Drift Limits Research Articles

The Structural Performance of Reinforced Concrete Members with Monolithic Non-Structural Walls under Static and Dynamic Loads

The required base shear and drift limit for post-disaster management buildings have increased in the Japanese Building Code following major seismic events. One method to satisfy these requirements for reinforced concrete frame buildings is to cast exterior non-structural concrete wall elements to be monolithic with frame elements, but without anchoring the longitudinal wall reinforcing. This provides additional stiffness and strength while limiting significant damage in the non-structural wall. In this study, the structural performances of such elements were evaluated using static and dynamic experimental tests. The result indicates that non-structural walls that were neither isolated by seismic slits nor anchored to the adjacent walls with longitudinal reinforcements experienced less damage and higher deformability compared with walls having seismic slits. The confinement reinforcing impact was not observed on the strength and drift capacity of the beam member, owing to the large number of transverse reinforcements. However, the confinements limited the damage and nearly prevented concrete crushing. The maximum horizontal load of the specimen could be predicted using cross-sectional analysis, and the authors propose a simple equation to predict it with sufficient accuracy.

ANALISIS DINAMIK RESPON STRUKTUR GEDUNG BERATURAN DAN KETIDAKBERATURAN HORIZONTAL

ABSTRACTIndonesia is a country with geographical location where 4 large tectonic plates meet. Therefore, if a collision or frictionhits the country, it is vulnerable to earthquakes. This condition makes the buildings more vulnerable to earthquakes. The effect of earthquake force and the performance of the resulting structure will be different if the same load is applied to a regular building and to an irregular building. The method to calculate the effect of the earthquake on the analysis of high-rise building structures in this study used dynamic analysis with spectrum response referred to SNI 03-1726-2012 and 2013 ETABS software program assistance (13.1.1 build 1035). This study aimed to compare the performance of the structure based on the deflection value and the story drift limits in regular and irregular buildings. In this study, the response of structural performance on three building models was calculated with variations in horizontal structure irregularity and then the results were compared. In this research, the biggest deflection was resulted on the re-entrant corner irregularity model C in the x-direction of 7,219 mm and the y-direction of 4,244 mm. Based on the deflection value in the x-direction and y-direction on all building models, the story drift due to the effect of the earthquake plan was less than

Rapid Detection Device of Methamphetamine Based on Improved Light Emitting Diode Induced Fluorescence Detector

In recent years, drug abuse has become a major public health problem, drug-driving poses serious threats to the public security. For the urgent need to rapidly on-site screen drug evidence and drug abusers, we have developed a fluorescent drug detection device based on LED induction (FD-LED). The core part of the device is 365 nm high-intensity LED excitation light source, FD-LED detector' performance was tested by the fluorescent brightener OB. In this study, the FD-LED detector was evaluated, and the influence of baseline noise, baseline drift, sensitivity, detection limit and quantitative limit on the detector was analyzed, the result showed that the proposed detector had good stability and sensitivity, at the same time, the chromatographic detection conditions were set, the solution based on methamphetamine C1 sample was collocated, and combined with liquid chromatography, a detection system for methamphetamine was developed. The results showed that the minimum detection amount of the sample was 1.0 × 10–9 g/ml, and the signal-concentration relationship was obvious in the range of 1.0 ng/ml∼15.6 ng/ml. This device could provide an effective method for roadside drug testing and clinical diagnosis, and give helpful assistance to law enforcement officers.

Seismic Design of Mid-Rise Reinforced Concrete Structures According to TEC 2007 and TBEC 2018

Reinforced concrete (RC) structure are widely used structural system in buildings across the Turkey. The new Turkish standard on earthquake, TBEC 2018: Turkish Building Earthquake Code, was published on 2018 which is replaced for the old earthquake code, TEC 2007: Turkish Earthquake Code-2007. This paper aims to present a comparison between the seismic design provisions of these two codes for the design of mid-rise RC structures. The code provisions in both codes are evaluated and differences in terms of ductility and strength for the design of mid-rise RC structures are highlighted and presented. It was shown that the design base shear is higher when using TBEC 2018 code. A 4-story building is designed according to both codes and then the performance of the structure was evaluated. Due to differences on allowable drift limit, the R and Cd factors, the structure showed different behaviour when design according to both codes which are discussed in detail in this paper. A cost analysis was also carried out and compared for both buildings.

Eccentric steel brace retrofit for seismic upgrading of deficient reinforced concrete frames

The paper presents a simplified static force-based procedure for seismic retrofit design of RC frames using internal eccentric steel braces (ESBs), connected to long beam at distance of L/8 from beam ends, to enhance seismic resistance of the frame. The technique uses the linear static procedure given in ASCE 7-16 for calculation of appropriate design base shear for frame analysis, and the AISC 360-16 seismic provisions for preliminary design of steel braces. Response modification factor R was derived based on simplified kinematics of rigid frame response and flexure hinging of link beam, to reduce the elastic base shear force for lateral load analysis of frame and design of steel braces. This shifts plastic hinges from columns, and reduces joint shear deformation, by means of capacity protected braces and beam shear. The procedure was used for the preliminary design of ESB retrofitting technique for a two-story RC frame, employing hollow box steel sections. Quasi-static cyclic tests were performed on both as-built and ESB retrofitted portal frame panels under multiple-levels of lateral displacements demands. The tests performed on frames were analysed to understand the damage mechanism and retrieve the essential seismic response properties: force–displacement capacity curves, hysteretic cyclic response and hysteretic damping, and to establish performance-based story drift limits. The experimental data was used to calibrate finite element based nonlinear numerical models in SeismoStruct. Nonlinear static pushover analysis of considered two-story ESB retrofitted frame was carried to quantify structure ductility and response modification factors. The preliminary design was verified through nonlinear time history analysis (NLTHA) for both design base earthquakes and maximum considered earthquakes. Proposed seismic design of ESB retrofit for multi-stories RC frames having three to six stories has been presented and verified through NLTHA. It indicates the promising behaviour of ESB retrofit technique as well as the efficiency of the proposed simplified design procedure.

Seismic performance of semi-rigid steel-concrete composite frames

Steel-concrete composite frames with semi-rigid connections can be designed to resist earthquakes in low to moderate seismic zones by ensuring that they have adequate strength, stiffness and ductility. However, the design of semi-rigid composite frames to ensure desirable seismic performance is a complex problem due to several issues such as calculation of flexural stiffness of the composite beam, evaluation of the storey drifts and defining the secant stiffness of the nonlinear connection. In this paper, issues in the design of semi-rigid composite frames are discussed and proposed preliminary design guidelines for semi-rigid steel-concrete composite frames to satisfy the drift limits and give acceptable performance. Seismic performance of frames designed as per the force based design and direct displacement based design is compared and found that direct displacement based design is not promising in low seismic zones in terms of utilisation of material.

Design strategies to achieve target collapse risks for reinforced concrete wall buildings in sedimentary basins

Studies of recorded ground motions and simulations have shown that deep sedimentary basins can greatly increase the damage expected during earthquakes. Unlike past earthquake design provisions, future ones are likely to consider basin effects, but the consequences of accounting for these effects are uncertain. This article quantifies the impacts of basin amplification on the collapse risk of 4- to 24-story reinforced concrete wall building archetypes in the uncoupled direction. These buildings were designed for the seismic hazard level in Seattle according to the ASCE 7-16 design provisions, which neglect basin effects. For ground motion map frameworks that do consider basin effects (2018 USGS National Seismic Hazard Model), the average collapse risk for these structures would be 2.1% in 50 years, which exceeds the target value of 1%. It is shown that this 1% target could be achieved by: (1) increasing the design forces by 25%, (2) decreasing the drift limits from 2.0% to 1.25%, or (3) increasing the median drift capacity of the gravity systems to exceed 9%. The implications for these design changes are quantified in terms of the cross-sectional area of the walls, longitudinal reinforcement, and usable floor space. It is also shown that the collapse risk increases to 2.8% when the results of physics-based ground motion simulations are used for the large-magnitude Cascadia subduction interface earthquake contribution to the hazard. In this case, it is necessary to combine large changes in the drift capacities, design forces, and/or drift limits to meet the collapse risk target.

Empirical Models for Lateral Stiffness and Strength of Masonry-Infilled RC Frames Considering the Influence of Openings

Lateral load behavior of reinforced concrete (RC) frames infilled with fly-ash brick masonry having various sizes of central openings was investigated experimentally. Results showed that the infilled frames with openings exhibited significantly different lateral load behavior than the corresponding infilled frames without openings. The drift limit states corresponding to commencement of major events during the lateral loading (initiation of major cracks in frame members, peak load, and 80% of postpeak load) were found to improve significantly due to the presence of openings when designed in accordance with current earthquake standards. The presence of openings in masonry infills modifies two of the most important design parameters, lateral stiffness and strength, for which nonlinear prediction models were developed by carrying out statistical analyses of the experimental results. Empirical models were used to estimate the stiffness and strength of frames tested in past studies and were found to be more accurate and consistent compared with several existing predictive relations. A normalized lateral load–drift relationship for different performance levels of such frames was also propounded based on the observed damage events. The empirical equations can be used very conveniently to simulate the variations of stiffness and strength (global response) of the infilled frames with openings under lateral loads.

Seismic Performance of a New Type Concrete-Filled Precast Concrete Tubular Column

To investigate the seismic behaviour of a new type of concrete-filled precast concrete tubular column, five concrete-filled precast concrete tubular columns varying in concrete strength and stirrup ratio were tested under cyclic loading. The behaviours of the failure mode, hysteretic curve, skeleton curve, bearing capacity, deformability, displacement ductility and energy dissipation were studied to evaluate the seismic resistance performance of the columns. The results show that the failure mode of the concrete-filled precast concrete tubular columns was flexural failure, and the hysteretic curve had a plump shuttle shape, which indicates that the concrete-filled precast concrete tubular column has good energy dissipating capacity. The bearing capacity of the specimen was increased with increasing concrete strength of the precast tube. The stirrup ratio has little effect on its bearing capacity, whereas it has a significant effect on the deformation, ductility and energy dissipation. The story drift of the specimens can meet the requirements of the elastic plastic story drift limit value of 1/50 of the code in China, and the ductility coefficient is greater than 3, which demonstrates that the concrete-filled precast concrete tubular column has excellent seismic properties.

Estimation of drift limits for different seismic damage states of RC frame staging in elevated water tanks using Park and Ang damage index

Damage to elevated water tanks in past earthquakes can be attributed to the poor performance of their supporting frame staging. In order to ascertain the performance of these elevated water tanks, it is crucial to categorize the damage in quantifiable damage states. Among various parameters to quantify the damage states, the top drift of frame staging can be conveniently correlated to the different damage levels. In literature, drift limits corresponding to different damage states of the frame staging of the elevated water tank are not available. In the present study, drift limits for RC frame staging in elevated water tanks corresponding to different seismic damage states have been proposed. Various damage states of the elevated water tank have been determined using the Park and Ang damage index. The Park and Ang damage index utilizes results of both pushover analysis and incremental dynamic analysis. Twelve models of elevated water tanks have been developed considering variation in staging height and tank capacity. Incremental dynamic analysis has been performed using the suite of twelve actual earthquake ground motions. Based on the regression analysis between damage indexes and drift, limiting drift values for each damage state are proposed.

Seismic collapse safety assessment of concrete beam-column joints reinforced with different types of shape memory alloy rebars

In this study the seismic collapse safety of five different types of SMA-RC beam-column joints is compared with regular steel-RC beam-column joints through numerical analysis. Nonlinear static push over analysis is performed for all types of beam-column joints to determine the performance limit states of these connections. From the push over analysis, a damage state framework is proposed considering the maximum drift limit corresponding to different performance criteria such as cracking, yielding, spalling, and crushing. Through incremental dynamic analysis (IDA), collapse fragility curves are developed to assess the collapse performance of SMA-RC beam-column joints and conventional steel-RC beam-column joints using twenty earthquake ground motions. The collapse safety assessment is expressed in terms of collapse margin ratio considering maximum and residual drift as the demand parameters. The collapse margin ratio of SMA-RC beam-column joints is 20–30% greater than steel-RC beam-column joints in terms of maximum drift, and 25–60% higher in terms of residual drift.

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Abstract

Performance Analysis of Steel Portal Structures with Braces Designed Based on Allowable Interstory Drift Limits

Abstract. The earthquake resistant steel frame structure is designed to be able to withstand large inelastic deformations in the case of an earthquake. The applicable regulations still allow the use of elastic design methods in the form of pushover analysis and time history analysis evaluation as the basis for the design. The building under consideration consists of six floors with the function as an office building. The location of the building is in Banda Aceh with soft soil conditions. The structural analysis used the help of the Extended Three Dimensional Analysis of Building System Program (ETABS). The method of analysis of steel portal structures used was pushover analysis. Analysis of the given load was static loading based on 1987 PPPURG, and earthquake dynamic loading used a variety of response spectrum procedure analysis based on SNI 03-1726-2012. Structural analysis was assumed to be the strong column weak beam concept. From the results of calculations, it is found that the steel portal structures (with and without braces) designed based on allowable interstory drift limits have met the requirements. The performance level of the steel portal structure without bracing was LS, while the performance level of the steel portal structure using bracing was IO. The largest amount of steel used in terms of weight was found in the case of a portal without braces.

Experimental Investigations into Earthquake Resistance of Steel Frame Retrofitted by Low-Yield-Point Steel Energy Absorbers

This paper is the world’s first to highlight an experimental investigation into the earthquake responses of a steel frame retrofitted by novel metallic bending energy absorbers made of low-yield-point steel with the yield strength of approximately 100 MPa. New results have been achieved by conducting comprehensive shaking table tests on a quarter-scaled model of a two-story, one-span building structure subjected to incremental intensity levels of input earthquake records. The detailed information of the specimens, material properties, monitoring sensors, and dynamic loading mechanisms has been presented. The experimental results in terms of seismic phenomena, dynamic characteristics, acceleration, inter-story drift ratios, and strain distributions are also analyzed by the data collected from a wide range of sensors. It is found that the seismic failure of the specimens depends largely on the energy absorbers, which dissipate the majority of seismic input energy in order to prevent the parent steel frame from being damaged by a severe earthquake. In addition, the retrofitted structure sufficiently satisfies the design criteria considering allowable drift limits under both frequent and rare earthquakes. This indicates the influential role of the novel low-yield-point absorber, in that the overall seismic performance of the retrofitted structure can be improved adequately for survival in high-intensity seismic fortification areas.

Experimental and numerical study regarding a fabricated CFST frame composite wall structure

This paper presents fabricated concrete-filled steel tube (CFST) frame sandwich-insulation composite wall structures, which comprise CFST columns, H-shaped steel beams and a sandwich-insulation composite wall with or without openings. The seismic behaviors of four full-size specimens were investigated under low-cyclic loading, including the failure mode, hysteretic behavior, strength, ductility, strength and stiffness degradation, energy dissipation capacity and strains. The experimental results indicated that the proposed fabricated structures had good seismic behavior. The fabricated composite wall had a significant effect on the bearing capacity of the structures and the stiffness and energy dissipation capacity. The ductility of the fabricated CFST frame sandwich-insulation composite wall structure can meet the requirements of the elastic-plastic inter-story drift limit of seismic design in practical engineering. Although the tested structures had the same opening ratio, the structure with window openings had better seismic performance than the structure with door openings. Furthermore, the equivalent compression strut model was used to calculate the bearing capacity of the proposed structures. The errors between the test and calculation results were within 10%. The equivalent compression strut model can provide useful design guidance for fabricated CFST frame sandwich-insulation composite wall structures.

Performance-based multi-objective collaborative optimization of steel frames with fuse-oriented buckling-restrained braces

A multi-objective collaborative optimal design procedure for steel frames equipped with buckling-restrained braces (BRBs) is proposed under the framework of performance-based seismic design (PBSD) in order to minimize the damage of the primary structure as well as the material cost. For this purpose, a so-called BRB energy dissipation ratio is defined and introduced in the optimization to characterize the involvement of fuse-type BRBs in hysteretic energy dissipation in building stories. Three groups of constraints obtained from the rules on geometrical and conceptual design, the requirements regarding strength and stability, and the PBSD-based story drift limits are considered. To address the discrete-continuous hybrid design variables, a hybrid coding scheme is proposed to modify the non-dominated sorting genetic algorithm II (NSGA-II). The rationality of the proposed procedure is demonstrated by a case study on a seven-story planar steel frame with BRBs. The demonstration indicates that the proposed optimization procedure can make BRBs play the role of a structural fuse successfully in steel frames. The BRB energy dissipation ratios of case C are distributed nearly uniformly along the structural height. The weak-beam-strong-column design principle can be satisfactorily achieved through the maximization of the story BRB energy dissipation ratios. Additionally, the modified hybrid coding NSGA-II algorithm is computationally efficient and stable.

Evolution of the Norwegian plateau icefield Hardangerjøkulen since the ‘Little Ice Age’

The maximum ‘Little Ice Age’ (LIA) glacier extent provides a significant baseline to assess long-term glacier change and to place currently observed rates of glacier recession in a broader temporal context. To that end, we examine the evolution of the plateau icefield Hardangerjøkulen since the LIA. First, we reconstruct Hardangerjøkulen’s maximum LIA extent (~AD 1750) and subsequent recession based on the glacial landform record and aided by historical map interpretation. Ice-marginal moraines, glacial drift limits, trimlines, and identifiable erosion and weathering boundaries provide evidence of a LIA icefield with an area of 110 km2. Existing LIA model simulations of Hardangerjøkulen are not yet fully able to reproduce our reconstructed extent. Second, we compile a set of remotely sensed icefield outlines from successive time points in the 20th and 21st century to calculate icefield area and length change since the LIA. This reveals a substantial reduction in icefield size, with a total area loss of 41 km2 (37%; 2% 10 a–1) by 2010 and a cumulative frontal retreat averaging 1.3 km (29%; 5 m a–1) by 2013. Icefield recession has been greatest since the end of the 20th century, when rates of areal shrinkage increased to 6.5–10% 10 a–1 in 1995–2010, and the rate of average terminus retreat accelerated to 17 m a–1 in 2003–2010. Third, we present a relative dating approach, based on the known age of the different icefield outlines, that allows bracketing ages to be assigned to all ice-marginal landforms between any two outlines. This approach shows that episodes of moraine formation vary temporally between individual outlet glaciers of Hardangerjøkulen, suggesting that the moraine record of a single outlet glacier alone may not be sufficient to derive an icefield-wide picture of past ice advances, and thereby climate fluctuations.

New proposed drift limit states for box-type structural systems considering local and global damage indices

The maximum displacement responses under the seismic motions are usually considered as an indicator for damage evaluation. It is obvious that appropriate selection of drifts corresponding to various damage levels plays an important role in safety and economy of a design project. Despite the extensive use of the box-type structural system in mass construction and housing industry, there is no special design requirement for this structural system. Due to three-dimensional behavior and interaction of intersecting walls and slabs, it is expected that this system presents different seismic performance in comparison to the conventional shear wall buildings. This study evaluates the overall and story failure mechanism as well as global and local damage indices in this structural system. Maximum allowable drift ratios of 0.45%, 0.65%, and 0.8% are suggested for the immediate occupancy, life safety, and collapse prevention levels, respectively. Moreover, a damage index based on the maximum relative inter-story drifts is proposed to assess the failure in the height domain. According to the assessments, the story and global failure occurring due to considerable damages in main load bearing elements reveals high importance of local damage indices in box-type structural system. Based on the results, it is concluded that the proposed maximum values for drifts in different standards and codes are not reliable. Considering the shear-control behavior and depending on the expected performance levels, the proposed local damage indices are considered as accurate control indicators for box-type structural system.

Suitable intensity measure for probabilistic seismic risk assessment of non-ductile Australian reinforced concrete buildings

This study investigates the suitability of various intensity measures for conducting probabilistic seismic risk assessment of low- to mid-rise non-ductile reinforced concrete buildings with various plan configurations located in low-to-moderate seismic regions. Probabilistic seismic demand models are developed by conducting three-dimensional nonlinear time history analyses. The building response is defined to be dependent on component response and interstorey drift limits. In total the suitability of eleven intensity measures is evaluated by examining five criteria: efficiency, practicality, proficiency, sufficiency, and hazard computability. Based on the first four criteria it is identified that peak ground velocity, peak ground displacement, and maximum spectral displacement response are the most suitable intensity measures. Hazard computability is then utilised to select the optimum intensity measure for a hazard model in accordance with the Australian standards.

Framework for seismic vulnerability assessment of reinforced concrete buildings in Australia

ABSTRACTThe project ‘Cost-Effective Mitigation Strategy Development for Building Related Earthquake Risk’ under the Bushfire and Natural Hazards Cooperative Research Centre (BNHCRC) aims to develop knowledge to facilitate evidence-based informed decision-making in relation to the need for seismic retrofitting, revision of codified design requirements and insurance policy. Seismic vulnerability assessment is an essential component in the project. The objective of this paper is to present the framework for carrying out vulnerability assessment of limited-ductile reinforced concrete (RC) buildings in Australia. This paper is organised into four parts: (i) overview of typical building construction in Australia and description of the three broad categories of vulnerable RC buildings identified by the authors; (ii) identification and overview of case study buildings for seismic vulnerability assessment; (iii) definition and description for each performance level and damage state, including recommended material strain limits and drift limits for RC buildings; and (iv) hazard-consistent ground motion inputs for dynamic analyses.