Performance-based Design Guidelines Research Articles

An improved method for statistics estimation of out-of-plane load resistance of masonry walls using design-code models and mechanics-based finite element models

The susceptibility of masonry walls to out-of-plane failure under seismic loading presents a significant engineering concern. In adherence to contemporary limit state design philosophy and as mandated by performance-based design guidelines, it is crucial to accurately estimate statistics parameters such as the mean and variance of out-of-plane resistance. To achieve this, two deterministic models are often considered within the Monte Carlo simulation framework: design-code models, known for their computational efficiency but potential for significant model error, and mechanics-based finite element models, noted for their accuracy but computational intensity. Relying solely on either model for statistics estimation presents challenges due to their respective inherent limitations. This study introduces an improved strategy that synergizes the strengths of both models, resulting in enhanced statistics estimators for the out-of-plane resistance of masonry walls. The proposed methodology involves the use of the control variate method by integrating numerous design-code model evaluations to boost computational efficiency while incorporating a limited number of finite element model evaluations to ensure accuracy. The constructions of the proposed estimators follow rigorous optimization procedures to minimize associated errors and variances. Theoretical derivations are provided for essential elements in the estimator constructions, such as model evaluation numbers for finite element and design-code models and control variate coefficients. Moreover, the accuracy of the proposed estimators is compared with that of the crude Monte Carlo estimator. A key benefit of the proposed estimators is their unbiased nature, and their accuracy is not compromised by the discrepancies between the finite element model and the design-code model. To demonstrate the practicality of these estimators, two case studies are illustrated: one focusing on unreinforced masonry walls and the other on reinforced masonry walls. The results indicate that design-code model-based estimators exhibit large bias, and compared to the estimators that solely rely on the finite element model, the proposed estimators achieve higher accuracy given the same computational budget.

Seismic Performance Evaluation of a Chilean RC Building Damaged during the Mw8.8 Chile Earthquake

Chile, recognized as one of the world’s most earthquake-prone nations, has gained valuable insights from significant earthquakes, such as those in 1985 and 2010, which have influenced updates to the nation’s design codes. Although Chile’s seismic design approach has been largely effective in recent earthquakes and demonstrated an “operational” performance level in most structures, performance-based design (PBD) methods have not yet been officially incorporated as valid approaches in the Chilean seismic design codes for buildings. However, in 2017, the Chilean Association on Seismology and Earthquake Engineering (ACHISINA) introduced a PBD approach, primarily for verification purposes, based on the Los Angeles Tall Buildings Structural Design Council (LATBSDC) framework. In this work, firstly, we provide an overview of Chile’s PBD methodology, focusing on the thresholds for various performance levels. These levels are established through experimental and numerical analysis, correlating performance with permissible damage levels. The second part of the paper examines the seismic performance of a residential building, designed before the 2010 Maule earthquake and subsequently damaged, using Chile’s PBD guidelines. This case study highlights the implementation and effectiveness of PBD for assessing seismic resilience in Chilean structures.

Vibration-based temporary monitoring of a 253 m tall skew-plan building in Istanbul

A 253 m tall office building in Istanbul with a parallelogram footprint, which has 62 stories in total, 54 tower stories above and 8 podium stories below grade, was monitored using 92 channels of accelerometers deployed on 20 different floors for about 4 days. The structural system of the building consists of reinforced concrete (RC) core shear walls with peripheral composite columns and two-story tall RC outriggers between floors 29 and 31. First 12 natural vibration periods and mode shapes of the building together with the modal directions for the translational modes were identified from the ambient vibration records. These dynamic properties were reproduced with the three-dimensional finite element model developed using gross section properties for all structural members without a need for model updating. The fundamental period of the building at the time of testing, 5.3 s, is expected to lengthen to 5.9 s and 7.8 s upon cracking in structural members for the prescribed service-level and design-level evaluations, respectively, in line with the recent performance-based design guidelines for tall buildings. Damping ratios for the first six vibration modes, with median values of 0.6% and coefficients of variation in the order of 0.3–0.4, were identified through statistical analysis using the random decrement technique. The simulated peak floor accelerations, when the building was subjected to the 2019 Mw 5.8 Marmara Sea earthquake ground motions recorded in the vicinity of the building, showed that ASCE 7-16 in-structure floor acceleration amplifications are exceeded at the lower floors but not reached at the upper floors.

A parametric study on the graphical approach to assess corrosion vulnerability of concrete mixes in chloride environment

Proper evaluation of corrosion risks is substantial for developing performance-based design guidelines which can ensure adequate durability of reinforced concrete structures in chloride prone environment. This study focused on a probabilistic approach to quantify and analyze corrosion vulnerability of a comprehensive mix range by incorporating uncertainties of multitudes of factors, which affect the chloride-induced corrosion phenomenon. Corrosion risks, in terms of corrosion probabilities, were evaluated for a wide range of cover values and target service live values of 60 concrete mixes while investigating the effect of different mix parameters (water to cementitious-materials (w/cm) ratios, target slump ranges, etc.). Inclusion of supplementary binders (fly-ash and slag), in replacement proportions of up to 40%, was also considered to investigate the effect of pozzolanic activity on corrosion probabilities. Profound correlations were also obtained between estimated corrosion probabilities and a convenient dimensionless parameter formulated from mix design parameters. The correlations were later implemented in developing generalised graphical guidelines which is deemed to be adept in quick and reliable estimation of tentative corrosion risks without conducting any destructive tests. This would also enable optimization of ideal binder type and mix design parameters while ensuring minimum corrosion risks for desired life-span.

Design of RC moment frame buildings consistent withearthquake resistant design philosophy

Earthquake Resistant Design Philosophy seeks (a) no damage, (b) no significant structural damage, and (c) significant structural damage but no collapse of normal buildings, under minor, moderate and severe levels of earthquake shaking, respectively. A procedure is proposed for seismic design of low-rise reinforced concrete special moment frame buildings, which is consistent with this philosophy; buildings are designed to be ductile through appropriate sizing and reinforcement detailing, such that they resist severe level of earthquake shaking without collapse. Nonlinear analyses of study buildings are used to determine quantitatively (a) ranges of design parameters required to assure the required deformability in normal buildings to resist the severe level of earthquake shaking, (b) four specific limit states that represent the start of different structural damage states, and (c) levels of minor and moderate earthquake shakings stated in the philosophy along with an extreme level of earthquake shaking associated with the structural damage state of no collapse. The four limits of structural damage states and the three levels of earthquake shaking identified are shown to be consistent with the performance-based design guidelines available in literature. Finally, nonlinear analyses results are used to confirm the efficacy of the proposed procedure.

Seismic design of RC frame structures based on energy-balance method

The force- and displacement-based design methodologies have been widely used in current seismic design practice. In both methodologies, inelastic behavior is determined indirectly since the seismic demands are derived from elastic acceleration response spectra. In this study, a novel energy-based design (EBD) approach is proposed in the determination of both seismic demand and dissipation capacities of reinforced concrete (RC) frame members through their inelastic behavior directly. In the case of frame-type RC structures, the distribution of demand plastic energy throughout the structure is achieved. The proposed EBD is then accomplished by comparing the demand plastic energy with the energy dissipation capacity of members while integrating performance-based design guidelines. A cantilever column and a benchmark frame, both from the literature, are analyzed in verification of the proposed methodology. Comparisons are made between force, displacement and EBD methodologies in terms of soil condition, member, system and ductility performance requirements. Member and global performance targets are found to be comparable in displacement and EBD methodologies. However, owing to lack of ductility considerations in the prior design methodologies, the proposed EBD showed more reliable result in the determination of both cross-sectional geometry and its rebar configuration. The proposed methodology provides better understanding of damage state limits of RC members by incorporating the plastic energy spectrum, which includes cyclic action, duration, and frequency content of ground motions, as well as inherent ductility in both demand and capacity determinations. The sensitivity analyses between code compliant-design and soft-story-mechanism buildings showed a distinct difference in the variations of seismic energy among the members and their corresponding damage distributions. EBD methodology provides better in depth understanding of the seismic design in terms of demand and capacity of member and overall structural system, and their corresponding performance.

Post-earthquake fire behavior and performance-based fire design of steel moment frame buildings

This paper presents an assessment of steel buildings subjected to post-earthquake fire, illustrated through the implementation of a ten-story case study building, which was designed in accordance with U.S. design codes. The building is located in a high seismic region (Los Angeles, CA), and designed for the associated seismic hazard levels using perimeter special moment frames (SMFs) to resist lateral (wind and seismic) loading and gravity interior frames with composite floor systems to resist gravity (dead and live) loading. The entire 3D building structure was idealized and analyzed using finite element models capable of modeling inelastic deformations, instability failures, and connection damage due to earthquakes and fire. The building models were subjected to eleven earthquakes followed by three different fire scenarios to simulate the effects of post-earthquake fires. The results from post-earthquake fire analyses were used to assess the impact of earthquake-induced damage on structural behavior and stability during fire. Assessments indicate that, for the type and design of structure considered in this research, earthquake-induced damage is generally limited to the perimeter moment frames and has limited influence on post-earthquake fire performance, which is governed by the strength and stability of gravity columns and floor systems. Analytical parametric studies were conducted to further assess and develop performance-based design guidelines for improving structural behavior and stability during post-earthquake fires. These studies indicate that partial or full collapse of the building structure can be prevented by sufficiently increasing the structural design (size) or fire protection (fireproofing thickness) of the critical gravity columns.

The use of digital image correlation for identifying failure characteristics of cross-laminated timber under transverse loading

The localised crack induced by external load on an individual cross laminated timber (CLT) structural element will generate stress concentrations, which leads to the failure of a structural member. A better understanding of the structural performance of CLT in terms of its strength and failure modes under transverse loading needs to be developed to ensure structural stability, safety and resilience of mass timber buildings. The monitoring and prediction of crack initiation and the failure modes of structural elements before and after localised deformation could enable the mitigation of severe damage in timber buildings. In this study, four-point bending tests were conducted and the digital image correlation (DIC) technique was used as a cost-effective solution to monitor the crack initiation and growth behaviour and predict the failure types of Australian radiata pine CLT panels under out-of-plane loading. Both a speckled surface pattern and the natural grain of the timber were used in the DIC analysis. This will aid with the development of efficient performance-based design guidelines for timber buildings. Based on the crack growth rates and strain fields, the DIC technique can predict the failure locations and modes, namely rolling shear or delamination. This study also highlighted that DIC analysis with a natural grain of timber can be used to measure the crack growth rates in CLT.

Inelastic behavior of a bridge bent subjected to truck impact: Experimental and computational study

A unique field experimental study was conducted to investigate the behavior of a reinforced concrete pier bent subjected to impact by a surrogate truck model. The bent was a two-bay, one-story frame that represented a realistic highway structure. It was tested at half scale at the FHWA-FOIL facility. The surrogate truck model consisted of a pendulum with a specially designed impactor that was progressively crushed to represent the impact demands associated with truck collision. The bent was proportioned such that the two exterior columns had different capacities, thereby accommodating two separate tests. After validating the pre-test simulation model using the measured and other experimental data, parametric simulations were conducted to gain insight into the failure response of the bent and to critique the AASHTO truck impact guidelines. The necessity for developing performance-based design guidelines for truck-versus-pier crashes was highlighted.

Extreme Wind Fragility Assessment for Window System Failure in Lightweight Steel Frame Structure in Korea

In this research, we concentrate on defining the initial step in the framework of probability risk assessment of wind loads by developing wind fragility on small-scale residential facilities in South Korea, i.e., the window system installed in a lightweight steel frame house. The study was to develop a fragility model using random variables according to the wind loads parameters and the resistance capacity of the window system. Design- and material-based experimental results in typical residential facilities in South Korea provided capacity parameters, i.e., resistance capacity of the window system, which allow us to obtain the failure probability of the window system under various limit conditions and consequently be used to evaluate the vulnerability of windows in this small residential steel house. The study has successfully proved that the most vulnerable are the leeward windows, i.e., opposite to the wind direction. Usage of this methodology could lead to a more predictable structure performance and facilitate the introduction of performance-based design guidelines for this component of building. Fragilities such as those presented here also can be convolved with wind hazard curves to develop a risk assessment tool, which can evaluate the potential impact of a natural hazard in public planning and mitigate the consequent economic losses and social disruption.

Response History Analysis for the Design of New Buildings in the NEHRP Provisions and ASCE/SEI 7 Standard: Part II - Structural Analysis Procedures and Acceptance Criteria

This paper represents the second part of a series of four publications on response history analysis for new buildings. It specifically focuses on modeling assumptions, consideration of important effects in the analysis, and interpretation of analysis results via global and local acceptance criteria. A statistical basis for development of both force- and deformation-controlled acceptance criteria consistent with the collapse probability goals of ASCE/SEI 7 is illustrated. More explicit sub-classifications of force- and deformation-controlled actions are proposed within the statistical framework. Additional philosophical discussion and simple probabilistic arguments are presented on the topic of consideration of unacceptable response, and guidance on addressing unacceptable response is given. Similarities and differences between the new requirements and those in other performance-based design guidelines are also enumerated.

Seismic performance of reinforced concrete dual-system buildings designed using two different design methods

This paper aims to assess seismic performance and cost efficiency of a 42-story reinforced concrete dual-system building, i.e. a centrally located core wall building with perimeter special moment-resisting frames, hypothetically located in Los Angeles, California. The building was designed based on two different design approaches by a renowned structural engineering company: (a) following the prescriptive design requirements of the International Building Code (IBC 2006) and (b) following performance-based design guidelines described in Los Angeles Tall Building Structural Design Council (LATBSDC 2008). Detailed analytical models were developed for each building design to assess seismic performance of the buildings at different hazard levels in terms of various response quantities. Comparisons revealed that a performance-based designed building experienced modestly less damage associated with smaller interstory drifts and lower core wall stresses, even though the difference between two designs was modest and excellent performance was observed in both buildings. From a financial point of view, the performance-based designed building required higher initial costs due to larger member sizes, yet, lower annual repair costs due to smaller amount of damage/loss. Copyright © 2015 John Wiley & Sons, Ltd.

Evolution and Future of Building Codes in the USA

While harmonization of structural design codes in Europe has been a carefully coordinated and organized process, significant similar changes in American codes occurred in the late 1990s and early 2000s through completely different processes. These changes included the imposition of a single national code, the clear separation between the load and resistance parts of the design into distinct documents, and extensive attempts at streamlining the inclusions of the latest research results into the codes, among others. The paper first traces the development of design codes in the USA to provide a context for these recent developments. It then describes two examples of current code development processes: (a) the “loads” code or ASCE 7-10 and (b) the “steel” code or AISC 360-10. Finally, this paper describes the new building code regulatory landscape and the first attempts at generating performance-based design guidelines, in the form of seismic provisions for tall buildings in high seismic zones.

Fragility assessment for roof sheathing failure in high wind regions

This paper presents a fragility assessment for roof sheathing in light frame constructions built in high wind regions. A fragility methodology is developed to assess the performance of roof sheathing subjected to uplift (suction) pressures. The majority of single-family housing in the United States is woodframe construction. A review of the performance of woodframe buildings after recent hurricanes has shown that the majority of wind damage (insured losses) was the result of a breach in the building envelope. Loss of roof sheathing and broken windows result in water penetration causing extensive interior damage and associated property and contents losses. The aim of this study was to develop a fragility model for roof sheathing uplift using available fastener test data, recently developed wind load statistics, and a code-based approach for evaluating pressures. Five baseline structures considering different roof shapes, geographic locations, nail types, and enclosure conditions were investigated using simulation and system reliability concepts. Fragilities and complementary fragilities (or survivorship curves) of roof sheathing removal considering different levels of damage are developed as a function of basic wind speed (3 s gust wind speed at 33 ft (10 m) above the ground in open terrain). The fragility models presented in this paper can be used to develop performance-based design guidelines for woodframe structures as well as tools for condition assessment and loss estimation for use with the existing building inventory.