It wasn't the size of cracks in concrete beams & columns which bothered me, mostly thin & squiggly cracks, but the number. There were hundreds of cracks, seen on 3 or 4 sides of concrete columns & beams. I wondered what cracks were obscured by covering structures?
Over the last week, TV news reported stories about why CTV bldg, Madras St, had collapsed in the Feb 22 quake, killing 115 people. Yet across the road, corner Madras St & Cashel St, the IRD bldg stood firm during 4 major quakes.
A TV reporter had gone to USA & spoken to a US bldg expert who experimented on quake shaking of modern bldgs. He opined that the CTV bldg collapsed, as reinforcing steel was not strong enough in concrete columns, which had collapsed & steel reinforcement mesh in concrete floors had broken at weld joins & sheared off joins to the concrete lift shaft. Pity the CTV lift shaft was demolished soon after the rest of the CTV disaster site was rubble cleared. That stopped any forensic investigation of that monumental disaster.
Before the Feb 22 quake, people who'd worked in the CTV bldg had complained that the bldg shook when heavy vehicles passed. And that was long after the Sept 4, mag 7.1 quake & after Christchurch City Council had green stickered CTV bldg 3x. Were other Christchurch modern bldgs in such shaky, parlous state too? Since the quakes, bldg codes had been revised to obviate such a disaster again.
Over the last few weeks I'd noticed many small cracks in Northlands Mall undercover car park, ground floor, on concrete columns & concrete roof / floor beams. The cracks had been cleaned up making the roof / floor beams look like zebra stripes, scores of vertical stripes on horizontal concrete beams.
Mon 21.08.11. North-western car park, Langdons Rd side: I noticed 100s of "roof bolts" were glued on concrete cracks, on 3 sides of white painted, concrete beams, presumably to strengthen horizontal concrete roof / floor beams. Those ground floor concrete roof / floor beams carried great weight, as the car park continued 2 concrete roofs / floors above.
I noticed similar "bolts" on concrete columns on the south side of the car park bldg near the lift shaft.
For a couple of 1980s years, when I worked for DeBeers mining company, I wrote job descriptions for Paterson Job Evaluation meetings. One of the job descriptions I wrote was Roof bolt Installer: A mining team of rock drillers drilled holes in mine tunnel roofs & installed long, steel roof bolts to pin & hold up rocky roofs, obviating tunnel collapse.
I'd seen those roof bolts installed on Moncks Bay cliff side, Main Rd, & Sumner cliff side, Nayland St, to stop rock falls on housing below.
In my wanderings around quake broken Christchurch over the last months, I'd seen several quake crushed cars, crunched by fallen bricks & concrete. I'd seen quake leaning blocks of flats, with leaning undercover parking & a crushed car under a block of flats where undercover parking had collapsed - block of flats off Springfield Rd.
Tues. 23.08.11. Around midday I went for a last shop at Northlands, Mall Pak 'n Save & a closer look at undercover parking. What I found:
North-west ground floor car park, Langdons Rd side: Hundreds of plastic nipples, each about 3 cms diameter with a central screw & nipple on top, glued to grey filler, on concrete column cracks & roof / floor concrete beam cracks. Not bolts as guessed, as I found two nipples had fallen off, so I could examine them. (Injection nipple sold at Bunnings, $4.95 each).
Images, quake damaged Langdons Rd & Sissons Rd:
23.08.11. Plastic, injection nipples (left broken) with grey filler, Northlands Mall car park, post June 13 quake
23.08.11. Back entrance to Northlands Mall, north-west car park, Langdons Rd, post June 13 quake
23.08.11. Injection nipples & filler on outside quake cracks, first floor, north-west car park, concrete driveway, Northlands Mall, Langdons Rd, post June 13 quake
23.08.11. Injection nipples & filler on outside quake cracks, north-west wall concrete column, supporting first floor, concrete car park driveway, Northlands Mall, Langdons Rd, post June 13 quake
23.08.11. Injection nipples & filler on inside quake cracks, north-west wall concrete column, supporting first floor, concrete park driveway, Northlands Mall, Langdons Rd, post June 13 quake
23.08.11. Injection nipples & filler on quake cracks, ground floor, north-west concrete roof, Northlands Mall car park, Langdons Rd, post June 13 quake
23.08.11. Quake cracks ready for filler, central concrete roof beam, ground floor, north-west car park, Northlands Mall, Langdons Rd, post June 13 quake
23.08.11. Injection nipples & filler, central concrete roof beam, ground floor, north-west car park, Northlands Mall, Langdons Rd, post June 13 quake
23.08.11. Quake cracked corner column, ready for filler, Langdons Rd, north-west car park entrance, Northlands Mall, post June 13 quake
23.08.11. Injection nipples & filler on concrete southern wall in lift alley, north-west car park outside concrete wall, Northlands Mall, post June 13 quake
23.08.11. Langdons Rd view of quake cracked, central concrete roof beam, ground floor, north-west car park, Northlands Mall, post June 13 quake
23.08.11. Langdons Rd side view of Northlands Mall entrance, with injection nipples on filler, inside north-west, concrete column & roof beam, post June 13 quake
23.08.11. Injection nipples on filler, inside southern concrete roof beam, ground floor, north-west car park, Northlands Mall, post June 13 quake
23.08.11. Quake cracked, central concrete roof beam, ready for filler, ground floor, north-west car park, Northlands Mall, post June 13 quake
North-west, first floor car park, Langdons Rd side: No hard plastic nipples. 9 central, flat concrete columns, each with a thick blue horizontal stripe around the yellow painted column. It was alarming that each column, near the roof, had two horizontal strips of recently cut concrete filled with new cement, like someone had angle-grinded investigation slits through each column then sealed with cement, at exactly the same height on each column. Hopefully NOT quake cracks!
23.08.11. Slits on yellow, central concrete columns, near concrete & / or steel roof beams. Slits sealed with cement in all 9 central columns, first floor, north-west car park, Northlands Mall, post June 13 quake
First floor, north-west car park, southern wall, Langdons Rd side: 11 white painted, concrete pillars, each with fine cracks, gutter pipes attached with drain holes by each pillar. Two more pillars beyond, both ends of the bldg, without drain pipes.
23.08.11. Cement repaired, quake cracked, southern concrete column, with gutter pipe, first floor, north-west car park, Langdons Rd entrance, Northlands Mall, post June 13 quake
North-east car park, Sissons Rd side, a stream ran on the north side of the car park: Ground floor, fewer hard, plastic nipples on horizontal roof / floor beams. 6 concrete columns, south side, & 3 corner concrete columns had hard plastic nipples glued to cracks.
23.08.11. Injection nipples & filler on ground floor quake cracks, cnr concrete column & roof beam, north-east car park, Sissons Rd side, Northlands Mall, post June 13 quake
23.08.11. Injection nipples on concrete filler, outside cnr column, first floor, north-east car park, Sissons Rd side, Northlands Mall, post June 13 quake
23.08.11. Quake cracks & some filler repairs on concrete column & roof beam, gutter pipe attached, north-east ground floor car park, Northlands Mall, post June 13 quake
North-east car park, Sissons Rd side: First floor, middle horizontal concrete roof beams OK, white painted, some with recent, patchy cement repairs.
North-east car park, Sissons Rd side: First floor, south side, outside, 6 concrete columns, more hard, plastic nipples glued to filled cracks.
23.08.11. Injection nipples on filler, southern, outside, concrete column, first floor, north-east car park, Northlands Mall, post June 13 quake
23.08.11. Quake cracked, concrete column & repair, with gutter pipe & drain, first floor, North-east car park, Northlands Mall, post June 13 quake
Near cars' exit driveway: cracked concrete footpath, polystyrene filler between the car park floor & side-constructed driveway. Polystyrene expansion / contraction (?) filler was covered with a metal strip.
23.08.11. Polystyrene filler between first floor, north-east car park & driveway join, by quake spalled, concrete footpath, Northlands Mall, post June 13 quake
Two workmen hovered outside, one wearing an orange, Hi Vis vest, another wearing a yellow, Hi Vis vest, "WATERPROOFING" label on his back. Double speak: Leak proofing, quake cracked concrete.
26.10.11. Sissons Rd entrance to north-east car park showing stream along north side of the car park, Northlands Mall
Quakes or no quakes, I wondered why all that cracked concrete on 2 car park ground floor & first floor roof / floor beams & support columns needed leak proofing at all?
Call me phobic, but I disliked tons of quake cracked concrete, glued by epoxy resin, above my head. Never mind quake weakened steel inside the concrete. After 4 major quakes & 8 000 aftershocks, I would shop elsewhere.
Coda: Post 23.12.11 quake swarm, including 5.8, 5.3, 6.0 mag quakes, Northlands Mall car park was closed & fence cordoned for safety checking. Langdons Rd entrance, glass sliding doors were broken & boarded. Gotta ask why planners, engineers, architects & builders continued using glass sliding doors in a quake zone?
In quake power cuts, glass sliding doors became death traps. When the 23.12.11 quakes struck, people headed for mall exits en masse. If doors jammed closed, imagine the mayhem.
Across Langdons Rd, the Public Library was closed. On nearby Main Nth Rd, National Bank was closed for safety checking.
|03.02.12 Fence cordoned car park, Northlands Mall, Langdons Rd|
|03.02.12 Fence cordoned car park signs, Northlands Mall, Langdons Rd|
03.02.12. 10 000 quakes hence, I took a closer look at the Langdons Rd car park, still fence cordoned. Concrete beams on both car park floors were supported by metal beams & scaffolding. Workmen continued epoxy resin glueing. Fence signs read:
CHECKS HAVE BEEN
|03.02.12. Fence cordoned car park sign, Northlands Mall, Langdons Rd|
Mon 13.02.12. On my way to the bank, wandering past Langdons Rd car park, I noticed that metal brackets were bolted from each roof / floor, concrete panel to middle & side concrete beams of ground floor & first floor of the Langdons Rd car park - scores of brackets. Thus many roof / floor concrete panels were bracket-bolted to already cracked & epoxied concrete beams. As it was nearly a year post 22.02.11 quake, I wondered why Northlands Mall & engineers took so long to install brackets? Meanwhile 10s of 1 000s of drivers had used the quake cracked car parks.
Post quakes, that expediency was experienced all over Christchurch. Broken roads & bridges were used for years, until closed & / or detoured for lengthy repairs by SCIRT. Short of abandoning the whole of Christchurch for years as a health hazard, Christchurch citizens had to just get on with it.
Despite the plethora of demolition, construction & rebuild signs to the contrary, normal Health & Safety requirements in Christchurch were quietly suspended for many years post quakes. Imagine all the sewage bacterial spores, liquefaction dust, bitumen, asbestos, silicon & brick dust citizens inhaled.
Thurs 15.03.12. The Press reported that 14 shops would be closed at Northlands Mall, near Hoyts cinema (closed for months post quakes) & Langdons Rd carpark, belatedly quake strengthened.
My first memory of serious quake damages, morning of the 04.09.10, mag 7.1 quake, was Papanui HS reservoir spewing stones & water across Langdons Rd, between the school & Northlands Mall, Langdons Rd, north-west car park.
Gotta ask why engineers took more than a year post 22.02.11 quake to effect closure, only after revision of bldg codes / standards? Trouble with pre-quakes, bldg codes, was that Council allowed bldg owners to quake-strengthen bldgs at a fraction of the current bldg code, with many years to do so. Those dodgy bldg codes & slow strengthening of quake prone bldgs, if any, proved lethal.
Only reason why Council, engineers & bldg owners pulled finger, was they were being named & shamed at the Royal Commission of Inquiry, as to why so many Christchurch bldgs failed in the quakes.
Wed 04.04.12. Luke visited Northlands Mall & picked up an information notice which read:
"Kiwi Income Property Trust advises that part of Northlands Shopping Centre is to be strengthened to comply with the new earthquake loadings standard now applicable in Christchurch.
14 out of Northlands 126 shops will be closed while the strengthening work is carried out. The Centre and remaining 112 stores will continue to trade as normal.
Although this may cause inconvenience, Northlands has performed well throughout the prolonged period of earthquakes and aftershocks with moderate damage only. Strengthening work however does need to be conducted in defined areas against the requirements of the New Building Standards.
Canterbury Earthquake Recovery Authority (CERA) has issued notices to more than 7 000 Christchurch building owners to undertake Detailed Engineering Evaluations (DEEs) to assess the performance of their buildings against the requirements of the New Building Standards..."
Snag with bldg codes / standards: Codes were regularly revised by engineers pre 2010-2011 quakes, but proved useless in Christchurch quakes, as Council had a laissez -faire attitude to building codes, allowing owners of old bldgs to get their bldgs up to 30% code over 30 years. That fraction over a long time proved "She'll be right" fatal. Many CBD bldgs failed in the 22.02.11, mag 6.3 quake, killing people. Death toll 185, some outside the CBD.
Hence Christchurch red zone CBD became a post quake, CERA wasteland, with hundreds of demolitions, as some quake damaged bldgs were too expensive to strengthen & repair. Bldg owners, engineers & Council had much to answer for.
Oct 2012. Like Northlands Mall car parks, quake cracks in many concrete bldgs around Christchurch were epoxy glued. It remained to be seen how effective epoxy glue repairs would be in future quakes.
Mar 2013. Northlands Mall car parks looked flash, the cracks painted over. The mall bldg was grubby, some shops board-cordoned inside. There were many post quake bldgs in Christchurch with quake cracks epoxy glued & painted over.
Content & pics Copyright Mark JS Esslemont.
See Performance of multi-storey concrete buildings in the Darfield Earthquake
See Northlands mall to close 14 shops (The Press / Stuff Co).