Techno Press
Tp_Editing System.E (TES.E)
Login Search


eas
 
CONTENTS
Volume 10, Number 1, January 2016
 

Abstract
Steel plate shear walls (SPSWs) have been shown to be efficient lateral force-resisting systems, which are increasingly used in new and retrofit construction. These structural systems are designed with either stiffened and stocky or unstiffened and slender web plates based on disparate structural and economical considerations. Based on some limited reported studies, on the other hand, employment of low yield point (LYP) steel infill plates with extremely low yield strength, and high ductility as well as elongation properties is found to facilitate the design and improve the structural behavior and seismic performance of the SPSW systems. On this basis, this paper reports system-level investigations on the seismic response assessment of multi-story SPSW frames under the action of earthquake ground motions. The effectiveness of the strip model in representing the behaviors of SPSWs with different buckling and yielding properties is primarily verified. Subsequently, the structural and seismic performances of several code-designed and retrofitted SPSW frames with conventional and LYP steel infill plates are investigated through detailed modal and nonlinear time-history analyses. Evaluation of various seismic response parameters including drift, acceleration, base shear and moment, column axial load, and web-plate ductility demands, demonstrates the capabilities of SPSW systems in improving the seismic performance of structures and reveals various advantages of use of LYP steel material in seismic design and retrofit of SPSW systems, in particular, application of LYP steel infill plates of double thickness in seismic retrofit of conventional steel and code-designed SPSW frames.

Key Words
steel plate shear walls; low yield point steel; seismic retrofit; nonlinear time-history analysis; seismic demand

Address
Tadeh Zirakian: Department of Civil Engineering and Construction Management, California State University, Northridge, CA, USA

Jian Zhang: Department of Civil and Environmental Engineering, University of California, Los Angeles, CA, USA

Abstract
In this study, graph product rules are applied to the dynamic analysis of regular skeletal structures. Graph product rules have recently been utilized in structural mechanics as a powerful tool for eigensolution of symmetric and regular skeletal structures. A structure is called regular if its model is a graph product. In the first part of this paper, the formulation of time history dynamic analysis of regular structures under seismic excitation is derived using graph product rules. This formulation can generally be utilized for efficient linear elastic dynamic analysis using vibration modes. The second part comprises of random vibration analysis of regular skeletal structures via canonical forms and closed-form eigensolution of matrices containing special patterns for symmetric structures. In this part, the formulations are developed for dynamic analysis of structures subjected to random seismic excitation in frequency domain. In all the proposed methods, eigensolution of the problems is achieved with less computational effort due to incorporating graph product rules and canonical forms for symmetric and cyclically symmetric structures.

Key Words
seismic analysis; regular skeletal structures; graph product rules; canonical forms

Address
A. Kaveh and P. Zakian: Centre of Excellence for Fundamental Studies in Structural Engineering, School of Civil Engineering, Iran University of Science and Technology, Narmak, Tehran-16, Iran

Abstract
Unconventional computer vision and image processing techniques offer significant advantages for experimental applications to shaking table testing, as they allow the overcoming of most typical problems of traditional sensors, such as encumbrance, limitations in the number of devices, range restrictions and risk of damage of the instruments in case of specimen failure. In this study, a 3D motion optical system was applied to analyze shake table tests carried out, up to failure, on a natural-scale masonry structure retrofitted with steel reinforced grout (SRG). The system makes use of wireless passive spherical retro-reflecting markers positioned on several points of the specimen, whose spatial displacements are recorded by near-infrared digital cameras. Analyses in the time domain allowed the monitoring of the deformations of the wall and of crack development through a displacement data processing (DDP) procedure implemented ad hoc. Fundamental frequencies and modal shapes were calculated in the frequency domain through an integrated methodology of experimental/operational modal analysis (EMA/OMA) techniques with 3D finite element analysis (FEA). Meaningful information on the structural response (e.g., displacements, damage development, and dynamic properties) were obtained, profitably integrating the results from conventional measurements. Furthermore, the comparison between 3D motion system and traditional instruments (i.e., displacement transducers and accelerometers) permitted a mutual validation of both experimental data and measurement methods.

Key Words
3D optical measurement; passive markers; steel reinforced grout; shaking table; structural damage monitoring; modal analysis

Address
Gerardo De Canio, Alessandro Giocoli, Ivan Roselli: Qualification of Materials and Components Laboratory, ENEA, Via Anguillarese 301 - 00123 Rome, Italy

Gianmarco de Felice, Stefano De Santis, Fabrizio Paolacci: Department of Engineering, Roma Tre University, Via Vito Volterra 62 - 00146 Rome, Italy

Abstract
The seismic performance of moment frames could vary according to the rotation capacity of their connections. The minimum rotation capacity of moment connections for steel intermediate moment frames (IMF) was defined as 0.02 radian in AISC 341-10. This study evaluated the seismic performance of IMF frames with connections having a rotation capacity of 0.02 radian. For this purpose, thirty IMFs were designed according to current seismic design provisions considering different design parameters such as the number of stories, span length, and seismic design categories. The procedure specified in FEMA P695 was used for conducting seismic performance evaluation. It was observed that the rotation capacity of 0.02 radian could not guarantee the satisfactory seismic performance of IMFs. This study also conducted seismic performance evaluation for IMFs with connections having the rotation capacity of 3% and ductile connections for proposing the minimum rotation capacity of IMF connections.

Key Words
rotation capacity; connections; intermediate moment frame; seismic performance; seismic design

Address
Sang Whan Han, Sung Jin Ha:Department of Architectural Engineering, Hanyang University, Seoul 133-791, Republic of Korea

Ki-Hoon Moon: Disaster Prevention Research Team, Daewoo Institute of Construction Technology, Suwon,
Kyungki-do 440-210, Republic of Korea

Abstract
In this paper we investigate the existence of SH-waves in fiber-reinforced layer placed over a heterogeneous elastic half-space. The heterogeneity of the elastic half-space is caused by the exponential variations of density and rigidity. As a special case when both the layers are homogeneous, our derived equation is in agreement with the general equation of Love wave. Numerically, it is observed that the velocity of SH-waves decreases with the increase of heterogeneity and reinforced parameters. The dimensionless phase velocity of SH-waves increases with the decreases of dimensionless wave number and shown through figures.

Key Words
heterogeneity; fiber reinforced medium; SH-waves

Address
Rajneesh Kakar: 163/1, C-B, Jalandhar-144022, India

Abstract
In this paper, using the probabilistic methods, the seismic demand of buckling restrained braced frames subjected to earthquake was evaluated. In this regards, 4, 6, 8, 10, 12 and 14-storybuildings with different buckling restrained brace configuration (including diagonal, split X, chevron V and Inverted V bracings) were designed. Because of the inherent uncertainties in the earthquake records, incremental dynamical analysis was used to evaluate seismic performance of the structures. Using the results of incremental dynamical analysis, the "capacity of a structure in terms of first mode spectral acceleration", "fragility curve" and "mean annual frequency of exceeding a limit state" was determined. "Mean annual frequency of exceeding a limit state" has been estimated for immediate occupancy (IO) and collapse prevention (CP) limit states using both Probabilistic Seismic Demand Analysis (PSDA) and solution "based on displacement" in the Demand and Capacity Factor Design (DCFD) form. Based on analysis results, the inverted chevron (^) buckling restrained braced frame has the largest capacity among the considered buckling restrained braces. Moreover, it has the best performance among the considered buckling restrained braces. Also, from fragility curves, it was observed that the fragility probability has increased with the height.

Key Words
buckling restrained braced frame; performance-based earthquake engineering; incremental dynamic analysis; fragility curve; mean annual frequency

Address
Behrouz Asgarian: Civil Engineering Faculty, K. N. Toosi University of Technology, Tehran, Iran

Edris Salehi Golsefidi: Babol Noshirvani University of Technology, Mazandaran, Iran

Hamed Rahman Shokrgozar: Faculty of Technical and Engineering, University of Mohaghegh Ardabili, Ardabil, Iran

Abstract
For seismic retrofitting of masonry walls, the use of fibre reinforced cement-based mortar for bonding the fibre grids can eliminate some of the shortcomings related to the use of resin as bonding material. The results of an experimental testing program on masonry walls retrofitted with fibre reinforced mortar and fibre grids are presented in this paper. Seven squat masonry walls were tested under unidirectional lateral displacement reversals and constant axial load. Steel anchors were used to increase the effectiveness of the bond between the fibre grids and the masonry walls. Application of fibre grids on both lateral faces of the walls effectively improved the hysteretic behaviour and specimens could be loaded until slip occurred in the horizontal joint between the masonry and the bottom concrete stub. Application of the fibre grids on a single face did not effectively improve the hysteretic behaviour. Retrofitting with fibre reinforced mortar only prevented the early damage but did not effectively increase deformation capacity. When the boundaries of the cross sections were not properly confined, midplane splitting of the masonry walls occurred. Steel anchors embedded in the walls in the corners area effectively prevented this type of failure.

Key Words
squat masonry walls; fibre reinforced mortar; fibre grids; experimental testing; seismic retrofitting; hysteretic behaviour; strength; energy dissipation capacity

Address
Viorel Popa, Radu Pascu, Andrei Papurcu: Department of Reinforced Concrete Structures, Technical University of Civil Engineering of Bucharest, 124 Lacul Tei, Sector 2, 020396, Bucharest, Romania

Emil Albota: Department of Structural Mechanics, Technical University of Civil Engineering of Bucharest, 124 Lacul Tei, Sector 2, 020396, Bucharest, Romania

Abstract
In seismic fragility and risk analysis, the definition of structural limit state (LS) capacities is of crucial importance. Traditionally, LS capacities are defined according to design code provisions or using deterministic pushover analysis without considering the inherent randomness of structural parameters. To assess the effects of structural randomness on LS capacities, ten structural parameters that include material strengths and gravity loads are considered as random variables, and a probabilistic pushover method based on a correlation-controlled Latin hypercube sampling technique is used to estimate the uncertainties in LS capacities for four typical reinforced concrete frame buildings. A series of ten LSs are identified from the pushover curves based on the design-code-given thresholds and the available damage-controlled criteria. The obtained LS capacities are further represented by a lognormal model with the median mC and the dispersion βC. The results show that structural uncertainties have limited influence on mC for the LSs other than that near collapse. The commonly used assumption of βC between 0.25 and 0.30 overestimates the uncertainties in LS capacities for each individual building, but they are suitable for a building group with moderate damages. A low uncertainty as βC=0.1~0.15 is adequate for the LSs associated with slight damages of structures, while a large uncertainty as βC=0.40~0.45 is suggested for the LSs near collapse.

Key Words
limit state; pushover analysis; RC frame; uncertainty analysis; correlation-reduced Latin hypercube sampling

Address
Xiaohui Yu, Dagang Lu: Ministry-of-Education Key Lab of Structures Dynamic Behavior and Control, School of Civil Engineering, Harbin Institute of Technology, Harbin 150090, China

Bing Li: School of Civil and Environmental Engineering, Nanyang Technological University, 639798, Singapore

Abstract
Composite Lightweight (CL) insulated walls have gained wide adoption recently because the exterior claddings of steel building frames have their cost effectiveness, good thermal and structural efficiency. To investigate the seismic behavior, lateral stiffness, ductility and energy dissipation of steel frames with the CL infill walls, five one-story one-bay steel frames were fabricated and tested under cyclic loads. Test results showed that the bolted connections allow relative movement between CL infill walls and steel frames, enabling the system to exhibit satisfactory performance under lateral loads. Additionally, it is found that the addition of diagonal steel straps to the CL infill wall significantly increases the initial lateral stiffness, load-carrying capacity, ductility and energy dissipation capacity of the system. Furthermore, the test results indicate that the lateral stiffness values of the frames with the CL infill wall are similar to those of the bare steel frames in large lateral displacement.

Key Words
composite lightweight infill wall; steel frame; bolted connection; cyclic test; energy

Address
Hetao Hou, Jian Zhou, Bing Qu, Haideng Ye, Haining Liu and Jingjing Li: School of Civil Engineering, Shandong University, Jinan, Shandong, 250061, P.R. China

Chung-Che Chou: Department of Civil Engineering, National Taiwan University, 10617, Taipei, Taiwan

Minglei Wu: Shandong Engineering Consulting Institute, Jinan, Shandong, 250013, P.R. China

Bing Qu: Department of Civil and Environmental Engineering, California Polytechnic State University, San Luis Obispo, CA 93407, USA

Abstract
A single rigid footing constructed on sandy-clay soil was modeled and analyzed using FLAC software under static conditions and vertical ground motion using three accelerograms. Dynamic analysis was repeated by changing the elastic and plastic parameters of the soil by changing the percentage of cement grouting (2, 4 and 6 %). The load-settlement curves were plotted and their bearing capacities compared under different conditions. Vertical settlement contours and time histories of settlement were plotted and analyzed for treated and untreated soil for the different percentages of cement. The results demonstrate that adding 2, 4 and 6 % of cement under specific conditions increased the dynamic bearing capacity 2.7, 4.2 and 7.0 times, respectively.

Key Words
vertical ground motion; cement-improved soils; dynamic vertical settlement; shallow footing; normal stress

Address
Alireza Kholdebarin, Ali Massumi: Department of Civil Engineering, Faculty of Engineering, Kharazmi University, Tehran, 15719-14911, Iran

Mohammad Davoodi: Department of Geotechnical Earthquake Engineering, International Institute of Earthquake Engineering and Seismology, IIEES, Tehran, Iran

Abstract
Seismic codes are the best available guidance on how structures should be designed and constructed to ensure adequate resistance to seismic forces during earthquakes. Seismic provisions of Indian standard code, International building code and European code are applied for buildings with ordinary moment resisting frames and reinforced shear walls at various locations considering the effect of site soil conditions. The study investigates the differences in spectral acceleration coefficient (Sa/g), base shear and storey shear obtained following the seismic provisions in different codes in the analysis of these buildings. Study shows that the provision of shear walls at core in low rise buildings and at all the four corners in high rise buildings gives the least value of base shear.

Key Words
base shear; spectral acceleration coefficient; storey shear; shear wall; natural period; design response spectrum

Address
Jayalekshmi B.R. and Chinmayi H.K.: Department of Civil Engineering, National Institute of Technology Karnataka, Surathkal 575-025, India

Abstract
The Maximum seismic responses of steel buildings with perimeter moment resisting frames (MRF), modeled as complex MDOF systems, are estimated for several incidence angles of the horizontal components and the critical one is identified. The accuracy of the existing rules to combine the effects of the individual components is also studied. Two and three components are considered. The critical response does not occur for principal components and the corresponding incidence angle varies from one earthquake to another. The critical response can be estimated as 1.40 and 1.10 times that of the principal components, for axial load and interstory shears, respectively. The rules underestimate the axial load but reasonably overestimate the shears. The rules are not always inaccurate in the estimation of the combined response for correlated components. On the other hand, totally uncorrelated (principal) components are not always related to an accurate estimation. The correlation of the individual effects (ρ) may be significant, even for principal components. The rules are not always associated to an inaccurate estimation for large values of ρ, and small values of ρ are not always related to an accurate estimation. Only for perfectly uncorrelated harmonic excitations and elastic analysis of SDOF systems, the individual effects of the components are uncorrelated and the rules accurately estimate the combined response. The degree of correlation of the components, the type of structural system, the response parameter under consideration, the location of the structural member and the level of structural deformation must be considered while estimating the level of underestimation or overestimation.

Key Words
critical response; steel buildings; seismic design codes; combination rules; effect of individual components; correlation of effects; MDOF and SDOF systems

Address
Alfredo Reyes-Salazar, Federico Valenzuela-Beltran, Eden Bojorquez-Mora and Arturo López Barraza: Facultad de Ingeniería, Universidad Autónoma de Sinaloa, Ciudad Universitaria, Culiacán Sinaloa, Mexico

David de Leon-Escobedo: Facultad de Ingenieria, Universidad Autónoma del Estado de Mexico, Ciudad Universitaria, Toluca, Estado de Mexico, Mexico

Abstract
Tuned mass dampers (TMDs) have been frequently proposed to mitigate the detrimental effects of dynamic loadings in structural systems. The effectiveness of this protection strategy has been demonstrated for wind-induced vibrations and, to some extent, for seismic loadings. Within this framework, recent numerical studies have shown that beneficial effects can be achieved by placing a linear TMD on the roof of linear elastic structural systems subjected to pulse-like ground motions. Motivated by these positive outcomes, closed-form design formulations have been also proposed to optimize the device

Key Words
inelastic structure; optimization; pulse-like ground motion; tuned mass damper

Address
Giuseppe Quaranta: Department of Structural and Geotechnical Engineering, Sapienza University of Rome, via Eudossiana 18, 00184 Rome, Italy

Fabrizio Mollaioli and Giorgio Monti: Department of Structural and Geotechnical Engineering, Sapienza University of Rome, via Gramsci 53, 00197 Rome, Italy


Techno-Press: Publishers of international journals and conference proceedings.       Copyright © 2017 Techno-Press
P.O. Box 33, Yuseong, Daejeon 34186 Korea, Tel: +82-42-828-7996, Fax : +82-42-828-7997, Email: info@techno-press.com