Vulnerable buildings and their rehabilitation are important problems for earthquake regions. In recent decades the goal of building rehabilitation and strengthening has gained research attention and numerous techniques have been developed to achieve this. However, most of these strengthening techniques disturb the occupants, who must vacate the building during renovation. In this study, a new strengthening alternative for RC structures, namely exterior shear walls, has been experimentally investigated under reversed cyclic loading. Using the proposed technique, it is possible to strengthen structures without disturbing their users or vacating the building during renovation. In this technique, shear walls are installed in parallel to the building’s exterior sides. It has been observed that the usage of exterior shear walls considerably improve the capacity and sway stiffness of RC structures. The experimental results have also been compared and found to be in agreement with the numerical solutions. Post attached exterior shear walls behaved as a monolithic member of the structure.
Design considerations for the exterior shear wall-strengthened buildings have also been discussed in the paper.
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This paper provides a brief review of recent work on the development of solutions for the seismic design and retrofit of steel structures by va rious members of the U.S. research community, including solutions being developed at the Univers ity at Buffalo for the seismic retrofit of bridges and buildings.
Author: Michel Bruneau | Size: 3.8 MB | Format:PDF | Quality:Unspecified | Publisher: Center for Earthquake Engineering Research, and Professor, Department of Civil, Structural, and Environmental Engineering, 105 Red Jacket Quadrangle, University at Buffalo, Buffalo, NY, 14261, USA. | pages: 16
This paper provides a brief review of recent work on the development of solutions for the seismic
design and retrofit of steel structures by various members of the U.S. research community,
including solutions being developed at the University at Buffalo for the seismic retrofit of bridges
and buildings.
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HOW HAVE CHANGES IN BUILDING CODE PROVISIONS FOR REINFORCED CONCRETE FRAME STRUCTURES IMPROVED SEISMIC SAFETY?
Author: . B. Liel , C. B. Haselton , and G. G. Deierlein | Size: 0.3 MB | Format:PDF | Quality:Unspecified | Publisher: Dept. of Civil Engineering, Stanford University, Stanford | pages: 10
This study provides an analytical comparison of seismic performance of a typical California office building designed according to the 1967 Uniform Building Code and the 2003 International Building Code. The seismic performance predictions are based on a performance assessment method developed by the Pacific Earthquake Engineering Research (PEER) Center, which employs incremental nonlinear dynamic time-history analyses. Comparisons are made for a four-story reinforced concrete (RC) moment frame building designed to be representative of a) pre-1970 non-ductile reinforced concrete construction and b) modern (2003) ductile reinforced concrete construction. The plan and elevation of the building are identical for both structures; differences are evident in the magnitude of design loading, the relative strength of structural elements, and detailing of beams, columns, and beam column joints. For each building, a nonlinear dynamic analysis model captures the behavior of the important failure modes up to the onset of collapse, accounting for uncertainties in structural behavior, modeling, and ground motions. The performance quantity of interest in this study is the collapse risk, particularly mean annual frequency of collapse. By comparing the computed
collapse risk for the two structures, performance improvements in RC frame buildings over the three decades since the San Fernando earthquake can be
quantified.
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Finite-element analyses are performed for the response to lateral monotonic, slow-cyclic, and seismic loading of rigid footings carrying tall slender structures and supported on stiff clay. The response involves mainly footing rotation under the action of overturning moments from the horizontal external force on—or the developing inertia at—the mass of the structure, as well as from the aggravating contribution of its weight (P-delta effect). Emphasis is given to the conditions for collapse of the soil-foundation-structure system. Two interconnected mechanisms of nonlinearity are considered: detachment from the soil with subsequent uplifting of the foundation (geometric nonlinearity) and formation of bearingcapacity failure surfaces (material inelasticity). The relation between monotonic behavior (static “pushover”), slow-cyclic behavior, and seismic response is explored parametrically. We show that with “light” structures uplifting is the dominant mechanism that may lead to collapse by dynamic instability (overturning), whereas “very heavy” structures mobilize soil failure mechanisms, leading to accumulation of settlement, residual rotation, and ultimately collapse.
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FURTHER PROBING OF THE SUITABILITY OF PUSH- OVER ANALYSIS FOR THE SEISMIC ASSESSMENT OF BRIDGE STRUCTURES
Author: ALESSIO LUPOI University of Rome “Sapienza”, Dpt. of Structural and Geotechnical Engineering, PAOLO FRANCHIN University of Rome “Sapienza”, Dpt. of Structural and Geotechnical Engineering, .PAOLO E. PINTO University of Rome “Sapienza”, Dpt. of Structural and Geotechnical Engineering, | Size: 0.67 MB | Format:PDF | Quality:Unspecified | pages: 16
The applicability of non-linear static analyses for the assessment of less-thanregular bridges has been subject of recent research by a number of authors ([11,13,14]), with mixed results. The study presented in the paper intends to provide a further example of application of the approach to a bridge whose characteristics are such as to test it in a rather extreme case. This is an existing important highway viaduct built in the sixties, of total length equal to 420m, with 11 spans of 33m each and a continuous RC deck pinned over the piers. These latter, whose height varies irregularly between 14m and 41m, consist of slender single-bay frames with intermediate transverse beams. Among the numerous proposals available, the multi-modal nonadaptive approach as proposed by Chopra et al. [4] has been chosen as the preferred compromise between accuracy and complexity. The selected structure is characterised by at least two modes providing comparable contributions to the transversal response. In view of the final comparison of the results with those from non-linear dynamic analyses, the critical question of the choice of the reference response dof to be monitored has been investigated as well as the approximation of the method as a function of the intensity of the seismic action (inducing a variable degree of inelasticity in the structure).
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Influence of Nonlinear SSI on the Seismic Response of Reinforced Concrete Multistory Frames
Author: E. Saez, F. Lopez-Caballero, A. Modaressi-Farahmand Razavi | Size: 0.57 MB | Format:PDF | Quality:Unspecified | Publisher: The 12 th International Conference of International Association for Computer Methods and Advances in Geomechanics (IACMAG) 1-6 October, 2008 Goa, India | Year: 2008 | pages: 8
In general, the soil-structure interaction effects are assumed beneficial in the and thus ignored. Nevertheless, a more precise knowledge of the expected structural seismic response can allow to reduce the cost of the structure and to improve the earthquake engineering practice. This paper concerns the assessment of the effects of non-linear soil behaviour on the structural seismic demand evaluation. Special emphasis is placed on
the modelisation hypothesis and its consequences on the predicted seismic response.
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SIMPLIFIED DYNAMIC ANALYSIS OF ECCENTRIC BUILDINGS WITH A SETBACK. 2: THE EFFECT OF STIFFNESS IRREGULARITY
Author: GEORGE K. GEORGOUSSIS* | Size: 0.22 MB | Format:PDF | Quality:Unspecified | Publisher: THE STRUCTURAL DESIGN OF TALL AND SPECIAL BUILDINGS Struct. Design Tall Spec. Build. (2009) | Year: 2009 | pages: 16
The effect of stiffness irregularity is investigated in eccentric buildings with a setback. Stiffness irregularity is
assumed to be created when some of the lateral load resisting bents are curtailed at the top of the base structure.
The methodology suggested in the companion paper for assessing vibration frequencies, base shears and torques
is extended to include the effect of curtailed bents. Their contribution is evaluated by an indirect method after
the modal stiffness of the symmetrical counterpart structure is determined and the modal contribution of the full height bents is assessed by Southwell’s approach. A number of numerical examples, representing common types of building structures, are presented to illustrate the procedure and provide an insight into the response of such setback buildings. The results are compared with more accurate results obtained by three-dimensional dynamic analyses.
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This report provides technical information on pervious concrete’s application, design methods, materials, properties, mixture proportioning, construction methods, testing, and inspection.
The term “pervious concrete” typically describes a near-zero-slump, open-graded material consisting of portland cement, coarse aggregate, little or no fine aggregate, admixtures, and water. The combination of these ingredients will produce a hardened material with connected pores, ranging in size from 0.08 to 0.32 in. (2 to 8 mm), that allow water to pass through easily. The void content can range from 15 to 35%, with typical compressive strengths of 400 to 4000 psi (2.8 to 28 MPa). The drainage rate of pervious concrete pavement will vary with aggregate size and density of the mixture, but will generally fall into the range of 2 to 18 gal./ min/ft2 (81 to 730 L/min/m2). Pervious concrete is widely recognized as a sustainable building material, as it reduces stormwater runoff, improves stormwater quality, may recharge groundwater supplies, and can reduce the impact of the urban heat island effect.
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Progressive Collapse Simulation of Reinforced Concrete Structures: Influence of Design and Material Parameters and Investigation of the Strain Rate E.ects
Author: Berta Santafé Iribarren | Size: 5 MB | Format:PDF | Quality:Unspecified | Publisher: Université Libre de Bruxelles Royal Military Academy Faculty of Applied Sciences Polytechnical Faculty | Year: 2011 | pages: 188
The finite element formulation adopted here is based on a multilevel approach where the response at the structural level is naturally deduced from the behaviour of the constituents (concrete and steel) at the material level. One-dimensional nonlinear constitutive laws are used to model the material response of concrete and steel. These constitutive equations are introduced in a layered beam approach, where the cross-sections of the structural members are discretised through a finite number of layers. This modelling strategy allows deriving physically motivated relationships between generalised stresses and strains at the sectional level. Additionally, a gradual sectional strength degradation can be obtained as a consequence of the progressive failure of the constitutive layers. This means that complex nonlinear sectional responses exhibiting softening can be obtained even for simplified one-dimensional constitutive laws for the constituents. This numerical formulation is used in dynamic progressive collapse simulations to study the structural response of a multi-storey planar frame subject to a sudden column loss. The versatility of the proposed methodology allows assessing the influence of the main material and design parameters in the structural failure. Furthermore, the e.ect of particular modelling options of the progressive collapse simulation technique, such as the column removal time or the strategy adopted for the structural verification, can be evaluated. The potential strain rate e.ects on the structural response of reinforced concrete frames are also investigated. To this end, a strain rate dependent material formulation is developed, where the rate e.ects are introduced in both the concrete and steel constitutive response. These e.ects are incor-
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P-DELTA EFFECTS OX THE INELASTIC SEISMIC RESPONSE OF REINFORCED CONCRETE SHEAR WALL BUILDINGS
Author: JIANHUA TU DEPARTEMENT DES GÉNIES CIVIL, GÉOLOGIQUE ET DES MMES ÉCOLE POLYTECHNIQUE DE MONTRÉAL | Size: 7.2 MB | Format:PDF | Quality:Unspecified | Year: 2000 | pages: 193
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