Zealand Code Research Articles

New Zealand's Codes of Welfare for pigs and laying hens

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Informed Consent To Medical Treatment: The Common Law And New Zealand's Code Of Patients' Rights

Informed Consent To Medical Treatment: The Common Law And New Zealand's Code Of Patients' Rights

Evaluation in industry of a draft code of practice for manual handling

This paper reports findings from a study which evaluated the draft New Zealand Code of Practice for Manual Handling. The evaluation assessed the ease of use, applicability and validity of the Code and in particular the associated manual handling hazard assessment tools, within New Zealand industry. The Code was studied in a sample of eight companies from four sectors of industry. Subjective feedback and objective findings indicated that the Code was useful, applicable and informative. The manual handling hazard assessment tools incorporated in the Code could be adequately applied by most users, with risk assessment outcomes largely consistent with the findings of researchers using more specific ergonomics methodologies. However, some changes were recommended to the risk assessment tools to improve usability and validity. The evaluation concluded that both the Code and the tools within it would benefit from simplification, improved typography and layout, and industry-specific information on manual handling hazards.

The Seismic Design and Performance of Reinforced Concrete Beam-Column Knee Joints in Buildings

The seismic performance of eleven half-scale and three full-sized reinforced concrete beam-column knee joints was tested under inelastic cyclic loading. Twelve joints were designed to the current New Zealand Concrete Standard, NZS 3101 while the remaining two were designed to the 1964 New Zealand Code, which contained few seismic provisions. All the 1995 designs approached or exceeded their nominal beam strengths in both directions and only degraded in strength at displacement ductility factors greater than 2, while the 1960 designs failed prematurely in joint shear at about 70% of the beam nominal strengths. Many of the half-scale joints failed when cover concrete split off in the joint zone, allowing loss of anchorage and slip of the top beam bars. Two full-scale joints were designed to carry the maximum specified code joint shear stress (0.2 fc′), and one subsequently failed due to joint shear when the concrete compressive strength did not reach the specified design value. A third full-size joint was tested with distributed beam reinforcement. This joint performed in a ductile manner to displacement ductility 4 but failed in the second cycle at that displacement, due to buckling of several rows of beam bars.

New Zealand Code of Welfare for Broiler Chickens

New Zealand Code of Welfare for Broiler Chickens

Advanced analysis of composite frames

AbstractThe issue of design codes is becoming continually challenged throughout the world. Over the last decade, design codes in structural engineering have seen an increase in harmonization with the preparation of regional codes and material specific model codes. In particular, this has been highlighted by European code releases in most construction materials. In Australasia, there have also been an increasing number of design codes published as combined Australian and New Zealand codes. In Asia there have been initial moves to create a regional code in concrete structures. In addition to the harmonization of international codes, many structural design codes are moving away from prescriptive methods and toward performance‐based approaches. The gradual shift toward international harmonization and performance‐ based specifications puts increased pressure on design engineers to have appropriate software and design tools to assess the real behaviour of structures. Considerable research has been conducted into advanced analysis methods in steel and composite members and frames over the last two decades. Whilst their use has been limited mainly to considering investigations of structural failure and very special structures, the emergence of performance based international codes may see an increased need and reliance on these approaches. This paper highlights the recent development in advanced analysis of composite members and frames, and discusses the issues that are essential for design implementation. Some illustrative examples are also given to demonstrate the benefits of using advanced analysis for designing real‐sized structures.

Ductility demand for uni-directional and reversing plastic hinges in ductile moment resisting frames

In a major earthquake the beams in moment resisting frames may develop either reversing or unidirectional plastic hinges. The form of plastic hinge depends upon the ratio of the moments induced by the gravity loading to those induced by the seismic actions. Where this ratio is low the plastic hinges form at the ends of the beams and the sign of the inelastic rotation changes with the direction of sway. These are reversing plastic hinges, and the magnitude of the rotation that they sustained is closely related to the inter-storey displacement. However, when the moment ratio exceeds a certain critical value, unidirectional plastic hinges may form. In this case negative moment plastic hinges develop at the column faces and the positive moment plastic hinges form in the beam spans. As the earthquake progresses the positive and negative inelastic rotations accumulate in their respective zones so that peak values are always sustained at the end of the earthquake. With this type of plastic hinge no simple relationship exists between inter-storey drift and inelastic rotation.
 Several series of time history analyses have been made to assess the relative magnitudes of inelastic rotation that are imposed on the two forms of plastic hinge. It is found that with design level earthquakes typically the unidirectional plastic hinge is required to sustain 21/ 2 to 4 times the rotation imposed on reversing plastic hinges, with the curvature ductilities ranging up to 140. These values are appreciably in excess of the values measured in tests using standard details. This indicates that in structures where unidirectional plastic hinges may form, the design displacement ductility and or the allowable inter-storey drift should be reduced below the maximum values currently permitted in the New Zealand codes. The problems associated with the formation of unidirectional plastic hinges can be avoided by adding positive moment flexural reinforcement in the mid regions of the beams. By this means the potential positive moment plastic hinges can be restricted to the beam ends.

Seismic performance behavior of beam-column connections in prestressed concrete bridges

Test results for four prestressed concrete beam-column connections subjected to reversed cyclic loading are reported. The specimens were part of an experimental program designed to investigate the effect of design provisions/specifications and concrete strength on seismic performance behavior of such connections. The major design parameters varied in the specimens were the design code (AASHTO versus New Zealand codes) and the concrete strength (high versus normal strength concrete). From the test results, it was concluded that both the AASHTO and New Zealand codes provide sufficient capacities for earthquake-resistant design, and before spalling of the concrete cover, the stiffness degradation of the specimen with high strength concrete was less serious than that with normal strength concrete. To account accurately for the hysteretic behavior, a new set of rules for such connections to predict the hysteretic loops is proposed.

Stirrup Effectiveness in Reinforced Concrete Beams under Flexure and Shear

The so-called shear failure of slender beams is known to be due to combined action of flexure and shear which causes beam failure moment to be lower than ultimate moment in pure flexure, even for beams with stirrups. Current design procedures for shear strength analysis provide simple superposition of stirrup and concrete capacities, hence ignoring any stirrup influence on concrete mechanisms and/or any dependence of stirrup action on the failure mode. By contrast concrete shear resisting mechanisms, made of the beam and arch action contributions, can interact with stirrups in different ways. Latter interaction results in a truss mechanism variable contribution and in some enhancement of beam action contribution. A stirrup effectiveness function is introduced, which provides the ratio of effective mean shear stress increase due to stirrup inclusion and the conventional one drawn from 45 deg truss model. On these bases a mechanical model is proposed to provide mean ultimate shear stress ofRC beams with stirrups. By testing the proposed model against available experimental results from different authors, more accurate prediction is obtained than ACI Code, Eurocode, New Zealand Code and Zsutty's formula. Thus, a design formula is proposed which is simple and results in a reasonably conservative design.

Response of low-rise buildings to moderate ground shaking, particularly the May 1990 Weber earthquake

In the Weber earthquake of 13 May 1990 the stronger component of the ground motions recorded in Dannevirke was similar in strength to the El Centro S00E record from the 1940 Imperial Valley earthquake which underlies the New Zealand loadings code, The Modified Mercalli intensity in Dannevirke however was only about MM7 1⁄2, whereas the intensity corresponding to the 1984 earthquake code is about MM8 1⁄2 for the Dannevirke area. This paper compares the strength of the Dannevirke record in terms of spectral accelerations with (i) the above El Centro record, (ii) the Matahina dam record of the 1987 Edgecumbe earthquake, and (iii) the loadings of the 1984 and 1992 New Zealand codes. Also described in the paper are time-history analyses of one- and two- storey buildings subjected to the above ground motions in an attempt to explain why the damage levels were lower than might be expected from the strength of the recorded accelerograms. Comparisons are made of the seismic performance of moment-resisting frames and walled structures. Comments are made on two of the provisions of the 1992 loadings code.

An evaluation of the New Zealand code torsional provision

This study evaluates the New Zealand torsional provision in the 1984 and 1992 editions of the New Zealand loading code (NZS 4203) based on the inelastic responses of a single mass model having lateral load resisting elements in two orthogonal directions and subjected to bidirectional base excitations. It is shown that for systems having torsional stiffnesses that exceed a minimum value, the provision in NZS 4203:1984 will restrict the ductility demands on the resisting elements no more than those of a similar but torsionally balanced system. This minimum torsional stiffness depends on the structural eccentricity of the system. For systems with torsional stiffness less than the minimum, the stiff edge elements can experience additional ductility demand because the 1984 edition of the Code permits excessive strength reduction on the stiff edge elements. In the 1992 edition, the Code imposes a minimum torsional stiffness of a structure in the farm of edge displacement ratios. With this new requirement, the danger of additional ductility demand on the stiff edge element is eliminated. Therefore, the torsional provision in the current edition will ensure no additional ductility demands on all lateral force elements caused by torsion.

Design of torsionally unbalanced structural systems based on code provisions I: Ductility demand

AbstractUsing a three element single mass model, this paper presents the ductility demands on the elements of torsionally unbalanced systems when subjected to strong earthquake shaking. Torsionally unbalanced systems based on nine structural configurations are considered, ranging from torsionally stiff systems with the centre of rigidity (CR) centrally located to torsionally flexible systems with CR eccentrically located. The strength of the elements is designed based on the Canadian and New Zealand codes, and the Uniform Building Code (UBC) of the United States. It is shown that all three codes can limit the ductility demands on the elements to that of a similar but torsionally balanced system when the system is torsionally stiff. However, substantial additional ductility demands on the element at the stiff edge of the system exist for torsionally flexible systems when the New Zealand code or UBC is used. The large ductility demand is caused by the low strength of the stiff‐edge element permitted by these codes.

Design of torsionally unbalanced structural systems based on code provisions II: Strength distribution

AbstractThis paper presents the results of an analytical study of the strength distribution of lateral load resisting elements in torsionally unbalanced systems designed based on codified torsional provisions. It is shown that the element strength can be expressed conveniently as the element strength of a similar but torsionally balanced system multiplied by a strength factor. This strength factor depends on three system parameters, namely, the location of the element relative to the centre of rigidity, and the torsional stiffness and eccentricity of the structure. In addition, it depends on the design coefficients of the code specified design eccentricity expressions. The influence of each of these factors on the element strength distribution is discussed. A new set of values for the design coefficients is proposed. By means of examples, it is shown that the proposed torsional provision is an improvement over those suggested in the National Building Code of Canada and the New Zealand code.

Shear reinforcement of reinforced concrete inelastic interior beam-column joints

"Equilibrium of forces" is the principle used in the current New Zealand code requirements for shear reinforcement of beam column joint. This principle, however, yields irrational or empirical aspects of the current code requirements. The latter principle as well as a simplification of stress distribution along the periphery of the joint can yield a design equation to calculate the necessary amounts of shear reinforcement in inelastic interior joint. Normally, this design equation requires smaller amounts of shear reinforcement than the current New Zealand code, especially for the following cases: a) the joint shear stress is small, b) the axial force is small, c) the amount of top beam reinforcement is larger than at the bottom, and d) the amounts of vertical shear reinforcement is large.

Ductile Design Approach for Reinforced Concrete Frames

In the design of multistorey moment-resisting reinforced concrete frames to resist severe earthquakes the emphasis should be on good structural concepts and detailing of reinforcement. Poor structural concepts can lead to major damage or collapse due to column sidesway mechanisms or excessive twisting as a result of soft storeys or lack of structural symmetry or uniformity. Poor detailing of reinforcement can lead to brittle connections, inadequate anchorage of reinforcement, or insufficient transverse reinforcement to prevent shear failure, premature buckling of compressed bars or crushing of compressed concrete. In the seismic provisions of the New Zealand concrete design code special considerations are given to the ratio of column flexural strength to beam flexural strength necessary to reduce the likelihood of plastic hinges forming simultaneously in the top and bottom of columns, the ratio of shear strength to flexural strength necessary to avoid shear failures in beams and columns at large inelastic deformations, the detailing of beams and columns for adequate flexural strength and ductility, and the detailing of beams, columns and beam-column joints for adequate shear resistance and bar anchorage. Differences exist between current United States and New Zealand code provisions for detailing beams and columns for ductility and for the design of beam-column joints.

Seismic design of masonry structures to the new provisional New Zealand Standard NZS 4230p

Background to seismic design aspects of the provisional New Zealand Code of Practice for Masonry Structural Design is given. Emphasis is given to reasons for differences in the provisional code from an earlier draft code. The changes include improved compatibility with the current Loadings Code NZS 4203 and the Concrete Design Code NZS 3101, provisions of simplified rules to ensure adequate ductility capacity, and additional information to provide guidance for ductile design of masonry frames. Some experimental results are presented to provide support for the provisions.

Optimum design of reinforced concrete shear walls

The recently published New Zealand Code of Practice for the Design of Concrete Structures (NZS 3101:1982) and the newly amended Code of Practice for General Structural Design and Design Loadings for Buildings (NZS 4203) permit a variety of possible design approaches for reinforced concrete shear wall structures. A series of wall designs for dimensionally similar four-storey and eight-storey buildings has been carried out and a comparison of construction cost estimates obtained together with an assessment of the relative design effort required for the different design options.

Comparison of recent New Zealand and United States seismic design provisions for reinforced concrete beam-column joints and test results for four units designed according to the New Zealand Code

Comparison of recent New Zealand and United States seismic design provisions for reinforced concrete beam-column joints and test results for four units designed according to the New Zealand Code

Comparison of recent New Zealand and United States seismic design provisions for reinforced concrete beam-column joints and test results from four units designed according to the New Zealand code

A comparison is made of the seismic design provisions for reinforced concrete beam-column joints required by the new New Zealand concrete design code NZS 3101 and recently proposed United States procedures. Large differences are shown to exist between these new provisions of the two countries. Results are reported of cyclic load tests which were conducted according to the requirements of the new NZS 3101. The test results showed that location of plastic hinges in beams away from the column faces may be of considerable advantage in the design of joints, when member sizes are small and joint shears are high, due to less congestion of reinforcement and better anchorage conditions.

Reliability-based risk factors

Risk factors are used in some codes to allow for the higher than normal consequences of the failure of essential or important structures. A classification of high-risk structures is given, based on different reasons for high importance. Risk factors are then related to reliability factors, defined as the increases in reliability required compared with that for a normal building. By assuming reasonable values for reliability factors, a set of risk factors is derived. Some of these correspond closely to those specified in the New Zealand code, while others differ markedly.