A COMPARISON BETWEEN THE TECHNICAL SPECIFICATIONS FOR ELASTOMERIC SEISMIC PROTECTION BEARINGS EN 15129 VS ISO 22762 PRESENTED BY : VIRENDRA GHODKE AUTHORS: MOUSTAFA IMAM, PASCAL SAVIOZ 24-10-2014 9th Austroads Bridge Conference, Sydney, New South Wales 2014 Seismic Isolation Seismic Isolation It is the process of decoupling/separation of the structure from the ground movement, while damping the amount of energy which is input to the structure. But How??? Seismic Isolation Solutions to isolate the structure from the ground movement By Balloons? By Magnetic levitation? Seismic Isolation Main requirements of an isolation technique 1. Transmit vertical loads from the structure to the foundation at all times. 2. In service case allow rotation and service displacements. 3. In seismic event case Allow the structure to deform/move with a frequency lower than that of the earthquake. 4. Lowering the shock acceleration of the seismic event reducing the tendency of the upper floors to move faster than lower floors. 5. Providing a restoring force to the structure Seismic Isolation Using Base isolation Base isolation Results in shifting/increasing the natural vibration period of the structure Period Shifting abefore Which results in decreasing the natural vibration frecuancy Which results in The structure will move at a frequancy lower than that of the earthquake aafter W/O Seismic Isolation T Seismic Isolation Seismic Isolation Seismic Protection – Isolators RESTON®PENDULUM Curved Surface Slider LASTO®LRB Lead Rubber Bearing LASTO®HDRB High Damping Rubber Bearing Seismic Protection – Sliding Isolators PENDULUM Curved Surface Slider Pendulum MONO Pendulum Duplo Seismic Protection – Sliding Isolators PENDULUM MONO & DUPLO Upper Sliding Surface Upper Sliding Surface Sliding Material Calotte Calotte Lower Sliding Surface Seismic Protection – Sliding Isolators Pendulum MONO (Single curved surface) Pendulum DUPLO (Double curved surface) NSd: Max. vertical load in service condition NEd, max : Initial force capacity prior to sliding dEd : Max displacement in seismic condition FXY, d : Post yield stiffness Seismic Isolation LRB In terms of dimensional properties, Similar to LNR & HDRB But Has a lead core which provides for damping External steel plates Internal steel plates Rubber Layers Steel Shims Lead Core Seismic Isolation HDRB Both are the same in terms of dimensional properties But HDRB uses a mixed rubber compound (Natural Rubber + Additives) with high damping External steel plates Internal steel plates Rubber Layers Steel Shims Seismic Isolation Difference between the performance of LNR, LRB and HDRB EN15129 Vs ISO22762 Standards EN15129 ISO22762 First Issue 2009 2005 Latest Issue 2010 2010 Device Range All Seismic devices Elastomeric EU WG9 members: JPN, GBR, CZE, USA, CAN, CHN, IND, MYS, THA Countries EN15129 Vs ISO22762 Material Testing Differences Brittleness point Test Tensile Properties Low Temp. Ageing Properties EN15129 Sampling Frequency Ozone ISO22762 Hardness Resistance ISO22762 EN15129 Adhesion Comp. Set Shear bond EN15129 Vs ISO22762 Isolator Testing Conditions Requiring New Set of Type Tests Increase in upper service temp. > 5 °C Different Rubber Compounds Variation of shape factor by 10% Decrease in lower service temp. > 3 °C Increase in permanent loads > 30% EN15129 Increase in max. displacement > 5% Increase of max. vertical load > 10% Decrease of min. vertical load > 10% + EN15129 ISO22762 Increase in dimensions by 10% Decrease in dimensions by 50% Different type of attachment Different molding conditions EN15129 Vs ISO22762 Isolator Testing Capacity in Compressio n Required Tests Cyclic Compressive fatigue Tensile Properties Compressio n Stiffness Creep EN15129 ISO22762 ISO22762 Differences Horizontal characteristi cs Lateral capacity EN15129 ISO22762 Sampling Frequency 2 ITT 20% FPC 1 ITT N/A FPC Scaling General scaling criteria mentioned Scaled test pieces defined Variation & Dependence of horizontal Characteristic EN15129 Vs ISO22762 Design Rules: Construction EN15129 Type I (ISO 22762) Type C (EN 15129) – with separate connection plates Type II (ISO 22762) Type C (EN 15129) – without separate connection plates Type III (ISO 22762) Type B (EN 15129) ISO22762 EN15129 Vs ISO22762 Design Rules: Dimensions Differences Max. effective Diameter/side length EN15129 ISO22762 1200 mm Unlimited ISO22762 gives more flexibility for large bearings EN15129 has a more practical view (manufacturing limitations) 1 Lead Plug 2 Cover Rubber added after vulcanization 3 Cover Rubber Vulcanized with Isolator EN15129 Vs ISO22762 Design Rules: Shear Strain X γ = Tr Differences Shear Strain EN15129 ISO22762 Service ≤ 100% ≤ 70% Seismic ≤ 250% ≤ 300% Tr ISO22762 is more flexible ending in smaller bearings EN15129 gives larger bearings (conservative) X EN15129 Vs ISO22762 Design Rules: Summary Shear Strain EN15129 ISO22762 Comment Shape Factors 1st shape factor defined 1st & 2nd shape factors defined ISO22762 has deeper analysis of dimensions Compressive stiffness Similar approach - Shear Stiffness Similar approach - Equivalent Damping Ratio Defined for Rubber Defined for Rubber and Isolator ISO22762 has a better Definition of HDRB Shear Strain Conservative Flexible ISO22762 has flexibility with experimentally driven approach Total Shear Strain Similar approach - Reinforcing Plate Min 2mm Min 3mm Similar approach Stability Defined with an acceptance criteria Gives flexibility to calculate the actual conditions and criteria - EN15129 Vs ISO22762 Conclusion Aspect EN15129 Design ISO22762 Almost identical Testing Simple and well defined Similar to EN15129 with a conservative approach Manufacturing Limitation Considered in all aspects Has a more theoretical approach Might have manufacturing problems HDRB Not well defined Deeply defined Price of device High due to some conservative factors Generally 20% lower Price of testing Standard price due to simple and well defined procedure Generally 15~25% higher Final Comment Safe bearings from ISO22762 might be Unsafe in EN15129, however the final testing procedure will result in bearings safe in both standards Thank You For Your Attention Questions? 9th Austroads Bridge Conference, Sydney, New South Wales 2014