Seismic Capacity Of Buildings Research Articles

Energy dissipation capacity for waffle-flat-plate structures subjected to bi-directional seismic loadings

The seismic capacity of buildings is usually studied through separate analysis of two orthogonal directions, then combined using empirical rules. Nevertheless, the three-dimensional nature of seismic action gives rise to interaction among its different components, especially the two horizontal ones, which can cause substantial discrepancy between the actual 3D response and the one obtained by combining uniaxial responses. The present study addresses this problem for waffle-flat-plate (WFP) structures with an irregular layout of columns from the standpoint of energy dissipation capacity. A portion of a WFP prototype structure that was built in Laboratory was subjected, simultaneously, to two horizontal components of a far-field seismic record upon a shake-table. Several shakings of increasing intensity were applied until the collapse of the structure. Afterwards, a numerical model of the specimen was developed and validated with the experimental results. The numerical model was subjected to several sets of ground motions having diverse ratios of energy input from the horizontal components. When the total energy dissipated by the structure through cumulative plastic deformations until failure was obtained for each set of accelerograms, a fairly stable quantity was found to be concentrated within a narrow range of values. Moreover, the specimen subjected to bi-directional seismic loading showed a higher ultimate energy dissipation capacity than under uni-directional loadings.

Foreword Special issue Empowering communities for non-structural seismic risk mitigation: the central role of communication

This special issue of “Annals of Geophysics” concerns the dissemination of knowledge on the prevention of damage mainly due to non-structural elements during earthquakes and its practical application at houses, schools and offices by common citizens, companies and institutions. The seismic capacity of buildings and other civil engineering structures and infrastructures are object of regulations for design and construction, and in some cases also the design, fabrication and mounting of electrical and mechanical equipments. Consequently, even in strong earthquakes many collapses of buildings and infrastructures are avoided. However, with few exceptions, design procedures do not aim at avoiding seismic vibrations from being transferred to the structures, but enable the structures to resist to the effects of those vibrations

Study of Strong-Column Weak-Beam Concept on Seismic Capacity of Buildings of Varying Heights

Study of Strong-Column Weak-Beam Concept on Seismic Capacity of Buildings of Varying Heights

Seismic capacity and vulnerability assessment considering ageing effects: case study—three local Portuguese RC buildings

A high percentage of reinforced concrete (RC) buildings in Portugal were designed and built before the introduction of modern seismic codes. This research aims to assess the seismic capacity and vulnerability of RC buildings in the city of Lisbon. For that purpose, nonlinear static procedures have been used and fragility curves have been developed. These buildings are reaching the end of their nominal life. Therefore, ageing effects have been taken into account, as well as the presence of smooth rebar. To do so, a sensitivity analysis has been performed by considering the chloride-induced corrosion of the reinforcement steel rebar and the degradation of the concrete cover. To illustrate the effects of ageing and the procedure adopted for the seismic fragility assessment of old RC structures, three RC buildings with masonry infills have been selected as case studies. They were all built between 1960 and 1980, and they are representative of the current building stock in Lisbon. The seismic capacity of the buildings has been determined by means of nonlinear static analyses of three-dimensional numerical models. The N2 method and its extended version have been considered to determine the target displacement. The seismic safety of the buildings has been estimated in terms of the demand/capacity ratio for each vertical structural element (columns and walls) according to the bending and the shear failures. Then, a set of fragility curves has been developed for all buildings to represent the probability of RC elements reaching or exceeding the significant damage limit state. Results have shown that the concrete strength degradation has had more influence than reduction of the rebar diameter in the seismic capacity. When considering steel corrosion, it has been demonstrated that the corrosion rate has reduced the capacity more than the time of exposure. It can be concluded that ageing affects the seismic behaviour of RC structures, increasing the vulnerability of these buildings.

Damage characteristics and seismic capacity of buildings during Nepal M s 8.1 earthquake

The extensive damage to buildings caused by the Nepal Ms 8.1 earthquake has attracted much attention by the international community. After the preliminary scientific investigations on the different affected areas in Nepal, the construction and damage characteristics of five different types of buildings commonly existing in Nepal were discussed and the reasons of their disaster performance were analyzed. Types of buildings investigated include reinforced concrete (RC) frame structures, rubble structures, brick-wood structures, raw soil structures, and brick-wood structures of historic buildings. In addition, the weak links of the seismic design were pointed out, which was very important for the post-earthquake reconstruction and recovery, and gave a preliminary explanations for the damage experienced.

Study on Application of Mortar Splint in the Reinforced Masonry Structure

The paper probes into the application of masonry strengthening with mortar splint in the reinforced masonry structure. By optimizing the reinforcement scheme, computing and comparing the indexes of the compound seismic capacity of the building before and after it is strengthened, it can be concluded that the method of masonry strengthening with mortar splint can greatly improve the compound seismic capacity of buildings and achieve the goal of building’s strengthening.

Consideration of the near‐fault effect on seismic design code for sites near the Chelungpu fault

In this paper, based on the concept of UBC97, the modification of the design response spectrum in the current Taiwan seismic design code for sites near the Chelungpu Fault is proposed by defining the so‐called near‐source factors to increase the seismic capacity of buildings against near‐fault ground motions. The near‐source factors can be defined for different structural period ranges by the near‐fault attenuation functions for PGA and spectral acceleration demands at 0.3 and 1. 0 second periods, respectively. These attenuation functions are determined from the data recorded at sites near the Chelungpu Fault during the Chi‐Chi (Taiwan) Earthquake on September 21, 1999. Furthermore, the normalized inelastic near‐fault design base shear coefficients can be defined by the normalized near‐fault design response spectrum as well as the reduction factor for a specified ductility ratio and structural period as defined by the seismic design code. Finally, based on the near‐fault ground motion data recorded during the Chi‐Chi (Taiwan) Earthquake, the demand of the normalized inelastic base shear coefficients can be determined numerically by the EPP model. It can be used to verify the capacity of buildings defined by the modified seismic design code to resist the threat of near‐fault ground motions.

The Mexico Earthquake of September 19, 1985—Evaluation of the Seismic Capacity of Buildings in Mexico City

As a consequence of the 1985 Mexico City earthquake, the authorities of the city have decided to evaluate the seismic capacity of the buildings without damage with the purpose of detecting those with the most vulnerability, in order to take the preventive actions necessary to improve the security of the citizens in future earthquakes. Based on the census of the structures of the city, the procedure of evaluation used considers three levels of increasing precision permitting a progressive selection of the buildings in bad condition. Work is now under process in the main districts of the city with good results.