Influence of Soil-Structure-Interaction on Nonlinear Time History Seismic Response of RC Frames

Modern regulations require from engineers to take into account a non-linear behavior and the appearance of plastic hinges in the selected structural elements during the earthquake. Also, regulations more insist on considering the soil-structure interaction (SSI) in the computation of dynamic response of buildings. In this paper, the nonlinear time history analysis of multi-storey RC frame structure is carried out taking into account SSI according to the Eurocode 8 and FEMA 450 recommendations. In order to illustrate the impact of the SSI, the response of the structure is calculated with and without the influence of the soil. Nine accelerograms are selected to correspond to the frequency spectra defined in EC8. Two standard types of soil, (ie. type B and C) according to the EC8, are adopted. The appropriate conclusions and recommendations for further work in this area are carried out

Linear Transient Analysis of Laminated Composite Plates using GLPT

The objective of this work is to study the transient response of laminated composite plates under different types of dynamic loading. For this purpose, laminated composite plate is modeled using Reddy’s generalized layerwise plate theory (GLPT). This theory assumes layerwise linear variation of displacements components. Transverse displacement is constant through the thickness of the plate. Using the assumed displacement field, linear kinematic relations, as well as Hooke’s constitutive law, equations of motion are derived using Hamilton’s principle. Analytical solution for cross-ply laminates is derived using the Navier method. Numerical solution is obtained using FEM. Governing partial differential equations in both solutions are reduced to a set of ordinary differential equations in time using Newmark integration scheme. The equations of motion are solved using constant-average acceleration method. Effects of time step, mesh refinement and lamination scheme on accuracy of transient response are considered. Illustrative comments are given about the influence of shear deformation on transient response. Finally, different schemes of dynamic loading are investigated. Good agreement is obtained with results from the literature.Obiectivul acestei lucrări este de a studia răspunsul tranzitoriu al plăcilor compozite laminate sub diferite tipuri de încărcare dinamică. În acest scop, placa compozită laminată este modelată folo-sind teoria generalizată a plăcilor propusă de Reddy (GLPT). Această teorie presupune variația liniară a componentelor deplasării în raport cu straturile plăcii. Deplasarea transversală este constantă în grosimea plăcii. Ecuațiile de mișcare sunt derivate folosind principiul lui Hamilton, utilizând câmpul de deplasare asumat, relațiile liniare cinematice, precum și legea constitutivă a lui Hooke. Soluția analitică pentru plăci laminate din fibre din lemn încrucișate este derivată folosind formula lui Navier. Soluția numerică este obținută cu ajutorul metodei elementului finit. Ecuațiile cu derivate parțiale în ambele soluții sunt reduse la un set de ecuații diferențiale ordinare în timp, utilizând Metoda Newmark. Ecuațiile de mișcare sunt rezolvate folosind metoda de inte-grare implicită Newmark β. Sunt luate în considerare efectele integrării numerice în timp, pas cu pas, ale rafinării discretizării și ale sistemului de laminare asupra acurateței răspunsului tranzitoriu. Sunt prezentate comentarii ilustrative despre influența deformării cauzate de forfecare asupra răspunsului tranzitoriu. În cele din urmă, sunt investigate diferite scheme de încărcare dinamică. Rezultatele obținute sunt în concordanță cu cele din literatura de specialitate

Free vibrations of delaminated composite and sandwich plates

The aim of this paper is comparison of fundamental dynamic characteristics of intact and damaged laminated composite and sandwich plates. Generalized Layerwise Plate Theory is used for analysis of different plates with presence of delaminations. Jumps in displacement field are incorporated using Heaviside step functions. Different layerwise FE are derived. Mathematical model is coded in MATLAB® for free vibrations analysis of laminated composite and sandwich plates. Effects of plate aspect ratio, lamination scheme, degree of orthotropy and delamination position on fundamental dynamic characteristics are analyzed. All numerical solutions are compared with existing dat

Pushover analysis of bridges including soil-structure interaction effects

This paper deals with the effects of soil-structure interaction (SSI) on the displacement capacity of multi-span RC bridge founded on shallow foundations. Modal pushover analyses are carried out in transverse direction. Target displacement of the monitoring point is calculated using N2 method The SSI is considered through boundary springs according to NEHPR Two different soil properties are considered according to EN1998-1. Analyses are carried out using SAP2OOO, considering fixed- and flexible-base models. The obtained results are discussed

Bending analysis of cross-laminated-timber (CLT) panels using layered finite elements

Cross-laminated timber panels are composite wood products with an increasing application in civil engineering. The low environmental impact and high mechanical performance encourage the use of CLT in modern buildings instead of traditional mineral-based building materials. The complex CLT-specific material characteristics, characterized by the high shear deformations across the plate thickness, complicate an accurate kinematic description of CLT. The traditional computational models used in standards for design of timber structures are generally based on beam theories, limiting the design approaches to slender panels. Therefore, the application of complex numerical models is required for a more intensive use of CLT. In the paper, the full layerwise theory of Reddy served as a basis for the formulation of layered quadrilateral finite elements for the analysis of CLT panels. Original procedure for post-processing of stresses is presented. The model is validated against the numerical and experimental data in the literature. Excellent agreement is achieved.Панели од унакрсно ламелираног дрвета (CLT) су композитни производи чија примена у грађеви-нарству је све већа. Мали утицај на животну средину и добре механичке карактеристике доводе до примене CLT панела у модерним зградама, уместо традиционалних (минералних) грађевинских материјала. Сложене материјалне карактеристике специфичне за CLT, које одликују високе смичу-ће деформације по дебљини панела, компликују прецизно описивање кинематике CLT панела. Tрадиционални прорачунски модели, примењени у стандардима за прорачун дрвених конструкција, генерално се заснивају на теоријама греде и ограничени су на танке панеле. Са тим у складу, примена сложених нумеричких модела неопходна је за повећану примену CLT панела. У овом раду, Reddy-ева слојевита теорија плоча била је основ за формулисање слојевитих четвороугаоних коначних елемената за анализу CLT панела. Дата је оригинална процедура за прорачун напона. Прецизност модела је потврђена поређењем са нумеричким и експерименталним подацима из литературе, и добијено је одлично поклапање резултата

Transient Response of Cross-Ply Laminated Composite Plates

This paper describes the transient response of cross-ply laminated composite plates. Possibility of achieving the transient response of cross-ply composites by the use of Reddy’s generalized laminated plate theory (GLPT) is evaluated in this work. Layerwise linear variation of displacements components, as well as linear kinematic relations and Hook’s law are assumed. Navier solution is applied for expansion of generalized displacements in double trigonometric series. The governing partial differential equations are reduced to a set of ordinary differential equations in time. The equations of motion are solved using Newmark’s integration schemes. Transient response is calculated with an example of simply supported (0/90) laminate. Different number of layers and variants of stacking sequences are taken into consideration by parametric study. Transient response is investigated using different schemes of dynamic loading (forcing functions). For all loading types, results taking into account the influence of time step are presented. Results are compared with those of other theories existing from the literature. Variety of new results is presented.U ovom radu opisan je dinamički odgovor cross-ply laminatnih kompozitnih ploča. Razmatrana je mogućnost određivanja dinamičkog odgovora cross-ply kompozita korišćenjem Reddy-eve Opšte laminatne teorije ploča (GLPT). Pretpostavljena je slojevita linearna varijacija komponenata pomeranja, kao i linearne kinematičke relacije i Hook-ov zakon. Navier-ovo rešenje je primenjeno za razvoj generalisanih pomeranja u dvostruke trigonometrijske redove. Uslovne parcijalne diferencijalne jednačine su redukovane na sistem običnih diferencijalnih jednačina po vremenu. Jednačine kretanja su rešene primenom Newmark-ovih integracionih šema. Dinamički odgovor je sračunat na primeru slobodno oslonjene cross-ply (0/90) laminatne ploče. U parametarskoj analizi su razmatrani uticaji broja slojeva u laminatu, kao i različite varijante šema laminacije. Dinamički odgovor je sračunat za različite šeme dinamičkog opterećenja (forcing functions). Za sve tipove opterećenja prezentovani su rezultati koji uzimaju u obzir uticaj vremenskog inkrementa. Rezultati su upoređeni sa nekim rezultatima po drugim teorijama koji postoje u literaturi. Prikazano je i mnoštvo novih rezultata

Bending analysis of cross-laminated-timber (CLT) panels using layered finite elements

Cross-laminated timber panels are composite wood products with an increasing application in civil engineering. The low environmental impact and high mechanical performance encourage the use of CLT in modern buildings instead of traditional mineral-based building materials. The complex CLT-specific material characteristics, characterized by the high shear deformations across the plate thickness, complicate an accurate kinematic description of CLT. The traditional computational models used in standards for design of timber structures are generally based on beam theories, limiting the design approaches to slender panels. Therefore, the application of complex numerical models is required for a more intensive use of CLT. In the paper, the full layerwise theory of Reddy served as a basis for the formulation of layered quadrilateral finite elements for the analysis of CLT panels. Original procedure for post-processing of stresses is presented. The model is validated against the numerical and experimental data in the literature. Excellent agreement is achieved.Панели од унакрсно ламелираног дрвета (CLT) су композитни производи чија примена у грађеви-нарству је све већа. Мали утицај на животну средину и добре механичке карактеристике доводе до примене CLT панела у модерним зградама, уместо традиционалних (минералних) грађевинских материјала. Сложене материјалне карактеристике специфичне за CLT, које одликују високе смичу-ће деформације по дебљини панела, компликују прецизно описивање кинематике CLT панела. Tрадиционални прорачунски модели, примењени у стандардима за прорачун дрвених конструкција, генерално се заснивају на теоријама греде и ограничени су на танке панеле. Са тим у складу, примена сложених нумеричких модела неопходна је за повећану примену CLT панела. У овом раду, Reddy-ева слојевита теорија плоча била је основ за формулисање слојевитих четвороугаоних коначних елемената за анализу CLT панела. Дата је оригинална процедура за прорачун напона. Прецизност модела је потврђена поређењем са нумеричким и експерименталним подацима из литературе, и добијено је одлично поклапање резултата

Application of Composite Structures in Multi-Storey Car Parks

Postoji veliki broj primenjenih rešenja u projektovanju višespratnih garaža: različita konstrukcijska rešenja razlikuju se u načinu na koji se projektuju međuspratne konstrukcije. Primena spregnutih konstrukcija u projektovanju međuspratnih konstrukcija rezultuje: smanjenjem utroška čelika, smanjenjem građevinske visine, kraćim vremenom građenja. U ovom radu su analizirane osnovne metode projektovanja spregnutih greda od čelika i betona, u skladu sa Evrokodom. Analizirana su tri različita tipa čeličnih greda spregnutih sa betonskom pločom na profilisanom limu: greda u vidu klasičnog vruće valjanog I - profila, STUB sistemi spregnute grede i spregnuta greda u vidu saćastog čeličnog nosača. Data je komparativna analiza primene tri sistema spregnute grede. Usvojeno rešenje primenjeno je u konstrukciji koja je opisana u drugom delu ovog rada. U drugom delu rada je detaljno izložen proračun noseće čelične konstrukcije javne garaže dimenzija 31x70 m u osnovi, spratnosti P+3, sa detaljima čelične konstrukcije.There is a great variety of applied solutions in multi-storey car parks design: the various construction types differ from one another by the way the floors are built. Applying of composite structures in floor design results in: reduction in steel consumption, reduction of the structural height, shorter construction period. This research deals with main design methods for composite beam from steel and concrete, according to Eurocode. There were analyzed three solutions for steel beam in combination with concrete slab on profiled steel sheet: standard hot rolled I - profile, composite Stub girder, and castellated composite beam. Comparative analysis of application of three solutions for composite beam was given. The admited solution is applied in the construction of which is described in the second part of this paper. The second part of this paper is exposed to the detailed calculation of main steel construction of public car park, with dimensions of 31x70 m in the basis, with B+3 floors, and with structural steel detailing