T. NISHIKAWA, Y. NAKANO, Y. TSUCHIYA, Y. SANADA, H. SAMESHIMA, and M. AFRIDI. Building Survey Team of JSCE-AIJ Joint Reconnaissance Team.

Transcription

1 CDA Seminar on Pakistan Earthquake of October 8, /26/05 Damage Observations and Issues Related to Building Performance T. NISHIKAWA, Y. NAKANO, Y. TSUCHIYA, Y. SANADA, H. SAMESHIMA, and M. AFRIDI Building Survey Team of JSCE-AIJ Joint Reconnaissance Team.ppt / - 1 -

2 Contents Damage Overview Findings from Surveys and Recommendations QUICK REPORT OF DAMAGE INVESTIGATION ON BUILDINGS AND HOUSES DUE TO OCTOBER 8, 2005 PAKISTAN EARTHQUAKE Takao NISHIKAWA Yoshiaki NAKANO Yoshihiro TSUCHIYA Yasushi SANADA Hiromi SAMESHIMA Building Survey Team Japan Society of Civil Engineers (JSCE) and Architectural Institute of Japan (AIJ) November 26, 2005.ppt / - 2 -

3 Surveyed Areas (1) (4) Al-Safa Heights (5) Sughra Tower-1 (1) Margala Towers (2) Al-Mustafa Towers (3) Park Towers (6)-(7) PIMS Hotel Tobishima Corporation Embassy JICA NHA CDA to Geological Survey.ppt of Pakistan / - 3 -

4 Surveyed Areas (2) Battal Balakot Epicenter Muzaffarabad Abbottabad Nathiagali Islamabad.ppt / - 4 -

5 Islamabad Margala Towers No. 5 Nos. 1-3.ppt / - 5 -

6 Islamabad Margala Towers Extensive Damage to URM Walls Damage to Expansion Joints However, No Major Damage to Structural Members.ppt / - 6 -

7 Islamabad Margala Towers Schmidt Hammer Tests in Building Nos. 2-4 Non-destructive test to estimate concrete strength from hardness of concrete surface. It is often referred to estimate concrete strength especially when destructive tests are difficult to perform. Test results 12 N/mm 2 (No. 2) 17 N/mm 2 (No. 3) 15 N/mm 2 (No. 4: collapsed) Generally lower than requirements for Japanese high-rise buildings.ppt / - 7 -

8 Islamabad Margala Towers Reinforcement Detections 90-degree hooks although 135-degree specified in structural drawings 30cm 15cm.ppt / - 8 -

9 Islamabad Margala Towers Reinforcement Detections 90-degree hooks although 135-degree specified in structural drawings 30cm 15cm.ppt / - 8 -

10 Islamabad Margala Towers Reinforcement Detections 90-degree hooks although 135-degree specified in structural drawings 30cm 15cm.ppt / - 8 -

11 Islamabad Margala Towers Why the tower was collapsed? Various Possible Reasons Low Quality of Concrete? Poor Reinforcement Detailing? Low Member Strength? Larger Building Weight? Soil Conditions? Soil Amplification? Long-period Ground Motions?...ppt / - 9 -

12 Islamabad Margala Towers Why the tower was collapsed? Various Possible Reasons Low Quality of Concrete? Poor Reinforcement Detailing? Low Member Strength? Larger Building Weight? Soil Conditions? Soil Amplification? Long-period Ground Motions?.. Possible Surveys Concrete core tests Rebar exposure Seismic Capacity Seismic Capacity Soil Profile Microtremor Response Spectra...ppt /

13 Islamabad Al-Mustafa Towers Cracks in URM Walls No Visible Damage to Structure Schmidt Hammer Test 28 N/mm 2 Margala Towers.ppt /

14 Islamabad Park Towers Cracks in Beams of: Basement Open corridor in upper stories.ppt /

15 Islamabad Park Towers Cracks in Beams of: Basement: Mid-span Vertical Loads Initiated before Open corridor in upper stories EQ Repaired Cracks CFRP sheets.ppt /

16 Islamabad Park Towers Cracks in Beams of: Basement: Mid-span Open corridor in upper stories: Beam-ends Caused by EQ West Building East Building.ppt /

17 Islamabad Park Towers Cracks in Beams of: E ast B eam of W est F ram e Basement: Mid-span Open corridor in upper stories: Beam-ends Caused by 10F E a s t B e a m o f E a s t F r a m e 10F 9F 9F EQ 8F 7F 6F 5F 4F 3F 2F 1F West Building 8F 7F 6F 5F 4F 3F 2F 1F East Building No major difference in crack patterns between two buildings Two buildings behaved in the same manner Quantitative damage surveys are essential.ppt /

18 Islamabad Park Towers Pounding at Expansion Joints Wider gaps between adjacent buildings are recommended.ppt /

19 Islamabad Other Issues Poor Detailing of Rebars Beam rebars out of column reinforcement cage 90-degree hooks of shear reinforcement.ppt /

20 Battal Primary School 2-story School Designed to Japanese Building Code Flexural cracks at the top of a column Extensive shear cracks in an URM wall.ppt /

21 Battal Primary School Flexural Cracks Exposing Reinforcing Bars Shear reinforcement: with 135-degree hooks No buckling of main bars observed.ppt /

22 Battal Primary School Evidence of Strong Shaking but Survived the EQ Schmidt Hammer Tests: 21 N/mm 2 Seismic Capacity Evaluation: C B =0.48 (C B = Strength / Building Weight : Base Shear Coef.).ppt /

23 Battal Jamia Mosque Columns Seriously Damaged URM Walls Had Extensive Shear Cracks Seismic Capacity Evaluation: C B =0.14 (C B = Strength / Building Weight : Base Shear Coef.).ppt /

24 Abottabad Poor Shear Reinforcement in Members Poor Reinforcement Detailing in Beams.ppt /

25 Abottabad Poor Shear Reinforcement in Members Small diameter (6mm to 8mm) and wide space (30cm) 90-degree hooks No shear reinforcement in beam-column joints Upper Column Beam Lower Column.ppt /

26 Abottabad Poor Reinforcement Detailing in Beams Anchored straightly into beam-column joints No bent into core concrete Beam-column connection failure Pin-connected frames rather than moment resisting frames.ppt /

27 Abottabad Poorly Repaired Damaged Buildings.ppt /

28 Abottabad Poorly Repaired Damaged Buildings.ppt /

29 Abottabad Poorly Repaired Damaged Buildings Technical guidelines for post-earthquake rehabilitation are most needed.ppt /

30 Abottabad Quality of Reinforcing Bars Brittle failure without necking at fractured section Also observed in other areas Muzaffarabad.ppt /

31 Muzaffarabad Vulnerable Buildings in Use Quick inspection of damaged buildings needed.ppt /

32 Summary of Investigations (1/5) Concrete Quality No ready-mixed concrete Honeycombs Coarse/fine aggregate Damage vs. strength Reinforcement Quality Brittle failure None Light Collapse.ppt /

33 Summary of Investigations (2/5) Properly anchored beam rebars in joints to avoid Easy pulled-out failure Pin-connected frames ( moment resisting frames) Shear Reinforcement and Concrete Confinement Too small and widely spaced shear reinforcement 90-degree hooks ( 135-degree hooks) for poor ductility and axial load carrying capacity.ppt /

34 Summary of Investigations (3/5) Nonstructural Damage to URM (Unreinforced Masonry) Walls Falling debris: hazardous to occupants Lateral resistance and stiffness from RC and/or RM Walls Beam-Column Joints No shear reinforcement in practice Joint failure with buckling of rebars.ppt /

35 Summary of Investigations (4/5) Pounding Gaps large enough to avoid pounding Site Effects Site effects and resulting amplified ground motions Microtremor measurements Strong Motion Observations Observed damage vs. input ground motions Design EQ loads determination.ppt /

36 Summary of Investigations (5/5) Quantitative Post-Earthquake Inspection Safety evaluation of damaged buildings to aftershocks Quick inspection system, procedures, and inspectors Rehabilitation Strategies and Techniques Damaged sections not fully recovered to the original Buckled rebars still in use Tilted buildings (obviously hazardous) not re-centered Technical guides to properly repair/strengthen damaged buildings.ppt /