Quick Search

Newsletter No 34 - April 2014

Download PDF Version Download PDF document
Download Word Version Download Word document

Report Overview

Two reports in this issue are about older structures; firstly the finding of a large number of reinforced concrete cantilever balconies with the critical top reinforcement in the bottom, and secondly advice from Westminster City Council on suspended plaster ceilings in theatres. Normally the identity of reporters is confidential but in this case the City Council want safety information that they have recently discovered to be disseminated as widely as possible. Concerns on site matters are included in reports on a mobile tower blown off a building, collapses of twin wall shuttering systems and another case of anchors failing under load. There follow two issues about bolts, problems with a lightweight steel frame, and pouring high strength concrete into the wrong shutters. Some of the reports have been edited to reduce their length but the full reports can be seen on new web site. As always thanks are due to reporters who sent in their concerns and to the CROSS panel of experts who provide the comments.

Overview of Reports in this Newsletter

435 Balcony strengths of blocks of flats - further experiences

In recent years, says a reporter, his firm has been undertaking structural assessments of cantilevered reinforced concrete walkways on a large number of two storey blocks of local authority-owned residential flats. In the majority of cases the walkways have been found to be under strength.

436 Mobile scaffold tower falls 7 storeys

A report has been received about a potentially high impact event on a city centre site during very high winds. Despite numerous controls to prevent falling objects, a mobile tower, which was not being used, was blown across the floor plate and hit the edge protection. Such was its momentum that the tower toppled over the guardrail and fell 7 storeys (27 metres) to the ground.

402 Safety concerns with twin wall system

Concrete twin wall systems are hybrid in-situ/precast building products used to construct concrete walls quickly. The product comprises of two leaves of reinforced concrete held apart by reinforcement lattices. The product is used by standing it vertically over starter bars, then filling the void between the leaves with structural concrete. Panels are typically 3m high, up to 8m long and the leaves are in the range 65-80mm thick with a 50-100mm void. A panel can weigh 10T or more.

429 Failure of epoxy resin bonded anchors in concrete

A reporter expresses concern about adhesive bonded anchors made by injecting epoxy resin into drilled holes to fix threaded bars at a pre-determined design depth. During a lifting operation for a section of the guide-wall, the anchors failed progressively when the crane lifted the section 500mm off the ground. The anchors detached from the resin and came out of the holes.

392 Grades of weldable quality bolts

Further to previous reports on this topic, a reporter says grade 8.8 bolts are not required to be manufactured as being weldable according to the relevant product standards e.g., ISO 898-1 and -2. In general, fasteners, whether grade 4.6 or Grade 8.8, are not supplied as weldable items in their respective product standards and should not be welded.

416 Structural bolts and CE marking - advice wanted

Can you please help in connection with the required documents for purchasing and using Structural Bolts?

383 Lightweight steel roof partial collapse

A hall constructed from thin cold rolled steel sections riveted together started collapsing when tiles were loaded on one side only.

406 High strength concrete incident

This relates to a project where the concrete in the walls was C40, and in the in-line columns was C60. The walls were in the same width as the columns so difficult to distinguish which was which from the top of the shutter.

Previous page

Email Updates

How to Report

Online submission:
Submit by post: