Behavior of plate on elastic foundation under impact load

مقدم أطروحة جامعية

Abbas, Sura Ammuri

مشرف أطروحة جامعية

Fattah, Muhammad Yusuf
Hammud, Muhammad J.

الجامعة

الجامعة التكنولوجية

الكلية

-

القسم الأكاديمي

قسم هندسة البناء و الإنشاءات

دولة الجامعة

العراق

الدرجة العلمية

ماجستير

تاريخ الدرجة العلمية

2013

الملخص الإنجليزي

Concrete slabs (plates) supported directly by the soil continuum is a very common construction form.

The behavior of the slab when it carries external loads is influenced by the soil, and the behavior of the soil is, in turn, influenced by the action of the slab under load.

Developing a realistic mathematical model for this complex soil-structure interaction problem is essential in order to provide safe and economical designs.

In the past, many researchers have worked on this problem, which is referred to as "beams and plates on elastic foundations." In many practical design problems of this type, the soil continuum is layered and may be resting over a rigid rock or a relatively stronger soil.

In this study, nonlinear three-dimensional finite element analysis has been used to conduct a numerical investigation of the effect of applied impact load on the foundation based on sandy soil using the finite element method by ANSYS (Version 11) computer program.

The 8-node brick elements in ANSYS are used to represent the concrete of foundation and the soil under the foundation which are denoted by Solid65 for concrete and Solid45 for the soil, and the interface is modeled by using threedimensional surface-to-surface (Target170 and Contact174) contact elements connected with concrete and soil.

First, the analysis is carried out on previously solved problems to verify the capabilities of the program and make a comparison between the results obtained from the finite element analysis and the available experimental results.

This comparison shows a good agreement.

As a case study, a concrete foundation with dimensions (3×3×0.3) m placed on the foundation soil (15 m) deep and (9 m) away from the edge of plate is subjected to impact load.

A parametric study is carried out to investigate the effect of several parameters including: foundation thickness and dimensions (geometry), modulus of elasticity of soil, eccentricity of impact load and the damping ratio.

It was concluded that as the foundation thickness increases, the time for maximum displacement to take place increases due to geometrical damping induced by the PDF created with foundation, for example when the thickness of foundation increases from (t = 0.3 to 0.5 and 0.75) m for amplitude load (P = 25, 75 and 100) kN, the maximum vertical displacement at the center of foundation decreases by about (45 and 58) %, and the maximum vertical stress decreases by about (22 and 50) %, respectively.

When the dimensions of foundation and damping ratio increase, the oscillation of vertical displacement decreases, which means that the foundation becomes more stable.

When the length of foundation increases from (L = 3 to 6) m, the maximum vertical displacement at the center of foundation increases by about (13, 19 and 21) %, respectively under the same amplitudes of load, while the maximum vertical stress decreases by about (42, 48 and 57) %, respectively.

When the modulus of elasticity for soil decreases from (Es=50 to 20 and 10) MPa, the maximum vertical displacement at the center of foundation increases by about (14 and 19) %, respectively.

On the other hand, the decrease in the modulus of elasticity for soil leads to a small decrease in the maximum vertical stress depending on the amplitude of load.

The time at which the maximum vertical displacement takes place increases as the soil modulus of elasticity increases.

The load eccentricity increases the displacement and decrease the stress at the foundation center.

This is attributed to non-uniformly distributed stresses on the loaded area, where the loads are concentrated locally within the loaded area.

The presence of damping leads to a considerable decrease in the foundation displacements and stresses.

The increase in the damping ratio reduces the vertical displacement of the foundation at the same time whatever was the damping ratio.

التخصصات الرئيسية

العلوم الهندسية والتكنولوجية (متداخلة التخصصات)

الموضوعات

• الخواص الميكانيكية

• APA
• MLA
• AMA

لغة النص

الإنجليزية

نوع البيانات

رسائل جامعية

رقم السجل

BIM-418474