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Significant attention has been recently paid to the determination of floor acceleration demands used for the design of acceleration-sensitive non-structural components in buildings. This study makes a contribution through the use of experimental shake table data from one 6-storey and two 3-storey reinforced concrete buildings tested at the E-Defense testing facility. All buildings were exposed to multiple excitations, and floor acceleration demands were studied through peak floor accelerations and floor response (acceleration) spectra. The obtained ratios of peak floor to peak ground accelerations confirmed findings from previous studies. The ratio distributions along the height provided in Eurocode 8, ASCE 7-16 and NZS 1170.5 were found to be conservative. Besides the known properties of floor response spectra, the results for two of the buildings revealed that in some cases, spectra can have two prominent peaks corresponding to the fundamental mode period of different damage states or degree of nonlinearity during a single shaking event. A prerequisite for this occurrence, which in this paper is termed the “Elongated Fundamental Mode Effect”, is that due to the characteristics of the input motion, a significant part of the energy is involved both before and after the change of structural response nature, from (mostly) linear elastic to nonlinear. Among others, such change is perceptible through an extension of the fundamental period. The Elongated Fundamental Mode Effect was investigated by using scalograms generated through the Continuous Wavelet Transform, which was found to be an efficient tool for the visualization of energy localization in the time–frequency domain.

Shake-table tests of a 3-story reinforced concrete building with cladding casted to be monolithic with frame elements, with seismic slits or cut reinforcing bars present in some cladding elements t...

A brand-new structural type, termed thick wall-thick slab structure, has been developed in recent years based on the reinforced concrete wall structure in Japan. This type of structural system can not only maintain high seismic performance, but also provide large interior space and improve the flexibility of the architectural design that is more favored by architects. In the present study, an equivalent cross-sectional area concept in which a coefficient termed the equivalent cross-sectional area ratio is proposed to estimate the flexural strength of the horizontal member of the interior wall-slab joints, which are critical assemblies in the thick wall-thick slab structures. To capture the stress condition of slab flexural reinforcement for calculating the equivalent cross-sectional area ratio, the method of finite-element analysis was employed in this work. The finite-element modeling was calibrated firstly using two isolated interior wall-slab joints from literature and consequently applied to a parametric numerical study. Finally, results from these finite-element analyses are adopted to propose the equivalent cross-sectional area ratio for modifying the current code formula to predict the flexural strength of interior wall-slab joints in TWTS structures subjected to lateral force.

Pushover analysis is widely used in modern practical structural design to evaluate collapse modes and member forces at the safety limit state. All members, including shear walls, need to be modeled properly to assure the accuracy of pushover analysis. As such, functions to predict initial stiffness, crack strength, yield or ultimate strength, stiffness degrading ratio to the yielding point, ultimate deformation, and ultimate shear strength must be acceptably accurate. While several theoretical, semi-theoretical, and empirical functions have been proposed and are commonly used in practice, the accuracies of these functions have not been verified comprehensively. The Ministry of Land, Infrastructure, Transportation and Tourism and the Building Research Institute launched a project in Japan from 2012 to 2015 to develop a comprehensive database of experimental data from 507 reinforced concrete wall experiments conducted between 1975 to 2013 to confirm the accuracy of the functions. In this paper, the comparisons between values predicted using the functions against experimental results from the database are presented. It was found that (i) the predicted initial stiffness tends to be higher than that from experimental tests, (ii) the predicted ultimate flexural and shear strengths were generally smaller than those from experimental tests, and its accuracy appears to be dependent on the presence of boundary columns and the existence of openings, and (iii) the predicted deformation corresponding to yield and at ultimate shear strength tends to be smaller than those from experimental tests.

Capacity curve estimated from seismic floor accelerations can provide an informative description of the structural behavior soon after an earthquake. Detailed information on instrumented buildings ...

In this paper, the plastic design with mechanism control (PDMC) for steel moment resisting frames (MRFs) is presented. The PDMC method in rigid plastic analysis, by considering the second-order effects, is guaranteed the achievement of global mechanism and prevented undesired mechanisms such as the soft story, which leads to decrease the ductility and energy dissipation capacity of the structures. The concept of PDMC is based on the plastic rotation of columns in developing a mechanism in which for a specified target displacement, the global mechanism has a minimum plastic rotation among all other undesired collapse mechanisms. In the presented method, the design conditions for story mechanisms are derived by using an energy equilibrium equation. For demonstrating the accuracy of the proposed design procedures, both pushover and nonlinear incremental dynamic analyses (IDAs) are applied to evaluate the structural performance. The results show that the designed structures comprise high seismic performance and the design objective that was to obtain a global mechanism is achieved.

Following the observation of severe damage to structurally isolated non-structural reinforced concrete walls after major earthquakes, researchers began to reassess the effectiveness and connection detail of non-structural walls to moment-resisting frames. A method to control damages to the non-structural wall, is to cast exterior non-structural concrete wall elements to be monolithic with frame elements, without anchoring the wall longitudinal bar. The non-anchorage of the wall longitudinal bar significantly increases the drift capacity of the wall and decreases damage. Using an experimental approach, this study assesses the influence of reinforcement detailing and quantity of the transverse reinforcements on the strength and drift capacity of the non-structural hanging wall. This study further evaluates the workability mechanism of the transverse reinforcements and reinforcement detailing with concrete. The non-anchorage of hanging walls, having boundary confinements, was found to exhibit a higher drift and strength capacity than similar walls with the anchored detailing without boundary confinements. The strength capacity of the anchored detailing hanging walls with minimum amounts of reinforcements was higher than that of the non-anchored specimen. The boundary confinements were found to be more influential on the capability of the hanging wall when placed along with non-anchored detailing reinforcement.

In this paper, optimum plastic design using mechanism control (PDMC) for steel moment resisting frames (MRFs) is presented. The PDMC method in the solid plastic analysis, by considering the second-order effects, achieve the global mechanism and prevent undesired mechanisms, which leads to decrease the ductility and energy dissipation capacity of structures, is guaranteed. The concept of the PDMC is based on the plastic rotation of columns in developing a mechanism in which for a specified target displacement, the global mechanism has a minimum plastic rotation of columns among all other undesired collapse mechanisms. In terms of involving optimization to the PDMC procedure, two methods are considered: 1) based on the sum of the reduced plastic moment of columns in each story, 2) based on the plastic moment of all members. For both methods, minimum structural weight is obtained by defining a linear programming problem. To show the accuracy of the design procedure, three frames consisting of four, eight, and twelve-story MRFs are designed by two methods, then they evaluated under the pushover and the IDA analyses. The results indicate that the designed frames by the second method have less weight compared with those designed using the first method. However, frames designed by both mentioned methods had high seismic performance and the design goal that is attaining to the global mechanism is achieved.

This paper focuses on the development and verification of a unified calculation method for estimating the yield of reinforced concrete (RC) beams, columns, and walls deformation considering flexural deformations, shear deformations, and bar slip deformations. Each component of yield deformation is considered independently, and the estimated yield deformation is the sum of these three parts. To verify the accuracy of this method, yield deformation results from a database of experimental results from tests performed in Japan on RC components was compared against those predicted by the proposed methods. The results show that the proposed method provides a reasonable prediction of the yield deformation and show that the proposed method has a better estimate of yield deformation than other previous methods. Sensitivity analysis on the influence of the rigidity reduction rate due to the shear effect, and the anchorage length in the bar slippage calculation, was performed. It was found that the rigidity reduction rate factor could influence the accuracy for walls. The influence of other material and member characteristics are also discussed herein.

Recently, earthquake damage to non-structural walls has become one of the important issues in Japan. Some buildings were demolished after the 2011 Tohoku Earthquake due to damage of non-structural walls without any significant damage in structural members. After that, several projects were launched to develop a new method to take into account the effect of non-structural walls (hanging, standing, and wing walls). In this paper, experimental test results for beam-column joints with non-structural walls are presented. The objectives of the tests were to investigate the equivalent length and hinge location of beams with hanging and standing walls. The results showed that the yield hinge located at the surface of the wing walls and beam-column joint should be modelled as rigid to estimate the deformation of the beams, regardless of the thickness and height of the wall. A tri-linear modelling method for beams with hanging and standing walls was also proposed, and its applicability was confirmed with the test results.

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.

Safety evaluations of existing buildings considering aftershocks are essential for occupants after an earthquake. To this end, a capacity-curve-based method is proposed using the seismic response data from the mainshock, which is quantitatively suitable for a damage prediction after an aftershock. The predicted maximum response during the mainshock–aftershock sequence is the intersection of the demand curve and the capacity curve of the structure, after which the damage class can be judged. The feasibility of the proposed method is verified using a numerical method, and comparisons are made between the results of proposed method and the code-specified method in Japan. It is shown that the proposed method can provide a good estimate for damage evaluation for aftershocks.

Efficient and quantitative damage inspection is essential for safety assessment of existing structures after an earthquake event. This paper proposes an approach for assessing the damage condition of reinforced concrete (RC) buildings using seismic response data in terms of the relationship between the mass-normalized force and deformation of an equivalent single-degree-of-freedom system, which enables a quick diagnosis of the overall structural condition in a quantitative manner. An experimental investigation is presented, and comparison between the proposed and code-specified visual-inspection methods is made based on the result of a full scale six-story RC wall-frame building shaking table test. We show that the damage-evaluation results using the proposed method agree fairly well with those of the visual inspection during the tests.