Prototype Frame Research Articles

Seismic capacity of masonry infilled RC frame strengthening with expanded metal ferrocement

This research was to investigate the behavior of masonry infilled reinforced concrete frame strengthening with expanded metals under cyclic loading. In this study, a prototype frame was chosen from a three-story reinforced concrete building that was not designed for earthquake load. Three specimens were built to full scale of 1:1 ratio including, the reinforced concrete bare frame (BF), the brick masonry infilled frame (W) and the masonry infilled frame strengthening with an expanded metal sheet (W-SR). The specimens were tested under constant vertical load and cyclic lateral load. The infilled frame strengthening with expanded metal sheet (W-SR) provided the lateral strength, stiffness and energy dissipation capacity of 1.25, 1.26, 1.27 times those of the brick masonry infilled frame (W), respectively. An analytical model based on an equivalent strut was proposed for masonry infill panels. In this approach, the nonlinear behavior obtained from the masonry prism test results was employed to determine the lateral strength and stiffness of the masonry panel model. The hysteretic behavior of the infill panel and infilled frame was evaluated using a nonlinear structural analysis program, RUAUMOKO. The results of the hysteretic behavior were compared with the experimental results to validate the proposed model.

EVALUATION METHOD OF CONTRIBUTION FACTOR OF STRUCTURAL COMPONENTS FOR SEISMIC CAPACITY ASSUMING INVARIABLE INTER-STORY DRIFT BEFORE AND AFTER DAMAGED AND INVESTIGATION OF APPLICABILITY TO RC FRAMES WITH BEAM YIELDING MECHANISM

Main purpose of this study is to investigate residual seismic capacity of damaged buildings. An evaluation method of residual seismic capacity (R) using contribution factors of structural components (Er) was proposed. Er is evaluated by assuming invariable inter-story drift distribution for a building even after damage to focus on the investigation of effect of location of components. Then, modeling methods of damaged buildings were discussed using SDOF models. Finally, it was shown that the proposed method can estimate Rappropriately for buildings with uniform inter-story drift distribution but cannot for buildings with non-uniform distribution through dynamic analyses of prototype frames.

Light Weight Freight Rolling Stock Bogie Frame: Design Methodology Validated with Field Oscillation Trials

Indian railway has improved the laden to tare weight ratio by producing lighter as well as higher strength bogie frame of freight rolling stock. Bogie frame is the crucial component of the rail vehicle which carries static load in the form of gross weight and dynamic loads arising from various track and wheel irregularities. The three piece freight vehicle bogie frame comprises two side frames and one bolster. The side frame; fitted with three piece bogie frame and responsible for the ride quality of the freight vehicle, is considered in present study. The locations suitable for weight reduction are found by finite element analysis (FEA), using side frame solid model in MSC FEA environment. International standards of the association of American railroad (AAR specification M-203) [1] load cases and boundary conditions are deployed for analysis in the context of the operating scenario of Indian railways. Typical Indian railway track signatures are used as input for transient analysis. Time dependent stresses at critical speeds are used for fatigue strength evaluation as per Goodman diagram. The modified design is approx. 13.90% lighter and sustains 25.00 ton axle load in comparison of earlier 22.00 ton. Suggested topological changes have been compared by using frequencies of the initial and modified designs. Further, based on Indian railways running conditions, actual assessment and trial of the modified design bogie frame prototype has been carried out by Research Designs and Standards Organisation (RDSO) [2]. The results of the trial are found to be satisfactory and within the prescribed range.

Effectiveness of Clay Damper for Reduction in Vibration Amplitudes

Very soft clay is considered to be a poor construction material because of high compressibility and low shear strength. Again, a deep soft clay layer amplifies the stress amplitude during seismic wave propagation. Hence, it is a common practice either to avoid a soft clay layer or to improve the properties of the clay layer for founding a structure in the soft clay. In spite of all these demerits, the high damping ratio of a soft clay layer may be effectively used as an effective damper for reduction of stress amplitudes. Care must be taken over retention of moisture content of the clay and prevention of oozing out of the soft clay under a vertical stress. In the present study the soft clay has been wrapped with two layers of geomembrane in the form of a geocell of thickness 100 mm and has been placed below the foundation of a prototype frame structure. Two layers of geocells have been used for effective reduction of stress amplitude. Horizontal vibration has been imparted to the ground and acceleration-time histories at different locations like ground, foundation, tie beam, floor beam have been recorded. Comparison of results between a structure resting over clay damper and a structure resting over ground has been made. It is observed that the stress amplitude has been reduced to 40–50% of the normal value due to installation of the clay dampers. Hence, if properly designed, the soft clay may be effectively used to reduce the vibration during earthquakes.

Parametric study of seismic performance of structures with multiple rocking joints

Abstract Research has demonstrated that base rocking lateral force resisting systems have excellent seismic performance which has resulted in their implementation in practice. However, such systems are limited in height because of force demands that are amplified by higher-mode effects. The use of multiple rocking joints, together with energy dissipation, has been proposed to mitigate higher-mode effects in rocking systems. Previous research has shown that placing a second rocking joint at the mid-height of a rocking steel braced frame, combined with the utilization of energy dissipation devices, is effective in reducing the effects of higher modes in rocking steel frames. Here, a parametric study using nonlinear response history analysis for a suite of earthquake ground motions is described that investigates the efficiency of higher-mode mitigation from multiple rocking joints and the optimal locations for second rocking joints. The parametric study is based on three prototype rocking steel frames of different heights. Other parameters studied were selected to investigate a wide-range of rocking system behaviors and include the energy dissipation level, flexural and shear stiffness of the frames, yield displacement of the energy dissipators, frame bay width, and post-tensioned bar type. Results suggest that placing a second rocking joint within the lower 22%–50% of the building height reduces the maximum story moment by approximately 10%–35% in different systems, and that energy dissipation provided at the second rocking joint is effective in controlling shear force. The interaction between changing specific parameters and the structural seismic performance is also revealed in this study. Finally, dynamic analyses of the 20- and 30-story prototype frames with 3 rocking joints reveals that a third rocking joint helps reduce the overturning moment slightly for the 20-story frames, while the reductions in overturning moment and shear force are more obvious for the 30-story frames.

Tablet-Based Well-Being Check for the Elderly: Development and Evaluation of Usability and Acceptability.

BackgroundMany elderly people prefer to live at home independently. One of the major concerns raised by the family members is the safety and well-being of their elderly family members when living independently in a home environment. To address this issue, assistive technology solutions have been available in the market. Despite their availability and proliferation, these types of solutions are not popular with the elderly due to their intrusive nature, privacy-related issues, social stigma, and fear of losing human interaction. This study shares the experience in the development of a digital photo frame system that helps family members to check the well-being of the elderly, exploiting their desire to remain socially connected.ObjectivesThe aim of this study was to iteratively design, implement, and assess the usability, user friendliness, and acceptability of a tablet-based system to check the well-being of the elderly.MethodsOur study methodology comprises three separate stages: initial system development, contextual assessment, and comparative case study evaluation.ResultsIn the first stage, requirements were elicited from the elderly to design a well-being check prototype. In the second stage, areas for improvements (eg, privacy features) were identified. Also, additional features (such as medication prompts or food reminders) were suggested to help aged and health care service providers with effective but subtle monitoring of the elderly. These would lower their operating cost by reducing visits by care providers to the homes of the elderly. In the third stage, the results highlighted the difference (between users in India and Australia) in the levels of familiarity of the elderly with this technology. Some elderly participants at the Kalyani Institute for Study, Planning and Action for Rural Change, India latched onto this technology quickly while a few refused to use the system. However, in all cases, the support of family members was crucial for their willingness to use the technology.ConclusionsThis project has three major outcomes. First, a picture frame prototype was tested with the elderly to leverage the benefits of social communication. Second, the project helped us test and implement the “Silvercare” model for supporting the elderly through young retired people residing in the area. Finally, the project helped formalize the agile three-stage design methodology to develop information technology solutions for the elderly. Also, the project contributed to an ongoing European Union Project called Victoryahome, which involves more than 50 sites across 5 countries (Norway, Sweden, Netherlands, Portugal, and Australia) to assess the use of telepresence robots, wearable fall detectors, and medication dispensers for the elderly living independently.

Seismic safety evaluation of reinforced concrete masonry infilled frames using macro modelling approach

Many reinforced concrete buildings have been built with masonry infill walls for architectural needs without considering their mechanical contribution. However, ignoring the structural influence of infills may lead to significant inaccuracies in the prediction of the actual seismic capabilities of the structure. Aiming at providing numerical tools suitable for engineering practice, simplified methodologies for predicting the nonlinear seismic behaviour of infilled frame structures (IFS) have been proposed, mostly considering the contribution of the infill as an equivalent diagonal strut element. In this paper, an alternative plane macro-element approach for the seismic assessment of IFS is proposed, validated and applied to a benchmark prototype building. The model validation is focused on recent experimental and numerical results that investigate the influence of non-structural infills, also in the presence of different openings layouts. As a benchmark investigation, a multi-storey plane frame prototype, for which the results of pseudo-dynamic tests are available, is investigated and compared to the results obtained by using a commonly adopted single-strut model. The merits and drawbacks of the considered numerical approaches are highlighted.

Numerical investigation on design requirements for steel ordinary braced frames

The strength of beams and columns can significantly influence on the seismic performance of steel ordinary concentrically braced frames (OCBFs) due to the unbalanced forces that occur after buckling of braces. Current seismic provisions have required specific design requirements for beams and columns in steel OCBFs to sustain the loads induced under post-buckling limit state. To analyze the influence of the design requirements on collapse responses of steel OCBFs, this study carried out nonlinear static and dynamic analyses of 5- and 10-story prototype frames designed considering different design requirements relating to strengths of beams and columns. The analysis results showed that all prototype buildings satisfied the limitation of an inter-story drift ratio of 0.02 while significant differences are observed between the collapse capacities of each prototype building according to the design criteria of unbalanced forces. The collapse capacities of prototype frames were also evaluated using incremental dynamic analyses and FEMA P-695 methodology. It is observed that the collapse capacities of the prototype frames mainly depended on axial force-carrying capacities of the columns in the lower stories rather than those of the beams and that the use of strong columns improves the collapse capacities of the prototype frames.

Systematic design of unbonded fiber reinforced elastomeric isolators

Fiber reinforced elastomeric isolators (FREIs) comprise alternating bonded layers of elastomer and fiber reinforcement sheets. In an unbonded application the isolator is located in place without any bonding or mechanical fastening provided at its contact supports. The unbonded application results in an increased seismic isolation efficiency, however, it introduces few design limitations as it relies on friction to transfer shear loads, and no vertical tension can be taken by the isolator. These limitations may restrict the use of isolators where the superstructure overturning is of concern or in regions where large vertical ground accelerations are expected. This paper presents a systematic method for the design of structures supported on unbonded-FREIs. The design calculations conform the equivalent static force (ELF) procedure outlined in current seismic codes and account for the vertical component of earthquake in the analysis. A stability parameter has been introduced to verify both the overturning and sliding stability of the isolated system. The efficacy of the design method is illustrated by extensive response history simulations for several prototype frame structures.

Design and Engineering of a Target for X-Ray Thomson Scattering Measurements on Matter at Extreme Densities and Gigabar Pressures

Reconciling the experimental and system requirements during the development of a new target system is one of the most challenging tasks in the design and engineering of targets used in the National Ignition Facility.Targets for the GigaBar 3 campaign were meant to allow the detection of extremely weak Thomson scattering from matter at extreme densities in the face of very bright backlighter and laser entry hole plasma emissions. The problem was to shield the detector sufficiently while maintaining beamline and view clearances, and observing target mass restrictions.A new construction process, based on a rapid prototype frame structure, was used to develop this target. Details of the design process for these targets are described, and lessons from this development for production and target assembly teams are discussed.

Seismic optimization design for uniform damage of reinforced concrete moment-resisting frames using consecutive modal pushover analysis

In this study, a practical optimization procedure is developed for uniform damage design of reinforced concrete moment-resisting frames using consecutive modal pushover analysis based on the framework of performance-based earthquake engineering. Consecutive modal pushover, which can capture the higher-mode effect well, is employed to derive the inelastic seismic demands of structures subjected to considered seismic hazards. Furthermore, the optimization problems are formulated using the profile of inter-story drift ratios and component hinge rotations to redistribute the steel reinforcements from components with low damage to ones that experience high damage under the constant-cost constraint, until a state of uniform damage distribution prevails. By applying the proposed design procedure to two prototype frames with five and eight stories designed using the Chinese Seismic Design Code (GB 50011-2010), the efficiency of the method as well as the variation of steel reinforcements is demonstrated. The seismic performances of final solutions and prototype frames are compared through nonlinear dynamic analysis for scenarios of 22 ground motions matching well with the code-compliant spectrum. The results show that the proposed method allows for a significant reduction of maximum story drifts combined with more evenly distributed story drifts and component hinge rotations, indicating better seismic performance for the optimized structures.

Influential properties of hysteretic energy dissipating devices on collapse capacities of frames

Various advantages of hysteretic energy dissipating devices (HEDDs) have been recognized and their applications are getting popular. In parallel with this, current seismic codes prescribe a design procedure for structures employing HEDDs. According to one of seismic codes, ASCE/SEI 7, the minimum seismic base shear resisted by its seismic force-resisting systems (SFRSs) shall not be <75% of the total seismic base shear which is carried by a structure. This minimum base shear requirement for SFRSs is implicitly intended to provide safety in the event of malfunction of HEDDs. Although there are rigorous requirements for damped structures, further studies are still required to investigation of the collapse capacities of damped structures which have increasingly paid attention to earthquake engineering communities. In order to address this, this study carried out incremental dynamic analyses to evaluate the collapse performance of the 3- and 6-story prototype steel special moment-resisting frames (SMRFs) with and without HEDDs of which the strength capacities are different. The analysis results show that the collapse margin ratios of the prototype frames depend on the amount of base shear carried by their HEDDs and uncertainties on design requirements. The prototype structures with larger seismic base shear carried by HEDDs result in small variation in collapse capacity distribution and satisfy the minimum collapse margin ratio regardless of uncertainties on design requirements.

Experimental Verification of Subtle Frame Components Prototypes from High Performance Concrete for Energy Efficient Buildings

Mechanical properties of high performance concrete (HPC) enable design of subtle structural elements. Subtle HPC frame concept comes from the effort to integrate load bearing elements into building envelope in order to reduce risks of thermal bridges. Substantial advantages of subtle structural elements are material and energy savings during production, transportation, manipulation and assembling. Paper presents preparation and implementation of construction of experimental frame at University Centre UCEEB in Buštěhrad. Individual structural elements were made in prefa plant ŽPSV a.s. in Litice nad Orlicí. Construction of frame prototype is the result of long term research when the vertical and horizontal structural elements and their connections were successively designed and experimentally verified. This article shows experimental results of horizontal load bearing structures - floor panels and beams - in detail. Samples were tested by four-point bending test and also creep of floor panels was measured. Accomplished calculations, experimental verification and analysis have showed that subtle HPC frame is the effective solution from reliability aspects as well as from environmental and economical parameters. Minimal columns cross sections enable their complete implementation into building envelope and they also contribute to high quality architectonic solution of buildings interiors.

Seismic evaluation and retrofitting of reinforced concrete buildings with base isolation systems

A parametric study on the nonlinear seismic response of isolated reinforced concrete structural frame is presented. Three prototype frames designed according to the 1954 Hellenic seismic code, with number of floor ranging from 1 to 3 were considered. These low rise frames are representative of many existing reinforced concrete buildings in Greece. The efficacy of the implementation of both lead rubber bearings (LRB) and friction pendulum isolators (FPI) base isolation systems were examined. The selection of the isolation devices was made according to the ratio <TEX>$T_{is}/T_{fb}$</TEX>, where Tis is the period of the base isolation system and <TEX>$T_{bf}$</TEX> is the period of the fixed-base building. The main purpose of this comprehensive study is to investigate the effect of the isolation system period on the seismic response of inadequately designed low rise buildings. Thus, the implementation of isolation systems which correspond to the ratio <TEX>$T_{is}/T_{fb}$</TEX> that values from 3 to 5 is studied. Nonlinear time history analyses were performed to investigate the response of the isolated structures using a set of three natural seismic ground motions. The evaluation of each retrofitting case was made in terms of storey drift and storey shear force while in view of serviceability it was made in terms of storey acceleration. Finally, the maximum developed displacements and the residual displacements of the isolation systems are presented.

Uncertainties Influencing the Collapse Capacity of Steel Moment-Resisting Frames

Abstract In order to exactly evaluate the seismic collapse capacity of a structure, probabilistic approach is required by considering uncertainties related to its structural properties and ground motion. Regardless of the types of uncertainties, they influence on the seismic response of a structures and their effects are required to be estimated. An incremental dynamic analysis(IDA) is useful to investigate uncertainty-propagation due to ground motion. In this study, a 3-story steel moment-resisting frame is selected for a prototype frame and analyzed using the IDA. The uncertainty-propagation is assessed with categorized parameters representing epistemic uncertainties, such as the seismic weight, the inherent damping, the yield strength, and the elastic modulus. To do this, the influence of the uncertainty-propagation to the seismic collapse capacity of the prototype frame is probabilistically evaluated using the incremental dynamic analyses based on the Monte-Carlo simulation sampling with the Latin hypercube method. Of various parameters related to epistemic uncertainty-propagation, the inherent damping is investigated to be the most influential parameter on the seismic collapse capacity of the prototype frame.

Analytical and experimental study on mild steel dampers with non-uniform vertical slits

This study proposes a novel mild steel damper with non-uniform vertical slits. The influence of different shapes of vertical slits of the core energy plate on the energy dissipation and buckling resistance capacities is analyzed. Based on the theoretical analysis, formulas of key parameters of the dampers, including the elastic lateral stiffness, shear bearing capacity and yield displacement, are derived. The effectiveness of the proposed damper is demonstrated through pseudo static tests on four 0.25-scale specimens. Performance of these dampers, i.e. cyclic deformation, stress distribution, energy dissipation capacity, etc., are presented and discussed. Using the numerical models of dampers calibrated through test data, earthquake time-history analyses were conducted, and it is observed that the dampers significantly reduce the seismic responses of the prototype frame and have a desirable energy dissipation capacity.

Discussion of “seismic performance of buckling-restrained braced frames with varing beam-column connections”

The prototype frame models presented in the discussedpaper were initially designed as 7-story building withsymmetric plan view (3 by 5 bays) as shown in the Fig.2 of the discussed paper. The BRB members were installedaround the center of the perimeter moment-resisting framesfor the purpose of withstanding lateral loads during theseismic event. The detail description of the inside gravityload-resisting frame cannot be found in the discussedpaper. The authors should have exhibited the illustrationof the whole frame model as well. Although the behaviorof the whole frame building is controlled by the perimetermoment-resisting frames, including the gravity load-resistingframe in the analytical frame model is necessary to reflectrefined response mechanism (i.e., P-delta effect) duringanalyses. The prototype building presented in the discussedpaper can be modeled as the 2D frame model because itis designed to be symmetrical to the center axes with theuniform distribution of stiffness and mass.In order to simulate inelastic behavior during analyses,plastic hinges were assigned into the location of the framemember where plastic yielding is likely to occur. In thiscase, buckling failure due to geometric imperfection undercompression cannot be taken into consideration duringanalyses. Besides, it is difficult to predict plastic failuresoccurring at the locations where plastic hinges are notassigned. The discussers recommend for the authors touse the OpenSEES program (Mazzoni et al., 2006) ratherthan the SAP2000 package program next time. In theprogram, frame members can be modeled as nonlinearbeam-column elements with 2D discrete fiber sectionsand P-Delta coordinate transformation. These elementsare able to reproduce inelastic behavior resulting frommaterial nonlinearity as well as geometric imperfection.Furthermore, the failure state can be easily detectedthrough the whole frame member.

Experimental and Numerical Investigation of Ductile Top-Flange Beam Splices for Improved Buckling-Restrained Braced Frame Behavior

Buckling-restrained braced frame performance at high drifts is improved by providing beam splices that reduce demands in the gusset regions. Existing experimental data only consider web splices without a slab present. An alternative top-flange splice, proposed by others, was investigated experimentally and numerically. Two full-scale top-flange beam splices from a prototype frame were tested using the qualifying buckling-restrained brace frame cyclic loading protocol. During experimental testing, the gusset connection regions remained essentially undamaged through multiple cycles at 0.06 rad drift. The splice plates experienced low inelastic strains, but fatigue analyses indicate they could withstand over fourteen similar loading histories without requiring replacement. Finite-element models were used to investigate the influence of slabs on connections with web splices or top-flange splices. When slabs were considered, the top-flange splice transmitted over 70% less moment than the web splice.

Assessment of expected damage on buildings subjected to Lorca earthquake through an energy-based seismic index method and nonlinear dynamic response analyses

The city of Lorca (Spain) was hit on May 11th, 2011, by two consecutive earthquakes of magnitudes 4.6 and 5.2 M $$_\mathrm{w}$$ , causing casualties and important damage in buildings. Many of the damaged structures were reinforced concrete frames with wide beams. This study quantifies the expected level of damage on this structural type in the case of the Lorca earthquake by means of a seismic index $$I_{v}$$ that compares the energy input by the earthquake with the energy absorption/dissipation capacity of the structure. The prototype frames investigated represent structures designed in two time periods (1994–2002 and 2003–2008), in which the applicable codes were different. The influence of the masonry infill walls and the proneness of the frames to concentrate damage in a given story were further investigated through nonlinear dynamic response analyses. It is found that (1) the seismic index method predicts levels of damage that range from moderate/severe to complete collapse; this prediction is consistent with the observed damage; (2) the presence of masonry infill walls makes the structure very prone to damage concentration and reduces the overall seismic capacity of the building; and (3) a proper hierarchy of strength between beams and columns that guarantees the formation of a strong column-weak beam mechanism (as prescribed by seismic codes), as well as the adoption of counter-measures to avoid the negative interaction between non-structural infill walls and the main frame, would have reduced the level of damage from $$I_{v}$$ $$\,=\,$$ 1 (collapse) to about $$I_{v}$$ $$\,=\,$$ 0.5 (moderate/severe damage).

Simulation of Seismic Collapse in Nonductile Reinforced Concrete Frame Buildings with Masonry Infills

AbstractImproved analysis methods and guidelines are presented to simulate the seismic collapse of nonductile concrete frame buildings with masonry infills. The analysis tools include an inelastic dual-strut model that captures the post-peak behavior of the masonry infill and its interaction with the surrounding frame. The dual compression struts capture the column-infill interaction that can cause shear failure of the columns and loss of their vertical load carrying capacity. A rigid softening shear degradation model is implemented in the beam-column elements to capture the shear failure of nonductile RC columns. Guidelines are presented to determine the strut model parameters based on data from 14 experimental tests on infill frames. The models are applied in three-dimensional nonlinear dynamic analyses of a three-story nonductile concrete frame prototype building with infills. The incremental dynamic analyses technique is utilized to understand the effect of the infill-column interaction and the rockin...