Lightweight Concrete Block Structures

1. ------IND- 2006 0431 FIN EN- ------20060830 ------PROJET

Proposal 7 August 2006

B5 THE FINNISH BUILDING REGULATIONS

Lightweight Concrete Block Structures

Instructions 2006

Ministry of the Environment Decree

on lightweight concrete block structures

Adopted in Helsinki on the of 2006

In accordance with the Ministry of the Environment Decision, the following instructions for lightweight concrete block structures, applicable to construction, shall be enacted under Section 13 of the Land Use and Building Act (132/1999) adopted on the 5th of February 1999.

This Decree shall enter into force on the of 2006 and it shall repeal the Ministry of the Environment Decision of 13 March 1987 on lightweight concrete block structures. Previous instructions may be applied to permit applications initiated before this Decree entered into force.

In Helsinki on the of 2006

Ministry of the Environment

Senior Advisor for Building and Planning

THE FINNISH BUILDING REGULATIONS

MINISTRY OF THE ENVIRONMENT, Department of Housing and Building

Lightweight Concrete Block Structures

Instructions 2006

Contents

1GENERAL INSTRUCTIONS

1.1Scope

1.2Definitions

1.3Standards and symbols

1.4Mutual recognition

2MASONRY MATERIALS

2.1Lightweight concrete blocks

2.2Building mortars

2.3Reinforcement elements

2.4Masonry ties

2.5Lintels

3DESIGN OF STRUCTURES

3.1Plans

3.2Design criteria

3.2.1Methods of dimensioning

3.2.2General design criteria

3.2.3Loads

3.2.4Material characteristics of masonry walls

3.2.5Safety of structures

3.2.6Environmental stresses

3.3Structural instructions

3.3.1Joints and bonding

3.3.2Framework

3.3.3External walls

3.3.4Non-loadbearing partition walls

3.3.5Reinforced structures

3.3.6Deformation of structures

3.4Dimensioning of structures

3.4.1Loadbearing vertical structures

3.4.2Laterally loaded walls

3.4.3Bracing walls

3.4.4Local compression strength

3.4.5Reinforced masonry

3.4.6Masonry ties

4PRODUCTION OF STRUCTURES

4.1General

4.2Management of masonry work

4.3Storage of masonry materials on site

4.4Masonry work

4.4.1Bonding

4.4.2Joints

4.4.3Location of masonry ties and reinforcement elements in structures

4.4.4Accuracy of work

4.4.5Details of masonry work

4.4.6Masonry work in winter

4.4.7Temporary protection of structures

4.4.8Loading of structures

5QUALITY CONTROL

5.1General

5.2Quality control of materials and supplies

5.3Supervision of production of structures

6ACCEPTABILITY OF STRUCTURES

7DETERMINING THE STRENGTH PROPERTIES OF MASONRY WALLS BY WAY OF TESTS

7.1General

7.2Number of tests

7.3Test arrangements

7.4Review of test results

8FIRE TECHNICAL DIMENSIONING

8.1Dimensioning criteria

8.2Table dimensions for fire resistance

Appendix 1References

Appendix 2Symbols used

1

General instructions

1.1 Scope

These instructions apply to the strength, weather-resistance, long-term durability and fire resistance of structures produced by laying lightweight concrete blocks with a maximum nominal density of 1000 kg/m³ using building mortar or made in a similar way.

1.2 Definitions

Blockwork

refers to a structural element laid of blocks using building mortar

Building mortar

refers to a mixture of one or more inorganic binders, aggregate, water and sometimes blend components and/or additives used for laying of masonry, pointing and jointing

General-purpose mortar

refers to building mortar for traditional masonry work

Thin-joint mortar

refers to building mortar intended for thin pointing with a maximum size of aggregate of 2 mm

Light-weight mortar

refers to building mortar with a maximum dry and hardened density of 1300 kg/m3

Compression strength class of building mortar

refers to a class marked with an M after which the average compression strength given for mortar is stated as N/mm2

Masonry

refers to a building component formed of bricks or blocks and mortar

Masonry wall

refers to a structure formed of bricks or blocks and mortar used to determine the characteristic strength of a masonry wall (e.g. 1 m high masonry for characteristic compression strength of a masonry wall)

External leaf

refers to external surface masonry in an external wall attached to building frame

Cavity wall

refers to a wall structure formed of masonry walls tied to each other. A sandwich block structure is also regarded as a cavity wall

Lintel

refers to a beam used above openings in masonry which can also act as a sandwich structure with masonry; it is made of steel, masonry pieces, mortar, concrete or light-weight concrete or of a combination of these; reinforcement element may also be made of prestressing steel

1.3 Standards and symbols

The standards and other documents referred to in these instructions are listed in Appendix 1.

The symbols used in these instructions are given in Appendix 2.

1.4 Mutual recognition

Whenever these instructions refer to SFS Standards or quality control procedures, an EN Standard or another standard or a quality control procedure with the corresponding level of safety, valid in another country of the European Economic Area, may also be used in accordance with the principle of mutual recognition.

2

Masonry materials

2.1 Lightweight concrete blocks

Lightweight concrete blocks conforming to the SFS Manual XXXX are used for structures.

Explanatory note:

The SFS Manual XXXX sets out as to how the Standards SFS-EN 771-3 and SFS-EN 771-4 are applied when using these instructions until such time when the use of the Standard EN 1996 in the design of masonry is taken up.

The national implementing standard SFS-YYYY sets out the recommendations of the business community of national standardisation as requirements in different uses, for instance, for product characteristics conforming to the Standards SFS-EN 771-3 and SFS EN 771-4 as well as to the SFS Manual XXXX.

2.2 Building mortars

Building mortars conforming to the SFS Manual XXXX are used for structures.

Building mortar is selected so that, when it hardens, it will bind the masonry pieces into a uniform structure.

Mortars used for reinforced structures should provide the reinforcement with sufficient protection from corrosion.

Explanatory note:

The SFS Manual XXXX sets out as to how the Standard SFS-EN 998-2 is applied when using these instructions until such time when the use of the Standard EN 1996 in the design of masonry is taken up.

The national implementing standard SFS-YYYY sets out the recommendations of the business community of national standardisation as requirements in different uses, for instance, for product characteristics conforming to the Standard SFS-EN 998-2 as well as to the SFS Manual XXXX.

2.3 Reinforcement elements

Concrete reinforcing bars conforming to the Standard SFS 1215 or stainless steel bars conforming to the Standard SFS 1259, certified by an inspection body, approved by the Ministry of the Environment, are used to receive tensile stresses directed at the structures. Reinforcement elements may also consist of thin-jointed reinforcement elements conforming to the Standard SFS-EN 845-3 provided that their tensile strength at break, their bond and long-term durability have been established.

2.4 Masonry ties

Products used to tie and support an external leaf are made of corrosion resistant materials. They must withstand deformations and other stresses due to temperature changes without losing their acceptability.

Ties bent from stainless steel wire, or nails made from stainless steel are used to tie an external leaf. Steel ties coated with a hot galvanized layer of at least 50 m may also be used for under 5 m high external leaves.

To tie an external leaf, masonry ties conforming to the Standard SFS-EN 845-1 may be used provided that their compression strength, tensile strength, buckling strength/bending stiffness and long-term durability have been established.

2.5 Lintels

Prefabricated lintels conforming to the certified product declaration are used for structures. Prefabricated lintels conforming to the Standard SFS-EN 845-2 may also be used for structures provided that their loadbearing capacity, deflection, corrosion resistance of reinforcement elements and, if necessary, frost resistance and fire resistance have been established.

Explanatory note:

In addition to prefabricated lintels, any prefabricated steel beams, concrete beams and light-weight concrete beams dimensioned to function without the composite effect of masonry, lintels made on site and non-reinforced natural stone pieces when they are dimensioned as loadbearing structures, may also be used above the openings in masonry.

3

Design of structures

3.1 Plans

The plans set out the blocks and building mortars used, observing the CE marks or the marks conforming to the SFS Manual. In addition to usual information on structures, such as structural dimensions, location of the structures and useful loads, the plans set out, to the necessary extent, the following:

- reinforcement, its protection and anchoring

- quality, form, quantity and location of masonry ties

- waterproofing and damp-proofing and drainage of water

- expansion joints, their location and structure

- bonding of blocks

- type of a joint and thickness of a joint

- support of walls

- grooves, chases, recesses and holes

- working openings and working joints

- additional instructions concerning special conditions, such as masonry work in winter

- construction loads and support

3.2 Design criteria

3.2.1 Methods of dimensioning

Structures are dimensioned using a limit state design method observing the structural instructions set out in paragraph 3.3.

Structures are designed taking into account both the ultimate limit states and the service limit states.

3.2.2 General design criteria

Nominal sizes are used as dimensions in the calculations. All rejections of cross-section are taken into account in calculations. However, the structure width, in the lateral direction of the structure, may be assumed as the dimension of a joint that meets the limit dimensions of a slot joint and a recessed joint in accordance with paragraph 4.2.

When the recess of the joint is greater or the dimensions of the slot joint are different from those in paragraph 4.2, the thickness measured at the joint is used as the thickness of masonry in the calculations.

Vertical joints in masonry may be designed without mortar if the reduction in the horizontal bending and shearing strength is taken into account.

The distances of support centres are assumed as span lengths of the structures and their clearance height as the height of walls and pillars. However, there is no need to assume a greater value than the clearance of supports multiplied with a coefficient of 1.05 as span lengths.

The value L/200 corresponds to the service limit state of deflection of the structure. If the ratio of the span length of a horizontally reinforced wall loaded by earth pressure and the thickness h of the wall is L/h ≤ 25, it is considered that the structure meets the requirements for service limit state unless special requirements are set for deformations.

3.2.3 Loads

Design loads of the structures are calculated in accordance with the regulations concerning them.

It may be assumed that the vertical loads in masonry walls are distributed and transferred in accordance with Fig. 1.

Fig. 1.

Distribution of vertical loads in a wall.

It may be assumed that the loads are evenly distributed onto the entire supporting surface on the supports of horizontal structures and at the lower ends of walls and pillars.

When horizontal structures transfer horizontal loads onto more than one bracing wall, it may be assumed that the loads are distributed onto bracing walls in proportion to their rigidity. If necessary, the asymmetrical location of bracing walls is taken into account in the distribution of horizontal loads.

Distribution of bending moments and shear forces in structures are calculated in accordance with the elasticity theory. When wall structures are dimensioned for wind loads, masonry may be calculated using the broken line theory. If necessary, cracking of the structure and stresses due to restraint action are taken into account.

No more than 20% may be deviated from the distribution of bending moments conforming to the elasticity theory in continuous structures when other quantities of force are corrected to correspond to the altered distribution.

On ordinary ground, the earth pressure loads are calculated in accordance with Fig. 2. If necessary, the effect of compaction of made-up ground is taken into account.

MURTOTILA – ULTIMATE STATE

kitkamaa – non-cohesive soil

koheesiomaa – cohesive soil

KÄYTTÖTILA – SERVICE STATE

Fig. 2.

Calculation of earth pressure load. The design value of earth pressure load is set out in Fig. a). Distribution of load in accordance with Fig. b) may also be used in a horizontally reinforced wall. Symbols in Figs. a) and b) are:

p1 is the design value of earth pressure due to the weight of soil (kN/m2);

p2 is the design value of earth pressure due to surface load and, moreover in cohesive soil, to cohesion (kN/m2);

His the filling height (m);

qis the surface load (kN/m2);

cis the cohesion of cohesive soil (kN/m2).

3.2.4 Material characteristics of masonry walls

The strength characteristics of masonry walls are determined by way of tests in accordance with section 6, or specific values determined for masonry walls from mean values/characteristic values set out for masonry pieces and mortars conforming to the SFS Manual XXXX with their use requiring that the joints and bonds meet the requirements set out in paragraph 3.3.1, are used in the design.

The values in Table 1a are used for lightweight aggregate blocks as characteristic values of compression strength of masonry walls built using general-purpose mortar or thin-joint mortar and the values in Table 1b for autoclaved lightweight concrete blocks.

Table 1a.

Characteristic strengths of lightweight aggregate block masonry walls

Table 1b.

Characteristic strengths of lightweight concrete block masonry walls

1 When using building mortar M 100/500 or thin-joint mortar with the shearing strength (SFS-EN 1052-3) of at least 0.06 fqm for lightweight aggregate block masonry walls and of at least 0.05 fb for autoclaved lightweight concrete block walls. When using other mortars, the strength value must be based on separate surveys.

Symbols in the table are:

fckis the characteristic value of compression strength of a masonry wall;

fqm is the mean value of compression strength of lightweight aggregate concrete mix advised by the manufacturer;

fbis the mean value of normalized compression strength of autoclaved lightweight concrete advised by the manufacturer;

fxk1is the characteristic value of tensile strength in bending in fracture plane parallel with horizontal joints;

fxk2is the characteristic value of tensile strength in bending in vertical fracture plane against the direction of horizontal joints but, however, no more than the bending capacity of masonry pieces in fracture plane;

fvkis the characteristic value of shearing bond strength, see the SFS Manual XXXX.

When no mortar is used in vertical joints in masonry work, the characteristic values of compression strength in Table 1 may be used except when the compression is in the vertical direction against the end of the masonry piece in which case the effect of vertical joints without mortar is taken into account using a reduction coefficient of 0.5.

When no mortar is used in vertical joints in masonry work, the characteristic values of tensile strength in bending in Table 1 may be used in both directions if the cross-sectional area of reinforcement, symmetrically located in horizontal joints, is a total of at least 0.03% of the area of cross-section of masonry. If this requirement is not met, the characteristic values fxk2 in Table 1 should be reduced with a coefficient of 0.7.

Fig. 3.

Bending strength of a masonry wall in different directions.

Case 1: Bending strength in the fracture plane in the direction of horizontal joints.

Case 2: Bending strength in the vertical fracture plane against the direction of horizontal joints.

Values in Table 1 are used as a characteristic value fvk of shear strength of reinforced masonry.

When calculating deformations due to short-term loading, the value below is used for the coefficient of elasticity in masonry:

Ec = 750 fqm from lightweight aggregate blocks to masonry

and

Ec = 750 fb from autoclaved lightweight concrete blocks to masonry

where

fqm is the mean value of compression strength of lightweight aggregate concrete mix advised by the manufacturer

fbis the mean value of normalized compression strength of autoclaved lightweight concrete advised by the manufacturer.

When calculating deformations due to long-term loading, the value below is used for the coefficient of elasticity in masonry:

Ecc = Ec/(1 + )(3.1)

where

= 2 for masonry made of lightweight aggregate blocks

= 1 for masonry made of autoclaved lightweight concrete blocks.

With lightweight aggregate blocks, a value of 0.6 mm/m for shrinkage after masonry work and for moisture deformation, due to a masonry wall getting wet and drying, is used for both, and a value of 0.2 mm/m with autoclaved lightweight concrete blocks.

A value of 6 x 10-6 °C-1 for the thermal expansion coefficient of the length of masonry may be used for lightweight aggregate blocks and for autoclaved lightweight concrete blocks.

A lower yield limit or a limit of 0.2 is used as the characteristic strength of reinforcement, and the coefficient of elasticity of the said steel grade as the coefficient of elasticity.

3.2.5 Safety of structures

When surveying the ultimate limit state of loadbearing structures, the design strength is obtained by dividing the characteristic strength of material with the partial safety figure of material conforming to Table 2.

Table 2.

Partial safety figures for materials

The safety figure of reinforcement is used as the partial safety figure for material in steel masonry ties and the safety figure of masonry as the partial safety figure for anchoring.

If necessary, the surveys of service limit state show that deformations and cracks do not exceed the requirements imposed on usability of a structure nor are they otherwise detrimental. A value of 1.0 is used as the partial safety figure for material in the surveys of service state limit.

3.2.6 Environmental stresses

When designing structures located next to the open air, the environmental stresses including deformations due to changes in temperature and moisture, rain and wind pressure as well as frost attack due to repeated freezing, should be taken into account. External stresses depend on the climate, on the location, form and height of the building as well as on the details of the structure.

The diagonal rain stress depends primarily on the wind pressure directed at the wall. Particular attention to water tightness should be paid when the building has no guttering, is high or located in an exposed place. Joints of the external leaf are made as tight as possible. When designing a wall, it should be remembered that water may seep through the external leaf, and care should be taken to conduct water away.