Structural Dynamics

Reinforced Concrete (R/C) buildings with masonry infills are amongst the most common structural systems in many countries with regions of high seismicity. The infill walls are usually considered as non-structural elements and, thus, are not taken into account in analytical models. However, numerous researches have shown that they can significantly affect the seismic response of the structures. Moreover, historical earthquakes have shown that successive seismic events may occur in regions of high seismicity. Such a sequence of earthquakes has the potential to increase the damage level of the structures, since any rehabilitation between the successive ground motions is practically impossible due to lack of time. The aim of the present study is to examine the role of masonry infills on the damage response of 3D R/C buildings with various structural systems subjected to seismic sequences. For the purposes of the above investigation a comprehensive assessment is conducted using 54 3-dimensional R/C buildings with different heights, structural systems and distribution of masonry infills. The buildings are analyzed by means of nonlinear time history analysis for 80 bidirectional seismic sequences. In order to account for the influence of the incident angle on the structural response, the two horizontal accelerograms of each ground motion are applied along horizontal orthogonal axes forming 12 different angles with the structural axes. The results revealed that the influence of the successive earthquake phenomenon on the structural damage is larger for the infilled buildings compared to the bare structures. Furthermore, when buildings with masonry infills are analyzed for seismic sequences, it is of great importance to account for the orientation of the seismic motion.

This report presents the work I did as part of my graduation project. It consists of designing, studying and dimensioning the JW Marriott Tower in Casablanca Marina.
Being one of the largest cities in Africa, Casablanca plans to develop its international character by enriching its heritage of skyscrapers which are the symbol of power, energy and splendour of cities.
Having a unique architecture for the first time in Morocco, the tower presents enormous difficulties in terms of design and study since they work on the limits of current standards and regulations.
In this project I present initially a dossier about towers, their construction systems and their most used materials. Subsequently I explain the final design I have developed in accordance with the architectural plans and then I present the geotechnical context of the area and define the general hypothesis.
In the study and dimensioning phase, I study the structure in two approaches: a static approach and a dynamic approach. The static approach consists in studying the static behaviour of the tower vis-a-vis the permanent the exploitation loadings before dimensioning the structural elements outside the bracing system. In the dynamic approach I study the different horizontal and vibratory stresses, starting with the wind and then the seismic calculation.
After determining these stresses, I study the seismic design of the plates and shells as well as the foundations and the retaining walls and their stabilities and justifications in accordance to the ultimate, service and accidental states.

This research work mainly focuses on stabilization of Ikpayongo laterite using cement blended with Rise Husk Ash (RHA) and Carbide Waste (CW) to promote its physical characteristics. The blending of cement with Rice Husk Ash (RHA) and carbide waste (CW) was done in proportion to determine the required proportion suitable for the stabilization of Ikpayongo laterite. Atterberg limit test, Compaction test, California Bearing Ratio (CBR) test, Specific Gravity, Unconfined Compressive Strength (UCS) test and Durability test were conducted on the laterite sample. The blend of cement with RHA and CW at interval of 0% to 10% displayed better results than the cement treated soil at some percentages. The result showed that at 2% and 10% cement content the MDD of the natural soil reduced from 2.015Mg/m3 to 1.917Mg/m3 and increased to 1.987Mg/m3 respectively, it also reduced to 1.870Mg/m3 when treated with 2% blend of 80% cement 10% RHA 10% CW and increased at 10% of the cement blend. The CBR v...

A new approach to shield structures from soil vibrations is proposed. It is based on the dynamic behaviour of a soil layer over a bedrock, not to transmit soil vibration. This can be achieved artificially by a stiff obstacle at a certain depth under the structure's foundation. A comparison to the shielding effect of a stiff wall constructed as a wave barrier shows the effectiveness of the proposed approach.

One of the main tasks in structural health monitoring process is to create reliable algorithms that are capable of translating the measured response into meaningful information reflecting the actual condition of the monitored structure. The authors have recently introduced a novel unsupervised vibration-based damage detection algorithm that utilizes self-organizing maps to quantify structural damage and assess the overall condition of structures. Previously, this algorithm had been tested using the experimental data of Phase II Experimental Benchmark Problem of Structural Health Monitoring, introduced by the IASC (International Association for Structural Control) and ASCE (American Society of Civil Engineers). In this paper, the ability of this algorithm to quantify structural damage is tested analytically using an experimentally validated finite element model of a laboratory structure constructed at Qatar University.

This paper presents a basic tutorial on epistemic uncertainty q uantification methods. Epistemic uncertainty, characterizing lack-of-knowledge, is often prevalent in engineering applications. However, the methods we have for analyzing and propagating epistemic uncertainty are not as nearly widely used or well-understood as methods to propagate aleatory uncertainty (e.g. inherent variability characterized by probability distributions). We examine three methods used in propagating epistemic uncertainties: interval analysis, Dempster-Shafer evidence theory, and second-order probability. We demonstrate examples of their use on a problem in structural dynamics.

A simply supported bridge is modelled to investigate the effect of a strain rate dependent modulus of elasticity on the dynamic response of the structure to a moving load. The bridge is modelled as a one-dimensional discretized finite element beam and the moving load is represented by a point force. A constant modulus of elasticity is traditionally employed when simulating the dynamic response of structures under moving loads. In this paper, a time-variant modulus is used to calculate strains and displacements and compare them to the traditional approach for different speeds and bridge spans. The time-variant modulus is obtained from the strain rate of the structure which is used in turn to update the strain. The results show significant changes in the modulus and in the resulting load effect as load magnitude and speed increase.

The in-plane behavior of screen grid insulated concrete form (SGICF) walls was evaluated using full scale shake table experiments. The wall specimens utilized dry fit insulated form blocks made from recycled expanded polystyrene granules that were bonded together with cement. When stacked, the cavities in the blocks formed a grid of cores that are evenly spaced vertically and horizontally. Each wall was built on top of a foundation block that was designed such that failure would occur within the walls themselves. The walls consisted of four circular vertical cores and five circular horizontal cores reinforced with a single rebar placed nominally in the center of each core. Fiber-reinforced concrete was used in one of the walls to evaluate the effect on failure modes, drift capacity and shear strength. The results showed that the use of fiber-reinforced concrete in the cores had not significantly improved the drift capacity and had exhibited lower strengths than the wall with conventional concrete. These outcomes were mainly attributed to voids in the cores that had resulted despite similarities in workability of the concrete mixes and in techniques used to place the concrete in the walls.

Concrete is basic construction material used for many kind of structure. However, in the majority essential structures such as nuclear plants, Power plants, Weapon Industries, weapons storage places, water retaining structures like dams, & etc., concrete structures have to be designed as self-protective structure endow with defense against any disaster or consciously engendered unpleasant incidents such as terrorist attack, war, missile attacked by war jets, and dynamic loading, dynamic local impact damage and global damage generated by kinetic missiles (steel rods, steel pipes, turbine blades, etc.). This study inquisitively is paying attention on verdict the numerical simulation on the behavior of concrete structures against local impact effect generated by hard missile. The fallout conquer from this study can be used for making design counsel and design procedures for seminal the dynamic retort of the target to foil local and global impact damage. This paper only endow with the appraisal of prior analytical model investigation connected with our study.

— Development of SCC is a desirable achievement in the construction industry in order to overcome the problems associated with cast-in-place concrete. SCC is not affected by the skills of workers, shape, size and amount of reinforcing bars used or arrangement of different structural elements, but due to its high fluidity and resistance to segregation, it can be pumped to longer distances. The main reasons for the employment of self-compacting concrete is to shorten the construction period, and to assure compactions in the structure, especially in confined zones where vibration is difficult, and to eliminate noise due to vibration. A simple mix design for SCC proposed by Nan su et al. is used for achieving the trial mixes. The trial mix which satisfies the rheological properties as per EFNARC guidelines and the corresponding developed mix which gives maximum compressive and splitting tensile strengths are used in the present work. Cement is replaced with varying percentages of silica fume (SF) ranging from (0-15%) at an interval of 2.5%. SCC with 5% silica fume shows better results when compared to other replacement levels. Hence it is found that silica fume can be effectively used as an alternate for cement replacement.

The use of self-organizing maps and artificial neural networks for structural health monitoring is presented in this paper. The authors recently developed a nonparametric structural damage detection algorithm for extracting damage indices from the ambient vibration response of a structure. The algorithm is based on self-organizing maps with a multilayer feedforward pattern recognition neural network. After the training of the self-organizing maps, the algorithm was tested analytically under various damage scenarios based on stiffness reduction of beam members and boundary condition changes of a grid structure. The results indicated that proposed algorithm can successfully locate and quantify damage on the structure.

The research themes of geography of industry are continually evolving. The dynamic development of this sector of the economy after 1945 in the conditions of the socialist economy, in which the processes of industrialisation of the country were treated as priorities, as well as the processes of economic transformation in Poland after 1989, influencing the changes in the previously developed socioeconomic structures, including industry structures, influenced the shaping of the research problem of this sub-discipline of geography in Poland. These changes, leading to the adaptation of these structures to the changing management principles, take place under the influence of impulses from the international environment associated with building a knowledge-based economy and moving from the industrial and post-industrial phase to the infor-mational phase of civilisation development. These essential issues of transformation of industrial structures in the period of economic transformation and the development of a knowledge-based economy have become the subject of interest of many researchers, including economic geographers. The article presents the evolution of the themes and the main directions of research on structural changes in Polish industry in the conditions of transition from the centrally planned economy to market economy. In conclusion, it is shown that Polish geography of industry has undertaken significant scientific and economic problems of structural changes in industry during the period of economic transformation, continually updating its research priorities. Researchers quickly reacted to changes in the legal and political conditions of the functioning of the national economy, despite numerous barriers, related to, among other things, limited access to data on industrial activities, resulting in the lower interest of geographers in industrial research. The paper ends with recommendations regarding future possible research directions and a comprehensive bibliography of the studies.

Il periodo di vibrazione fondamentale svolge un ruolo fondamentale nella valutazione della domanda sismica. Il suo valore dipende dalle distribuzioni di massa e rigidezza nella struttura in esame ed è in genere valutato mediante analisi numeriche o, per alcune tipologie strutturali ricorrenti, mediante formulazioni empiriche semplificate. Nel presente articolo vengono presentati i risultati di una campagna sperimentale di identificazione dinamica di torri in muratura ricadenti nel territorio molisano. Queste ...

Predkladaná monografia monografia prináša výber niektorých výsledkov výskumu v oblasti dynamiky dopravných stavieb, ktorý sa na Katedre stavebnej mechaniky SvF ŽU v Žiline realizoval v ostatných rokoch. Logicky pojednáva o všetkých  dôležitých skutočnostich, bez ktorých  dynamická analýza dopravných stavieb nie je možná. Robí tak preto, aby si čitateľ jednoznačne uvedomil, že očakávaný výsledok výskumu je možné dosiahnúť  len organickým spojením relatívne samostatne existujúcich skutočností.

Turbo Generator foundation is one of the Paramount structures; if not the most one; in power generation plants. For the Turbo Generator foundation design, finite element (FE) is the commonly acknowledged analysis tool in structural engineering field. As the turbine and generator are relatively rigid compared either to the foundation or to the soil in analysis, both machines contributes in the finite element model through their masses applied at their center of gravity. Those elevated masses are connected to the foundation using rigid links / rigid beam elements in order to transfer loads / masses from the machines CG level to the foundation level. Rigid links are usually simulated in the analysis model as beam elements with a large Young's modulus value relative to other elements presented in the model (e.g., 100 times stiffer than the elements they are linked to) [1]. The aim of this paper is to examine study and recommend the most efficient rigid links Young's modulus value and modeling method in order to simulate the actual behavior of the system to reach the optimum dynamic and static analysis results of the Turbo Generator foundation. the analysis result indicates that using Young's modulus for the rigid link equal to ten-thousand-time steel young's modulus provide the most realistic dynamic behavior for the machine foundation.

Being an alternative to conventional wired sensors, wireless sensor networks (WSNs) are extensively used in Structural Health Monitoring (SHM) applications. Most of the Structural Damage Detection (SDD) approaches available in the SHM literature are centralized as they require transferring data from all sensors within the network to a single processing unit to evaluate the structural condition. These methods are found predominantly feasible for wired SHM systems; however, transmission and synchronization of huge data sets in WSNs has been found to be arduous. As such, the application of centralized methods with WSNs has been a challenge for engineers. In this paper, the authors are presenting a novel application of 1D Convolutional Neural Networks (1D CNNs) on WSNs for SDD purposes. The SDD is successfully performed completely wireless and real-time under ambient conditions. As a result of this, a decentralized damage detection method suitable for wireless SHM systems is proposed. The proposed method is based on 1D CNNs and it involves training an individual 1D CNN for each wireless sensor in the network in a format where each CNN is assigned to process the locally-available data only, eliminating the need for data transmission and synchronization. The proposed damage detection method operates directly on the raw ambient vibration condition signals without any filtering or preprocessing. Moreover, the proposed approach requires minimal computational time and power since 1D CNNs merge both feature extraction and classification tasks into a single learning block. This ability is prevailingly cost-effective and evidently practical in WSNs considering the hardware systems have been occasionally reported to suffer from limited power supply in these networks. To display the capability and verify the success of the proposed method, large-scale experiments conducted on a laboratory structure equipped with a state-of-the-art WSN are reported.

Output-only algorithms are needed for modal identification when only structural responses are available. The recent years have witnessed the fast development of blind source separation (BSS) as a promising signal processing technique, pursuing to recover the sources using only the measured mixtures. As the most popular tool solving the BSS problem, independent component analysis (ICA) is able to directly extract the time-domain modal responses, which are viewed as virtual sources, from the observed system responses; however, it has been shown that ICA loses accuracy in the presence of higher-level damping. In this study, the modal identification issue, which is incorporated into the BSS formulation, is transformed into a time-frequency framework. The sparse time-frequency representations of the monotone modal responses are proposed as the targeted independent sources hidden in those of the system responses which have been short-time Fourier-transformed (STFT); they can then be efficiently extracted by ICA, whereby the time-domain modal responses are recovered such that the modal parameters are readily obtained. The simulation results of a multidegree-of-freedom system illustrate that the proposed output-only STFT-ICA method is capable of accurately identifying modal information of lightly and highly damped structures, even in the presence of heavy noise and nonstationary excitation. The laboratory experiment on a highly damped three-story frame and the analysis of the real measured seismic responses of the University of Southern California hospital building demonstrate the capability of the method to perform blind modal identification in practical applications.

Tall  building  designs  are  changing  with  the  emerging  demand  of  various  architectural
features and efficient design based on  structural geometry. With the growing demand, tall
building  structures  are  paving  way  towards  challenging  aspects  of  design  with
unconventional  expressions.  More  slender  structures  are  proposed  with  economic  and
structurally efficient design. This  necessitates the study of wind loading effect on various
geometrical  shapes  and  also  the  interference  behaviour  due  to  surrounding  buildings  and
their spacing in the neighbourhood. Sufficient availability of pressure and force coefficients
for  symmetric  and  regular  buildings  are  provided  in  various  international  codes,  but  they
lack the study of interference effect and unsymmetrical building plans. The present research
work  is  a  numerical  study  of  wind  interference  effect  and  its  optimization  caused  by  the
change of inter-spacing of interfering buildings and also the varying wind angle of attack on
a pentagonal plan shaped building which serves as principle building

This paper presents the study of traffic load variations effect on the dynamic analysis of cable-stayed bridges. Time histories of displacement, velocity, acceleration, normal force, and bending moment are presented for different traffic load speeds. This study is concerned with harp bridges having five spans considering single plane of cables with 140 m for exterior spans, and 280 m for interior spans. The total length of the bridge is 1120 m. The own weight of all structural elements, and traffic load including impact are taken into account. In the dynamic analysis, the energy method, based on the minimization of the total potential energy (TPE) of structural elements, via conjugate gradient technique is used. The procedure is carried out using the iterative steps to acquire the final configuration. All prepared computer programs in FORTRAN language for this work and their verification is written by the second author. The conclusion, which have been drawn from the present work are outlined.