[PDF] Blind Predictions Of The Seismic Response Of A Two Story Woodframe House eBook

Author : Nicola Ruggieri
Publisher : Springer
Page : 0 pages
File Size : 20,17 MB
Release : 2016-10-06
Category : Technology & Engineering
ISBN : 9783319366524

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This book presents a selection of the best papers from the HEaRT 2013 conference, held in Cosenza, Italy, which provided a valuable forum for engineers and architects, researchers and educators to exchange views and findings concerning the technological history, construction features and seismic behavior of historical timber-framed walls in the Mediterranean countries. The topics covered are wide ranging and include historical aspects and examples of the use of timber-framed construction systems in response to earthquakes, such as the gaiola system in Portugal and the Bourbon system in southern Italy; interpretation of the response of timber-framed walls to seismic actions based on calculations and experimental tests; assessment of the effectiveness of repair and strengthening techniques, e.g., using aramid fiber wires or sheets; and modelling analyses. In addition, on the basis of case studies, a methodology is presented that is applicable to diagnosis, strengthening and improvement of seismic performance and is compatible with modern theoretical principles and conservation criteria. It is hoped that, by contributing to the knowledge of this construction technique, the book will help to promote conservation of this important component of Europe’s architectural heritage.

Author : Ioannis Christovasilis
Publisher :
Page : 272 pages
File Size : 29,81 MB
Release : 2011
Category :
ISBN :

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In support of the performance-based seismic design procedures for light-frame wood structures, developed within the NSF-funded NEESWood Project, a dual study with experimental and analytical components was conducted. In the context of the experimental investigation, a full-scale, two-story, light-frame wood townhouse building was tested on the twin relocatable tri-axial shake tables operating in unison, at the University at Buffalo UB-NEES site. The test structure performed well under the Design (DE) and Maximum (MCE) levels of shaking and the experimental results demonstrated the beneficial effect of wall-finishes on improving its seismic response. The analytical task focused on the development, implementation and validation of a novel numerical framework, suitable for nonlinear inelastic, static and dynamic two-dimensional (2D) analysis of light-frame wood structures.^The 2D building model is based on a sub-structuring approach that considers each floor diaphragm as rigid body with three kinematic, and potentially dynamic, degrees-of-freedom and a sub-structure model is developed for each individual single-story wall assembly that interacts with the adjacent diaphragms and generates the resisting quasi-static internal forces. The 2D shear wall model takes explicit consideration of all sheathing-to-framing connections and offers the option to simulate deformations in the framing members and contact/separation phenomena between framing members and diaphragms, as well as any anchoring equipment (i.e. anchor bolts, holdown devices), typically installed in light-frame shear walls to develop a vertical load path that resists overturning moments.^Corotational descriptions are used to solve for displacement fields that satisfy the equilibrium equations in the deformed configuration, accounting for geometric nonlinearity (large rotations - small deformations) and P-Delta effects. These attributes result in a nonlinear element capable of capturing the lateral response of shear walls up to their complete failure and, thus, the side-sway collapse of the structure. To validate the proposed numerical framework, a number of simulation examples are presented, based on existing experimental results from pseudo-static tests of single- and two-story full-scale shear wall specimens, as well as unidirectional shake-table tests of a symmetric single-story full-scale structure.

Author : Zhengxiang Yi
Publisher :
Page : 293 pages
File Size : 34,87 MB
Release : 2020
Category :
ISBN :

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Woodframe construction is commonly used for single and multifamily residential buildings in the United States. In many parts of California, multifamily woodframe residential buildings are constructed with open first stories, which have much less strength and stiffness compared to the ones above. In older single-family residences, the "crawl space" is constructed with unbraced and unbolted cripple walls. Both these conditions lead to a soft-story response during seismic loading, resulting significant damage, economic losses and even collapse. This type of vulnerability is often addressed through seismic retrofits, which can be mandated by local jurisdictions (e.g., the Los Angeles Soft-Story Ordinance) or incentivized by state or local entities (e.g., the California Earthquake Authority Brace and Bolt Program). A key challenge in implementing these retrofit programs (mandated or incentivized) is quantifying the improvements in performance at the individual and portfolio scale and creating design procedures that maximize the overall benefit. This research integrates nonlinear structural modeling, performance-based assessments and advanced statistical and machine learning techniques to quantify the benefit of soft-story woodframe building retrofit and develop optimal design solutions that maximize regional performance. The considered construction types include single-family houses with unbraced cripple walls developed as part of the recently completed Pacific Earthquake Engineering Research Institute (PEER) and California Earthquake Authority (CEA) project and multi-family residences with soft, weak and open front wall lines (SWOF). An end-to-end computational platform is developed to automate the construction and analysis of archetype numerical models in OpenSees and conduct seismic evaluations based on the PEER performance-based earthquake engineering framework. The performance of existing and retrofitted buildings is assessed in terms of collapse safety and direct (due to earthquake damage) economic losses. The effect of retrofit and various structural characteristics is illuminated for the single-family cripple wall houses. 2^k full factorial experiment design combined with hypothesis testing is used to identify the most influential structural properties. Two story buildings performed worse than their one-story counterparts and pre-1945 buildings performed better than pre-1955 construction. Building performance is found to be positively correlated with cripple wall heights and cripple wall retrofits provided significant overall improvements. Surrogate models are developed as a compact statistical link between key structural characteristics and seismic performance. Several machine learning algorithms are investigated for predicting the building median collapse intensity and expected annual loss using the cripple wall height, seismic weight, damping ratio and material properties as features. The XGBoost algorithm provides the most accurate prediction and on average, limits the prediction error to less than 10%. Using the well-developed machine learning models, additional sensitivity analyses are conducted and the effect of model uncertainty on collapse safety and expected annual losses is quantified using Monte Carlo simulation. For the SWOF buildings, a multi-scale cost-benefit analysis of the Los Angeles Soft-Story Ordinance Retrofit is performed. Individual buildings take an average of four to five years for the reduced earthquake losses to exceed the one-time retrofit cost. At the portfolio-scale, the average cost-benefit ratio is found to be 0.32 for the hypothetical M 7.1 Puente Hills scenario earthquake. A stochastic event-set cost-benefit assessment is also performed, where all events (approximately 8,000) that are significant to the region are considered. From this assessment, it is determined that the probability of achieving a desirable cost-benefit ratio (value between 0.0 and 1.0) within a 50-year period is approximately 0.9. Lastly, a retrofit design optimization framework is proposed with the goal of maximizing performance-based benefits at the regional scale. The methodology relies a machine learning-based surrogate model to predict seismic performances of retrofitted buildings given the design parameters. Then, a stochastic optimization algorithm is implemented to find the retrofit designs that maximize the improvement in seismic performance for the entire portfolio under a set of pre-defined constraints. The algorithmic retrofit leads to collapse losses that are comparable to the Los Angeles Ordinance guidelines while using only 60% of the resources. The performance-oriented framework is shown to address the inefficiency of conventional strength-based retrofit policies.

Author : Ioannis P. Christovasilis
Publisher :
Page : 200 pages
File Size : 40,73 MB
Release : 2009
Category : Earthquake resistant design
ISBN :

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"This report is the first in a series of reports resulting from the NEESWood Project. It documents the benchmark shake table test program of a full-scale two-story wood frame townhouse building. The experimental program focused on the various construction elements that could significantly influence the seismic response of these types of buildings. The testing was divided into five phases: (1) engineered wood structural (shear) walls alone; (2) wood structural walls incorporating viscous fluid dampers; (3) installation of gypsum wallboard to engineered wood structural walls; (4) installation of gypsum wallboard to interior partition walls and ceilings; and (5) installation of stucco as exterior wall finish. Two kinds of tri-axial historical ground motions were used for the tests: a Design Basis Earthquake (DBE) with a probability of exceedance of 10% in 50 years, or a return period of 475 years; and a Maximum Credible Earthquake (MCE) with a probability of exceedance of 2% in 50 years, or a return period of 2,475 years"-- Page iv.

Author : M. J. Tait
Publisher :
Page : 43 pages
File Size : 43,31 MB
Release : 2011
Category : Buildings
ISBN :

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The objective of this research was to evaluate the response of base isolated residential wood-frame and masonry buildings using Stable Unbonded Fiber Reinforced Elastomeric Isolator (SU-FREI) bearings in several seismic regions in Canada. Two model-scale bearing types were fabricated and tested to obtain mechanical properties and ultimate deformation limits. A shake table test of a scaled model two-storey base isolated building was conducted to investigate its response behaviour. The primary test output was the acceleration and drift experienced by the building and the lateral deformation in the SU-FREI bearings. A one-degree of freedom (1-DOF) nonlinear modelling approach, using the response spectrum technique, was developed to permit the rapid prediction of the peak response acceleration of an isolated building. Isolation systems were designed for both a two-storey masonry building and a single storey wood frame building. Peak response acceleration and base shear force were predicted for both buildings. The level of seismic mitigation was evaluated using a comparative assessment of linear elastic non-isolated masonry and wood frame buildings. Results from this study show that a substantial reduction in the peak response acceleration and peak base shear can be achieved in both low-rise masonry and wood frame buildings by implementing SU-FREI base isolation systems.