Field Of Structural Engineering Research Articles

RETROFITTING OF REINFORCED CONCRETE BEAMS USING FIBRE REINFORCED POLYMER (FRP) COMPOSITES – A REVIEW

Rehabilitation and strengthening of old structures using advanced materials is a contemporary research in the field of Structural Engineering. During past two decades, much research has been carried out on shear and flexural strengthening of reinforced concrete beams using different types of fibre reinforced polymers and adhesives. Strengthening of old structures is necessary to obtain an expected life span. Life span of Reinforced Concrete (RC) structures may be reduced due to many reasons, such as deterioration of concrete and development of surface cracks due to ingress of chemical agents, improper design and unexpected external lateral loads such as wind or seismic forces acting on a structure, which are also the reasons for failure of structural members. The superior properties of polymer composite materials like high corrosion resistance, high strength, high stiffness, excellent fatigue performance and good resistance to chemical attack etc., has motivated the researchers and practicing engineers to use the polymer composites in the field of rehabilitation of structures. This paper reviews fourteen articles on rehabilitation of reinforced concrete (RC) beams. The paper reviews the different properties of Glass Fibre Reinforced Polymer (GFRP) and Carbon Fibre Reinforced Polymer (CFRP) composites and adhesives, influence of dimensions of beams and loading rate causing failure. The paper proposes an enhanced retrofitting technique for flexural members and to develop a new mathematical model.

Laboratory study of soil-CFRP interaction using pull-out test

Soil is a material which is weak in tension; however, different materials such as geotextiles are used to address this inadequacy. In recent years more than one million square metres of geotextiles were used for reinforcing soil. Nevertheless, there are several significant problems associated with geotextiles, such as creep, low modulus of elasticity and susceptibility to aggressive environments. Carbon fibre reinforced polymer (CFRP) was introduced over two decades ago to the field of structural engineering and it can also be used in geotechnical engineering. CFRP has all the benefits associated with geotextiles and it boasts a higher strength, higher modulus, no creep and reliability in aggressive environments. In this investigation, the interface properties of CFRP-sand and fine sand were investigated using the pull-out test. The pull-out test device was designed and assembled using a triaxial loading device and a direct shear device. In the pull-out test, the normal force applied by the triaxial loading and pull-out force is applied by a direct shear device. CFRP samples were prepared in the lab. Precast and cast-in-place samples were tested. The pull-out force and corresponding displacements of each of the materials were recorded and compared.

A paperless course on structural engineering programming: investing in educational technology in the times of the Greek financial recession

This paper presents the structure of an undergraduate course entitled ‘programming techniques and the use of specialised software in structural engineering’ which is offered to the fifth (final) year students of the Civil Engineering Department of Aristotle University Thessaloniki in Greece. The aim of this course is to demonstrate the use of new information technologies in the field of structural engineering and to teach modern programming and finite element simulation techniques that the students can in turn apply in both research and everyday design of structures. The course also focuses on the physical interpretation of structural engineering problems, in a way that the students become familiar with the concept of computational tools without losing perspective from the engineering problem studied. For this purpose, a wide variety of structural engineering problems are studied in class, involving structural statics, dynamics, earthquake engineering, design of reinforced concrete and steel structures as well as data and information management. The main novelty of the course is that it is taught and examined solely in the computer laboratory ensuring that each student can accomplish the prescribed ‘hands-on’ training on a dedicated computer, strictly on a 1:1 student over hardware ratio. Significant effort has also been put so that modern educational techniques and tools are utilised to offer the course in an essentially paperless mode. This involves electronic educational material, video tutorials, student information in real time and exams given and assessed electronically through an ad hoc developed, personalised, electronic system. The positive feedback received from the students reveals that the concept of a paperless course is not only applicable in real academic conditions but is also a promising approach that significantly increases student productivity and engagement. The question, however, is whether such an investment in educational technology is indeed timely during economic recession, where the academic priorities are rapidly changing. In the light of this unfavourable and unstable financial environment, a critical overview of the strengths, the weaknesses, the opportunities and the threats of this effort is presented herein, hopefully contributing to the discussion on the future of higher education in the time of crisis.

Study on System Reliability of Gravity Dam

Reliability analysis is an emerging field of structural engineering which is very significant in structures of great importance like arch dams, large concrete dams etc. The research objective is to design and construct a new method for the analysis of the system reliability of dam. The failure paths are searched out after failure mode and composite performance functions are set. Bayes formula and Cauchy-Schwarz Inequality are adopted to deduce the upper limit of failure probabilities in some failure modes that can obtain the failure probability of system of dam. A test example is given to verify this method. Compared with other conventional algorithm, this method has the strong points: more failure paths are considered and more safety methods are used to estimate the system reliability of dam.

Assessing Cracks in Reinforced Concrete Structure Using Acoustic Emission

Acoustic emission (AE) is an important nondestructive evaluation (NDE) technique used in the field of structural engineering. In this study AE technique with a new approach was employed to investigate the process of fracture formation in reinforced concrete structure. A number of reinforced concrete (RC) frames were tested under cyclic load and were simultaneously monitored using AE. The AE test data using intensity analysis method were analyzed. This is based on calculating two values called the historic index (HI) and severity (Sr). The results showed that HI and Sr increase with increasing of loading cycle and trend of HI and Sr showed that these parameters are able to indicate the levels of damage. Also, the results indicated that AE can be considered as a viable method to investigate the process of fracture formation in reinforced concrete structure.

A Note From the Guest Editor

The Action COST TU0904 enables researchers in different specialisms and countries to understand better the recent advances in research in parallel fields, as well as their limitations, so that they see their own research in context and identify opportunities. Practitioners, including fire engineers and building/fire control authorities, benefit from exposure to research findings, discussion with the research community and the sharing of best practice. Their input makes researchers aware of real-world constraints, and requirements for new research. The Action divides its membership loosely into three themed Working Groups, although clearly its overall mission of promoting integration means that these groups must interact on many of the key activities. The Working Groups are: WG1 Fire Behaviour and Life Safety focuses on the behaviour and effects of fire in buildings, combining this research-based knowledge with the most effective means of protecting human life against the occurrence of fire in the built environment. This includes active measures in fire-fighting with the effects of building form on the inherent risk to inhabitants. WG2 Structural safety covers the response of different building types to fires and the rapidly developing research field of structural fire engineering, including new materials and technologies and passive protection measures.Crucial problems of structural fire engineering concern change of use of buildings and the current imperatives of sustainability, energy saving and protection of the environment after fire. WG3 Integrated Design brings together design, practice and research across the disciplines of fire in the built environment. In structural design this includes integration of fire resistance with all the other functional requirements of a building, from concept onwards, rather than simply adding fire protection after all other processes are complete. Active input from practitioners, regulators and fire-fighters through this group is vital to the success of the Action. The Action started in March 2010, and now has 22 nations of the EU and New Zealand participants. Its first deliverable, State of the Art Report attempts to bring together the current state of research, mainly in the participating countries but set into the context of knowledge world-wide. The deliverable, Case Studies presents current practice and accumulated knowledge in fire engineering.The authors, experts of the Action, are trying to include on the selected fire engineering applications clear explanations of the decision processes, the scientific assumptions and the practical constraints, as well as how different aspects of fire engineering are integrated. The deliverable, Fire Brigade Reports and Investigations consists of contribution to organisation of national fire and rescue arrangements in different EU, of contribution to comparability of national statistics and recommendations for questions to be included in standardised national fire fighters reports, and of lessons learned from the particular disasters. The current activity of Actionis focussed to Benchmark studies, contribution to Eurocodes backgrounds and Educational dimension in area of structural fire design. The papers in this issue allowed experts in Action to inform about its research findings in Proceedings of Action Conference 29 April 2011 outside the Action as well.

Special Issue on Dynamics and Analysis of Large-Scale Structures

With this special issue, the ASCE Engineering Mechanics Institute wishes to recognize the contributions and accomplishments of the late Professor AhmedM. Abdel-Ghaffar to the field of structural and earthquake engineering. It is a tribute to his memory by his students, colleagues, and friends who were fortunate to cross paths with him during his outstanding career. We all share with him the passion and love for long-span bridges and dams and we feel that the best way to commemorate him is through our work. With an undergraduate degree from Cairo University and a Ph.D. from Caltech, Ahmed did seminal work on dynamics and identification of long-span bridges and dams during his academic career at the University of Illinois, Princeton University, and finally at the University of Southern California. He was a pioneer for his time: he was among the first engineers to recognize the importance of monitoring structural vibrations and to use them to learn more about the structural conditions, planting the seeds forwhat would become, in modern times, structural health monitoring. He was among the first to understand the importance of nonlinear dynamics andmechanics when dealing with long, slender structures or with complex materials such as soil. For his students, he was always an example to emulate: his enthusiasm in his work, in both research and teaching, instilled in many of us a passion for academia that has changed our lives. For his colleagues, Ahmed was an unlimited source of ideas, never afraid to try new directions and always ready for new challenges. Ahmed was a scholar in the true sense of the word.

Effects of experimental learning – outcomes of an empirical study in the vocational field of structural engineering

Pedagogic approaches to TVET offer a limited range of teaching strategies which make use of experimental learning.Thus experiments were developed for teachers of structural engineering and timber processing technologies and were subject to empirical evaluation by a researcher at the Otto-von-Guericke-University Magdeburg and Kassel University. This paper summarises the outcomes of the research and the empirical evaluation.The results of the study confirm that experimental training has a positive influence on learning achievement. In particular, it can be inferred that experimentally designed training is particularly supportive for the development of procedural knowledge.

Thermal and mechanical characteristics of cement nanocomposites

AbstractWidespread applications and advantages of different types of composite materials have drawn researchers’ attention toward the science and technology of composites. Among these materials, cementitious composites have a special place, as they have many applications in various fields of structural and civil engineering. Due to the importance of cementitious composites and their behavior, investigation of their properties is of great importance. Thus in the present study, thermal and mechanical properties of the self-compacting cementitious composites containing different fractions of nano TiO2 have been investigated. Mechanical properties were assessed through compressive, split tensile and flexural tests. The thermal properties were assessed through thermogravimetric analysis (TGA) and conduction calorimetry tests. Accelerated peak appearance in conduction calorimetry tests and more weight loss in thermogravimetric analysis could indicate that TiO2 nanoparticles could lead to strength development at earlier ages and improve the properties of the self-compacting cementitious composites.

Study of Dynamic Behavior of Multilayered Clamped Composite Skewed Hypar Shell Roofs under Impact Load

With advancement in the field of structural engineering, hunt for smarter materials has channelised the research towards the application of composite material. It is the high specific weight and specific stiffness of this material that have drawn the interest of different industrial sectors. Civil engineers also picked up composites to use it as a roofing material. Laminated composite shells, which can cover large column-free area and reduces dead weight of structure, show vulnerability under sudden impact due to their low transverse shear resistances. This study utilises finite element tool to investigate the dynamic response of a multilayered laminated composite hypar shells for fully clamped boundary condition. This class of shells is unique in a sense that the curvature has only the radius of cross curvature and these shells do not admit easy closed form solution particularly when the boundary conditions are complicated. Contact behavior of impactor and impacted mass has been modeled by modified Hertzian contact law and time-dependent equations are solved using Newmark’s time integration technique. Basic aim is to analyse the shell for symmetrically placed multilayered angle and cross ply lamination under different impact velocities.

A uniform methodology to establish test parameters for watertightness testing: Part I: A critical review

Many of the standards and codes related to watertightness of building components in use today have a long history and in most cases their roots were conceived decades ago. Irrespective of the broad spectrum of research on wind loads, rainfall and wind driven rain (WDR) intensity, little information is available concerning the scientific basis for watertightness test methods or performance criteria. This paper provides an overview of existing methodologies to establish test conditions and a critical review of calculation methods for wind and WDR loads on buildings, from the viewpoint of establishing test parameters for watertightness testing. The operative standard in the field of structural engineering is extended with a gust model to calculate wind loads for varying configurations, return periods and gust lengths, and model implications are discussed. A state-of-the-art on intensity–duration–frequency curves of horizontal rainfall intensity is given, and a new approach to accommodate conflicting models is presented. Furthermore, based on recent advances in WDR research, an adapted semi-empirical model is suggested to calculate extreme WDR intensities on building façades. For two locations boundary conditions for watertightness testing were calculated based on datasets extending over 10 years of 10-min averaged values. Finally, constraints and challenges in extreme value analysis in respect to cut-off values, fitting algorithms, goodness-of-fit (GOF) criteria and co-occurrence of rain and wind are discussed.

A Comparative Experimental Investigation of 3D Angle-Interlock Woven Composite between Quasi-Static Tension and Three-Point Bending Loading Conditions

As one new kind of 3D textile structural composite which has a strong potential in the application field of structural engineering, the mechanical behavior of 3D angle-interlock woven composite (3DAWC) needs to be extensively investigated. In this paper, a comparative experimental analysis of 3DAWC between quasi-static tension and three-point bending loading conditions were described, which has not been well studied so far. To evaluate the mechanical properties of the 3DAWC, the stress-strain/deflection curves were obtained under quasi-static tension and three-point bending loading, respectively. Furthermore, the Young’s modulus and peak values in stress were also compared. All of these results show that the 3DAWC has good integral performance.

Recent Lessons Learned in Structural Fire Engineering for Composite Steel Structures

The knowledge in the field of structural fire engineering has been greatly advanced through assessment of a number of real fires (WTC, Torre Windsor, Broadgate, etc.) and, especially, by the Cardington series of full scale structural fire tests. This knowledge has been used to validate and verify the use of computational finite element models that have expanded the range of structures that can be investigated under severe fire exposure. This paper presents a selection of key lessons learned by the authors through the assessment of structures in fire for real commercial building projects. The key areas of sensitivity that have been encountered are described and a discussion of each point presented. The paper is aimed at describing potential weaknesses that have been observed in the commercial work of the authors, often driven by the requirements for efficient ambient structural design. The paper concludes with some suggested advice for structural engineers aimed at increasing the general robustness of building structures. This is based on designing out as far as possible in the ambient design of a structure the potential weaknesses identified in past project work.

순차적 크리깅 메타모델의 민감도 검증법

메타모델은 설계 프레임워크 안에서 높은 효율성과 우수한 예측 능력, 타 프로그램과 쉬운 연동성때문에 공학분야에서 지난 10 년간 최적설계 기법들과 함께 발전해왔다. 메타모델을 구성하기 위해서는 실험계획법, 메타모델링 기법, 검증법과 같은 절차가 요구된다. 검증법은 메타모델의 정확성을 판단하기 때문에 순차적 크리깅 메타모델에서 정확한 크리깅 메타모델을 구성하기 위한 표본점의 개수를 결정한다. 크리깅 메타모델과 같은 보간모델은 표본점에서의 응답을 항상 지나기 때문에 기존 방법으로 메타모델의 정확성을 판단하기 위해서는 추가적인 해석이나 메타모델의 재구성이 요구된다. 본 연구에서는 이러한 추가적인 해석과 메타모델의 재구성을 요구하지 않는 메타모델의 해석적 민감도를 이용하는 민감도 검증법을 제안한다. 14 개의 2 차원 수학예제와 공학예제를 이용하여 이 방법의 타당성을 검증한다.

Monotonic Behaviors of Steel Frames with Sandwich Composite Panel Infills: Theoretical and Numerical

Abstract: Analysis of infilled frames is one of the most complicated problems in the structural engineering field. This complication is mainly attributed to the existence of the variety and complex of the infills and the difficulty in modeling the infill-frames interaction. In the present paper, with the aim to study the integral behavior of the single-story single-bay steel frames with sandwich composite panel infills, a proper computational model (the panel is simplified into an equivalent pin-jointed diagonal strut) is proposed. In the theoretical study, both of the panels and steel frames are assumed to be in the linear elastic state for simplicity’s sake, and then the cross-section area of the equivalent strut is obtained by imposing the initial lateral stiffness of actual structure equal to that of simplified model. As a support of the discussion, several numerical models under monotonic lateral loadings are performed by software ABAQUS, in order to verify the theoretical analysis. Finally, results from theoretical study and numerical modeling are compared, which give a satisfactory correlation between them.

Buckling instabilities of elastically connected Timoshenko beams on an elastic layer subjected to axial forces

We study the buckling instability of a system of three simply supported elastic Timoshenko beams, joined together by Winkler elastic layers, and each subjected to the same compressive axial load. The model of the Timoshenko beam includes the effects of axial loading, shear deformation, and rotary inertia. Explicit analytical expressions are derived for the critical buckling load of single, double, and triplebeam systems. It can be observed from these expressions that the critical buckling load depends on the Winkler elastic layer stiffness modulus K , and that the instability of the system increases with an increase in the numbers of beams and elastic layers. These results are of considerable practical interest and have wide application in engineering practice. Vibration and buckling problems of beams and beam-columns on elastic layers occupy an important place in many fields of structural and layer engineering, occurring often in mechanical and civil engineering applications. Their solution demands modeling of the mechanical behavior of the beam, the mechanical behavior of the soil, and the form of the interaction between the beam and the soil. As far as the beam is concerned, most engineering analyses are based on classical Bernoulli‐Euler beam theory, in which straight lines or planes normal to the neutral beam axis remain straight and normal after deformation. This theory thus neglects the effect of transverse shear deformations, a condition that holds only in the case of slender beams. To confront this problem, the well-known Timoshenko beam model, in which the effect of transverse shear deflections is considered, can be used. Matsunaga [1996] studied the buckling instabilities of a simply supported thick elastic beam subjected to axial stresses. Taking into account the effects of shear deformations and thickness changes, the buckling loads and buckling displacement modes of thick beams were obtained. Based on the power series expansion of displacement components, a set of fundamental equations of a one-dimensional higherorder beam theory was derived through the principle of virtual displacement. Several sets of truncated approximate theories were applied to solve the eigenvalue problems for a thick beam. The convergence properties of the buckling loads of a simply supported thick beam were examined in detail and comparison of the results with previously published ones was made.

Toward a probabilistic acoustic emission source location algorithm: A Bayesian approach

Acoustic emissions (AE) are stress waves initiated by sudden strain releases within a solid body. These can be caused by internal mechanisms such as crack opening or propagation, crushing, or rubbing of crack surfaces. One application for the AE technique in the field of Structural Engineering is Structural Health Monitoring (SHM). With piezo-electric sensors mounted to the surface of the structure, stress waves can be detected, recorded, and stored for later analysis. An important step in quantitative AE analysis is the estimation of the stress wave source locations. Commonly, source location results are presented in a rather deterministic manner as spatial and temporal points, excluding information about uncertainties and errors. Due to variability in the material properties and uncertainty in the mathematical model, measures of uncertainty are needed beyond best-fit point solutions for source locations. This paper introduces a novel holistic framework for the development of a probabilistic source location algorithm. Bayesian analysis methods with Markov Chain Monte Carlo (MCMC) simulation are employed where all source location parameters are described with posterior probability density functions (PDFs). The proposed methodology is applied to an example employing data collected from a realistic section of a reinforced concrete bridge column. The selected approach is general and has the advantage that it can be extended and refined efficiently. Results are discussed and future steps to improve the algorithm are suggested.

The Research Status and Prospect of Passive Energy Dissipation Technology in Fields of Structural Engineering

This paper generalizes the research status of passive energy dissipation technology in the field of Structural Engineering. Many achievements has been gotten since its emergence, including the manufacture of dampers, the experimental research and control effect analysis for energy dissipation systems, as well as the studies on its optimal design theory, which plays an important role in protecting people's life safety. However, the current design idea mainly focuses on the security, thus the energy dissipation structures will still suffer great economic losses even in moderate earthquakes. As a result, it is quite necessary to introduce the performance-based seismic design idea to study the design theory for passive energy dissipation. This paper has detailed three key problems in performance-based design of passive energy dissipation and put forward some strategy. Finally, it marks out that to study the performance-based design theory in passive energy dissipation system is of great significance in promoting the sustainable development of society.

Seismic evaluation of soil–foundation–superstructure system considering geometry and material nonlinearities of both soils and structures

In this paper, in order to increase the accuracy of numerical simulations using finite element methods related to soil–structure interaction problems, the influence of the geometric and material nonlinearities of structures was carefully investigated. By introducing proper models dealing with the geometric and material nonlinearities of structures, the authors have proposed a numerical method for the modeling of the nonlinearity of soils that have been carefully investigated in past research, and also for the modeling of structures based on finite deformation schemes. The accuracy of the numerical analysis related to the structures was firstly verified with an Abaqus (2008) calculation. The calculation was conducted with a program named DBLEAVES (Ye, 2007, 2011). Furthermore, 2D soil–water coupled dynamic analyses, in the finite deformation schemes of both soils and structures, were conducted on a soil-group pile foundation–superstructure system to investigate the seismic behavior of an elevated bridge during a major earthquake, in which strong nonlinear behavior of geometry and material are expected for both the soils and the structures. The applicability of the proposed numerical method to soil–structure interaction problems encountered in many fields of geotechnical and structural engineering was carefully checked. The main purpose of the research is to propose a numerical method by which it is possible to describe the soil–structure interaction problems with a level of accuracy that can satisfy the needs of both the geotechnical and structural engineering fields.

Displacement Measurement of Bending Tests Using Digital Image Analysis Method

Over the last few years due to sharp increase in experimental investigations in the field of structural engineering, the necessity for reliable and precise deformation measurement is felt more than ever. The most common experimental test in the field of structural engineering is bending test in which beam's deformation is evaluated in order to calculate other structural parameters. One of the most usual techniques for obtaining beam's deformation is utilizing Linear Variable Differential Transformer (LVDT) sensors. However, non-mechanical procedures for displacement measurement have shown much interest between researchers. Photogrammetry, Digital Image Correlation (DIC) method and Particle Image Velocimetry (PIV) are some of the new image-based methods for displacement measurement. Due to the advantages of PIV method in the field of experimental fluid mechanics and Geotechnics, the current study has been focused on the performance of PIV method for displacement measurement of bending test in structural engineering. To reach the aforementioned goal, one steel I-beam was subjected to four-point flexural loading and the load-displacement curve was plotted using PIV method. The experimental results obtained from the PIV method showed excellent agreement with LVDT's data. It is concluded that due to the lower cost and potential of obtaining whole displacement field on common bending tests, PIV method could be widely used as an alternative to conventional measurement techniques in structural engineering. Over the last few years due to extreme increase in experimental investigations in the field of structural engineering, the necessity for accurate deformation measurement is felt more than ever. It is obvious that further calculations could be seriously affected by accuracy of the evaluated displacement fields. Bending test is the most common test in the field of structural engineering in which beam's deformation should be evaluated in order to calculate any other structural parameters. Utilizing Linear Variable Differential Transformer (LVDT) is a primitive technique for obtaining deformation of bending tests. Although there are certain benefits of LVDTs such as high accuracy and simple installation, there are also some disadvantages such as high cost, inability to obtain the whole displacement field and extra charges for data acquisition. Photogrammetry is another technique which is applied to