Techno Press
Tp_Editing System.E (TES.E)
Login Search
Found 1272 results:

Abstract
Several theoretical and analytical formulations for the prediction of shear strength in reinforced concrete (RC) beam-to-column joints have been recently developed. Some of these predictive models are included in the most recent seismic codes and currently used in practical design. On the other hand, the influence of the stiffness and strength degradations in RC joints on the seismic performance of RC framed buildings has been only marginally studied, and it is generally neglected in practice-oriented seismic analysis. To investigate such influence, this paper proposes a numerical description for representing the cyclic response of RC exterior joints. This is then used in nonlinear numerical simulations of RC frames subjected to earthquake loading. According to the proposed strategy, RC joints are modelled using nonlinear rotational spring elements with strength and stiffness degradations and limited ductility under cyclic loading. The proposed joint model has been firstly calibrated against the results from experimental tests on 12 RC exterior joints. Subsequently, nonlinear static and dynamic analyses have been carried out on two-, three- and four-storey RC frames, which represent realistic existing structures designed according to old standards. The numerical results confirm that the global seismic response of the analysed RC frames is strongly affected by the hysteretic damage in the beam-to-column joints, which determines the failure mode of the frames. This highlights that neglecting the effects of joints damage may potentially lead to non-conservative seismic assessment of existing RC framed structures.

Key Words
RC frames; joints; seismic analysis

Address
Carmine Lima, Enzo Martinelli: Department of Civil Engineering, University of Salerno, Via Giovanni Paolo II n. 132, 84084 Fisciano, Italy Lorenzo Macorini and Bassam A. Izzuddin: Department of Civil and Environmental Engineering, Imperial College London, South Kensington, London SW7 2AZ, United Kingdom

Abstract
Near-fault ground motions are characterized by high values of the ratio between the peak of vertical and horizontal ground accelerations, which can significantly affect the nonlinear response of a base-isolated structure. To check the effectiveness of different base-isolation systems for retrofitting a r.c. framed structure located in a near-fault area, a numerical investigation is carried out analyzing the nonlinear dynamic response of the fixed-base and isolated structures. For this purpose, a six-storey r.c. framed building is supposed to be retrofitted by insertion of an isolation system at the base for attaining performance levels imposed by current Italian code in a high-risk seismic zone. In particular, elastomeric (e.g., high-damping-laminated-rubber bearings, HDLRBs) and friction (e.g., steel-PTFE sliding bearings, SBs, or friction pendulum bearings, FPBs) isolators are considered, with reference to three cases of base isolation: HDLRBs acting alone (i.e., EBI structures); in-parallel combination of HDLRBs and SBs (i.e., EFBI structures); FPBs acting alone (i.e., FPBI structures). Different values of the stiffness ratio, defined as the ratio between the vertical and horizontal stiffnesses of the HDLRBs, sliding ratio, defined as the global sliding force divided by the maximum sliding force of the SBs, and in-plan distribution of friction coefficient for the FPs are investigated. The EBI, EFBI and FPBI base-isolation systems are designed assuming the same values of the fundamental vibration period and equivalent viscous damping ratio. The nonlinear dynamic analysis is carried out with reference to near-fault earthquakes, selected and scaled on the design hypotheses adopted for the test structures.

Key Words
r.c. base-isolated structures; elastomeric bearings; friction bearings; nonlinear dynamic analysis; near-fault ground motions

Address
Dipartimento di Ingegneria Civile, Universita della Calabria, Rende (Cosenza), Italy

Abstract


Key Words


Address


Abstract
The analytical method is used to develop new models for an elevated tank to estimate its natural period. The equivalent mass- spring method is used to configure the developed analytical models. Also direct method is used for numerical verification. The current study shows that developed models can have a good estimation of natural period compared with concluded results of finite elements. Additional results show that, the dependency of impulsive period to soil stiffness condition is higher than convective period. Furthermore results show that considering the fluid- structure- soil interaction has remarkable effects on natural impulsive and convective periods in case of hard to very soft soil.

Key Words
elevated tanks; fluid- structure- soil interaction; analytical method; impulsive; convective

Address
Pouyan Abbasi Maedeh: International Campus, Kharazmi University, Tehran, I.R. Iran Ali Ghanbari: Faculty of Engineering, Kharazmi University, Tehran, I.R. Iran Wei Wu: Faculty of Engineering, University of Bodenkultur, Wien, Austria

Abstract
The underlying goal of the present paper is to investigate soil and structural uncertainties on impedance functions and structural response of soil-shallow foundation-structure (SSFS) system using Monte Carlo simulations. The impedance functions of a rigid massless circular foundation resting on the surface of a random soil layer underlain by a homogeneous half-space are obtained using 1-D wave propagation in cones with reflection and refraction occurring at the layer-basement interface and free surface. Firstly, two distribution functions (lognormal and gamma) were used to generate random numbers of soil parameters (layer´s thickness and shear wave velocity) for both horizontal and rocking modes of vibration with coefficients of variation ranging between 5 and 20%, for each distribution and each parameter. Secondly, the influence of uncertainties of soil parameters (layer´s thickness, and shear wave velocity), as well as structural parameters (height of the superstructure, and radius of the foundation) on the response of the coupled system using lognormal distribution was investigated. This study illustrated that uncertainties on soil and structure properties, especially shear wave velocity and thickness of the layer, height of the structure and the foundation radius significantly affect the impedance functions, and in same time the response of the coupled system.

Key Words
impedance function; circular foundation; cone model; Monte Carlo simulations

Address
Geomaterials Laboratory, Civil Engineering Department, Hassiba Benbouali University of Chlef, P.O Box 151, Chlef 02000, Algeria

Abstract
This paper studies soil properties uncertainty and its implementation in the seismic response evaluation of structures. For this, response sensitivity of two 4- and 12-story RC shear walls to the soil properties uncertainty by considering soil structure interaction (SSI) effects is investigated. Beam on Nonlinear Winkler Foundation (BNWF) model is used for shallow foundation modeling and the uncertainty of soil properties is expanded to the foundation stiffness and strength parameters variability. Monte Carlo (MC) simulation technique is employed for probabilistic evaluations. By investigating the probabilistic evaluation results it

Key Words
soil uncertainty; soil structure interaction; seismic response; probabilistic assessment

Address
Faculty of Civil and Environmental Engineering, Tarbiat Modares University, Jalal-al-Ahmad Highway, Tehran, Iran

Abstract


Key Words


Address


Abstract
In this study, two geometrically identical multi-storey steel buildings with different lateral load resisting systems are structurally analyzed under same earthquake conditions and they are compared with respect to their construction costs of their structural systems. One of the systems is a steel structure with eccentrically steel braced frames. The other one is a RC wall-steel frame system, that is a steel framed structure in combination with a reinforced concrete core and shear walls of minimum thickness that the national code allows. As earthquake resisting systems, steel braced frames and reinforced concrete shear walls, for both cases are located on identical places in either building. Floors of both buildings will be of reinforced concrete slabs of same thickness resting on composite beams. The façades are assumed to be covered identically with light-weight aluminum cladding with insulation. Purpose of use for both buildings is an office building of eight stories. When two systems are structurally analyzed by FEM (finite element method) and dimensionally compared, the dual one comes up with almost 34% less cost of construction with respect to their structural systems. This in turn means that, by using a dual system in earthquake zones such as Turkey, for multi-storey steel buildings with RC floors, more economical solutions can be achieved. In addition, slender steel columns and beams will add to that and consequently more space in rooms is achieved.

Key Words
steel building with braced frames; steel building with RC wall-steel frames; dual structural systems; earthquake resisting frames; composite beams; construction cost comparison

Address
Department of Architecture, Structural and Earthquake Engineering Working Group, Istanbul Technical University, Taskisla Campus, 34437 Taksim, Istanbul, Turkey

Abstract
For energy-based seismic design, a simplified normalized cumulative hysteretic energy spectrum proposed for obtaining hysteretic energy as energy demand is the main objective in this paper. The dimensionless parameter, βEh, is presented to express hysteretic energy indirectly. The βEh spectrum is constructed directly through subtracting the hysteretic energy of single degree-of-freedom (SDOF) system energy equation. The simplified βEh spectral formulation as well as pseudo-acceleration spectrum of modern seismic provisions is developed based on the regression analysis of the large number of seismic responses of SDOF system subjected to earthquake excitations, which considers the influence of earthquake event, soil type, damping ratio, and ductility factor. The relationship between PGV and PGA is established according to the statistical analysis relied on a total of 422 ground motion records. The combination of βEh spectrum and PGV/PGA equation allows determining the cumulative hysteretic energy as a main aseismic design indicator.

Key Words
nonlinear SDOF system; hysteretic energy; response spectrum; damping ratio; ductility

Address
School of Civil Engineering, Suzhou University of Science and Technology, Suzhou, Jiangsu, 215011, China

Abstract
In this paper, the seismic performance of reinforced concrete braced frames (RC-BF) under far- and near-fault motions was investigated. Four-, eight-, 12- and 16-story RC-BFs were designed on the basis of a code-design method for a high risk seismic zone. Nonlinear static and dynamic analyses of the frames have been performed using OpenSees software. To consider diverse characteristics of near-fault motions, records with forward-directivity and fling-step effects were employed. From the results obtained in the analytical study it is concluded that the used design method was reasonable and the mean maximum drift of the frames under all ground motion sets were in acceptable range. For intermediate- and high-rise buildings the near-fault motions imposed higher demands than far-faults.

Key Words
reinforced concrete; steel-brace; dual system; nonlinear analysis; far- and near-fault motions

Address
Reyhaneh Eskandari, Davoud Vafaei: Department of Civil Engineering, Chabahar Maritime University, Chabahar, Iran Javid Vafaei: Department of Civil and Environmental Engineering, Amirkabir University of Technology, Tehran, Iran Mohammad Ebrahim Shemshadian: Department of Civil, Environmental, and Geo-Engineering, University of Minnesota (Twin Cities), Minneapolis, USA

[prev] [51] [52] [53] [54] [55] [56] 57 [58] [59] [60] [next]
Techno-Press: Publishers of international journals and conference proceedings.       Copyright © 2024 Techno-Press ALL RIGHTS RESERVED.
P.O. Box 33, Yuseong, Daejeon 34186 Korea, Email: info@techno-press.com