Seismic Rehabilitation—Benefits of Component Testing

Partial Capacity Design (PCD) has been developed by using magnification factor to keep some columns undamaged during major earthquake. By doing so, the structures will experience the partial side sway mechanism which is also stable, instead of the beam sidesway mechanism. However, in some cases, structures designed by PCD method failed to show the partial side sway mechanism since unexpected damages were still occurred at some columns. In this research, modification of PCD method is proposed by using two structural models in the design process. The first model is used to design beams and columns which are allowed to experience plastic damages, while the second model is used to design columns which are intended to remain elastic when the structure is subjected to a target earthquake. Two nominal earthquakes corresponding to Elastic Design Response Spectrum (EDRS) level with seismic modification factors (R) of 8.0 and 1.6 are used in the first and second structural models, respectively. It should be noted that the second model is identical to the first model except that the stiffnesses are reduced for elements to simulate potential plastic damages. This proposed method is applied to symmetrical 6 and 10 storey buildings with seismic load according SNI 1726:2012 and with soil classification of SE in Surabaya city. A Non-linear Static Procedure (NSP) or pushover analysis and Non-linear Dynamic Procedure (NDP) or time history analysis are employed to evaluate the performance of the structure. The evaluation is conducted at three earthquake levels which are nominal earthquake that is used in second model, earthquake corresponding to EDRS level, and maximum considered earthquake (MCER) specified by the code (50% higher than EDRS level). The building performances satisfy the drift criteria in accordance with FEMA 273. However, the partial side sway mechanism was not achieved at NDP analysis at maximum seismic load, MCER.

One design alternative of earthquake resistant building is Partial Capacity Design (PCD) method. Unlike the commonly used capacity design method, PCD allows a safe failure mechanism which is called partial sidesway mechanism. In this mechanism, all beams and some columns are allowed to experience plastic damages while some selected columns are designed to remain elastic (called elastic columns). A new approach to predict the required strengths needed to design each structural member, called modified-PCD (M-PCD) is proposed. In this research six- and ten-story reinforced concrete buildings were designed using M-PCD, and their seismic performances are investigated. The base shear force resisted by the elastic columns was set to approximately 70% of the total base shear. Both nonlinear static procedure (NSP) and nonlinear dynamic procedure (NDP) are used to analyze the structures. The results show that the expected partial side sway mechanism is observed, and the drifts of the buildings are acceptable.

The most significant expectation for ages has been building structures which are as high as possible, without column and wide-spanned in architecture. Also it is vital to cover these structures as spatial trusses. Similarly; economic, rapid, safe and aesthetical solutions in space systems are possible by spatial steel structures. In last decades, ATC 40, FEMA 273, 274, 356 and recently 440 are the most commonly used resources for seismic analysis procedures enduring with computing in civil engineering. These procedures are defined as displacement based performance analysis. On the other hand, nonlinear static procedures as basic step of these methodologies still have some problems in theoretical background. Some of the researchers are not satisfied with the accuracy of current performance based design methodologies. There are some question marks on how accurate capacity and demand spectrums demonstrate the structural capacity and earthquake demand respectively. In this study, comparison of improved nonlinear static procedures in FEMA- 440 has been made for spatial steel trusses supported on steel columns. For this, numerical models which are set up by taking structural properties of evaluable structures are investigated by using improved nonlinear static procedures which are given in FEMA- 440. Differences and harmonies of methods are still been determined. Key words: Spatial steel structures, nonlinear seismic procedures.

Modeling parameters (MP) of reinforced concrete columns are a critical component of performance-based seismic assessment methodologies because in these approaches damage is estimated based on element deformations calculated using non-linear models. To ensure model fidelity and consistency of assessment results, performance-based seismic assessment methods in ASCE 41, ACI 369.1, and ACI 374.3R prescribe modeling parameters calibrated using experimental data. This paper introduces a new set of equations to calculate reinforced concrete column non-linear modeling parameters optimized for design verification of new buildings using response history analysis. Unlike modeling parameters provided in ACI 369.1 and ASCE 41, intended for columns of older non-ductile buildings, the equations for modeling parameters anl and bnl presented in this study were calibrated to simulate the load-deformation envelope of reinforced concrete columns that meet the detailing requirements of modern seismic design codes. Specifically, the proposed equations are intended for use with provisions in ACI 374.3R, Chapter 18 and Appendix A of ACI 318-19 and Chapter 16 of ASCE/SEI 7-16. The proposed equations were calibrated using the ACI Committee 369 column database, which includes column configuration parameters, material properties, and deformation capacity modeling parameters inferred from the measured response of columns under load reversals. Dimension reduction techniques were applied to visualize different clusters of data in 2D space using the negative log-likelihood score. This technique allowed decreasing the non-linearity of the problem by identifying a subset of columns with load-deformation behavior representative of new construction conforming to current codes requirements. A Neural Network model (NN) was calibrated and used to perform parametric variations to identify the most relevant input parameters and characterize their effect on modeling parameters, and to stablish the degree of non-linearity between each input variable and the model output. Developing equations for modeling parameters applicable to a wide range of columns is challenging, so this research considered subsets of the database representative of new construction columns to calibrate simple practical equations. Linear regression models including the most relevant features from the parametric study were calibrated for rectangular and circular columns. The proposed linear regression equations were found to provide better estimates of new construction column modeling parameters than the available tables in ACI 374.3R and ASCE 41-13, and the equations ASCE 41-17.

California legislation requires acute-care hospital buildings designed prior to the 1973 code to be evaluated, and if necessary, retrofitted to Life Safety (LS) in order to keep providing acute care until 2030. Innovative and cost-effective solutions are required in order to meet the requirements of the regulatory agency, namely the Office of Statewide Health Planning and Development (OSHPD), as well as the owner expectations. This paper presents a case study of a six-story steel moment frame structure built in 1972 that is retrofitted using supplemental viscous damping. The building is located near two major Southern California active faults. In addition, the building is triangular in plan with non-parallel lateral force resisting systems. Because of the retrofit methodology, Non-linear Dynamic Procedure (NDP) per ASCE 41-06 is required. The building will be retrofitted by adding new primary external damped 3bay moment frames and modifying the existing moment frame base connections to prevent brittle failure by allowing controlled frame uplift. The basic retrofit criterion is to upgrade to LS under an earthquake with a 10% probability of exceedence in 50 years (475 year return period), namely BSE-1 earthquake. This paper presents some of the challenges found by the authors from a constructability perspective, as well as in the implementation of the NDP for a nonconventional building geometry near two major fault lines while satisfying the acceptance criteria delineated by OSHPD and ASCE 41-06. INTRODUCTION AND BACKGROUND After the Northridge Earthquake in 1994, the California legislature enacted Senate Bill 1953 (SB 1953) with the intent of assuring the public that acute care hospital buildings would remain operational after a major seismic event. In order to address high seismic risk buildings, all hospitals were required to perform an 1620 Structures Congress 2012 © ASCE 2012

Experimental study on steel reinforced high-strength concrete columns under cyclic lateral force and constant axial load

در طراحی بر اساس عملکرد، تعیین نیازهای لرزه‌ای یک گام مهم و اساسی در روند طراحی می‌باشد. نیازها را می‌توان به‌کمک روش‌های خطی یا غیرخطی تعیین نمود. دستورالعمل به‌سازی لرزه‌ای ساختمان‌های موجود، روش‌های تحلیلی مختلفی را به‌منظور ارزیابی و تعیین نیازها معرفی می‌نماید. از آن‌جایی که انتظار می‌رود اعضای سازه‌ای تحت اثر نیروی لرزه‌ای رفتار غیرخطی از خود بروز دهند، لذا منطقی است که در تعیین نیازهای اعضا، روش‌های غیرخطی مورد استفاده قرار گیرند. از بین دو روش غیرخطی، روندهای استاتیکی شامل تحلیل‌های بارافزون نسبت به روندهای تاریخچه زمانی مقبولیت بیش‌تری دارند. لذا در این مقاله به بررسی روش‌های غیرخطی و تفاوت‌های موجود بین روش‌های استاتیکی و دینامیکی غیرخطی برای تخمین نیازهای لرزه‌ای ‌پرداخته می‌شود و نتایج و آثار استفاده از روش‌های بارافزون در تخمین نیاز لرزه‌ای اعضا تحت اثر زمین‌لرزه‌های حوزه‌ی دور و نزدیک مورد بحث و بررسی قرار می‌گیرد.مقایسه‌ی نتایج حاصل از روش بارافزون با نتایج تحلیل تاریخچه‌ی زمانی غیرخطی نشان می‌دهد که روش‌های بارافزون در سطوح فوقانی سازه نیازهای لرزه‌ای را در حد پایین‌تری تخمین می‌زنند. این امر اهمیت ارتباط مشارکت مدهای بالاتر را در سازه‌های میان‌مرتبه و بلندمرتبه مشخص می‌نماید.

Punching shear behavior of ultra-high-performance fiber-reinforced concrete and normal strength concrete composite flat slabs

This research investigates numerically the potential failure of different framed structures after removal of a corner column. This study is directed towards the role of the joint above the removed column in terms of framed structures stability and internal forces redistribution utilizing linear static, nonlinear static and nonlinear dynamic analysis procedures. First, the preliminary linear static analysis as a part of more detailed nonlinear static and dynamic analysis to model reinforced concrete frames is performed. For nonlinear numerical models, three different moment-rotation capacity curves are considered for the joint above the removed column. These curves are taken according to FEMA 356 regulation according to the reinforcement condition at the joint location to represent normal joint, anchorage deficient joint and shear deficient joint. In linear static models, the results confirmed that, the more moment the joint can resist at the removed column location, the less moment is generated at the beam’s other end. In nonlinear static analysis, the model with normal plastic hinge properties recorded a higher carrying capacity than the model with both shear and anchorage plastic hinges. Nonlinear dynamic analysis with less assumptions offer the more representative modeling for the considered case study which is obvious from its closer perdition of internal forces and deflection compared to the reference findings.

Design of safe structures with resistance to progressive collapse is of paramount importance in structural engineering. In this paper, an efficient optimization technique is used for optimal design of steel moment frames subjected to progressive collapse. Seismic design specifications of AISC-LRFD code together with progressive collapse provisions of UFC are considered as the optimization constraints. Linear static, nonlinear static and nonlinear dynamic analysis procedures of alternate path method of UFC are considered in design process. Three design examples are solved and the results are discussed. Results show that frames, which are designed solely considering the AISC-LRFD limitations, cannot resist progressive collapse, in terms of UFC requirements. Moreover, although the linear static analysis procedure needs the least computational cost with compared to the other two procedures, is the most conservative one and results in heaviest frame designs against progressive collapse. By comparing the results of this work with those reported in literature, it is also shown that the optimization technique used in this paper significantly reduces the required computational effort for design. In addition, the effect of the use of connections with high plastic rotational capacity is investigated, whose results show that lighter designs with resistance to progressive collapse can be obtained by using Side Plate connections in steel frames.

Cyclic behaviour of lightly-reinforced concrete columns with short lap splices subjected to unidirectional and bidirectional loadings

In situ estimation of parameters in chemical models describing groundwater pollutant transport and fate is considered. During tracer tests, the observed breakthrough of a conservative species yields information characterizing the hydraulic behavior of a multiple‐well system. A streamline advective solute transport model incorporating the chemical model of interest is scaled so that it applies to all streamlines in the flow system. The hydraulic and chemical data are coupled through a combination integral which calculates the production well effluent concentration of a reactive tracer as a function of time. This mathematical model is combined with the measured effluent data and a nonlinear estimation procedure to estimate the parameters in the chemical models. The procedure is tested in controlled laboratory experiments. A later paper will present a field application.

Since the revision of the 10 CFR50.46 in 1988, the best-estimate codes may be used in safety demonstration and licensing, provided that uncertainties are added to the relevant output parameters before comparing them with the acceptance criteria. The uncertainty of output parameters comes principally from the lack of knowledge of the input parameters (initial and boundary conditions of the calculated transient, empirical models of the code, etc.). The application of the best estimate plus uncertainty analysis can be made in three steps in a statistical evaluation:1. The determination of the input parameters (IP) statistical characteristics.2. The modelling and understanding of the output parameters.3. The evaluation of the 95th percentile with a high degree of confidence.The first step is generally done manually according to expert judgments and comparing experimental data. The user effect is also very important in the determination of the statistical characteristics: range of variation and probability law. To reduce this user effect and to help the experts in their evaluation, IRSN has been developing a fully automated methodology and approach. This methodology is called DIPE: Determination of Input Parameters uncertaintiEs. This paper presents the advantages and limits of the application of DIPE for the physical models input parameters of CATHARE V2.5_1, a thermal-hydraulics code used in safety demonstration. DIPE will be applied to separate effect tests data used in the code qualification such as CANON and MARVIKEN.

Response of laminated glass-CLT structural components to reverse-cyclic lateral loading

In-plane flexural behavior of hollow brick masonry walls with horizontal holes