How to collect additional information

This guide will discuss the sources of information that can be used in the seismic assessment for VIIA. The primary source of the information is the inspection report. The report also contains drawings and pictures (in the inspection folder). The goal of the inspection is to assess if the drawings are complying to the real situation and register the deviations with measurements.

Note

In principal the inspection report should satisfy the requirement to be able to schematise the structure for seismic analysis. Only in exceptional cases other sources of information should be considered. This implies that we rely on the contents of the report, unless we are very sure the report is wrong.

Before starting to model the object, it is important to observe whether a desk study (NL: bureaustudie) and an inspection (NL: opname) have been carried out. It is possible that a 3D scan of the object may also have been done. Also, some previous MRS analysis objects may be requested to be re-assessed. Here, a review of the building document and the inspection report should also be performed, and it is necessary to investigate if additional information is necessary; in this case a new inspection needs to be scheduled for the object. There is a list of translations of common Dutch words/phrases that are encountered in the inspection documents that you can find in section How to translations Dutch-English.

The questions that need to be answered in this step are:

  • What information is available (desk study and inspection)?

  • What is unclear?

  • Which relevant information is missing?

It is also relevant that the geotechnical advisers already identifies possible geotechnical hazards from the available information. Particularly, the possible presence of liquefaction susceptible terrains is important to estimate initial required strengthening measures, which can be proposed in advance. If the required geotechnical information is not available, additional soil research is required. This is done by third parties, which may lead to planning conflicts. Geotechnical information databases may be consulted initially to estimate the expected liquefaction risk.

Note

Because of the impact of assumptions or interpretations in this step, choices have to be discussed in advance with the lead engineer, in particular if it’s not possible to conduct further field investigations/inspections. These assumptions are part of the final engineering report and also include quality agreements (as the BKCL and the issuelog). Make sure that these are processed to avoid duplication.

The use of assumptions, based on engineering judgement due to the lack of sufficient information and the existence of uncertainties relevant to the analysis, must be declared in the BKCL document and submitted to the projectleader (who will discuss with the client). Based on this document, agreements related to the adequacy of the assumptions and the request of additional information are performed. These agreements should also be mentioned in the technical advisory report (TVA, NL: Technisch Versterkings Advies). For tenderspecifications for PraktijkAanpak the BKCL is not required.

It is important for the use of engineering assumptions to consult the relevant Basis of Design report (BoD, or NL: Uitgangspuntenrapport, UPR) in combination with the standarisation starting points (see How to standardise the unknown information from inspection). Assumptions can also be made in consultation with the knowledge-team, the lead engineer or senior structural engineer. Also the geotechnical advisor may have assumptions that need to be discussed with the client.

Some examples of assumptions for the analyses are:

  • connections between walls

  • connections between walls and floors (support conditions)

  • expected structural weak spots of the structure

  • type and dimensions of the foundation

  • expected strengthening measures (some may included from the start in the model)

  • use of typical dimensions for covered elements such of lintels, roof, ceilings, etc.

  • assumptions based on building typology (other objects from the same (style) period, structural characteristics, etc.)

At the start of the object, the following sources will be available:

Available sources of information

Desk study:

Bureaustudie includes structural/architectural drawings, calculations and other reports, often obtain from the owner or municipality sometimes from the original structural engineer, architect and geotechnical adviser. If not all of these parties were initially consulted and if theparties concerned still existed, additional desk study might provide additional info if required. This has to be consulted via the project leader. Also, the geotechnical advisor should request if additional desk study is required.

Inspection report:

An inspection can be carried out in order to verify, modify or update the information gathered during desk study. This inspection includes photographs and drawings of the findings. In occasions, the basic inspection visual techniques proved insufficient for the NLPO or NLTH analysis. It is possible to propose to the project leader to have an additional inspection to be carried out, but this is rare. In an additional inspection the structural engineer will participate on the inspection to find out the additional information as accurate as possible. (Note: The engineer must be in possession of the VCA certificate. VCA is short for ‘Safety, Health and Environment Checklist Contractors’ and the purpose is to make sure everyone works in a safe manner. With this certificate you indicate that you observe safe working practices while bearing in mind the environment and your own health as well as that of others). If destructive tests are necessary, then this must be clearly communicated in advance since difficulties may arise from the building owner.

Basis of Design

In the Basis of Design report, see Basis of Design.

3D scan

This scan can give you the opportunity to look into the building. Cross-sections can be also retrieved from the scan. Refer to howto-guide for additional information how to handle the software to use the scans: How to read 3D scan)

When key critical information for the analysis is missing or cannot be assessed from the above sources, an additional inspection can be requested. Consider the following as aspects to further investigate if considered critical:

  • Identification of primary and secondary seismic elements

  • type of connections (not connected, sliding, hinged, or rigid)

  • dilatation joints in floors, masonry

  • number of cavity anchors (per m2) (observe also NCG guidelines in the prevailing ABSC document, see Basis of Design)

  • essential dimensions (wooden beam layers / compressive layer / beams / floors / walls

  • whether or not the masonry is load-bearing, type of lintels and supports, type of masonry and quality

  • request related to the geotechnical adviser about the soil or foundations. They can indicate locations where it is necessary to dig and measure dimensions of strip footings. The excavating team must be arranged by the head inspector. Additional soil investigations to be performed by an external company only if the geotechnical risk is high.

The preparation of the list of unknown information must be done according to the specific requirements for the NLTH assessment. You can think of the following items:

  • Is the information really needed in the calculations? Is it crucial or not? When answering this question, consult the head engineer.

  • Is a destructive test necessary (last resort), or can it also be done with an endoscope, metal detector or likewise?

  • Consult the additional inspection with the team leader and head inspector prior to the inspection, they often know what is or is not possible. A list is created within VIIA for additional inspections for missing information.

Warning

In the case of an inspection, the structural engineer may participate with the inspection if he holds a VCA certificate and has the correct personal protection equipment (PPE). If this is not the case, the structural engineer is only allowed to watch (with the compulsory PPE), and not, for example, climb a staircase, lift ceiling panels, stand in a dug hole or enter in confined space.

The following checklist is useful in case the structural engineer participates in the inspection: LINK.

Basis of Design

The Basis of Design document contains the general modelling, analysing and assessment approach in VIIA. This document is discussed with the client. When starting an object, the prevailing Basis of Design is set and used throughout the process (unless specific reasons, in consultation of the lead engineer, a newer version might be adopted). If you need to deviate from the Basis of Design (or for example some material is not present), you can make a proposal. This proposal is discussed with technical master and lead engineer and sent for validation to knowledge-team. If adopted and of general use, it will be added to the next Basis of Design. But in your TVA you should always add all deviations from the Basis of Design.

For each analysis method a Basis of Design (BoD) document is available (also referred to as the UPR, the starting point document or Uitgangspuntenrapport). The actual versions are:

Basis of Design NLTH, v12.0: BoD-NLTH 12.0

Basis of Design SBS, v1.0: BoD-SBS 1.0

Basis of Design NLPO, v1.0: BoD-NLPO 1.0

Basis of Design MRS, v4.0: BoD-MRS 4.0

Older versions:

  • Basis of Design NLTH, v11.0 (also used for NLTH-REF):

BoD-NLTH 11.0

NPR versions (English):

NPR versions (Dutch):

Other documents:

Interaction with knowledge development

When executing an analysis on an object that is part of the production process, knowledge development may also be included during the development of the project. Knowledge development is discussed if it appears that there are opportunities to accelerate production or if there are specific aspects for a particular object that must be further researched. If research only applies to a specific object, it is permitted to perform a short-term study. Long-term studies can be planned for wide application topics.

For undertaking regarding research activities consult the head engineer, the coordinating structural engineer or the senior structural engineers. This should have a maximum duration of about two weeks. It may also be that there are knowledge development opportunities that are important for several objects. For these studies, a separate budget must be requested from CVW. This is done in consultation with one or more of the aforementioned structural engineers.

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Figure 1 Interaction with the knowledge-team.