BY Eng.\ Ayman Abdo Mohamed Hussein Zagazig University Faculty of Engineering Structural Eng. Depart. التحكــــم فى تصــــــادم المنشــــــآت المعزولة زلزاليــــــا POUNDING CONTROL OF BASE ISOLATED STRUCTURES BY Eng.\ Ayman Abdo Mohamed Hussein

Under Supervision of : Prof. Dr. Sayed Abd El-Salam Dr. Ass. Prof. Dr. Zagazig University Faculty of Engineering Structural Eng. Depart. Under Supervision of : Prof. Dr. Sayed Abd El-Salam Professor of Structure Engineering Faculty of Engineering Zagazig University Dr. H. E. Abd-El-Mottaleb Department of Structural Engineering Zagazig University Ass. Prof. Dr. Atef Eraky Bakry Department of Structural Engineering Zagazig University

OUTLINES Introduction Modeling Effect of pounding on adjacent structures Control of Base Isolated Buildings Pounding Conclusions and future work

INTRODUCTION  base isolation and pounding phenomenon Base-isolated The base isolation technique used for protect the strategically important structures. The basic goal of the base isolation is to increases the lateral flexibility and also increases the effective damping through the energy dissipated  But It must be more flexible, but it must still be stiff enough to resist pounding. Base-isolated Fixed base

INTRODUCTION  Pounding occurs between the adjacent structures: The 1985 Mexico City Earthquake Pounding

Objectives 1- Establish a reliable analytical model to simulate building pounding. 2- Assess the effect of gap width in pounding response. 3- Assess the effect of real earthquake ground motions is studied to find the pounding response. 4- Study the pounding for buildings with different characteristics. 5- Assess the benefit of using supplemental viscous damping devices to reduce impact forces, and story drift in the buildings subjected to pounding.

OUTLINES Introduction Modeling Effect of pounding on adjacent structures Control of pounding in isolated structures Conclusions and future work

Base Isolated Structures Modeling Previous Works Pounding in Fixed Base Structures Pounding in Base Isolated Structures Vasant and R. S. jangid - Kun YE et al. - Robert J. - Shehata E.-Muthukumar - Chris et al. -Abdullah et al. Vasant and R. S. jangid -Kun et al. - Panayiotis et al. - Anagnostopoulos S. Pounding Control Vasant mastagar and R. S. jangid - Nawawi, et al. - Orlando, et al. - Zhong, L. - Klein et al. - Yang and Xu

Modeling Fixed Base Structures Equation of Motion For the two Buildings

Modeling m1v1 + m2v2 m1u1 + m2u2 IMPACT Partially elastic collision Most collisions fall between elastic and perfectly inelastic collisions (e=0 1.0) For concrete collision e= 0.5 - 0.75 (e=.65) m1u1 + m2u2 Before collision m1v1 + m2v2 After collision When Fext = 0, =

Modeling Classical Theory of Impact:

Modeling Base Isolated Structures ** Bilinear model Equation of Motion

Modeling Base Isolated Structures

Modeling Equations of the Total Energy

Modeling Using viscous dampers in the reduction of pounding force at the Points of Collision

Modeling Equation of motion assuming connected damper

OUTLINES Introduction Modeling Effect of pounding on adjacent structures Control of pounding in isolated structures Conclusions and future work

FBP FB First Story Effect of pounding on adjacent structures 1- Fixed Base Buildings ( Harmonic Excitation wex= 4.0 rad) FB FBP First Story

FB FBP Second Story Effect of pounding on adjacent structures Fixed Base Buildings ( Harmonic Excitation ) FB FBP Second Story

base BI BIP Effect of pounding on adjacent structures 2- Base Isolated Buildings ( Harmonic Excitation ) BI BIP base

BI BIP Second Story Effect of pounding on adjacent structures Base Isolated Buildings ( Harmonic Excitation ) BI BIP Second Story

FBP BIP Effect of pounding on adjacent structures PARAMETRIC STUDY 1- mass ratio(mB/mA) MA MB building A MB=2.0 MA building A MB=0.5 MA MB FBP BIP building B building B ωn = √K/ M λ = MB/ MA

2- plastic shear capacity Base of A Effect of pounding on adjacent structures BI BIP 2- plastic shear capacity F X Base of A First of A Qp Second of A

2- plastic shear capacity Effect of pounding on adjacent structures 2- plastic shear capacity building A at wex= 4.0 rad. building A at wex= 1.6 rad.

2- plastic shear capacity First of B Effect of pounding on adjacent structures BI BIP base of B 2- plastic shear capacity First of B Second of B

BIP BI Base of A First of A Second of A Effect of pounding on adjacent structures 3- post- pre stiffness ratio BIP BI Kp F X Qp Kp Ke α = Ke Base of A First of A Second of A

BI BIP Base of B First of B Second of B Effect of pounding on adjacent structures BI BIP Base of B First of B Second of B

Effect of pounding on adjacent structures 4-Effect of Separation Distance No of impacts Max rel disp. BIP of A Max rel disp. FBP Max rel disp. BIP of B

Effect of pounding on adjacent structures Behavior of Buildings under Earthquake Excitations Elcentro Northridge Elcentro Spec. accel. (cm/sec2) frequency (d) Northridge Loma Kobe Loma Kobe Time history Fourier spectrum

FB & FBP BI & BIP Effect of pounding on adjacent structures Top disp. Of A Top disp. Of A Top disp. Of B Top disp. Of B Upper disp. against Northridge earthquake

FB & FBP BI & BIP Effect of pounding on adjacent structures Base shear. against Northridge earthquake

FB FBP Effect of pounding on adjacent structures Effect of Mass Ratio Upper story of building A Upper story of building B

BIP BI Effect of pounding on adjacent structures Effect of Mass Ratio Upper story of building A Upper story of building B

FBP BIP Effect of pounding on adjacent structures Effect of separation distance FBP BIP

BI BIP Effect of pounding on adjacent structures Effect of plastic shear capacity BI BIP Upper story of building A Upper story of building B

BI BIP Effect of pounding on adjacent structures Effect of post-pre stiff ratio BI BIP Upper story of building A Upper story of building B

OUTLINES Introduction Modeling Effect of pounding on adjacent structures Control of pounding in isolated structures Conclusions and future work

Building A Building B Control of pounding in isolated structures base first second

Control of pounding in isolated structures (ton) The effect of frequency of the excitation and yield disp. on the total energy the energy ratio (TEc /TE) at wex=2.0 rad.

Control of pounding in isolated structures

Control of pounding in isolated structures Effect of damper stiffness & post stiffness

Control of pounding in isolated structures Effect of yield disp. & post stiffness

Control of pounding in isolated structures Effect of Structure Damping & Yield Disp.

Control of pounding in isolated structures Effect of Natural Freq. & Damper Stiffness

Control of pounding in isolated structures Damper Stiffness & Structure damping

Base First floor Second floor Control of pounding in isolated structures The optimum parameters of the damper Base Kd =20000 t/m, α = 0.0, Fy= 33.0 ton >>> wo=10 First floor Second floor

OUTLINES Introduction Modeling Effect of pounding on adjacent structures Control of pounding in isolated structures Conclusions and future work

Conclusions 1- Pounding increases the lighter floors response in adjacent base isolated buildings while decreases the heavier floors response. 2- Pounding increases the response of the floors of the adjacent fixed base buildings. 3- For the isolated buildings at the resonance region, the very small and very high isolator plastic shear capacity increases the bounded response, while away the resonance region, the decrease of plastic shear capacity decrease the response.

Conclusions 4- While small post-pre stiffness ratio decrease obviously the floors responses of the unbounded base isolated building. 5- When sufficient gap is allowed between the adjacent base isolated buildings, the effect of the pounding decreases. 6- The response of the base isolated bounded and unbounded depends on the power of the earthquake and frequency content. 7- When the use of viscous dampers, these damper have optimum yield force that minimize the energy.

Conclusions 8- The optimum yield force for the connected dampers increases for the stiff buildings rather than the flexible ones. 9- Connected dampers with small post-pre stiffness ratio are more efficient than that with large values for all cases of dampers. 10- After a specific value of connected dampers stiffness, the increase of the stiffness reduce slightly system response.

Future works The present study could be complemented with additional research in the following areas: Experimental shake-table testing of scaled buildings models to study the effects of pounding. The developed program may be extended to investigate other cases of pounding such that which occurred in the buildings with different story levels.

Thank You

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