- PROGRAM: Exhibition, Performance Hall, Research Center, Gardens
- CLIENT: UNESCO, Ministry of Information and Culture of Afghanistan
- PARTNER IN CHARGE: Alessandro Orsini, Nick Roseboro
- PROJECT ARCHITECT: Giorgia Gerardi
- TEAM: Simone Catania, Rigo Gonzalez, Richard W. Off, Anna Laura Pinto
- STRUCTURAL: Stephen Melville – Format Engineers
- ENVIRONMENTAL: Nadir Abdessemed & Krista Palen – Transsolar KlimaEngineering
- RENDERS: Architensions
VERNACULAR TECTONIC, LOCAL RESOURCES AND HISTORY
The design for the Bamiyan Cultural Center stems from the vernacular architecture language, tectonic and local resources. The project aims at the “building site” as a place of extraordinary history and culture being the center of artistic and religious development from the 1st to the 13th century. Strategically nested on the slope of the site’s cliff, accommodating three terraced levels, each one with open views towards the Buddha cliff, the building is conceived as a series of semi-arches connected to each other through a clerestory window that allows the penetration of indirect natural light. The different parts of the program have been arranged following the sun path to maximize irradiation during the winter season. A basic module of 5mx5mx5m has been established. This element has been placed and repeated on a Cartesian grid allowing maximum flexibility for future additions. The module changes in height to correspond to different functions: private, public, circulation. Architecturally expressed as a carved space from a block of sandstone, the module adopts a tectonic system derived from the vernacular architecture of Afghanistan. A hybrid structure of bricks on the interior and reinforced concrete on the exterior clad in sand local stone grant to build an economically sustainable system that can be easily assembled and produced by local work force.
LOCAL CONSTRUCTION STRATEGY “PAKHSA”
The structure of the Bamiyan Cultural Centre aims to use the local materials by combining what can be easily obtained near to the site in a simple but creative way. From our own research we understand that concrete and masonry can be sourced locally together with some timber plus mud bricks made in a technique known as ‘Pakhsa’. The form of the structure is a cascading assembly of half single curvature vaults that step down following the natural contours of the site. Structural Action: The half vault form is used in a number of ways, from simple free standing cantilevering canopies which can be up to 6m in height to interconnected back to back and free standing structures to one or more forms connected by intermediate roofs and walls. The material used in the structure and its behavior depends on the context within the site. Where a canopy is a freestanding cantilever it is subject to considerable overturning moments and deflection must be carefully controlled. The structure is working in both compression on the inside and tension at the rear of the section. In this case our design employs both lightly reinforced concrete working in tension and locally fired bricks working in compression within a hybrid structure with the masonry placed on the inside of the space, concrete on the outer. The width of the masonry element of the wall and arch decreases over height. It is the pre-compression provided by the deflected arch form that keeps the masonry stable. The horizontal shear at the concrete/masonry interface is provided by some perpendicular bricks placed within the wall. Refer to figure. By combining two materials in this way an over-reliance on expensive concrete can be avoided and its volume reduced, thus also reducing the embodied energy within the building frame. The proposed sequence of construction is illustrated in this submission. There are some instances where two different height arch forms face each other, the difference in height creating a clerestory window. In this case the design is either two cantilevering structures relying upon moment fixity at the base with the deflection at the tip being controlled to strict limits to avoid damaging any glazing or the roof itself spans in the perpendicular direction to side walls. We have analyzed the structure based on low Youngs modulus concrete and a low anticipated masonry compressive strength (5N/mm2) with the result that the deflections are relatively low and within acceptable values for a structure supporting glazing. See figures. The pre-arched or pre-buckled shape in composite action with a backing concrete wall means that a non-staggered lapped masonry construction can be used instead of the traditional keyed coursing. This gives the masonry wall a more contemporary grid like feel. Some of the internal spaces are defined as two half-vault structures facing each other and supporting a roof. In this case the roof structure will be thin lightly reinforced concrete, which spans onto the hybrid masonry/concrete arch structures. The structural action is similar to the above. In this case the soffit of the ceiling may be clad in thin masonry brick slips. These are bonded to the underside of the concrete slab with a simple key formed in the back of the brick, thus avoiding complex and difficult to source commercial products. There are some instances where the cantilever half vault form is greater than 5.5m in height. It would be possible to design these as free standing but the wall thickness would be prohibitively large and would impact on the free space within the building. A larger building may be possible but this in turn would lead to costly, time consuming and energy inefficient ground excavation. Therefore in the case of the structural frame exceeding the base 5.5m high module it will be braced by perpendicular side walls from thin reinforced concrete or masonry construction. Many of the low internal walls or those not required to carry high vertical loads will be built from the local Pakhsa mud brick. Use of this construction will also save on concrete and masonry. Stability against wind and notional horizontal load will be provided by a combination of the short half vault structures acting as vertical cantilevers or braced by side walls or by the tall structural elements being braced by perpendicular internal walls. Foundations: We have limited information on the ground conditions but to avoid costly and inefficient deep excavation we have designed the cellular superstructure to spread the vertical and horizontal loads over the widest area possible and hence the compressive stress under footings is limited and simple shallow strip footings may suffice. The stepped nature of the building also serves to avoid the need for deep excavation. The overturning moments resulting from out of balance loads applied to the structure will be transferred to the ground via direct compression. The concrete walls used in the superstructure are required to also act as retaining walls due to the stepped nature of the site. Reinforced concrete is an ideal material for this as it is strong, easy to construct and most importantly can be made relatively watertight. The lateral earth pressure is taken by the walls either as vertical cantilevers or as two way spanning between floor and roof and side walls. The design of the landscape aims at the fusion of the landscape with the building inserting into the grid interior green courtyards that refer to most prominent aspect of the built environment in Afghanistan. The placement and orientation of the courtyards is designed to maximize light and warmth in all seasons. The outdoor sand stone paving areas depart from the building creating soft-scape and hard-scape programmatic zones such as viewing terraces and platforms for the sculpture garden.
ENVIRONMENTAL STRATEGY WITH CONTINUOUS RELIABLE ENERGY
The building is designed to bring in daylight and absorb passive solar heat wherever possible to minimize the need for artificial lighting and heating. In the summer the building is designed to cool with natural ventilation. Air is brought in through the facade and as it heats up it rises and flows out through the clerestories. The cooling effect is improved by the façade which is made of thermally massive materials: local sandstone, structural bricks, and cast in place concrete. This mass will also take advantage of the natural diurnal swings of this dessert climate. In the colder months the sun’s energy will heat up the mass of the building slowly over the day, and will come through into the space to keep it warm at night. These same materials when coupled with the natural ventilation/night flushing system keep the building on summer days. The program of the center has been organized to maximize the positive effects of the climate. The east facade has classrooms and workshops that will be used earlier in the day, which will benefit from the free heat of the morning sun. The west facade has a study center and library which will mainly be used in the afternoon when the spaces will have maximum available heat and daylight. The north facade has exhibition spaces which require diffuse indirect light to protect the art and artifacts. Finally, the areas of the south facade will heat up ¬first in the winter and this air will be circulated throughout the building. The center is designed to minimize energy needed for heating, cooling or lighting. However, at night or in the coldest part of winter some electricity may be required. Since the electricity grid connection is not reliable, a 5 kW Maglev Vertical wind turbine is used to provide energy during these times when PV (solar panels) would not be functional and at a lower capital cost per kW of energy capacity. These turbines are small, can generate energy with winds as low as 3.2 m/s and are very quiet. The units can be placed within the boundary of the site without disturbing the architecture or the surrounding pristine environment and the system can simply be easily expanded in the future if the cultural center’s program requires it.