The construction of reinforced concrete buildings with unreinforced infill is common practice even in seismically active country such as Bhutan, which is located in high seismic region of Eastern Himalaya. All buildings constructed prior 1998 were constructed without seismic provisions while those constructed after this period adopted seismic codes of neighbouring country, India. However, the codes have limited information on the design of infilled structures besides having differences in architectural requirements which may compound the structural problems. Although the influence of infill on the reinforced concrete framed structures is known, the present seismic codes do not consider it due to the lack of sufficient information. Time history analyses were performed to study the influence of infill on the performance of concrete framed structures. Important parameters were considered and the results presented in a manner that can be used by practitioners. The results show that the influence of infill on the structural performance is significant. The structural responses such as fundamental period, roof displacement, inter-storey drift ratio, stresses in infill wall and structural member forces of beams and column generally reduce, with incorporation of infill wall. The structures designed and constructed with or without seismic provision perform in a similar manner if the infills of high strength are used.

With the advancement in knowledge of inelastic response of structures, the design and construction practices of reinforced concrete buildings have been changing worldwide. Most of the codes are incorporating the near-fault factors and performance based designs in the seismic codes. However, further investigation is needed to identify the physical behaviour of multi-storey buildings to near-fault ground motions. At present, quantitative evaluation of response and its mitigation to near field ground motions is a popular topic in earthquake engineering field. The present study discusses the inelastic response of symmetric and asymmetric multi-storey buildings to near-fault ground motions. The possibility of design approach is based on ‘expendable top storey’ for the multi-storey RC- buildings to near field records. If such behaviour is feasible one can conceive of a structure whose top storey is permitted and designed to undergo large inelastic deformations while reducing damage in the lower storey. The concept was first proposed in an earlier research (RaghuPrasad, 1977). Such a concept juxtaposes the often-mentioned ‘soft first storey’ concept. Further in this report, the performance evaluation of multi-storey buildings near Chiplun fault in Mumbai, India is also discussed. The thesis is organized in the following chapters: Introduction in Chapter-1 contains detailed literature review on inelastic response of symmetric and asymmetric buildings, response of buildings to near-fault records, elastic and inelastic vibration absorber concepts and performance based designs. The literature reveals that considerable amount of research has been carried out on the elastic, inelastic response of structures and vibration absorber concepts to ordinary ground motions. Recently, the effect of near field ground motions on the response of multi-storey buildings is gaining much importance. Most of the research publications are available on response of symmetric buildings subjected to near field ground motions. But many problems are yet to be investigated. They are, identification of important ground motion parameters in near fault records, vibration absorber concepts and torsional response of structures subjected to pulse type ground motions. These problems are clearly mentioned in the recently published state-of-the-art review by Shuang and Li-Li (2007). In this report an attempt has been made to solve these problems. Effect of near-fault ground motions on symmetric multi-storey buildings in Chapter-2, describes simplified non-dimensionalized equations of motion to study the response behaviour of multi-storey buildings to near fault records. The non-dimensionalized equations of motion are expressed in terms of near fault ground motion parameters. The objective is to find a relation between ductility demand and near field ground motion parameters through neural network approach. For this a neural network modeling was done to predict the ductility demand in terms of peak ground acceleration, peak ground velocity, epicentral distance and pulse period of the near field ground motion. A thorough sensitive analysis is carried out, to ascertain which parameters are having maximum influence on ductility demand. In this chapter further, a comparative study is made on the inelastic seismic response of multi-storey buildings to pulse type and non pulse type ground motions. The study shows that, it is necessary to consider the effect of near fault ground motions separately and make provisions for the design in the codes of practice accordingly. Vibration absorber effect in multi-storey buildings in chapter-3, discusses the behaviour of top storey as a vibration absorber during near field ground motions. For this purpose, a five storey symmetric building model is considered as an example problem to demonstrate the effectiveness of the proposed concept. Response of the structure is obtained for the various combinations of absorber storey parameters such as mass ratio, frequency ratio and yield displacement ratio. Here mass ratio means mass of the absorber storey to that of the bottom storey and similarly for the frequency and yield displacement ratios. Observing the storey-wise variation of these responses, we can say that for a range of mass ratios, frequency ratios and yield displacement ratios, the inelastic response of top storey is large compared to the lower storeys. This range is termed as ‘effective range’. Further, in this range the top storey absorbs the vibration energy of the structure by keeping the lower storeys in elastic state i.e. acts as a vibration absorber. The top storey can also be termed as ‘expendable top storey’. Effect of near-fault ground motions on asymmetric multi-storey buildings in Chapter-4, discusses the inelastic response of asymmetric buildings to single horizontal component and two horizontal components of near fault ground motions viz., fault normal and fault parallel components. For numerical investigations eight building models are considered. Eccentricity has been created by keeping the stiffness and mass centre separately. The building models are subjected to strong motion records of Imperial Valley Array-5 (1979) and Northridge-Sylmar (1994). A detailed study on the effect of base shear strength, eccentricity and pulse period of near fault ground motions on the response is investigated. Performance of multi-Storey buildings in Chapter-5, reported a detailed procedure for the performance evaluation of structures. The procedure is applied to find the performance evaluation of multi-storeyed buildings located in near fault region. Chiplun fault in Mumbai, India has been chosen for the study because several features of that fault are clearly published (RaghuKanth and Iyengar, 2006). Results of performance evaluation of five and ten storeyed symmetric buildings with and without infill panels are studied. Ground motion records consistent with the hazard spectrum for the design are considered. The performance of the building near the Chiplun fault in Mumbai, India shows operational under UHS-500 (uniform hazard spectrum) event and it collapses when the building is exposed to UHS-2500 record. The thesis is concluded in Chapter-6 with an overall summary of the report and suggestions for further scope of the work.

Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2006. / The predominately manual, time-consuming and error-prone procedure currently used in engineering offices for the calculation of preliminary column forces in multi-storey buildings constitutes the motive for the research described in this study. Identifying the current procedure as in need of improvement, techniques and prototype software posing a semi-automated alternative, are developed. Influence areas used for load-assignment are established with the use of a Voronoi diagram calculated for a specific floor geometry. The forces transferred to the columns are based solely on the size of the influence areas thus calculated. The definition of the floor geometry, as well as the definition of loads and other necessary input parameters, are performed in a CAD-system, into which the Voronoi functionality is integrated. The accuracy of the forces obtained with the implemented procedure and, consequently, the accuracy of the forces as they are calculated in current practice, is determined through comparison with the results of finite element analyses. The comparative analysis of a sample of typical floor geometries allows an evaluation of the results and the identification of tendencies observed regarding the errors obtained. It is concluded that calculating column forces based on influence areas, i.e. solving a geometrical problem without taking any stiffness properties into account, is unsafe. The implication hereof is twofold. Firstly, it serves as a warning concerning the technique currently used in practice and secondly, it steers the investigation in the direction of a finite element analysis: using the influence areas as a basis for automatic meshing, a semi-automated analysis can be performed relatively inexpensively, using plate elements.

Implementation of intensive forestry (fertilization, cultivation of non-native tree species, and clone cultivation) on part of the forested land area in Sweden and an increased construction of wood-framed multi-storey buildings can contribute to reduce the net carbon dioxide emissions of the built environment. This thesis evaluates the acceptance of and interest in intensive forestry and multi-storey wood frames among different actors, and some of the underlying reasons for their approach. The results of quantitative and qualitative studies among members of the general public, private forest owners, architects, and contracts managers in Sweden are presented in six different papers. Both intensive forestry and multi-storey wood frames lack sufficient acceptance and compliance with relevant institutions such as priorities, norms, and regulations in the eyes of the studied actors. The acceptance of intensive forestry would be larger among members of the general public if they would perceive such practices to have less negative environmental effects and perceive a greater need to increase forest growth. Among the private forest owners, the interest to cultivate non-native tree species would be larger if there were more positive attitudes towards the economic consequences. Architects and contracts managers associate multistorey wood frames with several disadvantages and uncertainties, primarily with respect to fire safety, stability, durability, and sound proofing. The contracts managers’ perceptions have stronger implications for the prospects for wood frames, than the architects’ perceptions do. Promotional activities aimed to change such perceptions may improve the prospects for more wood framed multi-storey buildings in Sweden. The path dependency of Swedish multi-storey construction however implies that such activities are not enough for multi-storey wood frames to diffuse to greater extent. Broader changes to the wider context of the decisions taken in construction projects, e.g. to policy or economic environments, which change the priorities of the construction industry actors, are needed.

The environmentally friendly and high performance multi-storey LVL timber system developed at the University of Canterbury (UC) consisting of post-tensioned frames and shear walls is referred to as the Pres-Lam system. It is possible that this structural system has the ability to increase productivity and reduce construction costs when compared with concrete and steel construction materials. As the Pres-Lam system is a new technology, the actual construction time and cost are still unknown. The outcome of this research will add value to the construction industry and encourage the industry to consider the Pres-Lam system for future projects. Previous research has shown that construction using this type of structural system is feasible for multi-storey buildings. In case study (1), this research revisited the research done for the actual Biological Sciences building under construction at the University of Canterbury based on the latest information available from the UC timber research team. This research compared the construction time and cost of three virtual buildings (Pres-Lam, Concrete and Steel) for Case Study (1). The research has been able to optimise the performance of the Pres-Lam system having increased open spaces with large column spacing. The proposed fully prefabricated double “T” timber concrete composite (TCC) floor system was used and found to reduce construction time. This has also shown that the LVL components in the Pres-lam system can be fully prefabricated at a factory. In case study (1), the predicted estimated construction time for the structural system was 60 working days (12 weeks) as compared to the concrete structure which required 83 working days. In the construction time analysis only the construction time of the structural building portion was compared instead of the overall construction time of the building project. The construction cost estimation for the concrete, steel and optimised Pres-Lam overall buildings including claddings and architectural fittings were produced and compared. The construction cost analysis concluded that the construction cost of the Pres-Lam building has been estimated to be only 3.3% more than the steel building and 4.6 % more than the concrete building. In case study (2), this research evaluated the deconstructability of the Pres-Lam system and found that the Pres-Lam system was potentially a very sustainable building material where 90% of the deconstructed materials can be recycled and reused to construct a new office building at the University of Canterbury. The reconstruction time of the STIC office building has been predicted to be 15 weeks and the estimated cost for the reconstruction to be $260,118. This will be used for future construction planning, monitoring and control.

Roof venting is often utilised in large warehouses to remove smoke in order to reduce damage to a building and its contents, and to maintain access for fire-fighters. In New Zealand, the Compliance Document for the New Zealand Building Code C clauses recommends 15 % opening area for unsprinklered single floor buildings. This opening area is required to be designed for effective fire venting. There is no justification for why 15 % is required, and no definition of how fire venting qualifies as being effective. Fire Dynamics Simulator (FDS) was used to simulate the performance of various roof venting strategies in two different-sized industrial warehouses (both larger than 1,500 m²) with a 50 MW fire with both a rapid and an extreme t³ growth rate. In particular, roof venting areas of 15 %, 10 %, and 5 % of the floor area were tested with each of the following inlet areas for make-up air: 100 %, 50 %, and 0 % of roof venting area. In each of these cases, the vents were treated as permanently-open holes in the roof. It was shown that roof venting with 15 % geometric area is ample to provide and maintain tenability for fire-fighters. With sufficient inlet area for make-up air, smaller venting areas could also be employed. Further simulations were run to test the effect of square-shaped vents that opened simultaneously at 100°C compared with square-shaped vents that opened sequentially at 100°C, 200°C, and 300°C, and strip-shaped vents that opened progressively as each portion of a vent reached activation temperatures of 200°C and 300°C. Vents that opened at 100°C were intended to represent mechanical vents, while vents opening at higher temperatures were intended to represent plastic sky-light or drop-out type vents. The activation temperature proved to be more influential than the opening sequence or shape: there was a significant advantage to be gained by having vents that activated at 100°C as opposed to 200°C or 300°C. The role of downstands in aiding the effectiveness of roof venting was also investigated, with downstand depths of 10 %, 20 %, and 30 % of the ceiling height being simulated. Downstands were shown to be incredibly useful for exhausting smoke and hot gases, provided their installation was appropriately coordinated with placement of roof venting. It is concluded that a clear definition of effective fire venting must not only include the area of roof venting, but equally important is the definition of required inlet area for make-up air, as it plays a crucial role in the effectiveness of the specified roof venting area. In addition, the clear aerodynamic area should be specified. This could be achieved by use of a discharge coefficient that describes the proportion of the roof venting area that is clear aerodynamic area for a particular material, vent, and geometric area. Development of a clear definition of effective fire venting will help to determine how an economic fire protection system can be continued to be used, while going a long way to ensuring predictable and tenable conditions for fire-fighters in New Zealand.

See appended files.

A fundamental task in structural stability analysis is to ensure the safety of structures throughout their operational life so as to prevent catastrophic consequences either at ambient or elevated temperatures. This thesis concerns the stability of unbraced steel frames due to abnormal loadings or fire loads, and develops practical methods to evaluate the stability capacity of unbraced steel frames at ambient temperature or in fire. The problem of determining the elastic buckling strengths of unbraced steel frames subjected to variable loadings can be expressed as an optimization problem with stability constraints based on the concept of storey-based buckling. The optimization problem can be solved by the linear programming method, which is considerably simpler and more suitable for engineering practice than the nonlinear programming method. However, it was found that the frame buckling strength obtained from the linear programming method based on Taylor series approximation on column stiffness may be overestimated in some cases. Thus, a secant approximation of the column stiffness was introduced, and a modified linear programming method based on the secant approximation was proposed. Numerical examples show that the linear programming method in light of the secant approximation can yield conservative results and maintain simplicity. In spite of the convenience of the modified linear programming method, numerical examples show that the linear programming method cannot accurately detect the maximum and minimum frame buckling strengths in some cases. Therefore, an alternative method to assess the lateral stiffness of an axially loaded column derived by using two cubic Hermite elements to signify the column is proposed. Unlike the column stiffness obtained from the Euler-Bernoulli beam theory containing transcendental functions, the stiffness in the proposed method includes only polynomials. Thus, the column stiffness within the proposed method enables the minimization and maximization problems to be solved by efficient gradient-based nonlinear programming algorithms, which overcome the inability of linear programming algorithm to detect the minimum frame buckling strength in some cases. The accuracy of the column stiffness associated with the proposed method was compared with that of the Euler-Bernoulli beam theory. Four unbraced steel frames were investigated to demonstrate the efficiency of the proposed method. It is known that the evaluation of the lateral stability of steel frames subjected to elevated temperatures is different from that at ambient temperature due to the degradation of material strength. Thus, the storey-based buckling method at ambient temperature was extended to evaluating the stability of unbraced steel frames subjected to elevated temperature. To simulate a steel column exposed to the elevated temperature, an analytical model was proposed to examine the effects of axial loading, elevated temperature, and thermal boundary restraints on the lateral stiffness of steel columns in unbraced frames. The procedure of evaluating the stability capacity of unbraced steel frames at elevated temperature was then concluded. Numerical examples are presented to demonstrate the evaluation procedure of the proposed method. The column model was then refined to evaluate the lateral stiffness of steel column subjected to non-uniform elevated temperature distributions along the longitudinal direction. The lateral stiffness equation of the column model was derived based on the Euler-Bernoulli beam theory. The procedure to evaluate the stability capacity of unbraced steel frames subjected to non-uniform elevated temperature distributions was then concluded. The numerical examples were investigated with the proposed method for non-uniform elevated temperature distributions. Finally, initial attempts were made to evaluate the stability of unbraced steel frames with fire-protected columns at different fire scenarios. A degradation factor charactering the variation of the Young's Modulus of steel at elevated temperature was introduced. The objective and constraint functions were constructed, and optimal tools were used to determine the buckling strength of an unbraced steel frame at different fire scenarios.

The purpose of this Master Thesis is to study how the value stream mapping concept can be applied along the construction supply chain for prefabricated massive timber floor elements. Identification and qualification of waste are starting points to propose suggestions on how to reduce and/or eliminate them. In order to use the value stream mapping along the construction supply chain, pertinent data has been collected and analyzed. To conduct the value stream mapping, the first three steps of the lean thinking principles in construction have been followed. The first step aims at defining the customer and his value as well as the value for the delivery team and how it is specified in the product. The second step is based on identifying the value stream and this is done through defining the resources and activities needed to manufacture, deliver and install the floor elements. This is conducted by using the VSMM methodology. In addition the current practice should be standardized and key component suppliers should be defined and located. The third and last step identifies non-value adding activities, in other words waste and suggestions on how to remove and/or reduce waste have been reached. Wastes from product defects, transportation waste and waste of waiting were to be found in the construction supply chain. Propositions to reduce and/or eliminate wastes were to implement a more careful planning of the manufacturing process and production schedule, to apply lean production principles in the manufacturing facility and decrease and or eliminate storage time. The study made has shown that in the supply chain of massive timber floor elements at Limnologen there is a big potential to lower costs and increase customer value as value added-time accounted for only 2% of the total time.

<p>The purpose of this Master Thesis is to study how the value stream mapping concept can be applied along the construction supply chain for prefabricated massive timber floor elements. Identification and qualification of waste are starting points to propose suggestions on how to reduce and/or eliminate them. In order to use the value stream mapping along the construction supply chain, pertinent data has been collected and analyzed. To conduct the value stream mapping, the first three steps of the lean thinking principles in construction have been followed. The first step aims at defining the customer and his value as well as the value for the delivery team and how it is specified in the product. The second step is based on identifying the value stream and this is done through defining the resources and activities needed to manufacture, deliver and install the floor elements. This is conducted by using the VSMM methodology. In addition the current practice should be standardized and key component suppliers should be defined and located. The third and last step identifies non-value adding activities, in other words waste and suggestions on how to remove and/or reduce waste have been reached. Wastes from product defects, transportation waste and waste of waiting were to be found in the construction supply chain. Propositions to reduce and/or eliminate wastes were to implement a more careful planning of the manufacturing process and production schedule, to apply lean production principles in the manufacturing facility and decrease and or eliminate storage time. The study made has shown that in the supply chain of massive timber floor elements at Limnologen there is a big potential to lower costs and increase customer value as value added-time accounted for only 2% of the total time.</p>