket for the structural rehabilitation of shear damaged reinforced concrete beams is experimentally investigated. Five beams were constructed and subjected to monotonic loading in order to exhibit shear failure. The damaged specimens were restored using relatively thin reinforced jackets and retested by the same four-point bending loading. The self-compacting concrete jacket applied, encasing the bottom width and both vertical sides of the initially tested beams (U-formed jacketing), has a small thickness (25 mm) and includes small (5) steel bars and U-formed stirrups. Test results and comparisons between the experimental behaviour of the beams indicated that the examined jacketing technique is a reliable rehabilitation method since the capacity of the retrofitted beams was fully restored or ameliorated with respect to the initial specimens. Discussion of the ability of the applied jacket to enhance the overall structural performance of the examined beams and, potentially, to alter their failure mode to a more ductile one is also included. Calculations of the flexural and shear strength of the tested beams and evaluation of the monolithic factors for the capacity at yield and at ultimate of the jacketed beams were also performed and are commented on. Constantin E. Chalioris and Constantin N. Pourzitidis Copyright © 2012 Constantin E. Chalioris and Constantin N. Pourzitidis. All rights reserved. Analytical Solution for the Pressure Oscillations Caused by Trains of Solitary Waves within Confined Coastal Aquifers Wed, 14 Nov 2012 09:57:14 +0000 An exact analytical solution is proposed for the pressure oscillations within deep coastal aquifers under the action of tidal level time-variations attributable to train of solitary waves originating off-shore. The purpose of the study is to relate the characteristics of the response of the system to amplitude, steepness, and asymmetry of the soliciting waves, in order to assess its vulnerability to events like violent seaquakes and consequent tsunamis. The time needed by the forcing perturbations, approximated by consecutive triangular impulses, to attain their maximum is assumed to be always smaller than the aquifer diffusive time, in order to evaluate the consequences of the sudden raise of water level along the shoreline, typical of those quite extreme phenomena. Marilena Pannone Copyright © 2012 Marilena Pannone. All rights reserved. Designing Laterally Loaded RC Stiffened Plates: Energy Balance Concept Wed, 14 Nov 2012 09:49:42 +0000 Plates are most widely used structural systems to build and/or enclose the space along with some other structural elements, namely, walls, columns, and so forth. in any building. Design procedure for proportioning plates has been recommended in various design codes based upon empirical relations and some factors found on basis of the results of an extensive series of tests and well-established performance record of various plate/slab systems constructed in the past. These guidelines have a number of inherent limitations in the form of assumptions, thereby, forcing the designers to proportion the plate system within the domain of these limitations. A procedure to design reinforced concrete stiffened-plates is presented using an energy-balance concept and it can be used for both a single panel as well as multipanel rectangular plate system with any value of aspect ratio, number of panels, and orthotropy. To validate the results from the proposed design procedure, these are compared with the results from well-established literature on the plate analysis and are found to be in good agreement. Working procedure is illustrated with the help of design examples. Harvinder Singh Copyright © 2012 Harvinder Singh. All rights reserved.