Patent Publication Number: US-2022220693-A1

Title: Modular access cover

Description:
TECHNICAL FIELD 
     The present disclosure is directed towards access covers, such as may be used in industrial applications to cover large openings. 
     BACKGROUND 
     Access covers are used to prevent unauthorised access to controlled areas, such as water and electrical infrastructure pits or other underground areas, by blocking the entrance or opening which leads into the controlled area. 
     Infrastructure pits are concrete structures which provide access to underground or underfloor services, such as sewer pipes and electrical cables. The openings to these infrastructure pits may be at ground or floor level, and covered by an access cover which when installed is aligned to sit substantially level with the surrounding ground or floor structure. In this way, the access cover does not form a tripping hazard. 
     In order for the access cover to sit flush with the ground, a step or rebate is formed in the surrounding concrete to support the edges of the access cover. Forming steps in the concrete can be time-consuming, especially if the shape of the access cover is complex. The size and quantity of the steps or rebates to be formed in the surrounding concrete may be affected by the size of the opening. 
     The size of the opening also affects the size of the access cover. Generally, the larger the access cover, the heavier, bulkier, and more unwieldy it is to handle. Modular or multi-part access covers allow smaller and lighter individual covers to be joined together to cover a large opening, which provides handling efficiencies compared to using a single large access cover to cover the same opening. 
     It is desired to address or ameliorate one or more shortcomings associated with prior access covers, or to at least provide a useful alternative thereto. 
     SUMMARY 
     Some embodiments relate to an access cover assembly comprising: 
     a first set of modular access covers and a second set of modular access covers, wherein in each set, adjacent covers are coupled; and 
     a support frame comprising end frame pieces, side frame pieces, wall boxes, and a support beam; 
     wherein the end frame pieces and side frame pieces define a support plane to support the first and second sets of modular access covers; 
     wherein the wall boxes define a support surface to support the support beam and the end frame pieces, wherein the support surface is offset from the support plane and wherein the wall boxes are connected to the end frame pieces and receive respective ends of the support beam; and 
     wherein the end frame pieces, side frame pieces and the support beam define first and second recessed portions of the support frame which respectively receive and support the first and second sets of modular access covers on the support plane. 
     The support beam may divide the first set of modular access covers from the second set of modular access covers. The support frame may be configured to be set into a concrete foundation which defines an opening to an underground or underfloor area. 
     The support frame may further comprise corner pieces, wherein each one of the corner pieces connects the end frame pieces and the side frame pieces at an angle to define a corner of the support frame. The end frame pieces or the side frame pieces may comprise a plurality of modular side frame members connected end-to-end. 
     The end frame pieces, side frame pieces, wall boxes, and corner pieces may each comprise a ledge that defines an upper surface which extends from a wall, wherein the upper surface of each ledge extends along and partly defines the support plane. Each one of the end frame pieces, side frame pieces, wall boxes, and corner pieces may have: (i) a drawcut configuration, wherein an angle between the wall and the ledge is an obtuse angle; or (ii) an undercut configuration, wherein the angle between the wall and the ledge is an acute angle. 
     At least one first modular access cover of the first set of modular access covers and at least one second modular access cover of the second set of modular access covers may comprise: a base plate, oppositely disposed first and second end walls, and a first connecting portion disposed adjacent the first end wall. 
     The first connecting portion of each at least one first modular access cover and each at least one second modular access cover may be configured to align with a second connecting portion adjacent the second end wall of an adjacent modular access cover to allow fixed coupling of adjacent modular access covers. The second connecting portion may include a projecting tab that comprises a tab body which substantially spans part of a length of the second end wall. 
     The first connecting portion may define a bore, wherein the bore may be configured to receive a connector and to guide the connector to engage with the tab body when the first connecting portion is aligned with the second connecting portion, to thereby fixedly couple the adjacent modular access covers. 
     The end walls and the first connecting portion of the at least one first modular access cover and/or the at least one second modular access cover may be integrally formed with the base plate. 
     The connected ones of the first set of modular access covers may be detachable from each other and connected ones of the second set of modular access covers may be detachable from each other. The first set of modular access covers and the second set of modular access covers may comprise different numbers and/or sizes of modular access covers. 
     The first and second sets of modular access covers and the support beam may be detachable from the respective end and side frame pieces to permit access through the opening to the underground or underfloor area. 
     Some embodiments relate to a support beam for an access cover assembly, the support beam comprising: 
     a support surface for supporting an edge of at least one modular access cover; 
     a first wall and a first end surface at a first end of the support beam, and a second wall and a second end surface at a second end of the support beam; and 
     a plurality of stiffeners disposed along the support beam between the first and second ends; 
     wherein an angle between the first wall and the support surface is an obtuse angle to form a drawcut configuration; 
     wherein an angle between the second wall and the support surface is an acute angle to form an undercut configuration; and 
     wherein the first and second end surfaces are configured to engage with first and second wall boxes, and the first and second end surfaces are substantially coplanar with the support surface. 
     The support surface may comprise first and second laterally opposite support surfaces. 
     The support beam may be integrally-formed through: (i) a metal casting process; or (ii) a moulding process; or (iii) a fibreglass composite lay-up process. 
     A web of the support beam may define a first lifting aperture at the first end of the support beam, and a second lifting aperture at the second end of the support beam. The web may taper at the first and second ends of the support beam. 
     Some embodiments relate to method of assembling the access cover assembly of embodiments described herein, the method comprising: 
     connecting the end frame pieces, side frame pieces, wall boxes, and the support beam to form the support frame; 
     positioning the first set of modular access covers and the second set of modular access covers in the first and second recessed portions respectively. 
     The method may further comprise bolting the first set of modular access covers together, bolting the second set of modular access covers together, and bolting the first and second sets of modular access covers to the support frame to secure the first and second sets in the respective first and second recessed portions. 
     Some embodiments relate to a modular access cover, comprising: 
     a base plate having first and second end walls, and side walls; 
     ribs disposed on the base plate and connecting the end walls and side walls to define a series of cavities; and 
     a connecting portion adjacent the second end wall; 
     wherein an angle between the first end wall and the base plate is an acute angle to form an undercut configuration, and wherein an angle between the second end wall and the base plate is an obtuse angle to form a drawcut configuration; 
     wherein the connecting portion is configured to allow fixed coupling of the modular access cover to an adjacent modular access cover; and 
     wherein the series of cavities is configured to receive and contain a filler material. 
     The modular access cover may further comprise a tab which extends outwards from the first end wall, the tab having a tab body which defines a tab hole and a supporting surface. 
     A length of the tab body may be at least approximately 50% of the length of the first end wall. The length of the tab body may be at least approximately 70% of the length of the first end wall. The tab body may extend outwards along the length of the first end wall. The tab body may extend equally outwards along the length of the tab body. 
     The connecting portion may overlap the supporting surface of the tab of an adjacent modular access cover. The connecting portion may comprise a body which defines a bore, the bore configured to receive a connector and guide the connector to engage with the tab hole of an adjacent modular access cover and allow fixed coupling of the modular access cover and the adjacent modular access covers. 
     The base plate may comprise a reverse surface disposed opposite the ribs, and wherein the reverse surface and the supporting surface of the tab body are substantially coplanar. The base plate, ribs, end walls and side walls may be integrally formed. A height of the end walls and side walls above the base plate may be equivalent to a height of the ribs above the base plate. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       Embodiments are described in further detail below, by way of example, with reference to the accompanying drawings, in which: 
         FIG. 1  is a perspective view of a modular access cover assembly, according to some embodiments; 
         FIG. 2  is a perspective view of a support frame for the modular access cover assembly of  FIG. 1 , according to some embodiments; 
         FIG. 3A  is a section view of the modular access cover of  FIG. 1 , showing the assembly of the covers, according to some embodiments; 
         FIG. 3B  is the same section view of  FIG. 3A , showing a subsequent step in the assembly of the covers, according to some embodiments; 
         FIG. 4  is a perspective view of an undercut frame piece for the frame of  FIG. 2 , according to some embodiments; 
         FIG. 5  is an end view of the frame piece of  FIG. 4 ; 
         FIG. 6  is a perspective view of a drawcut frame piece for the frame of  FIG. 2 , according to some embodiments; 
         FIG. 7  is an end view of the frame piece of  FIG. 6 ; 
         FIG. 8  is a perspective view of an left-handed undercut corner piece for the frame of  FIG. 2 , according to some embodiments; 
         FIG. 9  is a perspective view of a right-handed undercut corner piece for the frame of  FIG. 2 , according to some embodiments; 
         FIG. 10  is a perspective view of a drawcut corner piece for the frame of  FIG. 2 , according to some embodiments; 
         FIG. 11  is a perspective view of a support beam and wall boxes for the frame of  FIG. 2 , according to some embodiments; 
         FIG. 12  is a section view of the support beam of  FIG. 11 , according to some embodiments; 
         FIG. 13  is a perspective view of the wall boxes of  FIG. 11 , according to some embodiments; 
         FIG. 14  is a perspective view of a modular access cover in the assembly of  FIG. 1 , according to some embodiments; 
         FIG. 15A  is a section view of the covers of  FIG. 1 , showing a first step in their assembly, according to some embodiments; 
         FIG. 15B  is the section view of  FIG. 15A , showing a subsequent step in the assembly of the covers, according to some embodiments; 
         FIG. 16A  is a section view of the modular access cover of  FIG. 1 , showing the disassembly of the covers, according to some embodiments; 
         FIG. 16B  is the same section view of  FIG. 16A , showing a subsequent step in the disassembly of the covers, according to some embodiments; 
         FIG. 17  is a perspective view of a modular access cover assembly comprising two pairs of wall boxes configured to support two support beams, according to some embodiments; 
         FIG. 18  is a block diagram of a method for assembling the assembly of  FIG. 1 , according to some embodiments; 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure is directed towards access covers. Access covers may be assembled into a single structure, which may be made of steel, for example. Some covers have cavities that are filled with a filler material, such as concrete, to add weight and strength to the cover. 
     The size of existing single-piece covers is limited by the materials used. For example, a single-piece cover would typically weigh 300 kg/m 2 . Openings may range in size from 1 m 2  to 80 m 2 , for example. Typically, lifting the cover is performed by two or more workers using a lifting tool which engages with sockets built into the cover. The size of the cover is thereby restricted to allow workers to safely manually lift the cover and avoid the need for powered lifting equipment such as hydraulic jacks or forklifts. 
     According to the Australian Standard 3996-2019, the serviceability design load for the access cover may ranging from 6.7 kN to 600 kN, depending on the load class (usage) of the cover. For example, Class A covers are typically used in areas accessed by pedestrians only; Class B covers in areas for low-speed vehicular access; Classes C, D and E covers in areas where higher-speed vehicular access is required; and Classes F and G for industrial areas such as docks, wharves, and airports. 
     Modular or multi-part access covers allow a larger opening to be covered without suffering from the size and weight limitations. Specifically, a larger opening can be covered by an assembly of interconnected access covers, with each of the interconnected access covers having similar size and weight to the single-piece cover. This may, for example, allow individual covers to be manually lifted in and out of position while enabling coverage of a larger opening compared to single-piece covers. 
     The present disclosure includes an access cover assembly for covering an opening to an underground or underfloor area. The assembly is designed to be load bearing, and may for example be designed to cater to a range of load classes (Classes A-G) as described in the Australian Standard 3996-2019. The assembly comprises a support frame which is set into a step or rebate that is cut or formed into the perimeter of the opening. The support frame includes a recessed portion which is configured to receive and support a plurality of modular covers, thereby covering the opening. The recessed portion may include a combination of undercut and drawcut surfaces, which engage with corresponding undercut and drawcut surfaces of the modular covers to retain the modular covers in the support frame. The support frame further comprises a support beam, which spans the opening and provides additional support to the modular covers. In particular, the support beam tapers towards its ends, where it meets the support frame. This allows the ends of the support beam to connect to the support frame (via structures called wall boxes) at the same height of the step or rebate. In this way, a deeper additional step or rebate does not need to be formed into the existing step or rebate, thereby simplifying construction at the installation site. 
       FIG. 1  shows an access cover assembly  100  for covering an opening, such as the opening to an underground or underfloor area. The access cover assembly  100  comprises a first set of modular access covers  110  and a second set of modular access covers  120 . The first and second sets of modular access covers  110 ,  120  each comprise a plurality of modular access covers, such as covers  900  ( FIG. 9 ). The individual covers  900  in each set  110 ,  120  may be any shape and may be different from each other, but are preferably rectangular-shaped for ease of manufacturing, installation, and combination with other covers  900 . In some embodiments, the first set and the second set of modular access covers  110 ,  120  each comprise different numbers and/or sizes of the modular access covers. 
     The individual covers  900  in each set  110 ,  120  are placed adjacent to each other, and the adjacent covers  900  are coupled. Coupling the covers  900  is achieved by placing adjacent covers  900  in contact with each other. A retainer  130  may be used to maintain the desired level of contact between adjacent covers  900 , so that the covers  900  may be able to resist an applied load, such as a person standing on the cover  900 . For example, the retainer  130  may be a moulding or specially-shaped feature that is integrally-formed with or attached to all or some of the individual covers  900  so that the cover  900  is able to support any adjacent covers  900 . In some embodiments of the assembly  100 , a fastener such as a bolt, pin, or rivet may be used to further secure the covers  900  once they are coupled and retained in place by the retainer  130 . The retainer  130  may be used to collectively refer to the connecting portion  970  and the tab  980  later disclosed herein in relation to  FIG. 14 . Fasteners used to couple covers  900  together are preferably removably engageable with the covers  900  in order to facilitate decoupling of the covers  900  when access through the cover assembly  100  is required. 
     The assembly  100  further comprises a support frame  200  for supporting and holding the first and second sets of covers  110 ,  120  in place. The support frame  200  is placed in contact with the structure surrounding the opening to be covered by the assembly  100 . For example, the structure surrounding the opening may be a pavement or concrete slab, which defines the opening to an underground or underfloor area. In applications where it is desired for the access cover assembly  100  to sit flush with the ground, a step or rebate is formed in the surrounding structure. The support frame  200  sits on this step or rebate, and the loads applied to the assembled cover  100  are transferred to the surrounding structure. 
       FIG. 2  shows an example support frame  200  in more detail, with the first and second sets of covers  110 ,  120  removed for clarity. The support frame  200  comprises end frame pieces  202  and side frame pieces  204 . The end frame pieces  202  and/or the side frame pieces  204  may comprise a plurality of modular frame pieces  300 ,  400  ( FIGS. 4 and 6 ) connected end-to-end. In some embodiments, the side frame pieces  204  comprise a flange or other means to connect to an end frame piece  202 , or vice versa. The support frame  200  may additionally comprise corner pieces  206 , wherein the corner pieces  206  connect one of the end frame pieces  202  to one of the side frame pieces  204  at an angle to thereby define a corner of the support frame  200 . 
     When the various frame pieces  202 ,  204  and corner pieces  206  are assembled to form the support frame, the end frame pieces define a first end  210  and a second end  220  of the support frame  200 . The first end  210  and the second end  220  may be oppositely disposed, and perpendicularly connected by the corner pieces  206  to the side frame pieces  204  to define a rectangle-shaped support frame  200 . Other shapes of support frame  200  are possible by connecting the side frame pieces  204  to each other via corner pieces  206  set at desired angles, such as at 45° or at 60°. This modular approach means a variety of frame and panel sizes can be combined to enable various shapes of openings to be covered. 
     The end frame pieces  202 , side frame pieces  204 , and corner pieces  206  combine to define a recessed portion  208  to receive the first and second sets of modular access covers  110 ,  120  in the frame  200 . The recessed portion  208  consists of undercut and drawcut surfaces in order to retain the first and second sets of covers  110 ,  120  in the frame  200 . As described in more detail in relation to  FIGS. 4 to 7 , an undercut is defined as an acute angle, while a drawcut is define as an obtuse angle. The individual covers ( 900 ,  FIG. 14 ) comprise at least one undercut side which is retained in an corresponding undercut surface of the recessed portion  208 . The remaining surfaces of the recessed portion  208  may be drawcut to correspond to the drawcut sides of the covers  900 . 
     In some embodiments, such as shown in  FIG. 14 , the individual covers are rectangular, with one undercut side and the remaining three sides being drawcut. When the covers  900  are placed into the rectangular frame  200 , the covers  900  are aligned with the end and side frame pieces  202 ,  204  so that each individual cover  900  has its side walls  940  supported by the side frame pieces  204 , and its end walls  920 ,  930  supported by adjacent covers  900  and/or the end frame pieces  202 . 
     In some embodiments, the access cover assembly  100  and support frame  200  are generally symmetric about a longitudinal axis where the support beam  700  is supported in the middle of the end frame pieces  202  and a same combination of covers  900  can be located on each lateral side of the support beam  700 . However, in various installations, symmetry may not be practically achievable or desirable. In some embodiments, the access cover assembly  100  and support frame  200  are generally asymmetric in at least along a longitudinal axis of the assembly  100 . In asymmetrical assembly configurations, the position of the support beam  700  may be positioned closer to one side frame  204  than the other (opposite) side frame  204 . The example access cover assembly  100  shown in  FIG. 1  is asymmetrical about a central longitudinal axis that is parallel to the direction of extent of the support beam  700 . 
       FIGS. 3A and 3B  are partial cross-sections of the assembly  100 , taken along the line A-A marked on  FIG. 1 .  FIG. 3A  shows an early stage of the placement of the individual covers  900  into the frame  200 . Placing the individual covers  900  into the recessed portion  208  involves placing a first one  900 - 1  of the cover  900  into the first end  210 . The cover  900  has an undercut side which is aligned with the undercut surface at the first end  210  in the recessed portion  208 , as indicated by arrow  230 . For example, the first end  210  of the support frame  200  may have undercut end frame pieces  202  to receive and support the undercut end wall  920  of the first individual cover  900 - 1 . The side wall  940  of cover  900 - 1  is also aligned to be supported by the side frame piece  204 . 
     Once the first individual cover  900 - 1  is in place, subsequent individual covers  900  are successively added into the recessed portion  208 , as shown in  FIG. 3B . As indicated by arrow  240 , a second individual cover  900 - 2  is inserted into the recessed portion  208  and positioned so that its undercut side is aligned with the drawcut of the cover  900 - 1  already in place. This process is repeated with additional covers  900  until all the covers of the set  110 ,  120  are in place in the frame  200 . In this way, each of the individual covers  900  in each of the sets  110 ,  120  has their undercut sides all aligned towards the same end of the support frame  200 . 
     If the first end  210  of the support frame  200  has undercut end frame pieces ( 300 ,  FIGS. 4 and 5 ), the second end  220  of the support frame  200  must have drawcut end frame pieces ( 400 ,  FIGS. 6 and 7 ) in order to allow the last-installed cover  900  in the set  110 ,  120  to be inserted and removed. The side frame pieces  204  may be drawcut for the same reason. 
     In use, when a load is applied generally perpendicular to the first or second sets of covers  110 ,  120 , the angle of the drawcut side walls  940  of the individual covers  900  converts this load into an axial load that pushes the covers  900  towards the first and second ends  210 ,  220  of the frame  200 . In particular, the axial load forces the set of covers  110 ,  120  into the undercut at the first end  210  of the frame  200 , which prevents the cover  900  from slipping out of the frame  200  at the first end  210 . The set of covers  110 ,  120  may be fastened to the frame  200 , for example by a bolt or similar retaining mechanism. 
     Turning again to  FIG. 2 , with additional reference to  FIG. 11 , in some embodiments the support frame  200  further comprises a support beam  700  and wall boxes  800 . The wall boxes  800  are shaped to correspond to each end of the support beam  700  to provide support to each end of the support beam  700 . The support beam  700  has a first beam end  702  disposed opposite a second beam end  704 ; the first beam end  702  is connected to a first wall box  800 , and the second beam end  704  is connected to a second wall box  800 . The first and second wall boxes  800  are connected to the end frame pieces  202  at the first and second end  210 ,  220  respectively. Connecting the wall boxes  800  to the end frame pieces  202  allows beam loads to be transferred into the rest of the support frame  200 . 
     The support beam  700  provides support to the edges of the first and second sets of covers  110 ,  120 . In some embodiments, the support beam  700  divides the first set of modular access covers  110  from the second set of modular access covers  120 , as shown in  FIG. 1 . In this way, each individual cover  900  in the first and second sets of modular access covers  110 ,  120  has at least two edges which are supported by the frame  200 . For example, in the embodiment of the assembly  100  shown in  FIG. 1 , each individual cover  900  is rectangular-shaped and has one side edge supported by one of the side frame pieces  204 , and the opposite side edge  204  supported by the support beam  700 . Meanwhile, the end edges are supported by adjacent covers  900  and/or the end frame pieces  202 . 
     Continuing to refer to  FIG. 2 , in embodiments of the support frame  200  comprising the support beam  700 , the end frame pieces  202 , side frame pieces  204  and the support beam  700  define first and second recessed portions  208 - 1 ,  208 - 2  of the support frame  200 . The first recessed portion  208 - 1  receives and supports the first set of modular access covers  110 , and the second recessed portion  208 - 2  receives and supports the second set of modular access covers  120 . The recessed portions  208 - 1 ,  208 - 2  may enable upper portions of the first and second sets of covers  110 ,  120  to sit substantially level with an upper portion of the support frame  200 . 
     When assembled, the end frame pieces  202 , side frame pieces  204 , and corner pieces  206  define a lower portion of the support frame  200 . When the first and second sets of covers  110 ,  120  are placed in the recessed portions  208 - 1 ,  208 - 2 , respective lower portions of the first and second sets of covers  110 ,  120  are aligned with the lower portion of the support frame  200 . 
       FIGS. 4 and 5  show an undercut embodiment of a frame piece  300 .  FIGS. 6 and 7  show a drawcut embodiment of a frame piece  400 . In some embodiments, the frame pieces  300 ,  400  are modular, so that they may be used either as an end frame piece  202  or a side frame piece  204 , with the only distinction being the location it is installed as part of the support frame  200 . 
       FIG. 4  is a perspective view of the frame piece  300 , and  FIG. 6  is a perspective view of the frame piece  400 . The frame pieces  300 ,  400  each comprise a wall  310 ,  410  and a ledge  320 ,  420  which extends from the wall  310 ,  410  at an angle  330 ,  430 , as is more clearly shown in the end views of  FIGS. 5 and 7 . In particular,  FIGS. 5 and 7  respectively show the frame pieces of  FIGS. 4 and 6  as would be installed in a rebate surrounding an opening to be covered. 
     The angle  330 ,  430  between the ledge  320 ,  420  and the wall  310 ,  410  may be acute or obtuse, ranging approximately between 45° and 135°. In some embodiments, the angle  330 ,  430  ranges approximately between 70° and 110°. In some embodiments, the angle  330 ,  430  ranges approximately between 80° and 100°. If the angles  330 ,  430  are too acute or too obtuse, it may be more difficult to add and remove the covers  900  from the undercut and drawcut parts of the frame  200 . In some embodiments, the angle  330 ,  430  is 82° or 98°, as this allows sufficient contact with the covers  900  in the undercut and drawcut parts of the frame  200 , while allowing reasonable addition and removal of the covers  900 . In some embodiments, the angle  330  is acute, and the frame piece  300  is said to have an undercut configuration, as shown in  FIGS. 4 and 5 . In the undercut configuration, the angle  330  may be approximately 82°. In some embodiments, the angle  430  is obtuse, the frame piece  400  is said to have a drawcut configuration, as shown in  FIGS. 6 and 7 . In the drawcut configuration, the angle  430  may be approximately 98°. 
     The wall  310  and the ledge  320  define the recessed portions of the support frame  200 . As assembled, the frame pieces  300 ,  400  define a support plane  340 ,  440  of the assembly  100 , wherein the support plane  340 ,  440  is coincident with the ledge  320 ,  420 . The ledge  320 ,  420  is disposed in the lower portion of the support frame  200  and provides support to the lower portion of the individual cover  900 . Specifically, when the bottom edge or surface ( 912 ,  FIGS. 14 to 15B ) of the cover  900  is placed in contact with the ledge  320 ,  420 , the load applied to the cover  900  is transferred to the ledge  320 ,  420  and into the support frame  200 . 
     Continuing to refer to  FIGS. 4 to 7 , the frame pieces  300 ,  400  further comprise end plates  350 ,  450 , a base plate  360 ,  460 , and stiffeners  370 ,  470 . The end plates  350 ,  450  are placed at the ends of the wall  310 ,  410  and ledge  320 ,  420  to demarcate the end of the frame piece  300 ,  400  and provide some support to maintain the angle  330 ,  430  between the wall  310 ,  410  and ledge  320 ,  420 . The end plate  350 ,  450  also provides a location for connecting adjacent frame pieces  300 ,  400 . A series of holes  352 ,  452  may be formed in the end plate  350 ,  450  so as to accommodate a fastener, such as a bolt, and a nut tightened onto the bolt to adjoin and retain the end plate  350 ,  450  with the end plate  350 ,  450  of the adjacent frame piece  300 ,  400 . 
     The base plate  360 ,  460  extends from the wall  310 ,  410  on an opposite side to the ledge  320 ,  420 . As shown in  FIGS. 5 and 7 , the base plate  360 ,  460  is configured to be placed in contact with the structure  390  surrounding the opening, such as the step  392  or rebate. Alternatively, the step  392  may be cut or formed to be slightly larger than the frame piece  300 ,  400 , as it may be too difficult or expensive to cut or form the structure to the exact dimensions required. Packers may then by placed on the step  392 , and the frame piece  300 ,  400  placed on these packers. The packers may to bring the frame piece  300 ,  400  to the desired position on the step  392 . To assist the frame piece  300 ,  400  with being located on the step  392  or edge of the surrounding structure  390 , the ledge  320 ,  420  may comprise a lip  380 ,  480  which extends generally perpendicularly to the ledge  320 ,  420 . When the frame piece  300 ,  400  is aligned on the step, the lip  380 ,  480  extends downward so that it abuts or is substantially coplanar with the sheer face  394  of the opening, thereby providing an indication that the frame piece  300 ,  400  is properly located on the step  392 . 
     As shown in  FIGS. 5 and 7 , the distance X from the base plate  360 ,  460  to the lip  380 ,  480  sets the minimum width of the rebate required to accommodate the frame piece  300 ,  400 . The distance X may be approximately 100 mm, or range between 50 mm and 200 mm. Meanwhile, the height H of the end plate  350 ,  450  sets the minimum depth of the rebate required to accommodate the frame piece  300 ,  400 . Height H may be approximately 100 mm, or range between 50 mm and 200 mm. 
     As shown in  FIGS. 4 and 6 , the stiffeners  370 ,  470  connect the wall  310 ,  410  to the base plate  360 ,  460  and provide structural reinforcement to the frame piece  300 ,  400 . The frame piece  300 ,  400  may comprise a plurality of the stiffeners  370  disposed between the end plates  350 ,  450 . The number of stiffeners  370 ,  470  may vary according to the length of the frame piece  300 ,  400 , as measured between the end plates  350 ,  450 . The frame piece  300 ,  400  may range between 300 mm and 2000 mm in length. In some embodiments, the frame piece  300 ,  400  is 500 mm long, 750 mm long, or 1000 mm long. By way of example, the 500 mm-long frame piece  300 ,  400  has five of stiffeners  370 ,  470 . The 750 mm-long frame piece  300 ,  400  has seven of stiffeners  370 ,  470 . The 1000 mm-long frame piece  300 ,  400  has 11 of stiffeners  370 ,  470 . The stiffeners  370 ,  470  may be equally disposed between the end plates  350 ,  450 . 
       FIGS. 8 and 9  show undercut embodiments of a corner piece  500 . In particular,  FIG. 8  shows a “left-hand” undercut embodiment of the corner piece  500 , and  FIG. 9  shows a “right-hand” undercut embodiment of the corner piece  500 . The requirement for left-handed and right-handed (i.e. mirrored) undercut embodiments is as a result of the relative geometry of the junction where undercut and drawcut sides meet. In embodiments where an undercut is only at one end of the frame  200 , and the rest of the frame  200  has a drawcut configuration, mirrored versions of the undercut corner pieces are required. 
     The corner pieces  500  comprise an undercut wall  510 , a drawcut wall  520 , and a ledge  530  which extends from the walls  510 ,  520  at an undercut angle and at a drawcut angle. The undercut angle is the angle between the undercut wall  510  and the ledge  530 . The drawcut angle is the angle between the drawcut wall  520  and the ledge  530 . The undercut and drawcut angles correspond to the undercut and drawcut angles of the individual covers  900  which are in contact with the corner pieces  500 . The ledge  530  supports the bottom edge (reverse surface  912 ) of the individual cover  900 . 
       FIG. 10  shows a drawcut embodiment of a corner piece  600 , where two drawcut walls  610 ,  620  meet. As the drawcut sides  610 ,  620  are symmetrical in their angles, it is possible to simply rotate the drawcut corner piece  600  to fit on opposing drawcut corners of the frame  200  and no mirrored versions are required. The corner piece  600  further comprises a ledge  630  which extends from the walls  610 ,  620  at a drawcut angle. The drawcut angle is the angle between the drawcut walls  610 ,  620  and the ledge  630 . The drawcut angle corresponds to the drawcut angle of the individual cover  900  which is in contact with the corner piece  600 . The ledge supports the bottom edge (reverse surface  912 ) of the individual cover  900 . 
     The corner pieces  500 ,  600  further comprise respective end plates  540 ,  640 . The end plates  540 ,  640  are placed at the ends of the walls  510 ,  520 ,  610 ,  620  and the ledges  530 ,  630  to demarcate the end of the corner pieces  500 ,  600  and provide some support to maintain the angle between the walls  510 ,  520 ,  610 ,  620  and respective ledges  530 ,  630 . The end plate  540 ,  640  also provides a location for connecting adjacent frame pieces  300 ,  400 . A series of holes  542 ,  642  may be formed in the end plate  540 ,  640  so as to accommodate a fastener, such as a bolt, and a nut tightened onto the bolt to adjoin and retain the end plate of the corner piece  500 ,  600  with the end plate  540 ,  640  of the adjacent frame piece  300 ,  400 . The end plates  540 ,  640  are positioned relative to each other at a corner angle, which is typically 90°, although other angles are possible depending on the desired shape of the frame  200 . 
       FIG. 11  is an exploded view showing the support beam  700 , wall boxes  800 , and wall box base plates  850 . The support beam  700  comprises a first flange  710 , a second flange  720 , and a web  730 . The beam  700  comprises oppositely disposed first and second ends  702 ,  704 , with a plurality of stiffening plates  740  disposed along the beam  700  between the first and second ends  702 ,  704  to improve the resistance of the beam  700  to applied loads such as bending and torsion. The first flange  710 , second flange  720 , and web  730  may be arranged as per a conventional I-beam, as can be more clearly seen in  FIG. 12 . 
       FIG. 12  is a partial cross-section view of the beam  700 , with the ends  702 ,  704  of the beam  700  hidden to more clearly show the profile of the flanges  710 ,  720  and web  730 , and the placement of the stiffening plates  740 . The beam  700  has a depth, D, as measured between the first and second flanges  710 ,  720  parallel to the web  730 . The beam  700  has a width, W, as measured between the respective extremities of the first and second flanges  710 ,  720  perpendicular to the web  730 . The depth D and width W of the beam  700  may range in size depending on various factors, such as the material properties of the beam  700 , the length of the beam  700 , and the amount of load to be carried by the beam  700 . In some embodiments, the depth D may be in the range of approximately 50 mm to 4000 mm, depending on the load class. In some embodiments, the width W may be in the range of approximately 500 mm to 1000 mm, depending on the load class. For example, a Class F or G-rated assembly  100  may have a beam  700  measuring 4000 mm deep and 1000 mm wide. 
     The first flange  710  defines a support surface  712  for supporting an edge of at least one of the individual modular access covers. When assembled as part of the frame  200 , the support surface  712  is coincident with the support plane  340 ,  440 . The first flange  710  may also have a pair of ridges  714 ,  716  which extend generally perpendicularly from the first flange  710 . The ridges  714 ,  716  restrict the lateral movement of the individual covers when the covers are placed in contact with the support surface  712 , as indicated by arrows  718 . The ridges  714 ,  716  are angled relative to the support surface  712  to form a drawcut which corresponds to the drawcut angle of the covers. The support surface  712  may comprise first and second laterally opposite support surfaces, which are separated by the ridges  714 ,  716 . 
     A ridge stiffening plate  742  connects the ridges  714 ,  716  to reinforce the ridges  714 ,  716  against lateral forces imposed by the covers. The flanges  710 ,  720  are joined by the web  730  and a pair of web stiffening plates  744  disposed either side of the web  730 . Several pairs of the web stiffening plates  744  may be disposed along the length of the beam  700  between the first and second ends  702 ,  704 . This essentially partitions the longer flange  710 ,  720  into a series of shorter flanges, which has a higher resistance to bending for a given load. 
       FIG. 11  shows the placement of the web stiffening plates  744  along the length of the beam  700 .  FIG. 11 , which shows a beam  700  measuring approximately 3 m long, has 21 of ridge stiffening plate  742  and three pairs of web stiffening plates  744  distributed along its length. The three pairs of web stiffening plates  744  may be distributed so that there is a pair of web stiffening plates  744  toward each end  702 ,  704  of the beam  700 , and a pair of web stiffening plates  744  approximately at the middle of the beam  700 . 
     The number of stiffening plates  742 ,  744  can be adjusted depending on the length of the beam  700 . For example, a 1.5 m long beam  700  may have 11 of ridge stiffening plate  742  and three of web stiffening plates  744 . The beam  700  may also come in 2 m and 2.5 m lengths, although varying lengths of beams may be made depending on the size of the opening to be covered. 
     Continuing to refer to  FIG. 11 , the web  730  tapers upwardly towards the first and second ends  702 ,  704  of the support beam  700 . Tapering the web  730  allows for a deeper beam in the midsection of the beam  700 , where the bending moments and shear stresses are highest, and a shallower beam at the ends  702 ,  704  where the moments and stresses are at their lowest. Having a shallower beam at the ends  702 ,  704  also allows the ends of the beam  700  to better fit into the frame  200 . By fitting the first and second ends  702 ,  704  of the beam  700  into the frame  200 , this reduces or removes the need to build a deep rebate into the surrounding structure to accommodate the full depth of the beam  700 . Accordingly, only a small (and single size of) rebate is required for the frame  200 , which reduces build time, complexity, and cost on site. 
     The tapering of the web  730  may begin at the end-most plates  744  and end at the first and second ends  702 ,  704 , thereby defining first and second tapered portions  732 ,  734  of the web  730 , respectively. In the first and second tapered portions  732 ,  734 , the second flange  720  angles towards the first flange  710 . A first and second end plate  736 ,  738  may connect the first and second flanges  710 ,  720 . The web  730  may also define a first lifting aperture  746  at the first end  702  of the support beam  700 , and a second lifting aperture  748  at the second end  704  of the support beam  700 . The lifting apertures  746 ,  748  may be located in the tapered portions  732 ,  734 . 
     At the first and second ends  702 ,  704  of the beam  700 , the first flange  710  extends beyond the end plates  736 ,  738  to terminate in a first wall  750  at the first end  702 , and terminate in a second wall  752  at the second end  704 . The ridges  714 ,  716  may adjoin the first and second end walls  750 ,  752 . The first and second walls  750 ,  752  are angled relative to the support surface  712  of the first flange  710 . Where the angle between the walls  750 ,  752  and the support surface  712  is an acute angle, an undercut configuration is formed. Where the angle between the walls  750 ,  752  and the support surface  712  is an obtuse angle, a drawcut configuration is formed. In some embodiments, the first end  702  of the beam  700  is undercut to correspond to the undercut at the first end  210  of the frame  200 . In some embodiments, the second end  704  of the beam  700  is drawcut to correspond to the drawcut at the second end  220  of the frame  200 . 
     The first and second walls  750 ,  752  may extend to form respective first and second box structures  754 ,  756 . The first and second box structures  754 ,  756  are shaped to have substantially the same depth as the frame pieces  300 ,  400  so that the rebate formed in the structure surrounding the opening can be a consistent size and shape. 
     A first end surface  760  may be defined on the underside of the first flange  710  at the first end  702  of the support beam  700 , spanning from the first end plate  736  to the extremity of the beam  700  at the first end. Similarly, a second end surface  762  may be defined on the underside of the second flange  720  at the second end  704  of the support beam  700 , spanning from the second end plate  738  to the extremity of the beam  700  at the second end. The first and second end surfaces  760 ,  762  may be substantially coplanar with the support surface  712 , or parallel to and slightly offset therefrom. 
     As can be seen in  FIG. 11 , the wall box  800  is shaped to conform to the shape of the first and second box structures  754 ,  756 . The wall box  800  comprises a base plate  850  for attaching the wall box  800  to the frame pieces  300 ,  400 . When the support frame  200  is assembled, the wall box  800  envelops the box structure  754 ,  756 , and the wall box base plate  850  adjoins the wall box  800  and the respective end surface  760 ,  762 . 
     Turning now to  FIG. 13 , the wall box  800  comprises a wall  810  and end plates  820  extending perpendicularly at each end of the wall  810 . The wall  810  and end plates  820  are angled relative to each other to accommodate the drawcut of the box structure  754 ,  756 . The end plates  820  may also have an end face  822 , and a step  830  extending from the end face  822  at the same angle as the angles  330 ,  430  to define an undercut or drawcut configuration. When the wall box  800  is assembled as part of the frame  200 , the wall box step  830  sits level with the ledge  320 ,  420 , and the end face  822  sits level with the wall  310 ,  410  of the frame piece. The wall box  800  further comprises a base plate  850  for attaching the wall box  800  to the frame pieces  300 ,  400 . The wall  810  and end plates  820  define a mating surface  840  which is attached to the base plate  850 . 
     The wall box base plate defines a surface  852  to support the support beam  700  and the end frame pieces  202 . The surface  852  is offset from the support plane  340 ,  440  by the height of the step  830 . The height of the step  830  is equivalent to the height of the lip  380 ,  480  of the end frame pieces  202 , so that the wall box step  830  sits level with the ledge  320 ,  420  (with which support plane  340 ,  440  is coincident). The height of the step  830 , and thereby the offset of surface  852  from the support plane  340 ,  440 , may be between 10 mm to 100 mm, such as 15 mm to 40 mm or 20 mm to 35 mm, for example. In some embodiments, the height of the step  830  is approximately 27 mm. The base plate  850  comprises a central portion  860  and wings  870  extending both sides of the central portion  860 . In use, the mating surface  840  is coupled to the central portion  860 , and the first and second end surfaces  760 ,  762  of the support beam  700  rest on the central portion  860 . The wings  870  may comprise a flap  880  extending perpendicularly to the wings  870 . The flap  880  may allow the base plate  850  to be connected to the frame pieces  300 ,  400  via apertures  890  defined in the flap  880 . As can be seen in  FIG. 2 , when frame  200  is assembled, the end frame piece  202  sits on the wings  870 . With additional reference to  FIGS. 5 and 7 , the wall box base plate  850  sits on the step  392 , and packers may be placed in the gap between the top of the step  392  and the bottom of the frame pieces  202 ,  204  to support the frame pieces  202 ,  204 . The use of packers allows the step  392  to be cut as a flat surface, and may be placed under the frame pieces  202 ,  204  at intervals of 200 mm to 300 mm to support the frame pieces  202 ,  204 . 
       FIG. 14  shows an embodiment of one of the modular access covers  900  which is joined to other covers  900  to form the first and second sets of covers  110 ,  120 . The cover  900  comprises a base plate  910  having first and second end walls  920 ,  930  and side walls  940  extending from the base plate. The first and second end walls  920 ,  930  may be oppositely disposed to each other, and the side walls  940  connect the end walls  920 ,  930  to define a cavity  950  with the base plate  910 . The base plate  910  comprises a reverse surface  912  disposed opposite the cavity  950 , which defines an underside of the cover  900 . The reverse surface  912  may be substantially flat and smooth. 
     In some embodiments, the cover  900  is rectangular. The angle between the end walls  920 ,  930  and the base plate  910 , and the angle between the side walls  940  and the base plate  910  may be in the region of 70° to 110° to define an undercut or drawcut configuration. For example, a suitable angle would be 98°. 
     The cover  900  further comprises ribs  960  disposed on the base plate  910 . The ribs  960  may be arranged in a grid pattern, such as shown in  FIG. 14 . The ribs  960  may extend generally perpendicularly from the base plate  910  and connect to the end walls  920 ,  930  and side walls  940  to divide the cavity  950  into a series of smaller cavities  950 . The cavity or cavities  950  are configured to receive and contain a filler material, such as cement or concrete. Filling the cavities  950  with a filler material increases the strength and the weight of the cover  900 , and allows a smooth, flat contact surface to be created on the cover  900 . In use, a load can be applied to the contact surface without falling into the cavities  950 . A non-slip or high-friction coating may be applied to the contact surface to improve grip, for example when walking on the cover  900 . 
     The cover  900  further comprises a connecting portion  970 . The connecting portion  970  is configured to fixedly couple the cover  900  to an adjacent cover  900 . The connecting portion  970  may extend from one or more of the end walls  920 ,  930 . In some embodiments, the connecting portion  970  may extend from one or more of the side walls  940 , or a combination of side walls  940  and the end walls  920 ,  930 . One or more of the connecting portions  970  may be attached to one or more of the ribs  960  for additional rigidity. 
     In some embodiments, the base plate  910 , end walls  920 ,  930 , side walls  940 , ribs  960 , and connecting portion  970  are integrally formed, for example by moulding or casting, to reduce the need to manufacture and assemble separate parts. The base plate  910  may define at least one aperture  914  extending from the cavity  950  through to the reverse surface  912 . The aperture  914  may provide drainage for any liquid contained in the cavity  950 , if the cavity  950  has not been filled with filler material. In embodiments of the cover  900  where casting/moulding of molten material is used to form the cover  900 , the aperture  914  may allow for stress and heat to dissipate as the cover  900  cools. The end walls  920 ,  930 , side walls  940 , ribs  960 , and connecting portion  970  may be of substantially equal height. In some embodiments, the ribs  960  and/or the connecting portion  970  are shorter than the height of the end walls  920 ,  930  and side walls  940 . 
     The cover  900  has a length L, as measured between the first and second end walls  920 ,  930 . The cover  900  has a width W, as measured between the side walls  940 . The cover  900  has a depth D, as measured between the top of the first and second end walls  920 ,  930  and the reverse surface  912 . The length L and width W of the cover  900  may range between approximately 125 mm to approximately 1000 mm. The depth D of the cover  900  may range between approximately 50 mm to approximately 100 mm. In some embodiments, the cover  900  may be made in a variety of set sizes which, when combined, can be used to cater to the majority of opening sizes and shapes. This reduces the amount of custom covers required to be made for each opening to be covered. The approximate set sizes in millimetres of the cover  900  may be (L×W×D): (1) 750×125×73; (2) 500×250×73; (3) 750×750×81; (4) 1000×125×73; (5) 500×750×73; (6) 500×500×73. However, other sizes of covers  900  may be manufactured if required. 
     In some embodiments, the cover  900  further comprises a tab  980 . The tab  980  is configured to engage with the connecting portion  970  to allow coupling of adjacent covers  900  together. The tab  980  comprises a tab body  982  which substantially spans the length of the first end wall  920  and defines a tab hole  984 . The tab body  982  may additionally define a supporting surface  986 . The reverse surface  912  and the supporting surface  986  may be substantially coplanar. In some embodiments, the reverse surface  912  and the supporting surface  986  are parallel and offset from each other. 
     The tab  980  and the connecting portion  970  cooperate as part of the retainer  130  (previously described in relation to  FIG. 1 ) to maintain the desired level of contact between adjacent covers  900  when the covers  900  are placed under load. In particular, the tab  980  extends outwards from the first end wall  920  along part of the length of the first end wall  920 . In some embodiments, the length of the tab body  982  is at least approximately 50% of the length of the first end wall  920 . The length of the tab body  982  may be at least approximately 70% of the length of the first end wall  920 . A longer tab body  982  provides greater contact area with the first end wall  920  and allows the tab  980  to be more sturdily supported by the first end wall  920 . However, the length of the tab  980  should not cause to the tab  980  to interfere with the ledge  320 ,  420  of the frame pieces  300 ,  400  when the cover  900  is being placed into the frame  200 . If the tab  980  is too long, it will interfere with the ledge  320 ,  420  as the tab  980  is being tucked under the adjacent cover  900 . 
     The tab  980  may extend outwards an equal distance from the first end wall  920  along the length of the tab body  982  so that the area of supporting surface  986  is relatively consistent along the length of the tab body  982 . As shown in  FIGS. 15A and 15B , when covers  900  are placed adjacent to each other, the connecting portion  970  of one cover  900  overlaps the tab  980  of the other cover  900 , so that the reverse surface  912  of one cover  900  contacts the supporting surface  986  of the other cover  900 . 
       FIG. 15A  is an exploded cross-section detail view of adjacent covers  900 . The connecting portion  970  may be formed as an integral part of cover  900  when it is cast. The connecting portion  970  comprises a body  972  which defines a bore  974 . The bore  974  extends through the reverse surface  912  of the cover  900 . The bore  974  is configured to receive a connector or fastener  990  and guide the connector  990  to engage with the tab hole  984  and thereby fixedly couple the covers  900 , as shown in  FIG. 15B . In some embodiments, the tab hole  984  is threaded so that the connector  990  may engage and retain the tab  980 , as in use, the underside of the cover  900  is not accessible for a nut to be tightened over the end of the bolt  990 . 
       FIG. 15B  is the cross-section view of  FIG. 15A  with the adjacent covers  900  coupled to each other. As shown, the second end wall  930  and reverse surface  912  of one cover  900  is placed adjacent to the first end wall  920  and supporting surface  986  of another cover  900 , and the bore  974  of the connecting portion  970  is aligned with the tab hole  984  to receive a connector  990  therethrough. The connector  990  may be a removable fastener, such as a bolt, to fixedly but releasably couple the covers  900  together. 
     Removing the connector  990  allows the covers  900  to be detached from each other. Once the covers  900  are detached, individual covers  900  may be detached from the support beam  700  and the end and side frame pieces  202 ,  204  to permit access through the opening to the underground or underfloor area covered by the assembly  100 .  FIGS. 16A and 16B  show the detachment of one cover  900  from another cover  900 ; for clarity, the frame  200  is not shown. To detach connected covers  900 , the connector  990  is first removed, as shown in  FIG. 16A . As marked by arrow  250  in  FIG. 16B , the cover  900  may then be tilted up at the second end wall  930  to separate the tab  980  from the reverse surface  912  of the adjacent cover  900 , and the cover  900  removed. This is essentially the reverse operation shown in  FIG. 3B . The size and weight of the covers  900  may deter the risk of unauthorised removal, or accidental dislodgement when a heavy vehicle travels over it. However, the covers  900  may thus be too heavy to safely lift manually, and so powered lifting equipment such as hydraulic jacks or cranes may be used to lift the covers  900 . 
     In the first and second sets of covers  110 ,  120 , all the individual covers  900  have the tab  980 , with the exception of the covers  900  at the first end  210  which engage with the undercut in the frame. As shown  FIGS. 16A and 16B  (and  FIGS. 3A and 3B ), in the endmost cover  900  in the first and second sets  110 ,  120  does not have the tab  980 , as it is supported on all sides by the frame  200  or the tab  980  of the adjacent cover. 
     The frame piece  300 ,  400 , corner piece  500 A,  500 B,  600 , beam  700 , wall box  800 , and cover  900  may be made from the same material as each other, or made from different materials to each other. The frame piece  300 ,  400 , corner piece  500 A,  500 B,  600 , beam  700 , wall box  800 , and cover  900  may be made from a rigid material such as metal, plastic, fibreglass or composite. In some embodiments, the frame piece  300 ,  400 , corner piece  500 A,  500 B,  600 , beam  700 , wall box  800 , and cover  900  may be made from a combination of these materials. Preferably, the frame piece  300 ,  400 , corner piece  500 A,  500 B,  600 , beam  700 , wall box  800 , and cover  900  is made from steel. The steel may be galvanised or painted to resist corrosion. The frame piece  300 ,  400 , corner piece  500 A,  500 B,  600 , beam  700 , wall box  800 , and cover  900  may be made from several parts which are attached together, such as by welding. The wall and ledge of the frame piece  300 ,  400  and corner piece  500 A,  500 B,  600  may be extruded so that the angle between the wall and the ledge is accurately formed in order to accommodate the corresponding undercut or drawcut of the individual cover. The end plates and the stiffeners may then be welded to the wall and ledge. In some embodiments, the frame piece  300 ,  400  is a single body, wherein the wall and ledge, base plate, stiffeners, and end plates are integrally formed to avoid the need to attach multiple pieces together. Similarly, the corner piece  500 A,  500 B,  600 , beam  700 , wall box  800 , and cover  900  may be integrally-formed, single bodies. Forming the frame piece  300 ,  400 , corner piece  500 A,  500 B,  600 , beam  700 , wall box  800 , and cover  900  as single bodies may be achieved by casting the steel, injection moulding the plastic, or laying the fibreglass in a corresponding mould. 
     In some embodiments, the assembly  100 - 2  may include multiple laterally spaced and parallel support beams  700 . Sets of access covers  900  are positionable on each lateral side of each of the multiple support beams  700 .  FIG. 17  is a perspective view of a modular access cover assembly  100 - 2 , according to some embodiments. As shown in  FIG. 17 , the assembly  100 - 2  shows the support frame  200 , a single set of covers  110 , and one support beam  700  supported by a first pair of wall boxes  800 . The support frame  200  additionally includes a second pair of wall boxes  800  spaced laterally from the first pair of wall boxes. The second pair of wall boxes  800  is configured to receive the ends of a second support beam  700  that is parallel to and laterally spaced from the first support beam  700 . By having two pairs of wall boxes  800 , the support frame  200  is configured to include two support beams  700  and three sets of access covers  900 , with each support beam  700  having a set of access covers  900  on each lateral side thereof. The use of multiple support beams  700  may be desirable to allow a larger opening to be covered. The assembly  100 - 2  is otherwise identical to the assembly  100  described above. 
       FIG. 18  is a flow chart of a method  1000  for assembling the access cover assembly  100 . At  1010 , at jig or scaffolding may be used to hold the various pieces of the frame  200  in position while connecting the pieces together. In some embodiments, the beam  700  is the heaviest and bulkiest piece of the frame  200 , and so is the first piece located in the jig, with the other frame pieces built around the beam  700 . 
     At  1020 , the method  1000  involves connecting the wall boxes  800  to the support beam  700 , and then connecting the end frame pieces  202  to the wall boxes  800 . The corner pieces  206  may then be attached to the end frame pieces  202 , and then the side frame pieces  204  attached to the corner pieces  206  to form the support frame  200 . Removable fasteners such as nuts and bolts may be used to connect the various pieces of the frame  200 . In some embodiments, a plurality of the end frame pieces  202  are connected together. In some embodiments, a plurality of the side frame pieces  204  are connected together. The end and side frame pieces  202 ,  204  are connected by the corner pieces  206 . A spirit level may be used to ensure the frame  200  has been assembled evenly. 
     Once the frame  200  is assembled, the covers  900  may be inserted individually into the recessed portions  208  of the frame  200 . Alternatively, the individual covers  900  may be preassembled to form the first set of covers  110  and the second set of covers  120 , before assembling the sets  110 ,  120  with the frame  200 . The edges of the covers  900  are supported on the ledges  320 ,  420  and may be substantially coincident with the support plane  340 ,  440 . 
     At  1030 , the method  1000  may additionally involve positioning the first set and the second set of covers  110 ,  120  in the first and second recessed portions  208 - 1 ,  208 - 2  respectively. The method  1000  may further involve, at  1040 , bolting the first set of covers  110  together, and bolting the second set of covers  120  together. At  1050 , the method  1000  may involve bolting the first and second sets  110 ,  120  to the frame  200  to secure the first and second sets  110 ,  120  in the respective first and second recessed portions  208 - 1 ,  208 - 2 . 
     The assembly  100  may be assembled according to the method  1000  in a factory, and then transported to site. Fully tightening the nuts to secure the bolts is recommended prior to transport to reduce the risk of the assembly  100  separating into its constituent parts. In some embodiments of method  1000 , the assembly  100  is instead assembled at the installation site, which avoids the need to transport the assembly  100 , especially if the assembly  100  is too large to be cost-effectively transported. 
     The assembly  100  caters for a large variety of opening sizes and shapes using a few modular parts. For example, around six different cover sizes may be combined to cover a variety of opening sizes and shapes. Assembly may involve the assembly of approximately 20-30 parts which are bolted together to cover a variety of opening sizes and shapes. The parts, methods, and assemblies disclosed herein may reduce the complexity and assembly time compared to conventional multi-part access covers. 
     In particular, the present disclosure provides a tapered beam which fits into the frame, meaning only a single, smaller rebate is required to be built on site to support the assembly  100 . In conventional multi-part systems, beams have a consistent depth along the length of the beam, and typically, the depth of the beam is considerably larger than the depth of the cover to allow the beam to provide the desired resistance to bending loads. This means that when an assembled access cover is installed on site, a step or rebate has to be formed or built into the concrete floor to accommodate the different depths of the beam and the covers. 
     The tapered beam may be cast or moulded as a single piece. The covers and frame pieces may also be moulded as single-piece constructions. This may minimise manufacturing errors compared to conventional multi-part access covers which use fabrication techniques such as cutting and welding to assemble a multi-part product. 
     Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present disclosure as it existed before the priority date of each of the appended claims. 
     Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps. 
     It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the above-described embodiments, without departing from the broad general scope of the present disclosure. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.