Vertical Component Of Earthquake Research Articles

Research on the Dynamic Characteristics and Seismic Response of Space Frames

Research findings on dynamic characteristics and seismic response of space frames are introduced in this paper. It has been found that the response of space frames due to the vertical component of earthquake is larger than that due to the horizontal component of earthquake. The theoretical and practical methods for calculating forces in the members of space frame due to vertical earthquake, which is used in Chinese code of space frame, are introduced.

3D Analyses of Buildings under Vertical Component of Earthquakes

This study first investigates how to perform the 3D dynamic analysis of buildings under the vertical component of earthquakes. The analysis results indicate that (1) dividing a main girder into two elements is required to perform the vertical earthquake analysis; (2) including secondary beams for the building analysis is similar to refine modeling of the building (at this time, one building member, such as a secondary beam or a portion of the main girder, modeled by a two-node beam element can also produce an accurate result); (3) neglecting the floor stiffness in the vertical direction is suitable, if the floor thickness is not too thick; and (4) the required vertical effective mass ratio is suggested to be 80%. In the second part of this paper, 1,080 time-history analyses and 180 static analyses of reinforced concrete buildings were performed in order to investigate the relationships of extreme column axial forces and beam moments between vertical earthquake and dead loads. The analysis results indicate...

Nonlinear treatment of liquid-filled storage tanks under earthquake excitation by a quasistatic approach

Liquid-filled storage tanks under earthquake excitation are loaded by hydrodynamic pressure due to the interactive motion with the containing fluid. The dynamic response and the buckling of these tanks have been studied by many authors both experimentally and theoretically, but a unified design procedure is still lacking. To gain insight more easily into the load carrying behavior and failure mechanism of anchored tanks, a quasistatic approach is presented in this paper instead of solving the coupled problem in the time domain. For these purposes, a nonlinear finite element procedure is applied using pressure eigenforms as equivalent loads. The numerical model used for the investigations is discretized by mixed ring shell elements taking geometric and physical nonlinearities into account. Different superpositions of the pressure eigenforms which are calculated by a special interactive model lead to different behavior of the tank-fluid system depending on the intensity of the horizontal and the vertical earthquake component. The results obtained are compared with classical values and with simplified design procedures provided in Eurocode 8, Part 4.

Structural responses considering the vertical component of earthquakes

The guidelines in the NEHRP Provisions and the Mexican Code regarding the effects of the vertical component of earthquakes on the response of frames are re-evaluated. Using a time domain nonlinear finite element program developed by the authors, the seismic responses of frames are evaluated realistically by simultaneously applying the horizontal and vertical components of earthquake motion. Three steel frames and 13 recorded earthquake motions are considered. The same response parameters are then estimated using the two codes, and their error is evaluated. It is found that, if the frames remain elastic, the NEHRP Provisions estimate the maximum horizontal deflection at the top of the frames and the bending moment in the columns very accurately; the Mexican Code overestimates them. If the frames develop plastic hinges, the Mexican Code conservatively overestimates them, but the NEHRP Provisions underestimate them in some cases. Both codes significantly underestimate the axial loads in columns. The underestimation increases as the frames develop plastic hinges. The underestimation is more for interior columns than for exterior columns. If the ratio R of the PGA of the vertical and horizontal components of an earthquake is higher than normal, the underestimation increases as R increases. The underestimation is not correlated with frame height. The vertical component may increase the axial load significantly. Since they are designed as beam–columns, the increase in the axial load will have a very detrimental effect on the performance of the columns. In light of the results obtained in this study, the design requirements for the vertical components need modification. At the very least, further study is required.

Vertical Seismic Forces on Elevated Concrete Slabs

The effect of the vertical component of earthquakes on structures has been the source of extensive discussion among structural engineers for a long time. The issue of considering the effect in the design of structures has not yet been resolved. The topic was once again brought into the forefront when extensive damage, which appeared to have been caused by vertical ground motion, was observed in numerous structures after the January 17, 1994, Northridge earthquake. Soon after the Northridge earthquake a major insurance company contracted with our office to initiate a structural investigation of 36 insured subterranean parking structures beneath 2 to 4 stories condominiums located in the northwest Los Angeles metropolitan area. The analytical part of the investigation included the determination of horizontal and vertical seismic loads the structures sustained during the Northridge earthquake. The seismic loads acting on the parking structures, in the horizontal direction, were determined in accordance with the“Minimum Design Lateral Forces and Related Effects” procedure of the “Earthquake Design” section of the 1991 Uniform Building Code (UBC). The seismic forces acting on the parking structures, in the vertical direction, were obtained from a simplified response spectra procedure outlined in this paper as there is no explicit requirement and method for this direction in UBC.

Hydrodynamic pressures and response of gravity dams to vertical earthquake component

AbstractHydrodynamic pressures and structural response of concrete gravity dams, including dam‐reservoir interaction, due to the vertical component of earthquake ground motions are investigated. The response of the dam is approximated by the deformations in the fundamental mode of vibration, and the effects of deformability of bed rock on hydrodynamic pressures are recognized in the analysis. Expressions for the complex frequency response functions for the dam displacement, dam acceleration and lateral hydrodynamic force are derived. These results along with the Fast Fourier Transform algorithm are utilized to compute the time‐history of responses of dams of 100, 300 and 600 ft height, with full reservoir, for different values of elastic modulus of mass concrete: 3.0, 3.5, 4.0, 4.5 and 5.0 million psi, to the vertical component of El Centro, 1940, and Taft, 1952, ground motions. It is concluded that the hydrodynamic forces caused by vertical ground motion are affected substantially by damreservoir interaction and depend strongly on the modulus of elasticity of the dam. The dam response to the vertical component of ground motion is compared with that due to the horizontal component. It is concluded that because the vertical component of ground motion causes significant hydrodynamic forces in the horizontal direction on a vertical upstream face, responses to the vertical component of ground motion are of special importance in analysis of concrete gravity dams subjected to earthquakes.