Experimental Study of the Lateral Spreading Pressure Acting on a Pile Foundation During Earthquakes

Nagao, Takashi; Shibata, Daisuke

doi:10.48084/etasr.3217

Cited by 6 publications

(8 citation statements)

References 12 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Therefore, various design codes, such as the Japanese Specifications for Highway Bridges (JSHB) [4], apply the SRM calculation equation in accordance with the FW. When the seismic load is large or when a large lateral spreading pressure is considered to act during an earthquake [5], the FW should be widened to enhance seismic resistance. However, when using the SRM calculation equation adopted in the design code, the SRM significantly decreases as the FW increases, and an increase in the SR proportional to the increase in the FW cannot be expected.…”

Section: Imentioning

confidence: 99%

See 1 more Smart Citation

Evaluation Methods of Vertical Subgrade Reaction Modulus and Rotational Resistance Moment for Seismic Design of Embedded Foundations

Nagao

Tsutaba

2021

Eng. Technol. Appl. Sci. Res.

Self Cite

View full text Add to dashboard Cite

In a seismic design of embedded foundations, the vertical Subgrade Reaction (SR) acting on a foundation bottom surface and the Rotational Resistance Moment (RRM) generated by the SR are calculated using an SR Modulus (SRM). The SRM and RRM depend on both ground rigidity and Foundation Width (FW). However, the SRM and RRM calculation methods adopted in design codes might not properly consider their FW dependency. In this study, SRM and RRM evaluation methods for embedded foundations subjected to a seismic load were examined by conducting a two-dimensional finite element analysis under the condition where ground rigidity and FW were changed considering the nonlinearity of the ground. The results show that when the seismic load is large and the nonlinearity of the ground appears, the SR distribution is different from the assumption in the design code. The FW dependency of the SRM was lower than the assumption of the design code. Furthermore, methods to calculate the SRM and RRM in accordance with the FW and ground rigidity are proposed.

show abstract

Section: Imentioning

confidence: 99%

“…τ m = σ m ' sin φ (5) where σ m ' is the effective confining pressure and φ is the shear resistance angle.…”

Section: A Analytical Modelmentioning

confidence: 99%

Evaluation Methods of Vertical Subgrade Reaction Modulus and Rotational Resistance Moment for Seismic Design of Embedded Foundations

Nagao

Tsutaba

2021

Eng. Technol. Appl. Sci. Res.

Self Cite

View full text Add to dashboard Cite

show abstract

“…As shown in Figure 1, the model foundation was embedded by 45 mm into the stronger lower layer. By similitude [17], the horizontal loading rate on the model was determined to be 1/31.6 of the actual scale, in which the horizontal loading rate was 20cm/s as in [1]. The maximum displacement under loading was 10mm, which by similitude corresponds to an actual displacement of 10m.…”

Section: A Experiments Outlinementioning

confidence: 99%

“…In the following, the loading side is referred to as the rear side, and the side where displacement occurs by loading is referred to as the front side. The measured data were subjected to (i) a Fast Fourier Transform, (ii) low-pass filtering at 1Hz, and then (iii) an inverse Fast Fourier Transform to obtain smooth time history data as in [1].…”

Section: B Measured Quantitiesmentioning

confidence: 99%

“…As ships have become bigger, so wharfs have had to be made deeper, and this increase in water depth results in increased seismic load. In addition, it has been noted that (i) lateral spreading pressure may act during a massive earthquake and (ii) the maximum lateral spreading pressure may exceed the one specified in seismic design codes [1]. Many damages to pile foundations during the 1995 Kobe Earthquake have been reported [2], and a pier in Kobe port buckled at points below the ground surface, which was caused by the lateral spreading pressure [3].…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

An Experimental Study on the Way Bottom Widening of Pier Foundations Affects Seismic Resistance

Nagao

2020

Eng. Technol. Appl. Sci. Res.

Self Cite

View full text Add to dashboard Cite

The resistance of a pier to horizontal loads, like seismic loads, is due to the flexural rigidity of its foundations and the horizontal subgrade reaction. In the event of a massive earthquake, the latter becomes very small because of the softening of the ground, while the structure may experience a large inertial force and lateral spreading pressure. Therefore, structures with high seismic resistance are required in areas with high seismicity. When a wide caisson is used as a pier foundation, a rotational resistance moment caused by the vertical subgrade reaction acting on the foundation bottom can be expected. Although this rotational resistance moment increases if the foundation is widened, in design practice the subgrade reaction coefficient is evaluated as being low under such circumstances. Therefore, even if the foundation is widened, the rotational resistance moment does not increase greatly. Rotational resistance commensurate with the increased construction cost due to foundation widening cannot be expected. In the present study, horizontal loading experiments were performed at one pier with a normal foundation and at one with widened at the bottom foundation, and the way that the widening affected the seismic performance was examined. The results show that compared with the normal foundation, the bottom-widened one experienced far less displacement and offered higher earthquake resistance.

show abstract

Distribution of the Subgrade Reaction Modulus for Anchor Piles With Various Inclination Angles

Oda¹

2023

GEOMATE

View full text Add to dashboard Cite

In a seismic design of a pile foundation, a subgrade reaction generated with a displacement of piles when the seismic load is applied must be appropriately evaluated. The ratio of the subgrade reaction to the amount of displacement of a pile is defined as the subgrade reaction modulus (SRM). There are two ideas about the SRM's depth distribution: one assumes a constant depth distribution, while another assumes a monotonously increasing depth distribution. There are various types of pile foundations based on different inclination angles of a pile. In design practice, SRM is not seen as being dependent on the pile type. In this study, we targeted anchor piles with the main goal of bearing a horizontal load and conducted a horizontal loading experiment. We prepared a model considering that anchor piles are usually not embedded into the bedrock and evaluated the depth distribution of SRM by changing the inclination angle of the pile from 0 to 30° with 10° intervals. The experimental result showed that though SRM increases monotonously in the depth direction, the distribution was different from what was assumed in design practice, where a local maximum was present at a specific depth in the ground, and the value decreased below that depth. We then proposed equations to calculate the degree of change in SRM corresponding to the inclination angle of a pile. Furthermore, it was shown that the position of a local maximum for SRM depends on the location of the rotational center for the pile.

show abstract

Experimental Study of the Lateral Spreading Pressure Acting on a Pile Foundation During Earthquakes

Cited by 6 publications

References 12 publications

Evaluation Methods of Vertical Subgrade Reaction Modulus and Rotational Resistance Moment for Seismic Design of Embedded Foundations

Evaluation Methods of Vertical Subgrade Reaction Modulus and Rotational Resistance Moment for Seismic Design of Embedded Foundations

An Experimental Study on the Way Bottom Widening of Pier Foundations Affects Seismic Resistance

Distribution of the Subgrade Reaction Modulus for Anchor Piles With Various Inclination Angles

Contact Info

Product

Resources

About